A high-strength and corrosion-resistant steel plate for hot input welding of crude oil storage tanks and its manufacturing method

Abstract

The present invention discloses a high-strength corrosion-resistant steel plate for large heat input welding of crude oil storage tanks and a manufacturing method. The composition of the steel plate by weight percentage includes: C: 0.07 - 0.12, Si: 0.25 - 0.45, Mn: 1.40 - 2.0, P ≤ 0.012, S ≤ 0.005, Cu: 0.1 - 0.4, Ni: 0.1 - 0.5, Mo: 0.10 - 0.30, V: 0.01 - 0.05, Ti: 0.005 - 0.035, B: 0.0005 - 0.0035, Sn: 0.01 - 0.06, La: 0.001 - 0.03, Ca: 0.0002 - 0.005, Zr: 0.001 - 0.02, O ≤ 0.0030, N: 0.0045 - 0.0065, and the balance is Fe and unavoidable impurities. The steel plate for crude oil storage tanks of the present invention has good mechanical, welding and corrosion resistance properties, satisfying that the average value of transverse impact energy at -20°C ≥ 80 J, yield strength ≥ 490 Mpa, tensile strength is 610 - 730 MPa, A ≥ 17%, the average value of impact energy in the welding heat affected zone ≥ 47 J, and the average annual corrosion rate ≤ 1.0 mm / a.

Description

Technical Field

[0001] The present invention belongs to the field of low-alloy corrosion-resistant steels, and relates to a high-strength corrosion-resistant steel plate for crude oil storage tanks used in high heat input welding, which has good welding performance and excellent corrosion resistance in the crude oil environment. Background Art

[0002] Nowadays, the global economy and technology are developing rapidly. Crude oil, as a strategic material, is an important material to ensure national energy security, serving as a reserve on the one hand and an industrial raw material and power consumption on the other hand. To meet the increasing energy demand, crude oil storage tanks at home and abroad are continuously developing towards large-scale. The larger the volume of the crude oil storage tank, the lower the steel consumption index per unit volume, the lower its cost, and at the same time, the floor area of the tank farm will also become smaller.

[0003] As a steel storage tank, the processing requirements of crude oil storage tanks are relatively high. It not only needs to ensure good corrosion resistance in an acidic corrosion environment with a relatively high sulfur content, but also requires welding technology to make the tank body meet the storage requirements. The harsh service environment has greatly shortened the actual service life of crude oil storage tanks that were expected to have a service life of 20 years during the design process. When designing the steel for crude oil storage tanks, in addition to excellent corrosion resistance, the mechanical properties and welding performance of the steel should also be considered. In terms of mechanical properties, the steel should have a high yield strength and tensile strength, good toughness, and high uniformity and stability. In terms of welding, after welding with a large heat input, the plastic toughness of the heat-affected zone of the weld does not decrease significantly, and the mechanical properties of the joint can meet the same requirements as the base metal.

[0004] The patent application with publication number CN1662668A provides a steel for crude oil tanks and its manufacturing method. In this steel, the corrosion resistance of the storage tank is improved by adding a large amount of expensive corrosion-resistant alloying elements. This method has a high cost, and the corrosion resistance is only slightly improved. Most importantly, it only solves the internal corrosion problem of the crude oil tank and does not mention the mechanical properties and welding performance of the steel plate.

[0005] JP-A-49-37814 and JP-B-4-13406 have disclosed reducing the carbon content and using Ti-B technology to reduce the welding crack sensitivity, and adding B to ensure the hardenability of the steel. However, neither of them involves high heat input welding and is not suitable for the high heat input welding process in the actual production of large crude oil storage tanks.

[0006] The patent application with the publication number CN102242309A provides a steel for crude oil storage tanks used in large heat input welding with the addition of B and its manufacturing method. During the production process, the contents of N and O are strictly controlled. By using second-phase particles to promote the formation of intragranular ferrite that is beneficial to improving the toughness of the heat-affected zone of high heat input welding, the welding performance is improved. However, this method has complex processes and great operation difficulty in the actual production process, and whether the corrosion resistance is improved is not mentioned.

