JP2010051990A - Method of manufacturing necked elbow - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the product of a necked elbow in which thickness deviation is eliminated over the entire length, also the generation of wrinkles and local flattening in a bent portion are suppressed and excellent dimensional property and quality characteristics are secured. <P>SOLUTION: A method is for manufacturing the necked elbow by combining a necked part forming process for reducing the diameter by using a symmetrical die and a bent part forming process for performing bending until reaching a prescribed bending angle by holding the pipe stock with a bending arm and in this bent portion forming process, by thickening the wall thickness on the outer peripheral side of the pipe stock than the wall thickness on the inner peripheral side of the pipe stock and, simultaneously, providing a prescribed amount Os of offset on the bending arm, bending work is performed. It is preferable that the relationship between the amount Os (mm) of offset and the finished diameter d (mm) is Os/d=0.09-0.18. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an elbow with a neck that is used in a piping system and is provided with a straight pipe for connection at an end, and more specifically, dimensional characteristics (flatness, unevenness over the entire length of the neck and the bent portion. The present invention relates to a method for producing an elbow with a neck that is excellent in meat ratio) and quality characteristics (wrinkles, etc.) and is optimal for high-efficiency production.

  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 the annular gap corresponding to the wall thickness of the molding die constitutes a molding die, and a curved pipe having a predetermined curvature can be molded.

  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 to improve the weldability of pipes. It becomes necessary to do.

  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 provided with a neck part longer than JIS standards. For this reason, it is required to efficiently manufacture an elbow with a neck having a predetermined neck length while ensuring excellent dimensional characteristics and quality characteristics.
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

  The present applicant responded to the demand for the production efficiency of the elbow with neck, and when the elbow forming process by push-through is performed, the die having the eccentric center axis of the die hole diameter and the central axis of the exit side ( (Hereinafter referred to as “eccentric dies”), a method of manufacturing an elbow with a neck in one stroke by pushing out the raw tube and bending it at the same time as the diameter reduction processing (see Japanese Patent Application No. 2007-007118). .

  FIG. 1 is a diagram for explaining the configuration of an eccentric die in comparison with a die in which the inlet side central axis and the outlet side central axis of the die hole diameter coincide with each other (hereinafter referred to as “symmetrical die”). a) shows a symmetrical die, and (b) shows an eccentric die.

  In the symmetric die 1a, the entrance side central axis and the exit 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 in the A portion of the eccentric die 1b and the die angle β is large, and the die angle β is almost zero (0 °) in 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.

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

  When the bending moment to be applied to the raw pipe can be suppressed during the bending process, a means having a simple structure such as a bending arm having a turning function can be adopted as the bending means. In this way, when a relatively simple structure can be adopted as a bending means, the elbow with a neck is reduced in diameter by one stroke regardless of both necks or one neck in combination with the action of the eccentric dies described above. And can be efficiently manufactured by bending.

  FIG. 2 is a view for explaining a method of manufacturing an elbow with both necks by a diameter reduction process and bending process consisting of one stroke, (a) shows a forming process of the front end side neck, and (b) shows a bending part. The molding process is shown, and (c) shows the molding 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)).

  According to the molding method shown in FIG. 2, an elbow with a neck can be efficiently manufactured, but the dimensional characteristics at the neck portion are deteriorated, and the occurrence of uneven thickness is particularly remarkable. Further, since compressive stress acts on the inner peripheral side of the bent tube, the inner peripheral side is thicker and wrinkles are likely to occur on the inner peripheral side.

  Further, in the bending process using the bending arm arranged on the eccentric die exit side, the bending moment applied to the bending portion increases as the bending process progresses after being pushed out from the eccentric die. For this reason, since a new plastic deformation arises in a bending part, it becomes easy to produce local flatness.

  The present invention has been made in view of the problems in the method of manufacturing such an elbow with a neck, and eliminates fluctuations in thickness (uneven thickness) over the entire length of the neck portion and the bent portion, The purpose is to provide a method for producing an elbow with a neck that suppresses local flattening, has excellent dimensional characteristics and quality characteristics, and is optimal for high-efficiency production.

