论文部分内容阅读
我厂在1974～1975年期间,球铁曲轴较脆,皮下气孔也较多。其原因是:由于炉料变动频繁(特别是焦炭含硫高),为保证球化,球化剂由1.5%增至2.2%(占原铁水重量),使含硅量增加。为避免终硅量过高,就减少了炉前孕育硅量,这导致铸态出现大量游离渗碳体。在一般正火工艺后(920±10℃、3小时),金相组织中仍有较多的游离渗碳体,造成了曲轴发脆的质量问题。同时,因球化剂加入量的增大,使球铁的残余镁量达0.08～0.1%,残
I plant in the 1974-1975 period, the ductile iron crankshaft is more crisp, more hypodermic pores. The reason is: due to frequent changes in the charge (especially the high sulfur coke), in order to ensure the ball, nodularization agent increased from 1.5% to 2.2% (the original molten iron weight), the silicon content increased. In order to avoid the excessive amount of silicon, the amount of silicon in the furnace is reduced, which leads to a large amount of free cementite in the as-cast state. After the normalizing process (920 ± 10 ℃, 3 hours), there are still more free cementite in the microstructure, which leads to the brittle quality problem of crankshaft. At the same time, the addition of nodulizer increases the amount of magnesium in the ductile iron up to 0.08-0.1%