Analysis and countermeasures for the corner crack of the spring frame of the exit side frame Xiao Gonglin (Qishuyan Motorcycle Vehicle Factory Forging and Casting Plant, Changzhou 213011, Jiangsu Province) is the main reason for the high degree, and proposes corresponding improvement measures for small batch production. After adopting improvement measures The crack is significantly reduced.
The problem of the proposed export side frame is the first time that the Qishuyan Locomotive and Rolling Stock Plant has moved to the North American market to provide railway accessories to BARBER. The side frame is used for trucks with a load of 125t, which is the key part of the vehicle running part. Its quality directly affects the safety of the vehicle operation and the reputation of the factory. In the design and production process, the overall process of the casting is ensured by taking effective technological measures. Quality, but there are still some unsatisfactory places, the crack in the corner of the spring cap is one of the more prominent problems.
The side frame is a box-type thin-walled casting, and the wall thickness of the corner portion of the spring cap is large, and the stress is concentrated. In order to eliminate the shrinkage cavities in this part, the original process has three external cold irons on each corner of the spring cap. Although the shrinkage hole problem is solved, there are still cracks at the corners of 99% of the spring caps, and The crack of the part must be eliminated after several welding repairs, which requires a lot of labor and material costs, which restricts the progress of production and the improvement of economic benefits to a certain extent. 2 Defective properties Through observation, it is found that the cracks are located in cold iron and cold iron. The junction, the length is different, the longest is about 50mm, the shape of the shape is meandering and irregular; the crack extends inward from the surface of the casting, the surface is wide and the inside is narrow. From these characteristics, it can be judged that the crack is a hot crack. Ingredients and inclusions The castings are made of C-grade steel, and the elements such as CrMoPS have a tendency to undergo thermal cracking. However, statistical analysis of the chemical composition, metallographic structure and inclusion morphology of the castings shows that the chemical components are controlled. J is within the specification, the metallographic structure is uniform, and the inclusions are in good condition. Therefore, these factors are not the direct cause of the occurrence of cracks in the place. 3.2 The casting process analysis wall thickness of the spring cap is designed to be 38mm, and the wall thickness of the adjacent spring cap and the center guide frame is 9mm. This creates a large hot section at the corner of the spring cap. When the molten steel fills the cavity, the thickness of the casting varies greatly, changing the original simultaneous solidification mode, the spring cap and the central guide at the flow hole. The castings are solidified first, and the thicker parts of the adjacent corners are solidified and lag. Therefore, the first solidified part hinders the shrinkage of the thicker parts to a certain extent, resulting in a cracking tendency.
3.3 Cold iron process In order to eliminate the shrinkage hole in the corner part of the spring cap, 3-50mmK50mmK 50mm outer cold iron is set on the corner part of each side of the spring cap, when the molten steel fills the cavity, although the cold iron feeding zone can be better The problem of solidification and shrinkage is solved. However, since the thickness of cold iron exceeds the thickness of the hot section and the distance between cold iron and cold iron is large, the stress difference between the cold iron and the shrinkage zone is bound to be large, resulting in cold iron and cold. At the iron junction, the crack tendency is large. 3.4 Pouring temperature Randomly extracting the side frame of the crack at the corner of the 100 spring caps. The statistical casting temperature distribution results in 30 castings on the side frame, although the internal control of the casting is in 1575~1. The pouring temperature is 1570~1585*C, and the casting temperature of the cracked casting is controlled within the specified temperature range, but a clear tendency can be found, that is, the higher the pouring temperature, the greater the probability of cracking, at 1585~1580 The side frame between *C accounts for 53% of the total number of cracks. The higher the casting temperature, the larger the shrinkage of the casting, and the greater the tendency to form shrinkage holes (loose). The casting of the Institute of Casting Railways, Bachelor of Engineering Now the main contracting technology work is the higher the shrinkage stress. 4 Countermeasures 4.1 Improvement of the cold iron process will be set in the corner of the elastic cap 6- 50 melon 50 melon cold iron to 2-30 melon 30 The melon must be 310mm cold iron (see), so that the solidification sequence of the spring cap angle part is controlled, reducing the stress formed by successive solidification, so that the crack generation is greatly improved. 4.2 Controlling the pouring temperature is not In the case of affecting the filling cavity, the pouring temperature should be controlled as much as possible within 1570~1580*C, which reduces the overall shrinkage of the casting and minimizes the generation of cracks. 5 Effect In order to verify the improvement effect of the cold iron process, small A total of 22 batches were produced in batches. A total of 300 side frames were subjected to magnetic particle inspection on the side frames. It was found that 135 cracks occurred in the corners of the spring caps, and the crack probability was 45%, which was 99% lower than before the improvement. Among the 22 heats produced, 15 castings (210 total side frames) were controlled at a temperature of 1570~1580 °C, and the cracks at the corners of the spring caps were counted. 80 side frames exist The crack rate is 38%, which is lower than the improved crack probability of 45%. After the improvement measures are taken, the crack length of the spring cap corner is 5~10mm, the depth is about 5mm, and no crack appears from the surface. The phenomenon of internal extension is easier to remove than the original crack. 6 Conclusion The main reason for the crack at the corner of the spring frame of the side frame is that the cold iron process is unreasonable and the site pouring temperature is high. Small batch production shows that by improving the spring cap angle part The cold iron process and lowering the casting temperature range of the site can reduce the tendency of cracks in the corners of the spring cap and reduce the amount of work required to remove cracks in the site.
(Continued from page 38) The internal combustion engine wheel has a very high processing precision for the oil-filled press-fit process on the axle assembly surface. Therefore, it is particularly important to select the press-fit lubricant. If the lubricating oil is not used well, it will cause hopping phenomenon during the press-fit process, and the press-fit curve will produce jitter. Lubricating oils are usually made from mineral oils and vegetable oils. Vegetable oil requires high processing precision for lubricating parts. As mentioned above: the ideal state of the oil-filled press-fit state requires the surface roughness of the hub hole to be Ra3.2m. At this time, the vegetable oil is easier to store on the assembly surface and is less prone to hopping. Therefore, it is recommended to use vegetable oil as a lubricating agent. For example, in the past, for a long time, the DF type internal combustion engine wheel used oil as a lubricant in the oil-filling press, and often jumped tons, reflected on the curve, the peak of the curve rises stepwise, see change After the vegetable oil is used as a lubricant, the phenomenon of jumping ton is greatly reduced. 3 Conclusion The internal combustion engine wheel is a more rigorous press-fit process for the oil-injection press-fit process. This paper only discusses the factors affecting the quality of the oil-filled press-fit. It can be seen that as long as the regulations on standard product drawings and technical documents are strictly implemented, and constantly improved in practice, it is possible to control the quality of the wheel-to-oil injection press.
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