灰铸铁件加工面麻点状小孔缺陷的分析及防止灰铸铁件加工面麻点状小孔缺陷的分析及防止.pdfVIP

缺 Defects and Countermeasures 陷 与 对 策 灰铸铁件加工面麻点状小孔缺陷的分析及防止 许德隆 （中国北车集团 大连机车车辆有限公司，辽宁 大连 116021） 摘要：采用金相方法对HT300 铸件加工面麻点状小孔缺陷的形貌、分布特征和产生原因进行了分析。认为：麻点是由许 多尺寸在0.3 mm 以下的小孔组成，多产生在凝固过程中冷速较慢的厚壁部位，主要分布在石墨密集区域，特别是在石 墨封闭或半封闭区域；铸件w （C）和w （Si）量偏高，凝固过程中局部冷速过慢，切削用量偏大都有可能引起这种缺陷。提 出了预防这种缺陷的四条措施。 关键词：麻点状小孔缺陷；石墨剥落；预防措施 中图分类号：TG251 文献标识码：A 文章编号：1003－8345 （2009）06－0082－07 Analysis and Prevention of Pocked Spots Defect on Cutting-Machined Surface of Gray Iron Casting XU De-long （Dalian Locomotive and Vehicle Co. Ltd., China North Vehicle Group Co. Ltd., Dalian 116021, China） Abstract: By using metallographic method, the morphology, distribution feature and formation reason of the pocked spots- shaped pinholes on the machined surface of HT300 grade gray cast iron casting was analyzed. It was considered that the pocked spots are actually many small pinholes sized less than 0.3 mm, they are normally existing in the heavy section area which cooling relatively slowly during solidification process, and mainly in the graphite-dense area, especially in the area enclosed or nearly enclosed by graphite. This type of defect may be caused by too high w （C）and w （Si）of casting, too slow cooling of local area and too big cutting feed. Four measures were proposed to prevent this type of defect. Key words: pocked spot-shaped pinholes defect; graphite scaling off; prevention measures 灰铸铁的切削加工表面时常出现麻点缺陷， 肉眼观察为小黑点的缺陷，实际是形态各异的小 孔，因而易被误认为是表面缩松或是非金属夹杂 物。这种缺陷比较容易出现在HT300 以下的各 种牌号铸件，产生部位多在凝固过程中冷速较慢 的厚壁部位。