Pouring system for improving shrinkage porosity defect of differential shell

Abstract

The utility model discloses a pouring system for improving the shrinkage porosity defect of a differential shell, which comprises a sand core positioned on the outer side of a casting, a concave riser base formed on the sand core on one side of the casting, a heating block made of a heating material arranged in the riser base, and the size of the heating block is smaller than that of the riser base; in the state after pouring, an exothermic riser is formed at the riser base, the heating block is located in the exothermic riser, and the exothermic riser is located on one side of the outer portion of the casting. According to the scheme, during production, only the heating block needs to be put into the riser nest before mold closing, and the original stable production process does not need to be changed; the heating block has efficient heating efficiency and acts with molten iron, and the temperature of the molten iron can be increased by 200-300 DEG C instantly, so that the solidification time of the molten iron at the top of the riser is delayed, the problems that the heat storage amount of the riser is small and feeding is insufficient are thoroughly solved, and the feeding efficiency of the riser is improved; the poor shrinkage porosity is reduced to about 1% from the original more than 90%, and two-month production proves that the process is stable and feasible.

Description

Technical Field

[0001] This utility model belongs to the field of casting technology, and specifically relates to a gating system for improving the shrinkage porosity defect of differential housing. Background Technology

[0002] The differential housing is a crucial component of the differential in an automotive transmission system. It houses and protects the internal gears and other components of the differential, and is currently typically manufactured using casting. This particular differential housing casting is a typical rotating body structure, made of QT600-3 material, with a maximum wall thickness of approximately 30mm and a weight of approximately 14.5kg. During quality inspection, shrinkage porosity defects were found in approximately 90% of the differential housing. Shrinkage porosity refers to the formation of scattered and fine shrinkage cavities in areas where the casting did not receive sufficient feeding from the liquid metal or alloy during the final solidification process. These cavities are often found along the axial direction of the casting wall, in thicker sections, at the root of risers, and near the ingate. When the volume of shrinkage porosity and shrinkage cavity are the same, the distribution area of ​​shrinkage porosity is much larger than that of shrinkage cavity. Shrinkage porosity is hidden inside the casting and is not easily detected externally. Further dissection revealed that the shrinkage porosity defect was mainly located at the small end shaft head of the differential. The shrinkage porosity at the small end shaft head indicated that the feeding channel was blocked and sequential solidification was not achieved. Analysis of the parts with shrinkage porosity inside the casting revealed that the riser at the small end shaft head of the differential housing was too far from the sprue inlet. The molten iron had a long travel distance and a large climbing height, resulting in a low temperature when the molten iron reached the riser. The molten iron at the riser solidified before the casting, and the feeding capacity was insufficient, thus causing shrinkage porosity in the casting.

[0003] The existing technical solutions for this type of riser feeding capability and their limitations are as follows.

[0004] Option 1: Increase the size of the gating system to raise the riser temperature and ensure its feeding capacity. However, based on the mold layout, increasing the size of the gating system connected to this riser is insufficient to make the riser reach a temperature sufficient to feed the casting. Therefore, this option can only be used as an auxiliary measure and cannot completely solve the shrinkage porosity problem.

[0005] Option 2: Modify the riser neck size so that it lags behind the solidification of the casting, ensuring unobstructed feeding channels. However, this option cannot completely solve the shrinkage porosity problem and can only be used as a supplementary measure.

[0006] Option 3: Eliminate the riser and add a chill at the corresponding sand core shaft head position in the casting to solve the shrinkage porosity problem. However, monitoring of the actual production process revealed that adding the chill resulted in an excessively high defect rate for the sand core, leading to high production costs and low production efficiency. Utility Model Content

[0007] The technical problem to be solved by this utility model is to provide a casting system for improving the shrinkage defect of differential housing, solving the problem of the gradual appearance of shrinkage defect in differential housing, and avoiding significant negative impact on production efficiency and cost.

[0008] According to the technical solution of this utility model, this utility model provides a gating system for improving the shrinkage porosity defect of differential housing, including a sand core located on the outside of the casting, a recessed riser pit formed on the sand core on one side of the casting, and a heating block made of heating material placed in the riser pit, the size of the heating block being smaller than the riser pit; in the state after casting, a heating riser is formed at the riser pit, the heating block is located inside the heating riser, and the heating riser is located on one side of the outside of the casting.

[0009] Furthermore, it has multiple castings arranged side by side, each of which is connected to a heat-generating riser.

