KR20150003078A - Fuel tank of projectile using friction stir welding and its manufacturing method thereof - Google Patents

Abstract

The present invention relates to a method of manufacturing a fuel tank for a projectile using friction stir welding which improves corrosion resistance for a joint portion, reduces a fraction defective of the joint portion, and minimizes bending of the joint portion when welding to reduce the asymmetry of the tank. The method includes: a step of manufacturing a cylindrical body having a first length (L) and a diameter (D), and end covers corresponding to the upper and lower ends of the cylindrical body; and a step of carrying out friction stir welding on the cylindrical body and the end covers.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a fuel tank for a projectile using friction stir welding,

The present invention relates to a fuel tank for a projectile capable of reducing the vibration of the projectile and capable of successfully emitting the projectile by reducing the occurrence of corrosion resistance and occurrence of defects on the joint and eliminating the asymmetry of the object to be welded generated in the welding process of the fuel tank for the projectile And a method for producing the same.

Generally, launch vehicle propulsion engines use a propellant containing a fuel such as kerosene to generate the necessary thrust and an oxidant such as liquid oxygen which is the source of oxygen required for combustion. These propellants are stored in large capacity tanks in order to continuously obtain the thrust of the projectile, and generate thrust according to their consumption.

Conventional tanks (propellant tanks) in which the propellant is stored are divided into a fuel tank and an oxidant tank. The propellant tank is composed of a body for storing the propellant and a dome-shaped end cover for closing both ends of the body.

The fuel tank and the oxidant tank thus manufactured are arranged in a line in a line through a centering operation while being spaced apart from each other by a predetermined distance, and various pipes, valves, and sensors are additionally installed.

The fuel tank of the projectile is basically made of an aluminum alloy material in order to lighten the projectile, and it is practically impossible to machine the parts of the projectile having a large size by turning. Therefore, the parts are manufactured by dividing them into sub-pieces of appropriate size, and then welded to manufacture / assemble the final parts. Generally, it is not easy to weld the parts for manufacturing the fuel tank of the projectile with aluminum material. The reason for this is that when the aluminum alloy is welded, the welded product is distorted due to heat, and the material size of the projectile is large and the welded portion is relatively large, so that a twist phenomenon occurs.

In addition, since conventional propellant tanks are joined by conventional tungsten arc welding (TIG) or variable polarity plasma arc welding (VPPAW), the plurality of cylindrical bodies forming the body, and the end cover, Occurs. That is, there is a problem that the corrosion resistance of the joint portion is lowered, deformation of the joint portion occurs, and defects occur at the joint portion.

Conventional propellant tanks act as a source of cracks in the process of launching into the atmosphere due to pore defects formed during welding such as normal tungsten arc welding (TIG) or variable polarity plasma arc welding (VPPAW) There were other problems that acted as structural defects of the launch vehicle.

These problems arise during the process of melting the tungsten arc welding or the variable polarity plasma arc welding together with the dissimilar materials of the electrode.

A related prior art is Korean Patent Publication No. 2000-0045606 (published on July 25, 2000, entitled "Method for manufacturing a tank for propellant for satellites").

The present invention relates to a fuel for a projectile using friction stir welding that can improve the corrosion resistance of the joint portion and reduce the occurrence of defects on the joint portion by joining the components constituting the fuel tank for a projectile by using friction stir joining Tank and a method of manufacturing the same.

The present invention also relates to a fuel tank for a projectile and a method of manufacturing the same, which can reduce the vibration of the projectile and eliminate the occurrence of warpage (asymmetry) of the welding object during the welding process of the projectile fuel tank.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems.

According to another aspect of the present invention, there is provided a method of manufacturing a fuel tank using friction stir joining, comprising the steps of: preparing a cylindrical body having a first length L and a diameter D and a hemispherical end cover corresponding to an upper end and a lower end of the cylindrical body, And a step of friction stir joining the cylindrical body and the hemispherical end cover.

Specifically, the cylindrical body finally has a first length L through friction stir welding circumferentially one or more cylindrical pieces having a diameter D having at least one second length ln shorter than the first length L. [

More specifically, the cylindrical piece is formed by bending cylindrical end portions of a metal material having a length ℓn and a circumferential length (D x π) of a second length shorter than the first length L, and then subjecting the both end portions to friction stir welding Thereby producing the cylindrical pieces having the second length ln.

More specifically, the cylindrical piece is friction stir welded to both longitudinal ends of two or more cylindrical sub-pieces having a second length ln with a radius D / 2 to produce the cylindrical pieces having a second length ln do.