[0007] The publication number CN101215669A provides a high-strength thick plate for large oil storage tanks and its low-cost manufacturing method. To reduce production costs and reduce the content of trace alloys in steel, but this method reduces the corrosion resistance of the steel for crude oil storage tanks and cannot guarantee the safe service life of crude oil storage tanks. Summary of the Invention

[0008] In order to ensure the safety and service life of corrosion-resistant crude oil storage tanks and improve production efficiency, the present invention provides a high-strength corrosion-resistant steel plate for crude oil storage tanks used in large heat input welding. Under the welding heat input of 50 - 100 KJ / cm, the steel plate has good welding performance, and in the corrosion environment of the wall plate of the crude oil storage tank, the average annual corrosion rate C.R.ave ≤ 1.0 mm / a, meeting the requirements of long-term storage of crude oil in crude oil storage tanks and reducing the time cost of producing large crude oil storage tanks.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A high-strength corrosion-resistant steel plate for crude oil storage tanks used in large heat input welding, characterized in that the composition of the steel plate by weight percentage includes C: 0.07 - 0.12, Si: 0.25 - 0.45, Mn: 1.40 - 2.0, P ≤ 0.012, S ≤ 0.005, Cu: 0.1 - 0.4, Ni: 0.1 - 0.5, Mo: 0.10 - 0.30, V: 0.01 - 0.05, Ti: 0.005 - 0.035, B: 0.0005 - 0.0035, Sn: 0.01 - 0.06, La: 0.001 - 0.03, Ca: 0.0002 - 0.005, Zr: 0.001 - 0.02, O ≤ 0.0030, N: 0.0045 - 0.0065, and the rest is Fe and unavoidable impurities; in the heat-affected zone near the weld of the steel plate, 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 precipitation particles accounts for 70 - 80%, and among the particles with a size of 0.5 - 1.5 μm that can hetero-nucleate, the number of (Ti,V,B)(C,N) composite precipitation particles accounts for 70 - 80%, and it satisfies 0.25 ≤ 12.98Ti + 2.72V + 0.06B + 0.14C + 0.13N ≤ 0.35.

[0011] Preferably, the steel plate is suitable for high heat input welding with a heat input of 50 - 100 KJ / cm.

[0012] Preferably, in the heat affected zone of the near-seam welding of the steel plate, the number density of (V,Ti)(C,N) composite precipitation particles in particles with a size of 20 - 80 nm that can inhibit the growth of austenite grains is 6.88×105 particles / mm 3 ~8.49×105 particles / mm 3 , and the number density of (Ti,V,B)(C,N) composite precipitation particles in particles with a size of 0.5 - 1.5 μm that can hetero-nucleate is 5.52×104 particles / mm 3 ~7.74×104 particles / mm 3 .

[0013] Preferably, the average annual corrosion rate C.R.ave of the steel plate in an accelerated corrosion environment of a Cl solution with a pH value of 0.85 and a concentration of 10% is ≤1.0 mm / a. -

[0014] Preferably, the yield strength Rp0.2 of the steel plate ≥490 MPa, the tensile strength Rm ≥610 Mpa, the elongation after fracture A ≥17%, the impact energy -20℃ KV2 ≥80 J, and the impact energy of the welding heat affected zone -20℃ KV2 ≥47 J.

[0015] The present invention also discloses a manufacturing method of the high-strength corrosion-resistant steel plate for crude oil storage tanks with high heat input welding, which is characterized in that controlled rolling and controlled cooling processes are adopted for production, and the specific process parameters are: the heating temperature is controlled at 1190 - 1210℃, the rolling temperature during the rough rolling process is controlled at 1050 - 1090℃, the rolling temperature during the finish rolling process is controlled at 800 - 930℃, the water entry temperature is controlled at 760 - 800℃, and the re-heating temperature is controlled at 530 - 570℃.

[0016] In the composition design of the steel plate of the present invention:

[0017] C: Carbon element is the main strengthening element of traditional steel. When the carbon content increases, segregation will occur, reducing the overall corrosion resistance. At the same time, it will increase the carbon equivalent, which is not conducive to refining the M-A island components, reducing the toughness of the heat affected zone of high heat input welding, and increasing the welding crack sensitivity. In order to ensure the mechanical properties and welding performance of the steel, and at the same time effectively improve the corrosion resistance of the steel, it is necessary to appropriately reduce the C content. Therefore, the preferred content of C in the present invention is 0.07 - 0.12.

