engleski

Characteristics of Warm Baths for the quenching of Tool Steels

Quenching of tool steels in a warm bath, i.e. martempering process, is implemented in order to reduce the residual stresses, strain and risk of rupture of steels and also to obtain a martensitic microstructure with the required properties. The implementation of this process is limited to steels with good hardenability, used for tools with a limited thickness. Acceptable steel properties were obtained by prescribing proper parameters of austenization and quenching. The paper describes the problems in the selection of optimal martempering parameters, such as optimum temperature and holding time in the warm bath, and in achieving them depending on the hardened steel, the weight and size of the tool. The characteristics of the cooling in a specially designed salt bath are described. Special features of its design include the workpiece cooling rate control by adding a small amount of water (up to 2%) to the salt AS140, by the regulation of temperature and by the agitation of molten salt. Such regulated and intense quenching allows the application of martempering process on tools with large cross-sectional area that are made of steel with medium to low hardenability. This was confirmed on the tool steel EN 90MnCrV8.

martempering process; cooling curve; quenching; tool steel; EN 90MnCrV8

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