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

Abstract

This invention provides a high-yield-strength Grade E steel plate capable of withstanding welding with a high heat input of 100 kJ / cm, and its preparation method, belonging to the technical field of steel plates for high heat input welding. By optimizing alloying elements and controlling the chemical composition of the steel plate to satisfy the corresponding formula, this invention can control the size and distribution of second-phase particles in the steel, resulting in a sufficient number of nano-sized particles that can inhibit austenite grain growth and micron-sized particles that can nucleate within the grains. This combination of controlling austenite grain size and intragranular microstructure improves the steel plate's resistance to high heat input welding. Experimental results show that the Grade E steel plate provided by this invention has a yield strength of not less than 370 MPa, a tensile strength of not less than 446 MPa, an elongation of not less than 19%, a longitudinal impact KV2 of not less than 262 J at -40℃, and a KV2 of not less than 124 J in the near-weld heat-affected zone at -40℃ with a heat input of 100 kJ / cm.

Description

Technical Field

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

[0002] With economic and social development, structural designs in various fields such as high-rise buildings, energy storage and transportation, shipbuilding, and marine engineering are increasingly characterized by higher strength and larger scale, leading to a significant increase in the strength and thickness of steel plates required. Against this backdrop, the construction of large steel structures is gradually adopting welding technologies capable of high heat input welding, resulting in a substantial improvement in manufacturing efficiency. However, traditional steels suffer from a severe reduction in low-temperature toughness at weld joints under high heat input welding conditions, becoming a key issue restricting production efficiency and the reliability of engineering quality. Currently, both domestic and international efforts are focused on developing steels for high heat input welding, and preventing the deterioration of the heat-affected zone during welding is crucial for this development.

[0003] High heat input welding processes are characterized by high peak temperatures and long high-temperature dwell times. In the coarse-grained heat-affected zone near the fusion line, abnormal austenite grain growth and severe microstructure coarsening can occur. Therefore, preventing the reduction in low-temperature toughness of the weld joint after high heat input welding can be achieved by controlling the microstructure of the heat-affected zone and the austenite grain size.

[0004] Traditional V-Ti-N technology controls the Ti-to-N ratio in steel by increasing the N content, resulting in a large number of TiN particles. TiN then pins austenite grains during the welding thermal cycle, preventing austenite grain growth. Simultaneously, V(C,N) promotes acicular ferrite nucleation within the grains, improving the internal microstructure. However, this technology often increases the N content to over 100 ppm. Excessive N content generates a large amount of free N in the steel, severely impacting welding performance under high heat input. Furthermore, excessive N content also affects the aging properties of the steel. Therefore, this technology remains only at the laboratory research stage and lacks practical applications.

[0005] How to avoid the aging problems caused by the increase of nitrogen content, while ensuring the weldability of steel plates under high heat input, has become an urgent problem to be solved in this field. Summary of the Invention

[0006] 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 possesses excellent resistance to high heat input welding, can withstand a welding heat input of 100 kJ / cm, and has a yield strength of not less than 370 MPa.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] 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 1.20%–1.42%, P ≤0.015%, S ≤0.005%, Ni ≤0.09%, Cu ≤0.07%, Mo ≤0.06%, V 0.01%–0.09%, Ti 0.005%–0.030%, Al 0.005%–0.025%, Ce ≤0.002%, N 0.0045%–0.0080%, O 0.0005%–0.0030%, and the balance Fe.

[0009] The contents of Ti, V, C and N satisfy the following condition: 0.06% ≤ 2.35Ti + 0.31V + 0.02C + 0.02N ≤ 0.08%.

[0010] Preferably, the chemical composition by mass percentage is: C 0.05%–0.11%, Si 0.15%–0.26%, Mn 1.21%–1.41%, P ≤0.015%, S ≤0.005%, Ni 0.01%–0.08%, Cu 0.01%–0.06%, Mo 0.01%–0.06%, V 0.046%–0.087%, Ti 0.015%–0.025%, Al 0.006%–0.023%, Ce 0.0005%–0.0017%, N 0.005%–0.0075%, O 0.0016%–0.0025%, and the balance Fe.

[0011] Preferably, the chemical composition by mass percentage is: C 0.06%–0.10%, Si 0.16%–0.25%, Mn 1.25%–1.38%, P ≤0.015%, S ≤0.005%, Ni 0.03%–0.07%, Cu 0.02%–0.05%, Mo 0.02%–0.05%, V 0.056%–0.081%, Ti 0.016%–0.024%, Al 0.015%–0.018%, Ce 0.0011%–0.0015%, N 0.006%–0.007%, O 0.0017%–0.0024%, and the balance Fe.

