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Home , Annealing (metallurgy), Carbonitriding

Atmosphere solutions for metals processing tell me more About us Air Products’ technical services and equipment Air Products touches the lives of make us different consumers around the globe in positive ways every day. The Metals processors need innovative • Optimize your furnace process to company is recognized for its ways to improve , brazing, lower operating costs innovative culture, operational , and neutral • Perform state-of-the-art metallo- excellence and commitment to operations. That’s why graphic and chemical analyses safety and the environment. Our more and more are turning to (SEM, ESCA, SAM, ISS, SIMS) aim at Air Products is to develop Air Products’ Atmosphere Solutions. lasting relationships with our • Provide safety training We ensure that each Atmosphere customers and communities • Test atmospheres using your Solution is right for each customer. based on human qualities: an parts in our lab furnaces understanding of their needs, Our experienced industry special- integrity and honesty in the way ists and field support personnel can: • Demonstrate our system at your we do business, and a passion for facility • Help you choose the right exceeding expectations. atmosphere composition • Select and provide blending and Air Products today flow control equipment • More than 18,000 employees • Perform on-site atmosphere around the world analyses for consistent dimen- • Operations in more than 40 sional control, control, countries and physical and metallurgical properties

Metals processing For over 50 years, metals processors around the world have come to rely on Air Products’ industrial gases, gas atmospheres, equipment and technical support to help improve product quality, reduce operating costs and increase productivity. We offer industrial gases, gas handling equipment and technology, additives, global supply capability and—most importantly— unmatched industry experience and technical know-how to help you succeed. Air Products’ specialists are ready to help you with atmosphere solutions for metals processing.

2 Any -containing atmosphere resistance of the material. Our Annealing such as dissociated can 100% atmospheres Gas atmospheres for annealing can allow chrome-nitride formation in achieve the low dew point, strong range from nitrogen-based blends many stainless . Although the reducing potential, and control with hydrogen for carbon steels (to surface appearance may be necessary for superior surface improve microstructure, surface acceptable, resultant intergranular cleanliness without nitride appearance and reduce residual nitrides may reduce corrosion formation. (See Figures 1 and 2) stresses) to 100% hydrogen (for stainless steels or for faster batch Figure 1: Stainless annealing atmosphere composition processing of components). Atmosphere Component Dissociated Ammonia Air Products’ Atmospheres N2% 25 0–70 For virtually any annealing H2% 75 30–100 operation, Air Products has an O2 ppm 10–35 5 atmosphere that’s ready to perform. Dew Point °F –20 to –60 –90

Whether you are annealing ferrous NH3 ppm 5–100 — or nonferrous metals, our wide range of atmosphere solutions can ensure that your special atmosphere Figure 2: Oxidation reduction for 18% chromium at 2000 ˚F requirements can be fully satisfied. +20 Nitrogen, typically the main 0 Oxidizing atmosphere component, provides the inert base that prevents –20 Reducing undesirable reactions from –40 occurring. Often, a reducing agent such as hydrogen or a hydrocarbon (˚F) Point Dew –60 Atmosphere Dissociated Systems is added to adjust atmosphere NH3 –80 reducing potential. 100 Since many of our atmospheres 0 20 40 60 80 100 contain none of the unreacted Hydrogen, % hydrocarbons that are typically found with traditional exothermically-generated Figure 3: Effect of atmospheric composition on heating and cooling rates atmospheres, the improvement in surface quality often allows for a 2200 significant reduction in post-heat- treatment cleaning or pickling costs, sometimes by as much as 80%. 1800

Air Products offers a complete range of atmosphere systems that excel in 1400 a wide variety of annealing applications. 100% H (˚F) Temperature 1000 2 75% H2

Stainless steel annealing 600 30% H2 Our nitrogen/hydrogen atmospheres and pure hydrogen 200 atmospheres provide the highest 0 5 10 15 20 25 30 possible atmosphere quality for Time, min. stainless steel strip, and tube The higher thermal conductivity of pure hydrogen over other atmospheres provides improved product applications. and heating efficiency. 3 Figure 4: Carbon and steel annealing atmosphere composition Annealing (continued) Atmosphere Air Products’ Component Endothermic Exothermic Atmospheres Carbon and annealing N2% 40 70–98 90–100 When annealing sheet or coil H2% 40 2–15 0–10 product in high convection bell O2 ppm 10–150 10–75 5 furnaces, the use of 100% hydrogen Dew Point °F +10 to +50 –30 to +50 –90 can reduce cycle time by as much CO% 20 2–12 — as 50%, allowing for potential CO2% <1 1–10 — production increases (see Figure 3). CH4% <1 <1 0–1 And the extremely low density of pure hydrogen atmospheres reduces Figure 5: Nonferrous (i.e., Cu) annealing atmosphere composition furnace fan power needs, allowing power cost savings as high as 35%. Atmosphere Dissociated Air Products’ Component Exothermic Ammonia Atmospheres

