Normalizing rolling process high-toughness wind power steel plate and preparation method thereof

Abstract

The invention provides a normalizing rolling process high-toughness wind power steel plate and a preparation method thereof, and relates to the technical field of high-strength structural steel production. The steel plate provided by the invention comprises the following components in percentage by mass: 0.11%-0.15% of C, 0.30%-0.40% of Si, 1.50%-1.70% of Mn, 0%-0.02% of Al, 0.03%-0.04% of Nb, 0.06%-0.11% of V, 0.01%-0.015% of N and the balance of Fe and other inevitable impurities. And the thickness t of the steel plate is 60-120mm. The high-strength and high-toughness wind power steel plate prepared by the invention has the advantages of high thickness, high strength, high toughness, low production cost and simple preparation process flow.

Description

Technical Field

[0001] The present invention relates to the technical field of high-strength structural steel production, and in particular to a normalizing rolling process high-strength and toughness steel plate for wind power and a preparation method thereof. Background Art

[0002] Wind energy resources are a clean and renewable energy source. The construction of wind power projects continues to extend to the high-altitude and cold northwest and deep sea areas with abundant wind sources. In extremely harsh environments such as sandstorms, sea waves and tides, and polar high and cold regions, the alternating impact large loads have put forward higher requirements on the strength, thickness, and welding performance of wind power steel plates.

[0003] Chinese patent CN103014282A provides "a method for producing high-strength and good low-temperature toughness wind power steel plates". The composition of the patented steel plates contains precious metal elements such as Ni, which increases the production cost. The preparation process adopts controlled rolling air cooling + tempering heat treatment. The process flow is relatively complicated, and the core impact energy at -40℃ is ≥82J, which cannot meet the future demand for wind power steel.

[0004] Chinese patent CN112831724A provides "a S420 high-strength low-temperature structural steel and its normalizing rolling preparation method". The composition of the structural steel contains a large amount of precious metal elements such as Ni and Cr, which increases the production cost. The cooling process is relatively complicated and requires slow cooling for 48 hours. The production efficiency is low. The thickness of the produced steel plate is ≤80mm and the elongation is ≥21.5%, which is relatively low, affecting the strength and toughness of the steel.

[0005] In summary, developing a steel plate to solve the above-mentioned shortcomings, which is used to produce components such as towers of wind turbine generator sets, is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] The purpose of the present invention is to provide a high-strength and high-toughness steel plate for wind power generation by a normalizing rolling process and a preparation method thereof, so as to achieve the advantages of high strength and high toughness of the steel plate for wind power generation.

[0007] The technical solution adopted by the present invention to solve the above technical problems is: On the one hand, the present invention provides a high-strength and toughness steel plate for wind power generation produced by a normalizing rolling process. The steel plate for wind power generation is produced by a normalizing rolling process. The steel plate components include, by mass percentage, C: 0.11% to 0.15%, Si: 0.30% to 0.40%, Mn: 1.50% to 1.70%, Al: 0% to 0.02%, Nb: 0.03% to 0.04%, V: 0.06% to 0.11%, N: 0.01% to 0.015%, and the remainder is Fe and other inevitable impurities; the steel plate thickness t is 60 to 120 mm.

[0008] Furthermore, in terms of mass percentage, the steel plate composition includes C: 0.11%-0.13%, Si: 0.30%-0.35%, Mn: 1.53%-1.65%, Al: 0%-0.01%, Nb: 0.03%-0.035%, V: 0.06%-0.1%, N: 0.013%-0.015%, and the remainder is Fe and other inevitable impurities; the steel plate thickness t is 60-120 mm.

[0009] Furthermore, the metallographic structure of the steel plate is ferrite and pearlite, wherein the ferrite content is 80% to 90%, and the average grain size of the ferrite is 6 to 10 μm.

[0010] Furthermore, the mechanical properties of the steel plate are: yield strength ≥380MPa, tensile strength ≥500MPa, elongation ≥30%, and impact energy at -50°C ≥100J.

[0011] Furthermore, the carbon equivalent CEV of the steel plate is ≤0.48%, and the welding cold crack sensitivity index PCM is ≤0.24%.

[0012] On the other hand, the present invention also provides a method for preparing a high-strength and toughness steel plate for wind power generation by a normalizing rolling process, which is used to prepare the above-mentioned steel plate, comprising the following steps: S1, heating the steel billet to 1200-1250°C and keeping the temperature uniform; S2, rolling; air cooling to room temperature after rolling, the cooling rate is 4℃ / min~6℃ / min.

