An E-grade steel plate with a yield strength of not less than 370 MPa that can withstand 350 kJ / cm high heat input welding

Abstract

An E-grade steel plate with a yield strength of not less than 370 MPa capable of withstanding welding with a high heat input of 350 kJ / cm is disclosed. This steel plate belongs to the field of steels for high heat input welding. The E-grade steel plate comprises, by mass percentage: C 0.04–0.12, Si 0.10–0.35, Mn 1.45–1.58, P ≤0.015, S ≤0.005, Ni 0.25–0.40, Cu 0.08–0.18, Mo ≤0.05, 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 in the above composition is 0.0005-0.0030, with the remainder being iron and unavoidable impurities; the content of Ti, V, B, C, and N in the above composition satisfies 0.6≤15.32Ti+5.79V+0.06B+0.18C+0.15N≤0.9. Under the condition of a welding heat input of 350kJ / cm using multi-wire submerged arc welding, the impact energy of the weld heat-affected zone at -40℃ is not less than 60J.

Description

Technical Field

[0001] The invention belongs to the field of steel for high heat input welding, and specifically relates to an E-grade steel plate with a yield strength of not less than 370MPa that can withstand 350kJ / cm high heat input welding. Background Art

[0002] With the development of large-scale and long-span components, thick steel plates have been widely used in large welded structures in the fields of shipbuilding, high-rise buildings, bridges, petrochemicals, offshore platforms, etc. The use of medium and thick plate (32-80mm) structures accounts for more than 40% of the number of all specifications of components. The high heat input welding process has the characteristics of high peak temperature and long high temperature residence time. In order to improve welding efficiency and reduce production costs, large steel structures are often welded by high heat input welding methods. However, under the conditions of high line energy welding, traditional steel will have problems such as abnormal growth of austenite grains and severe coarsening of the structure in the heat affected zone of the steel plate welding, resulting in a significant decrease in the toughness of the heat affected zone of the steel plate welding, which seriously affects the mechanical properties of the welded joint and becomes a key issue restricting production efficiency and engineering quality reliability.

[0003] At present, foreign companies represented by Nippon Steel, JFE, and Posco of South Korea have successfully developed ultra-large-wire welding energy steel plates with an allowable energy of 200-600kJ / cm, and have obtained industrial applications. Some domestic companies have also increased their research and development efforts and successfully developed large-wire-energy-resistant welding steel plates, but their applications are limited to less than 300kJ / cm energy. Therefore, the present invention is committed to solving the technical bottleneck of welding energy above 300kJ / cm, while ensuring the strength of the steel plate, by controlling the heat-affected zone structure and austenite grain size to prevent the reduction of low-temperature toughness of the welded joint after large heat input welding.

[0004] The invention patent with publication number CN104498827A discloses a method for manufacturing a 355MPa grade steel resistant to 310kJ / cm high-wire energy welding. Low carbon (0.10%) and low carbon equivalent are used to ensure that the steel plate has high low-temperature toughness and welding adaptability. Strictly control the content of alloying elements Ti to form dispersed Ti2O3 particles and TiN particles, promote the nucleation of intracrystalline needle-shaped ferrite, inhibit the coarsening of austenite grains during welding, and reduce the embrittlement of the heat-affected zone of high-wire energy welding. Through Nb and Ti microalloying, grain refinement and precipitation strengthening, the strength of the steel plate is guaranteed. However, the Ti2O3 mentioned in the patent belongs to a high-melting-point oxide formed in the liquid phase, the size is not easy to control, and it is not easy to form a dispersed distribution state in the steel, and it is easy to produce coarse inclusions that affect low-temperature toughness. Therefore, relying solely on TiN cannot maintain the austenite grain size in high heat input welding.

