The steel castings of coupler body are the key parts of vehicle connection, which have a significant impact on driving safety. During the driving process of freight cars, the steel castings of coupler body will be frequently pulled and compressed. The coupler head is the main stress part, and there shall be no shrinkage and shrinkage defects. There shall be no cracks on the surface of steel castings and important corners. According to the simulation analysis results of the mold filling and solidification process of the original process of the hook body, the following analysis conclusions are obtained:
(1) During the mold filling process, the flow velocity at the coupler tail pin hole facing the inner gate is large, and the liquid steel continues to fill the mold. When flowing into the coupler head, the downward impact speed is large, the sand core and mold are greatly impacted by the liquid steel, and the erosion will be more serious. It is very easy to form sand flushing, slag inclusion and sand sticking defects around the corresponding parts. There may be air hole defects on the large plane of the hook body, which seriously affect the quality of steel castings, so it needs to be optimized;
(2) During the solidification process, there is an independent liquid phase area at the inner and outer corners of the hook head, the root of the traction table in the hook cavity, and the corner at the junction of the hook head and the hook body (i.e. the hook neck), which makes it difficult to feed the riser, forms a hot joint, and finally produces shrinkage porosity defects, which needs to be optimized;
(3) It can be seen from the stress field simulation results that during the solidification process of the hook tongue under the original process conditions, the stress at the riser root, most around the hook tail pin hole, the corner of the hook body and hook head and the corner of the complex surface inside the hook head are higher, and the tendency of thermal cracks is great, which needs to be optimized.
The coupler steel castings have actual effect during operation, which is mainly manifested in fracture and wear. In addition to subjective factors such as post-treatment, quality inspection and flaw detection, casting defects are the source of their failure, that is, the defects of sand sticking and slag inclusion on the surface of steel castings and shrinkage cavity and micro crack in the interior of steel castings produced in the casting process. These defects become the parts of stress concentration during use, resulting in macro cracks or fine debris, Finally, it will cause fracture and serious wear.