[0013] Furthermore, the rolling of S2 adopts two-stage rolling. In the first stage, the parameters are: the starting rolling temperature is 1130-1180°C, and the final rolling temperature is ≥1080°C.

[0014] Furthermore, the total rolling reduction of the first stage rolling is greater than 50%, the single rolling reduction of at least two rolling passes is greater than 18%, and the rolling roller speed is ≤1.5m / s.

[0015] Furthermore, in the second stage of rolling, the parameters are: starting rolling temperature 1000-1050°C, and final rolling temperature ≥950°C.

[0016] Furthermore, the total rolling reduction of the second stage rolling is greater than 40%, the single rolling reduction of at least two rolling passes is greater than 16%, and the rolling roller speed is ≤1.5m / s.

[0017] Compared with the prior art, the advantages of the present invention are: The present invention reduces production costs by reasonably adjusting the proportion of alloy elements, adopting lower C content and higher N content, and adding micro-alloy elements such as 0.03% to 0.04% Nb element and 0.06% to 0.11% V element, thereby achieving the advantages of high strength and high toughness of steel plates for wind power. The present invention combines the normalizing rolling process, obtains fine-grained ferrite and pearlite structures through a two-stage rolling process, and has a simple preparation process flow, thereby obtaining a high-strength and high-thickness steel plate for wind power with a yield strength of ≥380MPa, a tensile strength of ≥500MPa, an elongation of ≥30%, and an impact energy of ≥100J at -50℃, and has good mechanical performance indicators, achieving high strength and toughness control. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference numerals refer to like components throughout the drawings.

[0019] Figure 1 This is the metallographic structure diagram of the steel plate surface in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0021] On the one hand, the present invention provides a high-strength and tough steel plate for wind power generation produced by a normalizing rolling process. The steel plate for wind power generation is produced by a normalizing rolling process. The steel plate components include, by mass percentage, C: 0.11%-0.15%, Si: 0.30%-0.40%, Mn: 1.50%-1.70%, Al: 0.01%-0.02%, Nb: 0.03%-0.04%, V: 0.06%-0.11%, N: 0.01%-0.015%, and the remainder is Fe and other inevitable impurities; the steel plate thickness t is 60-120 mm.

[0022] Normalizing rolling is a rolling method that performs final deformation within a certain temperature range. It can make the material state the same as that of supplementary normalizing, and its mechanical property specifications are also the same as those of supplementary normalizing. The high-strength and toughness steel plate for wind power described in the embodiment of the present invention refers to a steel plate with a yield strength of ≥380MPa and a tensile strength of ≥500MPa, which is used for wind power towers.

[0023] The present invention reasonably adjusts the ratio of alloy elements, adopts a lower C content and a higher N content, and adds micro-alloy elements such as 0.03% to 0.04% Nb and 0.06% to 0.11% V to refine the ferrite grain size of the phase transformation during the rolling process of the steel plate, thereby improving the strength and toughness of the steel. The addition of Nb and V elements in the composition is conducive to the refinement of the ferrite phase transformation.

[0024] By adding Al, a nitrogen-fixing element, the free nitrogen is prevented from destroying the toughness of the heat-affected zone, and the steel has a good nitrogen-fixing effect.

[0025] In some embodiments, the high-strength and toughness steel plate for wind power produced by the normalizing rolling process includes, by mass percentage, C: 0.11%~0.13%, Si: 0.30%~0.35%, Mn: 1.53%~1.65%, Al: 0%~0.01%, Nb: 0.03%~0.035%, V: 0.06%~0.1%, N: 0.013%~0.015%, and the remainder is Fe and other unavoidable impurities; the steel plate thickness t is 60~120mm.

[0026] On the basis of the above embodiment, the steel plate composition further includes, by mass percentage: P: 0.002%-0.005%, S: 0.001%-0.003%.

[0027] The reasons for limiting the composition of the ingot of the high-strength and toughness steel plate for wind power generation by normalizing rolling process and the method for producing the same in the present invention are explained below, and only % is used to represent the mass percentage in the composition.

[0028] C is an element that increases the hardenability and hardenability of steel, and can significantly increase the strength and hardness of steel. For relatively thick steel plates, when the carbon content is too low, it is difficult to ensure the strength of the thick plate, but when the C content is higher than 0.15%, the plasticity, toughness and welding performance of the steel will be significantly reduced. Therefore, the C content of the present invention is controlled within 0.11%≤C≤0.15%.

[0029] Si improves the strength and hardness of steel by solid solution strengthening. When the Si content exceeds 0.40%, the plasticity and toughness of the steel will be greatly reduced and the temper brittleness of the steel will be increased. Therefore, the Si content of the present invention is controlled within 0.30%≤Si≤0.40%.

