JP2002066624A - Manufacturing method for thick-walled small-diameter pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a thick-walled small-diameter pipe having excellent quality, completely eliminating a layer of a mill scale in hot rolling and also eliminating microcracks that occur when a material is pipe-rolled. SOLUTION: In the method for manufacturing the thick-walled small-diameter pipe by repeating a process that conducts pipe rolling and a heat treatment of the pipe material in plural times, a shaving process is conducted on an internal peripheral surface of the pipe material prior to pipe rolling in the last process but one or two from the final. The smoothness is improved by eliminating microcracks including a layer of a mill scale of the internal peripheral surface, and then a pressure endurable to a repeated application of an internal pressure is also enhanced as well as pressure resistance is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thick-walled small-diameter tube, and more particularly, to a method for manufacturing a high-quality thick-walled small-diameter tube by removing fine cracks on the inner peripheral surface of the tube caused by drawing. .

[0002]

2. Description of the Related Art In a thick-walled small-diameter pipe used for a fuel injection pipe of a diesel engine, a high smoothness of an inner surface of the pipe is required to reduce passage resistance in the pipe and prevent blockage of an injection nozzle. 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] This type of thick-walled small-diameter pipe is made by subjecting a pipe to be processed (raw carbon steel pipe) to cold drawing comprising repetition of drawing and heat treatment, but the pipe to be processed is a seamless pipe. Since it is made by the hot rolling process, it has a black scale layer containing cracks and concave wrinkles on the inner peripheral surface of the tube. In this case, even if the pipe to be processed is subjected to a treatment to remove the black skin layer by a chemical means such as an acid solution, the black skin layer is completely removed to make the inner peripheral surface of the pipe to be processed a uniform steel surface. Is difficult, and often a black scale layer remains.

[0004] For this reason, when used in a fuel injection pipe of a diesel engine, a part of the black scale layer in use is peeled off and the nozzle is clogged.

Therefore, in Japanese Patent Publication No. 51-21391, when a pipe to be processed is dropped into a thick thin pipe,
Thick, thin-diameter carbon steel pipes in which the black skin layer on the inner peripheral surface of the pipe to be processed is removed in advance by mechanical means (mechanical cutting and grinding) (hereinafter referred to as initial internal cutting) to make the entire inner surface of the pipe a steel skin. The present applicant has proposed a manufacturing method of By this proposed method,
The inner surface where there is almost no black scale layer on the inner surface has high smoothness,
It is possible to obtain a thick-walled small-diameter carbon steel pipe excellent in roundness and uniformity.

[0006]

In the above-mentioned proposed initial internal cutting method, the black scale layer, impurities, wrinkles, scratches, etc. remaining on the inner peripheral surface of the pipe to be processed in the hot rolling step are almost eliminated. Although it can be removed, if there is large unevenness or eccentricity in the pipe to be processed, these may slightly remain. It is not possible to remove defects newly generated in the tube process.

[0007] In the production of this kind of thick-walled small-diameter pipe, a concave wrinkle is formed on the inner peripheral surface of the pipe to be processed after the initial internal milling, and the wrinkle is closed to form a fine pipe. It changes into a crack, and even if the inner skin is removed by the above-mentioned proposed method to remove the black scale layer, a crack of a maximum of 80 μm may occur. If the above-described initial internal cutting is not performed, cracks up to 300 μm may occur. Further, since the pipe to be processed is manufactured in a hot rolling step, the pipe is often uneven in thickness and eccentricity. Conventionally, such a work pipe is pushed into a work pipe fixed to a jig while rotating a cutting tool as represented by a gun drill method which is one of the deep hole processing methods. Cutting work. (This machining is a so-called gun drill, a method using a tool that emphasizes the straightness of the hole, and this method is used to prevent eccentricity and bending of the machined hole.) Cutting while pushing the tool in this way Therefore, a large cutting resistance is applied to the tool, and if the arbor is not thickened, the tool is bent due to the pushing force, and machining cannot be performed. If the arbor is thickened to increase rigidity, the tool will go straight without following the inner peripheral surface if the pipe is eccentric due to uneven wall thickness. However, black scales sometimes remained without cutting.

