High-toughness alloy brake disc and its preparation method

Abstract

The present invention relates to the technical field of brake disc production, specifically to a high-toughness alloy brake disc and its preparation method. The high-toughness alloy brake disc comprises the following chemical components in mass percentage: niobium: 0.3 - 1.0%; antimony: 0.05 - 0.25%; molybdenum: 0.5 - 1.5%; copper: 0.5 - 1.5%; tin: 0.1 - 0.4%; titanium: 0.05 - 0.2%; boron: 0.002 - 0.008%; lanthanum: 0.05 - 0.1%; neodymium: 0.03 - 0.08%; cerium: 0.03 - 0.15%; and the balance is gray iron matrix. The present invention realizes high impact resistance, salt spray corrosion resistance and excellent thermal conductivity in the environment of -40°C to 600°C through niobium-antimony-molybdenum-boron composite microalloying, triple inoculation and step annealing processes, combined with PEO coating and laser micro-texture surface treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of brake disc production, and particularly to a high-toughness alloy brake disc and a preparation method thereof. Background Art

[0002] In fields such as automobiles and rail transit, as a key safety component, the performance of the brake disc directly affects braking reliability and service life. Although traditional gray iron brake discs have certain cost advantages, their comprehensive performance has significant defects under extreme working conditions: at a low temperature environment of -40°C, the impact energy ≤ 10J, and brittle fracture is likely to occur at the grain boundaries due to stress concentration. Especially in cold regions or winter working conditions, the safety risk increases significantly. When the temperature rises to 600°C, the tensile strength ≤ 150MPa. During braking, the material softens due to frictional heat generation, and the braking performance drops sharply, which may cause the phenomenon of thermal fade and threaten driving safety. The salt spray life ≤ 500h. In coastal areas or high-humidity, high-salt spray environments, electrochemical corrosion is likely to occur, resulting in surface rust and a decrease in structural strength, shortening the service life of the brake disc. Chinese Patent Application CN108441752A, with a publication date of August 24, 2018, discloses a ductile iron for automotive brake discs and a preparation method thereof; the mass percentages of each element component in the ductile iron are: C: 3.2 - 3.6%, Si: 2.8 - 3.2%, Cr: 0.4 - 0.8%, Mn: 0.2 - 0.6%, Al: 0.2 - 0.8%, Ni: 0.2 - 0.8%, Mg: 0.2 - 0.8%, Cu: 0.2 - 0.6%, Mo: 0.2 - 0.4%, Ta: 0.08 - 0.10%, Y: 0.04 - 0.06%, Sb: 0.02 - 0.03%, S ≤ 0.02%, P ≤ 0.04%, and the balance is Fe and inevitable impurities. Although it enhances the strength and toughness of the brake disc, it cannot adapt to working conditions with relatively harsh environments.

[0003] Moreover, although traditional high-nickel alloy brake discs can partially improve performance, the price of nickel element is high, resulting in a manufacturing cost increase of more than 30%. And nickel resources rely on imports, and the supply chain stability is poor. In addition, the traditional alloy composition design is single, lacking a multi-element synergistic strengthening mechanism; the inoculation treatment, heat treatment, and surface protection technologies in the preparation process are backward, making it difficult to optimize the graphite morphology, control the residual stress, and construct a surface corrosion-resistant and wear-resistant layer, which limits the improvement of the comprehensive performance of the brake disc. Summary of the Invention

[0004] In view of the deficiencies in the above prior art, the objective of the present invention is to provide a high-toughness alloy brake disc. Through niobium-antimony-molybdenum-boron composite microalloying, triple inoculation, and step annealing processes, combined with PEO coating and laser micro-texture surface treatment, high impact resistance (≥18 J), salt spray corrosion resistance (≥1500 h), and excellent thermal conductivity in the environment of -40°C to 600°C are achieved.

[0005] Another objective of the present invention is to provide a preparation method for the high-toughness alloy brake disc, which has remarkable effects and does not require large-scale adjustment of the original process, reducing the production cost.

[0006] The present invention is realized by adopting the following technical solutions:

[0007] The described high-toughness alloy brake disc includes chemical components with the following mass percentages: niobium: 0.3 - 1.0%; antimony: 0.05 - 0.25%; molybdenum: 0.5 - 1.5%; copper: 0.5 - 1.5%; tin: 0.1 - 0.4%; titanium: 0.05 - 0.2%; boron: 0.002 - 0.008%; lanthanum: 0.05 - 0.1%; neodymium: 0.03 - 0.08%; cerium: 0.03 - 0.15%; magnesium: 0.005 - 0.02%; barium: 0.01 - 0.05%; silicon: 0.1 - 0.2%; the rest is gray iron matrix; the mass fractions of each element in the gray iron matrix are: carbon: 3 - 3.4%; silicon: 1.6 - 2.2%; manganese: 0.5 - 0.8%; sulfur: 0.05 - 0.1%; phosphorus: 0.05 - 0.1%; the rest is iron and inevitable impurities. The raw materials of the gray iron matrix are one or more of pig iron, scrap steel, and return scrap.

