Johnson Matthey Metal Joining - Silver Brazing Alloys and Fluxes

Johnson Matthey Metal Joining - Silver Brazing Alloys and Fluxes

Index Page

About Johnson Matthey plc and JM Metal Joining 4

What is Brazing and Some Advantages of the Brazing Process 4

Understanding Brazing and Terms Used in Brazing 6

The Six Steps of Successful Brazing 7 Simple Steps to Make Brazing Easier

The Silver-flo Range of Cadmium Free Silver Brazing Alloys 10 A Range of General Purpose Brazing Alloys

The Easy-flo Range of Cadmium Bearing Silver Brazing Alloys 14 A Range of General Purpose Brazing Alloys

Silver Brazing Alloys for Brazing Tungsten Carbide 16 Including Base Metal Brazing Alloys

Silver Brazing Alloy for Brazing Stainless Steel 20 Argo-braze 56, a Special Alloy Used for Brazing Stainless Steel in Wet Service Conditions

The Sil-fos and Copper-flo Ranges 22 Alloys for Joining Copper to Copper and its Alloys

Johnson Matthey Brazing Fluxes 26 Fluxes for Use with Silver Brazing Alloys

Product Availability, Packaging and Quality 34

Brazing and Soldering Alloy Reference Chart 36

Health and Safety in Brazing 38

3 Johnson Matthey plc

Johnson Matthey is a world leader in all aspects of precious metals technology. Building on 180 years of expertise in assaying and refining, the name of Johnson Matthey has become synonymous with the highest levels of quality and customer service. Today Johnson Matthey has worldwide businesses in Chemicals and Catalysts, Precious Metals and Colours and Coatings. The Company is continually changing and developing new technologies to meet the current and future needs of our customers.

Johnson Matthey Metal Joining

What is Brazing What is Brazing? Brazing is a versatile joining process. It is used to join most metals and alloys commonly used in engineering. It is a thermal joining process in which a molten brazing alloy is drawn into a capillary gap between the metals being joined. Brazing alloys have a melting point above 450˚C but always below the melting point of the metals being joined.

Some Advantages of The Properties of a Brazed Joint. Brazing as a Process • Strong and ductile - well made brazed joints can be at least as strong as the parent metals being joined and will withstand demanding service conditions. • Leak tight - brazing produces leak tight joints widely used on liquid and gas pipework installations. • Electrical conductivity - brazed joints offer good electrical conductivity and are used in applications where this property is important. • Joint appearance - brazed joints have smooth, neat fillets.

4 About Johnson Matthey - Metal Joining

Johnson Matthey have over 70 years experience in the brazing and soldering industry and have a global manufacturing capability. Our aim is to provide our customers with value for money whilst maintaining our renowned product quality and service. We recognise that customers face ever increasing challenges, and we intend to offer full technical product support. When you buy our products, you will receive not only the best quality, but also a solution to your brazing and soldering requirements. We serve customers in all industry sectors, from domestic appliances to aerospace. Our product range has evolved to meet their needs. We actively look to work in partnership with customers, the goal often being to increase the efficiency of their brazing and soldering processes. Johnson Matthey constantly monitor advances in materials technology using the expertise of our sites worldwide as well as that of our partners in the industry. This combined expertise enables us to offer the best solutions to metal joining problems and in many cases significantly reduces process costs.

Johnson Matthey - Metal Joining Quality

All branches of Metal Joining have been accredited with ISO 9002 and numerous customer quality approvals. Certification to national and international standards is available and all our products are supported by full COSHH documentation.

Some Features of Brazing • An outstanding feature of brazing is its ability to join different metals and components of dissimilar size and mass. • Brazing is also capable of joining tungsten carbide, ceramics and similar non-metallic materials. • Successful silver brazing takes place at relatively low temperatures (600˚C-900˚C). Unlike welding the parent materials are not melted.

The Brazing Process • Brazed joints can be made using a wide range of heating methods. • It is easy to set up for brazing and by following the correct procedures good results will be achieved. • Brazing is an economical process for joining small numbers of components through to mass production. • Many brazing processes can be automated allowing reliability and control as well as reducing costs.

5 Welding Typical design

Understanding Brazing and the Terms Used in this Booklet

Thermal Joining Processes and Where Brazing Fits In

Soldering and Brazing Thermal joining processes in which the molten filler metal is drawn into a capillary gap between two closely fitting surfaces. By definition:- Soldering takes place at temperatures below 450˚C and Brazing above 450˚C. Both processes occur below the melting point of the metals being joined. Silver Brazing Is a type of brazing using filler metals containing silver which melt between 600˚C and 900˚C. Silver soldering/Hard soldering are terms synonymous with Silver Brazing (not soldering). Fusion Welding A thermal joining process in which the mating faces are softened or made liquid by the application of heat or pressure or by both. Filler metal with a similar composition to the parent may or may not be added. Braze/Bronze Welding A thermal joining process using a hand torch and filler metal with a lower melting point than the parent metals. The process uses copper based filler metals melting above 850˚C and does not rely on capillary attraction.

Terms Associated with the Brazing Process and Brazing Alloys

Brazing Alloy A filler metal which melts above 450˚C but below the metals being joined. Flux A chemical compound applied to the parent metals to protect them from oxide formation during heating and to promote flow and wetting of the brazing alloy. Parent Metals The materials to be joined by brazing. Wetting When molten brazing alloy flows over and adheres to the parent metals. Joint Gaps The gap between the parent metals to be joined by the brazing alloy. Capillary Attraction The force that draws a molten brazing alloy into the joint gap. Solidus The highest temperature at which filler metal is completely solid. Liquidus The lowest temperature at which filler metal is completely liquid. Melting Range The temperature range over which the brazing alloy melts. Eutectic An alloy, with a single melting point, rather than a melting range, is known as a eutectic alloy.

Terms Associated with Metallurgical Problems in Brazed Joints

Liquation When a brazing alloy with a long melting range is heated too slowly, the phase with the lowest melting point begins to flow first. The material left behind has a changed composition and a higher melting point. It will not flow readily. An unsound and unsightly joint is the usual result of liquation. Dezincification This is a form of galvanic corrosion, generally associated with two phase brass alloys, in which the zinc rich beta phase is selectively leached out of the brass, leaving a sponge like matrix of the copper rich phase. This can occur when brazed joints are exposed to salt or seawater. Intergranular Nickel and nickel-based alloys are prone to cracking during brazing with silver brazing alloys. The cracking is Penetration known as intergranular penetration or stress cracking. It usually follows the grain boundaries and only occurs when components are subject to high stresses either in the material or created through the brazing process. Crevice or When silver brazed joints in stainless steel are exposed to water or humidity in service, joint failure may result Interfacial Corrosion from a specific form of interfacial or crevice corrosion along the stainless steel - brazing alloy interface.

6 Brazing Typical Design

Optimum overlap Optimum Overlap 3-4 x thinnest part = 1 x dia of tube

The Six Steps of Successful Brazing

In Achieving a Successful Brazed Joint Six Basic Steps Should Be Considered.

1. Joint Design Brazed joints should always have a capillary gap into which the molten filler metal can flow. Joint strength will vary with the joint gap and the degree of overlap between parent metals. The optimum joint gap at brazing temperature is shown in the table of physical properties for each product. Different expansion rates of the parent metals will affect the joint gap at brazing temperature. For lap joints use an overlap length of 3 to 4 times the thickness of the thinnest parent metal part in the joint. For tubular parts the overlap should be one tube diameter for sizes up to 1inch diameter tube.

2. Choice of Brazing Alloy Alloys should be chosen on their suitability for a particular application. Consideration should be given to the component design, the parent metals, the brazing process and the economics of the job. The brazing alloys that are easiest to use are the high silver, free flowing alloys with low melting ranges. Alloys with higher brazing temperatures and longer melting ranges are more difficult to use.

3. Pre-cleaning The components that are to be joined should be free from grease and any surface oxide prior to brazing. Grease and oil are best removed using a degreasing solvent. Hot, soapy water may also be effective. Surface oxide can be removed with a medium graded abrasive cloth. This will promote good bonding.

4. Fluxing the Joint The choice of flux is as important as the choice of filler metal. More details can be found on pages 26-33. Ideally flux should be applied to both components before assembly and prior to heating. The flux must melt and become active below the melting point of the brazing alloy. It must stay active right through the brazing cycle removing the oxides formed on the parent metals. If the flux residues appear blackened and glassy the flux has probably been exhausted during heating. This could be because either insufficient flux has been used or the components have been overheated. Alternatively a flux with greater time and temperature stability should be used.

5. Heating the Joint and Several heating methods are used for silver brazing in air. They include hand torch, fixed burner, induction and Applying the Alloy resistance heating. In addition for torch or fixed burners different fuel gas combinations are available from oxy- acetylene, oxy-propane, through to air natural gas. For brazing it is essential that the parent metals be heated evenly to the correct temperature. At the correct temperature for brazing the flux should be clear and flow over the joint area. When brazing copper with an alloy from the Sil-fos and Copper-flo range the metal should be a dull cherry red indicating the correct temperature has been reached. Brazing rod, strip or wire should then be touched onto the joint mouth when brazing temperature is reached. Free flowing alloys will flow into and around the joint by capillary attraction. A sluggish flowing alloy should be applied along the entire joint, building up an alloy fillet. Molten brazing alloy always flows to the hottest part of the joint, Heating should continue as the alloy flows into the joint. For torch brazing indirect heating should be used. Once brazing is complete heating should be discontinued.

6. Removing the Flux When the alloy has solidified the joint can be water quenched to help remove flux residues. Residues After Brazing During cooling care must be taken not to damage the component or cause cracking due to thermal shock. It is important to remove flux residues after brazing. More details can be found on pages 26-33.

