A kind of textured reinforced steel ring-gray cast iron bimetallic composite brake drum

Abstract

This invention belongs to the field of brake drum manufacturing technology, specifically relating to a textured reinforced steel rim-gray cast iron bimetallic composite brake drum, comprising a steel rim shell and a gray cast iron liner. The gray cast iron liner is formed by casting molten gray cast iron onto the inner wall of the steel rim shell through a centrifugal forming composite casting process. The microstructure of the brake drum, from the inside out, includes: a gray cast iron layer, an interface layer, and a refined grain layer; the grains in the refined grain layer are deformed grains from the steel rim shell prepared by a spinning process; the grains in the interface layer are equiaxed grains. This invention enables the brake drum to maintain the high strength and toughness of the fine deformed grains of the steel rim during service. The strength and toughness of the steel rim significantly improve the brake drum liner's resistance to failure caused by high-temperature deformation and stress concentration. The fine grains and high toughness of the original spinning deformation under the composite forming of the steel rim effectively constrain the high-temperature cracking and deformation of conventional composite brake drums, thereby synergistically improving the overall strength and thermal conductivity of the brake drum.

Description

Technical Field

[0001] This invention belongs to the field of brake drum manufacturing technology, specifically relating to a textured reinforced steel ring-gray cast iron bimetallic composite brake drum. Background Technology

[0002] As automobiles continue to evolve towards higher speeds and heavier loads, the requirements for braking systems are becoming increasingly stringent. The interface and internal structure of bimetallic composite brake drums are key factors affecting their toughness and strength.

[0003] The steel outer ring is typically manufactured using a large plastic deformation spinning process. During subsequent bimetallic casting, the temperature rise causes coarsening of the deformed grains and destruction of recrystallized grains, resulting in a significant reduction in strength. This means that the existing bimetallic brake drum's interface and lining microstructure still exhibit relatively large grain sizes, failing to realize the full potential of the bimetallic brake drum. Furthermore, during the high-temperature molten iron casting process, the original deformed grains of the steel ring coarsen and even grow significantly due to the heat, making it impossible to maintain the fine grains and high strength and toughness achieved before deformation. When the bonding strength between the outer shell and the inner liner is insufficient, the inner liner of the bimetallic brake drum is prone to cracking and deformation during service. A steel outer ring is required as a reinforcing layer. However, due to limitations such as the thickness of the steel outer ring, the bonding state with the gray cast iron, and the inherent thickness requirements of the steel ring, the high-temperature thermal shock during the preheating and casting of the steel ring coarsens and changes the deformation characteristics and mechanical properties of the spun steel ring. At the same time, insufficient preheating will prevent the interface from achieving metallurgical fusion, and even cause bimetallic interface separation and cracking. These processes combined cause wear and fracture of the brake drum interface, reducing the safety factor of the brake drum and causing safety accidents.

[0004] Based on the above reasons, the technical problem to be solved by this invention is how to improve the strength and thermal conductivity of the bimetallic composite brake drum during service by improving the interface and internal structure of the bimetallic composite brake drum. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a textured steel ring-gray cast iron bimetallic composite brake drum. The outer steel ring of the brake drum maintains the low-temperature deformation grains of the outer wall surface of the spun steel ring. Combined with the grain refinement in the interface, uniform and fine equiaxed grains are formed. This allows the bimetallic composite brake drum to maintain the high strength and toughness of the fine deformation grains of the steel ring during service. The strength and toughness of the steel ring significantly improve the failure of the inner gray cast iron layer of the composite brake drum caused by high-temperature deformation and stress concentration. The fine grains and high toughness of the original spun deformation under the composite forming of the steel ring effectively constrain the high-temperature cracking and deformation of conventional composite brake drums, thereby synergistically improving the overall strength and thermal conductivity of the bimetallic composite brake drum.

