Fundamental Study on Metal Cutting and Forming under Dry Condition

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1. Dry Metal Forming with Coated ToolsTo realize dry metal forming processes without lubrication, the frictional behavior of some working metals sliding over tool surfaces without lubricant is studied. It is found that DLC is effective to reduce the friction with aluminum under dry condition. The oxide layer formed on the steel surface raises the friction to a great extent. The coefficient of friction is sensitively affected by the roughness of the tool surface irrespective of the coated material.2. Measurement of Friction in Cold Upsetting with Mist LubricationFrictional behavior under semi-dry condition is measured with the ring compression test. Small quantity of mist lubricant is sprayed onto the cemented tungsten carbide (WC) tool surfaces polished to the mirror surfaces, and the pure aluminum specimens are compressed. It is found that spraying small quantity of lubricant (0.5g/m2) is effective to reduce the friction in comparison with the friction without lubrication. The mist lubrication causes very small dots of lubricant particles on the tool surface, and the lubrication mechanism of mist lubricant is discussed.3. Lubrication and Friction of Magnesium Alloys in Warm ForgingIn order to realize precision forging of magnesium alloys, the frictional behavior of ZK60 (Mg-6%Zn-0.5%Zr) is studied. At room temperature, the friction test of ZK60 sliding over the surfaces of cemented carbide tool with and without TiC+TiCN+TiN and DLC (diamond like carbon) coating is carried out. It is found that the DLC coated film is effective to reduce the coefficient of friction and the oxide film of magnesium increases friction. Several liquid lubricants are applied onto the tool surfaces by controlling the film thickness and the effect of lubrication on friction is examined.