Production method of thin-specification and wide-width wind power steel plate with thickness of less than 12mm

Abstract

The invention discloses a manufacturing method of a thin-specification wide-width wind power steel plate with the thickness smaller than 12 mm. The thin-specification wide-width wind power steel plate comprises, by weight, 0.07%-0.10% of C, 0.20%-0.30% of Si, 1.40%-1.55% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.005% of S, 0.020%-0.030% of Nb, 0.020%-0.035% of Als and the balance Fe and inevitable impurities. The low-carbon-Mn-Nb microalloying design is adopted, the mechanical property and the impact property are guaranteed, meanwhile, the performance of the steel plate in the length direction and the width direction is uniform, stable and reliable, the good plate shape is achieved, the problem of high strength-low temperature toughness-thin specification and width-plate shape matching is effectively solved, and the steel plate is used for manufacturing wind power towers.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wind power steel production, and particularly relates to a production method of thin-gauge wide-width wind power steel plates with a thickness of less than 12 mm. BACKGROUND

[0002] Wind power steel plates are mainly used for manufacturing wind power towers, and the annual demand is more than ten million tons. According to statistics, a 10-megawatt wind turbine is as high as 140 meters, and about 450 tons of steel plates are required. The steel plates need to withstand harsh environments such as strong winds, sandstorms and low temperatures, and have requirements such as high strength and high toughness, fatigue resistance, low temperature resistance and easy welding. The yield strength of 355 MPa steel plate is still the mainstream product, and although the demand proportion of thin-gauge wide-width steel plates with a thickness of less than 12 mm is not large, it is directly related to the contract package acceptance capacity and the stability of the quality, which needs attention.

[0003] A domestic factory produces Q355NE wind power steel plates with a thickness of less than 12 mm and a width of more than 3000 mm, and the performance of the steel plates in the length and width directions is unstable, especially the impact energy appears in batches of unqualified, which brings great loss to the enterprise and downstream users, and needs to be solved urgently.

[0004] Chinese patent CN 114525453 A discloses "a thin-gauge bridge steel and a production method thereof". The patent provides a method for producing thin-gauge bridge steel by composite rolling. The disadvantage is that it is suitable for producing composite bridge steel plates, but not for conventional steel materials.

[0005] Chinese patent CN 110735085 A discloses "a manufacturing method of thin-gauge Q345qE and Q370qE steel plates". The patent does not control rolling, and the steel plate cooling stage adopts the method of natural air cooling without water spraying accelerated cooling. The steel plate has good performance, good plate shape control, reduces the manufacturing difficulty of thin-gauge Q345qE and Q370qE, and has the advantages of thin thickness specification. The disadvantage is that it needs to be opened and rolled, which increases energy consumption and reduces production efficiency.

[0006] Chinese patent CN 102766806 B discloses "an ultra-wide thin-gauge bridge structural steel plate and a production method thereof". The Q345q bridge steel with a thickness of 6-12 mm is produced by normalizing. The disadvantage is that the delivery is normalized, and the carbon equivalent is high. SUMMARY

[0007] The purpose of the present application is to provide a production method of thin-gauge wide-width wind power steel plates with a thickness of less than 12 mm, and the produced steel plates meet the requirements of yield strength ≥355 MPa, tensile strength 470-630 MPa, elongation after fracture ≥22%, impact energy at-40℃ ≥100 J, and the performance of the steel plates in the length and width directions is stable and reliable.

[0008] To solve the above technical problems, the present application adopts the following technical solutions:

[0009] The main steps and process parameters of the production method of the thin specification wide-width wind power steel plate with a thickness of 12 mm or less are as follows:

[0010] S1 molten iron pretreatment: the molten iron is desulfurized and dephosphorized by KR stirring method, S in the molten iron is less than or equal to 0.005%, and P is less than or equal to 0.015%;

[0011] S2 converter smelting: the temperature of the molten iron entering the converter is greater than 1260℃, and the P content of the molten steel is less than or equal to 0.010%, and the S content is less than or equal to 0.004%;

[0012] S3 LF refining: the composition of the molten steel is accurately controlled in the LF stage, and the S content is less than or equal to 0.004% after deoxidization and alloying;

[0013] S4 RH vacuum treatment: in this treatment mode, the vacuum time is kept for more than 15 minutes, the pure degassing time is greater than 15 minutes, and the soft blowing time is greater than 15 minutes, so that the hydrogen content of the off-line molten steel is less than or equal to 1.6 ppm, the oxygen content is less than or equal to 30 ppm, and the nitrogen content is less than or equal to 50 ppm;