[0008] The gray iron matrix provides basic carbon (C) to support graphitization, silicon (Si) promotes the formation of flake graphite, and manganese (Mn) stabilizes pearlite; niobium (Nb) combines with carbon to form nanoscale NbC (size ≤ 50 nm), pins the grain boundaries to inhibit crack propagation, and reduces the ductile-brittle transition temperature; antimony (Sb) inhibits the segregation of phosphorus (P) at the grain boundaries, reduces low-temperature brittleness, and stabilizes the pearlite lamellar spacing (≤ 0.2 μm); molybdenum (Mo) forms Mo2C hard phases, improves the high-temperature softening resistance, and delays the initiation of thermal cracks; copper (Cu) increases the matrix electrode potential, inhibits electrochemical corrosion, and improves the melt fluidity; tin (Sn) forms a SnO2 protective layer at high temperatures, inhibits oxidation and spalling, and refines the graphite distribution; titanium (Ti) combines with N and S to form TiN / TiS, reduces the porosity (≤ 0.5%), refines the primary austenite grains, trace boron (B) adsorbs on the grain boundaries, inhibits grain growth, and improves the hardenability; cerium (Ce) neutralizes impurities (O, S), purifies the melt, and promotes the nucleation of A-type graphite.

[0009] The preparation method of the described high-toughness alloy brake disc includes the following steps:

[0010] (1) Heat the gray iron matrix raw material to 1500 - 1550 °C, hold the temperature until it melts completely, then first add ferromolybdenum (Fe - Mo), electrolytic copper (Cu), ferroboron alloy and tin ingot (Sn), then cool the temperature to 1420 - 1450 °C, add ferroniobium (Fe - Nb) and ferrotitanium (Fe - Ti), then add lanthanum (La), neodymium (Nd) and cerium (Ce) mixed with magnesium, and press antimony into the bottom of the molten pool in the form of pure metal blocks;

[0011] (2) Composite inoculation treatment:

[0012] In - furnace pre - inoculation: Add ferrosilicon barium alloy (FeSiBa) at 1460 - 1500 °C;

[0013] Ladle inoculation: Add ferrosilicon niobium - cerium (FeSiNb - Ce) in the ladle before pouring;

[0014] In - stream instantaneous inoculation: Add nano - graphite powder to the pouring stream through a wire feeder;

[0015] (3) Casting process: Keep the pouring temperature at 1340 - 1400 °C, the outer mold of the casting mold is a metal mold, and the inner cavity is a resin sand core. Directional solidification is adopted: surface → core to obtain a high - toughness alloy brake disc matrix;

[0016] (4) Carry out step - by - step isothermal annealing treatment on the high - toughness alloy brake disc matrix:

[0017] Austenitization: Heat to 900 - 940 °C and hold the temperature for 1.5 - 3 hours;

[0018] Pearlite transformation: Cool in the furnace to 720 - 760 °C and hold the temperature for 2 - 4 hours;

[0019] Stress relief: Cool in the furnace to 500 - 600 °C, hold the temperature for 1 - 3 hours, and air - cool to room temperature to obtain the matrix of the annealed high - toughness alloy brake disc;

[0020] (5) Plasma electrolytic oxidation (PEO): Using sodium silicate and sodium molybdate as electrolytes, generate an Al2O3 - MoSi2 composite ceramic layer on the surface of the matrix of the annealed high - toughness alloy brake disc, and then process it by laser micro - texturing to obtain a high - toughness alloy brake disc. The high - toughness alloy brake disc includes an alloy brake disc and an outer treatment layer, and the Al2O3 - MoSi2 composite ceramic layer serves as the outer treatment layer.

[0021] In the step (1) described above, the niobium content in ferroniobium is 65%; the titanium content in ferrotitanium is 30%; the boron content in ferroboron alloy is 18 - 20%. Before adding, lanthanum, neodymium and cerium are all mixed with magnesium to form a spheroidizing agent, and then directly added to the furnace bottom.

