JP5430159B2 - Manufacturing method of different diameter steel pipe - Google Patents

Description

  The present invention includes, for example, a thick large-diameter portion that supports the steering on the driver side, a thin small-diameter portion that supports interior components on the passenger seat side, the small-diameter portion, and the large-diameter portion. A large-diameter portion with a large plate thickness, a small-diameter portion with a thin plate thickness, and a tapered portion that connects the small-diameter portion and the large-diameter portion, such as a reinforcement for an instrument panel having a tapered portion to be connected. And manufacturing a different-diameter steel pipe provided with a centering process.

As a reinforcing member for an instrument panel of an automobile, for example, as shown in FIG. 1, a large-diameter portion 2 with a large plate thickness and a small-diameter portion 3 with a thin plate thickness are arranged side by side in the axial direction. Different diameter steel pipes 1 are attached to the body of the automobile. In the figure, 4 is a tapered portion.
The large-diameter part that has sufficient rigidity due to its large cross-sectional area is fitted with heavy objects such as automobile steering supports and speedometers, and the small-diameter part that has relatively low rigidity due to its small cross-sectional area. Lightweight interior parts such as radios can be attached. Moreover, the connection part of a large diameter part and a small diameter part is made into the taper shape instead of the step part which bent | curved linearly on the relationship of intensity | strength.

As such a different diameter steel pipe, normally, a large-diameter portion having a large thickness and a small-diameter portion having a small thickness and a tapered portion connecting them are individually manufactured, and then these members are combined and welded together. It was. Alternatively, the large-diameter portion with a large plate thickness is reduced in diameter, and the small-diameter portion with a thin plate thickness is inserted and welded.
However, in that case, the number of parts increases, so that each member is overlapped and welded by a certain length, so that the weight becomes heavier by the overlapped portion and the weight of the automobile cannot be reduced, and the welding process is reduced. Therefore, there is a problem that the process cost becomes high.

Therefore, in order to omit the welding process for cost reduction, a method has been proposed in which a single steel pipe is partially processed so as to have different cross-sectional areas in the longitudinal direction of the steel pipe.
For example, in Patent Document 1, a large-diameter portion front stage portion that substantially matches the plate thickness and outer diameter of the large-diameter portion, and a taper connected to the large-diameter portion pre-stage portion, the large-diameter portion plate A thick portion pre-stage portion that substantially matches the thickness, and an intermediate portion that is connected to the thick portion pre-stage portion and substantially matches the outer diameter of the small-diameter portion, the intermediate portion being the thick-wall pre-stage portion A hollow stepped portion having a gradually changing portion pre-stage portion that gradually decreases from the plate thickness of the portion, and a small-diameter pre-stage portion that is connected to the pre-gradual portion pre-stage portion and substantially matches the plate thickness of the small diameter portion. Form a pipe, and then apply pressure from the inside to the outside of the gradually changing portion and the thick portion before the portion of the hollow stepped pipe to substantially match the plate thickness of the large diameter portion. Forming a gradually changing portion that gradually decreases from a thickness of the thick portion and a thickness of the thick portion to a thickness substantially equal to a thickness of the small diameter portion, and the taper portion That methods have been proposed.

  In this document, a thick-walled portion and a thick-walled portion that substantially match the plate thickness of the large-diameter portion by applying pressure from the inside to the outside of the step portion before the gradually changing portion and the thick-walled portion preceding step portion of the hollow stepped pipe. In order to form a gradually changing portion that gradually decreases from a plate thickness of the portion to a plate thickness that substantially matches the plate thickness of the small diameter portion to form a tapered portion, a hole portion having the same shape as the outer peripheral surface shape of the desired tapered portion is formed. Use the dice you have. And in the state where the step portion of the hollow stepped pipe inserted through the die and the step portion of the thick wall portion are positioned in the hole portion, using the high pressure fluid The part in front of the thick part is inflated.

  Further, in Patent Document 2, a step of preparing a die having a hole having a small outer dimension with respect to a cross section of a hollow material made of metal, and an end of the hollow material are gripped by a gripping body, and the hollow material is A step of drawing by pulling with the gripping body through the hole portion, and after drawing the hollow material to a predetermined length through the die, the hollow material is pushed back in a direction opposite to the drawing direction, A step of forming in the hollow material a portion having a cross-sectional portion having a small outer dimension with respect to a cross section of the hollow material before passing through a die, and a portion not performing the drawing process in the hollow material and the drawing process. There has been proposed a method including a step of performing a swaging process on a stepped portion generated between the stepped portion and the stepped portion.

