Gas storage tank for low-temperature gas and method for manufacturing gas storage tank for low-temperature gas

Abstract

A gas storage tank for cryogenic gas, which stores liquefied gas at-10 DEG C to-80 DEG C, is provided with: a plurality of gas storage tank plates made of carbon manganese steel; and welding the welding parts of the plurality of gas storage tank plates, wherein the welding material for forming the welding parts is a welding material for 9% nickel steel or a welding material for high manganese steel.

Description

Technical Field

[0001] The invention relates to a gas storage tank for low-temperature gas and a method for manufacturing the gas storage tank for low-temperature gas.

[0002] This application claims priority based on patent application No. 2022-170366 filed in Japan on October 25, 2022, and the contents are incorporated herein by reference. Background Art

[0003] Various articles made of metal materials are required to have the strength and toughness required for the articles. For example, Patent Document 1 discloses a steel sheet with a yield strength of 500 N / mm 2 Above and tensile strength is 610N / mm 2 High-strength steel above.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2008-25014 Summary of the invention

[0007] Technical issues to be solved by the invention

[0008] However, in a gas tank that contains low-temperature liquefied gas whose cargo temperature is below -10°C, the thickness, strength, toughness, etc. of the material forming the gas tank are specified by regulations. Therefore, the required toughness is also required to be ensured in the welded portion where the steel plates constituting the gas tank are joined to each other. In particular, in a gas tank for ships, from the viewpoint of preventing brittle fracture, it is sometimes required by regulations to perform heat treatment after welding to eliminate welding residual stress. However, the toughness of the welded portion may be reduced after the heat treatment. Therefore, even if a steel material such as that disclosed in Patent Document 1 is used for the steel plate, the required toughness may not be ensured in the welded portion.

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a cryogenic gas tank and a method for manufacturing a cryogenic gas tank that can ensure sufficient toughness in a welded portion.

[0010] Means for solving technical problems

[0011] In order to solve the above-mentioned problems, the low-temperature gas storage tank involved in the present invention is a low-temperature gas storage tank for storing liquefied gas at -10°C to -80°C. The low-temperature gas storage tank includes a plurality of storage tank plates and a welding portion. The plurality of storage tank plates are made of carbon manganese steel. The welding portion is welded with a plurality of the storage tank plates. The welding material forming the welding portion is a welding material for 9% nickel steel or a welding material for high manganese steel.

[0012] The manufacturing method of the cryogenic gas storage tank according to the present invention is a manufacturing method of the cryogenic gas storage tank for storing liquefied gas stored at -10°C to -80°C. The manufacturing method of the cryogenic gas storage tank includes a step of preparing a gas storage tank plate and a step of joint welding. In the step of preparing the gas storage tank plate, a plurality of gas storage tank plates made of carbon manganese steel are prepared. In the step of joint welding, the gas storage tank plates are joint-welded to each other using a welding material for 9% nickel steel or a welding material for high manganese steel.

[0013] Effects of the Invention

[0014] According to the cryogenic gas tank and the method for manufacturing the cryogenic gas tank of the present invention, sufficient toughness can be ensured in the welded portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a cross-sectional view of a low-temperature gas storage tank according to an embodiment of the present invention.

[0016] Figure 2 It is a cross-sectional view showing a welded portion between steel plate materials constituting the low-temperature gas storage tank according to the embodiment of the present invention.

[0017] Figure 3 This is a diagram comparing the toughness (absorbed energy value in a Charpy impact test) of a welding material of a weld portion according to an embodiment of the present invention and a welding material made of the same metal as a general gas tank plate material.

[0018] Figure 4 This is a flowchart showing the steps of a method for manufacturing a cryogenic gas storage tank according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] Below, reference Figures 1 to 4 , a cryogenic gas storage tank and a method for manufacturing a cryogenic gas storage tank according to an embodiment of the present invention are described.

