LOW PRESSURE SECONDARY CASTING PROCESS FOR ALUMINUM WHEELS
Patent Information
- Application Number
- MA46399
- Authority / Receiving Office
- MA · MA
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2018-03-13
- Filing Date
- 2019-03-11
- Publication Date
- 2021-03-10
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
The conventional low-pressure aluminum wheel casting process faces challenges with low-pressure holding pressure and poor heat exchange between the mold and molten aluminum alloy, leading to inferior internal structure compactness and production efficiency.
A low-pressure casting secondary pressure process is introduced, involving low-pressure filling and secondary extrusion, where molten aluminum is rapidly solidified by water cooling and mechanical pressure is applied through extrusion rods to enhance solidification and crystallization, with specific timing and pressure control to optimize the casting process.
This process significantly reduces the low-pressure holding time, improves production efficiency by 20%, enhances the strength of aluminum wheel castings by 30%, and achieves yield strength and elongation values of 260-290 MPa and 5-10% respectively for the spokes.
Abstract
Description
Field of the Invention
[0001] The present invention relates to a casting process, and specifically, relates to an aluminum wheel casting process.Background of the Invention
[0002] The low-pressure casting process is a mainstream forming process in the aluminum wheel manufacturing industry. The conventional low-pressure casting process pressure is not more than 100 kPa, and the internal structure compactness of a casting is far lower than that of a forging process. Although the industry has implemented technological renovation on a water cooling process in recent years, it has also encountered a development bottleneck after a certain degree of improvement on material properties and casting production efficiency.Summary of the Invention
[0003] The present invention provides a casting process, which solves the problems of low-pressure holding pressure during low-pressure casting and poor heat exchange between a mold and molten aluminum alloy.
[0004] The technical solution adopted by the present invention is: a low-pressure casting secondary pressure process for an aluminum wheel includes low-pressure filling and secondary extrusion. Molten aluminum alloy in a holding furnace enters a mold through a center sprue under the action of compressed air, until the cavity is full; a center sprue spreader is lowered to be in clearance fit with a center sprue bushing, and the aluminum alloy at the center sprue is rapidly solidified by cooling the mold with water to close the mold cavity. At the same time, five extrusion rods at corresponding positions of the wheel center of an aluminum wheel move down to apply mechanical pressure for secondary pressure feeding of the aluminum wheel to realize sequential solidification, until the molten aluminum alloy is completely crystallized and solidified, and the mold is opened to take a casting out.
[0005] According to the low-pressure casting secondary pressure process of the present invention, the crystallization and solidification of the rim of the aluminum wheel are still completed under low-pressure casting holding pressure, so a low pressure holding delay stage should be set after the cavity is full of the molten aluminum alloy and before the sprue spreader is lowered to seal the low pressure in the holding furnace, in which the pressure holding time is between 10 and 20 seconds.
[0006] According to the low-pressure casting secondary pressure process of the present invention, the sprue spreader is in clearance fit with the center sprue with a clearance distance of 0 to 2 mm. In the present invention, the clearance fit surface of the sprue spreader and the center sprue is a tapered surface, and in order to facilitate de-molding, the tapered angle is between 0° and 5°.
[0007] According to the low-pressure casting secondary pressure process of the present invention, the molten aluminum alloy at the sprue spreader and the center sprue needs to be rapidly frozen under a forced water cooling condition to seal the mold cavity. Before the center extrusion rods move down, a water cooling holding delay stage is set, and the delayed pressure holding time is between 10 and 20 seconds.
[0008] According to the low-pressure casting secondary pressure process of the present invention, the maximum feeding pressure, acting on the molten aluminum alloy in the closed mold cavity, of the center extrusion rods can reach 1000 times the pressure feeding capacity of ordinary compressed air in low-pressure casting.
[0009] The speed of lowering the center extrusion rods is crucial to final molding and crystallization of the casting, and the lowering stage is divided into the first low speed and then high speed. Thus, no overflow flash is ensured for the casting, and forced pressure feeding is realized.
[0010] The lowering speed at the low-speed stage of the lowering process of the center extrusion rods is 0 to 0.2 mm / s. The lowering speed at the high-speed stage of the lowering process of the center extrusion rods is 0.5 to 0.8 mm / s.
[0011] Five center extrusion rods are provided in the present invention, with cross section diameters of 50 mm.
[0012] Finally, in the aluminum alloy wheel manufactured by the low-pressure casting secondary extrusion process according to the present invention, the low-pressure casting pressure holding time is shortened from 100s to 50s, and the production efficiency of the overall casting process is improved by 20%; the strength of the aluminum wheel casting is improved by 30%, and the yield strength of the spokes reaches 260-290 MPa; and the elongation of the spokes reaches 5%-10%.Brief Description of the Drawings
[0013] The present invention will be further illustrated below in conjunction with the drawings and embodiments. Fig. 1 is a schematic diagram of a device for a low-pressure casting secondary pressure process for an aluminum wheel according to the present invention. Fig. 2 is a schematic diagram of a crystallization and solidification stage of a rim after the cavity is full of aluminum alloy under low pressure. Fig. 3 is a schematic diagram of a stage at which the aluminum alloy at a center sprue is frozen to close the mold cavity after a center sprue spreader is lowered and a forced water cooler is started. Fig. 4 is a schematic diagram of a stage at which the center extrusion rods are lowered to implement secondary pressure until the entire crystallization and solidification process of the aluminum wheel is completed.
