WO2013191323A1

WO2013191323A1 - Method for molding spherical storage container using aluminum thick plate

Info

Publication number: WO2013191323A1
Application number: PCT/KR2012/006066
Authority: WO
Inventors: 윤종헌; 이정환
Original assignee: 한국기계연구원
Priority date: 2012-06-21
Filing date: 2012-07-30
Publication date: 2013-12-27

Abstract

The present invention relates to a method for molding a spherical storage container using an aluminum thick plate and, more specifically, to a method for molding a spherical storage container using an aluminum thick plate, in which an inside curvature has a target curvature. The method for molding a spherical storage container using an aluminum thick plate, according to the present invention, is a method for molding a storage container which is formed as a spherical shape by allowing a plurality of plates mainly made of aluminum to be bonded, and the method for molding the spherical storage container comprises: the first step of positioning the plates on a die which is formed by allowing a surface thereof that supports the plates to have a target curvature; the second step of pressing the plates by moving a punch which is formed by allowing a surface thereof that faces the plates to have a larger curvature than the target curvature; and moving the punch to the original position. Thus, according to the present invention, since the inside curvature of the storage container is formed to have the target curvature, an elastic restoring force is reduced such that a degree of precision in measurement can be improved, and it is possible to determine an exact storage capacity and to load a desired capacity.

Description

Forming method of spherical shape storage container using aluminum thick plate

The present invention relates to a method for forming a spherical shape storage container using an aluminum thick plate, and more particularly, to a method for forming a spherical shape storage container using an aluminum thick plate having an internal curvature of a target curvature.

Aluminum is a silver-white soft metal, which can be made of thin foil or wire because of its malleability and ductility, and its properties vary depending on the purity. It is often used as a material for wires.

In addition, aluminum is used as a major material for aircraft, ships and vehicles because of its light and durable characteristics, and easily reacts with oxygen, but after the oxide film is formed, the film is blocked from contact with oxygen, so it does not rust well and is polished. This is often used for parts that need to last long.

Aluminum plates are widely used in transport ships that carry liquid gas, such as LNG or LPG, and these liquid gases are liquid gases due to rapid increase in consumption due to high oil prices and reactor accidents. The demand for transport ships for transporting the situation is increasing.

A liquid gas carrier is a ship that carries liquid gas from a production base to a receiving base. It is usually called an LNG ship or an LPG ship, or an LG Carrier or an LPG Carrier, depending on the type of liquid gas. Also called).

Liquefied natural gas, for example, is a gas obtained by liquefying natural gas mainly composed of methane at sub-atmospheric pressure of 162 ° C. The volume ratio of liquid and gas is about 1/600, and the specific gravity of the liquefied state is 0.43 to 0.50.

In addition, the LNG ship is divided into independent tank type and membrane type according to the shape of the cargo hold, the independent tank type is designed to have a double structure of the tank in which the LENG is stored, and the independent aluminum sphere tank (sphere) It is made to be independent of the hull.

Independent tank type has the advantage of accurate analysis of storage tank stability and reliability. Membrane type can take advantage of relatively inexpensive ship and deck space, freely deforms according to the change of tank capacity, and secures the clock. This has the advantage of reducing the cost and the cost of passage of the Suez Canal.

The independent tank type storage tank is constructed by welding a plurality of aluminum plate patches formed with a constant curvature to maintain a spherical shape. When the curvature of the curved plate is not constant, a shape of a perfect shape in the welding process is achieved. Since it becomes difficult to assemble the spherical shape, it is necessary to accurately secure the curvature according to the surface forming and to predict the elastic restoration amount of the thick plate due to the spring back.

As such, when the storage tank is not formed in a spherical shape, the capacity of the storage tank may be inaccurate and may change the transport capacity of the liquid gas.

On the other hand, according to the Republic of Korea Patent Publication No. 2009-0116037, while bending the corner forming plate member to be a three-dimensional curved surface with the same radius of curvature can be shortened as much as possible, while reducing the cost of production, Corner for gas storage tank of liquefied petroleum gas transportation ship that can improve quality and productivity without recycling secondary method by means, and can recycle not only flat plate member but also plate member bent in any shape. Disclosed is an invention relating to a three-dimensional curved surface bending apparatus for a secondary plate member.

