Development of low tungsten substitute tool steels

Abstract

Tunsten is a very important alloying element in high speed tool steel, hot and cold work die steel and permanent magnet alloys, but its ore deposits are limited to a few countries. Continuous development user the years to reduce tungsten content in convent- ional 18-4-1 high speed steel i.e. 18% tungsten, 1% chromium and 1% vanadium, has led to increase of molybdenum, cobalt, chromium or vanadium. These steels have a hyper eutectoid structure in the fully hardened state in which complex carbides are embedded in martensite matrix. Both of these constituents in high speed steel retain higher hardness at high temperature than their counterpart in plain carbon steel. Many such high speed steels with low amount or without tungsten have been developed. These low tung- sten steels' apart from replacing the non-available alloying elements have the additional advantage of requiring lower hardening temperature than high speed tool steel containing 18% tungsten, thus avoiding the formation of coarse grain size in steel.