Annealing is a metal heat treatment process that refers to heating a metal slowly to a certain temperature, holding it for a sufficient time, and then cooling it at a suitable rate.
The purpose of annealing:
(1) To reduce hardness and improve machinability;
(2) Reduce residual stresses, stabilize dimensions, and reduce deformation and cracking tendencies;
(3) Refine the grain, adjust the organization, and eliminate organizational defects;
(4) Uniform material organization and composition, improve material properties or for future heat treatment to make organizational preparation.
Annealing processes include complete annealing, spheroidal annealing, isothermal annealing, graphite annealing, diffusion annealing, stress relief annealing, incomplete annealing, post-weld annealing, and so on.
The specific process of the three commonly used annealing:
1, complete annealing
The Purpose of grain refinement, is uniform organization, eliminate internal stresses and processing defects, reduce hardness, and improve cutting performance and cold plastic deformation capacity.
They were used to refine the medium and low carbon steel by casting, forging, and welding after the mechanical properties of poor coarse superheated organization. The workpiece will be heated to ferrite all transformed into austenite temperature above 30 ~ 50 ℃, held for a while, and then slowly cooled with the furnace, the austenite again in the cooling process, you can make the organization of the steel fine.
2, stress relief annealing
Used to eliminate the internal stress of steel castings and weldments. For steel products after heating the beginning of the formation of austenite temperature below 100 ~ 200 ℃, insulation, and cooling in the air, you can eliminate internal stress.
3, incomplete annealing
Heating temperature between Ac1 ~ Accm, cooling rate: in 500 ~ 600 ℃ above, carbon steel is 100 ~ 200 ℃ / h, alloy steel is 50 ~ 100 ℃ / h, high alloy steel is 20 ~ 60 ℃ / h, mainly used for over eutectic steel.
Quality inspection standards for annealing:
Scope of inspection: 1. Annealing temperature, heating time, holding time. 2. Surface quality and hardness test of products after annealing. 3.
