Effect Of Pouring Temperature On Casting

Low casting temperature may cause defects

(1) After liquid slag inclusion treatment, single small holes will appear on the surface of gray cast iron castings. The diameter of the hole is generally 1 ~ 3mm. In some cases, there are only 1-2 small holes. Metallographic study showed that these pores appeared together with a small amount of liquid slag, but no sulfur segregation was found. The research shows that the defect is related to the pouring temperature. When the pouring temperature is higher than 1380 ℃, no such defects are found in the casting, so the pouring temperature should be controlled between 1380-1420 ℃. It is worth mentioning that the design of the gating system has not changed to eliminate this defect. Therefore, this defect can be attributed to the low pouring temperature and the formation of molten iron when pouring in a micro reducing atmosphere.

(2) Manganese sulfide porosity this kind of porosity is located below the surface of gray cast iron, mostly above the surface, and often exposed after processing. The pore diameter is about 2 ~ 6 mm, and sometimes there is a small amount of slag in the pore. The metallographic study shows that this defect is due to the low pouring temperature and the high content of manganese and sulfur in molten iron, resulting in manganese segregation and slag mixing.

This sulfur content and appropriate manganese content (0.5% ~ 0.65%) can significantly improve the purity of molten iron, thus effectively preventing such defects.

(3) Porosity and porosity caused by sand core gas are often caused by poor exhaust of sand core. Because the sand core is hardened in the core box during the core making process, the number of air holes in the sand core is usually insufficient. In order to form vent holes, additional drilling may be performed after the core has hardened.