Annealing
WHAT A heat or thermal treatment process by which a previously cold rolled steel coil is made more suitable for forming and bending. The steel sheet is heated to a designated temperature for a sufficient amount of time and then cooled. WHY The bonds between the grains of the metal are stretched when a coil is cold rolled, leaving the steel brittle and breakable. Annealing recrystallizes the grain structure of steel by allowing for new bonds to be formed at the high temperature. HOW There are two ways to anneal cold rolled steel coils D1batch and continuous. (1) BATCH (BOX). Three to four coils are stacked on top of each other, and a cover is placed on top. For up to three days, the steel is heated in a non oxygen atmosphere (so it will not rust) and slowly cooled. (2) CONTINUOUS. Normally part of a coating line, the steel is uncoiled and run through a series of vertical loops within a heater: The temperature and cooling rates are controlled to obtain the desired mechanical properties for the steel.
