JP2005279750A - Drawing apparatus for tube stock and manufacturing method for drawn tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drawing apparatus for a tube stock and a manufacturing method for a drawn tube that can prevent or suppress the occurrence of surface scratches of drawn tubes for example in the transportation thereof and that also can prevent fractures or the like in the working in a succeeding process. <P>SOLUTION: The drawing apparatus performs drawing of the tube stock by putting it through a dies 1, wherein the dies 1 are composed of a bearing section 3 which has a specific inside diameter and determines a working shape of the tube stock and an approach section 2 of which the inside diameter decreases from the entrance end of the tube stock for guiding it to the bearing section 3 toward the exit end of the tube stock. In the part of the dies in which the bearing section 3 and the approach section 2 are combined and with which the tube stock comes in contact during the drawing, there is installed at least in one place a circumferential projection 4 so that the inside diameter of the dies decreases discontinuously from the entrance end to the exit end of the tube stock. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drawing technique for a metal pipe, and more particularly to a drawing technique for a copper pipe used as a heat transfer pipe for an air conditioner or the like.

  For a drawn tube manufactured by drawing a tube through a die, high surface accuracy is required. For example, the inner surface shape of the die in a cross section parallel to the drawing axis is specified as a straight line. There has been disclosed a drawing apparatus configured by smoothly connecting curves having a radius of curvature (see Patent Document 1).

  However, when the drawn tube is transported after manufacturing, there is a problem that dent marks, scratches, etc. occur on the outer surface of the drawn tube and the surface accuracy deteriorates. Depending on the properties (length, width, depth, orientation, etc.) of these surface wrinkles, it is difficult to remove them even if the drawing tube is redrawn in the subsequent process. In some cases, an internal defect may occur due to entrapment.

  Therefore, if the vicinity of the outer surface of the pipe material can be worked and hardened to a certain degree or more during drawing, these wrinkles can be prevented or reduced to a level that can be removed by drawing again in a later process. It is possible to keep.

  However, when drawing is performed with a conventional drawing apparatus using a die 101 configured by smoothly connecting the approach portion 102 and the bearing portion 103 as shown in FIG. 6, only in the vicinity of the outer surface of the drawing tube. Since the entire tube is work hardened, there is a problem that breakage of the drawn tube is likely to occur due to a combination of increased processing load and embrittlement of the material in the subsequent drawing process, etc. .

  In particular, in the case of a material that is easily plastically deformed and excellent in lubricity, such as a thin-walled copper tube, the same degree of strain is generated on the outer surface and inner peripheral surface of the tube by drawing, and the tube It is known that the whole is work hardened.

On the other hand, in order to impart strain only to the vicinity of the outer surface of the tube material and to work harden only the vicinity of the outer surface, drawing can be performed without using lubricating oil, or a die having a rougher surface roughness than usual. Performing a drawing process using a wire has a problem that causes an increase in the drawing load and rough surface of the die, resulting in deterioration of surface accuracy and seizure.
JP 7-195115 A

  Therefore, the present invention solves the above problems, prevents or suppresses surface flaws during conveyance of the drawn tube, and prevents breakage and the like during processing in a subsequent process. An object of the present invention is to provide a pipe drawing apparatus and a method of manufacturing a drawn pipe.

  According to the first aspect of the present invention, there is provided a pipe drawing apparatus for drawing a pipe through a pipe, and the die has a constant inner diameter and determines a pipe shape outlet-side bearing portion that determines a processing shape of the pipe. An approach portion whose inner diameter is reduced from the tube material inlet side to the tube material outlet side for guiding the tube material to the bearing portion, and is a portion where the bearing portion and the approach portion are combined and during drawing. A circumferential protrusion or a circumferential step is provided in at least one portion where the tubular material comes into contact so that the inner diameter of the die is discontinuously reduced from the tubular material inlet side to the tubular material outlet side. This is a pipe material drawing device.

  According to a second aspect of the present invention, there is provided at least one circumferential portion at a location where the tubular material comes into contact during the drawing process, at a location closer to the tubular material inlet than the protrusion or the step provided on the die outlet side. The pipe material drawing apparatus according to claim 1, wherein a concave groove is provided.

