ABSTRACT
The first deliberate attempt to develop an alloy steel was made by Sir Robert Hadfield during the 1880s, but most of these materials are products of the twentieth century. Steel was not originally classified as 'alloy steel' unless it contains more than 2" manganese and/or other elements with amounts at least between 0.1" and 0.5". The main disadvantage of chromium as an alloying element is that, it increases grain growth during the heat-treatment. The primary requirement of a tool or die steel is that it shall have considerable hardness and wear-resistance, combined with reasonable mechanical strength and the toughness. The elements that are used increase the depth of hardening of steel, so alloy steel has a bigger 'ruling section' than plain-carbon steel. This is because alloying elements slow down the austenite to martensite transformation rates, so it is possible to make oil-harden or the air-harden as suitable steel.
