JPH01138035A - Pipe expansion method for seamless tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for obtaining a thin-walled, large-diameter seamless pipe that is difficult to produce directly by roll piercing or hot extrusion.

[Prior art]

For example, pipes without welded parts, so-called seamless pipes, are generally used as piping or joints for piping related to nuclear power generation. This applies to items that have welded parts.
It is necessary to inspect the welded parts during periodic inspections, and the work for such inspections involves work in a contaminated environment, which poses safety issues.In addition, the period when the plant is shut down for periodic inspections may be extended. Because it will be.

By the way, the above-mentioned nuclear power generation-related plumbing pipes and their joints are required to have fairly large diameters and thin walls, whereas conventional roll perforation rolling methods or hot extrusion methods are required to have large diameters and thin walls. There was a problem in that it was difficult to obtain seamless pipes of different diameters.

Therefore, the present applicant has proposed a method for obtaining a thin-walled, large-diameter seamless pipe as shown in FIGS. The base end of the base tube A is attached to a mandrel 34 equipped with a plug 33 at the tip, which is made up of a tapered part 31 whose diameter gradually increases toward the distal end and a parallel part 32 that continues to the large diameter end. The plug 3 is inserted from the side and pushed toward the distal end side, and is successively heated by the heating means 35 provided near the plug 33.
3 was proposed (Japanese Patent Laid-Open No. 61-56746).

According to this method, the raw pipe A is sequentially heated by the heating means 35 and gradually expanded in diameter and thinned by the plug 33, so it is relatively easy to produce a seamless pipe with a thin wall and large diameter, which has been difficult to obtain in the past. can be obtained.

[Problem that the invention seeks to solve]

However, the above-mentioned method is not without problems that need to be solved. For example, depending on the force that pushes the raw tube A toward the tip of the mandrel 34, a force that exceeds the buckling stress is applied to the raw tube A, causing the intermediate portion to buckle and bulge outward, deforming it into a so-called lantern shape ( There is a problem that it becomes a lantern (hereinafter referred to as a lantern). In addition, during the process of expanding the diameter of the raw tube A, internal cracks may occur, which is thought to be caused by the difference between the amount of strain on the outer surface and the amount of strain on the inner surface exceeding the deformability of the material. Also, related to the occurrence of buckling, internal cracking, etc. mentioned above, in order to prevent the occurrence of various defects and perform proper processing, the conditions for heating the raw tube A by the heating means 35 must be strictly controlled. There is also the problem of needing to be managed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for obtaining a thin-walled, large-diameter seamless pipe without incurring the above-mentioned problems and without machining. It is an object.

[Means for solving problems]

The method for expanding a seamless pipe according to the present invention includes loosely inserting a movable plug having an outer diameter with an enlarged diameter on the downstream side in the raw pipe feeding direction into a fixed die having a through hole with a diameter enlarged on the downstream side in the raw pipe feeding direction. , the raw pipe is intermittently fed into the gap formed between the two, and the movable plug is intermittently reciprocated in association with the intermittent feeding of the raw pipe to expand the diameter and reduce the thickness of the raw pipe. It is characterized by

[Effect]

According to the method of the present invention, the raw material tube is intermittently fed into the gap formed between the fixed die and the movable plug, and the movable plug is intermittently reciprocated in association with the intermittent feeding. Each time the movable plug makes an intermittent reciprocating motion, the tube is subjected to forging compression to expand its diameter and reduce its thickness.

In this way, the raw tube subjected to the diameter expansion and thickness reduction process is forged compressed while the inner and outer circumferences are regulated by the gap formed between the fixed die and the movable plug, so when using the method of the present invention,
The formation of lanterns, which has been a problem in the past, is suppressed by restricting the inner and outer peripheries, and the occurrence of internal cracks is suppressed due to the quality of the wood, which is compressed by forging. In addition, by forging, it is easier to obtain a beautiful surface texture, and by forging from the thickest parts first, uneven thickness can be corrected. Further, the forging compression can be performed without heating the raw pipe depending on various conditions such as the degree of processing, and there is no need to heat the raw pipe under strict control as in the past.

〔Example〕

The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a schematic explanatory diagram showing an apparatus used to carry out the method of the present invention. In the figure, reference numeral 1 denotes an air cylinder, and a ratchet mechanism 2 is provided on the tip side of a rod 1a of the air cylinder 1.
By suppressing the force that causes the rod 1a to advance each time the rod 1a advances by a certain amount, the rod 1a
can be made to protrude intermittently in multiple stages.