[0020] (Structure of a cryogenic gas storage tank)

[0021] like Figure 1 As shown, the cryogenic gas storage tank 1 of this embodiment is a cryogenic gas storage tank capable of storing liquefied gas at -10°C to -80°C, such as liquefied carbon dioxide, for example. The cryogenic gas storage tank 1 is different from an extremely cryogenic gas storage tank capable of storing liquefied gas at -160°C or below, such as liquefied natural gas (LNG), for example.

[0022] The cryogenic gas storage tank 1 is provided on the hull of a ship, the floating body of an offshore floating device, a liquefied gas storage facility on land, and the like. The cryogenic gas storage tank 1 illustrated in the present embodiment is cylindrical. The cryogenic gas storage tank 1 comprises a cylindrical portion 2 and a mirror plate portion 3. The cylindrical portion 2 extends along its central axis direction Dc. In the present embodiment, the cylindrical portion 2 is formed into a cylindrical shape, and the cross-sectional shape orthogonal to its central axis direction Dc is circular. The mirror plate portion 3 is respectively arranged at both ends of the central axis direction Dc of the cylindrical portion 2. Each mirror plate portion 3 is spherical such as a hemisphere, and closes the opening of the central axis direction Dc of the cylindrical portion 2. In addition, the cryogenic gas storage tank 1 is not limited to a cylindrical shape, and may also be other shapes such as a sphere and a square.

[0023] Figure 2 It is a cross-sectional view showing a welded portion between steel plate materials constituting the low-temperature gas storage tank according to the embodiment of the present invention.

[0024] like Figure 2 As shown, the cryogenic gas storage tank 1 is formed by welding a plurality of steel storage tank plates 20. The storage tank plates 20 constituting the cryogenic gas storage tank 1 are made of the specifications specified in JIS-G3128, JIS-G3140 or other equivalent specifications, and the minimum tensile strength is 590N / mm 2 Up to 940N / mm 2 The gas tank plate 20 is formed of a high-tensile steel plate (so-called high-strength material). As such a gas tank plate 20, carbon manganese steel can be exemplified. Carbon manganese steel contains at least carbon (C) and manganese (Mn). Carbon manganese steel contains, for example, less than 0.2% of carbon and less than 2.0% of manganese.

[0025] In the present embodiment, the gas tank plates 20 have a V-shaped groove portion 21V with a V-shaped cross-section. In the groove portion 21V, the ends 20a of the gas tank plates 20 facing each other have an inclined surface 20s respectively. The inclined surfaces 20s of the gas tank plates 20 facing each other are formed so that the interval in the opposing direction Da gradually approaches from the surface 20f on the first side Dt1 in the plate thickness direction Dt toward the surface 20g on the second side Dt2 in the plate thickness direction Dt. The groove portion 21V extends along the opposing direction Da of the gas tank plates 20 and a direction orthogonal to the plate thickness direction Dt of the gas tank plates 20 (direction perpendicular to the plate thickness direction Dt of the gas tank plates 20). Figure 2 In addition, in the present embodiment, the groove portion 21V is exemplified as a V-shaped groove, but it is not limited to the V-shaped groove, and may also be an X-shaped groove or the like.

[0026] The ends 20a of the gas tank plates 20 facing each other are joined to each other via the welding portion 30. The welding portion 30 is formed between the ends 20a of the gas tank plates 20. The welding material forming the welding portion 30 is a metal of a different type from the gas tank plate 20. Generally, as the welding material forming the welding portion 30, a metal of the same series as the gas tank plate 20, that is, a welding material of a common material containing carbon and manganese is used. In this embodiment, the welding material of the welding portion 30 is, for example, a welding material for 9% nickel steel. The welding material for 9% nickel steel contains more nickel (Ni) than the gas tank plate 20. In addition, the welding portion 30 has an austenitic structure, which is different from the gas tank plate 20.

