WO2024090305A1

WO2024090305A1 - Tank manufacturing method

Info

Publication number: WO2024090305A1
Application number: PCT/JP2023/037696
Authority: WO
Inventors: 亨尚渡部; 俊之久保
Original assignee: 三菱造船株式会社
Priority date: 2022-10-25
Filing date: 2023-10-18
Publication date: 2024-05-02
Also published as: JP2024062503A

Abstract

A tank manufacturing method for manufacturing a tank by joint-welding steel sheets from which the tank is to be configured, the method comprising: a step for performing welding such that a plurality of weld layers are formed successively toward the surface side of the sheets between opposing ends of the sheets; and a step for removing a portion of the surface layer part of the underlying weld layer prior to the overlying weld layer being layered on the underlying weld layer.

Description

Tank manufacturing method

The present disclosure relates to a method for manufacturing a tank.
This application claims priority to Japanese Patent Application No. 2022-170369, filed in Japan on October 25, 2022, the contents of which are incorporated herein by reference.

Various articles manufactured using metallic materials are required to have the required strength and toughness according to the article. For example, Patent Document 1 discloses a configuration in which a modified layer with improved toughness is formed between the front weld layer and the back weld layer of a multi-layer butt welded joint of steel plates by applying compressive residual stress through ultrasonic impact treatment.

JP 2008-229692 A

In tanks that store low-temperature liquefied gas, where the cargo temperature is -10°C or below, regulations stipulate the thickness, strength, toughness, etc., of the material that forms the tank. For this reason, the welds that join the steel plates that make up the tank are also required to have the required toughness. In contrast, even if a modified layer with improved toughness is formed using the configuration disclosed in Patent Document 1, there is a possibility that the toughness will not be improved in areas other than the modified layer. To increase the toughness of the welds, it is desirable to increase the toughness more uniformly throughout the entire weld.

The present disclosure has been made to solve the above problems, and aims to provide a method for manufacturing a tank that can increase toughness more uniformly throughout the entire weld.

In order to solve the above problems, the method of manufacturing a tank according to the present disclosure is a method of manufacturing a tank by joint-welding steel plates that constitute the tank. The method of manufacturing the tank includes a step of performing welding and a step of removing a part of the surface layer of a lower weld layer. The step of performing welding is performed such that a plurality of weld layers are sequentially stacked between the ends of the opposing plates toward the surface side of the plates. The step of removing a part of the surface layer of a lower weld layer removes a part of the surface layer of a lower weld layer before the upper weld layer is stacked on the lower weld layer.

The tank manufacturing method disclosed herein allows for more uniform toughness to be achieved throughout the entire weld.

1 is a cross-sectional view of a tank manufactured by a tank manufacturing method according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view showing a weld between steel tank plate materials constituting a tank according to an embodiment of the present disclosure. 4 is a flowchart showing the steps of a method for manufacturing a tank according to an embodiment of the present disclosure. 10A to 10C are diagrams illustrating a process of obtaining a reheating range in a welded layer and a process of setting a range for removing a part of a surface layer of the welded layer in a method for manufacturing a tank according to an embodiment of the present disclosure. FIG. 13 is a diagram showing a state in which a first welded layer has been formed by a welding process according to an embodiment of the present disclosure. 1 is a diagram showing a state in which a portion of a surface layer portion of a first welded layer has been removed by a step of removing a portion of a surface layer portion of a lower welded layer according to an embodiment of the present disclosure. FIG. FIG. 11 is a diagram showing a state in which a second welded layer has been formed by a welding process according to an embodiment of the present disclosure. 1 is a diagram showing a state in which a portion of a surface layer portion of a second welded layer has been removed by a step of removing a portion of a surface layer portion of a lower welded layer according to an embodiment of the present disclosure. FIG. FIG. 11 is a diagram showing a state in which an outermost welded layer has been formed by a step of forming an outermost welded layer according to an embodiment of the present disclosure.

