Semi-solid aluminum alloy knuckle, manufacturing method and vehicle

Abstract

The application relates to a semi-solid aluminum alloy steering knuckle, a manufacturing method and a vehicle, which comprises the following steps: injecting a semi-solid aluminum alloy slurry into a mold and performing die casting forming to obtain a steering knuckle blank; wherein a sealing plate is arranged on the mold to make a mounting arm connecting hole on the steering knuckle blank into a blind hole with one end open and the other end closed; the steering knuckle blank is machined to make the blind hole into a through hole; and post-processing is continuously performed to obtain a semi-solid aluminum alloy steering knuckle. In view of the welding defects of the steering knuckle connecting hole, the mold is improved to some extent, so that the originally die-cast through hole becomes a semi-closed blind hole, so that the semi-solid aluminum alloy slurry does not intersect at a large area of the part body, but sequentially advances forward, and in this way, the welding defects are avoided and even eliminated.

Description

Technical Field

[0001] This invention relates to the field of automotive parts manufacturing technology, specifically to a semi-solid aluminum alloy steering knuckle, its manufacturing method, and a vehicle. Background Technology

[0002] Aluminum is the most abundant metallic element in the Earth's crust. It has advantages such as low melting point, low density, good plasticity, and corrosion resistance. The density of aluminum and aluminum alloys is about 1 / 3 that of iron, which has the advantage of being lightweight. It is the second most used metal in automobiles after steel. In recent years, the application of aluminum alloys in chassis parts has developed rapidly and has been widely used in parts such as calipers, wheels, and control arms.

[0003] Semi-solid metals were first discovered by Professor Flemings and his doctoral student Spencer at MIT, who also found their rheological properties. As an alternative to traditional casting and forging processes, semi-solid metal processing technology is rapidly developing. In the absence of shear force, semi-solid slurries with a solid fraction of 0.5-0.7% resemble solids, exhibiting self-supporting properties. However, when shear force is applied, the viscosity of the material significantly decreases, allowing it to flow like a liquid. This unique characteristic makes semi-solid processes an attractive alternative to traditional casting. The temperature of semi-solid metals lies between the solidus and liquidus of alloys. There are two methods for preparing semi-solid metals: heating and cooling. The method of processing semi-solid metals using die casting is called semi-solid die casting. In terms of filling capacity, tolerances, surface finish, and production efficiency, semi-solid die casting is comparable to conventional die casting and has significant advantages over metal mold and sand casting. Furthermore, semi-solid die casting can effectively reduce internal porosity and shrinkage defects in castings, resulting in high density. It can also be strengthened through heat treatment to meet product requirements.

[0004] Compared to traditional die casting technology, the biggest advantage of semi-solid die casting lies in the smooth flow of the slurry during the die casting process. The slurry is less prone to air entrapment and shrinkage during solidification, thus reducing porosity defects. The casting can also be subsequently heat-treated for strengthening. In contrast, the flow in ordinary die casting is relatively chaotic and uncontrollable. Utilizing this characteristic, the molten metal can be orderly filled into the metal mold cavity according to the designed sequence, pushing air to the end of the cavity and finally expelling it through the venting channel, avoiding gas entrapment and reducing porosity defects. Semi-solid molten metal is a non-Newtonian fluid, belonging to the shear-thinning fluid category. When at rest, semi-solid metal has solid properties with a high apparent viscosity, allowing it to maintain its shape for easy transfer. Once shear is applied to the slurry, its apparent viscosity rapidly decreases, and its fluidity significantly increases. Under low flow stress, it fills the cavity, reducing energy consumption and mold wear.

[0005] Steering knuckles are crucial chassis components subjected to complex stresses. They require materials with high strength, toughness, and fatigue resistance, which conventional aluminum alloy properties and casting processes cannot achieve. Research and development of high-performance aluminum alloy steering knuckles began abroad over a decade ago, with some large-scale applications already implemented in Europe, America, and Japan. Europe and America primarily use forged aluminum alloy steering knuckles, while Japan uses extrusion-cast aluminum alloy steering knuckles. Semi-solid extrusion casting is an advanced casting process that can also meet the performance requirements of steering knuckles.

[0006] The related technology CN106378432A provides a method for producing aluminum alloy steering knuckles using a horizontal extrusion casting machine. The main methods are: (1) mold casting and overflow system design; (2) cooling water channel design; and (3) local pressurization design. This scheme, implemented using a horizontal extrusion casting machine, can produce qualified aluminum alloy steering knuckles. By controlling each process step, automated production can be achieved. However, the above-mentioned extrusion casting scheme also has some disadvantages, such as high requirements for molds and equipment, and the presence of certain oxide scale inclusions. Extrusion casting requires the application of static pressure during solidification to achieve rheological filling, high-pressure solidification, and a small amount of plastic deformation. This requires the equipment to have sufficient pressure and to act continuously for a certain period of time, placing high demands on both the equipment and the mold.

[0007] Related technology CN106917014A provides a method for extruding and casting an aluminum alloy steering knuckle for automobiles. Specifically, the prepared aluminum alloy material is placed in a crucible furnace and heated to melt. When the aluminum alloy reaches a certain temperature, it undergoes refinement, modification, and degassing treatments. Then, the molten alloy is poured into the feeding chamber of the extrusion casting machine through a gating system. Under the action of the bottom piston, the molten metal fills the mold cavity and solidifies under piston pressure. The casting is then subjected to solution treatment and aging to obtain a steering knuckle with high comprehensive mechanical properties. This method also targets the extrusion casting process for preparing steering knuckles using a horizontal extrusion casting machine. Extrusion casting also has some drawbacks, such as high requirements for molds and equipment, and the presence of oxide scale and inclusions.

