Forging forming process for aluminum casting chassis supporting arm implanted with steel plate framework

Abstract

The invention discloses a forging forming process for an aluminum casting chassis supporting arm implanted with a steel plate framework, and relates to the technical field of metal composite material forming. The method comprises the following steps: 1, pretreating a steel plate framework; 2, assembling the mold; 3, performing semi-solid extrusion; 4, sequentially carrying out segmented heat treatment of solid solution at 535 DEG C for 2 hours, water quenching and aging at 175 DEG C for 8 hours; and 5, the cooling rate is controlled to be 5 DEG C / min under a 0.15 T rotating magnetic field, and solidification is completed. Through a quadruple synergistic mechanism of micro anchoring structure-gradient coating-semi-solid extrusion-segmented heat treatment, the shear strength of a composite interface reaches 60-105 MPa, the tensile strength of a final component reaches 311-322 MPa, the fatigue life is prolonged to 120 million times from 500 million times, the lightweight target that the weight is reduced by 50% compared with that of a pure steel part is achieved, and the production cost is reduced. The defects of insufficient strength, infirm aluminum / steel interface bonding, pore shrinkage and brittle phase of a traditional aluminum casting piece are overcome.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal composite material forming, and particularly relates to a forging forming process for an aluminum casting chassis support arm with a steel plate framework. BACKGROUND

[0002] Traditional aluminum alloy chassis support arms are difficult to meet the requirements of heavy load working conditions due to the material strength limitation (the tensile strength is usually less than or equal to 300 MPa). Simply increasing the thickness of the aluminum part will lead to a significant increase in weight, which violates the lightweight goal.

[0003] The prior art attempts to embed a steel framework in an aluminum casting, but there are still the following problems: 1. Interface bonding defects: the difference in thermal expansion coefficients of aluminum (about 24x10⁻ 6 / ℃) and steel (about 12x10⁻ 6 / ℃) leads to cracks at the interface during cooling; the wettability of aluminum liquid on the steel surface is poor, and the bonding strength is insufficient (<50 MPa).

[0004] 2. Porosity and shrinkage: gas residues form pores during casting, reducing the density (porosity >3%).

[0005] 3. Formation of brittle phases: Fe and Al elements diffuse to form brittle phases such as FeAl3, and the impact toughness decreases by more than 40%.

[0006] Therefore, a forging forming process for an aluminum casting chassis support arm with a steel plate framework is proposed to provide a technical solution to the above problems. SUMMARY

[0007] The purpose of the present application is to provide a forging forming process for an aluminum casting chassis support arm with a steel plate framework to solve the existing problems: interface bonding defects: the difference in thermal expansion coefficients of aluminum (about 24x10⁻ 6 / ℃) and steel (about 12x10⁻ 6 / ℃) leads to cracks at the interface during cooling; the wettability of aluminum liquid on the steel surface is poor, and the bonding strength is insufficient (<50 MPa); porosity and shrinkage: gas residues form pores during casting, reducing the density (porosity >3%); formation of brittle phases: Fe and Al elements diffuse to form brittle phases such as FeAl3, and the impact toughness decreases by more than 40%; and to provide an aluminum alloy chassis support arm strengthening process by embedding a steel plate framework and using high-temperature extrusion-heat treatment linkage, which is more suitable for manufacturing automobile lightweight structural parts.

[0008] To solve the above technical problems, the present application is realized by the following technical scheme: The present application is a forging forming process for an aluminum casting chassis support arm with a steel plate framework, comprising the following steps: First step: pretreatment of steel plate skeleton: sand blasting treatment is carried out on the 1mm thick steel plate skeleton to a surface roughness Ra=6.3μm, after pickling in 10% HCl solution, a gradient transition layer is formed by electroless nickel plating, and then preheating is carried out at 450±20℃; Second step: mold assembly: the pretreated steel plate skeleton is placed in the mold cavity at the preset position; Third step: semi-solid extrusion: the aluminum alloy melt is heated to 700±10℃ and then poured into the mold, when the melt reaches 680±5℃ semi-solid state, a dynamic pressure of 40MPa is applied for 10 seconds, and vacuum casting is carried out at the same time, with a vacuum degree of-0.1MPa; Fourth step: heat treatment: sequential segmented heat treatment of 535℃ solution for 2 hours→water quenching→175℃ aging for 8 hours; Fifth step: magnetic field assisted solidification: solidification is completed at a cooling rate of 5℃ / min under a rotating magnetic field of 0.15T.

[0009] Further, the material of the steel plate skeleton is high-strength steel with a tensile strength of ≥600MPa.

