Low-carbon-emission, low-temperature-resistant and high-strength steel for wind power anchor bolt and preparation process

Abstract

The steel for the wind power anchor bolt comprises the following chemical components in percentage by mass: 0.40 to 0.46 percent of C, 0.70 to 1.10 percent of Mn, 0.20 to 0.28 percent of Si, less than or equal to 0.010 percent of P, less than or equal to 0.010 percent of S, 1.10 to 1.45 percent of Cr, 0.18 to 0.25 percent of Mo, 0.030 to 0.070 percent of Al, 0.03 to 0.10 percent of Ni, less than or equal to 50ppm of N, less than or equal to 12ppm of O, less than or equal to 1.5 ppm of H and the balance of Fe and inevitable impurities. The production method comprises the steps of burdening, electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, straightening, heat treatment and flaw detection. By adjusting technological parameters and chemical components, the strength, plasticity and low-temperature impact of the wind power anchor bolt are considered, and batch production and application can be achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wind power fasteners, and particularly relates to a low-carbon emission low-temperature-resistant high-strength wind power anchor bolt steel and a preparation process. BACKGROUND

[0002] With the continuous change of the world energy pattern, in the new energy of electric power, in recent years, wind power develops rapidly with the characteristics of green and high efficiency, high-strength bolt steel is widely used in wind turbine generators, and with the promotion of the globalization process of the wind power industry, higher requirements are put forward for the stability of the wind power anchor bolt steel in the extreme environment, and the preparation of the wind power anchor bolt steel from low-carbon emission steel materials will become one of the necessary conditions for future export.

[0003] At present, there is no low-carbon emission index for the wind power anchor bolt steel in China. Compared with traditional carbon metallurgy, hydrogen metallurgy uses hydrogen as fuel and reducing agent, which can make ironmaking free from dependence on fossil energy and solve the problem of carbon emission from the source. Compared with the traditional "blast furnace + converter" long process with the same production scale, the implementation of the hydrogen metallurgy demonstration project of Hesteel can reduce carbon dioxide emission by 50-70%, and the addition of 30% DRI can reduce the carbon emission of per ton of steel from 2-2.5 tons to about 1.0 ton. In addition, the emissions of sulfur dioxide, nitrogen oxides and smoke dust are reduced by more than 30%, 70% and 80% respectively.

[0004] The performance of the national standard wind power anchor bolt steel is that the tensile strength is greater than or equal to 1040 MPa, the yield strength is greater than or equal to 940 MPa, the elongation is greater than or equal to 9%, the reduction of area is greater than or equal to 48%, and the impact energy at-40 DEG C is greater than or equal to 27J. With the increase of export orders in recent years, customers have put forward higher requirements for the strength and plasticity of the wind power anchor bolt steel in the low-temperature environment, that is, the tensile strength is greater than or equal to 1130 MPa, the yield strength is greater than or equal to 1040 MPa, the elongation is greater than or equal to 15%, the reduction of area is greater than or equal to 55%, the impact energy at-45 DEG C is greater than or equal to 80J, and the difference between the surface hardness and the core hardness is less than or equal to 1.5HRC.

[0005] In recent years, many domestic steel plants have tried to develop wind power anchor bolt products meeting the above performance, but due to the inability to adjust the process to balance the strength, plasticity and low-temperature impact of the wind power anchor bolt, batch production and application have not been realized. Therefore, it is imperative to invent a low-carbon emission low-temperature-resistant high-strength wind power anchor bolt steel and a preparation process. SUMMARY

[0006] The application provides a low-carbon emission low-temperature-resistant high-strength wind power anchor bolt steel and a preparation process, which can realize batch production and application by adjusting process parameters and chemical composition to balance the strength, plasticity and low-temperature impact of the wind power anchor bolt.

[0007] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows: a low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel, the chemical composition and mass percentage of the wind power anchor bolt steel are as follows: C: 0.40-0.46%, Mn: 0.70-1.10%, Si: 0.20-0.28%, P≤0.010%, S≤0.010%, Cr: 1.10-1.45%, Mo: 0.18-0.25%, Al: 0.030-0.070%, Ni: 0.03-0.10%, N≤50ppm, O≤12ppm, H≤1.5ppm, and the rest is Fe and inevitable impurities.