The Korean Laid-open Patent includes an upper punch fixedly installed on a lower surface of a ram reciprocating up and down of a press, and a lower die fixedly installed on an upper surface of a bed under the ram and in contact with the upper punch by lowering the ram. Disclosed is a configuration in which curved surfaces corresponding to each other are formed on the lower surface of the punch and the upper surface of the lower die, respectively, and the curved surface is formed to have the same curvature after the corner forming plate member is bent into a three-dimensional curved surface between the upper punch and the lower die. .

In addition, Korean Patent Laid-Open Publication No. 2008-0000880 discloses an invention relating to a structure of a bending roller device for three-dimensional molding, and the published patent is capable of storing and transporting crude oil or various gases in a liquid or gaseous state. Disclosed is a three-dimensional forming apparatus for manufacturing a large or elliptical large tank structure installed on a ship and onshore.

The above-mentioned patent discloses that the upper and lower roller shapes may have a convex or concave surface to form a flat member such as ferrous or non-ferrous metal having a predetermined thickness to have a three-dimensional curved surface, thereby effectively producing a three-dimensional curved shape. Disclosed are inventions that provide equipment and methods.

It is an object of the present invention to provide a method for forming a spherical shape storage container using an aluminum thick plate having an inner surface having a target curvature.

Another object of the present invention is to provide a method for forming a spherical shape storage container capable of securing a precise molding dimension by reducing the amount of elastic recovery generated after the curved surface of an aluminum thick plate.

In the method of forming a spherical shape storage container using an aluminum thick plate according to the present invention, a method of forming a spherical shape storage container while joining a plurality of plates made of aluminum as a main material, wherein the surface supporting the plate is a target. Positioning the plate on a die formed to have a curvature; A second step of compressing the plate by moving a punch formed such that a surface facing the plate has a curvature greater than the target curvature; And a third step of moving the punch to its original position. It is configured to include.

In another aspect, a molding method of a spherical shape storage container using an aluminum thick plate according to the present invention is a method of forming a spherical shape while a plurality of plates made of aluminum as a main material are joined to support a plate. Positioning the plate on a die whose surface is formed to have a curvature greater than a target curvature; A second step of compressing the plate by moving a punch formed such that a surface facing the plate has a target curvature; And a third step of moving the punch to its original position. It is configured to include.

According to the molding method of the spherical shape storage container using the aluminum plate according to the present invention, the inner surface of the storage container is formed to have a target curvature, the internal curvature is formed to be constant, the effect of accurate calculation of storage capacity and loading of the desired capacity You can expect.

In addition, the internal curvature of the storage container can be expected to reduce the molding load while maintaining a constant, it is possible to expect the effect that the molding of the storage container becomes easier as the molding load is reduced.

The curvature and dimensional accuracy of the curved plate forming the storage container can be expected to be improved, and the productivity and work efficiency for manufacturing the storage container such as welding between the curved plate can be expected to be improved.

Since the internal curvature of the storage container is kept constant, the effect of maintaining the internal pressure of the storage container can be expected to be constant, it is possible to expect the effect of extending the life of the storage container by maintaining a constant internal pressure.

As the internal pressure is distributed evenly due to the storage container that maintains a constant internal pressure, it is possible to expect the effect of improving the safety of the storage container, thereby reducing the maintenance cost according to the use of the storage container. .

1 is a perspective view showing a vessel using a storage container molded by a method of forming a spherical shape storage container using an aluminum plate according to an embodiment of the present invention.

Figure 2 is a schematic view showing a mold used in the method of forming a spherical shape storage container using an aluminum thick plate according to an embodiment of the present invention.

Figure 3 is a partially enlarged view showing the elastic recovery amount measurement position by the molding method of the spherical shape storage container using an aluminum thick plate according to an embodiment of the present invention.

