Method for casting an iron brake disc body in an aluminium alloy material

Abstract

The application belongs to the technical field of brake disc materials, and particularly discloses a method for casting an iron brake disc body with an aluminum alloy material, aiming to solve the technical problem that cast iron and aluminum alloy dissimilar metals are difficult to be directly compound cast. The method realizes high-quality metallurgical combination of the cast iron base body and the aluminum alloy material by setting a transition layer structure and controlling casting process parameters. The application can effectively overcome interface defects caused by the difference in melting points and fluidity of the two metals, improve the bonding strength and air tightness, and thus prepare a composite brake disc body with both wear resistance of cast iron and light weight advantage of aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of brake disc material technology, and in particular to a method for combining cast iron brake disc body with cast aluminum alloy material. Background Technology

[0002] With the rapid development of the automotive industry and increasingly stringent requirements for energy conservation and emission reduction, vehicle lightweighting has become an important direction for technological upgrading in the industry. Brake discs, as the core component of the braking system, withstand intense frictional heat and thermal cycling during braking. While traditional cast iron brake discs offer good wear resistance and high thermal stability, their high density (approximately 7.1~7.3 g / cm³) and low thermal conductivity (approximately 45~60 W / (m·K)) result in significant weight and limited heat dissipation, making them prone to thermal fade under high-frequency or heavy-load braking, affecting safety and comfort. Aluminum alloys, on the other hand, have a low density (approximately 2.7 g / cm³, about one-third that of cast iron) and excellent thermal conductivity (approximately 160~237 W / (m·K), 3~4 times that of cast iron). Combining these two materials in a composite casting retains the wear resistance and thermal stability of cast iron while leveraging the lightweight and high thermal conductivity of aluminum alloys to improve heat dissipation and service life, making it a key research focus at present.

[0003] However, the differences in their physicochemical properties pose significant technical challenges to the composite process. In the existing technology, patent CN121669940B employs a hot-pressing process for layered composite bonding. This process requires sophisticated equipment, is costly, and makes it difficult to form complex parts in a single operation. More importantly, the coefficients of thermal expansion of the two materials differ by nearly double (aluminum alloy approximately 23 × 10⁻⁶). -6 / ℃, cast iron approximately 12×10 -6 High-temperature cycling (temperature range of -℃) can easily generate thermal stress, leading to a decrease in interface strength and even delamination. Another prior art patent, CN113775676B, uses a rib-connected casting process, which improves the bonding strength, but the difference in casting shrinkage (approximately 2.5% for aluminum alloy and 1.2% for cast iron) can easily cause micro-gaps or pores at the interface, resulting in adhesion problems; furthermore, the rib connection limits heat dissipation optimization. In addition, this solution does not involve a thermal expansion difference compensation mechanism, making it prone to fatigue cracking under repeated thermal cycling; if the entire casting is followed by water quenching heat treatment, the cast iron part is prone to rusting, increasing the process difficulty and processing cost.

[0004] In summary, existing technologies still have significant shortcomings in terms of interface bonding reliability, thermal expansion matching, heat dissipation optimization, and cost control. There is an urgent need to solve technical problems such as poor bonding between aluminum alloy and cast iron composite interfaces, cracking caused by thermal expansion mismatch, limited heat dissipation efficiency, and complex manufacturing processes, in order to achieve an effective balance between lightweight, high heat dissipation, and high reliability in brake discs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for combining cast iron brake discs with cast aluminum alloy materials, in order to solve the problems in the above-mentioned background technology, such as poor bonding between aluminum alloy and cast iron composite interfaces, easy cracking due to mismatch of thermal expansion coefficients, limited heat dissipation efficiency, and complex production processes.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for combining cast iron brake discs with cast aluminum alloy materials includes the following specific steps: S1. Pre-treat the cast iron brake disc body, prepare the cast iron brake disc body using metal mold sand casting process, and machine the composite interface of the cast iron brake disc body to be machined to produce either a sawtooth joint groove or a dovetail joint groove. The groove depth is controlled to be 3-8 mm, the groove width is controlled to be 5-12 mm, the groove spacing is controlled to be 8-20 mm, and the surface roughness is controlled to be within the range of Ra 3.2-Ra 12.5 micrometers. S2, the interface of the cast iron brake disc is activated and coated with a transition layer. After activation, a transition layer coating is applied to the interface. The transition layer coating is made of a mixture of nickel powder, aluminum powder and silicon powder. The thickness of the transition layer is controlled to be 0.1-0.5 mm. S3. Heat the cast iron brake disc and the aluminum alloy separately. Place the cast iron brake disc in a resistance furnace or induction heating furnace for heating. The heating temperature of the cast iron is controlled at 450-650℃, and the holding time is calculated as 1 hour for every 25 mm of wall thickness. Place the aluminum alloy ingot in an aluminum alloy melting furnace for heating and melting. The melting temperature is controlled at 680-750℃, and the temperature of the aluminum alloy liquid is controlled within the range of 720-760℃. After refining and degassing, remove the slag and let it stand. S4. Perform aluminum alloy liquid pouring and interface composite, transfer the cast iron brake disc body to the casting mold for positioning and installation. The preheating temperature of the casting mold is controlled at 200-350℃. Position the mold and the cast iron brake disc body, and use either vacuum die casting or low-pressure casting process to pour aluminum alloy liquid. The vacuum degree of vacuum die casting is controlled at -0.05 to -0.08Mpa, the filling speed is controlled at 0.5-3m / S, and the pressure of low-pressure casting is controlled at 0.02-0.08Mpa. S5 controls the solidification and cooling process to achieve interfacial metallurgical bonding. During solidification, the temperature gradient is controlled by the principle of sequential solidification. The solidification sequence is adjusted by using insulating risers and cooling water channels. Induction heating is used to assist in controlling the cooling rate in the interfacial area, so that the solidification process adopts bidirectional solidification control. The solidification time of the interfacial area is delayed by 15%-25% compared with the central area of ​​the aluminum alloy. S6, heat treatment is performed on the aluminum alloy area using a segmented solution treatment process. After heat preservation, the aluminum alloy heat dissipation area is subjected to directional high-pressure water spraying to complete water quenching, followed by artificial aging treatment. After aging, it is air-cooled to room temperature. S7 involves quality inspection and precision machining of the brake discs after they have been cast.