[0030] Mn element is a good deoxidant and desulfurizer, which can refine grains and improve the strength of steel. 1% Mn can increase the tensile strength by about 100 MPa. However, when the Mn content exceeds 1.70%, the component segregation of the steel is serious, which affects the uniformity of the structure of the steel plate. Therefore, the Mn content of the present invention is controlled within 1.50%≤Mn≤1.70%.

[0031] The Al element can be used for deoxidation and nitrogen determination, improving the purity and fatigue strength of steel, and improving its wear resistance. However, when the Al content is too high, the inclusions of aluminum and oxygen increase, the steel is prone to cracking, and the fatigue life and welding performance of the steel are affected. Therefore, the Al content of the present invention is controlled within 0.005%≤Al≤0.01%.

[0032] The Nb element can delay austenite recrystallization, reduce phase transition temperature, refine grain size, increase steel plate strength and improve low temperature toughness. However, when the Nb content is high, it will affect toughness and welding performance, so the Nb content of the present invention is controlled within 0.03%≤Nb≤0.04%.

[0033] V is a strong carbide-forming element that can combine with C in steel to form carbides. When carbides are dispersed and precipitated, they can refine the grains, improve the strength and toughness of the steel plate, and improve the welding performance of the steel plate. However, when the V content exceeds 0.11%, carbides will aggregate and reduce the strength of the steel. Therefore, the V content of the present invention is controlled to be 0.06%≤V≤0.11%.

[0034] The N element has a solid solution strengthening effect, and combines with Cr, Ti, Al and other elements in the steel to form stable nitrides, thereby increasing the strength and hardness of the steel, improving fatigue performance, etc. When the nitrogen content exceeds 0.015%, the number and size of nitrogen inclusions will increase, which will damage the comprehensive mechanical properties of the steel. Therefore, the nitrogen content of the present invention is controlled within 0.01%≤N≤0.015%.

[0035] P is an impurity element in steel, which will damage the toughness of the steel plate and the heat affected zone of welding. Therefore, the P content is controlled below 0.005%.

[0036] S is an impurity element in steel, which will form sulfide inclusions and become a crack source. Therefore, the S content is controlled below 0.003%.

[0037] In some embodiments, the metallographic structure of the high-strength and toughness wind power steel plate produced by the normalizing rolling process is ferrite and pearlite, wherein the ferrite content is 80% to 90%, and the average grain size of the ferrite is 6 to 10 μm.

[0038] By adopting a lower C content and a higher N content, and adding micro-alloying elements such as 0.03% to 0.04% Nb and 0.06% to 0.11% V, the austenite recrystallization during the steel plate rolling process is suppressed, the austenite of the steel is flattened during the rolling process, the area of ​​the deformed austenite is increased, and the γ→α phase transformation is promoted. At the same time, Nb micro-alloying also plays a certain precipitation strengthening role, which is also beneficial to the refinement of the ferrite phase transformation.

[0039] In some embodiments, the high-strength and toughness steel plate for wind power generation produced by the normalizing rolling process has the following mechanical properties: yield strength ≥380MPa, tensile strength ≥500MPa, elongation ≥30%, and -50°C impact energy ≥100J. In some embodiments, the yield strength is 460MPa.

[0040] The steel plate for wind power produced by the present invention achieves good strength-toughness matching, meets the performance requirements of high-strength and high-toughness steel plates for wind power, has good mechanical performance indicators, and also has a good high-strength level.

[0041] In some embodiments, the carbon equivalent CEV of the steel plate is ≤0.48%, and the welding cold crack sensitivity index PCM is ≤0.24%.

[0042] In order to ensure that the strength of wind power steel plates does not decrease significantly after normalizing and has good welding performance, the carbon equivalent should not be too large or too small. Therefore, the carbon equivalent is controlled at 0.40%≤CEV≤0.48%, and the welding cold crack sensitivity index PCM≤0.24%. The calculation formulas of each index are shown in (1) and (2) below: CEV(%)=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15 (1) PCM(%)=C+Si / 30+Mn / 20+Cu / 20+Ni / 60+Cr / 20+Mo / 15+V / 10+5B (2) The present invention adopts multiple technologies to achieve the effects of grain refinement, precipitation strengthening and heat affected zone toughening.

[0043] On the other hand, the present invention also provides a method for preparing a high-strength and toughness steel plate for wind power generation by a normalizing rolling process, which is used to prepare the steel plate described in any of the above embodiments, comprising the following steps: S1, heating the steel billet to 1200-1250°C and keeping the temperature uniform; S2, rolling; air cooling to room temperature after rolling, the cooling rate is 4℃ / min~6℃ / min.