Figure 4 is a graph showing the results of measuring the elastic restoring force according to the thickness and size of the aluminum plate by the molding method of the sphere-shaped storage container using the aluminum plate according to an embodiment of the present invention.

5 is a graph showing the plastic strain in the thickness direction according to the molding method of the spherical shape storage container using an aluminum plate according to an embodiment of the present invention.

6 is a graph showing a molding load measurement result according to the molding method of the spherical shape storage container using an aluminum thick plate according to an embodiment of the present invention.

7 is a schematic view showing a state in which a plate is molded by a mold used in the method of forming a spherical shape storage container using an aluminum thick plate according to an embodiment of the present invention.

8 is a block diagram showing a process according to the molding method of the spherical shape storage container using an aluminum thick plate according to an embodiment of the present invention.

Description of the main symbols in the drawings

1. Vessel 10. Storage Container

20. Plate 31. First Step

32. The Second Step 33. The Third Step

34. Fourth Step 40. Die

50. Punch

Hereinafter, a concrete storage container using an aluminum plate according to the present invention and a manufacturing method thereof will be described in detail with reference to the accompanying drawings, for example, a storage container for storing liquefied natural gas.

However, the spirit of the present invention is not limited to the implementation state by the embodiments described below, and those skilled in the art to understand the spirit of the present invention using other embodiments falling within the scope of the same technical spirit It may be easily proposed, but this will also be included in the technical idea of the present invention.

In addition, terms used in the present specification or claims are concepts selected for convenience of description, and in grasping the technical contents of the present invention, they should be appropriately interpreted as meanings corresponding to the technical idea of the present invention.

1 is a perspective view showing a vessel using a storage container molded by the method of forming a spherical shape storage container using an aluminum plate according to an embodiment of the present invention.

Liquefied natural gas is a state in which natural gas is liquefied by compressing about 600 times at a temperature of minus 162 ° C. Therefore, the outer wall of the storage container for storing liquefied natural gas is resistant to low temperature brittleness and has excellent corrosion resistance and mechanical properties. I) is mainly used.

In the following description, the aluminum thick plate will be referred to as a metallic plate including a metal plate having a thickness of at least 10 mm of aluminum.

Since the molding method of manufacturing a block type mold by forming a large curved surface of the storage container 10 to which the aluminum thick plate is applied is practically difficult, a plurality of curved plates are formed by using a lattice-shaped mold, and then the curved plates are joined. As a result, the storage container 10 is molded.

That is, the storage container 10 for transporting the liquefied natural gas is formed in the shape of a sphere having a predetermined diameter and having an internal space, and a plurality of vessels are mainly installed in the vessel 1, and the vessel ( The liquid liquefied natural gas is accommodated in the internal space of the storage container 10 installed in 1) and is transported to a desired position by the movement of the vessel 1.

The storage container 10 has a diameter of 40m or more on an inner surface thereof to store a large amount of liquid or gaseous storage material in the inner space thereof. Of course, smaller or larger configurations are possible, but larger diameters would be desirable to store large amounts of storage material.

As such, the storage container 10 for forming a large internal space is formed by curvedly forming a plurality of plates 20 to form a large curved surface and then joining them to form a shape thereof.

At this time, the plate 20 formed of a thick aluminum plate is subjected to curved molding at a warm temperature (about 300 ℃ to 450 ℃) in order to reduce the molding load and the elastic recovery amount generated in the large surface forming.

FIG. 2 is a schematic view showing a lattice mold used in a method of forming a spherical shape storage container using an aluminum thick plate according to an embodiment of the present invention, and FIG. 3 is a spherical shape storage using an aluminum thick plate according to an embodiment of the present invention. It is a partial enlarged view which shows the elastic restoring amount measurement position according to the shaping | molding method of a container.

Figure 4 is a graph showing the results of measuring the elastic restoring force according to the thickness and size of the aluminum plate by the method of forming a spherical shape storage container using an aluminum plate according to an embodiment of the present invention, Figure 5 is according to an embodiment of the present invention It is a graph which shows the plastic strain generation direction by the shaping | molding method of the spherical shape storage container using aluminum thick plate.

