JP2008173650A - Elbow product with neck and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elbow product with necks which is excellent in dimensional property regardless of a neck length by suppressing the occurrence of an ellipse and thickness deviation over the entire length of a neck part and a bent part. <P>SOLUTION: This method is a method for forming an elbow with both necks by applying bending work by holding a tube stock by bending means following to diameter reducing work using a symmetric die while punching the tube stock inserted into a guide tube successively or continuously from the inserting side. In this method of manufacturing the elbow with necks, when reducing the diameters of the neck parts, the wall-thickness of the tube stock is thickened uniformly in the peripheral direction by using the symmetric die and a straight tube part of a prescribed length is punched without holding the bending means and, successively, when reducing the diameter of the bent part, the wall-thickness on the outer peripheral side of the bend of the tube stock is thickened as comparing with the wall-thickness on the inner peripheral side of the bend by switching the symmetric die to an eccentric die and simultaneously bending work is applied until reaching the prescribed bending angle by holding the tube stock by the bending means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an elbow with a neck which is used in a piping system and is provided with a straight pipe for connection at an end, and more specifically, dimensional characteristics (roundness, wall thickness variation over the entire length of the neck and the bent part) The present invention relates to an elbow product with a neck that is superior to the above and a manufacturing method thereof.

  Elbow piping used in power generation and chemical plants is composed of an elbow and a straight pipe welded to both ends of the elbow. As elbow forming methods used for elbow piping, there are a push-bending method and a mandrel method, but the mandrel method is widely applied mainly for normal wall thickness products (t / D ≦ 15%).

  In the case of manufacturing an elbow by the mandrel method, for example, mandrel pipe bending (Hamburg bending) as shown in FIG. 3.6 on page 41 of Non-Patent Document 1 is the most popular elbow processing method. In this mandrel pipe bending, processing is performed in a state where the raw tube and the mandrel are heated, and the shape of the mandrel is characterized in that the outer diameter of the raw tube is gradually increased toward the product side. The raw tube is bent while being expanded. It has been empirically recognized that the elbow product obtained in this way has a small thickness reduction on the bending outer periphery side and also suppresses wrinkles on the bending inner periphery side.

  Patent Document 1 proposes a bent pipe manufacturing apparatus that forms an elbow by a push-bending method using a mandrel by cold working. That is, in the proposed manufacturing apparatus, a guide mold having a workpiece introduction tunnel, an inner mold having an arc-shaped mold surface that is provided above the guide mold and matches the inner curvature of the curved pipe, and a curved pipe An outer mold having an arcuate mold surface that matches the outer curvature, and a curved tunnel constructed based on the clamping of the outer mold and the inner mold so that the workpiece can be inserted and removed from the upper opening side. The bending mold for forming an annular gap corresponding to the thickness of the metal plate constitutes a molding die, and a curved pipe having a predetermined curvature can be formed.

  The above-described processing method and manufacturing apparatus relate to elbow molding, and can ensure a certain quality and production efficiency. However, as elbows used in piping systems, elbows with necks with a straight pipe part for connection at one or both ends are useful for improving the welding workability of pipes. There is a strong demand to do this.

  When manufacturing an elbow with a neck, for example, when manufacturing an elbow with a neck by a mandrel tube bending method, which is a typical representative processing method, the above-described apparatus configuration (see page 41 of Non-Patent Document 1, FIG. 3.6). ), It is necessary to form a long elbow tube with the neck length of the end portion taken into account, and then put a portion corresponding to the neck portion into a mold and correct it into a straight tube.

  That is, in the production of a conventional elbow with a neck, since a processing operation consisting of a two-step process of bending a pipe and a subsequent necking process is required, the manufacturing process becomes complicated and the length of the neck to be formed is reduced. Is limited, and JIS B 2312 and the like are limited to a short neck length, for example, about 16 to 30 mm, on the premise of the conventional bending method.

  In actual piping work, when a straight pipe is welded to the neck, workability can be greatly improved by using an elbow having a neck portion longer than JIS standards. For this reason, it has been strongly demanded to efficiently manufacture an elbow with a neck having a predetermined neck length.