[0006] This invention achieves effective metallurgical fusion at the interface by maintaining fine deformed grains in the outer wall layer of a spun steel ring of a specific thickness, through rapid and efficient high-temperature preheating of the inner thin-walled layer and subsequent liquid-solid forming. Steel outer rings are typically manufactured using a large plastic deformation spinning process. During subsequent bimetallic casting, the temperature rise leads to coarsening of deformed grains and destruction of recrystallized grains, resulting in a significant reduction in strength. Therefore, by introducing a water-cooled iron sleeve device during the high-temperature casting process and forcibly cooling the outer wall of the spun steel ring, while simultaneously employing high-frequency localized heating inside the steel outer ring, a gradient temperature control can be achieved between fine deformed grains in the thicker layer of the spun steel ring's outer wall and rapid high-temperature preheating at a certain depth on the inner surface. This ensures good fusion between the gray cast iron and the inner surface of the steel outer ring, refines the interface layer structure, maintains the fine deformed grains in the thicker layer on the outer surface of the steel outer ring, and thus improves the performance of the bimetallic composite brake drum. The high-frequency induction heating device rapidly heats the inner wall of the steel outer shell, with a heating zone depth of 1.3-2.0mm and a temperature reaching 680-710℃. The remaining areas are close to or maintain room temperature. The outer wall of the spun steel ring is equipped with a water-cooled iron sleeve device, which ensures that the outer layer of the spun steel ring is not affected by heat during high-temperature casting and that the interface layer structure is kept in a strongly cooled state during subsequent centrifugal casting. This results in an excellent bonding interface layer, ensuring fine deformed grains in the thicker layer of the outer wall of the spun steel ring and a gradient temperature of rapid preheating at a certain depth on the inner surface, while greatly refining the interface structure and improving the performance of the brake drum.

[0007] The present invention is specifically implemented through the following technical solution.

[0008] A textured reinforced steel rim-gray cast iron bimetallic composite brake drum includes a steel rim shell and a gray cast iron liner. The gray cast iron liner is formed by casting molten gray cast iron into the inner wall of the steel rim shell through a centrifugal forming composite casting process.

[0009] The microstructure of the bimetallic composite brake drum, from the inside out, includes: a gray cast iron layer, an interface layer, and a refined grain layer.

[0010] The grains in the refined grain layer are deformed grains from the steel ring shell prepared by a spinning process;

[0011] The grains in the interface layer are equiaxed crystals.

[0012] Furthermore, the microstructure of the bimetallic composite brake drum is achieved through the following process:

[0013] First, the steel ring shell is prepared by spinning process (this process is existing technology); then, gray cast iron molten iron is poured into the inner wall of the steel ring shell by centrifugal forming composite casting process. In the centrifugal forming composite casting process, the inner wall of the steel ring shell is first heated by a high-frequency induction heating device (rapid heating). After the heating is completed, the water-cooled iron sleeve device located on the outer wall of the steel ring shell is activated to cool the outer wall of the steel ring shell. Then, the gray cast iron molten iron is poured into the inner wall of the steel ring shell.

[0014] Through the above process, the low-temperature deformation grains of the outer wall of the spun steel ring can be maintained, while the rapid induction heating of the inner wall enables the rapid fusion and formation of gray cast iron molten iron and the inner wall of the spun steel ring during the centrifugal casting process. Under the strong cooling conditions of the outer wall of the spun steel ring, the grains at the interface are refined, forming uniform and fine equiaxed grains. This allows the bimetallic composite brake drum to maintain the high strength and toughness of the fine deformation grains of the steel ring during service. The strength and toughness of the steel ring significantly improve the failure of the inner gray cast iron of the composite brake drum caused by high-temperature deformation and stress concentration. The fine grains and high toughness of the original spun deformation under the composite forming of the steel ring effectively constrain the high-temperature cracking and deformation of conventional composite brake drums, thereby synergistically improving the overall strength and thermal conductivity of the bimetallic composite brake drum.

[0015] Furthermore, when the inner wall of the steel ring shell is heated by the high-frequency induction heating device, the heating time is 8-12 seconds, which raises the temperature of the inner wall of the steel ring shell to 680-710℃, while the outer wall surface remains at a low temperature in the deeper thickness range, thus preserving the fine grains of the spinning deformation.

[0016] Furthermore, when heating the inner wall of the steel ring shell using a high-frequency induction heating device, the three heating rods of the high-frequency induction heating device are inserted into the steel ring shell. An 80kW high-frequency generator is used, with the working voltage set to three-phase 380V, the output current to 2600A, the oscillation frequency to 30KHz, and the cooling water pressure to 0.18MPa. The high-frequency induction heating device remains stationary while the steel ring shell rotates.

