460MPa-grade high-toughness super-thick high-strength structural steel plate with thickness of 130-160mm and production method thereof

Abstract

The invention relates to a 460MPa-grade high-toughness super-thick high-strength structural steel plate with the thickness of 130-160mm and a production method of the 460MPa-grade high-toughness super-thick high-strength structural steel plate, belonging to the technical field of metallurgy. The carbon equivalent CEV of the steel plate is less than or equal to 0.48%; the upper yield strength is larger than or equal to 460 MPa, the tensile strength is 540-600 MPa, and the ductility is larger than or equal to 20%; charpy impact energy at the 1 / 4 position and 1 / 2 position of the thickness of the steel plate at-20 DEG C is greater than or equal to And the flaw detection result meets the NB / T47013.3 requirement. A normalizing rolling and water mist cooling mode is adopted for production, the water mist cooling speed is controlled to be 1-3 DEG C / s, the positions of different thicknesses of the extra-thick steel plate are evenly cooled, it is guaranteed that the internal stress of the extra-thick steel plate is fully released, the risk that cracks are generated in the subsequent cutting machining process of the extra-thick steel plate is avoided, and weldability is facilitated; moreover, in the production method, heat treatment is omitted, energy consumption is reduced, and the production cost is favorably controlled.

Description

Technical Field

[0001] The invention belongs to the technical field of iron-based alloys, and in particular relates to a structural steel plate and a production method thereof. Background Art

[0002] In recent years, the country's large-scale equipment has been continuously updated and developed. Extra-thick steel plates are widely used in the construction of ships, marine engineering, bridges, high-rise buildings, pressure vessels, energy and chemical industries, and have become an important steel material in the development of the national economy. For 460MPa-grade high-toughness, extra-thick, high-strength structural steel plates, the traditional method often uses steel ingots or composite billets to first open the billet and roll it, and then heat and roll it into extra-thick steel plates. However, ingots and composite billets have the defects of low yield, low production efficiency and high production cost in production. The use of continuous casting billets can greatly reduce production costs and improve production efficiency. However, for the production of 460MPa-grade high-toughness, extra-thick, high-strength structural steel plates with a thickness of ≥130mm, the continuous casting billet type currently used is 150-450mm thick, and there is a small rolling compression ratio. If the high strength and toughness of the final steel plate is to be ensured, especially the performance and weldability at the 1 / 2 thickness position, the production is very difficult.

[0003] In order to improve the high strength and toughness of 460MPa grade extra-thick high-strength structural steel plates, the current main method is to add normalizing or tempering heat treatment processes after continuous casting billets, and to increase phase changes to make the structural properties of the extra-thick high-strength structural steel plates in the thickness direction uniform.

[0004] Chinese patent publication number CN 114686776 A discloses a 460MPa grade high toughness extra thick plate and its manufacturing method. The composition adopts a low carbon and high manganese design (C: 0.04-0.06%, Mn: 1.50-1.70%), and the process adopts offline normalizing + weak water cooling after normalizing. Although the increase in Mn content in the composition can make up for the decrease in strength caused by the decrease in C content, the Mn element is an element that is easy to segregate. Too high a content can easily cause the center segregation of the continuous casting billet to increase, and cracks are likely to occur in the subsequent steel plate cutting and welding stages, affecting the normal production and use of extra thick steel plates. The method is suitable for the production of steel plates with a thickness of 65-100mm.

[0005] Chinese patent publication number CN 116043128 A discloses a 460E extra-thick steel plate and its production method. The composition also adopts a low-carbon high-manganese design (C: 0.04-0.07%, Mn: 1.75-1.95%), and the process adopts a single heating rolling to form an intermediate billet, and a secondary heating rolling + DQ rapid cooling method to form a plate. Although the production thickness of the steel plate reaches 60-150mm, the Mn content in the composition is too high, which is easy to cause the center segregation of the continuous casting billet to increase, and it is easy to form MnS inclusions, which makes it easy to crack during the later cutting and welding of the extra-thick steel plate. In addition, the use of two heating rolling will cause a significant reduction in production efficiency, a low yield rate and an increase in steel rolling energy consumption, which will lead to an overall increase in production costs. Furthermore, the secondary heating rolling + DQ rapid cooling method is easy to cause stress accumulation in the steel plate and cannot be fully released, resulting in deformation during processing such as steel plate cutting, and the maximum production thickness of the steel plate is only 150mm.