[0012] Preferably, the contents of Ti, V, C and N satisfy the following conditions: 0.065% ≤ 2.35Ti + 0.31V + 0.02C + 0.02N ≤ 0.075%.

[0013] 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:

[0014] The alloy raw materials are sequentially smelted, cast, hot rolled, rough rolled, and finish rolled to obtain high yield strength E-grade steel plates that can withstand welding with a high heat input of 100kJ / cm.

[0015] Preferably, the deformation amount of the hot rolling is 50-60%.

[0016] Preferably, the process includes heat preservation after hot rolling and before rough rolling.

[0017] Preferably, the insulation temperature is 1050–1300°C, and the insulation time is 2 hours.

[0018] Preferably, the temperature of the rough rolling is 1000-1050°C, and the total deformation of the rough rolling is 15-20%.

[0019] Preferably, the finishing rolling temperature is 750–950°C, and the total deformation of the finishing rolling is 2–8%.

[0020] 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 1.20%–1.42%, P ≤ 0.015%, S ≤ 0.005%, Ni ≤ 0.09%, Cu ≤ 0.07%, Mo ≤ 0.06%, V 0.01%–0. The composition of the steel plate is as follows: Ti ≤ 0.009%, Ti 0.005%–0.030%, Al 0.005%–0.025%, Ce ≤ 0.002%, N 0.0045%–0.0080%, O 0.0005%–0.0030%, and the balance Fe. The contents of Ti, V, C, and N satisfy the following condition: 0.06% ≤ 2.35Ti + 0.31V + 0.02C + 0.02N ≤ 0.08%. This invention, by optimizing alloying elements and controlling the chemical composition of the steel plate to satisfy the above relationship, can control the size and distribution of second-phase particles in the steel. This results in the generation of sufficient nanoscale particles that can inhibit austenite grain growth and micron-sized particles that can nucleate within the grains. By combining the control of austenite grain size with the intragranular structure, the welding performance of the steel plate under high heat input can be improved without increasing the N content. Experimental results show that the E-grade steel plate provided by this invention has a yield strength of not less than 370MPa, a tensile strength of not less than 446MPa, an elongation of not less than 19%, a longitudinal impact KV2 of not less than 262J at -40℃, and a heat input of 100kJ / cm near the seam heat-affected zone KV2 of not less than 124J at -40℃. Attached Figure Description

[0021] Figure 1Microstructure of the heat-affected zone of Grade E steel plate prepared in Example 1 under a welding heat input of 100 kJ / cm;

[0022] 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

[0023] 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 1.20%–1.42%, P ≤0.015%, S ≤0.005%, Ni ≤0.09%, Cu ≤0.07%, Mo ≤0.06%, V 0.01%–0.09%, Ti 0.005%–0.030%, Al 0.005%–0.025%, Ce ≤0.002%, N 0.0045%–0.0080%, O 0.0005%–0.0030%, and the balance Fe.

[0024] The contents of Ti, V, C and N satisfy the following condition: 0.06% ≤ 2.35Ti + 0.31V + 0.02C + 0.02N ≤ 0.08%.

[0025] 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 0.04% to 0.12% C, preferably 0.05% to 0.11%, more preferably 0.06% to 0.10%, and even more preferably 0.08% to 0.09%. In this invention, C is the main element determining the strength of the steel and has a significant impact on the MA component in the heat-affected zone. When C is below 0.04%, it is difficult to obtain the required strength; when C is above 0.12%, hardened structures appear 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%.

[0026] 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 0.26%, more preferably 0.16% to 0.25%, and even more preferably 0.18% to 0.23% 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%.

[0027] 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 1.20% to 1.42% Mn, preferably 1.21% to 1.41%, more preferably 1.25% to 1.38%, and more preferably 1.32% to 1.35%. In this invention, Mn has an atomic radius similar to Fe and readily forms substitutional solid solutions, making it an element that ensures the strength of the steel plate. When the Mn content is below 1.20%, the strength decreases, and the harmful effects of sulfides increase. When the Mn content is above 1.42%, the MA component content increases, and the toughness of the heat-affected zone deteriorates. Therefore, the Mn content is controlled within the range of 1.20% to 1.42%.

