In view of various casting defects in the trial production of railway steel castings, combined with the actual production conditions of the factory, the following solutions and precautions are put forward to serve the mass production of hook body and hook tongue. Hot crack: increase the fillet radius at the connection between the pouring riser and the parts to reduce the internal stress. It can be considered to set anti crack ribs. The anti crack ribs solidify quickly, establish the strength earlier, and can withstand large tensile stress, which is conducive to preventing the occurrence of hot cracks; Make the connection corner between the pouring riser and the steel casting body cool and solidify evenly, and apply thermal insulation coating on the mold near the connection corner; The steel castings shall not be unpacked and desanded too early, and the cooling shall not be too fast; Controlling the pouring temperature and the content of forming elements (s, P) in the low melting point phase of the alloy, and reducing the linear shrinkage of the alloy by controlling the content of alloy composition; The mold (core) sand at sensitive parts should not be too compact, and the strength should be controlled; Slow and uniform cooling after pre normalizing and other heat treatment processes; The cracks at the corners of the complex curved surface of the hook shoulder and hook head can be eliminated by placing and adjusting the formed cold iron. Cold crack: strictly control the sand falling cleaning, pouring and riser cutting process to avoid collision and extrusion. When cutting, pay attention to the cutting speed and rhythm, cut steadily or step by step, and avoid flat cutting from the root; Considering the ambient temperature, the root of the pouring riser shall be preheated before cutting. After cutting, it shall be put into the furnace for insulation or placed in situ in time. It is forbidden to lift away immediately; Sufficient cutting allowance shall be reserved. If the allowance is too large, supplementary cutting shall be carried out in time; After cutting, do not place it at the vent and do not touch water. The residual oxide slag around the pouring riser after cutting should be cleaned up in time while it is hot; If it still cannot be solved, the introduction of new pouring and riser cutting technology can be considered. Welding crack: when the ambient temperature is low, preheating treatment shall be carried out before welding. Preheating can slow down the cooling rate after welding, facilitate the overflow of diffused hydrogen in the weld metal, avoid hydrogen induced cracks, reduce the hardening degree of weld and heat affected zone, reduce welding stress and improve the crack resistance of welded joints.
Pore defect: strictly control the water content of molding sand, do not cut off the flow during pouring, do not fill the mold too fast, and fill the mold smoothly to ensure the smooth discharge of gas in the mold.
Sand inclusion defect: appropriately increase the content of starch additive in molding sand, leave space for thermal expansion of quartz sand, reduce the influence of expansion, and ensure that the molding (core) sand at the parts easy to be mixed with sand is compact and uniform. If necessary, zirconium sand with high fire resistance and low expansion rate can be considered to replace silica sand.
Mechanical sand sticking defect: to improve the coating quality of the sand core surface at the easy sand sticking position, the anti sand sticking coating can be considered. The coating should be uniform. If necessary, the coating can be appropriately thickened, the pouring temperature and the height of the gate cup can be appropriately reduced to reduce the impact of liquid steel on the sensitive sand core.