High-toughness alloy brake disc and preparation method thereof

Abstract

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

Description

Technical Field

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

[0002] In the fields of automobiles, rail transit, etc., brake discs are key safety components, and their performance 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: in a low temperature environment of -40℃, the impact energy is ≤10J, and brittle fractures are prone to occur at the grain boundaries due to stress concentration, especially in cold areas or winter conditions, and the safety risks are significantly increased. When the temperature rises to 600℃, the tensile strength is ≤150MPa. The frictional heat generated during braking causes the material to soften, and the braking performance drops sharply, which may cause thermal decay and threaten driving safety. The salt spray life is ≤500h. In coastal areas or high humidity and high salt spray environments, electrochemical corrosion is prone to occur, resulting in surface rust, reduced structural strength, and shortening the service life of the brake disc. Chinese patent application CN108441752A, published on August 24, 2018, discloses a ductile iron for automobile brake disc and its preparation method; the mass percentage of each element in the ductile iron is: 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%, the balance is Fe and inevitable impurities. Although it enhances the strength and toughness of the brake disc, it cannot adapt to the working conditions with relatively harsh environment.

[0003] Moreover, although traditional high-nickel alloy brake discs can partially improve performance, the high price of nickel has increased manufacturing costs by more than 30%, and nickel resources rely on imports, with poor supply chain stability. In addition, traditional alloy composition design is single and lacks a multi-element synergistic strengthening mechanism; the inoculation treatment, heat treatment and surface protection technology in the preparation process are backward, making it difficult to achieve graphite morphology optimization, residual stress control and surface corrosion and wear-resistant layer construction, limiting the improvement of the overall performance of the brake disc. Summary of the invention

[0004] In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a high-toughness alloy brake disc, which achieves high impact resistance (≥18J), salt spray corrosion resistance (≥1500h) and excellent thermal conductivity in an environment of -40°C to 600°C through niobium-antimony-molybdenum-boron composite microalloying, triple inoculation and graded annealing process, combined with PEO coating and laser microtexturing surface treatment.

[0005] Another object of the present invention is to provide a method for preparing a high-toughness alloy brake disc, which has significant effects and does not require large-scale adjustments to the original process, thereby reducing production costs.

[0006] The present invention is achieved by adopting the following technical solutions: The high-toughness alloy brake disc includes 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%; 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 unavoidable impurities. The gray iron matrix raw material is one or more of pig iron, scrap steel and recycled materials.

[0007] 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 nano-scale NbC (size ≤50nm), pinning the grain boundary to inhibit crack propagation and reduce the ductile-brittle transition temperature; antimony (Sb) inhibits phosphorus (P) from segregating at the grain boundary, reducing low-temperature brittleness; stabilizes the pearlite interlamellar spacing (≤0.2μm); molybdenum (Mo) forms Mo 2 C hard phase, improves high temperature softening resistance; delays thermal crack initiation; copper (Cu) increases the matrix electrode potential, inhibits electrochemical corrosion; improves melt fluidity; tin (Sn) forms SnO at high temperature 2 Protective layer, inhibiting oxidation and spalling; refining graphite distribution; titanium (Ti) combines with N and S to form TiN / TiS, reducing porosity (≤0.5%); refining primary austenite grains, trace boron (B) adsorbed on grain boundaries, inhibiting grain growth; improving hardenability; cerium (Ce) neutralizes impurities (O, S) and purifies the melt; promoting nucleation of A-type graphite.

