JP4631130B2 - Modified tubular product and manufacturing method thereof - Google Patents

Description

表１から明らかなように、外管が、外径：６５ｍｍ、肉厚：２．３ｍｍで拡管率が１２．３％の場合には、形状がやや不良であったが応力の負荷が小さい用途には使用できる程度であり、それ以外は全て良好であった。
【００３８】
図８は、表１の試験No.６のハイドロフォーム加工後の外観写真を示す図である。内管の膨出部５ａ表面と外管６の表面とが同一面となった状態で圧着されていることが分かる。
【００３９】
【発明の効果】
本発明によれば、溶接や接着剤を使用することなく部分的に補強された異形管状製品を最小限の重量増により製造することができる。また、既存の金型を用いて容易にハイドロフォーム加工することができる。
【図面の簡単な説明】
【図１】本発明の異形管状製品の製造方法を説明するためのハイドロフォーム用金型部の縦断面図である。
【図２】溶接により部分強化された異形管状製品斜視図である。
【図３】テラード素管をハイドロフォーム加工することにより得られる異形管状製品の斜視図である。
【図４】形状不良を説明するための製品の縦断面図である。
【図５】ハイドロフォーム加工後の外管と内管との境界部を拡大した縦断面図である。
【図６】本実施例で用いた金型のダイス溝形を示す図である。
【図７】ハイドロフォーム加工時の内圧、軸押し、ポンチの動作パターンを示す図である。
【図８】本発明の製造方法により得られた異形管状製品の外観図である。
【符号の説明】
１ 異形管状製品
２ 補強材
３ 溶接部
４ａ 上金型
４ｂ 下金型
５ 鋼管（素管）
６ 補強用鋼管
７ａ、７ｂ 軸押し工具
８ 液体導入口[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a modified tubular product having a partially strengthened portion manufactured by hydroforming a steel pipe and a method for manufacturing the same.
[0002]
[Prior art]
A metal pipe (hereinafter simply referred to as a pipe) is set in a pair of upper and lower molds, liquid is introduced into the pipe, pressure is applied to the liquid, and axially from the pipe end as necessary. A hydroforming process (hydraulic bulging process) for obtaining a deformed tubular product having a shape in a mold by expanding a base pipe by applying a compressive force has been adopted for manufacturing automobile parts and the like.
[0003]
The deformed tubular product manufactured in this way may be required to have a partially high bulge portion. In that case, a thick pipe or a high-strength pipe may be used, but there are problems such as an increase in the weight of the product and an increase in material cost.
[0004]
As a method for partially reinforcing a deformed tubular product by hydroforming to solve the above problem, there is a method of joining another part having high strength to a portion where the strengthening of the deformed tubular product is necessary by welding or the like.
[0005]
FIG. 2 is a perspective view of a deformed tubular product partially reinforced by welding.
[0006]
A reinforcing member 2 is joined by a welded portion 3 to a part of the modified tubular product 1 manufactured by hydroforming.
[0007]
However, in order to obtain such a product, there is a problem that a process for welding and joining another reinforcing component is required separately from the hydroforming process. In addition, when welded, in addition to the problem that the dimensional accuracy of the product decreases due to thermal strain, there arises a problem of interference between weld spatter and weld beads and other parts.
[0008]
In the document "Proceedings of INTERNATIONAL SEMINAR ON RESENT STATUS & TREND OF THBE HYDROFORMING" july 2 1999 p76 A method for producing a deformed tubular product by using and hydroforming is disclosed.
[0009]
FIG. 3 is a perspective view of a deformed tubular product obtained by hydroforming a terrado tube. FIG. 3A shows an example of a product having a rectangular cross section, and FIG. 3B shows an example of a product having a circular cross section. These deformed tubular products 1 are joined by a welded portion 3 with a reinforcing metal tube 2 indicated by hatching in a part thereof.
[0010]
However, there is a problem that a process for welding the metal pipes is required separately from the hydroforming process in order to manufacture the metal base pipe. In addition, since the metal pipes are partially different in strength, when hydroforming, the low-strength part is more likely to swell than the high-strength part, and wrinkles occur near the weld and a satisfactory product is obtained. There is no current situation.
[0011]
Japanese Patent Application Laid-Open No. 11-5125 discloses a hydraulic bulge processing method in which a reinforcing hollow member coated with an adhesive is inserted on the outside of a metal base tube to be hydroformed to perform hydroforming. .
[0012]
However, for example, when a product with a complicated shape such as a center pillar reinforcement for automobiles is molded by hydroforming, it is common to perform pre-press molding called preform, which is bonded immediately before hydroforming. The agent cannot be applied. When the reinforcing steel pipe is inserted before the preform, there is a problem that it is bonded at an unexpected position during the preform.
[0013]
[Problems to be solved by the invention]
An object of the present invention is to provide a deformed tubular product that is partially reinforced without using welding or an adhesive and a method for manufacturing the deformed tubular product.
[0014]
[Means for Solving the Problems]
The present inventors have various experiments to solve the above problems, studies and as a result, the pressure in the fluid inserted into reinforcing the steel was introduced into the containing tube in that state having an inner diameter larger than the outer diameter of the steel tube It has been found that if the steel pipe and the reinforcing steel pipe are expanded simultaneously by loading and expanding, the reinforcing steel pipe is firmly fastened to the steel pipe .
[0015]
The present invention has been made based on good Una finding this, the gist is as follows.
[0016]
(1) the liquid is injected into the steel pipe, a method for producing a profiled tubular product by hydroforming to bulge the steel pipe loaded with pressure in the liquid, a predetermined portion of the bulging portion to be of steel, the steel tube A steel pipe for reinforcement having an inner diameter larger than the outer diameter is inserted, and the steel pipe and the steel pipe for reinforcement are expanded to form a product shape by liquid pressure so that the expansion ratio of the steel pipe for reinforcement is 0.5% or more. A method for producing a deformed tubular product having a partially reinforced portion.
[0017]
The expansion ratio of the reinforcing steel pipe is desirably 10% or less .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described.
[0019]
FIG. 1 is a longitudinal sectional view of a mold part for hydrofoam for explaining a method for producing a modified tubular product of the present invention, and FIG. 1 (a) is a state immediately before hydroforming a steel pipe , FIG. ) Is a state after hydroforming, and FIG. 1C is a longitudinal sectional view of the product.
