Vibratory stress relieving – it’s advantages as an alternative to thermal treatment

The aim of this study was to investigate the use of vibration to reduce the residual stress resulting from the welding process. Butt weld joints were subjected to vibration immediately after welding. The existing methods for relieving residual stress from welds are: mechanical, heat and electromagnetic. The mechanical method may be performed by hammering or vibration. The heat method consists of heating the whole welded piece or each weld, one by one. The electromagnetic method uses the electromagnetic hammer technique. In the heat treatment the part is heated until the yield point is reduced to less than the residual stress, which in turn causes local plastic distortion, decrease of the residual stress intensity and reduction of hardness. The vibration method introduces energy into the part by means of vibrations. For the stressed atomic structure there is no difference between the energy introduced through heat and the energy introduced through vibrations. The applied energy reorganizes the crystalline structure, relieving stress and stabilizing the piece, without distortion [1]. The article deals with reducement of welding stresses with the help of vibration treatment and to compare it with the classical heat treatment. The experiments were performed by a welding of structural low-alloy steel 16GS plates. Therefore the result is submitted by the mechanical tests and metal magnetic memory control. Several specimens, after welding and vibrotreatment, were cut off the welded plates and submitted for tensile, impact, hardness tests and metallographic analysis. The specimens, which were treated by vibration treatment, had strength and elasticity properties changed similarly as after the heat treatment. The metal magnetic memory test shows that this control method is suitable for evaluation of residual welding stresses variations after the weldment’s treatment