[0007] As a preferred option, the sand coating material in S1 is organic resin sand or silica sand, the thickness of the sand coating layer is controlled at 3-8 mm, the air permeability of the sand coating layer is controlled at 80-150 air permeability units, the pouring temperature is controlled in the range of 1380-1450℃, and the metal mold sand coating casting process ensures that the density of the cast iron brake disc reaches more than 95%, and the spheroidization rate of ductile iron is greater than or equal to 85%.

[0008] As a preferred embodiment, in S1, the interface to be composited on the cast iron brake disc is machined, and the machined sawtooth joint groove adopts an isosceles trapezoidal structure with a tooth top width of 2-5 mm, a tooth bottom width of 3-8 mm, and a tooth depth of 4-8 mm; or the machined dovetail joint groove has a dovetail angle controlled at 50-70 degrees and a dovetail depth of 5-10 mm; the joint area increase coefficient reaches 1.8-2.5 times.

[0009] Preferably, the activation treatment in S2 is either sandblasting or chemical etching. The sandblasting treatment uses brown corundum sand with a particle size of 0.5-1.5 mm and the sandblasting pressure is controlled at 0.4-0.8 MPa. The chemical etching treatment uses a 5%-15% dilute hydrochloric acid solution for 5-30 minutes.

[0010] Preferably, the transition layer coating in S2 is made of a mixture of nickel powder, aluminum powder and silicon powder, with a nickel powder mass fraction of 40%-60%, an aluminum powder mass fraction of 30%-45%, and a silicon powder mass fraction of 5%-15%. The binder is ethyl silicate, and the coating viscosity is controlled at 18-25 seconds (French cup 4). The coating method is brushing or spraying. After coating, the coating is allowed to dry naturally for 10-30 minutes before being dried. The drying temperature is 120-180℃, and the holding time is 30-60 minutes.

[0011] Preferably, the aluminum alloy in S3 comprises the following alloying elements: silicon content of 8.0%-9.0%, manganese content of 0.30%-0.35%, magnesium content of 0.15%-0.28%, titanium content of 0.10%-0.12%, strontium content of 0.008%-0.01%, zinc content not exceeding 0.1%, lead content not exceeding 0.03%, tin content not exceeding 0.05%, copper content not exceeding 0.1%, iron content not exceeding 0.2%, and the balance being aluminum; the refining process employs argon blowing or hexachloroethane degassing, with the degassing time controlled at 10-20 minutes and the refining temperature controlled at 730-740℃, resulting in a hydrogen content in the refined aluminum liquid of less than or equal to 0.15 ml / 100g aluminum.

[0012] As a preferred option, the S4 casting mold adopts a bimetallic composite mold structure. The main body of the mold is made of cast iron, and the inner surface of the mold cavity is coated with graphite-based coating or titanium nitride coating, with the coating thickness controlled at 0.05-0.2 mm. The gating system adopts a bottom-pouring gating system, with the cross-sectional area of ​​the ingate controlled at 2-8 square centimeters, the cross-sectional area of ​​the runner controlled at 3-12 square centimeters, and the cross-sectional area of ​​the sprue controlled at 4-15 square centimeters. The total cross-sectional area of ​​the gating system is designed according to the ratio of the flow-blocking section to the cross-sectional area of ​​the ingate at 1:2-1:4. During the pouring process, the interface area of ​​the cast iron brake disc is continuously heated to maintain the temperature at 350-500℃. After pouring, the pressure is held for 10-30 seconds.

[0013] Preferably, in S5, the distance between the cooling water channel and the interface is controlled to be 15-30 mm, and the cooling water flow rate is controlled to be 5-20 liters per minute; the insulating riser is set in the thick part of the aluminum alloy, and the riser feeding efficiency is greater than or equal to 30%; the solidification time is controlled to be 1-2 seconds per square centimeter of aluminum alloy cross-sectional area, and the aluminum alloy is removed from the box after cooling to below 200°C; during the cooling process, induction heating is used to assist in controlling the cooling rate of the interface area. During the solidification and cooling process, a transition layer is formed at the interface. The transition layer structure is a composite gradient structure with alternating layers of Ni-Al intermetallic compounds, Al-Fe intermetallic compounds, and Al-Fe-Si ternary compounds. The side closest to the cast iron is dominated by FeAl3, Fe2Al5, and Fe-Ni solid solutions, the middle layer is dominated by nickel-rich tough phases such as NiAl3 and Ni2Al3, and the side closest to the aluminum alloy is dominated by Al3FeSi, AlFeSi, and a small amount of Ni-Al phase. The total thickness of the transition layer is controlled within the range of 0.1-0.5 mm.

[0014] As a preferred option, the solution treatment temperature in S6 is controlled at 500-540℃, and the holding time is calculated as 1.5-2 hours per 25 mm thickness. After the holding time is completed, a multi-nozzle annular cooling pipe is used to perform directional high-pressure water spray cooling on the aluminum alloy heat dissipation area. The spray angle is controlled so that the cooling water does not contact the working surface of the cast iron brake disc, thereby ensuring that the cast iron part does not participate in water quenching. The artificial aging treatment temperature is controlled at 160-200℃, and the aging time is controlled at 6-12 hours. After aging, the parts are air-cooled to room temperature.

[0015] As a preferred embodiment, in S7, the brake disc after casting is subjected to X-ray non-destructive testing to detect whether there are porosity, slag inclusions, or incomplete fusion defects in the interface bonding area; the interface bonding strength is tested by shear test, and the bonding strength requirement is greater than or equal to 60 MPa; heat dissipation fins are set in the aluminum alloy area, with the fin thickness controlled at 2-5 mm, the fin height controlled at 8-20 mm, the fin spacing controlled at 5-15 mm, and the fins connected to the aluminum alloy substrate using a gradual transition structure, with the length of the gradual transition zone controlled at 3-8 mm; after machining, surface treatment is performed, using electrophoretic coating or powder coating, with the coating thickness controlled at 20-40 micrometers.

[0016] The present invention has the following beneficial effects: 1. This invention significantly increases the bonding area between aluminum alloy and cast iron by machining serrated or dovetail-shaped mechanical bonding grooves at the interface of the cast iron brake disc. The mechanical interlocking effectively prevents interface slippage, and the bonding area increase coefficient reaches 1.8-2.5 times. The proportion design of nickel powder, aluminum powder, and silicon powder in the transition layer coating forms a composite gradient structure containing nickel-rich phases at the interface. The high nickel content reacts in situ with the molten aluminum during casting, generating uniformly distributed Ni-Al intermetallic compounds. These nickel-rich phases have good toughness, effectively hindering the excessive growth and aggregation of brittle Fe-Al phases, and acting as a buffer layer to significantly alleviate the thermal stress concentration caused by the difference in thermal expansion coefficients between cast iron and aluminum alloy. The synergistic effect of metallurgical bonding and mechanical interlocking makes the interface bonding strength greater than or equal to 60 MPa, effectively avoiding interface cracking under thermal cycling conditions. Sandblasting or chemical etching pretreatment ensures a clean and activated bonding interface, reducing the interface wetting angle to below 30 degrees and significantly improving wettability.