  In order to solve the above-mentioned problems, the present inventors have examined the elbow molding process by push-through diameter reduction bending.As a result, by appropriately switching between a symmetrical die and an eccentric die, and simultaneously arranging the eccentric die properly, By extruding the raw tube and bending at the same time as the diameter reduction processing, uneven thickness can be eliminated over the entire length of the neck portion and the bending portion, regardless of whether both necks or one neck is formed, It was noted that an elbow with a neck could be manufactured by an efficient molding process consisting of one stroke.

  FIG. 3 is a diagram schematically illustrating a process of forming an elbow with a neck having no unevenness over the entire length, wherein (a) shows a forming process of the neck part, and (b) shows a forming process of the bent part. Is shown. As shown in FIG. 3A, 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 wall thickness of the tube evenly in the circumferential direction at the neck portion, and it is possible to eliminate the occurrence of uneven thickness due to the forming process.

  In the bending part forming process shown in FIG. 3B, 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.

  Next, when the rear end side neck portion is molded, as shown in FIG. 3A, 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, the occurrence of uneven thickness due to the forming process of the rear end side neck portion 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, as shown in FIG. 3B, when the diameter reduction process is performed using an eccentric die in the bending portion forming process, the exit side central axis of the die hole diameter is matched with the pass line of the raw pipe. Then, the eccentric H is moved downward from the pass line of the raw pipe along the entrance-side central axis of the die hole diameter.

  As shown in FIG. 4, as a method of correcting the eccentricity H when the diameter reduction processing is performed in the bending portion forming process, when the diameter reduction processing is performed in the bending portion forming process, the die hole diameter of the eccentric die is changed. It is possible to adopt a method in which the eccentric center H is moved upwardly from the pass line of the raw pipe by making the inlet side central axis coincide with the pass line of the raw pipe and the outgoing center axis of the die hole diameter.

  In FIG. 3 described above, the molding process has been described for the elbow product with both necks. However, the content of the molding process is not limited to the elbow product with both necks, but also for the elbow product with one neck. Applicable.

  By the way, in the molding process shown in FIG. 3, the combined stress effect is produced by combining the diameter reduction process and the bending process in the bending part molding process, and the required bending moment can be reduced. On the exit side of the die, the bending moment applied to the bent portion may increase with the progress of the bending process.

  For example, if a phenomenon in which the bending moment is maximized in the intermediate process of elbow product bending, a new plastic deformation occurs in the blank tube pushed out of the eccentric die. For this reason, it becomes easy to produce local flatness in the bending part of an elbow product.

  Furthermore, wrinkles generated on the inner peripheral side of the bent portion are caused by compressive stress during bending. Therefore, if the bending moment required for the bending process 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.

  In general, the elbow with a neck is formed by a method of clamping a pipe end of a pipe using a bending arm for turning as a bending means while pushing the pipe sequentially or continuously. In this case, the bending moment accompanying the bending process is affected by the arrangement condition of the bending arm turning center and the speed ratio λ indicated by the ratio of the bending arm turning speed and the punching speed.

  The present invention has been completed on the basis of the examination results and knowledge based on the process of forming the neck elbow shown in FIG. 3 in one stroke, and includes the following elbows (1) and (2). The manufacturing method is the gist.

(1) Neck part forming process in which diameter reduction processing is performed using a symmetric die while sequentially or continuously pushing out the raw tube inserted in the guide tube, and the diameter reduction processing is performed by switching to an eccentric die, A method of manufacturing an elbow with a neck in combination with a bending part forming process in which the raw tube is held by a bending arm and bent to a predetermined bending angle, and in the bending part forming process, At the same time as increasing the thickness of the bending pipe on the outer peripheral side compared to the thickness on the inner side of the bending, the turning center of the bending arm was moved from the exit end position of the eccentric die to the die entry side. This is a method of manufacturing an elbow with a neck, characterized in that it is bent at a position and provided with a predetermined offset amount Os.

