JPH0638573Y2 - Mounting structure for plugs for pipe drawing - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of use] The present invention relates to a mounting structure for a pipe drawing plug, and more particularly to a mounting structure for a pipe drawing plug that can reversely use the drawing plug.

[Conventional technology]

Typical plugs used when manufacturing pipes by drawing are cylinder type, taper type and lens type,
These are used in combination with R-type, trumpet-type, and intermediate-type dies, respectively. Among them, cylindrical plug and R
The combination of the die dies is widely adopted because the shape of the tool is simple, the tool can be easily machined, and a relatively high degree of machining can be obtained. The cylindrical plug is a cylindrical plug provided with an internal thread portion at the axial center of the base end portion. The internal thread portion is screwed into an external thread portion provided at the tip of the mandrel to support the plug by the mandrel. The plug has a high hardness since the tool steel made of carbon steel or alloy steel is heat-treated and the surface is subjected to surface treatment such as chrome plating or is made of cemented carbide. At the time of drawing, as shown in FIG. 3, the plug (1) is positioned inside the die (2), and the raw tube (3) is moved to the die (2).
The diameter reduction process is performed by using, and the wall thickness reduction process is performed by using the die (2) and the plug (1), and the product is drawn out to a predetermined size. At this time, the blank pipe (3) begins to contact the plug (1) at point a in the figure, and is subjected to a diameter reduction thinning process up to a point b corresponding to the minimum inner diameter portion of the die (2). This completes the contact with the plug (1). When the drawing process of the raw pipe (3) having the same size specifications is repeated in the state shown in FIG. 3, the contact points a to c of the plug (1) with the raw pipe (3) are almost at the same position. The wear occurs between points a and c in (1), especially between points a and b. When the plug (1) wears, the inner diameter of the drawn pipe (4) becomes smaller, and the wall thickness becomes thicker accordingly, and the surface of the worn part of the plug (1) becomes rough and Since the inner skin of (4) deteriorates,
Replace the plug (1) with a new one. However, in the plug (1) shown in FIG. 3, the surface on the mandrel (5) side from the contact start point, that is, the point a, is not worn. Therefore, when the plug (1) is replaced, this portion is wasted and the plug (1) is wasted. There was a problem that the basic unit of was worse. Further, in order to solve this problem, a plug shortened only in a non-wearing portion is used, or a plug provided with a female threaded portion penetrating the shaft center so that the worn side can be reversed and used as the mandrel (5) side. There is a method to be used, and according to these methods, improvement of the plug unit consumption can be expected.

However, if the plug has the length necessary for drawing, even if plugs with the same outer diameter are used, due to the degree of processing (area reduction rate) during different drawing processing due to setup, the strength of the raw pipe, etc. When the pulling force becomes large, the plug is pulled in the drawing direction and its position moves, which is a so-called pull-in phenomenon, so that there is a problem that it is extremely difficult to set the initial position of the plug. Further, since the point a, which is the contact start point, also differs when the metal thinning rate differs, the required plug length also varies depending on the metal thinning rate, and there is the problem that an extremely multidimensional plug must be prepared. In addition, in each case, a new problem occurs that the plug is broken into a ring shape, the basic unit of the plug does not improve so much, and in some cases, it worsens. The reason for this is that there is a threaded portion on the inner surface of the plug corresponding to the points a and b where the largest radial compression force is applied to the plug, and that this threaded portion supports the pulling force applied in the pull-out direction of the plug. Especially.

That is, when radial contraction force is applied to the threaded portion, stress concentrates on the threaded portion. Further, when a pulling force in the pulling direction is applied to this portion, the threaded portion is torn off and broken into a ring shape. In order to solve such a problem, as a plug having no threaded portion on the inner surface of the plug, there is a plug described in Japanese Utility Model Laid-Open No. 62-131715. Although the internal structure of this plug is not shown, as shown in FIG. 4, the step (7) of the shank (6) is tapered and the through hole (8) of the plug (1) is The taper angle and dimensions are almost the same as the taper of the stepped portion (7). By tightening with the tightening nut (9), both tapered portions are brought into close contact with each other, and cemented carbide, ceramic or the like with low transverse rupture strength is used. It is presumed that the internal structure prevents the plug from cracking.

[Problems to be solved by the device]

However, since the through hole of the plug is tapered, the tip side and the base end side cannot be used upside down when locally worn. Therefore, although it is possible to prevent the plug from cracking, there is a problem that the basic unit of the plug cannot be improved.

The present invention has been made in view of the above circumstances, and its purpose is to eliminate the need to adjust the initial setting position due to the movement of the plug position due to the difference in the pulling force, and to reverse the use of the plug. It is an object of the present invention to provide a mounting structure for a plug for pipe withdrawal, which is capable of preventing breakage of the plug.

