A thick steel plate for container with high strength and low welding crack sensitivity and its production method

Abstract

The present invention relates to a thick steel plate for a container with high strength and low welding crack sensitivity. The chemical composition of the steel plate is as follows by mass percentage: C: 0.04%-0.06%, Si: 0.15%-0.30%, Mn: 1.60%-1.70%, P≤0.005%, S≤0.001%, Ni: 0.05%-0.13%, Cr: 0.20%-0.30%, Mo: 0.10%-0.20%, Nb: 0.01%-0.02%, V: 0.08%-0.15%, Al: 0.01%-0.02%, Cu≤0.02%, B≤0.003%, Zr: 0.003%-0.008%, V+Zr≤0.15%, and the balance is Fe and unavoidable impurities. The steel plate of the present invention has a yield strength of ≥700MPa; a tensile strength of 800-950MPa; an elongation of ≥19%; an impact energy absorption at -50°C of ≥100J; and a crack tip opening displacement CTOD value of δ R Between 0.800 and 0.820; the crack extension Δa is between 0.62 and 0.65, and the low welding crack sensitivity coefficient Pcm≤0.22.

Description

Technical Field

[0001] The present invention relates to the field of pressure vessel steel manufacturing, in particular to a thick steel plate for a container with low strength and welding crack sensitivity and a production method thereof. Background Art

[0002] Low welding crack sensitivity steel, also known as CF steel, is a type of low-alloy high-strength steel with excellent weldability that began to be developed after 1970. Its main advantage is that it does not require preheating before welding or only requires slight preheating without generating cracks. It is mainly used in the construction of pressure vessel steel for fixed storage tanks.

[0003] Low-weld crack sensitivity (CF) steel plates are primarily used in oil and liquefied natural gas (LNG) storage tanks. For these tank steels, subsequent weldability must be considered, ensuring the plate's tensile strength and ensuring that all properties meet national standards after quenching and tempering. With the increasing size of pressure vessel equipment and the increasing size of fixed storage tanks, the demand for pressure vessel steel plates is also increasing. Therefore, the research and development of higher-strength steels with low weld crack sensitivity is becoming increasingly urgent.

[0004] In the existing patent CN201110117614.4 "Steel for nuclear vessels with tensile strength greater than 690 MPa and production method", in order to ensure that the steel plate has good low welding crack sensitivity and good comprehensive mechanical properties, the rolling temperature of the steel plate is reduced. However, due to the low final rolling temperature, the steel plate is difficult to roll during the actual production process and the waiting time is long.

[0005] While the existing patent CN201711150709.X, "770MPa-Grade Low Weld Crack Sensitivity Pressure Vessel Steel and Its Manufacturing Method," has a low Pcm value, the pursuit of a low Pcm value results in significant variations in the content ratios of key elements such as C and Mn, leading to lower tensile strength. The mechanical properties of the steel plate after quenching and tempering may fall below the standard. To address this issue, it is urgent to develop high-strength pressure vessel steel with excellent low weld crack sensitivity through novel composition design. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a thick steel plate for containers with high strength and low welding crack sensitivity, which is suitable for containers for storing petroleum and liquefied natural gas.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions:

[0008] A thick steel plate for containers with high strength and low welding crack sensitivity. The chemical composition of the steel plate is as follows by mass percentage: C: 0.04% to 0.06%, Si: 0.15% to 0.30%, Mn: 1.60% to 1.70%, P≤0.005%, S≤0.001%, Ni: 0.05% to 0.13%, Cr: 0.20% to 0.30%, Mo: 0.10% to 0.20%, Nb: 0.01% to 0.02%, V: 0.08% to 0.15%, Al: 0.01% to 0.02%, Cu≤0.02%, B≤0.003%, Zr: 0.003% to 0.008%, V+Zr≤0.15%, and the balance is Fe and unavoidable impurities.

[0009] The invention discloses a thick steel plate for a container with high strength and low welding crack sensitivity, the thickness of which is 50 to 60 mm.

