JP2719495B2 - Metal tube thickening processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for increasing the thickness of a part of a metal tube.

[0002]

2. Description of the Related Art Metal pipes used in automobiles and the like are processed by increasing the thickness of only those parts that require strength, and by reducing the thickness of the other parts to the same thickness as thin pipes to reduce the overall weight. May be attempted.

As a processing method for increasing the thickness of only a part of the pipe, as shown in FIG. 2, a high-frequency coil 22 or the like is used to apply a compressive force in the axial direction indicated by an arrow P to the raw pipe 21.
A method of partially heating and compressing the material in a required range (width) by partially heating the material 1 and sequentially performing the heating and compression to increase the required thickness (width) is known. (See Nikkan Kogyo Shimbun, published in 1982, Masanobu Nakamura, pipe processing method, page 182) 23 is a mandrel, and 24 is a cooling water injection pipe.

[0004]

In the prior art, the heating length (heating width) is limited to about 3 to 6 times the wall thickness.
If it exceeds that, there is a problem that it buckles.

[0005] Further, it is difficult to obtain a uniform wall thickness over the entire thickness increasing range, and there are other problems such as a large and complicated processing apparatus. Therefore, an object of the present invention is to provide a method for increasing the thickness of a metal tube that can solve these problems.

[0006]

In order to achieve the above object, a method for increasing the thickness of a metal pipe according to the present invention is characterized in that a metal pipe (1) is pushed into its rear end by applying a pressing force to its rear end. ) To reduce the front end of the tube (1).
A) a first step of further reducing the pipe while applying a force smaller than the pushing force and in the opposite direction to the front end of A);
The tube (1A) obtained in the step (1) is inserted into an outer mold for restraining the outer diameter of the raw tube (1), and a force is applied in the axial direction from the front end side contracted in the first step while the front end is And a second step of inserting the core metal (13) into the tube and expanding its outer diameter to the outer diameter of the raw tube.

[0007]

In the first step, the force in the opposite direction applied to the front end of the pipe suppresses the volumetric movement in the axial direction, and promotes the increase in the thickness of the constricted pipe (tip). In addition, since the compressing force acts in the axial direction also in the second step, the volume movement in the axial direction is suppressed, and the pipe is expanded while being thick.

[0008]

FIG. 1 shows the steps of a method for increasing the thickness of a meat according to the present invention.
FIG. 1A shows a metal tube, that is, a base tube 1 having an outer diameter D ₀ ,
A wall thickness of cylindrical of t _0.

FIG. 1B shows a first step. Reference numeral 2 denotes a buckling prevention guide, and reference numeral 3 denotes a contracted tube type which is fastened to the buckling prevention guide 2. Reference numeral 4 denotes a pressing die for applying an axial load, which is fitted into the contracted tube die 3 from the left.

Reference numeral 5 denotes a hydraulic cylinder, and its piston rod 6 is connected to the pressing die 4 for applying an axial load. Reference numeral 7 denotes a hydraulic pump for supplying a hydraulic pressure to the hydraulic cylinder 5, and reference numeral 8 denotes a relief valve which is connected by piping as shown.

In the first step, the tip of the tube 1 into which the metal core 9 has been inserted from one side is inserted into the buckling prevention guide 2 from the right side in the figure, and the metal core 9 is pushed by a pushing means (not shown) as shown by an arrow B. Then, the front end (the left end in the figure) of the tube 1 is inserted into a contraction type (drawing die) 3 to contract the tube.

At this time, the mold 4 pushes the contracted front end of the tube 1 to the right by the force of the hydraulic cylinder 5, but the force is
It is set smaller than the pushing force for pushing the tube 1 from the right. The tube 1 is pushed into the contraction mold 3 from the right side and contracted, and at the same time, is pressed from the left side by the hydraulic cylinder 5 through the mold 4, so that the tube 1 is subjected to contraction processing without force by the mold 4. The thickness of the contracted tube portion (front end) is greater than that of the tube.