[0008] CN105642860A discloses a semi-solid die-casting method for turbocharger impellers. Specifically, a semi-solid billet or slurry is pressed or poured into the die-casting machine's slurry cup. A pressure injection rod then forces the semi-solid billet or slurry from the slurry cup through the sprue cavity into the mold cavity, directly filling the mold to obtain the product. The resulting waste includes a sprue and a sprue handle. The diameter of the sprue is smaller than the diameter of the sprue handle, and the dimensional difference between the two forms a step to remove oxide scale from the billet surface. The ratio between the thickness of the sprue handle and the diameter of the sprue is between 0.5 and 2.5. The impeller consists of a thick central portion and thin blades, with 8 to 30 thin blades. The impeller includes large and small blades of different sizes, evenly distributed along the outer diameter, and is centrally symmetrical. Products prepared using this method have the advantages of a short process flow, less waste, and low cost.

[0009] The semi-solid die-casting method for turbocharger impellers described above still has some drawbacks, such as:

[0010] Disadvantage 1: This technology is suitable for parts with centrosymmetry, where there is no possibility of slurry confluence during the filling process. For non-centrosymmetric parts, and parts where slurry confluence is possible, the confluence of semi-solid slurry can cause welding defects, and the above technology has no good solution. Specifically, after the semi-solid metal fluid separates in the mold, it travels a certain distance and then rejoins. This process of separation and rejoining is called welding. In liquid phase casting, due to the higher temperature, the fluids usually bond together after confluence, possessing a certain strength, and welding defects are negligible. In semi-solid die casting, due to the relatively lower molding temperature, the rejoining of fluids becomes a problem; confluence and welding should be minimized. In addition, because contaminants accumulate on the slurry surface, such as mold coatings, mold corrosion products, and impurities, the rejoining ability of the slurry surface is also reduced after contamination.

[0011] Disadvantage 2: Steering knuckles are asymmetrical, branched parts, typically exhibiting some eccentricity. The semi-solid slurry flow paths differ in each direction, and branches with longer slurry flow paths are prone to defects such as shrinkage cavities at their ends. This is because as the filling length increases, heat loss increases, the solid content of the casting rises, filling resistance increases, and the difficulty of compensation for shrinkage increases. However, the semi-solid die-casting method used for turbocharger impellers described above involves parts with relatively uniform slurry flow distances in each branch; therefore, it cannot effectively address the end-shrinkage problem in steering knuckle-type parts.

[0012] Disadvantage 3: The steering knuckle part has multiple connecting holes at its end. The aforementioned semi-solid die casting method does not offer a solution for designing these holes in the casting to avoid defects. If a through hole is created using conventional die casting, under semi-solid conditions, the semi-solid slurry will converge from both sides of the through hole towards the middle, easily leading to welding defects and causing the part to crack.

[0013] The related technology CN105798256A provides a high-strength aluminum alloy semi-solid die-casting process. This process involves heating an aluminum billet to a semi-solid state to obtain a semi-solid slurry (semi-solid thixotropic route), or melting the aluminum alloy raw material, performing melt purification treatment, and obtaining a semi-solid slurry (semi-solid rheological route) through dendrite breakage and controlled solidification techniques. The semi-solid slurry is then pressed into a mold cavity using a die-casting machine, held under pressure to solidify, and the mold is opened to remove the part. Finally, heat treatment is performed to obtain the finished steering knuckle. The resulting steering knuckle material has a tensile strength of 377 MPa, a yield strength of 320 MPa, and an elongation of 3.5%.

[0014] The aforementioned semi-solid die-casting process for high-strength aluminum alloys still has some drawbacks, such as:

[0015] Disadvantage 1: This technology does not involve specific casting design work to avoid casting defects, and there are no part drawings or physical objects; there are no effective solutions for casting defects such as welding defects.

[0016] Disadvantage 2: This technology has no effective solution for the problem of shrinkage at the end of the steering knuckle.

[0017] Disadvantage 3: The steering knuckle part has multiple connecting holes at its end. This technology does not offer a solution on how to design such holes in the casting to avoid defects.

[0018] Disadvantage 4: The elongation of the material obtained by the rheological die casting method in this technology is 3.5%, which is too low to meet the performance requirements of steering knuckle parts. Steering knuckles are key chassis components with high requirements for strength and toughness, and generally require an elongation of ≥8 (or 10%). Materials with an elongation of 3.5% cannot be practically used. Summary of the Invention

[0019] This application provides a semi-solid aluminum alloy steering knuckle, a manufacturing method, and a vehicle, which can solve the casting defects of the end connection hole of the semi-solid aluminum alloy steering knuckle part and avoid welding defects.

[0020] In a first aspect, embodiments of this application provide a method for manufacturing a semi-solid aluminum alloy steering knuckle, which includes the following steps:

[0021] The semi-solid aluminum alloy slurry is injected into a mold and die-cast to obtain a steering knuckle blank;

[0022] In this process, a sealing plate is provided on the mold so that the mounting arm connection hole on the steering knuckle blank becomes a blind hole with one end open and the other end closed.

[0023] The steering knuckle blank is machined to make the blind hole a through hole;

[0024] Further post-processing was carried out to obtain a semi-solid aluminum alloy steering knuckle.

[0025] In response to welding defects in steering knuckle connection holes, this application has made certain improvements to the mold, turning the original die-cast through hole into a semi-closed blind hole. This prevents the semi-solid aluminum alloy slurry from converging over a large area on the part body, instead allowing it to advance sequentially. This method avoids or even eliminates welding defects.

[0026] In conjunction with the first aspect, in one embodiment, the mounting arm connection hole is a shock absorber mounting arm connection hole or a steering tie rod mounting arm connection hole.

[0027] In conjunction with the first aspect, in one embodiment, the manufacturing method further includes:

[0028] The opening of the slag collection bag is placed in front of the slurry flow direction to collect the gas and slag that are discharged when the slurry flows to form the blind hole.

[0029] In conjunction with the first aspect, in one embodiment, the opening of the slag collection bag is located near the side of the blind hole opening, so as to offset the slag collection bag.

