球铁转向节的白口和反白口缺陷

Chill and Reverse Chill Defects of Nodular Iron Knucle

白口和反白口缺陷是球铁件转向节的常见缺陷。引起白口的主要原因是随流孕育量不足以及铸件局部冷却速度过快;防止措施是确保足够的随流孕育量,提高浇注温度。引起反白口的主要原因是残余镁量,特别是残余稀土量过高,防止措施是采用稀土含量较低的球化剂,提高球化处理温度和浇注温度。

Both the chill and reverse chill are defects often found in the nodular iron knucle castings. The insufficient stream inoculation and too fast cooling of local area of the casting is the main reason causing the chill defect. Therefore, in order to prevent the chill defect, it is must to ensure sufficient stream inoculation and to increase the pouring temperature. Too high residual magnesium content, and especially too high residual rare earth content is the main reason causing reverse chill defect. So the measures to prevent the reverse chill is to adopt the nodularizing alloy with lower RE content, and to increase both the nodularizing and pouring temperature.