[0017] 2. This invention employs a segmented heating control process, heating the cast iron to 450-650℃ and the molten aluminum alloy to 720-760℃ before pouring. This allows the two materials to converge in temperature before being combined, effectively reducing the temperature gradient during pouring. During solidification and cooling, a sequential solidification principle and induction heating are used for auxiliary control, delaying the solidification time of the interface region by 15%-25% compared to the central region of the aluminum alloy, ensuring coordinated solidification rates on both sides of the interface. The gradient structure design of the transition layer allows the coefficient of thermal expansion to gradually transition from the cast iron side to the aluminum alloy side, significantly alleviating the phenomenon of thermal stress concentration.

[0018] 3. This invention utilizes vacuum die casting or low-pressure casting processes in the aluminum alloy region, achieving a density of over 98% and a porosity of less than or equal to 1%, resulting in a significant improvement in thermal conductivity. The thermal conductivity of the aluminum alloy material reaches 160-237 W / (m·K), approximately 3-4 times that of cast iron, allowing for rapid heat transfer to the aluminum alloy heat dissipation area. The heat dissipation fin structure design increases the heat dissipation area by 30%-50%, and the gradual transition structure avoids stress concentration, resulting in an overall improvement in heat dissipation efficiency of 2-3 times and effectively preventing braking heat decay.

[0019] 4. This invention uses a metal mold sand casting process to prepare cast iron brake discs, which ensures stable process control and high yield. It eliminates the need for hot pressing equipment, reduces equipment requirements, and is easy to operate. The aluminum alloy area undergoes a segmented solution treatment process with precise control of process parameters. The cast iron part does not participate in water quenching heat treatment, thus avoiding rusting. The overall process reduces the number of steps by 3-5 compared to existing layered composite processes, shortens the production cycle by 20%-30%, and reduces production costs by 25%-35%, making it suitable for large-scale industrial production.

[0020] 5. In this invention, the cast iron brake disc retains the wear resistance and thermal stability of cast iron, and the friction surface is made of cast iron to ensure braking performance; the aluminum alloy material achieves weight reduction, reducing the overall weight of the brake disc by 25%-35%; the synergistic heat dissipation design of high thermal conductivity aluminum alloy and cast iron meets the requirements of high-frequency braking and heavy-load conditions; the reliability of interface bonding and thermal expansion matching issues are solved simultaneously, significantly improving service life, and achieving a balance between lightweight, high heat dissipation, and high reliability in overall performance. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall technical solution architecture of the present invention; Figure 2 This is a schematic diagram illustrating the core principle framework for the interface bonding between cast iron brake discs and aluminum alloy materials. Detailed implementation method. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a method for bonding cast iron brake discs with cast aluminum alloy materials. The method comprises seven core steps, which respectively complete the pretreatment of the cast iron brake disc, activation treatment of the bonding interface and coating of the transition layer, segmented heating of the two materials, pouring of the aluminum alloy molten metal and interface bonding, control of the interface metallurgical bonding during solidification and cooling, heat treatment of the aluminum alloy region, and final quality inspection and finishing. The following provides a detailed technical description of each step.

[0023] S1. Pretreatment of the cast iron brake disc body. The core technology of this step is the use of a metal mold sand casting process to prepare the cast iron brake disc body. The preheating temperature of the metal mold is set at 200-350℃. This temperature range is determined based on the following engineering considerations: when the preheating temperature is below 200℃, the contact between the metal mold surface and the high-temperature molten iron will create an excessive temperature difference, leading to severe chilling of the casting and the formation of white iron structure; when the preheating temperature exceeds 350℃, it will lead to accelerated thermal fatigue of the metal mold and shorten the mold's service life. The thickness of the sand coating layer is controlled at 3-8 mm. This thickness range ensures that the sand coating layer has sufficient thermal insulation performance while maintaining good collapsibility. The air permeability of the sand coating layer is controlled at 80-150 permeability units. This air permeability index ensures that the gas generated during the metal mold sand casting process can be smoothly discharged, avoiding the formation of porosity defects. The sand coating material uses organic resin sand or silica sand. Organic resin sand has good high-temperature strength and collapsibility, while silica sand has excellent thermal shock resistance. Both materials can meet the functional requirements of the sand coating layer. The pouring temperature is controlled between 1380-1450℃. This temperature range ensures that the molten iron has good fluidity, completely filling the sand-coated mold cavity, while avoiding excessively high pouring temperatures that could cause the sand coating to burn off. The metal mold sand casting process ensures that the density of the cast iron brake disc reaches over 95%, and the spheroidization rate of ductile iron is greater than or equal to 85%. This means that the cast iron matrix possesses excellent mechanical properties and a uniform microstructure, laying the foundation for subsequent composite bonding with aluminum alloys.

[0024] After the cast iron brake disc body is prepared, the interface to be composite is machined to produce either a serrated or dovetail joint groove. The serrated joint groove has an isosceles trapezoidal tooth shape, with a tooth tip width of 2-5 mm, a tooth root width of 3-8 mm, and a tooth depth of 4-8 mm. The dovetail joint groove has a dovetail angle controlled at 50-70 degrees, a dovetail depth of 5-10 mm, a groove depth controlled at 3-8 mm, a groove width controlled at 5-12 mm, and a groove spacing controlled at 8-20 mm. The surface roughness is controlled within the range of Ra 3.2-Ra 12.5 micrometers. This roughness range ensures sufficient mechanical engagement capability at the interface while avoiding stress concentration due to excessive surface roughness. The design of the serrated or dovetail mechanical joint groove significantly increases the bonding area between the aluminum alloy and cast iron, with a bonding area increase factor of 1.8-2.5 times. The mechanical engagement effectively prevents interface slippage.

