Hot or warm working steel tool, especially punch

摘要

A hot or warm working element of steel has a superficial oxygen-containing mixed layer with iron sulphide and nitride particles in which the S/N ratio is 0.5-10. Also claimed is a process for producing a hot or warm work steel element involving: (a) supplying colourless and yellow ammonium sulphide solutions in the wt. ratio of 6-1:1 to a gas generator to produce a mixture of the solutions for producing a main gas; (b) placing a steel element in a reaction chamber and supplying the chamber with a mixed gas which contains the main gas and nitrogen carrier gas, and which has a hydrogen sulphide concentration of 100-600 ppm and an ammonia concentration of 0.1-1.0%; (c) supplying nitrogen and ammonia gas from different sources to the reaction chamber to increase the ammonia concentration to 10-70%; (d) heating the reaction chamber to 460-600 deg C to effect sulpho-nitriding of the steel element; and (e) slowly cooling the treated element at 30-250 deg C/hr..