Research On Laser Quenching Process Of 2738 Die Steel With Industrial Robot

To avoid premature failure of automotive dies,they can be surface strengthened.Laser hardening can improve the surface hardness of the die while maintaining the good strength and toughness inside the die.It can also improve the fatigue strength,wear resistance,corrosion resistance and impact toughness of the die,and ultimately improve the service life of the die.The main factor influencing these properties is the process parameters of laser quenching.In this paper,2738 die steel is used as research material to study the influence of various process parameters on quenching quality,and a mathematical model within a certain process parameters is built.The main research contents are divided into the following aspects:1)Based on the six-axle flexible production robot of Shanghai Xinshida SR20 and the single-mode continuous optical fiber laser of Zhongkexianwei laser Technology Co.,Ltd,a laser quenching workstation for the robot is built.Formes a optical fiber laser quenching robot with maximum power of 1500 W and its rectangular spot size is 2mm×10 mm.It provides a basic solution for laser quenching of automotive dies.2)The relationship between the spot moving speed and the quality of hardened layer is studied.And the mathematical model of the quenching width and depth is established under the condition that the output power of laser remains unchanged and the spot moving speed changes.The disparity between the predicted value of the hardened layer depth model and the measured value is within 7.43%,and the gap between the predicted value of the hardened layer width model and the measured value is within 3.66%.3)The mathematical model of influence of laser output power P and spot moving speed V on quenching quality is established.The difference between predicted value and measured value of depth D of hardened layer is within 2.08%.The difference between the predicted and measured values of the mathematical model for the width of hardened layer W is within 0.94%.4)When the incident angle of laser beam changes,the change of quenching quality is analyzed,including the size of hardened layer,surface microhardness and section microhardness.The results show that when the incident angle of laser beam changes,the surface hardness of hardened layer is asymmetric with the center of laser beam as the boundary,and the hardness difference is about 100hv0.1.When the incident angle deviation is greater than 8 °,the depth of hardened layer will decrease by 25% ? 49%.The mathematical model of the depth of hardened layer and the two factors of incident offset angle and spot moving speed is established.The error between the predicted value and the measured value is within 7.64%.5)The lapping experiments of hardened layers are carried out.The theoretical analysis and hardness interpolation method are used to analyze theoretical bottom flatness,intuitive micro bottom flatness,surface hardness flatness and uniformity,and section hardness flatness.The overall quality of the two lapping rates is compared.The results show that the theoretical 50%lapping rate hardened layer bottom flatness is better than 30% lapping rate,and the intuitive morphology also proves it.However,the spline interpolation of section hardness shows that the section hardness of 30% lap ratio is more uniform than that of 50% lap ratio.