Tube forming (secondary processing of pipe materials and product design), edited by Japan Society for Technology of Plasticity, Corona, November 25, 2002 JP-A-6-114453

  From the viewpoint of welding workability, when examining a method for manufacturing a necked elbow having a predetermined neck length, it is necessary to pay attention to dimensional characteristics over the entire length of the product elbow of the necked elbow.

  For example, in the neck part of the elbow with a neck, when the occurrence of an ellipse or uneven thickness is significant, a gap occurs in the end face shape after bevel processing when butt welding is performed, and the pipe joint pressure test becomes incompatible, A situation occurs in which the tensile strength of the weld cannot be sufficiently secured.

  In addition, when flaring a neck elbow, the pipe end is expanded in a circular shape with an expander or a flare tool, and the flare pipe end is tightened with a flare nut using a flare fitting. If uneven thickness occurs, sufficient joining cannot be performed and there is a risk of leakage of internal fluid.

  The present invention has been made in view of the product quality of such an elbow with a neck and a problem in the manufacturing method thereof, eliminates ellipse and uneven thickness over the entire length of the neck portion and the bent portion, and has excellent dimensional characteristics. An object of the present invention is to provide an elbow product with a neck and a manufacturing method thereof.

  In order to solve the above-mentioned problems, the present inventors have studied elbow forming processing by push-through, and as a result, in order to efficiently form an elbow with a neck, in order to efficiently form the neck elbow, the inlet side central axis and the outlet side central axis And a die in which the input center axis and the exit center axis of the die hole diameter are eccentric (hereinafter referred to as “eccentric die”) We focused on the fact that it is effective to push out the raw tube and reduce the diameter and to perform bending.

  That is, tensile stress acts on the outer peripheral side of a tube bent from a straight pipe, and compressive stress acts on the inner peripheral side, so that the outer peripheral wall thickness is reduced and the inner peripheral side wall thickness is increased. At the same time, wrinkles are likely to occur on the inner peripheral side. In addition, when reducing the diameter, the thickness of the pipe can be increased uniformly in the circumferential direction by using a symmetrical die, whereas the thickness of the pipe is partially increased in the circumferential direction by using an eccentric die. You can increase the meat.

  FIG. 1 is a diagram showing the configuration of a symmetric die and an eccentric die that can be employed in the present invention, where (a) shows a symmetrical die and (b) shows an eccentric die. The symmetric die 1a is a die in which the inlet side central axis and the outlet side central axis of the die hole diameter coincide with each other, and the die angle α is uniformly provided in the circumferential direction. On the other hand, the eccentric die 1b is a die in which the inlet side central axis and the outlet side central axis of the die hole diameter are eccentric, and the die angle β changes in the circumferential direction. As shown in FIG. 1B, the taper surface is formed at the A portion of the eccentric die 1b and the die angle β is large, and the die angle β is almost zero (0 °) at the B portion, and the taper surface is not formed.

  In the case of bending the base tube, the B part (die dies) is positioned so that the A part (the part where the die angle β is large) of the eccentric die 1b shown in FIG. The eccentric die 1b is arranged so that the portion where the angle β is not provided is located on the inner side of the bending. When the eccentric die 1b arranged in this way is used to reduce the diameter by pushing out the tube, the plastic deformation is mainly performed in the A part, the outer diameter is reduced, and the wall thickness is increased. The deformation itself is small and there is almost no wall thickness variation.

  For this reason, after the subsequent bending process is performed, on the outer periphery side of the bending (arrangement position of the eccentric die A part), the increase in thickness due to the diameter reduction process and the decrease in thickness due to the bending process are offset, and the reduction in thickness is reduced. can do.

  Furthermore, by combining the diameter reduction process and bending process in the forming process, the tube cross-section becomes plastically deformed by the punching diameter reducing process of the element pipe, and the part to be processed by bending the element pipe in that state The effect of combined stress can be produced. That is, by bending the raw pipe in a plastically deformed state, a required bending moment to be newly applied for bending can be reduced.

