Heat-resistant cast steel for exhaust manifold and preparation method of heat-resistant cast steel
Through microalloyation and laser cladding technology, a multi-alloyed heat-resistant cast steel material has been developed, which solves the problems of heat resistance and cost of exhaust manifolds at high temperatures, and achieves high-temperature performance improvement and cost reduction. It is suitable for high temperatures Exhaust manifold material.
Patent Information
- Application Number
- CN202411161638.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-23
- Publication Date
- 2025-01-07
AI Technical Summary
Existing exhaust manifold materials have challenges in terms of heat resistance and cost at high temperatures, especially the high cost and poor heat crack resistance of high Ni duct iron and high Ni cast steel, resulting in poor material performance at high temperatures.
Multi-alloyed heat-resistant cast steel materials were developed through microalloying method, and high-temperature smelting was used to use 304 scrap steel, ferrochromium, nickel, ferromanganese, cobalt iron and other materials, and microalloys such as silicon calcium barium and rare earth composite silicon calcium manganese are added. , multiple slag removal and refining were performed, followed by laser cladding to improve the density and mechanical properties of the cladding layer.
It realizes the maintenance of strength and oxidation resistance at high temperatures of 1050℃, reduces the Ni alloy content, reduces material costs, and improves service life. It can replace high-nickel cast iron and high-temperature heat-resistant cast steel materials to meet the exhaust manifold high temperature working requirements.
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Figure BDA0005006614640000141 
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of heat-resistant cast steel, and in particular to heat-resistant cast steel for an exhaust manifold and a preparation method thereof. Background Art
[0002] As people's environmental awareness continues to increase, relevant automobile emission regulations are constantly upgraded, and the requirements for automobile exhaust emissions are becoming more and more stringent. Reducing engine displacement will affect torque and power. In order to ease the conflict between exhaust emissions, fuel consumption rate and automobile power performance, technologies such as turbocharging, direct injection / common rail direct injection, variable valve timing, and stratified combustion have been widely developed and applied. However, with the introduction of these technologies, the engine operating temperature has increased significantly, causing the gas emission temperature to rise accordingly, some approaching or even exceeding 1000℃. Higher requirements are placed on the application of heat-resistant materials for exhaust manifolds.
[0003] At present, in order to meet the requirements of increasing exhaust temperature of engines, some domestic and foreign manufacturers have begun to develop the application of heat-resistant cast steel in exhaust manifolds. When the gas exhaust temperature is close to 800℃, the exhaust manifold material uses SiMo ductile iron, which still has good heat resistance. Compared with traditional cast iron (gray iron, ductile iron, vermicular iron) and SiMo ductile iron, high Ni austenitic ductile iron has higher high temperature performance (maximum operating temperature is close to 950℃), but due to the high content of Ni elements, the cost is high and the application is subject to certain restrictions. In addition, the matrix of high Ni ductile iron is austenite, with a large linear expansion coefficient, and there is graphite in the organization that constitutes the starting point of destruction, so the heat cracking resistance is poor; when the surface temperature of the exhaust manifold is close to 1000℃, 1.4848 or 1.4837 is usually used as the basis for developing heat-resistant cast steel materials, but with the continuous rise in the prices of Cr and Ni, affected by the rising cost of raw materials, the demand for low Cr and Ni alloy heat-resistant cast steel is increasing. Therefore, it is urgent to develop a nickel-saving heat-resistant cast steel for exhaust manifolds. Summary of the invention
[0004] The purpose of the present invention is to provide a heat-resistant cast steel for an exhaust manifold and a preparation method thereof, mainly through a microalloying method, to develop a multi-element alloyed heat-resistant cast steel material, weaken and eliminate high-temperature oxidation, improve high-temperature strength, high-temperature corrosion, creep resistance and thermal strength, replace high-Ni ductile iron and high-Ni cast steel, reduce the Ni alloy content to reduce material costs, so as to solve the problems raised in the prior art.