[0008] Further, the diameter of the wind power anchor bolt steel is Φ20-55mm; the wind power anchor bolt steel is quenched and tempered through a heat treatment process, the tempering sorbite area content of the product surface is ≥92%, and the rest is ferrite and bainite, and the surface core hardness difference is ≤1.5HRC.

[0009] Further, the wind power anchor bolt steel has a tensile strength of ≥1130MPa, a yield strength of ≥1040MPa, an elongation of ≥15%, a reduction of area of ≥55%, and an impact energy at-45℃ of ≥80J.

[0010] Another purpose of the present application is to provide a production method of the above-mentioned low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel, the production method comprises the following steps: batching, electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, straightening, heat treatment, and flaw detection; in the batching step, scrap steel + 20-30% direct reduced iron (DRI) is used as raw material; in the rolling step, the compression ratio is 1.5-1.7, the rolling speed is 0.21-0.24m / s, the opening rolling temperature is 1050±15℃, and the final rolling temperature is 950-980℃.

[0011] Further, in the electric furnace smelting step, high-pull supplementary blowing is adopted, and the end-point composition of the electric furnace is controlled to be C≥0.06% and P≤0.008%.

[0012] Further, in the LF refining step, lime, refining slag, and slag refining agent are added to ensure good fluidity of the refining slag, the basicity R is ≥3.2, the white slag retention time is ≥25 minutes, and the aluminum control is 300-700ppm.

[0013] Further, in the RH refining step, the vacuum degree is maintained at 90-100Pa for 10-20min, and the soft blowing time is 20-25min.

[0014] Further, in the continuous casting step, the superheat is 20-30℃, the crystallizer electric stirring frequency is 4Hz±0.5Hz, and the current is 190A±10A; the terminal electromagnetic stirring current is 140-160A, and the frequency is 8-10HZ.

[0015] Further, the continuous casting process, the continuous casting billet specification is 150-165mm*150-165mm, and the continuous casting constant speed is controlled to be 1.4-1.5m / min.

[0016] Further, the heating process controls the soaking section temperature of the heating furnace to be 1130-1180℃; the rolling process controls the phosphorus removal water pressure to be 25-30MPa, and the saw cutting, pit slow cooling, and 24-36 hours; the heat treatment process controls the quenching temperature to be 850-890℃, the medium water, the heat preservation time to be 90-120 minutes, the tempering temperature to be 580-615℃, the heat preservation time to be 150-180 minutes, and the water cooling temperature to be 25-40℃; and the flaw detection process adopts ultrasonic and magnetic flux leakage flaw detection, and the round steel surface crack is less than or equal to 0.2mm.

[0017] The beneficial effects generated by the above technical scheme are as follows: 1. The optimal matching of the strength and toughness in the low-temperature environment of-45℃ is achieved through the adjustment control of the mass percentage of each component and the strengthening effect of the Ni element. 2. The harmful residual elements such as Ti (titanium), arsenic (As), tin (Sn), antimony (Sb), and lead (Pb) in the steel can be effectively reduced, the comprehensive performance of the round steel can be improved, and the carbon emission can be reduced by 1.0-1.1 tons by using scrap steel + 20-30% direct reduced iron (DRI) as the raw material. 3. The content of the elements S and P and non-metallic inclusions in the steel grade can be reduced, and the purity and uniformity of the molten steel can be improved by using the LF furnace refining and RH vacuum degassing operation. 4. The segregation degree of the casting blank can be effectively improved by using the electromagnetic stirring process of the first stirring and the last stirring of the continuous casting low superheat control 20-28℃ crystallizer. 5. The austenite grain is prevented from growing excessively by using the first large compression ratio 1.5-1.7 low-speed rolling 0.21-0.24m / s, the steel rhythm is strictly controlled, the steel is balanced, and the hot rolling state organization and performance fluctuation of the bar can be reduced. 6. The tensile strength of the wind power anchor bolt steel produced by the application is greater than or equal to 1130MPa, the yield strength is greater than or equal to 1040MPa, the elongation is greater than or equal to 15%, the reduction of area is greater than or equal to 55%, the impact energy at-45℃ is greater than or equal to 80J, and the requirement that the difference between the core hardness and the surface hardness is less than or equal to 1.5HRC is met. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is the center organization chart of the product of Example 1 (1 / 2R metallographic structure 95%); Figure 2 It is the center organization chart of the product of Comparative Example 2 (1 / 2R metallographic structure 78%); Figure 3 It is the center organization chart of the product of Comparative Example 3 (1 / 2R metallographic structure 75%). DETAILED DESCRIPTION

