800MPa-grade steel plate with uniform performance for extra-thick container and manufacturing method of 800MPa-grade steel plate

Abstract

The invention belongs to the field of metal materials, and particularly relates to a 800MPa-grade uniform-performance extra-thick steel plate for a container and a manufacturing method of the 800MPa-grade uniform-performance extra-thick steel plate, and the 800MPa-grade uniform-performance extra-thick steel plate comprises the following chemical components in percentage by weight: 0.18%-0.23% of C, 0.15%-0.37% of Si, 0.98%-1.24% of Mn, less than or equal to 0.01% of P, less than or equal to 0.005% of S, 0.11%-0.32% of Ni, 0.04%-0.18% of Cr, 0.02%-0.04% of V and the balance of Fe and inevitable impurities. Through brand new chemical component design, a three-stage / two-stage efficient slab heating system, an optimal design three-stage rolling process, a two-stage cooling process, a high-temperature short-time tempering heat treatment mode and a special production and manufacturing process are adopted, and the high-strength and high-uniformity super-thick steel plate for the container with good comprehensive performance is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials, and in particular relates to an 800MPa-grade steel plate for ultra-thick containers with uniform performance and a manufacturing method thereof. Background Art

[0002] With the rapid development of the global economy and the continued growth in energy demand, the demand for high-strength, corrosion-resistant, and high-temperature-resistant container steel plates is increasing in industries such as the petroleum, chemical, and power plants. These industries require equipment capable of withstanding high-temperature and high-pressure environments, and high-strength container steel plates are a key material for their manufacture. As a key material for pressure vessel manufacturing, the uniformity of the microstructure and properties of pressure vessel steel plates is directly related to the safe operation of the equipment. Internal structural inhomogeneities in the steel plates, such as uneven grain size and uneven inclusion distribution, can lead to inconsistent mechanical properties, causing stress concentration during stress loading and increasing the risk of equipment failure. Therefore, steel plates with uniform microstructure and properties ensure that all parts of the equipment are evenly stressed when subjected to the design pressure, avoiding damage caused by excessive localized stress. Furthermore, this uniformity in microstructure and properties provides the steel plates with improved corrosion and high-temperature resistance, enabling them to withstand the erosion of media and high-temperature environments, thereby extending the service life of the equipment. Therefore, the development of extra-thick steel plates with high strength and uniform properties for pressure vessels has become an inevitable trend.

[0003] Patent document CN118497618A discloses "an economical 800MPa grade high-strength steel plate and its production method". The steel plate is composed of the following components in weight percentage: C: 0.14~0.17%, Si: 0.15~0.30%, Mn: 1.30~1.40%, P≤0.015%, S≤0.005%, As≤0.010%, Als: 0.015~0.035%, Nb: 0.030~0.045%, Cr: 0.40~0.55%, Ti: 0.008~0.020%, B: 0.0008~0.0020%, N≤0.0050%, and the balance is Fe and other unavoidable impurities. At the same time, the content of the above elements also satisfies the relationship: CEV=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15≤0.50%. The above-mentioned components are subjected to tempering treatment in sequence to produce steel plates with thicknesses of 15 to 45 mm. No process design research has been conducted on steel plates with thicknesses above 45 mm, and only the impact energy at -20°C has been studied. However, the impact toughness in low-temperature environments below -20°C has not been involved. Therefore, it is not suitable for the production of large-scale high-strength and extra-thick container steel.