Hereinafter, a method for manufacturing a tank according to an embodiment of the present disclosure will be described with reference to FIGS.
(Tank configuration)
As shown in FIG. 1, the tank 1 of this embodiment is a tank capable of storing liquefied gas such as liquefied carbon dioxide. The tank 1 is installed in the hull of a ship, the floating body of an offshore floating facility, a liquefied gas storage facility on land, or the like. The tank 1 illustrated in this embodiment is cylindrical. The tank 1 includes a tubular portion 2 and a head plate portion 3. The tubular portion 2 extends in its central axis direction Dc. In this embodiment, the tubular portion 2 is formed in a cylindrical shape, and the cross-sectional shape perpendicular to the central axis direction Dc is circular. The head plate portions 3 are disposed at both ends of the tubular portion 2 in the central axis direction Dc. Each head plate portion 3 has a spherical shape such as a hemisphere, and closes an opening in the central axis direction Dc of the tubular portion 2. The tank 1 is not limited to a cylindrical shape, and may be other shapes such as a spherical shape or a rectangular shape.

FIG. 2 is a cross-sectional view showing a weld between steel plates constituting a tank according to an embodiment of the present disclosure.
2, the tank 1 is formed by joint-welding a plurality of steel plates 20. The plates 20 constituting the tank 1 are formed of a metal material such as high-strength tempered steel. In this embodiment, the thickness of the plate 20 in the plate thickness direction Dt is, for example, about 10 to 100 mm.

In this embodiment, the plate materials 20 have a groove portion 21V with a V-shaped cross section, which is a V-shaped groove. In the groove portion 21V, the ends 20a of the plate materials 20 facing each other have an inclined surface 20s. The inclined surfaces 20s of the plate materials 20 facing each other are formed so that the distance between them in the facing direction Da of the plate materials 20 gradually decreases from the surface 20f of the first side Dt1 in the plate thickness direction Dt to the surface 20g of the second side Dt2 in the plate thickness direction Dt. The groove portion 21V extends in a direction perpendicular to the facing direction Da of the plate materials 20 and the plate thickness direction Dt of the plate materials 20 (a direction perpendicular to the paper surface of FIG. 2).

The ends 20a of the opposing plate materials 20 are joined together via a weld 30. The weld 30 is formed between the ends 20a of the plate materials 20. The weld 30 is formed by multi-layer welding. In multi-layer welding, the weld 30 is formed between the ends 20a of the opposing plate materials 20 by repeating welding multiple times. Multi-layer welding is suitable for reducing the amount of heat input to the plate material 20 during each welding.

The welded portion 30 has a plurality of welded layers 31. In this embodiment, six welded layers 311 to 316 are formed as the welded layers 31 of the welded portion 30 (see FIG. 9). Note that in FIG. 2, only five welded layers 311 to 315 out of the six welded layers 311 to 316 are illustrated. The welded layers 311 to 316 are stacked in order from the second side Dt2 in the plate thickness direction Dt toward the surface 20f of the first side Dt1 in the plate thickness direction Dt. Note that the number of layers of the plurality of welded layers 31 is set depending on the plate thickness of the plate material 20, etc., and can be changed as appropriate.
A portion of the surface layer 31a of each of the welded layers 311 to 315 is removed, as will be described in detail later.

(Tank manufacturing method procedure)
Fig. 3 is a flowchart showing the procedure of the method for manufacturing a tank according to an embodiment of the present disclosure. Fig. 4 is a diagram showing a schematic diagram of a process for obtaining a reheating range in a welded layer and a process for setting a range for removing a part of a surface layer of the welded layer in the method for manufacturing a tank according to an embodiment of the present disclosure.
As shown in FIG. 3, the manufacturing method S10 of the tank 1 according to this embodiment includes a step S11 of obtaining a reheat range in the welded layer, a step S12 of setting a range for removing a portion of the surface layer of the welded layer, a step S13 of performing welding, a step S14 of removing a portion of the surface layer of the lower welded layer, a step S15 of forming the outermost welded layer, and a step S16 of removing at least a portion of the outermost welded layer.

