JP3920581B2 - Manufacturing method for thick thin tube - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a thick thin tube, and particularly to a method for efficiently producing a thick thin tube that can be suitably used as a fuel injection tube of a diesel engine.
[0002]
[Prior art and problems]
For example, a thick-walled thin pipe used as a fuel injection pipe of a diesel engine is required to have a high smoothness of the pipe inner peripheral surface in order to reduce passage resistance in the pipe and prevent the injection nozzle from being blocked. Further, in order to withstand repeated fatigue under high pressure, it is required to reduce defects on the inner peripheral surface of the pipe, particularly fine cracks.
[0003]
Here, the thick-walled thin pipes that are usually used for this purpose are drawn pipes using a draw bench and heat treatment for seamless blanks formed by hot rolling such as Mannesmann mill drilling and mandrel mill rolling. It is manufactured by subjecting it to a cold drawing process consisting of repeated processing to obtain a desired pipe diameter and then cutting it into product dimensions.
[0004]
For this reason, cracks due to hot rolling, formation of a black skin layer containing concave wrinkles, and the occurrence of small hair cracks due to repeated tube drawing and heat treatment are unavoidable, and the inner peripheral surface is smooth and free from defects. In order to obtain a pipe body, it has been conventionally practiced to cut or polish the inner peripheral surface of the pipe at various stages.
[0005]
For example, in Japanese Examined Patent Publication No. 51-21391, prior to stretching a seamless element tube formed by hot rolling into a thick thin tube as a product, a black skin layer on the inner peripheral surface of the seamless element tube is previously provided. It is described that it is removed by mechanical cutting.
Japanese Patent Laid-Open No. 5-154536 discloses mechanical defects such as hair cracks existing on the inner peripheral surface of a pipe to be processed prior to final pipe drawing or pipe drawing in a process in the vicinity thereof. The removal by cutting or polishing is described.
Furthermore, in JP-A-9-57329, the inner peripheral surface of a hot-rolled seamless blank tube is polished by shot blasting prior to drawing or in the middle of multiple drawing operations. It is described to do.
[0006]
Here, the process such as cutting or polishing of the inner peripheral surface of the pipe as described above is effective in producing a thick and thin tube having a smooth and defect-free inner peripheral surface. Cutting or polishing performed at a point close to the point is very effective because hair cracks and the like due to subsequent processing are few.
[0007]
However, the closer the drawing process is to the final stage, the thinner the pipe diameter and the longer the pipe length. Cutting or polishing the inner peripheral surface of such a small and long tube body is a very difficult operation, regardless of the method, and is an inefficient and expensive operation. The reliability of the cutting or polishing is never high, and there are not a few cases where defects are found on the inner peripheral surface in the inspection of the final product.
[0008]
The present invention has been made in view of the problems of the above-described conventional technology, and its purpose is to have a thickness having a smooth and defect-free inner peripheral surface that can be suitably used as a fuel injection pipe of a diesel engine. An object of the present invention is to provide a method for efficiently producing a thin-walled tube.
[0009]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention repeats a process of performing a drawing process and a heat treatment process on a seamless element pipe a plurality of times, and in a method of manufacturing a thick thin pipe, prior to the final drawing process. after cutting to length the product dimensions by the final Shinkan processing a processed tube was facilities cutting or polishing the inner peripheral surface of the cut piece, the Shinkan machining of the final, the inner peripheral surface It was decided to perform the forging process using the pressing force by the press on the cut or polished cut product .
[0010]
According to the above-described method for producing a thick thin tube according to the present invention, the inner peripheral surface is cut or polished only at the stage of leaving the final drawn tube, so that the inner surface is smooth and free from defects. A thick thin tube having a peripheral surface can be provided, and the cutting or polishing process is performed on a cut product that has been cut to a length corresponding to a product dimension by the final tube drawing process. Short and easy cutting or polishing can be performed accurately.
[0011]
In addition, according to the above-described method for manufacturing a thick thin tube according to the present invention, prior to the final drawing process, the pipe to be processed is cut into a length corresponding to the product dimensions by the final drawing process. Therefore, it is possible to perform the final tube drawing process by forging process using pressing force by pressing, for example, forging process using parts former used for molding various parts such as bolts and nuts. Compared with the tube drawing process using a draw bench such as that described above, the machining can be performed in a short time, and the chucking cost for drawing is not required, and the product yield can be improved.
[0012]
The “final tube drawing” in the present invention does not mean the final one tube drawing, but means the final tube drawing.
In other words, the work of extending the seamless blank tube to the product dimensions is performed in multiple stages. This is the amount of one-time expansion, that is, the outer diameter processing degree Re [= [(the outer diameter of the tube before processing−the outer diameter of the tube after processing) / the outer diameter of the tube before processing] × 100] This is because the pulling-out force of the tube must be set to be equal to or less than the breaking load on the side of the die passing through the tube, and the tube cannot be drawn at once. When the case of a carbon steel pipe is shown as a representative example, it is carried out at an outer diameter processing degree Re = 20 to 30%.
Therefore, in the case of this carbon steel pipe, the “final tube drawing” referred to in the present invention is a stage in which product dimensions are obtained by tube drawing of the outer diameter processing degree Re = 20 to 30% once in the present invention. Means.