For superior quality and control, our N2% 70–98 25 90–100 nitrogen-based atmospheres H2% 2–15 75 0–10 perform for virtually any type of O2 ppm 10–75 10–35 5 ferrous product, including sheet, Dew Point °F –30 to +50 –20 to –60 –90 strip, and wire. A 4%–10% hydrogen CO% 2–12 — — level provides the reducing potential CO2% 1–10 — — to prevent oxidation and decarbur- CH4% 0.02–0.10 — — ization. Detrimental carbon deposits NH3 ppm — 50–100 — are eliminated. Harmful emissions are minimized. Small, controlled amounts of Figure 6: Electrical steel annealing atmosphere composition hydrocarbon maintain the carbon Atmosphere Component Exothermic Air Products’ Atmospheres potential necessary for consistent N2% 70–98 84–100 quality. (See Figure 4) H2% 2–15 0–16 O2 ppm 10–75 5 Dew Point °F –30 to +50 –50 to +70 Nonferrous annealing CO% 2–12 —

Our atmosphere systems for CO2% 1–10 — nonferrous annealing can maintain CH4% 0.02–0.10 — the consistency necessary for oxide- free surfaces and consistent metallurgical properties for Electrical steel annealing nonferrous materials, such as aluminum or and tube, Our nitrogen/hydrogen Both electrical properties like core wire, and strip products. A 1%–10% atmospheres with controlled loss and permeability and hydrogen level in a nitrogen base oxidant additions provide optimum insulating properties provided by provides the necessary reducing electrical properties in motor, oxide bluing can be maximized potential for maximum surface transformer, and generator through the precise monitoring of quality and minimum cleaning. lamination grade steels. Superior the atmosphere blend. Our (See Figure 5) atmosphere quality and consistency atmosphere solutions have achieved allow for improved lamination up to a 15% improvement in quality or equal lamination quality electrical quality over other from lower grade feedstock atmospheres. material. (See Figure 6)

4 Figure 7: Brazing atmosphere composition Brazing Atmosphere Dissociated Air Products’ Our brazing Atmosphere Solutions Component Exothermic Ammonia Atmospheres** maintain atmosphere composition N2% 70–98 25 98 to optimize part strength and H2% 2–20 75 2 integrity. Product surfaces remain O2 ppm 10–75 10–35 5 clean without sacrifice to product Dew Point °F –30 to +50 –20 to –60 * quality. Wettability can be CO% 2–10 — — controlled. CO2% 1–6 — — CH % 0.02–0.10 — — Nitrogen is used as the carrier gas 4 NH ppm — 50–100 — with small percentages of hydrogen 3 as the reducing agent. Small Special additions of hydrocarbon may be Base Material Consideration H2% Dew Point added to control and reduce the — 2 Low dew point to compensate for Iron Oiled Parts 3 Controlled if required. Iron High Carbon 2 Low Stringent control over the dew Iron Wide Joint Gap 2 Controlled point-to-hydrogen ratio allows for Stainless Steel — 30–100 Controlled the brazing of high-carbon steels, Brass Low Melting Point 5–25 Low stainless steels, and nonferrous * Controlled at different levels, depending upon application. metals (see Figure 7). Improvements ** Typical in the mechanical strength of the brazed joint and part surface quality Brazing surfaces are clean Decarburization is prevented are achieved through the consistent control of filler metal flow. Cutting oils and other residues For brazing medium- or high-carbon often interfere with proper braze parts, decarb caused by excessive flow. Air Products’ Atmosphere dew point can be a major problem. Braze wettability is optimized Solutions can produce atmospheres The dew point of nitrogen is less Because of furnace dew point flexi- humidified to eliminate these car- than minus 90 °F, and oxygen and bility and hydrogen content, atmo- bonaceous materials from the braz- carbon dioxide levels are below sphere reducing potential can be ing surface. With the change in dew 5 ppm—conducive to decarburiza- controlled to vary braze wettability. point, the reducing potential of the tion prevention. In cases where minimum braze flow nitrogen-based atmosphere still is desired, such as wide-gapped remains superior to that of an exo- joint brazing, the reducing potential thermic gas system due to the pres- can be decreased with high dew ence of small amounts of hydrogen. points and reduced hydrogen levels. Product quality is not sacrificed. For narrow-gapped joints or high Flux can be eliminated. Cleaning wettability needs, the atmosphere operations are usually unnecessary. reducing potential can be increased with low dew points and increased hydrogen levels. Photo courtesy of Handy & Harman Photo

5 Carburizing/neutral hardening Atmosphere solutions can be controlled Air Products’ Atmosphere Solutions gas—20% CO, 40% H2, and 40% N2. With Air Products’ Atmosphere are available for carburizing, neutral The benefit of Air Products’ Solutions, endogas composition is hardening, , Atmosphere Solutions is superior virtually duplicated by blending and nitrocarburizing. Nitrogen, atmosphere control for consistent pure nitrogen with liquid methanol methanol, and a small amount of part quality, operational cost savings, at the injection point of the furnace enriching gas are blended at the fur- significant increases in operational hot zone. nace to provide a furnace atmo- productivity, and ease of operation. sphere essentially identical in com- (See Figure 8) By varying the amount of enriching position to that of , the furnace carbon potential can be adjusted to meet your specific atmosphere requirements.

