KR101489479B1 - Manufacturing method of elbow of double pipe type - Google Patents

Abstract

The present invention relates to a method for manufacturing a double tube type elbow having an outer tube and an inner tube formed of different materials. The method for manufacturing a double tube type elbow is as follows: making a double sheet by forming a metal layer for an inner tube by welding a metal material different from the material of the metal sheet for an outer tube on one side surface of a metal sheet for an outer tube corresponding to the outer tube of a double tube type elbow; making a cut sheet which is a part of the elbow by cutting the double sheet at a predetermined size; heat-treating the cut sheet after weld; forming the cut sheet heat-treated after weld using a mold to be bent, cooling an elbow unit, welding the elbow unit again, and heat-treating the elbow unit; and welding the elbow units heat-treated after welding to adhere to each other in a whole tube shape. The method for manufacturing a double tube type elbow can solve a problem of uneven protrusions on a curved part of an inner tube, easily manufacture an elbow with a large diameter by welding and attaching elbow units each other, ensure physical uniformity of the inner tube by attaching the cut sheets previously processed in a dual sheet form to be in a bent form; and ensure hardness and ductility of the manufactured elbow through a first heat treatment process, which is performed before the cut sheet is formed to be bent, to meet the requirement and solve the problem of partial deformation or crack of the inner tube caused by long-period use of the elbow.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method of an elbow,

The present invention relates to a method of manufacturing a double pipe type elbow having an outer appearance and an inner pipe of different materials, wherein a metal of a different material from that of the outer appearance metal plate is welded to one side of the outer appearance metal plate corresponding to the outer appearance of the double pipe type elbow After forming a double plate by forming a metal layer for the inner tube, the double plate is cut to a predetermined size to make a cutting plate which is a part of the elbow, the cutting plate is heat-treated after welding, and the heat- The present invention relates to a method of manufacturing a double tube type elbow in which a plurality of elbow units welded after heat treatment are welded to each other and joined together by a complete tubular elbow.

In general, the elbow forming method varies depending on the shape of the elbow, but first, the elbow made of a single steel is formed into a bent elongated shape by cutting a straight tube into a predetermined length, then bending the straight tube, A double pipe type elbow formed by forming an inner pipe of another material on the inner surface of a single steel in order to improve characteristics such as corrosion resistance, abrasion resistance, or chemical resistance to a fluid to be transferred to a single steel, And a metal material constituting the inner tube is welded to the inside of the inner tube.

The following are representative prior art techniques for elbow molding.

That is, Korean Patent Laid-Open No. 10-2001-0016787 continuously relates to a method of manufacturing an elbow for welding (the same concept as an 'elbow'), in which a guiding process in which a first pipe member is guided from the outside, A high-frequency heating step of heating the outer surface of the first pipe member with a high frequency; and an external force applying step of applying an external force acting on the first pipe member to move the first pipe member to the left, A first diameter increasing step of gradually increasing a diameter of the first pipe member at a second pipe member located outside of the first guide increasing part, and a second diameter increasing step of increasing the diameter of the second pipe increasing member, A second diameter increasing step in which the diameter of the guide increasing portion is gradually increased; and a second diameter increasing step of guiding the third pipe guide portion of the roller member to a circular shape It consisted of a roller machining process to produce an elbow.

Also, in the above-mentioned prior art, the diameter of the first pipe member sufficiently heated by the high-frequency heating coil part is guided to the first guide increasing part and the second guide increasing part which are gradually increased without going through a separate pressing step, Since the third pipe member disposed on the outside of the guide increasing portion and guiding the third pipe member outside the second guide increasing portion is naturally maintained in a circular shape and does not require a separate pressing process, .

However, if the conventional technique is applied to the forming of the elbows of the deformed steel having different materials, the inner tube corresponding to the inside of the deformed steel is damaged during the first and second diameter increasing process or the roller forming process, There is a problem to be solved, and continuous research and development is required to solve this problem.

The present invention relates to a method for manufacturing a double tube type elbow, and a method for manufacturing a double tube type elbow. The method for manufacturing a conventional elbow includes the steps of forming a straight tube and then molding the tube into a curved shape using a mold or a press As a result, a pressing force applied at the time of molding caused a problem of projecting and protruding portions on the bent portion of the inner tube;

When manufacturing an elbow with a large inner diameter, it is difficult to produce a corresponding mold, or it has been difficult to form a straight tube in a curved shape;

In addition, when manufacturing an elbow having a large inner diameter, it is not possible to uniformly perform the welding process on the inner surface of the bent outer shape, thereby causing a problem of lowering the inner uniformity of the inner tube.

To stabilize the inner tube welded to the inside of the outer tube, the general post-weld heat treatment conditions are only aimed at the required hardness and ductility of the manufactured elbow, and the partial degeneration or cracking of the inner tube due to the lack of durability of the manufactured elbow And it is a main object of the present invention to provide a solution to this problem.