[0025] S2, activation treatment and transition layer coating of the interface between the cast iron brake disc and the metal body. This step uses either sandblasting or chemical etching to activate the interface. Sandblasting uses brown fused alumina abrasive with a particle size of 0.5-1.5 mm, and the sandblasting pressure is controlled at 0.4-0.8 MPa. Brown fused alumina abrasive has high hardness and strong grinding ability, effectively removing oxide scale and contaminants from the interface surface. The particle size range of 0.5-1.5 mm ensures that the treated surface achieves the required cleanliness and activation without becoming excessively rough. The sandblasting pressure setting of 0.4-0.8 MPa ensures a balance between treatment efficiency and surface quality. Chemical etching uses a 5%-15% dilute hydrochloric acid solution for 5-30 minutes. This method is suitable for interfaces with complex shapes or deep porous structures, removing the surface oxide layer through chemical reaction and forming a microscopically roughened surface.

[0026] After activation treatment, a transition layer coating is applied to the bonding interface. This transition layer coating is made from a mixture of nickel powder, aluminum powder, and silicon powder. The nickel powder mass fraction is 40%-60%, the aluminum powder mass fraction is 30%-45%, and the silicon powder mass fraction is 5%-15%. This formulation design ensures that the transition layer can form an Al-Fe intermetallic compound gradient structure during casting, achieving a synergistic effect of metallurgical bonding and mechanical interlocking. The transition layer coating is prepared as follows: nickel powder, aluminum powder, and silicon powder are mixed according to the specified ratio, and then a binder is added and stirred evenly. Ethyl silicate is used as the binder. The coating viscosity is controlled at 18-25 seconds per 4-viscosity cup. It is applied by brushing or spraying, and allowed to air dry for 10-30 minutes before being oven-dried. The transition layer thickness is controlled at 0.1-0.5 mm. After application, it is oven-dried at 120-180℃ for 30-60 minutes. The interfacial wetting angle is reduced to below 30 degrees, and wettability is significantly improved.

[0027] Optimization and control of the interfacial microstructure play a crucial role in the solidification and cooling process. The interfacial transition layer exhibits a composite gradient structure with alternating layers of Ni-Al intermetallic compounds, Al-Fe intermetallic compounds, and Al-Fe-Si ternary compounds. The layer closest to the cast iron is dominated by FeAl3, Fe2Al5, and Fe-Ni solid solutions, which form a good metallurgical bond with the aluminum alloy matrix. The intermediate layer is dominated by nickel-rich, ductile phases such as NiAl3 and Ni2Al3, while the layer closest to the aluminum alloy is dominated by Al3FeSi, AlFeSi, and a small amount of Ni-Al phases. The total thickness of the transition layer is controlled within the range of 0.1-0.5 mm. This thickness range ensures sufficient strength and toughness in the transition layer while avoiding increased brittleness due to excessive thickness.

[0028] S3 involves heating the cast iron brake disc and the aluminum alloy separately. The pre-treated cast iron brake disc is placed in a resistance furnace or induction heating furnace and heated to 450-650℃, with a holding time of 1 hour per 25 mm wall thickness. This heating process ensures a uniform temperature distribution within the cast iron brake disc, creating conditions for temperature field matching during subsequent casting. After heating, the cast iron brake disc is transferred to a holding device to maintain the temperature. The holding device uses resistance heating or gas heating to maintain temperature fluctuations within ±10℃. During the heating of the cast iron brake disc coated with the transition layer to 450-650℃, the binder tetraethyl orthosilicate in the transition layer undergoes complete decomposition and high-temperature sintering under high temperature, causing its organic groups to volatilize and ultimately transform into a hard and dense inorganic silica (SiO2) gel network framework. This SiO2 network firmly anchors nickel powder, aluminum powder, and silicon powder to the cast iron surface, forming a high-temperature resistant inorganic ceramic layer. This process not only avoids the large number of pore defects caused by the instantaneous volatilization of organic matter when the subsequent aluminum liquid is poured (720-760℃), but also greatly improves the adhesion strength of the transition coating at high temperatures and its resistance to aluminum liquid erosion.

[0029] Aluminum alloy ingots are heated and melted in an aluminum alloy melting furnace at a controlled temperature of 680-750℃. The aluminum alloy contains the following alloying elements: silicon (8.0%-9.0%), manganese (0.30%-0.35%), magnesium (0.15%-0.28%), titanium (0.10%-0.12%), strontium (0.008%-0.01%), zinc (not exceeding 0.1%), lead (not exceeding 0.03%), tin (not exceeding 0.05%), copper (not exceeding 0.1%), and iron (not exceeding 0.2%), with the balance being aluminum. This aluminum alloy exhibits excellent casting performance and heat treatment strengthening capabilities. Silicon improves fluidity, magnesium provides aging strengthening, and titanium refines grains and improves microstructure. The temperature of the molten aluminum alloy is controlled within the range of 720-760℃. After refining and degassing, the slag is removed and the mixture is allowed to stand. The refining process employs argon purging or hexachloroethane degassing, with a degassing time controlled at 10-20 minutes. The refining temperature of the aluminum alloy melt is controlled at 730-740℃, and the hydrogen content of the refined aluminum melt is less than or equal to 0.15 ml / 100g aluminum. The refining and degassing process ensures that the dissolved hydrogen content in the aluminum alloy melt is reduced to a minimum, avoiding the formation of pinhole defects during solidification.

[0030] S4. Perform aluminum alloy molten casting and interface bonding. Transfer the cast iron brake disc to a specialized casting mold for positioning and installation. The casting mold employs a bimetallic composite mold structure; the main body is made of cast iron, and the inner surface of the mold cavity is coated with either graphite-based paint or titanium nitride coating, with the coating thickness controlled at 0.05-0.2 mm. Graphite-based paint offers excellent lubricity and thermal shock resistance, while titanium nitride coating provides high hardness and a low coefficient of friction. Both coatings effectively prevent the adhesion of the aluminum alloy molten metal to the mold. The mold preheating temperature is controlled at 200-350℃. Position the mold and cast iron brake disc with a positioning accuracy controlled at ±0.1 mm to ensure accurate positioning of the cast iron brake disc within the mold, guaranteeing the quality of the interface bonding.

[0031] The aluminum alloy molten metal is poured using either vacuum die casting or low-pressure casting. In vacuum die casting, the vacuum level is controlled between -0.05 and -0.08 MPa, and the filling speed is controlled between 0.5 and 3 m / s. Vacuum die casting effectively removes gas from the mold cavity by creating a negative pressure environment within the pressure chamber and mold cavity, thus improving the density of the aluminum alloy. The filling speed range of 0.5-3 m / s ensures that the molten aluminum alloy fills the cavity at an appropriate flow rate, avoiding air entrapment. In low-pressure casting, the pressure is controlled between 0.02 and 0.08 MPa. Low-pressure casting uses lower gas pressure to propel the molten aluminum alloy upwards smoothly to fill the cavity, making it particularly suitable for castings with complex shapes and uneven wall thicknesses.

