Ive been doing wps(s) for companies for about 2 years now and there's a section in there for "type of peening used" and I have never once filled it out. I was wondering what industry its normally used in.

DEFINITION OF PEENING: Peening is a cold working process in which the surface of the component is deliberately deformed, in the basic method, by hammering. During peening, the surface layer attempts to expand laterally but is prevented from doing so by the elastic nature of the sub-surface, bulk material. This results in the development of beneficial, compressive residual stresses in the surface layer, which are balanced by tensile residual stresses elsewhere

Peening is generally used in an attempt to reduce the residual tensile stresses by mechanically deforming the weld. The deformation of the weld requires sever mechanical work. The mechanical work induces compressive stresses in the weld, thus relieves the tensile stresses. However, the bulk of the distortion is due to sharp thermal gradients between the weld, HAZ, adjacent base metal, and the surrounding base metal that experiences little temperature increase from the welding operation.

Generally speaking, any carbon steel or high strength low alloy steel that experiences a 220 degree F temperature increase can result in plastic deformation if the surrounding base metal is held to a lower temperature. Since the cooler base metal acts as restraint, the base metal that experiences temperature increases greater than the delta "T" of 220 degrees F will experiences plastic deformation. That deformation is the distortion attributed to the welding operation.  It is the thermal gradient that is the problem. That is why preheat can reduce the total distortion if the entire component is preheated to a temperature well above ambient.

We put the same theory to use when we use heat to camber a beam or use heat to straighten a member that is already distorted. Confining the heating operation to a defined area to increase the thermal gradient between the heated region versus the unheated regions enhances the amount of distortion resulting from the cambering/straightening operation. I often clamp angles to the member being heated and pack the back side of the angles with wet rags to confine the heating to the specific area being heated.

The temperature to which one heats the steel can be limited to 800 or 900 degrees F if one is concerned with changing the mechanical properties of the carbon or high strength low alloy steel. The member still moves at those temperatures and the temperature is still below the temperature at which there is the potential to damage the properties of the steel.

Best regards - Al