JP4422219B2 - Metal tube for hydrofoam and method for forming and processing the same - Google Patents

Description

【００１９】
【表２】

【００２０】
【発明の効果】
金属管の表面に潤滑剤層を形成し、傾きの摩擦係数μが０．０７以下であることにより、ハイドロフォーム加工において、同じ材料の金属管でも、より高加工度の加工成形を破断や座屈を起こさずに行うことができる。そして加工部の肉厚減少の程度が小さく、かつ表面の擦り疵やかじりの発生が抑えられる。
【００２１】
特に、高分子合成ワックスと水性樹脂を成分とする固体潤滑剤を採用した場合は、加工成形において優れた特性が安定して得られるほか、金属管を加工工程に移送するとき、あるいは加工工程で金型にセットするとき、潤滑剤層が安定で取扱いが容易である。
【図面の簡単な説明】
【図１】本発明の対象とするハイドロフォーム加工法の例を示す断面図である。
【図２】本発明における高面圧下での摺動試験を行うための工具の例を示す斜視図である。
【図３】本発明における高面圧下での摺動試験の例を示す側面図である。
【図４】実施例のＴ成形試験における成形高さを示すグラフである。
【図５】実施例のＴ成形試験における限界成形高さを示すグラフである。
【符号の説明】
１…金属管 ２…試験片
３…成形品 ４，５…金型
６，７…シリンダー ８…液導入孔
９…凸金型 １０…ビード部
１１…凹金型[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a metal pipe for hydrofoam, in which a metal pipe such as a steel pipe is mounted in a mold, and is processed into a predetermined shape while being pushed in the pipe axis direction by applying internal pressure in the pipe, and a hydrofoam processing and molding method. is there.
[0002]
[Prior art]
Products such as steel pipes that have been formed by hydroforming are being used in automotive parts. As shown in the example of the T-shaped tube forming test in FIG. 1, the metal tube 1 is placed in the molds 4 and 5, and a liquid is introduced into the metal tube 1 from the liquid introduction hole 8 to apply internal pressure. In this method, the cylinders 6 and 7 for pushing are pressed from both sides to apply a compressive load in the direction of the tube axis and press the cylinder into a predetermined shape.
The obtained molded product 3 is lightweight and can be molded with high accuracy up to a complicated shape. Therefore, application to automobile parts and the like is progressing for the purpose of reducing the weight by reducing the number of parts and reducing the number of parts.
[0003]
It is known that for bulge processing that is processed only with internal pressure without being pushed in the direction of the tube axis with respect to the material metal tube, a soft material, a material with a high n value, and a material with a high r value should be selected. For hydroforming, it was known that soft materials were good.
[0004]
The present inventors have analyzed the deformation mode of hydroforming, and are studying the influence of material properties on its workability. It has been clarified that a metal tube whose r value in the tube axis direction is larger than the r value in the tube circumferential direction has excellent workability, and a patent application has been filed in Japanese Patent Application No. 8-336480.
[0005]
[Problems to be solved by the invention]
The quality of the hydroforming process is evaluated based on the fact that the metal tube can be formed without causing breakage or buckling, and the thickness distribution of the processed part and the state of occurrence of scratches on the surface. Therefore, the suitability of the lubricant is an important issue in addition to the excellent workability of the material metal tube as in the above application. However, the quantitative influence of lubrication characteristics in hydroforming has not been clarified so far.
[0006]
Therefore, the present invention provides a metal tube having excellent lubrication characteristics for hydroforming, in which a metal tube such as a steel tube is mounted in a mold and processed into a predetermined shape while being pushed in the tube axis direction by applying internal pressure in the tube. And a method for forming the same.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a metal tube of the present invention is a metal tube for hydrofoam that is processed into a predetermined shape while applying an internal pressure to the tube and pushing it in the tube axis direction. In a sliding test under high surface pressure, with a strip-shaped test piece sandwiched between the mold and the test piece, the “friction coefficient of inclination” μ defined by the equation (1) is obtained, and μ is 0.07 or less. A metal pipe for hydrofoam, characterized in that a lubricant is selected and a layer of the selected lubricant is provided on the pipe surface .
μ = ΔF / (2 × ΔP) (1)
ΔF is the pulling tension increment when the test piece passes through the bead part ΔP is the load increment in the bead molding direction when the test piece passes through the bead part and the lubricant layer is composed of a polymer synthetic wax and an aqueous resin It is preferable to consist of a solid lubricant.
[0008]
The method according to claim 1 is a sliding test under high surface pressure in which a strip-shaped test piece is sandwiched between a convex mold having a bead portion and a concave mold on a metal tube and the test piece is pulled out. (1) “Friction coefficient of inclination” defined by the equation μ is obtained, a lubricant with μ of 0.07 or less is selected, the layer of the selected lubricant is formed on the tube surface, It is a hydroforming process forming method characterized in that it is mounted in a mold and processed into a predetermined shape while being pushed in the tube axis direction by applying internal pressure in the tube.
The lubricant layer is preferably formed of a solid lubricant composed of a polymer synthetic wax and an aqueous resin.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the hydroforming process according to the present invention, as in the T-shaped tube forming test example shown in FIG. The molded product 3 is processed by applying a compressive load in the direction of the tube axis with the cylinders 6 and 7 for pushing from both sides and pushing. The target metal pipe 1 is manufactured by forming a metal plate into a tubular shape and welding the butt portion, or may be a seamless pipe.