[0022] In the said step (2), the barium content in the silicon-barium alloy is 4 - 6%, and the addition amount of the silicon-barium alloy is 0.2 - 0.5% of the total mass of the raw materials; the niobium content in the niobium-cerium ferrosilicon is 5 - 8%, the cerium content is 1 - 3%, and the addition amount of the niobium-cerium ferrosilicon is 0.3 - 0.6% of the total mass of the raw materials; the average particle size of the nano graphite powder is 20 - 100 nm, and the addition amount of the nano graphite powder is 0.03 - 0.1% of the total mass of the raw materials.

[0023] In the said step (3), the water cooling rate of the outer mold is 30 - 40 °C / s, the inner cavity is naturally cooled, and the hardness difference of directional solidification is ≤ 40 HB.

[0024] After the treatment in the said step (4) is completed, the residual stress is ≤ 50 MPa, and the pearlite lamellar spacing is 0.15 - 0.3 μm.

[0025] In the said step (5), the concentration of sodium silicate is 10 - 15 g / L, the concentration of sodium molybdate is 2 - 5 g / L, and the pH of the electrolyte is 10 - 12; the voltage of plasma electrolysis is 400 - 500 V, the pulse frequency is 50 - 200 Hz, and the treatment time is 20 - 40 minutes; the thickness of the Al2O3-MoSi2 composite ceramic layer is 15 - 35 μm, and the thermal conductivity is 35 - 45 W / (m·K).

[0026] In the said step (5), during laser micro-texturing, the wavelength of the fiber laser is 1064 nm, the power is 300 - 800 W, the scanning speed is 5 - 15 mm / s, the diameter of the micro-pits is 30 - 80 μm, the depth is 10 - 30 μm, and the spacing is 150 - 300 μm.

[0027] NbC and Mo2C synergistically improve the high-temperature strength (tensile strength at 600 °C ≥ 200 MPa); antimony (Sb) and cerium (Ce) combine to purify the grain boundaries and improve the impact toughness (impact energy at -40 °C ≥ 20 J); molybdenum (Mo) and Cu synergistically enhance the salt spray corrosion resistance (salt spray life ≥ 1500 h); Cu and Sn combine to form a Cu-Sn oxide film to block oxygen penetration; Sn and Ce synergistically improve the uniformity of graphite morphology (the proportion of type A ≥ 85%); Ti and B synergistically inhibit grain coarsening (grain size ≥ 7 grades); B and Nb synergistically refine the eutectic cell size (≤ 100 μm); Ce and Sb combine to inhibit phosphorus brittleness and improve the low-temperature toughness.

[0028] As rare earth elements, lanthanum and neodymium significantly improve the low-temperature toughness, high-temperature strength, and corrosion resistance of alloys by purifying the melt, refining the microstructure, optimizing the graphite morphology, and strengthening the grain boundaries. Lanthanum combines with impurity elements such as oxygen and sulfur to form high-melting-point compounds such as La2O3 and LaS, reducing the gas and inclusions in the melt and improving the alloy purity. And during solidification, it adsorbs at the grain boundaries, inhibits grain growth, and refines the primary austenite and eutectic clusters. It can also promote the uniform distribution of A-type graphite, reduce the aspect ratio of graphite, and thus improve the thermal conductivity and mechanical properties. Neodymium synergizes with cerium and lanthanum to further neutralize the oxygen and sulfur impurities in the melt and reduce the oxidation loss of alloying elements such as Nb and Mo. Neodymium combines with carbon to form nanoscale NdC particles, pinning dislocations and grain boundaries, enhancing the creep resistance of the matrix, especially inhibiting material softening at high temperatures (600°C). Neodymium optimizes the grain boundary chemical environment, reduces the segregation of phosphorus (P), and lowers the ductile-brittle transition temperature (impact energy at -40°C ≥ 20 J).

[0029] Smelting-inoculation synergy: Ferroniobium (Fe-Nb) and nano-graphite powder synergistically form a "NbC-graphite" dual-phase nucleation core, refining graphite to an aspect ratio ≤ 4:1; Cerium (Ce) neutralizes oxygen and sulfur in the melt, reducing the oxidation loss of Nb (recovery rate ≥ 90%).

[0030] Casting-annealing synergy: Rapid cooling in a metal mold inhibits coarse graphite, and the pearlite lamellar spacing is refined to 0.15 - 0.3 μm during annealing, improving the thermal conductivity; Directional solidification reduces thermal stress, and step annealing further eliminates residual stress, increasing the thermal fatigue life by 60 - 100%.

[0031] Surface treatment synergy: The PEO ceramic layer provides chemically inert protection, and laser micro-texturing improves the heat dissipation path, synergistically reducing the peak temperature of the friction surface by 80 - 120°C; Micro-pits store oxidation wear debris, reducing scratches on the disk surface by hard particles (wear rate reduced by 30 - 50%).

