Alloy steel for high-strength wind power bolt bar and preparation process of alloy steel

Abstract

The invention discloses alloy steel for a high-strength wind power bolt bar and a preparation process of the alloy steel, and relates to the technical field of alloy steel preparation. The specific preparation process comprises the steps that a 42CrMoA steel billet is taken to be subjected to normalizing, quenching and tempering thermal refining, pre-straightening, turning peeling and fine straightening are sequentially conducted after air cooling, and a crude product is obtained; and after solid boronizing treatment is conducted on the crude product, primary laser remelting is conducted on the surface, after treatment is finished, the surface is ground, cleaned and dried, after laser cladding of alloy powder is conducted on the surface, secondary laser remelting is conducted, and the alloy steel is obtained. Wherein tungsten carbide and cerium oxide are added into the alloy powder to serve as cladding powder, and the strength of a cladding layer is optimized; the alloy steel prepared by the invention has good mechanical properties.

Description

Technical Field

[0002] The invention relates to the technical field of alloy steel preparation, in particular to a high-strength alloy steel for wind power bolt rods and a preparation process thereof. Background Art

[0004] Wind power generation technology has the advantages of low emissions and low pollution, and is one of the important choices for the domestic electric energy sustainable development strategy. With the widespread use of wind energy as a clean and efficient renewable energy source, large-scale and high-power wind turbines have been put into operation. In service, wind turbines have gradually exposed some fault problems, among which the faults are related to the fatigue fracture damage of high-strength bolt rods. Wind power bolt rods are important fasteners used to connect key components in wind power generation equipment. It usually consists of a head and a screw, and is widely used in the connection of key parts such as tower sections, nacelle and tower, generator and nacelle, blades and hubs, etc., to connect the various components of the wind turbine tightly together, thereby ensuring the safe operation of the entire system. The use environment of wind power bolt rods includes but is not limited to harsh conditions such as extreme temperatures, high and low temperature erosion, vibration, corrosion and heavy loads. In a low temperature environment, the plasticity and toughness of the bolt rod material will be weakened, which is easy to cause fracture. At the same time, due to long-term exposure to large alternating stress, the bolt rod is also prone to fatigue fracture;

[0005] The quality of wind turbine bolt rods directly affects the bearing capacity, service life and safety performance of wind turbines. Therefore, wind turbine bolt rods need to have high strength, fatigue resistance and corrosion resistance to ensure the safe operation of wind turbines in harsh environments. Summary of the invention

[0007] The object of the present invention is to provide a high-strength alloy steel for wind power bolt rods and a preparation process thereof, so as to solve the problems raised in the prior art.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A preparation process of high-strength alloy steel for wind power bolt rods, characterized in that it specifically includes the following process steps:

[0010] Step 1: Take 42CrMoA steel billet and perform normalizing, quenching and tempering treatment, and then perform pre-straightening, turning and peeling, and fine straightening in sequence after air cooling to obtain a rough product;

[0011] Step 2: After the rough product of step 1 is subjected to solid boronizing treatment, the surface is subjected to a laser remelting. After the treatment, the surface is ground, cleaned and dried, and then alloy powder is laser clad on the surface, followed by a second laser remelting.

[0012] Preferably, in step 1, normalizing is performed at 850-870°C for 1 hour; quenching is performed at 830-850°C for 1 hour; and tempering is performed at 550-580°C for 1.5 hours. The above quenching and tempering treatment eliminates the internal stress of the steel billet, refines the grains, improves the comprehensive mechanical properties, and provides good organizational preparation for the subsequent solid boronizing treatment.

[0013] Preferably, the chemical composition of the alloy powder in step 2 includes, by mass fraction, 0.40-0.42% C, 0.22-0.25% Si, 0.73-0.75% Mn, 0.015-0.017% P, 0.020-0.022% S, 1.12-1.14% Cr, 0.22-0.24% Mo, 0.025-0.028% Al, 0.05-0.20% Ni, 0.01-0.05% Ti, and the balance is Fe and unavoidable impurities; the alloy powder introduces Ni and Ti elements into 42CrMoA to optimize the alloy powder composition.

[0014] Preferably, tungsten carbide particles and cerium oxide powder are added to the alloy powder; wherein the particle size of the tungsten carbide particles is 50-100 μm, and the amount used is 3-5wt% of the alloy powder; the particle size of the cerium oxide powder is 100-150 nm, and the amount used is 2-5wt% of the alloy powder.