In step S11 of acquiring the reheat range in the welded layer, the reheat range in the lower welded layer 31 is acquired. Here, in step S13 of performing welding, which will be described later, welding is repeated multiple times from the second side Dt2 toward the first side Dt1 in the plate thickness direction Dt to sequentially stack and form the welded layers 311-315 and the outermost welded layer 316. At this time, the lower welded layer 31, which is formed first, receives welding heat when welding the upper welded layer 31 later. In step S11 of acquiring the reheat range in this welded layer, as shown in FIG. 4, when the upper welded layer 31B is stacked on the lower welded layer 31A, the reheat range A in the lower welded layer 31A due to the heat input from the upper welded layer 31B is acquired. That is, the heat input from the upper welded layer 31B does not necessarily extend to the entire lower welded layer 31A, but the area of the lower welded layer 31A that extends from the part that contacts (actually, partially overlaps) with the upper welded layer 31B is taken as reheat area A. Reheat area A is the area where the toughness of the lower welded layer 31A is increased by the heat input from the upper welded layer 31B, and it recovers to a preset standard or higher.

In step S12, the range for removing a part of the surface layer of the welded layer is set based on the reheat range A acquired in step S11 for acquiring the reheat range in the welded layer. The part of the surface layer 31a of the lower welded layer 31 is removed in step S14 for removing a part of the surface layer of the lower welded layer, which will be described later in detail. The range for removing the part of the surface layer 31a of the lower welded layer 31 is set so that the toughness of the entire lower welded layer 31 remaining after removing this range is increased (recovered) to a standard level by the heat input from the upper welded layer 31B. In this embodiment, the range for removing the part of the surface layer 31a of the lower welded layer 31 is set by the thickness T in the plate thickness direction Dt of the range B other than the reheat range A in the lower welded layer 31. The removal of the surface layer 31a can be performed, for example, by cutting using a tool such as a disc grinder.

In the welding process S13, welding is performed between the ends 20a of the opposing plate materials 20. Specifically, welding is performed from the second side Dt2 in the plate thickness direction Dt between the inclined surfaces 20s of the opposing plate materials 20 in the direction in which the welded portion 30 extends (the direction perpendicular to the paper surface in FIG. 2).

In process S14 for removing a portion of the surface portion of the lower welding layer, a portion of the surface portion 31a of the lower welding layer 31 is removed before the upper welding layer 31 is laminated on the lower welding layer 31. In process S14 for removing a portion of the surface portion of the lower welding layer, the welding layer 31 formed by welding in process S13 for performing welding is regarded as the lower welding layer 31. In process S14 for removing a portion of the surface portion of the lower welding layer, a portion of the surface portion 31a of the lower welding layer 31 is removed based on the dimension T set in process S12 for setting the range for removing the portion of the surface portion of the welding layer. A grinder, for example, is used to remove the portion of the surface portion 31a of the lower welding layer 31.

The above-mentioned welding process S13 and process S14 of removing part of the surface of the lower welded layer are repeated a predetermined number of times to form the welded layers 311 to 315 in sequence.

Fig. 5 is a diagram showing a state in which a first welded layer is formed by a step of performing welding according to an embodiment of the present disclosure, and Fig. 6 is a diagram showing a state in which a part of a surface layer portion of a first welded layer is removed by a step of removing a part of a surface layer portion of a lower welded layer according to an embodiment of the present disclosure.
Specifically, first, as shown in Fig. 5, in a welding step S13, welding is performed between the ends 20a of the opposing plate materials 20 at a position on the second side Dt2 in the plate thickness direction Dt to form a first welded layer 311. Next, as shown in Fig. 6, in a part of the surface layer portion of the lower welded layer removal step S14, a part of the surface layer portion 31a of the first welded layer 311 is removed by a dimension T before a second welded layer 312 (corresponding to the upper welded layer 31) is laminated on the first welded layer 311 (corresponding to the lower welded layer 31).