  According to a third aspect of the present invention, there is provided a method of manufacturing a drawn pipe, wherein a drawn pipe is manufactured by drawing a pipe using the drawing apparatus according to the first or second aspect.

  According to the present invention, by providing a circumferential protrusion or step on the inner surface of the die that the tube material contacts during the drawing process, the strain is concentrated only in the vicinity of the outer surface of the tube material, and only in the vicinity of the outer surface. Can be hardened and the toughness of the entire drawn tube after processing can be maintained. As a result, it is possible to prevent or suppress the occurrence of surface flaws during conveyance of the drawn tube and to prevent breakage during processing in the subsequent process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1
FIG. 1 shows a cross section parallel to the drawing axis direction of a die of a pipe drawing apparatus according to Embodiment 1 of the present invention. The die 1 is usually held in a die case (not shown) and attached to the apparatus. The inner surface of the die 1 has an approach portion 2 on the tube material insertion side (hereinafter referred to as “tube material inlet side”) and a bearing portion 3 on the tube drawing side (hereinafter referred to as “tube material outlet side”). Further, the bearing portion 3 is provided with a circumferential protrusion 4.

  The approach part 2 is connected to the bearing part 2 with its inner diameter continuously reduced from the pipe inlet side toward the pipe outlet side, and guides the pipe material to the bearing part 2.

  The bearing portion 3 has a constant inner diameter and has a substantially cylindrical shape parallel to the drawing axis direction of the tube material. By passing the tube material guided from the approach portion 2 through the bearing portion 3, the bearing portion 3. The tube is deformed to the same thickness as the inner diameter, and the processed shape of the tube material is determined.

  The circumferential projection 4 is formed in a shape in which a cross-sectional shape parallel to the tube drawing axis direction projects in a semicircular shape from the bearing portion 3. For this reason, the inner diameter of the bearing portion 3 (that is, the inner diameter of the die 1) is discontinuously reduced from the tube material inlet side to the tube material outlet side at the bottom portion 4a of the protrusion 4 on the tube material inlet side. This discontinuous reduction in the inner diameter concentrates on the outer surface side of the pipe material and applies a local load to generate a large processing strain, so the outer surface side is processed more than the inner peripheral surface side and the center of the wall thickness. The degree of curing increases.

  Furthermore, since the skirt 4a of the protrusion 4 has a groove shape that is recessed from the periphery, it acts as a lubricating oil reservoir, and is strongly compressed compared to other approach parts 2 and bearing parts 3 that do not have the protrusion 4. A good lubrication state can be maintained even at the portion of the protrusion 4 that is to be diameter processed. As a result, an increase in load at the portion of the protrusion 4 can be suppressed, and the occurrence of seizure can be prevented. Further, even when metal powder is generated from the tube material during processing, the groove-shaped skirt 4a acts as a metal powder reservoir, and thus has an effect of preventing generation of wrinkles due to metal powder at the portion of the protrusion 4.

  The protrusion 4 preferably has a cross-sectional shape parallel to the tube drawing axis direction (that is, the center axis of the die) having no corners except for both skirts, and an arc or a curve with a smoothly changing curvature. As a result, breakage and wear of the protrusions 4 can be prevented, and the introduction of the lubricating oil can be satisfactorily performed at the portions of the protrusions 4, and an increase in load can be suppressed, and seizure can be reliably prevented.

The amount of change (d ₃ -d ₄ ) of the height of the protrusion 4, that is, the inner diameter of the die 1 (in this example, the inner diameter of the bearing portion 3) at the portion of the protrusion 4, is a raw pipe (pipe material before drawing) It is desirable that the thickness is 4 times or less, more preferably 2 times or less, particularly 1 time or less. If the height of the protrusion 4 is too high, a load is applied to the entire thickness of the tube material, and the effect of locally working and hardening the vicinity of the outer surface is reduced. This is because the possibility of excessive increase or seizure increases.