[0008] The method for preparing the high-toughness alloy brake disc comprises the following steps: (1) The gray iron matrix raw material is heated to 1500-1550°C and kept warm until it is completely melted. Then, ferromolybdenum (Fe-Mo), electrolytic copper (Cu), iron-boron alloy and tin ingot (Sn) are added first, and then the temperature is lowered to 1420-1450°C, and ferroniobium (Fe-Nb) and ferrotitanium (Fe-Ti) are added. Then, lanthanum (La), neodymium (Nd) and cerium (Ce) mixed with magnesium are added, and antimony is pressed into the bottom of the molten pool in the form of pure metal blocks; (2) Composite inoculation treatment: Pre-incubation in the furnace: adding silicon-barium alloy (FeSiBa) at 1460-1500℃; Ladle inoculation: Add ferrosilicon containing niobium and cerium (FeSiNb-Ce) into the ladle before pouring; Instant inoculation with the flow: adding nano graphite powder to the casting flow through the wire feeder; (3) Casting process: The pouring temperature is maintained at 1340-1400℃, the outer mold of the casting is a metal mold, the inner cavity is a resin sand core, and directional solidification is adopted: surface → core, to obtain a high-toughness alloy brake disc matrix; (4) Graded isothermal annealing treatment of high-toughness alloy brake disc substrate: Austenitizing: heat to 900-940℃, keep warm for 1.5-3 hours; Pearlite transformation: furnace cooling to 720-760℃, keeping warm for 2-4 hours; Stress relief: furnace cooling to 500-600℃, keeping warm for 1-3 hours, air cooling to room temperature, and obtaining the annealed matrix of high-toughness alloy brake disc; (5) Plasma electrolytic oxidation (PEO): Sodium silicate and sodium molybdate are used as electrolyte to generate Al on the surface of the substrate after annealing of the high-toughness alloy brake disc. 2 O 3 -MoSi 2 The composite ceramic layer is then processed by laser microtexturing to obtain a high-toughness alloy brake disc. The high-toughness alloy brake disc includes an alloy brake disc and an outer treatment layer, Al 2 O 3 -MoSi 2 The composite ceramic layer is used as the outer treatment layer.

[0009] 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 iron-boron alloy is 18-20%, and the lanthanum, neodymium and cerium are mixed with magnesium as a spheroidizing agent before being added, and then directly added to the furnace bottom.

[0010] In the step (2), the barium content in the silicon-barium alloy is 4-6%, and the amount of the silicon-barium alloy added is 0.2-0.5% of the total mass of the raw materials; the niobium content in the niobium-cerium ferrosilicon is 5-8%, and the cerium content is 1-3%, and the amount of the niobium-cerium ferrosilicon added is 0.3-0.6% of the total mass of the raw materials; the average particle size of the nano-graphite powder is 20-100nm, and the amount of the nano-graphite powder added is 0.03-0.1% of the total mass of the raw materials.

[0011] 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 the directional solidification is ≤40HB.

[0012] After the step (4) is completed, the residual stress is ≤50MPa and the pearlite lamella spacing is 0.15-0.3μm.

[0013] In the step (5), the concentration of sodium silicate is 10-15 g / L, the concentration of sodium molybdate is 2-5 g / L, 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; Al 2 O 3 -MoSi 2 The thickness of the composite ceramic layer is 15-35 μm, and the thermal conductivity is 35-45 W / (m·K).

[0014] In the step (5), during laser microtexturing, the wavelength of the fiber laser is 1064 nm, the power is 300-800 W, the scanning speed is 5-15 mm / s, the micropit diameter is 30-80 μm, the depth is 10-30 μm, and the spacing is 150-300 μm.

[0015] NbC and Mo 2 C synergistically improves high-temperature strength (tensile strength at 600℃ ≥ 200MPa); antimony (Sb) and cerium (Ce) combine to purify grain boundaries and improve impact toughness (impact energy ≥ 20J at -40℃); molybdenum (Mo) and Cu synergistically enhance salt spray corrosion resistance (salt spray life ≥ 1500h); 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 (type A accounts for ≥ 85%); Ti and B synergistically inhibit grain coarsening (grain size ≥ level 7); B and Nb synergistically refine the size of eutectic clusters (≤ 100μm); Ce and Sb combine to inhibit phosphorus embrittlement and improve low-temperature toughness.