  When the bending moment to be applied to the raw pipe can be suppressed during bending, a means having a simple structure such as a bending arm that does not require a turning drive can be employed as the bending means. Thus, when a relatively simple structure can be adopted as a bending means, an elbow with a neck can be efficiently manufactured by a diameter reduction process and a bending process consisting of one stroke in combination with the action of the eccentric die described above. .

  FIG. 2 is a view for explaining a method of manufacturing an elbow with both necks by a diameter reducing process and bending process consisting of one stroke, (a) shows a process of forming a front end side neck, and (b) shows a bending part. The forming process is shown, and (c) shows the forming process of the rear end side neck. For forming the elbow 2 with a neck, a guide tube 4 for guiding the raw tube 3 and a device 5 for sequentially or continuously extracting the raw tube 3 from the insertion side are provided. Subsequent to the diameter processing, bending is performed by clamping the tube end of the raw tube 3 with the bending arm 6.

  In the neck formation on the distal end side, the straight pipe portion corresponding to the neck length N1 is pushed out without clamping the pipe end of the raw pipe with the bending arm 6 (FIG. 2A). Next, the bending portion is formed by clamping the tube end of the raw tube 3 with the bending arm 6 to shift to bending, and bending is performed until a predetermined bending angle is reached (FIG. 2B). Further, in the neck forming on the rear end side, after the bending process proceeds to a predetermined bending angle, the clamp of the bending arm 6 is released from the pipe end of the raw pipe 3, and the straight pipe portion having the neck length N2 is pushed. Pull out (FIG. 2 (c)).

  If the molding method shown in FIG. 2, the elbow with a neck can be efficiently manufactured, and the dimensional characteristics in the bent portion can be greatly improved. Since the occurrence of uneven thickness becomes prominent, the product quality cannot be denied. In this molding method, in order to improve the dimensional characteristics in the neck portion as well, the function of the eccentric die in the neck portion is eliminated, or as a pretreatment of the raw tube, the front neck side, or the front end side and the rear end side It has been found that it is effective to perform a diameter reduction process of a predetermined length corresponding to the neck portion.

The present invention has been completed on the basis of the above examination results and knowledge, and the gist of the present invention is the necked elbow product (1) and the method for producing the necked elbow (2) to (4).
(1) It is an elbow product with a neck that is excellent in dimensional characteristics without the generation of an ellipse and uneven thickness due to molding over the entire length of the neck portion and the bent portion. The elbow product with a neck can have an ellipticity of 5% or less and a thickness deviation of 6% or less among dimensional characteristics after molding.

The uneven thickness ratio defined in the present invention is defined by {(nominal thickness−minimum thickness) / (nominal thickness)} × 100 (%), as shown in the following formula (3).
(2) The steel tube inserted into the guide tube is sequentially or continuously pushed out from the insertion side, and subsequently subjected to bending by holding the tube with a bending means following the diameter reduction processing using a symmetric die. A method of forming an elbow with a single neck, and when the diameter of the neck portion is reduced, the thickness of the raw pipe is uniformly increased in the circumferential direction using the symmetric die, and without being held by the bending means. The straight pipe part of a predetermined length is punched out, and subsequently, when the diameter of the bending part is reduced, the symmetrical die is switched to the eccentric die, and the thickness of the bending outer peripheral side of the base pipe is changed to the thickness of the inner side of the bending. A method of manufacturing an elbow with a neck characterized in that the thickness is increased as compared with the above, and the blank tube is held by a bending means and bent until a predetermined bending angle is reached.
(3) The steel tube inserted into the guide tube is continuously or continuously pushed out from the insertion side, and subsequently subjected to the bending process by holding the tube with a bending means following the diameter reducing process using a symmetric die. A method of forming an elbow with both necks, and when the diameter of the neck portion at the front end side is reduced, the thickness of the raw tube is increased uniformly in the circumferential direction using the symmetric die and held by the bending means. The straight pipe part of a predetermined length is punched out, and when the diameter of the bent part is reduced, the symmetrical die is switched to the eccentric die, and the thickness of the bent pipe on the outer peripheral side is changed to the thickness on the inner peripheral side of the bent pipe. At the same time as increasing the thickness compared to the thickness, the base tube is held by a bending means and bent to a predetermined bending angle, and the eccentric die is symmetrical when the rear end side neck portion is reduced in diameter. Switch to a die and the meat of the tube Is a method of manufacturing an elbow with a neck (hereinafter referred to as “No. 1”). 1 manufacturing method).
(4) A method of forming an elbow with a neck by subjecting the raw tube inserted into the guide tube to bend-reducing and bending while sequentially or continuously pushing out from the insertion side. As a process, a diameter reducing process of a predetermined length corresponding to the front end side neck part or the front end side and the rear end side neck part is performed, and in the diameter reducing process, the bending of the raw tube is performed using an eccentric die. This is a method for manufacturing an elbow with a neck characterized in that the thickness on the outer peripheral side is increased as compared with the thickness on the inner peripheral side of bending, and subsequently bending is performed (hereinafter referred to as “second manufacturing method”). ).