[0014] S5 slab continuous casting: dynamic soft reduction is adopted, the soft reduction position is 8, 9 and 10 segments, and the total soft reduction amount is 7-8 mm; electromagnetic stirring is adopted, the stirring position is at the outlet of the 3rd segment and the inlet of the 4th segment, the electromagnetic stirring frequency is 5 Hz, and the current is 350 A; protective casting is adopted throughout the process, the mold uses special low-carbon protective slag, and the molten steel is strictly prohibited from contacting air; the constant speed process is adopted, the casting speed is controlled at 0.95-1.0 m / min, the casting speed is kept constant, and the casting speed is strictly prohibited from being frequently changed; finally, a 250 or 300 mm thick continuous casting billet is produced, and the center segregation of the continuous casting billet is controlled to be less than or equal to 3.0 level of C class;

[0015] S6 heating: the slab is heated in a walking beam furnace, and cold charging, hot charging and direct charging can be used, the atmosphere in the furnace is strictly controlled, the slab heating temperature and heating time are ensured, the heating temperature is 1210℃-1240℃, the total time in the furnace is greater than 270 min, the heating segment time is greater than 120 min, and the soaking segment time is greater than 30 min, so that the alloy elements are fully solid-solved, and the slab temperature is uniform;

[0016] S7 rolling: the rolling adopts two-stage controlled rolling, usually referred to as rough rolling stage and finish rolling stage; rough rolling is carried out on a 3800 mm rough rolling mill, the rolling temperature is higher than 1170℃, and the single pass relative reduction rate is controlled to be more than 15% for at least two passes; the finish rolling opening thickness is 4 times the finished product thickness, the finish rolling opening temperature is less than 1000℃, and the finish rolling temperature is less than 800℃;

[0017] S8 cooling: the steel plate is air cooled after rolling without accelerated cooling;

[0018] The chemical composition of the steel plate is C: 0.07-0.10%, Si: 0.20-0.30%, Mn: 1.40-1.55%, P: ≤0.015%, S: ≤0.005%, Nb: 0.020-0.030%, Als: 0.020-0.035%, and the balance of Fe and inevitable impurities.

[0019] Further, the chemical composition of the steel plate is C: 0.08%, Si: 0.22%, Mn: 1.50%, P: 0.014%, S: 0.001%, Nb: 0.025%, Als: 0.022%, and the balance of Fe and inevitable impurities.

[0020] Further, the chemical composition of the steel plate is C: 0.08%, Si: 0.24%, Mn: 1.49%, P: 0.011%, S: 0.001%, Nb: 0.028%, Als: 0.025%, and the balance of Fe and inevitable impurities.

[0021] Further, the chemical composition of the steel plate is C: 0.09%, Si: 0.25%, Mn: 1.51%, P: 0.011%, S: 0.002%, Nb: 0.027%, Als: 0.023%, and the balance of Fe and inevitable impurities.

[0022] Further, the rough rolling opening temperature is 1200-1225°C.

[0023] Further, the finish rolling opening temperature is 972-987°C.

[0024] Further, the finish rolling final rolling temperature is 774-796°C.

[0025] The main components in the application are described in detail:

[0026] Carbon: Carbon is the most important and economical solid solution strengthening element, but the increase of carbon content will reduce plasticity and impact toughness, and deteriorate the welding performance. Reducing carbon while needing other alloys to make up for the strength will increase the manufacturing cost. The appropriate amount of carbon is controlled at 0.07-0.10% in combination with the production process.

[0027] Silicon: Silicon has a solid solution strengthening effect, but also deteriorates plasticity and toughness, and the appropriate amount is controlled at 0.20-0.30%.

[0028] Manganese: Manganese has a solid solution strengthening effect, but too high Mn will affect the welding performance of the steel, and also exacerbate the center segregation of the casting blank, causing serious banded structure of the product, and further affecting the impact toughness. The appropriate amount of Mn is controlled at 1.40-1.55%.

[0029] Nb: fine-grain strengthening and precipitation strengthening, suitable amount of Nb: 0.020-0.030%.

[0030] Compared with the prior art, the present application has the beneficial technical effects:

[0031] (1) A manufacturing method of a thin-gauge 355MPa-grade wind power steel plate, suitable for a thickness of ≤12mm.

[0032] (2) The present application adopts low-carbon-Mn-Nb micro-alloying design in terms of components, which can effectively prevent abnormal growth of austenite grains during heating and rolling stages, ensure the grain size of austenite, ensure the grain size of subsequent natural cooling phase change, ensure the strength, and the present application adopts air cooling mode, avoiding the problem of poor plate shape of thin-gauge steel plates caused by accelerated cooling.