[0010] Further, the thickness of the gradient transition layer is 5μm, and the phosphorus content is 8-12wt%.

[0011] Further, the steel plate skeleton is provided with a dovetail groove array and a through hole, the depth of the dovetail groove array is 0.5mm, the width is 1mm, the diameter of the through hole is 2mm, and the pitch is 10mm.

[0012] Further, the steel plate skeleton is provided with a dovetail groove array and a through hole, the side wall angle of the dovetail groove is 45°, the through hole is arranged in a honeycomb shape, the pore size is 1.5mm, and the pitch is 8mm.

[0013] Further, in the heat treatment process, the solution stage adopts stepwise heating, with a temperature rise of 5℃ per minute.

[0014] Further, the gradient transition layer contains 0.5wt% nano-SiC particles with a particle size of 50nm.

[0015] Further, the mold cavity is embedded with a PT100 temperature sensor+PID temperature control module, and a local oil cooling channel is arranged in the corresponding area of the dovetail groove array, and a piezoelectric ceramic vibrator is installed at the bottom of the mold.

[0016] Further, in the heat treatment process, three-zone gradient cooling is adopted in the water quenching stage, with a flow rate of 30℃ / s in zone I, 15℃ / s in zone II, and 5℃ / s in zone III, and the flow rate is controlled by a flow guide plate.

[0017] The present application has the following beneficial effects: The present application realizes the lightweight target of reducing the weight of pure steel parts by 50% through the fourfold synergistic mechanism of "micro-anchoring structure-gradient coating-semi-solid extrusion-section heat treatment", so that the composite interface shear strength reaches 60-105 MPa, the final component tensile strength reaches 311-322 MPa, the fatigue life is improved from 500,000 times to 1,200,000 times, and the difference in thermal expansion coefficient is reduced from 12x10 6 / ℃ to 8.2x10 6 / ℃, which effectively solves the problems of insufficient strength of traditional aluminum castings, poor aluminum / steel interface bonding, porosity, and brittle phase defects, and is suitable for new energy vehicle chassis support arms, with a cost reduction of 30% compared to explosive compounding, and a qualified rate of >95%. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0019] Embodiment one: A forging forming process for an aluminum casting chassis support arm with an embedded steel plate framework, comprising the following steps: First step: In order to overcome the problem of aluminum / steel interface bonding, multiple synergistic strengthening measures are adopted. First, the steel plate framework is pretreated: the 1mm thick steel plate framework is sandblasted to a surface roughness Ra=6.3μm to increase the surface roughness and contact area, and after acid pickling in a 10% HCl solution, a gradient transition layer is formed by chemical nickel plating, with a thickness of 5μm and a phosphorus content of 8-12wt%, which improves the wettability of the aluminum liquid and blocks the mutual diffusion of Fe / Al elements, inhibiting the generation of FeAl3 brittle phase (no brittle phase peak is detected by XRD, and the diffusion layer thickness is ≤1μm), and then preheating at 450±20℃ to reduce thermal stress. The material of the steel plate framework is specifically a high-strength steel with a tensile strength of ≥600MPa, and the steel plate framework is provided with a dovetail groove array and a through hole. The depth of the dovetail groove array is 0.5mm, the width is 1mm, the diameter of the through hole is 2mm, and the spacing is 10mm. By designing the dovetail groove array (depth 0.5mm / width 1mm) and the through hole (diameter φ2mm / space 10mm) on the steel plate framework as an anchoring structure, the aluminum liquid forms a "nanosize rivet" type mechanical lock after filling, which improves the interface tensile strength to 167.2MPa; Second step: mold assembly: place the pretreated steel plate framework into the mold cavity at the preset position; Third step: semi-solid extrusion: pour the aluminum alloy melt into the mold after heating to 700±10℃, apply a dynamic pressure of 40MPa for 10 seconds when the melt reaches 680±5℃ semi-solid state, and conduct dynamic extrusion densification. The porosity is reduced to below 0.5% after 10 seconds of pressure retention. Vacuum casting is performed simultaneously, with a vacuum degree of -0.1MPa. This stage effectively eliminates porosity and shrinkage defects through vacuum casting (-0.1MPa), and refines the grains to ≤20μm (traditional process 50-100μm), significantly improving the density to >99.5%. Fourth step: heat treatment: sequentially perform segmented heat treatment of 535℃ solid solution for 2 hours → water quenching → 175℃ aging for 8 hours, to eliminate residual stress and inhibit the generation of brittle phases. The interface shear strength is increased to 104.77MPa after aging. The solid solution stage uses stepwise heating, with a temperature increase of 5℃ per minute. Fifth step: magnetic field assisted solidification: complete solidification under the control of a 0.15T rotating magnetic field with a cooling rate of 5℃ / min. By precisely controlling the pouring temperature (700±10℃) and cooling rate (stepwise heating solid solution at a rate of 5℃ / min), and using magnetic field assisted solidification (0.15T rotating magnetic field), component segregation is effectively reduced.