[0028] The high yield strength Grade E steel plate provided by this invention, capable of withstanding welding with a high heat input of 100 kJ / cm, contains P ≤ 0.015% by mass percentage. 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; therefore, the P content is limited to below 0.015%.

[0029] 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 contains S ≤ 0.005%. 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%.

[0030] 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 Ni ≤ 0.09%, preferably 0.01% to 0.08%, more preferably 0.03% to 0.07%, and more preferably 0.04% to 0.06%. In this invention, Ni can significantly improve the toughness of the matrix and the weld heat-affected zone; however, Ni is expensive, and adding too much will lead to a sharp increase in cost. Therefore, the Ni content is controlled within the range of ≤ 0.09%.

[0031] 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 Cu ≤0.07%, preferably 0.01% to 0.06%, more preferably 0.02% to 0.05%, and more preferably 0.03% to 0.04%. In this invention, an appropriate amount of Cu promotes the nucleation of acicular / blocky ferrite; however, excessively high Cu content can cause hot cracks during rolling, adversely affecting weldability. Therefore, the Cu content is controlled within the range of ≤0.07%.

[0032] 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 Mo ≤ 0.06%, preferably 0.01% to 0.06%, more preferably 0.02% to 0.05%, and more preferably 0.03% to 0.04%. In this invention, an appropriate amount of Mo can significantly improve the strength and tempering stability of the steel plate, refine the grains in the weld heat-affected zone, and improve 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 ≤ 0.06%.

[0033] 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 0.01% to 0.09% V, preferably 0.046% to 0.087%, more preferably 0.056% to 0.081%, and even more preferably 0.058% to 0.076%. In this invention, V has a strong precipitation strengthening effect and contributes significantly to improving strength. When the V content is below 0.01%, precipitation strengthening cannot be prominently displayed; when the V content is above 0.09%, 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 0.01% to 0.09%.

[0034] 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 0.005% to 0.030% Ti, preferably 0.015% to 0.025%, more preferably 0.016% to 0.024%, and more preferably 0.019% to 0.021%. 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 solid solution form, 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%.

[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 0.005% to 0.025% Al, preferably 0.006% to 0.023%, more preferably 0.015% to 0.018%, and even more preferably 0.017%. 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%.

[0036] 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 Ce ≤ 0.002%, preferably 0.0005% to 0.0017%, more preferably 0.0011% to 0.0015%, and more preferably 0.0012% to 0.0013%. 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 ≤ 0.002%.

[0037] 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 0.0045% to 0.0080% N, preferably 0.005% to 0.0075%, and more preferably 0.006% to 0.007%. 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%.

[0038] 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 0.0025%, and more preferably 0.0017% to 0.0024%. In this invention, O is an unavoidable impurity element in the steelmaking process and will not have a significant adverse effect on the performance of the steel plate; therefore, the O content is controlled within the range of 0.0005% to 0.0030%.

[0039] 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.

[0040] In this invention, the contents of Ti, V, C and N satisfy the following conditions: 0.06% ≤ 2.35Ti + 0.31V + 0.02C + 0.02N ≤ 0.08%, preferably 0.065% ≤ 9.91Ti + 7.46Nb + 0.05B ​​+ 0.20C + 0.08N ≤ 0.075%.

[0041] The present invention provides a method to suppress the growth of austenite grains in the heat-affected zone of near-seam welds of Grade E steel plates, where the number density of (V,Ti) and (C,N) composite precipitates is 1.83 × 10⁻⁶ particles with a size of 20–80 nm. 5 pcs / mm 3 Up to 3.36×10 5 pcs / mm 3 Between these ranges, in particles with sizes of 0.5–1.5 μm that can heterogeneously nucleate, the number density of (Ti,V)(C,N) composite precipitates is 2.88 × 10⁻⁶. 4 pcs / mm 3 Up to 5.12×10 4 pcs / mm 3 between.

[0042] This invention controls the morphology of second-phase particles in steel by controlling the content of alloying elements, resulting in two main types of particles: 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. The steel plate's chemical composition, by mass percentage, satisfies the relationship 0.06% ≤ 2.35Ti + 0.31V + 0.02C + 0.02N ≤ 0.08%, and the heat-affected zone near the seam can inhibit austenite grain growth. When the number of (V,Ti)(C,N) composite precipitates accounts for 60-70% in large particles with a size of 20-80 nm, and the number of (Ti,V)(C,N) composite precipitates accounts for 60-70% in particles with a size of 0.5-1.5 μm that can undergo heterogeneous nucleation, austenite grain growth can be effectively suppressed during high heat input welding. At the same time, a large number of acicular ferrites with heterogeneous nucleation are generated inside the grains, refining the microstructure, improving toughness, and maintaining a certain strength.