[0019] The preferred embodiments of the application are introduced below, so that the technical scheme is more clear and convenient to understand. Embodiment

[0020] The production method of the low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel comprises the steps of batching, electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, straightening, heat treatment, and flaw detection. (1) The batching process uses scrap steel 20% and direct reduced iron (DRI) as raw materials. (2) The electric furnace smelting process adopts high-pull compensation blowing, and the end composition C of the electric furnace is controlled to be 0.064%, and P is 0.007%. (3) The LF refining process adds lime, refining slag, and slag refining agent to ensure good fluidity of the refining slag, the basicity R is 3.2, the white slag retention time is 28 minutes, and the aluminum control is 300 ppm.

[0021] (4) The RH refining process has a vacuum degree of 92 Pa for 17 min, and soft blowing time is 23 min.

[0022] (5) The continuous casting process has a superheating degree of 26℃, a crystallizer electric stirring frequency of 4 Hz, and an electric current of 190 A; the end electromagnetic stirring current is 160 A, and the frequency is 10 Hz. The continuous casting square billet is 160 mm x 160 mm, the constant casting speed is controlled to be 1.4 m / min, and the specific water quantity is 0.45 L / kg.

[0023] (6) The heating process controls the soaking section temperature of the heating furnace to be 1150℃, and the heating time is 245 min.

[0024] (7) The rolling process has a compression ratio of 1.5, a rolling speed of 0.22 m / s, a rough rolling temperature of 1045℃, a finish rolling temperature of 970℃, a phosphorus removal water pressure of 28.5 MPa, sawing, pit slow cooling, and 24 hours.

[0025] (8) The heat treatment process has quenching at 880℃, medium water, holding for 120 minutes, tempering at 590℃, holding for 160 minutes, and water cooling to 28℃.

[0026] (9) The flaw detection process adopts ultrasonic national standard 4162-A level, 0.5 mm magnetic flux leakage detection, and the round steel surface is free of cracks.

[0027] The chemical composition and mass percentage content of the wind power anchor bolt steel obtained in the embodiment are shown in Table 1, and the specification performance is shown in Table 2. The tempering sorbite area content of the product surface is 92.5%, the balance is ferrite 6.7%, and bainite 0.8%, and the metallographic structure diagram is shown in Figure 1 , (the same as the drawings of the remaining embodiments, and thus omitted). Embodiment

[0028] The production method of the low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel comprises the following steps: batching, electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, straightening, heat treatment and flaw detection. (1) A batching process is adopted, using scrap steel + 22% direct reduced iron (DRI) as raw materials. (2) An electric furnace smelting process is adopted, high-ladle-replenishing-blowing is adopted, the end-point composition C of the electric furnace is controlled to be 0.072%, and P is controlled to be 0.007%. (3) An LF refining process is adopted, lime, refining slag and slag refining agent are added to ensure good fluidity of the refining slag, the basicity R is 3.3, the white slag is kept for 25 minutes, and the aluminum control is 400 ppm.

[0029] (4) An RH refining process is adopted, the vacuum degree is 98 Pa and is kept for 18 minutes, and soft blowing is kept for 25 minutes.

[0030] (5) A continuous casting process is adopted, the superheat degree is 21℃, the frequency of the crystallizer electric stirring is 4.5 Hz, the current is 190 A, the current of the terminal electromagnetic stirring is 140 A, the frequency is 9 Hz, the continuous casting square billet is 165 mm x 165 mm, the constant speed of the continuous casting is controlled to be 1.4 m / min, and the water quantity is 0.45 L / kg.