[0027] In the case where the welding material of the weld 30 is a welding material for 9% nickel steel, the welding material contains 30 to 80% nickel, and the rest contains molybdenum, chromium and iron. Moreover, in addition to molybdenum, chromium and iron, niobium may also be contained in the rest. Here, in the case where the welding material of the weld 30 is a welding material for 9% nickel steel, the nickel content is preferably set to 40 to 75%. Furthermore, in the case where the welding material of the weld 30 is a welding material for 9% nickel steel, the nickel content is preferably 50 to 70%. As such a welding material for 9% nickel steel, Hastelloy (registered trademark), Inconel (registered trademark) and the like can be exemplified.

[0028] In such a welded portion 30 , after welding, a heat treatment is performed under predetermined conditions to reduce the residual stress of the welded portion 30 .

[0029] Figure 3 This is a diagram comparing the toughness (absorbed energy value in a Charpy impact test) of a welding material of a weld portion according to an embodiment of the present invention and a welding material made of the same metal as a general gas tank plate material.

[0030] like Figure 3 As shown, the welding material of the weld portion 30 (9% nickel steel welding material) containing more nickel than the gas tank plate material 20 has a higher absorbed energy value at a predetermined temperature in the Charpy impact test than the welding material (eutectic welding material composed of the same series of metals as the general gas tank plate material) containing more nickel (Ni) than the gas tank plate material 20. The Charpy impact test is a test in which a hammer is used to impact a test piece of the weld portion 30 to break the test piece, and the amount of energy required to break the test piece is obtained as the absorbed energy value to evaluate toughness.

[0031] Furthermore, the welding material of the weld portion 30 (welding material for 9% nickel steel) has a higher absorbed energy value at a predetermined temperature in a Charpy impact test than a welding material that does not contain more nickel (Ni) than the gas tank plate material 20 (eutectic welding material composed of a metal of the same series as a general gas tank plate material) even after heat treatment after welding.

[0032] (Steps of manufacturing method of cryogenic gas storage tank)

[0033] Figure 4 This is a flowchart showing the steps of a method for manufacturing a cryogenic gas storage tank according to an embodiment of the present invention.

[0034] like Figure 4 As shown, the manufacturing method S10 of the low-temperature gas tank 1 according to the embodiment of the present invention includes: a step S11 of preparing a tank plate material 20; a step S12 of welding a joint; and a step S13 of performing a heat treatment.

[0035] In the step S11 of preparing the tank plate material 20 , a plurality of tank plate materials 20 made of carbon manganese steel are prepared in order to form the low-temperature gas tank 1 .

[0036] In the joint welding step S12, if Figure 2 As shown, between the end portions 20a of the gas tank plates 20 facing each other, the welding material of the welding portion 30 containing more nickel (Ni) than the gas tank plates 20 as described above is used to perform joint welding by arc welding or the like. Thus, the gas tank plates 20 are joined to each other via the welding portion 30. Here, in the step S12 of the joint welding, arc welding is exemplified as a method of joint welding, but hot wire method or laser welding may also be used. When the joint welding is performed by these hot wire methods or laser welding, heat input to the welding portion 30 can be suppressed. Thus, the metal of the welding portion 30 is diluted by the components of the gas tank plate 20 (base material), so that the degradation of the metal properties of the welding portion 30 and the heat-affected range of the gas tank plate 20 around the welding portion 30 can be suppressed.

[0037] In the heat treatment step S13, the weld 30 is heat treated under pre-set conditions. In the heat treatment step S13, the weld 30 and the heat-affected area around it may be heat treated locally, or the entire cryogenic gas storage tank 1 may be heat treated. The heat input by the heat treatment in step S13 relieves the residual stress in the weld 30 and the heat-affected area around it.