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) Through the dual-phase strengthening of NbC and Mo2C formed by niobium and molybdenum, the high-temperature tensile strength ≥ 230 MPa (traditional gray iron ≤ 150 MPa); Cerium and antimony synergistically purify the grain boundaries, making the impact energy at -40°C reach 27 J (traditional gray iron ≤ 10 J).

[0034] (2) Through the triple inoculation technology (nano-graphite powder + niobium-cerium ferrosilicon), graphite is refined to an aspect ratio ≤ 4:1, improving the thermal conductivity by 20%; The step annealing process makes the pearlite lamellar spacing ≤ 0.2 μm, and the hardness uniformity fluctuation ≤ 5 HB; The combination of laser micro-texturing and PEO coating makes the friction coefficient fluctuation ≤ 5%, and the salt spray life ≥ 2200 h.

[0035] (3) By purifying the melt, refining the microstructure, optimizing the graphite morphology, and strengthening the grain boundaries, this method significantly improves the low-temperature toughness, high-temperature strength, and corrosion resistance of the alloy. Moreover, it is compatible with traditional casting production lines, requiring no additional equipment investment, and is applicable to high-load braking scenarios (such as new energy heavy trucks and racing vehicles). Description of the Drawings

[0036] Figure 1 It is a stepwise isothermal annealing broken line graph of Embodiment 1 of the present invention. Specific Embodiments

[0037] To make the objectives and technical solutions of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] Test Methods:

[0039] Impact energy at -40°C: GB / T229 "Metallic materials - Charpy pendulum impact test method";

[0040] Tensile strength at 600°C: GB / T228 "Metallic materials - Tensile test";

[0041] Salt spray corrosion life: GB / T10125 "Artificial atmosphere corrosion test - Salt spray test";

[0042] Number of thermal fatigue cycles: The specimen is heated to 400°C and then quenched in water to room temperature. The surface crack propagation is recorded for each cycle until the main crack length ≥ 1 mm;

[0043] Thermal conductivity: GB / T22588 "Measurement of thermal diffusivity or thermal conductivity by the flash method";

[0044] Hardness: GB / T231.1 "Metallic materials - Brinell hardness test - Part 1: Test method";

[0045] Friction coefficient fluctuation: SAEJ2522 "Performance testing of friction materials for passenger vehicle braking systems".

[0046] Embodiment 1

[0047] A high-toughness alloy brake disc, including the following chemical components by mass percentage: niobium: 0.3%; antimony: 0.05%; molybdenum: 0.5%; copper: 0.5%; tin: 0.1%; titanium: 0.05%; boron: 0.002%; lanthanum: 0.05%; neodymium: 0.03%; cerium: 0.03%; magnesium: 0.005%; barium: 0.01%; silicon: 0.1%; the rest is gray iron matrix; the mass fractions of each element in the gray iron matrix are: carbon: 3%; silicon: 1.6%; manganese: 0.5%; sulfur: 0.05%; phosphorus: 0.05%; the rest is iron and unavoidable impurities.

[0048] Preparation method of a high-toughness alloy brake disc, comprising the following steps:

[0049] (1) Heat pig iron to 1500 °C, hold the temperature until it is completely melted, then first add ferromolybdenum, electrolytic copper, ferroboron alloy and tin ingot, then cool down to 1420 °C, add ferroniobium and ferrotitanium, and then add lanthanum, neodymium and cerium mixed with magnesium, and press antimony into the bottom of the molten pool in the form of a pure metal block;

[0050] (2) Composite inoculation treatment:

[0051] In-furnace pre-inoculation: Add ferrosilicon barium alloy at 1460 °C;

[0052] Ladle inoculation: Add niobium-cerium ferrosilicon in the ladle before pouring;

[0053] In-stream instantaneous inoculation: Add nano-graphite powder to the pouring stream through a wire feeder;

[0054] (3) Casting process: Keep the pouring temperature at 1340 °C, the outer mold of the casting mold is a metal mold, and the inner cavity is a resin sand core. Directional solidification is adopted: surface → core to obtain the matrix of the high-toughness alloy brake disc;

[0055] (4) Perform step-by-step isothermal annealing treatment on the matrix of the high-toughness alloy brake disc:

[0056] Austenitization: Heat to 900 °C and hold for 1.5 hours;

[0057] Pearlite transformation: Furnace cool to 720 °C and hold for 2 hours;

[0058] Stress relief: Furnace cool to 500 °C, hold for 1 hour, and air cool to room temperature to obtain the matrix of the high-toughness alloy brake disc after annealing;

[0059] (5) Plasma electrolytic oxidation: Use sodium silicate and sodium molybdate as the electrolyte to generate an Al2O3-MoSi2 composite ceramic layer on the surface of the matrix of the high-toughness alloy brake disc after annealing, and then treat it by laser micro-texturing to obtain the high-toughness alloy brake disc.

