High yield strength e-grade steel plate capable of withstanding 100 kj / cm large heat input welding and method for manufacturing the same

Abstract

The application provides a high yield strength E-grade steel plate capable of bearing 100kJ / cm large heat input welding and a preparation method thereof, and belongs to the technical field of steel plates for large heat input welding.The application controls the chemical composition of the steel plate to meet a corresponding relation formula by optimizing the proportion of alloy elements, simultaneously refines the grains and controls the phase change, simultaneously refines the structure while refining the grains, and makes the heat affected zone near the welding gap have excellent low-temperature toughness, so that the large heat input welding performance and yield strength of the steel plate are improved.The experimental results show that the E-grade steel plate provided by the application has a yield strength greater than 500MPa, a tensile strength greater than 620MPa, an elongation greater than 19%, a yield strength ratio less than 0.85, a 40 DEG C longitudinal impact of the base material greater than 250J, and a-40 DEG C impact energy of the near-weld heat affected zone after 100kJ / cm large heat input greater than 120J.

Description

Technical Field

[0001] This invention relates to the field of steel plates for high heat input welding, and in particular to a high yield strength steel plate capable of withstanding welding with a high heat input of 100 kJ / cm and its preparation method. Background Technology

[0002] With the rapid development of my country's social economy and the continuous progress in various fields such as high-rise buildings, energy storage and transportation, bridge and railway engineering, the requirements for the strength, weldability, and corrosion resistance of steel plates have increased significantly. Against this backdrop, the construction of large steel structures has gradually adopted welding technologies capable of high heat input welding, greatly improving manufacturing efficiency. However, traditional steels exhibit severe performance degradation of weld joints under high heat input welding conditions, becoming a key issue restricting production efficiency and the reliability of project quality. Currently, both domestic and international efforts are vigorously developing steels for high heat input welding. However, this leads to the problem that the strength and toughness of the heat-affected zone decrease significantly with increasing welding heat input. Therefore, preventing the deterioration of the heat-affected zone's performance during the welding process is crucial for developing steels for high heat input welding.

[0003] To address the aforementioned issues, numerous scholars have conducted beneficial explorations in this area and discovered that the main means of controlling the low-temperature toughness of the coarse-grained heat-affected zone in high-heat-input welding is to control the growth of austenite grains and the microstructure of the coarse-grained heat-affected zone during the welding process.

[0004] Invention patents with publication numbers CN103343284, CN102154587, and CN106086650, etc., describe TiN as a commonly used particle for controlling austenite grain growth during high-heat-input welding. TiN has a high melting point, and a certain size and number of TiN particles can pin austenite grain boundaries, refine grains, and improve low-temperature toughness. However, TiN dissolves rapidly at high temperatures exceeding 1400℃, losing its ability to control austenite grain size and failing to meet performance requirements.

[0005] The invention patents published under CN109321851, CN109321846, CN109321815, CN102605248, and CN102373371 employ oxide metallurgy technology to control austenite grain growth through inclusions. This involves strictly controlling the oxygen content during steelmaking and combining it with other alloying elements such as Mg, Ca, and Zr to form numerous fine, dispersed inclusions in the steel. This not only inhibits austenite grain growth during high heat input welding but also provides nucleation sites for acicular ferrite. However, in practical applications, oxide metallurgy technology faces challenges such as difficulty in oxygen control and insufficient inclusion refinement. Large inclusions can negatively impact low-temperature toughness.

[0006] Invention patents with publication numbers CN109097685 and CN106086650, among others, utilize vanadium-nitrogen alloys to increase the nitrogen content in steel. By leveraging the nucleation effects of vanadium (VN) and boron (BN), nucleation sites are provided for acicular ferrite, thus improving the intragranular microstructure. This is another technological approach for high-heat-input welding steel. This approach is low-cost and offers stable production. However, in practical applications, while this approach can effectively nucleate, it cannot effectively control grain size. Therefore, it is not suitable for situations with high heat input. Furthermore, increasing the nitrogen content in the steel can also lead to aging issues.

