WO2002074462A1

WO2002074462A1 - Thick-walled small diameter pipe producing method

Info

Publication number: WO2002074462A1
Application number: PCT/JP2002/002349
Authority: WO
Inventors: Shigetsugu Kameda
Original assignee: Sanoh Industrial Co., Ltd.
Priority date: 2001-03-21
Filing date: 2002-03-13
Publication date: 2002-09-26
Also published as: DE60208011D1; JP3920581B2; EP1375019A4; EP1375019A1; EP1375019B1; JP2002273512A; DE60208011T2

Abstract

A method of efficiently producing a thick-walled small diameter pipe having a smooth flawless inner peripheral surface, which can be suitably used for a fuel injection pipe for diesel engines, is provided. In producing a thick-walled small diameter pipe by applying a plurality of times of stretching to a seamless raw pipe, the method comprises the steps of cutting the work pipe into lengths for which the product size is taken into consideration, prior to the final stretching, applying cutting or grinding to the inner peripheral surface of such length, and effecting the final stretching by forging utilizing a pressing force provided by a press.

Description

Description Method for manufacturing thick-walled small-diameter pipes Technical field

The present invention relates to a method for manufacturing a thick-walled small-diameter pipe, and more particularly to a method for efficiently manufacturing a thick-walled small-diameter pipe that can be suitably used as a fuel injection pipe for a diesel engine. . Background art

For example, thick-walled small-diameter pipes used as fuel injection pipes for diesel engines are required to have high smoothness on the inner peripheral surface of the pipe in order to reduce passage resistance in the pipe and prevent blockage of the injection nozzle. In addition, it is necessary to reduce defects, especially minute cracks, on the inner peripheral surface of the pipe so that it can withstand repeated high-pressure fatigue.

Here, as the thick-walled small-diameter pipe usually used for this purpose, a seamless raw pipe formed by hot rolling such as Mannesman mill drilling and mandrel mill rolling is used. Then, the seamless pipe is formed to have a desired pipe diameter by cold drawing comprising repetition of drawing and heat treatment using a draw bench or the like. Then, a pipe having a desired pipe diameter is cut into product dimensions, and a thick-walled small-diameter pipe used as a fuel injection pipe of a diesel engine is manufactured.

However, in the case of the manufacturing method as described above, a black scale layer including cracks and concave seams formed by hot rolling such as mannesman mill drilling and mandrel mill rolling is formed on the inner and outer surfaces of the seamless shell. In addition, fine cracks caused by repeated pipe drawing using a draw bench and heat treatment are repeated. Is formed on the inner and outer surfaces of the pipe having the desired diameter.

Therefore, in order to obtain a smooth and defect-free inner peripheral surface of the tube, the inner surface of the tube is cut or polished at various stages.

For example, Japanese Patent Publication No. 51-21391 discloses that a seamless raw tube formed by hot rolling is previously drawn into a thick thin tube as a product. It is described that the black scale layer on the inner peripheral surface of the steel is removed by mechanical cutting.

In addition, Japanese Patent Application Laid-Open No. 5-154553 / 1996 discloses that, prior to the final pipe drawing or the pipe drawing in a process in the vicinity thereof, minute cracks existing on the inner peripheral surface of the pipe to be processed. It is described that defects such as defects are removed by mechanical cutting or polishing.

Further, Japanese Patent Application Laid-Open No. 9-573329 discloses that the inner peripheral surface of a hot-rolled seamless tube is subjected to a process prior to or during a plurality of times of drawing. It is described that polishing is performed by a shot blast process at the stage of (1).

Here, the steps of cutting or polishing the inner peripheral surface of the tube as described above are effective in producing a thick-walled small-diameter tube having an inner peripheral surface that is smooth and free from defects. Cutting or polishing performed at a point near the stage is very effective because cracks and the like due to subsequent processing are slight.

