Worm-like graphite control preparation method for high-thermal-conductivity wear-resistant brake disc

Abstract

The invention provides a vermicular graphite control preparation method of a high-thermal-conductivity wear-resistant brake disc, and belongs to the technical field of brake disc preparation, and the vermicular graphite control preparation method comprises the following steps: (1) smelting; (2) adjusting components; (3) wire feeding vermicularizing treatment; (4) pouring and instantaneous inoculation; (5) heat treatment; according to the method disclosed by the invention, the dissolving activity and the diffusion efficiency of carbon atoms in molten iron are improved by accurately controlling the furnace charge ratio and pretreating the graphitized carburant, the hard spot defect caused by non-uniform carburant is avoided, and a good foundation is laid for subsequent graphite form control; rare earth magnesium alloy with specific components and dosage is adopted as a vermicularizing agent, and a synergistic process of reverse rotating ladle casting and wire feeding is combined, so that the vermicularizing agent is promoted to be dispersed and distributed in molten iron, component segregation is eliminated, the graphite nucleation process is optimized, the spheroidizing decline phenomenon is inhibited, the consistency and reproducibility of vermicularizing treatment are improved, and homogenization control over the graphite form is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of brake disc preparation, and in particular to a method for controlling the preparation of worm-shaped graphite for a high-heat-conductivity, wear-resistant brake disc. Background Art

[0002] The brake disc is a key component in a car's braking system. Its primary function is to generate braking force through friction, slowing or stopping the vehicle. The brake disc is a round metal disk mounted on the wheel. When the driver presses the brake pedal, the brake pads in the brake caliper clamp tightly against the disc, slowing the wheel down to a stop through friction.

[0003] Conventional brake disc manufacturing processes lack control over graphite morphology, making it prone to loss of control and increasing material brittleness. Furthermore, uneven graphite distribution leads to uneven thermal conductivity, which can easily cause localized thermal stress concentration under high-temperature braking conditions. This makes it difficult for the brake disc to meet high-performance requirements in terms of thermal fatigue resistance, wear resistance, and thermal stability. Optimizing the manufacturing process to achieve a high proportion of directional vermicular graphite is urgently needed to improve the overall performance of the brake disc.

[0004] Therefore, a method for controlling the preparation of worm-like graphite for high thermal conductivity and wear-resistant brake discs is proposed. Summary of the Invention

[0005] The present invention aims to solve the problems raised in the background technology and provides a method for controlling the preparation of worm-like graphite for a high-heat-conductivity and wear-resistant brake disc.

[0006] The specific technical solutions are as follows:

[0007] A method for controlling and preparing worm-like graphite for a high-thermal-conductivity, wear-resistant brake disc comprises the following steps:

[0008] (1) Melting: A medium frequency induction furnace is used to melt the molten iron. The charge ratio is as follows: 33% to 37% of recycled iron and 60% to 62% of scrap steel. When the temperature is raised to 1180 to 1240°C, a graphitized recarburizer with a carbon content of 82% to 88% is added.

[0009] (2) Composition adjustment: After the molten iron is smelted, the chemical composition is adjusted to the following mass percentages: C 3.2% to 3.9%, Si 2.3% to 2.9%, Cu ≤ 0.4%, Cr ≤ 0.01%, S ≤ 0.02%, P ≤ 0.05%, Mn ≤ 0.5%, and the balance is Fe;

[0010] (3) Wire feeding vermicularization treatment: The molten iron is transferred to a ladle with vermicularizer, inoculant and covering agent in the ladle pit, and 0.1% to 0.3% of the total mass of the molten iron is added by wire feeding process, with a wire feeding speed of 4 to 7 m / s and a ladle rotation speed of 14 m / min;

[0011] (4) Pouring and instantaneous inoculation: When the molten iron temperature reaches 1360-1380°C, pouring is carried out, and a barium silicon inoculant with a mass fraction of 0.1%-0.15% is added simultaneously for secondary instantaneous inoculation. After natural cooling, the casting is cleaned;

[0012] (5) Heat treatment: After cleaning the casting, heat it in a furnace to 790-820°C and keep it there for 90-120 min, cool it down to 700-720°C at a rate of 25°C / min and keep it there for 40-60 min, and then cool it to room temperature at a rate of 25°C / min to obtain a brake disc casting with a worm-like graphite content of ≥90%.