[0018] ​Si: Silicon can dissolve in ferrite and austenite, thereby increasing the hardness and strength of the steel, compensating for part of the strength loss caused by reducing the carbon mass fraction. At the same time, silicon can increase the compactness and chemical stability of the rust layer on the steel matrix, enhancing the corrosion resistance of the steel plate. However, when the silicon mass fraction is too high, it can promote the nucleation of grain boundary ferrite, inhibit the formation of acicular ferrite, increase the mass fraction of M-A island components, reduce the plasticity and toughness of the steel, and lower the welding performance of the steel. Therefore, the preferred content of Si in the present invention is 0.25 - 0.45.

[0019] Mn: The increase in Mn content can compensate for part of the strength loss caused by low carbon, and can also promote the nucleation ability of oxides on ferrite and promote the formation of ferrite. Manganese forms MnS with a relatively high melting point with sulfur, which can prevent the formation of FeS and the occurrence of hot brittleness. Mn is also a good deoxidizer and desulfurizer, and is often used for composite deoxidation together with silicon and titanium to form composite inclusions with a relatively high sulfur capacity, effectively inducing the nucleation of intragranular acicular ferrite. However, when the Mn content is relatively high, it will cause segregation bands of manganese in the steel, which is not conducive to improving the corrosion resistance of the steel. Therefore, the preferred content of Mn in the present invention is 1.40 - 2.0.

[0020] Cu: Copper elements can be enriched in the rust layer, can form a good protective rust layer, and the firm combination between it and the steel matrix ensures the stability of the rust layer, thereby significantly improving the corrosion resistance of the steel plate. However, excessive copper elements will reduce the toughness of the heat affected zone during welding and cause surface cracks in the steel plate during manufacturing. Therefore, the preferred content of Cu in the present invention is 0.10 - 0.40.

[0021] Ni: Nickel is a very important element for improving the low-temperature toughness of steel. It is a pure solid solution element in steel, can strengthen the ferrite matrix, and has an obvious effect of reducing the ductile-brittle transition temperature. In the liquid or solid state, it can be mutually soluble with iron in any proportion, can inhibit the formation of coarse proeutectoid ferrite, refine the ferrite grains, and improve the low-temperature toughness of the steel. Nickel is an element that expands the austenite phase region, can affect the diffusion rate of carbon and alloying elements, prevent the formation of pearlite, improve hardenability, and slow down the tendency of hardening and cracking during welding. Nickel elements can be enriched in the rust layer, can effectively prevent the contact between chloride ions in the corrosion environment and the matrix, and effectively improve the corrosion resistance of the steel. However, nickel is a relatively expensive metal, and adding a large amount will increase the cost of the steel. Therefore, the preferred content of Ni in the present invention is 0.10 - 0.50.

[0022] Mo: Molybdenum is an element that reduces the austenite phase region, can effectively reduce the bainite transformation temperature and avoid ferrite phase transformation, so that a complete bainite structure can be obtained within a wide cooling rate range. It can be dissolved in ferrite, austenite and carbide in steel, and can also improve the stability of carbides, thereby improving the strength of steel. Stable oxides of molybdenum or molybdates can be formed in the rust layer, making it difficult for the matrix to interact with chloride ions, inhibiting the occurrence of pitting corrosion and improving the corrosion resistance of steel. However, considering the cost issue and avoiding the appearance of too many MA components, the molybdenum content should be controlled at a lower level. Therefore, the preferred content of Mo in the present invention is 0.10 to 0.30.

[0023] V, Ti: V has a strong affinity with elements such as carbon and nitrogen. The vanadium-nitrogen compounds precipitated in austenite can inhibit the growth of austenite grains. The vanadium-nitrogen compounds precipitated in the ferrite region can increase the nucleation core of intracrystalline ferrite. The two aspects jointly promote grain refinement and significantly improve the welding performance of low-carbon low-alloy steel. Titanium has a strong affinity with oxygen, nitrogen and carbon. It is a good deoxidizer and an effective element for fixing nitrogen and carbon. Titanium oxide is considered to be the most effective nucleation inclusion in steel. It can effectively promote the nucleation of acicular ferrite and is widely used in oxide metallurgy. Titanium can form fine and dispersed TiN particles in steel, which can only be slowly dissolved when heated to above 1400°C in steel. During the welding thermal cycle, TiN particles effectively hinder the coarsening of austenite grains, which is conducive to the improvement of toughness. TiN particles can effectively promote the formation of acicular ferrite and effectively improve the welding performance of steel. Considering the cost, the preferred content of V in the present invention is 0.01-0.05, and the preferred content of Ti is 0.005-0.035.