[0032] The gating system adopts a bottom-pouring gating system, with the cross-sectional area of ​​the ingate controlled at 2-8 square centimeters, the runner at 3-12 square centimeters, and the sprue at 4-15 square centimeters. The total cross-sectional area of ​​the gating system is designed according to a flow-blocking section to ingate cross-sectional area ratio of 1:2-1:4. The bottom-pouring gating system is characterized by molten metal entering from the bottom of the cavity and rising steadily, which is beneficial for the floating of inclusions and the expulsion of gas. The cross-sectional area ratio design of the ingate, runner, and sprue follows fluid mechanics principles to ensure that the molten aluminum alloy maintains a stable flow state during the flow process, avoiding secondary oxidation and gas entrapment.

[0033] During the casting process, the interface area of ​​the cast iron brake disc is continuously heated and maintained at 350-500℃. This temperature control ensures that the interface is in an activated state at the moment of casting, which is beneficial for the wetting and bonding of the molten aluminum alloy with the transition layer. After casting, pressure is maintained for 10-30 seconds. This pressure-holding process compensates for shrinkage porosity caused by the solidification shrinkage of the aluminum alloy, improving the density of the casting. The solidification and cooling stage then begins.

[0034] S5 controls the solidification and cooling process to achieve interfacial metallurgical bonding. During solidification, a sequential solidification principle is adopted to control the temperature gradient, and the solidification sequence is adjusted through insulating risers and cooling channels. A two-way solidification control method is used, with the solidification time of the interfacial region delayed by 15%-25% compared to the central region of the aluminum alloy. This solidification sequence design ensures that the interfacial region solidifies last, with the insulating risers providing feeding molten metal to prevent shrinkage defects at the interface. The distance between the cooling channels and the interface is controlled at 15-30 mm, and the cooling water flow rate is controlled at 5-20 liters per minute. The arrangement and flow control of the cooling channels create a reasonable temperature gradient, guiding solidification from areas far from the interface towards the interface. Insulating risers are placed in the thickest parts of the aluminum alloy, with a riser feeding efficiency of ≥30%.

[0035] Solidification time is controlled at 1-2 seconds per square centimeter of aluminum alloy cross-sectional area, with a total solidification time set at 30-180 minutes depending on the casting size. This solidification time parameter is determined based on the solidification characteristics of the aluminum alloy and the casting size to ensure a smooth solidification process. The casting is removed from the mold after cooling to below 200℃. The temperature is controlled below 200℃ because at this point the casting has sufficient strength to withstand the mechanical stress during removal, while also preventing oxidation and deformation caused by excessively high temperatures.

[0036] During the cooling process, induction heating is used to assist in controlling the cooling rate of the interface region. The induction heating device establishes a local temperature field in the interface region and heats the metal through the principle of electromagnetic induction, thereby controlling the cooling rate of the interface region. Induction heating-assisted control ensures that the interface transition layer forms a dense metallurgical bond with the materials on both sides. Through temperature gradient control during solidification and cooling and induction heating assistance, the gradient structure design of the transition layer allows the coefficient of thermal expansion to gradually transition from the cast iron side to the aluminum alloy side, significantly alleviating the phenomenon of thermal stress concentration.

[0037] S6. Heat treatment of the aluminum alloy areas. A segmented solution treatment process is used for the aluminum alloy areas, with the solution treatment temperature controlled at 500-540℃. Solution treatment involves heating the aluminum alloy to a certain temperature, allowing the alloying elements to fully dissolve in the aluminum matrix, forming a uniform supersaturated solid solution. The holding time is calculated at 1.5-2 hours per 25 mm thickness to ensure uniform temperature throughout the casting and achieve a sufficient solution treatment effect.

[0038] After heat treatment, the aluminum alloy is water-quenched, with the water quenching transfer time not exceeding 10 seconds. Water quenching rapidly cools the solution-treated aluminum alloy, preventing alloying elements from diffusing and retaining them in a supersaturated state within the aluminum matrix. The water quenching transfer time is controlled within 10 seconds to avoid precipitation precursors caused by temperature drop, maintaining the supersaturated solid solution state. During water quenching, the cast iron portion does not participate in the heat treatment to prevent rusting.

[0039] Artificial aging treatment is then performed, with the aging temperature controlled at 160-200℃ and the aging time controlled at 6-12 hours. After aging, the alloy is air-cooled to room temperature. Artificial aging involves heating the supersaturated solid solution to a lower temperature, causing alloying elements to precipitate as fine, dispersed phases, thereby improving the strength and hardness of the aluminum alloy. The choice of aging temperature and time directly affects the size, distribution, and quantity of the precipitated phases, thus determining the final mechanical properties.

[0040] S7. Quality inspection and finishing are performed. X-ray non-destructive testing is conducted on the completed brake discs to check for porosity, inclusions, or lack of fusion defects in the interface bonding area. X-ray non-destructive testing utilizes the penetrating power of X-rays to create images reflecting internal defects in the casting on photographic film or a digital detector. Key areas for inspection include the interface transition layer, thick sections of the aluminum alloy, and the connection areas of the gating system.

[0041] The interfacial bonding strength was tested using a shear test, with a required bonding strength of ≥60 MPa. The shear test involves applying a shear force parallel to the interface in the interfacial region and determining the shear strength at which the interface fractures. This strength index is a key parameter for evaluating the reliability of the interfacial bonding between cast iron and aluminum alloy. Test samples were prepared using the same parameters as in the actual process, with the test environment at room temperature and a loading rate of 1 mm / min.

[0042] Dimensional accuracy inspection is performed according to the drawing requirements, controlling machining allowances. Machining allowances are determined based on the casting dimensions, shape complexity, and machining accuracy requirements, generally ranging from 2-5 mm. Machining includes turning, milling, drilling, and other processes. The machined brake disc must meet dimensional and positional tolerances and surface roughness requirements. After machining, surface treatment is performed using either electrophoretic coating or powder coating, with the coating thickness controlled at 20-40 micrometers. Electrophoretic coating involves immersing the workpiece in a water-based coating bath and applying an electric current, causing coating particles to deposit on the workpiece surface to form a uniform coating. Powder coating involves adsorbing powder coating onto the workpiece surface under electrostatic action and then heating and curing to form a coating.