The present invention has been made to solve the above-

A welding process of welding a metal plate for an outer appearance and a metal of a different material to one side of the outer appearance metal plate to form a metal plate for an inner tube to form a double plate; A cutting step of cutting the double plate subjected to the welding process to a shape having a size corresponding to half of the elbow when the tubular elbow is cut in the longitudinal direction to form a cutting plate; A first heat treatment step of determining the heating temperature according to the material of the metal layer for the inner tube and performing post-welding heat treatment (PWHT); The cutting plate subjected to the first heat treatment process is placed in the inlet hole of the mold having the inlet hole corresponding to one half of the elbow and then the elbow is bent in a curved shape corresponding to half of the elbow when the elbow is cut in the longitudinal direction A molding step of molding the unit; A second heat treatment step of performing heat treatment (PWHT, Post Weld Heat Treatment) on the elbow unit by demolding the elbow unit subjected to the molding process, determining the heating temperature according to the metal material for the inner tube, and re-welding the elbow unit; A cold step of cooling the elbow unit subjected to the second heat treatment process; A joining step of forming a tapered part at both ends of the cold-rolled elbow unit and then welding a pair of tapered elbow units to form a double-tube type elbow and performing a glazing treatment on the welded part; A method of manufacturing a double tube type elbow is presented.

In the method of manufacturing a double tube type elbow according to the present invention as described above, a metal plate for an inner tube is formed on one side of a metal plate for outer appearance by welding to form a double plate, and then the double plate is formed as a single elbow A portion of the elbow is first made of a pair of pieces (elbow unit), and then each of the elbow units is formed into a curved shape and joined to form a single elbow, thereby solving the problem of protrusions and protrusions on the inner tube being bent Effect can be obtained;

Since a plurality of elbow units are welded and joined together, it is possible to easily obtain an elbow having a large inner diameter;

Since a plurality of cutting plates preformed in the form of a double plate are joined in a bent shape, the effect of securing the physical uniformity of the inner pipe can be obtained;

The hardness and ductility of the manufactured elbow can be secured in accordance with the required value through the first heat treatment process, which is performed before the cutting plate is formed into a bent shape, and the problem of partial degeneration or cracking of the inner tube due to long- Can be obtained.

1 is a perspective view showing an elbow manufactured by a method for manufacturing a double pipe type elbow according to the present invention.
2 is a process block diagram showing a process sequence of a method for manufacturing a double-tube type elbow according to the present invention.
Figs. 3 to 4 are perspective views showing a double plate of a method for manufacturing a double-tube type elbow according to the present invention; Fig.
5 is a perspective view showing a cutting plate of a method for manufacturing a double pipe type elbow according to the present invention.
6 is a plan view showing a cutting plate of a method for manufacturing a double pipe type elbow according to the present invention.
7A to 7B are graphs showing temperature changes with time in the first heat treatment step and the cold step of the method for manufacturing a double-tube type elbow according to the present invention.
8 to 10 are perspective views showing a molding process of a method for manufacturing a double-tube type elbow according to the present invention.
11 is a perspective view showing a pair of elbow units in the joining step of the method for manufacturing a double-tube type elbow according to the present invention.

The present invention relates to a method of manufacturing a double pipe type elbow having an outer tube and an inner tube of different materials, wherein a metal of a material different from that of the outer tube metal sheet 11a is welded to one side of the outer tube metal sheet 11a, (S100) for forming a double plate (13) by forming a plurality of projections (12a); A cutting step S200 of cutting the double plate 13 subjected to the welding process S100 to a shape having a size corresponding to half of the elbow when the tubular elbow is cut in the longitudinal direction, and; A first heat treatment step (S300) of determining the heating temperature according to the material of the inner metal tube layer 12a and then performing post-weld heat treatment (PWHT) on the cutting plate 14 subjected to the cutting process (S200) ; The cutting plate 14 subjected to the first heat treatment process S300 is placed in the inlet groove 21 of the metal mold 20 having the inlet groove 21 of a shape corresponding to half of the elbow, (S400) of forming a curved elbow unit (15) corresponding to one half of the elbow when cut in the direction of the elbow unit (15); After the elbow unit 15 processed in the forming step S400 is demolded from the metal mold 20, the heating temperature is determined according to the material of the metal tube 12a for the inner part of the elbow unit 15, , Post Weld Heat Treatment) (S500); A cold step (S600) for cooling the elbow unit (15) processed in the second heat treatment step (S500); A pair of tapered elbow units 15 are welded to each other to form a double tube type elbow and a welded portion 17 is formed by welding a pair of tapered elbow units 15 by welding a portion of both ends of the elbow unit 15 subjected to the cold process S600, (S700) for performing a glinding process on the elongated tubular elbows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown.