[0016] Lanthanum and neodymium, as rare earth elements, significantly improve the low-temperature toughness, high-temperature strength and corrosion resistance of the alloy 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 generate La with a high melting point. 2 O3 , LaS and other compounds, reduce the gas and inclusions in the melt, and improve the purity of the alloy. And it is adsorbed on the grain boundary during the solidification process, inhibiting grain growth and refining the primary austenite and eutectic groups. It can also promote the uniform distribution of type A graphite and reduce the aspect ratio of graphite, thereby improving thermal conductivity and mechanical properties. Neodymium cooperates with cerium and lanthanum to further neutralize 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 nano-scale NdC particles, pinning dislocations and grain boundaries, enhancing the creep resistance of the matrix, and especially inhibiting the softening of the material at high temperatures (600°C). Neodymium reduces the segregation of phosphorus (P) and lowers the ductile-brittle transition temperature (-40°C impact energy ≥20J) by optimizing the chemical environment of the grain boundaries.

[0017] Smelting-incubation synergy: Niobium iron (Fe-Nb) and nano-graphite powder work together to form a "NbC-graphite" dual-phase nucleation core, refining the graphite to an aspect ratio of ≤4:1; cerium (Ce) neutralizes oxygen and sulfur in the melt and reduces Nb oxidation losses (yield ≥90%).

[0018] Casting-annealing synergy: Rapid cooling of the metal mold suppresses coarse graphite, and the pearlite interlamellar spacing is refined to 0.15-0.3μm during annealing, improving thermal conductivity; directional solidification reduces thermal stress, and graded annealing further eliminates residual stress, increasing thermal fatigue life by 60-100%.

[0019] Surface treatment synergy: PEO ceramic layer provides chemical inertness protection, laser micro-texturing improves the heat dissipation path, and synergistically reduces the peak temperature of the friction surface by 80-120°C; micro-pits store oxidized debris and reduce scratches on the disk surface by hard particles (wear rate is reduced by 30-50%).

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) Formation of NbC and Mo by niobium and molybdenum 2 C dual-phase strengthening makes the high-temperature tensile strength ≥230MPa (traditional gray iron ≤150MPa); cerium and antimony synergistically purify the grain boundaries, making the -40℃ impact energy reach 27J (traditional gray iron ≤10J).

[0021] (2) Through the triple inoculation technology (nanographite powder + niobium-cerium ferrosilicon), graphite is refined to an aspect ratio of ≤4:1, improving thermal conductivity by 20%; the graded annealing process makes the pearlite interlamellar spacing ≤0.2μm and the hardness uniformity fluctuation ≤5HB; laser microtexturing combined with PEO coating makes the friction coefficient fluctuation ≤5% and the salt spray life ≥2200h.

[0022] (3) This method significantly improves the low-temperature toughness, high-temperature strength and corrosion resistance of the alloy by purifying the melt, refining the microstructure, optimizing the graphite morphology and strengthening the grain boundaries. It is also compatible with traditional casting production lines and does not require additional equipment investment, making it suitable for high-load braking scenarios (such as new energy heavy trucks and racing vehicles). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a line graph of graded isothermal annealing of Example 1 of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose and technical solution of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0025] Test method: -40℃ impact energy: GB / T229 "Charpy pendulum impact test method for metallic materials"; 600℃ tensile strength: GB / T228 "Tensile test of metal materials"; Salt spray corrosion life: GB / T10125 "Artificial atmosphere corrosion test salt spray test"; Thermal fatigue cycle number: heat the sample to 400℃ and then quench it to room temperature. Record the surface crack extension in each cycle until the main crack length is ≥1mm; Thermal conductivity: GB / T22588 "Flash method for measuring thermal diffusivity or thermal conductivity"; Hardness: GB / T231.1 "Metallic Brinell hardness test Part 1: Test method"; Friction coefficient fluctuation: SAEJ2522 "Passenger car brake system friction material performance test".

[0026] Example 1 A high-toughness alloy brake disc, comprising the following chemical compositions in 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 a 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.