  The width of the protrusion 4, that is, the distance between both skirts of the protrusion 4 is preferably 1 time or more, more preferably 1.5 times or more, particularly 2 times or more the height of the protrusion 4. This is because if the width of the protrusion 4 is too small, the possibility that the protrusion 4 is broken increases.

[Embodiment 2]
FIG. 1 shows a cross section parallel to the drawing axis direction of a die of a pipe drawing apparatus according to Embodiment 2 of the present invention. Unlike the first embodiment, the protrusion 4 is provided on the approach portion 2. Of course, it is necessary to provide the protrusion 4 at a site where the pipe material contacts. In this case as well, it is clear that the same effects as those of the first embodiment can be obtained.

[Embodiment 3]
FIG. 3 shows a cross section parallel to the drawing axis direction of the die of the pipe drawing apparatus according to Embodiment 3 of the present invention. In the first embodiment, it is an example in which a circumferential concave groove 6 is further provided on the tube inlet side from the protrusion 4. Since lubricating oil and metal powder can also be held in the groove 6, a larger amount of lubricating oil and metal powder can be held than by holding only the skirt 4 a of the protrusion 4 of the first embodiment. Suppression of load increase, prevention of seizure, and prevention of wrinkles due to metal powder can be achieved.

[Embodiment 4]
FIG. 4 shows a cross section parallel to the drawing axis direction of the die of the pipe drawing apparatus according to Embodiment 4 of the present invention. In the third embodiment, a circumferential step 5 is provided instead of the protrusion 4. The step 5 is formed in a smooth shape in which the cross-sectional shape parallel to the tube drawing axis direction rises substantially perpendicularly from the bearing portion 3 and then moves horizontally through a ¼ arc-shaped curved portion. Therefore, the inner diameter of the bearing portion 3 (that is, the inner diameter of the die 1) is discontinuously reduced at the rising portion of the step 5, and an effect of locally work hardening the outer surface side as in the first embodiment can be obtained. . Furthermore, in this example, since the circumferential concave groove 6 is provided on the pipe material inlet side of the step 5, it is possible to ensure a high retaining function such as lubricating oil as in the third embodiment.

The amount of change (d ₃ -d ₅ ) of the inner diameter of the die 1 (in this example, the inner diameter of the bearing portion 3) at twice the height of the step, that is, the portion of the step 5, is the same as described in the first embodiment. For this reason, it is desirable that the thickness is 4 times or less, further 2 times or less, particularly 1 time or less of the wall thickness of the raw pipe (pipe material before drawing).

[Embodiment 5]
FIG. 5 shows a cross section parallel to the drawing axis direction of the die of the pipe drawing apparatus according to the fifth embodiment of the present invention. This is an example in which the die 1 is divided into an approach portion 2 and a bearing portion 3 and these are combined to form one die 1 and a circumferential protrusion 4 is provided on the bearing portion 3. As described above, by forming the member separately provided with the protrusion 4 and the member not provided with the protrusion 4, for example, even if the portion of the protrusion 4 is worn, it is necessary to replace the entire die 1. Since only the bearing portion 3 can be exchanged, the manufacturing cost of the die 1 can be greatly reduced.

[Modification]
In the said Embodiment 1-5, although the example which provided the protrusion 4 or the level | step difference 5 in only one place was shown, you may provide in two or more places. In this case, the approach portion 2 and the bearing portion 3 may be divided and provided at one or more locations, may be provided only at the approach portion, or may be provided at two locations or more only at the bearing portion 3.

  When two or more protrusions 4 and / or steps 5 are provided, only the protrusions 4 may be provided, only the steps 5 may be provided, or the protrusions 4 and the steps 5 may be used in combination.

  The concave groove 6 may be provided in any part on the pipe inlet side of the protrusion 3 or the step 4 as long as the pipe is in contact with the pipe during the drawing process. In order to achieve this, it is desirable to provide it as close as possible to the protrusion 3 or the step 4 as shown in FIGS.

  In the fourth embodiment, the example in which the step 5 and the concave groove 6 are provided at the same time is shown. However, when a sufficient amount of lubricating oil or the like can be held at the skirt of the step 5 without providing the concave groove 6, Only 5 may be provided.