Figure 6 is a graph showing the molding load by the molding method of the spherical shape storage container using an aluminum thick plate according to an embodiment of the present invention.

In the present invention, for example, a lattice mold is manufactured for actual large-surface molding conditions, and an example of experiment and molding analysis will be described. The aluminum plate to be used for the experiment and molding analysis has a length of 1186 × 790 mm in length and width. For example, a configuration in which the main material having a thickness of 20 or 30 mm is made of a metal plate in which aluminum is used will be described.

When fabricating the lattice-shaped mold shown in FIG. 2, the mold is formed by a method of removing stepped steps using precision machining after assembling the lattice mold in order to generate an accurate target curvature and improve the surface quality of the sheet. Will be produced.

The thickness of the aluminum plate, the curvature of the mold, and the like to analyze the elastic restoring force and the molding load of the aluminum plate according to the molding conditions and process conditions based on the aluminum plate formed to have a curvature by the lattice-shaped mold For example, the result of the molding analysis by applying the grid spacing of the mold as a variable will be described.

In the following description, the configuration of the present invention will be described through a number of experiments while varying the molding conditions for comparative analysis of the molding conditions. The molding conditions for each type used are shown in the table below.

Table 1

division	Die curvature (mm)	Punch Curvature (mm)	Plate thickness (mm)
Case 1	1,500	1,530	30
Case 2	1,500	1,520	30

Through comparison of

cases

1 and 2, the difference in elastic restoring force was tested for the same die curvature (1/1500) and the thickness of aluminum thick plate (30 mm) when the bending punch was different. Restoration amount is the result of experiment by comparing the curvature of the mold by measuring the amount of elastic restoration restored after removing the punch.

Meanwhile, in order to measure the elastic restoration amount according to various molding conditions, as shown in FIG. 3, the aluminum thick plate pressed by the lattice-shaped mold measures the size after molding of the thick plate in the x-axis direction.

Of course, the elastic recovery amount can be measured in different directions, but since the curved aluminum sheet has the same curvature in the horizontal, vertical and diagonal directions, the elastic recovery amount is in the x-axis direction, which is the longest side of the aluminum thick plate. It would be desirable to measure.

Hereinafter, with reference to Figure 4 will be described the experimental results according to the mold curvature and the thickness of the aluminum thick plate.

As shown in FIG. 4, the elastic restoration amount according to the

molding condition cases

1 and 2 is measured as 6.5 and 5.6 mm at x = 560 mm, respectively. A value of x of 560 mm means a position spaced about 560 mm from the central portion of the storage container 10.

By comparing the

cases

1 and 2, the punch curvature is applied differently, i.e., 1/1520 and 1/1530, with respect to the same thickness of the aluminum thick plate, that is, the die curvature (1/1500) of the aluminum thick plate equal to 30 mm. The elastic recovery of the thick plate is tested.

In case 2, the lower curvature contacting the mold is the same as in case 1, while the upper punch is formed by using a punch with a relatively high curvature, which not only reduces the elastic recovery amount by 14% but also reduces the molding load by 41%. It can be seen that the results.

In case 2, the curvature of the lower surface of the aluminum thick plate, that is, the surface in contact with the lower die, is the same as that of case 1, but the curvature of the surface in contact with the upper punch has an increased curvature. It is largely generated and the amount of elastic recovery is reduced, so that the experimental results can be interpreted.

In addition, when the upper and lower molds with different curvatures are completely closed, the aluminum thick plate is not in perfect contact with the mold, resulting in a reduction in molding load.

On the other hand, Figure 7 is a schematic diagram showing a state in which the plate is formed by a mold used in the method of forming a spherical shape storage container using an aluminum thick plate according to an embodiment of the present invention, Figure 8 is an aluminum according to an embodiment of the present invention It is a block diagram which shows the process by the shaping | molding method of the spherical shape storage container using a thick plate.