[0024] B: The presence of boron can significantly improve the hardenability of steel plates and increase strength. In the high temperature stage of high heat input welding, it is segregated at the grain boundaries, reducing the phase transformation point of the weld heat affected zone and inhibiting the growth of granular bainite. During the cooling process, the B inside the grains will combine with N to form BN, which becomes the nucleation core of acicular ferrite, improves the intracrystalline structure, and improves the low-temperature toughness of the weld heat affected zone. Excessive B elements will be segregated in large quantities at the grain boundaries, weakening the effect of reducing the phase transformation point, and will form larger inclusions, which have an adverse effect on the impact toughness of the weld heat affected zone. Therefore, the preferred content of B in the present invention is 0.0005~0.0035.

[0025] Sn: Tin element can effectively inhibit pitting corrosion and general corrosion of steel. The main reason is that tin element can be enriched in the rust layer, improving the compactness of the rust layer of steel. Meanwhile, it can form a protective film on the surface of the steel matrix, significantly increasing the self-corrosion potential of the steel in an acidic corrosion environment and effectively enhancing the corrosion resistance of the steel in an acidic corrosion environment. However, tin element is prone to segregate at grain boundaries, seriously affecting the mechanical properties and welding performance of the steel plate. Therefore, the preferred content of Sn in this invention is 0.01 - 0.06.

[0026] P, S: Sulfur and phosphorus are inevitable harmful impurity elements in steel. They can form segregation in steel, significantly reducing the plasticity and toughness of the steel, causing great harm to weldability and also having an adverse effect on corrosion resistance. Therefore, the contents of P and S in steel should be reduced as much as possible. For this purpose, the content of P in this invention should be controlled at ≤0.012, and the content of S should be controlled at ≤0.005.

[0027] La: Rare earth La can be used as a deoxidizer and desulfurizer, playing a role in purification and conditioning. Meanwhile, La can also react with oxides and sulfides in steel to form fine spherical rare earth inclusions, reducing pitting corrosion induced by inclusions and improving the corrosion resistance of steel. However, when too much La element is added, it will lead to a large number of inclusions. The rare earth La element will solid-solution segregate at grain boundaries, easily causing temper brittleness and also having a certain adverse effect on corrosion resistance and welding performance. For this reason, the preferred content of La in this invention is 0.001 - 0.03.

[0028] Ca: Ca is beneficial to the corrosion resistance of steel. During the corrosion reaction, it dissolves in water to become an alkali, inhibiting the decrease of the pH value on the surface of the steel and significantly improving the resistance of the steel to local corrosion. In addition, the Ca element modifies the malignant sulfide inclusions in the steel, which can not only improve the welding performance of the steel but also further improve the resistance to local corrosion. For this reason, the preferred content of Ca in this invention is 0.0002 - 0.005.

[0029] Zr: Zr in steel can preferentially combine with S to form sulfides, reducing the generation of MnS and improving the pitting corrosion resistance of the steel plate. A trace amount of Zr can achieve the above effects. As a strong deoxidizing element, compared with Al and Ti for deoxidation, Zr will form more oxide particles and the distribution is more uniform. However, excessive Zr will significantly reduce the toughness of the steel plate. For this reason, the preferred content of Zr in this invention is 0.001 - 0.2.

[0030] N: Controlling the N content is of special significance for welding with high heat input. An appropriate N content can form TiN, VN, BN, etc., which can effectively refine grains, improve the intragranular structure, induce the nucleation of acicular ferrite, and effectively improve the toughness of the heat-affected zone of welding. For this reason, the preferred content of N in this invention is 0.0045 - 0.0065.

[0031] For the steel of the present invention, on the basis of containing the above alloy elements within the above suitable ranges, it is also necessary to satisfy 0.25 ≤ 12.98Ti + 2.72V + 0.06B + 0.14C + 0.13N ≤ 0.35.

