JP2019098352A - Method for manufacturing tube with hollow step - Google Patents

Abstract

To provide a method for manufacturing a tube with a hollow step that can manufacture the tube with a hollow step easier than before, and can achieve characteristics of strength and dimension accuracy which are equal to or higher than conventional characteristics thereof.SOLUTION: In the method for manufacturing a tube with a hollow step, an original tube 10 is prepared, and a drawing device 5 comprising a large-diameter die 51 and a small-diameter die 52 which are arranged on a coaxial wire is used. A two-step simultaneous drawing processing is performed in which a tip of the original tube 10 is processed so that an outer diameter of the tip becomes smaller than a small-diameter part 12 to form a mouth-forming part 15 and the large-diameter die 51 and the small-diameter die 52 are sequentially passed, with the mouth-forming part 15 put in the lead, and the drawing processing is stopped before the whole length of the original pipe 10 passes through the small-diameter die 52. This can achieve the small-diameter part 12 formed by passing the large-diameter die 51 and the small-diameter die 52, a large-diameter part 11 formed just by passing the large-diameter die 51, and a boundary part 13, interposed between the small-diameter part 12 and the large-diameter part 11, which is made of a part which is being reduced in a diameter at an entry side of the small-diameter die 52.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a hollow stepped tube that can be used, for example, for instrument panel reinforcement in an automobile.

  In recent years, weight reduction of transport devices such as automobiles has been required from the viewpoint of environmental protection. In order to achieve this weight reduction, aluminum alloys, which are lighter than steel materials, are often used as materials for structures. In the case where an aluminum alloy is used as a structure, in one structure, different strength may be required depending on the part, or changing of dimensions such as an outer diameter in the longitudinal direction may be required.

  For example, in Patent Document 1, it is proposed that, in instrumental reinforcement, parts having different shapes in the longitudinal direction be configured by bolting hollow extruded materials having different cross-sectional shapes.

JP 2001-253368 A

  However, as in Patent Document 1, it is necessary to prepare two types of hollow materials having different diameters in the manufacturing method in which hollow materials having different cross-sectional shapes, that is, a large diameter hollow material and a small diameter hollow material are combined. In addition, although a small diameter hollow material is inserted into the large diameter hollow material, and a bolt is penetrated and connected in an overlapping portion, in this configuration, the weight increase due to the bolt occurs, and as a material The benefits of using an aluminum alloy are reduced. In addition, since the hollow members are separate bodies only by mechanically integrating the bolted structure, the stability of the integration remains uneasy due to loosening of the bolts and the like. In addition, it is conceivable to integrate hollow materials having different diameters by welding, but also in this case, there is no difference in that two types of hollow materials having different diameters need to be prepared, and further, an increase in the number of welding processes In addition, the influence of heat during welding may make it difficult to maintain dimensional accuracy.

  The present invention has been made in view of the above background, and it is possible to manufacture a hollow stepped tube more easily than in the prior art, and also to provide the same level of strength and dimensional accuracy as the prior art. It provides a method of manufacturing a tube.

One aspect of the present invention is a hollow step having a large diameter portion, a small diameter portion having an outer diameter smaller than the large diameter portion, and a boundary portion interposed therebetween, which is a hollow tube integrally A method of manufacturing a tube,
Prepare a hollow tube whose outer diameter is larger than the above-mentioned large diameter portion,
Using a drawing apparatus including a large diameter die having a hole diameter corresponding to the outer diameter of the large diameter portion and a small diameter die having a hole diameter corresponding to the outer diameter of the small diameter portion,
Forming the mouthpiece by processing the end of the raw tube so as to have an outer diameter smaller than that of the small diameter portion;
Two-step simultaneous drawing processing in which the large diameter die and the small diameter die are sequentially passed with the attachment portion at the top, and the drawing process is stopped before the entire length of the raw tube passes the small diameter die And
The small diameter portion formed by passing the large diameter die and the small diameter die, the large diameter portion formed by passing only the large diameter die, and the diameter reduction halfway on the entry side of the small diameter die Obtaining the above-mentioned boundary part interposed between the above-mentioned narrow diameter part and the above-mentioned wide diameter part consisting of a part of a state
It is in the manufacturing method of the hollow stepped tube.

