Study On The Effects Of Laser Surface Quenching Upon The Microstructures And Properties Of Steel Wire Cutter

Laser quenching,which uses laser as the heat source,is a kind of surface hardening technologys.The surface of the material is rapidly heated to the austenitizing temperature range by the laser beam and then is cooled at a rapid speed,which realizes phase transformation and quenching strengthen.The quickly change of temperature is due to the conduction of heat from the surface to the base metal.Steel wire cutter is widely used in the printing and packaging industries as a die cutter.And the existing preparation process of steel wire cutter has many problems,such as high pollution,high energy consumption and low production efficiency.So the purpose of this study is seeking optimal laser quenching process of steel cutting body and cutting edge.Firstly,the laser quenching parameters of cutting body and edge were optimized through the combination of finite element temperature field analysis and experiments.The influences of laser power,scanning speed and defocusing amount on the microstructure,hardness and impact toughness were studied.After that,artificial neural network and genetic algorithm were used to model the process of laser quenching of cutting body.And the better parameter combinations were obtained.The results showed that:(1)The effects of single-pass laser and over-lap laser quenching on the microstructures and properties of steel wire cutter were studied.In the single laser quenching test,the microstructure of the quenched zone mainly consists of three parts:the original tissue zone,the heat affected zone and the quench hardening zone.The originally organized zone consists of ferrite and cementite.The heat affected zone consists of acicular martensite and unmelted carbide.Quenching hardened zone is formed of acicular martensite.The hardness of hardened zone increases with the increase of laser power,increases first and then decreases with the increase of scanning speed,and decreases with the increase of defocus amount.Under the optimum laser process parameter(laser power is 800W,scanning speed is 40mm/s,defocus amount is 80mm),the micro-hardness of cutting body is 382.2HV0.2,which compared with the commercially available steel wire knife blade microhardness increased 12.4%,at the same time,the uniformity of the organization has greatly improved.Impact toughness is 35.36J/cm2,which is close to the commercial standard.The softening zone of the over-lap laser quenching test is composed of tempered martensite and tempered sorbite.And the optimum overlap ratio is 10%.Under this parameter,the entire surface of the blade body can be quenched.(2)For the cutting edge part,the microstructure of the quenching zone is acicular martensite.The microhardness of quenching zone increases with the increase of laser power,increases first and then decreases with the increase of scanning speed Under the optimum process parameters(laser power is 150W,scanning speed is 1600mm/min,defocus amount is 50mm),the microhardness is 610.2HV0.2,which is 19.6%higher than the market standard.(3)The optimum laser quenching parameters(laser power is 853W,scanning speed is 44mm/s,defocus amount is 86mm)were obtained through the artificial neural network coupled with genetic algorithm.The predicted microhardness was 390HV0.2,which coincided well with the experimental result 393.6HV0.2 And the test results compared to the best parameters obtained before increased 3%.