[0044] The present invention reasonably adjusts the ratio of alloy elements, adopts a lower C content and a higher N content, and adds micro-alloy elements such as 0.03% to 0.04% Nb and 0.06% to 0.11% V to refine the ferrite grain size of the phase transformation during the rolling process of the steel plate, thereby improving the strength and toughness of the steel. The addition of Nb and V elements in the composition is conducive to the refinement of the ferrite phase transformation.

[0045] In some embodiments, the insulation time of S1 is controlled at 80-100 min.

[0046] In some embodiments, the rolling of S2 is carried out in two stages. In the first stage, the parameters are as follows: the starting rolling temperature is 1130-1180°C, and the final rolling temperature is ≥1080°C.

[0047] In some embodiments, the total rolling reduction of the first stage rolling is greater than 50%, at least two rolling passes have a single rolling reduction greater than 18%, and the rolling roller speed is ≤1.5 m / s.

[0048] In some embodiments, the second stage rolling has the following parameters: starting rolling temperature is 1000-1050°C, and final rolling temperature is ≥950°C.

[0049] In some embodiments, the total rolling reduction of the second stage rolling is greater than 40%, at least two rolling passes have a single rolling reduction greater than 16%, and the rolling roller speed is ≤1.5 m / s.

[0050] By generating a large number of deformation bands and high dislocation density in austenite crystals, the nucleation rate of ferrite is increased to obtain a fine grain structure.

[0051] In some embodiments, the metallographic structure of the steel plate obtained according to the above preparation method is ferrite and pearlite, wherein the ferrite content is 80% to 90%, and the average grain size of the ferrite is 6 to 10 μm.

[0052] In some embodiments, the mechanical properties of the steel plate are: yield strength ≥380 MPa, tensile strength ≥500 MPa, elongation ≥30%, and -50°C impact energy ≥100 J. Example 1

[0053] This embodiment provides a method for preparing a high-strength and toughness steel plate for wind power generation by a normalizing rolling process, comprising the following steps: The billet was heated to 1220°C and kept at this temperature for 80 minutes. The first stage rolling temperature was 1150°C, and the total deformation of the first stage rolling was 55.6%, of which the finishing rolling temperature was 1024°C, the reduction rate was 40%, and the finishing rolling temperature was 968°C. After rolling, it was air-cooled to room temperature at a cooling rate of 4°C / min.

[0054] The steel plate obtained in Example 1 has a thickness of 120 mm, and the chemical composition (wt.%) of the steel plate is C: 0.13%, Si: 0.32%, Mn: 1.63%, Nb: 0.033%, V: 0.064%, Al: 0.01%, N: 0.014%, and the rest is Fe and unavoidable impurities.

[0055] The surface metallographic structure of the steel plate obtained in Example 1 is as follows Figure 1 shown.

[0056] like Figure 1As shown, the average grain size of the wind power steel plate is 9 μm, and it is composed of fine-grained ferrite and pearlite. Example 2

[0057] This embodiment provides a method for preparing a high-strength and toughness steel plate for wind power generation by a normalizing rolling process, comprising the following steps: The billet was heated to 1230°C and kept at this temperature for 90 minutes. The starting temperature of the rough rolling was 1170°C, and the total deformation of the first stage of rolling was 50%. The starting temperature of the finishing rolling was 1010°C, the reduction rate was 50%, and the final rolling temperature of the finishing rolling was 950°C. After rolling, it was air-cooled to room temperature at a cooling rate of 5°C / min.

[0058] The steel plate obtained in Example 2 has a thickness of 80 mm, and the chemical composition (wt.%) of the steel plate is C: 0.13%, Si: 0.31%, Mn: 1.64%, Nb: 0.031%, V: 0.097%, Al: 0.007%, N: 0.013%, and the rest is Fe and unavoidable impurities. The average grain size of the wind power steel plate is 7 μm, and it is composed of fine-grained ferrite and pearlite. Example 3

[0059] This embodiment provides a method for preparing a high-strength and toughness steel plate for wind power generation by a normalizing rolling process, comprising the following steps: The billet was heated to 1210°C and kept at this temperature for 85 minutes. The starting temperature of the rough rolling was 1180°C, the total deformation of the rough rolling was 52%, the starting temperature of the finishing rolling was 1040°C, the reduction rate was 50%, the final rolling temperature of the finishing rolling was 980°C, and the billet was air-cooled to room temperature after rolling at a cooling rate of 6°C / min.