[0005] To achieve the above object, the present invention provides the following technical solutions:
[0006] A heat-resistant cast steel for an exhaust manifold, the components of which are, by mass percentage, C: 0.30-0.50%, Si: 1.0-2.5%, Mn≤1.5%, P≤0.04%, S≤0.03%, Cr: 24-28%, Mo≤0.5%, Ni: 3.0-6.0%, Co; 0.14-0.20%, V: 0.15-0.20%, Nb: 0.35-0.45%, Te≤0.005%, Ce≤0.05%, and the balance is Fe and unavoidable impurities.
[0007] A method for preparing heat-resistant cast steel for an exhaust manifold, comprising:
[0008] S1: adding 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt into the furnace in sequence for high-temperature smelting at a smelting temperature of 1700-1710°C, adding silicon, calcium and barium during smelting, performing slag removal for no less than 3 times, adding ferroniobium and ferrovanadium 15 minutes before the furnace is discharged, and the furnace is discharged at 1680-1700°C to obtain molten steel;
[0009] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1520-1580°C to obtain heat-resistant cast steel.
[0010] S3: After the surface of the heat-resistant cast steel produced by S2 is ground, cleaned and dried with anhydrous ethanol, laser cladding is performed. Coaxial synchronous powder feeding is used to sequentially clad powders A and B on the preset surface of the heat-resistant cast steel. The thickness of the single cladding layer is 0.4 to 0.5 mm, and a heat-resistant cast steel with a cladding layer thickness of 0.8 to 1.0 mm is obtained.
[0011] The amount of silicon, calcium and barium used is 0.1-0.3% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese used is 0.1-0.2% of the mass of the terminal molten steel in S2.
[0012] Powder A comprises: 60-70% high chromium cast iron powder A, 10-20% titanium carbonitride powder, and 20% micron titanium carbide powder;
[0013] The chemical composition of the high chromium cast iron powder A is calculated by mass percentage as follows: C: 2.0-3.0%, Cr: 12.0-18.0%, Si: 0.6-1.5%, Mn: 1.0-2.0%, Ni: 2.3-2.5%, Mo: 0.5-3.0%, V: 0.4-0.5% and the balance is Fe.
[0014] Powder B comprises: 60-70% high chromium cast iron powder B, 10-20% titanium carbonitride powder, 10-15% micron titanium carbide powder, and 5-10% nano titanium carbide powder;
[0015] Among them, the chemical composition of high chromium cast iron powder B is calculated by mass percentage: C: 3.0-4.0%, Cr: 14.0-25.0%, Si: 0.6-1.0%, Mn: 1.0-1.5%, B: 0.8-1.0%, V: 0.4-0.5%, Ni: 0.4-0.5%, Mo: 3.0-5.0% and the balance is Fe.
[0016] The particle size of micron titanium carbide is 2-4 μm, and the particle size of nano titanium carbide powder is 300-500 nm.
[0017] The laser cladding parameters were set as follows: under argon protective atmosphere, laser power 3500-3800 W, spot diameter 3-5 mm, scanning speed 100-300 mm / min, overlap rate between each pass 30-40%;
[0018] The powder feeding speed of the coaxial synchronous powder feeding is 20-40g / min, and the nozzle height is 15mm.
