Casting and forging integrated forming process method for Al-Cu complex-shaped thin-wall motor shell end cover
By combining liquid pressure filling and semi-solid pulling with integral forging, the defect control problem of Al-Cu alloy motor housing end caps was solved, and the production of high-quality castings with complex structures was realized.
Patent Information
- Application Number
- CN202511630104.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-09
- Publication Date
- 2026-02-27
AI Technical Summary
Existing casting processes are difficult to effectively control shrinkage porosity, shrinkage cavities, and cracks in Al-Cu alloy motor housing end caps, especially in complex structures where defects caused by insufficient feeding are difficult to completely eliminate.
A casting-forging integrated forming method combining liquid pressure filling and semi-solid pull-down is adopted. The compensation space is constructed by retracting the cavity, and then integral forging is performed to form material flow to improve the quality of the casting.
It significantly reduces defects such as shrinkage porosity, shrinkage cavities, and cracks, improves the mechanical properties and microstructure density of the motor housing end cover, and achieves high-quality aluminum alloy casting production.
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Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a thin-walled aluminum alloy motor shell end cover with a complex shape, and provides an Al-Cu component optimization and casting-forging integrated forming method added with Er and Zr, and belongs to the motor shell end cover preparation field. BACKGROUND
[0002] The motor shell is a thin-walled die casting, has a complex structure and is prone to distortion, and requires good air tightness and high strength, so that forming is difficult and the process is complex. At present, the Al-Si alloy is mainly used for the motor shell end cover and is formed through gravity casting or extrusion casting process. The Al-Si alloy has excellent casting performance but poor mechanical properties, and isolated liquid phase zones are easily formed at thick wall positions due to insufficient feeding, and the tensile strength is only 179 MPa. In order to improve the quality, the pouring and cooling systems are optimized through ProCAST simulation, although the shrinkage holes at the thick wall positions are effectively eliminated, the elongation is only 4.02% after T6 heat treatment. The semi-solid extrusion forging (solid phase rate 40%) is adopted, so that the 6061 alloy reaches 368.9 MPa after T6 treatment, and the shrinkage defects are reduced by 80%, which shows that plastic deformation has a certain influence on performance improvement. However, the traditional die casting Al-Si alloy does not have enough time for the gas to escape from the cavity due to the fast filling and cooling speed, and the pores in the casting will expand during the heat treatment process, which leads to the decrease of the mechanical properties of the casting.
[0003] Therefore, the Al-Cu alloy (such as ZL205A) with higher specific strength and heat treatable strengthening becomes the preferred material for the force structure part. However, the solid-liquid two-phase region is wide (more than 100 DEG C), so that the feeding channel is easily blocked by the dendrites in advance when the metal liquid solidifies and shrinks, and shrinkage and shrinkage defects are generated. The traditional casting process is difficult to make up for these problems due to the limitation of liquid feeding, so that the casting process control of the Al-Cu alloy is challenged. The traditional gravity casting can be heat treated and strengthened, but the metal liquid itself depends on gravity to fill the mold, and the feeding capacity is limited, and "feeding lag" is easily formed in the thin-walled corner, far from the gate and other areas, and the defect rate is often more than 15%, and the grain is coarse (the average size is often more than 200 mu m), which further aggravates the formation of shrinkage between dendrites. The extrusion casting realizes high-pressure solidification by applying a high pressure of 60-100 MPa, which can significantly improve the density and mechanical properties. However, for the complex structure parts such as the ship motor end cover, the pressure will be unevenly attenuated in the transmission process, so that the complex parts such as the root of the cooling fin and the shaft hole wall far from the injection pressure area still have shrinkage and shrinkage defects caused by insufficient feeding, and the defects in the number and distribution area are obviously improved, but still cannot be completely eliminated.
[0004] In order to break through the limitation of single process, the application adopts an innovative forming method of liquid pressure filling: in the semi-solid state, the retreat type cavity is built by the downward pull of the downward pull rod to provide compensation space for the solidification shrinkage of the metal liquid, and then the alloy is integrally forged to produce a special extrusion casting mode of material flow, namely extrusion casting-integrally forging integrated molding, namely casting-forging integrated molding. It aims to solve the defect control problem of complex thin-walled Al-Cu alloy motor shell end cover.