[0005] The invention patent with publication number CN103343284A discloses a production method for 80~140KJ / cm high-energy line welding Q345 grade steel plate, which is characterized by adding 0.1~0.2% Ti element and controlling the Ti / [N] element content ratio to between 2.4 and 3.2, optimizing the more stable TiN precipitation particles in steel at high temperature, pinning the austenite grain boundary, inhibiting grain growth, and increasing the needle-shaped ferrite precipitation nucleus during post-weld cooling to promote ferrite formation. However, the patent increases the N content to 0.06%. Under higher heat input, a large amount of free N will be generated, affecting the low-temperature thermal properties of the heat-affected zone. In addition, it is difficult to control the Ti / N element content ratio in industrial production, which has a great impact on production efficiency.

[0006] The invention patent with publication number CN102459656A discloses a thick plate that can be welded with a large heat input of 150kJ / cm. The patent proposes to use the element ratio to control the content of B element so that it is enriched at the austenite grain boundary, thereby reducing the energy at the grain boundary, making it very difficult for the proeutectoid ferrite (and pearlite) to nucleate at the grain boundary, inhibiting the hardening of the HAZ and reducing the formation of MA components. At the same time, the nucleation effect of BN and V (C, N) is used to refine the ferrite and bainite structures, and the low-temperature toughness of the HAZ is controlled from three aspects: hardness, MA, and effective crystal grain size. In addition, B also has the function of improving the hardenability of steel, which is beneficial to improving the strength of the steel plate. However, the patent essentially uses the control and nucleation ability of the fine oxides of oxide metallurgy technology on the grain boundary. The complex production process reduces the production stability, and the technology does not give full play to the role that V (C, N), BN, etc. should play.

[0007] The invention patent with publication number CN109097685A discloses a steel plate for high-energy line welding and its preparation method. The patent adopts VN-Ti microalloying and B microalloying technology to improve the high heat input welding performance of the steel plate, and the yield strength of the steel plate can reach 400-420MPa. By optimizing the alloy element content, BN-MnS-(Ti,V)(C,N) and BN-MnS-Al2O3 particles are precipitated in the heat affected zone of welding, which promotes the nucleation of intracrystalline ferrite and improves the low-temperature toughness of the heat affected zone of welding. However, the patent technology only mentions the use of TiN to pin austenite grains. When the heat input is increased to 350kJ / cm, the pinning effect of TiN will be severely reduced, and the austenite grain size cannot be effectively controlled, and other particles are required for assistance.

[0008] In summary, combining the control of the heat affected zone structure with the austenite grain size is a necessary means to regulate the low temperature toughness of the heat affected zone in high heat input welding. In order to improve the above problems and make the steel plate adapt to high heat input welding with higher heat input, the present invention proposes to optimize the alloy elements, optimize the proportion of precipitated particles in the steel and give full play to the characteristics of different precipitated particles in the steel, combine the control of the heat affected zone structure with the austenite grain size, and manufacture an E-grade steel plate with a yield strength of not less than 370MPa that can adapt to 300kJ / cm high heat input welding. Summary of the invention

[0009] The purpose of the present invention is to make up for the deficiencies of the above-mentioned prior art and to provide an E-grade steel plate with a yield strength of not less than 370MPa that can withstand welding with a large heat input of 350kJ / cm. When the heat input of the steel plate reaches 350kJ / cm using multi-wire submerged arc welding, the impact energy of the welding heat affected zone at -40°C is not less than 60J.

[0010] The technical solution adopted by the present invention is: an E-grade steel plate with a yield strength of not less than 370MPa that can withstand 350kJ / cm high heat input welding, wherein the E-grade steel plate comprises, by mass percentage: C 0.04-0.12, Si 0.10-0.35, Mn 1.45-1.58, P ≤0.015, S ≤0.005, Ni 0.25-0.40, Cu 0.08-0.18, Mo ≤0.05, 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 the rest is iron and unavoidable impurities;

[0011] Ti, V, B, C and N in the E-grade steel plate composition,

[0012] Satisfies 0.6≤15.32Ti+5.79V+0.06B+0.18C+0.15N≤0.9.