[0007] In summary, existing technologies cannot meet the requirements for high heat input welding performance of steel plates, and the yield strength of the steel plates is too low, all below 500 MPa, indicating a serious lack of strength. This makes it difficult to meet the growing demand for high-strength steel plates in the steel structure manufacturing industry. Therefore, improving the high heat input welding performance and yield strength of steel plates has become an urgent problem to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a high-yield-strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm, and a method for preparing the same. The Grade E steel plate provided by this invention combines excellent resistance to high heat input welding with high yield strength, capable of withstanding a welding heat input of 100 kJ / cm, and a yield strength of not less than 500 MPa.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] This invention provides a high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm. Its chemical composition, by mass percentage, is: C 0.04%–0.12%, Si 0.10%–0.35%, Mn 1.60%–1.78%, P ≤0.015%, S ≤0.005%, Ni 0.25%–0.40%, Cu 0.20%–0.30%, Mo 0.16%–0.25%, V 0.010%–0.090%, Ti 0.005%–0.030%, B 0.0005%–0.0035%, Al 0.005%–0.025%, Ce 0.021%–0.035%, N 0.0045%–0.0080%, O 0.0005% to 0.0030% and balance Fe;

[0011] The contents of Ti, V, B, C and N satisfy the following condition: 0.1% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.25%.

[0012] Preferably, the chemical composition by mass percentage is: C 0.05%–0.11%, Si 0.15%–0.33%, Mn 1.62%–1.77%, P ≤0.013%, S ≤0.004%, Ni 0.26%–0.38%, Cu 0.22%–0.28%, Mo 0.17%–0.23%, V 0.015%–0.045%, Ti 0.006%–0.016%, B 0.0009%–0.0025%, Al 0.011%–0.023%, Ce 0.024%–0.031%, N 0.0055%–0.0080%, O 0.0016%–0.0028%, and the balance Fe.

[0013] Preferably, the chemical composition by mass percentage is: C 0.06%–0.1%, Si 0.17%–0.28%, Mn 1.63%–1.76%, P ≤0.011%, S ≤0.003%, Ni 0.27%–0.35%, Cu 0.23%–0.27%, Mo 0.18%–0.22%, V 0.019%–0.035%, Ti 0.009%–0.015%, B 0.0011%–0.0022%, Al 0.015%–0.023%, Ce 0.025%–0.029%, N 0.0055%–0.0070%, O 0.0017%–0.0026%, and the balance Fe.

[0014] Preferably, the contents of Ti, V, B, C and N satisfy the following condition: 0.15% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.20%.

[0015] This invention also provides a method for preparing high yield strength E-grade steel plates capable of withstanding welding with a high heat input of 100 kJ / cm, as described in the above technical solution, comprising the following steps:

[0016] The alloy raw materials are successively smelted, cast, rough rolled and finish rolled to obtain high yield strength E-grade steel plates that can withstand welding with a large heat input of 100kJ / cm.

[0017] Preferably, the process includes heat preservation after casting and before rough rolling.

[0018] Preferably, the insulation temperature is 1050–1300℃, and the insulation time is 1–3 hours.

[0019] Preferably, the temperature of the roughing roll is 1000-1050°C, the number of passes in the roughing roll is 5-7, and the total reduction rate of the roughing roll is not less than 55%.

[0020] Preferably, the finishing rolling temperature is 750–950°C, and the finishing rolling passes are 4–6.

[0021] Preferably, the total reduction rate of the last three passes of the finishing mill is ≥35%.

[0022] This invention provides a high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm. Its chemical composition, by mass percentage, is: C 0.04%–0.12%, Si 0.10%–0.35%, Mn 1.60%–1.78%, P ≤0.015%, S ≤0.005%, Ni 0.25%–0.40%, Cu 0.20%–0.30%, Mo 0.16%–0.25%, V 0.010%–0.090%, Ti 0.005%–0.030%, B 0.0005%–0.0035%, Al 0.005%–0.025%, Ce 0.021%–0.035%, N 0.0045%–0.0080%, O The content of Ti, V, B, C, and N is 0.0005% to 0.0030% and the balance is Fe; the contents of Ti, V, B, C, and N satisfy the following condition: 0.1% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.25%. This invention optimizes the alloy element ratio and controls the chemical composition of the steel plate to satisfy the above relationship, allowing grain refinement and phase transformation to occur simultaneously. While refining the grains, the microstructure is also refined, resulting in excellent low-temperature toughness in the heat-affected zone near the weld seam, thereby improving the steel plate's resistance to high heat input welding and its yield strength. Experimental results show that the E-grade steel plate provided by this invention has a yield strength greater than 500MPa, a tensile strength greater than 620MPa, an elongation greater than 19%, a yield ratio less than 0.85, and a longitudinal impact energy of over 250J at -40℃ for the base material. After a high heat input of 100kJ / cm, the impact energy of the heat-affected zone near the weld seam at -40℃ is over 120J. Attached Figure Description