[Means for Solving the Problems]

The present invention is directed to a stepped portion formed to have a smaller diameter in the axial length direction and an equal diameter than the large diameter portion, and further to this stepped portion, a male screw portion is formed on the circumferential portion of the tip extending to the stepped portion with the same diameter. And a through hole having an equal diameter in the axial length direction, which fits in a step fit state of the plug holding tool in a loose fit state, and has a length required for the drawing process. A pipe consisting of a plug made of tool steel having double bending strength and more, and a tightening nut that is screwed into the male screw part of the plug holder and holds the plug between the large diameter part. The gist is the mounting structure of the plug for drawing.

[Action]

As described above, in the plug holder of the mounting structure for the pipe drawing plug according to the present invention, the shape of the step portion following the large diameter portion has the same diameter in the axial direction. Further, the cylindrical plug fitted in the step portion having the same diameter in the axial length direction also has a through hole having the same diameter in the axial length direction at the shaft center. Therefore, the plug can be used upside down. In addition, since these fittings are fitted in a clearance fit because they are used upside down, since the amount of deformation of the plug increases by the clearance, it is usually easy to crack. However, in the present invention, since the tool steel is used as the material of the plug, which has a high bending strength that does not break even if it is deformed in the radial direction by pipe drawing, even if the amount of deformation due to the gap increases, the plug steel is used. Will not be broken. In addition, since the inside of the plug is not threaded, the plug will not be broken due to the stress concentration in the thread valley.

The tool steel having high bending strength in the present invention is, for example,
The tool steel specified in JIS G4401, G4403 and G4404 is hardened and tempered, and the plug body has a wall thickness / outer diameter of 20%.
At that time, bending strength of 500 kgf / mm ² or more is preferable. If the thickness / outer diameter of the plug body is greater than 20%, the bending strength is 50.
It may be 0 kgf / mm ² or less, but it must have a high bending strength so that it will not break even if pipe drawing is performed. Plug (14)
The tool steel is used as the material of, and the cemented carbide is not used. Because the cemented carbide has a small bending resistance, the mandrel (10) is used by fitting it in the step (12) I clearance fit state. Then, it is cracked by the radial compressive force. On the other hand, tool steel has a large transverse rupture strength, and there is no risk of cracking even if the tool steel is fitted and used in a clearance fit state.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In the figure, (10) is a mandrel as a plug holder, and a large diameter part (11), a step part (12) and a male screw part (13) are formed on the tip side of the mandrel (10). The outer diameter of the large diameter portion (11) is smaller than the outer diameter of the plug (14) described later and is slightly larger than the through hole of the plug (14). The step portion (12) is formed following the large diameter portion (11), has a smaller diameter than the outer diameter of the large diameter portion (11), and has an equal diameter in the axial direction.
The length of the step portion (12) is slightly shorter than the length of the plug (14). Following the tip of the mandrel (10), that is, the stepped portion (12), a male screw portion (13) having an outer diameter not exceeding the outer diameter of the stepped portion (12) is formed. The plug (14) is a so-called cylindrical plug having an outer diameter that is equal in the axial direction. The outer diameter of the plug (14) is a dimension corresponding to the inner diameter of the pipe after drawing, and both ends are chamfered into an appropriate shape such as R.
A through hole (15) having an equal diameter in the axial direction is provided at the center of the plug (14). The diameter of the through hole (15) is the same as the mandrel (10).
The size is such that it fits into the stepped portion (12) formed in the above in a loose fit state. The clearance fit is the mandrel (1
This is because the plug (14) can be easily attached to and detached from the step (12) of (0). The length of the plug (14) should be slightly longer than twice the length required for drawing so that if only the tip side is worn, the base side and tip side can be reversed and reused. is there. The material of the plug (14) is tool steel made of carbon steel, alloy steel or the like and having a high bending strength of 500 kgf / mm ² or more. The tightening nut (16) is screwed into the male screw part (13) formed at the tip of the mandrel (10), and is fitted to the stepped part (12) of the mandrel (10) with a loose fit. ) Is fastened and fixed between the large diameter part (11).

