Effects of Vacuum Melting and Vacuum Annealing on the Properties of Austenitic Stainless Steels

Abstract

Two applications of vacuum technology to metallurgy are discussed. One concerns the consumable-electrode vacuum-arc remelting of AISI 316 stainless steel. An air-melted and a vacuum-arc remelted heat are compared with respect to composition, processing and welding, room- and high-temperature mechanical properties, magnetic permeability, inclusion count, and behavior in the Huey corrosion test. The vacuum heat was lower in carbon, oxygen, and hydrogen than the air-melted heat. The low oxygen and hydrogen were attributed to the melting process, while the low carbon was not. Both heats were similar in processing and welding behavior as well as in mechanical and physical properties. In Huey corrosion tests of sensitized material, the air-melted steel was attacked much faster than the vacuum-melted material. However, this difference was ascribed to the difference in carbon content between the two steels. Thus, in this study, no differences attributable to the consumable-electrode vacuum-arc remelting process were observed. The other application was the vacuum annealing of AISI 301 strip. This material was compared with air-annealed and hydrogen-annealed stock. The air-annealed and vacuum-annealed steels had similar mechanical properties. However, the hydrogen-annealed steel had half of the ductility, 80 per cent of the formability and 75 per cent of the strength of the other materials. The increase in hydrogen content of the steel, when annealed in hydrogen, is considered responsible for these differences.