[0013] The above-mentioned method for controlling the preparation of vermicular graphite for high thermal conductivity and wear-resistant brake discs, wherein the vermicular graphite in the brake disc casting obtained in step (5) is uniformly distributed, the graphite morphology has an aspect ratio of 5 to 20, and the proportion of spherical graphite is ≤5%.

[0014] In the above-mentioned method for controlling the preparation of vermicular graphite for high thermal conductivity and wear-resistant brake discs, the vermicular agent in step (3) is a rare earth magnesium alloy, and the amount added is 0.8% to 1.2% of the mass of the molten iron.

[0015] The above-mentioned method for controlling the preparation of worm-like graphite for high thermal conductivity and wear-resistant brake discs, wherein the wire feeding process parameters in step (3) meet the following requirements: wire feeding speed 5-6 m / s, ladle rotation speed 14 m / min and the rotation direction is opposite to the wire feeding direction.

[0016] In the above-mentioned method for controlling the preparation of worm-like graphite for high thermal conductivity and wear-resistant brake discs, the first stage holding temperature in step (5) is 800-810° C., and the holding time is 100-110 minutes.

[0017] In the above-mentioned method for controlling the preparation of worm-like graphite for high thermal conductivity and wear-resistant brake discs, the second stage insulation temperature in step (5) is 710-715° C. and the insulation time is 45-55 minutes.

[0018] In the above-mentioned method for controlling the preparation of worm-like graphite for high thermal conductivity and wear-resistant brake discs, the barium silicon inoculant in step (4) has a particle size of ≤0.5 mm and is added instantaneously into the casting stream by pneumatic injection.

[0019] In the above-mentioned method for controlling the preparation of worm-like graphite for high thermal conductivity and wear-resistant brake discs, the graphitized recarburizer in step (1) is pre-calcined at 600-650° C. for 2-3 hours to remove volatile matter.

[0020] The present invention also provides a high thermal conductivity and wear-resistant brake disc, which is prepared by the above-mentioned worm-shaped graphite controlled preparation method of the high thermal conductivity and wear-resistant brake disc. The parallelism of the working surface is ≤0.04mm, the surface roughness Ra ≤1.6μm, the thermal conductivity coefficient is ≥45W / (m·K), and the tensile strength at room temperature is ≥350MPa.

[0021] The above-mentioned high thermal conductivity and wear-resistant brake disc, wherein the middle air duct of the high thermal conductivity and wear-resistant brake disc is a trumpet-shaped structure with a small inner diameter and a large outer diameter, and the cone angle θ of the inner wall of the air duct is 8°~15°. When the rotation speed of the high thermal conductivity and wear-resistant brake disc is ≥800rpm, a centrifugal negative pressure zone is formed in the air duct, which increases the air flow velocity at the rounded corner through hole of the working surface by 30%~50%.

[0022] The above-mentioned high thermal conductivity and wear-resistant brake disc, wherein the rounded through holes are evenly distributed along the circumference of the brake disc, the hole diameter d = 3 to 5 mm, and the distance L from the hole center to the inner wall of the air duct is 1.2d to 1.8d.

[0023] The present invention also provides a high-precision intelligent processing method for brake discs, wherein the casting prepared by the above-mentioned vermicular graphite controlled preparation method for high thermal conductivity and wear-resistant brake discs is used as a blank, comprising the following steps:

[0024] (a) Double-end surface grinding: Two independently controlled grinding machines are used to simultaneously process the end surfaces of a high-heat-conductivity, wear-resistant brake disc (10), with a grinding pressure of F1 = F2 and 5N≤F1≤15N, and a grinding wheel linear speed of V = 25-35m / s;

[0025] (b) Robotic finishing: A FANUC six-axis robot clamps the highly thermally conductive and wear-resistant brake disc and uses a visual positioning device to position it. The robot then completes the drilling, dynamic balancing, and boring processes in sequence, with a single-piece processing cycle of ≤75s.

[0026] In the above-mentioned high-precision intelligent processing method for brake discs, in step (a), the grinding wheels of the two grinders rotate in opposite directions, and the angle α between the grinding wheel axis and the normal direction of the end face of the high thermal conductivity and wear-resistant brake disc is 0.5°~1.5°.