Next, another embodiment will be described. In the embodiment shown in FIG. 1, the plug (14) is directly attached to the tip of the mandrel (10), whereas in this embodiment, the shank (17) is provided with the plug (14) as shown in FIG. The shank (17) is attached to the mandrel (10). The shank (17) has a large diameter portion (11) formed on the base end side, and subsequently, a step portion (12) and a male screw portion (13). The outer diameter of the large diameter portion (11) is smaller than the outer diameter of the plug (14), and the through hole (1
5) has a larger diameter, and a female screw portion (18) is formed on the end face of the large diameter portion (11) at its axial center.
8) is screwed onto the male thread (19) at the tip of the mandrel (10). The step portion (12) is formed following the large diameter portion (11), has a diameter smaller than the outer diameter of the large diameter portion (11), and has an equal diameter in the axial direction, and its length is that of the plug (14). A little shorter than the length. Following the step (12), a male screw part (13) having an outer diameter not exceeding the outer diameter of the step (12) is formed. Plug (14),
The tightening nut (16) is the same as that shown in Fig. 1, so it is omitted, but the through hole (15) provided in the shaft center of the plug (14) has a large diameter of about 60% of the outer diameter of the plug (14). can do. This is because the female screw is not formed and there is no risk of ring-shaped fracture starting from the screw portion, and the thickness of the plug (14) can be reduced to about 20% of the outer diameter. Therefore, as the plug (14), those having various outer diameters corresponding to the inner diameter of the pipe after withdrawal and having through holes of about 60% of the outer diameter are prepared, and the shank (17) As for the large diameter part (11), the internal thread part (18) provided on the shaft center has a common dimension corresponding to the male thread part (19) of the mandrel (10), and the large diameter part (11) and the step part (12) , If the male screw part (13) has various sizes according to the size of the plug (14),
Without changing the mandrel (10), the wall thickness
It is possible to use plugs (14) with various sizes of about 20%. In the above-mentioned embodiment, the plug (14) has an outer diameter of a circle with an equal diameter in the axial direction, but has a polygonal shape such as a quadrangle, a hexagon or the like in a front view, an ellipse, and a straight or spiral groove in the axial direction. The plug may be formed, and may have the same dimension in the axial direction. By the way, a plug having the structure shown in FIG. 2 as an example of the present invention and having an outer diameter of 90 mm, a through hole diameter of 50 mm, and a length of 90 mm is used, and as a comparative example, the outer diameter and the length are the same as above, but it is effective instead of the through hole. The incidence of ring-shaped cracks was investigated using a plug having a female thread of 44.5 mm in diameter that was directly screwed and fixed to a mandrel. Each of the plugs is made of alloy steel tool steel and is heat-treated and surface-treated. 300 plugs were used for both plugs, and the plugs were subjected to a drawing process with a working ratio of 20%. According to the present invention,
While all of them could be used until the plug life, in the comparative example, 10% cracked in a ring shape until the plug life was reached. As described above, the plug having the structure for mounting the pipe drawing plug according to the present invention can be used reversely, and the excellent result that the breakage of the plug can be prevented is obtained.

[Effect of device]

As described above, with the pipe drawing plug mounting structure of the present invention, even if the plug position moves due to the difference in the drawing force, the initial setting position adjustment is not necessary and the axial center of the plug is threaded. Since there is no plug, breakage of the plug can be prevented, and since the plug can be used upside down, the basic unit of the plug can be improved, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a mounting structure of a plug for pipe drawing according to the present invention, FIG. 2 is a cross-sectional view showing another embodiment of the present invention, and FIG. 3 is a conventional plug having an axial center with a screw. FIG. 4 is a cross-sectional view showing a situation in which is attached to a mandrel and is being drawn, and FIG. 4 is a cross-sectional view showing another conventional example. 1, 14 …… Plug, 2 …… Die 3 …… Element tube, 4 …… Tube 5,10 …… Mandrel, 6,17 …… Shank 7,12 …… Step section, 8,15 …… Through hole 9 , 16 ...... Tightening nut, 11 …… Large diameter part 13, 19 …… Male thread part, 18 …… Female thread part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideaki Maruyama Inventor Hideaki Maruyama 1 Nishinomachi, Higashimukaijima, Amagasaki City, Hyogo Sumitomo Kinzoku Kogyo Co., Ltd. Steel Pipe Works (56) ) Corona Publishing Company (1972) Page 1009

Claims (1)

[Scope of utility model registration request] 1. A male screw is formed on a step portion formed to have a smaller diameter than that of the large diameter portion and having an equal diameter in the axial direction, and a circumferential portion of a tip extending to the step portion and having the same diameter continuously following the step portion. And a through hole of equal diameter in the axial direction that fits into the stepped portion of this plug holder in a loose fit condition, and the length of the plug holder is the length required for drawing. It is composed of a plug made of tool steel having double bending strength or more, and a tightening nut that is screwed to the male screw part of the plug holder and holds the plug between the large diameter part. Mounting structure for plugs for pipe withdrawal processing.