[0030] To facilitate venting and slag removal and optimize casting quality, the opening of the slag collection pouch is positioned in front of the slurry flow direction to collect the gas and inclusions discharged when the slurry flows and forms the blind hole. Simultaneously, the opening of the slag collection pouch is positioned close to the side of the blind hole opening, thus offsetting the slag collection pouch. Since the connecting hole becomes a semi-closed blind hole during die casting, the semi-solid aluminum alloy slurry in this area propagates sequentially forward in the same direction. By offsetting the slag collection pouch and placing it close to the side of the blind hole opening, gases and inclusions prone to defects are more easily guided to the slag pouch and vent for discharge, thereby optimizing casting quality.

[0031] In conjunction with the first aspect, in one embodiment, the manufacturing method further includes:

[0032] A first protrusion is provided on the inner wall of the mold to form a first groove at the thick part of the steering tie rod mounting arm of the steering knuckle blank.

[0033] At the steering tie rod mounting arm of the steering knuckle, during die casting, two streams of slurry converge from both sides and then propel forward to fill the arm. Because of this convergence of two streams, welding defects are prone to occur. To address this issue, a first protrusion is provided on the inner wall of the mold to form a first groove at the thickest part of the steering tie rod mounting arm in the steering knuckle blank. The presence of this first groove reduces the wall thickness at this location, increasing the shear effect of the semi-solid aluminum alloy slurry during filling and enhancing its fluidity. Simultaneously, it reduces the free flow space of the semi-solid aluminum alloy slurry, lowering the risk of welding defects caused by the convergence of the slurry.

[0034] In conjunction with the first aspect, in one embodiment, there are three first protrusions and three corresponding first grooves, which are distributed in a triangular pattern.

[0035] In conjunction with the first aspect, in one embodiment, the manufacturing method further includes:

[0036] A second groove is provided on the inner wall of the mold to form a second protrusion at the thick part of the steering tie rod mounting arm of the steering knuckle blank for accommodating welding defects;

[0037] The steering knuckle blank is machined to remove the second protrusion.

[0038] To eliminate welding defects in the thick part of the steering tie rod mounting arm of the steering knuckle, a second groove is provided on the inner wall of the mold to form a second protrusion for accommodating welding defects in the thick part of the steering tie rod mounting arm of the steering knuckle blank. The protrusion is designed to squeeze the welding defects into the protrusion, and then the protrusion is removed by machining, thereby eliminating the welding defects.

[0039] In conjunction with the first aspect, in one embodiment, the manufacturing method further includes:

[0040] A smooth transition surface is provided on the inner wall of the mold to eliminate the damper mounting arm reinforcing ribs of the steering knuckle blank.

[0041] In conjunction with the first aspect, in one embodiment, the die-casting injection speed is 0.1 to 5 m / s, and the applied pressure is 50 to 150 MPa.

[0042] In conjunction with the first aspect, in one embodiment, after injecting a slurry of semi-solid aluminum alloy into a mold and die-casting it, the manufacturing method further includes:

[0043] Pressurization and solidification are carried out.

[0044] In conjunction with the first aspect, in one embodiment, the holding pressure is 83–123 MPa and the holding time is 20–40 s.

[0045] In conjunction with the first aspect, in one embodiment, the steering knuckle blank is locally pressurized during pressure holding and solidification.

[0046] In conjunction with the first aspect, in one embodiment, the semi-solid aluminum alloy is A356.2 aluminum alloy, and its chemical composition, by mass percentage, includes:

[0047] The elemental composition is 0.40-0.45% Mg, 0.10-0.20% Ti, 6.5%-7.5% Si, ≤0.12% Fe, ≤0.05% Mn, ≤0.1% Cu, ≤0.05% Zn, and the remainder is Al.

[0048] In conjunction with the first aspect, in one embodiment, the solid content of the semi-solid aluminum alloy slurry is 40-55%.

[0049] In conjunction with the first aspect, in one embodiment, the post-processing includes: heat treatment of the steering knuckle blank.

[0050] In conjunction with the first aspect, in one embodiment, the heat treatment includes: solution treatment at 520–540°C for 3.5–6 hours, followed by aging treatment at 160–180°C for 3.5–6 hours.

[0051] In conjunction with the first aspect, in one embodiment, the heat treatment includes: solution treatment at 540°C for 4 hours, followed by aging treatment at 170°C for 5 hours.

[0052] In conjunction with the first aspect, in one embodiment, before heat treatment of the steering knuckle blank, the post-treatment further includes: removing the slag bag and flash of the steering knuckle blank, and cutting off the gating.

[0053] Secondly, embodiments of this application provide a semi-solid aluminum alloy steering knuckle, which is manufactured using any of the semi-solid aluminum alloy steering knuckle manufacturing methods described above.

[0054] Thirdly, embodiments of this application provide a vehicle that includes a semi-solid aluminum alloy steering knuckle as described above.

[0055] The beneficial effects of the technical solutions provided in this application include at least the following:

[0056] (1) In response to the welding defects in the steering knuckle connection hole, this application has made certain improvements to the mold, so that the original die-cast through hole has become a semi-closed blind hole, so that the semi-solid aluminum alloy slurry does not have a large area of ​​convergence at the part body, but advances forward in sequence, thereby avoiding or even eliminating welding defects.

[0057] (2) To facilitate venting and slag removal and optimize casting quality, the opening of the slag collection bag is positioned in front of the slurry flow direction to collect the gas and inclusions discharged when the slurry flows to form the blind hole. Simultaneously, the opening of the slag collection bag is positioned close to the side of the blind hole opening, thus offsetting the slag collection bag. Since the connecting hole becomes a semi-closed blind hole during die casting, the semi-solid aluminum alloy slurry here propagates sequentially in the same direction. By offsetting the slag collection bag and positioning it close to the side of the blind hole opening, gases and inclusions prone to defects are more easily guided to the slag bag and vent for discharge, thereby optimizing casting quality.

