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众所周知,钢板弹簧的脱碳层,将影响它的疲劳强度。脱碳层的深浅不一,影响也有所不同。按国家标准规定,汽车钢板弹簧热处理后的脱碳层,每边不得超过其板厚的3％。在生产中脱碳层深度的测定,已成为重要检验项目之一。检查脱碳层深度的常规方法,是金相法。但这种方法须破坏产品,而且也比较麻烦,在现场应用中有局限性。用本文介绍的洛氏硬度法测定汽车板簧的脱碳层,不用剖切产品,迅速方便,且可同时得到三个参数:表面硬度(即脱碳层的硬度)、脱碳层深度和脱碳层下面的硬度。根据这三个参数,在实际生产中,还可判断淬火、回火后的工件硬度低的原因,是由于脱碳还是由于工艺操作中的温度不够(或保温时间不足)造成的。现将这种方法介绍于下。
As we all know, decarburization of leaf springs, will affect its fatigue strength. The depth of decarburization layer, the impact is also different. According to the national standard, the decarburized layer after heat treatment of automobile leaf spring shall not exceed 3% of its thickness on each side. Determination of the depth of decarburization in production has become one of the important inspection items. The conventional method of examining the depth of the decarburized layer is the metallographic method. However, this method must destroy the product, but also more troublesome, there are limitations in the field application. Using the Rockwell hardness method described in this article to determine the decarburized layer of automobile leaf spring, it is quick and convenient without cutting the product. And three parameters can be obtained at the same time: the surface hardness (the hardness of decarburized layer), the depth of decarburized layer and off Hardness under the carbon layer. According to these three parameters, in actual production, but also determine the hardness of the workpiece after quenching, tempering low due to decarbonization or due to the temperature in the process of operation is not enough (or lack of holding time) caused. Now this method is introduced below.