[0027] In the above-mentioned high-precision brake disc intelligent processing method, the visual positioning device in step (b) adopts 3D line laser scanning, and the positioning accuracy is ≤0.02mm.

[0028] The present invention has the following beneficial effects:

[0029] 1. The method for controlling and preparing worm-shaped graphite for high thermal conductivity and wear-resistant brake discs provided by the present invention improves the solubility activity and diffusion efficiency of carbon atoms in molten iron by precisely controlling the charge ratio and pretreating the graphitizing carburizer, avoids hard point defects caused by uneven carburization, and lays a good foundation for subsequent graphite morphology control; adopts rare earth magnesium alloy with specific composition and dosage as a vermicularizing agent, combines the synergistic process of reverse rotating ladle and wire feeding, promotes the dispersion and distribution of vermicularizing agent in molten iron, eliminates component segregation, optimizes the graphite nucleation process, inhibits the spheroidization decay phenomenon, improves the consistency and reproducibility of vermicularizing treatment, and realizes the uniform control of graphite morphology; adopts pneumatic injection method to add fine-grained barium silicon inoculant for secondary instantaneous inoculation during the pouring process, realizes ultrafine inoculation of melt, and has It effectively eliminates the white cast tendency and refines the eutectic clusters, thereby improving the processing integrity of the brake disc working surface; the staged heat treatment process optimizes the matrix structure. In the first stage, the matrix fully completes the austenitization transformation, providing a structural basis for subsequent pearlite refinement and improving the strength and toughness matching of the material; in the second stage, the formation of a matrix structure dominated by fine lamellar pearlite is induced, which synergizes with the vermicular graphite to jointly improve the thermal conductivity and wear resistance of the brake disc; a high proportion of directional generation and uniform distribution of vermicular graphite is achieved, forming a continuous heat conduction network, which can effectively suppress local thermal stress concentration under high-temperature braking conditions, significantly improving the thermal conductivity uniformity and thermal fatigue resistance of the brake disc, while avoiding the problem of increased brittleness caused by the loss of control of graphite morphology in traditional processes, and enhancing the wear resistance and thermal stability of the brake disc.

[0030] 2. The high thermal conductivity and wear-resistant brake disc provided by the present invention and the prepared brake disc matrix have both high thermal conductivity and low thermal expansion characteristics, and at the same time have strong and wear-resistant properties, meeting the requirements of high-precision processing. It solves the problem of thermal decay caused by heat accumulation during braking from the essence of the material, and improves the stability of the brake disc under complex working conditions; the middle air duct adopts a trumpet structure with a small inner diameter and a large outer diameter, and uses rotating centrifugal force to generate directional negative pressure airflow, which significantly enhances the airflow exchange efficiency in the working surface area, breaks through the heat dissipation bottleneck of traditional straight-tube air ducts, and effectively improves the heat dissipation capacity of the brake disc; the rounded through holes are evenly distributed along the circumference of the brake disc, and the spatial coupling design with the air duct forms a local airflow acceleration effect, which enhances the powder discharge ability during braking while reducing the noise and vibration caused by the vortex in the air duct, thereby improving the reliability and comfort of the brake disc during operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A flow chart of a method for controlling and preparing worm-like graphite for a high-heat-conductivity, wear-resistant brake disc provided by an embodiment of the present invention;

[0032] Figure 2 A flowchart of the graphite morphology control factor GMF equation provided in an embodiment of the present invention;

[0033] Figure 3 This is a graph showing the relationship between the proportion of vermicular graphite and performance indicators in Example 1;

[0034] Figure 4 A schematic structural diagram of a high thermal conductivity and wear-resistant brake disc provided by an embodiment of the present invention;

[0035] Figure 5 Streamline diagram of air flow velocity in the air duct of a high thermal conductivity and wear-resistant brake disc provided by an embodiment of the present invention;

[0036] Figure 6 is a graph showing the relationship between thermal conductivity and tensile strength in Example 2;

[0037] Figure 7 This is a relationship diagram between processing efficiency and processing quality in Example 3.

[0038] In the attached figure:

[0039] 10. High thermal conductivity and wear-resistant brake disc; 20. Air duct; 30. Rounded through hole. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0041] Among them, the drawings are only used for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0042] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "inside", "outside" and the like indicate an orientation or position relationship based on the orientation or position relationship shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0043] In the description of the present invention, unless otherwise expressly specified or limited, when the term "connection" or the like appears to indicate a connection relationship between components, such term should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be internal communication between two components or an interaction between two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances.

