JPH08276224A - Die for forming tapered square tube - Google Patents

Abstract

PURPOSE: To obtain a die for forming a tapered square tube whose life is satisfactorily long and economicity is higher. CONSTITUTION: The die 2 for forming the tapered square tube consists of a truncated pyramid-shaped male die 3 and a female die 4 corresponding to the male die. The female die 4 is taken as an insert structure consisting of a core die 10 which is brought into contact with the outside of a square tube 1a of a base stock and a hollow reinforcing ring die 11 which is fit on the outer periphery of that core die 10. At the time of drawing, large surface pressure acts on the inside 10a of the core die 10 of the female die 4, but a portion of the horizontal component of the surface pressure is effectively borne with the reinforcing ring die 11. That is, the core die 10 is reinforced with the ring die. By using kinds of steel having high wear resistance for the core die 10 and kinds of steel having high tensile strength and toughness for the reinforcing ring, the forming die whose life is satisfactorily long and economicity is higher is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding die for a tapered rectangular tube, which comprises a truncated square pyramidal male mold and a corresponding female mold for obtaining a tapered rectangular pipe by drawing a material rectangular pipe. Regarding the type.

[0002]

2. Description of the Related Art For example, a tapered square tube 1 having a truncated quadrangular pyramid shape as shown in FIG. 5 is used for a connecting portion of rectangular steel tube columns having different diameters in a steel structure building. As a method of manufacturing this kind of taper rectangular tube, a square metal tube which is a rectangular steel tube cut into a predetermined length is formed into a tapered square tube molding die consisting of a truncated square pyramid male mold and a corresponding female mold. Although a method of forming by drawing has been proposed, the male and female dies in the conventional die for forming a tapered rectangular tube are all integrated by cold die steel such as SKD11.

[0003]

When forming a taper square tube with the above-mentioned die for forming a taper square tube, the male square is covered with the material square tube, and the female die is lowered by, for example, a hydraulic press machine. The material square tube is drawn into a tapered square tube by the and the female mold. The material square tube is, for example, 12 mm thick × 350 mm long × 350 m wide.
Since the size is large, such as m, a large surface pressure acts on the inner surface of the female die during this drawing, but the horizontal component of this surface pressure pushes the female die outward, and this pushing force causes the female die to expand. A tensile stress is generated in the circumferential direction. If the external shape of the female mold is cylindrical, the internal surface of the female mold is quadrangular and the external surface is circular. And near the corners on the inner surface side, it becomes severe especially near the corners on the inner surface side, and cracks may occur at the corners with low toughness materials. Therefore, the female die is required to have high tensile strength and toughness. In addition, since strong friction occurs between the inner surface of the female die and the material square tube, the female die is also required to have high wear resistance. On the other hand, existing die steels have various steel types with their respective characteristics, but those with high toughness tend to have low wear resistance, and those with high wear resistance tend to have low toughness. I can't find anything that satisfies.
Therefore, it is not easy to obtain a die with a long life and excellent cost efficiency.

The present invention has been made in view of the above circumstances, and is a molding die for a tapered rectangular tube which can withstand a large surface pressure and friction when the tapered rectangular tube is molded and has a long life and is excellent in economic efficiency. The purpose is to provide.

[0005]

SUMMARY OF THE INVENTION The present invention for solving the above problems comprises a truncated square pyramidal male mold for drawing a raw material rectangular tube to obtain a tapered rectangular tube, and a female mold corresponding thereto. Forming a tapered rectangular tube, wherein the female mold is a core mold having a truncated quadrangular pyramid inner surface in contact with the outer surface of the material rectangular tube, and a hollow reinforcing ring fitted to the outer periphery of the core mold. It is characterized in that it is configured with a mold.

According to a second aspect of the present invention, the mating surface of the core die and the reinforcing ring die in the die for forming the tapered rectangular tube according to the first aspect is concentric with the quadrangular pyramid on the inner surface of the core die and has the same curving direction. It is characterized by forming a conical surface.