[0017] Specifically, three heating rods of the high-frequency induction heating device are inserted into the steel ring shell to rapidly heat the inner wall of the steel ring shell under centrifugal rotation. Afterwards, the heating rods are removed and gray cast iron molten metal is quickly poured in, achieving interface fusion between the inner wall of the steel ring and the gray cast iron molten metal. During high-temperature pouring, the water-cooled iron sleeve device is activated in advance. The outer wall of the steel ring after centrifugal forming retains a certain thickness and maintains the fine grains before spinning deformation, thus possessing high strength and toughness. The steel ring-gray cast iron interface achieves metallurgical bonding due to high-temperature rapid preheating, without casting defects, interface cracks, or other interface defects.

[0018] Furthermore, when the inner wall of the steel ring shell is heated by the high-frequency induction heating device, the heating depth of the inner wall of the steel ring shell is 1.3-2.0mm.

[0019] Furthermore, when the water-cooled iron sleeve device cools the outer wall of the steel ring shell, the flow rate of the circulating water is 10-20 L / min, the initial water temperature is room temperature, and the cooling intensity of the water-cooled iron sleeve is 8.5-12℃ / s.

[0020] Furthermore, in the centrifugal forming and composite casting process of gray cast iron molten iron, the steel ring shell is used as a centrifugal mold for rotation, with a rotation speed of 600-750 r / min.

[0021] Furthermore, the pouring temperature for gray cast iron molten iron is 1400℃.

[0022] Furthermore, the inner wall of the steel ring outer shell adopts a macroscopic corrugated undulating structure, and the outer wall retains spun deformation grains within a relatively deep thickness, resulting in strength and toughness far exceeding those of conventional steel rings.

[0023] Furthermore, the gray cast iron molten iron is composed of the following raw materials in weight percentages: C 3.20%-3.30%, Si 1.79%-1.91%, Mn 0.89%-1.04%, S 0.094%-0.125%, P 0.120%-0.170%, with the remainder being Fe and unavoidable trace impurities.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] This invention provides a textured reinforced steel ring-gray cast iron bimetallic brake drum. The outer steel ring of the brake drum retains the low-temperature deformed grains of the spun steel ring's outer wall surface. Combined with grain refinement at the interface, it forms uniform and fine equiaxed grains. This allows the bimetallic composite brake drum to maintain the high strength and toughness of the fine deformed grains of the steel ring during service. The steel ring's strength and toughness significantly improve the failure of the inner gray cast iron layer of the composite brake drum caused by high-temperature deformation and stress concentration. The fine grains and high toughness of the original spun deformation under the composite forming of the steel ring effectively constrain the high-temperature cracking and deformation of conventional composite brake drums, thereby synergistically improving the overall strength and thermal conductivity of the bimetallic composite brake drum. Compared with the manufacturing process of ordinary gray cast iron / low carbon steel composite brake drums, this invention does not require preheating of the entire spun steel ring and ensures the fine deformed grain structure of the outer layer of the spun steel ring. Specifically, this is reflected in:

[0026] 1. The high-frequency induction heating device can heat the inner wall of the steel outer shell to 680-710°C in about 8-12 seconds, achieving the composite casting level. This shortens the production cycle of the bimetallic composite brake drum. In particular, it ensures the different microstructure requirements of the outer and inner layers of the spun steel ring and the large gradient temperature control. This allows the outer layer to be spun and deformed into its original fine grain structure, while the rapid high-temperature preheating of the inner layer ensures that the metallurgical bonding layer of the bimetallic interface is quickly formed under a small temperature difference after the high-temperature molten iron is poured. This saves energy, reduces costs, and ensures a tight fusion between the inner gray cast iron molten metal and the outer steel ring after pouring, reducing the temperature difference and avoiding fusion defects and interface casting defects.

[0027] 2. The water-cooled iron jacket device on the outside of the steel shell has a circulating water flow rate of 10-20 L / min and an initial water temperature of room temperature. This water-cooling device accelerates heat dissipation during high-temperature casting. Under the rotational pushing action of the spinning steel ring, it generates a significant cooling effect on the casting layer interface, resulting in a significantly refined interface layer structure with uniform, fine equiaxed crystals. The grain size measured on the outer steel ring of the interface layer reaches 7.5. Water cooling ensures that the interface layer structure exhibits a suitable temperature gradient, with low anisotropy of the equiaxed crystals. This results in uniform deformation during the service of the bimetallic brake drum, improving the strength of the structure and enhancing the practical applicability of the bimetallic composite brake drum.