Therefore, the case where the final pipe drawing process is performed by dividing into a plurality of pipe drawing processes by forging using a part former, for example, is also included in the scope of the technical idea of the present invention.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although the embodiment of the manufacturing method of the above-described thick thin tube according to the present invention will be described in detail, the present invention is not limited to the following embodiment.
[0014]
First, a draw bench that has been conventionally used for a carbon steel seamless blank (JIS G 3455) having an outer diameter of 34 mm and a wall thickness of 4.5 mm formed by hot rolling such as Mannesmann mill drilling and mandrel mill rolling. A cold drawing process consisting of repeated drawing and heat treatment was used to obtain a tubular body having an outer diameter of 11 mm and a wall thickness of 2.0 mm [FIG. 1 (a)].
In this process, it is preferable to carry out the cutting or polishing process of the pipe inner peripheral surface which has been conventionally performed because the pipe diameter is still relatively large and can be easily performed. It is not a process.
[0015]
Subsequently, the tubular body having an outer diameter of 11 mm and a wall thickness of 2.0 mm is cut into a length of 150 mm by a cutting machine (FIG. 1B).
This cutting length is cut to a length that becomes the product length by the subsequent tube drawing process.
[0016]
Subsequently, the inner peripheral surface of the cut product is cut or polished [FIG. 1 (c)].
The means for cutting or polishing the inner peripheral surface of the cut product may be any means such as shot blasting or fluid polishing, as well as cutting or polishing means using a conventionally known lathe, broaching machine, honing machine, etc. You may perform combining these means suitably.
Regardless of which method is employed, the object to be cut or polished in the present invention is as short as about 150 mm in length as described above, and therefore can be easily and accurately performed.
[0017]
The inner peripheral surface of the pipe after cutting or polishing is completely free of the black skin layer formed during hot rolling, and the concave wrinkles generated in the process of drawing the tube and the concave wrinkles. Defects such as fine hair cracks formed (defects of 50 μm or more) need to be completely removed.
[0018]
Subsequently, the final product is drawn so that the cut product whose inner peripheral surface has been cut or polished has an outer diameter of 8 mm, a wall thickness of 2.0 mm, and a length of 230 mm [FIG. 1 (d). ].
In this final tube-drawing process, since the pipe to be processed is as short as about 150 mm in length, it is possible to perform extrusion molding using a part former used for molding various parts such as bolts and nuts.
[0019]
For example, as shown in FIG. 2, a pipe to be processed is pushed into a die having a drilled hole with a reduced diameter by a mechanical press using hydraulic pressure, hydraulic pressure, or a clamp mechanism, and the pipe is drawn by forging.
This final tube drawing process can be performed in a short time as compared with the conventional tube drawing process using a draw bench, and the chucking cost for drawing is not required, so that the product yield can be improved.
[0020]
The thick-walled thin tube manufactured in this way has an inner peripheral surface that is sufficiently smooth and free from defects, although there is a concern that slight hair cracks (at most 10 μm) generated by the final drawing process exist. It can be used as a fuel injection pipe of a diesel engine.
[0021]
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 thin pipe of the present invention can be applied to a thick thin pipe used for a purpose other than a fuel injection pipe of a diesel engine. This applies to all thick and thin pipes that are severe.
Needless to say, the present invention can be applied to all types of thick-walled thin pipes such as carbon steel, alloy steel, and stainless steel.
Furthermore, as described above, the final tube drawing process can be carried out in a plurality of tube drawing processes.
[0022]
【The invention's effect】
As described above, according to the method for manufacturing a thick-walled thin tube according to the present invention, the inner peripheral surface is cut or polished only at the stage of leaving the final tube-drawing process. It is possible to provide a thick-walled thin tube having no inner peripheral surface, and the cutting or polishing process is performed on a cut product that has been cut to a product size by a final tube drawing process. Therefore, there is an effect that cutting or polishing can be easily performed with high accuracy.
[0023]
In addition, according to the method for manufacturing a thick-walled thin pipe according to the present invention, the pipe to be processed is cut to a length in consideration of the product dimensions prior to the final pipe drawing, so that the final pipe drawing is performed. Can be performed by forging using a pressing force by a press, for example, forging using a part former used for forming various parts such as bolts and nuts, and a conventional draw bench is used. Compared with the conventional tube drawing process, the machining can be performed in a short time, and the chucking cost for drawing is not required, and the product yield can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram conceptually showing a method for producing a thick thin tube according to the present invention.
FIG. 2 is a diagram conceptually showing an example of a final tube drawing process.

Claims (2)

In the method of producing a thick and thin tube by repeating the process of drawing and heat-treating a seamless element pipe a plurality of times, prior to the final drawing process, the processed pipe is processed by the final drawing process. after cut into a product size length, and facilities cutting or polishing the inner peripheral surface of the cut piece, the Shinkan machining of the final, against the inner peripheral surface cutting or polishing processed the cut piece A method for producing a thick-walled thin pipe characterized by performing forging using a pressing force by a press . The method for producing a thick-walled thin pipe according to claim 1, wherein the final tube drawing is performed using a part former .

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