[0020]
First, a raw tube for hydrofoam is prepared as follows.
[0021]
That is, a reinforcing steel pipe having an inner diameter larger than the outer diameter of the steel pipe (hereinafter referred to as “element pipe ”) is prepared, and the reinforcing steel pipe is inserted into a predetermined portion to be reinforced in the planned bulge portion of the element pipe . The length of the reinforcing steel pipe may be set to a length to be reinforced, and a plurality of reinforcing steel pipes may be inserted if reinforcement at a plurality of locations is necessary. Further, the thickness may be arbitrarily selected depending on the purpose, and the material may not be the same as that of the raw tube but may be a material having higher strength.
[0022]
As shown in FIG. 1 (a), first, a base pipe 5 in which a prepared reinforcing steel pipe 6 is inserted is set inside a pair of upper and lower molds 4a and 4b mounted on a pressing device (not shown). Is sealed with the axial pressing tools 7a and 7b, and the liquid is introduced from the machining liquid inlet 8 to fill the inside of the base tube 5 with the liquid. As the liquid, water added with a rust inhibitor is generally used.
[0023]
Then, while increasing the pressure of the working fluid, gradually bulged axial pressing tool 7a, the base tube 5 by applying a pressing force in the axial direction to the base pipe 5 is advanced and 7b in the vertical direction as needed . Hydroforming is completed in the state shown in FIG. FIG.1 (c) is a longitudinal cross-sectional view of the irregular shape tubular product taken out from the metal mold | die. As described above, the bulging portion 5a and the reinforcing steel pipe 6 are firmly fastened by simultaneously bulging the base pipe 5 and the reinforcing steel pipe 6 inserted therein.
[0024]
When hydroforming is performed based on this method, only the raw pipe (hereinafter may be referred to as the inner pipe) only (hereinafter may be referred to as the single pipe section), the inner pipe and the reinforcing steel pipe (hereinafter referred to as the outer pipe ) Since there is a difference in strength from the double part (hereinafter referred to as a double pipe part) of the pipe (which may be referred to as a pipe), the following shape defects may occur during pipe expansion. FIG. 4 is a diagram for explaining the shape defect, and FIG. 4 (a) is a longitudinal sectional view of a deformed tubular product in which the shape defect 11 occurs when the raw tube inserted into the reinforcing steel pipe is hydroformed. FIG. 4B is an enlarged view of the boundary portion between the single tube and the double tube.
[0025]
This defective shape 11 occurs when the strength difference between the double tube portion and the single tube portion is large and the expansion rate of the outer tube is large. In other words, if the strength difference is large, the single pipe part swells more easily than the double pipe part during hydroforming, so that the single pipe part bulges more than necessary, and the single pipe bulge part is located between the double pipe and the mold. The part wraps around and the shape defect 11 occurs.
[0026]
This defective shape not only makes the shape of the product unclear, but when a load is applied to the product, the strength may be lower than in the case of the inner tube alone due to stress concentration.
[0027]
To prevent good Una defective shape this is拡菅ratio of the outer tube is desirably suppressed to 10% or less, more preferably 5% or less. The tube expansion rate is the rate of increase in tube circumference.
[0028]
In the case of hydroforming such that a flat portion on the product shape processing,拡菅ratio of the outer tube because no out off Rattonesu between the single tube portion拡菅rate is small and the double tube portion of the outer tube The content is preferably 0.2% or more, and more preferably 0.5% or more. Next, the preferable shape of the pipe end part of the reinforcing steel pipe will be described.
[0029]
FIG. 5 is an enlarged longitudinal sectional view of the boundary between the outer tube and the inner tube after hydroforming. 5A, when the end surface 12 of the outer tube 6 is vertical, FIG. 5B shows a case where the inner tube is chamfered over the entire outer tube end, and FIG. FIG. 5D shows the case where the part inner surface is chamfered, and FIG. 5D shows the case where the part that intersects the further chamfered surface and the outer tube inner surface is a curved surface (R).
[0030]
In the case of the end face of the outer tube as shown in FIG. 5 (a), there is a case where the bent portion 13 having a steep angle is generated in the inner tube due to the thickness of the outer tube portion, and the strength is reduced due to stress concentration. Therefore, it is not suitable for an application with a large stress load.
[0031]
Therefore, it is desirable to chamfer the end surface of the outer tube in advance as shown in FIG. If the chamfering angle θ is large, there is no effect, and if it is too small, problems such as an increase in the load of chamfering processing, danger of workers due to sharp edges, and deformation of the chamfered part during handling occur. It is desirable to do.
[0032]
As shown in FIG. 5 (c), the above problem can be solved by leaving a part of the inner surface that is not chamfered.
[0033]
As shown in FIG. 5D, it is further preferable that chamfering is performed and a portion where the chamfered surface intersects the inner surface of the outer tube is a curved surface (R).
[0034]
【Example】
FIG. 6 shows the die groove shape of the mold used in this example. Using this mold, the inner tube was inserted into the outer tube shown in Table 1, and hydroformed by the method shown in FIG. Both the outer pipe and the inner pipe used the carbon steel pipe STKM11A for mechanical structure. As the outer tube, a tube not chamfered and a chamfered tube with various chamfer angles were prepared.
[0035]
The die groove dimensions of the mold were as follows.
[0036]
D1 = 73mm
L1: 500mm
L2: 275mm
FIG. 7 is an operation pattern of internal pressure, axial push, and punch during hydroforming. After hydroforming, the boundary between the outer tube and the inner tube was observed to check for shape defects. The results are shown in Table 1.
[0037]
[Table 1]