[0007]

In the above structure, when the raw material rectangular tube is drawn by the male mold and the female mold, a large surface pressure acts on the inner surface of the female core mold. Both the tensile stress in the circumferential direction generated in the core die and the tensile stress in the circumferential direction generated in the reinforcing ring die on the outer periphery oppose the horizontal component of the surface pressure. Therefore, the core type itself is not required to have a particularly large counter force against the horizontal component of the surface pressure. Further, since the reinforcing ring type does not come into contact with the material square tube, wear resistance is not particularly required. Therefore, by using a steel type with high wear resistance for the core type and a steel type with high tensile strength and toughness for the reinforcing ring type on the outer periphery of the core type, it is possible to obtain a die for a tapered rectangular tube with a sufficiently long life. To be

According to the second aspect of the present invention, since the fitting surfaces of the core die and the reinforcing ring die are conical surfaces, both can be easily fitted in close contact with each other, and the pressing for drawing is performed. The load acts to more closely fit the core type and the reinforcing ring type. Therefore, the reinforcing ring type can effectively handle a part of the horizontal component of the surface pressure acting on the core type, and effectively functions as a reinforcement of the core type.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a molding die 2 for a tapered rectangular tube according to an embodiment of the present invention. The molding die 2 includes a truncated square pyramid male die 3 and a corresponding female die 4. In FIG. 1, 1a is a material square tube to be drawn into the tapered square tube 1, 5 is a male holder, 6 is a female holder,
Reference numeral 7 indicates a pedestal of the press machine, and 8 indicates a ram of the press machine.

As shown in detail in FIGS. 3 and 4, the female die 4 includes a core die 10 having a truncated quadrangular pyramid-shaped inner surface 10a which contacts the outer surface of the material rectangular tube 1a, and the core die 10 of the core die 10. The core structure 10 and the reinforcing ring mold 1 have a nested structure composed of a hollow reinforcing ring mold 11 fitted to the outer periphery.
The mutual fitting surface 12 with 1 is a conical surface which is concentric with the quadrangular pyramid of the inner surface 10a of the core mold 10 and has the same constriction direction (that is, a conical surface which constricts upward in the illustrated example). The taper angle α of the conical surface is, for example, 2 ° in the illustrated example.

The core mold 10 and the reinforcing ring mold 11 are respectively fixed to the female mold holder 6 with bolts, and the bottom surface of the core mold 10 is fixed with bolts 13 by interposing wedges 14 on the bottom surface of the reinforcing ring mold 11. It is pressed upward by, for example, 12 pressing members 15 that are clamped and fixed. In this case, by tightening the bolt 13 and then driving the wedge 14 further toward the center side, the pressing member 1
The core die 10 is strongly pressed upward by the tip portion of 5, so that the fitting surfaces of the core die 10 and the reinforcing ring die 11 can be sufficiently brought into close contact with each other. In this way, since the fitting surface 12 has a conical surface shape, it is easy to closely fit the core mold 10 and the reinforcing ring mold 11.

Regarding the material used, for example, the core type 10
It is appropriate to use SKD11 (JIS standard), which is a type of cold die tool steel, and use SKT4 (JIS standard), which is a type of hot die tool steel, for the reinforcing ring die 11.
SKD11 has excellent wear resistance, and SKT4 has excellent toughness and sufficiently high tensile strength.

When forming a tapered rectangular tube with the above-mentioned molding die 2, the material rectangular tube 1a is covered on the male die 3 as shown in FIG. 1, and the ram 8 of the hydraulic press or the like is lowered to lower the female die 4. As a result, the material rectangular tube 1a becomes a male mold 3 and a female mold 4 as shown in FIG.
Although the taper rectangular tube 1 is drawn by and, a large surface pressure acts on the inner surface 10a of the core die 10 of the female die 4 during this draw forming. For the horizontal component of this surface pressure, the core type 10
The tensile stress in the circumferential direction that occurs on the outer circumferential surface and the tensile stress in the circumferential direction that occurs in the reinforcing ring mold 11 on the outer circumference thereof oppose each other. Therefore, since the core mold 10 itself is not required to have a particularly large counter force against the horizontal component of the surface pressure, wear resistance may be mainly considered. In addition, the reinforcing ring type 11
Does not come into contact with the raw material square tube 1a, so wear resistance is not particularly required, and tensile strength and toughness may be mainly considered. Therefore, as described above, the core die 10 is made of a steel type having high wear resistance such as SKD11, and the reinforcing ring die 11 is made of a steel type having high tensile strength and toughness such as SKT4. A molding die for a sufficiently long rectangular taper can be obtained.