Japanese Patent No. 3736865 JP-A-5-293535

  According to the said patent document 1, the pipe with a hollow step is manufactured by utilization of the core drawing process. However, it is difficult to obtain a different-diameter steel pipe having a large outer diameter change or a large plate thickness change by a single process by using a steel pipe that is not excellent in workability as a raw material. Therefore, it is manufactured through a plurality of manufacturing steps including a step of reducing the diameter of the steel pipe end, a step of centering to a predetermined length by a mold arranged inside and outside the steel pipe, and a step of correcting the shape of the tapered portion. ing. However, since these are independent processes, the work efficiency is poor and the manufacturing cost is increased.

  Patent Document 2 proposes a method of manufacturing a different diameter pipe using an aluminum pipe. According to this document, a manufacturing method is proposed in which two stages of independent centering are performed, and then the tapered portion is swaged. However, since this method is also an independent process, as in Patent Document 1, the work efficiency is poor, and it has been a factor that increases the manufacturing cost.

  As a method of manufacturing a steel pipe having a relatively long processed portion, the centering method described in Patent Documents 1 and 2 is optimal from the viewpoint of easy control of the outer diameter and the plate thickness. It is. In particular, when using ERW steel pipes made of steel materials, it is easy to secure the load necessary for processing and for the purpose of correcting the bending of the processed part due to the difference in strength between the base metal part and the welded part. However, it is preferable to employ a centering method in which the material is pulled from the exit side of the processing.

However, since all of the conventional methods require a plurality of independent processes, there is a chronic problem that the work efficiency is low and the manufacturing cost is high, and the handling of materials between processes is also increased. For this reason, there was a problem that scratches on the steel pipe were likely to occur.
The present invention has been devised in order to solve such a problem, and an instrument having different diameters and thicknesses in the axial direction by performing multi-stage diameter reduction processing at the time of one-pass centering processing. Provided is a method for efficiently producing a different diameter steel pipe used for a reinforcement for a panel.

In order to achieve the object, the manufacturing method of the different diameter steel pipe according to the present invention uses a die having a hole whose inner diameter is smaller than the outer diameter of the raw pipe, and a plug inserted into the steel pipe to control the plate thickness. when manufacturing the different-diameter steel tube with a tapered portion connecting said large diameter portion and the small diameter portion from one of the steel pipe by core pull machining a thick large-diameter portion and the plate thickness of thin small diameter portion of the thickness of an object The outer diameter of the small-diameter steel pipe and the die with the same minimum inner diameter and taper angle as the taper angle are set as the final stage, and before that, the minimum inner diameter decreases from the previous stage toward the final stage, and the desired variant One or more dies having the same taper angle as that of the steel pipe are continuously arranged, and the parts other than the final stage die are arranged as split dies, and the workpiece pipe passes through the dies of each stage and at the same time other than the final stage. Divide the dice in order from the previous stage Then, the head cone shape part having the same taper angle as that of the target different-diameter steel pipe and the outer diameter of the small-diameter part of the target different-diameter steel pipe in front thereof are subtracted by twice the thickness of the small-diameter part. A plug having an outer diameter cylindrical portion is arranged in a final stage die and pulled out .

  According to the method of the present invention, in a method of manufacturing a different diameter steel pipe such as a reinforcement for an instrument panel that usually requires two or more steps, a plurality of processes can be performed simultaneously through one drawing step. Since it can obtain the target different diameter steel pipe, it can be manufactured more efficiently than the conventional method.

FIG. 1 is an overall view of different diameter steel pipes having different cross-sectional areas in the longitudinal direction. FIG. 2 is a diagram showing a centering process in the two-stage molding. However, (a) is when the blank tube is inserted (b) is the state where the plug is inserted (c) is the state during the centering process (d) is the state after the completion of the first stage processing (e) is the end of the second stage processing Shown later. FIG. 3 is a diagram showing a centering process in three-stage molding. However, (a) shows the state after the completion of the first stage of processing (b) shows the state after the end of the second stage of processing (c) shows the state after the end of the third stage of processing. FIG. 4 is a diagram showing the transition of the outer diameter and the plate thickness of the different diameter steel pipe in the example.

In the case of coreing a steel base tube, as a result of various investigations, the diameter of the outer diameter is limited to about 25% of the outer diameter by one processing due to the hardness of the material. For this reason, when the difference in the outer diameter of the different diameter steel pipe exceeds 25%, two or more forming steps are required, which is a cause of a decrease in productivity.
Therefore, in the case of the present invention, when the degree of processing is high and two or more forming steps are required, a plurality of dies are arranged in series along the processing direction. For this reason, a multi-stage centering process can be performed by a single centering process, and a different-diameter steel pipe having a target shape can be manufactured.

When forming with all the dies arranged in multiple stages, different diameter parts for each forming die, that is, a plurality of taper parts, are formed in one steel pipe. Then, the shape of the tapered portion can be corrected by forming only with the final stage die. Of course, when a plurality of taper portions may exist as a product, it may be formed with all dies from start to finish.
Hereinafter, the method of the present invention will be specifically described with reference to the drawings.