Specifically, in the welding step S100, as shown in FIGS. 3 to 4, a metallic plate 12a for internal use is formed by welding a metal made of a different material from the metallic plate 11a for external appearance on one side of the metallic plate 11a for external appearance, The step of forming the plate 13 is a step of welding and forming a metal layer to be the inner tube 12 on one side of the flat metal plate for outer appearance 11a.

That is, the outer metal sheet 11a is made of the outer surface 11 of the elbow after being cut, heat-treated, molded, joined and cooled through the following processes to provide a resistance against the pressure of the fluid conveyed into the inside of the elbow As the structure, any one of a rolled steel sheet or a forged steel sheet made of a general metal material can be used, and various kinds of materials can be used according to the purpose of using an elbow such as a fresh water facility, a petrochemical facility, a power generation facility, a gas facility or a recycling facility .

The shape, such as the thickness, the width or the shape, of the metallic plate for external appearance 11a can be variously used in accordance with the purpose for which the elbow is used. More specifically, as shown in Figs. 1 and 2, .

That is, when the outer periphery of the outer appearance metal plate 11a is formed in a circular shape, when the outer appearance metal sheet 11a is cut as shown in FIG. 6 in the following cutting step (S200), the outer circumference of the metal plate is separated This is because the configuration that satisfies the outer portion of the bent elbow without the molding step (S400) can be achieved. A more detailed description of the metal plate 11a for outer appearance of the circular shape will be described later.

The inner metal layer 12a formed on one side of the outer metal plate 11a is formed by welding a metal different from the metal plate for outer appearance 11a. The material may be of a kind capable of providing properties such as corrosion resistance, abrasion resistance, or chemical resistance to fluids such as stainless steel, nickel alloy, Hastelloy or aluminum alloy. That is, if the entire elbow is made of a special material such as stainless steel, nickel alloy, Hastelloy or aluminum alloy, the elbow itself may have properties such as corrosion resistance, abrasion resistance or chemical resistance to fluid, If the special material is used, the economical efficiency due to the expensive special material is lowered. Therefore, the inner metal layer 12a is formed on one side of the outer metal plate 11a to form the double plate 13.

At this time, the double plate 13 is subjected to a bending process such that the inner metal tube layer 12a faces inward in the following forming step (S400), and the inner tube metal layer 12a is formed on the inside of the manufactured elbow .

The method of welding the inner metal layer 12a to the outer metal plate 11a may be performed by a variety of welding methods according to the judgment of a person skilled in the art by using a metal material for forming the inner metal plate 12a, The metal forming the inner metal layer 12a is melted due to the thermal energy caused by electric or sparking in the welding method which is divided into arc welding, gas welding or special welding, And is welded to one side of the metal plate 11a.

That is, the metal forming the inner metal layer 12a is made of a material to be welded (for example, a welding rod), the material to be welded is placed on one side of the outer metal sheet 11a and is melted by thermal energy, The welded material is welded to one side of the outer appearance metal plate 11a, thereby forming the inner metal plate 12a.

In addition, when the inner metal layer 12a is formed on one side of the outer metal plate 11a by welding, the inner metal plate 12a is formed around the center of the outer metal plate 11a as shown in Fig. The metal to be welded can be configured to be radially welded, and the welded material can be configured to be welded in a linear shape (or a waveform) as shown in Fig. That is, the welding direction of the workpiece is freely selectable according to the judgment of a person skilled in the art in consideration of the ease of the welding process (S100) or the pressure resistance of the inner tube (12) against the pressure of the fluid flowing into the manufactured elbow.

 Also, it is obvious that the melting temperature of the metal forming the metal tube 12a can be varied depending on the material of the metal used, and the thickness of the metal tube 12a for forming the metal tube can be varied depending on the application But it has a thickness of 2 to 12 mm so as to ensure durability against fluid flowing in contact with the inner tube 12 formed by the inner metal tube layer 12a and to prevent the bending applied in the molding step S400 The effect of making it possible to maintain a certain thickness even if a certain portion of the metal tube for inner tube 12a which is stretched at the time of bending the cutting plate 14 by the force is thinned by stretching.

In addition, since the welding process S100 of the above-described construction forms the metal tube 12a for internal use on one side of the flat metal plate 11a by welding, the conventional tubular external tube 11 is welded to the inside tube 12, it is possible to obtain an effect of securing the physical uniformity of the inner tube 12. [0064]

Further, in the cutting step (S200), the double plate (13) treated in the welding step (S100) is cut into a shape having a size corresponding to half of the elbow when the tubular elbow is cut in the longitudinal direction, (Corresponding to the cutting plate 14 in the cutting step S200 and corresponding to the elbow unit 15 in the forming step S400), the tubular elbows are divided into a plurality of pieces A step of joining together a plurality of pieces produced in the joining step (S700) to form a complete tubular elbow.