Referring to these figures, a first step 31 of positioning the plate 20 on a die is formed such that the surface supporting the plate 20, whose main material is made of aluminum, has a target curvature.

The mold pressed to form the curved surface of the plate 20 includes a die 40 for supporting the plate 20 and a punch 50 for pressing the plate 20 supported on the die 40. It is configured by.

Referring to FIG. 7, the die 40 is relatively positioned on the lower side to support the plate 20 placed on the upper side, and the punch 50 is relatively placed on the plate on the lower side ( By pressing 20, the plate 20 is formed in a shape having a curvature.

FIG. 7A illustrates an embodiment in which the upper surface of the die 40 has a target curvature, and in FIG. 7B, the lower surface of the punch 50 has a target curvature. An embodiment is shown.

In addition, while the plate 20 is formed to have a target curvature formed in the recessed surface, each plate 20 is formed so that the surface formed to have a target curvature forms the inner surface of the storage container 10 Combined.

This is to form a surface having a target curvature of the plate 20 to form the inner surface of the storage container 10 so that the internal storage volume of the storage container 10 is uniformly formed, and to maintain a uniform internal pressure For sake.

Meanwhile, in order to form the recessed surface of the plate 20 to have a target curvature, either the die 40 or the punch 50 is formed to have the same curvature as the target curvature and the plate ( 20).

In addition, the surface of the die 40 or the surface of the punch 50 that has a surface formed to have the same curvature as the target curvature is formed to have a curvature larger than the target curvature.

Referring to FIG. 7A in detail, for example, when viewed from the side so that the surface recessed upwardly of the plate 20, that is, the surface rounded to have a curvature projecting upward, has a target curvature. The die 40 is formed to have an approximately "∩" shape.

The upper surface of the die 40 is formed to be recessed upwardly to have the same curvature as the target curvature, the inner surface of the surface that is pressed upwards and is pressed upward while the plate 20 is supported on the upper surface of the die 40 The die 40 is molded to have a target curvature corresponding to the top surface of the die 40.

The lower surface of the punch 50 for pressing the plate 20 while moving downward from the upper surface of the die 40 formed to have the same curvature as the target curvature is formed by the upper surface of the die 40 It is recessed upwardly to have a curvature larger than the curvature, for example, about 1-50% larger curvature.

As such, as the plate 20 is pressed, the surface for forming the inner surface to have the target curvature becomes the upper surface of the die 40, and the upper surface of the die 40 has the same curvature as the target curvature. Is formed.

On the other hand, the lower surface of the punch 50 that is pressed in the upper surface direction of the die 40 is formed to have a greater curvature than the upper surface of the die 40. That is, Rd, which is the top curvature of the die 40 shown in the drawing, has a smaller value than Rp, which is the bottom curvature of the punch 50, which is expressed by a formula, where Rd <Rp.

Referring to FIG. 7B in detail, the bottom surface of the punch 50 is recessed downward to have the same curvature as the target curvature so that the recessed surface of the plate 20 has a target curvature. Is formed.

When the punch 50 is viewed from the side, the punch 50 is formed to have a substantially "∩" shape, and a surface recessed upwardly of the plate 20, that is, a surface rounded to have a curvature projecting upward is aimed at. In order to have a curvature, the die 40 is installed to have a substantially "∩" shape when viewed from the side.

The upper surface of the die 40 positioned below the lower surface of the punch 50 formed to have the same curvature as the target curvature and supporting the plate 20 is more than the curvature formed by the lower surface of the punch 50. It is formed recessed downward to have a large curvature.

At this time, the surface for forming the recessed surface of the plate 20 to have a target curvature becomes the lower surface of the punch 50, the surface supporting the plate 20 to have a greater curvature than the target curvature. It becomes an upper surface of the die 40 formed.

That is, Rd, which is the upper surface curvature of the die 40 shown in FIG. 7B, has a larger value than Rp, which is the lower surface curvature of the punch 50. Expressed by the formula, Rp <Rd is do.