[0027] The method for preparing a high-toughness alloy brake disc comprises the following steps: (1) Pig iron is heated to 1500°C and kept warm until it is completely melted. Then, ferromolybdenum, electrolytic copper, iron-boron alloy and tin ingot are added. Then, the temperature is lowered to 1420°C, ferroniobium and ferrotitanium are added, and then lanthanum, neodymium and cerium mixed with magnesium are added. Antimony is pressed into the bottom of the molten pool in the form of pure metal blocks. (2) Composite inoculation treatment: Pre-incubation in the furnace: adding silicon-barium alloy at 1460°C; Ladle inoculation: Add ferrosilicon containing niobium-cerium into the ladle before pouring; Instant inoculation with the flow: adding nano graphite powder to the casting flow through the wire feeder; (3) Casting process: The pouring temperature is maintained at 1340°C, the outer mold of the casting is a metal mold, the inner cavity is a resin sand core, and directional solidification is adopted: surface → core, to obtain a high-toughness alloy brake disc matrix; (4) Graded isothermal annealing treatment of high-toughness alloy brake disc substrate: Austenitizing: heat to 900℃ and keep warm for 1.5 hours; Pearlite transformation: furnace cooling to 720℃, keeping warm for 2 hours; Stress relief: furnace cooling to 500°C, keeping warm for 1 hour, air cooling to room temperature, and obtaining the annealed matrix of the high-toughness alloy brake disc; (5) Plasma electrolytic oxidation: Sodium silicate and sodium molybdate are used as electrolytes to generate Al on the surface of the substrate after annealing of the high-toughness alloy brake disc. 2 O 3 -MoSi 2 The composite ceramic layer is then processed by laser microtexturing to obtain a high-toughness alloy brake disc.

[0028] In step (1), the niobium content in ferroniobium is 65%; the titanium content in ferrotitanium is 30%; the boron content in the iron-boron alloy is 18%. Before being added, lanthanum, neodymium and cerium are mixed with magnesium as a spheroidizing agent and then directly added to the furnace bottom.

[0029] In step (2), the barium content in the silicon-barium alloy is 4%, and the amount of silicon-barium alloy added is 0.2% of the total mass of the raw materials; the niobium content in the niobium-cerium ferrosilicon is 5%, and the cerium content is 1%, and the amount of niobium-cerium ferrosilicon added is 0.3% of the total mass of the raw materials; the average particle size of the nano-graphite powder is 20nm, and the amount of the nano-graphite powder added is 0.03% of the total mass of the raw materials.

[0030] In step (3), the water cooling rate of the outer mold is 30°C / s, the inner cavity is cooled naturally, and the hardness difference of directional solidification is 40HB.

[0031] After step (4) is completed, the residual stress is 50 MPa and the pearlite lamellar spacing is 0.15 μm.

[0032] In step (5), the concentration of sodium silicate is 10 g / L, the concentration of sodium molybdate is 2 g / L, 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; Al 2 O 3 -MoSi 2 The thickness of the composite ceramic layer is 15 μm and the thermal conductivity is 35 W / (m·K).

[0033] In step (5), during laser microtexturing, the wavelength of the fiber laser is 1064 nm, the power is 300 W, the scanning speed is 5 mm / s, the micropit diameter is 30 μm, the depth is 10 μm, and the spacing is 150 μm. Figure 1 .

[0034] Example 2 A high-toughness alloy brake disc, including the following chemical components in 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 gray iron matrix; the mass fractions of each element 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.

