Basic Research On The Effect Of Laser Quenching On The Surface Properties Of 45 Steel

45 steel has become one of the preferred materials for manufacturing shaft parts and transmission parts（such as gears）due to its good toughness,plasticity and high strength.However,the hardness of 45 steel itself is lower than other high hardness alloy steels,which seriously affects the economic value of 45 steel.The laser irradiation on the surface of 45 steel can make the surface of 45 steel heated and quenched so as to improve the hardness of 45 steel.On the basis of maintaining good cutting performance and mechanical properties of 45 steel,the wear resistance of 45 steel is improved,so as to significantly improve the economic value of 45 steel.Due to the comprehensive influence of various factors,it is difficult to accurately grasp the specific changes of laser phase transformation hardening layer through experiments.In this paper,the temperature field of 45 steel surface during laser quenching was simulated and analyzed by ANSYS software.Through changing the laser process parameters,the change law of temperature field of 45 steel specimen surface in the process of laser quenching was studied,and the depth and width of hardened layer were predicted by the temperature field results.The CO₂ laser was used to conduct the laser quenching experiment on the surface of 45 steel specimen to verify the accuracy of the numerical simulation results,and the hardness change of 45 steel specimen after laser quenching was measured by a hardness tester.Through research and analysis,the following conclusions are drawn:（1）The depth and width of hardened layer on the surface of 45 steel specimen was proportional to the laser output power,and inversely proportional to the laser scanning rate and spot diameter.The heat absorbed by the laser beam on the surface of the specimen during quenching was mainly transmitted to the matrix along the depth direction of the layer,and the heat conduction along the direction perpendicular to the laser scanning was relatively slow.（2）After laser quenching,the hardness of the hardened layer of 45 steel specimens is basically between 550～800HV,and the microhardness decreases rapidly with the increase of depth.After that,the microhardness is basically maintained between220～230HV and the matrix hardness is basically the same.It is found that the surface hardness of 45 steel specimens is significantly increased by 2.5～3.5 times,which is equivalent to the original hardness of the matrix.（3）The width and depth of the hardened layer obtained from the laser quenching simulation analysis on the surface of 45 steel specimen are basically the same as those obtained from the experiment,but there are still some errors,and the accuracy of the analog simulation value needs to be further improved.