Metallife protects weld stress

Reduce Weld Stress

Residual tensile stress from welding is created because the weld consumable is applied in its molten state. This is its hottest, most expanded state. It then bonds to the base material, which is much cooler. The weld cools rapidly and attempts to shrink during the cooling. Because it has already bonded to the cooler and stronger base material, the weld is unable to shrink. The net result is a weld that is, essentially, "stretched" by the base material.

The heat affected zone is usually most affected by the residual stress and hence where premature failure will usually occur. Inconsistency in the weld filler material, metal chemistry, weld geometry, porosity, etc..., acts as stress risers for the residual and applied tensile stress to initiate die fatigue failure

The graph demonstrates a number of interesting changes in stress levels when welding, thermal stress relieving and after MetaLLife. Tensile stresses generated from welding are additive with applied load stresses. This is why these combined stresses accelerate failure at welded locations.

The top line shows the tensile stresses present as welded. If stress tempering is followed, the material is normalized to have close to neutral properties. As shown a normal stress temper followed by MetaLLife, however, produces the highest level of compressive fatigue resistant benefit

As shown, MetaLLife is extremely beneficial in reversing the residual stress from welding that tends to cause failure. Our recommendation is to make sure that any welded tool is heat stress tempered and then MetaLLife processed to provide the benefits mentioned.