[0044] Example 1: This example provides a method for controlling the preparation of worm-like graphite for a high thermal conductivity and wear-resistant brake disc, such as Figure 1-3 As shown, Figure 3 The relationship between the proportion of vermicular graphite and thermal conductivity and tensile strength is shown. As the proportion of vermicular graphite increases, the thermal conductivity and tensile strength also show corresponding change trends. The specific steps include:

[0045] (1) Melting: A medium frequency induction furnace is used to melt the molten iron. The charge ratio is as follows: 33% to 37% of recycled iron and 60% to 62% of scrap steel. When the temperature is raised to 1180 to 1240°C, a graphitized recarburizer with a carbon content of 82% to 88% is added.

[0046] (2) Composition adjustment: After the molten iron is smelted, the chemical composition is adjusted to the following mass percentages: C 3.2% to 3.9%, Si 2.3% to 2.9%, Cu ≤ 0.4%, Cr ≤ 0.01%, S ≤ 0.02%, P ≤ 0.05%, Mn ≤ 0.5%, and the balance is Fe;

[0047] (3) Wire feeding vermicularization treatment: The molten iron is transferred to a ladle with vermicularizer, inoculant and covering agent in the ladle pit, and 0.1% to 0.3% of the total mass of the molten iron is added by wire feeding process, with a wire feeding speed of 4 to 7 m / s and a ladle rotation speed of 14 m / min;

[0048] (4) Pouring and instantaneous inoculation: When the molten iron temperature reaches 1360-1380°C, pouring is carried out, and a barium silicon inoculant with a mass fraction of 0.1%-0.15% is added simultaneously for secondary instantaneous inoculation. After natural cooling, the casting is cleaned;

[0049] (5) Heat treatment: After cleaning the casting, heat it in a furnace to 790-820°C and keep it there for 90-120 min, cool it down to 700-720°C at a rate of 25°C / min and keep it there for 40-60 min, and then cool it to room temperature at a rate of 25°C / min to obtain a brake disc casting with a worm-like graphite content of ≥90%.

[0050] By precisely controlling the charge ratio, melting temperature, wire feeding process parameters and staged heat treatment, a high proportion of directional generation of vermicular graphite can be achieved, significantly improving the thermal conductivity uniformity and thermal fatigue resistance of the brake disc, while avoiding the increased brittleness caused by the loss of control of graphite morphology in traditional processes.

[0051] The brake disc casting obtained in step (5) has uniform distribution of vermicular graphite, a graphite aspect ratio of 5 to 20, and a proportion of spherical graphite of ≤5%. By limiting the morphological distribution of vermicular graphite and the upper limit of spherical graphite, a continuous heat conduction network can be formed in the matrix, effectively suppressing local thermal stress concentration under high-temperature braking conditions, and effectively enhancing wear resistance and thermal stability.

[0052] The creeping agent in step (3) is a rare earth magnesium alloy, and the amount added is 0.8% to 1.2% of the mass of the molten iron. By using a rare earth magnesium alloy with a specific composition and dosage as a creeping agent, the graphite nucleation process is optimized, the spheroidization decay phenomenon is suppressed, and the consistency and reproducibility of the creeping treatment are effectively improved.

[0053] The wire feeding process parameters in step (3) are as follows: a wire feeding speed of 5 to 6 m / s, a ladle rotation speed of 14 m / min, and a rotation direction opposite to the wire feeding direction. The synergistic effect of the reverse rotation of the ladle and the wire feeding generates strong shear turbulence, promotes the dispersion and distribution of the creeping agent, eliminates component segregation, and thus achieves uniform control of the graphite morphology.

[0054] In step (5), the first stage holding temperature is 800-810°C and the holding time is 100-110 minutes. By optimizing the first stage heat treatment parameters, the matrix is ​​fully austenitized, providing a structural basis for subsequent pearlite refinement and effectively improving the strength and toughness matching of the material.

[0055] In step (5), the second stage holding temperature is 710-715°C and the holding time is 45-55 minutes. This provides precise control of the second stage heat treatment temperature range and time, inducing the formation of a matrix structure dominated by fine-flaked pearlite, and synergistically with the vermicular graphite to improve thermal conductivity and wear resistance.