[0020] Furthermore, through the "micro-anchoring structure - gradient coating - semi-solid extrusion - segmented heat treatment" fourfold synergistic mechanism of this forming process, the composite interface shear strength reaches 60-105MPa (increased by 74%-130% compared to the traditional process of 30-60MPa), the final component tensile strength reaches 311-322MPa (increased by 19.6-23.8% compared to the traditional die casting 260MPa), the fatigue life is increased from 50 million times to 120 million times (an increase of 140%), and the thermal expansion coefficient difference is reduced from 12×10⁻ 6 / ℃ to 8.2×10⁻ 6 / ℃ (a decrease of 32%), thus achieving the lightweight goal of reducing the weight of pure steel parts by 50%. It effectively solves the problems of insufficient strength of traditional aluminum castings, poor aluminum / steel interface bonding, porosity and shrinkage, and brittle phase defects, and is more suitable for new energy vehicle chassis support arms (meeting ISO 12106 standards). Compared with explosive compounding, the cost is reduced by 30%, and the qualified rate is >95%.

[0021] Example Two: This example is an improvement based on Example One, a steel plate framework implanted aluminum casting chassis support arm forging forming process, including the following steps: First step: pretreatment of steel plate skeleton: sandblasting treatment is performed on the 1mm thick steel plate skeleton to a surface roughness Ra=6.3μm, and then an electrochemical anodic oxidation method is used to construct a nano-porous structure on the surface of the steel plate skeleton, with a pore size of 50-100nm and a depth of 2μm, thereby forming a three-dimensional nano network, which can embed the nickel layer in the nano-pores after chemical nickel plating, and the nano-pores can greatly improve the adhesion between the plating layer and the substrate, finally forming a dual interface of "mechanical lock + chemical bonding"; And an Al2O3-ZrO2 composite coating is prepared on the surface of the gradient transition layer, with a current density of 4A / dm 2 , and a time of 30min, thereby greatly improving the corrosion resistance and interface bonding strength; Subsequently, acid washing is performed in a 10% HCl solution, a gradient transition layer is formed by chemical nickel plating, and the thickness of the gradient transition layer is 5μm, with a phosphorus content of 8-12wt%, which improves the wettability of the aluminum liquid and blocks the mutual diffusion of Fe / Al elements, thereby inhibiting the generation of FeAl3 brittle phase (no brittle phase peak is detected by XRD, and the diffusion layer thickness is ≤1μm), and then preheating at 450±20℃; The steel plate skeleton is provided with a dovetail groove array and a through hole, the dovetail groove side wall has an inclination angle of 45°, the through hole is arranged in a honeycomb shape, the hole diameter is 1.5mm, and the spacing is 8mm, thereby effectively improving the mechanical locking force and reducing the stress concentration coefficient; Second step: mold assembly: place the pretreated steel plate skeleton into the mold cavity at the preset position; Third step: semi-solid extrusion: pour the aluminum alloy melt into the mold after heating to 700±10℃, apply a dynamic pressure of 40MPa for 10 seconds when the melt reaches a semi-solid state of 680±5℃, install an ultrasonic generator on the outside of the mold in advance, and at this time, apply a 20kHz ultrasonic vibration simultaneously, with an amplitude of 5μm, and the vibration is transmitted to the mold cavity through the transducer, thereby further reducing the porosity, refining the grain size, and greatly improving the flowability of the aluminum liquid; simultaneously perform vacuum casting with a vacuum degree of -0.1MPa; Fourth step: heat treatment: perform segmented heat treatment in the order of 535℃ solid solution for 2 hours → water quenching → 175℃ aging for 8 hours; at this time, the solid solution stage adopts a stepwise heating method, with a temperature increase of 5℃ per minute; Fifth step: magnetic field assisted solidification: complete solidification under a rotating magnetic field of 0.15T with a controlled cooling rate of 5℃ / min.

[0022] Furthermore, an innovative chassis support arm forging process is provided, which cooperates with the implantation of a high-strength steel plate skeleton to strengthen the aluminum alloy matrix, achieving a synergistic improvement in light weight and high strength.