[0058] (3) At the steering tie rod mounting arm of the steering knuckle, during die casting, two streams of slurry converge from both sides and then propel forward to fill the steering tie rod mounting arm. Because of the convergence of these two streams, welding defects are prone to occur here. To address this issue, a first protrusion is provided on the inner wall of the mold to form a first groove at the thickest part of the steering tie rod mounting arm of the steering knuckle blank. The presence of the first groove reduces the wall thickness at this location, increasing the shear effect of the semi-solid aluminum alloy slurry during filling, increasing the fluidity of the semi-solid aluminum alloy slurry, and simultaneously reducing the free flow space of the semi-solid aluminum alloy slurry, thus lowering the risk of welding defects caused by the convergence of the semi-solid aluminum alloy slurry.

[0059] (4) In order to eliminate the welding defects at the thick part of the steering tie rod mounting arm of the steering knuckle, a second groove is provided on the inner wall of the mold to form a second protrusion for accommodating the welding defects at the thick part of the steering tie rod mounting arm of the steering knuckle blank; the protrusion is designed so that the welding defects can be squeezed into the protrusion, and then the protrusion is removed by machining, thereby eliminating the welding defects.

[0060] (5) In order to reduce the risk of welding defects at the shock absorber mounting arm and avoid the formation of welding defects at the shock absorber mounting arm, it is necessary to reduce the slurry confluence. In order to reduce the slurry confluence, it is necessary to reduce the number of fluid sources. Therefore, this application modifies the traditional design by setting a smooth transition surface on the inner wall of the mold to eliminate the shock absorber mounting arm reinforcing rib of the steering knuckle blank. The slurry confluence point is changed from 2 to 0. Here, the slurry filling presents the characteristic of a single filling front edge flat (curved) surface advancing smoothly forward, which will not produce welding defects and meets the design requirements of semi-solid casting.

[0061] (6) In order to solve the problem of the risk of shrinkage defects at the end of semi-solid aluminum alloy steering knuckle parts, this application reduces the risk of shrinkage defects by local pressure. Specifically, after the semi-solid aluminum alloy slurry is injected into the mold and after die casting, the slurry is held under pressure to solidify and gradually cool into a steering knuckle blank. During the holding pressure solidification, the gradually cooling steering knuckle blank is locally pressurized to eliminate possible end shrinkage defects.

[0062] (7) The steering knuckle is a crucial component of the chassis, supporting the weight of the vehicle body and bearing the steering torque and braking torque during braking. Its high performance requirements directly affect the overall reliability of the vehicle. Furthermore, the steering knuckle is part of the unsprung mass, and reducing its weight significantly improves vehicle ride comfort and handling stability. Conventional aluminum castings have lower performance, limiting their application. After repeated experiments, the applicant selected A356.2 aluminum alloy and adjusted the Mg and Ti element composition requirements to the upper limit of the standard. Specifically, the Mg requirement was adjusted from 0.30-0.45% to 0.40-0.45%, and the Ti content was adjusted from no more than 0.20% to 0.10-0.20%. Magnesium improves strength and machinability, while titanium significantly refines grains, increases strength, and reduces hot cracking. Other elemental chemical compositions are: Si 6.5%-7.5%, Fe ≤0.12%, Mn ≤0.05%, Cu ≤0.1%, and Zn ≤0.05%. The T6 heat treatment process was used, involving solution treatment at 540℃ for 4 hours, followed by aging treatment at 170℃ for 5 hours. The mechanical properties achieved after heat treatment were: tensile strength ≥310MPa, yield strength ≥230MPa, and elongation after fracture ≥10%.

[0063] In summary, the semi-solid rheo-die casting process described in this application boasts advantages such as high production efficiency, excellent filling capacity, high surface finish of castings, and fewer internal porosity and shrinkage defects, making it one of the mainstream directions for the future development of aluminum alloy casting technology. The steering knuckle production process has been changed from ductile iron sand casting to high-solid-phase semi-solid aluminum alloy rheo-die casting. Combined with optimized structural design, the weight has been reduced by 50%, demonstrating significant lightweighting effects. Through CAE analysis optimization of the casting process and heat treatment strengthening, the mechanical properties and internal quality of the steering knuckle castings are excellent. Both destructive force bench tests and durability bench tests have been verified, indicating promising application prospects. The development of the semi-solid rheo-die casting steering knuckle has provided a solid foundation for mastering the structural design of parts based on the characteristics of the semi-solid rheo-die casting process and the key points of casting quality inspection, laying a good foundation for promoting this process to more parts in the future. Attached Figure Description

[0064] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 Simulation diagram of the connecting hole designed for conventional die casting process;

[0066] Figure 2 Simulation diagram of casting filling for connecting holes designed for conventional die casting process;

[0067] Figure 3 A schematic diagram showing cracks appearing at the connection hole of a part manufactured using a conventional die-casting process;

[0068] Figure 4 A simulation diagram of a semi-closed blind hole provided for an embodiment of this application;

[0069] Figure 5 A simulation diagram of the filling process for a semi-closed blind hole provided in an embodiment of this application;

[0070] Figure 6 Results of the arm filling test for the steering tie rod;

[0071] Figure 7 The simulation diagrams for the inflated arm of the steering tie rod are shown, where a represents the case with 73% inflatation and b represents the case with 88% inflatation.

[0072] Figure 8 This is a schematic diagram of the first groove on the steering tie rod mounting arm provided in an embodiment of this application;

[0073] Figure 9 The simulation diagram of the filling of the steering tie rod mounting arm with the first groove provided for the embodiment of this application is shown, where a is the case when the filling is 73% and b is the case when the filling is 88%.

