The quenching process/medium selected depends on the alloy, the desired microstructure, and the properties of the end-product. In addition to rapidly cooling the parts, the quench medium must prevent oxidation during cool down and provide an even, consistent cooling to minimize residual stress, distortion or possibility of cracking.
Gases are typically used as the quench medium in vacuum furnaces. nitrogen, argon and helium can all be used. The minimum cooling rate requirement is the key factor in determining which gas is used. Helium is used when high cooling rates are desired. Cooling rates can also be increased with higher gas pressure and velocity.
Air Products' gas quenching capabilities enable the determination and selection of the optimum gas or gas blend for any specific operation. Gas quenching produces a cleaner surface than quenching with oil or other liquids, and eliminates the need for cleaning after quenching. Downstream processes such as straightening or machining can be reduced or eliminated with less distortion due to uniform cooling rates. Elimination of oil as the "quenchant" has a positive environmental impact, related to waste oil disposal and the associated fumes in the furnace work area. Safety issues related to oil fires are also eliminated.
Air Products' gas quenching capabilities enable the determination and selection of the optimum gas or gas blend for any specific operation. Gas recovery and recycle systems are another possible solution for reducing overall operating costs where helium or argon is used as the quench medium.
Our application engineers can work with you to fully understand your particular needs and then recommend industrial gas-based technologies and process improvement solutions that can help you operate more efficiently.
Photo Courtesy of Solar Atmospheres
Applications Engineer, North America
Gas Quenching With Air Products’ Rapid Gas Quenching Gas Mixture
Safety and environmental considerations make gas quenching an attractive alternative to liquid quenching. The advantages of gas quenching include cleaner product, minimum distortion, and elimination of environmental problems associated with gas quenching. However, gas quenching has not been widely used because of limited cooling rate. Air Products’ RGQ gas mixture increases the gas cooling rate over 100% helium at a given gas pressure and velocity.