[0033] (3) The present application obtains ferrite+pearlite microstructure by controlling rolling temperature and air cooling, and the performance of the steel plate in the length direction and the width direction is stable and reliable. BRIEF DESCRIPTION OF DRAWINGS

[0034] The present application will be further described below in combination with the drawings.

[0035] Figure 1 It is an optical metallographic structure diagram of the near-surface of the steel plate of Example 2 of the present application.

[0036] Figure 2 It is a high-magnification fracture appearance diagram of the steel plate of Example 2 of the present application. DETAILED DESCRIPTION

[0037] The present application will be further described below in combination with the drawings.

[0038] The chemical composition of the steel plate of the present application is as follows in terms of percentage by weight: C: 0.07-0.10%, Si: 0.20-0.30%, Mn: 1.40-1.55%, P: ≤0.015%, S: ≤0.005%, Nb: 0.020-0.030%, Als: 0.020-0.035%, and the balance being Fe and inevitable impurities. In addition, the present application also provides a manufacturing method of the steel plate.

[0039] The main steps and process parameters are as follows:

[0040] S1 molten iron pretreatment: the molten iron is desulfurized and dephosphorized by KR stirring method, S in the molten iron is ≤0.005%, and P is ≤0.015%;

[0041] S2 Converter smelting: the temperature of molten iron into the converter is greater than 1260℃, to ensure that the P of molten steel is less than or equal to 0.010%, and the S is less than or equal to 0.004%.

[0042] S3 LF refining: the composition of molten steel is accurately controlled in the LF stage, deoxidation and alloying, and the S is less than or equal to 0.004%.

[0043] S4 RH vacuum treatment: in this treatment mode, the vacuum time is kept for more than 15 minutes, the pure degassing time is greater than 15 minutes, and the soft blowing time is greater than 15 minutes, to ensure that the hydrogen content of off-line molten steel is less than or equal to 1.6ppm, the oxygen content is less than or equal to 30ppm, and the nitrogen content is less than or equal to 50ppm.

[0044] S5 slab continuous casting: dynamic soft reduction, electromagnetic stirring, protective casting and constant speed process are adopted, and finally 250 or 300mm thick continuous casting billets are produced, and the center segregation of the billets is controlled to be less than or equal to 3.0 level of class C.

[0045] S6 heating: the slab is heated in a walking beam furnace, and cold charging, hot charging and direct charging can be used, the atmosphere in the furnace is strictly controlled, the slab heating temperature and heating time are ensured, the heating temperature is 1210℃-1240℃, the total time in the furnace is greater than 270min, the heating time is greater than 120min, and the soaking time is greater than 30min, to ensure that the alloy elements are fully solid-solved and the slab temperature is uniform.

[0046] S7 rolling: the rolling adopts two-stage controlled rolling, usually referred to as rough rolling stage and finishing rolling stage. Rough rolling is carried out on a 3800mm rough rolling mill, the opening rolling temperature is above 1170℃, and the single pass relative reduction rate is controlled to be more than 15% for at least two passes. The finishing rolling opening rolling thickness is 4 times the finished product thickness, the finishing rolling opening rolling temperature is less than 1000℃, and the finish rolling temperature is less than 800℃.

[0047] S8 cooling: the steel plate is air cooled after rolling without accelerated cooling.

[0048] The application will be described in detail below in combination with actual examples.

[0049] Table 1 lists the chemical composition of the examples, and Table 2 lists the rolling process parameters of the examples.

[0050] Table 1 Chemical composition of the examples of the application (wt%)

[0051] Examples C Si Mn P S Nb Als 1 0.08 0.22 1.50 0.014 0.001 0.025 0.022 2 0.08 0.24 1.49 0.011 0.001 0.028 0.025 3 0.09 0.25 1.51 0.011 0.002 0.027 0.023

[0052] Table 2 Rolling parameters of the examples of the application

[0053]

[0054] The mechanical properties, low temperature impact properties and cold bending properties of the steel plates of the examples of the application are tested, and the results are shown in Table 3.

[0055] Table 3 Mechanical properties of the steel plate of the embodiment of the present application

[0056]

[0057]

[0058]

[0059] The present application adopts low-carbon-Mn-Nb micro-alloying design combined with specific process flow to produce a 355MPa wind power steel plate with thickness below 12mm and width above 3000mm, the yield strength of the steel plate is ≥355MPa, the tensile strength is 470-630MPa, the elongation after fracture is ≥22%, the impact energy at-40℃ is ≥100J, the performance of the steel plate in length direction and width direction is stable and reliable, and the steel plate has good shape and is used for manufacturing wind power tower.

[0060] The above-described embodiments are only used to describe the preferred modes of the present application, and do not limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application defined by the claims.