[0010] Furthermore, it also has at least one intermediate feeding riser located between adjacent castings.

[0011] Furthermore, multiple castings are connected by a gating system. The casting is a differential housing casting. The axial direction of the differential housing casting is perpendicular to the plane of the gating system, and the axial direction of the differential housing casting is parallel to the height direction of the heating riser.

[0012] Furthermore, the heating block is fixedly positioned at the center of the bottom of the riser socket.

[0013] Furthermore, the heating element is rectangular in shape, with dimensions of 2mm × 2mm × 2.5mm.

[0014] Furthermore, the longitudinal cross-sectional shape of the heating element is trapezoidal.

[0015] Furthermore, the volume percentage of the heating block in the heating riser is 2% to 8%.

[0016] Compared with the prior art, the beneficial technical effects of this utility model are as follows:

[0017] This invention relates to a casting system for improving the shrinkage porosity defect in differential housings. In production, the heating block is simply placed in the riser socket before mold closing, without altering the existing stable production process. The heating block has high heating efficiency; when it interacts with molten iron, it can instantly raise the temperature of the molten iron by 200-300°C, thereby delaying the solidification time of the molten iron at the top of the riser. This completely solves the problems of low heat storage and insufficient feeding in the riser, improving the feeding efficiency of the riser. The percentage of poor shrinkage porosity has decreased from over 90% to about 1%. After two months of production, the process has proven to be stable and feasible. Furthermore, the cost of one heating block is only about 0.3 yuan, which saves production costs compared to other solutions that increase the feeding capacity of the riser. Attached Figure Description

[0018] Figure 1 This is a structural schematic diagram of the heating block, sand core, and casting in the casting system provided by this utility model.

[0019] Figure 2 This is a schematic diagram of the integral casting formed after the casting system provided by this utility model is cast.

[0020] Explanation of reference numerals in the attached figures:

[0021] 1. Casting; 2. Sand core; 3. Riser socket; 4. Heating block; 5. Heating riser; 6. Intermediate feeding riser; 7. Gating system. Detailed Implementation

[0022] This invention provides a casting system for improving the shrinkage defect of differential housing, solving the problem of the gradual appearance of shrinkage defect in differential housing, and avoiding significant negative impacts on production efficiency and cost.

[0023] Please see Figure 1 , Figure 2 This utility model discloses a gating system for improving shrinkage defects in a differential housing. Similar to existing technologies, it includes a sand core 2 located on the outside of the casting 1. The sand core is a sand block made by mixing sand with a binder, mainly used to form cavities or complex shapes inside the casting. More specifically, the gating system of this solution is similar to existing technologies in its basic structure. The basic structure required for the gating system and existing technologies related to differential housing casting can be found in, for example, Chinese invention patents with publication numbers CN117399561A and CN105598388A, which will not be elaborated here. The differential housing is an existing part. In order to form the complex structure of this housing part, a sand core is required, and the sand core includes parts located outside the left and right sides of the casting 1 (differential housing).

[0024] In this design, a recessed riser socket 3 is formed on the sand core 2 on one side of the casting 1. The riser socket structure is existing technology, used to form a riser after pouring. However, in some gating systems, riser sockets are not used or are placed in other locations. In this design, the riser socket 3 is located near the side and end of the casting 1 to provide better feeding and other effects. A heating block 4 made of heating material is placed inside the riser socket 3. The size of the heating block 4 is smaller than the riser socket 3. The heating material is a material that can generate heat efficiently upon contact with the poured molten iron, such as a thermite. The heating block 4 is, for example, a block obtained by dry pressing heating material powder.

[0025] Please see Figure 2In the post-cast state, a heated riser 5 (a riser with a heated block 4) is formed at the riser socket 3. The heated block 4 is located inside the heated riser 5, and the heated riser 5 is located on one side of the outside of the casting 1. This delays the solidification time of the molten iron at the top of the riser and improves the feeding efficiency of the riser, thus effectively improving the shrinkage porosity problem.

[0026] More specifically, the gating system has multiple cavities, meaning that after a single casting, the resulting structure has multiple castings 1 arranged side-by-side, each casting 1 connected to a heating riser 5. Furthermore, it also has at least one intermediate feeding riser 6, located between adjacent castings 1. The intermediate feeding riser 6 is a conventional riser, spaced apart from the heating riser 5. The multiple castings 1 are connected by a sprue 7. The casting 1 is a differential housing casting (rotating body), with its axial direction perpendicular to the plane of the sprue 7 and parallel to the height direction of the heating riser 5. In other words, this solution can be applied to horizontal molding line production processes; this structure is relatively simpler in design and more technologically mature.