[0005] In the application, the new Er, Zr micro-alloyed Al-Cu alloy will precipitate Al3(Er, Zr) dispersoids during T6 heat treatment. According to the latest research results, θ' phase directly precipitates on the {100} surface of Al3(Er, Zr) dispersoids, which provides a new way to improve the performance of motor shell end cover. Through suitable heat treatment process, Al3(Er, Zr) phase can significantly reduce the energy barrier of θ' phase nucleation and provide abundant nucleation sites, which helps to form finer and more dispersed θ' phase, and further improves the mechanical properties of motor shell end cover. SUMMARY
[0006] The main purpose of the application is to provide a new Al-Cu-Mn casting-forging integrated motor shell end cover with high casting performance, and to improve the cracks, pores, shrinkage porosity and other defects of complex thin-walled parts by optimizing process parameters, and to expand its application range.
[0007] In order to achieve the above purpose, the application provides the following technical scheme:
[0008] The chemical composition (wt.%) of the high-strength aluminum alloy used in the application is: Cu: 5.5%, Mn: 0.6%, Cd: 0.25%, Er: 0.1%, Zr: 0.15%, Ti: 0.1%, Fe: 0.08%, and the rest is Al.
[0009] The application adopts a forming method of liquid pressure filling to prepare Al-Cu-Mn casting-forging integrated motor shell end cover: in the semi-solid state, the retreat type cavity is built by the downward pull of the downward pull rod to provide compensation space for the solidification shrinkage of the metal liquid, and then the alloy is integrally forged to produce a special extrusion casting mode of material flow, namely extrusion casting-integrally forging integrated molding; including the following steps:
[0010] Step one
[0011] After the aluminum alloy is melted, it is kept at 680 ℃ for 5-6 h, nitrogen gas is introduced for stirring for 20 min at a speed of 400 r / min, and then it is kept still for 15 min, and then it is poured into a preheated to 250 ℃ pressure cylinder;
[0012] Step two
[0013] The integrated casting and forging preparation method is produced by the self-developed ZDL 400 integrated casting and forging machine equipment, which mainly consists of a mold loading module, a pressure injection module, a downward pulling module and a forging module, as shown in Figure 1 (a) shown in.
[0014] The mold loading module includes a cake cavity, a sprue, an ingate and a casting cavity connected with the overflow groove on the side of the casting cavity, and the ingate, the casting cavity and the overflow groove are located on the upper surface of the lower mold;
[0015] The pressure injection module is provided with a pressure injection cylinder, as shown in (b), the pressure injection cylinder has a nominal force of 150T and a stroke of 650mm, the hammer head (equivalent to the needle head) corresponding to the outlet of the pressure injection cylinder has a diameter of 60~80mm, the pressure injection cylinder is provided with an extrusion punch (equivalent to the piston) inside, the front of the extrusion punch is filled with metal liquid, and the rear is filled with nitrogen, the nitrogen is connected with the nitrogen gas jar for pressurization to assist the action of the extrusion punch, so as to achieve instantaneous pressurization and meet the requirements of the equipment on pressure and reaction time; the hammer head of the outlet of the pressure injection cylinder is connected with the cake cavity;
[0016] The downward pulling module includes a vertical retreat pulling rod, and the upper end surface of the retreat pulling rod is connected with the center position of the casting cavity;
[0017] The forging module includes: an upper forging block, which is located above the casting cavity; the upper forging block is controlled by a main forging cylinder to move up and down; and a downward pulling cylinder controls the upward and downward movement of the retreat pulling rod.
[0018] As shown in (c), the main forging cylinder has a nominal force of 300T and a stroke of 200mm, guide cylinders are arranged on both sides of the guide column to ensure the verticality of the movement; the downward pulling cylinder has a nominal force of 100T and a stroke of 120mm. The physical diagram of the integrated casting and forging machine is shown in (d).
[0019] As shown in (e), when there is only injection pressure, the retreat pulling rod does not retreat, and there is no forging pressure, it is extrusion casting. As shown in (f), when the retreat pulling rod retreats to form a retreat cavity, and then the upper forging block is pressed down, at this time, the excess un-solidified forging excess material flows into the retreat cavity in the central area, which is called flow retreat integrated casting and forging, that is, Figure 2 (b), the purple cylindrical rod is the retreat pulling rod, and the yellow upper part is the upper forging block; when the retreat pulling rod reaches the specified position to form a certain reserved cavity, the upper forging block starts to be pressed down at a set pressure, the casting produces plastic deformation, and the upper forging block stops and continues to be pressed when it reaches the specified position, that is, the upper surface of the casting, until the casting is completely solidified;
[0020] Step three
[0021] The castings are taken out for T6 heat treatment under solidification of injection pressure and forging pressure, 530 DEG C solid solution 8h, then water quenching, then 175 DEG C artificial aging 8h, and finally air cooling, and the heat treatment furnace is selected as a box type air circulation resistance furnace.
