Pouring temperature is the most common cause of low cast, iron liquid stay open long transportation and ladle and heat dissipation.Use ladle cover with insulation, can significantly reduce heat loss.(2) the sand core gas porosity caused by porosity and long-short porosity is often caused by sand core the venting is not good.Because core making sand core in the core and hardening, it often makes sand core porosity quantity is not enough.In order to form a vent, can be in core complement borehole after hardening.(3) after the liquid slag processing gray cast iron pieces of skin will find a monomer holes, the diameter of the hole is usually 1 to 3 mm.Individual cases, only 1 ~ 2 holes.Metallographic studies have shown that these holes with a small amount of liquid slag, but it did not find S segregation.Research has shown that this kind of defects associated with pouring temperature, pouring temperature higher than 1380 ℃, did not find the defects in casting, so the pouring temperature should be controlled in 1380-1420 ℃.Remarkably change the gating system design, to eliminate the defect, reason this kind of defects can be thought of as due to the low pouring temperature and liquid iron trace under the reducing atmosphere in pouring.L;The text - transform: none;The font - style: normal;The font - size: 12.0000 pt;The oledata.mso - the font - kerning: 1.0000 pt;">Such S content and appropriate Mn content (0.5% ~ 0.65%), can significantly improve the purity of molten iron, so as to effectively prevent this kind of defect.