[0031] (6) A heating process is adopted, the heating furnace controls the temperature of the soaking section to be 1152℃, and the heating time is 253 minutes.

[0032] (7) A rolling process is adopted, the compression ratio is 1.6, the rolling speed is 0.21 m / s, the opening rolling temperature is 1050℃, the final rolling temperature is 974℃, the phosphorus removal water pressure is 26.5 MPa, sawing is conducted, slow cooling in the pit is conducted for 36 hours.

[0033] (8) A heat treatment process is adopted, quenching is conducted at 865℃, the medium is water, the heat preservation time is 90 minutes, tempering is conducted at 600℃, the heat preservation time is 150 minutes, and then water cooling is conducted to 32℃.

[0034] (9) A flaw detection process is adopted, ultrasonic national standard 4162-A level and 0.5 mm magnetic flux leakage detection are adopted, and the surface crack of the round steel is less than or equal to 0.1 mm.

[0035] The chemical composition and mass percentage of the wind power anchor bolt steel obtained in the embodiment are shown in Table 1, and the specification performance is shown in Table 2. The tempering sorbite area content of the surface of the product is 93.4%, the balance is ferrite 5.5% and bainite 1.1%. Embodiment

[0036] The production method of the low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel comprises the following steps: batching, electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, straightening, heat treatment and flaw detection. (1) A batching process is adopted, using scrap steel + 25% direct reduced iron (DRI) as raw materials. (2) Electric furnace smelting process, high pull compensation blowing is adopted, the end point composition C of the electric furnace is controlled to be 0.08%, and P is controlled to be 0.008%; (3) LF refining process, lime, refining slag and slag refining agent are added to ensure good fluidity of the refining slag, the basicity R is 3.5, the white slag retention time is 28 minutes, and the aluminum control is 500 ppm.

[0037] (4) RH refining process, the vacuum degree is 98 Pa for 20 min, and the soft blowing time is 20 min.

[0038] (5) Continuous casting process, the superheat is 30 DEG C, the crystallizer electric stirring frequency is 3.5 Hz, the electric current is 180 A, the terminal electromagnetic stirring current is 150 A, the frequency is 8 Hz, the continuous casting square billet is 150 mm x 150 mm, the control continuous casting constant speed is 1.45 m / min, and the specific water amount is 0.45 L / kg.

[0039] (6) Heating process, the heating furnace controls the soaking section temperature to be 1130 DEG C, and the heating time is 259 min.

[0040] (7) Rolling process, the compression ratio is 1.7, the rolling speed is 0.24 m / s, the rough rolling temperature is 1065 DEG C, the finish rolling temperature is 969 DEG C, the phosphorus removal water pressure is 25 MPa, sawing is carried out, and the pit cooling is carried out for 30 hours.

[0041] (8) Heat treatment process, quenching at 850 DEG C, medium water, holding for 100 minutes, tempering at 615 DEG C, holding for 180 minutes, and then water cooling to 30 DEG C.

[0042] (9) Flaw detection process, ultrasonic national standard 4162-A level, 0.5 mm magnetic flux leakage detection is adopted, and the round steel surface crack is less than or equal to 0.15 mm.

[0043] The chemical composition and mass percentage of the wind power anchor bolt steel obtained in the embodiment are shown in Table 1, and the specification performance is shown in Table 2. The tempering sorbite area content of the product surface is 93.8%, the balance is ferrite 5.0% and bainite 1.2%. Embodiment

[0044] A production method of a low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel, the production method comprises the steps of batching, electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, straightening, heat treatment and flaw detection; (1) Batching process, scrap steel + 28% direct reduced iron DRI is used as raw material; (2) Electric furnace smelting process, high pull compensation blowing is adopted, the end point composition C of the electric furnace is controlled to be 0.07%, and P is controlled to be 0.006%; (3) LF refining process, adding lime, refining slag, slagging agent, ensuring good fluidity of the refining slag, basicity R: 3.8, white slag retention time 29 minutes, aluminum control: 600 ppm.

[0045] (4) RH refining process, vacuum degree 90 Pa for 10 min, soft blowing time 24 min.