[0023] Example Three: This embodiment is an improvement based on Example One, a steel plate skeleton implanted aluminum casting chassis support arm forging forming process, comprising the following steps: First step: first pretreatment steel skeleton: 1mm thick steel skeleton sandblasting treatment to surface roughness Ra = 6.3μm, after 10% HCl solution pickling, by electroless nickel plating to form a gradient transition layer, and the gradient transition layer contains 0.5wt% nano SiC particles, particle size is 50nm, and then form Ni-SiC composite coating, greatly improve the hardness, barrier Fe / Al diffusion capacity is enhanced; In other embodiments, 0.5wt% of lanthanum (La) element can also be added in the electroless nickel plating solution to form a Ni-P-La composite coating, further improve the hardness, and the interface conductivity is improved, and the electrochemical corrosion is inhibited; Subsequently preheated at 450±20℃, reduce thermal stress; wherein the steel skeleton material is specifically high strength steel with tensile strength ≥ 600MPa, the steel skeleton is provided with dovetail groove array and through hole, the depth of the dovetail groove array is 0.5mm, the width is 1mm, the diameter of the through hole is 2mm, and the pitch is 10mm; Second step: mold assembly: the pretreated steel skeleton is placed in the mold cavity at the preset position; Third step: semi-solid extrusion: the aluminum alloy melt is heated to 700±10℃ and poured into the mold, when the melt reaches 680±5℃ semi-solid state, 40MPa dynamic pressure is applied for 10 seconds, the porosity is reduced to below 0.5% after 10 seconds of pressure holding, dynamic extrusion densification is carried out, and vacuum casting is carried out at the same time, the vacuum degree is-0.1MPa; Fourth step: heat treatment: substep heat treatment is carried out in turn, 535℃ solid solution for 2 hours→water quenching→175℃ aging for 8 hours; wherein the solid solution stage adopts stepwise heating, 5℃ per minute; Here, after substep heat treatment, deep cryogenic treatment is carried out, by-80℃ for 2 hours, then air furnace temperature rises to room temperature, and then the residual stress is further reduced, and the impact toughness and dimensional stability are greatly improved; Fifth step: magnetic field assisted solidification: the cooling rate is controlled at 5℃ / min under the action of 0.15T rotating magnetic field to complete solidification, and then the pouring temperature and cooling rate are accurately controlled, and the magnetic field assisted solidification is adopted to effectively reduce the composition segregation.

[0024] Through the cooperation of various aspects, the aluminum steel interface bonding strength, density and fatigue performance are comprehensively improved under the premise of ensuring the industrialization feasibility, which is especially suitable for the high-end manufacturing demand of new energy vehicle lightweight parts.

[0025] Example four: This embodiment is an improvement on the basis of example one, a steel skeleton implanted aluminum casting chassis support arm forging forming process, comprising the following steps: First step: first pretreatment steel plate skeleton: 1mm thick steel plate skeleton is sandblasted to surface roughness Ra=6.3μm, after pickling in 10% HCl solution, a gradient transition layer is formed by electroless nickel plating, the thickness of the gradient transition layer is 5μm, the phosphorus content is 8-12wt%, the aluminum liquid wettability is improved and the Fe / Al element interdiffusion is blocked, the FeAl3 brittle phase is inhibited (XRD detection has no brittle phase peak, the diffusion layer thickness is less than or equal to 1μm), then preheat at 450±20℃ to reduce thermal stress; wherein the material of the steel plate skeleton is high-strength steel with tensile strength greater than or equal to 600MPa, the steel plate skeleton is provided with dovetail groove array and through hole, the depth of the dovetail groove array is 0.5mm, the width is 1mm, the diameter of the through hole is 2mm, and the pitch is 10mm; Second step: mold assembly: place the pretreated steel plate skeleton into the mold cavity at the preset position; and the mold cavity is embedded with PT100 temperature sensor+PID temperature control module, thereby realizing real-time control within ±1℃, and a local oil cooling channel is provided in the area corresponding to the dovetail groove array, thereby improving temperature uniformity and reducing thermal stress concentration, greatly shortening the aluminum liquid solidification period, effectively improving production efficiency, and a piezoelectric ceramic vibrator is installed at the bottom of the mold, with a frequency of 28kHz and an amplitude of 15μm, which can effectively reduce the porosity rate when started during the pressure maintaining stage; Third step: semi-solid extrusion: pour the aluminum alloy melt into the mold after heating to 700±10℃, apply a dynamic pressure of 40MPa for 10 seconds when the melt reaches 680±5℃ semi-solid state, which can reduce the porosity rate to less than 0.5% and realize dynamic extrusion densification, and at the same time, vacuum casting is carried out with a vacuum degree of-0.1MPa; Fourth step: heat treatment: carry out segmented heat treatment of 535℃ solid solution for 2 hours→water quenching→175℃ aging for 8 hours; and the solid solution stage adopts stepwise heating, with a temperature rise of 5℃ per minute; the water quenching stage adopts three-zone gradient cooling, with a cooling rate of 30℃ / s in zone I, 15℃ / s in zone II, and 5℃ / s in zone III, and the flow rate is controlled by a flow guide plate, thereby greatly reducing the thermal stress; Fifth step: magnetic field assisted solidification: finally, complete solidification by controlling the cooling rate at 5℃ / min under a rotating magnetic field of 0.15T.