  In the method of manufacturing the hollow stepped tube, the two-stage simultaneous drawing process is performed using a drawing apparatus provided with the large diameter die and the small diameter die, and as described above, the whole length of the raw tube is a small diameter die Stop this drawing process before passing through. Thus, it is possible to form the narrow diameter portion formed by passing the large diameter die and the small diameter die, and the large diameter portion formed by passing only the large diameter die, and the entry side of the small diameter die The boundary part which consists of a part of the state in the middle of diameter-reduction in in can be formed. Then, a hollow stepped tube in which the large diameter portion and the small diameter portion are integrally connected can be obtained by this boundary portion. That is, a hollow stepped tube can be formed from one raw tube only through one step of two-stage simultaneous drawing processing. Therefore, it is not necessary to prepare two types of materials, a raw tube for the large diameter part and a raw tube for the small diameter part, and it is sufficient to prepare only one kind of raw pipe, and the hollow step is easier than before. It is possible to produce a tube.

  The small diameter portion is formed through two drawing processes using the large diameter die and the small diameter die. Therefore, the diameter can be reduced to a size that is difficult in one molding, and it becomes possible to cope with wider applications.

  Not only the above-mentioned small diameter portion but also the large diameter portion is subjected to drawing processing. Therefore, the improvement effect of the dimensional accuracy by drawing process can be acquired in both site | parts. Furthermore, the strength improvement effect is also obtained by work hardening by the drawing process, and it becomes possible to adjust the strength by setting the degree of processing at the time of the drawing process.

  As described above, according to the above-described method for manufacturing a hollow stepped tube, a hollow stepped tube can be manufactured more easily than in the prior art, and the same strength and dimensional accuracy as those in the conventional hollow or more can be obtained. A stepped tube can be obtained.

In the embodiment, (a) a state when inserting the mouthpiece immediately before the start of the drawing process into the large diameter die, (b) a state when the forming of the small diameter part is started, (c) a state when the drawing process is completed, (D) Explanatory drawing which each shows the obtained hollow stepped tube.

  Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment, It can implement in a various aspect in the range which does not deviate from the summary of this invention.

  The cross-sectional shapes of the large diameter portion and the small diameter portion in the hollow stepped tube can adopt various shapes which can be drawn out, such as a circular shape or a polygonal shape, but the circular shape is particularly preferable. When the cross-sectional shape of the large diameter portion and the small diameter portion is circular (ring shape), bending rigidity from all directions can be enhanced, and molding is easier than in the case of other shapes. Further, by providing a flat surface on the side surface, connection with the front and rear parts may be facilitated, so the cross-sectional shape can be appropriately selected according to the required quality.

  The boundary portion formed between the large diameter portion and the small diameter portion is formed into a shape corresponding to the hole shape in the axial direction of the small diameter die. The axial hole shape of the die may be tapered or arc-shaped, but the external shape of the boundary can be controlled by selecting the shape.

  As the raw pipe, for example, an aluminum alloy pipe manufactured by extrusion processing can be used. Various known methods can be applied as a method of manufacturing the raw pipe. In addition, it is necessary to select the raw tube of the outer diameter larger than the outer diameter of the large diameter part of the hollow stepped tube to be obtained.

  As described above, as a drawing apparatus for drawing an element tube, a large diameter die having a hole diameter corresponding to the outer diameter of the large diameter portion and a small diameter die having a hole diameter corresponding to the outer diameter of the small diameter portion And a drawing apparatus in which both are arranged coaxially. The optimum range of the distance between the large diameter die and the small diameter die differs depending on the size of the hollow stepped tube to be obtained. At least the distance between the two dies must be equal to or greater than the length of the large diameter portion of the hollow stepped tube to be obtained. It is also conceivable to arrange the large diameter die and the small diameter die so as to be relatively movable and to change the above-mentioned interval, but also in this case, the length of the large diameter portion is longer than the length of the large diameter portion It is necessary to set a distance of

  In consideration of the processing stability, it is most preferable to set an interval at which the drawing process can be finished immediately after the full length of the blank passes through the large diameter die. That is, it is preferable to set the gap to such an extent that a slight allowance is added to the length of the large diameter portion of the hollow stepped tube to be obtained.

  While the drawing process is simultaneously performed by both the large diameter die and the small diameter die, the relatively stable processing state can be maintained, but after the rear end of the raw tube passes the large diameter die, the drawing operation can be performed with only the small diameter die Is not stable because there is nothing to support the large diameter part. Therefore, as described above, it is preferable to finish the drawing process immediately after the full length of the blank passes through the large diameter die. In addition, it is possible to finish drawing while leaving the rear end of the raw pipe on the entrance side of the large diameter die, but in this case, it is difficult to take out the hollow stepped pipe after forming from the drawing machine. Not only because the material yield also decreases.

  For example, the distance between the large diameter die and the small diameter die is preferably in the range of 600 mm to 1000 mm. In consideration of applications such as instrument panel reinforcement, which will be described later, a stable processing state can be ensured while securing the required lengths of the large diameter portion and the small diameter portion by setting the intervals within the above specific range. can do.