(2) The manufacturing method of the elbow with a neck of (1) described above includes the offset amount Os (mm) indicated by the distance between the turning center of the bending arm and the exit end position of the eccentric die, and the finish of the eccentric die. It is desirable that the relationship with the diameter d (mm) satisfies the following formula (1).
Os / d = 0.09-0.18 (1)

  Furthermore, in order to eliminate the occurrence of flatness and wrinkles stably, the speed ratio λ (Vφ / V) expressed by the ratio of the bending arm turning speed Vφ (R · ω) and the blank tube punching speed Vw (mm / s). It is desirable to manage Vw) in the range of 0.9 to 1.1. If the speed ratio λ (Vφ / Vw) is out of this range, that is, if the bending arm turning speed Vφ is excessively slow or fast, flatness and wrinkles are likely to occur. Furthermore, since an excessive load acts on the swivel arm, it is not desirable from the viewpoint of equipment maintenance.

  According to the method of manufacturing an elbow with a neck of 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 perform bending. At the same time, by properly selecting the offset amount of the bending arm (distance between the turning center and the exit tip position of the eccentric die), and further controlling the speed ratio (ratio between the bending arm turning speed and the punching speed) In spite of forming both necks or one neck, it can be manufactured with high efficiency.

  In addition, the resulting elbow-equipped elbow product eliminates uneven thickness over the entire length of the neck and bend, and suppresses wrinkling and local flatness in the bend, ensuring excellent dimensional characteristics and quality characteristics. it can.

  FIGS. 5A and 5B are views showing the external shape of a necked elbow product to which the present invention is applied. FIG. 5A shows an elbow product with one neck and FIG. 5B 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).

  An elbow 2 with a single neck shown in FIG. 5 (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 an elbow 2 with a double neck shown in FIG. 5 (b). Provides a neck portion with a length N made of a straight pipe for welding at both ends of the bent portion.

  FIG. 6 is a diagram showing a schematic apparatus configuration example for carrying out the method for manufacturing an elbow with a neck according to 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 7 is provided on the distal end side of the guide tube 4. A die device 1 for reducing the diameter of the die stand 7 and a bending arm 6 as a bending means for bending are disposed.

  The die apparatus 1 includes an inclination mechanism, and performs switching between a symmetric die and an eccentric die in accordance with switching of the forming 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 in the exit area of the dice apparatus 1 and is fixed to the die stand 7. At this time, the bending arm 6 is disposed at a position where the turning center is moved from the exit side tip position of the eccentric die to the die entry side, with a predetermined offset amount Os. 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 repeats the holding or opening operation as the molding process of the neck portion or the bent portion is switched.

  Further, the die stand 7 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.

  The raw pipe 3 cut to the design dimension from the raw steel pipe is inserted into the guide tube 4 and the punching speed Vw (mm / s) is activated by the operation of the hydraulic cylinder of the pushing device 5 arranged on the rear end side of the guide tube 4. ) Is pushed into the die apparatus 1.

  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 thickness deviation accompanying a shaping | molding process does not generate | occur | produce.

  In the process of reducing the diameter of the bending portion, the die inclination angle θ is set to switch the symmetric die to the eccentric die, and the die stand 7 corrects the eccentricity H in conjunction with this, and at the same time, the arm of the bending arm 6 The clamp holds the tube 3 and the bending arm 6 is bent at a turning speed Vφ (R · ω) until a predetermined bending angle φ is reached.

  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.

  In the process of reducing the diameter of the rear end side neck portion, the die tilt angle θ is set to zero (zero) in order to switch from the eccentric die to the symmetric die after the bending arm 6 reaches the predetermined bending angle φ. At the same time, the die stand 7 is lowered to make the eccentricity H zero (zero), and at the same time, the holding of the blank tube by the arm clamp of the bending arm 6 is released, and the neck portion of a predetermined length is pushed out.