[0010]
The present invention is such a metal tube for hydroforming, and in a sliding test under high surface pressure, the “friction coefficient of inclination” μ defined by the equation (1) is 0.07 or less. It has a lubricant layer. As shown in FIGS. 2 and 3, the sliding test under high surface pressure is performed by holding the strip-shaped test piece 2 between the convex mold 9 having the bead portion 10 and the concave mold 11 and pulling the test piece 2. It is a test to pull out. The “coefficient of friction of inclination” μ is determined by the equation (1) from the increment ΔP of the drawing tension P when the test piece 2 passes through the bead portion 10 and the increment ΔF of the bead forming direction load F.
[0011]
The lubricant layer can be formed on the metal tube in advance, or can be formed in a pre-process. As the forming means, a method of immersing in a lubricant solution, a method of spraying a lubricant solution, a method of applying with a roll, a bar, a brush or the like, an electrostatic coating method, or the like can be used.
It is preferable to use a metal tube in which a lubricant layer made of a solid lubricant is formed in advance, and it is particularly preferable to employ a solid lubricant made of a polymer synthetic wax and an aqueous resin.
[0012]
Here, as the polymer synthetic wax, a polyolefin wax having a particle size of 3 μm or less and a softening point of 120 ° C. or less and a mixture of more than 120 ° C. were mixed in a weight ratio of 9/1 to 1/9. Dispersion in which a spherical polyolefin wax having a polar group and a molecular weight of 1000 to 4000 and an acid value of 1 to 20 is dispersed in water or an aqueous solution using an ethylenically unsaturated carboxylic acid or its anhydride or a carboxyl group-containing derivative as a binding component In the total solid content.
[0013]
Examples of the aqueous resin include olefin acrylic resin, acrylic resin, and vinyl acetate resin that do not contain a volatile solvent.
Further, if necessary, silica (spherical silica sol having a diameter of 5 to 50 nm) can be blended.
[0014]
When the friction coefficient μ of the inclination is 0.07 or less, even with a metal tube made of the same material, for example, the forming height h in the T-shaped tube forming test of FIG. It can be done without buckling. And the degree of thickness reduction of the processed part is small, and the generation of scratches and galling on the surface is suppressed.
In particular, when a lubricant layer made of a solid lubricant as described above is used, excellent properties can be stably obtained in processing and molding, and when a metal tube is transferred to the processing process or set in a mold in the processing process. The lubricant layer is stable and easy to handle.
Next, in the method of the present invention, a lubricant layer having a friction coefficient μ of 0.07 or less is formed on a metal tube, and then mounted in a mold and processed by hydroforming. The lubricant layer can be formed on the metal tube in advance, or can be formed in a pre-processing step. The forming means can be performed by a method of immersing in a lubricant solution as described above, a method of spraying a lubricant solution, a method of applying with a roll, a bar or a brush, an electrostatic coating method, or the like.
As the lubricant, it is preferable to employ a solid lubricant composed of a polymer synthetic wax and an aqueous resin.
Such an excellent effect as described above can be obtained by the method of the present invention.
[0015]
【Example】
A steel pipe with an outer diameter of 60.5mmφ and a length of 300mm manufactured by forming a steel plate with 1.6mm thickness (SPCC specified in JIS G3141) into a tubular shape and butt-welding is used, and a lubricant layer is applied to the outer surface. The formed metal tube 1 was subjected to a T forming test as shown in FIG. The T-molding test uses split molds 4 and 5 with a die hole diameter of 60.5mm and shoulder radius of 20mm at the T overhang, and the maximum internal pressure value Pm is changed in the range of 20 to 40MPa. Performed at 50 mm.
As the lubricant layer of the metal tube 1, six types shown in Table 1 were formed. A and C are solid lubricants, which were applied with a brush and dried for 2 hours to perform a T molding test. B, D, E, and F are liquid lubricants, and a T molding test was performed immediately after application with a brush.
[0016]
As a result of the test, as shown in FIG. 4, the molding height h increases as the maximum internal pressure value Pm is increased, and if Pm is increased too much, fracture occurs during the molding and h decreases. The smaller the friction coefficient μ of the inclination is, the higher the molding height h is, and the maximum internal pressure value Pm leading to the fracture is higher, particularly when μ ≦ 0.07. The maximum molding height (limit molding height h _max ) that can be processed without breaking is also significantly improved when μ ≦ 0.07, as shown in FIG.
[0017]
Further, as shown in Table 2, when μ ≦ 0.07, the thickness reduction rate (t ₀ −t) / t ₀ × 100 (%) at the minimum thickness portion of the processed portion is small, and the processing The surface properties of the part were also good. t ₀ is the thickness before processing, and t is the thickness after processing. In Table 2, F broke. The surface texture ○ indicates that there is no scuffing or scuffing, Δ indicates that mild scuffing or scoring has occurred, and × indicates that severe scuffing or scoring has occurred.
[0018]
[Table 1]