[0004] Patent document CN114107819A discloses "an 800MPa grade tempering-resistant high-strength steel plate and its preparation method." The steel plate is composed of the following components by weight: C: 0.06-0.13%; Si: 0.30-0.60%; Mn: 1.4-1.8%; P≤0.0010%; S≤0.0005%; As≤0.010%, Als: 0.015-0.045%; Nb: 0.03-0.05%; Cr: 0.20-0.40%; Mo: 0.1-0.40%; Ti: 0.008-0.020%; B: 0.0008-0.0020%; N: ≤0.0060%, with the remainder being Fe and unavoidable impurities. The above composition contains high-content elements Cr and Mo, which are added in large quantities, increasing the production cost of the steel plate. Furthermore, the example steel plates do not specifically analyze the production and mechanical properties of steel plates thicker than 50 mm. Furthermore, the aforementioned method only studies impact toughness at -20°C, not low-temperature impact toughness below -20°C, nor does it address internal microstructure uniformity. This method is unsuitable for large-scale production of high-strength, extra-thick steel for containers. Summary of the Invention

[0005] The present invention aims to provide an 800 MPa-grade, uniform, and extra-thick container steel plate and its manufacturing method. Through a novel chemical composition design, a three-stage / two-stage efficient slab heating system, an optimized three-stage rolling process, a two-stage cooling process, and a high-temperature, short-time tempering heat treatment, the resulting high-strength, high-uniformity extra-thick container steel plate exhibits excellent overall performance. The plate exhibits excellent strength, low-temperature toughness, high-temperature serviceability, and shape, meeting the manufacturing and application requirements for high-performance storage tank steel plates. This method offers low cost and is suitable for large-scale production.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] Disclosed is an 800MPa-grade steel plate for extra-thick containers with uniform performance. The chemical composition of the steel is as follows, by weight percentage: C: 0.18%-0.23%, Si: 0.15%-0.37%, Mn: 0.98%-1.24%, P≤0.01%, S≤0.005%, Ni: 0.11%-0.32%, Cr: 0.04%-0.18%, V: 0.02%-0.04%, with the balance being Fe and unavoidable inclusions; and Pcm%=C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B≤0.30, and CE%=C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B≤0.45.

[0008] The reasons for limiting the amounts of each chemical element C, Si, Mn, P, S, Ni, Cr, and V in the steel plate of the present invention are detailed as follows:

[0009] Carbon (C) is a key element in steel that influences its performance, significantly impacting its strength, toughness, and corrosion resistance. A certain amount of C is added to steel to ensure its strength, hardness, and wear resistance, guaranteeing its serviceability. To maintain its toughness and maintain a good toughness-ductility balance at low temperatures, the present invention sets the C content range to 0.18% to 0.23%.

[0010] Si is an essential element in steel. Because it readily combines with oxygen in steel, it is often used as a deoxidizer. Si dissolves in ferrite and austenite, providing solid solution strengthening and improving the material's wear resistance and strength. However, it can increase the number of non-metallic inclusions in the steel plate, negatively impacting its low-temperature impact energy. Therefore, the present invention sets the Si content range to 0.15% to 0.37%.

[0011] Mn is a good deoxidizer and desulfurizer. A certain amount of Mn in steel can eliminate or reduce the hot brittleness caused by sulfur, thereby improving the steel's hot workability. However, Mn easily combines with sulfur and segregates at grain boundaries, affecting the steel's resistance to hydrogen-induced cracking. Therefore, the present invention sets the Mn content range to 0.98% to 1.24%.

[0012] S and P are harmful elements in steel and must be strictly controlled to ensure the purity and plasticity of the steel. Therefore, the present invention limits the content of S to P≤0.01% and S≤0.005%.

[0013] As a key alloying element in steel, nickel improves steel strength while ensuring toughness, plasticity, and other process properties. Adding nickel to steel lowers the pearlite transition temperature and refines the pearlite structure in the steel plate. Furthermore, nickel reduces the carbon content at the eutectoid point and increases the amount of pearlite in the steel plate, thereby improving service properties such as strength, wear resistance, and corrosion resistance. The present invention sets the nickel content range to 0.11% to 0.32%.

[0014] Cr is a strong carbide-forming element and easily combines with C to form fine carbide particles. Chromium carbide particles have a high melting point. During the phase transformation process, they can effectively prevent dislocation movement, increase the grain boundary area, reduce the austenite grain size, and prevent grain growth, ensuring a good strength and toughness match of the steel plate while ensuring high-temperature service performance. Cr also has a high affinity for O, which is beneficial to improving the oxidation resistance of the steel plate. Cr can increase the hardenability of the steel plate, play a role of secondary hardening, increase the hardness of the steel plate, and ensure that the steel plate has good wear resistance and good tempering stability. When excessive Cr is added to steel, dendritic segregation is easily formed, which will reduce the plasticity of the steel and increase the possibility of crack formation. The present invention sets the Cr content range at Cr: 0.04% to 0.18%.