[0028] 3. Refined grains improve the strength of polycrystalline materials while also enhancing their plasticity and toughness. Finer grains mean more grains per unit volume, allowing the same amount of deformation to be distributed across more grains, resulting in more uniform deformation and preventing excessive local stress concentration, thus avoiding the generation and propagation of cracks at the interface. With refined interface layer grains, the bonding strength of the bimetallic composite brake drum prepared in this invention is increased by 16% compared to the 259 MPa of ordinary brake drums, reaching 300 MPa, demonstrating superior performance.

[0029] 4. The high-temperature casting molten iron uses ordinary gray cast iron molten iron, which not only ensures good metallurgical bonding inside during casting, but also makes the inner layer of the prepared bimetallic brake drum have good tensile strength and high thermal conductivity.

[0030] 5. The inner surface of the outer steel ring has a corrugated undulating structure with a large roughness, which increases the contact area between the steel ring and the water flow, ensuring that the heat conduction area is increased under a suitable circulating water flow speed, thus achieving a good high heat conduction effect.

[0031] In summary, the combination of the copper block embedded in the outer wall of the spun steel ring and the water-cooled iron sleeve device in this invention accelerates the heat dissipation of the high-temperature casting system. Under strong cooling conditions, it ensures the different microstructure requirements of the outer and inner layers of the spun steel ring and the large gradient temperature control, so that the outer layer spun deformation microstructure is the original fine grains, while the rapid high-temperature preheating of the inner layer ensures that the metallurgical bonding layer of the bimetallic interface is quickly formed under a small temperature difference after the high-temperature molten iron is poured, which refines the grains at the interface and forms uniform and fine equiaxed grains. This reduces the stress concentration effect and makes the deformation more uniform during the service of the bimetallic composite brake drum, thereby improving the bonding strength and thermal conductivity of the bimetallic composite brake drum. This provides a research idea for further development of bimetallic composite brake drums that can reliably serve in complex road conditions. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the water-cooled iron sleeve device used in this invention; in the diagram, 1 is the water inlet, 2 is the water outlet, and 3 is the cooling pipe;

[0033] Figure 2 This is a schematic diagram of the high-frequency induction device and the triangular heating rod of the present invention; in the figure, 4 is the heating rod, and Figure (b) is a schematic diagram of the three heating rods in Figure (a) arranged in a triangular shape;

[0034] Figure 3 The image shows the microstructure of the bimetallic brake drum in Example 1. Detailed Implementation

[0035] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0036] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0037] This invention discloses a textured reinforced steel ring-gray cast iron bimetallic brake drum. The brake drum shell is manufactured by a spinning process, which is existing technology. A water-cooled iron sleeve device (the specific structure of this device is existing technology) is installed on the outer layer of the spun steel ring. Three heating rods of a high-frequency induction heating device (the specific structure of this device is existing technology) are inserted into the coarse section of the steel shell. The parameters of the 80kW high-frequency induction heating device are: operating voltage of three-phase 380V, oscillation frequency of 30kHz, and cooling water pressure of 0.18MPa. After heating for 8-12 seconds, the high-frequency induction heating device is removed, and then molten gray cast iron at 1400℃ is poured. The inner wall of the spun steel ring is heated to 680-710℃ by high-frequency induction heating, with a heating depth of approximately 1.3-2.0mm. The high-frequency induction heating device heats a thin layer of the inner wall of the steel shell, and the water-cooled iron sleeve device and the high-frequency induction heating device can slide relative to the spun steel ring, i.e., it is manufactured through a "spinning" process.

[0038] The molten iron used for high-temperature casting is ordinary gray cast iron, which, by weight percentage, includes C: 3.20%-3.30%, Si: 1.79%-1.91%, Mn: 0.89%-1.04%, S: 0.094%-0.125%, P: 0.120%-0.170%, with the remainder being Fe and unavoidable trace impurities. The ordinary gray cast iron ensures good metallurgical bonding during casting and also gives the bimetallic brake drum good bonding strength and high thermal conductivity between the inner and outer layers after manufacturing.

[0039] During high-temperature casting, the water-cooled iron jacket device is activated in advance. The flow rate of the circulating water in the water-cooled iron jacket device outside the spinning steel ring is 10-20L / min, and the initial water temperature is room temperature. The water-cooled iron jacket device accelerates the heat dissipation during high-temperature casting, resulting in fine-grained deformation of the outer spinning deformation structure. Meanwhile, the rapid high-temperature preheating of the inner layer ensures that the metallurgical bonding layer of the bimetallic interface is quickly formed under a small temperature difference after the high-temperature molten iron is poured. This eliminates metallurgical defects at the interface and ensures a strong cooling effect on the interface layer, greatly refining the relevant structure and improving the tensile strength and thermal conductivity of the structure.