[0015] Alloy powder laser cladding adopts coaxial powder feeding process, laser power is 800-1000W, scanning speed is 2-5mm / s, powder feeding voltage is 10-12V, and protective atmosphere argon gas flow rate is 12-15L / min.

[0016] In step 2, the solid boronizing treatment is to evenly apply the boronizing agent to the surface of the rough product with a coating thickness of 3-5 mm, keep it at 950-970°C for 5-7 hours, and then take it out for air cooling; wherein the boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon by mass fraction.

[0017] In one laser remelting, the laser power is 150-200W, the scanning rate is 5-10mm / s, and the defocus is +5mm.

[0018] In the secondary laser remelting, the laser power is 800-1000W, the scanning speed is 2-5mm / s, and the defocus is +10mm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention uses 42CrMoA steel billet as main steel, and performs quenching and tempering treatment and laser cladding. The quenching and tempering treatment obtains fine and uniform tempered bainite structure through quenching and high-temperature tempering, thereby improving the comprehensive mechanical properties of the steel billet. After the quenching and tempering treatment, solid-state boronizing is performed, and cerium oxide is added to the boronizing agent to promote the diffusion of boron in the steel billet and increase the thickness of the boronizing layer. Laser remelting is performed again to form eutectic boride, eliminate surface defects and internal stress concentration of the boronizing layer, and improve the brittleness of the boronizing layer. The boronizing layer is laser treated to obtain a remelting layer and a transition layer, and metallurgical reactions occur between the remelting layer and the transition layer as well as between the transition layer and the steel billet to improve the bonding strength between the boronizing layer and the steel billet; and at the same time, the bonding strength between the subsequent laser cladding layer and the substrate is improved.

[0021] 2. The alloy powder for laser cladding is mainly composed of 42CrMoA steel powder. Ni and Ti elements are introduced to optimize the chemical composition of the alloy powder. Ti is added to reduce the adverse effects of sulfides on the mechanical properties of alloy steel, and at the same time, it is alloyed with carbon and tungsten in tungsten carbide particles to improve the mechanical properties of the cladding layer; Ni is added to improve the impact resistance of the cladding layer; tungsten carbide and cerium oxide are added to the alloy powder; rare earth oxides reduce internal defects in the cladding layer and refine the grain size; the cladding layer is subjected to secondary laser remelting, which is equivalent to tempering the cladding layer again, further improving the overall mechanical properties of the steel.

[0022] 3. The processing equipment used in the present invention is relatively simple, the materials are easily available, and the parameter setting mainly revolves around the fiber laser. The operation is simple, and automatic operation can be realized, which effectively reduces the production cost. DETAILED DESCRIPTION

[0024] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0025] The particle size of tungsten carbide particles is 50-100 μm;

[0026] The particle size of cerium oxide powder is 100-150nm;

[0027] 5% PAG quenching agent was added during quenching, the brand was AQUA-QUENCH BW / C;

[0028] Example 1: A process for preparing alloy steel, the steps are as follows:

[0029] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 850°C for 1h and tempering treatment at 580°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0030] Step 2: Take alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain mixed powder; wherein the chemical composition of the alloy powder includes by mass fraction: 0.40% C, 0.23% Si, 0.75% Mn, 0.015% P, 0.020% S, 1.12% Cr, 0.22% Mo, 0.028% Al, 0.20% Ni, 0.03% Ti, and the balance is Fe and unavoidable impurities;

[0031] Step 3: After the crude product of step 1 is subjected to solid boronizing treatment, the boronizing agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the surface is laser remelted once. After the treatment, the surface is ground, cleaned and dried, and then the mixed powder prepared in step 2 is laser clad on the surface, and then laser remelted for a second time to obtain the alloy steel.

[0032] The amount of tungsten carbide is 5wt% of the alloy powder; the amount of cerium oxide powder is 3wt% of the alloy powder.

[0033] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon in mass fraction.

[0034] Laser cladding adopts coaxial powder feeding process, with laser power of 1000W, scanning speed of 5mm / s, powder feeding voltage of 12V, and gas flow rate of protective atmosphere argon of 15L / min.

[0035] In one laser remelting, the laser power is 150W, the scanning speed is 10mm / s, and the defocus is +5mm.