[0032] The above formula is the control coefficient for evaluating the size and quantity of the second-phase precipitation particles in the heat-affected zone of the welding of the crude oil storage tank wall panel by each element composition. By strictly controlling the contents of C, N, V, Ti, and B elements, among the particles with a size of 20 - 80 nm that can inhibit the growth of austenite grains in the near-weld heat-affected zone, the quantity of (V,Ti)(C,N) composite precipitation particles accounts for 70 - 80%, and among the particles with a size of 0.5 - 1.5 μm that can hetero-nucleate, the quantity of (Ti,V,B)(C,N) composite precipitation particles accounts for 70 - 80%. When the coefficient > 0.35, the size of the precipitation particles in the welding heat-affected zone increases, pinning the austenite grain boundaries and weakening the effect of inhibiting grain growth; when the coefficient < 0.25, the quantity of the precipitation particles in the welding heat-affected zone decreases, reducing the quantity of the nucleation cores for acicular ferrite and being unfavorable for improving the toughness of the welding heat-affected zone.

[0033] The steel for the crude oil storage tank wall panel made through the above composition design can replace the corrosion-resistant steel with traditional anti-corrosion coatings for the large crude oil storage tank wall panel, and can store crude oil for a long time without the need for regular maintenance work like traditional steel. The corrosion-resistant steel for the large crude oil storage tank wall panel of the present invention has the following beneficial effects:

[0034] (1) By controlling trace alloy elements such as Cu, Sn, Ni, and Mo in the present invention, a dense passivation film is formed on the surface of the steel, ensuring excellent corrosion resistance of the steel plate. At the same time, alloy elements such as Mg, V, Ti, and B are added to promote the formation of a microstructure beneficial to toughness in the welding heat-affected zone under the condition of high heat input welding, and the adverse effect of Sn element on the low-temperature impact toughness caused by grain boundary segregation is reduced through high heat input.

[0035] (2) The high-strength corrosion-resistant steel plate for high heat input welding of the present invention can replace the steel used for traditional anti-corrosion coatings. The added alloy elements have a wide source and low cost, are suitable for industrial mass production, and also improve the operation safety of large crude oil storage tanks. Description of the Drawings

[0036] Figure 1 It is the metallographic structure of the coarse-grained heat-affected zone of the steel plate in Example 4 of the present invention when the simulated welding heat input is 85 kJ / cm;

[0037] Figure 2 It is the metallographic structure of the coarse-grained heat-affected zone of the steel plate in Comparative Example 1 of the present invention when the simulated welding heat input is 85 kJ / cm;

[0038] Figure 3 Schematic diagram of the accelerated corrosion test environment for simulating the actual corrosion of the wall plate of an oil storage tank adopted by the present invention, where 1 is a water bath heating device, 2 is a beaker, 3 is an immersion corrosion solution, and 4 is an immersion corrosion test coupon sample;

[0039] Figure 4 Macrographic corrosion morphology after corrosion for the examples and comparative examples. Specific implementation manners

[0040] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific implementation manners.

[0041] The present invention provides a high-strength corrosion-resistant steel plate for large heat input welding of crude oil storage tanks, characterized in that the composition of the steel plate by weight percentage includes C: 0.07 - 0.12, Si: 0.25 - 0.45, Mn: 1.40 - 2.0, P ≤ 0.012, S ≤ 0.005, Cu: 0.1 - 0.4, Ni: 0.1 - 0.5, Mo: 0.10 - 0.30, V: 0.01 - 0.05, Ti: 0.005 - 0.035, B: 0.0005 - 0.0035, Sn: 0.01 - 0.06, La: 0.001 - 0.03, Ca: 0.0002 - 0.005, Zr: 0.001 - 0.02, O ≤ 0.0030, N: 0.0045 - 0.0065, and the rest is Fe and inevitable impurities. And the steel plate satisfies that among the particles with a size of 20 - 80 nm that can inhibit the growth of austenite grains in the heat-affected zone of near-seam welding, the number of (V,Ti)(C,N) composite precipitation particles accounts for 70 - 80%, among the particles with a size of 0.5 - 1.5 μm that can hetero-nucleate, the number of (Ti,V,B)(C,N) composite precipitation particles accounts for 70 - 80%, and satisfies 0.25 ≤ 12.98Ti + 2.72V + 0.06B + 0.14C + 0.13N ≤ 0.35.