[0040] The outer steel ring has a corrugated undulating surface on its inner surface, which increases the contact area between the steel ring and the water flow. This ensures that the heat conduction area is increased at a suitable circulating water flow rate, resulting in a good high heat conduction effect.

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0042] Example 1

[0043] A textured reinforced steel rim-gray cast iron bimetallic composite brake drum includes a high-speed spun-deformed steel rim shell and a gray cast iron liner. The gray cast iron liner is formed by high-temperature centrifugal casting of molten iron and is bonded to the inner wall of the steel rim shell. The composition of the ordinary gray cast iron molten metal cast at high temperature is: C: 3.20%, Si: 1.79%, Mn: 0.89%, S: 0.112%, P: 0.154%, with the remainder being Fe.

[0044] Heating is achieved using a high-frequency induction heating device, such as Figure 2 As shown, the three heating rods 4 are arranged in a triangular pattern. The heating rods are inserted into the steel casing. An 80kW high-frequency induction heating machine is used, with the operating voltage set to three-phase 380V, the oscillation frequency to 30kHz, the output current to 2600A, and the cooling water pressure to 0.18MPa. The high-frequency induction heating device remains stationary while the steel casing rotates at 300r / min. The high-frequency induction heating device provides uniform heating for 8 seconds, reaching a temperature of 680℃. Using these process parameters, the heating depth of the spun steel ring is approximately 1.3mm. During high-temperature casting, the water-cooled iron sleeve device is activated in advance (e.g.,...). Figure 1 As shown, 1 is the water inlet, 2 is the water outlet, and 3 is the cooling pipe. The rotation speed of the brake drum spun steel ring is 600 r / min. The flow rate of the circulating water in the water-cooled iron sleeve device outside the spun steel ring is 10 L / min. The initial water temperature is room temperature. The cooling intensity of the water-cooled iron sleeve is 8.5 C / s. The thickness of the copper block on the outer wall of the spun steel ring is 1.5 mm. The pouring temperature of the gray cast iron molten iron is 1400 °C. After cooling, the water-cooled iron sleeve composite bimetallic brake drum is obtained.

[0045] Example 2

[0046] A textured reinforced steel rim-gray cast iron bimetallic composite brake drum includes a high-speed spun-deformed steel rim shell and a gray cast iron liner. The gray cast iron liner is formed by high-temperature centrifugal casting of molten iron and is bonded to the inner wall of the steel rim shell. The ordinary gray cast iron molten metal composition of the high-temperature composite casting is C: 3.25%, Si: 1.84%, Mn: 0.96%, S: 0.094%, P: 0.120%, with the remainder being Fe.

[0047] Heating is achieved using a high-frequency induction heating device, such as Figure 2 As shown, the three heating rods 4 are arranged in a triangular pattern. The heating rods are inserted into the steel casing. An 80kW high-frequency induction heating machine is used, with the operating voltage set to three-phase 380V, the oscillation frequency to 30kHz, the output current to 2600A, and the cooling water pressure to 0.18MPa. The high-frequency induction heating device remains stationary, while the steel casing rotates at 300r / min. The high-frequency induction heating device provides uniform heating for 10 seconds at a temperature of 700℃. Using these process parameters, the heating depth of the spun steel ring is approximately 1.5mm. During high-temperature casting, the water-cooled iron sleeve device is activated in advance (e.g.,...). Figure 1 As shown, 1 is the water inlet, 2 is the water outlet, and 3 is the cooling pipe. The rotation speed of the brake drum spun steel ring is 700 r / min. The flow rate of the circulating water in the water-cooled iron sleeve device outside the spun steel ring is 15 L / min. The initial water temperature is room temperature. The cooling intensity of the water-cooled iron sleeve is 12 C / s. The thickness of the copper block on the outer wall of the spun steel ring is 2.4 mm. The pouring temperature of the gray cast iron molten iron is 1400℃. After cooling, the water-cooled iron sleeve composite bimetallic brake drum is obtained.