  When the raw pipe is processed using the drawing apparatus, the tip end of the raw pipe is processed to have an outer diameter smaller than that of the small diameter portion to form a mouthpiece. Specifically, the tip end of the raw tube is crushed so as to reduce its diameter, and a fitting portion is provided so that it can be clamped by a chuck that applies a pulling force. Then, a two-stage simultaneous drawing process in which the large diameter die and the small diameter die are sequentially passed is performed with the attachment portion at the top.

  The timing at which the mouthpiece is clamped by the chuck can be either before or after the mouthpiece passes through the large diameter die. Also, move the large diameter die and the small diameter die relatively movable, and at the start of the drawing, reduce the distance between the large diameter die and the small diameter die, and pass the small diameter die from the beginning It is also possible to use a method in which the attachment portion is clamped by a chuck and the distance between the large diameter die and the small diameter die is moved to a predetermined distance with the start of the drawing process.

  It is preferable to supply a drawn oil to the material on the inlet side of each of the large diameter die and the small diameter die. The drawn oil preferably has a viscosity of about 200 to 300 cst. By selecting a drawing oil in this viscosity range, it is possible to appropriately supply the material in the processing hole of the die in a state of being supplied to the material, processing at a high processing degree becomes easy to be performed, and also to prevent seizure due to lack of oil. Connect.

  It is preferable that the drawing by the small diameter die be performed by inserting and arranging a plug for controlling the inner diameter of the small diameter portion in the hollow tube. Although the insertion arrangement of the plug is not an essential requirement, by doing this, effects such as the stability improvement of the inner surface shape of the obtained small diameter portion and the accuracy improvement of the inner diameter can be obtained.

  As a plug to be used, a plug may be fixed by a rod as used in a usual drawing process, or a floating plug without a rod may be used. When a floating plug is used, the drawing of the raw tube is temporarily stopped immediately before the start of processing by the small diameter die, and after inserting and arranging the floating plug so that the plug is stably positioned at the processing portion of the small diameter die It is also possible to squeeze the outer peripheral surface of the raw tube processed into a part slightly inward and fix the plug position before the small diameter die and then start the drawing operation with the small diameter die.

  The hollow stepped tube is preferably for instrument panel reinforcement. As instrument panel reinforcements for automobiles, as described in the above-mentioned Patent Document 1, they are disposed along the width direction of the vehicle body inside the dashboard of the automobile, and various steering shafts, The mounting brackets for supporting instruments, air conditioners, air bags, etc. are fixed. And, generally, the instrument panel reinforcement is configured to have a large diameter tube on the driver side and a small diameter tube located on the front passenger seat side. Therefore, the hollow stepped tube integrally provided with the large diameter portion and the small diameter portion and the boundary portion interposed between them manufactured by the above-described manufacturing method may be applied to instrument panel reinforcement it can.

  And, the instrument panel reinforcement consisting of the hollow stepped tube manufactured by the above manufacturing method comprises one piece of parts manufactured from one raw pipe, and the large diameter portion, the boundary portion and the small diameter portion Is completely integrated. Therefore, higher structural stability can be easily secured as compared to the case where the large diameter portion and the small diameter portion are connected by bolting or welding. Further, since both the large diameter portion and the small diameter portion are drawn, the outer diameter dimension accuracy is very high, and can be suitably used as an automobile part. In addition, the strength characteristics required for the large diameter portion and the small diameter portion are adjusted relatively by adjusting the dimensions of the raw pipe, the hole diameter of the large diameter die and the small diameter die, and the like and adjusting the processing degree of each portion. It can be easily coped with.

  It is preferable to perform the drawing process by the said large diameter dice | dies in the range of a 5-10% cross-section reduction rate. If the reduction in area in drawing by a large diameter die is less than 5%, there is a possibility that sufficient working hardness can not be obtained. On the other hand, when the cross-sectional reduction rate in drawing by a large diameter die exceeds 10%, when drawing processing by a small diameter die, there is a possibility that the total cross-section reduction rate becomes large and the material breaks in the middle of processing.

  It is preferable that the drawing process by the small diameter die is performed in the range of the reduction in area where the total reduction in area of the large diameter die and the small diameter die is 40 to 60%. In the case of a reduction in area where the reduction in area by drawing with a small diameter die is less than 40%, the reduction in area of the small diameter portion finally obtained is low. If the cross-sectional area is smaller than the large diameter portion, the weight reduction effect by providing the small diameter portion may not be obtained sufficiently. On the other hand, if the reduction in area in drawing by a small diameter die exceeds 60%, the material may break in the process of processing exceeding the processing limit.