[0036] In the secondary laser remelting, the laser power is 1000W, the scanning speed is 3mm / s, and the defocus is +10mm.

[0037] Example 2: A process for preparing alloy steel, the steps are as follows:

[0038] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 850°C for 1h, quenching treatment at 830°C for 1h and tempering treatment at 550°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0039] Step 2: Take alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain mixed powder; wherein the chemical composition of the alloy powder includes by mass fraction: 0.42% C, 0.23% Si, 0.75% Mn, 0.017% P, 0.022% S, 1.12% Cr, 0.22% Mo, 0.028% Al, 0.05% Ni, 0.01% Ti, and the balance is Fe and unavoidable impurities;

[0040] Step 3: After the crude product of step 1 is subjected to solid boronizing treatment, the boronizing agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the surface is laser remelted once. After the treatment, the surface is ground, cleaned and dried, and then the mixed powder prepared in step 2 is laser clad on the surface for a second laser remelting to obtain the alloy steel.

[0041] The amount of tungsten carbide is 3wt% of the alloy powder; the amount of cerium oxide powder is 2wt% of the alloy powder.

[0042] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon in mass fraction.

[0043] Laser cladding adopts coaxial powder feeding process, with laser power of 800W, scanning speed of 3mm / s, powder feeding voltage of 10V, and gas flow rate of protective atmosphere argon of 12L / min.

[0044] In one laser remelting, the laser power is 150W, the scanning speed is 5mm / s, and the defocus is +5mm.

[0045] In the secondary laser remelting, the laser power is 800 W, the scanning speed is 2 mm / s, and the defocus is +10 mm.

[0046] Embodiment 3: A process for preparing alloy steel, the steps are as follows:

[0047] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 830°C for 1h and tempering treatment at 550°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0048] Step 2: Take alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain mixed powder; wherein the chemical composition of the alloy powder includes by mass fraction: 0.40% C, 0.23% Si, 0.75% Mn, 0.017% P, 0.022% S, 1.12% Cr, 0.22% Mo, 0.028% Al, 0.10% Ni, 0.03% Ti, and the balance is Fe and unavoidable impurities;

[0049] Step 3: After the crude product of step 1 is subjected to solid boronizing treatment, the boronizing agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the surface is laser remelted once. After the treatment, the surface is ground, cleaned and dried, and then the mixed powder prepared in step 2 is laser clad on the surface for a second laser remelting to obtain the alloy steel.

[0050] The amount of tungsten carbide is 3wt% of the alloy powder; the amount of cerium oxide powder is 5wt% of the alloy powder.

[0051] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon in mass fraction.

[0052] The laser cladding adopts a coaxial powder feeding process with a laser power of 1000W, a scanning speed of 5mm / s, a powder feeding voltage of 10V, and a gas flow rate of argon gas as the protective atmosphere of 15L / min.

[0053] In one laser remelting, the laser power is 150W, the scanning speed is 10mm / s, and the defocus is +5mm.

[0054] In the secondary laser remelting, the laser power is 1000W, the scanning speed is 2mm / s, and the defocus is +10mm.

[0055] Example 4: A process for preparing alloy steel, the steps are as follows:

[0056] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 850°C for 1h and tempering treatment at 580°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0057] Step 2: Take alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain mixed powder; wherein the chemical composition of the alloy powder includes by mass fraction: 0.41% C, 0.23% Si, 0.75% Mn, 0.016% P, 0.020% S, 1.12% Cr, 0.22% Mo, 0.028% Al, 0.015% Ni, 0.05% Ti, and the balance is Fe and unavoidable impurities;

[0058] Step 3: After the crude product of step 1 is subjected to solid boronizing treatment, the boronizing agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the surface is laser remelted once. After the treatment, the surface is ground, cleaned and dried, and then the mixed powder prepared in step 2 is laser clad on the surface for a second laser remelting to obtain the alloy steel.

[0059] The amount of tungsten carbide is 5wt% of the alloy powder; the amount of cerium oxide powder is 5wt% of the alloy powder.

[0060] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon in mass fraction.

[0061] Laser cladding adopts coaxial powder feeding process, with laser power of 1000W, scanning speed of 5mm / s, powder feeding voltage of 12V, and gas flow rate of protective atmosphere argon of 15L / min.

[0062] In one laser remelting, the laser power is 150W, the scanning speed is 5mm / s, and the defocus is +5mm.