[0038] (Effect)

[0039] In the cryogenic gas storage tank 1 and the manufacturing method S10 of the cryogenic gas storage tank 1 of the above-mentioned embodiment, the welding material forming the weld 30 is a 9% nickel steel welding material. In the cryogenic gas storage tank 1 for storing liquefied gas at -10°C to -80°C, the tensile strength of the storage tank plate 20 is required to exceed 590N / mm 2, a high-strength steel plate containing carbon and manganese is used. Usually, as a welding material for forming the weld 30, a welding material of a common material containing carbon and manganese of the same series as the gas tank plate 20 is used, but when such a welding material is heat-treated after welding, the toughness sometimes decreases. In contrast, the toughness of the 9% nickel steel welding material before heat treatment is higher than that of the common material welding material. Therefore, even if the weld 30 formed by the 9% nickel steel welding material is heat-treated after welding, the toughness reduced by the heat treatment will be higher than that of the common material welding material. Therefore, sufficient toughness can be ensured in the weld 30.

[0040] Furthermore, in the above-described embodiment, by using the welding material as a metal different from the type of metal of the gas tank plate material 20 , a welding material with high toughness can be selected, and sufficient toughness can be ensured in the welded portion 30 even after heat treatment.

[0041] Furthermore, in the above-mentioned embodiment, the welding material contains more nickel than the gas tank plate material 20. The welding material containing more nickel than the gas tank plate material 20 has higher toughness before heat treatment than the welding material of the same material. Therefore, even if the weld portion 30 is heat-treated after welding, sufficient toughness can be ensured in the weld portion 30.

[0042] Furthermore, in the above-mentioned embodiment, the 9% nickel steel welding material contains 30 to 80% nickel. The toughness of the 9% nickel steel welding material containing 30 to 80% nickel before heat treatment is higher than that of the common material welding material. Therefore, even if the weld 30 is heat-treated after welding, sufficient toughness can be ensured in the weld 30.

[0043] Furthermore, in the above-mentioned embodiment, the 9% nickel steel welding material contains 40 to 75% nickel. The toughness of the 9% nickel steel welding material containing 40 to 75% nickel before heat treatment is particularly high compared to the common material welding material. Therefore, even if the weld 30 is heat-treated after welding, sufficient toughness can be ensured in the weld 30.

[0044] Furthermore, in the above-mentioned embodiment, the 9% nickel steel welding material contains 50 to 70% nickel. The toughness of the 9% nickel steel welding material containing 50 to 70% nickel before heat treatment is higher than that of the common material welding material. Therefore, even if the weld 30 is heat-treated after welding, sufficient toughness can be ensured in the weld 30.

[0045] Furthermore, in the above embodiment, by making the tensile strength exceed 590 N / mm 2 The steel material used as the gas tank plate material 20 can ensure sufficient toughness in the welded portion 30 in the cryogenic gas tank 1 that stores liquefied gas at -10°C to -80°C.

[0046] (Other Implementations)

[0047] As mentioned above, although the embodiment of the present invention is described in detail with reference to the drawings, the specific structure is not limited to this embodiment, and design changes and the like within the scope not departing from the gist of the present invention are also included.

[0048] In the above-mentioned embodiment, as the welding material of the weld 30, the welding material for 9% nickel steel is mainly exemplified, but as the welding material of the weld 30, the welding material for high manganese steel can also be used. The welding material for high manganese steel refers to a welding material used for welding high manganese steel containing more than 11%. Specifically, the welding material for high manganese steel contains more than 15% manganese. The welding material for high manganese steel preferably sets the manganese content to 15 to 30%, and more preferably sets the manganese content to 18 to 27%. The weld 30 formed by the welding material for high manganese steel has an austenitic structure, unlike the gas tank plate 20 made of carbon manganese steel.

[0049] The high manganese steel welding material has higher toughness before heat treatment for relieving residual stress than the welding material made of the same material as the gas tank plate 20. Therefore, even if the weld 30 is heat-treated after welding with the high manganese steel welding material, sufficient toughness can be ensured in the weld 30, similar to the above-mentioned 9% nickel steel welding material.