[0013] Furthermore, among the particles with a size of 20-80 nm in the heat-affected zone near the fusion line of the E-grade steel plate after welding, which can inhibit the growth of austenite grains, the number of (V, Ti) (C, N) composite precipitated particles accounts for 80-90% and the number density is 1.95×10 6 -3.34×10 6 Pieces / mm 3 .

[0014] Furthermore, among the particles with a size of 0.5-1.5 μm that have heterogeneous nucleation in the heat-affected zone near the fusion line after welding of the E-grade steel plate, the number of composite precipitated particles of (Ti, V, B) (C, N) accounts for 70-80% and the number density is 2.68×10 5 -4.32×10 5 Pieces / mm 3 .

[0015] Furthermore, the yield strength ReL of the E-grade steel plate is ≥370MPa, the tensile strength Rm is ≥510MPa, and the KV2 of the heat-affected zone of the near-seam welding is ≥60J at -40°C after a large heat input of 350kJ / cm.

[0016] Furthermore, the heat affected zone of the E-grade steel plate near the weld is an area where the peak temperature near the weld is between 1250-1400°C and the temperature above 500°C is maintained for 300-500s.

[0017] Furthermore, the E-grade steel plate is produced by vacuum furnace smelting, controlled rolling and controlled cooling processes, and the specific process parameters are: controlling the heating temperature between 1050-1300°C and keeping warm for more than 3 hours, controlling the rolling temperature of the rough rolling process between 1000-1050°C, and controlling the rolling temperature of the finishing rolling process between 750-950°C.

[0018] Furthermore, in the rough rolling process, the rough rolling passes are 5-7 passes with large reduction, and the total rough rolling reduction rate is not less than 60%.

[0019] Furthermore, in the finishing rolling process, the number of finishing passes is 4-6 and the reduction ratio of the last three passes is ≥35%.

[0020] Furthermore, the cooling control process parameters of the E-grade steel plate are: the cooling start temperature is controlled at 760-800°C, the cooling rate is controlled at 10-20°C / s, and the red-return temperature is controlled at 540-570°C.

[0021] The role of each element in the steel and the corresponding composition design are as follows:

[0022] C: C is the main element that determines the strength of steel and is also the element that has the greatest impact on the MA component in the heat-affected zone. When C is lower than 0.05%, it is difficult to obtain the required strength; when C is higher than 0.12%, the hardened structure and MA component in the weld heat-affected zone increase significantly, which deteriorates the toughness, and welding cracks are easily generated when C is high. The C content of the present invention is controlled at 0.04-0.12.

[0023] Si: Si is a deoxidizing element and also a strengthening element. When Si is less than 0.05%, the deoxidizing effect is poor, and the steel plate surface is prone to pitting and red rust; but when Si is greater than 0.35%, it promotes the coarsening of the structure, increases the MA component, and increases the sensitivity of cold and hot cracks in welding. In the present invention, Si is controlled at 0.10-0.35.

[0024] Mn: Mn is a solid solution element, and it can improve both strength and toughness by expanding the austenite phase region, lowering the phase transformation point and refining the ferrite grains; thus, it can replace part of C, appropriately reduce the C content, and additionally improve the low-temperature toughness of the heat-affected zone of welding. When the Mn content is lower than 1.10%, the strength is reduced, and the harmful effects of sulfides are enhanced; but when the Mn content is higher than 1.80%, the MA component content is increased, and the toughness of the heat-affected zone deteriorates. In the present invention, Mn is controlled at 1.45-1.58%.

[0025] P: P is an impurity element that increases the brittleness of steel and should be reduced as much as possible. However, the cost of metallurgical removal of P is very high, and limiting it to less than 0.015% can ensure performance requirements.

[0026] S: When the sulfur content in steel is high, S exists in the form of FeS-Fe eutectic around the steel grains, reducing the mechanical properties of the steel. Its content is similar to that of phosphorus, the lower the better. In actual production, it is usually controlled at S≤0.005%.

