Firstly, the original sand casting process of 17 type coupler body and 16 type coupler tongue is simulated and analyzed, and the improved sand casting process scheme is proposed and simulated. From the simulation results of the improved sand casting process scheme and the trial production of products, it can be seen that the trial production quality of the improved sand casting process scheme is greatly improved compared with the original sand casting process, Qualified steel castings can be obtained under the condition that the subsequent processing and sand casting process is reasonable and stable. Therefore, we can draw the following main conclusions:
(1) For the coupler body of type 17 coupler, under the original sand casting process conditions, according to the simulation results, there may be erosion, slag inclusion and sand sticking defects at the coupler tail pin hole and the lower part of the coupler head facing the inner gate, and there may be air hole defects on the large plane of the coupler body. Hot joints are easy to form at the inner and outer corners of the coupler head, the root of the traction table in the coupler cavity, and the junction corner of the coupler head and the coupler body (i.e. coupler neck), resulting in shrinkage and shrinkage defects, The overall stress level of the hook body is high, especially in the connection corner of the hook head and body and most of the pin hole of the hook tail. The hot crack tendency is large at the root of the pouring riser, the corner of the hook body and the hook head and the corner of the complex surface inside the hook head. After the actual pouring verification, all parts are indeed easy to form the above defects.
(2) For the hook body of type 17 coupler, the sand casting process is improved and optimized as follows: change the introduction position of the inner gate and place it on one side of the hook body, the sprue adopts the formed fire-resistant sprue, the two ordinary sand mold risers at the head of the hook body are changed into three cylindrical insulation risers, a insulation riser is set at the upper part of the hook body, a small dark riser is added at the position of the inner gate, the sand mold outlet and the riser outlet are staggered, and the formed cold iron is added at the hot joint. The simulation results of improved sand casting process show that the velocity around the pin hole is smaller and more uniform in the mold filling process, which is conducive to avoiding sand flushing and slag inclusion; During solidification, the feeding channel at the riser is unobstructed, and the riser can play an effective feeding role. The distribution of independent liquid phase area is better than that of the original sand casting process. The internal corners of the hook head contain a small amount of shrinkage cavities, most of which are concentrated in the pouring and riser system, and the design of the pouring and riser system is more reasonable than that of the original sand casting process; The stress field simulation results show that the stress level is significantly lower than that of the original sand casting process. The parts with large stress are mainly the riser root, the corner between the hook body and the hook head and the corner of the complex surface inside the hook head. The possible parts of thermal crack are basically the same as the parts with large equivalent stress.
(3) For the coupler body of type 17 coupler, after the actual pouring verification, after improving the sand casting process, the surface quality of the large plane on the coupler body, the complex curved surface inside the coupler head and the steel castings around the coupler tail pin hole is better, the probability of air holes, slag inclusion and sand sticking defects is greatly reduced, the number of shrinkage holes in the coupler head is significantly reduced, and the number of cracks at the root of the pouring riser, the junction of the coupler head of the coupler body and the corner of the complex surface inside the coupler head are also greatly reduced, Under the condition of subsequent reasonable cutting and welding repair, qualified steel castings can be obtained, and the overall effect of improving sand casting process is good.
(4) For the coupler tongue of type 16 vehicle, under the conditions of the original sand casting process, according to the simulation results, there may be defects such as slag and sand inclusion, shrinkage cavity and looseness around the coupler tongue pin hole, the inner wrist surface and the pressure push table. The stress of the guard pin flange and traction flange is large and the hot crack tendency is large.
(5) For the coupler knuckle of type 16 car, the sand casting process is improved and optimized as follows: four pieces in a box, symmetrically arranged, changing the introduction position of the inner gate, placing it between the pin hole on the back of the coupler knuckle and the coupler tail, removing the central large riser, and separately placing the concealed riser of the thermal insulation top above the compression push table of the part. The simulation results of improved sand casting process show that the liquid steel velocity around the pin hole is more uniform in the mold filling process, which can effectively avoid erosion and slag inclusion; During solidification, the insulation concealed riser above the pressure push table can effectively feed the thick part, and the shrinkage cavity at the guard pin flange and traction flange is loose and transferred to the middle of the hook tongue to avoid the main stress parts; The stress field simulation results show that the overall stress level of the hook tongue is slightly higher than that of the original sand casting process, but the stress of the key parts such as the inner wrist surface of the hook tongue is small, and the parts with large stress are basically the same as that of the original sand casting process. The hot crack tendency of the traction flange, the coupler tail stop and the inner corner of the hook wrist is still large, which is slightly better than that of the original sand casting process.
(6) For the coupler tongue of type 16 car, the actual pouring verification shows that the riser feeding effect of the original sand casting process is general and a large amount of liquid steel is wasted; There are obvious erosion and slag inclusion defects around the pin holes of more than half of the hook tongue products, 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. The optimized sand casting process changes greatly, and the mold must be purchased and processed again, with a long cycle. Therefore, the sand casting process scheme of hook tongue trial production and early batch production is still continuously improved on the basis of the original sand casting process.