The present invention has been made in view of the current situation of such a thick-walled small-diameter pipe as described above. In addition to completely removing the black scale layer during rolling, even if fine cracks are newly generated during the elongation after the initial internal milling, they are reliably removed, and the inner peripheral surface is of high quality and the internal pressure is assured repeatedly. It is an object of the present invention to provide a method for obtaining a thick-walled small-diameter tube in which the thickness is particularly increased.

[0009]

Means for Solving the Problems In order to achieve the above object, a method for manufacturing a thick-walled small-diameter pipe according to the present invention comprises repeating a process of performing a drawing process and a heat treatment process on a pipe to be processed a plurality of times,
In the method of manufacturing a thick-walled small-diameter pipe, prior to the drawing process in a process one or two steps before the final process, a shaving process is performed on an inner peripheral surface of the pipe to be processed. Is what you do. That is, after shaving the inner peripheral surface of the pipe to be processed, the pipe drawing and the heat treatment are performed twice to three times.
It repeats many times.

[0010] In the method for manufacturing a thick-walled small-diameter tube according to the present invention,
Preferably, after the initial internal milling, a process including a drawing process and a heat treatment process on the pipe to be processed is repeated a plurality of times, and when manufacturing a pipe having a desired inner or outer diameter, one of the final steps of reducing the diameter is performed. Prior to the elongation process in the process two or three before,
For example, by moving a core metal having a cutting blade at one end relative to the processed pipe and moving the processed metal inside the processed pipe, and relatively rotating the processed pipe and the core metal,
Even if the pipe to be processed has uneven thickness or eccentricity, the pipe is cut in accordance with the inner peripheral surface to completely remove the black scale layer at the time of hot rolling. Even if fine cracks, concave wrinkles or the like are newly generated in the tube process, they can be removed. In this case, the diameter is reduced near the final drawing process, and it is processed by tension.
A large cutting resistance is not applied to the core metal, and only the cutting torque and the thrust force due to tension act on the core metal.
Cutting is performed under a tensile load. For this reason, the cutting blade of the small-diameter core metal performs cutting so as to follow the inner peripheral surface of even the eccentric wall and the eccentric processed pipe, and the black scale layer is completely removed.

Further, when the pipe to be processed is fixed and the core metal is rotated during the cutting process, the long core metal generates self-excited vibration due to the cutting resistance to increase the roughness of the machined surface. By rotating the pipe without processing, the self-excited vibration of the cored bar can be prevented, the processing can be stabilized, and the roughness of the processed surface can be reduced.

The pipe to be machined whose inner peripheral surface has been cut in this way is subjected to a drawing process and a heat treatment process one or two steps before the final step or the final step, thereby guaranteeing a high quality internal pressure repetition. A thick-walled small-diameter tube with a particularly increased pressure is produced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a method for manufacturing a thick and small-diameter tube according to the present invention. FIG. 1 (a) is a block diagram showing one embodiment, and FIG. 1 (b) is a block diagram showing another embodiment. FIG. 2 is a schematic view showing an example of an apparatus for shaving an inner peripheral surface of a pipe to be processed in the same method for manufacturing a thick-walled small-diameter pipe, and FIG. 3 is a schematic sectional view taken along line AA of FIG. 1 is a drawing process and a heat treatment process, 1a is a drawing process, 1b is a heat treatment process, 2 is an inner peripheral surface cutting process, 2-1 is a pipe holder,
2-2 is a holding moving body, 2-3 is a core holding body, 2-4 is a core, 2-5 is a cutting blade, 2-6A to 2-6J are rotating devices,
2-7 is a pipe feeder, 2-8 is a product receiving stand, 2-9 is a pipe chuck, and 10A to 10J are pipes to be processed.

