CRACK SUSCEPTIBILITY OF MEDIUM AND HIGH ALLOYED TOOL STEELS UNDER CONTINUOUS-CASTING CONDITIONS

Hot tensile tests after partial melting of the specimens were carried out on medium and high alloyed tool steels and their mechanical proper ties (maximum force and reduction of area) were determined in the temp erature range between liquidus and 900 degrees C. Cooling conditions a nd strain rates were varied in this range. The temperature ranges of r educed ductility were determined, the metallurgical reasons for embrit tlement were investigated by means of metallographic and microprobe an alysis. The crack susceptibility is related to an enrichment of carbon and carbide forming elements in cold and hot working steels, and to t he high S content in the segregated zone of the laminate forming steel s. The crack susceptibility can be minimized by low strain rates combi ned with a strong secondary cooling.