Post-weld heat treatment to eliminate stress

Post-weld heat treatment to eliminate stress

The welding residual stress is caused by the uneven temperature distribution of welding parts and the thermal expansion and cold contraction of welding metal, so the welding construction will inevitably produce residual stress.

The most common method to eliminate residual stress is high temperature tempering, the weldment in heat treatment furnace heated to a certain temperature (below Ac1) and heat preservation time, using the material yield limit under high temperature is reduced, the internal stress of high local produce plastic flow, elastic deformation gradually reduce, plastic deformation gradually increase and reduce stress.

The influence of post-weld heat treatment on tensile strength and creep limit of metal is related to the temperature and holding time of heat treatment.

The effect of post-weld heat treatment on the impact toughness of weld metal varies with different types of steel

Stress relief method, electrical heating

The heating element USES the resistance heat generated when an alternating current of power frequency (50 ~ 60 hz) passes through the element to heat the workpiece.

Electric heating elements are usually arranged around or on both sides of the heating room to ensure uniform temperature in the heating room.

There are also elements in a radiation tube to indirectly heat the workpiece.

For outer hot salt bath furnace or metal bath furnace, the heating element is arranged in the space outside the crucible and inside the shell.

This heating method can also be used in a floating particle furnace for alumina particles.

It is suitable for the whole workpiece heating and sufficient electric power area.

Workpiece resistance after heating the alternating current directly through the workpiece resistance, the workpiece itself resistance produces heat to increase the temperature of the workpiece.

This method is suitable for the integral heating of workpiece with uniform cross section.

Another way is to use the rolling copper wheel to press on the metal workpiece, through the alternating current of low voltage and large current, using the contact resistance between the copper wheel and the workpiece to generate heat and heat the surface of the workpiece.