[0056] In step (4), the barium silicon inoculant has a particle size of ≤0.5 mm and is added instantaneously to the casting stream by pneumatic injection. The pneumatic injection of the fine-grained barium silicon inoculant achieves ultrafine inoculation of the melt at the moment of casting, effectively eliminating the tendency toward white cast iron, refining the eutectic, and improving the machining integrity of the working surface.

[0057] In step (1), the graphitized recarburizer is pre-calcined at 600-650°C for 2-3 hours to remove volatiles. Pre-treatment of the recarburizer removes volatile impurities, effectively improving the solubility and diffusion efficiency of carbon atoms in the molten iron, and avoiding hard point defects caused by uneven recarburization.

[0058] In summary, the controlled preparation method of worm-shaped graphite for high thermal conductivity and wear-resistant brake discs provided in this embodiment improves the solubility activity and diffusion efficiency of carbon atoms in molten iron by accurately controlling the charge ratio and pretreating the graphitizing carburizer, avoids hard point defects caused by uneven carburization, and lays a good foundation for subsequent graphite morphology control; uses rare earth magnesium alloy with specific composition and dosage as a vermicularizing agent, combines the synergistic process of reverse rotating ladle and wire feeding, promotes the dispersion and distribution of the vermicularizing agent in the molten iron, eliminates component segregation, optimizes the graphite nucleation process, inhibits the spheroidization decay phenomenon, improves the consistency and reproducibility of the vermicularizing treatment, and realizes the uniform control of the graphite morphology; uses pneumatic injection to add fine-grained barium silicon inoculant for secondary instantaneous inoculation during the pouring process, and realizes ultrafine inoculation of the melt. It effectively eliminates the white cast tendency and refines the eutectic clusters, improving the processing integrity of the brake disc working surface; the staged heat treatment process optimizes the matrix structure. In the first stage, the matrix fully completes the austenitization transformation, providing a structural basis for subsequent pearlite refinement and improving the strength and toughness matching of the material; the second stage induces the formation of a matrix structure dominated by fine lamellar pearlite, which synergizes with worm-like graphite to jointly improve the thermal conductivity and wear resistance of the brake disc; it achieves a high proportion of directional generation and uniform distribution of worm-like graphite, forming a continuous heat conduction network, which can effectively suppress local thermal stress concentration under high-temperature braking conditions, significantly improving the thermal conductivity uniformity and thermal fatigue resistance of the brake disc, while avoiding the problem of increased brittleness caused by the loss of control of graphite morphology in traditional processes, and enhancing the wear resistance and thermal stability of the brake disc.

[0059] By controlling the process parameters, the graphite morphology control factor GMF equation satisfies:

[0060]

[0061] Among them, 800≤GMF≤1200,

[0062] The parameters are defined as follows:

[0063] V r : ladle rotation speed (unit: m / min);

[0064] V w : Wire feeding speed (unit: m / s), when the ladle rotation direction is opposite to the wire feeding direction V w Take a negative value, |V w | is its absolute value;

[0065] D: Direction factor, D = 1.5 when in opposite directions, D = 1.0 when in the same direction;

[0066] C eq : Carbon equivalent, C eq=C+0.33×Si (C and Si are the mass percentages in the iron liquid after adjustment in step (2)). The carbon equivalent determines the graphitization potential. eq It is beneficial to the formation of vermicular graphite and enhances the graphite nucleation ability;

[0067] W m : The amount of creeping agent added (unit: %), that is, the percentage of the mass of the creeping agent to the mass of the molten iron. The amount of creeping agent directly affects the efficiency of graphite morphology conversion and regulates the intensity of the creeping reaction;

[0068] T c : Temperature when the graphitizing recarburizer is added in step (1) (unit: °C);

[0069] T c -1150, temperature threshold controls the recarburizer dissolution activity (>1150℃ to avoid hard spots), used to suppress smelting defects;

[0070] The temperature-time integral determines the degree of pearlite refinement, synergizes with graphite to improve strength and toughness, and is used to optimize the matrix structure;

[0071] T1, t1: holding temperature and holding time of the first stage in step (5) (unit: °C, min);

[0072] T2, t2: holding temperature and holding time of the second stage in step (5) (unit: °C, min).

