Steel plate for normalized high-performance fused salt storage tank and manufacturing method of steel plate

Abstract

The invention discloses a steel plate for a normalized high-performance fused salt storage tank and a manufacturing method of the steel plate, and belongs to the field of steel plate manufacturing. The steel plate for the normalized high-performance molten salt storage tank comprises the following components in percentage by weight: 0.18 to 0.20 percent of C, 0.32 to 0.4 percent of Si, 1.4 to 1.5 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.002 percent of S, 0.01 to 0.02 percent of V, 0.010 to 0.020 percent of Nb, 0.020 to 0.030 percent of Al, less than or equal to 0.0006 percent of B and the balance of Fe. And the balance of Fe and inevitable impurities. The steel plate for the normalized high-performance molten salt storage tank adopts Si-Mn-Nb-V-Al microalloy component design, and the alloy cost of the steel plate is greatly reduced. Through the design of low-temperature controlled rolling and low-temperature normalizing treatment in the rolling stage, the impact energy of the process is greater than or equal to 100J at the temperature of-47 DEG C at present, and the tensile strength is greater than or equal to 485MPa and the yield strength is greater than or equal to 181MPa in high-temperature stretching at the temperature of 410 DEG C.

Description

Technical Field

[0001] The invention relates to steel plate manufacturing, and in particular to a normalized high-performance steel plate for a molten salt storage tank and a manufacturing method thereof. Background Art

[0002] At present, the American standard A516Gr70 grade is generally used for the manufacture of cold tanks in molten salt energy storage projects at home and abroad. In order to ensure sufficient toughness and high temperature performance, precious metals such as Ni and Mo are added to ensure the performance of the steel plate. For example, the patent with publication number CN115354219A "A SA516Gr70 steel plate with excellent high temperature strength at 200-400℃ and its manufacturing method" has the chemical composition weight percentage of steel: C: 0.16-0.20%, Si: 0.20-0.40%, Mn: 1.20- 1.50%, P:≤0.006%, S:≤0.001%, Ni:0.10~0.20%, Mo:0.04~0.10%, Cr:0.10~0.20%, Nb:0.01~0.02%, V:0.01~0.03%, Ti:0.01~0.03%, Alt:0.02~0.05%, B:≤0.0005%, Pb:≤0.0005%, Sn:≤0.0005%, the balance is Fe and unavoidable impurity elements.

[0003] The patent with publication number CN114645209A, "A steel plate for medium and high temperature pressure vessels and its preparation method", has the following components by weight percentage: C≤0.2%, Si≤0.55%, Mn:1.20~1.7%, P≤0.015%, S≤0.008%, Alt:0.02~0.03%, Nb:0.008~0.02%, Ti:0.01~0.03%, N:0.003%~0.009%, and the balance is Fe and residual elements. Although precious alloys Ni and Mo are not added, the impact toughness can only meet the 0℃ impact energy ≥100J. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a normalized high-performance steel plate for molten salt storage tanks; another purpose of the present invention is to provide a method for manufacturing a normalized high-performance steel plate for molten salt storage tanks.

[0005] Technical solution: A normalized high-performance steel plate for molten salt storage tanks, comprising, by weight percentage, C: 0.18-0.20%, Si: 0.32-0.4%, Mn: 1.4-1.5%, P≤0.015%, S≤0.002%, V: 0.01-0.02%, Nb: 0.010-0.020%, Al: 0.020-0.030%, B≤0.0006%; the rest is Fe and unavoidable impurities.

[0006] C: The role of C in steel is mainly to improve the strength of steel. The role of C in steel is solid solution strengthening. Generally, the addition of carbon can effectively improve the tensile and yield strength of steel. With the increase of C element, the toughness and welding performance of steel are reduced. Considering the matching of strength and toughness, the C element is designed to be 0.18-0.20%.