  In the method of manufacturing an elbow with a neck according to the present invention, in the apparatus configuration shown in FIG. 6, the turning center of the bending arm is arranged at a position moved from the exit end position of the eccentric die to the die entry side. An offset amount Os indicated by the distance between the turning center and the exit end position of the eccentric die is provided.

  By appropriately selecting the offset amount Os and performing the bending process, the bending moment applied to the blank pipe pushed out from the eccentric die is not increased. Therefore, new plastic deformation does not occur in the raw pipe that has passed through the eccentric die outlet side, flat deformation accompanying bending is eliminated, and local flatness can be prevented from occurring in the bent portion. Similarly, since the compressive stress on the inner side of the bending can be reduced, wrinkles caused by the compressive stress can be prevented.

The appropriate offset amount Os has been confirmed to be related to the punching dimension of the raw tube, and the relationship between the offset amount Os (mm) of the bending arm and the finishing diameter d (mm) of the eccentric die is as follows (1) It is desirable to satisfy the formula.
Os / d = 0.09-0.18 (1)

  In the above formula (1), if the Os / d value is less than 0.09, an increase in the bending moment applied to the blank pipe pushed out from the eccentric die is observed, and new plastic deformation occurs, resulting in bending. Due to the accompanying deformation, local flattening easily occurs in the bent portion.

  On the other hand, if the Os / d value exceeds 0.18, an increase in the bending moment can be avoided after punching out from the eccentric die, but a wrinkle starting point occurs on the inner circumference side of the bend, and wrinkles occur in the bent portion. It becomes easy to do.

  In the method of manufacturing an elbow with a neck according to the present invention, in order to reduce the flatness generated in the bent portion and eliminate wrinkles at the same time, the turning speed Vφ (R · ω) of the bending arm and the punching speed Vw (mm It is desirable to operate at a speed ratio λ (Vφ / Vw) represented by a ratio of 0.9 to 1.1. That is, when the speed ratio λ (Vφ / Vw) is out of this range, specifically, when the bending arm turning speed Vφ is excessively slow or fast, flatness and wrinkles are likely to occur. Since an excessive load acts on the swivel arm, it is not desirable for equipment maintenance.

  Using a push-through device comprising the device configuration example shown in FIG. 6, a raw tube (carbon steel) having an outer diameter of 60.5 mm, a wall thickness of 3.8 mm, and a length of 400 mm is prepared and pushed by an eccentric die. An elbow with both necks with a blanking dimension of 55 mm was produced. In this case, the reduction ratio by the forming process corresponds to 10%.

  Using a symmetric die having a die half angle α of 7.5 °, the punching speed Vw of the raw tube was constant at 2.5 mm / s, and the neck portion was formed. Next, the die was tilted simultaneously with the start of the bending process, and the tilt angle was changed to θ = α to switch to an eccentric die. The turning speed Vφ (R · ω) of the bending arm at this time was controlled, and the speed ratio λ (Vφ / Vw) and the bending arm offset amount Os (mm) were set.

  In this embodiment, the tip side neck portion is reduced in diameter by 100 mm, then switched to an eccentric die, the element tube is clamped by a bending arm, and bending is performed until a predetermined bending angle is obtained. Changed the slope of the die back to a symmetrical die, reduced the diameter of the neck at the rear end, measured the flatness of the bent portion, and evaluated the occurrence of local flatness and wrinkles.

FIG. 7 is a diagram illustrating a measurement position after the elbow with neck forming process. The average diameter d0 was calculated from the short diameter d1 and the long diameter d2 at the corresponding measurement position, and the flattening ratio Fr was obtained from the following (2). Table 1 shows the calculated flatness Fr and the evaluation results.
Fr (%) = {(d2-d1) / d0} × 100 (2)

  From the results of Table 1, when the offset amount Os is not provided (Test Nos. 1 and 2), the bending moment increases in the intermediate process of bending, the flatness increases, and local flatness is observed in the bent portion. It was done.