[0046] (5) Continuous casting process, superheat 20℃, crystallizer electric stirring frequency 4Hz, current 200A; end electromagnetic stirring current 160A, frequency 8HZ. Continuous casting billet 160mmx160mm, control continuous casting constant speed 1.5m / min, specific water volume 0.45L / kg.

[0047] (6) Heating process, heating furnace control soaking section temperature 1180℃, heating time 263min.

[0048] (7) Rolling process, compression ratio 1.5, rolling speed 0.23m / s, opening rolling temperature 1035℃, final rolling temperature 950℃, dephosphorization water pressure 30MPa, sawing, pit slow cooling, 32 hours.

[0049] (8) Heat treatment process, 890℃ quenching, medium water, holding for 90 minutes, 580℃ tempering, holding for 165 minutes, water cooling to 25℃.

[0050] (9) Flaw detection process, using ultrasonic national standard 4162-A level, 0.5mm magnetic flux leakage detection, round steel surface crack ≤0.1mm.

[0051] The chemical composition and mass percentage of the wind power anchor bolt steel obtained in the embodiment are shown in Table 1, and the specification performance is shown in Table 2. The tempering sorbite area content on the surface of the product is 94.1%, the balance is ferrite 4.6% and bainite 1.3%. Embodiment

[0052] A production method of a low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel, the production method comprising the steps of batching, electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, straightening, heat treatment, and flaw detection; (1) Batching process, using scrap steel + 30% direct reduced iron DRI as raw material; (2) Electric furnace smelting process, using high-pull compensation blowing, controlling the electric furnace endpoint composition C to be 0.06%, P: 0.005%; (3) LF refining process, adding lime, refining slag, slagging agent, ensuring good fluidity of the refining slag, basicity R: 3.5, white slag retention time 30 minutes, aluminum control: 700ppm.

[0053] (4) RH refining process, vacuum degree 100 Pa for 15 min, soft blowing time 23 min.

[0054] (5) Continuous casting process, superheat 24℃, crystallizer electric stirring frequency 4Hz, current 190A; end electromagnetic stirring current 160A, frequency 8HZ. Continuous casting square billet 150mmx150mm, control continuous casting constant speed 1.4m / min, specific water quantity 0.45L / kg.

[0055] (6) Heating process, heating furnace control soaking section temperature 1170℃, heating time 267min.

[0056] (7) Rolling process, compression ratio 1.5, rolling speed 0.22m / s, roughing temperature 1053℃, finish rolling temperature 980℃, phosphorus removal water pressure 28.5MPa, sawing, pit cooling, 24-36 hours.

[0057] (8) Heat treatment process, 880℃ quenching, medium water, holding 90min, 590℃ tempering, holding 160min, water cooling to 40℃.

[0058] (9) Flaw detection process, adopt ultrasonic national standard 4162-A level, 0.5mm magnetic flux leakage detection, round steel surface crack ≤0.2mm.

[0059] The chemical composition and mass percentage of the wind power anchor bolt steel obtained in the embodiment are shown in Table 1, and the specification performance is shown in Table 2. The tempering sorbite area content on the surface of the product is 94.8%, and the balance is ferrite 3.8% and bainite 1.4%.

[0060] Comparative Example 1 The production method of the wind power anchor bolt steel comprises the following process flow: adopting batching (scrap steel + 30% DRI) - electric furnace - LF refining - RH - continuous casting - heating - rolling - straightening - flaw detection; Converter smelting process, high pull blow control, control converter endpoint composition C≥0.06%, P 0.005%.

[0061] LF refining process, add lime, refining slag, slagging agent, ensure good fluidity and alkalinity R3.2 of refining slag, white slag holding time 28min, aluminum control: 600ppm.

[0062] RH refining process, vacuum degree 100Pa for 18min, soft blowing time 23min.

[0063] Continuous casting process, continuous casting square billet (150-165mm)x(150-165mm), superheat 24℃, crystallizer electric stirring frequency 4Hz, current 190A; end electromagnetic stirring current 160A, frequency 8HZ; control continuous casting constant speed 1.4m / min, specific water quantity 0.45L / kg.