[0019] Compared with the prior art, the invention has the following beneficial effects: the invention realizes intergranular strengthening, high temperature oxidation resistance, high temperature corrosion resistance and creep resistance of cast steel by microalloying method, and the maximum working temperature can reach 1050°C; the C content in the raw material formula of cast steel is appropriately reduced to improve the oxidation resistance of the alloy, and microalloys such as iron tellurium and iron cerium are added to achieve the effect of grain refinement and improve the chromium depletion phenomenon; the heat-resistant cast steel obtained by casting is subjected to laser cladding on the preset surface, and the cladding powder is obtained by compounding high chromium cast iron and ceramic particles, and the chemical composition of high chromium cast iron is similar to that of base steel. The ceramic particles are titanium carbide particles and titanium carbonitride particles of different sizes to improve the density of the cladding layer, and the ceramic particles are added to the cladding layer as a reinforcing material, which not only improves the wettability of the cladding alloy and the substrate, but also helps to disperse the load during friction, reduce local stress concentration, reduce wear and thus extend the service life, and further achieve the refinement of carbides in high chromium cast iron, improve mechanical properties, improve the connectivity between cladding layers through changes in the chemical composition of the cladding powder, and further improve the working performance of the heat-resistant cast steel. DETAILED DESCRIPTION
[0020] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0021] In the experiment, the particle size of micron titanium carbide was 2-4 μm, the particle size of nano titanium carbide powder was 300-500 nm, and the particle size of titanium carbonitride powder was 1-2 μm;
[0022] Embodiment 1: A method for preparing heat-resistant cast steel for exhaust manifold comprises:
[0023] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0024] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0025] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0026] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.15%, Nb: 0.35%, Te: 0.003%, Ce: 0.03%, and the balance is Fe and unavoidable impurities.
[0027] Embodiment 2: A method for preparing heat-resistant cast steel for exhaust manifold comprises:
[0028] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0029] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0030] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0031] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.20%, Nb: 0.40%, Te: 0.004%, Ce: 0.04%, and the balance is Fe and unavoidable impurities.
[0032] Embodiment 3: A method for preparing heat-resistant cast steel for exhaust manifold comprises:
[0033] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0034] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0035] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0036] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.15%, Nb: 0.41%, Te: 0.004%, Ce: 0.05%, and the balance is Fe and unavoidable impurities.
[0037] Embodiment 4: A method for preparing heat-resistant cast steel for exhaust manifold comprises:
[0038] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0039] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0040] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0041] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.15%, Nb: 0.45%, Te: 0.005%, Ce: 0.05%, and the balance is Fe and unavoidable impurities.
[0042] Example 5: Based on Example 4, laser cladding is performed, and a method for preparing heat-resistant cast steel for an exhaust manifold comprises:
[0043] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0044] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0045] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0046] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.15%, Nb: 0.45%, Te: 0.005%, Ce: 0.05%, and the balance is Fe and unavoidable impurities.
[0047] S4: The prepared heat-resistant cast steel was pre-treated, and after surface grinding and anhydrous ethanol cleaning, it was dried and laser clad. The powder feeding speed of the coaxial synchronous powder feeding was 20g / min, the nozzle height was 15mm, and under the argon protective atmosphere, the laser power was 3800W, the spot diameter was 5mm, the scanning speed was 300mm / min, and the overlap rate between each pass was 40%. The two powders A and B were clad on the pre-prepared surface of the heat-resistant cast steel in sequence. The single layer thickness of the cladding layer was 0.4mm, and the heat-resistant cast steel sample 1 with a final cladding layer thickness of 0.8mm was obtained;
[0048] Powder A includes: 60% high chromium cast iron powder A, 20% titanium carbonitride powder, and 20% micron titanium carbide powder;
[0049] The chemical composition of the high chromium cast iron powder A is as follows in mass percentage: C: 2.4%, Cr: 15.0%, Si: 0.8%, Mn: 1.3%, Ni: 2.5%, Mo: 0.5%, V: 0.4% and the balance is Fe.
[0050] Powder B includes: 60% high chromium cast iron powder B, 20% titanium carbonitride powder, 10% micron titanium carbide powder, and 10% nano titanium carbide powder;
[0051] The chemical composition of the high chromium cast iron powder B is as follows in mass percentage: C: 3.0%, Cr: 25.0%, Si: 1.0%, Mn: 1.5%, B: 1.0%, V: 0.5%, Ni: 0.5%, Mo: 5.0% and the balance is Fe.