Wherein the friction stir welding step comprises rotating the friction stir welding tool at a speed of 400 to 1000 rpm after penetrating the friction stir welding tool through the work and simultaneously rotating the tool with the friction stir welding tool at a speed of 50 to 300 mm / The bonding operation is carried out while moving.

More preferably, in the step of friction stir welding, the friction stir welding tool is rotated at a speed of 500 to 700 rpm and the friction stir welding tool is moved at a speed of 50 to 80 mm / min to perform a bonding operation Conduct.

The hemispherical end cover may be composed of a dome core panel or a cap and a dome core panel.

The cylindrical body and the hemispherical end cover use one or more aluminum materials.

The dome core panel is manufactured through spinning processing.

The dome core panel is manufactured through a step of friction stir welding the at least one dome core panel piece in the vertex direction of the sphere.

Both end portions are reinforced with a certain thickness of the both end portions so that the thickness of both end portions becomes the same thickness as the base material after the friction stir welding.

Alternatively, after the friction stir welding is performed between the both end portions, the covering pieces are positioned between the both end portions so that the both end portions have the same thickness as the base material.

As described above, according to the present invention, since the cylindrical body and the cylindrical body and the end cover are joined by the friction stir welding, it is possible not only to improve the corrosion resistance of the joint portion but also to reduce the occurrence of defects on the joint portion . Further, there is an advantage that the occurrence of warpage at the joint portion is suppressed, and the asymmetry of the fuel tank for the projectile is removed, thereby improving the reliability of the fuel tank.

1 is a flowchart showing a method of manufacturing a fuel tank for a projectile using friction stir welding according to the present invention,
FIG. 2 is a view showing a manufacturing process of the cylindrical body of FIG. 1,
FIG. 3 is a view showing another manufacturing process of the cylindrical body of FIG. 1,
FIG. 4 is a view showing a manufacturing process of the end cover of FIG. 1,
FIG. 5 is a view showing another manufacturing process of the end cover of FIG. 1,
FIG. 6 is a view showing a joining process of the cylindrical body and the end cover of FIG. 1, and FIG.
FIGS. 7 to 9 are views showing friction stir welding embodiments according to the present invention, showing friction stir welding with respect to a cylindrical body and an end end of an end cover. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference symbols whenever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The present invention provides a propellant fuel tank of a fuel tank, preferably a propellant, to which a joint portion is joined by frictional stir welding (FSW). In the present invention, the fuel tank has a first length L and a diameter D And a hemispherical end cover corresponding to the upper and lower ends of the cylindrical body, respectively, and friction stir welding the cylindrical body and the hemispherical end cover.

In the case of manufacturing a fuel tank for a projectile using a normal welding method, particularly tungsten arc welding (TIG) or variable polarity plasma arc welding (VPPAW), a micro twist of a shape distorting the symmetry of the projectile fuel tank . Even if this asymmetry occurs in a small range (within 0.1 degree), the projectile generates vibration in the projectile in the course of launching. Such vibration acts to advance internal defects (inclusions and voids) of cracks, which are inevitably generated in a conventional welding method, as cracks. As a result, the asymmetry of the fuel tank for the projectile causes the vibration of the projectile, and this vibration acts as a crack in the internal defect existing in the weld.

In the present invention, the body 110 and the end cover 120 are made of a lightweight aluminum material, which does not react with the propellant, especially hydrogen peroxide provided by the oxidizer, and can maintain rigidity. That is, a variety of aluminum alloy materials can be used as the material of the cylindrical body 110 and hemispherical end cover 120 constituting the fuel tank for the projectile, and mainly Al2219 and Al2159 can be employed. In addition, the cylindrical body 110 and the hemispherical end cover 120 may be made of different aluminum alloy materials, if necessary.

The reason why the fuel tank for the projectile is made of aluminum material is to reduce the weight of the projectile to increase the accuracy of launching the projectile and to enter the orbit of the projectile successfully. In addition, the relative weight of the fuel tank occupied by the total weight of the projectile (projectile) is reduced, thereby reducing the fuel amount of the projectile necessary for entering the orbit.

Hereinafter, a method of manufacturing a tank using the friction stir welding according to the present invention will be described in detail.

≪ Production of cylindrical body &

In order to manufacture the cylindrical body 110, first, a plurality of cylindrical pieces 116 are formed by rolling the metal plates 112 into a cylindrical shape, and then the ends of the manufactured cylindrical pieces 116 are joined to manufacture the cylindrical body 110 can do.

As the metal plate 112 forming the body 110, a metal plate 112 made of aluminum is used as described above. Here, the length, width, and thickness of the metal plate 112 can be variously provided.