[0043] This invention optimizes the alloy element ratio so that, although some particles with a size of 20–80 nm that can inhibit austenite grain growth dissolve during the welding thermal cycle, their overall quantity is still sufficient to suppress austenite grain growth and control the austenite grain size in the heat-affected zone. Optimizing the alloy element ratio also allows for the presence of a large number of particles with a size of 0.5–1.5 μm that can undergo heterogeneous nucleation. These particles promote the nucleation of intragranular acicular ferrite, optimizing the microstructure and distribution of the weld heat-affected zone. Furthermore, optimizing the alloy element ratio results in a bimodal distribution of the two types of second-phase particles, fully utilizing their characteristics in solid-state reactions to control the high heat input welding performance of the steel. This avoids complex liquid-phase reaction control and enables stable mass production.

[0044] 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:

[0045] The alloy raw materials are sequentially smelted, cast, hot rolled, rough rolled, and finish rolled to obtain high yield strength E-grade steel plates that can withstand welding with a high heat input of 100kJ / cm.

[0046] The present invention does not impose any special limitations on the smelting and continuous casting operations; operations familiar to those skilled in the art can be used.

[0047] In this invention, the total deformation of the hot rolling is preferably 50-60%; the hot rolling temperature is preferably 1200℃.

[0048] In this invention, the process of hot rolling followed by rough rolling preferably includes heat preservation; the heat preservation temperature is preferably 1050–1300°C; and the heat preservation time is preferably 2 hours. This heat preservation before rough rolling allows the billet to be fully austenitized and its composition to be homogenized.

[0049] In this invention, the temperature of the rough rolling is preferably 1000-1050°C; the total deformation of the rough rolling is preferably 15-20%.

[0050] In this invention, the temperature of the finishing rolling is preferably 750-950°C, more preferably 800-900°C; the total deformation of the finishing rolling is preferably 2-8%.

[0051] 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.

[0052] In this invention, the cooling is preferably performed using laminar water. This invention does not have a specific limitation on the source of the laminar water; commercially available products well-known to those skilled in the art can be used. This invention also does not have a specific limitation on the operation of the laminar water cooling; operations well-known to those skilled in the art can be used.

[0053] This invention is simple to operate and suitable for industrial production.

[0054] 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.

[0055] Examples 1-8

[0056] 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.

[0057] Comparative Examples 1-2

[0058] The chemical composition of the steel plate is shown in Table 1.

[0059] Table 1. Chemical composition (wt%) of the steel plates in Examples 1-8 and Comparative Examples 1-2

[0060]

[0061]

[0062] The preparation methods of the steel plates in Examples 1-8 and Comparative Examples 1-2 are as follows:

[0063] (1) The steel ingot was smelted in a vacuum induction furnace and then cast to obtain a 75kg steel ingot;

[0064] (2) The steel ingot obtained in step (1) is hot-rolled with a deformation of 50% into a slab with a thickness of 60 mm;

[0065] (3) The slab obtained in step (2) is loaded into a heating furnace, the heating temperature is controlled at 1150℃, and the temperature is kept for 2 hours. Then, rough rolling is performed at 1050℃ with a total deformation of 20%. Then, fine rolling is performed at 850℃ with a total deformation of 5% to produce a plate with a thickness of 18mm.

[0066] (4) The plate obtained in step (3) is cooled by laminar water to obtain a steel plate.

[0067] Performance tests were conducted on the steel plates of Examples 1-8 and Comparative Examples 1-2, and the results are shown in Table 2. The impact test specimens were cut from the center of the steel plate, with the longitudinal axis of the specimen perpendicular to the length of the steel plate, the notched surface perpendicular to the surface of the steel plate, and the notch axis located at the center of the steel plate. The specimen dimensions were 10×10×55mm, and the impact test method was performed according to GB / T229. The values ​​in parentheses in the table are average values.