That is, according to the method of manufacturing a thick-walled small-diameter pipe according to the present invention, as shown in FIGS. 1 (a) and 1 (b), a pipe drawing and heat treatment 1b are performed on a pipe to be processed. In the method of manufacturing the thick-walled small-diameter pipe by repeating the processing step 1 a plurality of times, the method shown in (a) is the above-mentioned step (previous stage) just before the final drawing and heat treatment processing step 1
Prior to the elongation process 1a, the inner peripheral surface of the pipe to be machined is shaved in an inner peripheral surface shaving step 2. In addition, the method shown in FIG. 2B is the drawing process 1a in the above-mentioned process two steps before the final drawing process and heat treatment process 1.
Prior to this, a method of shaving the inner circumferential surface of the pipe to be processed in the inner circumferential surface shaving step 2 is provided.

As described above, the inner peripheral surface of the pipe to be processed is shaved before one or two of the final drawing and heat treatment steps 1 and prior to the drawing 1a in the above step. A high-quality thin-walled tube with a particularly high internal pressure guarantee pressure is produced.

Next, in the inner peripheral surface cutting apparatus shown in FIGS. 2 and 3, the holding moving body 2-2 and the cored bar holding body 2-3 are sandwiched by the pipe holding base 2-1. It is movably mounted on a base (not shown) in the transfer direction indicated by arrow Y. These holding moving body 2-2 and core metal holding body 2-3
Has a cutting blade 2-5 connected to one end thereof.

The metal core holder 2-3 holds and fixes the metal core 2-4 at one end where the cutting blade 2-5 is formed, and moves in the axial direction (Y direction) of the metal core 2-4. Possibly, the holding moving body 2-2 holds and fixes the core metal 2-4 on the other end side,
It is configured to be movable in the axial direction (Y direction) of the cored bar 2-4. The holding moving body 2-2 and the core metal holder 2-3 can hold a large number (for example, 10) of core metals 2-4 at the same time.

The pipe 10A faces the metal core holder 2-3.
Pipe chuck 2 to engage and chuck
The pipe chuck 2-9 is provided with rotating devices 2-6A to 2-6J, and is configured to rotate these pipes around an axis.

A pipe feeder 2-7 is provided on one side of the pipe holding base 2-1 and a product receiving base 2-8 is provided on the other side. And the pipe holder 2
1, holding moving body 2-2, cored bar holding body 2-3, pipe feeder 2-7, product receiving stand 2-8, and rotating device 2-6A-2.
The operation of the pipe chuck 2-9 provided with -6J is configured to be performed by a control signal from a control circuit (not shown).

In the case of the pipe inner peripheral surface cutting apparatus having the above structure, the holding moving body 2-2 holding and fixing the end of the cored bar 2-4 in the direction opposite to the cutting blade 2-5 is attached to the pipe holding base 1. It moves in the approaching direction, and the cutting blade 2-5 side of the cored bar 2-4 passes through the inside of the pipe chuck 2-9 and is held and fixed to the cored bar holder 2-3.

Subsequently, a core metal holder 2-3 holding and fixing the cutting blade 2-5 side of the core metal 2-4 and rotating devices 2-6A to 2-6A-2.
The pipe chuck 2-9 provided with 6J is moved in a direction away from the pipe holding base 2-1. Pipes 10A to 10J having an outer diameter of 9.5 mm and a wall thickness of 2.55 mm are supplied from a pipe supplier 2-7 to a pipe holder 2-1. A chamfered end of each pipe is used as a core holder. The core bar 2-4 is disposed at a position opposed to an end of the core bar 2-4 held and fixed to the 2-3. From this state, the cored bar holder 2-3, the pipe chuck 2-9, and the rotating devices 2-6A to 2-6J move in a direction approaching the pipe holder 2-1 and the cored bar 2-4 moves the pipe 10A to be processed. 10J to 10J, and a pipe chuck 2 is attached to the processed pipes 10A to 10J.
-9 and the rotating devices 2-6A to 2-6J are externally fitted, and the pipes to be processed 10A to 10J are inserted into the pipe chuck 2-9. Each of the cutting blades 5 held by 2-3 protrudes, and the core metal 2-4 is connected to the pipe 10 to be processed.
A to 10J are inserted, and the other end protrudes toward the holding moving body 2-2.