The outer diameter D ₀ and the outer diameter D ₂ and the thickness t ₀ and the thickness t ₂ of the small-diameter portion of the blank tube of the small-diameter portion of the blank tube is 40 <[1- {D _{² 2} - ( It is desirable that D ₂ −2 × t ₂ ) ² } / {D ₀ ² − (D ₀ −2 × t ₀ ) ² }] × 100 <60. If it is out of this range, there is a risk that the drawing out may occur.

  The material of the raw pipe is not particularly limited, but in consideration of securing processability and predetermined strength, it is preferable to use a 3000 series, 5000 series or 6000 series aluminum alloy.

  With an alloy such as 6000 series that can obtain strength by heat treatment, the hollow stepped tube after drawing may be subjected to aging treatment (heat treatment). As an aging treatment, it can carry out on the conditions hold | maintained at the temperature of 180 degreeC-220 degreeC for 1 to 4 hours, for example. In this case, when there is a demand for strength that the difference in strength due to work hardening of the large diameter portion and the small diameter portion is small, this can be coped with by performing the aging treatment. For example, when the difference in area reduction rate between the large diameter portion and the small diameter portion is 40%, the strength difference due to work hardening may reach about 25 Hv, but by subjecting this to an aging treatment, the strength difference is 10 Hv or less. can do. That is, even if there is a processing history in which the cross-sectional reduction rate is different in the longitudinal direction, it is possible to obtain a hollow stepped tube having substantially the same strength in the entire length by adding heat treatment. In this case, when machining the hollow stepped tube, there is an advantage that the same processing can be easily performed regardless of the part.

  In the case of using a 3000 or 5000 series alloy, as described above, the degree of processing may be adjusted by setting the outer diameter of the blank and the hole diameter of the large diameter die and the small diameter die to adjust the strength of each part. It is possible.

  The Example concerning the manufacturing method of the said hollow stepped tube is described. In this example, as shown in FIG. 1D, the large diameter portion 11, the small diameter portion 12 having a smaller outer diameter than the large diameter portion 11, and the boundary portion 13 interposed therebetween are integrally provided. The hollow stepped tube 1 which is a hollow tube is manufactured.

  As a drawing apparatus, as shown in FIGS. 1A to 1C, a large diameter die 51 having a hole diameter corresponding to the outer diameter φ70 mm of the large diameter portion 11 and a hole diameter corresponding to the outer diameter φ55 mm of the small diameter portion 12 A drawing and drawing apparatus 5 is used which is provided on a coaxial line with a small diameter die 52 having a diameter D and a gap D (in this example, D = 600 mm in this example) equal to or greater than the desired length of the large diameter portion 11.

  Then, first, a hollow extruded material made of an aluminum alloy classified by material and quality shown in Table 1 was prepared as the raw tube 10. The dimensions of the raw pipe (hollow extruded material) 10 are a cylindrical pipe having an outer diameter of 76 mm, a plate thickness of 2.0 mm, and a length of 1800 mm, and having a circular cross-sectional shape.

  Next, the tip of each raw tube 10 is processed to have an outer diameter smaller than that of the small diameter portion 12 to form the mouthing portion 15. In this example, a portion having a length of about 200 mm at the tip end is contracted to form a mouthpiece part 15 until the outer diameter becomes about φ30 mm.

  Then, as shown in FIGS. 1A to 1C, a two-step simultaneous drawing process in which the large diameter die 51 and the small diameter die 52 are sequentially passed is performed with the attachment portion 15 at the top. At this time, as shown in the figure, the plug 6 connected to the tip of the rod 61 is inserted into the inside from the rear end opening of the raw tube 10 and disposed on the entry side of the small diameter die 52. The plug 6 has a tip outer diameter of 51.2 mm, and the target value of the thickness of the small diameter portion 12 is 1.4 mm.

  In the two-step simultaneous drawing process, the drawing process is stopped before the entire length of the raw pipe 10 passes the small diameter die 52. In this example, the rear end 19 of the raw pipe 10 stops immediately after passing through the large diameter die 51. Thus, the hollow stepped tube 1 shown in FIG. 1 (d) is obtained. In the present example, no additional heat treatment was performed on all the hollow stepped tubes 1.

