Study On Distribution Of Residual Stress Of Single-layer Fuse-adding And Elimination Of Stress By Hammer Peening

The working environment of hot forging dies is very bad.Under the long-term action of repeated high temperature,high load and alternating stress,the surface strength and wear resistance of hot forging dies will be reduced.At the same time,fatigue failure and even crack formation will occur,which seriously affects the service life of hot forging dies.Therefore,it has great research value and academic significance to study the crack repair technology and residual stress elimination technology of hot forging die to improve the life of hot forging die.For this reason,the numerical simulation analysis of single-pass and multi-pass surfacing of 45 hot-working die steel sheets was carried out,and the variation law of temperature field and stress field during surfacing process was studied and analyzed.Then,the finite element model of hammering with welding is established,and the influence of hammering process parameters on residual stress of surfacing parts and the relieving stress degree are explored,and the hammering process parameters are optimized.Finally,the experiment of surfacing 45 hot-working die steel plate is carried out,and the residual stress of surfacing parts is tested by the small hole method,which verifies the accuracy of the numerical simulation results.The numerical simulation provides certain data support and reasonable hammering scheme for surfacing repair of actual hot forging die.The main contents and conclusions of this paper are as follows:1.The finite element model of single-layer single-pass and single-layer multi-channel surfacing of 45 hot work die steel was established by ABAQUS finite element analysis software.The temperature and stress fields of the surfacing part in single-layer single-channel and single-layer multi-pass surfacing process were analyzed.The temperature and stress fields of surfacing parts always change with the welding process.The residual stresses on single-layer multi-pass surfacing weldments are asymmetrically distributed along the vertical weld direction and symmetrically distributed along the parallel weld direction at room temperature.Subsequently,surfacing experiment of 45 hot working die steel plate was carried out,and residual stress was measured by small hole method.By comparison,the simulation results of residual stress of single pass welding and multi-pass welding are basically consistent with the actual results.2.The finite element model of single-layer single-pass welding with 45 hot work die steel was established by ABAQUS finite element analysis software.The effects of hammering process parameters(hammering intervening temperature,hammering pressure and hammer head vertical moving speed)on the residual stress of surfacing parts and the degree of relieving stress were studied and analyzed.The results show that the hammer penetration temperature has a great influence on the distribution of residual stress,followed by the hammer pressure,while the vertical velocity of hammer head has a little influence on the residual stress of surfacing parts when hammering at low temperature.3.Design-expert software was used to design a set of single-layer single-pass surfacing hammering experimental scheme,and the numerical analysis of surfacing was carried out according to the experimental scheme.Then the hammering parameters of single-layer single-pass surfacing were optimized by multi-objective particle swarm optimization,and the optimal combination of hammering parameters was obtained(hammering intervention temperature 750?,hammer head vertical moving speed 2000 mm/min and hammering pressure 0.1MPa).The lateral and longitudinal residual stresses obtained by the optimal hammering parameters combination are 16.71% and 14.26% lower than those without hammering,respectively.4.The finite element model of single-layer and multi-pass hammering of 45 hot-working die steel sheet was established by using Abaqus finite element analysis software,and the optimum parameters of single-layer and single-pass hammering were used to hammer.The influence of horizontal distance of hammers on the residual stress of surfacing parts was studied and analyzed.The results show that the smaller the moving distance of hammer head is,the more obvious the effect of hammering on eliminating residual stress is.