来源：http://www.jnhjgs.cn 发布时间：2021-11-17 17:14:34 点击：
Manganese sulfide pore
Causes of defects: such pores are located below and mostly on the surface of gray iron castings, and are often exposed after processing. The diameter of pores is about 2 ~ 6mm. Sometimes there is a small amount of slag in the hole. Metallographic study shows that this defect is caused by the mixture of MNS segregation and slag. The reason is that the pouring temperature is low and the content of Mn and s in molten iron is high.
Solution: such s content and appropriate Mn content (0.5% ~ 0.65%) can significantly improve the purity of molten iron, so as to effectively prevent such defects.
Porosity caused by core gas
Causes of defects: pores and porous pores are often caused by poor exhaust of sand core. Because the sand core is mostly hardened in the core box during core making, the number of exhaust holes of the sand core is often insufficient.
Solution: in order to form an exhaust hole, add drilling after the core is hardened.
Liquid slag inclusion
Causes of defects: it is worth mentioning that changing the gating system design failed to eliminate this defect, so this defect can be considered to be formed due to low pouring temperature and molten iron pouring in micro reducing atmosphere. After processing, individual small holes will be found under the skin of gray iron castings, and the diameter of the holes is generally 1 ~ 3mm. In some cases, there are only 1 ~ 2 small holes. Metallographic study shows that these small holes appear together with a small amount of liquid slag inclusion, but there is no segregation of S.
Solution: the research shows that this defect is related to the pouring temperature. When the pouring temperature is higher than 1380 ℃, this defect is not found in the casting, so the pouring temperature should be controlled at 1380 ~ 1420 ℃.