[0019]
[Table 2]

[0020]
【The invention's effect】
By forming a lubricant layer on the surface of the metal tube and having a coefficient of friction μ of inclination of 0.07 or less, even in the metal foam of the same material in hydroforming, it is possible to break and form a higher degree of work forming. It can be done without bending. And the degree of thickness reduction of the processed part is small, and the generation of scratches and galling on the surface is suppressed.
[0021]
In particular, when a solid lubricant composed of a polymer synthetic wax and a water-based resin is used, excellent properties can be stably obtained in processing and molding, and when a metal tube is transferred to the processing step or in the processing step. When set in the mold, the lubricant layer is stable and easy to handle.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a hydroforming method targeted by the present invention.
FIG. 2 is a perspective view showing an example of a tool for performing a sliding test under high surface pressure in the present invention.
FIG. 3 is a side view showing an example of a sliding test under high surface pressure in the present invention.
FIG. 4 is a graph showing a molding height in a T molding test of an example.
FIG. 5 is a graph showing a limit molding height in a T molding test of an example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Metal pipe 2 ... Test piece 3 ... Molded article 4, 5 ... Mold 6, 7 ... Cylinder 8 ... Liquid introduction hole 9 ... Convex die 10 ... Bead part 11 ... Concave die

Claims (4)

A metal tube for hydroforming that is processed into a predetermined shape while being pushed in the axial direction of the tube by applying internal pressure to the tube. The test piece is formed by sandwiching a strip-shaped test piece between a convex mold having a bead portion and a concave mold. In the sliding test under high surface pressure, the “friction coefficient of inclination” μ defined by the equation (1) is obtained, a lubricant having μ of 0.07 or less is selected, and the lubricant of the selected lubricant is selected. A metal pipe for hydrofoam characterized by having a layer on the pipe surface .
μ = ΔF / (2 × ΔP) (1)
ΔF is the pulling tension increment when the test piece passes through the bead portion. ΔP is the load increment in the bead forming direction when the test piece passes through the bead portion.   2. The metal tube for hydroform according to claim 1, wherein the lubricant layer is made of a solid lubricant composed of a polymer synthetic wax and an aqueous resin. In a sliding test under high surface pressure, a strip-shaped test piece is sandwiched between a convex mold having a bead portion and a concave mold on a metal tube, and the test piece is pulled out. “Friction coefficient of inclination” μ is determined, a lubricant having μ of 0.07 or less is selected, the layer of the selected lubricant is formed on the tube surface, and then the tube is mounted in a mold. A hydroform processing molding method characterized in that an internal pressure is applied to the inside of the pipe and the pipe is pushed in the axial direction to be processed into a predetermined shape.   4. The hydroforming process molding method according to claim 3, wherein the lubricant layer is formed of a solid lubricant composed of a polymer synthetic wax and an aqueous resin.

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