Study On Ultrasonic Rolling Surface Strengthening Technology Of H13 Die Steel

Ultrasonic Rolling（USRP）is an emerging surface nanotechnology which can significantly improve workpiece and surface properties.In order to solve the problem of time-consμming and laborious manual polishing of H13 mold steel,the effect of ultrasonic rolling treatment on the surface properties of H13 mold steel was studied,and the feasibility of adopting ultrasonic rolling process instead of polishing process was explored.In this paper,HK30C Huayun Haokeng metal surface processing equipment manufactured by Shandong Huayun Electromechanical Technology Co.,ltd.was used to conduct ultrasonic rolling processing of H13 mold steel.The microstructure of the surface layer of processed samples was analyzed by means of dof digital microscope;X-ray stress analyzer was used to measure the residual stress along the surface of the sample,and compared with ANSYS analysis results;the surface roughness was measured by the surface roughness tester;Vickers hardness tester was used to measure the surface hardness of samples before and after rolling.The main results of this paper are as follows:（1）ANSYS finite element simulation analysis shows that after ultrasonic rolling surface treatment,residual compressive stress exists on the surface of H13steel,and the compressive stress distribution is relatively close,which decreases with the deepening of the sample depth.Through residual stress measurement,the residual compressive stress of-671.3 MPa does exist on the surface of the actual sample,which is consistent with the simulation results;（2）After ultrasonic rolling surface treatment,the surface of H13 mold steel forms a smooth surface,the surface quality is improved,and the surface roughness is reduced from 1.024μm to 0.065μm after finishing machining;（3）After ultrasonic rolling surface treatment,the surface grain of H13 mold steel was refined,and the surface grain diameter was refined from 2μm to 0.44μm,showing a small fragmentation.With the deepening of depth,the degree of grain refinement slowed down.When the grain reached a certain depth,the grain was close to the untreated H13 mold steel;（4）After ultrasonic rolling surface treatment,Vickers hardness on the surface of H13 mold steel increased from an average 554.86 HV₂ to 613.18 HV₂,and the improvement of hardness was mainly due to the combined effect of machining hardening and grain refinement;（5）From the experimental analysis of friction coefficient,wear amount and wear morphology,it is concluded that ultrasonic rolling treatment can improve the wear resistance of H13 die steel surface;（6）According to the crack fracture test,the common sample broke after 27,431cycles,while the ultrasonic rolled sample broke after 849,596 cycles.Compared with the crack fracture and a-n curve,the fatigue strength of ultrasonic rolling samples is higher than that of ordinary samples.