Next, the holding moving body 2-2 moves in the Y 'direction, and the protruding end of the cored bar 2-4 from the other end of the pipes 10A to 10J is held and fixed to the holding moving body 2-2. Then, the holding and fixing of the cored bar 2-4 by the cored bar holder 2-3 on the cutting blade 2-5 side is released, and the cored bar holder 2-3 slightly moves in the Y 'direction to cut the inner peripheral surface. The operation starts. Next, the pipes to be processed 10A to 10A are processed by the pipe chuck 2-9.
J are chucked, respectively, and rotating devices 2-6A to 2-6
By rotating J, the pipes to be processed 10A to 10A
10J is about 3000 around the axis as indicated by the arrow.
It rotates at a rotation speed of ４4000 rpm.

The holding moving body 2-2 is about 100 to 3
The cutting blade 2-5 which is moved at a speed of 00 mm / min in a direction Y "away from the pipe holding base 2-1 and is not rotating.
Moves in the Y ″ direction while following the inner peripheral surfaces of the pipes 10A to 10J that are being rotationally driven, and performs cutting on the inner peripheral surfaces of the pipes 10A to 10J under the supply of cutting oil. The cutting oil is supplied to the cutting blade 2-5 from the end of the pipe to lubricate and cool the cutting edge of the cutting blade 2-5.
Sharpening is performed to discharge chips. Next, core metal 2-4
The cutting operation is completed when the cutting blade 2-5 comes out of the pipe to be processed, the rotation of the pipe to be processed is stopped, and the metal core holder 2 is kept until the pipe chuck 2-9 comes off the end of the pipe to be processed. -3 and the pipes 10A to 10J to be processed are moved to the product receiving stand 2-8.

[0024]

Example 1 A pipe to be processed is JIS G3 which is a hot drawn material.
455 STS 370 with outer diameter 34mm, wall thickness 4.5m
First, the inner and outer surfaces are scaled down by pickling at a temperature of 60 ° C. for 30 minutes to 1 hour with a 20% sulfuric acid solution using a carbon steel pipe of m length, and then washed with water and neutralized with an aqueous solution of caustic soda. Processing was performed. Next, the pipe was immersed in a bonderite solution (manufactured by Nippon Parkerizing Co., Ltd.) to form a zinc phosphate coating on the inner and outer surfaces of the pipe to be processed. Subsequently, a swaging process was performed to insert the end of the pipe to be processed into a drawing die, and the pipe was immersed in lubricating oil. Then, using a plug and a die, the outer diameter is 27 mm and the wall thickness is 3.7.
After performing the first tube drawing process so as to obtain a diameter of 10 mm, a bright DX gas is used to perform annealing at 800 ° C. for 10 minutes, and then a second time such that the outer diameter is 21 mm and the wall thickness is 3.6 mm. , And a third drawing and annealing process were performed so that the outer diameter was 15 mm and the wall thickness was 3.0 mm, and then the outer diameter was 9.5 mm and the wall thickness was 2. 55mm
After the fourth tube drawing process was performed, straightening process, fixed length cutting, and one end chamfering process were performed. Next, prior to the final pipe drawing, the inner peripheral surface, which is a main part of the present invention, was cut by the cutting device shown in FIGS. 2 and 3. Thereafter, after the chips were discharged and the cutting oil was removed, annealing was performed, followed by oil immersion in lubricating oil, and a fifth process of drawing and annealing as a final step was performed. In the fifth final step, final pipe drawing is performed so that the outer diameter becomes 6.4 mm and the wall thickness becomes 2.0 mm, and dimensional inspection is performed after straightening, and fixed-size cutting, chamfering, triethane washing, Annealing was performed to complete all steps.

Thus, according to this embodiment, all 5
After the fourth step in the process, the pipes to be processed 10A to 10A
Since the cutting process is performed following the inner peripheral surface of J, even if there is uneven thickness or eccentricity, the black scale layer at the time of hot rolling is completely removed, and in the process of the drawing process up to that time The resulting concave wrinkles and up to 80μ formed on the basis of these wrinkles
m fine cracks are removed. According to the micrograph of the inner peripheral surface of the thick-walled small-diameter tube manufactured in this example, the inner peripheral surface has almost no fine cracks, has high smoothness, and has excellent roundness and uniformity. A high quality thick thin tube was obtained.