[0068] Table 2 Mechanical properties of steel plates and heat-affected zones near weld seams in Examples 1-8 and Comparative Examples 1-2

[0069]

[0070] As shown in Table 2, the impact absorption energy (longitudinal impact KV2 at -40℃) of the weld near-seam heat-affected zone of the steel plates in Comparative Examples 1 and 2 is less than 40J, indicating poor low-temperature toughness. The impact absorption energy (KV2 at -40℃) of the weld near-seam heat-affected zone of the steel plates in Examples 1 to 8 of the present invention is much greater than 40J under the condition of 100kJ / cm heat input, indicating excellent low-temperature toughness. This shows that the Grade E steel plate of the present invention, which can withstand a welding heat input of 100kJ / cm and has a yield strength of not less than 370MPa, has excellent resistance to high heat input welding performance.

[0071] As can be seen from the above embodiments and comparative examples, the E-grade steel plate provided by the present invention has excellent resistance to high heat input welding performance, can withstand welding heat input of 100kJ / cm, and has a yield strength of not less than 370MPa.

[0072] Figure 1 Microstructure of the heat-affected zone of Grade E steel plate prepared in Example 1 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.

[0073] from Figures 1-2 It can be seen that, Figure 1 The microstructure of the E-grade steel plate shown is mainly blocky ferrite. Figure 2 The microstructure of the E-grade steel plate shown is mainly granular bainitic. Due to the very low carbon content of ferrite, its properties are similar to pure iron, exhibiting excellent plasticity and toughness. For bainitic structures, when the carbide size is constant, the higher the carbon content in the steel, the greater the number of carbides, leading to increased strength and hardness of bainite, but decreased plasticity and toughness. When the carbon content is constant, the lower the transformation temperature, the more dispersed the carbides, increasing the strength and hardness of bainite while only slightly reducing plasticity and toughness. When the carbides are granular, the bainite exhibits good plasticity and toughness, but lower strength and hardness. Therefore, the performance of Example 1 is superior to that of Comparative Example 2.

[0074] 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 1.20%~1.41%, P≤0.015%, S≤0.005%, Ni≤0.09%, Cu≤0.07%, Mo≤0.06%, V 0.01%~0.09%, Ti 0.005%~0.030%, Al 0.005%~0.025%, Ce0.0005%~0.0017%, N 0.005%~0.0080%, O 0.0005%~0.0030%, and the balance Fe; The contents of Ti, V, C, and N satisfy the following condition: 0.065% ≤ 2.35Ti + 0.31V + 0.02C + 0.02N ≤ 0.075%; 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, hot rolled, 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 deformation amount of the hot rolling is 50-60%; The insulation temperature is 1050~1300℃, and the insulation time is 2h; The roughing temperature is 1000~1050℃, and the total deformation of the roughing is 15~20%. The finishing rolling temperature is 750~950℃, and the total deformation of the finishing rolling is 2~8%.

2. The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm as described in claim 1, characterized in that, The chemical composition, by mass percentage, is as follows: C 0.05%~0.11%, Si 0.15%~0.26%, Mn 1.21%~1.41%, P≤0.015%, S≤0.005%, Ni 0.01%~0.08%, Cu 0.01%~0.06%, Mo 0.01%~0.06%, V 0.046%~0.087%, Ti 0.015%~0.025%, Al 0.006%~0.023%, Ce 0.0005%~0.0017%, N 0.005%~0.0075%, O 0.0016%~0.0025%, and the balance Fe.

3. The high yield strength E-grade steel plate capable of withstanding welding with a high heat input of 100 kJ / cm as described in claim 2, characterized in that, The chemical composition, by mass percentage, is as follows: C 0.06%~0.10%, Si 0.16%~0.25%, Mn 1.25%~1.38%, P≤0.015%, S≤0.005%, Ni 0.03%~0.07%, Cu 0.02%~0.05%, Mo 0.02%~0.05%, V 0.056%~0.081%, Ti 0.016%~0.024%, Al 0.015%~0.018%, Ce 0.0011%~0.0015%, N 0.006%~0.007%, O 0.0017%~0.0024%, and the balance Fe.

4. 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 as described in any one of claims 1 to 3 comprises the following steps: The alloy raw materials are sequentially smelted, cast, hot rolled, 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 deformation amount of the hot rolling is 50-60%; The insulation temperature is 1050~1300℃, and the insulation time is 2h; The roughing temperature is 1000~1050℃, and the total deformation of the roughing is 15~20%. The finishing rolling temperature is 750~950℃, and the total deformation of the finishing rolling is 2~8%.

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