Fig. 7 is a diagram showing a state in which a second welded layer is formed by a step of performing welding according to an embodiment of the present disclosure, and Fig. 8 is a diagram showing a state in which a part of a surface layer portion of the second welded layer is removed by a step of removing a part of a surface layer portion of a lower welded layer according to an embodiment of the present disclosure.
Next, as shown in Fig. 7, in a welding step S13, welding is performed between the ends 20a of the opposing plate materials 20 such that a second welded layer 312 (corresponding to the upper welded layer 31) is laminated on a first side Dt1 in the plate thickness direction Dt with respect to a first welded layer 311 (corresponding to the lower welded layer 31). At this time, the first welded layer 311 is reheated by the heat input when welding the second welded layer 312. A part of the surface layer 31a of the first welded layer 311 has been removed. Therefore, the heat input from the second welded layer 312 increases (in other words, recovers) the overall toughness of the first welded layer 311 from which a part of the surface layer 31a has been removed.

Next, as shown in FIG. 8, in step S14, which removes a portion of the surface of the lower welded layer, a portion of the surface 31a of the second welded layer 311 is removed by a dimension T before the third welded layer 313 (corresponding to the upper welded layer 31) is laminated on the second welded layer 312 (corresponding to the lower welded layer 31).

After this, the third welded layer 313 to the fifth welded layer 315 are stacked in sequence by repeating the process S13 of welding and the process S14 of removing part of the surface of the lower welded layer in the same manner.

FIG. 9 is a diagram showing a state in which an outermost welded layer is formed by the step of forming an outermost welded layer according to an embodiment of the present disclosure.
9, in step S15 of forming the outermost welded layer, a sixth welded layer 316 located closest to the first side Dt1 (closest to the surface 20f) in the plate thickness direction Dt is formed by welding so as to be laminated on the fifth welded layer 315. The outermost welded layer 316 located closest to the first side Dt1 (closest to the surface 20f) in the plate thickness direction Dt is formed so as to rise from the surface 20f to the first side Dt1 in the plate thickness direction Dt.

Next, in step S16 of removing at least a part of the outermost welded layer, at least a part of the welded layer 31 located closest to the surface 20f of the plate material 20 is removed. Among the multiple welded layers 31, the welded layers 311 to 314 have their toughness restored and their residual stress alleviated by the heat input when the other welded layers 31 are formed later. The welded layer 315 has their toughness restored and their residual stress alleviated by the heat input when the outermost welded layer 316 is formed later. In contrast, the outermost welded layer 316 formed last on the first side Dt1 in the plate thickness direction Dt has residual stress. Therefore, at least a part of the outermost welded layer 316 located closest to the surface 20f of the plate material 20 is removed. As a result, the part of the outermost welded layer 316 that has not been reheated is removed, and the residual stress is locally reduced. Note that FIG. 2 illustrates a case in which all of the welded layer 316 is removed.
In this manner, the plate materials 20 in this embodiment are joined together. As a result, a welded portion 30 in which a plurality of weld layers 31 are stacked is formed between the ends 20a of the plate materials 20 that face each other.

(Action and Effect)
In the manufacturing method S10 of the tank according to the embodiment, before the upper welded layer 31 is laminated on the lower welded layer 31, a part of the surface layer 31a of the lower welded layer 31 is removed. As a result, when the upper welded layer 31 is welded to be laminated on the lower welded layer 31, heat is input from the upper welded layer 31 to the lower welded layer 31. Since a part of the surface layer 31a of the lower welded layer 31 has been removed, the lower welded layer 31 is reheated by the heat input from the upper welded layer 31, and the toughness of the lower welded layer 31 is increased. Each time a plurality of welded layers 31 are sequentially laminated, the entire welded portion 30 is finally reheated by the heat input from the upper welded layer 31, and the toughness is increased. As a result, the toughness can be increased more uniformly throughout the entire welded portion 30. In addition, by reheating the entire welded portion 30, the residual stress in the welded portion 30 can also be reduced.