[0060] The steel plate obtained in Example 3 has a thickness of 60 mm, and the chemical composition (wt.%) of the steel plate is C: 0.11%, Si: 0.31%, Mn: 1.54%, Nb: 0.030%, V: 0.063%, Al: 0.008%, N: 0.011%, and the rest is Fe and unavoidable impurities. The average grain size of the wind power steel plate is 6 μm, and it is composed of fine-grained ferrite and pearlite.

[0061] Test example The mechanical properties of the steel plates obtained in Examples 1-3 were tested, and the test results are shown in Table 1:

[0062] It can be seen from the results that Examples 1-3 all achieved good strength and toughness, meeting the performance requirements of 460 MPa-grade high-strength and toughness steel plates, and especially had good low-temperature impact energy levels.

[0063] The high-strength and toughness steel plate for wind power of the present invention reasonably adjusts the proportion of alloy elements and effectively saves resources, and cooperates with the processing method of normalizing rolling process to simplify the production process and reduce process costs. The microstructure of the steel plate is ferrite and pearlite, and the average grain size is less than 10μm. The thickness of the wind power steel plate is 60~120mm, and the yield strength is ≥380MPa, the tensile strength is ≥500MPa, the elongation is ≥30%, and the impact energy at -50℃ is ≥100J. The comprehensive mechanical properties of the steel plate are good, which is conducive to the rapid development of industries such as wind power steel and wind power equipment in the future.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-strength and tough steel plate for wind power generation by normalizing rolling process, characterized in that: The wind power steel plate is made by normalizing rolling process. Calculated by mass percentage, the steel plate components include C: 0.11%-0.15%, Si: 0.30%-0.40%, Mn: 1.50%-1.70%, Al: 0%-0.02%, Nb: 0.03%-0.04%, V: 0.06%-0.11%, N: 0.01%-0.015%, and the remainder is Fe and other inevitable impurities; the steel plate thickness t is 60-120 mm.

2. The high-strength and toughness steel plate for wind power generation by normalizing rolling process according to claim 1, characterized in that: Calculated by mass percentage, the steel plate components include C: 0.11% ~ 0.13%, Si: 0.30% ~ 0.35%, Mn: 1.53% ~ 1.65%, Al: 0% ~ 0.01%, Nb: 0.03% ~ 0.035%, V: 0.06% ~ 0.1%, N: 0.013% ~ 0.015%, and the remainder is Fe and other inevitable impurities; the steel plate thickness t is 60 ~ 120mm.

3. The high-strength and toughness steel plate for wind power generation by normalizing rolling process according to claim 1, characterized in that: The metallographic structure of the steel plate is ferrite and pearlite, wherein the ferrite content is 80%~90%, and the average grain size of the ferrite is 6~10μm.

4. The high-strength and toughness steel plate for wind power generation by normalizing rolling process according to claim 1, characterized in that: The mechanical properties of the steel plate are: yield strength ≥380MPa, tensile strength ≥500MPa, elongation ≥30%, and impact energy at -50℃ ≥100J.

5. The high-strength and toughness steel plate for wind power generation by normalizing rolling process according to claim 1, characterized in that: The carbon equivalent of the steel plate CEV≤0.48%, and the welding cold crack sensitivity index PCM≤0.24%.

6. A method for preparing a high-strength and tough steel plate for wind power generation by normalizing rolling process, used for preparing the steel plate according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1, heating the steel billet to 1200-1250°C and keeping the temperature uniform; S2, rolling; air cooling to room temperature after rolling, the cooling rate is 4℃ / min~6℃ / min.

7. The method for preparing a high-strength and tough steel plate for wind power generation by normalizing rolling process according to claim 6, characterized in that: The rolling of S2 adopts two-stage rolling. In the first stage, the parameters are: starting rolling temperature 1130~1180℃, and final rolling temperature ≥1080℃.

8. The method for preparing a high-strength and tough steel plate for wind power generation by normalizing rolling process according to claim 7, characterized in that: The total rolling reduction of the first stage rolling is greater than 50%, at least 2 rolling passes have a single rolling reduction greater than 18%, and the rolling roller speed is ≤1.5m / s.

9. The method for preparing a high-strength and tough steel plate for wind power generation by normalizing rolling process according to claim 7, characterized in that: The second stage of rolling, parameters: starting rolling temperature 1000 ~ 1050 ℃, final rolling temperature ≥ 950 ℃.

10. The method for preparing a high-strength and tough steel plate for wind power generation by normalizing rolling process according to claim 9, characterized in that: The total rolling reduction of the second stage rolling is greater than 40%, at least 2 rolling passes have a single rolling reduction greater than 16%, and the rolling roller speed is ≤1.5m / s.

Images