Controlled cooling of wire rod leaving hot rolling mill - to obtain microstructure for drawing fine steel wire

摘要

Process (a) involves rapid cooling e.g. with water to 850-650 degrees C and holding at temp. for transforming the austenite into ferrite, and possibly allowing grain growth to a favourite size, e.g. above ASTM 9. (b) Controlled cooling to 625-400 degrees C. and holding at temp. or permitting a slow cool during more than 15 seconds, to ppte. carbon as carbides. (c) cooling if required to permit coiling of the wire rod. Step (a) may consist of controlled cooling, but the end temp. of the rod must be 850-650 degrees C. In step (b) cooling is pref. to 550-450 degrees C; with holding for min. 30 seconds. The process is pref. applied to steel contg. 0.15% carbon. A microstructure is obtd. which permits drawing into very fine wire without the need for an intermediate anneal. The tensile strength and the 0.2% elastic limit are lower than when conventional methods of controlled cooling are used.