What kind of internal stress is residual stress?

According to the size of the scope of action, it can be divided into three categories:

The first type of internal stress (also known as "macro stress") runs through the entire interior of the object;

The second type of internal stress exists inside a single grain, and when this balance is disrupted, the grain size changes;

The third type of internal stress refers to the interaction force between atoms.

2 categories of residual stress

Residual stress is the engineering name for the first type of internal stress.

The root cause of residual stress formation

Microscopically, the change in the interaction force between atoms caused by the inhomogeneity of material composition or structure caused by different atoms or different arrangements of the same atoms is reflected on the macroscopic level.

Which forming processes cause residual stress?

Casting, forging, welding, spraying, and various types of machining will cause residual stress in the material.

Welding residual stress control method

Process measures and methods in the manufacturing process

Adopting process parameters, welding methods and forced cooling measures with low line energy

Use reasonable welding sequence and direction to adjust residual stress distribution

1) Weld the weld with large shrinkage and the weld with large stress first;

2) When the welds intersect, first weld the short weld, and then weld the straight through long weld;

Take technological measures to reduce the restraint of the weld to compensate for the shrinkage of the weld;

Hammer the layers in the middle of the multi-layer weld to extend it and reduce the stress and restraint;

Pre-stretch to compensate for weld shrinkage (mechanical or thermal)

Local heating to form deformation in the corresponding part of the component that can compensate for the shrinkage of the weld;

Low stress deformation free welding method

Methods of Eliminating Welding Residual Stress

1) The use of mechanical force or impact energy is divided into welding seam rolling method, mechanical stretching method, hammering method, vibration method, and explosion method.

2) Heat treatment of overall high temperature annealing, local high temperature annealing, temperature difference stretching method (low temperature stress relief method), pseudo-welding heating method.