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我厂对截面尺寸大于25mm的碳钢模具,如T8A钢制凸凹模(150×180×45.5mm),为减少淬火变形和开裂采用碱液分级淬火工艺,淬硬层浅、硬度偏低。采用水油淬火,模具在水中停留时间难于掌握,停留时间过长引起模具变形超差或开裂;停留时间过短产生部分非马氏体相变,硬度偏低。采用氯化钙水溶液淬火法,处理后虽然避免了开裂,但模具缺口处尺寸缩小,表面突起严重。为了避免碳钢模具淬火变形,从减少热应力和组织应力着想,采用了氯化钙——硝盐浴两步淬火法。氯化钙水溶液比重为1.20～1.42,硝盐浴的成分为:50%KNO_3
I plant on the cross-sectional size of more than 25mm carbon steel mold, such as T8A steel punch (150 × 180 × 45.5mm), in order to reduce quenching deformation and cracking using lye quenching process, hardened layer shallow, low hardness. The use of oil and water quenching, the mold in the water dwell time difficult to grasp, stay too long cause mold deformation tolerance or cracking; stay too short to produce some non-martensitic transformation, low hardness. Using calcium chloride solution quenching method, although the treatment to avoid cracking, but the mold at the size of the gap reduction, the surface of the process of serious. In order to avoid quenching deformation of carbon steel mold, from the reduction of thermal stress and stress of the organization, the use of calcium chloride - salt bath two-step quenching method. The specific gravity of calcium chloride aqueous solution is 1.20 ~ 1.42, the composition of the nitrate salt bath is: 50% KNO3