[0023] Figure 1 Microstructure of the heat-affected zone of Grade E steel plate prepared in Example 2 under a welding heat input of 100 kJ / cm;

[0024] Figure 2 Microstructure of the heat-affected zone of steel plate prepared for welding under the condition of 100 kJ / cm welding heat input. Detailed Implementation

[0025] This invention provides a high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm. Its chemical composition, by mass percentage, is: C 0.04%–0.12%, Si 0.10%–0.35%, Mn 1.60%–1.78%, P ≤0.015%, S ≤0.005%, Ni 0.25%–0.40%, Cu 0.20%–0.30%, Mo 0.16%–0.25%, V 0.010%–0.090%, Ti 0.005%–0.030%, B 0.0005%–0.0035%, Al 0.005%–0.025%, Ce 0.021%–0.035%, N 0.0045%–0.0080%, O 0.0005% to 0.0030% and balance Fe;

[0026] The contents of Ti, V, B, C and N satisfy the following condition: 0.1% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.25%.

[0027] The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm, provided by this invention, comprises 0.04% to 0.12% C, preferably 0.05% to 0.11%, more preferably 0.06% to 0.1%, and even more preferably 0.07% to 0.08% by mass percentage. In this invention, C is the main element determining the strength of the steel and also the element with the greatest influence on the MA component in the heat-affected zone. When the C content is below 0.04%, it is difficult to obtain the required strength; when the C content is above 0.12%, a hardened structure appears in the weld heat-affected zone, the MA component increases significantly, toughness deteriorates, and high C content easily leads to welding cracks. Therefore, the C content is controlled within the range of 0.04% to 0.12%.

[0028] The high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm, provided by this invention, comprises 0.10% to 0.35% Si, preferably 0.15% to 0.33%, more preferably 0.17% to 0.28%, and even more preferably 0.19% to 0.26% by mass percentage. In this invention, Si is a deoxidizing element and also a strengthening element. When the Si content is below 0.10%, the deoxidation effect is poor, and the steel plate surface is prone to pitting and red rust. However, when the Si content is greater than 0.35%, it promotes microstructure coarsening, increases the MA component, and increases the sensitivity to both cold and hot welding cracks. Therefore, the Si content is controlled within the range of 0.10% to 0.35%.

[0029] The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention, by mass percentage, comprises 1.60% to 1.78% Mn, preferably 1.62% to 1.77%, more preferably 1.63% to 1.76%, and even more preferably 1.67% to 1.73%. In this invention, Mn is a solid solution element, and by expanding the austenite phase region and lowering the phase transformation point, it refines the ferrite grains, thereby simultaneously improving strength and toughness. This allows it to replace some C, appropriately reducing the C content and further improving the low-temperature toughness of the weld heat-affected zone. However, when the Mn content exceeds 1.78%, the MA component content increases, and the toughness of the heat-affected zone deteriorates. Therefore, the Mn content is controlled within the range of 1.60% to 1.78%.

[0030] The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention, by mass percentage, contains P ≤ 0.015%, preferably ≤ 0.013%, and more preferably ≤ 0.011%. In this invention, P is an impurity element that increases the brittleness of the steel and should be reduced as much as possible. However, metallurgical de-P removal is very costly, so the P content is limited to below 0.015%.

[0031] By mass percentage, the high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention comprises S ≤ 0.005%, preferably ≤ 0.004%, and more preferably ≤ 0.003%. In this invention, when the sulfur content is high, it exists in the form of FeS-Fe eutectic around the steel grains, which will reduce the mechanical properties of the steel. Its content is similar to that of P, and the lower the better. Therefore, the S content is limited to below 0.005%.

[0032] The high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention, by mass percentage, comprises 0.25% to 0.40% Ni, preferably 0.26% to 0.38%, more preferably 0.27% to 0.35%, and even more preferably 0.33%. In this invention, Ni can significantly improve the toughness of the matrix and the weld heat-affected zone, and enhance the steel plate's resistance to welding with high heat input. However, Ni is a precious metal, and adding too much will increase costs; therefore, the Ni content is controlled within the range of 0.25% to 0.40%.