However, the closer the drawing process is to the final stage, the smaller the pipe diameter and the longer the pipe length. Cutting or polishing the inner peripheral surface of such a small and long tube is a very difficult task, whatever the method. In addition, since it was a very difficult task, sufficient cutting or polishing could not be performed, and there were not a few defects found on the inner peripheral surface during the inspection of the final product. The present invention has been made in view of the above-mentioned problems of the related art, and has an object to provide a smooth and defect-free inner peripheral surface that can be suitably used also as a fuel injection pipe of a diesel engine. An object of the present invention is to provide a method for efficiently producing a thick-walled small-diameter tube. Disclosure of the invention

According to the present invention, in order to achieve the above-mentioned object, a seamless pipe is subjected to a plurality of drawing operations to produce a thick-walled small-diameter tube. In consideration of this, it was cut into lengths, and the inner peripheral surface of the cut product was cut or polished.

According to the method for manufacturing a thick-walled small-diameter pipe according to the present invention described above, since the inner peripheral surface is cut or polished only at the stage of leaving the final drawn pipe, it is smooth and free from defects. A thick-walled small-diameter tube having an inner peripheral surface can be provided. In addition, since this cutting or polishing process is performed on a cut product that has been cut into lengths in consideration of product dimensions, the length is short, and cutting or polishing can be performed easily and accurately. Becomes

In addition, according to the method for manufacturing a thick-walled small-diameter pipe according to the present invention described above, the pipe to be processed is cut into a length in consideration of the product dimensions before the final pipe drawing. Pipe processing can be easily performed by forging using the pressing force of a press, for example, using a part former used for molding various parts such as ports and nuts. Compared to pipe drawing using a simple draw bench, the processing can be performed in a shorter time, the chucking cost for drawing is not required, and the product yield can be improved.

In the present invention, “final pipe drawing” does not refer to the last one pipe drawing, but means the final pipe drawing. In other words, the operation of drawing the seamless tube to the product size is performed in multiple stages. This is the amount of one pipe extension, that is, the degree of outer diameter processing at one time R e [= [(tube outer diameter before processing – pipe outer diameter after processing) pipe outer diameter before processing] X 100] This is because the pipe pulling force must be set to be less than the breaking load on the die passing side of the pipe, and the pipe cannot be stretched at once. As a representative example, the case of carbon steel pipe is shown, and the outer diameter reduction is performed at Re = 20 to 30%.

Therefore, in the case of this carbon steel pipe, the “final pipe drawing” referred to in the present invention is a subsequent pipe drawing with a degree of outer diameter reduction of R e = 20 to 30%, and the product dimensions Means the stage where

Therefore, a case where the final drawing process is performed by performing a plurality of drawing processes by forging using a parts former, for example, is also included in the scope of the technical idea of the present invention described above. . BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram conceptually showing steps of a method for producing a thick-walled small-diameter tube according to the present invention. FIG. 2 is a view conceptually showing an example of a final pipe drawing process. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the method for manufacturing a thick-walled small-diameter tube according to the present invention will be described in detail, but the present invention is not limited to the following embodiments.

First, a carbon steel seamless tube (JISG 3455) with an outer diameter of 34 mm and a wall thickness of 4.5 mm formed by hot rolling such as mannes man mill drilling and mandrel mill rolling was compared with the conventional method. Drawben being done A cold drawing process consisting of repetition of drawing and heat treatment using a tube is performed to obtain a tube with an outer diameter of 1 lmm and a wall thickness of 2.0 mm (Fig. 1 (a)). In this process, the cutting or polishing step of the inner peripheral surface of the pipe, which has been conventionally performed, is preferably performed because the pipe diameter is relatively large and can be easily performed. Not an essential step.

Subsequently, the tube having an outer diameter of 1 lmm and a wall thickness of 2.0 mm is cut into a length of 150 mm by a cutting machine [FIG. 1 (b)].

The cut length of this tube is cut to a length that will be the product length by the subsequent drawing process.

Subsequently, the inner peripheral surface of the cut product is cut or polished (FIG. 1 (c)).