[0048] Example 3

[0049] A textured reinforced steel rim-gray cast iron bimetallic composite brake drum includes a high-speed spun-deformed steel rim shell and a gray cast iron liner. The gray cast iron liner is formed by high-temperature centrifugal casting of molten iron and is bonded to the inner wall of the steel rim shell. The composition of the ordinary gray cast iron molten metal cast at high temperature is C: 3.30%, Si: 1.91%, Mn: 1.04%, S: 0.125%, P: 0.170%, with the remainder being Fe.

[0050] Heating is achieved using a high-frequency induction heating device, such as Figure 2As shown, the three heating rods 4 are arranged in a triangular pattern. The heating rods are inserted into the steel casing. An 80kW high-frequency induction heating machine is used, with the operating voltage set to three-phase 380V, the oscillation frequency to 30kHz, the output current to 2600A, and the cooling water pressure to 0.18MPa. The high-frequency induction heating device remains stationary while the steel casing rotates at 300r / min. The high-frequency induction heating device provides uniform heating for 12 seconds, reaching a temperature of 710℃. Using these process parameters, the heating depth of the spun steel ring is approximately 2.0mm. During high-temperature casting, the water-cooled iron sleeve device is pre-activated (e.g., ...). Figure 1 As shown, 1 is the water inlet, 2 is the water outlet, and 3 is the cooling pipe. The rotation speed of the brake drum spun steel ring is 750 r / min. The flow rate of the circulating water in the water-cooled iron sleeve device outside the spun steel ring is 20 L / min. The initial water temperature is room temperature. The cooling intensity of the water-cooled iron sleeve is 12 C / s. The thickness of the copper block on the outer wall of the spun steel ring is 3 mm. The pouring temperature of the gray cast iron molten iron is 1400℃. After cooling, the water-cooled iron sleeve composite bimetallic brake drum is obtained.

[0051] Please see Figure 1 This is a schematic diagram of the water-cooled iron sleeve device used in this invention. The temperature of the circulating water in the water-cooled iron sleeve device is room temperature. As in Example 3, the flow rate of the circulating water in the pipe is 20 L / min, the number of windings is 16, and the diameter of the cooling pipe is 8 mm. After heating for 12 seconds in a high-frequency induction heating device, the water-cooled iron sleeve device is started. The water-cooled iron sleeve device is located outside the high-temperature casting metal cavity. During the high-temperature casting process, the metal cavity rotates continuously, and the heat dissipation in all directions is relatively uniform, ensuring the uniformity of the interface layer structure of the bimetallic composite brake drum and making the interface structure more refined.

[0052] Please see Figure 2 The schematic diagram of the high-frequency induction heating device and the heating head used in this invention illustrates that the high-frequency induction heating device heats a thin layer on the inner wall of the steel outer shell. The high-frequency induction heating device is turned on, and the parameters are set as follows: operating voltage of three-phase 380V, oscillation frequency of 30KHz, output power current of 2600A, and cooling water pressure of 0.18MPa. These process parameters ensure that only the thin layer area close to the heating rod on the inner wall of the spun steel ring experiences temperature increases, with a depth of approximately 2.0mm (Example 3). During the high-temperature casting process, the high-temperature molten iron transfers heat to the inner wall of the spun steel ring, melting part of the metal inner wall at the heated thin layer. Simultaneously, the water-cooled iron sleeve device provides a strong cooling effect on the interface layer, while the copper block closely attached to the outer wall of the spun steel ring provides better heat dissipation, ensuring that heat is quickly conducted away during heat dissipation, resulting in grain refinement. The synergistic effect of the high-frequency induction heating device and the water-cooled iron sleeve device ensures that no cold shut occurs during the high-temperature casting process and that the interface structure is strongly cooled, refining the grains and thus forming a good interfacial bond.

[0053] Please see Figure 3 The image shows the microstructure of the bimetallic brake drum in Example 1. Figure 3 As can be seen, the system comprises a gray cast iron layer, an interface layer, and a refined grain layer. The refined grain layer maintains the low-temperature deformation grains of the outer wall of the spun steel ring. The interface layer exhibits significantly refined grains, forming uniform and fine equiaxed grains. This grain refinement ensures that the brake drum undergoes more uniform deformation during service without causing excessive local stress concentration, thus preventing the generation and propagation of cracks at the interface. With the refinement of the interface layer grains, the average diameter of the interface grains increases by 37.78%, and the grain size of the interface layer increases from 6 to 7.5. The bimetallic composite brake drum prepared in this invention exhibits a 16% increase in bonding strength compared to ordinary brake drums, reaching 300 MPa. The lining hardness increases by 22%, and the thermal conductivity increases by 37%, demonstrating excellent performance. Specific comparisons are shown in Table 1 below.