[0052] Embodiment 6: Based on Embodiment 4, laser cladding is performed, and a method for preparing heat-resistant cast steel for an exhaust manifold comprises:
[0053] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0054] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0055] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0056] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.15%, Nb: 0.45%, Te: 0.005%, Ce: 0.05%, and the balance is Fe and unavoidable impurities.
[0057] S4: The prepared heat-resistant cast steel was pre-treated, and after surface grinding and anhydrous ethanol cleaning, it was dried and laser clad. The powder feeding speed of the coaxial synchronous powder feeding was 20g / min, the nozzle height was 15mm, and under the argon protective atmosphere, the laser power was 3800W, the spot diameter was 5mm, the scanning speed was 300mm / min, and the overlap rate between each pass was 40%. The two powders A and B were clad on the pre-prepared surface of the heat-resistant cast steel in sequence. The single layer thickness of the cladding layer was 0.4mm, and the heat-resistant cast steel sample 1 with a final cladding layer thickness of 0.8mm was obtained;
[0058] Powder A includes: 70% high chromium cast iron powder A, 10% titanium carbonitride powder, and 20% micron titanium carbide powder;
[0059] The chemical composition of the high chromium cast iron powder A is as follows in mass percentage: C: 2.4%, Cr: 15.0%, Si: 0.8%, Mn: 1.3%, Ni: 2.5%, Mo: 0.5%, V: 0.4% and the balance is Fe.
[0060] Powder B includes: 70% high chromium cast iron powder B, 10% titanium carbonitride powder, 10% micron titanium carbide powder, and 10% nano titanium carbide powder;
[0061] The chemical composition of the high chromium cast iron powder B is as follows in mass percentage: C: 3.0%, Cr: 25.0%, Si: 1.0%, Mn: 1.5%, B: 1.0%, V: 0.5%, Ni: 0.5%, Mo: 5.0% and the balance is Fe.
[0062] Example 7: Based on Example 4, laser cladding is performed, and a method for preparing heat-resistant cast steel for an exhaust manifold comprises:
[0063] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0064] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0065] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0066] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.15%, Nb: 0.45%, Te: 0.005%, Ce: 0.05%, and the balance is Fe and unavoidable impurities.
[0067] S4: The prepared heat-resistant cast steel was pre-treated, and after surface grinding and anhydrous ethanol cleaning, it was dried and laser clad. The powder feeding speed of the coaxial synchronous powder feeding was 20g / min, the nozzle height was 15mm, and under the argon protective atmosphere, the laser power was 3800W, the spot diameter was 5mm, the scanning speed was 300mm / min, and the overlap rate between each pass was 40%. The two powders A and B were clad on the pre-prepared surface of the heat-resistant cast steel in sequence. The single layer thickness of the cladding layer was 0.4mm, and the heat-resistant cast steel sample 1 with a final cladding layer thickness of 0.8mm was obtained;
[0068] Powder A includes: 70% high chromium cast iron powder A, 10% titanium carbonitride powder, and 20% micron titanium carbide powder;
[0069] The chemical composition of the high chromium cast iron powder A is as follows in mass percentage: C: 2.4%, Cr: 15.0%, Si: 0.8%, Mn: 1.3%, Ni: 2.5%, Mo: 0.5%, V: 0.4% and the balance is Fe.
[0070] Powder B includes: 70% high chromium cast iron powder B, 10% titanium carbonitride powder, 15% micron titanium carbide powder, and 5% nano titanium carbide powder.
[0071] The chemical composition of the high chromium cast iron powder B is as follows in mass percentage: C: 3.0%, Cr: 25.0%, Si: 1.0%, Mn: 1.5%, B: 1.0%, V: 0.5%, Ni: 0.5%, Mo: 5.0% and the balance is Fe.
[0072] Comparative Example 1: Powder B in Example 7 was adjusted, and the specific steps were as follows:
[0073] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0074] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0075] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0076] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.15%, Nb: 0.45%, Te: 0.005%, Ce: 0.05%, and the balance is Fe and unavoidable impurities.