[0035] The method for preparing a high-toughness alloy brake disc comprises the following steps: (1) Pig iron and scrap steel are added into the furnace in a mass ratio of 1:1, heated to 1530°C, kept warm until melted, then ferromolybdenum, electrolytic copper, iron-boron alloy and tin ingot are added first, then cooled to 1440°C, ferroniobium and ferrotitanium are added, and then lanthanum, neodymium and cerium mixed with magnesium are added, and antimony is pressed into the bottom of the molten pool in the form of pure metal blocks; (2) Composite inoculation treatment: Pre-incubation in the furnace: adding silicon-barium alloy at 1480°C; Ladle inoculation: Add ferrosilicon containing niobium-cerium into the ladle before pouring; Instant inoculation with the flow: adding nano graphite powder to the casting flow through the wire feeder; (3) Casting process: The pouring temperature is maintained at 1380°C, the outer mold of the casting is a metal mold, the inner cavity is a resin sand core, and directional solidification is adopted: surface → core, to obtain a high-toughness alloy brake disc matrix; (4) Graded isothermal annealing treatment of high-toughness alloy brake disc substrate: Austenitizing: heat to 920℃, keep warm for 2 hours; Pearlite transformation: furnace cooling to 740℃, keeping warm for 3 hours; Stress relief: furnace cooling to 550°C, keeping warm for 2 hours, air cooling to room temperature, and obtaining the annealed matrix of the high-toughness alloy brake disc; (5) Plasma electrolytic oxidation: Sodium silicate and sodium molybdate are used as electrolytes to generate Al on the surface of the substrate after annealing of the high-toughness alloy brake disc. 2 O 3 -MoSi 2 The composite ceramic layer is then processed by laser microtexturing to obtain a high-toughness alloy brake disc.

[0036] In step (1), the niobium content in ferroniobium is 65%; the titanium content in ferrotitanium is 30%; the boron content in the iron-boron alloy is 19%. Before being added, lanthanum, neodymium and cerium are mixed with magnesium as a spheroidizing agent and then directly added to the furnace bottom.

[0037] In step (2), the barium content in the silicon-barium alloy is 5%, and the amount of silicon-barium alloy added is 0.3% of the total mass of the raw materials; the niobium content in the niobium-cerium ferrosilicon is 6%, and the cerium content is 2%, and the amount of niobium-cerium ferrosilicon added is 0.5% of the total mass of the raw materials; the average particle size of the nano-graphite powder is 50nm, and the amount of the nano-graphite powder added is 0.07% of the total mass of the raw materials.

[0038] In step (3), the water cooling rate of the outer mold is 35°C / s, the inner cavity is cooled naturally, and the hardness difference of directional solidification is 40HB.

[0039] After step (4) is completed, the residual stress is 50 MPa and the pearlite lamellar spacing is 0.2 μm.

[0040] In step (5), the concentration of sodium silicate is 12 g / L, the concentration of sodium molybdate is 3 g / L, 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; Al 2 O 3 -MoSi 2 The thickness of the composite ceramic layer is 25 μm and the thermal conductivity is 40 W / (m·K).

[0041] In step (5), during laser microtexturing, the wavelength of the fiber laser is 1064 nm, the power is 500 W, the scanning speed is 10 mm / s, the micropit diameter is 50 μm, the depth is 20 μm, and the spacing is 200 μm.

[0042] Example 3 A high-toughness alloy brake disc, comprising the following chemical compositions in 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 rest is a gray iron matrix; the mass fractions of each element in the gray iron matrix are: carbon: 3.4%; silicon: 2.2%; manganese: 0.8%; sulfur: 0.1%; phosphorus: 0.1%; the rest is iron and unavoidable impurities.

[0043] The method for preparing a high-toughness alloy brake disc comprises the following steps: (1) Pig iron, scrap steel and recycled materials are added into the furnace in a mass ratio of 1:2:1, heated to 1550°C, kept warm until melted, then ferromolybdenum, electrolytic copper, iron-boron alloy and tin ingot are added first, then cooled to 1450°C, ferroniobium and ferrotitanium are added, and then lanthanum, neodymium and cerium mixed with magnesium are added, and antimony is pressed into the bottom of the molten pool in the form of pure metal blocks; (2) Composite inoculation treatment: Pre-incubation in the furnace: adding silicon-barium alloy at 1500°C; Ladle inoculation: Add ferrosilicon containing niobium-cerium into the ladle before pouring; Instant inoculation with the flow: adding nano graphite powder to the casting flow through the wire feeder; (3) Casting process: The pouring temperature is maintained at 1400°C, the outer mold of the casting is a metal mold, the inner cavity is a resin sand core, and directional solidification is used: surface → core, to obtain a high-toughness alloy brake disc matrix; (4) Graded isothermal annealing treatment of high-toughness alloy brake disc substrate: Austenitizing: heat to 940℃, keep warm for 3 hours; Pearlite transformation: furnace cooling to 760℃, keeping warm for 4 hours; Stress relief: furnace cooling to 600℃, keeping temperature for 3 hours, air cooling to room temperature, and obtaining the annealed matrix of high-toughness alloy brake disc; (5) Plasma electrolytic oxidation: Sodium silicate and sodium molybdate are used as electrolytes to generate Al on the surface of the substrate after annealing of the high-toughness alloy brake disc. 2 O 3 -MoSi 2 The composite ceramic layer is then processed by laser microtexturing to obtain a high-toughness alloy brake disc.