A reinforcing rib 114 may be formed on one side of the metal plate 112. The reinforcing ribs 114 are provided for imparting rigidity to the metal plate 112. The reinforcing ribs 114 are formed by a conventional method such as milling or etching or by a conventional friction stir welding Device (not shown). At this time, it is preferable that the reinforcing ribs 114 are formed in a structure that is excellent in coping ability against various combined loads and concentrated loads, for example, a structure in which a reinforcing rib in a regular triangular shape is repeated.

The cylindrical body 116 is bent in a cylindrical shape such that the opposite ends 113 of the metal plate 112 are opposed to each other using a conventional roll bending machine, And both ends 113 of the metal plate 112 facing each other are friction stir welded. When the metal plate 112 is bent, one side of the metal plate 112 having the reinforcing ribs 114 is bent so as to form an inner diameter portion of the cylindrical piece 116.

More specifically, the embodiment of making the cylindrical body 110 includes an end portion of at least one cylindrical piece 116 having a diameter D, having at least one second length ln shorter than the first length L of the cylindrical body 110 And the cylindrical body 110 having the first length L is finally manufactured by friction stir welding in the circumferential direction. A concrete method of manufacturing the cylindrical piece 116 is to bend cylindrical end portions 113 of a metal material having a length ℓn and a circumferential length (D x π) of a second length shorter than the first length L, To produce cylindrical pieces 116 having a second length ln.

Another embodiment for fabricating the cylindrical piece 116 is to frictionally stir both longitudinal ends 117 of two or more cylindrical sub-pieces 115 having a second length ln with a radius D / 2 to form a second length ln The cylindrical pieces 116 can be manufactured. Here, the second length ln may be one or more and several different lengths can be selected (see FIG. 3).

When a plurality of cylindrical pieces 116 are prepared by the above-described method, the ends of the cylindrical pieces 116 are turned back to each other, and then friction stir welding is performed to manufacture the cylindrical body 110. Here, the surface of the cylindrical piece 116 manufactured before the joining process of any one cylindrical piece 116 and another cylindrical piece 116, and the both ends 113 and 117 may be subjected to a grinding process.

On the other hand, the joining of the bending metal plate 112 to both ends and the joining of any one cylindrical piece 116 to another cylindrical piece 116 are performed by passing a friction stir welding tool on the joining portion, The agitating bonding tool is rotated and at the same time the bonding operation is performed while moving the friction stir welding tool.

Preferably, in the step of friction stir welding, a tool for friction stir welding is passed through a workpiece, and then the tool for friction stir welding is rotated at a speed of 400 to 1000 rpm and at the same time a tool for friction stir welding The bonding operation is carried out while moving.

More preferably, the friction stir welding tool is rotated at a speed of 500 to 700 rpm and the friction stir welding tool is moved at a speed of 50 to 80 mm / min to perform a bonding operation.

If the rotational speed of the tool for friction stir welding is less than 400 rpm, sufficient plastic flow of the material is not generated, and the strength (yield strength, tensile strength) of the joint is lowered and the grain refinement is not sufficiently generated and the elongation rate is lowered . If the rotational speed of the tool for friction stir welding exceeds 1000 rpm, the plastic flow is excessively generated and the flattening of the joint portion is hindered. In this case, too, the phenomenon that the strength of the bonding decreased again occurred.

When the moving speed of the friction stir welding tool is less than 20 mm / min, the progress speed of the tool is slow and the bonding strength of the material is rather low. This is understood to be due to the fact that the plastic flow of the material is not sufficiently generated due to the extremely low speed of movement of the tool. When the moving speed of the friction stir welding tool exceeds 300 mm / min, the friction stir welding tool is not able to withstand the rigidity of the work and is cut off, thereby deteriorating the efficiency of the continuous welding operation .

The working conditions for the friction stir welding can be defined by the rotational speed of the friction stir welding tip (t) and the advancing speed of the tip (t) at the time of welding. The rotational speed of the tip t and the advancing speed of the tip t generally depend generally on the type of the tip t and the material of the friction stir welding object. A step of friction stir welding for joining the cylindrical body 110 and the hemispherical end cover 120 and a step of joining the cylindrical pieces 116 in the circumferential direction and a step of joining the cylindrical sub- And a friction stir welding step.

The working conditions for the friction stir welding may vary depending on the respective friction stir welding steps. The reason for this is that the working conditions of the friction stir joining can be different when the respective parts (cylindrical body and hemispherical end cover) are selected from different aluminum materials and applied with different thicknesses. These joining conditions may be different depending on the position and thickness of joints. However, when the thickness of joints is the same, the difference in working conditions of friction stir welding is not significant depending on the difference of materials.

