Relief of Residual Stresses in 800 MPa Grade High Strength Steel Weldments by Explosion Treatment and its Effect on Mechanical Properties

The explosion treatment technique has been used in the relief of residual stresses in 800 MPa grade high strength steel manual welded joints. The residual stresses on surface and through thickness of the weldment were measured for both as-welded and explosion-treated sample, the mechanical properties of welded joints under different conditions were also tested. The effect of explosion treatment on the fracture toughness of materials with a residual defect was investigated by crack opening displacement （COD） test. The results show that explosion treatment can reduce not only the surface residual stress but also the residual stress through thickness in the welded joints. The effect of explosion treatment on the mechanical properties and a residual defect in welded joint were inconspicuous.

Study of relieving weld residual stresses in large pressure steel pipes of hydropower station by local explosion treatment

From comparing the test of local explosion treatment(LET)with the locaf heat treatment (LHT)in welded plates and welded steel pipes in field,LET has excellent effect of stress relief and high efficiency. Whereas the effect of stress relief for LHT with 575℃×1.5hr is poor.The mechanical properties of welded joints after LET are basically the same as those of as-welded joints.The practically measuring results on 4 large steel-pipe surfaces indicate that the welding residual tensile stresses in welds,which mostly is compression residual stress,are basically relieved.