[0006] Chinese patent publication number CN 117758152 A discloses a 130-150mm thick low-cost S460NL steel plate and its production method. The invention adopts a low-carbon, high-manganese, and high-vanadium design (C: 0.04-0.06%, Mn: 1.80-2.00%, V: 0.050-0.060%) in terms of composition, and adopts a three-stage heating for steel rolling + two-stage rolling for rough rolling and finishing rolling + two-stage repeated cooling and repeated warming + short-time tempering process. First of all, excessive Mn and V content can easily lead to aggravated central segregation of continuous casting billets, and the probability of cracks in subsequent cutting of steel plates is high. In addition, the steel rolling cooling process adopts two-stage repeated cooling and repeated warming, in which the first stage is cooled and warmed up for 2-4s after controlled cooling, which is extremely short in time control and difficult to control. After repeated cooling and reheating in two stages, short-term tempering is carried out. The connection between the two processes is very high, and the scheduling requirements for crane hoisting at the production site are high. Therefore, the above process control is difficult, and the maximum thickness of the steel plate is only 150mm.

[0007] Chinese Patent Publication No. CN 104805374 A discloses a Q460E steel plate with a thickness exceeding 120 mm and a manufacturing method thereof. In terms of composition, this invention adopts a medium-carbon high-manganese high-vanadium design (C: 0.15 - 0.19%, Mn: 1.50 - 1.75%, V: 0.07 - 0.14%), but excessive amounts of V and Cu (0.25 - 0.35%) are added. The addition of excessive V easily exacerbates the center segregation of continuous casting billets, resulting in a relatively high alloy cost and an increased risk of crack generation during subsequent cutting and processing of extra-thick steel plates, thereby leading to a relatively high overall production cost; in terms of process, a two-stage rolling + DQ rapid cooling + normalizing method is adopted. Although the thickness of the steel plate samples is 120 - 130 mm, an off-line normalizing process is added in the production process, increasing the process cost and having a relatively long production cycle, and the delivery period cannot be ensured. Moreover, its maximum carbon equivalent reaches 0.52%, which is not conducive to the subsequent welding of the steel plate, easily generates welding cracks, and has a relatively high use risk.

[0008] Chinese Patent Publication No. CN 115341139 A discloses a super-thick Q460GJ steel plate with a thickness above 100 mm and a manufacturing method thereof. In terms of composition, this invention also adopts a medium-carbon high-manganese high-vanadium design (C: 0.14 - 0.18%, Mn: 1.51 - 1.68%, V: 0.066 - 0.083%), and in terms of process, a controlled rolling and controlled cooling + normalizing + weak water cooling after normalizing method is adopted. An excessive C content in the composition is not conducive to the low-temperature impact toughness of the steel plate, increases the carbon equivalent and the cold crack sensitivity index, and is not conducive to the welding of the steel plate. In addition, the addition of excessive V will result in a relatively high alloy cost and increase the production cost.

[0009] Chinese Patent Publication No. CN 114686776 A discloses a 460 MPa grade high-toughness super-thick plate with a maximum thickness of 100 mm and a manufacturing method thereof. In terms of process, a controlled rolling + secondary ultra-fast cooling + normalizing + weak water cooling after normalizing method is adopted, in which an air cooling of 20 - 25 s is required between the secondary ultra-fast coolings, and the time control is difficult. Under the normal large-scale production conditions of actual steel mills, it is difficult to achieve batch production with this process. In addition, the cooling rate after normalizing reaches 8 - 12 °C / s, which is bound to lead to non-uniform microstructure and properties in the thickness direction of the steel plate, thereby generating internal stress, resulting in plate shape problems such as warping of the steel plate, or causing welding problems such as cracking of the welded joints during subsequent welding of the steel plate. The thicker the steel plate, the more serious the above problems are. Summary of the Invention

[0010] The purpose of the present invention is to provide a 460 MPa grade high-toughness super-thick high-strength structural steel plate with a thickness of 130 - 160 mm and a production method thereof.

