JPS63260632A - Liquid pressure bulging method - Google Patents

Abstract

PURPOSE:To easily perform the bulging formation extending the bulging extension part by interposing a liquid between a piston and pipe for bulging a bulging scheduled part and bulging it by feeding ultrahigh liquid pressure to the pipe inside. CONSTITUTION:The liquid Q of an oil, etc., is interposed between the bulging scheduled part of a pipe blank 1 subjected to die closing between upper and lower dies 2, 3 and the piston 6 enabling to bulge it in T shape. An ultrahigh pressure liquid P is fed to the blank 1 from the pistons 5, 5 for compression of pipe blanks 1, 1' to compress with pressure the blank 1 in the axial direction. The bulging scheduled part is bulged so as to push down the piston 6 via the interposed liquid Q and since the interposed liquid Q exists uniformly among the outer peripheral face 1e of the blank 1 and upper and lower dies 2, 3 an uniform action is exerted on the bulging base part 1c to be deformed in R shape as well. The bulging part extension part 1d extending straightly along the hole 4 of a die at bulging time is thus subjected to bulged forming in length.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a hydraulic bulge processing method, and in particular, when a portion of a pipe material to be bulged is bulged, the bulge is particularly rounded. This invention relates to a hydraulic bulge processing method that makes it possible to bulge out the straight part as much as possible without reducing the thickness of the material.

[Conventional technology]

BACKGROUND ART Hydraulic bulge processing has been known as one of the methods for processing a pipe into a T-shape or the like. More specifically, a pipe material to be processed is loaded between an upper mold and a lower mold, compression pistons are applied to both ends of the pipe material, and the pipe is clamped from the inside of each piston. In addition to making it possible to supply ultra-high-pressure liquid into the material, a bulge-permitting piston is placed in a hole provided in the mold at a position corresponding to the portion of the pipe material to be bulged, and the ultra-high-pressure liquid is supplied into the pipe material. supply,
This is a method of machining a pipe material into a T-shape or the like by bulging the portion to be bulged by a predetermined amount as the bulge-allowing piston retreats.

Conventionally, when the pipe material is bulged, the pressure receiving surface of the bulge-allowing piston 6 contacts only the portion of the pipe material to be bulged, and the rounded portion is directly along the wall of the lower mold 3. [Problem to be solved by the invention] Therefore, when the pipe material is bulged, the piston moves backward to allow the pipe material to bulge out in a T-shape. The drag force of this bulge-permitting piston, which acts only on the end face of the part to be bulged, is lower than the internal pressure of the pipe in order to prevent the pipe material from bursting during the bulging process and to properly bulge it. , is set quite large. Therefore, the differential pressure between the inner and outer pressures in the area to be bulged is relatively small.

However, in areas other than the part where the pipe material is to be bulged out, such a large drag force does not act, and as mentioned above, the pipe material is only forced along the wall of the lower mold, and in effect, the part of the pipe material other than the part where the bulge is to be processed does not act. Since only atmospheric pressure acts on the surrounding area, the differential pressure between the internal and external pressures is large (internal pressure > external pressure), and thinning is likely to occur especially at the base of the bulging part, which is deformed into a rounded shape during bulging processing. In some cases, pinholes and the like may occur. As a result, it has become difficult to lengthen the extended portion of the bulge that extends straight along the hole of the mold during the bulging process.

Therefore, it is an object of the present invention that the pressure difference between the internal and external pressures is uniform in all parts of the pipe material, and that the pipe material is pushed forward. To provide a hydraulic bulge processing method capable of forming a long bulging part extending straight along a hole in a mold without causing pinholes or cracks.

[Means for solving problems]

The present invention has been made in view of the above points, and has the following technical means.

That is, in the present invention, a pipe material l to be processed is loaded between an upper mold 2 and a lower mold 3, and both ends 1', 1' of this pipe material l are
A compression piston 5.5 is applied to the piston 5.5 of each line number to make it possible to supply the ultra-high pressure liquid P into the clamped pipe material 1, and also to prevent the pipe material 1 from expanding. A bulge-permitting piston 6 is arranged in a hole 4 made in the mold at a position corresponding to the portion 1a to be processed, and ultra-high pressure liquid P is supplied into the pipe material 1, and the bulge-permitting piston 6 is placed in the hole 4 provided in the mold at a position corresponding to the portion 1a to be processed. In the hydraulic bulge processing method in which the pipe material 1 is bulged by a predetermined amount as the pipe 6 retreats to form a T-shape, etc.; A liquid Q such as oil is interposed between the pressure receiving surface 6a of the bulge-permitting piston 6 and the outer circumferential surface 1e of the pipe material 1, and ultra-high hydraulic pressure F is supplied into the pipe material 1 to form the bulging portion 1a. The piston 6 is allowed to bulge out through the intervening liquid Q.
This is a hydraulic bulge processing method characterized by making it possible to apply the intervening hydraulic pressure Q to the bulging part base 1c which is deformed into the rounded shape of the pipe material bulging part while retracting the pipe material. .