[0022] The motor shell end cover mold chart is as shown in Figure Figure 2 (c) shown, (d) is the wall thickness analysis chart of the motor shell end cover, the end cover wall thickness is 6mm, and the end cover rib thickness is 7mm.
[0023] In the step two, the time is calculated from the beginning of injection into the casting cavity, and through multiple tests, it is found that the motor end cover organization is dense, without cracks, shrinkage porosity and other defects by adopting 6.0s retreat and 6.1s forging.
[0024] The enrichment of the Er element at the solid-liquid interface increases the composition undercooling degree of the solid-liquid interface front, promotes the dendrite growth, reduces the secondary dendrite arm spacing, and refines the grains; the Al3Zr generated by the peritectic reaction refines the grains as a heterogeneous nucleation core in the solidification process; in the aging process, the Al3(Er, Zr) secondary phase provides non-uniform nucleation sites for the main strengthening phase θ' phase, and reduces the size of the θ' precipitated phase. On the other hand, the segregation of the Er element on the θ' phase improves the interface stability and increases the strength of the alloy.
[0025] Compared with the prior art, the motor shell end cover with complex shape, long filling time and variable cross-section filling section can realize effective control of the microstructure and casting defects of the aluminum alloy motor end cover, and obtain high-quality aluminum alloy castings with refined solidification structure and eliminated casting hot cracks.
[0026] Compared with the prior art, the motor shell end cover with complex shape, long filling time and variable cross-section filling section can realize effective control of the microstructure and casting defects of the aluminum alloy motor end cover, and obtain high-quality aluminum alloy castings with refined solidification structure and eliminated casting hot cracks.
[0027] The Al-Cu alloy has more excellent mechanical properties, high-temperature properties and the like than the Al-Si alloy, and the present application has a broader application scenario.
[0028] The casting and forging integrated forming technology with flow type retreat has the advantages of reducing defects, short process and the like. The shrinkage, shrinkage hole, crack and the like are reduced. Through the combined action of the mold and the optimization of the casting and forging integrated forming process parameters, large deformation forging is realized, and there is no waste, the forming shape is high, and the performance is excellent. The forging pressure promotes the flow of the liquid phase between the dendrites, thereby effectively supplementing the pore defects generated in the solidification process. BRIEF DESCRIPTION OF DRAWINGS
[0029] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description of exemplary embodiments of the present application taken in conjunction with the accompanying drawings, in which like reference characters refer to the like parts throughout the different views. The exemplary embodiments of the present application, however, can be embodied in many different forms.
[0030] Figure 1 (a) ZDL 400 integrated casting and forging machine structure schematic diagram (b) injection system design (c) upper forging cylinder and lower drawing cylinder design (d) integrated casting and forging machine physical diagram (d) extrusion casting principle diagram (e) integrated casting and forging principle diagram;
[0031] Figure 2 Motor shell end cover mold diagram: (a) pouring system schematic diagram (b) integrated casting and forging forming process design diagram (c) mold physical diagram (d) wall thickness size diagram;
[0032] Figure 3 X-ray detection results of motor shell end cover (a) extrusion casting (b) yielding flow type integrated casting and forging;
[0033] Figure 4 Macroscopic morphology of motor shell end cover (a) extrusion casting (b) yielding flow type integrated casting and forging;
[0034] Figure 5 Defect proportion statistics of steering knuckle under different forming processes: (a) X-ray detection results; (b) macroscopic section statistics
[0035] Figure 6 Hardness curve at different positions;
[0036] Figure 7 Average grain size curve at different positions;
[0037] Figure 8 The sample physical diagram obtained by the integrated casting and forging process method provided by the embodiment 1 of the present application is shown;
[0038] Figure 9 The sample physical diagram obtained by the integrated casting and forging process method provided by the comparative example 1 of the present application is shown. DETAILED DESCRIPTION
[0039] The present application will be further described in detail below in combination with the implementation examples, but the present application is not limited to the following examples.