7 Silver-Flo Alloys Easy-Flo Alloys Silver Brazing Alloys Cadmium Free Range 10 Cadmium Containing Range 14 for Tungsten Carbide 16 JMMJ Silver Brazing Alloys and Fluxes Product Guide

Argo-braze 56 Sil-fos & Copper-flo Alloys Brazing Fluxes Product Availability Brazing Stainless Steel for Wet Conditions 20 Joining Copper & Copper Alloys 22 26 34

Guide to Alloy forms Rods commonly available from stock Flux Coated Rods Each product section shows the alloy forms that are commonly Strips available from stock in the form of an icon. Other forms can be Wire made to order. Please check with Johnson Matthey for Powder more details 10

Rings

Washers

Foil

Paste Silver-Flo Alloys Cadmium Free Range

Some Features of the Silver-flo Range of Alloys

Johnson Matthey’s Silver-flo range forms • A very broad range of alloys which enables the customer to be able to select the optimum product for each brazing process in terms of both cost and alloy characteristics. a group of more than 20 cadmium free silver brazing alloys. These have been • Free flowing, low temperature silver brazing alloys that are easy to use and give strong neat joints. developed to meet the brazing needs

of all sectors of industry. Many of these • General purpose alloys with medium flow, melting ranges and cost. alloys are excellent substitutes for • Low silver content brazing alloys that fill wider joints and produce larger fillets. cadmium bearing alloys. Others can be

used for specialised applications. • The Silver-flo range are all cadmium free and suitable for the manufacture of food and drink handling equipment.

What Materials can be Joined with Silver-flo Products?

The following materials can be joined with the Silver-flo range of alloys and a suitable flux.

Copper and copper alloys including brasses, bronzes, nickel silvers, aluminium bronze and copper nickel. Nickel and nickel alloys. Refer page 13 - part 6. for special considerations. Steel - a wide range including carbon and low alloy steel. Stainless Steels. Refer page 20 if the resulting joint is to be exposed to a wet environment. Tungsten carbide and PCD segments. Refer page 16 for special alloys for this material.

Please Note:- These products cannot be used to braze aluminium, magnesium and their alloys. The lower melting point products are recommended for copper alloys with more than 2% lead content. Aluminium bronze and brasses with more than 2% aluminium require Easy-flo Aluminium Bronze flux. High zinc brasses generally require the use of an alloy with more than 16% silver.

10 The Silver-flo range - Features and Properties

Physical Properties of Silver-flo Alloys

Alloy Composition Melting Tensile/ BS1845: DIN 8513 EN 1044 Optimum Alloy forms commonly Ag Cu Zn Sn/Si Range ˚C Shear 1984 1986 1999 Joint Gap available from stock Strength mm N/mm2 General Purpose Low Temperature Alloys Silver-flo 67E 67 23 10 705-723 - - 0.075-0.2 Silver-flo 60 60 26 14 695-730 420/155 AG 13 L-Ag 60 AG 202 0.05-0.20 Silver-flo 56 56 22 17 5Sn 618-652 410/165 -(AWS Bag7) - AG 102 0.05-0.15 10 Silver-flo 56S 56 22 17 4.8Sn/0.2Si 618-652 410/165 0.05-0.15 Silver-flo 55 55 21 22 2 Sn 630-660 390/145 AG 14 L-Ag 55:Sn* AG 103 0.05-0.15 10 Silver-flo 453S 45 25 26.8 3Sn/0.2Si 640-680 - - 0.05-0.15 Silver-flo 452 45 27.75 25 2.25Sn 640-680 420/185 L-Ag 45:Sn* AG 104*** 0.05-0.15 10 Silver-flo 45 45 25 30 680-700 410/175 0.05-0.15 Silver-flo 44 44 30 26 675-735 545/185 L-Ag 44 AG 203 0.075-0.2 Silver-flo 43 43 37 20 690-775 400/165 AG 5 0.075-0.2 Silver-flo 40 40 30 28 2Sn 650-710 450/155 AG 20 L-Ag 40:Sn AG 105 0.075-0.2 10 Silver-flo 38 38 31 29 2Sn 660-720 430/175 0.075-0.2 Silver-flo 34 34 36.75 27 2.25Sn 630-730 420/195 L-Ag 34:Sn* AG 106*** 0.075-0.2 Silver-flo 33 33 33.5 33.5 700-740 535/225 0.075-0.2 Silver-flo 302 30 36 32 2Sn 665-755 460/135 AG 21 AG 107 0.075-0.2 Silver-flo 30 30 38 32 695-770 505/145 AG 204 0.075-0.2

Medium and High Temperature Alloys Silver-flo 25 25 41 34 700-800 420/175 L-Ag 25 AG205*** 0.075-0.2 Silver-flo 24 24 43 33 740-800 470/155 AG205*** 0.075-0.2 Silver-flo 20 20 40 39.9 0.1Si 776-815 330/145 L-Ag 20 AG 206 0.075-0.2 10 Silver-flo 18 18 45.75 36 0.255i 784-816 470/145 0.075-0.2 10 Silver-flo 16 16 50 34 790-830 505/165 0.075-0.2 10 Silver-flo 12 12 48 40 800-830 410/155 L-Ag 12 AG 207 0.075-0.2 Silver-flo 5 5 55 39.9 0.1Si 870-890 390/135 L-Ag 5* AG 208 0.075-0.2 Silver-flo 4 4 56 39.7 0.3Si 870-890 370/115 0.075-0.2 Silver-flo 2 2 57.9 40 0.1Si 880-890 340/145 0.075-0.2 10 Silver-flo 1 1 60 39 0.1Si 890-900 350/155 0.075-0.2 10

* Does not conform exactly to the requirements of DIN 8513 *** Does not conform exactly to the requirements of EN 1044 1999 ** Tensile and shear strength figures, figures relate to brazed mild steel specimens in accordance with DIN 8525

How to Select the Correct Alloy Is a Flux Required? Select from the products listed on the chart above and read about For brazing in air it is necessary to use a flux either as a paste, a the alloy characteristics on the following pages. Consult Johnson powder or from a flux coated rod. Note the melting range of the Matthey about the suitability and availability of the product selected. brazing alloy and match it with the active range of fluxes shown on In many cases selection is straightforward, however for new brazing page 27. A flux should be active before the alloy begins to melt and jobs it is wise to review all these criteria and undertake testing remain active at least 50˚C above the liquidus of the alloy. For more before starting production. information on fluxes see pages 26 to 33.

11 Silver-Flo Cadmium Free Alloys The Products Uses and Properties

Products, Uses and Properties

Silver-flo 55 56 56S The alloys in this group combine the lowest brazing temperatures with short melting ranges. They are very free flowing and produce neat joints with small fillets. They have excellent mechanical properties and are all 452 453S 45 suitable for sea water applications, being resistant to dezincification. (* See page 6) These alloys are often used as substitutes for cadmium containing alloys such as Easy-flo, Easy-flo No.2, DIN Argo-flo and Argo-flo. Their narrow melting ranges make them ideal for applications where liquation may be a problem. (See page 6)

Silver-flo 55 is the most widely used alloy being available in all common forms. Silver-flo 56 has a marginally lower melting point and meets the requirements of AWS A5.8 for type BAg-7. Silver-flo 56S and Silver-flo 453S contain tin and a controlled addition of silicon. This makes the alloys free flowing giving smooth fillets and good aesthetic joint appearance. Silver-flo 452 is a free flowing alloy containing tin recommended where the presence of silicon is not desirable. Silver-flo 45 is a tin free version of Silver-flo 453S and Silver-flo 452 with a narrow melting range.

Silver-flo 40 38 Silver-flo 40 and 38 offer a combination of good flow with an ability to fill joint gaps that cannot be tightly controlled. Their characteristics make them suitable for both hand feeding and preplacement in automated brazing. Silver-flo 40 is the more widely used of the two alloys.

Silver-flo 302 The long melting range of Silver-flo 302 makes it ideal for applications where fillets are required or close tolerance joint gaps cannot be maintained. It is extensively used for brazing pipework in the refrigeration and air conditioning industries, often in the form of a flux coated rod for site or maintenance work.

Silver-flo 44 34 Though largely superseded by other Silver-flo alloys, these materials still have some limited applications. The short melting range of Silver-flo 33 also makes it a good alloy for step brazing (refer page 13 - part 4). 33 30

Silver-flo 25 24 20 When brazing copper and mild steel components these alloys are an ideal compromise between the more expensive high silver - low melting point alloys and the basic high temperature brass alloys (Brass or Bronze 18 16 Welding process). These alloys are capable of filling larger joint gaps than the free flowing high silver alloys. Also they can be used for step brazing or colour matching purposes. (refer page 13 - parts 4 and 5) Silver-flo 25 is a general purpose alloy with good fillet forming properties. Silver-flo 24 is used in aerospace component manufacture and by model engineers. Silver-flo 20 and 18 both contain a small addition of silicon which has been found to improve wetting and the surface finish of the brazing alloy fillet. Silver-flo 16 is a useful alloy where step brazing is a consideration.

Silver-flo 12 5 4 These alloys are included here largely for reference purposes as there is limited demand for them. They can be used as alternatives to brass alloys in automated brazing operations. They are used for brazing tungsten 21 carbide tips to tools and saw blades, where the small silver addition enhances their flow characteristics. They have limited availability.

12 The Silver-flo range - The Products and Technical Considerations

Technical Considerations of the Silver-flo Products

1 Silver-flo Alloys These alloys may be prone to cracking if quenched from high temperatures (in excess of 300˚C). They should Containing Tin not be quenched when used to braze components with widely differing coefficients of thermal expansion.

2 Silver-flo Alloys These alloys may be used to braze steel assemblies but are not recommended where steel components are Containing Silicon subject to high impact or fatigue stress in service as the silicon forms a brittle iron intermetallic.

3 Alloys Resistant to When brazing assemblies which come into contact with sea water and other aqueous solutions with a high Dezincification ion concentration, it is important that both the parent metal and the brazing alloy are resistant to dezincification (See page 6). Silver-flo alloys 60, 56, 55, 452, 453S, 44 and 43 all offer excellent resistance to dezincification and are widely used in brazing on offshore installations and in shipbuilding. Silver-flo 55 is the most widely used alloy, it has a low brazing temperature and excellent flow characteristics.

4 Sequential Brazing To build up an assembly in two or more brazing operations, it may be necessary to use brazing alloys with (Step Brazing) successively lower melting points. This technique will avoid disturbing the previously brazed joints. There are a number of alloys which have short melting ranges and are ideal for this work. E.g.

1st Brazing Operation 2nd Brazing Operation 3rd Brazing Operation Silver-flo 18 (784 - 816ºC) Silver-flo 33 (700 - 740ºC) Silver-flo 55 (630 - 660ºC)

Silver-flo alloys 24, 20 and 16 are also suited to step brazing.

