Geometrical dimensional accuracy of steel pipes after stress relief heat treatment

After the stress-relieving heat treatment, the test results of the steel pipe are analyzed and it is concluded that:

1.The geometrical accuracy of the steel pipe is basically unchanged;

2.The elongation, section shrinkage and surface roughness of the steel pipe meet the technical requirements;

3.The impact energy of the steel pipe is increased by 83% compared with the cold working state, but the technical requirements of the hydraulic cylinder cylinder are still not reached;

4.The tensile strength, yield strength and hardness of steel pipes are greatly reduced on the basis of cold working;

5.The metallographic structure of the steel pipe is slightly improved compared to the cold working state, but it is far from the technical requirements of the hydraulic cylinder cylinder.

Since the stress relief annealing is mainly to eliminate the internal stress of the metal, the heating temperature does not exceed the phase transition temperature of the material in the heat treatment process, but is close to the recrystallization temperature, so the microstructure of the metal material does not change substantially during the stress relief annealing process. When the hydraulic cylinder used in the general environment has low requirements on material properties, impact toughness and fatigue strength, it can be produced by the above heat treatment process.