That is, the double plate 13 formed by the welding process S100 is formed in a plate shape as shown in FIGS. 3 to 4. However, when the elbow is developed into a plurality of pieces as shown in FIG. 5 through the cutting process S200 And is cut into a cutting plate 14 in a plate shape satisfying the piece. (At this time, each cutting plate 14 is bent through the following molding step (S400).)

More specifically, the cutting plate 14 of the cutting step (S200) is provided with a pressing die having a stronger strength than the materials of the outer metal plate 11a and the inner metal plate 12a constituting the double plate 13 And the double plate 13 is cut by a cutting force using a flame.

The shape of the cutting plate 14 may be any shape as long as it has a shape corresponding to each piece when the elbow is developed into a plurality of pieces and the bending is performed in the forming step S400, It is preferable that it has a size corresponding to half of the elbow when cut in the longitudinal direction.

At this time, the cutting plate 14 is bent in the direction in which the inner metal tube layer 12a is positioned inside the elbow by the pressing force applied in the molding step (S400), thereby forming a piece corresponding to the longitudinal half of the elbow.

It will also be appreciated by those skilled in the art that the cutting plate 14 may be configured to have a size smaller than the longitudinal half of the elbow, so that three or more of the cutting plates 14 may be continuously joined to form a single tubular elbow have. Hereinafter, the term 'half of an elbow' means that a single tubular elbow can be divided into a plurality of pieces.

"형태로 절단한 절단판(14)으로 구성하여, 절단판(14)을 관형의 엘보를 길이방향으로 절단했을 때 엘보의 절반에 해당하는 크기를 가지는 형태로 용이하게 만들 수 있다.5, the outer metal plate 11a is formed to have a circular outer periphery, the inner metal plate 12a is formed on one side of the outer metal plate 11a, and then the metal plate 12a having a circular outer periphery The double plate (13) is divided into a fan shape and a "

Shaped cutting plate 14 so that the cutting plate 14 can be easily formed into a shape having a size corresponding to half of the elbow when the tubular elbow is cut in the longitudinal direction.

"형태의 절단판(14)은 도 5 내지 6 같이 이중판(13)의 외주(외관용 금속판(11a)의 원형 외주와 대응함.)에 대응하는 바깥쪽의 구부러진 외주를 가지고, 안쪽의 구부러진 내주를 가지며, 상기 바깥쪽의 구부러진 외주와 안쪽의 구부러진 내주를 양쪽에서 연결하는 직선 변(14a)을 한 쌍 가진다.That is,

Shaped cutting plate 14 has an outer bent outer periphery corresponding to the outer periphery of the double plate 13 (corresponding to the circular outer periphery of the outer appearance metal plate 11a) as shown in Figs. 5 to 6, and the inner bent inner periphery And has a pair of straight sides 14a connecting the outer bent outer periphery and the inner bent inner periphery at both sides.

At this time, the outer curved outer circumference forms a curved outer portion of the elbow after the molding step (S400), and the inner curved inner circumference forms a curved inner portion of the elbow after the forming process (S400), and the outer bent A pair of straight sides 14a connecting the outer periphery and the bent inner periphery on both sides form a part of the inlet and the outlet of the elbow, respectively.

"형태의 절단판(14)이 부채꼴 형태 임의의 중심점을 중심으로 90°의 각을 가지며 절단되면 90°의 구부러짐 각을 갖는 엘보를 만들 수 있고, 90°보다 큰 각을 가지며 절단되면 둔각을 갖는 엘보를 만들 수 있으며, 90°보다 작은 각을 가지며 절단되면 예각을 갖는 엘보를 만들 수 있는 효과를 얻을 수 있다.6,

Shaped cutting plate 14 can be made into an elbow having a bending angle of 90 DEG when cut at an angle of 90 DEG around an arbitrary center point of a sector shape and having an angle larger than 90 DEG and having an obtuse angle An elbow can be made, and an elbow having an angle of less than 90 degrees and having an acute angle can be obtained.

"형태 절단판(14)의 직선 변(14a)의 길이는 엘보의 인입구와 인출구 일부를 형성하기 때문에, 직선 변(14a)의 길이가 길면 직경이 큰 엘보를 만들 수 있고, 직선 변(14a)의 길이가 짧으면 직경이 작은 엘보를 만들 수 있으므로, 필요한 엘보의 직경에 따라 직선 변(14a)의 길이를 자유롭게 조절하여 절단판(14)을 만들 수 있다.
together "

Since the length of the straight line 14a of the shape cutting plate 14 forms a part of the inlet and the outlet of the elbow, an elbow having a large diameter can be formed if the straight line 14a is long, It is possible to freely adjust the length of the straight side 14a according to the diameter of the elbow to make the cutting board 14. [

In the first heat treatment step (S300), the cutting plate (14) subjected to the cutting process (S200) is subjected to post-weld heat treatment (PWHT) after determining the heating temperature according to the material of the inner metal tube layer (12a) (12a) welded to the inside of the outer appearance metal sheet (11a) by a welding method to control the hardness and ductility of the elbow to be produced, 14 so that cracks do not occur.

