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一、前言由我厂生产的GCr15滚珠钢,拉成φ3mm钢丝后,提供给用户单位磨制φ3mm小滚珠,其加工工艺的流程为:首先将φ3mm钢丝切成长度为3.5mm圆柱体,经镦粗后磨成φ3mm小滚珠,然后经860℃油淬再酸洗。酸洗后发现一个炉号有一批小滚珠在一定的轴向两端,存在着非常对称的两个小黑点,在1万粒中约占15％左右。这两个小黑点是怎样形成的?为什么如此对称?而且又不是全部滚珠都有?为查明原因,特做了以下观察及分析。二、分析步骤 1.金相观察首先将数个具有黑点的滚珠镶嵌成金相试样,沿两个黑点连线的平行方向研磨抛
First, the foreword GCr15 ball steel produced by our factory, pulled into φ3mm steel wire, provided to the user unit mill φ3mm small ball, the process of processing: First φ3mm wire cut into a length of 3.5mm cylinder, upsetting Rough grinding into φ3mm small ball, and then quenched by 860 ℃ acid pickling. After pickling found a number of small balls in a certain number of axial ends, there are two very symmetrical black spots, accounting for about 15% of the 10,000. How these two black spots formed? Why so symmetrical? And not all the balls have? To find out the reason, made the following observations and analysis. Second, the analysis steps 1. Metallographic observation First of all, with a few black ball inlaid mosaic specimen, along the parallel connection of two black spots polishing