The proper control of distortion after thermal treatment of powertrain components in the automotive industry is an important measure to secure a high part quality and to minimize subsequent hard machining processes, thereby reducing the overall production costs. Vacuum carburizing (low pressure carburizing) with subsequent high pressure gas quenching represents an innovative heat treatment technology to reduce the distortion in surface hardening processes. Vacuum carburizing is offering a high carbon transfer, which leads to a reduction of process time compared with atmospheric gas carburizing. The use of oxygen-free hydrocarbons prevents surface oxidation on the part surface. High pressure gas quenching is a dry quenching method and has many important ecological and economical advantages compared with liquid quenching. The most significant advantage of gas quenching is a very uniform heat transfer. The predictability of movement during quenching is more certain and uniform throughout the load, thereby reducing hard machining costs. Further improvements can be achieved by using "Dynamic Quenching" processes where the quenching severity is varied during quenching by stepwise control of either gas velocity or gas pressure. Proper fixturing is another factor to control the distortion of the parts. Modern carbon composite materials are well suited for gas quenching due to their good high temperature deformation resistance combined with low thermal mass. To carry out vacuum carburizing with high pressure gas quenching in a cost-effective way, furnace systems are available which guarantee a high throughput and can be sized to various process and production demands.
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