Means for cutting or polishing the inner peripheral surface of the cut product may be any known means such as shot blasting or fluid polishing in addition to cutting or polishing means using a conventionally known lathe, broaching machine, honing machine or the like. Alternatively, these means may be combined as appropriate.

Regardless of which method is adopted, the object to be cut or polished in the present invention is as short as about 150 mm in length as described above, so that it can be easily and accurately performed.

After cutting or polishing, the inner circumferential surface of the pipe has the black scale layer formed during hot rolling completely removed, and the concave wrinkles generated in the course of the drawing process and the concave wrinkles. It is necessary that defects such as fine cracks (defects of 50 zm or more) formed based on JIS have been completely removed. Subsequently, the above-described cut or polished inner peripheral surface is subjected to a final drawing process so that the product has an outer diameter of 8 mm, a wall thickness of 2.0 mm, and a length of 23 O mm. [Fig. 1 (d)].

In this final pipe drawing, the pipe to be processed is as short as about 150 mm in length. As a result, extrusion molding using performers used for molding various parts such as porto and nuts becomes possible.

For example, as shown in FIG. 2, a pipe A to be processed is pressed into a die 1 having a hole having a reduced diameter by a press device 2 using a hydraulic, hydraulic, or clamp mechanism, and the pipe A to be processed is forged. It is extended by processing.

In FIG. 2, reference numeral 3 denotes a plug inserted into the pipe A to be processed. This final pipe drawing can be performed in a shorter time than the conventional pipe drawing using a draw bench, and the chucking cost for drawing is not required, so that the product yield can be improved. .

The thick-walled small-diameter pipe manufactured in this way has some cracks (at most 10 xm) generated by the final drawing process, but has a sufficiently smooth and defect-free inner circumference. It becomes a thick-walled small-diameter pipe having a surface, and can be suitably used as a fuel injection pipe of a diesel engine.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments.

For example, the method for producing a thick-walled small-diameter tube of the present invention can be applied to a thick-walled small-diameter tube used for an application other than a fuel injection tube of a diesel engine. It can be suitably used for the production of thick-walled small-diameter tubes.

Needless to say, the present invention can be applied to the production of all kinds of thick-walled small-diameter pipes such as carbon steel, alloy steel, and stainless steel.

Further, as described above, the final pipe drawing can be performed in a plurality of pipe drawing steps.

According to the method for manufacturing a thick and small-diameter pipe according to the present invention described above, since the inner peripheral surface is cut or polished only at the stage of leaving the final drawn pipe, it is smooth and defective. Can provide a thick-walled small-diameter tube with an inner peripheral surface At the same time, the cutting or polishing process is performed on cut products that have been cut into lengths that take product dimensions into account, so the length is short, and cutting or polishing can be performed easily and accurately. There is an effect.

Further, according to the method for manufacturing a thick-walled small-diameter pipe according to the present invention, the pipe to be processed is cut into a length in consideration of product dimensions before the final pipe drawing. Processing can be easily performed by forging using the pressing force of a press, for example, using a part former used for molding various parts such as ports and nuts. The process can be performed in a shorter time compared to the used pipe forming process, and the need for a chuck for pulling out is eliminated, so that the product yield can be improved. Industrial availability

As described above, the method for manufacturing a thick-walled small-diameter pipe according to the present invention is a method for efficiently manufacturing a thick-walled small-diameter pipe, such as a fuel injection pipe of a diesel engine, whose internal surface properties are strictly required. Suitable for.

Claims

The scope of the claims

1. When the seamless tube is subjected to multiple drawing processes to produce a thick and small-diameter tube, prior to the final drawing process, the pipe to be processed is cut into lengths taking into account the product dimensions. A method for producing a thick-walled small-diameter tube, characterized by performing cutting or polishing on the inner peripheral surface of the cut product.

2. The final pipe drawing is performed by forging using a pressing force of a press on the cut product whose inner peripheral surface is cut or polished. A method for producing a thick-walled small-diameter tube as described in the above.