[0077] S4: The prepared heat-resistant cast steel was pre-treated, and after surface grinding and anhydrous ethanol cleaning, it was dried and laser clad. The powder feeding speed of the coaxial synchronous powder feeding was 20g / min, the nozzle height was 15mm, and under the argon protective atmosphere, the laser power was 3800W, the spot diameter was 5mm, the scanning speed was 300mm / min, and the overlap rate between each pass was 40%. The two powders A and B were clad on the pre-prepared surface of the heat-resistant cast steel in sequence. The single layer thickness of the cladding layer was 0.4mm, and the heat-resistant cast steel sample 1 with a final cladding layer thickness of 0.8mm was obtained;
[0078] Powder A includes: 70% high chromium cast iron powder A, 10% titanium carbonitride powder, and 20% micron titanium carbide powder;
[0079] The chemical composition of the high chromium cast iron powder A is as follows in mass percentage: C: 2.4%, Cr: 15.0%, Si: 0.8%, Mn: 1.3%, Ni: 2.5%, Mo: 0.5%, V: 0.4% and the balance is Fe.
[0080] Powder B includes: 70% high chromium cast iron powder B, 10% titanium carbonitride powder, and 20% micron titanium carbide powder.
[0081] The chemical composition of the high chromium cast iron powder B is as follows in mass percentage: C: 3.0%, Cr: 25.0%, Si: 1.0%, Mn: 1.5%, B: 1.0%, V: 0.5%, Ni: 0.5%, Mo: 5.0% and the balance is Fe.
[0082] Comparative Example 2: Adjust the powder A and powder B of Example 7, and the specific steps are as follows:
[0083] S1: 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt are added into the furnace in sequence for high-temperature smelting at a smelting temperature of 1710°C. Silicon, calcium and barium are added during smelting, and slag removal is performed three times. Ferroniobium and ferrovanadium are added 15 minutes before the furnace is discharged, and the furnace is discharged at 1700°C to obtain molten steel;
[0084] S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1580°C to obtain heat-resistant cast steel.
[0085] The amount of silicon, calcium and barium is 0.2% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese is 0.2% of the mass of the terminal molten steel in S2;
[0086] The chemical composition of the produced heat-resistant cast steel is as follows by mass percentage: C: 0.30%, Si: 2.0%, Mn: 1.3%, P: 0.02%, S: 0.01%, Cr: 25%, Mo: 0.3%, Ni: 4.0%, Co: 0.15%, V: 0.15%, Nb: 0.45%, Te: 0.005%, Ce: 0.05%, and the balance is Fe and unavoidable impurities.
[0087] S4: The prepared heat-resistant cast steel was pre-treated, and after surface grinding and anhydrous ethanol cleaning, it was dried and laser clad. The powder feeding speed of the coaxial synchronous powder feeding was 20g / min, the nozzle height was 15mm, and under the argon protective atmosphere, the laser power was 3800W, the spot diameter was 5mm, the scanning speed was 300mm / min, and the overlap rate between each pass was 40%. The two powders A and B were clad on the pre-prepared surface of the heat-resistant cast steel in sequence. The single layer thickness of the cladding layer was 0.4mm, and the heat-resistant cast steel sample 1 with a final cladding layer thickness of 0.8mm was obtained;
[0088] Powder A includes: 70% high chromium cast iron powder A, 10% titanium carbonitride powder, 15% micron titanium carbide powder, and 5% nano titanium carbide powder;
[0089] The chemical composition of the high chromium cast iron powder A is as follows in mass percentage: C: 2.4%, Cr: 15.0%, Si: 0.8%, Mn: 1.3%, Ni: 2.5%, Mo: 0.5%, V: 0.4% and the balance is Fe.
[0090] Powder B includes: 70% high chromium cast iron powder B, 10% titanium carbonitride powder, 10% titanium carbonitride powder, and 20% micron titanium carbide powder.
