DEPARTMENT OF WELDER Topic-

One of the processes to make permanent joint between two same or different metals is Brazing. Brazing gives much stronger joints than Soldering. Brazing uses a harder filler metal than Soldering, which commonly known as Spelter or Brazing . Spelter melts temperature that is above the red heat, but below the melting point of parts to be joint (workpiece).The melting point spelter ranging from 600 degree Celsius to 950 degree Celsius. In Brazing, at first joining metals are cleaned properly and heated up then spelter with Borax (as Flux) is spread over the joint. Brazing process is quite similar to Braze Welding.

Application:- Brazing is generally used to join Carbide tip on cutting tools, tapes and on their fittings, repairing of Cast Iron, Radiator etc.

DEPARTMENT OF WELDER Topic- BRAZING

Spelter There are so many types of Spelter like for the Brazing of Iron, and alloys spelter may be of Copper, Silver, Zinc etc. Filler metal (Spelter) used for Brazing mainly of two classes- i) Copper Base Alloys ii) Zinc Base Alloys There are various different alloys in each class but (Alloy of Copper and Zinc), sometime upto 20% of Tin are used mainly for the Brazing of Ferrous metal. Melting point of Copper and Zinc spelter is 600 degree Celsius and 900 degree Celsius. Silver Alloys (an alloy of Silver and Copper or may be of Silver, Copper and Zinc) are suitable for Brazing of any metal that is capable to being Brazed. They give a clean finish and a strong ductile joint. Melting point of Copper and Silver spelter is 600 degree Celsius and 850 degree Celsius and Silver and Zinc Spelter is 688 degree Celsius and 750 degree Celsius. Spelter are available in the form of Sheet, wire powder, rod etc. Filler metal are compound based on Aluminium, Magnesium, Copper, Silver and Nickel or may be alloys of Aluminium and Nickel , Copper and Zinc, Copper and Phosphorous, Silver and Nickel etc.

DEPARTMENT OF WELDER Topic- BRAZING

Flux:- Borax (Sodium Tetraborate Decahydrate / Na₂[B₄O₅(OH)₄]. 8H₂O) is widely used as flux. Borax with common Salt may also be used as Flux for Brazing.

Procedure of Brazing:-

DEPARTMENT OF WELDER Topic- BRAZING

I) CLEAN THE JOINT TO BEW BRAZED:- Before Brazing, surface should be cleaned properly to make it free from Oil, Dust, Grease layer of Oxide and other undesirable substances.

II) Apply the Flux on Work surface:- For Brazing, proper Flux should be applied on work surface. Borax or Borax with salt may be used as Flux in Brazing.

DEPARTMENT OF WELDER Topic- BRAZING

III) Clamping of job to be brazed:- The proper space between the pieces of job for Brazing is maintained and in that position it is made tight with clamp.

IV) Heating of job:- After clamping, job is heated upto 427 degree Celsius by different method of heating.

DEPARTMENT OF WELDER Topic- BRAZING V) Application of Filler Metal:- Proper amount of filler metal is placed on the job part to be Brazed, which spread over the joint due to Capillary Force. Then the job is lect for cooling.

V) Cleaning of Brazed parts:- After completion of total process some Flux may be there over the joint surface, so clean that salt joint should be submerged into Alum hot solution and then should be gently rubbed with brush.

DEPARTMENT OF WELDER Topic- BRAZING METHODS OF BRAZING

There are various types of Brazing. Some of them are as follows:- 1) Troch Brazing:- In this type of Brazing Oxy Acetylene or Oxy Hydrogen torch is used to heat up the joint and Brazing rod.

2) Dip Brazing:- To braze is to join two or more pieces of metal by means of flowing a filler metal between the joint interfaces at a temperature below the melting point of the base metal but above 900°F. The filler metal, upon cooling to the solid state, forms a strong metallic bond throughout the joined area.

DEPARTMENT OF WELDER Topic- BRAZING 3) Induction Brazing:- In this, as per the size and the shape of the tool tip is made. By placing Spelter, Flux and tip on the tool nose. Induction coil is connected to electricity, which heat them at proper temperature, so that spelter melts.

4) Furnace Brazing:- In this method, parts to be joined are placed in furnace for heating after applying Flux, Spelter on these parts.

DEPARTMENT OF WELDER Topic- BRAZING 5) Blow Pipe Brazing:- This method is used for small size jobs like small rings and ornaments etc. In this, part is placed on wood, charcoal and then flux and Spelter is applied for Brazing.