[Effect]

A liquid Q such as oil is applied between the portion 1a of the pipe material 1 to be bulged which is clamped between the upper and lower molds 2.3 and the bulge allowing piston 6 which allows this portion to bulge into a shape such as a single character. Then, the bulge allowing piston 6 is brought into contact with the portion 1a to be bulged.

Next, the compression pistons 5 at both ends 1' and 1' of the pipe material 1
．． The ultra-high pressure liquid P is supplied from 5 into the pipe material 1, and the pipe material 1 is pressurized and compressed in the axial direction while maintaining the liquid pressure P in the pipe 1. Since the outer peripheral surface 1e of the pipe material 1 is surrounded by the fixed upper and lower molds 2.3, the pipe material 1
The portion to be bulged is provided so as to be able to descend within a hole 4 formed in the mold, and a bulge allowing piston 6 is applied to the portion 1a to be bulged of the pipe material l via an intervening liquid Q.
It bulges out as if pushing down. At this time, the drag force of the retreating expansion permitting piston 6 is transmitted via the intervening liquid Q.
The intervening liquid Q is connected to the outer peripheral surface 1e of the pipe material 1, the lower mold 2,
3, it does not particularly act only on the end portion 1b of the bulge, but also acts uniformly on the base 1c of the bulge, which is deformed into a rounded shape during the bulging process. That is, the differential pressure (P-g) between the internal and external pressures is uniform at any position on the pipe material 1. Therefore, during the bulging process, thinning is less likely to occur in the bulging portion base 10 and the like.

The protruding portion ld extending straight along the hole 4 of the mold can be bulged out for a long time during the molding process.

〔Example〕

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1A to 1H are diagrams showing the process of expanding and forming a pipe material into a T-shape.

In FIG. 1(A), 1 indicates a pipe material such as a metal tube, which is loaded between an upper mold 2 and a lower mold 3 that are fixed by a mold clamping press (not shown). A hole 4 is drilled in the center of the lower die 3 as a space for bulging the pipe material 1 into a T-shape, and the bulging fabric of the pipe material 1 is formed in the hole 4 at the forward limit position. A bulge-permitting piston 6 is provided, which is applied to the portion 1a to be processed via an intervening liquid, which will be described later, and allows the portion 1a to be bulged while retracting.

This pipe material 1 is attached to both ends 1' and 1' of the pipe material 1.
A compression piston 5.5 is applied to pressurize and compress the liquid in the axial direction. It has injection holes 5a, 5a that enable supply.

Now, as shown in Fig. 1 (A) and (B), set the pipe material l between the upper and lower molds 2.3, apply the compression piston 5.5 to both ends 1' and 1', and then As shown in FIG. 1(C), ultra-high pressure liquid P is supplied into the pipe material 1 through the injection holes 5a, 5a of these pistons 5.5. Pipe material 1
The liquid P is supplied to the inside of the mold to the extent that sufficient hydraulic pressure is obtained for the bulging process, and the bulging permitting piston 6 is arranged in the hole 4 of the lower die 3 as shown in FIG. 1(D). The advance is limited and applied to the bulging portion 1a to be processed. At this time, conventionally, the portion 1 to be bulged is
Since the expansion permitting piston 6 was brought into contact with the point a, the problem occurred as described above.

As shown in FIGS. 1(A) to 1(C), the present invention provides a necessary and sufficient amount of oil etc. to be uniformly present in the gap between the outer peripheral surface 1e of the pipe material 1 and the upper and lower molds 2.3. Apply high pressure liquid Q to hole 4 in advance.
The intervening liquid is interposed between the pressure receiving surface 6a of the bulge allowing piston 6 and the portion 1a to be bulged, and the pressure receiving surface 6a of the bulge allowing piston 6 is applied to the portion 1a to be bulged. When pressing through Q, the outer circumferential surface 1e of the pipe material 1
This intervening liquid Q was also interposed between the upper and lower molds 2.3. At this time, this intervening liquid Q naturally flows into the upper and lower molds 2.
3. Sealed by compression piston 5.5 expansion permitting piston 6, etc.

The operation will be explained below.

As shown in Fig. 1 (D), ultra-high pressure P is applied inside the pipe material 1.
When the pipe material I is pressurized and compressed in the axial direction by the compression piston 5.5 as shown in FIG. 1(E), the outer peripheral surface 1e of the pipe material I is fixed. 2
．． The portion 1a to be bulged is bulged by pushing down the bulge-permitting piston 6, which is surrounded by 3 but is provided so as to be retractable, via the intervening liquid Q, and the internal pressure P of the pipe material 1 is compressed. The same state as before is maintained. When the pressurized compression of the compression piston 5.5 is further advanced, the bulging portion end 1b further pushes down the bulging permitting piston 6 via the intervening liquid Q. Conventionally, it has been difficult to make the protrusion extending portion 1d that extends straight along the hole 4 as long as shown in FIG. 1(F).