≪ Preparation of end cover &

The end cover 120 can be manufactured according to two embodiments of the present invention for manufacturing the end cover 120 that closes both ends of the cylindrical body 110. The end cover may be hemispherical or may have other shapes.

First, according to the first embodiment, the end cover 120 can be manufactured by molding a disk-shaped metal plate into a dome shape. If there is no metal plate of sufficient size, it is possible to use two plate-like metal plates joined together and then cutting the bonded metal plate into a circular plate shape. In the first embodiment, the disc-shaped metal plate can be formed into a dome shape through a normal spinning process (see Fig. 4).

According to the second embodiment, in the end cover 120, the flat plate-shaped metal plate 122b is processed into a disk-shaped cap 124b and a dome-shaped core panel 126b having a fan shape and curved convexly , Bonding the movable dome core panels 126b, and then joining the cap 124b to the bonded dome core panels 126b. The dome core panel 126b is fabricated by friction stir welding that starts at one or more dome core panels 126b in the apex direction of the sphere or in the circumferential direction of the cylindrical body 110 (see Fig. 5). In the second embodiment, the end cover may be formed only by the dome core panel without a cap.

It has been determined that the working conditions applied to manufacture the cylindrical body 110 are desirable even in the step of friction stir joining for manufacturing the end cover 120. [ The conditions of the friction stir welding employed in manufacturing the end cover 120 are such that the friction stir welding tool is passed through the workpiece and then the tool for friction stir welding is rotated at a speed of 400 to 1000 rpm and at a speed of 20 to 300 mm / The joining operation is carried out while moving the friction stir welding tool.

More preferably, the friction stir welding tool is rotated at a speed of 500 to 700 rpm and the friction stir welding tool is moved at a speed of 50 to 80 mm / min to perform a bonding operation.

The end cover 120 manufactured by the first and second embodiments may be made of a metal plate 122b made of aluminum having the same or different thickness as that of the metal plate 112 constituting the body 110. [

On the other hand, the end cover 120 manufactured by the first and second embodiments may be provided with holes through which piping, valves, sensors, etc. are mounted.

<Bonding of body and end cover>

When the cylindrical body 110 and the end cover 120 are manufactured as described above, the end cover 120 is joined to one end and the other end of the body 110 to manufacture the fuel tank 100 according to the present invention.

The end portions of the body 110 and the end cover 120 are joined to each other when the ends of the body 110 and the end cover 120 are brought into contact with each other at one end and the other end of the body 110, Are joined together through friction stir welding.

The joining process of the body 110 and the end cover 120 is performed by passing a tool for friction stir welding on the joining portion and then rotating the tool for friction stir joining while rotating the tool for friction stir joining, The bonding operation is carried out while moving.

Preferably, in the step of friction stir welding, a tool for friction stir welding is passed through a workpiece, and then the tool for friction stir welding is rotated at a speed of 400 to 1000 rpm and at the same time a tool for friction stir welding The bonding operation is carried out while moving.

More preferably, the friction stir welding tool is rotated at a speed of 500 to 700 rpm and the friction stir welding tool is moved at a speed of 50 to 80 mm / min to perform a bonding operation.

If the rotational speed of the tool for friction stir welding is less than 400 rpm, sufficient plastic flow of the material is not generated, and the strength (yield strength, tensile strength) of the joint is lowered and the grain refinement is not sufficiently generated and the elongation rate is lowered . If the rotational speed of the tool for friction stir welding exceeds 1000 rpm, the plastic flow is excessively generated and the flattening of the joint portion is hindered. In this case, too, a phenomenon that the strength of the joint was deteriorated was found.

When the moving speed of the friction stir welding tool is less than 20 mm / min, the progress speed of the tool is slow and the bonding strength of the material is rather low. This is understood to be due to the fact that the plastic flow of the material is not sufficiently generated due to the extremely low speed of movement of the tool. When the moving speed of the friction stir welding tool exceeds 300 mm / min, the friction stir welding tool is severed and the efficiency of the continuous welding operation is lowered.

When the friction stir welding is performed, it is general that the thickness of the friction stir welding portion becomes smaller than the thickness of the base material to be welded. This is because the material of the joint portion (both ends in the present invention) is generated due to the mass flow of the friction stir welding tip (t) causing the plastic flow of the material through high-speed rotation and movement under pressure. Therefore, in the present invention, an additional material of the same material as the base material is supplied in order to prevent a step in the thickness of the joined part due to the friction stir welding.

That is, both ends of a cylindrical body (including a cylindrical piece and a cylindrical sub-piece) and a hemispherical end cover (including a cap and a dome core panel) are joined by friction stir welding to each other so that both end portions have the same thickness as the base material, (See FIG. 7).