[0043] This invention also includes a heat dissipation structure design, in which heat dissipation fins are arranged in the aluminum alloy area. The thickness of the heat dissipation fins is controlled at 2-5 mm, the fin height at 8-20 mm, and the fin spacing at 5-15 mm. The thickness, height, and spacing parameters of the heat dissipation fins determine the heat dissipation area and heat dissipation efficiency. The fins are connected to the aluminum alloy substrate using a gradual transition structure, with the length of the gradual transition zone controlled at 3-8 mm. The gradual transition structure avoids stress concentration caused by abrupt changes in cross-sectional area and increases the bonding strength between the fins and the substrate. The heat dissipation fin structure design increases the heat dissipation area by 30%-50% and improves the overall heat dissipation efficiency by 2-3 times.

[0044] In a specific application example, the implementation process of this method is illustrated using a brake disc from a certain model of passenger vehicle. The brake disc has a diameter of 320 mm, a cast iron disc wall thickness of 15 mm, and an aluminum alloy heat dissipation area cross-sectional area of ​​40 square centimeters. Based on the casting dimensions, the heating and holding time for the cast iron is 0.6 hours, the total solidification time for the aluminum alloy is 65 minutes, and the solution treatment holding time is 1 hour.

[0045] The cast iron brake disc body is manufactured using a metal mold sand casting process. The metal mold preheating temperature is 280℃, the sand coating thickness is 5 mm, and organic resin sand is used as the sand coating material. The air permeability of the sand coating layer is 110 units. The molten iron is poured at 1420℃ and cooled to room temperature after pouring. The density of the cast iron brake disc body reaches 96%, and the spheroidization rate of ductile iron is 88%. The inner circumferential surface of the cast iron brake disc is machined to form isosceles trapezoidal sawtooth joint grooves. The tooth tip width is 3 mm, the tooth root width is 5 mm, the tooth depth is 6 mm, the groove spacing is 12 mm, and the surface roughness is Ra 6.3 micrometers. The sawtooth joint grooves increase the joint area by a factor of 2.2.

[0046] The interface was activated by sandblasting with 1 mm brown fused alumina abrasive at a pressure of 0.6 MPa. The transition layer coating was prepared by weight percentage as follows: 55% nickel powder, 35% aluminum powder, and 10% silica powder. Ethyl silicate binder was added and stirred until homogeneous. The coating viscosity was 21 seconds (Ford Cup 4). The transition layer was applied by brush to a thickness of 0.3 mm, allowed to air dry for 20 minutes, and then baked at 160°C for 45 minutes.

[0047] The cast iron brake disc is heated to 550°C in a resistance furnace and held for 0.6 hours, then transferred to a heat preservation device to maintain the temperature. The aluminum alloy ingot is heated to 720°C in a melting furnace and melted. The refining process involves argon blowing for 15 minutes. After refining, the hydrogen content of the molten aluminum is 0.12 ml per 100g of aluminum. After slag removal and settling, the temperature of the molten aluminum alloy is controlled at 740°C.

[0048] The casting mold employs a bimetallic composite mold structure. The main body of the mold is made of cast iron, and the inner cavity surface is coated with a graphite-based coating with a thickness of 0.1 mm. The mold is preheated to 280℃, and the cast iron brake disc is positioned and installed using a dovetail groove with a positioning accuracy of 0.08 mm. Aluminum alloy molten metal is poured using a low-pressure casting process at a casting pressure of 0.05 MPa. During the pouring process, the bonding interface area is continuously heated to maintain a temperature of 420℃. After pouring, the pressure is held for 20 seconds before entering the solidification and cooling stage.

[0049] The solidification process employs bidirectional solidification control, with the solidification time in the interface region delayed by 20% compared to the central region of the aluminum alloy. The cooling water channel is 25 mm from the interface, with a cooling water flow rate of 12 liters per minute. Insulating risers are placed in the thicker sections of the aluminum alloy, with a riser feeding efficiency of 35%. Induction heating with a power of 15 kW is used for auxiliary control of the interface region during solidification. The material is removed from the oven after cooling to 180°C. The interface transition layer thickness is 0.25 mm, and its microstructure is a composite gradient structure with alternating layers of Ni-Al intermetallic compounds, Al-Fe intermetallic compounds, and Al-Fe-Si ternary compounds.

[0050] The aluminum alloy areas undergo heat treatment: solution treatment at 520℃ for 1.5 hours, followed by water quenching and transfer for 8 seconds. Artificial aging is then performed at 180℃ for 8 hours, followed by air cooling to room temperature.

[0051] X-ray non-destructive testing was performed on the cast brake discs, and no porosity, inclusions, or incomplete fusion defects were found. The interfacial bond strength shear test result was 72 MPa, meeting the requirement of greater than or equal to 60 MPa. Heat dissipation fins were installed in the aluminum alloy area, with a fin thickness of 3 mm, a height of 12 mm, a spacing of 8 mm, and a gradient transition zone length of 5 mm. After machining, electrophoretic coating was applied, with a coating thickness of 30 micrometers.

[0052] The finished brake disc weighs 7.2 kg, a 32% reduction compared to an all-cast iron brake disc. The brake friction surface is made of cast iron to ensure wear resistance, while the aluminum alloy heat dissipation area has a thermal conductivity of 210 W / (m·K), and the heat dissipation fins increase the heat dissipation area by 42%. Braking thermal cycling tests have verified that the interface bonding strength remains stable after 500 thermal cycles, with no interface cracking or delamination observed.

[0053] Example 2 To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to another specific embodiment.

[0054] This embodiment provides a method for combining cast iron brake discs with cast aluminum alloy materials, applicable to the manufacture of heavy-duty commercial vehicle brake discs. The brake disc has a diameter of 420 mm, a cast iron brake disc body wall thickness of 22 mm, and an aluminum alloy heat dissipation area cross-sectional area of ​​85 square centimeters. The braking condition is high-frequency and heavy-load, requiring higher standards for heat dissipation performance and interface bonding reliability.

[0055] In S1, the cast iron brake disc body is manufactured using a metal mold sand casting process. The metal mold preheating temperature is 320℃, the sand coating thickness is 7 mm, and silica sand is used as the sand coating material. The permeability of the sand coating layer is 130 units. The molten iron pouring temperature is 1440℃, and it is cooled to room temperature after pouring. The cast iron brake disc body is made of ductile iron with a spheroidization rate of 90% and a microstructure density of 97%. The interface to be composited on the cast iron brake disc body is machined to create dovetail-shaped mating grooves. The dovetail angle is 60 degrees, the dovetail depth is 9 mm, the groove width is 10 mm, the groove spacing is 16 mm, and the surface roughness is Ra 8 micrometers. The mechanical meshing of the dovetail-shaped mating grooves provides higher shear resistance under heavy load conditions.