[0027] In some embodiments, the heating block 4 is fixedly disposed at the center of the bottom of the riser 3. For example, a groove is provided at the bottom of the riser 3 of the sand core 2 to embed or bond the heating block 4, thereby ensuring that the position of the heating block 4 is in the center of the heating riser 5 formed after casting and will not be biased to one side, thus ensuring uniform heating effect.

[0028] The heating block 4 can be shaped like a cuboid, with dimensions of 2mm × 2mm × 2.5mm. Alternatively, the heating block 4 can have a trapezoidal cross-section, such as a truncated pyramid. This type of block structure with a wider base makes it easier to place or fix more stably. The heating block 4 is relatively small; for example, its volume percentage in the heating riser 5 is 2% to 8%. The cost of one heating block 4 is only about 0.3 yuan, and this small heating block can effectively form a heating riser.

[0029] In summary, after considering costs, the inventors designed and adopted this simplest and most economical solution: using a heating block formed from a heating material. During production, the heating block only needs to be placed into the riser sand core cavity of the lower mold before mold assembly, without altering the existing stable production process. This heating block has highly efficient heating performance; when interacting with molten iron, it can instantly raise the temperature of the molten iron by 200-300°C, thereby delaying the solidification time of the molten iron at the top of the riser. This completely solves the problems of low heat storage and insufficient feeding in the riser, improving the feeding efficiency of the riser. Poor shrinkage porosity has been reduced from >90% to about 1%. After two months of production, this process has proven to be stable and feasible.

[0030] It should be noted that the concept of a heated riser is a conventional one. It refers to the addition of a heating agent to the riser material. After the molten metal is poured in, the heating agent reacts and generates heat, maintaining a higher temperature in a localized area during the casting's cooling process. This slows down the cooling rate in that area, ensuring sufficient feeding in critical parts of the casting and preventing defects such as shrinkage porosity and other defects, thus improving casting quality. However, existing heated risers have complex processes or structures. This solution simply requires placing a heating block into the riser socket to transform an ordinary riser into a heated riser, which is simple to operate and has a lower cost. In addition, the heating block of this solution can also be applied to other existing gating systems to improve shrinkage porosity defects.

Claims

1. A gating system for improving shrinkage defects in a differential housing, comprising a sand core (2) located outside the casting (1), characterized in that, A recessed riser cavity (3) is formed on the sand core (2) on one side of the casting (1). A heating block (4) made of heating material is placed in the riser cavity (3). The size of the heating block (4) is smaller than that of the riser cavity (3). In the post-pouring state, a heating riser (5) is formed at the riser cavity (3). The heating block (4) is located inside the heating riser (5). The heating riser (5) is located on one side of the outside of the casting (1).

2. The casting system for improving differential housing shrinkage defects according to claim 1, characterized in that, The castings (1) are arranged side by side, and each casting (1) is connected to a heating riser (5).

3. The casting system for improving differential housing shrinkage defects according to claim 2, characterized in that, It also has at least one intermediate feeding riser (6) located between adjacent castings (1).

4. The casting system for improving differential housing shrinkage defects according to claim 2, characterized in that, Multiple castings (1) are connected by a gating system (7). The casting (1) is a differential housing casting. The axial direction of the differential housing casting is perpendicular to the plane of the gating system (7). The axial direction of the differential housing casting is parallel to the height direction of the heating riser (5).

5. The casting system for improving differential housing shrinkage defects according to any one of claims 1-4, characterized in that, The heating block (4) is fixedly installed at the center of the bottom of the riser socket (3).

6. The casting system for improving differential housing shrinkage defects according to any one of claims 1-4, characterized in that, The heating block (4) is rectangular in shape and has a size of 2mm×2mm×2.5mm.

7. The casting system for improving differential housing shrinkage defects according to any one of claims 1-4, characterized in that, The longitudinal cross-sectional shape of the heating block (4) is trapezoidal.

8. The casting system for improving differential housing shrinkage defects according to any one of claims 1-4, characterized in that, The volume percentage of the heating block (4) in the heating riser (5) is 2% to 8%.

Images