[0073] Example:

[0074] Take typical parameter values:

[0075] V r =14m / min,V w =-5.5m / s (reverse wire feeding, |V w |=5.5,D=1.5);

[0076] C eq =3.6+0.33×2.6=4.458 (C=3.6%, Si=2.6%);

[0077] W m =1.0%;

[0078] T c =1210℃;

[0079] T1=805℃, t1=105min;

[0080] T2=712.5℃,t2=50min.

[0081] Calculation process:

[0082]

[0083] Result: GMF = 1030.2 (within the target range of 800-1200).

[0084] Technical effects:

[0085] Precise morphology control: When GMF is between 800 and 1200, the proportion of vermicular graphite is ≥90%, the aspect ratio is 5-20, and the proportion of pelletized graphite is ≤5%;

[0086] Synergistic performance improvement: The continuous heat conduction network suppresses thermal stress concentration and improves the strength and toughness matching of the matrix;

[0087] Process robustness: Dynamically balance multi-parameter fluctuations to ensure consistency in mass production.

[0088] like Figure 2 As shown, the GMF equation workflow is described:

[0089] 1. Parameter coupling: melting (T c ,C eq ), creep (V r ,V w ,D,W m ), the three-stage parameters of heat treatment (T1, t1, T2, t2) are integrated into the GMF equation;

[0090] 2. Dynamic feedback: Calculate GMF value in real time and adjust process parameters in reverse when it exceeds the limit (such as adjusting V w or T1);

[0091] 3. Morphology optimization: The GMF target range ensures the balance of graphite nucleation / growth dynamics and achieves the directional formation of worm-like graphite.

[0092] Embodiment 2: This embodiment provides a high thermal conductivity and wear-resistant brake disc, such as Figure 4-Figure 6 As shown, Figure 5 The air flow conditions in the air duct of a high-thermal-conductivity, wear-resistant brake disc were simulated to obtain the gas mass flow rate per unit time and calculate the heat convection coefficient of the air duct inner wall. Multi-factor experiments were conducted to compare the effects of air duct structural parameters on the air duct heat convection rate, and to determine an air duct structure with good heat dissipation performance and meeting mechanical requirements. Figure 6 The correlation between thermal conductivity and tensile strength is shown by the scatter plot and trend line. It can be seen that there is a certain positive correlation between thermal conductivity and tensile strength. The high thermal conductivity and wear-resistant brake disc is prepared by the worm-like graphite controlled preparation method of the high thermal conductivity and wear-resistant brake disc in Example 1, and its working surface parallelism is ≤0.04mm, surface roughness Ra≤1.6μm, thermal conductivity ≥45W / (m·K), and tensile strength at room temperature is ≥350MPa.

[0093] The brake disc prepared based on the method in Example 1 has a base that combines high thermal conductivity and low thermal expansion properties with strength and wear resistance, meets high-precision processing requirements, and solves the problem of brake thermal decay from the essence of the material.

[0094] The central air duct 20 of the highly thermally conductive, wear-resistant brake disc 10 features a bell-shaped structure with a small inner diameter and a large outer diameter. The inner wall of the air duct 20 has a taper angle θ of 8° to 15°. When the highly thermally conductive, wear-resistant brake disc 10 rotates at a speed of 800 rpm or higher, a centrifugal negative pressure zone forms within the air duct 20, increasing the airflow velocity at the rounded corner holes 30 on the working surface by 30% to 50%. This bell-shaped air duct structure utilizes centrifugal force to generate directional negative pressure airflow, significantly enhancing airflow exchange efficiency across the working surface and breaking through the heat dissipation bottleneck of traditional straight air ducts.

[0095] The rounded holes 30 are evenly distributed along the circumference of the brake disc, with a diameter of d ranging from 3 to 5 mm and a distance L between their centers and the inner wall of the air duct 20 of 1.2d to 1.8d. The spatial coupling between the rounded holes 30 and the air duct 20 creates a localized airflow acceleration effect, enhancing brake powder removal while reducing noise and vibration caused by eddy currents in the air duct.