[0042] Table 1 shows the chemical composition ratios (mass percentages) of Examples 1 - 5 and Comparative Examples 1 - 3 of the steel plate of the present invention (the balance is Fe).

[0043] Table 1 Chemical composition ratios of examples

[0044]

[0045] Table 2 shows the calculation results of the regulation tests of Examples 1 - 5 and Comparative Examples 1 - 3 of the steel plate of the present invention

[0046]

[0047] This example manufactures a high-strength corrosion-resistant steel plate for large heat input welding of crude oil storage tanks according to the following steps. The manufacturing steps are as follows:

[0048] (1) Smelting process: The molten steel is smelted in a converter, sent to an LF refining furnace for refining. In the later stage of LF (after desulfurization), according to the slag condition, quartz sand is added to adjust the slag basicity. The addition amount of quartz sand is 80 Kg - 120 Kg per furnace, controlling the basicity ≤ 9.0, and the target basicity ≤ 8.0. After the quartz sand is fully melted, a slag sample is taken for analysis before the LF ladle is lifted, controlling the basicity at 5 - 7, and the target basicity at 5 - 6, with the end point temperature ≥ 1620 °C. After the molten steel arrives at the station, the oxygen is determined after the refining furnace arrives at the station. Ferrosilicon or aluminum wire is used for deoxidation, and the oxygen content control range is 30 - 60 ppm, controlled according to the target of 40 ppm, and then ferrotitanium is added for alloying. When the VD furnace is under vacuum treatment, the vacuum degree ≤ 5.0 mbar, and the holding time ≥ 20 min.

[0049] (2) Casting process: The molten steel obtained after smelting is cast into continuous casting billets with a billet thickness of 260 mm (cross-section ≥ 2570 mm).

[0050] (3) Heating process: The cast billets are heated in a continuous casting furnace, with the temperature controlled at 1200 ± 10 °C, and the total heating time is 9 - 16 min / cm.

[0051] (4) Rolling process: The main process parameters of the embodiments of the present invention are shown in Table 3.

[0052] Table 3 Manufacturing process of the steel of the present invention

[0053]

[0054] The mechanical properties of the steel plates obtained by the above methods are respectively tested, and the results are shown in Table 4 below.

[0055] Table 4 Mechanical properties of the steel plates

[0056]

[0057] As can be seen from Table 4, the mechanical properties of the base metals of the steel plates prepared by this method all show good performance. The yield strength is above 490 MPa, the tensile strength is above 610 MPa, the elongation is greater than 20%, and the impact energy at -20 °C is greater than 100 J.

[0058] Machining samples are taken from the above steel plates. The sample processing size is a rectangular corrosion coupon of 25 mm × 60 mm × 5 mm, and it is placed in the experimental device as shown in Figure 3 shown. The experiment uses water bath heating, and the immersion solution is an acidic Cl solution with PH = 0.85 -Solution (in this example, an NaCl solution with a pH of 0.85 and a concentration of 10% was used), the corrosion period was 72 h, and the solution was replaced every 24 h. The experiment was carried out according to the standard of IMO "Inspection Guidelines for Corrosion-Resistant Steel for Cargo Oil Tanks of Crude Oil Tankers" to simulate the corrosion experiment of the inner bottom of the steel plate of the crude oil storage tank. After the experiment, the samples were derusted, the corrosion weight loss of each sample was calculated, and the average corrosion rate was calculated, as shown in Table 5. Figure 4 Figure Figure 4 shows the macroscopic corrosion morphology after corrosion of Example 4 (left in the figure) and Comparative Example 1 (right in the figure). After corrosion, obvious pitting pits appeared on the steel plate of Comparative Example 1, and the steel plate of the present invention has better corrosion resistance.