[0010] A high-strength, low-weld crack-sensitivity thick steel plate for containers, with yield strength ≥700MPa; tensile strength 800-950MPa; elongation ≥19%; impact absorption energy at -50°C ≥100J; crack tip opening displacement CTOD value δ R Between 0.800 and 0.820; the crack extension Δa is between 0.62 and 0.65, and the low welding crack sensitivity coefficient Pcm≤0.22.

[0011] The effects of the above chemical elements are analyzed as follows:

[0012] Carbon (C) forms various carbides with alloying elements in steel, strengthening it and directly increasing the strength of steel plates. While maintaining strength, keeping the C content near its upper limit improves the hardenability of the steel. However, higher C content affects the steel's weld crack sensitivity, potentially increasing welding difficulty and preheating temperatures. Therefore, the C content is limited to 0.04% to 0.06%.

[0013] Si is an effective deoxidizer in steel, and a certain amount of Si can increase the strength of steel plates and improve the hardenability of steel, but it also reduces plasticity and toughness. If the Si content is too high, the impact toughness of the heat-affected zone will deteriorate, so the Si content is limited to 0.15% to 0.30%.

[0014] Mn improves the strength and hardness of steel plates through solid solution strengthening, reduces the quenching temperature and austenite transformation temperature of steel, increases the steel's undercooling, refines the grain size, and reduces weld crack sensitivity. Therefore, Mn is limited to 1.60% to 1.70%.

[0015] P is a harmful element in steel and is also an element that is prone to segregation. Therefore, its content should be kept low during the steelmaking process. However, considering cost factors and meeting application requirements, the P content is controlled within a range that does not affect performance, so it is controlled below 0.005%.

[0016] S is also a harmful element in steel and has a great influence on the low-temperature impact toughness of steel. However, considering the operability and cost of steelmaking, the S content is controlled below 0.001%.

[0017] Nickel is the main element that stabilizes austenite in steel. Ni can exist in austenite and ferrite in a solid solution with Fe. Therefore, it can improve the strength of steel, refine grains, improve the low-temperature impact toughness of steel, lower the ductile-brittle transition temperature, and reduce weld crack sensitivity. However, due to the high cost of nickel, this patent reduces the Ni content and adjusts other elements to ensure low-temperature impact toughness. Therefore, the Ni content is limited to between 0.05% and 0.13%.

[0018] Cr in steel primarily increases its hardenability and improves its tempering stability during heat treatment. However, increased Cr content can increase weld crack sensitivity, so the Cr content is controlled between 0.20% and 0.30%.

[0019] Mo in steel is an element that reduces the austenite region and promotes ferrite transformation. Mo can dissolve in austenite and ferrite to increase the strength of the steel through solid solution strengthening, while also suppressing the occurrence of temper brittleness. Therefore, the Mo content is between 0.10% and 0.20%.

[0020] The addition of niobium (Nb) refines grains and increases steel plate thickness, while also delaying the recrystallization of high-temperature austenite. Nb also strengthens the steel after solid solution, improving its hardenability. Therefore, the Nb content is limited to 0.01% to 0.02%.

[0021] V, the primary element in this patent, dissolves into austenite at high temperatures, increasing the steel's hardenability. V ensures the steel's strength and hardness through precipitation strengthening, and appropriately increasing V can improve the core strength of thick steel plates through dispersion strengthening. Microalloying increases the formation of VC carbides in the steel, and these relatively stable carbides inhibit grain boundary movement and grain growth, improving the steel's tempering stability. Therefore, V is limited to 0.08% to 0.15%.

[0022] Al acts as a deoxidizer in steel and forms fine and dispersed AlN with N in the steel, which inhibits grain growth and improves the low-temperature toughness of the steel. Therefore, it is more appropriate to limit the Al content to 0.01% to 0.02%.

[0023] The addition of B can improve the hardenability of steel, inhibit the formation of proeutectoid ferrite, ensure the cold and hot workability of steel, and improve the welding performance of steel. Therefore, the B content is controlled below 0.003%.