[0040] Example 1
[0041] The alloy material used in the experiment is a 2 series aluminum alloy wafer ingot. A 400T integrated casting and forging machine is used. A 400 kg ingot is placed in the furnace, and the furnace temperature is raised to 680 ℃, and the temperature is maintained for 5-6 h. Before pouring, the operation of degassing and deslagging is required. Nitrogen is introduced and stirred for 20 min at a stirring speed of 400 r / min, and then it is left for 15 min. The specific composition of the alloy melt is Cu: 5.5%, Mn: 0.6%, Cd: 0.25%, Er: 0.1%, Zr: 0.15%, Ti: 0.1%, Fe: 0.08%, and the rest is Al.
[0042] The injection pressure is 15 MPa, the lower delay time is 6.0 s, the upper forging delay time is 6.1 s, and the upper forging pressure is maintained at 10 MPa. At this time, the integrated casting and forging is formed, the defect ratio is observed and counted, the hardness curve at different positions is recorded, and the average grain size curve at different positions is recorded.
[0043] Comparative Example 1
[0044] The alloy material used in the experiment is a 2 series aluminum alloy wafer ingot. A 400T integrated casting and forging machine is used. A 400 kg ingot is placed in the furnace, and the furnace temperature is raised to 680 ℃, and the temperature is maintained for 5-6 h. Before pouring, the operation of degassing and deslagging is required. Nitrogen is introduced and stirred for 20 min at a stirring speed of 400 r / min, and then it is left for 15 min. The specific composition of the alloy melt is Cu: 5.5%, Mn: 0.6%, Cd: 0.25%, Er: 0.1%, Zr: 0.15%, Ti: 0.1%, Fe: 0.08%, and the rest is Al.
[0045] The injection pressure is 15 MPa, the lower delay time is 6.0 s, the upper forging delay time is 6.1 s, and the upper forging pressure is maintained at 10 MPa. At this time, the integrated casting and forging is formed, the defect ratio is observed and counted, the hardness curve at different positions is recorded, and the average grain size curve at different positions is recorded.
[0046] Figure 3 The X-ray detection results of the motor shell end cover formed by extrusion casting and delay flow type integrated casting and forging are shown. In the extrusion casting, a large number of hole defects appear around the root of the heat dissipation fin far from the gate end. Since the density of these holes is low, they usually appear white under X-ray. The corresponding cross-sectional photo of the casting is shown in Figure 4, a large number of un-closed pores and shrinkage defects were observed. The position is prone to air entrapment due to large cross-sectional area change during pouring. The solidification speed difference is large, the metal liquid feeding is easily blocked by the fast solidified ribs, and the metal liquid flow and feeding are difficult due to the complex angle corners, and shrinkage holes are easily formed. In the flow-receding integrated casting and forging process, there are mainly a small amount of segregation, and no obvious hole defects. The receding eliminates part of the solidification shrinkage stress and strain, the receding system forms an open space for receding, releases the counterforce generated by the internal pressure of the casting, makes the forging force acting on the casting play the maximum effect, and strongly compresses the casting to form macroscopic volume shrinkage and microscopic intergranular shrinkage, effectively preventing the generation of defects, so compared with extrusion casting, this process can significantly reduce the generation of hole defects.
[0047] In order to more clearly compare the improvement of defects by forging, the X-ray detection results and the defect proportion in the macroscopic section of the motor shell end cover under different process conditions were counted, as shown in Figure 5 The proportion of white hole defects in the X-ray detection results of the extrusion casting motor shell end cover is 7.3%; the defect proportion of the motor shell end cover after integrated casting and forging is significantly reduced, and the defect proportion is only 2.5%. The defect classification and statistics of the motor shell end cover section under two process conditions are shown in Figure 5 (b). After receding and forging, large-sized hole defects almost disappear and are converted into small-sized shrinkage and shrinkage hole defects; the proportion of crack defects decreases, and the proportion of abnormal segregation defects increases, which is because the low-melting-point eutectic liquid at the solidification end of the forging pressure "closes" the shrinkage and cracks, thereby converting into abnormal segregation; the proportion of pores is significantly reduced, on the one hand because the process improvement reduces the number of pores; on the other hand, the proportion of pores is reduced due to the compression of the pores.
[0048] The defect proportion of the motor shell end cover without down-drawing is reduced to 7.3%; and the defect proportion of the motor shell end cover after down-drawing + forging is continuously and significantly reduced, and the defect proportion is only 2.5%. Through statistical observation of the macroscopic section, it is found that large-sized holes and cracks are converted into small-sized segregation after down-drawing. After down-drawing, the grain size is obviously refined, and the average grain size at a distance of 10 cm from the center is reduced from 160.23 μm to 138.23 μm, and the hardness at the center position is increased by 9.6 HV.