[0013] The outer diameter of the front end reduced pipe portion of the pipe 1 when the D _1,
When there is no pushing force to the right with a die 4, in the Nakamura correction formula, the thickness t ₁ of the reduced pipe section _{t 1 = t 0 (D 0} / D 1) 0.65 ... to become that (1) However, in the first step of FIG. 1B, the wall thickness of the constricted portion can be obtained to be larger than the expression (1).

In FIG. 1B, reference numeral 1A denotes a tube (work) whose front end is contracted, and the length of the contracted portion is indicated by L. In the first step, when the mold 4 is pushed leftward at the front end of the work (tube) 1, the oil in the hydraulic cylinder 5 is pushed out of the cylinder, but the flow rate thereof is controlled and controlled by the relief valve 8. Accordingly, the mold 4 moves to the left and retreats while applying a controlled force to the tube 1. This force is used as an axial load to form a thickened portion.

Next, in a second step of FIG. 1 (c), the tube 1A whose leading end is contracted in the first step is inserted into an outer mold 11 for restraining the outer diameter D ₀ of the raw tube, and the cylindrical body is cylindrical. The punch 13 is inserted into the tube 1A while pushing the tube 1A to the right with the mold 12 of the shape, and the punch 13 is pulled out to the right by the extracting means 14, whereby the tube 1A is drawn.
Is expanded, and the outer diameter of the portion is changed to the outer diameter D of the raw tube.
Align to ₀ .

The pressing die 12 is pressed by a hydraulic cylinder 15. 16
Is a hydraulic pump for supplying hydraulic pressure to the hydraulic cylinder 15, 17
Is a pressure adjusting valve for adjusting the pressure of the hydraulic pressure supplied to the hydraulic cylinder 15.

Thus, the portion contracted in the first step is
Expanded in the second step, the outer diameter D of the raw tube ₀With the same outer diameter as
A metal tube 1B having a partially thickened portion is completed (FIG. 1).
(D)). In the embodiment, the pipe (SUS409L)
Outer diameter D of T)₀Is 42.7 mm, wall thickness t₀= 1.2mm
Was increased in thickness to 1.75 mm in thickness. Also desired
The first and second steps are repeated several times to increase the thickness to
May go.

[0018]

According to the thickness increasing method of the present invention, the axial compression force is applied to the reduced tube portion during the first step of reducing the tube, so that the axial movement of the tube is suppressed and the wall thickness is increased. Is promoted. In addition, since a compressive force is applied in the axial direction also at the time of expanding the pipe in the second step, the volume movement in the axial direction is suppressed, and the pipe is expanded while being thick.

Accordingly, a greater increase in wall thickness over the desired range than in the prior art is possible. In addition, since it is cold-working, no heating equipment is required, and it can be realized by a combination of conventional contraction and expansion techniques, so that equipment and processing costs can be reduced.

Further, the product can be reliably processed without wrinkling or buckling.

[Brief description of the drawings]

FIG. 1 is a view showing a procedure of a process of the present invention, (a) is a longitudinal sectional view of a raw tube, (b) is a partial longitudinal sectional view showing a first process,
(C) is a partial longitudinal sectional view showing a second step, and (d) is a longitudinal sectional view of a completed product.

FIG. 2 is a longitudinal sectional view illustrating a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 pipe 1A pipe (after the 1st process) 1B pipe (after the 2nd process) 2 buckling prevention guide 3 contraction type 4 die for axial load loading 5 hydraulic cylinder 9 core metal 11 outer die 12 press die 13 punch 15 hydraulic pressure Cylinder

Claims (1)

(57) [Claims] 1. A metal pipe is inserted into a contraction mold by applying a pushing force to a rear end thereof to shrink a front end, and a front end of the contracted pipe is smaller than the pushing force and opposite to the pushing force. A first step of further contracting while applying a force in the direction, and inserting the tube obtained in the first step into an outer mold for restraining the outer diameter of the raw tube, and in the first step A second step of inserting a core into the front end and expanding the outer diameter to the outer diameter of the raw tube while applying a force in the axial direction from the front end side.