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我厂活塞销采用RJJ—90—9T井式气体渗碳炉渗碳,多年来一直存在着渗碳后高温出炉入缓冷坑冷却中活塞销氧化脱碳问题,工件外圆渗碳层碳浓度不足,淬火时引起软点、软块,金相组织为粗针状马氏体。要保证渗碳的活塞销不氧化、不脱碳,渗碳层均匀,必须有确实可行的工艺来实现。 一、活塞销渗碳后氧化、脱碳的原因 活塞销渗碳后氧化、脱碳,其主要原因是井式气体渗碳炉在打开炉盖装出炉时,有大量冷空气进入炉内,活塞销和料篮同时带入水汽,加上煤油燃烧时产生大量的二氧化碳,使活塞销在升温时表面就已形成氧化皮。曾做过试验,在活塞销出炉时,一升起炉盖就迅速把活塞销投入清水中,可看到销子表面有一层氧化皮剥落下来。
I plant piston pin RJJ-90-9T gas carburizing carburizing furnace carburizing, over the years there has been carburizing high temperature baked into the slow pit cooling piston pin oxidation decarburization, the workpiece carburizing carbon concentration Insufficient, causing soft point quenching, soft block, microstructure as coarse needle-like martensite. To ensure that the carburizing piston pin is not oxidized, not decarburization, carburized layer uniform, there must be a viable process to achieve. First, the pin after pin carburizing oxidation, decarburization reasons Piston pin carburizing oxidation, decarburization, the main reason is that pit-type gas carburizing furnace open the lid furnace, a large number of cold air into the furnace, the piston Pins and baskets are brought into the water vapor at the same time, and when the kerosene is burned, a large amount of carbon dioxide is generated, so that the surface of the piston pin is oxidized when it is heated. Had done the test, when the piston pin out of the furnace, a rising lid quickly put the piston pin into the water, you can see the pin surface has a layer of oxide flake off.