[0027] Ni: Ni can significantly increase the toughness of the matrix and coarse-grained heat-affected zone, but Ni is a precious metal element and adding too much will increase the cost. Therefore, the Ni element is controlled to 0.25-0.40.

[0028] Cu: A proper amount of Cu will promote the nucleation of acicular ferrite, but too high a Cu content will cause hot cracks during rolling and is not conducive to welding performance. Control the Cu content to 0.08-0.18.

[0029] Mo: A proper amount of Mo can significantly improve the strength and tempering stability of steel plates, refine the grains in the heat-affected zone of welding, and improve the toughness of welded joints. However, if Mo is added too much, it will seriously reduce the toughness of welded joints and increase production costs, so the Mo content is controlled to be ≤0.05.

[0030] V: V has a strong precipitation strengthening effect and contributes greatly to improving strength. When the V content is less than 0.005%, precipitation strengthening cannot be prominently exerted; when the V content is higher than 0.07%, the hardenability of the steel plate is enhanced, and the toughness of the steel plate and the heat-affected zone is reduced. In the present invention, V is controlled between 0.01-0.09.

[0031] Ti: Ti is the main element in steel for high-energy wire use. Ti combines with N to form TiN, which prevents the growth of austenite grains and can effectively improve the toughness of the heat-affected zone. The addition of Ti can also reduce the solid solution content of N and improve the aging properties of steel. When the amount of Ti is less than 0.008%, the number of beneficial nitrides formed is small, and the effect of inhibiting grain growth is weak; when the amount of Ti exceeds 0.025%, the amount of solid-dissolved Ti in the steel is too much, and the remaining Ti exists in the crystal in the form of solid solution, increasing the MA component and reducing the performance of the heat-affected zone. In the present invention, Ti is controlled at 0.005-0.030.

[0032] B: B is a characteristic element of the present invention. It allows solid solution B and BN to exist simultaneously in both the base material and the high-heat input welding HAZ, and simultaneously reflects the segregation and nucleation effects. The BN precipitated in the austenite acts as a phase transformation nucleus, and the toughness is improved by refining the structure of the HAZ, reducing the hardness, and reducing the MA. Therefore, it is necessary to contain more than 0.0002% of B. On the other hand, if the amount of B contained exceeds 0.002%, coarse B precipitates will be produced, and the toughness of the HAZ will deteriorate, so 0.002% is the upper limit. In order to improve the toughness of the HAZ, the amount of B can be controlled to 0.0005-0.0035.

[0033] Al: Al is the main deoxidizer and plays a major role in deoxidation during the steelmaking process, so the Al content is controlled at 0.005-0.025.

[0034] Ce: The addition of Ce element can refine the grains and improve the distribution of alloy elements in steel, but excessive addition of Ce will make the cost too high, so the Ce element is controlled at 0.021-0.035.

[0035] N: N is another important element of the present invention. N has two forms of existence, one is solid solution, which is not good for the performance of the base material, and the other is to form dispersed fine particles of N compounds, which improves the toughness of the heat affected zone of welding. High N content causes an increase in solid solution N, poor toughness and aging properties of the base material, and cracks are easily generated in the continuous casting billet. The present invention is 0.0045~0.0080.

[0036] O: O is an inevitable impurity element in the steelmaking process. It will not cause obvious adverse effects on the performance of the steel plate. The content can be controlled within 0.0005-0.0030.

[0037] In addition to reasonably controlling and optimizing the element range in the steel plate, the E-grade steel plate of the present invention also needs to accurately regulate the relative addition amounts of some key elements so that the steel plate of the present invention has uniform and excellent strength, toughness, and plasticity matching, and can withstand high-energy line welding.