[0033] The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention, by mass percentage, comprises 0.20% to 0.30% Cu, preferably 0.22% to 0.28%, more preferably 0.23% to 0.27%, and more preferably 0.25% to 0.26%. In this invention, an appropriate amount of Cu can also promote the nucleation of acicular / massive ferrite; however, excessively high Cu content will produce fine, dispersed Cu precipitates during hot rolling, impairing the low-temperature toughness of the steel plate and deteriorating the low-temperature toughness of the weld heat-affected zone. Therefore, the Cu content is controlled within the range of 0.20% to 0.30%.

[0034] By mass percentage, the high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention comprises 0.16% to 0.25% Mo, preferably 0.17% to 0.23%, more preferably 0.18% to 0.22%, and even more preferably 0.19% to 0.20%. In this invention, an appropriate amount of Mo can significantly improve the strength and tempering stability of the steel plate, and can also refine the grains in the weld heat-affected zone, improving the toughness of the weld joint; however, excessive Mo addition will severely reduce the toughness of the weld joint and increase production costs. Therefore, the Mo content is controlled within the range of 0.16% to 0.25%.

[0035] By mass percentage, the high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention comprises 0.010% to 0.090% V, preferably 0.015% to 0.045%, more preferably 0.019% to 0.035%, and even more preferably 0.026% to 0.028%. In this invention, V has a strong precipitation strengthening effect and contributes significantly to improving strength. When the V content is below 0.010%, precipitation strengthening cannot be prominently displayed; when the V content is above 0.090%, the hardenability of the steel plate increases, while the toughness of both the steel plate and the heat-affected zone decreases. Therefore, the V content is controlled within the range of 0.010% to 0.090%.

[0036] The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention, by mass percentage, comprises 0.005% to 0.030% Ti, preferably 0.006% to 0.016%, more preferably 0.009% to 0.015%, and more preferably 0.012% to 0.013%. In this invention, Ti is the main element in steel for high heat input. Ti combines with N to form TiN, which inhibits austenite grain growth and effectively improves the toughness of the heat-affected zone. The addition of Ti can also reduce the solid solution content of N, improving the aging properties of the steel. When the Ti content is below 0.005%, the number of beneficial nitrides formed is small, and the effect of inhibiting grain growth is weak. When the Ti content exceeds 0.030%, the amount of solid solution Ti in the steel is excessive, and the remaining Ti exists in the grain in the form of solid solution, increasing the MA component and reducing the performance of the heat-affected zone. Therefore, the Ti content is controlled within the range of 0.005% to 0.030%.

[0037] The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm, provided by this invention, comprises 0.0005% to 0.0035% B, preferably 0.0009% to 0.0025%, more preferably 0.0011% to 0.0022%, and more preferably 0.0015% to 0.0018% by mass percentage. In this invention, B is a characteristic element, ensuring that dissolved B and BN coexist in both the base material and the high heat input welding zone (HAZ), simultaneously exhibiting segregation and nucleation effects. The BN precipitated in austenite acts as a phase transformation nucleus, improving toughness through HAZ microstructure refinement, hardness reduction, and MA reduction. Therefore, it must contain at least 0.0005% B. On the other hand, if the B content exceeds 0.0035%, coarse B precipitates will form, deteriorating HAZ toughness. To improve HAZ toughness, the B content is controlled within the range of 0.0005% to 0.0035%.

[0038] The high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention, by weight percentage, comprises 0.005% to 0.025% Al, preferably 0.011% to 0.023%, and more preferably 0.015% to 0.023%. In this invention, Al is the main deoxidizer, mainly playing a deoxidizing role in the steelmaking process; therefore, the Al content is controlled within the range of 0.005% to 0.025%.

[0039] By mass percentage, the high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention comprises 0.021% to 0.035% Ce, preferably 0.024% to 0.031%, more preferably 0.025% to 0.029%, and more preferably 0.026% to 0.028%. The addition of Ce in this invention can refine the grains and improve the distribution of alloying elements in the steel; however, excessive Ce addition would lead to excessively high costs. Therefore, the Ce content is controlled within the range of 0.021% to 0.035%.

