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我厂生产的阀体、阀盖铸件,材质HT20-40,阀体重44～460kg,阀盖重10～265kg。曾有一段时间炸裂缺陷较为严重,通过用QC方法基本解决了这一问题。根据废品分析,原材料中所含的合金元素是产生炸裂缺陷的主要原因。原材料化验结果为:V 0.264%、Ti 0.002%、Cr 0.203%。从铸件上取样,经金相检查,石墨分布形态为E型和C型,其中E型占60%左右,石墨长度为4.5和18,基体组织为细片状珠光体,珠光体量约占98%。由于铬是强烈阻碍石墨化的元素(钒也是强烈阻碍石墨化的元素),促使石墨形成树
I plant the valve body, bonnet castings, material HT20-40, valve body weight 44 ~ 460kg, bonnet weight 10 ~ 265kg. There have been some serious burst defects, through the use of QC method basically solved this problem. According to the scrap analysis, the alloying elements contained in the raw materials are the main cause of the burst defects. Raw material test results: V 0.264%, Ti 0.002%, Cr 0.203%. Samples were taken from the castings and examined by metallography. The distribution of graphite was E and C, with Type E accounting for about 60% and graphite length being 4.5 and 18, with finely lamellar pearlite matrix and pearlite content of about 98% %. Since chromium is a strongly hindered graphitizing element (vanadium is also an element that strongly hinders graphitization), a graphite-forming tree is urged