[0096] In summary, the high thermal conductivity and wear-resistant brake disc provided in this embodiment adopts the brake disc matrix obtained by the preparation method of Example 1, which has both high thermal conductivity and low thermal expansion characteristics, and at the same time has strong and wear-resistant performance, meeting the requirements of high-precision processing, and solves the problem of thermal decay caused by heat accumulation during braking from the essence of the material, thereby improving the stability of the brake disc under complex working conditions; the middle air duct adopts a trumpet structure with a small inner diameter and a large outer diameter, and uses rotating centrifugal force to generate directional negative pressure airflow, which significantly enhances the airflow exchange efficiency in the working surface area, breaks through the heat dissipation bottleneck of traditional straight-cylinder air ducts, and effectively improves the heat dissipation capacity of the brake disc; the rounded through holes are evenly distributed along the circumference of the brake disc, and the spatial coupling design with the air duct forms a local airflow acceleration effect, which enhances the powder discharge ability during braking while reducing the noise and vibration caused by the vortex in the air duct, thereby improving the reliability and comfort of the brake disc during operation.

[0097] Example 3: Figure 7 As shown in FIG, the figure shows the relationship between processing efficiency (single-piece processing cycle) and processing quality (surface roughness) through a bar graph. It can be seen that with the improvement of processing efficiency, the surface roughness shows a downward trend, indicating that the processing quality has been improved. This embodiment provides a high-precision brake disc intelligent processing method, which adopts the worm-shaped graphite controlled preparation method of the high thermal conductivity and wear-resistant brake disc in Example 1 as the casting blank, comprising the following steps:

[0098] (a) Double-end surface grinding: Two independently controlled grinding machines are used to simultaneously process the end surfaces of the high thermal conductivity and wear-resistant brake disc 10, with a grinding pressure of F1 = F2 and 5N≤F1≤15N, and a grinding wheel linear speed of V = 25-35m / s;

[0099] (b) Robot finishing: A FANUC six-axis robot clamps the high-heat-conductivity, wear-resistant brake disc 10 and uses a visual positioning device to position it. The robot then completes the drilling, dynamic balancing, and boring processes in sequence, with a single-piece processing cycle of ≤75s.

[0100] The use of dual-grinding head synchronous processing technology completely solves the deformation accumulation problem caused by single-sided grinding through a two-way stress offset mechanism; the full-process integration of robots achieves a systematic improvement in processing accuracy.

[0101] In step (a), the grinding wheels of the two grinding machines rotate in opposite directions, and the angle α between the grinding wheel axis and the normal to the end surface of the high-thermal-conductivity, wear-resistant brake disc 10 is 0.5° to 1.5°. The counter-rotating grinding wheels combined with a micro-tilt design create a cross-shear force field at the grinding interface, suppressing grinding marks and improving surface texture uniformity, thereby avoiding microcracks caused by unidirectional stress.

[0102] The visual positioning device in step (b) uses 3D line laser scanning, with a positioning accuracy of ≤0.02mm. This 3D line laser scanning constructs a global spatial coordinate reference, providing a unified positioning reference for multi-process machining and effectively eliminating the reference drift error associated with traditional mechanical positioning.

[0103] In summary, the high-precision brake disc intelligent processing method provided in this embodiment adopts dual-grinding head synchronous processing technology, and through the bidirectional stress offset mechanism, it completely solves the deformation accumulation problem caused by single-sided grinding; the counter-rotating grinding wheel is combined with a micro-tilt design to form a cross-shear force field at the grinding interface, effectively suppressing grinding vibration marks and improving surface texture uniformity, avoiding microcracks caused by unidirectional stress, and significantly improving the processing accuracy and surface quality of the brake disc end face; the robot's full-process integrated processing is combined with a 3D line laser scanning visual positioning device to construct a global spatial coordinate benchmark, providing a unified positioning reference for multi-process processing, effectively eliminating the benchmark drift error of traditional mechanical positioning, and achieving a systematic improvement in processing accuracy; at the same time, through visual positioning and robot collaborative operation, the high-precision connection of drilling, dynamic balancing detection and boring and grinding processes is ensured, ensuring the consistency and stability of the overall processing accuracy of the brake disc.