Meanwhile, the plate 20 having the target curvature and the surface being compressed and having a larger curvature than the curvature of the surface having the target curvature (approximately, is formed to have the punch 50 moves and is supported by the die 40). When pressing), the plate 20 is supported on a surface formed to have a target curvature, and is pressed at a predetermined interval from a surface formed to have a curvature larger than the target curvature.

As such, when the surface having the target curvature and the surface to be compressed have a larger curvature than the curvature of the surface having the target curvature, the elastic restoring force generated while forming the plate 20 may be reduced. And, by the reduced elastic restoring force has the advantage that the precise molding is possible, which can be said to have been proved through the various experiments described above.

Referring to FIG. 8, the plurality of plates 20, the main material of which is formed of aluminum, are joined to each other, and the storage container 10 having a spherical shape is welded to the plurality of plates 20 formed to have a target curvature. It is produced by joint bonding by a bonding method such as.

At this time, looking at the molding method for forming the plate 20 to have a target curvature, first, the surface supporting the plate 20, the main material is formed of aluminum is formed to have a target curvature, or larger than the target curvature A first step 31 of positioning the plate 20 on the die 40 formed to have a curvature proceeds.

When the plate 20 is positioned at the molding position through the first step 31, the surface on which the plate 20 is pressed is formed to have a target curvature or is formed to have a larger curvature than the target curvature. The second step 32 of pressing the plate 20 by moving the punch 50 is performed.

When the plate 20 is molded to have a target curvature through the second step 32, a third step 33 of moving the punch 50 to its original position is performed.

After the third step 33, if the plate 20 is formed to have a target curvature through the third step 33, the plate 20 may be welded to form an inner surface with a surface having a target curvature. A fourth step 34 of joining joints is further proceeded.

The description of the present invention as described above is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains various modifications without departing from the essential characteristics of the present invention. Modifications may be possible.

According to the present invention, there is provided a method of forming a storage container having a spherical shape using an aluminum thick plate, by moving a punch formed so that a surface facing the plate has a curvature larger than the target curvature, and compressing the plate so that the plate is recessed. The inner surface of 20) is molded to have the same curvature as the target curvature.

Accordingly, the inner surface of the storage container has the advantage of being uniform, thereby having the advantage of having a uniform volume of the storage space, and has the advantage of improving safety.

Due to these various advantages and effects, the spherical shape storage container using the aluminum plate according to the present invention will be highly applicable to not only the storage container industry but also various related industries.

Claims

In the method of molding a storage container having a spherical shape while a plurality of plates of the main material is formed of aluminum bonded to each other,

Positioning the plate on a die formed such that a surface supporting the plate has a target curvature;

A second step of compressing the plate by moving a punch formed such that a surface facing the plate has a curvature greater than the target curvature; And

A third step of moving the punch to its original position; Forming method of a spherical shape storage container using an aluminum thick plate configured to include.
In the method of molding a storage container having a spherical shape while a plurality of plates of the main material is formed of aluminum bonded to each other,

Positioning the plate on a die formed such that a surface supporting the plate has a curvature greater than a target curvature;

A second step of compressing the plate by moving a punch formed such that a surface facing the plate has a target curvature; And

A third step of moving the punch to its original position; Forming method of a spherical shape storage container using an aluminum thick plate configured to include.
The method according to claim 1 or 2,

And the plate is formed of a thick plate having a thickness of at least 10 mm or more.
The method according to claim 1 or 2,

The plate is formed by a die or punch having a surface having a target curvature, and one surface thereof is formed to have a target curvature, and is pressed while being spaced apart from a surface of a die or punch having a surface having a curvature greater than the target curvature. Forming method of spherical shape storage container using aluminum thick plate.
The method according to claim 1 or 2,

And after the third step, a fourth step of jointly joining the plates to each other such that a surface formed to have a target curvature forms an inner surface of the storage container is further formed.
The method according to claim 1 or 2,

The plate is a method of forming a spherical shape storage container using an aluminum thick plate is pressed so that the surface formed indentation has a target curvature.