Specifically, since the inner metal tube layer 12a welded on one side of the outer metal plate 11a in the welding step S100 maintains a constantly heated state due to the welding heat even after the welding step S100, The fluidity of the fluid flowing into the inner pipe 12 formed by the inner metal pipe layer 12a permeates through the cracks and the inner metal pipe 12a is cooled by the outer metal plate 11a There is a problem that the formed outer plate 11 may be damaged and the property of the heat affected zone (HAZ) of the outer metal plate 11a structurally weakened due to the welding heat may also be impaired. The one heat treatment step (S300) realizes the effect of solving the above problems.

In particular, the first heat treatment step (S300) allows the inner metal tube layer 12a to be easily drawn by the heat treatment applied in the first heat treatment step (S300) When the bending process is performed, the welded inner metal layer 12a is bent so that cracks are not generated.

In this case, the post-welding heat treatment (PWHT) determines the heating temperature depending on the material of the inner metal layer 12a, and the heating temperature for the post-welding heat treatment is the heat treatment after welding of the American Society of Mechanical Engines It is desirable to apply the provisions of

That is, the regulation of the post-weld heat treatment of the American Society of Mechanical Engineers defines the heating or cooling conditions, the holding temperature and the holding time for stabilizing the periphery of the welded structure structurally weakened by the welding heat generated at the welding, In the first heat treatment step (S300), the outer metal sheet 11a to which the inner metal layer 12a is welded is applied according to the kind of material of the inner metal layer 12a by applying the post- It is possible to realize stabilization of physical properties such as the removal of residual stress in the metal layer 12a, the relaxation of stress concentration, or the stabilization of the structure, and the cracking is not generated in the metal layer 12a .

In addition, the present invention can be configured such that the first heat treatment step (S300) is performed at a heating temperature of 50 to 95% of the heat treatment temperature after welding according to the material of the metal tube for internal tube (12a), and the hardness and ductility of the manufactured elbow So that it can be adjusted smoothly.

That is, the post-welding heat treatment temperature not only realizes the effect as described above, but also determines the hardness and ductility of the manufactured elbow according to the degree of cold speed of the cutting plate 14 heated to the post-weld heat treatment temperature as shown in FIG. 7 Element. Specifically, when the cutting plate 14 heated and maintained at the heat treatment temperature for a predetermined period of time is rapidly cooled for a short time, the finished elbow becomes hard, and when the cutting plate 14 is slowly cooled for a long time, It is possible to obtain an effect of excelling in ductility.

For example, after the cutting plate 14 is subjected to the first heat treatment step (S300) at the post-welding heat treatment temperature as shown in FIG. 7A, the cutting plate 14 is pressed against the mold 20 during the following forming step (S400) The temperature of the cutting plate 14 is lower than the post-welding heat treatment temperature and the cutting plate 14 subjected to the forming step S400 is again subjected to the second heat treatment step S500 and then the cold step S600, However, if it is desired to have excellent ductility for the purpose of using the manufactured elbow, the cutting plate 14 heated to the post-welding heat treatment temperature during the forming step (S400) is temporarily cooled to increase the hardness of the finished elbow The ductility may be somewhat insufficient, and the hardness and ductility of the elbow may not be controlled smoothly depending on the purpose of use.

That is, in the first heat treatment step (S300) of the present invention, as shown in FIG. 7 (b), the cutting plate 14 is heated only to 50 to 95% of the heat treatment temperature after welding according to the material of the inner metal tube 12a, (Elbow unit 15) subjected to the forming process (S400) is heated again to the apex of the post-welding heat treatment temperature to give the flexibility to the cutting plate (14) It is possible to solve the problem that the hardness and ductility of the finished elbows do not meet the required values because the cutting plate 14 heated to the apex of the heat treatment temperature after welding is temporarily cooled in the molding step S400.

If the heating temperature in the first heat treatment step S300 is less than 50% of the post-welding heat treatment temperature depending on the material of the inner metal tube layer 12a, the cutting plate 14 is heated insufficiently, There is a possibility that the metal layer 12a may be broken. If the ratio exceeds 95%, there is a possibility that the heating temperature of the cutting plate 14 becomes too close to the post-welding heat treatment temperature of the material of the inner metal layer 12a, Lt; / RTI >

In relation to the above, the temperature holding time in the case where the first heat treatment step (S300) is performed at a heating temperature of 50 to 95% of the post-welding heat treatment temperature according to the material of the metal tube for inner tube 12a, It is preferably adjustable according to the judgment of a person skilled in the art to the extent that the film can be heated, but it is preferably treated at 25 to 35 minutes per inch thickness of the entire cutting plate 14.