[0050] <Note>

[0051] The cryogenic gas tank 1 and the method S10 for manufacturing the cryogenic gas tank 1 described in the embodiment can be understood, for example, as follows.

[0052] (1) A cryogenic gas storage tank 1 according to a first embodiment is a cryogenic gas storage tank 1 for storing liquefied gas at a temperature of -10°C to -80°C, and comprises: a plurality of tank plates 20 made of carbon manganese steel; and a weld 30 formed by welding the plurality of tank plates 20 to each other, wherein the welding material forming the weld 30 is a welding material for 9% nickel steel or a welding material for high manganese steel.

[0053] In the cryogenic gas storage tank 1, the welding material forming the welded portion 30 is a 9% nickel steel welding material or a high manganese steel welding material. In the cryogenic gas storage tank 1 storing liquefied gas at -10°C to -80°C, the tensile strength of the storage tank plate 20 is required to exceed 590N / mm 2, a high-strength steel plate containing carbon and manganese is used. Usually, as a welding material for forming the weld 30, a welding material of a common material containing carbon and manganese of the same series as the gas tank plate 20 is used, but when such a welding material is heat-treated after welding, the toughness is greatly reduced. In contrast, the toughness of the welding material for 9% nickel steel or the welding material for high manganese steel before heat treatment is higher than that of the welding material of the common material. Therefore, even if the weld 30 formed by using the welding material for 9% nickel steel or the welding material for high manganese steel is heat-treated after welding, the toughness after reduction by heat treatment is higher than that of the welding material of the common material. Therefore, sufficient toughness can be ensured in the weld 30.

[0054] (2) The cryogenic gas tank 1 according to the second aspect is the cryogenic gas tank 1 according to (1), wherein the welding material is a metal of a different type from that of the tank plate material 20 .

[0055] Thus, by using the welding material as a metal different from the type of metal of the tank plate material 20 , a welding material with high toughness can be selected even after heat treatment, and sufficient toughness can be ensured in the welded portion 30 .

[0056] (3) The cryogenic gas tank 1 according to a third aspect is the cryogenic gas tank 1 according to (1) or (2), wherein the welding material contains more nickel than the tank plate material 20 .

[0057] Thus, the toughness before heat treatment of the welding material containing more nickel than the gas tank plate material 20 is higher than that of the welding material of the same material. Therefore, even if the weld portion 30 is heat-treated after welding, sufficient toughness can be ensured in the weld portion 30.

[0058] (4) The cryogenic gas tank 1 according to a fourth aspect is the cryogenic gas tank 1 according to any one of (1) to (3), wherein the 9% nickel steel welding material contains 30 to 80% nickel.

[0059] Therefore, the toughness of the 9% nickel steel welding material containing 30 to 80% nickel before heat treatment is higher than that of the common material welding material. Therefore, even if the weld 30 is heat treated after welding, sufficient toughness can be ensured in the weld 30.

[0060] (5) The cryogenic gas tank 1 according to a fifth aspect is the cryogenic gas tank 1 according to (4), wherein the 9% nickel steel welding material contains 40 to 75% nickel.

[0061] Therefore, the toughness of the 9% nickel steel welding material containing 40 to 75% nickel before heat treatment is particularly higher than that of the common material welding material. Therefore, even if the weld 30 is heat treated after welding, sufficient toughness can be ensured in the weld 30.

[0062] (6) The cryogenic gas tank 1 according to a sixth aspect is the cryogenic gas tank 1 according to (5), wherein the 9% nickel steel welding material contains 50 to 70% nickel.

[0063] Thus, the toughness of the 9% nickel steel welding material containing 50 to 70% nickel before heat treatment is higher than that of the common material welding material. Therefore, even if the weld 30 is heat treated after welding, sufficient toughness can be ensured in the weld 30.

[0064] (7) The cryogenic gas tank 1 according to a seventh aspect is the cryogenic gas tank 1 according to any one of (1) to (3), wherein the welding material for high manganese steel is a welding material for welding high manganese steel containing 11% or more manganese.

