Microstrycture And Evolution Of Residual Stress In The Process Of 304 Stainless Steel Made By Arc Additive Manufactuiring

Arc additive manufacturing is a new manufacturing method based on 3D CAD model,which uses layered processing of 3D model and uses arc as heat source to melt the wire.Compared with traditional manufacturing technologies such as casting and machining,arc additive manufacturing technology has a large material utilization rate,which can reduce product production cycle and production cost;it can also be manufactured or repaired under any conditions.Therefore,arc additive manufacture of is highly valued by more and more enterprises and researchers.In this paper,residual stress evolution,microstructure properties and high temperature mechanical properties of 304 stainless steel arc additive manufacturing of different structure are studied.The main research contents are as follows:(1)Additive manufactured by CLOOS robot and narrow gap MIG welding system,conducted the additive manufacturing test of wag arc ring wall and straight wall,the additive manufacturing test of non-wag arc straight wall and ring wall,the arc additive manufacturing test of multi-layer and multi-channel,and obtained well-formed formed components.(2)The finite element model for the temperature field change trend and the evolution of the stress field in the 304 stainless steel arc additive manufacturing process were established based on the simufact.welding software,which was used to obtain the temperature field change during the additive manufacturing process.The arc heating during the arc additive manufacturing process causes partial remelting of manufactured layer.This effect only affects the previous layer,and the heat accumulation effect is less and less obvious as the cladding layer increases.The mises stress rises rapidly to a peak with the heating of the heat source.As the next heat source heats up,it will rapidly drop to a valley.As the next heat source leaves,the mises stress will reach a peak.Due to the heat accumulation effect,the additive manufacturing of each layer will have the effect of heat treatment on the additive manufacturing layer,and the stress value of the additive manufacturing layer is gradually reduced,and finally the temperature is cooled to room temperature as the arc additive is finished.Residual stress is formed afterwards.(3)The residual stress of the 304 stainless steel arc additive manufacturing component is measured,wherein each additive is made into three layers and then cooled to room temperature and then the residual stress is measured based on the blind hole method.As the number of layers increases,the substrate is added.The restraining effect of the manufacturing layer is gradually reduced,so that the residual stress decreases with the increase of the number of layers.(4)The microstructure of the longitudinal section of the 304 stainless steel arc additive was analyzed.The microstructure was mainly composed of austenite and residual ferrite.The microstructure was mainly composed of dendrites with different morphologies.As the number of layers in the arc additive manufacturing increases,the distance from the substrate increases,the cooling rate and temperature gradient of the additive manufacturing layer gradually decrease,and the microstructure morphology changes from cellular ferrite to skeleton ferrite.(5)The microhardness values of the samples prepared by the arc additive were all more than 200 HV,and the microhardness higher than that of the hot rolled 304 stainless steel was obtained.The high temperature tensile test results show that the yield strength of the Z axis is lower than that of the X axis and the Y axis,but the other high temperature mechanical properties are basically the same in the three coordinate directions,wherein the tensile strength exceeds that of the hot rolled 304 stainless steel;...