Embodiment 2 Next, the pipe drawing and heat treatment are repeated a total of five times on the pipe to be processed. Prior to the fourth step, the inner peripheral surface is cut using the same cutting device as in Embodiment 1. The working example is shown below. In this embodiment, the thickness is 3.45 mm at the third time.
The conditions of the steps up to the third time were all the same as in Example 1 except that the pipe drawing was performed, and the inner peripheral surface was cut prior to the fourth pipe drawing. The conditions were the same as in Example 1 except that the rotation speed of the pipe to be processed was about 2000 to 3000 rpm. After removing the cuttings from the inner surface of the obtained pipe to be processed, washing with triethane, annealing, and then performing a fourth pipe drawing process with an outer diameter of 9.5 mm and a wall thickness of 2.75 mm, dropping the swaging portion, annealing Then, after straightening and chamfering, the process was moved to the fifth final step. In the fifth step, final pipe drawing was performed so that the outer diameter was 6.4 mm and the wall thickness was 2.2 mm, and the subsequent processing was the same as in Example 1. According to the micrograph of the inner peripheral surface of the obtained thick-walled small-diameter pipe, the black scale layer at the time of hot rolling is completely removed by the shaving process according to the inner peripheral surface, and the concave shape generated in the process of drawing pipe. Wrinkles and up to 80μ formed based on these wrinkles
The fine cracks of m were significantly improved to a maximum of 30 μm and had high smoothness, and a thick-walled small-diameter tube excellent in roundness and uniformity was obtained.

Embodiment 3 An example in which the inner peripheral surface of a pipe to be processed is cut by broaching with a broaching machine will be described below. In this embodiment, all the steps up to the second step are the same as those in the first embodiment, as in the second embodiment.
The tube was drawn to a wall thickness of 3.1 mm. In performing the shaving process on the inner peripheral surface of the pipe to be processed subjected to the drawing process as described above, in this embodiment, the number of blades is 8 to 10 with a broaching machine.
Cutting speed 150-200mm / while forcibly lubricating using a broach with a cutting depth of 0.1mm and a length of about 600mm
The broaching in seconds and the second broaching with a cut depth of 0.1 mm and other conditions being substantially the same were performed. The same processing and processing as in Example 2 are then performed on the pipe to be processed, which has been cut in accordance with the inner peripheral surface thereof by these two broaching operations, to obtain a thick-walled small-diameter pipe having desired characteristics. Was completed.

Embodiment 4 An embodiment in which the inner peripheral surface of a pipe to be processed is shaved and then subjected to three times of drawing and heat treatment is described below. In this example, as in Example 2, all the steps up to the third time were the same as in Example 1, but prior to the fourth elongation, the pipe to be processed was processed under the same conditions as in Example 2. The inner peripheral surface is cut, and then the outer diameter is 12 mm and the wall thickness is 2.8 mm. The fourth pipe drawing is performed, the swaging part is dropped, and the outer diameter is obtained after straightening and chamfering after annealing. Is 9
A fifth elongation process with a thickness of 2.2 mm and a thickness of 2.2 mm was performed. After annealing, the tube was straightened and chamfered and then moved to the sixth final step. In the sixth step, final pipe drawing was performed so that the outer diameter was 6 mm and the wall thickness was 1.8 mm, and the subsequent processing was the same as in Example 1. Also in this example, a thick-walled small-diameter tube having desired characteristics as in Examples 1, 2, and 3 could be obtained.

It should be noted that when the initial internal cutting is incorporated into Examples 1 to 4, the finer cracks and the black scale layer at the time of hot rolling are effectively removed. In the above-described embodiment, an example of cutting by cutting has been described. However, the present invention is not limited to such cutting, and the inner peripheral surface of a pipe to be processed may be subjected to cutting by grinding. In this case, it is preferable not only to rotate the pipe to be processed, but also to rotate the grinding tool in a direction opposite to the rotation direction of the pipe to be processed to improve the relative grinding speed.

