JP2002153917A - Bulging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bulging method capable of highly stretching a branch pipe without generating any wrinkles or cracks in a metal pipe. SOLUTION: The metal pipe P having a bend or curved portion is subjected to the internal pressure to be bulged into a cavity part 15 for stretching on one side of a bulging die 10. Axial compression is applied to the metal pipe by an axial compression die 12 to form a bulge-stretching in the cavity part 15 for stretching while reducing the width of the cavity part 15 for stretching by moving dies 13 and 14. A counter die 16 provided in the cavity part for stretching is brought into contact with a top of a bulged part to preferably perform the bulge-stretching under a predetermined pressure. The T-shaped branch can be stretched to the height several times larger than a conventional value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bulging method for bulging one or more branch pipes by applying an internal pressure and an axial pushing force to a metal pipe.

[0002]

2. Description of the Related Art As shown in FIG. 11, a metal tube is set in a bulge-forming mold 2 having a projecting cavity 1 on one side, and both ends thereof are axially pressed by an axial pressing die 3. A method of bulging a T-shaped branch pipe by applying internal pressure while applying an internal pressure is conventionally known. However, in this method, the height at which the T-shaped branch pipe can be stretched and formed without generating wrinkles or cracks in the metal pipe is low, and it has been difficult to make the overhang height equal to or larger than the diameter of the metal pipe.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a bulge forming method capable of forming a branch pipe at a high extension without causing wrinkles or cracks in a metal pipe. It was done for.

[0004]

A bulging method according to the present invention, which has been made to solve the above-mentioned problems, is a method for bending or bending a bulge in a bulge processing mold having an overhanging cavity on one side. Internal pressure is applied to the metal tube having the bent portion to expand the bent portion into the overhanging cavity, and then the mold forming the overhanging cavity is moved to move the overhanging cavity. Axial compression is applied to the metal tube by the axial pressing type while reducing the width of
It is characterized in that a metal tube is formed by bulge overhang in the overhang cavity.

Preferably, a counter mold provided in the overhanging cavity is brought into contact with the apex of the bulging portion of the metal tube, and bulge overhanging is performed while holding it at a predetermined pressure. The die to be moved can be moved in conjunction with the axial pressing die. The bent or curved bent portion may be formed in a bulging mold, may be formed outside the bulging mold in advance, or may be formed outside the bulging mold in advance, and further formed in the bulging mold. You may shape | mold in the metal mold | die for a process. In addition, a plurality of branch pipes can be simultaneously bulge-formed by making the number of the projecting cavities of the mold and the number of the bent parts of the metal pipe plural, and axially compressing both ends of the metal pipe. When the number of branch pipes is two, bulge bulging can be performed by setting the moving speed of the mold forming the overhanging sinus to V and the moving speed of the counter mold to V / 2.

According to the present invention, there is provided a metal mold having a bent or curved bent portion, which is formed by expanding the bent portion into the overhanging cavity and forming the overhanging cavity. By moving and reducing the width of the overhanging cavity to perform the bulge overhanging, the branch pipe can be overhanged to a height several times the diameter of the metal pipe.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, reference numeral 10 denotes a bulge-forming mold (fixed mold) having a linear hollow portion 11 for accommodating a metal tube P therein. An axial pressing die 12 having a hole is arranged. A pair of dies 13, 1, which can be moved so as to approach and separate from each other while keeping parallel to the dies 10, on one side (upper side in the drawing) of the bulge processing dies 10.
4 are arranged. With these molds 13 and 14, a projecting cavity 15 for forming a branch pipe is formed beside the mold 10 for bulging. Therefore, these dies 13 and 14 are referred to as dies for forming the projecting cavity 15. Reference numeral 16 denotes a counter type provided in the overhanging cavity 15. The counter mold 16 is advanced and retracted by a cylinder (not shown).

In the present invention, as shown in FIG. 1, a metal pipe P having a bent portion 20 curved in a V shape is used. Such a bent portion 20 may be formed in advance on the outside, but a straight metal pipe P is inserted into the bulging die 10, and a light internal pressure and a strong internal pressure are applied by the axial pressing die 12. The bent portion 20 may be formed by applying an axial pressing force. Further, it may be formed outside the bulging mold in advance, and may be formed inside the bulging mold. In any case, the bent portion 2 of the metal pipe P
0 is an overhanging cavity 15 formed between the molds 13 and 14.
In the direction of. At this stage, the width of the overhanging cavity 15 is wide, and the counter mold 16 is slightly in contact with the bent portion 20 of the metal tube P, or is at a position slightly apart. The thickness of the metal tube P is substantially uniform at this stage.