[0074] Figure 10 This is a model diagram of the steering knuckle;

[0075] Figure 11 Simulation diagram of the filling process for the steering knuckle;

[0076] Figure 12 This is a partial filling test result;

[0077] Figure 13 The partial filling test results provided in this application embodiment after removing the reinforcing ribs of the shock absorber mounting arm;

[0078] Figure 14The simulation diagram of the filling process after removing the reinforcing ribs of the shock absorber mounting arm provided in the embodiments of this application;

[0079] Figure 15 The following is a simulation diagram of steering knuckle filling provided in the embodiments of this application; where a represents the case with 12.9% filling, b represents the case with 37.5% filling, c represents the case with 47.8% filling, d represents the case with 71.2% filling, e represents the case with 81.6% filling, f represents the case with 92% filling, g represents the case with 98.9% filling, and h represents the case with 100% filling.

[0080] Figure 16 The following is a simulation diagram of the solidification of a steering knuckle provided in an embodiment of this application; where a represents the case with a solid fraction of 45.5%, b represents the case with a solid fraction of 53.4%, c represents the case with a solid fraction of 63.7%, d represents the case with a solid fraction of 77.2%, e represents the case with a solid fraction of 83.2%, f represents the case with a solid fraction of 90%, g represents the case with a solid fraction of 94.6%, and h represents the case with a solid fraction of 97.5%.

[0081] Figure 17 Optical microscope images of steering knuckle tissue provided in embodiments of this application;

[0082] Figure 18 This is a diagram showing the location distribution of steering knuckle sample numbers provided in the embodiments of this application;

[0083] Figure 19 An X-ray image of a steering knuckle provided in an embodiment of this application.

[0084] In the diagram: 1. Mounting arm connection hole; 2. Slag collection bag; 3. Steering tie rod mounting arm; 4. First groove; 5. Shock absorber mounting arm reinforcing rib. Detailed Implementation

[0085] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0086] The steering knuckle component has multiple connection holes at its end, such as those for the shock absorber mounting arm and the steering tie rod mounting arm. If a through hole is to be created using conventional die-casting, this is achieved by using a slider or core-pulling mechanism on the mold. However, this semi-solid process inevitably introduces welding defects, leading to cracking of the component under stress. Figure 1The image shows a casting scheme for the connecting hole designed according to conventional die-casting processes. Figure 2 As shown, according to this scheme, the two semi-solid fluids will advance separately from both sides of the through-hole and converge in the middle. Welding defects are highly likely to occur at this point (circled in the diagram). See [link / reference]. Figure 3 As shown, the parts manufactured according to this method developed cracks at the connection holes (circled in the figure).

[0087] To address casting defects in the end connection holes of semi-solid aluminum alloy steering knuckle parts and avoid welding defects, this application provides a manufacturing method for a semi-solid aluminum alloy steering knuckle, comprising the following steps:

[0088] 101: A semi-solid aluminum alloy slurry is injected into a mold and die-cast to obtain a steering knuckle blank; wherein a sealing plate is provided on the mold so that the mounting arm connection hole 1 on the steering knuckle blank is a blind hole with one end open and the other end closed, such as... Figure 4 As shown.

[0089] 102: The steering knuckle blank is machined to make the blind hole a through hole.

[0090] 103: Continue post-processing to obtain a semi-solid aluminum alloy steering knuckle.

[0091] To address the welding defects in the steering knuckle connection holes, this application makes certain improvements to the mold, transforming the original die-cast through hole into a semi-closed blind hole. (See attached image.) Figure 4 This prevents the semi-solid aluminum alloy paste from converging over a large area on the part body, instead allowing it to advance sequentially. This method avoids or even eliminates welding defects, a point also confirmed by the filling simulation diagram of the semi-closed blind hole. Figure 5 As shown.

[0092] It should be noted that the aforementioned mounting arm connection hole 1 can be a shock absorber mounting arm connection hole or a steering tie rod mounting arm connection hole.

[0093] Furthermore, in order to facilitate the exhaust and slag removal, the manufacturing method further includes: placing the opening of the slag collection bag 2 in front of the slurry flow direction to collect the gas and slag that are discharged when the slurry flows to form the blind hole.

[0094] Furthermore, to optimize casting quality, see [reference needed]. Figure 4 As shown, the opening of the slag collection bag 2 is close to the side of the blind hole opening, so that the slag collection bag 2 is offset.

[0095] Because the connecting hole becomes a semi-closed blind hole during die casting, the semi-solid aluminum alloy slurry in this area propagates forward sequentially in the same direction. By offsetting the slag collection bag 2 and placing it closer to the opening of the blind hole, gases and inclusions prone to defects are more easily guided to the slag bag and vent for discharge, thereby optimizing the casting quality. Figure 5 As shown.

[0096] See Figure 6 and Figure 7 As shown, at the steering tie rod mounting arm of the steering knuckle, during die casting, two streams of slurry converge from both sides and then propel forward to fill the steering tie rod mounting arm. Because of the convergence of these two streams, welding defects are prone to occur here (e.g., Figure 6 (The point indicated by the middle arrow).

[0097] To solve the above problem, see Figure 8 As shown, the manufacturing method further includes: providing a first protrusion on the inner wall of the mold to form a first groove 4 at the thick part of the steering tie rod mounting arm 3 of the steering knuckle blank.

[0098] The presence of the first groove 4 reduces the wall thickness at this location, increasing the shear effect of the semi-solid aluminum alloy slurry during the filling process. This increases the slurry's fluidity while reducing its free flow space, thus lowering the risk of welding defects caused by slurry confluence. The filling simulation results are shown below. Figure 9 .

[0099] The number of the first groove 4 can be designed according to actual needs. For example, see [example]. Figure 8 As shown, there are three first protrusions and three corresponding first grooves 4, which are distributed in a triangular pattern.