The reinforcing ring die 11 needs to be in close contact with the outer periphery of the core die 10 in order to function as a reinforcement for the core die 10.
Since it has a conical surface, it is easy to fit the core die 10 tightly, and the pressing load during drawing makes the core die 10 and the reinforcing ring die 11 fit more closely. Acting on the core mold 10, it effectively functions as a reinforcement of the core mold 10.

Normally, there are a plurality of sizes of tapered rectangular tubes to be manufactured, and therefore the above-mentioned molding die 2 needs to be able to cope with these plural kinds of sizes. If a dedicated core die 10 having a truncated quadrangular pyramid inner surface is manufactured and the outer shape (shape of the fitting surface 12) of each core die 10 is the same in any size, the reinforcing ring die 11 is commonly used. Can be used.

The core mold 10 and the reinforcing ring mold 11
The steel types used for SKD11 and SKT listed in the examples
It is not limited to No. 4, but can be appropriately selected based on the selection criteria of steel type having high wear resistance for the core type and steel type having high tensile strength and toughness for the reinforcing ring type. Further, in the embodiment, the case of a regular square pyramidal tapered rectangular tube having four tapered surfaces, that is, a four-sided diaphragm tube is shown, but a three-sided diaphragm tube having one vertical surface and three tapered surfaces,
Alternatively, it is naturally applicable to a double-faced throttle tube having two vertical faces and the other two tapered faces.

[0017]

According to the present invention, the female mold has a nested structure consisting of a core mold having a truncated quadrangular pyramid-shaped inner surface and a reinforcing ring mold fitted to the outer periphery thereof. By using a steel type with high wear resistance and a steel type with high tensile strength and toughness as the reinforcing ring type, it is possible to obtain a die for a tapered rectangular tube with a sufficiently long life and excellent economic efficiency. Further, when the material contact surface is worn, only the core mold needs to be replaced, which is economical in this respect as well. In addition, although the core type needs quenching, of course, the part that needs quenching can be small, so heat treatment is easy and economical. Also, if dedicated core dies are manufactured for various sizes of tapered rectangular tubes, the reinforcing ring dies can be used in common, so that the production cost of the dies as a whole production type can be reduced. It is also economical in terms.

According to the second aspect, since the fitting surface of the core die and the reinforcing ring die is a conical surface, the reinforcing ring die effectively utilizes a part of the horizontal component of the surface pressure acting on the core die. It is possible to take charge of it and to surely exhibit the effect of the nested structure. Further, the processing of the conical surface is easier than the processing of, for example, the quadrangular pyramid surface, and the cost is low.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a molding die for a tapered rectangular tube according to an embodiment of the present invention, showing a state where a material rectangular tube is set in a male mold.

FIG. 2 is a diagram showing a point of time when the female die is lowered to draw the raw material square tube into a tapered square tube in the forming die of FIG.

FIG. 3 is an enlarged cross-sectional view of the female die in FIG.

FIG. 4 is a bottom view of FIG.

FIG. 5 is a perspective view showing an example of a tapered rectangular tube to be molded by a molding die for a tapered rectangular tube of the present invention.

[Explanation of symbols]

 1 Tapered Square Tube 1a Material Square Tube 2 Molding Tool for Tapered Square Tube 3 Male Mold 4 Female Mold 10 Core Mold 10a truncated square pyramidal inner surface (inner surface of core mold) 11 Reinforcement Ring Mold 12 Fitting surface

Claims (2)

[Claims] 1. A molding die for a tapered rectangular tube, comprising a truncated square pyramidal male mold and a corresponding female mold for obtaining a tapered rectangular pipe by drawing a material rectangular pipe. The female mold has a nested structure composed of a core mold having a truncated pyramidal inner surface in contact with the outer surface of the material rectangular tube and a hollow reinforcing ring mold fitted to the outer periphery of the core mold. Mold for forming tapered rectangular tubes. 2. The fitting surface of the core mold and the reinforcing ring mold is a conical surface concentric with a quadrangular pyramid of the inner surface of the core mold and having the same constriction direction. Molding taper square tube.