Some observations on ausforming of high-carbon, high-chromium die steel

The effect of 20, 40 and 60% metastable austenite deformation treatment on the strengthening mechanism of high-C, high-Cr die steel was investigated between a temperature range of 400°C and 550°C. The deformation of austenite prior to martensite or bainite transformation has been found to increase the hardness in tempered and untempered condition compared to non-deformed, similarly heat treated, high-C high-Cr die steel. The sub-zero treatment on ausformed and tempered specimens showed that the amount of retained austenite decreases with the increase of percentage reduction. The improvement in hardness and strength of deformed high-C high-Cr die steel was found to be due to the grain refinement as well as the elimination and transformation of retained austenite. In the present investigation considerable improvement in hardness has been achieved. This increase in hardness and strength at higher hardness levels is of immense value for increasing the efficiency of the steel. (Shri S.P. Chakraborty, Junior Scientific Assistant, Dr. R.K. Dubey, Scientist and Shri P.K. Gupte, Scientist and Head of General Metallurgy Division, National Metallurgical Laboratory)