  In the method of the present invention, as shown in FIG. 2, an apparatus in which a first-stage die 7, a second-stage die 8, and a plug 9 are arranged is used. In this apparatus, the dice are arranged in two stages, but it goes without saying that the dice may be arranged in three stages or more as shown in FIG. The apparatus includes a pushing device 10 for pushing the workpiece tube 14 into the die and a pulling device 12 for pulling the tube tip 11 pushed to the tip of the die in the first step.

  In FIG. 2, the first-stage die 7 is a split die, and has a die taper 13 having an outer diameter substantially the same as the outer diameter of the pipe to be reduced and the same taper angle as that of the different diameter steel pipe to be obtained. And having a through hole having the same diameter as the outer diameter of the die taper 13 of the second-stage die 8. The second-stage die 8 has a die taper 13 having the same outer diameter as the through-hole diameter of the first-stage die 7 and the same taper angle as that of the different diameter steel pipe to be obtained. It has a through hole with the same diameter as the diameter of the small diameter portion of the diameter steel pipe. Further, the plug 9 is provided in front of the truncated cone-shaped portion having the same taper angle as that of the different diameter steel pipe to be obtained. A cylindrical portion having an outer diameter obtained by subtracting the double portion and a cylindrical portion having an outer diameter obtained by subtracting twice the raw tube plate thickness from the through-hole diameter of the first-stage die 7 are provided behind the cylindrical portion.

Next, the aspect which performs the different diameter process from which a diameter and plate | board thickness differ in an axial direction with respect to a to-be-formed steel pipe with the above apparatuses is demonstrated.
As shown in FIG. 2A, the workpiece pipe 14 is set on the first-stage die 7 and the second-stage die 8 arranged in series, and the pushing device 10 causes the pipe tip 11 of the elementary pipe 14 to be Push it in until it protrudes from the step die 8. Subsequently, the pushing device 10 is removed, and the plug 9 is inserted into the workpiece tube 14 (FIG. 2B).

Thereafter, as shown in FIG. 2 (c), the tube tip 11 protruding from the second-stage die is grasped by the pulling device 12 and pulled. After pulling for a predetermined length (L in the figure), as shown in FIG. 2D, the first-stage die 7 is divided and removed from the workpiece tube.
After that, it is further pulled and the centering process is continued only with the second-stage die 8. When the corner A of the tapered portion formed by the first-stage die 7 shown in FIG. 2D coincides with the corner B of the tapered portion formed by the second-stage die 8, the pulling operation is finished ( 2 (e)), a different diameter steel pipe 1 is obtained.

  Next, the procedure in the case of molding in three steps will be described with reference to FIG. Of the first stage die 7, the second stage die 8, and the third stage die 15 arranged in series in (a), the first and second stages are divided dies. The workpiece tube 14 is inserted into these, and the plug 9 is inserted into the workpiece tube 14 and formed into a predetermined length by the tension device 12 (FIG. 3A).

Thereafter, as shown in FIG. 3B, the first-stage die 7 is divided and removed from the workpiece tube.
Thereafter, further pulling is performed, and the centering process is continued with the second-stage die 8 and the third-stage die. Then, molding is performed until the corner A of the tapered portion formed by the first-stage die 7 shown in FIG. 3A coincides with the corner B of the tapered portion formed by the second-stage die 8.

Further, as shown in FIG. 3C, the second-stage die 8 is also divided and removed from the workpiece tube.
After that, it is further pulled and the centering process is continued only with the third-stage die 15. Then, the taper portion corner C formed by the second-stage die 8 shown in FIG. 3B is molded until the corner D of the taper-portion portion formed by the third-stage die 15 is formed. A steel pipe 1 is obtained.

A steel pipe having an outer diameter of 70 mm, a plate thickness of 2.3 mm, and a total length of 2 m and a tensile strength of 270 N / mm ² is used as a base pipe, and a core of a different diameter steel pipe having an outer diameter of 45 mm and a plate thickness of 1.6 mm. Here are some examples of drawing.
The length of the centering process was 1 m, the inclination angle 6 of the taper portion 4 shown in FIG. 1 was 7 °, and the inclination length 5 was 100 mm. That is, the large diameter portion 2 of the different diameter steel pipe 1 to be formed has an outer diameter of 70 mm, a plate thickness of 2.3 mm, and a length of 1 m, and the small diameter portion 3 has an outer diameter of 45 mm, a plate thickness of 1.6 mm, and a length. The taper portion 4 has an inclination angle 6 of 7 ° and an inclination length 5 of 100 mm.
Since the extra material is elongated in the longitudinal direction by reducing the outer diameter and reducing the plate thickness in the centering process, it is longer than the raw tube after the process, and in this example, it is extended by about 100 mm.