[0091] The chemical composition of the high chromium cast iron powder B is as follows in mass percentage: C: 3.0%, Cr: 25.0%, Si: 1.0%, Mn: 1.5%, B: 1.0%, V: 0.5%, Ni: 0.5%, Mo: 5.0% and the balance is Fe.
[0092] Comparative Example 3: Select the common QTANi35Si5Cr2 high-Ni ductile iron on the market, the chemical composition is calculated by mass percentage: C: 2.30%, Si: 4.0%, Mn: 0.15%, P: 0.02%, S: 0.01%, Cr: 2.5%, Ni: 34.0%, and the balance is Fe and unavoidable impurities
[0093] Comparative Example 4: Common 1.4837 heat-resistant cast steel material on the market was selected, and the chemical composition was calculated by mass percentage as follows: C: 0.30%, Si: 2.5%, Mn: 0.15%, P: 0.02%, S: 0.01%, Cr: 25.0%, Ni: 14.0%, and the balance was Fe and unavoidable impurities.
[0094] Detection test:
[0095] High temperature tensile test: According to GB / T 228.2-2015 "Tensile test of metallic materials Part 2: High temperature test method", the samples of Examples 1-4 and Comparative Examples 3-4 were tested at several working temperatures. The results are shown in Table 1:
[0096] Table 1 Performance indicators of the test (working temperature)
[0097]
[0098] From the above data, the heat-resistant cast steel ZG40Cr27Ni4Si2V has achieved intergranular strengthening, high-temperature oxidation resistance, high-temperature corrosion resistance and creep resistance through the microalloying method, and has achieved room temperature and high temperature mechanical properties and service life that completely surpass the performance indicators of QTANi35Si5Cr2 high-nickel cast iron. It has a comparable effect to the performance indicators of 1.4837 heat-resistant cast steel materials, and meets the mechanical performance requirements of the maximum operating temperature of 1050°C. It can completely replace QTANi35Si5Cr2 high-nickel cast iron (maximum operating temperature of 950°C) and 1.4837 heat-resistant cast steel materials (maximum operating temperature of 1050°C), and the weldability of cast steel materials is completely superior to that of cast iron materials, and can be used as a new material for manufacturing high-temperature exhaust manifolds.
[0099] Hardness test: For the heat-resistant cast steels prepared in Examples 5-7 and Comparative Examples 1-2, the hardness of the cladding layer was measured using a Vickers hardness tester. The mass of the loaded weight was 200 g. The measurement results are shown in Table 2.
[0100] Wear resistance test: For the heat-resistant cast steel prepared in Examples 5-7 and Comparative Examples 1-2, a friction ball was used to carry out a wear performance test. The friction ball model was YG8, the diameter was 5 mm, the tungsten steel ball load was 50 N, the steel ball speed was 200 r / min, the rotation radius was 2 mm, and the time was 1 h. After the test, the sample was weighed and the wear rate was calculated. The measurement results are shown in Table 2.
[0101] Table 2
[0102]
[0103] Through the above experimental data, the sample with the best performance among the samples prepared in Examples 5-7 was prepared by Example 7. On the basis of Example 7, two groups of control experiments were carried out. The gradient change of the cladding layer helps to improve the hardness and wear performance of the cladding layer; Comparative Example 1 adjusts the cladding layer powder according to Example 7, and does not change the titanium carbide particle size, which affects both the hardness and the wear rate. The addition of titanium carbide of different particle sizes helps to improve the wear resistance of the cladding layer compared with the addition of a single particle size; Comparative Example 2 replaces the cladding powder to further verify that the double-size particles are better than the single particles, which affects both the hardness and the wear resistance.
[0104] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.
[0105] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
[0106] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.
Claims
1. A heat-resistant cast steel for an exhaust manifold, characterized in that: The components of the heat-resistant cast steel are as follows by mass percentage: C: 0.30-0.50%, Si: 1.0-2.5%, Mn≤1.5%, P≤0.04%, S≤0.03%, Cr: 24-28%, Mo≤0.5%, Ni: 3.0-6.0%, Co; 0.14-0.20%, V: 0.15-0.20%, Nb: 0.35-0.45%, Te≤0.005%, Ce≤0.05%, and the balance is Fe and unavoidable impurities.