  According to the elbow product with a neck of the present invention, there is no occurrence of ellipse and uneven thickness due to molding over the entire length of the neck portion and the bent portion, and the dimensional characteristics are excellent regardless of the neck length. The product quality can be improved.

  In addition, according to the method for manufacturing an elbow with a neck according to the present invention, by appropriately switching between a symmetrical die and an eccentric die, and simultaneously arranging the eccentric die appropriately, the raw tube is pushed out to reduce the diameter and bend it. To obtain an elbow product with a neck that is excellent in dimensional characteristics over the entire length and has no wrinkling on the inner side of the bend by an efficient manufacturing method consisting of one stroke regardless of both necks or one neck. Can do.

  3A and 3B are views showing the external shape of a necked elbow product to which the present invention is applied, wherein FIG. 3A shows an elbow product with one neck and FIG. 3B shows an elbow product with both necks. The shape of the necked elbow 2 is defined by a radius of curvature R and an outer diameter D, an inner diameter and a wall thickness t based on the axis, and a long elbow (curvature radius R is 1.5 × outer diameter D) depending on the application. Or it is divided into short elbows (the radius of curvature R is the outer diameter D).

  The elbow 2 with a single neck shown in FIG. 3 (a) is provided with a neck portion having a length N made of a straight pipe for welding at one end of a bent portion, and the elbow 2 with a double neck shown in FIG. 3 (b). Has a neck portion with a length N made of a straight pipe for welding at both ends of the bent portion.

In the following description, an embodiment of the present invention will be described first about a method for manufacturing a necked elbow, and further, dimensional characteristics of a necked elbow product obtained by the manufacturing method will be described. In the description of the embodiment, the elbow product with both necks is targeted. However, the contents are not limited to this, and the elbow product with one neck can be applied to the molding process.
(About the 1st manufacturing method of this invention)
FIGS. 4A and 4B are diagrams for schematically explaining a molding process for diameter reduction in the first manufacturing method of the present invention, in which FIG. 4A shows a molding process of a neck part, and FIG. 4B shows a molding process of a bent part. Is shown. As shown in FIG. 4 (a), in the forming process of the neck portion, the symmetric die 1a is used to reduce the diameter at a uniform die angle α in the circumferential direction, and after that, a straight length of a predetermined length is added without bending. Push out the tube. For this reason, it is possible to increase the thickness of the raw tube uniformly in the circumferential direction at the neck portion, and it is possible to eliminate the generation of an ellipse and uneven thickness due to the molding process.

  In the bending part forming process shown in FIG. 4B, the symmetric die 1a is switched to the eccentric die 1b to reduce the diameter, and the bending is continued until a predetermined bending angle is reached. Switching from the symmetric die 1a to the eccentric die 1b can constitute the eccentric die 1b by inclining the symmetric die 1a at the die inclination angle θ. By switching to the eccentric die 1b, the die angle β at the portion A of the eccentric die 1b becomes (α + θ, where θ <α).