[0064] Heating process, heating furnace control soaking section temperature 1151℃, heating time 228min.

[0065] Rolling process, roughing temperature 1053℃, phosphorus removal water pressure 28.8MPa, finishing temperature 969℃, 1 frame roller speed from 0.22m / s.

[0066] Heat treatment process, specifically: quenching at 880℃, holding for 90min, then water cooling; then tempering at 590℃, holding for 160min, then water cooling to 25-40℃.

[0067] The product surface tempering sorbite area content is 92%, the rest is ferrite 7% and bainite 1%.

[0068] Comparative example 2 The production method of the wind power anchor bolt steel comprises the following technological processes: adopting ingredients (scrap steel+30% DRI)-electric furnace-LF refining-RH-continuous casting-heating-rolling-straightening-inspection; Converter, high pull compensation blowing is adopted, and the end point composition of the converter is controlled to be C 0.06% and P 0.005%.

[0069] LF refining, lime, refining slag and slag dissolving agent are added to ensure good fluidity and alkalinity R3.2 of the refining slag, the white slag holding time is 28 minutes, and the aluminum control is 600ppm.

[0070] RH, vacuum degree 90-100Pa, holding for 18min, soft blowing time 23min.

[0071] Continuous casting square billet (150-165mm) x (150-165mm), superheat 24℃, crystallizer electric stirring frequency 4Hz, current 190A; end electromagnetic stirring current is 160A, frequency is 8HZ; control continuous casting constant speed 1.4m / min, specific water volume is 0.45L / kg.

[0072] Heating furnace control soaking section temperature 1151℃, heating time 228min.

[0073] Rolling, roughing temperature 1053℃, phosphorus removal water pressure 28.8MPa, finishing temperature 969℃, 1 frame roller speed from 0.22m / s.

[0074] Heat treatment, specifically: quenching at 880℃, holding for 90min, then water cooling; then tempering at 590℃, holding for 160min, then water cooling to 25-40℃.

[0075] The product surface tempering sorbite area content is 78%, the rest is ferrite 20% and bainite 2%.

[0076] Comparative example 3 The production method of the wind power anchor bolt steel comprises the following process flow: adopting ingredients (scrap steel+30% DRI)-electric furnace-LF refining-RH-continuous casting-heating-rolling-straightening-inspection; The converter smelting process adopts high pulling and supplementary blowing, and controls the converter end composition C≥0.06%, P is 0.005%.

[0077] The LF refining process adds lime, refining slag and slag dissolving agent, ensures the good fluidity and basicity R3.2 of the refining slag, the white slag retention time is 28 minutes, and the aluminum control is 600ppm.

[0078] The RH refining process maintains 90-100 Pa of vacuum degree for 18 min, and the soft blowing time is 23 min.

[0079] The continuous casting process is a continuous casting billet (150-165mm) x (150-165mm), the superheat is 24℃, the crystallizer electric stirring frequency is 4Hz, the current is 190A, the terminal electromagnetic stirring current is 160A, the frequency is 8HZ, and the control continuous casting constant speed is 1.4m / min, and the specific water quantity is 0.45L / kg.

[0080] The heating process controls the soaking section temperature of the heating furnace to be 1151℃, and the heating time is 228 min.

[0081] Rolling, the opening rolling temperature is 1053℃, the phosphorus removal water pressure is 28.8MPa, the finish rolling temperature is 969℃, and the speed of 1 rack roller is 0.22m / s.

[0082] The heat treatment process is specifically: quenching at 880℃ for 90 min, and then water cooling; then tempering at 590℃ for 160 min, and then water cooling to 25-40℃.

[0083] The tempering sorbite area content of the product surface is 75%, the residual amount is ferrite 23% and bainite 2%.

[0084] Comparative example 4 The production method of the wind power anchor bolt steel comprises the following process flow: adopting ingredients (scrap steel+30% DRI)-electric furnace-LF refining-continuous casting-heating-rolling-straightening-inspection; The converter smelting process adopts high pulling and supplementary blowing, and controls the converter end composition C is 0.06%, P is 0.005%.

[0085] The LF refining process adds lime, refining slag and slag dissolving agent, ensures the good fluidity and basicity R3.2 of the refining slag, the white slag retention time is 28 minutes, and the aluminum control is 600ppm.