In addition, in the above embodiment, when the upper welded layer 31 is laminated by welding, the lower welded layer 31 from which part of the surface layer 31a has been removed is reheated by heat input from the upper welded layer 31, thereby reheating the entire lower welded layer 31.

In addition, in the above embodiment, when the upper welded layer 31 is laminated on the lower welded layer 31, the reheat range A due to the heat input from the upper welded layer 31 extends to the entire lower welded layer 31 after removing part of the surface layer 31a, thereby improving the overall toughness of the lower welded layer 31.

In addition, in the above embodiment, the reheat range A in the lower welding layer 31 due to the heat input from the upper welding layer 31 is acquired. This makes it possible to appropriately set the range in which the part of the surface layer 31a of the lower welding layer 31 is removed so that the heat input from the upper welding layer 31 covers the entire lower welding layer 31 after the part of the surface layer 31a has been removed.

In addition, in the above embodiment, by removing at least a portion of the welded layer 316 located on the surface 20f side of the plate material 20, the portion of the welded layer 316 located on the surface 20f side that has not been reheated can be removed, and residual stress can be locally reduced.

Other Embodiments
Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not deviate from the gist of the present disclosure are also included.
In the above embodiment, the groove portion 21V has a V-shaped cross section, but is not limited thereto. For example, the groove portion may have an X-shaped cross section.

<Additional Notes>
A manufacturing method of the tank 1 described in the embodiment can be understood, for example, as follows.

(1) A manufacturing method of a tank 1 according to a first aspect is a manufacturing method of a tank 1 for manufacturing the tank 1 by joint-welding steel plates 20 constituting the tank 1, the manufacturing method including a step S13 of welding between the ends 20a of the plates 20 facing each other so that a plurality of welded layers 31 are sequentially stacked toward the surface 20f side of the plates 20, and a step S14 of removing a part of the surface layer 31a of the lower welded layer 31 before the upper welded layer 31 is stacked on the lower welded layer 31.
including.

In this manufacturing method of the tank 1, a portion of the surface portion 31a of the lower welded layer 31 is removed before the upper welded layer 31 is laminated on the lower welded layer 31. As a result, when attempting to reheat the lower welded layer 31, heat can be input to the entire lower welded layer 31, thereby increasing the toughness of the lower welded layer 31. As a result, the toughness of the welded portion 30 can be increased more uniformly. Furthermore, by reheating the welded portion 30, residual stress in the welded portion 30 can also be reduced.

(2) The manufacturing method of the tank 1 according to the second aspect is the manufacturing method of the tank 1 according to (1), and in the welding step S13, when the upper welding layer 31 is laminated to the lower welding layer 31 by welding, the lower welding layer 31 from which a part of the surface layer 31a has been removed is reheated by the heat input from the upper welding layer 31.

As a result, when the upper welded layer 31 is laminated by welding, the lower welded layer 31 from which part of the surface layer 31a has been removed can be reheated by the heat input from the upper welded layer 31. Therefore, each time multiple welded layers 31 are laminated in sequence, heat is input from the upper welded layer 31, and ultimately the entire welded portion 30 is reheated, thereby increasing the toughness of the entire welded portion 30.

(3) The manufacturing method of the tank 1 according to the third aspect is the manufacturing method of the tank 1 according to (1) or (2), and in step S14 of removing a portion of the surface layer 31a of the lower welded layer 31, the portion of the surface layer 31a of the lower welded layer 31 is removed so that when the upper welded layer 31 is laminated on the lower welded layer 31, the reheat range A due to the heat input from the upper welded layer 31 covers the entire lower welded layer 31 after the portion of the surface layer 31a has been removed.