At this time, if the temperature holding time is less than 25 minutes per 1 inch thickness, the holding time is short and the inside of the cutting plate 14 can not be sufficiently heated, and if it exceeds 35 minutes, , And it is preferable that the temperature holding time within the above range.

The forming step S400 is a step in which the cutting plate 14 subjected to the first heat treatment step S300 is inserted into the inlet groove 21 of the mold 20 having the inlet groove 21 corresponding to half of the elbow 10, the cutting plate 14 treated in the first heat treatment step (S300) is formed as a step of forming a curved elbow unit 15 corresponding to half of the elbow when the elbow is cut in the longitudinal direction, The cutting plate 14 heated in the first heat treatment step (S300) and heated to the post-weld heat treatment temperature (or the temperature of 50 to 95% of the heat treatment temperature after welding) is placed in the inlet groove 21 of the metal mold 20 And then pressing the cutting plate 14 to bend it.

Specifically, the mold 20 of the molding step (S400) is constituted by a pair of blocks as shown in Figs. 8 to 10, and the lower block 20b is provided with a lead-in groove 21 And the upper block 20a is provided with a projection 22 corresponding to the lead-in groove 21 so that a pressing force is applied to the cutting plate 14 located in the lead-in groove 21 of the lower block 20b And the cutting plate 14 is bent.

At this time, the lead-in groove 21 is formed in the lead groove 21 so that the elbow unit 15 made by bending the cutting plate 14 can be formed into a piece of a finished elbow (a piece corresponding to half when the elbow is cut in the longitudinal direction) And a curved surface of the arc corresponding to a part of the circumference of the elbow to be manufactured.

The protruding portion 22 corresponding to the lead-in groove 21 is formed by pressing the inner metal tube layer 12a of the cutting plate 14 in the direction of the lead-in groove 21 to make the inner tube 12 surface corresponding to the inner tube 12 to be. At this time, the outer metal plate 11a and the inner metal tube layer 12a, which are pressed by the protruding portion 22 and the lead-in groove 21, can have an effect of further increasing the density by the pressing force. The pressing force has a constant welding line and presses the welded inner metal layer 12a to press the irregularities by the welding line to remove irregularities or to reduce the height of irregularities.

In addition, the mold 20 is prevented from easily cooling the cutting plate 14 when the cutting plate 14 subjected to the first heat treatment step S300, which is located in the lead-in groove 21 and bent, is brought into contact with the metal mold 20 And can be preheated to a temperature range similar to that of the cut plate 14 that has been subjected to the first heat treatment step (S300) in order to prevent the physical properties of the bent elbow unit 15 from being weakened by cooling or being too hard . ≪ / RTI >

The method of pressing the cutting plate 14 into the lead-in groove 21 of the mold 20 and the pressing force and the pressing force can be configured in various ways according to the judgment of a person skilled in the art. However, the upper block 20a provided with the protrusion 22, So that the cutting plate 14 is bent into the inlet groove 21 and can be drawn in. At this time, the pressing force of the press can be variously adjusted in consideration of the physical strength depending on the material of the cutting plate 14, and in particular, the outer plate 11a for maintaining the main physical rigidity (fluid resistance) It is more preferable to consider it according to the material of

In connection with the above, the inner metal layer 12a of the elbow unit 15 bent by bending the cutting plate 14 in the forming step (S400) is in a state of being heat-treated after the welding through the first heat treatment step (S300) As a result, a certain portion of the inner tube 12 corresponding to the compressed portion due to the bending when bent at a certain angle in the molding step (S400) is damaged, Or a problem that the physical properties are weakened can be solved.

In the second heat treatment step S500, the elbow unit 15 subjected to the forming step S400 is demolded from the metal mold 20, and the elbow unit 15 is heated at a heating temperature according to the material for the metal tube 12a (PWHT, Post Weld Heat Treatment), which stabilizes the metal constituting the elbow unit 15 made by bending in the forming step (S400).

Specifically, since the elbow unit 15 subjected to the forming process (S400) is bent and bent while being forced into the lead-in groove 21 of the metal mold 20, A crack may be generated in the metal layer 12a for the inner tube 12 which becomes the inner tube 12. In the second heat treatment step S500, Similar to the first heat treatment step (S300), the external appearance metal sheet 11a and the internal metal layer 12a can be maintained in a constant heating state, thereby relieving the stresses of the metal.