[0015] Vanadium (V) is a strong carbonitriding element, forming precipitation-strengthening phases such as V (C, N) in steel. This increases the area of ​​grain boundaries and subgrain boundaries for nucleation, significantly refines the microstructure, and acts as a precipitation strengthening agent, ensuring the steel's strength-toughness balance and toughness. In high-temperature environments, vanadium carbides maintain the steel's strength and toughness while also improving its resistance to hydrogen corrosion. However, excessive V content increases brittleness and negatively impacts weldability. Therefore, the V content is preferably between 0.02% and 0.04%. Fine, dispersed Cr-C particles, which precipitate and persist stably at high temperatures, ensure the steel's strength and high-temperature serviceability, while V (C, N) particles, which precipitate at low temperatures, contribute to its toughness. The combination of these two phases ensures a good strength-toughness balance and excellent serviceability. Therefore, in this paper, the ratio of Cr to V carbides is set between 1.8 and 3.5.

[0016] The steel plate structure of the present invention is a structure in which the ratio of troostite, ferrite and spherical bainite calculated by volume percentage is in the range of (1-1.2):1:(1.5-1.8), wherein the size of the spherical bainite is not greater than 80 nm, the grain size is 7-9, the structural inclusion grade summary of the steel plate is not greater than 1.0, and the number ratio of second phase Cr and V carbides with a size in the range of 35-66 nm is 1.8-3.5.

[0017] The mechanical properties of the steel plate are: tensile strength R at room temperature m 820~840MPa, yield strength R el 770~785Mpa, elongation A≥22%; tensile strength R under -40℃ m 860~900MPa, yield strength R el 800~890Mpa, elongation A≥18%, transverse impact energy K V2 The average value is ≥185J; the yield strength ratio of the steel plate at T / 2 and T / 4 is in the range of 0.9 to 1.1, and at a temperature of 450°C, the yield strength of the steel plate can reach 204MPa.

[0018] According to the hydrogen-induced cracking (HIC) test GB / T8650-2006 and NACE-TM0284 "Evaluation Method for Hydrogen-Induced Cracking Resistance of Pipeline Steel and Pressure Vessel Steel", the steel plate crack sensitivity CSR%, crack length rate CLR%, and crack width rate CTR% are all 0; according to GB / T17897-2016 "Corrosion of Metals and Alloys - Ferric Chloride Pitting Corrosion Test Method for Stainless Steel", the steel plate corrosion rate is not more than 0.002g / m 2 .h.

[0019] According to GB / T3960-2016 "Test Method for Sliding Friction and Wear of Plastics", the volume wear of the steel plate is no more than 0.0003cm 3 .

[0020] The thickness of the finished steel plate of the present invention is 55 to 100 mm.

[0021] A method for manufacturing an 800MPa-grade, uniform-performance, extra-thick container steel plate, comprising smelting, continuous casting, heating, rolling, cooling, and heat treatment; specifically, comprising:

[0022] 1) Smelting process: Molten steel is smelted in a converter, using high-quality scrap steel and molten iron as raw materials. The charge size is controlled between 70 and 90 mm, and the molten iron content is controlled at more than 78% to ensure the purity of the steel, shorten the process time, and reduce the difficulty of subsequent processes. The converter dephosphorization and decarburization smelting parameter settings are strictly controlled, and the decarburization oxygen blowing is controlled at 315 to 400 seconds. In order to effectively reduce the content of harmful elements P, the dephosphorization oxygen blowing is controlled at 590 to 725 seconds, and the phosphorus mass fraction in the molten steel is controlled to be within 0.01%. Further deep desulfurization treatment is carried out in the LF refining furnace, and the desulfurization oxygen blowing is controlled at 575 to 700 seconds to control the sulfur content below 0.005%. Degassing is completed in the RH furnace, with the starting temperature controlled at 1638 to 1659°C and the oxygen blowing volume controlled at 18 to 28m 3 The net cycle time is 415 to 700 seconds, and the cooling time before pouring is 270 to 390 seconds. By optimizing the smelting process parameters, the oxidation of molten steel is reduced, the inclusion content in the steel is controlled, internal defects are reduced, and the internal quality of the ingot is improved.