[0060] In step (1), the niobium content in ferroniobium is 65%; the titanium content in ferrotitanium is 30%; the boron content in ferroboron alloy is 18%. Before adding, lanthanum, neodymium and cerium are all mixed with magnesium as a spheroidizing agent and then directly added to the furnace bottom.

[0061] In step (2), the barium content in ferrosilicon barium alloy is 4%, and the addition amount of ferrosilicon barium alloy is 0.2% of the total mass of the raw materials; the niobium content in niobium-cerium ferrosilicon is 5%, the cerium content is 1%, and the addition amount of niobium-cerium ferrosilicon is 0.3% of the total mass of the raw materials; the average particle size of nano-graphite powder is 20 nm, and the addition amount of nano-graphite powder is 0.03% of the total mass of the raw materials.

[0062] In step (3), the water cooling rate of the outer mold is 30 °C / s, the inner cavity is naturally cooled, and the hardness difference of directional solidification is 40 HB.

[0063] After the treatment in step (4), the residual stress is 50 MPa, and the pearlite lamellar spacing is 0.15 μm.

[0064] In step (5), the concentration of sodium silicate is 10 g / L, the concentration of sodium molybdate is 2 g / L, and the pH of the electrolyte is 10; the voltage of plasma electrolysis is 400 V, the pulse frequency is 50 Hz, and the treatment time is 20 minutes; the thickness of the Al2O3-MoSi2 composite ceramic layer is 15 μm, and the thermal conductivity is 35 W / (m·K).

[0065] In step (5), during laser micro-texturing, the wavelength of the fiber laser is 1064 nm, the power is 300 W, the scanning speed is 5 mm / s, the diameter of the micro-pit is 30 μm, the depth is 10 μm, and the spacing is 150 μm. The graded isothermal annealing line graph in Example 1 is shown in Figure 1 。

[0066] Example 2

[0067] The high-toughness alloy brake disc includes the following chemical components by mass percentage: niobium: 0.8%; antimony: 0.15%; molybdenum: 1%; copper: 1%; tin: 0.2%; titanium: 0.1%; boron: 0.005%; lanthanum: 0.08%; neodymium: 0.05%; cerium: 0.1%; magnesium: 0.01%; barium: 0.03%; silicon: 0.1%; the rest is the gray iron matrix; the mass fractions of the elements in the gray iron matrix are: carbon: 3.2%; silicon: 2%; manganese: 0.7%; sulfur: 0.08%; phosphorus: 0.07%; the rest is iron and inevitable impurities.

[0068] The preparation method of the high-toughness alloy brake disc includes the following steps:

[0069] (1) Add pig iron and scrap steel into the furnace according to the mass ratio of 1:1, heat to 1530 °C, keep warm until the melt is clear, then first add ferromolybdenum, electrolytic copper, ferroboron alloy and tin ingots, then cool down to 1440 °C, add ferroniobium and ferrotitanium, and then add lanthanum, neodymium and cerium mixed with magnesium, and press antimony into the bottom of the molten pool in the form of pure metal blocks;

[0070] (2) Composite inoculation treatment:

[0071] In-furnace pre-inoculation: Add ferrosilicon barium alloy at 1480 °C;

[0072] Ladling inoculation: Add niobium-cerium ferrosilicon in the ladle before pouring;

[0073] In-stream instantaneous inoculation: Add nano-graphite powder to the pouring stream through a wire feeder;

[0074] (3) Casting process: The pouring temperature is maintained at 1380 °C. The outer mold of the casting is a metal mold, and the inner cavity is a resin sand core. Directional solidification is adopted: from the surface to the core to obtain the matrix of the high-toughness alloy brake disc.

[0075] (4) Perform stepped isothermal annealing treatment on the matrix of the high-toughness alloy brake disc:

[0076] Austenitization: Heat to 920 °C and hold for 2 hours.

[0077] Pearlite transformation: Cool in the furnace to 740 °C and hold for 3 hours.

[0078] Stress relief: Cool in the furnace to 550 °C, hold for 2 hours, and air-cool to room temperature to obtain the annealed matrix of the high-toughness alloy brake disc.