[0063] In the secondary laser remelting, the laser power is 1000W, the scanning speed is 5mm / s, and the defocus is +10mm.

[0064] Example 5: A process for preparing alloy steel, the steps are as follows:

[0065] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 850°C for 1h and tempering treatment at 580°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0066] Step 2: Take alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain mixed powder; wherein the chemical composition of the alloy powder includes by mass fraction: 0.41% C, 0.23% Si, 0.75% Mn, 0.015% P, 0.020% S, 1.14% Cr, 0.24% Mo, 0.026% Al, 0.018% Ni, 0.04% Ti, and the balance is Fe and unavoidable impurities;

[0067] Step 3: After the crude product of step 1 is subjected to solid boronizing treatment, the boronizing agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the surface is laser remelted once. After the treatment, the surface is ground, cleaned and dried, and then the mixed powder prepared in step 2 is laser clad on the surface for a second laser remelting to obtain the alloy steel.

[0068] The amount of tungsten carbide is 5wt% of the alloy powder; the amount of cerium oxide powder is 5wt% of the alloy powder.

[0069] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon in mass fraction.

[0070] Laser cladding adopts coaxial powder feeding process, with laser power of 1000W, scanning speed of 5mm / s, powder feeding voltage of 12V, and gas flow rate of protective atmosphere argon of 15L / min.

[0071] In one laser remelting, the laser power is 150W, the scanning speed is 5mm / s, and the defocus is +5mm.

[0072] In the secondary laser remelting, the laser power is 1000W, the scanning speed is 3mm / s, and the defocus is +10mm.

[0073] Example 6: A process for preparing alloy steel, the steps are as follows:

[0074] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 850°C for 1h and tempering treatment at 580°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0075] Step 2: Take alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain mixed powder; wherein the chemical composition of the alloy powder includes by mass fraction: 0.42% C, 0.23% Si, 0.75% Mn, 0.016% P, 0.020% S, 1.12% Cr, 0.22% Mo, 0.028% Al, 0.015% Ni, 0.01% Ti, and the balance is Fe and unavoidable impurities;

[0076] Step 3: After the crude product of step 1 is subjected to solid boriding treatment, the boriding agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the surface is laser remelted again. After the treatment, the surface is ground, cleaned and dried, and then the secondary alloy powder prepared in step 2 is laser clad on the surface for a second laser remelting to obtain the alloy steel.

[0077] The amount of tungsten carbide is 3wt% of the alloy powder; the amount of cerium oxide powder is 5wt% of the alloy powder.

[0078] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon in mass fraction.

[0079] Laser cladding adopts coaxial powder feeding process, with laser power of 1000W, scanning speed of 5mm / s, powder feeding voltage of 12V, and gas flow rate of protective atmosphere argon of 15L / min.

[0080] In one laser remelting, the laser power is 150W, the scanning speed is 5mm / s, and the defocus is +5mm.

[0081] In the secondary laser remelting, the laser power is 1000W, the scanning speed is 3mm / s, and the defocus is +10mm.

[0082] Comparative Example 1: A control experiment of Example 1 without solid boronizing treatment, the specific steps are as follows:

[0083] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 850°C for 1h and tempering treatment at 580°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0084] Step 2: Take alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain mixed powder; wherein the chemical composition of the alloy powder includes by mass fraction: 0.40% C, 0.23% Si, 0.75% Mn, 0.015% P, 0.020% S, 1.12% Cr, 0.22% Mo, 0.028% Al, 0.20% Ni, 0.03% Ti, and the balance is Fe and unavoidable impurities;

[0085] Step 3: The surface of the rough product in step 1 is laser remelted once. After the treatment, the surface is ground, cleaned and dried, and then the mixed powder prepared in step 2 is laser clad on the surface for a second laser remelting to obtain the alloy steel.

[0086] The amount of tungsten carbide is 5wt% of the alloy powder; the amount of cerium oxide powder is 3wt% of the alloy powder.

[0087] Laser cladding adopts coaxial powder feeding process, with laser power of 1000W, scanning speed of 5mm / s, powder feeding voltage of 12V, and gas flow rate of protective atmosphere argon of 15L / min.

[0088] In one laser remelting, the laser power is 150W, the scanning speed is 10mm / s, and the defocus is +5mm.

[0089] In the secondary laser remelting, the laser power is 1000W, the scanning speed is 3mm / s, and the defocus is +10mm.

