氮气孔的产生及预防

Formation and Prevention of Nitrogen Fissure

介绍了铸件N2气孔缺陷的形状特征:通常发生的区域面积比较大,且比较分散,呈贯穿孔形式;分析认为N2气孔产生原因是:凝固过程中铁液温度降低时,N2在铁液中的溶解度降低,当N2析出不能及时排出时,就会在铸件内部形成N2气孔缺陷;N2的来源为铁液、空气和型芯材料。防止措施有:降低废钢使用量;采用优质增碳剂;降低有机树脂粘结剂中的w(N)量;提高CE及Si/C比;加入合金中和;采用含有Fe2O3的涂料。

The shape and characte ristics of the nitrogen fissure were described as following： the defects area was normally quite big, the defects distributed dispersedly and often appeared as perforated holes. The reason causing nitrogen was analyzed as： with temperature decrease in the solidification process the solubility of nitrogen in the iron melt reduced that led to the nitrogen separated from the melt as the gas morphology, and if it couldn＇t be expelled from the meh in time, it would form the fissure defect in the casting. The source of the nitrogen may the iron melt, air and core-making materials. The nitrogen fissure normally can be prevented by adopting following measures： reducing steel scrap amount in the melting charge; using hi-quality recarburater; reducing the nitrogen content of the resin binder; increasing CE and Si/C ratio; adding alloy to neutralize the nitrogen; using Fe2O3-containing coating.