5 Colour Matching For some applications a colour match between the brazing alloy and the parent metals is clearly desirable. The following Silver-flo alloys should be considered. Silver-flo 60, 56 and 55 alloys are silvery in colour and are suitable for use on nickel silver or stainless steel provided that there is no danger of interfacial corrosion (See page 6). Silver-flo 20, 18 and 16, alloys are more yellow or brass coloured. They are a reasonably good match for brass, but the melting point of the brazing alloy can be relatively close to that of the parent metal.

6 Brazing of Nickel Nickel and nickel based alloys are susceptible to cracking during brazing with silver brazing alloys. This Based Alloys cracking is often known as inter-granular penetration or stress cracking (See page 6). High nickel content copper alloys, such as 70:30 cupro-nickel, are also prone to this type of failure. Removing the source of stress will eliminate the problem. Silver-flo 60 is recommended where freedom from stress cannot be guaranteed. The relatively low zinc content and high brazing temperature make it less likely to initiate stress cracking.

13 Easy-Flo Range Cadmium Containing Range

Some Features of the Easy-flo Range of Alloys

Johnson Matthey’s ‘Easy-flo’ range forms • Low brazing temperature and melting range alloys.

a group of 7 alloys which have been • Excellent flow characteristics and mechanical properties. developed and established over 60 years. • Lower silver content than equivalent cadmium free alloys means cheaper alloys. Cadmium containing brazing alloys

generally represent the best combination • Alloys which fill tight joint gaps through to alloys which will fill wider gaps and build of melting range, flow characteristics and good fillets. mechanical properties. The higher the • Ideal for torch brazing or any other rapid heating method. silver content the more free flowing the alloys tend to be. Where suitable safety What Materials can be Joined with Easy-flo Products? precautions are in operation they would The following materials can be joined with the Easy-flo range of alloys and a suitable flux. normally be regarded as the most economical of brazing alloys. Copper and copper alloys including brasses, bronzes, nickel silvers, aluminium bronze and copper nickel. Nickel and nickel alloys. Refer page 13 - part 6 - the same special considerations apply for both Easy-flo and Silver-flo alloys. Steel - a wide range including mild, carbon and low alloy steel. Stainless Steels. Refer pages 20 - 21 if the resulting joint is to be exposed to a wet environment. Tungsten Carbide and PCD segments. Refer pages 16 - 19 for special alloys for this material.

Please Note:- These products cannot be used to braze aluminium, magnesium and their alloys. The low melting point products are recommended for copper alloys with more than 2% lead content. Aluminium bronze and brasses with more than 2% aluminium require Easy-flo Aluminium Bronze flux. High zinc brasses generally require the use of an alloy with more than 16% silver.

14 The Easy-flo Range - Features and Properties

The Physical Properties of the Easy-flo Alloy Range

Alloy Composition Melting *Tensile/ BS1845: DIN 8513 EN 1044 Optimum Alloy forms commonly Ag Cu Zn Cd Range ˚C Shear 1984 1986 1999 Joint Gap available from stock Strength mm N/mm2

Easy-flo 50 15 16 19 620-630 420/155 AG1 L-Ag50Cd AG 301 0.05-0.15 10

Easy-flo 2 42 17 16 25 608-617 390/155 AG2 AG 303 0.05-0.20 10

DIN Argo-flo 40 19 21 20 595-630 505/155 L-Ag40Cd AG 304 0.05-0.20 10 Argo-flo 38 20 22 20 608-655 505/155 AG3 0.05-0.20 Mattibraze 34 34 25 20 21 612-668 505/165 AG11 L-Ag34Cd AG 305** 0.075-0.20 Argo-swift 30 28 21 21 607-685 535/155 AG12 AG 306 0.075-0.20 Argo-bond 23 35 27 15 616-735 505/175 0.075-0.20

Other cadmium containing alloys can be supplied on request. * Figures relate to brazed mild steel specimens in accordance with DIN 8525. ** Does not conform exactly to the requirements of EN 1044 1999

How to Select the Correct Alloy Is a Flux Required? Select from the products listed on the chart above and read about For brazing in air it is necessary to use a flux either as a paste, a the alloy characteristics on the following pages. Consult Johnson powder or from a flux coated rod. Note the melting range of the Matthey about the suitability and availability of the product selected. brazing alloy and match it with the active range of fluxes shown on In many cases selection is straightforward, however for new brazing page 27. A flux should be active before the alloy begins to melt and jobs it is wise to review all these criteria and undertake testing remain active least at 50˚C above the liquidus of the alloy. For more before starting production. information on fluxes see pages 26 - 33.

The Easy-flo Range - The Products, Uses and Properties

Easy-flo These two silver brazing alloys combine the lowest liquidus temperature (*See page 6) and shortest melting ranges of any silver brazing alloys. As such they are regarded by many users as the best brazing alloys Easy-flo 2 available. Both alloys are particularly recommended where a minimum brazing temperature is desirable to preserve the properties of the parent metals. They are ideal where joints have a close and regular gap and will produce neat joints with optimum ductility and strength. Easy-flo No. 2 provides a lower cost option to Easy-flo whist retaining its favourable brazing characteristics.

Argo-flo DIN Argo-flo These general purpose alloys exhibit good all round brazing characteristics of short melting range, good flow, joint penetration and fillet forming capability. Mattibraze 34

Argo-swift Argo-bond Argo-swift and Argo-bond have wider melting ranges and increasing liquidus temperatures (See page 6). They are not normally recommended for applications with slow heating rates. They are good fillet forming alloys with an ability to bridge wide gaps.

Technical Considerations

Safety Precautions Today the potential danger from cadmium fume is widely recognised. The localised extraction of fumes with Cadmium during brazing is now virtually obligatory. The use of cadmium containing alloys is not permitted in the Containing Alloys manufacture of food and drink handling equipment and medical instruments. If cadmium containing alloys are felt likely to cause a health hazard then use a cadmium free alloy from the Johnson Matthey Silver-flo range. Full details on exposure levels (OES) are given in the specific Material Safety Data Sheets. These should always be consulted before use of a cadmium bearing brazing alloy.

15 Silver Brazing Alloys for Tungsten Carbide

Some Features of the Range

The unique properties of tungsten • Both cadmium free and cadmium containing alloys in the range.

carbide materials mean that they are • Nickel and manganese containing alloys for improved wetting on carbides which are widely used for tools and wear-parts. difficult to braze. Tungsten carbide has low ductility • Low temperature free flowing alloys for small carbides - Silver-flo 55, Easy-flo 2. and is relatively brittle hence it must be firmly supported by a backing • Nickel and manganese containing alloys for thicker joints on medium sized carbides. material, usually steel. • Tri-foil products for brazing large carbides. These contain a central copper shim and This range of Johnson Matthey Silver reduce the risk of cracking. Brazing alloys has been formulated to provide a solution to joining tungsten carbide.

16 Silver Brazing Alloys for Tungsten Carbide - Features and Properties

Physical Properties of the Alloys

Alloy Nominal Composition Melting Standards Optimum Alloy forms commonly Ag Cu Zn Cd Other Range ˚C BS1845 - 1984 Joint Gap mm available from stock /EN 1044 1999 Low Melting Point Free Flowing Alloys

Easy-flo 50 15 16 19 620 - 630 AG1/AG 301 0.05 - 0.15 10

Easy-flo No. 2 42 17 16 25 608 - 617 AG2/AG 303 0.05 - 0.15 10

Silver-flo 55 55 21 22 - 2 Sn 630 - 660 AG14/AG 103 0.05 - 0.15 10

Alloys for improved Wetting onto Carbide Easy-flo No. 3 50 15.5 15.5 16 3 Ni 634 - 656 AG9/AG 351 0.1 - 0.25 Argo-braze 49H 49 16 23 - 7.5 Mn/4.5 Ni 680 - 705 AG18/AG 502 0.1 - 0.25

Tri-foils for Brazing Larger Carbide Segments Easy-flo Tri-foil C* 50 15 16 19 620 - 630 Argo-braze 49LM Tri-foil* 49 27.5 20.5 - 2.5 Mn/0.5 Ni 670 - 710

Other Alloys Argo-braze 50 50 13.5 15.5 16 2Mn/3Ni 639 - 668 0.1 - 0.25 Argo-braze 40 40 30 28 2 Ni 670 - 780 - AWS BAg-4 - 0.1 - 0.25

Argo-braze 502 50 20 28 2 Ni 660 - 750 - AWS BAg-24 - 0.1 - 0.25 10 * Tri-foils have a copper core Base Metal Brazing Alloys for Tungsten Carbide

Metal Joining offer a number of base metal brazing alloys. These have proved suitable or were designed for high temperature brazing of tungsten carbide. Please consult a JM technical sales representative for more information. Product availability for Bronzes is limited as products are manufactured to special order.

Alloy Nominal Composition Melting Standards Comments and Joint Gap Cu Zn Mn Ni Other Range ˚C BS1845 1984 B-Bronze 97 - - 3 0.03 B 1081-1101 CU7/CU105 B & C Bronze are used for furnace brazing, C-Bronze 86.5 - 11 2.5 965-995 with no flux. Will fill gaps up to 0.5mm. F-Bronze 57.5 38.5 2 - 2 Co 890-930 F & D Bronze are for rock drills. D-Bronze 86 10 - - 4 Co 980-1030 For brazing in air use Tenacity 125 flux.

How to Select the Correct Brazing Alloy Is a Flux Required? The choice of brazing alloy will depend on a number of important On carbides which are easy to wet general purpose brazing fluxes factors. These are: - the size and composition of the carbide; the joint such as Easy-flo flux powder or paste and Mattiflux 100 flux paste configuration; the heating method; operator skill and the service are recommended. Where the carbides are more difficult to wet conditions of the completed component. Consult pages 18 and 19 of fluxes containing Boron such as Tenacity 6 Flux Powder and Mattiflux this booklet or contact a Johnson Matthey technical representative if 3A Flux Paste will be more suitable. more information is required.

17 Silver Brazing Alloys for Tungsten Carbide

Products, Uses and Properties

Low Melting Point Free Flowing Alloys

Easy-flo Easy-flo 2 Easy-flo/Easy-flo No. 2/Silver-flo 55 - The low melting temperature of these alloys allows strong thin joints to be produced whilst minimising stresses due to differential thermal expansion. Their use on tungsten carbide Silver-flo 55 is recommended for small tips with a maximum dimension of approximately 9mm.