A rod 1a with the ratchet mechanism 2 provided on the tip side
Further on the distal end side is a blank pipe A, which is a seamless pipe obtained by a roll piercing rolling method or a hot extrusion method, and is prepared in advance to be expanded next to the blank pipe A+ which is being expanded. A stock pipe holding member 3 is attached to hold the end portion of the stock pipe from the inner diameter side, and the stock pipe An whose end portion is held by the stock pipe holding member 3 is transferred on a conveyor roll 4 and fed to the stock pipe. The material is intermittently fed to the downstream side (the right side in FIG. 1 corresponds to this, hereinafter simply referred to as the downstream side, and the opposite side is referred to as the upstream side).

The rear end surface of the raw pipe A1 being expanded is the raw pipe A. The base tube A is pressed by the tip surface of the tube A. In synchronization with the intermittent feeding, intermittent feeding is also performed in the same way, but a driving roll 6, a rapid heating means (specifically, a high-frequency heating coil, etc.) 7, etc. are installed at the feeding position of the blank tube A1. The base pipe A,
A forward driving force is applied by a drive roll 6 as needed, and heating is performed by a rapid heating means 7.

Now, the fixed die 8 and the movable plug 9 are examples of jigs that directly act to expand the raw pipe A, and these will be explained in detail below.

The fixed die 8 has an inner diameter slightly larger than the outer diameter of the raw pipe A1 (specifically, 5 to 30% of the wall thickness of the raw pipe A is larger than the outer diameter of the raw pipe A1). The set insertion port 8a has an inner diameter larger than the inner diameter of the insertion port 8a (specifically, based on the target outer diameter of the diameter expansion tube A2, the outer diameter is larger than this by the thermal expansion bone during tube expansion). ) Consisting of an extraction port part 8c set to a constant size and an intermediate part 8b located between the drawing parts 8a and 8c, the inner diameter of which gradually increases exponentially toward the downstream side, the overall diameter of the through hole is enlarged on the downstream side. It has a shape with holes. The fixed die 8 has its central axis aligned with the base tube A. , A1 are fixedly arranged substantially in alignment with the feeding direction of A1. The through holes 8d formed in the radial direction of the fixed die 8 are for supplying lubricant into the fixed die 8.

The movable plug 9 has a constant outer diameter that is slightly smaller than the inner diameter of the raw pipe A (specifically, 5 to 30% smaller than the inner diameter of the raw pipe A by 5 to 30% of the wall thickness of the raw pipe A1). The guide part 9a is set and has a spherical tip on the upstream side, and the outer diameter is larger than the outer diameter of the guide part 9a (specifically, the enlarged diameter pipe A2
The molded part 9c is set to a constant dimension (based on the target inner diameter of The intermediate portion 9b gradually increases in diameter, and the overall shape is generally bullet-shaped with a diameter increasing on the downstream side. The movable plug 9 has a mandrel receiver supported in a horizontal position by a frame 11 and a downstream end 10 attached to a crank mechanism 12.
a is linked via a plug lock mechanism 13 to the upstream end 10b of a mandrel 10 which is pivotally connected and moves horizontally reciprocatingly, and is loosely inserted into the fixed die 8 as the mandrel 10 moves horizontally reciprocatingly. It is designed so that it can make reciprocating movements while being moved.

The plug lock mechanism 13 can protrude from the outer circumferential surface of the mandrel 1° and can be accommodated within the outer circumferential surface, and the movable plug 9 and the mandrel 1o are linked with each other while protruding from the outer circumferential surface. On the other hand, the movable plug 9 and the mandrel 10 are held within the outer peripheral surface.
The connection with is now cancelled. Further, the downstream end portion 10a of the mandrel 10 is formed by combining female and male threads, and the length of the mandrel 1° can be finely adjusted by adjusting the amount of thread engagement. Further, the crank mechanism 12 is placed on a movable base 15, and as the movable head 15 moves downstream, the crank mechanism 12 can move downstream together with the mandrel 1o. Note that the conveyance roller 14 disposed below the mandrel 10 is connected to the expanded diameter tube A.
2 from below.

When carrying out the method of the present invention using such an apparatus, first,
The rod 1a of the air cylinder 1 is moved in and out, and the raw pipe A is removed. (Dummy tube in the final step) is inserted from the side (in FIG. 1, from the front or back side of the page).

Then, while advancing the rod 1a of the air cylinder 1, the raw pipe A is removed using the ratchet mechanism 2. When feeding intermittently, the raw tube A. The raw pipe A adjacent to the downstream side of the raw pipe A is intermittently fed into the gap formed between the fixed die 8 and the movable plug 9 that has been loosely inserted therein in advance. A crank mechanism 12 is connected to the movable plug 9 in connection with the intermittent feeding of the raw pipe A1.
When the driving force is transmitted through the mandrel 10 to cause the movable plug 9 to make intermittent reciprocating motion, the raw pipe A1 is gradually expanded in diameter and thinned to become a diameter-expanded pipe A2.