[0023] 2) Continuous Casting Process: After vacuum is broken, casting is performed using a slab continuous caster. Key control is placed on the casting temperature, with the tundish molten steel pouring temperature set at 1560-1578°C, a superheat of 6-8°C, and a casting rate of 17-26 mm / s. High-temperature pouring refines the original as-cast structure. A soft reduction process is employed to improve the internal quality of the slab and reduce defects such as segregation and voids. The soft reduction rate is controlled at 3%-5%. After the slabs are removed from the production line, they are stacked for slow cooling. The stacking time is 24-36 hours, and the number of stacking sides is 3-4.

[0024] 3) Heating Process: The continuous casting slab is sent to the heating furnace for heating. The slab undergoes staged heating before being removed from the furnace. When the slab thickness is within the range of 320-360mm, a three-stage heating process is adopted, with the temperature range of the first heating section being 986-1023°C, the temperature range of the second heating section being 1210-1232°C, and the temperature range of the soaking section being 1085-1118°C. The total time the slab is in the furnace is controlled within 3.3-4.6 hours. When the slab thickness is within the range of less than 320mm, a two-stage heating process is adopted, with the temperature range of the first heating section being 1139-1235°C, the temperature range of the soaking section being 1065-1120°C, and the total time the slab is in the furnace is controlled within 2.3-3.1 hours. By using segmented heating, the uniformity of the internal structure of the steel slab is further improved, the original size of the precipitated phase particles is controlled, and overheating of the steel plate is avoided to improve heating efficiency, thereby ensuring the uniformity of the internal structure and properties of the steel plate and reducing the impact of large-sized inclusions on the service performance of the steel plate. The internal stress of the steel plate is fully released, while the temperature inside and outside the steel slab is uniform, which is conducive to further processing.

[0025] 4) Rolling process: The rolling adopts a three-stage controlled rolling method. The rolling temperature of the first stage recrystallization zone starts at 1132~1165℃, and the rolling end temperature is 1060~1073℃. The original austenite structure is fully refined. The "large-large-small cycle reduction" rolling control process is adopted. The rolling speed is 3.6~4.8m / s, the maximum reduction range is 9%~11%, and the small reduction range is controlled at 4%~6%. It reduces the deformation resistance of the steel plate, improves the steel plate yield rate, ensures sufficient recrystallization of the grains, refines the internal structure of the steel plate, and ensures the uniformity of the structure. After the first stage of rolling, the steel plate waiting time is controlled in the range of 30 to 45s; in the second stage, the rolling temperature of the non-recrystallization zone starts at 940 to 965°C, and the final rolling temperature is 850 to 862°C. The single-pass reduction adopts the "small-small-large cycle reduction" rolling control process, with the small reduction range being 5% to 8%, and the large reduction range being controlled at 10% to 12%; the "small-small-large cycle reduction" process is adopted, and the rolling process is accompanied by a phase transformation process, the ferrite content in the steel plate increases, the internal structure is further refined, the grain boundary area increases, and the austenite grains are further flattened and elongated. The third stage, grain refinement and strengthening rolling, begins at 830-845°C and ends at 810-822°C. A "small reduction" rolling control process is used for each pass, with a reduction range of 3%-5%. After rolling, the steel plate is leveled on a concave roller skin-pass mill, with a controlled crown of 45-56μm and a roughness of 0.16-0.25mm / m. This further uniformizes and refines the internal structure of the steel plate, ensuring excellent overall shape control.