[0011] Technical solution of the present invention: A structural steel plate, the chemical composition by mass percentage is C: 0.12 - 0.15%, Si: 0.10 - 0.25%, Mn: 1.10 - 1.30%, Al: 0.035 - 0.055%, Cr: 0.20 - 0.30%, Ni: 0.28 - 0.38%, Nb: 0.015% - 0.030%, V: 0.015% - 0.030%, Ti: 0.010% - 0.018%, Ca: 0.0008 - 0.0018%, P: ≤0.008%, S: ≤0.0015%, O: ≤0.0020%, N: ≤0.0040%, H: ≤0.00015%, and the balance is Fe and inevitable impurity elements; carbon equivalent CEV: ≤0.48%.

[0012] The reasons for the limitation of the steel plate composition in the present invention are described as follows: C: As a solid solution element, it can significantly improve the strength of the steel plate. At the same time, it also belongs to the hardenability element, which is the main element that aggravates the center segregation of continuous casting billets. However, in order to avoid adding too much precious alloys such as Cr and Ni and improve the ultra-low temperature impact toughness and welding performance of the steel plate, the carbon content is controlled as low as possible. In the present invention, the carbon content is controlled at 0.12 - 0.15%.

[0013] Si: It is mainly used for deoxidizing the primary molten steel. However, too high Si content will affect the surface quality of the steel plate and increase the cold crack sensitivity of the steel plate, especially for extra-thick steel plates. In the present invention, the Si content is controlled at 0.10 - 0.25%.

[0014] Mn: It is a hardenability element that promotes martensite transformation and is beneficial to improving strength and toughness. However, Mn is also the main element of center segregation in continuous casting billets. Too high content will cause the aggravation of center segregation in continuous casting billets and form MnS inclusions, which have adverse effects on the toughness and welding performance of the steel plate. In the present invention, the manganese content is specified as 1.10 - 1.30%.

[0015] Nb: It has the effects of refining grains, precipitation strengthening and precipitation hardening. Nb dissolved in austenite can improve the hardenability. The carbide precipitation phase of Nb has the effects of refining grains and increasing the matrix strength. However, too much Nb will weaken the toughness, cause cracks on the surface of continuous casting billets, and in addition, the alloy cost will also increase significantly. In the present invention, the Nb content is controlled at 0.015 - 0.030%.

[0016] Ti: Mainly fixes nitrogen in steel. Titanium nitride formed under appropriate conditions can prevent the coarsening of austenite grains during continuous casting billet heating and high-temperature rolling, especially when the welding temperature reaches 1300°C, improve the ultra-low temperature toughness of the base material and the welding heat-affected zone, and thus improve the welding performance. However, if the Ti content is less than 0.010%, the effect is poor; if it is greater than 0.020%, the excess Ti will precipitate in combination with other elements in the steel, resulting in a significant decrease in the toughness of the steel plate. Therefore, the Ti content of the present invention is controlled to be 0.010-0.018%.

[0017] Al: The most important deoxidizing element in the process of molten steel refining. Adding or feeding a certain amount of aluminum particles or aluminum wires into the molten steel can effectively reduce the formation of oxide inclusions in the molten steel, significantly improve the purity of the molten steel, and is especially significant for improving the internal quality of extra-thick steel plates. In addition, it can refine the grains. However, if the Al content is too high, cracks will appear on the surface of the continuous casting billet, forming an Al-based inclusion, thereby reducing the quality of the continuous casting billet. In the present invention, the Al content is controlled to be 0.035-0.055%.

[0018] P: a harmful element in steel, which is easy to segregate, will reduce the low temperature toughness of the steel plate and affect the weldability. In the present invention, P is specified to be ≤0.008%.

[0019] S: harmful element in steel, which forms MnS inclusions together with Mn element, causing cracks in the steel plate. In the present invention, S is specified to be ≤0.0015%.

[0020] O, N, H: harmful gas elements in steel. A high content will reduce the toughness of the steel plate and increase the risk of cracking, especially for extra-thick steel plates. In the present invention, the O content is strictly controlled to be ≤0.0020%; the N content is ≤0.00040%; and the H content is ≤0.00015%.