[0104] The above are only preferred embodiments of the present invention and do not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling and preparing worm-like graphite for high thermal conductivity and wear-resistant brake discs, characterized in that: The following steps are involved: (1) Melting: A medium frequency induction furnace is used to melt the molten iron. The charge ratio is as follows: 33% to 37% of recycled iron and 60% to 62% of scrap steel. When the temperature is raised to 1180 to 1240°C, a graphitized recarburizer with a carbon content of 82% to 88% is added. (2) Composition adjustment: After the molten iron is smelted, the chemical composition is adjusted to the following mass percentages: C 3.2% to 3.9%, Si 2.3% to 2.9%, Cu ≤ 0.4%, Cr ≤ 0.01%, S ≤ 0.02%, P ≤ 0.05%, Mn ≤ 0.5%, and the balance is Fe; (3) Wire feeding vermicularization treatment: The molten iron is transferred to a ladle with vermicularizer, inoculant and covering agent in the ladle pit, and 0.1% to 0.3% of the total mass of the molten iron is added by wire feeding process, with a wire feeding speed of 4 to 7 m / s and a ladle rotation speed of 14 m / min; (4) Pouring and instantaneous inoculation: When the molten iron temperature reaches 1360-1380°C, pouring is carried out, and a barium silicon inoculant with a mass fraction of 0.1%-0.15% is added simultaneously for secondary instantaneous inoculation. After natural cooling, the casting is cleaned; (5) Heat treatment: After cleaning the casting, heat it in a furnace to 790-820°C and keep it there for 90-120 min, cool it down to 700-720°C at a rate of 25°C / min and keep it there for 40-60 min, and then cool it to room temperature at a rate of 25°C / min to obtain a brake disc casting with a worm-like graphite content of ≥90%.

2. The method for controlling and preparing worm-like graphite for a high thermal conductivity and wear-resistant brake disc according to claim 1, characterized in that: The brake disc casting obtained in step (5) has worm-like graphite uniformly distributed, a graphite aspect ratio of 5 to 20, and a spherical graphite proportion of ≤5%.

3. The method for controlling and preparing worm-like graphite for a high thermal conductivity and wear-resistant brake disc according to claim 1, characterized in that: The creeping agent in step (3) is a rare earth magnesium alloy, and the added amount is 0.8% to 1.2% of the mass of the molten iron.

4. The method for controlling and preparing worm-like graphite for a high thermal conductivity and wear-resistant brake disc according to claim 1, characterized in that: The wire feeding process parameters in step (3) meet the following requirements: wire feeding speed 5-6 m / s, ladle rotation speed 14 m / min and the rotation direction is opposite to the wire feeding direction.

5. The method for controlling and preparing worm-like graphite for a high thermal conductivity and wear-resistant brake disc according to claim 1, characterized in that: In step (5), the first stage insulation temperature is 800-810° C., and the insulation time is 100-110 min.

6. The method for controlling and preparing worm-like graphite for a high thermal conductivity and wear-resistant brake disc according to claim 1, characterized in that: The second stage holding temperature in step (5) is 710-715° C., and the holding time is 45-55 min.

7. The method for controlling and preparing worm-like graphite for a high thermal conductivity and wear-resistant brake disc according to claim 1, characterized in that: The barium silicon inoculant in step (4) has a particle size of ≤0.5 mm and is added instantaneously into the casting stream by pneumatic injection.

8. The method for controlling and preparing worm-like graphite for a high thermal conductivity and wear-resistant brake disc according to claim 1, characterized in that: The graphitized recarburizer in step (1) is pre-calcined at 600-650° C. for 2-3 hours to remove volatile matter.

9. A high thermal conductivity and wear-resistant brake disc, characterized in that: The invention is prepared by the worm-like graphite controlled preparation method of any one of claims 1 to 8 for a high thermal conductivity and wear-resistant brake disc, and has a working surface parallelism of ≤0.04mm, a surface roughness Ra ≤1.6μm, a thermal conductivity coefficient ≥45W / (m·K), and a tensile strength at room temperature ≥350MPa.

10. The high thermal conductivity and wear-resistant brake disc according to claim 9, characterized in that: The middle air duct (20) of the high heat-conducting and wear-resistant brake disc (10) is a bell-mouth structure with a small inner diameter and a large outer diameter. The inner wall cone angle θ of the air duct (20) is 8° to 15°. When the rotation speed of the high heat-conducting and wear-resistant brake disc (10) is ≥800rpm, a centrifugal negative pressure zone is formed in the air duct (20), which increases the air flow velocity at the rounded corner through hole (30) on the working surface by 30% to 50%.

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