[0044] In step (1), the niobium content in ferroniobium is 65%; the titanium content in ferrotitanium is 30%; the boron content in the iron-boron alloy is 20%. Before being added, lanthanum, neodymium and cerium are mixed with magnesium as a spheroidizing agent and then directly added to the furnace bottom.

[0045] In step (2), the barium content in the silicon-barium alloy is 6%, and the amount of silicon-barium alloy added is 0.5% of the total mass of the raw materials; the niobium content in the niobium-cerium ferrosilicon is 8%, and the cerium content is 3%, and the amount of niobium-cerium ferrosilicon added is 0.6% of the total mass of the raw materials; the average particle size of the nano-graphite powder is 100nm, and the amount of the nano-graphite powder added is 0.1% of the total mass of the raw materials.

[0046] In step (3), the water cooling rate of the outer mold is 40°C / s, the inner cavity is cooled naturally, and the hardness difference of directional solidification is 40HB.

[0047] After step (4) is completed, the residual stress is 50 MPa and the pearlite lamellar spacing is 0.3 μm.

[0048] In step (5), the concentration of sodium silicate is 15 g / L, the concentration of sodium molybdate is 5 g / L, 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; Al 2 O 3 -MoSi 2 The thickness of the composite ceramic layer is 35 μm and the thermal conductivity is 45 W / (m·K).

[0049] In step (5), during laser microtexturing, the wavelength of the fiber laser is 1064 nm, the power is 300-800 W, the scanning speed is 15 mm / s, the micropit diameter is 80 μm, the depth is 30 μm, and the spacing is 300 μm.

[0050] Comparative Example 1 Compared with Example 1, the differences are that no niobium is added, the boron content is 0.008%, and no niobium-cerium-containing ferrosilicon inoculant is used.

[0051] Comparative Example 2 Compared with Example 1, the difference is that cerium and tin are not added and the PEO coating is eliminated.

[0052] Comparative Example 3 Compared with Example 1, the difference is that no Mo is added, the Cu content is 3%, and traditional single-stage annealing (900° C.×4 h) is adopted.

[0053] Comparative Example 4 A commercial high-nickel gray iron brake disc (Brembo-HP2000) is used, with a Ni content of 3.5%, a C content of 3.2%, a Si content of 2.0%, and a Mn content of 0.7%, without surface treatment.

[0054] Comparative Example 5 The difference compared with Example 1 is that lanthanum and neodymium are not added.

[0055] The test data of Examples 1-3 and Comparative Examples 1-5 are shown in Table 1.

[0056] Table 1: Test data of Examples 1-3 and Comparative Examples 1-5

[0057] From the data in Table 1, it can be seen that the impact energy of Comparative Example 1 (without Nb and Ce-Nb inoculant) is reduced by 50% (12J) due to the lack of NbC pinning the grain boundaries; the tensile strength is reduced to 160MPa due to the lack of Mo 2 C strengthening; salt spray life 800h, due to Ce deficiency causing intergranular corrosion sensitivity. Comparative Example 2 (no Ce, Sn, no PEO) salt spray life 1000h, because the impurities at the grain boundaries are not neutralized and there is no PEO coating protection; thermal conductivity 45W / (m·K), due to the uneven distribution of graphite caused by Sn deficiency. Comparative Example 3 (no Mo, high Cu): 600℃ tensile strength 150MPa, due to Mo 2 C hard phase is missing; friction coefficient fluctuates by 20% due to reduced surface hardness and thermal conductivity. The results of comparative example 5 (without La and Nd) show that the absence of rare earth elements leads to a 42% decrease in impact energy, a 59% decrease in salt spray life, and a 58% decrease in thermal fatigue life, further verifying the key role of La and Nd in grain boundary purification, phase change control, and crack resistance.