Low-pressure vacuum carburizing

Air Products has developed high- pressure gas solutions to meet the exacting demands of low- pressure vacuum carburizing tech- nologies. Gas quench capabilities up to 40 bar using nitrogen, argon or helium can be provided. Specific equipment is recommended based on the type and volume of gas required. High-pressure gas storage can be custom designed and opti- mized to satisfy the specific require- ments of the process and quench frequency. Photo courtesy of Photo Combustion Surface Atmosphere solutions are efficient

The elimination of endo-generation Figure 8: Carburizing/neutral hardening atmosphere composition and its associated maintenance pro- Atmosphere Component Endothermic Air Products’ Atmospheres duces the greatest impact on cost N2% 40 40 reduction. With Air Products’ H2% 40 40 Atmosphere Solutions, total gas CO% 20 20 flow and composition can be con- CO2% <1 <1 trolled easily and quickly to meet O2 ppm 10–150 5 the requirements of each phase of Dew Point °F +10 to +50 –10 to +40 the carburizing cycle. Because of the system’s rapid turndown capabili- ties, compensation necessary for minimizing air infiltration is elimi- nated, allowing flow rate reductions of up to 50%. Air Products’ atmos- phere control system automatically increases flow with an inert nitro- gen purge during charging, quench- ing, or furnace malfunction, enhanc- ing operation efficiency and safety.

6 Sintering Air Products’ Atmosphere Solutions for sintering provide an excellent means to improve the quality of the sintered components. Dimensional changes are minimized. The carbon levels in the core and surface of the powder metal part are better main- tained, leading to improved hard- ness control. The atmosphere sys- tems are also designed for improv- ing lubricant removal.

The furnace atmosphere equilibri- um is maintained through proper understanding of the furnace Photo courtesy of St. Mary’s Pressed Metals Pressed courtesy of St.Photo Mary’s design, processing conditions, and the appropriate atmosphere compo- sition and distribution in the fur- Figure 9: Sintering atmosphere composition nace. Air Products’ Atmosphere Solutions are primarily based on Air Products’ Nitrogen-based Atmospheres nitrogen, with small additions of Atmosphere N2 Dissociated reducing or oxidizing gases which Component N2–H2 Ammonia N2–Endo** provide the optimum atmosphere N2% 0–100 85–100 85–100 in each specific zone of the sinter- H2% 0–100 0–10 0–10 ing furnace. These atmospheres are CO% — — — carbon-neutral and reduce adverse Dew Point °F –90 to –10 –70 to –10 –50 to +30 carburizing and decarburizing tenden- O2% 5 5 5 cies that are typical in endothermic CO2% — — — type atmospheres. With Air Products’ CH4% <1 <1 1 Atmosphere Solutions, the variations in atmosphere composition and dew point that are typical with achieve additional control over dew tion of the type and amount of endothermic atmospheres and dis- points. By increasing the amount of these enriching gases, it is possible sociated ammonia are minimized. reducing gas used, we can sinter to obtain specific metallurgical (See Figure 9) stainless steel and other hard-to-sinter properties, surface quality, and alloys such as higher alloyed sinter dimensional control. hardenable grades. Air Products has Ferrous sintering also developed proprietary solutions Powder treating For sintering typical iron-based for more effective lubricant remov- parts, the nitrogen-based atmosphere al, copper infiltration and belt life Air Products also provides gases and system provides higher quality by extension. customized atmosphere solutions carbon control and higher sintered for a variety of other related tech- strength. By adjusting the reducing nologies, such as powder atomiza- Nonferrous sintering and other enriching gases, we can tion, powder annealing, hot isostatic tailor the atmosphere to better suit In nonferrous sintering applications, pressing, metal injection molding the specific requirements of the carbon control is not important and and powder . alloy and component being sintered. the sintered properties are more Small amounts of a hydrocarbon, dependent on the reducing power such as natural gas, can be used to of the atmosphere. By proper selec-

7 For more information, please contact us at:

Corporate Headquarters Air Products and Chemicals, Inc. 7201 Hamilton Boulevard Allentown, PA 18195-1501 T 800-654-4567 or +610-706-4730 F 800-272-4449 [email protected]

Europe Air Products PLC Hersham Place Molesey Road Walton-on-Thames Surrey KT12 4RZ UK T 44-0-1270-614314 [email protected]

Asia Air Products Asia Inc. 1001, 10/F, Sunning Plaza 10 Hysan Avenue, Causeway Bay Hong Kong T (852) 2527-1922 F (852) 2527-1827 [email protected]

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