  At this time, the base tube 3 is arranged such that the portion B having a small die angle β is positioned on the bending inner peripheral side so that the portion A having a large die angle β of the eccentric die 1b is positioned on the bending outer peripheral side. With the diameter reduction processing, the material mainly undergoes plastic deformation in the A portion and the outer diameter shrinks and the wall thickness increases. On the other hand, in the B portion, the plastic deformation of the material itself is small and there is almost no variation in the wall thickness. For this reason, by subsequently performing the bending process, in the portion A located on the outer periphery side of the bending, the increase in thickness by the diameter reduction process and the decrease in thickness by the bending process can be offset to reduce the decrease in thickness.

  In addition, by combining diameter reduction and bending in the forming process of the bending part, the pipe cross section becomes plastically deformed by punching diameter reduction of the element pipe, and the combined stress is obtained by bending the element pipe in that state. Thus, the required bending moment to be newly applied for bending can be reduced. Since the bending moment can be suppressed, the tensile stress on the outer periphery side of the bending and the compressive stress on the inner periphery side of the bending can be reduced, and wrinkles generated on the inner periphery side of the bending due to the compressive stress can be prevented.

  Next, when the rear end side neck portion is formed, as shown in FIG. 4A, the eccentric die 1b is switched to the symmetric die 1a, and the die angle α is uniform in the circumferential direction by the symmetric die 1a. The diameter of the straight pipe is reduced, and the straight pipe portion having a predetermined length is pushed out without bending. Thereby, generation | occurrence | production of the ellipse and thickness deviation accompanying the shaping | molding process of a rear-end side neck part can be eliminated.

  When diameter reduction processing is performed using an eccentric die, eccentricity H is generated between the entrance side central axis and the exit side central axis of the die hole diameter. For this reason, in the molding process shown in FIG. 4, as shown in FIG. 4 (b), when the diameter reduction processing is performed using the eccentric die in the bending part molding process, The eccentric center H is moved downward from the pass line of the raw pipe along the entrance-side central axis of the die hole diameter so as to coincide with the pass line of the raw pipe.

  FIGS. 5A and 5B are diagrams schematically illustrating another forming process of the diameter reducing process in the first manufacturing method of the present invention, in which FIG. 5A shows the forming process of the neck portion, and FIG. 5B shows the bending portion. The molding process is shown. In the molding process shown in FIG. 5, when diameter reduction processing is performed in the molding process of the bent portion, the entrance axis of the die hole diameter of the eccentric die is matched with the pass line of the raw pipe, and the exit side of the die hole diameter is matched. The central axis is moved upward from the pass line of the raw tube.

  The molding process shown in FIG. 5 differs from the molding process shown in FIG. 4 only in the method of correcting the eccentricity H of the eccentric die with respect to the pass line of the raw tube, and the neck shown in FIG. The molding process of the part and the molding process of the bending part shown in FIG. 5B are the same as the molding process shown in FIG.

  FIG. 6 is a diagram showing the relationship between the die inclination angle θ and the geometric ellipticity of the die in the first manufacturing method of the present invention. Here, the ellipticity can be defined by the following equation (1), specifically, calculated by the equation (2). The minor axis of the eccentric die is an elliptical minor axis when the hole shape of the eccentric die is projected on a plane perpendicular to the pass line axis.

Ellipticity = {(minor axis of eccentric die-hole diameter of symmetric die) / (hole diameter of symmetric die)}
× 100 (%) (1)
Ellipticity = 1-cos θ (2)
From the relationship shown in FIG. 6, since the die inclination angle θ when switching the symmetric die to the eccentric die is 10 °, the geometric ellipticity of the die can be kept below 2%. It can be said that the rate is sufficiently small. According to the study by the present inventors, the die inclination angle θ is set to about 10 to 12 ° in order to ensure the improvement in thickness deviation by the effect of the diameter reduction processing by the eccentric die and to exert the effect of preventing wrinkles. In this case, the geometric ellipticity of the die can be made 2.5% or less. In addition, the ellipticity of the pipe in actual production was as small as about 5%.
(About the 2nd manufacturing method of this invention)
FIG. 7 is a diagram schematically illustrating a bending part forming process in the forming process of the second manufacturing method of the present invention. In the bending part forming process, the base tube 3 inserted into the guide tube 4 is bent sequentially or continuously from the insertion side, and is subjected to a bending process together with a diameter reducing process to form the necked elbow 2.

