The coupler tongue produced by the final process scheme of early steel casting trial production has successfully passed the inspection and certification at all levels, but there are still casting defects such as cracks, pores and sand inclusion. Therefore, after the formal mass production, the process scheme has been adjusted based on the analysis results of casting defects.
The fillet radius of the connection between the pouring riser and the parts is increased, and the mold near the connection corner is painted with thermal insulation coating. The unpacking and sand dropping process of steel castings and the content of forming elements (s and P) of low melting point phase in the pouring alloy are strictly controlled. Attention is paid to temperature preservation and uniform cooling before and after heat treatment and machining process to control the occurrence of thermal crack defects; When cutting the pouring and riser, it shall be cut step by step after the cutting part is preheated. The first cutting allowance is 2-4cm. After cutting, it shall be put into the furnace for thermal insulation in time to control the tendency of cold crack defects; During the welding repair of cracks and other defects, the welding parts shall be preheated, and the welding parts shall be kept warm and cooled slowly after the welding repair to avoid the occurrence of welding cracks; Ensure the molding process specification, control the moisture and compaction uniformity of molding sand, pour stably, exhaust unobstructed, increase the coating thickness of sand core surface at the parts easy to stick sand, and avoid surface defects such as pores, sand inclusion and sand sticking.