Fundamental Study on Metal Cutting and Forming under Dry Condition

1.带涂层刀具的干式金属成形为实现无润滑的干式金属成形工艺，研究了某些加工金属在无润滑剂条件下滑动到刀具表面的摩擦行为。结果表明，在干燥条件下，DLC能有效地降低与铝的摩擦。钢表面形成的氧化层在很大程度上提高了摩擦力。摩擦系数受刀具表面粗糙度的影响很敏感，与涂层材料无关。半干条件下摩擦特性的测量采用环压试验法。将少量雾化润滑剂喷洒到抛光到镜面的硬质合金刀具表面，并对纯铝试件进行压缩。结果表明，喷洒少量润滑剂(0.5g/m~2)与不加润滑剂的摩擦相比，减摩效果显著。雾化润滑会在刀具表面形成极小的润滑剂颗粒，并对雾化润滑剂的润滑机理进行了探讨。为了实现镁合金的精密锻造，研究了ZK60(镁-6%锌-0.5%锆)的摩擦行为。在室温下，进行了ZK60在TiC+TiCN+TiN和类金刚石涂层硬质合金刀具表面的摩擦磨损试验。结果表明，DLC涂层能有效地降低摩擦系数，而镁的氧化膜增加了摩擦系数。通过控制油膜厚度，在刀具表面涂抹了几种液体润滑剂，考察了润滑对摩擦的影响。

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.