Claims
1. A method for integral casting and forging of end caps for Al-Cu type complex-shaped thin-walled motor housings, characterized in that, The chemical composition (wt.%) of Al-Cu alloys is as follows: Cu: 5.5%, Mn: 0.6%, Cd: 0.25%, Er: 0.1%, Zr: 0.15%, Ti: 0.1%, Fe: 0.08%, with the remainder being Al; A liquid pressure filling forming method is employed: in the semi-solid stage, a collapsible cavity is constructed by pulling down a pull rod, providing compensation space for the solidification and shrinkage of the molten metal. Subsequently, the alloy is integrally forged to generate a special extrusion casting method that produces material flow, namely extrusion casting-integrated forging forming, or simply casting-forging integrated forming; including the following steps: Step 1 The experimental materials used were provided by Guangdong Huihuang Metal Products Co., Ltd. After the aluminum alloy was melted, it was held at 680 ℃ for 5-6 hours. In order to remove gas and slag, nitrogen gas was introduced and stirred for 20 minutes at a speed of 400 r / min. Then it was allowed to stand for 15 minutes and then poured into an injection cylinder preheated to 250 ℃. Step Two The integrated casting and forging manufacturing method is produced by the independently developed ZDL 400 integrated casting and forging machine, which mainly consists of a mold loading module, an injection module, a pull-down module, and a forging module. The mold loading module includes a sprue cavity, a sprue, an ingate, and a casting cavity. The side of the casting cavity is provided with multiple branch overflow grooves. The ingate, the casting cavity, and the overflow grooves are all located on the upper surface of the lower mold. The injection module is equipped with an injection cylinder with a nominal force of 150T and a stroke of 650mm. The diameter of the hammer corresponding to the outlet of the injection cylinder is 60~80mm. The injection cylinder is equipped with an extrusion punch. The front of the extrusion punch is filled with liquid metal, and the rear is filled with nitrogen. The nitrogen is connected to a nitrogen cylinder for pressurization, which helps the extrusion punch to move and achieve instantaneous pressurization to meet the equipment's requirements for pressure and reaction time. The hammer at the outlet of the injection cylinder is connected to the cake chamber. The pull-down module includes an upright relief rod, the upper end of which is connected to the center of the casting cavity; The forging die includes: an upper forging block, which is located above the casting cavity; the upper forging block is controlled to move up and down by the main forging cylinder; and a pull-down cylinder controls the up and down movement of the retraction rod. As shown in Figure (c), the main forging cylinder has a nominal force of 300T and a stroke of 200mm. To ensure its verticality, guide cylinders are installed on both sides of the guide pillars; the pull-down cylinder has a nominal force of 100T and a stroke of 120mm. When only injection pressure exists, without retraction of the pull rod or forging pressure, it is called extrusion casting. When the pull rod retracts to create a retraction cavity, the upper forging block is pressed down. At this time, the excess unsolidified forging material flows into the retraction cavity in the central area, which is called flow retraction casting-forging integral forming. When the pull rod reaches the designated position and obtains a certain reserved cavity, the upper forging block moves down with a set pressure to start forging. The casting undergoes plastic deformation. When the upper forging block reaches the designated position, i.e. the upper surface of the casting, it stops and continues to hold pressure until the casting is solidified. Step 3 Solidify under injection pressure and forging pressure, remove the casting for T6 heat treatment, solution treatment at 530 ℃ for 8 h, followed by water quenching, artificial aging at 175 ℃ for 8 h, and finally air cooling. The heat treatment furnace is a box-type air circulation resistance furnace.
2. The method according to claim 1, characterized in that, In step two, when the casting and forging are integrated, the time is calculated from the start of injection into the casting cavity. Through multiple tests, it was found that using a 6.0s yielding and a 6.1s forging time resulted in a dense motor end cover with no cracks, shrinkage cavities, or other defects.
3. The Al-Cu type complex-shaped thin-walled motor housing end cap prepared according to the method of claim 1 or 2.
4. The Al-Cu complex-shaped thin-walled motor housing end cap prepared according to the method of claim 1 or 2, with an end cap wall thickness of 6 mm and an end cap rib thickness of 7 mm.