Such diameter expansion and thickness reduction processing is performed in multiple stages according to the intermittent reciprocating motion of the movable plug 9, as shown in FIG.

That is, as shown in the figure, the raw pipe A is subjected to forging pressure by the plug 9 each time it is intermittently fed, and is gradually expanded in diameter and thinned.

In this way, the raw pipe A is gradually expanded in diameter and thinned, and when the process is completed and the entire raw pipe A1 is made into the expanded diameter pipe A2, the movable base 15 is moved downstream, and the movable plug 9 By pulling out the mandrel 10 from inside the expanded diameter tube A2, the expanded diameter tube A2 is separated and carried out from the apparatus.

In this way, the raw pipe AI subjected to the diameter expansion and thickness reduction process is forged compressed while the inner and outer circumferences are regulated by the gap formed between the fixed die 8 and the movable plug 9, so in the case of the method of the present invention, The lantern formation, which has been a problem in the past, is suppressed by regulating the inner and outer peripheries, and the occurrence of internal cracks is essentially suppressed by forging compression. In addition, by forging, it is easier to obtain a beautiful surface texture, and by forging from the thickest parts first, uneven thickness can be corrected. In addition, if the degree of working is large and it is necessary to heat the raw tube A, it is sufficient to heat the raw tube A using the rapid heating means 7 and perform hot working or warm working, but the degree of working is small. In some cases, cold working is also possible, making it possible to process raw tube A1 as before.
There is no need to heat under strict control.

Note that increasing the feed rate of the raw tube A per time improves efficiency, but increases the amount of processing per time and affects product quality, so the capacity of the equipment, It is naturally limited by product quality (especially the quality of the tube surface), etc. - For boat fishing, the limit is 10 (11 m).Also, there are no particular conditions for the stroke of the intermittent reciprocating motion of the movable plug 9, but It needs to be larger than the amount fed per time through pipe A.Also, as a lubricant,
It is sufficient to supply water, but emulsion type oil can also be used.

In addition, in this embodiment, the insertion opening 8a of the fixed die 8
5 to 5 of the wall thickness of the raw pipe A1 by comparing the inner diameter with the outer diameter of the raw pipe A1.
The reason why the gap between the insertion opening portion 8a and the raw pipe A1 is limited to 30% is that the gap between the insertion port 8a and the raw pipe A1 is 5 to 3 times larger than the wall thickness of the raw pipe A1.
When it is below the 0% range, the base tube A1 is fixed die 8.
This is because if the gap exceeds the range of 5 to 30% of the wall thickness, the dimensional accuracy of the wall thickness of the enlarged diameter tube A2 after processing will deteriorate. Furthermore, the outer diameter of the guide part 9a of the movable plug 9 is limited to be smaller than the inner diameter of the raw pipe A1 by 5 to 30% of the wall thickness of the raw pipe AI. , is less than 5 to 30% of the wall thickness of the raw pipe A1, because scratches are likely to occur on the inner surface of the raw pipe A1, and the gap is in the range of 5 to 30% of the wall thickness. This is because when the diameter exceeds , the dimensional accuracy of the wall thickness of the enlarged diameter tube A2 after processing deteriorates.

Furthermore, the reason why the upstream end of the guide portion 9a is spherical is to prevent scratches from occurring on the inner surface of the raw pipe A.

(Effects) As detailed above, according to the method of the present invention, buckling of the raw pipe, which occurs in the conventional method when expanding a seamless pipe obtained by the roll piercing rolling method or the hot extrusion method, can be avoided. This eliminates problems such as cracking of the inner surface of the lantern or the occurrence of cracks on the inner surface of the raw tube, and its utility value is high.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram showing the apparatus used to carry out the method of the present invention, Fig. 2 is a schematic explanatory diagram showing multi-stage diameter expansion and thinning processing by the method of the present invention, Fig. 3 (A), (B) is a schematic explanatory diagram showing a conventional method for expanding a seamless pipe. 2...Ratchet mechanism 8...Fixed die 9...
Movable plug A. , A+ ... Base pipe A2 ... Expanded diameter pipe

Claims (1)

[Scope of Claims] 1. A movable plug having an outer diameter expanded on the downstream side in the raw tube feeding direction is loosely inserted into a fixed die having a through hole with a diameter expanded on the downstream side in the raw tube feeding direction, and the movable plug is loosely inserted between the two. The base pipe is intermittently fed into the gap formed in the base pipe, and the movable plug is intermittently reciprocated in association with the intermittent feeding of the base pipe to expand the diameter and reduce the thickness of the base pipe. Seamless pipe expansion method.