Study On Mechanism And Experiment Of Single-pass Surface Grind-hardening Technology

A new technology called grind-hardening utilizes grinding heat to induce martensitic phase transformation and strengthen the surface layer by raising surface temperature higher than austenitic temperature and cooling quickly. Grind-hardening integrate surface heat treatment process and grinding into one production line, which can decrease manufacturing cost, improve machining efficiency, and reduce production time. The grind-hardening theory and mechanism are studied to establish the basis of grind-hardening application.The mechanism between grind-hardening parameters and grind-hardening results is analyzed deeply on the basis of experiment. The grinding force ratio in grind-hardening consists with the grinding force ratio in grinding quenched steel, and is bigger than the grinding force ratio in grinding unquenched steel. The effect of grinding depth on work piece surface hardness and hardness layer depth is important factor. The hardness layer depth is reduced with the table speed increasing, but the surface hardness of work piece rises appreciably. The hardness layer depth of grinding entrance area is thinner than the one of grinding middle area and grinding exit area. The hardness layer depth of grinding middle area is uniform. The hardness layer depth of grinding exit area is thicker than the one of grinding middle area and grinding entrance area.The grinding wheel wear after grind-hardening is studied deeply. The mechanical wear of abrasive is showed because the hardness of chromium alloy particle in work piece is more rigid than the one of abrasive. There is stress crack on the wear flat. The unfreezing abrasive dusts adhere to the abrasive surface and improve the grinding wheel wear. The high inner stress of abrasive for alternating thermal and force induces abrasive fracture and crash. Grinding wheel loses the capability of accommodating dusts because big pieces of abrasive dusts and unfreezing abrasive dusts adhere to the abrasive interspaces.The probability statistical method is used to study the abrasive distribution in the grinding arc area. The calculation models of abrasive cut-in depth, the contact radius between abrasive and work piece, the radio between real contact area of abrasive and work piece and geometry contact area of grinding wheel and work piece are analyzed and set up. Then the preliminary parameters are offered to calculate energy partition of work piece in grind-hardening.