The die for the centering process was a two-stage process in order to reduce the diameter of the core pipe by more than 25% of the outer diameter. As shown in FIG. 2, two types of dies 7 and 8 were prepared. In the first stage die 7, the outer diameter is reduced from 70 mm to 60 mm (= (the amount of diameter reduction / outer diameter of the pipe before diameter reduction) × 100%) 15%, and the plug 9 inserted in the pipe is used. The plate thickness was 1.9 mm. In the second-stage die 8, the outer diameter was reduced to 25% from 60 mm to 45 mm, the die and the plug 9 inserted in the tube were used, and the plate thickness was 1.6 mm.
The dies 7 and 8 have a hole portion having a diameter of approximately 100 mm and substantially the same diameter as the outer diameter of the tube to be reduced, and the same inclination angle 6 as the predetermined different diameter steel pipe 1 on the tube insertion side continuously from the hole portion. A die taper 13 having an inclination length of 5 was provided. That is, the diameter of the hole of the first-stage die 7 was 60 mm, and the diameter of the hole of the second-stage die 8 was 45 mm. At this time, the clearance C ₁ between the first-stage die 7 and the plug 9 was 1.9 mm, and the clearance C ₂ between the second-stage die 8 and the plug 9 was 1.6 mm. Since the thickness of the taper portion 4 is greatly affected by the position of the plug 9 in the longitudinal direction, it is pre-adjusted so that the corner point of the second stage die 8 and the corner point of the plug 9 are the same position in the longitudinal direction. did.

In the centering process, first, as shown in FIG. 2A, the raw tube was pushed into the dies 7 and 8 without using the plug, and the steel tube tip 11 was protruded from the rear surface of the die 8 by about 50 mm. Next, the plug 9 was set at a predetermined position in the steel pipe (FIG. 2 (b)), the tip 11 was chucked on the pulling device 12 on the outlet side, and the pipe was pulled out (FIG. 2 (c)).
When the processing length L reaches 1 m, the first-stage die 7 is opened as shown in FIG. Further, the core A was processed until the corner A point of the material shown in FIG. 2D reached the corner B point of the die 8 (FIG. 2E). At this time, the drawing speed of the tube was 0.25 m / s.
As a result of performing the centering process, as shown in FIG. 4, the pipe outer diameter and the plate thickness distribution were almost predetermined values. Further, the time from the start of insertion of the raw tube 14 into the die 7 to the discharge of the different diameter steel pipe 1 was 20 seconds.

Comparative example

In addition, as a comparative example, the production efficiency was compared with the time from the start of insertion of the raw pipe into the die until the discharge of the different diameter steel pipe 1 instead of the two-stage continuous coreing process. In this case, the specifications of the core pipe and the different diameter steel pipe 1, the specifications of the dies 7, 8 and the plug 9 and the drawing speed in the core drawing process were the same as those in the example. As a result of performing the centering process, the same pipe outer diameter and plate thickness distribution as in the case of the example were obtained, but the time from the start of inserting the raw pipe 14 into the die 7 to the dispensing of the different diameter steel pipe 1 is It was 40 seconds, which was a result of relatively poor production efficiency.
The cause of the difference in processing time between the inventive example and the comparative example is whether or not there is a trouble of pushing back the steel pipe after the first stage of processing is finished and extracting it from the mold and inserting it into the second stage of the mold.

1: Different diameter steel pipe 2: Large diameter part 3: Small diameter part 4: Tapered part
5: Inclination length 6: Inclination angle 7: First stage die
8: Second stage die 9: Plug 10: Pushing device 11: Pipe tip
12: Tensile device 13: Die taper part 14: Base pipe 15: Third stage die

Claims (1)

A die having a hole whose inner diameter is smaller than the outer diameter of the raw pipe, and a large-diameter portion having a thick plate thickness from one steel pipe by a centering process using a plug inserted into the steel pipe to control the plate thickness. When manufacturing a different diameter steel pipe having a small diameter portion with a thin plate thickness and a tapered portion connecting the large diameter portion and the small diameter portion, the minimum inner diameter is the same as the outer diameter and taper angle of the small diameter portion of the target different diameter steel pipe. A die having a taper angle is used as the final stage, and before that, one or more dies having a taper angle equal to the taper angle of the target deformed steel pipe and having the smallest inner diameter from the previous stage toward the final stage are continuously provided. In addition, the die other than the final stage die is arranged as a split die, and at the same time as the workpiece pipe passes through each stage die, the non-final stage die is sequentially divided from the previous stage to remove the target different diameter steel pipe. Has the same taper angle as the taper angle A plug having a head cone shape portion and a cylindrical portion having an outer diameter obtained by subtracting twice the thickness of the small diameter portion from the small diameter outer diameter of the target different diameter steel pipe is disposed in the final stage die. A method for producing a steel pipe of different diameter, characterized by being pulled out .

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