Alloys for Improved Wetting onto Carbide

Easy-flo 3 Easy-flo No. 3 is a cadmium bearing alloy containing nickel. The nickel improves wetting on carbides and produces a less free flowing alloy. This gives a thicker brazed joint better able to accommodate higher stresses. The maximum size of carbide for use with Easy-flo 3 is approximately 19mm.

Argo-braze 49H Argo-braze 49H is a cadmium free alloy containing nickel and manganese. The manganese content improves the wetting on carbides containing titanium and tantalum which are difficult to wet under normal brazing conditions. Argo-braze 49H is widely used as a cadmium free substitute for Easy-flo No. 3 and has the same recommended maximum carbide size of approximately 19mm.

Tri-foils for Brazing Larger Carbide Segments

Easy-flo Tri-foil C In applications using larger tungsten carbide pieces it is necessary to artificially thicken the joint by introducing a shim or thin layer of base metal coated on each side with brazing alloy. This enables the Argo-braze 49LM carbide to be brazed to the base metal shim and the base metal shim to be brazed to the steel backing material. The thicker joint will allow for relief of stress of the component and thus reduce the incidence of cracking. Two tri-foil products are available:-

Easy-flo Tri-foil C is cadmium containing with a central shim of copper with Easy-flo brazing alloy on each face. Argo-braze 49LM Tri-foil is cadmium free and contains nickel and manganese to improve wetting on carbides.

Other Miscellaneous Products

Argo-braze 40 Argo-braze 40 is a cadmium free alloy containing 40% silver and 2% nickel. Provided that the higher liquidus of 780˚C can be tolerated it can be used for the brazing of carbide.

Argo-braze 502 Argo-braze 502 is a cadmium free alloy. In brazepaste form it is widely used in the induction brazing of carbide tips to circular saw blades.

Argo-braze 50 Argo-braze 50 is a cadmium containing alloy with nickel and manganese originally developed for brazing of tungsten carbide tool tips. The alloy now has limited availability.

18 Silver Brazing Alloys - The Products and Technical Considerations

Technical Considerations for Tungsten Carbide Brazing

Cracking in Tungsten carbides have low coefficients of thermal expansion compared with that of steel. This means that Tungsten Carbide they expand and contract less than steel does during heating and cooling. As a result stresses can be built up in the carbide. The magnitude of the stresses set up by the differences in expansion will be a function of the size of the piece of carbide being brazed. This can give rise to cracking of the carbide during or following brazing operations.

1. Joint Design to Help Increasing the joint clearance will provide a thicker layer of ductile brazing alloy capable of Avoid Cracking accommodating the stresses from differential expansion. On large carbides the use of thin backing materials can lead to cracking because they are not able to withstand the high stress resulting from contraction on cooling. Thicker backing materials or bodies to hold the carbide can reduce the incidence of failure. With long lengths of carbides bending or cracking can be a problem. Consideration should be given to the use of multiple pieces of carbide to overcome this.

2. Alloy Selection to Help Conventional free-flowing brazing alloys such as Easy-flo 2 or Silver-flo 55 capable of filling joint gaps of Avoid Cracking 0.05mm are satisfactory for brazing carbide with a length of up to 9mm. Carbide pieces of larger size can be stressed to such an extent that cracking occurs during brazing or in a subsequent grinding operation. For these applications the joint must be artificially thickened. Using either a less free-flowing brazing alloy (Easy-flo 3 or Argo-braze 49H) or a Tri-foil brazing alloy can do this.

3. Cooling and Finishing Slow uniform cooling of the carbide is always recommended to avoid stressing and possible cracking. the Carbide Assembly Quenching in water is not recommended. It is advisable to avoid thermal stresses during grinding and finishing of the carbide component.

Wetting of Brazing Alloys The carbide will be more easily wetted by the molten brazing alloy if the surface is ground shortly before brazing on Tungsten Carbide then degreased and kept clean before applying flux. The degree of wetting of brazing alloy onto a tungsten carbide piece will depend on its composition. Tungsten carbides with small additions of titanium or tantalum carbide are more difficult to wet than standard carbides. Wetting can be improved by the use brazing alloys containing of nickel or manganese (E.g. Argo-braze 49H or Easy-flo 3) and special boron modified fluxes such as Tenacity 6. Plating or coating the carbide with an easy to wet metal such as copper or nickel can also help overcome this problem.

Brazing Technique A heating pattern should be employed which brings both components to brazing temperature at the same time. Care should be taken to avoid overheating the carbide component as this will increase stresses. Once the brazing alloy is molten it is advisable to move the carbide slightly to improve wetting and displace trapped gas or flux.

Brazing of Polycrystalline Many of the principles outlined for the brazing of tungsten carbide segments apply to brazing of PCD segments. Diamond (PCD) Segments Brazing alloy and flux selection follows the same basic rules. Brazing alloys with melting points below 750˚C should be used to avoid degrading the PCD layer.

19 Argo-braze 56 Brazing Stainless Steel in Wet Conditions

Features of Argo-braze 56

Care must be exercised when selecting • Argo-braze 56 is known to be resistant to interfacial corrosion under most conditions irrespective of the grade of stainless steel used. alloys for brazing stainless steel where the completed joints will be exposed to • Argo-braze 56 does not contain zinc and is hence resistant to dezincification. water or humidity in service. In these conditions joint failure can result from corrosion usually referred to as "crevice" or "interfacial" corrosion because failure occurs at the brazing alloy/stainless steel interface.

20 Argo-braze 56 - Features and Properties

Physical characteristics of Argo-braze 56

Alloy Nominal Composition Melting Standards Optimum Alloy forms commonly Ag Cu In Ni Range ˚C EN 1044 Joint Gap mm available from stock

10 Argo-braze 56 56 27 14.5 2.5 600 - 711 AG403* 0.1-0.2mm

* Does not conform exactly to the requirements of EN 1044 The Product and its Properties

Argo-braze 56 The alloy has a long melting range (600 - 711˚C) and flows relatively slowly even when fully molten. This makes it ideal for building up good fillets around joints. Before application of the alloy the joint area should be at brazing temperature to avoid problems with liquation in which the low melting constituent of the alloy flows first before the alloy is fully molten. A rapid heating method such as induction or an oxy-acetylene torch is useful in avoiding the problem.

Which Flux is Required? On small components ‘Easy-flo Stainless Steel grade flux’ or ‘Mattiflux 100’ are recommended. Where prolonged heating is required Tenacity 5 should be used. Important note: - boron containing fluxes such as Tenacity 5A, Tenacity 6 and Mattiflux 3A should be avoided as boron is known to increase the risk of interfacial corrosion.

Technical Considerations - Interfacial or Crevice Corrosion

What is Interfacial or Interfacial crevice corrosion is a particular type of failure where silver brazed joints in stainless steel are Crevice Corrosion? exposed to water or humidity in service. In these conditions joint failure may result along the stainless steel - brazing alloy interface.

What Conditions To produce a joint failure by interfacial corrosion three criteria need to be satisfied. Produce Failure? 1). At least one member of the joint must be made from a stainless steel. 2). The brazing alloy must be susceptible to this form of attack. 3). The completed joint must be exposed to damp or wet environments in service.

What Materials All types of stainless steel are susceptible to attack by interfacial corrosion. are Affected? The nickel free, or low nickel ferritic and martensitic type stainless steels (e.g. Types 403, 410, 416, 420, 430, 431) are most susceptible to interfacial crevice corrosion. Austenitic grades of stainless steel (e.g. Types 302, 303, 304, 316, 321) are more resistant. Failures with these grades are rare provided the correct brazing alloys are chosen.

How Resistant are In general terms when brazing stainless steels in air, with a flux, the Easy-flo range of cadmium containing Normal Silver alloys are the least resistant to interfacial corrosion. Brazing Alloys? The cadmium free Silver-flo range and silver brazing alloys containing nickel offer greater resistance particularly on austenitic steels.

Other Alloys Resistant to Orobraze products gold based brazing alloys. Crevice Corrosion Pallabraze products palladium based brazing alloys. Include: - B Bronze and C Bronze copper based brazing alloys. JM P40 soft solder silver/tin alloys.

Please consult Johnson Matthey for more details about these products or on any other matter relating to this problem. 21 Sil-fos & Copper-flo Alloys Joining Copper & Copper Alloys

Silver Copper Phosphorus and Copper Phosphorus Brazing Alloys

Johnson Matthey produce a wide range of Some Features of the Range silver-copper-phosphorus and copper- phosphorus brazing alloys. Their • Self fluxing (no need for separate flux) brazing alloys for copper to copper work. outstanding feature is their ability to braze • Will join copper to brass with the use of a suitable flux. copper in air without the use of a flux. When a flux is used the alloys are suitable • Low cost/low silver alloys for joining copper pipework.

for brazing other copper-base alloys • Silver containing alloys (low phosphorus) with improved ductility and electrical except those containing iron and nickel. conductivity.

The most popular alloys available, with • These alloys are not suitable for joining alloys containing nickel or iron. their composition and melting ranges are given in the table on page 23. What Materials can be Joined with this Range?

Copper. Brass and bronze using a flux

22 Sil-fos & Copper-flo Alloys - Features and Properties

The Physical Properties of the Alloys

Nominal Composition (%) Melting Standards EN 1044 Optimum Alloy forms commonly Alloy Ag Cu P Other Range ºC BS1845 (1984) 1999 Joint Gap (mm) available from stock

Sil-fos 14.5 80.85 4.65 644-800* CP1 CP102** 0.05 - 0.2 10

Sil-fos 6 6 86.75 7.25 644-718* AWS BCuP-4 - 0.05 - 0.2 10

Sil-fos 5 5 89 6 644-815* CP4 CP104 0.05 - 0.2 10 Silbralloy 2 91.5 6.5 644-825* CP2 CP105** 0.05 - 0.2 Copper-flo - 92.6 7.4 714-810* CP3 CP202** 0.75 - 0.2 Copper-flo 2 - 92 6 2Antimony 690-825* CP5 CP301 0.75 - 0.2 Copper-flo 3 - 93.8 6.2 714-890* CP6 CP203 0.75 - 0.2 Sil-fos Plus 17.75 75 7.25 644 - CP101 0.05 - 0.2

Stan-fos - 86.25 6.75 7Tin 640-680 - CP302** 0.75 - 0.2 10

* The upper melting point is the true liquidus of the alloy. Brazing is usually carried out at temperatures significantly below those shown. ** Does not conform exactly to the requirements of EN 1044 1999

How to Select the Correct Alloy Is a Flux Required? Select the alloy from the above table and description on page 24 No flux is required when joining copper to copper (for all alloys which best meets the technical criteria of the job. Joint gap, ductility, except Stan-fos). For copper alloys such as brass a flux is required. melting range, flow and conductivity may be important. Balance this Choice of flux will depend on the size of the component, heating with cost and availability implications. Consult JM technical method and brazing alloy type. representative for more information if necessary.