[0038] 0.6≤CR*≤0.9: It is required that the five alloying elements Ti, V, C, B, and N related to the formation of precipitated particles be controlled according to "CR*=15.32Ti+5.79V+0.06B+0.18C+0.15N" to control the morphology of the second phase particles in the steel, so that there are mainly two different types of particles in the steel, namely particles with a size of 20-80nm that can inhibit the growth of austenite grains and particles with a size of 0.5-1.5μm that can heterogeneously nucleate. When the chemical composition of the steel plate satisfies the relationship of 0.6≤CR*≤0.9, during the 350kJ / cm high heat input welding process, the second phase particles can effectively inhibit the growth of austenite grains in the heat affected zone of the near-seam welding, and at the same time produce a large amount of heterogeneously nucleated acicular ferrite inside the grains, refine the organization, improve toughness, and maintain a certain strength. If CR* is too high or too low, it will not be possible to achieve the pinning of austenite grain boundaries by nano-scale precipitates and the promotion of heterogeneous nucleation of acicular ferrite by micron-scale precipitates.

[0039] The E-grade steel plate of the present invention limits the appropriate heating temperature, rough rolling temperature, finishing rolling temperature, initial cooling temperature and final cooling temperature of the steel billet, so that the base material forms a moderately refined multi-phase composite structure to obtain high plasticity and toughness mechanical properties; at the same time, second phase particles with a moderate size and quantity distribution are formed in the base material, so that the second phase particles can play a role in refining the structure, improving toughness and maintaining a certain strength in the welding heat affected zone.

[0040] The beneficial effects of the present invention are:

[0041] (1) Through reasonable design and optimization of the alloying element ratio, particles with a size of 20-80 nm that can inhibit the growth of austenite grains are dissolved during the welding thermal cycle, but the overall number is still sufficient to inhibit the growth of austenite grains and control the austenite grain size in the heat-affected zone; particles with a size of 0.5-1.5 μm that can heterogeneously nucleate are present in large quantities, promoting the nucleation of intracrystalline acicular ferrite and optimizing the microstructure and distribution of the welding heat-affected zone; at the same time, the above two types of second phase particles form a bimodal size distribution state, giving full play to the characteristics of the two types of particles in the solid-phase reaction to regulate the high heat input welding performance of the steel, avoiding complicated liquid-phase reaction control, and thus stably carrying out mass production;

[0042] (2) The microstructure of the present invention is mainly acicular ferrite and granular bainite, the yield strength ReL ≥ 370MPa, the tensile strength Rm ≥ 510MPa, and when the welding heat input reaches 350kJ / cm by multi-wire submerged arc welding, the KV2 of the welding heat affected zone at -40℃ can still meet ≥ 60J. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the microstructure diagram of the heat affected zone of the steel in Example 1 at a welding heat input of 350KJ / cm;

[0044] Figure 2 It is the microstructure diagram of the heat affected zone of the comparative example 2 steel with a welding heat input of 350KJ / cm. DETAILED DESCRIPTION

[0045] An E-grade steel plate capable of withstanding 350 kJ / cm high heat input welding and having a yield strength of not less than 370 MPa, the E-grade steel plate comprising, by mass percentage, C 0.04-0.12, Si 0.10-0.35, Mn 1.45-1.58, P ≤0.015, S ≤0.005, Ni 0.25-0.40, Cu 0.08-0.18, Mo ≤0.05, 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 the remainder being iron and unavoidable impurities;

[0046] Ti, V, B, C and N in the E-grade steel plate composition,

[0047] Satisfies 0.6≤15.32Ti+5.79V+0.06B+0.18C+0.15N≤0.9.

[0048] The chemical compositions, elemental relationships, and proportions of the two types of precipitated particles of Examples 1 to 8 and Comparative Examples 1-2 are shown in Table 1.

[0049] Table 1 Chemical compositions of the embodiments and comparative examples

[0050]

[0051] In the heat-affected zone near the fusion line of the E-grade steel plate after welding, among the particles with a size of 20-80 nm that can inhibit the growth of austenite grains, the number of (V, Ti) (C, N) composite precipitated particles accounts for 80-90% and the number density is 1.95×10 6 -3.34×10 6 Pieces / mm 3 .