[0021] Cr: An element that improves the hardenability of steel and can inhibit the formation of polygonal ferrite and pearlite, promote the transformation of low-temperature microstructures such as bainite or martensite, and thus improve strength. However, too high a Cr content will affect its toughness. The Cr content of the present invention is controlled to be 0.20-0.30%.

[0022] Ni: The most commonly used element in steel to improve low-temperature toughness. It can improve the corrosion resistance of steel plates to a certain extent by combining with P and Cr. However, due to its high price, its economic efficiency is poor. The Ni content of the present invention is controlled to be 0.28-0.38%.

[0023] V: A grain-refining element in steel. When added at a content of >0.02%, it can refine the grains during the cooling process of the rolled plate, especially for extra-thick steel. In addition, it can form carbides when combined with C, which can improve the corrosion resistance of steel under high temperature and high pressure environments. However, too much V content will be detrimental to the toughness and welding performance of the steel plate. Therefore, the V content in the present invention is controlled to be 0.015-0.030%.

[0024] Ca: The main modifying element of inclusions in steel, which can react with strip-shaped MnS to form spherical CaS, change the anisotropy in steel, and also modify the Al2O3 inclusions generated by Al deoxidation into low-melting-point inclusions, which are easy to float and remove, thereby improving the toughness of the steel plate. This effect is particularly important in extra-thick steel plates. In the present invention, the Ca content is controlled to be 0.0008 - 0.0018%.

[0025] CEV: The carbon equivalent formula CEV = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15; it has a great influence on the strength and weldability of the steel plate. When CEV is high, the strength is high, but the weldability decreases. Therefore, to ensure the weldability of the extra-thick steel plate, the CEV content in the present invention is controlled to be ≤0.48%.

[0026] The present invention further provides a production method of the above-mentioned 460 MPa grade high-toughness extra-thick high-strength structural steel plate with a thickness of 130 - 160 mm, and the specific process is as follows: Smelting: Smelt the molten steel according to the chemical composition design. As a preferred smelting scheme: After the hot metal is pretreated by KR, it is smelted by an electric furnace or a converter, and then the primary molten steel is sent to the LF furnace for refining treatment for fine-tuning the composition, and then sent to the VD or RH for degassing treatment. After the molten steel is degassed, a Ca wire is fed for treatment and soft argon blowing is carried out while standing.

[0027] Continuous casting: Preferably, a 450 mm billet type continuous caster is used and casting is carried out with low superheat and full argon protection. The superheat of the molten steel is controlled at 10 - 20 °C; to control the central segregation of the billet ≤ C1.0 grade and the porosity ≤ 1.0 grade, heavy reduction is carried out at the solidification end of the straight-arc segment of the billet, and the reduction amount is controlled at 14 - 19 mm.

[0028] Slow cooling of the billet: After the continuous casting billet is taken offline, it needs to be slow-cooled with a cover. Preferably, the starting temperature of slow cooling is required to be ≥600 °C and the time is ≥72 hours.

[0029] Heating: The continuous casting billet is moved into the heating furnace by a walking beam type, and the heating rate is 10 - 14 min / cm (the heating rate is the total time for heating the continuous casting billet to the target temperature divided by the thickness of the continuous casting billet). To ensure the effect of hot rolling at high temperature, the continuous casting billet is heated to 1220 - 1270 °C to make it fully softened, and insulation is started when the core temperature of the billet reaches its surface temperature, and the insulation time is ≥30 min. Promote the full solution of alloying elements to ensure the uniformity of chemical composition and mechanical properties in the steel.

[0030] Normalizing rolling: The compression ratio control of the continuous casting billet to the finished steel plate thickness is ≥2.8. The rolling process adopts a two-stage normalizing rolling process of rough rolling + finish rolling. Among them, the rough rolling starting temperature is 1050 - 1120 °C. The reduction per pass of the first 4 passes of longitudinal rolling in rough rolling is not less than 55 mm, and the cumulative reduction rate is not less than 60%. The total number of passes of rough rolling + finish rolling is controlled to be 6 - 10 passes. The finish rolling starting temperature is 900 - 920 °C. The odd passes are subjected to strong pressure descaling combined with water cooling of the intermediate billet (which belongs to an optimized differential temperature rolling method), and the cooling rate during the process is controlled at 5 - 15 °C / s. The finishing temperature is 850 - 870 °C.