[0040] The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention, by mass percentage, comprises 0.0045% to 0.0080% N, preferably 0.0055% to 0.0080%, and more preferably 0.0055% to 0.0070%. N is another important element in this invention; N exists in two forms: one is in solid solution, which is detrimental to the properties of the base material; the other is in the formation of dispersed fine-particle N compounds, which improves the toughness of the weld heat-affected zone. High N content leads to increased solid solution N, resulting in poor toughness and aging properties of the base material, and making the continuously cast billet prone to cracking. Therefore, the N content is controlled within the range of 0.0045% to 0.0080%.

[0041] By mass percentage, the high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm provided by this invention comprises 0.0005% to 0.0030% O, preferably 0.0016% to 0.0028%, and more preferably 0.0017% to 0.0026%. In this invention, O is an unavoidable impurity element in the steelmaking process, and excessive content will adversely affect the performance of the steel plate. Therefore, the O content is controlled within the range of 0.0005% to 0.0030%.

[0042] By mass percentage, the high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm² provided by this invention comprises the balance Fe. In this invention, Fe is a matrix element.

[0043] In this invention, the contents of Ti, V, B, C, and N satisfy the following conditions: 0.1% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.25%, preferably 0.15% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.20%, and more preferably 0.17% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.19%. By controlling the content of the above-mentioned elements, this invention enables the number of (V,Ti)(C,N) composite precipitates to account for 80-90% of the particles with a size of 20-80 nm that can suppress austenite grain growth in the heat-affected zone of near-seam welds, and the number of (Ti,V,B)(C,N) composite precipitates to account for 60-70% of the particles with a size of 0.5-1.5 μm that can heterogeneously nucleate.

[0044] Within the heat-affected zone of near-seam welds, the number density of (V,Ti)(C,N) composite precipitates with a size of 20–80 nm, which can suppress austenite grain growth, is 3.56 × 10⁻⁶. 5 pcs / mm 3 ~5.83×10 5 pcs / mm 3 Among heterogeneous nucleation particles with sizes ranging from 0.5 to 1.5 μm, the number density of (Ti,V,B)(C,N) composite precipitates is 3.21 × 10⁻⁶. 4 pcs / mm 3 ~4.64×10 4 pcs / mm 3 .

[0045] This invention controls the morphology of second-phase particles in steel by optimizing the content of alloying elements, resulting in two main types of particles in the steel: particles with a size of 20-80 nm that can inhibit austenite grain growth and particles with a size of 0.5-1.5 μm that can undergo heterogeneous nucleation. When the chemical composition of the steel plate satisfies the relationship 0.1% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.25%, the particles with a size of 20-80 nm that can inhibit austenite grain growth and particles with a size of 0.5-1.5 μm that can undergo heterogeneous nucleation in the heat-affected zone near the weld can meet the corresponding ratio. This effectively inhibits austenite grain growth during high heat input welding, while generating a large number of acicular ferrite particles that undergo heterogeneous nucleation within the grains, refining the microstructure, improving toughness, and maintaining a certain strength.

[0046] This invention refines grains and controls phase transformation simultaneously by controlling the type, size, and quantity of elements and second-phase particles. While refining grains, it also refines the microstructure, enabling the heat-affected zone near the weld seam to achieve excellent low-temperature toughness.

[0047] In this invention, multi-wire submerged arc welding is preferably used for welding high-yield-strength Grade E steel plates that can withstand a high heat input of 100 kJ / cm. In this invention, the heat-affected zone of near-weld welding is the area where the peak temperature near the weld is between 1250 and 1400°C, and the temperature above 500°C is maintained for 100 to 200 seconds.

[0048] This invention also provides a method for preparing high yield strength E-grade steel plates capable of withstanding welding with a high heat input of 100 kJ / cm, as described in the above technical solution, comprising the following steps:

[0049] The alloy raw materials are successively smelted, cast, rough rolled and finish rolled to obtain high yield strength E-grade steel plates that can withstand welding with a large heat input of 100kJ / cm.

[0050] The present invention does not impose any special limitations on the smelting and casting operations; operations familiar to those skilled in the art can be used.

[0051] In this invention, the process of heat preservation before rough rolling after casting is preferably included; the heat preservation temperature is preferably 1050-1300℃, and the heat preservation time is preferably 1-3 hours. Heat preservation before rough rolling in this invention enables the billet to be fully austenitized and has a uniform composition.