[0052] Among the particles with a size of 0.5-1.5 μm in the heat-affected zone near the fusion line after welding of the E-grade steel plate, the number of composite precipitated particles of (Ti, V, B) (C, N) accounts for 70-80% and the number density is 2.68×10 5 -4.32×10 5 Pieces / mm 3 .

[0053] The yield strength ReL of the E-grade steel plate is ≥370MPa, the tensile strength Rm is ≥510MPa, and the near-seam welding heat-affected zone KV2 is ≥60J at -40°C after a large heat input of 350kJ / cm.

[0054] The heat affected zone of the E-grade steel plate near the weld is a region where the peak temperature near the weld is between 1250-1400°C and the temperature above 500°C is maintained for 300-500s.

[0055] The E-grade steel plate is produced by vacuum furnace smelting, controlled rolling and controlled cooling processes, and the specific process parameters are: controlling the heating temperature between 1050-1300°C and keeping warm for more than 3 hours, controlling the rolling temperature of the rough rolling process between 1000-1050°C, and controlling the rolling temperature of the finishing rolling process between 750-950°C.

[0056] In the rough rolling process, the rough rolling passes are 5-7 passes with large reduction, and the total reduction rate of rough rolling is not less than 60%.

[0057] In the finishing rolling process, the finishing rolling passes are 4-6 passes and the reduction ratio of the last three passes is ≥35%.

[0058] Furthermore, the cooling control process parameters of the E-grade steel plate are: the cooling start temperature is controlled at 760-800°C, the cooling rate is controlled at 10-20°C / s, and the red-return temperature is controlled at 540-570°C.

[0059] The specific preparation method of the present invention is:

[0060] (1) Preparation of steel billets: The various chemical compositions listed in Table 1 were melted in a laboratory manner, heated and melted in a vacuum furnace, and the molten steel was refined at high temperature and high vacuum for 15 minutes. Then, argon gas was filled into the steel billet and alloys were added. The temperature was adjusted and the steel billet was cast into steel ingots.

[0061] (2) Thermomechanical rolling: First, heat the square ingot to 1050-1300℃ at a speed of 10℃ / s, keep it warm for more than 3 hours, and then carry out three stages of rough rolling, finishing rolling and cooling; the starting temperature of rough rolling is 1050-1100℃, the final rolling temperature of rough rolling is 1020-1080℃, the rolling passes are 5-7 including the widening pass, and the total reduction rate is not less than 55%; the starting temperature of finishing rolling is 850-900℃, the final rolling temperature of finishing rolling is 780-830℃, the finishing passes are 4-6, and the reduction rate of the last three passes is ≥35%; the starting temperature of the cooling stage is controlled to be 760-800℃, the cooling rate is controlled to be 10-20℃ / s during the cooling process, and the final cooling temperature is 540-570℃.

[0062] The mechanical properties of the steel plates obtained by the above method were tested respectively. The results are shown in Table 2. The yield strength is greater than 370MPa, the tensile strength is greater than 510MPa, the elongation is greater than 20%, the longitudinal impact of the parent material at -40℃ is greater than 250J, and the -40℃ impact energy of the heat affected zone near the weld after a large heat input of 350KJ / cm is greater than 120J.

[0063] Table 2 Mechanical properties of examples and comparative examples

[0064]

[0065] Although the compositions of Comparative Examples 1 and 2 are similar to those of the embodiments of the present invention, due to different control methods, the proportions of the two types of particles in Comparative Examples 1 and 2 are smaller than the proportion of particles controlled by the present invention, and the effects of the two types of particles cannot be maximized at the same time. Therefore, the -40°C low-temperature toughness of Comparative Examples 1 and 2, including the heat-affected zones near the structural seams, is significantly reduced after a large heat input of 350 kJ / cm.