[0065] Thus, the toughness of the welding material for high manganese steel containing more than 11% manganese before heat treatment is higher than that of the welding material of the common material. Therefore, even if the weld 30 is heat treated after welding, sufficient toughness can be ensured in the weld 30.

[0066] (8) The cryogenic gas storage tank 1 according to the eighth aspect is the cryogenic gas storage tank 1 according to any one of (1) to (7), wherein the tank plate material 20 has a tensile strength exceeding 590 N / mm 2 of steel.

[0067] Therefore, by exceeding the tensile strength of 590 N / mm 2 The steel material used as the gas tank plate material 20 can ensure sufficient toughness in the welded portion 30 in the cryogenic gas tank 1 that stores liquefied gas at -10°C to -80°C.

[0068] (9) A method S10 for manufacturing a cryogenic gas storage tank 1 according to a ninth aspect, wherein the cryogenic gas storage tank 1 stores liquefied gas stored at a temperature of -10°C to -80°C, the method S10 comprising: a step S11 of preparing a plurality of storage tank plates 20 made of carbon manganese steel; and a step S12 of welding joints of the storage tank plates 20 to each other using a welding material for 9% nickel steel or a welding material for high manganese steel.

[0069] The method S10 for manufacturing the cryogenic gas tank 1 can manufacture the cryogenic gas tank 1 capable of ensuring sufficient toughness in the welded portion 30 .

[0070] Industrial Applicability

[0071] According to the cryogenic gas tank and the method for manufacturing the cryogenic gas tank of the present invention, sufficient toughness can be ensured in the welded portion.

[0072] Explanation of symbols

[0073] 1-gas storage tank for low-temperature gas, 2-cylindrical portion, 3-mirror plate portion, 20-gas storage tank plate material, 20a-end portion, 20f, 20g-surface, 20s-inclined surface, 21V-groove portion, 30-welding portion, Da-opposing direction, Dc-center axis direction, Dt-plate thickness direction, Dt1-first side, Dt2-second side, S10-manufacturing method, S11-process of preparing gas storage tank plate material, S12-process of welding joints, S13-process of performing heat treatment.

Claims

1. A low-temperature gas storage tank, which is a low-temperature gas storage tank for storing liquefied gas at -10°C to -80°C, comprising: A number of gas tank plates made of carbon manganese steel; and Welding the welded parts of the plurality of gas tank plates to each other, The welding material forming the welded portion is a welding material for 9% nickel steel or a welding material for high manganese steel.

2. The cryogenic gas storage tank according to claim 1, wherein: The welding material is a metal of a different type from that of the gas tank plate.

3. The cryogenic gas storage tank according to claim 1 or 2, wherein: The welding material contains more nickel than the gas tank plate material.

4. The cryogenic gas storage tank according to claim 1 or 2, wherein: The 9% nickel steel welding material contains 30 to 80% nickel.

5. The cryogenic gas storage tank according to claim 4, wherein: The 9% nickel steel welding material contains 40 to 75% nickel.

6. The cryogenic gas storage tank according to claim 5, wherein: The 9% nickel steel welding material contains 50-70% nickel.

7. The cryogenic gas storage tank according to claim 1 or 2, wherein: The welding material for high manganese steel is a welding material used for welding high manganese steel containing more than 11% manganese.

8. The cryogenic gas storage tank according to claim 1 or 2, wherein: The gas tank plate has a tensile strength exceeding 590 N / mm 2 of steel.

9. A method for manufacturing a cryogenic gas storage tank, wherein the cryogenic gas storage tank stores liquefied gas stored at -10°C to -80°C, the method comprising: The process of preparing a plurality of gas tank plates made of carbon manganese steel; and A process of welding the gas tank plates to each other using a 9% nickel steel welding material or a high manganese steel welding material.

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