  The raw pipe 3 used for forming is cut from a raw steel pipe into a short dimension corresponding to the product dimension, and subjected to a diameter reduction process of a predetermined length corresponding to the front end side and the rear end side neck portion as a preliminary treatment. A punching force is applied to each one, and diameter reduction processing is performed with the eccentric die 1b. Subsequently, bending is performed while holding the element tube 3 with the clamp 7 of the bending arm 6 in the range from the C position to the D position corresponding to the bending portion of the necked elbow 2.

  At this time, the eccentric die 1b is disposed so that the portion where the die angle β is small is located on the bending outer peripheral side so that the portion where the die angle β of the eccentric die 1b is large is located on the bending outer peripheral side by bending. . After the diameter reduction is performed using the eccentric die 1b arranged in this way and the subsequent bending process is performed, the increase in thickness due to the diameter reduction and the decrease in thickness due to the bending process are offset on the outer periphery side of the bending. And we can reduce meat loss.

When the diameter reduction processing is performed using the eccentric dies, the eccentricity H is generated between the inlet side central axis and the outlet side central axis of the die hole diameter. Therefore, in the molding process shown in FIG. In order to absorb the eccentricity H, it is necessary that the eccentric die can be moved up and down.
(Elbow product with neck of the present invention)
The necked elbow product molded by the first and second production methods of the present invention can exhibit excellent thickness deviation characteristics over the entire length of the bent portion and the neck portion. Here, the thickness deviation rate can be defined by the following formula (3) by paying attention to the thinning of the outer periphery of the bending. For example, in JIS B 2312, the thickness tolerance of the pipe joint is −12.5% (+ not specified). However, it has been confirmed that the elbow product of the present invention can satisfy −6% or less.

Uneven thickness ratio = {(nominal thickness−minimum thickness) / (nominal thickness)} × 100 (%) (3)
As described above, the elbow product with a neck according to the present invention switches from a symmetric die to an eccentric die from the formation of the neck portion to the formation of the bent portion, and thus an ellipse is generated. However, as described above, in order to secure the effect of improving the uneven thickness and preventing wrinkles, it is effective to set the die inclination angle θ to about 10 to 12 °, so the ellipticity should be 5% or less. As a result, there is no problem in roundness as an elbow product.

  In addition, the elbow product with a neck of the present invention can suppress the bending moment accompanying the bending process even if the radius of curvature is small or the thickness of the thin wall. Can do.

  The necked elbow product of the present invention can be efficiently manufactured by a molding process consisting of one stroke regardless of both necks or one neck, and is limited to a neck length of 16 to 30 mm as defined in JIS B 2312 or the like. Therefore, it is possible to cope with the production of elbows with a long neck, for example, exceeding 1000 mm, which has been strongly demanded.

  FIG. 8 is a diagram showing a typical apparatus configuration example for carrying out the first manufacturing method of the present invention. A guide tube 4 for inserting the raw tube 3 and a punching device 5 for pressing the raw tube 3 sequentially or continuously from the insertion side are arranged. A die stand 8 is provided on the distal end side of the guide tube 4, and a die device 1 for performing a diameter reducing process on the die stand 8 and a bending arm 6 as a bending means for performing the bending process are disposed.

  The die device 1 includes an inclination mechanism, and switches between a symmetric die and an eccentric die in accordance with the switching of the formation process of the neck portion or the bent portion. In the case of reducing the diameter using a symmetric die, the thickness of the raw tube is increased uniformly in the circumferential direction. On the other hand, when diameter reduction processing is performed using an eccentric die, the eccentric die is arranged so that the portion where the die angle β is large is located on the bending outer peripheral side and the portion where the die angle β is small is located on the bending inner peripheral side. The wall thickness of the blank tube is increased on the outer peripheral side of the bending as compared with the inner peripheral side of the bending.