23 Sil-fos & Copper-flo Alloys Joining Copper & Copper Alloys

Products

Sil-fos Sil-fos is an alloy that gives ductile joints when joining copper to copper. It is the only alloy in this group that is available in foil form. Hence, it is often used as a preform in brazing particularly with resistance heating. Under reducing conditions (e.g. in atmospheres of cracked ammonia) Sil-fos brazes brass and other copper alloys without flux. Sil-fos finds its greatest use in electrical assemblies such as motors and busbars.

Sil-fos Plus This alloy is the eutectic composition with a melting point of 644˙C. The high phosphorus content ensures free flow and good capillary penetration but also gives restricted ductility.

Sil-fos 5 Sil-fos 5 provides the best combination of flow and ductility of the group and is a more free flowing alloy though less ductile than Sil-fos. It is mainly used on refrigeration, air conditioning and copper pipe work applications.

Sil-fos 6 Sil-fos 6 has the lowest melting point and most free flowing properties of any of the silver-copper- phosphorus alloys, apart from Sil-fos Plus. It the least ductile of the alloys in the group and is used in refrigeration and air conditioning applications.

Silbralloy Silbralloy contains 2% silver and combines good alloy flow with greater ductility than the Copper-flo range. It is is widely used in the brazing of copper hot water cylinders, refrigeration and air conditioning applications.

Copper-flo The standard copper-phosphorus alloy is free flowing and economical to use. Copper-flo is used in refrigeration, air conditioning and heat exchanger applications, often as preplaced rings.

Copper-flo 2 An alloy of copper, antimony and phosphorus that will self flux when brazing copper components such as hot water cylinders.

Copper-flo 3 An alloy less free flowing and slightly more ductile than Copper-flo with similar applications.

Stan-fos Unlike most phosphorus containing alloys Stan-fos must be used with a flux. It is free flowing and produces a smooth fillet.

24 Sil-fos & Copper-flo Alloys - The Products and Technical Considerations

Technical Considerations and Special Applications

Joint Gaps The best results are obtained where the joint gap is controlled within the range 0.05-0.15mm. Joint gaps less than 0.05mm will not allow full capillary flow and whilst gaps up to 0.2mm can be filled, gaps larger than this may create problems.

Heating Methods These brazing alloys have relatively long melting ranges and the parent metals brazed almost invariably have high values of thermal conductivity. For these reasons the work should be heated quickly to brazing temperature, and oxy-acetylene is preferable to either natural gas/compressed air or propane.

Flux Selection When joining copper base alloys e.g. brasses or bronzes the use of a flux is necessary. Easy-flo Flux Powder or Easy-flo Flux Paste are both widely used with good results. Tenacity No 4A may be used where long heating cycles are required.

Joint Appearance The alloys produce rough-textured braze fillets of greyish colour, and when permitted to run over the work will roughen the surface. In cases where good appearance is desired eg. electroplating operations, consideration should be given to the use of silver brazing alloys of the Easy-flo or Silver-flo type.

Brazing of Nickel, Nickel, nickel-base alloys, ferrous metals and copper alloys containing nickel and iron should not be brazed Nickel Based or Containing with these phosphorus-bearing alloys. Although the brazing alloys will wet and flow on such materials, the and Ferrous Metals brazed joints obtained are inherently brittle due to the formation of intermetallic compounds. (Iron and Steel)

Brazing of Tough When tough-pitch copper is being brazed it is subject to deterioration if heated to a high temperature in Pitch Copper reducing conditions. Tough-pitch copper contains dissolved cuprous oxide, which may be reduced by a reducing flame or atmosphere to leave small cavities in the metal. This effect is known as hydrogen embrittlement. When brazing these materials a neutral or slightly oxidising flame is therefore recommended.

Sulphurised Atmospheres Phosphorus containing brazing alloys should not be used in cases where they will be exposed to heavily and Elevated Temperature sulphurised gases at elevated temperatures. In air the maximum continuous service temperature is about Service 200˚C. At higher temperatures selective oxidation of the phosphorus in the alloy occurs, with consequent joint deterioration.

Water Service Conditions The alloys are widely used in plumbing applications and since they do not contain zinc, they cannot suffer from dezincification.

25 Brazing Fluxes

Some Features and Benefits of JM Fluxes

Flux plays a vital role in virtually all air • World leading Easy-flo flux powder which is excellent for hot rodding and as a general purpose flux. brazing processes. Use of the wrong flux or a poor application technique can have • Premixed flux pastes which are ready made for brushing straight onto the joint. This provides consistent viscosity and saves time in premixing flux powder. a dramatic effect on joint quality. Johnson

Matthey produce a range of fluxes • Special flux products to solve specific brazing problems eg. Fast heating cycles, red suitable for most brazing operations. The staining on brass and brazing of aluminium bronze. information in this data sheet is intended • Boron modified fluxes for improved wetting on tungsten carbide. to help the user select the most suitable Johnson Matthey flux for a particular • Medium temperature fluxes for extended heating cycles and larger components. application. • High temperature fluxes for low silver alloys and more demanding heating applications.

• All fluxes show improved coverage due to the incorporation of highly effective wetting agents.

26 Johnson Matthey Brazing Fluxes - Features and Properties

Johnson Matthey Brazing Fluxes

Flux Form Working EN 1045 Standard Flux Residue Removal RangeºC* Packaging (kg) Excellent General Purpose Fluxes Easy-flo Powder 550-800 FH10 0.25 0.5 5.0 50 Residues are generally soluble in hot water. Immersion for up to Easy-flo Paste 575-825 FH10 0.5 1.0 7.0 25 30 minutes followed by brushing in a stream of warm water is Mattiflux 100 Paste 550-800 FH10 0.5 1.0 7.0 25 recommended.

Fluxes for Special Applications Easy-flo Dipping Grade Paste 550-750 FH10 1.0 7.0 25 Residues are generally soluble in hot water. Immersion for up to Silver-flo Paste 550-775 FH10 1.0 7.0 25 30 minutes followed by brushing in a stream of warm water is Easy-flo Aluminium recommended. Bronze Grade Paste 550-775 FH11 1.0 Easy-flo Stainless Steel Grade Powder 550-775 FH10 0.25 0.5 5.0 Tenacity No. 2 Powder 550-800 FH10 0.5 5.0

Tenacity No. 14 Powder 550-750 FH10 0.5 5.0 Residues are virtually insoluble in water. Immersion in a warm 10% sulphuric acid solution followed by brushing in a stream of warm water is recommended.

Boron Modified ‘Brown Fluxes’ Tenacity No. 6 Powder 550-800 FH12 0.25 0.5 4.0 Residues are generally soluble in hot water. Immersion for up to Mattiflux 3A Paste 600-875 FH12 0.5 2.0 30 minutes followed by brushing in a stream of warm water is recommended.

Tenacity No. 5A Powder 600-900 FH12 0.5 Residues are virtually insoluble in water. Immersion in a warm 10% sodium hydroxide solution followed by brushing in a stream of water is recommended.

Medium Temperature Fluxes Tenacity No. 4A Powder 600-850 FH10 0.25 0.5 5.0 Residues are virtually insoluble in water. Immersion in a warm 10% Tenacity No. 5 Powder 600-900 FH10 0.25 0.5 5.0 sodium hydroxide solution followed by brushing in a stream of water is recommended.

High Temperature Fluxes Tenacity No.125 Powder 750-1200 FH21 0.4 4.0 Residues are insoluble in water. Grit blasting or other mechanical Paste 0.7 means of removal are necessary. Tenacity No. 12 Powder 800-1300 FH21 0.5 5.0

* The lower figure is the temperature at which the flux is capable of removing metal oxide. The upper figure is the maximum temperature at which the flux will remain effective long enough to make a sound brazed joint

27 Brazing Fluxes

The Products, Uses and Properties

General Purpose Fluxes for Low Temperature Silver Brazing

Easy-flo Powder Easy-flo flux is highly active with a working range up to 800˚C and can be used on most metals capable of being brazed with silver brazing alloys melting up to 750˚C. Easy-flo flux powder can be used to braze stainless steel provided that the brazing temperature is below 700ºC. Above 700ºC Tenacity No. 5 is generally recommended. Easy-flo flux powder is ideal for hot rodding or application as a water based paste.

Easy-flo Paste Easy-flo flux paste is a general purpose flux with better life at temperature and greater overheat resistance, being active to 825ºC. It suitable for use with brazing alloys which have a liquidus of up to 775ºC.

Mattiflux 100 Paste Mattiflux 100 paste is a smooth paste combining low melt viscosity with good resistance to overheating. It may be used with brazing alloys having a liquidus up to 750ºC and is particularly recommended for the brazing of mild steel.

Special Fluxes for Low Temperature Silver Brazing

Easy-flo Paste Dipping Grade is a thin, smooth paste which becomes highly active early in the brazing cycle. It exhibits minimum bubbling during preheat and is ideal Dipping Grade for induction or for very short heating cycles. The paste is recommended for use with brazing alloys which have a liquidus below 700ºC. The consistency of Dipping Grade paste may be readily adjusted by the addition of water.

Silver-flo Paste Silver-flo flux paste is a general purpose flux and is recommended for use with all silver brazing alloys which have a liquidus below 725ºC. This flux has been superseded by Mattiflux 100 paste.

Easy-flo Paste This flux is used on aluminium bronze and other copper based alloys containing from 2 to 10º aluminium where other fluxes are unable to Aluminium Bronze Grade dissolve aluminium oxide. It is recommended for brazing alloys which have a liquidus below 750ºC.

Easy-flo Powder This powder has an increased fluoride content which offers improved fluxing on stainless steel when used with brazing alloys having a liquidus up to 725ºC. Stainless Steel Grade

Tenacity No. 2 Powder Tenacity No. 2 is active early in its working range and it also exhibits a minimum of bubbling during preheating. This makes it ideal for induction brazing and other rapid heating methods.

