Development of a new multi-component white cast iron for cold work roll

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In order to develop a new multi-component white cast iron for cold work roll, the optimum chemical compositions were investigated, and the relationship between the solidification structure and the solidification conditions, and the characteristics of transformation and heat treatment, and abrasion wear characteristics were examined about the cast iron with the optimum chemical compositions. Following chemical composition is recommended as the optimum chemical composition. Carbon content is 1-1.5%. Chromium content is 5%. Molybdenum content is 5% or more. Vanadium content is 1% or more. The cast irons with optimum chemical compositions contain MC and M_2C eutectic carbides of 9% to 12%. Solidification structure of the cast irons depends on the cooling rate, and the secondary dendrite arm spacing and sizes of MC and M_2C carbides, which are shown as a function of the cooling rate, become smaller with an increase in cooling rate. Martensite and retained austenite coexist in the cast irons in hardened state because Mf was not observed in the cast irons. The hardnabihty of the cast irons is good because the noses of pearlite and bainite transformation are on a long time side. The curves of temper hardness of the cast irons show the secondary hardening which is usually seen in highly alloyed tool steels and multi-component white cast irons with high carbon, and the tempered hardness of the cast irons reached the maximum value(about 850HV) at around 800K. It's hardness is higher than the necessary hardness (800HV) for cold work roll. It is thought from the results of suga abrasion wear tests that abrasion wear resistance of the cast irons is somewhat lower than that of the multi-component white irons with high carbon.