On the other hand, when the offset amount Os was increased too much and the Os / d value reached 0.27 (Test Nos. 7 and 8), wrinkles occurred on the inner peripheral side of the bent portion at the die exit side position.
On the other hand, when the Os / d value specified in the present invention is in the range of 0.09 to 0.18 (test Nos. 3 to 6), increase in bending moment is suppressed in the intermediate process of bending, The flattening ratio Fr was reduced to less than 20%, and wrinkle generation was not observed.

  In this example, simultaneously with the measurement of the flattening ratio Fr, the diameter-reduced element pipe is increased in thickness at a portion where the die angle β of the eccentric die is large, and is offset with the decrease in thickness due to subsequent bending. It has been confirmed that the thickness variation is reduced and the thickness deviation rate is suppressed to 6% or less.

  According to the method of manufacturing an elbow with a neck of 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 perform bending. At the same time, by properly selecting the offset amount of the bending arm (distance between the turning center and the exit tip position of the eccentric die), and further controlling the speed ratio (ratio between the bending arm turning speed and the punching speed) In spite of forming both necks or one neck, it can be manufactured with high efficiency.

  In addition, the resulting elbow-equipped elbow product eliminates uneven thickness over the entire length of the neck and bend, and suppresses wrinkling and local flatness in the bend, ensuring excellent dimensional characteristics and quality characteristics. it can. Thereby, it can utilize widely as a shaping | molding processing method of the elbow with a neck used for elbow piping.

It is a figure explaining the structure of an eccentric die compared with a symmetrical die, (a) shows a symmetrical die, and (b) shows an eccentric die. It is a figure explaining the method of manufacturing the elbow with both necks by the diameter reduction process and bending which consist of 1 process, (a) shows the formation process of a front end side neck, (b) shows the formation process of a bending part. (C) shows the forming process of the rear end side neck. It is a figure which illustrates typically the process of shape | molding the elbow with a neck without uneven thickness over the full length, (a) shows the formation process of a neck part, (b) has shown the formation process of the bending part. . Another method for correcting the eccentricity H, which can be applied when reducing the diameter in the forming process of the bent portion, will be described. 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 shows the typical apparatus structural example for enforcing the manufacturing method of the elbow with a neck of this invention. It is a figure which shows the measurement position after elbow molding processing with a neck.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Die, die apparatus, 1a: Symmetrical die 1b: Eccentric die, 2: Elbow 3: Raw pipe, 4: Guide tube 5: Punching device, 6: Bending arm 7: Die stand

Claims (3)

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. Neck part forming process to reduce the diameter using
The symmetric die is switched to a die having an eccentric center axis on the die hole diameter and an eccentric center axis on the die side (hereinafter referred to as “eccentric die”) to reduce the diameter, and the raw tube is bent with a bending arm. A method of manufacturing an elbow with a neck in combination with a bending part forming process of holding and bending to a predetermined bending angle,
In the bending part forming process, the wall thickness of the bending outer circumference side of the base pipe is increased compared with the thickness of the bending inner circumference side by reducing the diameter, and at the same time, the turning center of the bending arm is brought out of the eccentric die. A method of manufacturing an elbow with a neck, characterized in that a bending is performed by providing a predetermined offset amount Os at a position moved from the side tip position to the die entry side. The relationship between the offset amount Os (mm) indicated by the distance between the turning center of the bending arm and the exit end position of the eccentric die satisfies the following formula (1). The manufacturing method of the elbow with a neck of Claim 1 characterized by the above-mentioned.
Os / d = 0.09-0.18 (1)   The speed ratio λ (Vφ / Vw) indicated by the ratio of the turning speed Vφ (R · ω) of the bending arm and the punching speed Vw (mm / s) of the raw tube is 0.9 to 1.1. The method for manufacturing an elbow with a neck according to claim 1 or 2.

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