[0079] (5) Plasma electrolytic oxidation: Using sodium silicate and sodium molybdate as electrolytes, generate an Al2O3-MoSi2 composite ceramic layer on the surface of the annealed matrix of the high-toughness alloy brake disc, and then process it by laser micro-texturing to obtain the high-toughness alloy brake disc.

[0080] In step (1), the niobium content in ferroniobium is 65%; the titanium content in ferrotitanium is 30%; the boron content in ferroboron alloy is 19%. Before adding lanthanum, neodymium, and cerium, they are all mixed with magnesium as a spheroidizing agent and then directly added to the furnace bottom.

[0081] In step (2), the barium content in silicobarium alloy is 5%, and the addition amount of silicobarium alloy is 0.3% of the total mass of the raw materials; the niobium content in niobium-cerium ferrosilicon is 6%, the cerium content is 2%, and the addition amount of niobium-cerium ferrosilicon is 0.5% of the total mass of the raw materials; the average particle size of nano-graphite powder is 50 nm, and the addition amount of nano-graphite powder is 0.07% of the total mass of the raw materials.

[0082] In step (3), the water cooling rate of the outer mold is 35 °C / s, the inner cavity adopts natural cooling, and the hardness difference of directional solidification is 40 HB.

[0083] After the treatment in step (4), the residual stress is 50 MPa, and the pearlite lamellar spacing is 0.2 μm.

[0084] In step (5), the concentration of sodium silicate is 12 g / L, the concentration of sodium molybdate is 3 g / L, and the pH of the electrolyte is 11; the voltage of plasma electrolysis is 450 V, the pulse frequency is 80 Hz, and the treatment time is 30 minutes; the thickness of the Al2O3-MoSi2 composite ceramic layer is 25 μm, and the thermal conductivity is 40 W / (m·K).

[0085] In step (5), during laser micro-texturing, the wavelength of the fiber laser is 1064 nm, the power is 500 W, the scanning speed is 10 mm / s, the diameter of the micro-pits is 50 μm, the depth is 20 μm, and the spacing is 200 μm.

[0086] Example 3

[0087] The high-toughness alloy brake disc comprises the following chemical components by mass percentage: niobium: 1.0%; antimony: 0.25%; molybdenum: 1.5%; copper: 1.5%; tin: 0.4%; titanium: 0.2%; boron: 0.008%; lanthanum: 0.1%; neodymium: 0.08%; cerium: 0.15%; magnesium: 0.02%; barium: 0.05%; silicon: 0.2%; the balance is gray iron matrix; the mass fractions of the elements in the gray iron matrix are: carbon: 3.4%; silicon: 2.2%; manganese: 0.8%; sulfur: 0.1%; phosphorus: 0.1%; the balance is iron and inevitable impurities.

[0088] The preparation method of the high-toughness alloy brake disc comprises the following steps:

[0089] (1) Add pig iron, scrap steel and return materials into the furnace according to the mass ratio of 1:2:1, heat to 1550 °C, keep warm until melting is complete, then first add ferromolybdenum, electrolytic copper, ferro-boron alloy and tin ingots, then cool down to 1450 °C, add ferroniobium and ferrotitanium, and then add lanthanum, neodymium and cerium mixed with magnesium, and press antimony into the bottom of the molten pool in the form of pure metal blocks;

[0090] (2) Composite inoculation treatment:

[0091] Pre-inoculation in the furnace: Add ferrosilicon barium alloy at 1500 °C;

[0092] Inoculation in the ladle: Add niobium-cerium ferrosilicon in the ladle before pouring;

[0093] In-stream instantaneous inoculation: Add nano-graphite powder to the pouring stream through a wire feeder;

[0094] (3) Casting process: Keep the pouring temperature at 1400 °C, the outer mold of the casting mold is a metal mold, the inner cavity is a resin sand core, and directional solidification is adopted: surface → core to obtain the high-toughness alloy brake disc matrix;

[0095] (4) Perform step-by-step isothermal annealing treatment on the high-toughness alloy brake disc matrix:

[0096] Austenitization: Heat to 940 °C and keep warm for 3 hours;

[0097] Pearlite transformation: Cool in the furnace to 760 °C and keep warm for 4 hours;

[0098] Stress relief: Cool in the furnace to 600 °C, keep warm for 3 hours, and air-cool to room temperature to obtain the annealed matrix of the high-toughness alloy brake disc;

[0099] (5) Plasma electrolytic oxidation: Using sodium silicate and sodium molybdate as the electrolyte, an Al2O3-MoSi2 composite ceramic layer is formed on the surface of the matrix after annealing of the high-toughness alloy brake disc, and then it is processed by laser micro-texturing to obtain a high-toughness alloy brake disc.