[0059] Table 5 Average Corrosion Rate of Simulated Wall Panels of Experimental Steel

[0060]

[0061] Furthermore, the 18 mm steel plate after finish rolling was processed into a Gleeble thermal simulation specimen of 10.5 mm×10.5 mm×80 mm, and a thermal simulation experiment with a heat input of 85 kJ / cm was carried out on a Gleeble-3500. The experimental steps were as follows: the specimen was heated to 1350 °C at a heating rate of 100 °C / s, held for 1 - 3 s, then the simulated plate thickness was set to 32 mm, and the heat input was 85 kJ / cm. Subsequently, the specimen was processed into a standard impact specimen of 10 mm×10 mm×55 mm, and an impact experiment was carried out at -20 °C, and the corresponding microstructure was observed.

[0062] The low-temperature impact properties of the simulated heat-affected zone of the weld are shown in Table 6.

[0063] Table 6 Low-Temperature Impact Properties of Simulated Heat-Affected Zone of Weld (Actual Welding)

[0064]

[0065] Figure 1 , 2 Figures 2 show the metallographic microstructures of the coarse-grained heat-affected zone of the steel plates of Example 4 of the present invention and Comparative Example 1 respectively when the simulated welding heat input is 85 kJ / cm. The above results show that after simulating a heat input of 85 kJ / cm for each example of the present invention, the average -20 °C impact energy of the coarse-grained heat-affected zone is greater than 100 J, and the low-temperature toughness is excellent.

[0066] It can be seen from the above table data that the steel plates produced according to the present invention have excellent corrosion resistance and good resistance to large heat input. Under the condition of large heat input, the coarse-grained heat-affected zone still has high toughness, and can be applied to the wall plate structure of large crude oil storage tanks and anti-corrosion structures in the ocean and ships, etc. It has the advantages of doubling the construction efficiency, low energy consumption, good economic benefits, and being suitable for industrial mass production.

Claims

1. A high-strength and corrosion-resistant steel plate for crude oil storage tanks used in high heat input welding, characterized in that, The composition of the steel plate by weight percentage contains C: 0.07 - 0.12, Si: 0.25 - 0.45, Mn: 1.40 - 2.0, P ≤ 0.012, S ≤ 0.005, Cu: 0.1 - 0.4, Ni: 0.1 - 0.5, Mo: 0.10 - 0.30, V: 0.01 - 0.05, Ti: 0.005 - 0.035, B: 0.0005 - 0.0035, Sn: 0.01 - 0.06, La: 0.001 - 0.03, Ca: 0.0002 - 0.005, Zr: 0.001 - 0.02, O ≤ 0.0030, N: 0.0045 - 0.0065, the balance being Fe and unavoidable impurities, and satisfying 0.25 ≤ 12.98Ti + 2.72V + 0.06B + 0.14C + 0.13N ≤ 0.35; in the heat affected zone of near-seam welding of the steel plate, among the particles with a size of 20 - 80 nm that inhibit the growth of austenite grains, the number of (V,Ti)(C,N) composite precipitation particles accounts for 70 - 80%, and the number density is 6.88×10 5 pieces / mm 3 ~8.49×10 5 pieces / mm 3 ; among the particles with a size of 0.5 - 1.5 μm for heterogeneous nucleation, the number of (Ti,V,B)(C,N) composite precipitation particles accounts for 70 - 80%, and the number density is 5.52×10 4 pieces / mm 3 ~7.74×10 4 pieces / mm 3 ; the steel plate is suitable for welding with a large heat input of 50 - 100 KJ / cm; the average annual corrosion rate C.R.ave of the steel plate in an accelerated corrosion environment of a Cl - solution with a pH value of 0.85 and a concentration of 10% ≤ 1.0 mm / a; the yield strength Rp0.2 of the steel plate ≥ 490 MPa, the tensile strength Rm ≥ 610 Mpa, the elongation after fracture A ≥ 17%, the impact energy -20°C KV2 ≥ 80 J, and the impact energy of the heat affected zone of welding -20°C KV2 ≥ 47 J.

2. A manufacturing method of the high-strength and corrosion-resistant steel plate for crude oil storage tanks used in high heat input welding according to claim 1, characterized in that, It is produced by the controlled rolling and controlled cooling process. The specific process parameters are as follows: the heating temperature is controlled at 1190 - 1210 °C, the rolling temperature in the rough rolling process is controlled at 1050 - 1090 °C, the rolling temperature in the finish rolling process is controlled at 800 - 930 °C, the water entry temperature is controlled at 760 - 800 °C, and the re - heating temperature is controlled at 530 - 570 °C.

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