易开盖用镀锡板开裂原因及改进措施

Cracking Cause of Tin Plate for Easy-Opening Lid and Improvements

某钢厂生产的易开盖用镀锡板在制盖过程中于铆钉处出现开裂,开裂率约为0.08%,低于客户预期质量要求,采用化学成分分析、力学性能测试、显微组织观察、夹杂物分析等方法对其开裂原因进行分析,并提出相应的改进措施。结果表明:易开盖铆钉处发生韧性开裂,铆钉边部存在的大尺寸Al_(2)O_(3)和CaO夹杂物和明显厚度减薄现象分别是镀锡板开裂的直接原因和间接原因。将冶炼过程中的钢包精炼炉(LF)精炼工艺改进为钢液真空循环脱气(RH)精炼工艺后,成品镀锡板内单位面积夹杂物数量为4.7个·mm^(-2),最大尺寸为15.5μm,明显低于工艺改进前的49.8个·mm^(-2)和38.9μm,未发现簇群状大尺寸夹杂物,RH精炼工艺对夹杂物的控制效果较好,同时镀锡板的化学成分、硬度、拉伸性能、显微组织均符合易开盖制盖要求,制盖开裂率降低至0.01%以下。

The tin plate for easy-opening lid produced by a steel factory cracked at the rivet during the lid making process,and the cracking rate was about 0.08%,which was lower than the customer’s expected quality requirements.The cracking reasons were analyzed by chemical composition analysis,mechanical property testing,microstructure observation and inclusion analysis,and the improvements were suggested.The results show that the ductile fracture occurred on the rivets of easy-opening lids.The presence of large Al_(2)O_(3)and CaO inclusions at the edge of the rivets and the obvious thickness thinning were the direct and indirect causes of the lidding cracking of the tin plate,respectively.After the ladle refining furnace(LF)refining process during the smelting process changed to the molten steel vacuum circulating degassing(RH)refining process,the number of inclusions per square millimeter in the finished tin plate was 4.7,and the maximum size was 15.5μm,which were significantly lower than the 49.8 per square millimeter and 38.9μm before the process improvement,and no cluster large inclusions were found,indicating that the RH refining process had a better control effect on the inclusions.The chemical composition,hardness,tensile properties and microstructure with the RH refining process were all met the requirements for easy-opening lids,and the cracking rate of lidding was reduced to less than 0.01%.