Optimization Of Grinding-hardening Parameters With Large Plane

Grinding-hardening is a new technology which utilizes the heat and mechanical composite effects generated in grinding to quench the surface of steel directly with a fast cooling.It can reduce the investments of human resource and equipments in heating process, and also can cut down the energy consumption and pollution.Therefore it will play an active role in the balance of nature.But in the process of grinding-hardening with large plane, the wheel needs horizontal feeding intermittently, between the adjacent grinding junction there exits a hardness area called "softening zone", which will affect the wear resistance of entire surface.Firstly, this paper gave a brief introduce to the grinding-hardening with lager plane, using the theory of mental heat treatment, grinding principle, heat transfer and mental material science.Then, based on the single factor experiment and orthogonal experiment, it studied the influence of grinding parameters and wheel overlap to hardened layer, microhardness and microstructure,using a laser scanning microscope, a microhardness tester and some other related equipment.Lastly, it performed a numerical simulation of grinding temperature field. The main points of this paper are as follows:(1)The distribution of microstructure in the transverse section: when the wheel overlap Cr≤1mm, it includes the first hardened zone, the first transition zone, unquenched zone, the second transition zone and the second hardened zone; when the wheel overlap Cr >1mm, it contains the the first hardened zone, the tempered zone, the second transition zone, wheel overlap zone and the second hardened zone. The distribution of microstructure in the depth direction: both the first grinding zone and the second grinding zone include the hardened zone, the transition zone and workpiece substrate.(2)In the transverse section of specimen, there exits a hardness area which is between two grinding zone called "softening zone". In the depth direction of specimen, the hardness curve of two grinding area can be divided into three parts:the high hardness area, the degressive hardness area and the low hardness area.(3)The results of the single factor experiment show that, with the increase of grinding depth or the decrease of workpiece feeding speed, the width of softening zone increased accordingly.But when wheel overlap increased, the width decreased firstly, and then increased. The orthogonal experiment concluded that the affecting order of various factors on the width of softening zone is: workpiece feeding speed(vw) > wheel overlap(Cr) > cutting depth(ap). Theoptimal parameters for grinding is: vw = 0.8m/min, Cr =1mm, ap =0.1mm.(4)The thickness model of hardened layer is established.The relationship between softening zone and grinding parameters or wheel overlap has been given.(5)Simulation of grinding-hardening temperature field has been taken by using ANSYS analysis software, it also forecast the thickness of hardened layer.