[0026] 5) Cooling Process: The uniform and fine structure further ensures the uniformity of the steel plate's performance and helps optimize the steel plate's strength-toughness balance. The fine grain strengthening mechanism increases the steel plate's strength, further improving its service performance, including wear resistance. Utilizing an online ultra-rapid cooling-water cooling segmented cooling method, combined with material fine grain strengthening, precipitation strengthening, and phase transformation strengthening mechanisms, the strip's mechanical properties are significantly improved. The introduction of low-angle grain boundaries during the cooling process enhances the steel plate's corrosion resistance. The ultra-rapid cooling start temperature for the first cooling stage is controlled at 742-750°C, with a cooling rate of 120-150°C / s. The water cooling start temperature for the second cooling stage is controlled at 422-436°C, with a cooling rate of 32-57°C / s.

[0027] 6) Heat Treatment Process: Due to the addition of elements such as C, Si, Mn, Ni, Cr, and V to the steel, the rolled steel plate achieves a ferrite + troostite + spheroidal bainite structure with excellent strength and toughness. However, the uneven grain size distribution of the steel plate leads to structural and thermal stress concentrations, which can easily cause delayed cracking during flame cutting. Therefore, timely heat treatment is necessary to soften and relieve stresses. To further control the internal structure of the steel plate while ensuring high production efficiency, the present invention utilizes a high-temperature, short-time tempering heat treatment to ensure that the steel plate maintains strength while maintaining appropriate plastic toughness, low-temperature impact toughness, corrosion resistance, and good processability. Therefore, the high-temperature tempering heat treatment of the steel is controlled at a temperature of 690-720°C, held at this temperature for 25-35 minutes, and then cooled to room temperature with a controlled cooling rate of 10-22°C / s.

[0028] The present invention optimizes the design of the smelting process, adopts a molten iron treatment process in conjunction with full-process protective casting, improves the purity of molten steel, ensures the internal quality of the ingot, strictly controls the influence of elements such as P, S, and O, and ensures the original structure grain; adopts a segmented high-efficiency slab heating process (three-stage heating / two-stage heating) to shorten the processing time, improve production efficiency and ensure the heating quality of the ingot. Through three-stage controlled rolling combined with two-stage cooling technology, the uniformity of the internal structure of the steel plate is further optimized, the uniformity and excellence of the performance of large-thickness steel plates are ensured, the plate shape is improved and production efficiency is guaranteed; the high-temperature short-time tempering heat treatment process improves the strength and toughness matching while adjusting the material's microstructure, improving the mechanical properties of the steel plate and ensuring the service performance of the steel plate. The present invention provides an 800MPa-grade and uniform performance extra-thick container steel plate and its manufacturing method, which are suitable for large-scale, efficient, high-strength grade extra-thick container steel production.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The present invention adds appropriate amounts of Ni, Cr, and V alloying elements to the strengthening elements C, Si, and Mn, strictly controls the contents of harmful elements P and S, and optimizes the production process to obtain uniformly refined ferrite + troostite + spherical bainite. The total inclusion grade of the steel plate is ≤1.0, and the grain size is between 7 and 9. The ratio of troostite, ferrite, and spherical bainite by volume percentage is in the range of (1 to 1.2):1:(1.5 to 1.8), and the size of the spherical bainite is not greater than 80 nm. The number ratio of second-phase Cr and V carbides in the size range of 35 to 66 nm is set at 1.8 to 3.5, and the second-phase Cr / V carbide particles in the size range of less than 66 nm are uniformly dispersed, thereby ensuring the steel plate's high plasticity, low-temperature toughness, and service properties such as corrosion resistance and wear resistance.

[0031] 2) The mechanical properties of the steel plate for storage tanks obtained by the unique production process of the present invention are 820MPa≤R m ≤840MPa、770MPa≤R el ≤785Mpa, A≥22%; under -40℃ condition, 860MPa≤R m ≤900MPa、800MPa≤R el ≤890Mpa, A≥18%, average transverse impact energy KV2 ≥185J; the yield strength ratio of the steel plate at T / 2 and T / 4 is in the range of 0.9 to 1.1, and at a temperature of 450°C, the yield strength of the steel plate can still reach 204MPa; that is, the steel plate has uniform performance and good strength-toughness matching and high and low temperature service performance.