Tenacity No. 14 Powder Tenacity No. 14 is used on brass where red staining due to oxidation of zinc is a problem. It is active at 450˚C and spreads rapidly giving good cover early in the heating cycle. It is recommended for use with alloys having a liquidus below 700ºC.

28 Johnson Matthey Brazing Fluxes - The Products and Technical Considerations

Boron Modified ‘Brown Fluxes’

Tenacity No. 6 Powder This flux is a boron modified flux for use on stainless steel, tungsten carbide and the refractory metals. Being dark brown in colour it is not always easy to observe the flow of the brazing alloy. This flux and Mattiflux 3A are unsuitable for use on low or nickel-free stainless steels if interfacial corrosion is likely to be a hazard in service.

Mattiflux 3A Paste This is a boron modified flux paste similar in application to Tenacity 6 above. The flux can be thinned with water and is used with alloys having a liquidus up to 825˚C.

Tenacity 5A is a boron modified flux with similar properties to Tenacity 5. It is Tenacity No. 5A Powder effective on stainless steel, tungsten carbide and refractory metals. The residues are insoluble in water and must be removed using sodium hydroxide solution or mechanical methods. The flux is not recommended where interfacial corrosion (See page 20) is a possible service hazard.

Medium Temperature Fluxes

Tenacity No. 4A Powder This general purpose flux is intended for use with brazing alloys which have a liquidus between 700º and 850ºC. Its residues are largely insoluble and may require removal with sodium hydroxide solution or mechanical methods.

Tenacity No. 5 Powder Tenacity No. 5 is active at 600ºC above which temperature it spreads and cleans rapidly and is effective with alloys with a liquidus up to 850˚C. Tenacity No. 5 is particularly recommended when brazing stainless steel at temperatures above 700ºC and also for brazing large assemblies in steel or copper wherever prolonged heating is necessary. The residues are insoluble in water and must be removed using sodium hydroxide solution or mechanical methods.

High Temperature Fluxes

Tenacity No. 125 Powder Tenacity No. 125 is high temperature flux which is effective on copper and copper based alloys, mild and low alloy steels and tungsten carbide with and Paste alloys melting between 800-1100˚C.

Tenacity No. 12 Powder Tenacity No. 12 is effective on copper and copper based alloys, mild steel and tungsten carbide when used with brazing alloys melting between 850- 1200˚C.

29 Brazing Fluxes

How to Apply the Flux

Flux Form - Premixed It is recommended that flux should be applied as a paste to the parts to be joined.

Paste or Powder? Powders can be made into pastes by stirring in water until the mixture has the consistency of thick cream. A few drops of liquid detergent added to the mixture will often improve the wetting of flux onto clean parent metals.

The flux should be applied to both joint surfaces before assembly. Application of flux after assembly places great demands on the fluidity of the molten flux and its ability to penetrate capillary joints.

Brushing Brushing is an effective method of applying a thin film of paste to the joint itself and to surrounding component surfaces.

Dipping Brazing flux may be applied by dipping one or more components of an assembly into a container of flux. This is most effective with a paste of a thin consistency.

Automatic Application Automatic application of flux is possible and can be used for mass production. Consult a Johnson Matthey representative for more details.

Hot Rodding This is a technique in which a warm brazing rod is dipped into flux powder and the flux adhering to the rod is transferred to the joint area. This is an effective fluxing method but difficult to achieve good penetration of capillary joints. A refinement on this technique is the use of flux coated brazing rods.

Flux Coated Rods Brazing flux can be applied by using a Johnson Matthey flux coated rod. This special technique is outlined on page 31.

30 Johnson Matthey Brazing Fluxes - How to Apply the Flux and Use of Flux Coated Rods

How to Use a Flux Coated Rod Correctly

Why and When to Use Flux coated rods combine flux and brazing alloy in a single a Flux Coated Rod convenient form. Flux coated rods offer several advantages. They:- Reduce brazing times particularly in production brazing; Ensure the correct type and amount of flux is used every time; Reduce the amount of handling of flux chemicals by operators.

Flux coated rods are suitable for use on joints where limited joint penetration of the alloy into the gap is required. For full flow of alloy into a longer capillary gap fluxing the joint before brazing is recommended.

Brazing Technique As the joint is heated the flux coated rod should be with Flux Coated Rods touched or wiped onto the joint area. This will apply some flux and protect the component from oxidation as the joint approaches brazing temperature. At brazing temperature the rod should again be touched onto the joint and held in position if the alloy begins to flow. Turning the rod between the fingers will ensure that the flux melts off the rod and onto the component evenly.

Avoid heating the rod directly with the torch flame as this will melt the flux off the rod leaving no flux available for the next joint.

31 Brazing Fluxes

Technical Considerations

Why Use a Flux? A molten brazing alloy will only wet and flow over a parent metal if both are substantially free of surface oxide.

Simply removing surface oxide before brazing is not effective, since a new oxide layer is rapidly formed on heating.

Thus, to achieve an oxide free surface, it is necessary either to:-

a) remove oxide as it is formed by the use of a suitable brazing flux. b) prevent oxidation during brazing by heating in a protective atmosphere or vacuum. c) use a self-fluxing brazing alloy - only applicable when brazing copper to copper.

Brazing fluxes are only designed to remove oxide films. Where other contaminants such as oil, paint and lacquer are present these should be removed before brazing, using either mechanical or chemical methods.

Heating Flux to Brazing Temperatures

The flux becomes white and solidifies as the water is driven off

32 Johnson Matthey Brazing Fluxes - Technical Considerations and How a Flux Works

Factors Which Affect How a Flux Works

Factors Which Affect The ability of any flux to perform satisfactorily during a brazing operation will depend on the brazing How a Flux Works temperature and time, the parent metals, and the volume of flux applied.

Temperature To be effective the flux must be both molten and active before the brazing alloy melts, and it must remain active until the brazing alloy flows through the joint and solidifies on cooling. The working ranges of Johnson Matthey brazing fluxes are given in the table on page 27. It is good practice to select a flux which is active at least 50˚C below the solidus of the brazing alloy and which is still active at a temperature at least 50˚C above the liquidus of the brazing alloy. This will ensure that the flux is effective during the brazing operation.

Time The flux has to remove the oxides on the component and must continue to remove fresh oxide until the completion of the brazing cycle. There is a limit to the amount of oxide that the flux can dissolve. The longer the heating cycle the more likely it is that the flux will become exhausted and the residues and components exhibit a blackened appearance. There is no fixed time for which a flux will be effective since this is dependent on the operating temperature and the type of parent metal. With long heating cycles flux exhaustion may occur and the use of flux with a higher working range would be recommended. For short rapid heating cycles it may be possible to use a flux above its recommended maximum working temperature.

Parent Materials Johnson Matthey fluxes are suitable for use on copper, brass, mild steel and most other common engineering materials. Special purpose fluxes exist for aluminium bronze, stainless steel, tungsten, molybdenum and tungsten carbide. Silver brazing fluxes are not effective on aluminium, magnesium, titanium or their alloys.

Flux Volume The volume of flux required will vary depending on the nature of the application. Usually it is sufficient to coat the joint faces and the surrounding component surfaces with a layer of paste using a brush. Using an excess of flux is in no way detrimental to the quality of the brazed joint, and can assist flux removal. Application of flux to surfaces away from the joint helps to prevent oxidation of the components. The use of too little flux can lead to flux exhaustion resulting in unsound brazed joints. It is always best to use too much rather than too little flux!

The flux becomes clear and watery as it The flux protects the component from approaches brazing temperature oxidation as the brazing alloy flows

33 Product Availability

Product Forms, Availability, Packaging and Quality

The Different brazing alloy forms

Brazing Rods Common diameters are 1.5, 2, 2.5 and 3mm. Other diameters eg. 0.75mm to 5mm are also possible. The standard length for rods is 600mm (500mm long rods can be specially produced if required).

Flux Coated Rods Common diameters are 1.5, 2, 2.5 and 3mm. Other diameters larger or smaller are possible. Thickness of flux coating can be altered. The standard length for rods is 500mm. Flux coated rods are limited to alloys with 20% silver minimum.

Strips Common dimensions are 5x1mm, 3x1mm, 3x1.2mm (Sil-fos) and 1.5x1mm. Standard strip length is 600mm. Other size strips can be made to order and can usually be extruded to the dimensions required.

Wire Wire is available either in loose coils or on reels. Wire diameters range from 0.5 to 3mm. Other diameters larger or smaller are possible.

Foil Foil can be supplied on loose coils or on reels. Typical widths range from 2mm to 100mm. Thickness ranges from 0.08mm to 0.5mm. Other sizes can usually be made to order.

Rings All brazing rings are manufactured to order. They are made ‘butt ended’ or with ends offset. Rings can be made in a vast range of sizes and from a wide range of wires.

Washers and Preformed Shapes All pre-formed shapes are made to order. A wide range of shapes including washers, clips, blocks and many foil shapes are possible.

34 Johnson Matthey - Product Forms, Availability, Packaging and Quality

Brazepastes and Powders 10 JM supply a complete range of brazepastes. All alloys can be produced as paste or powder. Refer to JM booklet ‘Brazepaste and Solderpaste Products’ for more details.

Product Availability Johnson Matthey hold a very broad range of products in stock at our sales offices. If we don’t carry an item that you use regularly please let us know. We will do our best to meet your needs.

This booklet indicates normal stock items at JM with icons. An icon indicates that the product is normally available in stock at Johnson Matthey. No icon indicates the product is not normally held in stock but can be produced.

Please consult your local JM office for availability on any particular item.

Product Packaging JM brazing materials can be packed according to customer requirements. Brazing rods and strips are normally packed in 0.5kg to 10kg cardboard tubes. Rods can be packed for resale in smaller quantities. Flux container sizes are shown on page 27.

Quality Procedures All branches of Metal Joining have been accredited with ISO 9002 and numerous customer quality approvals. Certification to national and international standards is available and all our products are supported by full COSHH documentation.

Please contact your local JM office to discuss any matter relating to quality of our products or services.

