Annealing for Metals/Materials Processing

Heating Treating Solutions

Air Products offers a wide range of technologies, gases, equipment, and cutting edge solutions for the heat treating industry.

Photo provided courtesy of Solar Atmospheres

Industrial Gases from a Global Leader

As a global leading manufacturer of nitrogen, oxygen, and argon, and a world-leading producer and supplier of hydrogen and helium, we ensure a reliable supply of industrial gases. Our excellent record of meeting on-time needs, coupled with our industry-leading safety standards, guarantees that you can depend on us. We provide technical support whenever you need it and offer world-class customer service to ensure your satisfaction.

Each Atmosphere Solution is Customised for Your Needs

We can help you choose the right atmosphere composition by selecting and providing blending and flow control equipment. Our team performs on-site atmosphere analyses to ensure consistent dimensional control, carbon control, and physical and metallurgical properties. We optimize your furnace process to lower operating costs and perform state-of-the-art metallographic and chemical analyses (SEM, ESCA, SAM, ISS, SIMS). Additionally, we provide safety training, test atmospheres using your parts in our lab furnaces, and demonstrate our system at your facility.

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Annealing Expertise and Solutions

Applying innovation and our expertise to solve our customers’ problems is our core strength

Since many of our atmospheres contain none of the unreacted hydrocarbons that are typically found with traditional exothermically-generated atmospheres, the improvement in surface quality often allows for a significant reduction in post-heat treatment cleaning or pickling costs, sometimes by as much as 80%. We also have a cooling application for temper rolling.

Improved surface quality and reduction in post-treatment cost

No unreacted hydrocarbons yields surface quality improvements and often allows a cleaning or pickling cost reduction

Consistent atmosphere for nonferrous annealing

Our consistent atmosphere systems maintain oxide-free surfaces and the desired metallurgical properties for nonferrous materials

Superior quality and control

Our nitrogen-based atmospheres protect ferrous parts; and 4–10% hydrogen prevents oxidation and decarburisation

Reduced cycle time

With our technical gases and expertise, you can reduce your process cycle time

Improved stainless steel annealing

Our nitrogen/hydrogen and pure hydrogen atmospheres provide the highest atmosphere quality for stainless steel strip, wire and tube products

Improved quality of annealed components

Air Products offers a complete range of atmosphere systems that excel in a wide variety of annealing applications

Ask the Expert

Guido Plicht

Commercial Technology Manager - Europe

“What’s the best hydrogen concentration for our nitrogen-hydrogen atmosphere for bright annealing of steels?”

Bright annealing of steels requires conditions that are reducing to steel oxides. Traditionally, the Ellingham diagram has been used to predict the conditions that correspond to oxidation of pure metals or reduction of their oxides. This method can be used to predict the conditions that should be reducing to iron oxides and the oxides of the alloying elements added to steels, such as chromium when stainless steels are considered. This traditional approach is not precise because it only uses thermodynamic data for pure metals and their oxides—it ignores the fact that iron and alloying elements form a solid solution. In addition, you can only determine the approximate equilibrium partial pressure ratio of hydrogen and water vapor for oxidation of a specific metal at a particular temperature.

Alternatively, you can use more accurate and convenient diagrams for steels and other alloys, which are created with the help of modern databases and computer programs, such as FactSage™ (thermochemical software and database package developed jointly between Thermfact/CRCT and GTT-Technologies) or Thermo-Calc software. Using the oxidation-reduction curves, presented as dew point of pure hydrogen or nitrogen-hydrogen atmospheres versus temperature, you can quickly select the atmosphere for annealing steels without formation of oxides. The diagram in Figure 1 was calculated using FactSage. This diagram shows that oxidation-reduction curves for Fe-18%Cr and Fe-18%Cr-8%Ni systems representing stainless steels are higher than the corresponding Cr/Cr₂O₃ curves. For alloys (e.g. steels), you can achieve more precise calculations using thermodynamic data from both the pure substances (i.e. pure metals and oxides) and solutions databases. Such diagrams can be produced specifically for the steels of interest and variety of atmosphere compositions.

These methods can help you troubleshoot and optimise your annealing operation by balancing hydrogen usage versus product quality.

Oxidation-reduction curves for pure chromium, Fe-18%Cr and Fe-18%Cr-8%Ni for the total pressure of 1 atm with a hydrogen partial pressure of 0.05 atm, corresponding N₂-5% H₂. (This diagram has been produced using thermodynamic data for solutions in addition to the data for pure elements and their oxides.)

Figure 1:

What’s the best hydrogen concentration for our nitrogen-hydrogen atmosphere for bright annealing of steels?

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How Annealing Works

Advanced Atmosphere Control System for Improving Annealing of Steel Components

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Articles and Brochures

Atmosphere Solutions for Advanced Materials Processing Brochure

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Nitrogen-Propane Protective Atmospheres for Annealing and Hardening Applications

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Temperature Influence on the Flammability Limits of Heat Treating Atmospheres