[0024] Zr is the main element of this patent. It can act as an oxygen, phosphorus and sulfur remover during the smelting process. It can be dissolved in austenite at high temperature to prevent the growth of austenite grains, refine the ferrite grains, improve the hardenability of steel, and increase the strength and hardness of steel. It also improves the welding performance of steel. Therefore, the Zr content is controlled below 0.003% to 0.008%.

[0025] A method for producing a thick steel plate for a container with high strength and low weld crack sensitivity, comprising smelting, continuous casting, heating, rolling, and heat treatment, wherein:

[0026] 1) Smelting: 20-35 minutes before the end of the oxygen top-blown converter, the V, Nb, and Zr contents are regulated, and LF furnace refining + RH vacuum treatment is used for further refining and composition adjustment;

[0027] 2) Continuous casting: At the end of the solidification of the continuous casting billet, heavy reduction is adopted, the total reduction is controlled at 45-60 mm, and the casting speed is controlled at 0.8-1.3 m / min;

[0028] 3) Rolling: Rough rolling, the starting rolling temperature is controlled at 1100-1150℃, the roller speed is controlled at 0.5-0.7m / s, and the relative reduction rate of a single pass is controlled at 12-18%, ensuring that the total reduction rate of rough rolling is ≥75%. In this stage, large deformation is used for rapid rolling to ensure that the dynamic recrystallization of the steel plate during the rough rolling process is complete; the starting rolling temperature of the finishing rolling is 920±50℃, the rolling temperature of the final rolling pass is controlled at 800-840℃ in the non-crystallization zone, the roller speed is controlled at 0.8-0.9m / s, the relative reduction rate of a single pass is 8-9%, ensuring that the total reduction rate of the finishing rolling pass is ≥25%, and small deformation is used for rapid rolling to ensure grain refinement of the steel plate;

[0029] 4) Heat treatment: The quenching temperature is controlled at 970±10℃, the tempering temperature is controlled at 610±10℃, and after the heat treatment, it is air-cooled to room temperature. The steel plate structure is tempered bainite + bainite, and the grain size is 9 to 11.

[0030] The smelting process includes: firstly, pre-treating the molten iron, adjusting the composition in an oxygen top-blown converter, blowing argon in a ladle, and then refining in an LF furnace for deep dephosphorization and desulfurization to reduce the phosphorus content in the molten iron to less than 0.005% and the sulfur content to less than 0.001%, ensuring that the argon soft blowing time is ≥7 minutes and the refining time is 30-60 minutes; then, RH vacuum treatment is used for further refining and composition adjustment, and the vacuum treatment time is 30-60 minutes to allow inclusions in the molten steel to fully float.

[0031] The continuous casting process is as follows: the casting process is carried out under argon protection, the secondary cooling water volume is controlled at more than 5000L / min, the casting superheat is guaranteed to be 15-25℃, and the billet straightening temperature is controlled at 1000±50℃ to ensure the quality of the casting.

[0032] The heating process is as follows: the casting is first heated to 600-650°C in a constant temperature furnace, simmered at 650-750°C for 180-240 minutes, and then heated to 1250-1300°C in a continuous heating furnace at a heating rate of 1.8-2.5 min / mm. After reaching the temperature, it is kept warm for 180-240 minutes, and the billet discharge temperature is controlled at 1150-1200°C.

[0033] The heat treatment process is as follows: the steel plates are stacked and slowly cooled before undergoing a quenching + tempering heat treatment process, the quenching heating rate is 1.0-1.5 min / mm, the holding time is 60-80 min, the tempering heating rate is 1.2-2.0 min / mm, the holding time is 30-60 min, and air cooling at room temperature is performed after the heat treatment is completed.

[0034] Compared with the existing technology, the beneficial effects of the present invention are:

[0035] This invention reduces the nickel content in the steel, ensuring excellent low-temperature toughness and lowering costs. To ensure high strength and hardness, the alloying element vanadium (V) content is increased, and niobium (Nb) is added to the steel. After microalloying, V and Nb strengthen the steel through solid solution and dispersion strengthening, ensuring excellent toughness and hardenability after quenching and tempering. The addition of Zr refines the grain size, increasing strength and imparting excellent weldability and low-temperature performance. The resulting microstructure is tempered bainite + bainite, with a grain size of 9 to 11. These measures ensure low weld crack susceptibility.