[0100] Furthermore, in order to eliminate welding defects at the thick part of the steering tie rod mounting arm of the steering knuckle, the manufacturing method further includes: providing a second groove on the inner wall of the mold to form a second protrusion for accommodating welding defects at the thick part of the steering tie rod mounting arm 3 of the steering knuckle blank; and machining the steering knuckle blank to remove the second protrusion.

[0101] In this embodiment, a protrusion is designed so that welding defects can be squeezed into the protrusion, and then the protrusion can be removed by machining, thereby eliminating the welding defects.

[0102] The applicant simulated the casting process of the semi-solid aluminum alloy steering knuckle to determine the location and extent of welding defects. PROCAST software was used for CAE simulation analysis of the casting process.

[0103] Simulation includes the following steps:

[0104] (1) Create a geometric model. Use CATIA software to create a geometric model, import the geometric model into ProCAST software through the software interface, and then perform a final check on the geometric model in ProCAST.

[0105] (2) Establish finite element mesh. Adapt the ProCAST software to partition the geometric model and establish surface mesh to ensure that the longitudinal section at the thinnest part of the mold cavity wall also has three layers of mesh.

[0106] (3) Set material properties. Set the mold material to H13 mold steel from the software database. Set the casting material to a semi-solid metal material from a self-created database. The physical properties of the self-created database material include density, coefficient of thermal expansion, solid fraction, and non-Newtonian fluid model parameters. The density and coefficient of thermal expansion are calculated using material property thermodynamics calculation software, the solid fraction is measured by DSC, and the non-Newtonian fluid model uses the Powerlawcut-off model, with model parameters obtained through experimental testing.

[0107] (4) Set boundary conditions. The mesh of the contact surface between the mold and the casting is set to coherent, and the interface heat transfer coefficient is set to 3000 W / (m²). 2 ·K), and the remaining parameters are set according to the specific experimental conditions.

[0108] (5) Set casting process parameters. Set the initial time step for the filling stage to 10. -4 seconds, maximum time step set to 10 -3 The parameters are: punch speed 0.4 m / s, initial slurry temperature 580℃, mold temperature 240-260℃, punch diameter 100 mm, and maximum time step during solidification 0.1 seconds. The free surface model is enabled (rapid filling), the gas model is enabled (no back pressure), the model slip algorithm is enabled (laminar flow), and the wall slip coefficient is set to 0.8.

[0109] (6) Analysis of simulation results. The software can be used to calculate the flow state, temperature field, velocity field, shear rate field, viscosity field, etc. of semi-solid metal during the casting process.

[0110] The casting uses a center gate, which ensures the shortest filling distance of the semi-solid slurry, reduces defects such as shrinkage porosity and shrinkage cavities at the end, and allows the casting to solidify sequentially from the edge to the center.

[0111] See Figure 10 The diagram shown is a model of the steering knuckle, which is made of cast iron and features large reinforcing ribs at the shock absorber mounting arm. The simulation results of the steering knuckle's filling process are shown below. Figure 11It is evident that in the initial model state, three streams of slurry converge at the shock absorber mounting arm, potentially creating two welding defects; partial filling test results also confirm this finding, see... Figure 12 As shown in the circle in the image, a welding defect has appeared.

[0112] To reduce the risk of welding defects at the shock absorber mounting arm and avoid the formation of welding defects at the shock absorber mounting arm, it is necessary to reduce slurry flow. To reduce slurry flow, it is necessary to reduce the amount of fluid source. Therefore, this application modifies the conventional design. Specifically, the manufacturing method further includes: setting a smooth transition surface on the inner wall of the mold to eliminate the shock absorber mounting arm reinforcing rib 5 of the steering knuckle blank.

[0113] Removing the middle reinforcing rib reduces grout flow, thereby lowering the risk of weld defects. Partial filling test results are shown below. Figure 13 The results of the filling simulation are shown below. Figure 14 The two methods mutually verified each other, reducing the number of slurry confluence points from two to zero. Here, the slurry filling exhibits a characteristic of a single, smoothly advancing flat (or curved) leading edge, preventing welding defects. To ensure component performance, the structural design of other locations can be further optimized to ensure the strength CAE analysis results meet the component's performance requirements.

[0114] right Figure 13 The partial filling test results were verified using fluorescent planing inspection, with samples taken every 3 mm. The inspection results were good, and no defects related to thermal joints were found. It can be seen that after removing the reinforcing ribs at the shock absorber mounting arm and optimizing the structural design of other locations, the strength CAE analysis results still meet the performance requirements of the part and eliminate the risk of welding defects at this location. The slurry front at this location is a flat (curved) surface filling, which meets the design requirements of semi-solid castings.

[0115] In step 101 above, during die casting, the injection speed is 0.1 to 5 m / s and the applied pressure is 50 to 150 MPa.

[0116] For components like steering knuckles, which are asymmetrical branched parts, there is usually a certain degree of eccentricity between the left and right sides. The semi-solid slurry flow is different in each direction. The branched parts with long slurry flow are prone to defects such as shrinkage cavities at the end. This is because as the filling length increases, heat loss increases, the solid phase fraction of the casting increases, the filling resistance increases, and the difficulty of feeding increases.

[0117] Therefore, in order to solve the problem of the risk of shrinkage defects at the casting end of semi-solid aluminum alloy steering knuckle parts, this application reduces the risk of shrinkage defects by applying local pressure. Specifically, after injecting semi-solid aluminum alloy slurry into the mold and after die casting, the manufacturing method further includes: holding the slurry under pressure to solidify it, so as to gradually cool it into a steering knuckle blank, and during the holding pressure solidification, applying local pressure to the gradually cooling steering knuckle blank, thereby eliminating possible end shrinkage defects.

[0118] The holding pressure is 83–123 MPa, and the holding time is 20–40 seconds.

[0119] The pressurization position, pressurization time, pressurization pressure, and pressurization depth of the steering knuckle blank can be determined according to actual manufacturing requirements.