  The surface hardness (Vickers hardness) of the large diameter portion 11 and the small diameter portion 12 was measured for all the hollow stepped tubes 1 obtained. Moreover, the surface hardness of the raw pipe 10 was also shown for reference. The surface hardness was measured at three points in the steady part of each part, and a value obtained by averaging these was used. In the state of the hollow stepped tube 1, it can be seen that the hardness is improved more than the surface hardness of the raw tube 10 in both the large diameter portion 11 and the small diameter portion 12, and the strength can be increased. In addition, in instrument panel reinforcement, it is considered that a hardness of at least 50 Hv or more is necessary in both the large diameter portion and the small diameter portion, but all hollow stepped tubes 1 produced in this example are It has been found that it meets the requirements and is applicable to instrument panel reinforcement.

(Example 2)
In this example, the results obtained by conducting a plurality of tests in which the dimensions of the large diameter portion and the small diameter portion are changed using the raw pipe in Example 1 are shown. As shown in Table 2, in this example, tests of three types of dimensions were performed on nine types of raw pipes, that is, a total of 27 types of tests were performed, and evaluation similar to that of Example 1 was performed. It should be noted that pass / fail only relates to the applicability to instrument panel reinforcement with respect to current requirements, and may be judged as pass in other applications.

  As shown in Table 2, in all materials, the surface hardness of the large diameter portion is 50 Hv or more when the reduction in area from the raw pipe to the large diameter portion is 5% or more (8.1%). More than 60% of the total reduction in area from the raw pipe to the small diameter part when the reduction in cross section from the raw pipe to the large diameter part exceeds 10% while satisfying the required strength in the mental panel reinforcement 63.5%), which led to the problem of processability in which the pipe was cut during the drawing process. Therefore, when applying the above-described method of manufacturing a hollow stepped tube, the drawing process with the large diameter die is performed in the range of 5 to 10% in area reduction rate from the raw pipe to the large diameter portion, and small diameter It is understood that it is preferable to carry out the drawing process using a die so that the total reduction in area from the raw pipe to the small diameter portion is in the range of 60% or less. In addition, when the total cross-sectional reduction rate is less than 40%, the weight reduction effect of the small diameter portion is low even if the strength is passed, so the instrument panel reinforcement is rejected.

DESCRIPTION OF SYMBOLS 1 hollow step tube 10 raw material pipe 11 large diameter part 12 small diameter part 13 boundary part 15 soldered part 5 drawing machine 51 large diameter dice 52 small diameter dice 6 plug

Claims (7)

A method of manufacturing a hollow stepped tube which is a hollow tube integrally provided with a large diameter portion, a small diameter portion having an outer diameter smaller than the large diameter portion, and a boundary portion interposed therebetween. ,
Prepare a hollow tube whose outer diameter is larger than the above-mentioned large diameter portion,
Using a drawing apparatus including a large diameter die having a hole diameter corresponding to the outer diameter of the large diameter portion and a small diameter die having a hole diameter corresponding to the outer diameter of the small diameter portion,
Forming the mouthpiece by processing the end of the raw tube so as to have an outer diameter smaller than that of the small diameter portion;
Two-step simultaneous drawing processing in which the large diameter die and the small diameter die are sequentially passed with the attachment portion at the top, and the drawing process is stopped before the entire length of the raw tube passes the small diameter die And
The small diameter portion formed by passing the large diameter die and the small diameter die, the large diameter portion formed by passing only the large diameter die, and the diameter reduction halfway on the entry side of the small diameter die Obtaining the above-mentioned boundary part interposed between the above-mentioned narrow diameter part and the above-mentioned wide diameter part consisting of a part of a state
Method of manufacturing hollow stepped tube.   The method for manufacturing a hollow stepped tube according to claim 1, wherein the drawing by the small diameter die is performed by inserting and arranging a plug for controlling the inner diameter of the small diameter portion in the blank.   The method for manufacturing a hollow stepped tube according to claim 1, wherein the hollow stepped tube is for instrument panel reinforcement.   The method for manufacturing a hollow stepped tube according to any one of claims 1 to 3, wherein the drawing by the large diameter die is performed in a range of a reduction in area of 5 to 10%.   The drawing process using the small diameter die is performed in a range of a reduction in area where the total reduction in area of the large diameter die and the small diameter die is 40 to 60%. Method for the production of hollow stepped tubes.   The method for manufacturing a hollow stepped tube according to any one of claims 1 to 5, wherein an arrangement distance between the large diameter die and the small diameter die is 600 mm or more and 1000 mm or less. The outer diameter D ₀ and the outer diameter D ₂ and the thickness t ₀ and the thickness t ₂ of the small-diameter portion of the blank tube of the small-diameter portion of the blank tube is 40 <[1- {D _{² 2} - ( ^{_{D 2 -2 × t 2) 2}} } / {D 0 2 - (D 0 -2 × t 0) 2} ] is in the range of × 100 <60, according to any one of claims 1 to 6 Method for the production of hollow stepped tubes.

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