JPH0739942A - Method for bending metallic tube - Google Patents

Abstract

PURPOSE:To provide a method for bending metallic tube, which prevents burning flaws causing in a contact part between a plug and the inside surface of a tube and preventing the vibration of a mandrel connected to the plug by the use of a simply structured device. CONSTITUTION:The method is for bending a straight metallic tube into a curved tube; a mandrel 3 with a plug 2 attached at the tip end is inserted into the rear end of a metallic tube 1; and a bending is performed while a lube oil is supplied through the mandrel 3 to a contact part between the plug 2 and the tube 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal pipe while preventing, for example, a seizure flaw which occurs on the inner surface of a material to be processed, particularly a contact portion with a plug, and a vibration of a mandrel connected to the plug during the manufacture of a U-vent pipe. Bending method.

[0002]

2. Description of the Related Art In bending a metal tube, a bent portion of the metal tube is apt to have cross-section deformation and wrinkles. Particularly in the case of severe bending where R (bending radius) / D (outer diameter of work material) is 1.5 or less, cross-section deformation and wrinkling are remarkable. A bending method using a mandrel is generally adopted to prevent the cross-section deformation and wrinkles occurring in the bent portion.

Bending methods and apparatuses for preventing the cross-section deformation and wrinkling of bent portions by using this mandrel are disclosed in Japanese Utility Model Publication No. 56-1728, Japanese Utility Model Publication No. 63-6993, and Japanese Patent Laid-Open No. 63-93. No. 235026, Japanese Utility Model Publication 1-14
It has been proposed in Japanese Patent No. 3615 and Japanese Patent Laid-Open No. 2-268927.

[0004]

However, even though the seizure flaw generated on the inner surface of the metal tube during bending and the undulation on the inner surface of the metal tube due to the vibration of the mandrel connected to the plug cause the deterioration of the product quality, The bending method and apparatus proposed in the above-mentioned publication are considered only for preventing the cross-sectional deformation and the generation of wrinkles at the bent portion, and the seizure flaw generated on the inner surface of the metal tube and the mandrel connected to the plug are considered. Vibration is not considered at all.

In view of this, Japanese Patent Publication No. 60-44055 discloses a device for preventing flattening and wrinkling of the pipe during bending, which prevents the inner surface of the pipe from being damaged.
A plurality of tops that can move in the direction along the pipe diameter facing both sides of the pipe axis of the pipe to be bent, stoppers made of elastic cushioning material attached between these tops and the inner surface of the pipe, A pressure transmitting member that transmits a force in the wall direction,
We have proposed a flattening prevention device for the tube that consists of the pressure generator. However, the tube flattening prevention device proposed in this Japanese Patent Publication No. 60-44055 has a complicated structure.

In view of the above problems, the object of the present invention is to
It is an object of the present invention to propose a method for bending a metal pipe, which uses a device having a simple structure to prevent seizure flaws generated at the contact portion between the plug and the inner surface of the pipe and vibration of the mandrel connected to the plug.

[0007]

In order to achieve the above object, the method for bending a metal pipe of the present invention is a bending process for bending a straight metal pipe into a bent pipe, the tip of which is provided. The mandrel with the plug attached to is inserted from the rear end of the metal tube, and lubricating oil is supplied in advance to the contact portion between the plug and the metal tube through the mandrel, or bending is performed while supplying the lubricating oil.

[0008]

In the method for bending a metal pipe of the present invention, a mandrel having a plug attached to its tip is inserted from the rear end of the metal pipe, and lubricating oil is previously supplied to the contact portion between the plug and the metal pipe through the mandrel. Alternatively, since the bending process is performed while supplying, the lubricating oil is applied to the inner surface of the metal tube, and the friction load between the inner surface of the metal tube and the plug is reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing the configuration of equipment showing an outline of the method of the present invention.

In the drawing, 3 is inserted into the metal tube 1,
A mandrel that supports a plug 2 whose outer diameter is smaller than the inner diameter of the metal tube 1 by 0.3 to 0.5 mm.
An oil supply nozzle 4 having, for example, two oil spray ports is provided in the rear portion of the plug 2 of the plug 2 and the lubricating oil stored in the oil storage tank 6 via the pipes 7 and 8 by the operation of the pump 5 is supplied. Oil is supplied from the oil supply nozzle 4 to the contact portion between the plug 2 and the metal tube 1. The metal tube 1 is attached to the rotary bending die 9 by a clamp 10 in a sandwiched manner. The pressure bending of the metal tube 1 is performed by pressing the metal tube 1 against the rotary bending die 9 by the pressure guide 11 and rotating the rotary bending die 9. .

In the method of the present invention, the metal tube 1 is bent by using the equipment having the above-described structure. After inserting the mandrel 3 into the metal tube 1, the pump 5 is operated to supply the lubricating oil from the oil supply nozzle 4 to the contact portion between the plug 2 and the metal tube 1, while rotating the rotary bending die 9 to rotate the metal tube. Bend 1 is performed. At this time, the frictional load is reduced by the lubricating oil on the contact surface between the inner surface of the bent metal tube 1 and the plug 2.

By the way, a steel pipe of STBA23 material (outer diameter φ19.05 mm, wall thickness 2.58 mm) has an outer diameter of 13.5.
Insert a 0 mm plug and operate the pump to add 200 cc / L of lubricating oil with a viscosity of 500 Cst to the contact area between the plug and the steel pipe.
When bending was performed while supplying min, there was no seizure flaw on the inner surface of the steel pipe, and vibration of the mandrel could be suppressed as much as possible.

In the present embodiment, two oil spray openings are formed in the oil supply nozzle, but the oil spray openings formed in the oil supply nozzle depend on the viscosity of the lubricating oil supplied and the diameter of the pipe in the mandrel. Change the diameter and number. Further, in the present embodiment, the case where the bending process is performed while supplying the lubricating oil to the contact portion between the metal tube and the plug has been described, but after the lubricating oil is supplied to the contact portion between the metal tube and the plug in advance, the mandrel You may insert and bend.

[0014]

As described above, according to the method of the present invention, the frictional load between the inner surface of the metal tube and the plug is reduced by the lubricating oil, so that seizure flaws on the inner surface of the metal tube and vibration of the mandrel are prevented. The quality of the metal tube can be improved. Further, since the load on the plug is reduced, the life of the plug is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of equipment showing an outline of a method of the present invention.

[Explanation of symbols]

 1 Metal Tube 2 Plug 3 Mandrel 4 Oil Supply Nozzle 5 Pump 9 Rotating Bending Die 10 Clamp 11 Pressure Guide

Claims (1)

[Claims] 1. A bending method for bending a straight tubular metal tube into a bent tube, wherein a mandrel having a plug attached to its tip is inserted from the rear end of the metal tube, and the mandrel is passed through the mandrel to insert the plug into the metal tube. Lubricating oil is previously supplied to the contact part,
Alternatively, a method of bending a metal pipe, which comprises bending while supplying.