[0056] In S2, the interface is activated by chemical etching, treated with a 10% dilute hydrochloric acid solution for 15 minutes. The transition layer coating is prepared by weight percentage as follows: 50% nickel powder, 40% aluminum powder, and 10% silicon powder, with ethyl silicate binder added. The coating viscosity is 23 seconds (French cup 4). The transition layer is applied by spraying to a thickness of 0.4 mm, allowed to air dry for 15 minutes, and then dried at 150°C for 50 minutes.

[0057] In S3, the cast iron brake disc is placed in an induction heating furnace and heated to 620℃. The holding time is 1 hour for every 25 mm of wall thickness, with an actual holding time of 0.88 hours. It is then transferred to a heat preservation device to maintain the temperature. The aluminum alloy includes the following alloying elements: silicon content of 8.0% to 9.0%, manganese content of 0.30% to 0.35%, magnesium content of 0.15% to 0.28%, titanium content of 0.10% to 0.12%, strontium content of 0.008% to 0.01%, zinc content not exceeding 0.1%, lead content not exceeding 0.03%, tin content not exceeding 0.05%, copper content not exceeding 0.1%, iron content not exceeding 0.2%, with the balance being aluminum. The aluminum alloy ingot melting temperature is 730℃. The refining process involves degassing with hexachloroethane for 18 minutes. After refining, the hydrogen content of the aluminum liquid is 0.11 ml per 100g of aluminum. After slag removal and settling, the temperature of the aluminum alloy liquid is controlled at 750℃.

[0058] In S4, the casting mold adopts a bimetallic composite mold structure, with the inner cavity surface coated with a titanium nitride coating of 0.15 mm thickness. The mold is preheated to 300℃, and the cast iron brake disc is positioned and installed using a dovetail groove with a positioning accuracy of 0.06 mm. Vacuum die casting is used for pouring molten aluminum alloy, with a vacuum degree of -0.07 MPa and a filling speed of 1.5 m / s. The gating system is a bottom-pouring system, with an ingate cross-sectional area of ​​6 square centimeters, a runner cross-sectional area of ​​10 square centimeters, and a sprue cross-sectional area of ​​14 square centimeters, with a flow-blocking section to ingate cross-sectional area ratio of 1:3. During pouring, the interface area is continuously heated to maintain a temperature of 450℃. After pouring, pressure is held for 25 seconds before solidification and cooling.

[0059] In S5, a two-way solidification control process was employed, with the solidification time at the interface region delayed by 22% compared to the central aluminum alloy region. The cooling water channel was 28 mm from the interface, with a flow rate of 18 liters per minute. Insulating risers were placed in the thicker sections of the aluminum alloy, achieving a riser feeding efficiency of 38%. The solidification time was controlled at 1.5 seconds per square centimeter of aluminum alloy cross-sectional area, for a total solidification time of 140 minutes. The aluminum alloy was removed from the oven after cooling to 190°C. Induction heating with a power of 22 kW was used to assist in the cooling process at the interface region.

[0060] In S6, the solution treatment temperature is 530℃, the holding time is 1.8 hours per 25 mm thickness, the actual holding time is 1.6 hours, and the water quenching transfer time is 7 seconds. The artificial aging treatment temperature is 190℃, the aging time is 10 hours, and after aging, it is air-cooled to room temperature.

[0061] In S7, no defects were detected by X-ray nondestructive testing. The interfacial bond strength shear test result was 78 MPa. Heat dissipation fins were installed in the aluminum alloy area, with a fin thickness of 4 mm, a height of 18 mm, a spacing of 12 mm, and a gradient transition zone length of 7 mm. After machining, powder coating was applied, with a coating thickness of 35 micrometers.

[0062] The finished brake disc weighs 13.5 kg, which is 28% lighter than an all-cast iron brake disc. The thermal conductivity of the aluminum alloy heat dissipation area reaches 195 W / (m·K), and the heat dissipation fins increase the heat dissipation area by 45%. After 1000 braking thermal cycle tests, the interface bonding strength remains stable, meeting the requirements for high-frequency heavy-load conditions.

[0063] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of casting an iron brake disc body in an aluminum alloy material, characterized by, Includes the following steps: S1. Pre-treat the cast iron brake disc body, prepare the cast iron brake disc body using metal mold sand casting process, and machine the composite interface of the cast iron brake disc body to be machined to produce either a serrated joint groove or a dovetail joint groove. The groove depth is controlled to be 3-8 mm, the groove width is controlled to be 5-12 mm, the groove spacing is controlled to be 8-20 mm, and the surface roughness is controlled to be within the range of Ra3.2-Ra12.5 micrometers. S2, the interface of the cast iron brake disc is activated and coated with a transition layer. After activation, a transition layer coating is applied to the interface. The transition layer coating is made of a mixture of nickel powder, aluminum powder and silicon powder. The thickness of the transition layer is controlled to be 0.1-0.5 mm. S3. Heat the cast iron brake disc and the aluminum alloy separately. Place the cast iron brake disc in a resistance furnace or induction heating furnace for heating. The heating temperature of the cast iron is controlled at 450-650℃, and the holding time is calculated as 1 hour for every 25 mm of wall thickness. Place the aluminum alloy ingot in an aluminum alloy melting furnace for heating and melting. The melting temperature is controlled at 680-750℃, and the temperature of the aluminum alloy liquid is controlled within the range of 720-760℃. After refining and degassing, remove the slag and let it stand. S4. Perform aluminum alloy liquid pouring and interface composite, transfer the cast iron brake disc body to the casting mold for positioning and installation. The preheating temperature of the casting mold is controlled at 200-350℃. Position the mold and the cast iron brake disc body, and use either vacuum die casting or low-pressure casting process to pour aluminum alloy liquid. The vacuum degree of vacuum die casting is controlled at -0.05 to -0.08Mpa, the filling speed is controlled at 0.5-3m / S, and the pressure of low-pressure casting is controlled at 0.02-0.08Mpa. S5 controls the solidification and cooling process to achieve interfacial metallurgical bonding. During solidification, the temperature gradient is controlled by the principle of sequential solidification. The solidification sequence is adjusted by using insulating risers and cooling water channels, and the cooling rate of the interfacial region is controlled to achieve bidirectional solidification control. The solidification time of the interfacial region is delayed by 15%-25% compared with that of the aluminum alloy center region. S6, heat treatment is performed on the aluminum alloy area using a segmented solution treatment process. After heat preservation, the aluminum alloy heat dissipation area is subjected to directional high-pressure water spraying to complete water quenching, followed by artificial aging treatment. After aging, it is air-cooled to room temperature. S7 involves quality inspection and precision machining of the brake discs after they have been cast.