[0052] In this invention, the temperature of the roughing roll is preferably 1000-1050°C; the number of passes in the roughing roll is preferably 5-7; and the total reduction rate of the roughing roll is preferably not less than 55%.

[0053] In this invention, the finishing rolling temperature is preferably 750-950°C, more preferably 800-900°C; the finishing rolling passes are preferably 4-6; and the total reduction rate of the last three finishing rolling passes is preferably ≥35%.

[0054] After finishing rolling, the present invention preferably cools the product obtained by finishing rolling to obtain a high yield strength E-grade steel plate that can withstand welding with a large heat input of 100kJ / cm.

[0055] In this invention, the cooling is preferably achieved using laminar water cooling.

[0056] The present invention does not impose any special limitations on the specific cooling operation; any operation known to those skilled in the art can be used.

[0057] The preparation method provided by this invention is simple to operate and suitable for industrial production.

[0058] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0059] Examples 1-8

[0060] The chemical composition of high yield strength E-grade steel plates capable of withstanding welding with a high heat input of 100 kJ / cm is shown in Table 1.

[0061] Comparative Examples 1-2

[0062] The chemical composition of the steel plate is shown in Table 1.

[0063] Table 1. Chemical composition (wt%) of the steel plates in Examples 1-8 and Comparative Examples 1-2

[0064]

[0065]

[0066]

[0067] The preparation methods of the steel plates in Examples 1-8 and Comparative Examples 1-2 are as follows:

[0068] (1) Prepare raw materials according to the design requirements of bridge steel, put pure iron into a vacuum furnace and heat it until it melts, refine the molten iron at high temperature and high vacuum for 15 minutes, then fill it with protective gas and add alloy, adjust the temperature, and cast it into steel ingots.

[0069] (2) The steel ingot obtained in step (1) is heated to 1200°C and held for 3 hours. Then, it is rough rolled at 1050°C with 6 passes and a total reduction of 55%. Then, it is finish rolled at 750-950°C with 5 passes and a total reduction of 35% for the last three passes. Finally, it is cooled by laminar water to obtain a steel plate.

[0070] Mechanical properties were tested on the steel plates of Examples 1-8 and Comparative Examples 1-2, and the results are shown in Table 2.

[0071] Table 2 Mechanical properties of steel plates and heat-affected zones near weld seams in Examples 1-8 and Comparative Examples 1-2

[0072]

[0073] As can be seen from Table 2, the yield strength of the steel plates of the present invention is greater than 500 MPa, the tensile strength is greater than 620 MPa, the elongation is greater than 19%, the yield strength ratio is less than 0.85, the longitudinal impact energy of the base material at -40℃ is greater than 250 J, and the impact energy of the heat-affected zone near the weld at -40℃ after a large heat input of 100 kJ / cm is greater than 120 J.

[0074] Although Comparative Examples 1 and 2 have similar compositions to those of the present invention, the proportions of the two types of particles in Comparative Examples 1 and 2 are smaller than those controlled by the present invention due to different control methods. As a result, the two types of particles cannot be maximized at the same time. Therefore, although Comparative Examples 1 and 2 also have good mechanical properties, their low-temperature toughness is significantly reduced at -40℃ near the heat-affected zone of the seam after a large heat input of 100 kJ / cm.

[0075] In summary, the high heat input welding of Grade E steel plates in this invention employs a multi-wire submerged arc welding method. In the near-weld weld heat-affected zone, among particles with a size of 20–80 nm that can suppress austenite grain growth, the number of (V,Ti)(C,N) composite precipitates accounts for 80–90%. Among particles with a size of 0.5–1.5 μm that can heterogeneously nucleate, the number of (Ti,V,B)(C,N) composite precipitates accounts for 60–70%, satisfying the condition 0.1% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.25%. In the near-weld weld heat-affected zone, among particles with a size of 20–80 nm that can suppress austenite grain growth, the number density of (V,Ti)(C,N) composite precipitates is 3.56 × 10⁻⁶. 5 pcs / mm 3 ~5.83×10 5 pcs / mm 3 Among heterogeneous nucleation particles with sizes ranging from 0.5 to 1.5 μm, the number density of (Ti,V,B)(C,N) composite precipitates is 3.21 × 10⁻⁶. 4 pcs / mm 3 ~4.64×10 4 pcs / mm 3 This resulted in Grade E steel plates with a yield strength of not less than 500MPa that can withstand welding with a high heat input of 100kJ / cm, which can be widely used in the construction of bridges with large spans, high parameters, and fully welded structures.