[0032] 3) According to the hydrogen-induced cracking (HIC) test GB / T8650-2006 and NACE-TM0284 "Evaluation Method for Resistance of Pipeline Steel and Pressure Vessel Steel to Hydrogen Induced Cracking", after 96 hours of testing in solution A and solution B, the crack sensitivity CSR (%), crack length rate CLR (%), and crack width rate CTR (%) of the steel plate were all 0, indicating that the steel plate had excellent resistance to hydrogen-induced cracking. According to GB / T17897-2016 "Corrosion of Metals and Alloys - Ferric Chloride Pitting Corrosion Test Method for Stainless Steel", the corrosion rate of the steel plate in solution A and solution B was no more than 0.002g / m 2 .h; According to the results, the steel plate has good corrosion resistance (resistance to hydrogen-induced cracking and pitting corrosion) throughout its thickness.

[0033] 4) According to GB / T3960-2016 "Test Method for Sliding Friction and Wear of Plastics", the test results show that the volume wear of the steel plate is no more than 0.0003cm 3 , the steel plate has good wear resistance. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the specific implementation methods of the present invention are further described below in conjunction with examples. The following examples are used to specifically illustrate the contents of the present invention. These examples are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0035] The production method adopted by the present invention is molten iron pretreatment - refining outside the furnace - vacuum degassing - slab continuous casting - stacking slow cooling - slab cleaning - three-stage / two-stage high-efficiency slab heating - three-stage rolling - two-stage cooling - high-temperature short-time tempering heat treatment, which produces steel plates for containers with a thickness of 55 to 100 mm. The produced steel plates have uniform microstructure and properties, good strength and toughness matching, and excellent corrosion resistance and wear resistance.

[0036] Table 1 shows the chemical composition of the embodiment of the present invention, Table 2 shows the smelting-continuous casting and heating process parameters of the embodiment steel, Table 3 shows the rolling, cooling and heat treatment process parameters of the embodiment steel, Table 4 shows the final mechanical properties of the embodiment, Table 5 shows the test results of the microstructure grain size and second phase particle evaluation, Table 6 shows the test results of the microstructure inclusion grade evaluation of the embodiment steel plate, and Table 7 shows the service performance test results of the embodiment - corrosion resistance (hydrogen-induced cracking test, pitting corrosion test) test, and friction and wear test results.

[0037] Table 1 Chemical composition of the examples (wt, %)

[0038]

[0039] Table 2 Example smelting-continuous casting and heating process parameters

[0040]

[0041] Table 3 shows the rolling, cooling and heat treatment process parameters of the example steel

[0042]

[0043] Table 4 Final results of mechanical properties of the examples

[0044]

[0045] Table 5 shows the test results of microstructure grain size and second phase particles evaluation

[0046]

[0047] Table 6 Test results of structural inclusion grade evaluation of the steel plate of the embodiment

[0048]

[0049] Table 7 is the service performance test results of the embodiment

[0050]