  The bending arm 6 is disposed so as to be supported on a surface that coincides with the exit surface of the die device 1, and is fixed to the die stand 8. At this time, the bending arm 6 may have a turning driving force as necessary.

  Although not shown, an arm clamp for holding the raw tube 3 is provided at the tip of the bending arm 6. The arm clamp needs to be repeatedly held or released as the neck or bend is formed, and it is divided into a left and right split structure to accommodate the formation of a long neck. Is desirable.

  Furthermore, the die stand 8 is provided with a device capable of moving up and down in conjunction with the die device 1 and the bending arm 6 in order to correct the eccentricity H when the diameter reduction processing is performed using the eccentric die. .

  FIG. 9 shows the relationship between the die inclination angle θ of the die device, the eccentricity H of the die stand, and the bending angle ψ of the bending arm in the neck portion forming process and the bending portion forming process. The raw pipe 3 cut to the design dimension from the raw steel pipe is inserted into the guide tube 4 and is pushed into the die device 1 by the operation of the hydraulic cylinder of the push-in device 5 arranged on the rear end side of the guide tube 4.

  In the process of reducing the diameter of the neck on the front end side, the wall thickness of the pipe is uniformly increased in the circumferential direction by using a symmetric die, and the straight pipe of a predetermined length is not held by the arm clamp of the bending arm 6. Push out the tube. For this reason, in the front end side neck part, the ellipse and thickness deviation accompanying a shaping | molding process do not generate | occur | produce.

  In the process of reducing the diameter of the bending portion, the die inclination angle θ is set in order to switch the symmetric die to the eccentric die, and the die stand 8 corrects the eccentricity H in conjunction with this, and at the same time, the arm of the bending arm 6 The clamp holds the raw tube 3 and the bending arm 6 performs bending until reaching a predetermined bending angle ψ.

  In the process of reducing the diameter of the bent portion at this time, the diameter-reduced element tube 3 is increased in thickness at a portion where the die angle β of the eccentric die is large, and is offset with the reduction in thickness due to subsequent bending. Therefore, the wall thickness variation is reduced. Also, the ellipse generated at this time is sufficiently suppressed to have an ellipticity of 5% or less, and does not cause a problem in dimensional characteristics.

  In the process of reducing the diameter of the rear end side neck portion, after the bending arm 6 reaches the predetermined bending angle ψ, the die inclination angle θ is set to zero (zero) in order to switch from the eccentric die to the symmetric die. At the same time, the die stand 8 is lowered to make the eccentricity H zero (zero), and at the same time, the holding of the raw tube by the arm clamp of the bending arm 6 is released, and the straight pipe portion of a predetermined length is pushed out. Therefore, the ellipse and the uneven thickness due to the molding process are not generated in the rear end side neck portion.

  According to the elbow product with a neck of the present invention, there is no occurrence of ellipse and uneven thickness due to molding over the entire length of the neck portion and the bent portion, and the dimensional characteristics are excellent regardless of the neck length. The product quality can be improved.

  In addition, according to the method for manufacturing an elbow with a neck according to the present invention, by appropriately switching between a symmetrical die and an eccentric die, and simultaneously arranging the eccentric die appropriately, the raw tube is pushed out to reduce the diameter and bend it. To obtain an elbow product with a neck that is excellent in dimensional characteristics over the entire length and has no wrinkling on the inner side of the bend by an efficient manufacturing method consisting of one stroke regardless of both necks or one neck. Can do. Thereby, it can utilize widely as a shaping | molding method of the elbow with a neck used for elbow piping.