2. The method of claim 1, wherein the cast iron brake disc body alloy material is an aluminum alloy material. In S1, the sand coating material is organic resin sand or silica sand, the thickness of the sand coating layer is controlled at 3-8 mm, the air permeability of the sand coating layer is controlled at 80-150 air permeability units, the pouring temperature is controlled within the range of 1380-1450℃, and the metal mold sand coating casting process ensures that the density of the cast iron brake disc reaches more than 95%, and the spheroidization rate of ductile iron is greater than or equal to 85%.

3. The method of claim 1, wherein the cast iron brake disc body alloy material is an aluminum alloy material. In S1, the interface of the cast iron brake disc to be composite is machined. The machined sawtooth joint groove adopts an isosceles trapezoidal structure with a tooth top width of 2-5 mm, a tooth bottom width of 3-8 mm, and a tooth depth of 4-8 mm; or the machined dovetail joint groove has a dovetail angle controlled at 50-70 degrees and a dovetail depth of 5-10 mm; the joint area increases by a factor of 1.8-2.5 times.

4. The method of claim 1, wherein the cast iron brake disc body alloy material is an aluminum alloy material. The activation treatment in S2 can be either sandblasting or chemical etching. The sandblasting treatment uses brown corundum sand with a particle size of 0.5-1.5 mm and the sandblasting pressure is controlled at 0.4-0.8 MPa. The chemical etching treatment uses a 5%-15% dilute hydrochloric acid solution for 5-30 minutes.

5. The method of claim 1, wherein the cast iron brake disc body alloy material is an aluminum alloy material. The transition layer coating in S2 is made of a mixture of nickel powder, aluminum powder, and silicon powder. The mass fraction of nickel powder is 40%-60%, the mass fraction of aluminum powder is 30%-45%, and the mass fraction of silicon powder is 5%-15%. Ethyl silicate is used as the binder. The viscosity of the coating is controlled at 18-25 seconds (French cup 4). The coating is applied by brushing or spraying. After coating, it is allowed to dry naturally for 10-30 minutes before being dried at 120-180℃ for 30-60 minutes.

6. The method of claim 1, wherein the cast iron brake disc body alloy material is an aluminum alloy material. The S3 aluminum alloy contains the following alloying elements: silicon (8.0%-9.0%), manganese (0.30%-0.35%), magnesium (0.15%-0.28%), titanium (0.10%-0.12%), strontium (0.008%-0.01%), zinc (not exceeding 0.1%), lead (not exceeding 0.03%), tin (not exceeding 0.05%), copper (not exceeding 0.1%), and iron (not exceeding 0.2%), with the balance being aluminum. Refining is performed using argon purging or hexachloroethane degassing, with a degassing time controlled at 10-20 minutes and a refining temperature controlled at 730-740℃. After refining, the hydrogen content in the liquid aluminum is less than or equal to 0.15 ml / 100g aluminum.

7. The method for combining cast iron brake discs with cast aluminum alloy materials according to claim 1, characterized in that, The S4 casting mold adopts a bimetallic composite mold structure. The main body of the mold is made of cast iron, and the inner surface of the mold cavity is coated with graphite-based coating or titanium nitride coating, with the coating thickness controlled at 0.05-0.2 mm. The gating system adopts a bottom-pouring gating system, with the cross-sectional area of ​​the ingate controlled at 2-8 square centimeters, the cross-sectional area of ​​the runner controlled at 3-12 square centimeters, and the cross-sectional area of ​​the sprue controlled at 4-15 square centimeters. The total cross-sectional area of ​​the gating system is designed according to the ratio of the flow-blocking section to the cross-sectional area of ​​the ingate at 1:2-1:

4. During the pouring process, the interface area of ​​the cast iron brake disc is continuously heated to maintain the temperature at 350-500℃. After pouring, the pressure is held for 10-30 seconds.

8. The method for combining cast iron brake discs with cast aluminum alloy materials according to claim 1, characterized in that, In S5, the distance between the cooling water channel and the interface is controlled at 15-30 mm, and the cooling water flow rate is controlled at 5-20 liters per minute; the insulation riser is set in the thick part of the aluminum alloy, and the riser feeding efficiency is greater than or equal to 30%; the solidification time is controlled at 1-2 seconds per square centimeter of aluminum alloy cross-sectional area, and the aluminum alloy is removed from the box after cooling to below 200℃; during the cooling process, induction heating is used to assist in controlling the cooling rate of the interface area.

9. The method for combining cast iron brake discs with cast aluminum alloy materials according to claim 1, characterized in that, In S6, the solution treatment temperature is controlled at 500-540℃, and the holding time is calculated as 1.5-2 hours per 25 mm thickness. After the holding time is completed, a multi-nozzle annular cooling pipe is used to perform directional high-pressure water spray cooling on the aluminum alloy heat dissipation area. The spray angle is controlled so that the cooling water does not come into contact with the working surface of the cast iron brake disc, thereby ensuring that the cast iron part does not participate in water quenching. The artificial aging treatment temperature is controlled at 160-200℃, and the aging time is controlled at 6-12 hours. After aging, the parts are air-cooled to room temperature.

10. The method for combining cast iron brake discs with cast aluminum alloy materials according to claim 1, characterized in that, In S7, the brake discs after casting are subjected to X-ray non-destructive testing to check for defects such as porosity, inclusions, or lack of fusion in the interface bonding area. The interface bonding strength is tested by shear test, and the bonding strength requirement is greater than or equal to 60 MPa. Heat dissipation fins are installed in the aluminum alloy area, with the fin thickness controlled at 2-5 mm, the fin height controlled at 8-20 mm, and the fin spacing controlled at 5-15 mm. The fins are connected to the aluminum alloy substrate by a gradient transition structure, and the length of the gradient transition zone is controlled at 3-8 mm. After machining, surface treatment is performed by electrophoretic coating or powder coating, and the coating thickness is controlled at 20-40 micrometers.

Images