As is apparent from Table 1, when the outer tube has an outer diameter of 65 mm, a wall thickness of 2.3 mm, and a tube expansion ratio of 12.3%, the shape was slightly poor but the stress load was small. In other cases, it was usable, and everything else was good.
[0038]
FIG. 8 is a view showing an appearance photograph after hydroforming of Test No. 6 in Table 1. It can be seen that the inner tube is crimped in a state where the surface of the bulging portion 5a and the surface of the outer tube 6 are the same surface.
[0039]
【The invention's effect】
According to the present invention, it is possible to produce a deformed tubular product that is partially reinforced without using welding or an adhesive with a minimum weight increase. Also, hydroforming can be easily performed using an existing mold.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal sectional view of a hydroforming mold part for explaining a method for producing a modified tubular product of the present invention.
FIG. 2 is a perspective view of a deformed tubular product partially reinforced by welding.
FIG. 3 is a perspective view of a modified tubular product obtained by hydroforming a terrado element tube.
FIG. 4 is a longitudinal sectional view of a product for explaining a shape defect.
FIG. 5 is an enlarged longitudinal sectional view of a boundary portion between an outer tube and an inner tube after hydroforming.
FIG. 6 is a view showing a die groove shape of a mold used in this example.
FIG. 7 is a diagram showing an operation pattern of internal pressure, shaft pushing and punching during hydroforming.
FIG. 8 is an external view of a modified tubular product obtained by the production method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Modified tubular product 2 Reinforcement material 3 Welded part 4a Upper die 4b Lower die 5 Steel pipe (element tube )
6 Reinforcing steel pipes 7a, 7b Shaft pushing tool 8 Liquid inlet

Claims (2)

In a method of manufacturing a deformed tubular product by hydroforming, in which a liquid is injected into a steel pipe and pressure is applied to the liquid to swell the steel pipe ,
In a state where a reinforcing steel pipe having an inner diameter larger than the outer diameter of the steel pipe is inserted into a predetermined portion of the planned expansion portion of the steel pipe , the hydraulic pressure is adjusted so that the expansion ratio of the reinforcing steel pipe is 0.5% or more. A method for producing a deformed tubular product having a partially reinforced portion, characterized in that a steel pipe and a reinforcing steel pipe are expanded and formed into a product shape. The method for producing a modified tubular product having a partially reinforced portion according to claim 1, wherein the expansion ratio of the reinforcing steel pipe is 10% or less.

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