[0054] Table 1 Performance Comparison of Bimetallic Brake Drums

[0055]

[0056]

[0057] It should be noted that the ordinary bimetallic composite brake drum here is prepared by the following process: first, a steel outer ring is prepared by a large plastic deformation spinning process, and then gray cast iron molten metal is injected into a sand mold with a preheated steel outer shell in the inner cavity, and cooled to obtain the product. The composition of the gray cast iron molten metal is the same as that in Example 1, and the pouring temperature is the same as that in Example 1.

[0058] In summary, the combination of the copper block embedded in the outer wall of the spun steel ring and the water-cooled iron sleeve device in this invention accelerates the heat dissipation of the high-temperature composite casting system. Under the cold conditions of strong gray cast iron, the grains at the interface are refined, forming uniform and fine equiaxed grains. This reduces the stress concentration effect and makes the deformation more uniform during the service of the bimetallic composite brake drum, thereby improving the bonding strength, thermal conductivity and life of the bimetallic composite brake drum. This lays a solid foundation for the practical application of bimetallic composite brake drums and opens up a new path for future applications.

[0059] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A texture-strengthened steel ring-gray cast iron bimetallic composite brake drum, characterized by, The microstructure of the bimetallic composite brake drum, from the inside out, includes: a gray cast iron layer, an interface layer, and a refined grain layer. The grains in the refined grain layer are deformed grains from the steel ring shell prepared by a spinning process; The grains in the interface layer are equiaxed crystals; The microstructure of the bimetallic composite brake drum is achieved through the following process: First, the steel ring shell is prepared by spinning process; then, gray cast iron molten iron is poured into the inner wall of the steel ring shell by centrifugal forming composite casting process. In the centrifugal forming composite casting process, the inner wall of the steel ring shell is first heated by a high frequency induction heating device. After the heating is completed, the water-cooled iron sleeve device located on the outer wall of the steel ring shell is activated to cool the outer wall of the steel ring shell. Then, the gray cast iron molten iron is poured into the inner wall of the steel ring shell. When the inner wall of the steel ring is heated by the high-frequency induction heating device, the heating time is 8-12 seconds to raise the temperature of the inner wall of the steel ring to 680-710℃. When the inner wall of the steel ring is heated by a high-frequency induction heating device, the heating depth of the inner wall of the steel ring is 1.3-2.0 mm. When heating the inner wall of the steel ring shell using a high-frequency induction heating device, the three heating rods of the high-frequency induction heating device are inserted into the steel ring shell. An 80kW high-frequency generator is used, with the working voltage set to three-phase 380V, the output power current to be 2600A, the oscillation frequency to be 30KHz, and the cooling water pressure to be 0.18MPa. The high-frequency induction heating device remains stationary while the steel ring shell rotates.

2. The texture-strengthened ring-gray cast iron bi-metallic brake drum according to claim 1, characterized in that, When the water-cooled iron jacket device cools the outer wall of the steel ring shell, the flow rate of the circulating water is 10-20 L / min, the initial water temperature is room temperature, and the cooling intensity of the water-cooled iron jacket is 8.5-12℃ / s.

3. The texture-reinforced steel rim-gray cast iron bimetallic composite brake drum according to claim 1, characterized in that, In the centrifugal casting process of gray cast iron molten iron, the steel ring shell is used as a centrifugal mold for rotation, and the centrifugal casting speed is 600-750 r / min.

4. The texture-strengthened band-gray cast iron bi-metallic brake drum according to claim 1, characterized in that, The pouring temperature for gray cast iron molten iron is 1400°C.

5. The texture-strengthened band-gray cast iron bi-metallic brake drum according to claim 1, characterized in that, The inner wall of the steel ring outer shell has a macroscopic corrugated undulating structure.

6. The texture-strengthened band-gray cast iron bi-metallic brake drum according to claim 1, characterized in that, The gray cast iron molten iron is composed of the following raw materials in weight percentages: C 3.20%-3.30%, Si 1.79%-1.91%, Mn 0.89%-1.04%, S 0.094%-0.125%, P 0.120%-0.170%, with the remainder being Fe and unavoidable trace impurities.

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