[0031] Water mist cooling: The steel plate is quickly moved to the cooling bed by the roller table. The starting cooling temperature is controlled at 780 - 820 °C. Water mist weak cooling is adopted, and the cooling rate is 1 - 3 °C / s. The final cooling temperature of the steel plate is 380 - 410 °C.

[0032] Slow cooling of the steel plate: When the surface temperature of the steel plate is 300 - 350 °C, it is hoisted offline and stacked for hydrogen diffusion slow cooling, and the slow cooling time is ≥48 hours.

[0033] Compared with the prior art, the advantages of the present invention are as follows: 1. The present invention is produced by adopting a normalizing rolling + water mist cooling method, and the water mist cooling rate is controlled low at 1 - 3 °C / s, which promotes uniform cooling of different thickness positions of the extra-thick steel plate, ensures the full release of internal stress in the extra-thick steel plate, avoids the risk of crack generation in the subsequent cutting and processing of the extra-thick steel plate, and is beneficial to weldability. Moreover, the heat treatment is saved in the production method, the energy consumption is reduced, and it helps to control the production cost.

[0034] 2. Medium carbon components are added with Mn-Ni-Cr hardenability elements as a new alloy system, combined with the composite action of Nb, V, Ti micro-alloying elements, to control the carbon equivalent and ensure the matching of the strength and low-temperature toughness of the steel plate, and ensure the welding performance.

[0035] 3. In the composition design, the contents of elements such as Si and Ni are controlled to inhibit the adverse effects brought by the oxide layer on the steel plate surface, and affect the appearance of defects on the steel plate surface such as pits, pockmarks, stippling, and folds.

[0036] 4. Al is equivalent to other micro-alloying elements and is low in price. However, due to the limited smelting level of steel mills, the Al content is often controlled between 0.020 - 0.030%. The present invention combines the actual smelting situation and increases the Al content to 0.035 - 0.055%. Considering that too high Al is not conducive to the surface quality of the steel plate, the present invention implements strong pressure descaling in the odd passes of the rolling process. Furthermore, grain refinement elements are added at high Al content, and the negative impact of too high Al content is avoided.

[0037] 5. In the component design, by adding Nb microalloying elements, the non-recrystallization temperature of austenite is increased, thereby increasing the cumulative reduction ratio per pass in the rough rolling stage of the continuous casting billet (not less than 60%), that is, increasing the high-temperature rolling permeability of the continuous casting billet, further bridging the possible defects in the core of the continuous casting billet, and improving the low-temperature toughness and welding performance of especially extra-thick steel plates.

[0038] 6. Adding Ti microalloying elements to the components can improve the weldability of extra-thick steel plates. In addition, it can also improve the crack problem that is prone to occur in Nb-containing steel billets.

[0039] For the 460MPa grade high-toughness extra-thick high-strength structural steel plate of the present invention with a thickness of 130 - 160mm, the upper yield strength ≥ 460MPa, the tensile strength is 540 - 600MPa, and the elongation ≥ 20%; the Charpy impact energy at -20°C at 1 / 4 and 1 / 2 of the plate thickness is ≥ 150J. The flaw detection results meet the requirements of NB / T47013.3. There are no defects such as pitting, scab, scale, fold, scar, and bubble on the surface of the steel plate, and the surface quality is good.

[0040] The method of the present invention can be extended and applied to other extra-thick high-strength steels such as steel for engineering machinery, steel for high-rise buildings, steel for bridges, high-strength marine ship plates, and steel for pressure vessels. Description of the Drawings

[0041] Figure 1 It is the typical microstructure at the 1 / 4 thickness position of the steel plate in Example 1 of the present invention, mainly composed of ferrite and pearlite, with uniform and fine microstructure, and it can be seen that there are dispersed and fine cementite tissues in the ferrite grains.

