Heat treatment of cold finished

When the cold-worked force element has a large amount of deformation during the forming process, it will cause significant cold-work hardening, thereby increasing the strength and hardness of the material, reducing plasticity and toughness, and generating large internal stress. In order to restore the mechanical properties of the material and eliminate or reduce the residual processing stress, heat treatment is performed on the cold-formed or warm-formed pressured components when necessary.


Whether a cold-worked pressure receiving element requires heat treatment depends mainly on the degree of cold working deformation and the use conditions of the pressure receiving element. Generally, the deformation rate is used as an index to measure the degree of deformation during cold working, and the cold-formed steel plate stress element is used. The deformation rate control index and other control conditions are as follows.


1) Deformation rate of cold-worked compression members
The deformation rate of the steel plate is calculated as follows:


Uniaxial stretching (such as barreling): deformation rate (%) = 50δ (1-Rf / Ro) / RF
Biaxial stretching (such as head molding): deformation rate (%) = 75δ (1-Rf / Ro) / RF
In the formula: δ-plate thickness
Rf-medium radius
Ro-Medium surface radius before forming (for flat plates, Ro is infinite)


2) Compression parts using cold-worked steel plates


When one of the following conditions is met and the deformation rate exceeds a certain range, a corresponding heat treatment should be performed after forming to restore the properties of the material.


The thickness of carbon steel and low alloy steel before forming is greater than 16mm;
For carbon steel and low alloy steel, the reduction after forming is greater than 10%;
For carbon steel and low alloy steel, impact test is required for the material.