[0036] Steel plate yield strength ≥700MPa; tensile strength 800~950MPa; elongation ≥19%; impact absorption energy at -50℃ ≥100J; crack tip opening displacement CTOD value δ R Between 0.800 and 0.820; the crack extension Δa is between 0.62 and 0.65, and the low welding crack sensitivity coefficient Pcm ≤ 0.22

[0037] The present invention regulates the contents of V, Nb and Zr 20-35 minutes before the oxygen top-blown converter, then adopts LF furnace refining + RH vacuum treatment to improve the micro-alloying effect of the alloy elements, and adopts full-process protective casting during the continuous casting process to ensure the purity of the steel billet. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the metallographic structure diagram of the steel plate of the present invention.

[0039] Figure 2 This is the metallographic structure of the steel plate welded joint of the present invention. DETAILED DESCRIPTION

[0040] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0041] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means more than two.

[0042] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0043] A thick steel plate for containers with high strength and low welding crack sensitivity. The chemical composition of the steel plate is as follows by mass percentage: C: 0.04% to 0.06%, Si: 0.15% to 0.30%, Mn: 1.60% to 1.70%, P≤0.005%, S≤0.001%, Ni: 0.05% to 0.13%, Cr: 0.20% to 0.30%, Mo: 0.10% to 0.20%, Nb: 0.01% to 0.02%, V: 0.08% to 0.15%, Al: 0.01% to 0.02%, Cu≤0.02%, B≤0.003%, Zr: 0.003% to 0.008%, V+Zr≤0.15%, and the balance is Fe and unavoidable impurities.

[0044] A method for producing a thick steel plate for containers with high strength and low weld crack sensitivity includes smelting, casting, heating, rolling, and heat treatment. The specific steps are as follows:

[0045] 1. Smelting

[0046] The molten iron is first pretreated. The V, Nb and Zr contents are adjusted 20-35 minutes before the end of the oxygen top-blown converter to form ZrC, ZrS and Nb- and V-containing precipitates in the molten steel. After the ladle is argon-blown, the molten iron is refined in an LF furnace to adjust the composition and undergo deep dephosphorization and desulfurization treatment to reduce the P content in the molten iron to less than 0.005% and the S content to less than 0.001%. The argon soft blowing time is ensured to be ≥7 minutes and the refining time is 30-60 minutes. RH vacuum treatment is then used to further refine and adjust the composition. The vacuum treatment time is 30-60 minutes to allow inclusions in the molten steel to fully float up, ensure the purity of the molten steel, and provide sufficient time for microalloying treatment of the molten steel.

[0047] 2. Continuous casting

[0048] The casting process of the continuous casting billet is carried out under argon protection throughout the casting process. At the end of the solidification of the continuous casting billet, a heavy reduction method is adopted, and the total reduction is controlled at 45 to 60 mm. The billet drawing speed is strictly controlled at 0.8 to 1.3 m / min, the secondary cooling water parameter is controlled at more than 5000 L / min, the casting superheat is guaranteed to be 15 to 25°C, and the billet straightening temperature is controlled at 1000±50°C to ensure the surface quality of the billet and reduce the generation of internal defects in the billet. ZrC and (Nb, V)C precipitates affect the deformation of austenite at high temperatures during the casting process, inhibit the growth of billet grains, eliminate defects such as segregation and looseness in the billet, and make the billet structure uniform.

[0049] 3. Heating

[0050] The casting billet is first heated to 600℃ in a constant temperature furnace, simmered at 650-750℃ for 180-240min, and then heated to 1250-1300℃ in a continuous heating furnace at a heating rate of 1.8-2.5min / mm. After reaching temperature, it is kept warm for 180-240min. The billet out-of-furnace temperature is controlled at 1150-1200℃ to ensure that the continuous casting billet is completely austenitized during the heating process and the precipitates are fully dissolved.

