Annealing

Annealing involves heating steel components above the critical temperature.30～50℃The steel is kept at a constant temperature within the heat treatment furnace for a period, followed by cooling to room temperature. The purpose of annealing is to refine the grain structure of the steel, reduce internal stresses and hardness, improve cutting properties, enhance toughness and plasticity, and facilitate welding and rolling processes.

Annealing includes annealing, non-annealing, stress annealing, isothermal annealing, and spheroidizing annealing.

①Annealing (Recrystallization Annealing): Heating subcrystalline steel toAC3 The above30～50℃Heat treated and cooled slowly in the furnace. Purpose: Refine structure, improve stress, hardness, and cutting properties, mainly used for (cast and forged) welded structures, achieving near-equilibrium structure.

②Annealed: To heat steelAC1 The above30～50℃Heat-treat and slow cool to achieve: hardness, improved machinability, and reduced internal stress, applicable to forgings and rolling parts of low-alloy and medium-high carbon steels.

③Stress Annealing: Heating the workpiece toAC1 The following100～200℃Post-heat treatment with controlled cooling, its purpose: to relieve internal stresses caused by welding, cold deformation processing, casting, forging, etc. The microstructure of the stress-relieved steel does not change. The stress relief...500～650℃Achieving stress relaxation through plastic deformation or creep deformation during the subsequent slow cooling process, such as the annealing of large spherical tanks.