[0120] For example, localized pressure can be applied to the thicker parts of the shock absorber mounting arm to eliminate potential end-shrinkage defects.

[0121] Localized pressurization involves applying pressure and compaction to specific areas of the casting using a pressurizing piston in a pressurizing cylinder to achieve a dense structure. The clearance between the pressurizing rod and the sleeve on one side is 0.1 mm. The pressurizing rod is made of the same material as the mold, H13 mold steel.

[0122] Current steering knuckles are typically made of ductile iron QTA casting, with a single piece weighing up to 4.6 kg. Two pieces are used per vehicle. On the one hand, the weight is too large, which is not conducive to weight reduction. On the other hand, the steering knuckles also need to meet the stringent performance requirements.

[0123] Therefore, this application needs to solve the problem of material selection for semi-solid aluminum alloy steering knuckles; only by using a suitable aluminum alloy grade, combined with a suitable casting process and heat treatment process, can the stringent performance requirements of the steering knuckle be met.

[0124] Currently, commonly used semi-solid rheo-die-cast aluminum alloys include grades 319, A357, and A356. Typical mechanical properties of these materials in the T6 heat-treated state are shown in Table 1.

[0125] Table 1 Mechanical properties of semi-solid cast aluminum alloy materials

[0126] 319-T6 255 152 6 357-T6 345 290 7 A356-T6 310 234 13

[0127] The steering knuckle is a crucial chassis component, supporting the vehicle's weight and bearing steering torque and braking torque. Its high performance requirements directly impact the overall vehicle reliability. Furthermore, the steering knuckle represents unsprung mass, and reducing its weight significantly improves ride comfort and handling stability. Conventional cast aluminum parts have lower performance, limiting their application.

[0128] This application selects A356-T6 as the material for the development of semi-solid aluminum alloy steering knuckles. This material has an elongation at break exceeding 10%, and its properties can be further improved through composition optimization, heat treatment optimization, and casting process optimization to meet the performance requirements of the parts. The castings are heat-treated according to the T6 heat treatment specification.

[0129] Furthermore, after repeated experiments, the applicant selected A356.2 aluminum alloy and adjusted the Mg and Ti elemental composition requirements to the upper limit of the standard. Specifically, the Mg requirement was adjusted from 0.30-0.45% to 0.40-0.45%, and the Ti content was adjusted from no more than 0.20% to 0.10-0.20%. Among these, magnesium can improve strength and machinability, while titanium can significantly refine grains, improve strength, and reduce hot cracking. The chemical composition of other elements is as follows: Si 6.5%-7.5%, Fe ≤0.12%, Mn ≤0.05%, Cu ≤0.1%, and Zn ≤0.05%.

[0130] Therefore, in this application, the semi-solid aluminum alloy is A356.2 aluminum alloy, and its chemical composition by mass percentage includes: 0.40-0.45% Mg, 0.10-0.20% Ti, 6.5%-7.5% Si, ≤0.12% Fe, ≤0.05% Mn, ≤0.1% Cu, ≤0.05% Zn, and the remainder is Al.

[0131] The semi-solid aluminum alloy slurry is obtained by melting aluminum alloy raw materials, performing melt purification treatment, and obtaining semi-solid slurry through dendrite crushing and controlled solidification technology. The solid content of the semi-solid aluminum alloy slurry is 40-55%.

[0132] After die casting, the steering knuckle blank undergoes post-processing, which includes pre-treatment, heat treatment, and shot peening, ultimately yielding a high-strength semi-solid aluminum alloy steering knuckle part.

[0133] The pretreatment includes removing the slag bag 2 and flash from the steering knuckle blank, and cutting off the gating.

[0134] The T6 heat treatment process is adopted, specifically: solution treatment at 520-540℃ for 3.5-6 hours, followed by aging treatment at 160-180℃ for 3.5-6 hours.

[0135] As a preferred option, the T6 heat treatment process is adopted, specifically: solution treatment at 540℃ for 4 hours, followed by aging treatment at 170℃ for 5 hours.

[0136] The mechanical properties achieved after heat treatment are: tensile strength ≥310MPa, yield strength ≥230MPa, and elongation after fracture ≥10%.

[0137] Following the improvements made to the end connection holes of the semi-solid aluminum alloy steering knuckle parts, the welding defects at the steering tie rod mounting arm of the steering knuckle, the welding defects at the shock absorber mounting arm, the feeding defects at the casting ends of the semi-solid aluminum alloy steering knuckle parts, and the material selection and heat treatment process of the semi-solid cast aluminum alloy, the results of the filling simulation analysis of the steering knuckle model are shown below. Figure 15 The results showed that the overall filling of the steering knuckle was stable, and the cavity was filled sequentially from the center gate, with no obvious risk of welding.

[0138] The results of the steering knuckle solidification simulation analysis of the steering knuckle model are shown below. Figure 16 Through design and gating system optimization, the solidification process of this product basically achieved sequential solidification from the edge to the center. The shrinkage compensation channel at the steering tie rod position was unobstructed. A hot spot existed at the shock absorber mounting arm position without spot cooling; however, the addition of spot cooling to the actual mold eliminated the potential risk of shrinkage porosity defects. Later trial production and fluorescent flaw detection results showed no shrinkage porosity or holes at this location. The final solidified area was the center gate position, which will be removed during subsequent machining.

[0139] Figure 17 The optical microscope image shows the microstructure of the high-strength semi-solid aluminum alloy steering knuckle part prepared by rheological die casting. As can be seen from the figure, the microstructure of the high-strength aluminum semi-solid alloy steering knuckle formed by rheological die casting is uniform. The α-aluminum is uniformly distributed in a spherical shape, and the metamorphism is normal, which meets the requirements of semi-solid structure. The eutectic silicon particles tend to be round, without needle-like or large silicon particles. There are no slender, dendritic, or rose-like phenomena, no liquid phase accumulation, and no solid-liquid phase separation morphology. The average silicon particle size is less than 8.0 μm, and the maximum silicon particle size is less than 10.0 μm.