[0042] Figure 2 It is the typical microstructure at the 1 / 2 thickness position of the steel plate in Example 2 of the present invention, mainly composed of ferrite, pearlite and a small amount of bainite. This is due to the existence of appropriate segregation in the thickness direction, but the microstructure gradient is not obvious compared with that at 1 / 4 of the thickness, and most of the bainite tissues are needle-like ferrite, which is beneficial to the improvement of the strength and toughness of the steel plate. Detailed Embodiments

[0043] The following further describes the present invention in detail with reference to the embodiments. The embodiments are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0044] The production process of the 460MPa grade high-toughness extra-thick high-strength structural steel plate of the present invention: converter > LF furnace refining > VD or RH vacuum degassing > Ca wire treatment > continuous casting > hydrogen removal treatment of continuous casting billet > heating of continuous casting billet > normalizing rolling > water spray cooling > slow cooling treatment of steel plate stacking.

[0045] The 460MPa grade high-toughness extra-thick high-strength structural steel plate and its production method in Examples 1 - 3 of the present invention include the following steps: (1) Smelting: After KR pretreatment, the molten iron is smelted in an electric furnace or converter, and then the primary molten steel is transferred to the LF furnace for refining and composition fine-tuning. After VD or RH vacuum degassing treatment, the Ca wire is fed after degassing and the argon gas is soft-blown. The smelting composition is shown in Table 1.

[0046] (2) Continuous casting: The molten steel is cast with low superheat and argon protection in a 450mm billet continuous casting machine. The temperature of the molten steel in the tundish is controlled at 10-20°C above the liquidus line. The heavy reduction process at the end of the solidification of the billet is adopted in the straight arc sector, with a reduction of 14-19mm. The relevant process parameters are shown in Table 2.

[0047] (3) Hydrogen expansion and slow cooling treatment of continuous casting billets: After the continuous casting billets are cut off the line, they are covered with hydrogen expansion and slow cooling treatment. The slow cooling starting temperature is ≥600℃ and the slow cooling time is ≥72 hours.

[0048] (4) Heating: The continuous casting billet is moved into the heating furnace by stepping, with an average heating rate of 10-14 min / cm. To ensure the high-temperature rolling effect, the billet is heated to 1220-1270°C. When the core temperature of the billet reaches its surface temperature, it is kept warm for ≥30 min.

[0049] (5) Normalizing rolling: The compression ratio of the ingot to the finished steel plate thickness is controlled to be ≥2.8. The rolling process adopts a two-stage normalizing rolling process of rough rolling + finishing rolling. The starting temperature of rough rolling is 1050-1120℃. The reduction of each longitudinal rolling in the first four passes of rough rolling is not less than 55mm, and the cumulative reduction rate is not less than 60%. The total number of rough rolling + finishing rolling passes is 6-10, and the starting temperature of finishing rolling is 900-920℃. The odd number of passes is strong pressing and descaling combined with water cooling of the intermediate billet (optimized differential temperature rolling method), and the cooling rate during the process is controlled to be 5-15℃ / s. The final rolling temperature is 850-870℃.

[0050] (6) Water mist cooling: After normalizing rolling, the steel plate is quickly transferred to the cooling bed via a roller. The initial cooling temperature is 780-820°C. Water mist weak cooling is adopted with a cooling rate of 1-3°C / s. The final cooling temperature of the steel plate is 380-410°C.

[0051] (7) Slow cooling of steel plates: When the surface temperature of the steel plates is 300-350°C, they are hoisted off the production line and stacked for hydrogen expansion and slow cooling. The slow cooling time shall be ≥ 48 hours.

[0052] (8) After normalizing rolling and water mist cooling, the steel plates are inspected for mechanical properties (transverse tensile strength, low-temperature longitudinal impact), flaw detection and surface quality.

[0053] Specific rolling, cooling process parameters and mechanical properties are shown in Tables 3 and 4.

[0054] In Examples 1 - 3, for the extra - thick high - toughness high - strength structural steel plate, the upper yield strength is 460 - 495 MPa, the tensile strength is 540 - 600 MPa, and the elongation is ≥20%; the Charpy impact energy at - 20 °C at 1 / 4 and 1 / 2 of the plate thickness is ≥150 J. The flaw detection result meets the requirements of NB / T47013.3. The extra - thick steel plate of the present invention has excellent mechanical properties and no defects such as cracks and delaminations. The surface quality of the steel plate is good, without defects such as pitting, scab, mill scale, folding, scar, and bubble.

