At the initial stage of trial production of hook body and tongue steel castings, the original process scheme is still used to pour the parts, which has poor effect and many casting defects. The casting defects of the hook body are mainly as follows: the section compactness of the designated part of the hook head and tail does not meet the requirements, there are many shrinkage defects, and the feeding effect of the riser is not ideal; There are air hole defects on the large plane and side of the hook body; There are obvious sand inclusion and rough surface problems on the surface of the inner gate around the coupler tail pin hole; Cracks are easy to occur at the root of pouring riser, the corner of hook body and hook head and the corner of complex surface inside the hook head. The main defects of the hook tongue are as follows: the section compactness of the formulated part of the guard pin flange does not meet the requirements, there are shrinkage holes, the feeding effect of the central large riser is general, and a large amount of liquid steel is wasted; More than half of the coupler knuckle steel castings have obvious erosion and slag inclusion defects around the pin hole, and the sand sticking is also serious, which makes it difficult to clean up; Through magnetic particle flaw detection, micro cracks appear from time to time at the gate root, the middle and upper part of the inner wrist surface of the hook tongue, the opening of the hook tongue and the corner of the guard pin flange.
In view of the problems in the production of the original process of the hook body and hook tongue, based on the simulation results of the original process and the improved and optimized process of the hook body and hook tongue, and combined with the actual production conditions, the factory has improved the sand casting process scheme.
The hook body is still one type and two pieces. A total of 5 thermal insulation risers are set at the hook head, shoulder, body and tail of the hook body to supplement and shrink specific hot joints and key parts. At the same time, in order to prevent the riser outlet from dropping sand into the mold cavity, the riser core adopts a special structure to stagger the sand mold outlet and riser outlet. The gate adopts an open gating system, and the inner gate is introduced from one side of the middle section of the hook body to avoid the impact of molten steel on the sand core sand mold at the coupler tail pin hole, avoid important stress and assembly parts, shorten the filling distance of liquid steel and avoid premature solidification. The formed refractory sprue is adopted. In view of the crack defects, the combined use of formed cold iron, luotie ore and riser is adopted to create cooling conditions for the steel castings to solidify at the same time or locally in sequence towards the riser, and process bars are set at the necessary parts. Different coatings are used for sand mold and sand core, and spraying and brushing processes are adopted respectively.
The coupler knuckle is still a type of eight pieces, and the central riser is changed to a thermal insulation riser to strengthen the feeding effect. In order to avoid pouring and sand flushing, the formed fire-resistant sprue is adopted. At the same time, the inner gate is placed in the middle between the pin hole on the back of the coupler knuckle and the coupler tail to avoid the impact of liquid steel on the sand core and sand mold at the pin hole and the defects of sand flushing and slag inclusion, so as to ensure the sand mold casting quality of important stress sensitive parts of the coupler knuckle pin hole. Different coatings are used for sand mold and sand core, and spraying and brushing processes are adopted respectively.
The hook body and tongue continue to be trial produced with the above improvement scheme, and the quality of trial produced steel castings is greatly improved, but there are still some problems, and the process scheme needs to be further optimized.