That is, when the protrusion extending portion 1d is lengthened to this extent, the protrusion base portion 1c is deformed into a rounded shape due to the protrusion processing.
This was because thinning was likely to occur. However, if the intervening liquid Q is used as in this embodiment, the drag force of the bulge-allowing piston 6 is applied not only to the bulging end 1b but also through the intervening liquid Q, as shown in FIG. 1(G). It also acts on the bulge base 1c, etc., where thinning is likely to occur. That is, the internal pressure of the pipe material 1 is uniform in all parts, but the external pressure is also uniform in all parts by passing through the intervening liquid Q. Q) is uniform, so there is little risk of thinning at specific locations such as the base of the bulge.

As mentioned above, even if the pressure compression of the compression pistons 5, 5 is increased, the internal pressure P of the pipe material 1 is kept constant while retracting the expansion permitting piston 6, so that the differential pressure between the internal and external pressures (F
−ζ) is always kept constant until the limit bulging process of the pipe material is performed.

Therefore, as shown in FIG. 1(G), the extended portion 1d of the protrusion can be formed into a longer bulge. In FIG. 1 (G), the arrow W points above the outer circumferential surface 1e of the pipe material 1.

It shows a partial enlargement of the bulge base 1c to show that the intervening liquid Q is interposed between the lower mold 2.3,
When the expansion molding is completed, as shown in FIG. 1(H), the ultra-high pressure liquid P inside the pipe material 1 is extracted and the pipe material 1 is removed from the mold 2.3.

By the way, the above-mentioned intervening liquid Q is applied to the outer circumferential surface 1e and upper surface of the pipe material 1.
By interposing it between the lower molds 2 and 3, the frictional resistance when the pipe material 1 is pressurized and compressed by the compression piston 5.5 is reduced, so that the pipe material 1 can be compressed smoothly; 0 that allows for good bulge processing
By reducing the frictional resistance, pinholes and the like, which were particularly likely to occur at the rounded bulge base 1c, become less likely to occur.

〔Effect of the invention〕

As can be seen from the above, when the pipe material is bulged into a T-shape, the portion to be bulged is shaped into a T-shape.
A liquid such as oil is interposed between the pressure-receiving surface of the piston that allows for expansion and the outer peripheral surface of the pipe material to allow it to expand in a shape such as a letter.
Ultra-high hydraulic pressure is supplied inside the pipe material to bulge the portion to be bulged, and while the bulge-permitting piston is retracted via the intervening liquid, the intervening liquid pressure is applied to the rounded shape of the bulged portion of the pipe material. Since it is possible to apply pressure to the base of the bulge that is deformed, it is possible to uniformly reduce the differential pressure between the internal and external pressures at any position on the pipe material, and therefore, it is possible to reduce the pressure difference uniformly at any position of the pipe material. It is possible to avoid thinning at the base of the bulge, which is prone to occur, and to reduce the frequency of pinholes and cracks. It is possible to easily realize a bulge forming process in which the extending portion of the protruding portion is made as long as possible.

[Brief explanation of drawings]

FIGS. 1(A) to 1(H) are diagrams showing an example, and sequentially show the steps of expanding and forming a pipe material into a T-shape. In addition, 190. Pipe material, 2. ,,upper mold,
390. Lower mold, 4. ,,hole. 504. Compression piston, 5a, injection hole. 6, , @ piston that allows expansion, 6a, , pressure receiving surface of piston that allows expansion, Plo, ultra-high pressure liquid supplied into the pipe, Foo, liquid pressure (internal pressure) inside the pipe, Q, 2.
Intervening liquid, Q16. This is the intervening hydraulic pressure (external pressure). M1 figure (83

Claims (1)

[Claims] A pipe material 1 to be processed is loaded between an upper mold 2 and a lower mold 3, and compression pistons 5, 5 are applied to both ends 1', 1' of this pipe material 1. The ultra-high pressure liquid P can be supplied from the inside of each piston 5, 5 into the clamped pipe material 1, and the portion 1 of the pipe material 1 to be bulged is
An expansion permitting piston 6 is placed in the hole 4 provided in the mold at the position corresponding to a, and an ultra-high pressure liquid P is supplied into the pipe material 1.
In the hydraulic bulge processing method in which the pipe material 1 is bulged by a predetermined amount with the retreat of the bulge-allowing piston 6 to process the pipe material 1 into a T-shape or the like; A liquid Q such as oil is interposed between the pressure-receiving surface 6a of the expansion-permitting piston 6 and the outer circumferential surface 1e of the pipe material 1 to enable expansion in a character shape, etc., and ultra-high hydraulic pressure is created within the pipe material 1. Pressurize @P@ to bulge the part 1a
The bulging portion base 1c is deformed by the intervening liquid pressure @Q into the rounded shape of the bulging portion of the pipe material while bulging and retracting the expansion permitting piston 6 via the intervening liquid Q.
A hydraulic bulge machining method that is characterized by making it possible to pressurize.