[0066] When the simulated welding heat input is 350KJ / cm, the microstructure of the heat affected zone of the steel in Example 1 is as shown in the attached figure. Figure 1 As shown in the figure, the heat affected zone structure of the steel plate in comparative example 1 is as shown in the figure. Figure 2 As shown. It can be seen that the heat-affected zone of the weather-resistant bridge steel plate of the present invention is mainly composed of acicular ferrite and pearlite, and this organization makes its heat-affected zone have good low-temperature toughness. In contrast, the chemical composition content and proportion of the comparative steel 2 are not within the scope of the innovative design technology defined in the present invention, and the obtained organization is composed of proeutectoid ferrite, granular bainite and a small amount of acicular ferrite. This organization is coarse and unevenly distributed. When subjected to impact loads, microcracks are easily generated, resulting in brittle fracture, which makes the low-temperature toughness of the welding heat-affected zone poor.

[0067] In summary, within the composition range and preparation process conditions of the present invention, an E-grade steel plate with a yield strength of not less than 370 MPa that can withstand 350 kJ / cm high heat input welding is achieved, which can be widely used in the construction of bridges with large spans, high parameters, and all-welded structures.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. An E-grade steel plate with a yield strength of not less than 370 MPa that can withstand 350 kJ / cm high heat input welding, characterized in that: The E-grade steel plate includes, by mass percentage, C 0.04-0.12, Si 0.10-0.35, Mn 1.45-1.58, P ≤0.015, S ≤0.005, Ni 0.25-0.40, Cu 0.08-0.18, Mo≤0.05, 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 the rest is iron and unavoidable impurities; Ti, V, B, C and N in the E-grade steel plate composition, Satisfy 0.6≤15.32Ti+5.79V+0.06B+0.18C+0.15N≤0.9; In the heat-affected zone near the fusion line of the E-grade steel plate after welding, among the particles with a size of 20-80 nm that can inhibit the growth of austenite grains, the number of (V, Ti) (C, N) composite precipitated particles accounts for 80-90% and the number density is 1.95×10 6 -3.34×10 6 Pieces / mm 3 ; In the heat-affected zone near the fusion line of the E-grade steel plate after welding, among the particles with a size of 0.5-1.5 μm, the number of composite precipitated particles of (Ti, V, B) (C, N) accounts for 70-80% and the number density is 2.68×10 5 -4.32×10 5 Pieces / mm 3 .

2. The E-grade steel plate according to claim 1, characterized in that: The yield strength ReL of the E-grade steel plate is ≥370MPa, the tensile strength Rm is ≥510MPa, and the near-seam welding heat-affected zone KV2 is ≥60J at -40°C after a large heat input of 350kJ / cm.

3. The E-grade steel plate according to claim 2, characterized in that: The heat affected zone of the E-grade steel plate near the weld is a region where the peak temperature near the weld is between 1250-1400°C and the temperature above 500°C is maintained for 300-500s.

4. The E-grade steel plate according to any one of claims 1 to 3, characterized in that: The E-grade steel plate is produced by vacuum furnace smelting, controlled rolling and controlled cooling processes, and the specific process parameters are: controlling the heating temperature between 1050-1300°C and keeping warm for more than 3 hours, controlling the rolling temperature of the rough rolling process between 1000-1050°C, and controlling the rolling temperature of the finishing rolling process between 750-950°C.

5. The E-grade steel plate according to claim 4, characterized in that: In the rough rolling process, the rough rolling passes are 5-7 passes with large reduction, and the total reduction rate of rough rolling is not less than 60%.

6. The E-grade steel plate according to claim 4, characterized in that: In the finishing rolling process, the finishing rolling passes are 4-6 passes and the reduction ratio of the last three passes is ≥35%.

7. The E-grade steel plate according to claim 4, characterized in that: The cooling control process parameters of the E-grade steel plate are: the cooling start temperature is controlled at 760-800°C, the cooling rate is controlled at 10-20°C / s, and the red-return temperature is controlled at 540-570°C.

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