[0100] In step (1), the niobium content in ferroniobium is 65%; the titanium content in ferrotitanium is 30%; the boron content in ferroboron alloy is 20%. Before adding lanthanum, neodymium, and cerium, they are all mixed with magnesium as a spheroidizing agent and then directly added to the bottom of the furnace.

[0101] In step (2), the barium content in silicobarium alloy is 6%, and the addition amount of silicobarium alloy is 0.5% of the total mass of the raw materials; the niobium content in niobium-cerium ferrosilicon is 8%, the cerium content is 3%, and the addition amount of niobium-cerium ferrosilicon is 0.6% of the total mass of the raw materials; the average particle size of nano-graphite powder is 100 nm, and the addition amount of nano-graphite powder is 0.1% of the total mass of the raw materials.

[0102] In step (3), the water cooling rate of the outer mold is 40 °C / s, the inner cavity uses natural cooling, and the hardness difference of directional solidification is 40 HB.

[0103] After the treatment in step (4), the residual stress is 50 MPa, and the pearlite lamellar spacing is 0.3 μm.

[0104] In step (5), the concentration of sodium silicate is 15 g / L, the concentration of sodium molybdate is 5 g / L, and the pH of the electrolyte is 12; the voltage of plasma electrolysis is 500 V, the pulse frequency is 200 Hz, and the treatment time is 40 minutes; the thickness of the Al2O3-MoSi2 composite ceramic layer is 35 μm, and the thermal conductivity is 45 W / (m·K).

[0105] In step (5), during laser micro-texturing, the wavelength of the fiber laser is 1064 nm, the power is 300 - 800 W, the scanning speed is 15 mm / s, the diameter of the micro-pits is 80 μm, the depth is 30 μm, and the spacing is 300 μm.

[0106] Comparative Example 1

[0107] Compared with Example 1, the difference is that niobium is not added, the boron content is 0.008%, and the niobium-cerium ferrosilicon inoculant is not used.

[0108] Comparative Example 2

[0109] Compared with Example 1, the difference is that cerium and tin are not added, and the PEO coating is removed.

[0110] Comparative Example 3

[0111] Compared with Example 1, the difference is that Mo is not added, the Cu content is 3%, and traditional single-stage annealing (900°C × 4h) is adopted.

[0112] Comparative Example 4

[0113] A commercial high-nickel gray iron brake disc (Brembo-HP2000) is adopted, with Ni content of 3.5%, C content of 3.2%, Si content of 2.0%, Mn content of 0.7%, and no surface treatment.

[0114] Comparative Example 5

[0115] Compared with Example 1, the difference is that lanthanum and neodymium are not added.

[0116] The test data of Examples 1-3 and Comparative Examples 1-5 are shown in Table 1.

[0117] Table 1: Test data of Examples 1-3 and Comparative Examples 1-5

[0118]

[0119] From the data in Table 1, it can be seen that in Comparative Example 1 (without Nb and without Ce-Nb inoculant), the impact energy decreased by 50% (12 J) due to the lack of NbC to pin the grain boundaries; the tensile strength dropped to 160 MPa due to the lack of Mo2C strengthening; the salt spray life was 800 h due to the sensitivity of grain boundary corrosion caused by the absence of Ce. In Comparative Example 2 (without Ce, Sn, and without PEO), the salt spray life was 1000 h because the grain boundary impurities were not neutralized and there was no PEO coating protection; the thermal conductivity was 45 W / (m·K) because the uneven distribution of graphite was caused by the absence of Sn. In Comparative Example 3 (without Mo, high Cu): the tensile strength at 600°C was 150 MPa due to the absence of Mo2C hard phase; the friction coefficient fluctuated by 20% due to the reduction of surface hardness and thermal conductivity. The results of Comparative Example 5 (without La, Nd) show that the absence of rare earth elements led to a 42% decrease in impact energy, a 59% reduction in salt spray life, and a 58% reduction in thermal fatigue life, further verifying the key role of La and Nd in grain boundary purification, phase transformation control, and crack resistance.