Further, in the above embodiment, an example has been described in which the core metal that does not rotate is moved along the inner peripheral surface of the pipe to be rotated, but the core metal is fixed without moving, and the pipe to be processed is rotated. The core metal can be pulled relatively to the pipe to be processed by moving it while moving it or both in the relative direction, and it is thin and has low rigidity and follows the inner peripheral surface A core metal that can be easily used can be used. When the pipe to be processed is short, the pipe to be processed may be stopped and the core metal may be rotated.

Further, in the above embodiments, the outer diameter is 6.
A case has been described in which a thick and small-diameter pipe used for a fuel injection pipe of a diesel engine of an automobile having a thickness of 4 mm and a thickness of 1.8 to 2.2 mm is manufactured. When used for diesel engines such as
A thick small-diameter tube having an outer diameter of 15 mm and a wall thickness of 1.8 mm to 5.5 mm can be manufactured.

According to these examples, the fine cracks of the thick-walled small-diameter tube are reduced at least to a maximum of about 30 μm, the notch sensitivity to the internal pressure is reduced, and the internal pressure repetition assurance pressure is increased to a maximum of 1500 kgf / cm ^2. A quality thick and small diameter tube can be obtained.

[0033]

As described above in detail, according to the present invention, it is possible to perform the pipe drawing in one or two steps before the final step of repeating the steps of pipe drawing and heat treatment of the pipe to be processed. By performing shaving in accordance with the inner peripheral surface of the pipe to be processed in advance, even if the processed pipe having uneven wall thickness and eccentricity, the black scale layer is completely removed during hot rolling, Reduces minute cracks on the inner peripheral surface, increases the smoothness of the inner peripheral surface, improves roundness and uniformity, improves pressure resistance, especially increases the high pressure resistance, high quality, internal pressure repeatability guaranteed pressure It is possible to provide a method for obtaining a thick and small-diameter tube.

[Brief description of the drawings]

FIGS. 1A and 1B illustrate a method of manufacturing a thick and small diameter tube according to the present invention, wherein FIG. 1A is a block diagram showing one embodiment, and FIG. 1B is a block diagram showing another embodiment.

FIG. 2 is a schematic view showing an example of an apparatus for shaving an inner peripheral surface of a pipe to be processed in the same method for manufacturing a thick and small diameter pipe.

FIG. 3 is a schematic sectional view taken on line AA of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drawing process and heat treatment process 1a Drawing process 1b Heat treatment 2 Inner peripheral surface cutting process 2-1 Pipe holding stand 2-2 Holding moving body 2-3 Core holding member 2-4 Core 2-5 Cutting Blade 2-6A to 2-6J Rotating device 2-7 Pipe feeder 2-8 Product holder 2-9 Pipe chuck 10A to 10J Pipe to be processed

Claims (7)

[Claims] 1. A method of manufacturing a thick-walled small-diameter pipe by repeating a process of performing a drawing process and a heat treatment process on a pipe to be processed a plurality of times, in a process one or two steps before the final process. A method for manufacturing a thick-walled small-diameter pipe, wherein a shaving process is performed on an inner peripheral surface of the pipe to be processed prior to a drawing process. 2. The method according to claim 1, wherein the shaving is cutting or grinding. 3. The method according to claim 2, wherein the cutting is performed by broaching. 4. The method according to claim 1, wherein the shaving is performed while rotating the pipe to be processed about an axis. 5. In the shaving process, a cutting blade is provided at one end of a core bar, the cutting blade is protruded to the outside, and the core bar is loosely fitted into a pipe to be processed. 3. The method according to claim 1, wherein the cutting is performed by rotating the cutting blade relatively in parallel with the axis and moving the cutting blade in the pipe to be processed. Method. 6. The method according to claim 5, wherein the core metal is pulled while rotating the pipe to be processed at a fixed position. 7. The method for producing a thick-walled small-diameter tube according to claim 5, wherein the core bar is fixed and the pipe to be processed is pulled while rotating.