[0086] Continuous casting process, continuous casting billet (150-165mm) x (150-165mm), superheat 24℃, crystallizer electric stirring frequency 4Hz, current 190A; end electromagnetic stirring current is 160A, frequency is 8HZ; control continuous casting constant speed 1.4m / min, specific water volume is 0.45L / kg.

[0087] Heating process, heating furnace control soaking section temperature 1151℃, heating time 228min.

[0088] Rolling process, open rolling temperature 1053℃, dephosphorization water pressure 28.8MPa, finish rolling temperature 969℃, 1frame roller speed from 0.22m / s.

[0089] Heat treatment process, specifically: quenching at 880℃, holding for 90min, then water cooling; then tempering at 590℃, holding for 160min, then water cooling to 25-40℃.

[0090] The product surface tempering sorbite area content is 93%, the balance is ferrite 4% and bainite 3%.

[0091] Each example and comparative example is detected according to standard GB / 228.1 "metal material tensile test part 1 room temperature test method" and GB / T229 "metal material charpy pendulum impact test method", and the results are shown in table 2.

[0092] Table 1 component content (wt%) of each example and comparative example of wind power anchor bolt steel

[0093] Table 2 performance of each example and comparative example

[0094] Examples 1-5 can meet the requirements of tensile strength ≥1130MPa, yield strength ≥1040MPa, elongation ≥15%, reduction of area ≥55%, impact energy at-45℃ ≥80J, and surface core hardness difference ≤1.5HRC.

[0095] In comparative example 1, C element is out of the lower limit of the control range, resulting in unqualified strength index.

[0096] In comparative example 2, Cr element is out of the lower limit of the control range, resulting in unqualified strength index, and insufficient hardenability, the core does not form martensite during quenching, and does not form tempered sorbite during tempering, resulting in low core hardness.

[0097] In the comparative example 3, the Mo element is beyond the lower limit of the control range, which causes the strength close to the lower limit to exist the risk of nonconformity, and the core does not form martensite during quenching and does not form tempered sorbite during tempering, resulting in the hardness of the core being low.

[0098] In the comparative example 4, the N element is nearly 1 times beyond the control due to not passing the RH, which causes the brittle nitride Fe4N to segregate at the grain boundary, resulting in plasticity nonconformity.

[0099] In the present application, the chemical composition design is good in matching of each alloying element, and the target composition is adjusted and controlled to achieve the best matching of strength and toughness. The addition of Ni can have good toughness and small notch sensitivity, the content of Mn, Cr and Mo is increased to ensure the tempering stability; and in order to improve the low temperature impact performance, the residual elements are controlled by scrap steel + direct reduced iron (DRI), the purity of the steel needs to be ensured, the content of P and S is less than 0.010%, and the content of Al is controlled to be 0.030-0.038% to refine the grain.

[0100] The manufacturing method of the low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel provided by the present application does not add new equipment compared with the existing manufacturing equipment.

[0101] Compared with the traditional “blast furnace + converter” long process technology with the same production scale, the carbon dioxide emission can be reduced by 50-70%, and the addition of 30% DRI can reduce the carbon emission of per ton of steel from 2-2.5 tons to about 1.0 ton. In addition, the emissions of sulfur dioxide, nitrogen oxides and smoke dust are reduced by more than 30%, 70% and 80% respectively.

[0102] The steel prepared by the experiment has a chemical range similar to that of the 42CrMoA steel in GB / T 3077-2015, and the strength and plasticity indexes are significantly higher than those of the national standard 42CrMoA steel. The manufacturing technical performance of the present application meets the requirements of the technical agreement, and the product qualified rate can reach more than 95%. The steel prepared has high purity, the non-metallic inclusions are A class ≤1.5 level, B class ≤1.5 level, C class ≤1.5 level, D class ≤0.5 level and DS ≤0.5 level, all of which exceed the national standard of special high-quality steel. At the same time, the overall heat treatment mechanical properties are tensile strength ≥1130MPa, yield strength ≥1040MPa, elongation ≥15%, reduction of area ≥55%, impact energy at-45℃ ≥80J, and the difference between the surface hardness and the core hardness is ≤1.5HRC. All the indexes are better than the performance indexes of the round steel manufactured by the prior art.