Claims

1. A high-toughness alloy brake disc, characterized in that, Comprising chemical components in the following mass percentages: niobium: 0.3 - 1.0%; antimony: 0.05 - 0.25%; molybdenum: 0.5 - 1.5%; copper: 0.5 - 1.5%; tin: 0.1 - 0.4%; titanium: 0.05 - 0.2%; boron: 0.002 - 0.008%; lanthanum: 0.05 - 0.1%; neodymium: 0.03 - 0.08%; cerium: 0.03 - 0.15%; magnesium: 0.005 - 0.02%; barium: 0.01 - 0.05%; silicon: 0.1 - 0.2%; the balance being gray iron matrix; the mass fractions of the elements in the gray iron matrix are: carbon: 3 - 3.4%; silicon: 1.6 - 2.2%; manganese: 0.5 - 0.8%; sulfur: 0.05 - 0.1%; phosphorus: 0.05 - 0.1%; the balance being iron and inevitable impurities; A method for preparing a high - toughness alloy brake disc, comprising the following steps: (1) Heating the gray iron matrix raw materials to 1500 - 1550 °C, holding until completely melted, then first adding ferromolybdenum, electrolytic copper, ferroboron alloy and tin ingots, then cooling to 1420 - 1450 °C, adding ferroniobium and ferrotitanium, and then adding lanthanum, neodymium and cerium mixed with magnesium, and pressing antimony into the bottom of the molten pool in the form of pure metal blocks; (2) Composite inoculation treatment: In - furnace pre - inoculation: Adding silicobarium alloy at 1460 - 1500 °C; Ladle inoculation: Adding niobium - cerium ferrosilicon in the ladle before pouring; In - stream instantaneous inoculation: Adding nano - graphite powder to the pouring stream through a wire feeder; (3) Casting process: Keeping the pouring temperature at 1340 - 1400 °C, the outer mold of the casting being a metal mold and the inner cavity being a resin sand core, adopting directional solidification: surface → core, to obtain the high - toughness alloy brake disc matrix; (4) Performing step - by - step isothermal annealing treatment on the high - toughness alloy brake disc matrix: Austenitization: Heating to 900 - 940 °C and holding for 1.5 - 3 hours; Pearlite transformation: Cooling in the furnace to 720 - 760 °C and holding for 2 - 4 hours; Stress relief: Cooling in the furnace to 500 - 600 °C, holding for 1 - 3 hours, and air - cooling to room temperature to obtain the annealed matrix of the high - toughness alloy brake disc; (5) Plasma electrolytic oxidation: Using sodium silicate and sodium molybdate as electrolytes to form an Al2O3 - MoSi2 composite ceramic layer on the surface of the annealed matrix of the high - toughness alloy brake disc, and then processing it by laser micro - texturing to obtain the high - toughness alloy brake disc; In the step (2), the barium content in the silicobarium alloy is 4 - 6%, and the addition amount of the silicobarium alloy is 0.2 - 0.5% of the total mass of the raw materials; the niobium content in the niobium - cerium ferrosilicon is 5 - 8%, the cerium content is 1 - 3%, and the addition amount of the niobium - cerium ferrosilicon is 0.3 - 0.6% of the total mass of the raw materials; the average particle size of the nano - graphite powder is 20 - 100 nm, and the addition amount of the nano - graphite powder is 0.03 - 0.1% of the total mass of the raw materials.

2. The high-toughness alloy brake disc according to claim 1, characterized in that In the step (1), the niobium content in the ferroniobium is 65%; the titanium content in the ferrotitanium is 30%; the boron content in the ferroboron alloy is 18 - 20%, and before adding, lanthanum, neodymium and cerium are all mixed with magnesium as a spheroidizing agent and then directly added to the furnace bottom.

3. The high-toughness alloy brake disc according to claim 1, wherein, In the step (3), the water cooling rate of the outer mold is 30 - 40 °C / s, the inner cavity is cooled naturally, and the hardness difference of directional solidification is ≤ 40 HB.

4. The high-toughness alloy brake disc according to claim 1, characterized in that, After the treatment in the step (4) is completed, the residual stress is ≤ 50 MPa, and the pearlite lamellar spacing is 0.15 - 0.3 μm.

5. The high-toughness alloy brake disc according to claim 1, characterized in that, In the step (5), the concentration of sodium silicate is 10 - 15 g / L, the concentration of sodium molybdate is 2 - 5 g / L, and the pH of the electrolyte is 10 - 12; the voltage of plasma electrolysis is 400 - 500 V, the pulse frequency is 50 - 200 Hz, and the treatment time is 20 - 40 minutes; the thickness of the Al2O3-MoSi2 composite ceramic layer is 15 - 35 μm, and the thermal conductivity is 35 - 45 W / (m·K).

6. The high-toughness alloy brake disc according to claim 1, wherein In the step (5), during laser micro-texturing, the wavelength of the fiber laser is 1064 nm, the power is 300 - 800 W, the scanning speed is 5 - 15 mm / s, the diameter of the micro-pits is 30 - 80 μm, the depth is 10 - 30 μm, and the spacing is 150 - 300 μm.

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