TEMPERING RESPONSE OF SUB-ZERO PROCESSED Cr-V LEDEBURITIC STEEL VANADIS 6

The ledeburitic steel Vanadis 6 has been austenitized at the temperatures 1000 - 1075 degrees C, nitrogen gas quenched and 2x tempered at the temperatures 480 - 600 degrees C. Each tempering cycle was 2 h. Sub-zero treatment carried out via various regimes has been inserted in-between quenching and tempering, except one set of specimens. The effect of sub-zero treatment on the tempering characteristics of the material has been investigated. It has been found that the martensite after sub-zero processing differs from that of conventionally transformed in terms of substructure. The sub-zero treatment induced a multiple reduction of the volume fraction of retained austenite. This makes a difference between as-tempered microstructure of sub-zero treated and no-sub-zero treated steel, which results in different as-tempered hardness.