[0140] from Figure 16 As shown in Figure a, the reinforcing ribs at the steering knuckle shock absorber mounting arm have been removed, and the gating system uses a center gate.

[0141] This application addresses issues such as welding defects at the mounting arm of the semi-solid aluminum alloy steering knuckle damper, the risk of shrinkage defects at the end of the casting, welding defects at the end connection hole, and welding defects at the steering tie rod mounting arm of the steering knuckle. The performance of the prepared parts meets the performance requirements of the steering knuckle. Specific test data are shown in Table 2, and the results have been verified through bench tests.

[0142] Table 3 Results of Mechanical Property Tests

[0143]

[0144]

[0145] See the above sample number location. Figure 18 As shown.

[0146] High-precision X-ray flaw detection was performed on the finished steering knuckle. See [link / reference]. Figure 19 As shown, there are no defects such as porosity or shrinkage, and no welding or shrinkage defects are observed in the larger areas. The dimensions of the prototype are qualified and meet the product definition requirements.

[0147] This application also provides a semi-solid aluminum alloy steering knuckle, which is manufactured using any of the semi-solid aluminum alloy steering knuckle manufacturing methods described above.

[0148] This application also provides a vehicle that includes a semi-solid aluminum alloy steering knuckle as described above.

[0149] In summary, the semi-solid rheo-die casting process described in this application boasts advantages such as high production efficiency, excellent filling capacity, high surface finish of castings, and fewer internal porosity and shrinkage defects, making it one of the mainstream directions for the future development of aluminum alloy casting technology. The steering knuckle production process has been changed from ductile iron sand casting to high-solid-phase semi-solid aluminum alloy rheo-die casting. Combined with optimized structural design, the weight has been reduced by 50%, demonstrating significant lightweighting effects. Through CAE analysis optimization of the casting process and heat treatment strengthening, the mechanical properties and internal quality of the steering knuckle castings are excellent. Both destructive force bench tests and durability bench tests have been verified, indicating promising application prospects. The development of the semi-solid rheo-die casting steering knuckle has provided a solid foundation for mastering the structural design of parts based on the characteristics of the semi-solid rheo-die casting process and the key points of casting quality inspection, laying a good foundation for promoting this process to more parts in the future.

[0150] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0151] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0152] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for manufacturing a semi-solid aluminum alloy steering knuckle, characterized in that, It includes the following steps: The semi-solid aluminum alloy slurry is injected into a mold and die-cast to obtain a steering knuckle blank; In this process, a sealing plate is provided on the mold so that the mounting arm connection hole (1) on the steering knuckle blank becomes a blind hole with one end open and the other end closed. The steering knuckle blank is machined to make the blind hole a through hole; Further post-processing was carried out to obtain a semi-solid aluminum alloy steering knuckle; The manufacturing method further includes: The opening of the slag collection bag (2) is placed in front of the slurry flow direction to collect the gas and slag that are discharged when the slurry flows to form the blind hole; The opening of the slag collection bag (2) is close to the side of the blind hole opening, so that the slag collection bag (2) is offset; A first protrusion is provided on the inner wall of the mold to form a first groove (4) at the thick part of the steering tie rod mounting arm (3) of the steering knuckle blank.

2. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that: The mounting arm connection hole (1) is either a shock absorber mounting arm connection hole or a steering tie rod mounting arm connection hole.

3. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that: There are three first protrusions and three corresponding first grooves (4), which are distributed in a triangular pattern.

4. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that, The manufacturing method further includes: A second groove is provided on the inner wall of the mold to form a second protrusion for accommodating welding defects at the thick part of the steering tie rod mounting arm (3) of the steering knuckle blank; The steering knuckle blank is machined to remove the second protrusion.

5. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that, The manufacturing method further includes: A smooth transition surface is provided on the inner wall of the mold to eliminate the damper mounting arm reinforcing rib (5) of the steering knuckle blank.

6. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that: The die-casting injection speed is 0.1~5m / s, and the pressure is 50~150MPa.

7. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that, After injecting a semi-solid aluminum alloy slurry into a mold and die-casting it, the manufacturing method further includes: Pressurization and solidification are carried out.

8. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 7, characterized in that, The holding pressure is 83~123MPa, and the holding time is 20~40s.

9. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 7, characterized in that, During the pressure holding and solidification period, the steering knuckle blank is locally pressurized.

10. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that: The semi-solid aluminum alloy is A356.2 aluminum alloy, and its chemical composition, by mass percentage, includes: The elemental composition is 0.40-0.45% Mg, 0.10-0.20% Ti, 6.5%-7.5% Si, ≤0.12% Fe, ≤0.05% Mn, ≤0.1% Cu, ≤0.05% Zn, and the remainder is Al.

11. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that: The solid content of the semi-solid aluminum alloy slurry is 40-55%.

12. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 1, characterized in that: The post-processing includes: heat treatment of the steering knuckle blank.

13. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 12, characterized in that: The heat treatment includes: solution treatment at 520~540℃ for 3.5~6 hours, followed by aging treatment at 160~180℃ for 3.5~6 hours.

14. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 13, characterized in that: The heat treatment includes: solution treatment at 540°C for 4 hours, followed by aging treatment at 170°C for 5 hours.

15. The manufacturing method of the semi-solid aluminum alloy steering knuckle as described in claim 12, characterized in that: Before heat treatment of the steering knuckle blank, the post-treatment also includes: removing the slag bag (2) and flash of the steering knuckle blank, and cutting off the gating.

16. A semi-solid aluminum alloy steering knuckle, characterized in that: It is manufactured using the manufacturing method of the semi-solid aluminum alloy steering knuckle as described in any one of claims 1 to 15.

17. A vehicle, characterized in that: It includes the semi-solid aluminum alloy steering knuckle as described in claim 16.

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