More specifically, the second heat treatment step (S500) also realizes stabilization of the outer metal plate 11a constituting the outer tube 11 of the elbow, but stabilizes the inner metal tube 12a constituting the inner tube 12 more And is welded to one side of the outer appearance metal plate 11a so that a crack is generated in the bent inner metal plate 12a having a constant bending angle and is not peeled off from one side of the outer appearance metal plate 11a .

That is, if the elbow unit 15 processed in the forming step (S400) is immediately cooled, the hardness of the elbow unit 15 can be strengthened. However, if the fluid conveyed to the inside of the elbow The inner tube 12 is separated from the inner surface of the outer tube 11 due to the difference in thermal conductivity between the outer tube 11 and the inner tube 12 which are made of different materials. .

The processing conditions of the second heat treatment step (S500) are the same as the processing conditions of the first heat treatment step (S300), as shown in Figs. 7A and 7B, , Stabilization of stress concentration, or stabilization of properties such as structure stabilization can be realized, and the inner pipe 12 can realize the effect of solving the problems of cracking and peeling.

However, in the second heat treatment step (S500), the heating temperature is determined according to the material of the inner metal tube layer 12a, and the heat treatment is performed after the welding again. The heating temperature at this time is a temperature corresponding to the peak of the heat treatment temperature And the holding time can also be appropriately adjusted within the range of the post-welding heat treatment condition. However, the outer metal plate 11a is made of a rolled steel pipe or a forged steel pipe, and the inner metal plate 12a is made of stainless steel, Nickel alloy system, Hastelloy system or aluminum alloy system is made of a metal material, it is treated at a heating temperature of 250 to 1200 DEG C, and the holding time of the heating temperature is set to the entirety of the elbow unit 15 And 25 to 35 minutes per 1 inch (inch) thickness of the film.

In the following description of the second heat treatment step (S500), a description common to the first heat treatment step (S300) will be replaced with a detailed description of the first heat treatment step (S300).

The cold step S600 is a step of cooling the elbow unit 15 subjected to the second heat treatment step S500 and adjusting the cold temperature or the cold time according to the intended use of the elbow so that the hardness and ductility of the elbow It is a process for controlling the same properties.

Specifically, the general cold of a metal is a treatment method for controlling the density of metal particles by causing the metal to be in a state lower than the recrystallization temperature of the metal and consequently controlling the physical properties of the manufactured metal. In the present invention, The elbow unit 15 subjected to the heat treatment process (S500) is allowed to be cold-made under the general cold condition so that it can be adjusted appropriately according to the use of the elbow.

That is, when the elbow unit 15 is processed in a state where the cold time is short or the cold temperature is low in the cold condition, the hardness of the elbow has a state in which the cold time is long or the ductility is weaker than the state in which the cold temperature is high, The hardness is weak but the ductility is low, so that a person skilled in the art can carry out the cold process (S600) appropriately according to the application of the elbow.

Further, in the bonding step S700, a tapered portion is formed on a portion of both ends of the elbow unit 15 subjected to the cold process (S600), and then a pair of elbow units 15 having a tapered shape are welded to form a double- And joining the elbow units 15 made of a part of the pieces to the tubular elbows to form a complete tubular elbow.

Specifically, in the joining step (S700), as shown in Fig. 11, a portion of both ends corresponding to the longitudinal direction of the elbow unit 15 subjected to the cold step (S600) is sliced so as to form a tapered portion, A pair of elbow units (15) are welded to each other to form a double-tube type elbow. At this time, the tapered portion can be processed by the same method as the plasma molding, and the double-tube type elbow can be made by welding the groove 16 formed between the tapered portions of the pair of elbow units 15. It is preferable that the welded portion 17 formed in the grooved and filled groove 16 is subjected to general gilding treatment to produce a smooth surface.

In order to stabilize the elbow unit 15 due to the welding heat applied in the joining step S700, the elbow unit 15 subjected to the cold process S600 is subjected to a third heat treatment process in the same process as the second heat process S500 (S600), and the joining step (S700) may be completed.

The elbow having completed the joining step S700 (or the joining step (S700) further processed in the second heat treatment step (S500) and the cold step (S600)) as described above, A process of forming a constant thread on the inner circumference or the outer circumference of the elbow may be further performed to fix the straight tube to the bolt and nut or to further process the step of forming a tapered inclined surface on the outer periphery of both elbows, have.

The following is a preferred embodiment of manufacturing an elbow by the method for manufacturing a double pipe type elbow according to the present invention.

1. Welding process

A plate of A-105 material with a radius of 800mm and a thickness of 3mm is fixed on the holder and welded to the upper surface of the original plate with a thickness of 3mm using a welding machine equipped with a SUS316 welding electrode to make a double plate.