[0090] Comparative Example 2: A control experiment of Example 1 without performing the first and second laser remelting, and the specific steps are as follows:

[0091] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 850°C for 1h and tempering treatment at 580°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0092] Step 2: Take alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain mixed powder; wherein the chemical composition of the alloy powder includes by mass fraction: 0.40% C, 0.23% Si, 0.75% Mn, 0.015% P, 0.020% S, 1.12% Cr, 0.22% Mo, 0.028% Al, 0.20% Ni, 0.03% Ti, and the balance is Fe and unavoidable impurities;

[0093] Step 3: After the crude product of step 1 is subjected to solid boronizing treatment, the boronizing agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the mixed powder prepared in step 2 is laser-clad on the surface to obtain the alloy steel.

[0094] The amount of tungsten carbide is 5wt% of the alloy powder; the amount of cerium oxide powder is 3wt% of the alloy powder.

[0095] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon in mass fraction.

[0096] Laser cladding adopts coaxial powder feeding process, with laser power of 1000W, scanning speed of 5mm / s, powder feeding voltage of 12V, and gas flow rate of protective atmosphere argon of 15L / min.

[0097] Comparative Example 3: A control experiment of Example 1, in which tungsten carbide and cerium oxide are not added to the mixed powder, and the specific steps are as follows:

[0098] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 850°C for 1h and tempering treatment at 580°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0099] Step 2: Take alloy powder, the chemical composition of which includes by mass fraction: 0.40% C, 0.23% Si, 0.75% Mn, 0.015% P, 0.020% S, 1.12% Cr, 0.22% Mo, 0.028% Al, 0.20% Ni, 0.03% Ti, and the balance is Fe and unavoidable impurities;

[0100] Step 3: After the crude product of step 1 is subjected to solid boronizing treatment, the boronizing agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the surface is laser remelted once. After the treatment, the surface is ground, cleaned and dried, and then the alloy powder prepared in step 2 is laser-clad on the surface, and then laser remelted for a second time to obtain the alloy steel.

[0101] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon by mass fraction.

[0102] Laser cladding adopts coaxial powder feeding process, with laser power of 1000W, scanning speed of 5mm / s, powder feeding voltage of 12V, and gas flow rate of protective atmosphere argon of 15L / min.

[0103] In one laser remelting, the laser power is 150W, the scanning rate is 10mm / s, and the defocus is +5mm.

[0104] In the secondary laser remelting, the laser power is 1000W, the scanning speed is 3mm / s, and the defocus is +10mm.

[0105] Comparative Example 4: A control experiment of Example 1 was performed to reduce the content of Ni and Ti in the alloy powder. The specific steps are as follows:

[0106] Step 1: Take a 42CrMoA steel billet and perform normalizing treatment at 870°C for 1h, quenching treatment at 850°C for 1h and tempering treatment at 580°C for 1.5h, and then perform pre-correction, turning and peeling, and fine correction in sequence after air cooling to obtain a rough product;

[0107] Step 2: Take the alloy powder, add tungsten carbide particles and cerium oxide powder, and heat bake at 120°C for 1.5 hours to obtain a mixed powder; wherein the chemical composition of the alloy powder includes, by mass fraction, 0.40% C, 0.23% Si, 0.75% Mn, 0.015% P, 0.020% S, 1.12% Cr, 0.22% Mo, 0.028% Al, and the remainder is Fe and unavoidable impurities;

[0108] Step 3: After the crude product of step 1 is subjected to solid boronizing treatment, the boronizing agent is evenly applied to the surface of the crude product with a coating thickness of 5 mm. After being kept at 970°C for 5 hours, it is taken out and air-cooled, and the surface is laser remelted once. After the treatment, the surface is ground, cleaned and dried, and then the mixed powder prepared in step 2 is laser clad on the surface for a second laser remelting to obtain the alloy steel.

[0109] The amount of tungsten carbide used is 5wt% of the primary alloy powder; the amount of cerium oxide powder used is 3wt% of the primary alloy powder.

[0110] The boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon in mass fraction.

[0111] Laser cladding adopts coaxial powder feeding process, with laser power of 1000W, scanning speed of 5mm / s, powder feeding voltage of 12V, and gas flow rate of protective atmosphere argon of 15L / min.

