QUENCHING OF STEELS IN A STREAM OF HIGH-P RESSURE GAS

Objective. It was to be investigated under what conditions steels can be quenched in a stream of gas and what hardness increase can be achie ved. To be included in the investigations were, in particular, low-all oy steels which generally demand a higher intensity of quenching than high-alloy steels, such as e.g. high-speed steels and high-alloy chrom ium steels. Nitrogen and helium were provided as quenching gases. For cost reasons, the helium was to be reutilised. Summary. Quenching in a stream of high-pressure gas can be regarded as an innovative method o f quenching steels. For certain applications this method represents a genuine alternative to quenching in liquid media. It is distinguished by a number of advantages compared with the conventional quenching tec hniques that are based on the principle of immersion in liquid quencha nts. To be able to fully exploit the advantages offered by this method , it is practical to combine gas quenching with a vacuum heat treatmen t. The hardness results achieved by doing so are by all means comparab le to those attained after quenching in liquid quenchants. The quench cracking behaviour is significantly better, and there is less deformat ion. The surface of the quenched parts remains metallically bright. Su bsequent cleaning becomes unnecessary. Special steels for gas quenchin g are not yet available at present. Endeavours to develop hardenable s teels further and to adapt them to the requirements of gas quenching a re gaining in importance in connection with the gas-stream quenching m ethod.