Claims

1. A high-toughness alloy brake disc, characterized in that: The chemical composition includes 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 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 rest is iron and inevitable impurities.

2. A method for preparing the high-toughness alloy brake disc according to claim 1, characterized in that: The following steps are involved: (1) The gray iron matrix raw material is heated to 1500-1550°C and kept warm until it is completely melted. Then, ferromolybdenum, electrolytic copper, iron-boron alloy and tin ingot are added first. Then, the temperature is lowered to 1420-1450°C, ferroniobium and ferrotitanium are added, and then lanthanum, neodymium and cerium mixed with magnesium are added. Antimony is pressed into the bottom of the molten pool in the form of pure metal blocks; (2) Composite inoculation treatment: Pre-incubation in the furnace: adding silicon-barium alloy at 1460-1500℃; Ladle inoculation: Add ferrosilicon containing niobium-cerium into the ladle before pouring; Instant inoculation with the flow: adding nano graphite powder to the casting flow through the wire feeder; (3) Casting process: The pouring temperature is maintained at 1340-1400℃, the outer mold of the casting is a metal mold, the inner cavity is a resin sand core, and directional solidification is adopted: surface → core, to obtain a high-toughness alloy brake disc matrix; (4) Graded isothermal annealing treatment of high-toughness alloy brake disc substrate: Austenitizing: heat to 900-940℃, keep warm for 1.5-3 hours; Pearlite transformation: furnace cooling to 720-760℃, keeping warm for 2-4 hours; Stress relief: furnace cooling to 500-600℃, keeping warm for 1-3 hours, air cooling to room temperature, and obtaining the annealed matrix of high-toughness alloy brake disc; (5) Plasma electrolytic oxidation: Using sodium silicate and sodium molybdate as the electrolyte, an Al2O3-MoSi2 composite ceramic layer is generated on the surface of the substrate after annealing of the high-toughness alloy brake disc, and then it is treated by laser microtexturing to obtain a high-toughness alloy brake disc.

3. The method for preparing a high-toughness alloy brake disc according to claim 2, 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 iron-boron alloy is 18-20%, and the lanthanum, neodymium and cerium are mixed with magnesium as a spheroidizing agent before being added, and then directly added to the furnace bottom.

4. The method for preparing a high-toughness alloy brake disc according to claim 2, characterized in that: In the step (2), the barium content in the silicon-barium alloy is 4-6%, and the amount of the silicon-barium alloy added is 0.2-0.5% of the total mass of the raw materials; the niobium content in the niobium-cerium ferrosilicon is 5-8%, and the cerium content is 1-3%, and the amount of the niobium-cerium ferrosilicon added is 0.3-0.6% of the total mass of the raw materials; the average particle size of the nano-graphite powder is 20-100nm, and the amount of the nano-graphite powder added is 0.03-0.1% of the total mass of the raw materials.

5. The method for preparing a high-toughness alloy brake disc according to claim 2, characterized in that: 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 the directional solidification is ≤40HB.

6. The method for preparing a high-toughness alloy brake disc according to claim 2, characterized in that: After the step (4) is completed, the residual stress is ≤50MPa and the pearlite lamella spacing is 0.15-0.3μm.

7. The method for preparing a high-toughness alloy brake disc according to claim 2, 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, 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 processing 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).

8. The method for preparing a high-toughness alloy brake disc according to claim 2, characterized in that: In the step (5), during laser microtexturing, the wavelength of the fiber laser is 1064 nm, the power is 300-800 W, the scanning speed is 5-15 mm / s, the micropit diameter is 30-80 μm, the depth is 10-30 μm, and the spacing is 150-300 μm.

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