[0076] Figure 1 Microstructure of the heat-affected zone of Grade E steel plate prepared in Example 2 under a welding heat input of 100 kJ / cm; Figure 2 Microstructure of the heat-affected zone of steel plate prepared for welding under the condition of 100 kJ / cm welding heat input.

[0077] from Figures 1-2 It can be seen that the metallographic structure of Example 2 under the welding heat input of 100kJ / cm is pearlite + ferrite, while the metallographic structure of Comparative Example 2 under the welding heat input of 100kJ / cm is blocky ferrite and granular bainite.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm, the chemical composition by mass percentage being: C 0.04%~0.12%, Si 0.10%~0.35%, Mn 1.62%~1.78%, P ≤0.015%, S ≤0.005%, Ni 0.25%~0.40%, Cu 0.22%~0.27%, Mo 0.16%~0.25%, V 0.010%~0.090%, Ti 0.005%~0.030%, B 0.0005%~0.0035%, Al 0.005%~0.025%, Ce 0.021%~0.035%, N 0.0045%~0.0080%, O 0.0005%~0.0030% and balance Fe; The contents of Ti, V, B, C, and N satisfy the following condition: 0.1% ≤ 10.15Ti + 1.65V + 0.06B + 0.13C + 0.1N ≤ 0.25%; The method for preparing the high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm comprises the following steps: The alloy raw materials are sequentially smelted, cast, heat-held, rough rolled and finish rolled. After the finish rolling is completed, the product obtained by the finish rolling is cooled to obtain a high yield strength E-grade steel plate that can withstand welding with a large heat input of 100kJ / cm. The cooling method is laminar water cooling; The insulation temperature is 1050~1300℃, and the insulation time is 1~3h; The roughing temperature is 1000~1050℃, the roughing passes are 5~7, and the total reduction rate of the roughing is not less than 55%. The finishing rolling temperature is 750~950℃, and the finishing rolling passes are 4~6. The total reduction rate of the last three passes of the finishing mill is ≥35%.

2. The high yield strength grade E steel plate according to claim 1, characterized in that, The chemical composition, by mass percentage, is as follows: C 0.05%~0.11%, Si 0.15%~0.33%, Mn 1.62%~1.77%, P ≤0.013%, S ≤0.004%, Ni 0.26%~0.38%, Cu 0.22%~0.27%, Mo 0.17%~0.23%, V 0.015%~0.045%, Ti 0.006%~0.016%, B 0.0009%~0.0025%, Al 0.011%~0.023%, Ce 0.024%~0.031%, N 0.0055%~0.0080%, O 0.0016%~0.0028%, and the balance Fe.

3. The high yield strength grade E steel plate according to claim 2, characterized in that, The chemical composition, by mass percentage, is as follows: C 0.06%~0.1%, Si 0.17%~0.28%, Mn 1.63%~1.76%, P ≤0.011%, S ≤0.003%, Ni 0.27%~0.35%, Cu 0.23%~0.27%, Mo 0.18%~0.22%, V 0.019%~0.035%, Ti 0.009%~0.015%, B 0.0011%~0.0022%, Al 0.015%~0.023%, Ce 0.025%~0.029%, N 0.0055%~0.0070%, O 0.0017%~0.0026%, and the balance Fe.

4. The high yield strength grade E steel plate according to any one of claims 1 to 3, characterized in that, The contents of Ti, V, B, C and N satisfy the following condition: 0.15%≤10.15Ti+1.65V+0.06B+0.13C+0.1N≤0.20%.

5. The method for preparing the high yield strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm as described in any one of claims 1 to 4 comprises the following steps: The alloy raw materials are sequentially smelted, cast, heat-held, rough rolled and finish rolled. After the finish rolling is completed, the product obtained by the finish rolling is cooled to obtain a high yield strength E-grade steel plate that can withstand welding with a large heat input of 100kJ / cm. The cooling method is laminar water cooling; The insulation temperature is 1050~1300℃, and the insulation time is 1~3h; The roughing temperature is 1000~1050℃, the roughing passes are 5~7, and the total reduction rate of the roughing is not less than 55%. The finishing rolling temperature is 750~950℃, and the finishing rolling passes are 4~6. The total reduction rate of the last three passes of the finishing mill is ≥35%.

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