35 Brazing Alloys and Solders

Alloy Composition Others Melting BS1845:1984 DIN 8513:1986 EN 1044 Range °C 1999 Silver Brazing Alloys - Cadmium free Ag Cu Zn Sn/Si Silver-flo 67E 67 23 10 - - 705 - 723 - - Silver-flo 60 60 26 14 - - 695 - 730 AG 13 L-Ag 60 AG202 Silver-flo 55 55 21 22 2 Sn - 630 - 660 AG 14 L-Ag 55:Sn* AG103 Silver-flo 56 56 22 17 5 Sn - 618 - 652 (AWS Bag7) - AG102 Silver-flo 56S 56 22 17 4.8 Sn, 0.2Si - 618 - 652 - - - Silver-flo 452 45 27.75 25 2.25 Sn - 640 - 680 - L-Ag 45:Sn* AG104* Silver-flo 453S 45 25 26.8 3 Sn, 0.2 Si - 640 - 680 - - - Silver-flo 45 45 25 30 - - 680 - 700 - - - Silver-flo 44 44 30 26 - - 675 - 735 - L-Ag 44 AG203 Silver-flo 43 43 37 20 - - 690 - 775 AG 5 - - Silver-flo 40 40 30 28 2 Sn - 650 - 710 AG 20 L-Ag 40:Sn AG105 Silver-flo 38 38 31 29 2 Sn - 660 - 720 - - - Silver-flo 34 34 36.75 27 2.25 Sn - 630 - 730 - L-Ag 34:Sn* AG106* Silver-flo 33 33 33.5 33.5 - - 700 - 740 - - - Silver-flo 302 30 36 32 2 Sn - 665 - 755 AG 21 - AG107 Silver-flo 30 30 38 32 - - 695 - 770 - - AG204 Silver-flo 25 25 41 34 - - 700 - 800 - L-Ag 25 AG205* Silver-flo 24 24 43 33 - - 740 - 800 - - AG205* Silver-flo 20 20 44 39.9 0.1 Si - 776 - 815 - L-Ag 20 AG206 Silver-flo 18 18 45.75 36 0.25 Si - 784 - 816 - - - Silver-flo 16 16 50 34 - - 790 - 830 - - - Silver-flo 12 12 48 40 - - 800 - 830 - L-Ag 12 AG207 Silver-flo 5 5 55 40 - - 830 - 870 - L-Ag 5* - Silver-flo 4 4 56 39.7 0.3 Si - 870 - 890 - - - Silver-flo 2 2 57.9 40 0.1 Si - 880 - 890 - - - Silver-flo 1 1 60 39 0.1 Si - 890 - 900 - - -

Silver Brazing Alloys - Cadmium Bearing Ag Cu Zn Cd - Easy-flo 50 15 16 19 - 620-630 AG1 L-Ag50Cd* AG301 Easy-flo 2 42 17 16 25 - 608-617 AG2 - AG303 DIN Argo-flo 40 19 21 20 - 595-630 - L-Ag40Cd AG304 Argo-flo 38 20 22 20 - 608-655 AG3 - - Mattibraze 34 34 25 20 21 - 612-668 AG11 L-Ag34Cd* AG305* Argo-swift 30 28 21 21 - 607-685 AG12 L-Ag30Cd AG306 Argo-bond 23 35 27 15 - 616-735 - - -

Special Silver Brazing Alloys Ag Cu Zn Cd Easy-flo No. 3 50 15.5 15.5 16 3Ni 634 - 656 AG9 L-Ag50CdNi AG351 Argo-braze 49H 49 16 23 - 7.5 Mn, 4.5 Ni 680 - 705 AG18 L-Ag49 AG502 Argo-braze 49LM 49 27.5 20.5 - 2.5 Mn, 0.5 Ni 670 - 710 - - - Argo-braze 50 50 13.5 15.5 16 2 Mn, 3 Ni 639 - 668 - - - Argo-braze 40 40 30 28 - 2 Ni 670 - 780 (AWS BAg-4) - - Argo-braze 502 50 20 28 - 2 Ni 660 - 750 (AWS BAg-24) - - Argo-braze 56 56 27 - - 2.5 Ni, 14.5 In 600 - 711 - L-Ag56InNi* AG403

Silver Copper Phosphorus Ag Cu P Sil-fos Plus 17.75 75 7.25 - 644 - - CP101* Sil-fos 14.5 80.85 4.65 - 644-800** CP1 L-Ag15P* CP102* Sil-fos 6 6 86.75 7.25 - 644-718** - (AWS BCuP-4) - Sil-fos 5 5 89 6 - 644-815** CP4 L-Ag5P CP104* Silbralloy 2 91.5 6.5 - 644-825** CP2 L-Ag2P* CP105*

Copper Phosphorus Alloys Ag Cu P Copper-flo - 92.5 7.5 - 714-810** CP3 L-CuP7* CP202* Copper-flo 2 - 92 6 2 Sb 690-825** CP5 - CP301 Copper-flo 3 - 93.8 6.2 - 714-890** CP6 L-CuP6 CP203 Stan-fos - 86.25 6.75 7 Sn 640-680 - - CP302*

* Not an exact equivalent. ** The working melting range for these alloys is lower than shown.

36 This chart is intended for reference purposes only. Not all alloys are available. Please consult Johnson Matthey for more details.

Base Metal/Copper Based Brazing Alloys Alloy Composition Others Melting BS1845:1984 AMS/AWS A5.8 EN 1044 Range °C 1999 Copper 99Cu - 1081 CU5 - CU103 96/4Copper-Tin 96Cu 4Sn - 945-1065 - - - B Bronze 97Cu 3Ni 0.02B - 1081-1101 CU7 - CU105 C Bronze 86.5Cu 11Mn 2.5 Ni - 965-995 - - - D Bronze 86Cu 10Mn 4Co - 980-1030 - - - F Bronze 58Cu 2Mn 2Co 38 Zn - 890-930 - - - Argentel No.1 60Cu 40Zn 0.2Si - 875-895 CZ6 - CU301 Argentel 48Cu 42Zn 10Ni - 920-980 CZ8 - CU302

Palladium and Gold High Purity Brazing Alloys Pd Ag Cu Ni Others Pallabraze 810 5 68.5 26.5 - - 807-810 PD1V - PD106 Pallabraze 840 10 67.5 22.5 - - 834-840 PD3V - PD104 Pallabraze 850 10 58.5 31.5 - - 824-850 PD2V - PD105 Pallabraze 880 15 65 20 - - 856-880 PD4V - PD103 Pallabraze 900 20 52 28 - - 876-900 PD5V - PD102 Pallabraze 950 25 54 21 - - 901-950 PD6V - PD101 Pallabraze 1010 5 95 - - - 970-1010 PD7V - PD204 Pallabraze 1090 18 - 82 - - 1080-1090 PD8V - PD203 Pallabraze 1225 30 70 - - - 1150-1225 - - - Pallabraze 1237 60 - - 40 - 1237-1237 PD14V - PD201

Au Cu Ni Others Orobraze 910 80 19 - 1 Fe 908-910 AU1V - AU101 Orobraze 940 62.5 37.5 - - 930-940 AU2V - AU102 Orobraze 950 82 - 18 - 950-950 AU5V 4787/BAu-4 AU105 Orobraze 970 50 50 - - 955-970 - - - Orobraze 990 75 - 25 - 950-990 AU6V - AU106 Orobraze 998 37.5 62.5 - - 980-998 AU3V BAu-1 AU103 Orobraze 1005 35 65 - - 970-1005 - - - Orobraze 1018 30 70 - - 996-1018 AU4V - AU104 Orobraze 1030 35 62 3 - 1000-1030 - BAu-3 - Orobraze 1040 70 - - 30 Ag 1030-1040 - - - Silver-Copper Eutectic 72 28 - 778-778 AG7V L-Ag72/BAg-8 AG401 IN 10 63 27 - 10 In 685-730 - - - IN 15 61 24 - 15 In 630-705 - - -

Nickel Based Brazing Alloys Name Ni Cr Fe B Others Specification HTN1 Bal 14 4.5 3.1 Si 4.5,Co.7 980-1060 HTN1 4775/BNi-1 NI101 HTN1A Bal 14 4.5 3.1 Si 4.5 980-1070 HTN1A 4776/BNi-1a NI101 HTN2 Bal 7 3.0 3.1 Si 4.5 970-1000 HTN2 4777/BNi-2 NI102 HTN3 Bal - 0.5 3.1 Si 4.5 980-1040 HTN3 4778/BNi-3 NI103 HTN4 Bal - 1.5 1.8 Si 3.5 980-1070 HTN4 4779/BNi-4 NI104 HTN5 Bal 19 - - Si 10.1 1080-1135 HTN5 4782/BNi-5 NI105 HTN6 Bal - - - P 11 875 HTN6 BNi-6 NI106 HTN7 Bal 14 - - P 10.1 890 HTN7 BNi-7 NI107

Soft Solder Alloys Name Sn Pb Ag Others BS.EN.29453 JM1090 10 90 - - 268-299 Alloy No 8 JM3070 30 70 - - 185-250 Alloy No 7 JM4060 40 60 - - 183-238 Alloy No 5 JM5050 50 50 - - 183-216 Alloy No 3 JM6040 60 40 - - 183-190 Alloy No 2 JM6236 62 36 2 - 177-189 Alloy No 30 JM6337 63 37 - - 183-183 Alloy No 1 P5 95 - 5 - 221-235 COMSOL 5 93.5 1.5 - 296 Alloy No 34 P40 96 - 4 - 221-221 Alloy No 28 97C 97 - - Cu 3 230-250 Alloy No 24 99C 99 - - Cu 1 230-235 Alloy No 23 LM10A 87 - 10 Cu3 214-217 - A25 - 97.5 2.5 - 304 Alloy No 32 A5 - 95 5 - 304-370 Alloy No 33 LM5 - - 5 Cd95 338-390 - LM15 - - 5 16Zn Cd79 280-320 - Plumbsol 97.5 - 2.5 - 221-225 - 37 Health and Safety in Brazing Brazing is firmly established throughout the Short exposures to high levels of cadmium world as a reliable, simple and safe method oxide fume can lead to pulmonary oedema of joining metal components. However and may be fatal. Prolonged or repeated as brazing operations entail the raising of over exposure to cadmium oxide fume is components to elevated temperatures and reported as causing renal damage. There the use of alloys and fluxes that contain is a symptomless latent period and any volatile constituents, a regard must be paid person thought to have been over exposed to safety precautions at the brazing work to cadmium oxide fume should be kept bench. under observation for 48 hours.