2. A method for preparing heat-resistant cast steel for exhaust manifold, characterized in that: The preparation method of the heat-resistant cast steel comprises: S1: adding 304 scrap steel, ferrochrome, nickel, ferromanganese and ferrocobalt into the furnace in sequence for high-temperature smelting at a smelting temperature of 1700-1710°C, adding silicon, calcium and barium during smelting to remove slag, adding ferroniobium and ferrovanadium 15 minutes before the furnace is discharged, and the furnace is discharged at 1680-1700°C to obtain molten steel; S2: Pour the molten steel in S1 into a ladle for refining, and add iron-tellurium, iron-cerium and rare earth composite silicon-calcium-manganese in sequence; after tapping, the final molten steel is obtained, poured into a shell-core mold for casting, and the casting temperature is 1520-1580°C to obtain heat-resistant cast steel.
3. The method for preparing heat-resistant cast steel for exhaust manifold according to claim 2, characterized in that: The amount of silicon, calcium and barium used is 0.1-0.3% of the mass of the molten steel in S1, and the amount of rare earth composite silicon, calcium and manganese used is 0.1-0.2% of the mass of the terminal molten steel in S2.
4. The method for preparing heat-resistant cast steel for exhaust manifold according to claim 2, characterized in that: The preparation method of the heat-resistant cast steel also includes: S3: After the surface of the heat-resistant cast steel produced in S2 is ground, cleaned and dried with anhydrous ethanol, laser cladding is performed. Coaxial synchronous powder feeding is used to sequentially clad powder A and powder B on the preset surface of the heat-resistant cast steel. The single-layer thickness of the cladding layer is 0.4 to 0.5 mm, and a heat-resistant cast steel with a cladding layer thickness of 0.8 to 1.0 mm is obtained.
5. The method for preparing heat-resistant cast steel for exhaust manifold according to claim 4, characterized in that: Powder A includes: 60-70% high chromium cast iron powder A, 10-20% titanium carbonitride powder, and 20% micron titanium carbide powder; powder B includes: 60-70% high chromium cast iron powder B, 10-20% titanium carbonitride powder, 10-15% micron titanium carbide powder, and 5-10% nano titanium carbide powder.
6. The method for preparing heat-resistant cast steel for exhaust manifold according to claim 5, characterized in that: The chemical composition of high chromium cast iron powder A is calculated by mass percentage as follows: C: 2.0-3.0%, Cr: 12.0-18.0%, Si: 0.6-1.5%, Mn: 1.0-2.0%, Ni: 2.3-2.5%, Mo: 0.5-3.0%, V: 0.4-0.5% and the balance is Fe.
7. The method for preparing heat-resistant cast steel for exhaust manifold according to claim 5, characterized in that: The chemical composition of high chromium cast iron powder B is calculated by mass percentage as follows: C: 3.0-4.0%, Cr: 14.0-25.0%, Si: 0.6-1.0%, Mn: 1.0-1.5%, B: 0.8-1.0%, V: 0.4-0.5%, Ni: 0.4-0.5%, Mo: 3.0-5.0% and the balance is Fe.
8. The method for preparing heat-resistant cast steel for exhaust manifold according to claim 5, characterized in that: The particle size of micron titanium carbide is 2-4 μm, and the particle size of nano titanium carbide powder is 300-500 nm.
9. The method for preparing heat-resistant cast steel for exhaust manifold according to claim 4, characterized in that: The parameters of laser cladding are set as follows: under argon protective atmosphere, laser power is 3500-3800W, spot diameter is 3-5mm, scanning speed is 100-300mm / min, overlap rate between each pass is 30-40%; powder feeding speed of coaxial synchronous powder feeding is 20-40g / min, and nozzle height is 15mm.