The blow hole defects produced by wet molding clay sand cast steel process are mainly intrusion blow hole and precipitation blow hole. Intrusive blow hole defect is that gas intrudes into liquid metal from the outside, mainly from molding sand, core sand, cold iron, etc., or may be involved during pouring. Intrusive blow hole defects mostly appear in the upper part of the casting near the surface of molding sand and core sand, mostly in a round or oval shape. The wet molding clay sand has high moisture content, improper pouring and improper exhaust, which are easy to produce intrusive blow hole defects.
Precipitated blow hole defect refers to the blow hole defect formed by the reduction of the solubility of the dissolved gas in the process of molten steel melting in the process of metal solidification. The gas in the precipitated blow hole defect is mostly hydrogen and nitrogen, which is mostly distributed in the whole casting section in the shape of pits. The pouring temperature is too high, the quality of furnace charge is poor or the control is improper, which is easy to bring in gas and induce the precipitated blow hole defect.
The blow hole defects in non important parts can be repaired by welding. The air hole defects in important parts may lead to the scrapping of the casting, and the blow hole defects hidden inside the casting will be a potential safety hazard. Therefore, in the production process of Wet Mold clay sand cast steel, on the premise of ensuring the properties of molding sand and core sand, it is necessary to strictly control the moisture of molding sand and core sand, ensure the smooth exhaust of sand mold, strictly control the pouring temperature, pouring speed and pouring mode, avoid gas involvement, and use high-quality furnace charge.