  Moreover, as a pipe material which can apply this invention, a copper alloy pipe, a steel pipe, an aluminum pipe, an aluminum alloy pipe etc. can be illustrated other than a copper pipe.

  In order to confirm the effect of the present invention, only the shape of the inner surface (processed surface) of the die was changed, and the drawing process was performed under the following processing conditions.

(Processing conditions)
Base tube: Phosphorus deoxidized copper annealed material, outer diameter 10.0 mm, wall thickness: 0.30 mm
Dice: Approach half angle 20 degrees, bearing inner diameter 9.5mm
Raw tube drawing speed: 10 m / min
Lubricating oil: Uses processing outer surface oil

[Invention Example 1]
A semicircular circumferential protrusion having a radius of 0.2 mm in cross-sectional shape parallel to the tube drawing axis direction is formed on the bearing portion.

[Invention Example 2]
A circumferential step with a height of 0.2 mm is formed on the bearing.

[Invention Example 3]
A semicircular projection having a semicircular shape with a radius of 0.2 mm in cross section parallel to the tube drawing axis direction and a semicircular concave groove with a cross section having a depth of 0.4 mm on the tube material inlet side in the bearing portion Forming.

[Comparative example]
No protrusions or steps are formed on the approach part and bearing part.

(Properties of the drawn tube)
Drawing was performed using the dies of Invention Examples 1 to 3 and Comparative Example, and the Vickers hardness was measured for each of the outer surface and inner surface of each drawn tube obtained. Table 1 shows the values obtained by arithmetically averaging the measured values of the hardness at a plurality of points and rounding off to one decimal place. As is clear from the table, in the comparative example corresponding to the prior art, both the inner and outer surfaces of the pipe have the same hardness (HV80), whereas in the inventive examples 1 to 3, the hardness of the inner surface of the pipe is all. Compared with (HV80), the hardness of the outer surface of the tube was increased (HV100 to 110), and it was confirmed that work hardening progressed locally.

Further, in Invention Example 3, when the inner surface of the die was observed after the drawing process, it was confirmed that the lubricating oil was accumulated in the concave groove, and it was confirmed that the occurrence of seizure or the like due to running out of the lubricating oil could be prevented.

FIG. 3 is a cross-sectional view parallel to the drawing axis direction of the die of the pipe drawing apparatus according to the first embodiment. FIG. 6 is a cross-sectional view parallel to the drawing axis direction of a die of a pipe drawing apparatus according to a second embodiment. FIG. 6 is a cross-sectional view parallel to the drawing axis direction of a die of a pipe drawing apparatus according to a third embodiment. It is sectional drawing parallel to the drawing axial direction of the die | dye of the pipe material drawing processing apparatus based on Embodiment 4. FIG. FIG. 10 is a cross-sectional view parallel to the drawing axis direction of a die of a pipe drawing apparatus according to a fifth embodiment. It is sectional drawing parallel to the drawing axial direction of the dice | dies of the conventional pipe | tube drawing apparatus.

Explanation of symbols

1: Die 2: Approach part 3: Bearing part 4: Projection 4a: Bottom part 5: Step 6: Concave groove

Claims (3)

In the pipe drawing device that pulls through the pipe in the die,
The die has a constant inner diameter and determines the processing shape of the tube material. The bearing portion on the tube material outlet side, and the inner diameter decreases from the tube material inlet side for guiding the tube material to the bearing portion toward the tube material outlet side. And an approach part to
The inner diameter of the die is reduced discontinuously from the tube material inlet side to the tube material outlet side in at least one portion of the bearing portion and the approach portion that are in contact with the tube material during drawing. A pipe drawing apparatus characterized by having a circumferential protrusion or a circumferential step as described above.   2. At least one circumferential concave groove is provided at a position where the tube material comes into contact during the drawing process and at a position closer to the tube material inlet side than the protrusion or the step provided on the die outlet side. 2. The pipe material drawing apparatus according to 1. A method for producing a drawn tube, wherein a drawn tube is produced by drawing a pipe using the drawing device according to claim 1.

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