[0055] Table 1 Melting Composition of Examples (wt%)

[0056] Table 2 Continuous Casting Process Control

[0057] Table 3

[0058] Table 4 Mechanical Properties

Claims

1. A structural steel plate, characterized in that: The chemical composition by mass percentage is as follows: C: 0.12 - 0.15%, Si: 0.10 - 0.25%, Mn: 1.10 - 1.30%, Al: 0.035 - 0.055%, Cr: 0.20 - 0.30%, Ni: 0.28 - 0.38%, Nb: 0.015% - 0.030%, V: 0.015% - 0.030%, Ti: 0.010% - 0.018%, Ca: 0.0008 - 0.0018%, P: ≤0.008%, S: ≤0.0015%, O: ≤0.0020%, N: ≤0.0040%, H: ≤0.00015%, and the balance is Fe and inevitable impurity elements; the carbon equivalent CEV: ≤0.48%.

2. The structural steel plate according to claim 1, characterized in that: The thickness of the steel plate is 130 - 160 mm; the upper yield strength ≥460 MPa, the tensile strength is 540 - 600 MPa, and the elongation ≥20%; the Charpy impact energy at -20°C at 1 / 4 and 1 / 2 of the steel plate thickness is ≥150 J; the flaw detection result meets the requirements of NB / T47013.

3.

3. A method for producing the structural steel plate according to claim 1, characterized in that: including Steel melting: Melting the steel water with reference to the chemical composition of the steel plate. Casting: Pouring the steel water into a continuous casting billet, and slow cooling the continuous casting billet. Heating: Heating the continuous casting billet to fully austenitize the structure, making the overall temperature uniform, and fully dissolving alloying elements. Normalizing rolling: The cumulative reduction ratio of rolling ≥2.8, adopting a two-stage normalizing rolling process of rough rolling + finish rolling. Among them, the rough rolling starting temperature is 1050 - 1120°C, the single-pass reduction of the first 4 longitudinal rolling passes in rough rolling is not less than 55 mm, and the cumulative reduction rate is not less than 60%; the total number of passes of rough rolling + finish rolling is 6 - 10, the finish rolling starting temperature is 900 - 920°C, the odd-numbered passes are strongly pressured for descaling combined with water cooling of the intermediate billet, differential temperature rolling, and the cooling rate during finish rolling is controlled at 5 - 15°C / s, and the finish rolling temperature is 850 - 870°C. Water mist cooling: The starting cooling temperature is 780 - 820°C, adopting weak water mist cooling, the cooling rate is 1 - 3°C / s, and the final cooling temperature is 380 - 410°C. Slow cooling: When the surface temperature of the steel plate is 300 - 350°C, hoist it offline and stack it for hydrogen-expansion slow cooling.

4. The method according to claim 3, characterized in that: Steel melting: After the hot metal is pretreated by KR, it is initially melted in an electric furnace or a converter. The initially melted steel water is sent to the LF furnace for refining and component fine-tuning, and then vacuum degassing treatment is carried out; after the steel water is vacuum degassed, Ca wire is fed in and soft blowing of argon gas is carried out to promote the floating of inclusions.

5. The method according to claim 3, wherein: Continuous casting: Adopting a 450 mm billet type continuous caster and pouring with low superheat and full argon protection throughout the process. The superheat of the steel water is controlled at 10 - 20°C; in order to control the center segregation of the continuous casting billet ≤C1.0 level and the porosity ≤1.0 level, heavy reduction is carried out at the solidification end of the straight-arc segment of the continuous casting billet, and the reduction amount is controlled at 14 - 19 mm.

6. The method according to claim 5, characterized in that: After the continuous casting billet is taken offline, it is slowly cooled with a cover. The starting temperature of slow cooling ≥600°C, and the slow cooling time ≥72 hours.

7. The method according to claim 3, wherein: Heating of the continuous casting billet: The continuous casting billet is step-fed into the heating furnace, the heating rate is 10 - 14 min / cm, and the continuous casting billet is heated to 1220 - 1270°C to make it fully softened. When the core temperature of the continuous casting billet reaches its surface temperature, start heat preservation, and the heat preservation time ≥30 min.

8. The method according to claim 3, wherein: The hydrogen-expansion slow cooling time of the steel plate ≥48 hours.

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