As a result, when the upper welded layer 31 is laminated on the lower welded layer 31, the reheat range A due to the heat input from the upper welded layer 31 extends to the entire lower welded layer 31 after part of the surface layer 31a has been removed, thereby increasing the overall toughness of the lower welded layer 31.

(4) The manufacturing method of the tank 1 according to the fourth aspect is a manufacturing method of the tank 1 according to any one of (1) to (3), and further includes a step S11 of acquiring a reheating range A in the lower welded layer 31 due to heat input from the upper welded layer 31 when the upper welded layer 31 is laminated on the lower welded layer 31, and a step S12 of setting a range for removing a portion of the surface layer 31a of the lower welded layer 31 based on the reheating range A acquired in the step S11 of acquiring the reheating range A, in a step S14 of removing a portion of the surface layer 31a of the lower welded layer 31.

This allows the range over which part of the surface layer 31a of the lower welded layer 31 is removed to be appropriately set so that the heat input from the upper welded layer 31 reaches the entire lower welded layer 31 after part of the surface layer 31a has been removed.

(5) The manufacturing method of the tank 1 according to the fifth aspect is any one of the manufacturing methods of the tank 1 according to (1) to (4), in which at least a portion of the welded layer 316, which is located closest to the surface 20f of the plate material 20, among the multiple welded layers 31, is removed.

By removing at least a portion of the welded layer 316 located on the surface 20f side of the plate material 20, the portion of the welded layer 316 located on the surface 20f side that has not been reheated can be removed, and residual stress can be locally reduced.

1...tank 2...tubular section 3...head plate section 20...plate material 20a...end 20f...surface 20g...surface 20s...inclined surface 21V...groove section 30...welding section 31...welding layer, 311-316...welding layer 31A...lower welding layer 31B...upper welding layer 31a...surface A...reheating range Da...opposing direction Dc...central axis direction Dt...plate thickness direction Dt1...first side Dt2...second side K...removal range S10...tank manufacturing method S11...process of obtaining reheating range in welding layer S12...process of setting range of removal of part of surface of welding layer S13...process of welding S14...process of removing part of surface of lower welding layer S15...process of forming outermost welding layer S16...process of removing at least part of outermost welding layer

Claims

A manufacturing method of a tank, comprising the steps of manufacturing a tank by joint welding of steel plate materials constituting the tank,
A step of welding between the opposing ends of the plate materials such that a plurality of weld layers are sequentially stacked toward a front surface side of the plate materials;
a step of removing a part of a surface layer of the lower welded layer prior to laminating the upper welded layer on the lower welded layer;
A method for manufacturing a tank comprising the steps of:
2. The method for manufacturing a tank according to claim 1, wherein, in the welding step, when the upper weld layer is laminated onto the lower weld layer by welding, the lower weld layer from which a portion of the surface layer has been removed is reheated by heat input from the upper weld layer.
3. The method for manufacturing a tank according to claim 1 or 2, wherein in the step of removing a portion of the surface portion of the lower welded layer, the portion of the surface portion of the lower welded layer is removed so that, when the upper welded layer is laminated on the lower welded layer, a reheat range due to heat input from the upper welded layer will cover the entire lower welded layer after the portion of the surface portion has been removed.
acquiring a reheat range in the lower welding layer due to heat input from the upper welding layer when the upper welding layer is laminated on the lower welding layer;
3. The method for manufacturing a tank according to claim 1 or 2, further comprising: a step of setting a range in which a portion of the surface portion of the lower welded layer is removed, in a step of removing a portion of the surface portion of the lower welded layer, based on the reheating range acquired in the step of acquiring the reheating range.
The method for manufacturing a tank according to claim 1 or 2, further comprising removing at least a portion of the welded layer located closest to the surface side of the plate material among the plurality of welded layers.