[0112] In one laser remelting, the laser power is 150W, the scanning rate is 10mm / s, and the defocus is +5mm.

[0113] In the secondary laser remelting, the laser power is 1000W, the scanning speed is 3mm / s, and the defocus is +10mm.

[0114] Detection test

[0115] The alloy steels prepared in Examples 1-6 and Comparative Examples 1-4 were tested and sampled according to GB / T 2975-2018;

[0116] 1. Test the tensile properties at room temperature according to GB / T 228.1;

[0117] 2. Low temperature impact test: According to GB / T 229, the low temperature impact test is carried out on the P300 pendulum impact tester;

[0118] 3. Hardness test: According to GB / T 4340.1, the microhardness is tested on HVS-1000 microhardness tester with a test force of 1000 gf and a dwell time of 10 s.

[0119] The above test data are shown in the following table:

[0120]

[0121] Conclusion: Combined with the above data, it can be seen that the comprehensive performance of the alloy steel prepared in Example 1 is better than that of the other examples; Comparative Examples 1-4 are all control experiments of Example 1, and the various processing steps in Example 1 play a synergistic role in comprehensively improving the mechanical properties of the alloy steel; meeting the processing performance of the bolt rod.

[0122] 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.

Claims

1. A preparation process of high-strength alloy steel for wind power bolt rods, characterized in that: The specific process steps include: Step 1: Take 42CrMoA steel billet and perform normalizing, quenching and tempering treatment, and then perform pre-straightening, turning and peeling, and fine straightening in sequence after air cooling to obtain a rough product; Step 2: After the rough product of step 1 is subjected to solid boronizing treatment, the surface is subjected to a laser remelting. After the treatment, the surface is ground, cleaned and dried. After the surface is laser clad with alloy powder, a second laser remelting is performed.

2. The preparation process of a high-strength alloy steel for wind power bolt rod according to claim 1, characterized in that: In step 1, normalizing is performed at 850-870°C for 1 hour; quenching is performed at 830-850°C for 1 hour; and tempering is performed at 550-580°C for 1.5 hours.

3. The preparation process of a high-strength alloy steel for wind power bolt rod according to claim 1, characterized in that: The chemical composition of the alloy powder in step 2 includes, by mass fraction, 0.40-0.42% C, 0.22-0.25% Si, 0.73-0.75% Mn, 0.015-0.017% P, 0.020-0.022% S, 1.12-1.14% Cr, 0.22-0.24% Mo, 0.025-0.028% Al, 0.05-0.20% Ni, 0.01-0.05% Ti, and the balance is Fe and unavoidable impurities.

4. The preparation process of a high-strength alloy steel for wind power bolt rod according to claim 1, characterized in that: Tungsten carbide particles and cerium oxide powder are added to the alloy powder; the particle size of the tungsten carbide particles is 50-100 μm, and the amount used is 3-5wt% of the alloy powder; the particle size of the cerium oxide powder is 100-150 nm, and the amount used is 2-5wt% of the alloy powder.

5. The process for preparing a high-strength alloy steel for wind power bolt rod according to claim 1, characterized in that: The laser cladding adopts a coaxial powder feeding process, with a laser power of 800-1000W, a scanning speed of 2-5mm / s, a powder feeding voltage of 10-12V, and a gas flow rate of argon gas of the protective atmosphere of 12-15L / min.

6. The process for preparing a high-strength alloy steel for wind power bolt rod according to claim 1, characterized in that: Solid boronizing treatment is to evenly apply the boronizing agent to the surface of the rough product with a coating thickness of 3-5mm, keep it at 950-970℃ for 5-7h, and then take it out for air cooling; wherein, the boronizing agent is composed of 40% boron carbide, 20% silicon carbide, 20% potassium fluoroborate, 5% cerium oxide and 15% activated carbon by mass fraction.

7. The process for preparing a high-strength alloy steel for wind power bolt rod according to claim 1, characterized in that: In one laser remelting, the laser power is 150-200W, the scanning rate is 5-10mm / s, and the defocus is +5mm.

8. The process for preparing a high-strength alloy steel for wind power bolt rod according to claim 1, characterized in that: In the secondary laser remelting, the laser power is 800-1000W, the scanning speed is 2-5mm / s, and the defocus is +10mm.

9. A high-strength alloy steel for wind power bolt rods, characterized in that: The alloy steel is prepared by the preparation process described in claims 1-8.

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