[0051] 4. Rolling

[0052] After the steel billet is taken out of the furnace, rough rolling is carried out, the starting rolling temperature is controlled at 1100-1150℃, the roller speed is controlled at 0.5-0.7m / s, and the relative reduction rate of a single pass is controlled at 12-18%, ensuring that the total reduction rate of rough rolling is ≥75%, the starting rolling temperature of finishing rolling is 920±50℃, the rolling temperature of the last pass is controlled at 800-840℃ in the non-crystallization zone, the roller speed is controlled at 0.8-0.9m / s, the relative reduction rate of a single pass is 8-9%, ensuring that the total reduction rate of the finishing pass is ≥25%, and ensuring that the recrystallization process occurs fully in the core and near the surface of the steel plate.

[0053] 5. Heat treatment

[0054] The steel plate is stacked and slowly cooled before undergoing a quenching + tempering heat treatment process. The quenching temperature is 970±10℃, the heating rate is 1.0~1.5min / mm, and the holding time is 60~80min. The tempering temperature is 610±10℃, the heating rate is 1.2~2.0min / mm, and the holding time is 30~60min. After the heat treatment, it is air-cooled at room temperature. The steel plate structure is tempered bainite + bainite, and the grain size is 9~11, ensuring that the steel plate has good comprehensive mechanical properties after heat treatment.

[0055] The preferred embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all fall within the scope of protection of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner unless there is any contradiction. In order to avoid unnecessary repetition, the present invention will no longer describe various possible combinations separately. In addition, the various different embodiments of the present invention can also be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

[0056] To make the objectives, technical solutions, and technical effects of the present invention more clear, the technical solutions in the embodiments of the present invention are now clearly and completely described. However, the embodiments described below are only some of the embodiments of the present invention, not all of them. In combination with the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0057] The chemical composition of the embodiment is shown in Table 1; the smelting and casting process is shown in Table 2. The thickness of the ingot is 250-360 mm. After heating, the ingot is rolled into a steel plate with a thickness of 50-60 mm in a 5500 mm wide and heavy plate rolling mill. The rolling process is shown in Table 3. After the heat treatment method of the quenching and tempering treatment, various mechanical property tests are carried out respectively. The heat treatment process is shown in Table 4. The test results of the embodiment are shown in Tables 5 and 6.

[0058] Table 1 Chemical composition of the examples (wt%)

[0059]

[0060] Table 2 Example smelting and casting process

[0061]

[0062]

[0063] Table 3 Example rolling process

[0064]

[0065] Table 4 Example heat treatment process

[0066]

[0067]

[0068] Table 5 Mechanical properties of the embodiment in the quenched and tempered heat treatment state

[0069]

[0070] Table 6 Grain size and non-metallic inclusion test results

[0071]

[0072] The crack tip opening displacement test was carried out on the steel plate. The test was carried out in accordance with GB / T2358-1994 "Test method for crack tip opening displacement of metallic materials". The crack tip opening displacement of the weld metal and heat affected zone of the sample weld joint was measured at -50℃. The CTOD value δ R The Δa value is 0.800-0.820, the crack extension is 0.62-0.65, and the calculated Pcm value is less than 0.22. This fully demonstrates the low sensitivity of the steel plate to weld cracks. Metallographic photographs show that the steel plate structure is tempered bainite + bainite, and the structure is uniform.