[0014] In which: 1-holding furnace, 2-bottom mold, 3-side mold, 4-top mold, 5-center sprue spreader, 6-center extrusion rod, 7-water cooling.Detailed Description of the Embodiments
[0015] As shown in Fig. 1 to Fig. 4, a low-pressure casting secondary pressure process for an aluminum wheel according to the present invention includes low-pressure filling and secondary extrusion. In the low-pressure filling process, after the cavity is full of molten aluminum alloy and the rim is completely crystallized and solidified under delayed low-pressure holding pressure, a center sprue spreader (5) is lowered, a forced cold water cooling (7) is started, and a period of time is delayed to freeze the aluminum alloy at a center sprue so as to close the mold cavity. In the secondary extrusion, center extrusion rods (6) are lowered for secondary pressurization to achieve extrusion deformation strengthened feeding, till the entire process of secondary pressurization for low-pressure casting of the aluminum wheel is completed.
[0016] According to the low-pressure casting secondary pressure process of the present invention, the crystallization and solidification of the rim of the aluminum wheel are still completed under low-pressure casting holding pressure, so a low pressure holding delay stage should be set after the cavity is full of the molten aluminum alloy and before the sprue spreader is lowered to seal the low pressure in the holding furnace, in which the pressure holding time is between 10 and 15 seconds.
[0017] According to the low-pressure casting secondary pressure process of the present invention, the sprue spreader is in clearance fit with the center sprue with a clearance distance of 0.5 to 2 mm, preferably. In the present invention, the clearance fit surface of the sprue spreader and the center sprue is a tapered surface, and in order to facilitate de-molding, the tapered angle is between 0.5° and 5°.
[0018] According to the low-pressure casting secondary pressure process of the present invention, the molten aluminum alloy at the sprue spreader and the center sprue needs to be rapidly frozen under a forced water cooling condition to seal the mold cavity.
[0019] Before the center extrusion rods move down, a water cooling holding delay stage is set, and the delayed pressure holding time is between 15 and 20 seconds.
[0020] According to the low-pressure casting secondary pressure process of the present invention, the maximum feeding pressure, acting on the molten aluminum alloy in the closed mold cavity, of the center extrusion rods can reach 1000 times the pressure feeding capacity of ordinary compressed air in low-pressure casting.
[0021] The speed of lowering the center extrusion rods is crucial to final molding and crystallization of the casting, and the lowering stage is divided into the first low speed and then high speed. Thus, no overflow flash is ensured for the casting, and forced pressure feeding is realized.
[0022] The lowering speed at the low-speed stage of the lowering process of the center extrusion rods is 0.1 to 0.2 mm / s. The lowering speed at the high-speed stage of the lowering process of the center extrusion rods is 0.5 to 0.7 mm / s.
Claims
1. A low-pressure casting secondary pressure process for an aluminum wheel, comprising low-pressure filling and secondary pressurization, wherein the holding pressure is delayed for a period of time after a mold cavity is full of molten aluminum alloy under the low-pressure filling process, and the mold cavity is closed after a rim is completely solidified under low pressure feeding; wherein five extrusion rods at corresponding positions of the wheel center of the aluminum wheel move down to apply mechanical pressure for secondary pressure feeding of the aluminum wheel to realize sequential solidification, until the forming process of crystallization and solidification of a casting is completed; a low pressure holding delay stage should be set after the cavity is full of the molten aluminum alloy and before a sprue spreader is lowered to seal the low pressure in a holding furnace, in which the pressure holding time is between 10 and 20 seconds; the sprue spreader is in clearance fit with a center sprue with a clearance distance of 0 to 2 mm; the clearance fit surface of the sprue spreader and the center sprue is a tapered surface, and in order to facilitate de-molding, the tapered angle is between 0° and 5°; before the center extrusion rods move down, a water cooling holding delay stage is set, and the delayed pressure holding time is between 10 and 20 seconds; the lowering stage of the center extrusion rods is divided into first low speed and then high speed, the lowering speed at the low-speed stage of the lowering process of the center extrusion rods is 0 to 0.2 mm / s, the lowering speed at the high-speed stage of the lowering process of the center extrusion rods is 0.5 to 0.8 mm / s, and the cross section diameters of the center extrusion rods are 50 mm.
2. The low-pressure casting secondary pressure process for an aluminum wheel according to claim 1, wherein the time of the low pressure holding delay stage set after the cavity is full of the molten aluminum alloy and before the sprue spreader is lowered to seal the low pressure in the holding furnace is between 10 and 15 seconds.
3. The low-pressure casting secondary pressure process for an aluminum wheel according to claim 1, wherein the sprue spreader is in clearance fit with the center sprue with a clearance of 0.5 to 2 mm; the clearance fit surface of the sprue spreader and the center sprue is a tapered surface, and the tapered angle is between 0.5° and 5°;4. The low-pressure casting secondary pressure process for an aluminum wheel according to claim 1, wherein before the center extrusion rods move down, a water cooling holding delay stage is set, and the delayed pressure holding time is between 15 and 20 seconds.
5. The low-pressure casting secondary pressure process for an aluminum wheel according to claim 1, wherein the lowering stage of the center extrusion rods is divided into first low speed and then high speed; the lowering speed at the low-speed stage of the lowering process of the center extrusion rods is 0.1 to 0.2 mm / s; and the lowering speed at the high-speed stage of the lowering process of the center extrusion rods is 0.5 to 0.7 mm / s.