水及其盐碱溶液和机油是目前普遍应用的淬火介质。它们都各具优缺点,水在低温时冷却能力过于激烈,油在高温时冷却能力过弱,因此水油淬火介质都不够理想。我厂生产的塔式起重机的轴、销多以中炭低合金钢40Cr 为主,其形状,尺寸变化较大。原热处理工艺:用 RJX—15—9型箱式电阻炉加热到840～860℃保温1小时,在机油中冷却。检查结果,硬度只有 HRc30—40,而且很不均匀(图纸要求 HRc40～50)。第一次工艺改进,将冷却介质改为10%食盐水,结果大部分工件在直角处开裂而 Water and its saline solution and oil are currently widely used quenching medium. They all have their own advantages and disadvantages, the cooling ability of water is too intense at low temperature, the cooling capacity of oil is too weak at high temperature, so water and oil quenching medium are not ideal. I plant crane shaft production, sales and more low-carbon steel 40Cr-based, its shape, size, larger changes. The original heat treatment process: RJX-15-9-type box-type resistance furnace heated to 840 ~ 860 ℃ insulation 1 hour, cooled in the oil. Check the results, only HRc30-40 hardness, and very uneven (drawings require HRc40 ~ 50). The first process improvement, the cooling medium is changed to 10% salt water, most of the workpiece as a result of cracking at right angles