Many of the recommendations in this Cadmium Oxide fume is reported as document are common sense, others carcinogenic and may cause cancer by are not so obvious. It is important that inhalation. management, safety officers and individual brazing operators make themselves The likelihood of any problems occurring fully conversant with all of these safety under normal brazing conditions is precautions and so minimise the chance of very limited and are normally the result accidents occurring. of extremely poor brazing practice. These conditions would include severe overheating of the molten alloy using an General Precautions intense heat source such as oxy-acetylene, The most versatile brazing alloys are those brazing in an enclosed or ill ventilated area based on the silver-copper-cadmium-zinc where fume build up is possible; or brazing or silver-copper-zinc systems. They are all without flux cover. distinguished by their low melting points and good flow properties. They should If cadmium containing alloys are felt likely never be overheated. Overheating is bad to cause a health hazard then consideration brazing practice and is likely to result in should be given to the use of a cadmium poor joints and increased evolution of fume. free alloy from the Johnson Matthey Silver- Metal and metal oxide fumes are irritating flo range. These alloys may still contain and can be harmful to health. Cadmium cadmium as an impurity, but at a very low oxide fumes are particularly poisonous. controlled limit of 0.025% maximum. This level allows brazing to be carried out under Operator well-being and safety will result normal conditions of ventilation without the from following the precautions given in this need for local exhaust ventilation as far as document and basic rules of safe brazing cadmium oxide fume is concerned. There practice. could, of course, be other factors which would make local exhaust ventilation Potential health and safety problems in necessary. brazing may arise in the following areas:- If brazing is to be carried out where 1 Metal and metal oxide fumes from the ventilation is poor, such as an enclosed pipe brazing alloys joint or any similar situation, then brazing of 2 Fumes from heating the flux any kind, or welding, must be carried 3 Fumes from brazing torches out with the operator using breathing 4 Equipment used to effect the brazed equipment, in conformance to factory joint regulations for working in confined spaces. Recommended safety precautions and working practices on each of these are Copper Oxide & Zinc Oxide given below. Copper and zinc oxide fumes under normal conditions are unlikely to be a problem but, if excessive, are irritating and can cause Section 1: Metal and Metal metal fume fever. Symptoms of metal fume Oxide Fumes fever are similar to those of influenza and often appear after a latent period of up to 1.1 General 10 hours; they will normally disappear after 24 hours with rest. Zinc oxide can also be All brazing operations raise the temperature irritating to the nose, mouth and throat. of the filler metal above its melting point hence it is unavoidable that metal fume (as the oxide of the elements present) will be Diphosphorus Pentoxide evolved. On overheating of phosphorus containing alloys corrosive diphosphorus pentoxide The Health and Safety Executive in their fumes may be evolved which are irritating Guidance Note EH40 list Occupational to mucous membranes, the respiratory Exposure Standards (OESs) for metals system, eyes and skin. Contact between commonly used in brazing alloys and these the fume and perspiration may produce a are given in specific product safety data mildly acidic reaction causing irritation of sheets. the eyes, skin and mucous membrane.

1.2 Specific Hazards 1.3 Atmospheric Sampling Cadmium Oxide Workshop personnel who may be exposed to excessive fumes during brazing Cadmium Oxide fume will always be operations should undergo tests of their evolved to some extent during brazing with working zone using personal air sampling alloys from the silver-copper-cadmium-zinc equipment to ensure that MELs and OESs range. The Control of Substances Hazardous are not exceeded. Alternatively portable to Health (COSHH) Regulations list the detection devices may be used to monitor exposure limits for Cadmium Oxide as a the atmosphere during brazing operations. MAXIMUM EXPOSURE LEVEL (MEL) which There are an increasing number of must never be exceeded. The level present companies specialising in environmental in the workplace must always be as low monitoring who can undertake the as practicable. The use of local extraction necessary testing. Where local exhaust is virtually obligatory when brazing with ventilation is installed regular checks on air cadmium containing alloys. flows and capture velocities should be made as required under HSE regulations.

38 Section 2: Fluxes Section 4: Brazing Equipment 4.6 General 2.1 Skin Contact Although brazing is a reliable, simple and Mechanised brazing operations should The Johnson Matthey Range of brazing safe method of joining metal components, always be set and adjusted by competent fluxes is based on fluorides, fluoroborates, there are a number of basic precautions to personnel. If machines fail to operate or borates, fluorosilicates and chlorides of follow when brazing. operate incorrectly local supervision should potassium with additions of boric acid and always be notified immediately. borax. • Brazing stations should be made from non flammable materials and suitable Section 5: On prolonged contact, these fluxes are refractory brick. Safety Precautions moderately irritating to skin. Extra care Operator well-being and safety will result • Hot brazed components must only be should be taken if the skin is broken as from observing the following basic handled with pliers or tongs unless immediate irritation will occur. If the precautions: irritation becomes a problem, operators gloves are worn. should use barrier creams. Any cuts or • Wear suitable protective clothing. abrasions, however slight, should be 4.1 Hand & Fixed Torch Gloves are recommended to prevent covered with an adhesive dressing. The Brazing skin contact with flux powders and use of flux paste eliminates the contact A torch should always be pointed away pastes. which could occur when mixing a flux from the operator or other people when powder with water before use. The use of being lit. • Always wear safety glasses or goggles. impervious gloves e.g. rubber or latex is Suitable tinted glasses should be worn if recommended to prevent skin contact. Fixed torches should be lit from the side or glare from brazing torches is a problem. from below. Do not reach over one unlit Tests have shown the fluxes are irritant to torch to light another. It is usual for all the • Local extraction should always be used the eyes. If flux does come into contact torches in a system to light simultaneously, when brazing with cadmium containing with the eyes they should be irrigated and very severe burns to the forearm can alloys. Good ventilation is essential in all immediately with water or isotonic saline result. brazing operations. for up to 20 minutes. Medical attention should be sought if there is any suspicion of • Avoid standing with the face directly eye damage. 4.2 Induction Brazing Never touch the work coil while the over the workpiece. All brazing machine is working. Although work coils atmospheres should be monitored to 2.2 Oral Ingestion are often water cooled, when machines ensure OESs and MELs are not being Fluxes are harmful if ingested. They should have been recently switched off the coils exceeded. be kept out of the reach of children and retain enough heat to cause a minor burn if away from food, drink and animal feeding they are touched. • Welding techniques must not be used stuffs. It is advisable not to smoke when when brazing. For example, the direct using these materials. Before meals, hands Hands should never be inserted into a work heating of a pool of molten brazing alloy must be washed and fingernails cleaned. In coil if a ring, a watch, a metal bracelet or must be avoided. the event of flux being swallowed, a doctor any other metal object is worn. The object should be called and, meanwhile, the will heat up rapidly and cause an extremely • Brazing in confined spaces should only patient should drink plenty of water or milk severe burn. be carried out using suitable breathing with calcium carbonate (chalk) mixed in. Do apparatus. not induce vomiting. 4.3 Furnace Brazing • Health and Safety information on Controlled atmosphere furnaces usually If powder fluxes are used, they should be specific alloys and fluxes showing have a curtain of burning gases at the inlet mixed in a special flux tray. Flux should current OESs and MELs is available on and outlet doors. Since these flames are never be put in a container such as a cup, a request. often colourless and virtually invisible, a mug or a bottle which might be used for piece of iron or steel gauze should be hung drinking or other purposes. Empty flux NOTE: Johnson Matthey PLC cannot anticipate all in the flame path, this will glow brightly containers must not be used for the conditions under which this information and our when a flame is present. products or the products of other manufacturers in storage of foodstuffs e.g. sugar, coffee, combination with our products will be used. powdered milk etc. Care should be taken when components This information relates only to the specific are removed from a furnace or from a material designated and may not be valid for such material used in combination with any other 2.3 Flux Fumes conveyor belt or container, since they may On heating, flux will fume slightly. With materials or in any process. Such information still be hot. is given in good faith, being based on the latest overheating, the fume will increase. Fumes information available to Johnson Matthey PLC generated include Hydrogen Fluoride, 4.4 Resistance Heating and is, to be best of Johnson Matthey PLC's Fluorine and Boron Trifluoride. Without knowledge and belief, accurate and reliable at the The hot electrodes should never be adequate ventilation, or as the result of bad time of preparation. However, no representation, touched. brazing practice, fume can cause irritation warranty or guarantee is made as to the accuracy of nasal passages and eyes. or completeness of the information and Johnson The electrical apparatus and the equipment Matthey PLC assumes no responsibility therefore which regulates the flow of a controlled and disclaims any liability for any loss, damage The workpiece should not be overheated atmosphere gas (if one is used) should or injury howsoever arising (including in respect and operators should avoid standing of any claim brought by any third party) incurred be set and adjusted only by competent directly over the work. Any annoyance from using this information. The product is supplied on personnel. fumes can be minimised by using the condition that the user accepts responsibility workshops with high roofs, good local to satisfy himself as to the suitability and 4.5 Salt Bath Brazing completeness of such information for his own ventilation and efficient extraction systems. particular use. Freedom from patent or any other The parts must be completely dry before proprietary rights of any third party must not be 2.4 Inhalation they are immersed in the bath. Any water assumed. on them is converted immediately into In acute cases, remove to fresh air, apply steam, causing a minor explosion in the artificial respiration and oxygen and bath and throwing out droplets of molten summon medical aid. Continue observation salt. The salt sticks to virtually anything it for 48 hours. (Note: Poisoning by inhalation touches and can cause very severe skin may also result from brazing metal fume or burns. torch gases). The components should be lowered very Section 3: Fumes from slowly into the bath to avoid splashing the Brazing Torches molten salt. Salt residues should be Torch fumes will be burnt gases, primarily scrubbed off the hands before meals and at oxides of carbon and nitrogen which the end of the day. The controls that govern are unlikely to cause problems in well the heat input to the salt bath should ventilated conditions. be set and adjusted only by competent Acknowledgments personnel. (1) Burner & Flame Technology Ltd - Stalybridge for the generous loan of flame brazing facilities (2) Lancashire Fittings - Harrogate for supply of Stainless Steel fittings. (3) PJW Productions Ltd - Stockport Manchester for supply of Tungsten Carbide Tools. 39 Johnson Matthey PLC Metal Joining York Way Royston Hertfordshire SG8 5HJ Johnson Matthey Tel: +44 (0)1763 253200 Fax: +44 (0)1763 253168 Email: [email protected] www: jm-metaljoining.com