[0007] Si: Si has a deoxidizing effect in the steelmaking process and can play a role in strengthening the parent material. Si can play a role in solid solution strengthening. At the same time, Si reduces the solubility of C in austenite, promotes C to dissolve and precipitate in the form of carbides. An appropriate amount of Si can accelerate the reduction effect of the welding metallurgical process and improve the anti-porosity ability of the weld metal. Excessive Si will reduce the plasticity and toughness of the weld metal. The content of silicon in the present invention is 0.32-0.40%.

[0008] Mn: Mn element can eliminate the adverse effects of S (hot crack tendency). In order to effectively prevent the occurrence of hot cracks caused by S, Mn / S≥10; with the increase of Mn content, the strength and elongation of thick steel plates increase; in addition, in order to improve the impact toughness of thick steel plates, Mn / C≥2.5, and with the increase of Mn / C, the impact toughness of steel plates improves; generally, when the Mn content is greater than 1.60%, the segregation tendency of Mn increases significantly, resulting in deterioration of the ductility of the steel plate; in the present invention, the Mn element is controlled between 1.40-1.50.

[0009] Nb: The present invention adds 0.010-0.020% of Nb element, the purpose of which is to utilize the fine grain strengthening of Nb element in the controlled rolling process, which can effectively improve the strength and toughness of the steel plate. However, the Nb element cannot be too high, as too high a content has a bad effect on welding performance. The present invention designs the Nb element to be 0.01-0.02%.

[0010] V: The V element is mainly combined with carbon to form VC, which plays a precipitation strengthening role, thereby effectively improving the strength of the steel plate. The V content of the present invention meets 0.01-0.02%.

[0011] Al: Al is an excellent deoxidizer. Al combines with N to eliminate the adverse effects of solid solution N on the impact toughness and aging embrittlement characteristics of steel plates. Al combines with N to form AlN particles, which refine the grain size of steel plates, increase the yield strength of steel plates, and improve the impact toughness of steel plates. When the Al content is ≤0.010%, there is no fine grain effect. When the Al content is greater than 0.015%, it begins to have a fine grain effect. When the Al content is greater than 0.020%, it is essentially fine grain steel. When too much Al is added (greater than 0.070%), the Al2O3 inclusion content in the steel increases sharply, the internal quality of the steel plate deteriorates, and the corner transverse crack defects of the continuous casting billet increase. The Al element of the present invention is controlled between 0.02-0.03.

[0012] B: B atoms will be enriched at the grain boundary, reducing the grain boundary binding energy, so that intergranular dissociation and fracture will occur when subjected to impact. Therefore, in the present invention, the B element is limited to ≤0.0006%.

[0013] The manufacturing method of the above normalized high-performance steel plate for molten salt storage tank is as follows:

[0014] S1. Smelting and casting

[0015] According to the above composition, the steel is smelted, and after the steel is tapped from the converter, the S element and gas element in the steel are effectively reduced through the LF+RH vacuum treatment system, and then the steel is cast by the continuous casting machine;

[0016] S2, Heating

[0017] Heating temperature: 1100±30℃, holding time 200-350min;

[0018] S3, rolling

[0019] In order to improve the impact toughness of the steel plate, controlled rolling is carried out in the rolling stage. The rolling is divided into two stages, rough rolling and finishing rolling. The slab needs to complete the rough rolling process in the austenite complete recrystallization zone, and then wait for the temperature on the intermediate roller with a waiting thickness of 1.8-3T. After the temperature drops to the austenite non-recrystallization zone, the finishing mill is rolled;

[0020] S4. Heat treatment

[0021] The rolled slab is heat treated by normalizing.

[0022] Preferably, in step S3, in order to ensure uniform and fine grains, the final rolling temperature is as low as possible on the basis of meeting the Ar3 temperature, the start rolling temperature is set at 790-900°C, and the final rolling temperature is set at 750-780°C.

