Research And Device Development For Reducing Welding Residual Stress Based On High Pressure Water Jet Method

Residual stress will inevitably occur in metal components due to non-uniform heating during welding.The existence of residual stress in welding has a great impact on structural integrity.However,the current methods of eliminating residual stress after welding are difficult to eliminate the residual stress at the dead corner of large weldments,which often results in the failure of welding equipment.High pressure water jet strengthening is a novel surface cold processing technology,which is not affected by the shape and position of welded parts.It is easy to strengthen the complex and narrow surface of parts.Moreover,it is green and pollution-free,which can make up for the shortcomings of traditional technology.It is a strengthening method with high research value and prospects,which may reduce or eliminate welding residual stress.Therefore,it is of great significance to study high pressure water jet technology to reduce welding residual stress.The main contents and conclusions of this paper are as follows:(1)In order to verify the feasibility of reducing welding residual stress by high pressure water jet strengthening,a portable high pressure water jet strengthening device is built in this paper.The strengthening device redesigns the nozzle and free-steering sprinkler system suitable for water jet strengthening,and combines the nozzle system with the wall-climbing trolley which can be adsorbed on the surface of steel structure and can walk straight.It can realize the automatic strengthening operation at high altitude for metal structures such as large pressure vessels,which is not limited to the position and structure of the weld seam and greatly improve the work efficiency.It provides a reference for industrialized application of high pressure water jet strengthening technology.(2)In order to explore the actual effect of high-pressure water jet strengthening,the high-pressure water jet strengthening test was carried out.In this paper,the residual stress of Q345 R steel welded joint before and after high pressure water jet impact was measured.The distribution of residual stress field after welding and after water jet strengthening was obtained.It was found that high pressure water jet strengthening can effectively reduce the welding residual stress,in which the maximum decreases of longitudinal and transverse residual stresses are 86.1% and 84.1% respectively.(3)In order to further explore the relevant laws of high pressure water jet in reducing welding residual stress,the finite element simulation of internal and external flow field of nozzle,welding process and water jet strengthening process was carried out by using finite element software FLUENT and ABAQUS,respectively.The characteristics of the jet flow field inside and outside the nozzle,the distribution of the impact pressure of the jet on the target surface,the welding temperature field,the welding residual stress field and the residual stress field after the action of the water jet were obtained.By comparing with the experimental data,the validity of the finite element simulation of water jet strengthening is verified.It is further proved that the high pressure water jet technology is a process which can effectively reduce the welding residual stress.