[0051] According to the above results, it can be concluded that the tensile strength R of the production of (55-100) mm thickness specifications at room temperature provided by the present invention is m 820~840MPa, yield strength R el 770~785Mpa, elongation A≥22%; tensile strength R under -40℃ m 860~900MPa, yield strength R el The steel plate has a yield strength of 800-890 MPa, an elongation A ≥ 18%, and an average transverse impact energy KV2 ≥ 185 J; the yield strength ratio of the steel plate at T / 2 and T / 4 is in the range of 0.9-1.1, and the yield strength of the steel plate can reach 204 MPa at a temperature of 450°C; the total inclusion grade of the steel plate is ≤ 1.0, and the microstructure is composed of ferrite + troostite + spherical bainite, with a grain size of 7-9, of which the size of the spherical bainite is not greater than 80 nm, and the second phase Cr / V carbide particles with a size below 66 nm are uniformly dispersed. The steel plate has excellent corrosion resistance (resistance to hydrogen-induced cracking and pitting corrosion) throughout its thickness. In other words, according to the hydrogen-induced cracking (HIC) test specified in GB / T8650-2006 and NACE-TM0284 "Method for evaluating the resistance of pipeline steel and pressure vessel steel to hydrogen-induced cracking," after 96 hours of testing in solution A and solution B, the crack sensitivity (CSR%), crack length ratio (CLR%), and crack width ratio (CTR%) were all 0, indicating excellent resistance to hydrogen-induced cracking. According to GB / T17897-2016 "Corrosion of metals and alloys - Test method for pitting corrosion of stainless steel using ferric chloride," the steel plate exhibited a corrosion rate of no more than 0.002 g / m in both solution A and solution B. 2 .h. And according to GB / T3960-2016 "Test method for sliding friction and wear of plastics", the test results show that the volume wear of the steel plate is no more than 0.0003cm 3 The steel plate has good wear resistance. That is, the (55-100) mm thick steel plate has excellent strength, low temperature toughness, high temperature service performance and plate shape, meeting the manufacturing and application requirements of high-performance storage tank steel plates.

Claims

1. An 800MPa grade, uniform performance, extra-thick steel plate for containers, characterized in that: The chemical composition of the steel by weight percentage is: C: 0.18%~0.23%, Si: 0.15%~0.37%, Mn: 0.98%~1.24%, P≤0.01%, S≤0.005%, Ni: 0.11%~0.32%, Cr: 0.04%~0.18%, V: 0.02%~0.04%, the balance is Fe and unavoidable inclusions; and Pcm%=C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B≤0.30, CE%=C+Si / 30+(Mn+Cu+Cr) / 20+Ni / 60+Mo / 15+V / 10+5B≤0.

45.

2. The 800MPa grade and uniform performance extra-thick container steel plate according to claim 1, characterized in that: The steel plate structure is composed of troostite, ferrite and spherical bainite in a volume percentage ratio range of (1-1.2):1:(1.5-1.8), wherein the size of spherical bainite is not greater than 80nm, the grain size is 7-9, the steel plate structure inclusion grade summary is not greater than 1.0, and the number ratio of second phase Cr and V carbides in the size range of 35-66nm is 1.8-3.

5.

3. The 800MPa grade and uniform performance extra-thick container steel plate according to claim 1, characterized in that: The mechanical properties of the steel plate are: tensile strength R at room temperature m 820~840MPa, yield strength R el 770~785Mpa, elongation A≥22%; tensile strength R under -40℃ m 860~900MPa, yield strength R el The yield strength of the steel plate is 800-890 MPa, the elongation A is ≥18%, and the average transverse impact energy KV2 is ≥185 J; the yield strength ratio of the steel plate at T / 2 and T / 4 is in the range of 0.9-1.1, and at a temperature of 450°C, the yield strength of the steel plate can reach 204 MPa.

4. The 800 MPa grade and uniform performance extra thick container steel plate according to claim 1, characterized in that: According to the hydrogen-induced cracking test GB / T8650-2006 and NACE-TM0284 "Evaluation Method for Hydrogen-Induced Cracking Resistance of Pipeline Steel and Pressure Vessel Steel", the steel plate crack sensitivity CSR%, crack length rate CLR%, and crack width rate CTR% are all 0; according to GB / T17897-2016 "Corrosion of Metals and Alloys - Ferric Chloride Pitting Corrosion Test Method for Stainless Steel", the steel plate corrosion rate is not more than 0.002g / m 2 .h.

5. The 800MPa grade and uniform performance extra-thick container steel plate according to claim 1, characterized in that: According to GB / T3960-2016 "Test Method for Sliding Friction and Wear of Plastics", the volume wear of the steel plate is no more than 0.0003cm 3 .

6. The 800MPa grade and uniform performance extra-thick container steel plate according to claim 1, characterized in that: The thickness of the finished steel plate is 55 to 100 mm.