[0023] Preferably, in step S4, in order to ensure uniform and fine structure after normalizing, the normalizing temperature is as low as possible on the basis of satisfying Ac3, the normalizing temperature is: 850-880°C, and the furnace time is ≥1.3T.

[0024] Beneficial effects:

[0025] (1) The present invention is directed to a normalized high-performance steel plate for molten salt storage tanks that adopts a Si-Mn-Nb-V-Al microalloy composition design, which greatly reduces the alloy cost of the steel plate.

[0026] (2) The present invention is designed for low-temperature controlled rolling and low-temperature normalizing treatment in the rolling stage. At present, the impact energy of the process is ≥100J at -47℃, and the high-temperature stretching at 410℃ satisfies the tensile strength ≥485MPa and the yield strength ≥181MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a metallographic photograph of Example 1. DETAILED DESCRIPTION

[0028] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example

[0030] The chemical composition ratios of various embodiments of the present invention are shown in Table 2.

[0031] Table 2 Chemical composition ratio (%)

[0032]

[0033] The production process parameters of each embodiment of the present invention are shown in Table 3, and the mechanical properties are shown in Table 4.

[0034] Table 3 Production process parameters

[0035]

[0036]

[0037] Table 4 Mechanical properties test

[0038]

[0039] It can be seen from the embodiments listed in Table 2, Table 3 and Table 4 that the tensile strength, yield strength, elongation after fracture, -47°C Charpy impact energy, and high-temperature tensile properties of the steel of the present invention all meet the conventional tensile properties of tensile strength 500-620MPa, yield strength ≥345MPa, elongation after fracture ≥21%, -47°C transverse impact energy ≥100J, and 410°C high-temperature tensile properties meet the tensile strength ≥485MPa yield strength ≥181MPa and the performance margin is large. Compared with the prior art, while ensuring the mechanical properties in the early stage, the types and contents of precious metal elements added to the steel plate smelting components are reduced, and the production and manufacturing costs are correspondingly reduced.

[0040] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A normalized high-performance steel plate for molten salt storage tanks, characterized in that: Including, by weight percentage, C: 0.18-0.20%, Si: 0.32-0.4%, Mn: 1.4-1.5%, P≤0.015%, S≤0.002%, V: 0.01-0.02%, Nb: 0.010-0.020%, Al: 0.020-0.030%, B≤0.0006%; the rest is Fe and unavoidable impurities.

2. A method for manufacturing a normalized high-performance steel plate for molten salt storage tanks according to claim 1, characterized in that: The following steps are involved: S1. Smelting and casting According to the above composition, the steel is smelted, and after the steel is tapped from the converter, the S element and gas element in the steel are effectively reduced through the LF+RH vacuum treatment system, and then the steel is cast by the continuous casting machine; S2, Heating Heating temperature: 1100±30℃, holding time 200-350min; S3, rolling During the rolling process, controlled rolling is carried out according to the rolling stage. The rolling is divided into two stages, rough rolling and finishing rolling. The slab needs to complete the rough rolling process in the austenite complete recrystallization zone, and then wait for the temperature on the intermediate roller with a waiting thickness of 1.8-3T. After the temperature drops to the austenite non-recrystallization zone, the finishing mill rolling is carried out; S4. Heat treatment The rolled slab is heat treated by normalizing.

3. The method for manufacturing a normalized high-performance steel plate for molten salt storage tank according to claim 2, characterized in that: In step S3, in order to ensure uniform and fine grains, the final rolling temperature is lowered on the basis of meeting the Ar3 temperature, the start rolling temperature is set at 790-900°C, and the final rolling temperature is set at 750-780°C.

4. The method for manufacturing a normalized high-performance steel plate for molten salt storage tank according to claim 2, characterized in that: In step S4, in order to ensure uniform and fine structure after normalizing, the normalizing temperature is reduced on the basis of meeting Ac3, the normalizing temperature is: 850-880°C, and the furnace time is ≥1.3T.

Images