Processing method of steel annealing for heat treatment

Heat treatment of steel is a processing technology that applies different heating, insulation and cooling measures to steel in the solid state range to change its internal organizational structure and improve the performance of steel. The ordinary heat treatment of steel includes four basic processes: annealing, normalizing, quenching and tempering.

Annealing is a metal heat treatment process in which the metal is slowly heated to a certain temperature, maintained for a sufficient time, and then cooled at a suitable speed (usually slow cooling, sometimes controlled cooling). The purpose is to soften materials or workpieces that have been cast, forged, welded or cut, to improve plasticity and toughness, to homogenize chemical composition, to remove residual stress, or to obtain desired physical properties.

Purpose of annealing:

① Reduce the hardness of steel, improve plasticity, in order to facilitate cutting and cold deformation processing.

② Refine the grain, eliminate the defects caused by casting, forging and welding, make the structure and composition of steel uniform, improve the performance of steel or prepare for future heat treatment.

③ Eliminate the internal stress in the steel to prevent deformation and cracking.

There is also a stress relief annealing, also known as low temperature annealing, mainly used to eliminate the residual stress in castings, hot rolled parts, forgings, welds and cold working parts. The operation of stress relief annealing is to slowly heat the steel with the furnace to 500~600 °C, hold for a period of time, slowly cool with the furnace to 200~300°C below the oven, and then cool in the air. There is no structural change in the process of stress relief annealing, and the residual stress is eliminated in the process of heating, holding and cooling.