[0026] Further, an aluminum alloy chassis support arm strengthening process by implanting a steel plate skeleton and adopting high-temperature extrusion-heat treatment linkage is provided, which can be applied to the manufacturing of automobile lightweight structural parts.

[0027] In the description of the specification, reference to "one embodiment", "an example", "a specific example" or the like means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. The appearances of the phrases "in one embodiment", "an example", "a specific example" or the like in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0028] The preferred embodiments of the application disclosed above are only to help explain the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made in light of the contents of the specification. The specification selects and specifically describes these embodiments in order to better explain the principles and practical application of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A process for forging and forming an aluminum cast chassis support arm for an implantable steel plate framework, characterized by, The method comprises the following steps: First step: pretreatment of steel plate skeleton: sandblasting treatment of 1mm thick steel plate skeleton to surface roughness Ra=6.3μm, acid pickling in 10% HCl solution, then forming a gradient transition layer by electroless nickel plating, and then preheating at 450±20℃; Second step: mold assembly: placing the pretreated steel plate skeleton into the mold cavity at the preset position; Third step: semi-solid extrusion: pouring the aluminum alloy melt into the mold after heating to 700±10℃, applying a dynamic pressure of 40MPa for 10 seconds when the melt reaches 680±5℃ semi-solid state, and simultaneously performing vacuum casting with a vacuum degree of-0.1MPa; Fourth step: heat treatment: performing segmented heat treatment of 535℃ solid solution for 2 hours→water quenching→175℃ aging for 8 hours in sequence; Fifth step: magnetic field assisted solidification: controlling the cooling rate at 5℃ / min under a rotating magnetic field of 0.15T to complete solidification.

2. A wrought forming process for aluminum cast chassis support arms for implant steel plate skeletons according to claim 1, characterized in that, The steel plate skeleton is made of high-strength steel with a tensile strength of ≥600MPa.

3. A wrought forming process for aluminum cast chassis support arms for implant steel plate skeletons as defined in claim 1, characterized in that, The thickness of the gradient transition layer is 5μm, and the phosphorus content is 8-12wt%.

4. The aluminum cast chassis support arm swage forming process of claim 1 wherein, The steel plate skeleton is provided with a dovetail groove array and through holes, the depth of the dovetail groove array is 0.5mm, the width is 1mm, the diameter of the through holes is 2mm, and the spacing is 10mm.

5. The aluminum cast chassis support arm swage forming process of claim 1 wherein, The steel plate skeleton is provided with a dovetail groove array and through holes, the side wall angle of the dovetail groove is 45°, the through holes are arranged in a honeycomb shape, the hole diameter is 1.5mm, and the spacing is 8mm.

6. The aluminum cast chassis support arm swage forming process of claim 1 wherein, During the heat treatment process, the solid solution stage adopts stepwise heating, with a temperature increase of 5℃ per minute.

7. The aluminum cast chassis support arm swage forming process of claim 1 wherein, The gradient transition layer contains 0.5wt% nano-SiC particles with a particle size of 50nm.

8. The aluminum cast chassis support arm swage forming process of claim 4, wherein, The mold cavity is embedded with a PT100 temperature sensor + PID temperature control module, and a local oil cooling channel is provided in the corresponding area of the dovetail groove array, and a piezoelectric ceramic vibrator is installed at the bottom of the mold.

9. The aluminum cast chassis support arm swage forming process of claim 6 wherein, During the heat treatment process, three-zone gradient cooling is adopted in the water quenching stage, with a flow rate of 30℃ / s in zone I, 15℃ / s in zone II, and 5℃ / s in zone III, and the flow rate is controlled by a flow guide plate.