7. A method for manufacturing an 800 MPa grade steel plate for use in extra-thick containers with uniform properties according to any one of claims 1 to 6, comprising smelting, continuous casting, heating, rolling, cooling and heat treatment; characterized in that: Specifically include: The heating process includes: when the thickness of the slab is within the range of 320-360 mm, a three-stage heating process is adopted, wherein the temperature interval of the first heating section is 986-1023° C., the temperature interval of the second heating section is 1210-1232° C., the temperature interval of the soaking section is 1085-1118° C., and the total furnace time of the slab is controlled within 3.3-4.6 hours; when the thickness of the slab is within the range of less than 320 mm, a two-stage heating process is adopted, wherein the temperature interval of the first heating section is 1139-1235° C., the temperature interval of the soaking section is 1065-1120° C., and the total furnace time is controlled within 2.3-3.1 hours; The rolling process includes: a three-stage controlled rolling method, wherein the first stage recrystallization zone starts at a rolling temperature of 1132-1165°C, and the rolling ends at a temperature of 1060-1073°C, and a "large-large-small cycle reduction" rolling control process is adopted, with a rolling speed of 3.6-4.8 m / s, a large reduction range of 9%-11%, and a small reduction range of 4%-6%. After the first stage of rolling, the steel plate waiting time is controlled in the range of 30-45 seconds; and no further rolling is performed in the second stage. The starting rolling temperature in the crystallization zone is 940-965°C, the final rolling temperature is 850-862°C, and the single-pass reduction adopts the "small-small-large cycle reduction" rolling control process, with the small reduction range being 5%-8% and the large reduction range being controlled at 10%-12%; in the third stage of grain refinement strengthening rolling, the starting rolling temperature is 830-845°C, the final rolling temperature is 810-822°C, and the single-pass reduction adopts the "small reduction" rolling control process, with the reduction range being 3%-5%; The cooling process includes: controlling the starting temperature of the ultra-fast cooling of the steel plate in the first cooling section to 742-750°C, and controlling the cooling rate to 120-150°C / s; controlling the starting temperature of the water cooling in the second cooling section to 422-436°C, and controlling the cooling rate to 32-57°C / s; The heat treatment comprises: high temperature tempering heat treatment of steel at a controlled temperature of 690-720° C., keeping the temperature for 25-35 minutes, cooling to room temperature with the furnace, and controlling the cooling rate at 10-22° C. / s.

8. The method for manufacturing an 800 MPa grade steel plate for a thick container with uniform performance according to claim 7, characterized in that: The smelting process includes: controlling the size of the charge to be between 70 and 90 mm, controlling the molten iron content to be above 78%, controlling the oxygen blowing for decarburization to be between 315 and 400 seconds, controlling the oxygen blowing for dephosphorization to be between 590 and 725 seconds, performing deep desulfurization treatment in an LF refining furnace, controlling the oxygen blowing for desulfurization to be between 575 and 700 seconds, completing degassing in an RH furnace, controlling the starting temperature to be between 1638 and 1659°C, and controlling the oxygen blowing rate to be between 18 and 28 m3 / s. 3 , net circulation time is 415~700s, and calming time before pouring is 270~390s.

9. The method for manufacturing an 800 MPa grade steel plate for a thick container with uniform performance according to claim 7, characterized in that: The continuous casting includes: the tundish molten steel casting temperature is 1560-1578°C, the superheat is set at 6-8°C, and the casting rate during casting is 17-26 mm / s; a continuous casting billet light reduction process is adopted, wherein the light reduction rate is controlled at 3%-5%, the billets are stacked for slow cooling after being cast, the stacking slow cooling time is 24-36 hours, and the number of stacking surfaces is 3-4.

10. The method for manufacturing an 800 MPa grade steel plate for a thick container with uniform performance according to claim 7, characterized in that: After rolling, the steel plate is leveled by a concave roller leveler to control the convexity to 45-56μm and the unevenness to 0.16-0.25mm / m.

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