Claims

1. A method for producing thin, wide-width wind turbine steel sheets with a thickness of less than 12mm, characterized in that, The main steps and process parameters are as follows: S1 molten iron pretreatment: Molten iron is desulfurized and dephosphorized by KR stirring method, with S≤0.005% and P≤0.015% in molten iron; S2 converter smelting: The temperature of the molten iron entering the furnace is greater than 1260℃, ensuring that the P of the molten steel exiting the furnace is ≤0.010% and S is ≤0.004%; S3 LF refining: The LF stage precisely controls the composition of molten steel, deoxidizes and alloys it, and S≤0.004%; S4 RH vacuum treatment: Using this treatment mode, the vacuum time is maintained for more than 15 minutes, the pure degassing time is greater than 15 minutes, and the soft blowing time is greater than 15 minutes, ensuring that the hydrogen content of the molten steel is ≤1.6ppm, the oxygen content is ≤30ppm, and the nitrogen content is ≤50ppm. S5 slab continuous casting: Dynamic light reduction is adopted, with light reduction positions at sections 8, 9, and 10, and a total reduction of 7-8mm; electromagnetic stirring is used, with stirring positions at the outlet of section 3 and the inlet of section 4, the electromagnetic stirring frequency is 5Hz, and the current is 350A; protective casting is used throughout the process, with the crystallizer using a special low-carbon protective slag, and contact between molten steel and air is strictly prohibited; constant casting speed process is used, with the casting speed controlled at 0.95-1.0m / min, and the casting speed is kept constant, and frequent changes in casting speed are strictly prohibited; finally, a 250 or 300mm thick continuous casting slab is produced, and the low-magnification center segregation of the slab is controlled below Class C 3.

0. S6 Heating: Slabs are heated in a walking beam furnace. Cold charging, hot charging, and direct charging are all possible. The furnace atmosphere is strictly controlled to ensure the slab heating temperature and heating time. The heating temperature is 1210℃~1240℃. The total furnace time is greater than 270min, of which the heating section time is greater than 120min and the soaking section time is greater than 30min, to ensure the full solidification of alloying elements and uniform slab temperature. S7 Rolling: The rolling process adopts a two-stage controlled rolling process, usually referred to as the roughing stage and the finishing stage; the roughing is carried out on a 3800mm roughing mill, with an initial rolling temperature of 1170℃ or higher, and the relative reduction rate per pass is controlled at least 15% or higher for at least two passes; the initial rolling thickness of the finishing is 4 times the finished product thickness, the initial rolling temperature of the finishing is <1000℃, and the final rolling temperature is <800℃; S8 cooling: Air cooling of the steel plate after rolling, without accelerating the cooling process; The chemical composition of the steel plate, by weight percentage, is C: 0.07-0.10%, Si: 0.20-0.30%, Mn: 1.40-1.55%, P: ≤0.015%, S: ≤0.005%, Nb: 0.020-0.030%, Als: 0.020-0.035%, with the balance being Fe and unavoidable impurities.

2. The method for producing thin, wide wind turbine steel plates with a thickness of less than 12 mm according to claim 1, characterized in that, The chemical composition of the steel plate by weight percentage is C: 0.08%, Si: 0.22%, Mn: 1.50%, P: 0.014%, S: 0.001%, Nb: 0.025%, Als: 0.022%, with the balance being Fe and unavoidable impurities.

3. The method for producing thin, wide wind turbine steel plates with a thickness of less than 12 mm according to claim 1, characterized in that, The chemical composition of the steel plate by weight percentage is C: 0.08%, Si: 0.24%, Mn: 1.49%, P: 0.011%, S: 0.001%, Nb: 0.028%, Als: 0.025%, with the balance being Fe and unavoidable impurities.

4. The method for producing thin, wide wind turbine steel plates with a thickness of less than 12 mm according to claim 1, characterized in that, The chemical composition of the steel plate by weight percentage is C: 0.09%, Si: 0.25%, Mn: 1.51%, P: 0.011%, S: 0.002%, Nb: 0.027%, Als: 0.023%, with the balance being Fe and unavoidable impurities.

5. The method for producing thin, wide wind turbine steel plates with a thickness of less than 12 mm according to claim 1, characterized in that, The roughing rolling temperature is 1200-1225℃.

6. The method for producing thin, wide wind turbine steel plates with a thickness of less than 12 mm according to claim 1, characterized in that, The initial rolling temperature for finishing rolling is 972-987℃.

7. The method for producing thin, wide wind turbine steel plates with a thickness of less than 12 mm according to claim 1, characterized in that, The finishing rolling temperature is 774-796℃.

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