[0073] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and basic spirit of the invention, and the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for producing a thick steel plate for a container with high strength and low welding crack sensitivity, characterized in that: The chemical composition of the steel plate is as follows by mass percentage: C: 0.04% to 0.06%, Si: 0.15% to 0.30%, Mn: 1.60% to 1.70%, P≤0.005%, S≤0.001%, Ni: 0.05% to 0.13%, Cr: 0.20% to 0.30%, Mo: 0.10% to 0.20%, Nb: 0.01% to 0.02%, V: 0.08% to 0.15%, Al: 0.01% to 0.02%, Cu≤0.02%, B≤0.003%, Zr: 0.003% to 0.008%, V+Zr≤0.15%, and the balance is Fe and unavoidable impurities; the production method includes smelting, continuous casting, heating, rolling, and heat treatment, wherein: 1) Smelting: 20-35 minutes before the end of the oxygen top-blown converter, the V, Nb, and Zr contents are adjusted, and LF furnace refining + RH vacuum treatment is used; 2) Continuous casting: At the end of the solidification of the continuous casting billet, heavy reduction is adopted, the total reduction is controlled at 45-60 mm, and the casting speed is controlled at 0.8-1.3 m / min; 3) Rolling: Rough rolling, the starting rolling temperature is controlled at 1100-1150℃, the roller speed is controlled at 0.5-0.7m / s, and the relative reduction rate of a single pass is controlled at 12-18%, ensuring that the total reduction rate of rough rolling is ≥75%. In this stage, large deformation is used for rapid rolling. The starting rolling temperature of finishing rolling is 920±50℃, the rolling temperature of the final rolling pass is controlled at 800-840℃ in the non-crystallization zone, the roller speed is controlled at 0.8-0.9m / s, the relative reduction rate of a single pass is 8-9%, ensuring that the total reduction rate of the finishing pass is ≥25%. In this stage, small deformation is used for rapid rolling; 4) Heat treatment: The quenching temperature is controlled at 970±10℃, the tempering temperature is controlled at 610±10℃, and after the heat treatment, it is air-cooled to room temperature. The steel plate structure is tempered bainite + bainite, and the grain size is 9 to 11.

2. The method for producing a thick steel plate for a container with high strength and low welding crack sensitivity according to claim 1, characterized in that: The thickness of the steel plate is 50 to 60 mm.

3. The method for producing a thick steel plate for a container with high strength and low welding crack sensitivity according to claim 1, characterized in that: The steel plate has a yield strength of ≥700 MPa; a tensile strength of 800-950 MPa; an elongation of ≥19%; an impact absorption energy of ≥100 J at -50°C; and a crack tip opening displacement CTOD value δ R Between 0.800 and 0.820; the crack extension Δa is between 0.62 and 0.65, and the welding crack sensitivity coefficient Pcm≤0.

22.

4. The method for producing a thick steel plate for a container with high strength and low welding crack sensitivity according to claim 1, characterized in that: The smelting process is as follows: the molten iron is first pretreated, the composition is adjusted in an oxygen top-blown converter, and after the ladle is argon-blown, deep dephosphorization and desulfurization are carried out in an LF furnace to reduce the phosphorus content in the molten iron to less than 0.005% and the sulfur content to less than 0.001%. The argon soft blowing time is ensured to be ≥7 minutes, and the refining time is 30 to 60 minutes. Then, RH vacuum treatment is used to further refine and adjust the composition, and the vacuum treatment time is 30 to 60 minutes.

5. The method for producing a thick steel plate for a container with high strength and low welding crack sensitivity according to claim 1, characterized in that: The continuous casting process: the billet is cast under argon protection throughout the casting process, the secondary cooling water volume is controlled at more than 5000L / min, the casting superheat is guaranteed to be 15-25°C, and the billet straightening temperature is controlled at 1000±50°C.

6. The method for producing a thick steel plate for a container with high strength and low welding crack sensitivity according to claim 1, characterized in that: The heating process is as follows: the casting billet is first heated to 600-650°C in a constant temperature furnace, simmered at 650-750°C for 180-240 minutes, and then heated to 1250-1300°C at a heating rate of 1.8-2.5 min / mm. After reaching the temperature, it is kept warm for 180-240 minutes, and the billet out-of-furnace temperature is controlled at 1150-1200°C.

7. The method for producing a thick steel plate for a container with high strength and low welding crack sensitivity according to claim 1, characterized in that: The heat treatment process is as follows: the steel plates are stacked and slowly cooled before undergoing a quenching + tempering heat treatment process, the quenching heating rate is 1.0-1.5 min / mm, the holding time is 60-80 min, the tempering heating rate is 1.2-2.0 min / mm, the holding time is 30-60 min, and after the heat treatment is completed, they are air-cooled to room temperature.

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