2. Cutting process

" 형태의 절단판을 만든다.
The original plate was divided into quarters by using a cutter equipped with a cutting blade, and cut into a fan shape. Each of the cut plates cut into a fan shape was cut 400 mm from the center of the circle,

"Form a cutting plate.

3. First heat treatment process

" 형태의 절단판을 800℃로 가열되는 가열로에 인입시키고, 35분을 유지시킨다.
The "

Quot; shaped cut sheet is fed into a heating furnace heated to 800 DEG C and held for 35 minutes.

4. Molding process

" 형태의 절단판의 하부(외관용 금속판이 하부에 위치됨.)를 금형 하부블록의 인입홈 위쪽에 놓은 후, 상부블록의 상부에 위치된 프레스를 가동시켜 상부블록의 하부에 구비된 돌출부가 "

" 형태의 절단판을 가압하여, "

" 형태의 절단판이 엘보를 길이방향으로 절단했을 때 엘보의 절반에 해당하는 형태로 구부러지도록 하여 엘보유닛 1개를 만든다.In the first heat treatment step,

(Located on the lower side of the metal plate for appearance) of the cutting plate is placed above the recessed groove of the mold lower block, and then the press located at the upper portion of the upper block is operated so that the protrusion provided at the lower portion of the upper block "

Quot; shaped < / RTI >

"Shaped plate cuts in the longitudinal direction of the elbow, it is bent in a shape corresponding to half of the elbow to make one elbow unit.

The above procedure is repeated to further make one elbow unit.

5. Second heat treatment process

A pair of the elbow units produced by the above molding process is drawn into a heating furnace heated to 800 DEG C and held for 35 minutes.

6. Cold process

The pair of elbow units subjected to the second heat treatment process are cooled so as to be cooled by 56 DEG C per hour.

7. Bonding Process

Each of the pair of elbow units subjected to the second heat treatment process is cut out by using a plasma molding machine on both sides in the longitudinal direction of the elbow unit to form a tapered portion, The inside is welded using SUS316 welding electrode, and the outside is welded using A-105 welding electrode to make double pipe type elbow.

Thereafter, the welded portion 17 of the double tube type elbow is subjected to a glinding treatment to complete the manufacture of the double tube type elbow.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It is possible to carry out various changes in the present invention.

11: Appearance 11a: Appearance metal plate
12: inner tube 12a: inner tube metal layer
13: double plate 14: cutting plate
14a: straight line side 15: elbow unit
16: groove 17: welded portion
20: mold 20a: upper block
20b: lower block 21: inlet groove
22:
S100: welding process S200: cutting process
S300: First heat treatment step S400: Molding step
S500: second heat treatment process S600: cold process
S700: Bonding process

Claims (5)

A welding step S100 of forming a double plate 13 by welding a metal of a material different from that of the metallic plate for external appearance 11a to one side of the external metallic plate 11a to form the metallic plate 12a for internal use;
A cutting step S200 of cutting the double plate 13 subjected to the welding process S100 to a shape having a size corresponding to half of the elbow when the tubular elbow is cut in the longitudinal direction, and;
A first heat treatment step (S300) of determining the heating temperature according to the material of the inner metal tube layer 12a and then performing post-weld heat treatment (PWHT) on the cutting plate 14 subjected to the cutting process (S200) ;
The cutting plate 14 subjected to the first heat treatment process S300 is placed in the inlet groove 21 of the metal mold 20 having the inlet groove 21 of a shape corresponding to half of the elbow, (S400) of forming a curved elbow unit (15) corresponding to one half of the elbow when cut in the direction of the elbow unit (15);
After the elbow unit 15 processed in the forming step S400 is demolded from the metal mold 20, the heating temperature is determined according to the material of the metal tube 12a for the inner part of the elbow unit 15, , Post Weld Heat Treatment) (S500);
A cold step (S600) for cooling the elbow unit (15) processed in the second heat treatment step (S500);
A pair of tapered elbow units 15 are welded to each other to form a double tube type elbow and a welded portion 17 is formed by welding a pair of tapered elbow units 15 by welding a portion of both ends of the elbow unit 15 subjected to the cold process S600, (S700) for performing a glazing process on the double-tube type elbows.
The method according to claim 1,
The outer metal plate 11a is made of,
And the outer circumference of the circular tubular elbow.
3. The method of claim 2,
The cutting plate (14)
"

&Quot;,< / RTI >
The method according to claim 1,
In the first heat treatment step (S300)
Wherein the heat treatment is performed at a heating temperature of 50 to 95% of the heat treatment temperature after welding according to the material of the metal tube for inner tube 12a.
5. The method of claim 4,
The heating temperature in the first heat treatment step (S300)
And a temperature holding time of 25 to 35 minutes per inch thickness of the entire cutting plate (14).

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