[0103] The above examples are only used to illustrate but not to limit the technical solutions of the present application. Although the present application is described in detail with reference to the above examples, those skilled in the art should understand that the present application can be modified or equivalently replaced without departing from the spirit and scope of the present application, and any modification or partial replacement should be covered in the scope of claims of the present application.

Claims

1. A low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel, characterized in that, The wind power anchor bolt steel has the following chemical components and mass percentage: C: 0.40-0.46%, Mn: 0.70-1.10%, Si: 0.20-0.28%, P≤0.010%, S≤0.010%, Cr: 1.10-1.45%, Mo: 0.18-0.25%, Alt: 0.030-0.070%, Ni: 0.03-0.10%, N≤50ppm, O≤12ppm, H≤1.5ppm, and the rest is Fe and inevitable impurities.

2. The low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel according to claim 1, characterized in that, The wind power anchor bolt steel has a diameter of Φ20-55mm; the wind power anchor bolt steel is quenched and tempered through a heat treatment process, and the tempering sorbite area content of the product surface is ≥92%, and the rest is ferrite and bainite; and the surface core hardness difference is ≤1.5HRC. 3.The low-carbon and low-temperature-resistant high-strength wind power anchor bolt steel according to claim 1, characterized in that, The wind power anchor bolt steel has a tensile strength of ≥1130MPa, a yield strength of ≥1040MPa, an elongation of ≥15%, a reduction of area of ≥55%, and an impact energy at-45℃ of ≥80J.

4. The production method of the low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel according to any one of claims 1-3, characterized in that, The production method comprises the following steps: batching, electric furnace smelting, LF refining, RH refining, continuous casting, heating, rolling, straightening, heat treatment, and flaw detection; in the batching step, scrap steel and 20-30% direct reduced iron (DRI) are used as raw materials; in the rolling step, the compression ratio is 1.5-1.7, the rolling speed is 0.21-0.24m / s, the opening rolling temperature is 1050±15℃, and the final rolling temperature is 950-980℃.

5. The method for producing a low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel according to claim 4, characterized in that, In the electric furnace smelting step, high-lifting complementary blowing is adopted, and the end-point composition of the electric furnace is controlled to be C≥0.06% and P≤0.008%.

6. The method for producing a low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel according to claim 4, characterized in that, In the LF refining step, lime, refining slag, and slag refining agent are added to ensure good fluidity of the refining slag, the basicity R is ≥3.2, the white slag retention time is ≥25 minutes, and the aluminum control is 300-700ppm.

7. The method for producing a low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel according to claim 4, characterized in that, In the RH refining step, the vacuum degree is maintained at 90-100Pa for 10-20min, and the soft blowing time is 20-25min.

8. The production method of the low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel according to any one of claims 4-6, characterized in that, In the continuous casting step, the superheat is 20-30℃, the crystallizer electric stirring frequency is 4Hz±0.5Hz, and the current is 190A±10A; the terminal electromagnetic stirring current is 140-160A, and the frequency is 8-10HZ.

9. The method for producing a low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel according to any one of claims 4-6, characterized in that, In the continuous casting step, the continuous casting billet specification is 150-165mm×150-165mm, and the continuous casting constant speed is controlled to be 1.4-1.5m / min.

10. The method for producing a low-carbon, low-temperature-resistant, high-strength wind power anchor bolt steel according to any one of claims 4-6, characterized in that, In the heating step, the heating furnace controls the soaking section temperature to be 1130-1180℃; in the rolling step, the phosphorus removal water pressure is 25-30MPa, sawing is performed, pit slow cooling is performed for 24-36 hours; in the heat treatment step, quenching is performed at 850-890℃, the medium is water, the holding time is 90-120min, tempering is performed at 580-615℃, the holding time is 150-180min, and then water cooling is performed at 25-40℃; in the flaw detection step, ultrasonic and magnetic flux leakage flaw detection are adopted, and the round steel surface crack is ≤0.2mm.

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