In another embodiment, between the opposite ends, after the friction stir welding, the end pieces are formed so as to have the same thickness as the base material, and the end pieces have a substantially "I" 140) (see FIG. 8).

In another embodiment, it is possible to position another overhang piece 150 having a generally "-" cross-sectional shape extending in the longitudinal direction or having a ring shape on the outside of the opposite ends opposite to each other for friction stir joining 9). Here, another covering piece 150 is bonded by arc welding before inserting the friction stir welding tip (t). The present invention can achieve a uniform thickness bonding without causing a thickness step even after the friction stir welding by means of the above-described covering 130 and the covering pieces 140 and 150. [

According to the manufacturing method of the fuel tank for a projectile using the friction stir joining of the present invention as described above, the cylindrical pieces 116 forming the cylindrical body 110 and the cylindrical pieces 116 forming the cylindrical body 110 and the end cover 120 Friction stir welding, it is possible not only to improve the corrosion resistance on the joint portion but also to reduce the occurrence of defects on the joint portion, thereby enhancing the reliability of the tank 100 to be manufactured.

The fuel tank for a projectile using the friction stir joining and the method of manufacturing the fuel tank for the projectile are not limited to the configuration and the operation manner of the embodiments described above. The embodiments may be configured so that all or some of the embodiments may be selectively combined so that various modifications may be made.

100: fuel tank for launch vehicle 110: cylindrical body
116: Cylindrical piece 120: End cover

Claims (14)

Fabricating a cylindrical body having a first length L and a diameter D and a hemispherical end cover corresponding to an upper end and a lower end of the cylindrical body, respectively; And
And joining the cylindrical body and the hemispherical end cover to each other by friction stir welding.
The method according to claim 1,
The cylindrical body is friction stir welded with at least one cylindrical piece having a diameter D, having at least one second length ln shorter than the first length L, to finally produce the cylindrical body having the first length L Wherein the friction stir welding is performed by using the friction stir welding.
The method of claim 2,
The cylindrical piece is formed by bending cylindrical end portions of a metal material having a length ℓn and a circumferential length (D x π) of a second length shorter than the first length L and then subjecting the both end portions to a friction stir welding process, Wherein the cylindrical pieces are manufactured by using the friction stir welding method.
The method of claim 2,
Characterized in that the cylindrical piece is made by friction stir welding both longitudinal ends of two or more cylindrical sub-pieces having a second length ln with a radius D / 2 to form the cylindrical pieces having a second length ln Wherein the friction stir welding is carried out by using the friction stir welding.
The method according to any one of claims 1 to 4,
Wherein the friction stir welding step comprises rotating the friction stir welding tool at a speed of 400 to 1000 rpm after penetrating the friction stir welding tool through the work and simultaneously rotating the tool with the friction stir welding tool at a speed of 50 to 300 mm / Wherein the joining operation is performed while moving the joining member.
The method of claim 5,
Wherein the friction stir welding step is performed by rotating the friction stir welding tool at a speed of 500 to 700 rpm while moving the friction stir welding tool at a speed of 50 to 80 mm / Wherein the friction stir welding is carried out by using the friction stir welding.
The method according to any one of claims 1, 2, 3, 4 and 6,
The hemispherical end cover
And a dome core panel. The method of manufacturing a fuel tank for a projectile using friction stir joining according to claim 1,
The method according to any one of claims 1, 2, 3, 4 and 6,
The hemispherical end cover
A method of manufacturing a fuel tank for a projectile using a friction stir joining, wherein a disk-shaped metal plate is formed into a dome shape through spinning.
The method according to claim 1,
Wherein the cylindrical body and the hemispherical end cover use at least one aluminum material. &Lt; RTI ID = 0.0 &gt; 15. &lt; / RTI &gt;
The method of claim 7,
Wherein the dome core panel is manufactured through a spinning process. &Lt; RTI ID = 0.0 &gt; 15. &lt; / RTI &gt;
The method of claim 7,
Wherein the dome core panel is fabricated through friction stir welding of at least one dome core panel piece in the vertex direction of the sphere.
The method according to claim 5 or 6,
Wherein both end portions are reinforced with a certain thickness of the both end portions so that the thickness of the both end portions becomes the same as the thickness of the base material after the friction stir welding.
The method according to claim 5 or 6,
Wherein the covering member is positioned between the both ends so that the thickness of the both end portions becomes equal to the thickness of the base material after the friction stir welding.
A fuel tank for a projectile manufactured using the method for manufacturing a fuel tank for a projectile according to any one of claims 1 to 13.

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