It is a figure which shows the structure of the symmetrical die | dye and eccentric die which can be employ | adopted by this invention, (a) is a symmetrical die, (b) has shown the eccentric die. It is a figure explaining the method of manufacturing the elbow with both necks by the diameter reduction process which consists of 1 process, and a bending process, (a) shows the formation process of a front end side neck, (b) shows the formation process of a bending part. , (C) shows the process of forming the rear end side neck. It is a figure which shows the external shape of the elbow product with a neck which this invention makes object, (a) has shown the elbow product with one neck, (b) has shown the elbow product with both necks. It is a figure which illustrates typically the molding process of the diameter reduction process in the 1st manufacturing method of this invention, (a) shows the molding process of a neck part, (b) has shown the molding process of the bending part. . It is a figure which illustrates typically the other forming process of the diameter reduction process in the 1st manufacturing method of this invention, (a) shows the forming process of a neck part, (b) shows the forming process of a bending part. ing. It is a figure which shows the relationship between the die inclination angle (theta) and the geometric ellipticity of a die in the 1st manufacturing method of this invention. It is a figure which illustrates typically the formation process of a bending part among the formation processes of the 2nd manufacturing method of this invention. It is a figure which shows the typical apparatus structural example for enforcing the 1st manufacturing method of this invention. The relationship between the die inclination angle θ of the die device, the eccentricity H of the die stand, and the bending angle ψ of the bending arm in the neck portion forming process and the bending portion forming process is shown.

Explanation of symbols

1: Die, Die device, 1a: Symmetric die 1b: Eccentric die, 2: Elbow 3: Raw pipe, 4: Guide tube 5: Punching device, 6: Bending arm 7: Clamp, 8: Die stand

Claims (5)

  An elbow product with a neck that is excellent in dimensional characteristics without the occurrence of ellipse and uneven thickness due to molding over the entire length of the neck and the bent part.   2. The elbow product with a neck according to claim 1, wherein, of the dimensional characteristics after molding, the ellipticity is 5% or less and the thickness deviation is 6% or less. A die in which the central axis of the die hole diameter coincides with the central axis of the outlet side (hereinafter referred to as a “symmetrical die”) while the core tube inserted into the guide tube is sequentially or continuously pushed out from the insertion side. A method of forming an elbow with a single neck by bending by holding the raw tube with a bending means following the diameter reduction processing using
When reducing the diameter of the neck part, the thickness of the raw pipe is increased uniformly in the circumferential direction using the symmetric die, and the straight pipe part of a predetermined length is punched out without being held by the bending means.
Subsequently, when the diameter of the bent portion is reduced, the symmetric die is switched to a die in which the entrance center axis and the exit center axis of the die hole diameter are eccentric (hereinafter referred to as “eccentric die”). A neck characterized in that the wall thickness on the outer periphery side of the tube is increased compared to the wall thickness on the inner periphery side of the tube, and the base tube is held by a bending means and bent until a predetermined bending angle is reached. A manufacturing method of an elbow. With both necks, the tube is inserted into the guide tube by pushing it out from the insertion side sequentially or continuously, followed by diameter reduction using a symmetric die, and then bending the tube by holding it with bending means. A method of molding an elbow,
When reducing the diameter of the front-end neck part, the thickness of the raw pipe is increased uniformly in the circumferential direction using the symmetric die, and the straight pipe part of a predetermined length is punched out without being held by the bending means. ,
Subsequently, when reducing the diameter of the bent portion, the symmetrical die is switched to an eccentric die, and the thickness of the bending outer peripheral side of the raw tube is increased compared to the thickness of the bending inner peripheral side. Hold it with bending means and apply bending until it reaches a predetermined bending angle.
Further, when the diameter of the neck portion at the rear end side is reduced, the eccentric die is switched to a symmetric die to increase the thickness of the raw tube uniformly in the circumferential direction, and at the same time, the holding of the bending means in the raw tube is released. A method of manufacturing an elbow with a neck, wherein a straight pipe portion having a predetermined length is pushed out. A method of forming an elbow with a neck by subjecting the raw tube inserted into the guide tube to bend and reduce the diameter while sequentially or continuously pushing out from the insertion side,
As a preliminary treatment of the raw tube, the diameter reduction processing of a predetermined length corresponding to the front end side neck portion, or the front end side and the rear end side neck portion has been performed,
At the time of the diameter reduction processing, with an eccentric die, the thickness of the outer peripheral side of the raw pipe is increased compared to the thickness of the inner peripheral side of the bending, and then the necking is performed. Elbow manufacturing method.

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