Next, as shown in FIG. 3, the internal pressure of the metal tube P is increased to inflate the metal tube P while the axial pressing die 12 is stopped. As a result, the bent portion 20 of the metal tube P swells into the overhanging cavity 15 and the opposite surface 21 (the lower surface in the drawing) also swells until it comes into close contact with the mold 10. The height of the bulge into the overhanging cavity 15 is regulated by the counter mold 16.

At this time, since the opposite surface 21 of the bent portion 20 of the metal tube P is elongated, the thickness is reduced, but the thickness of the bulging portion 22 does not change much. The height of the bulge into the overhanging cavity 15 at the stage of FIG. 3 is 0.2 to 1.5 times the diameter D of the metal tube P, and the width of the overhanging cavity 15 is It is preferably about 2 to 6 times the diameter D of P. The multiple can be appropriately set in the above range according to the material, the processed shape, and the like of the metal pipe P.

Next, as shown in FIG. 4, the molds 13 and 14 forming the overhanging cavity are moved inward to reduce the width of the overhanging cavity 15. At the same time, axial compression and internal pressure are applied to the metal tube P by the axial pressing die 12. Then, the swelling portion 22 of the metal tube P into the overhanging cavity 15 is pushed from the lateral direction, the width thereof is reduced, and the metal tube P is pushed up into the overhanging cavity 15. In addition, axial compression and internal pressure are applied to both ends of the metal tube P, and the material at both ends of the metal tube P is also moved toward the inside of the overhanging cavity 15, so that a high internal pressure as in the related art is required. In addition, the metal pipe P does not break unstably during processing in the mold. Therefore, the overhanging portion 22 not supported in the counter mold 16 is deformed strangely, and the metal tube P
As shown in FIG. 5, the overhanging portion 22 is formed in the overhanging hollow portion 15 so as not to be cracked or broken. As shown in the examples, it was confirmed that the overhang height achievable by the method of the present invention reached several times the diameter of the metal tube P.

In the steps from FIG. 4 to FIG. 5, it is preferable that the counter mold 16 is always brought into contact with the apex of the bulging portion 22 of the metal pipe P, and the bulge bulging is performed while holding it at a predetermined pressure. If the counter mold 16 is eliminated, the top of the bulging portion 22 may expand freely and its thickness may be reduced or cracked.
If bulge bulging is performed while pressing, metal flow is prevented at this portion by friction, and the wall thickness does not decrease. According to the experiment of the present inventor, the pressure introduced into the inside of the metal pipe P from the axial pressing die 12 was changed to the counter type 16
By adjusting the cylinder area, the counter mold 16 is gradually retracted while pressing the counter mold 16 against the apex of the bulging portion 22 at a pressure of about 90% of the internal pressure acting on the metal pipe P. Is preferred.

As described above, according to the present invention, the projecting cavity 15 is provided.
Can be performed simultaneously with the movement of the molds 13 and 14 and the axial pressing by the axial pressing die 12. Therefore, these two dies may be linked with each other and moved at the same distance at the same time.

In the steps from FIG. 4 to FIG. 5,
The bulged portion 22 of the metal tube P is bulge-extended in the projecting cavity 15 at the same time, and at the same time, the entire length of the metal tube P is shortened by axial pushing. As described above, at the stage of FIG. 3, the opposite surface 21 of the bent portion 20 of the metal pipe P has been stretched and its thickness has been reduced.
The thickness of 1 increases and returns. For this reason, the finished product processed by the method of the present invention has the advantage that the thickness variation is small and the uneven thickness is reduced.

Next, as in the embodiment shown in FIG. 6, the bent portion 20 of the metal tube P may be bent. The metal pipe P of this embodiment has a bent portion 2 bent at 90 degrees.
0 and mold 13 so that overhanging cavity 15 is reduced.
Performs bulging while moving the mold 14 leftward in the drawing. In this case, as described above,
The metal pipe P
Is not destroyed unstable. Therefore, counter type 16
The overhanging portion 22 that is not supported in the inside does not cause abnormal deformation and cause cracking or destruction of the metal tube P.
The bulge is formed in the overhanging cavity 15 at a high height.
Further, at the time of swelling, the branch pipes become higher along the molds 13 and 14 on both sides, so that the overhang portion 22 as shown is formed.

As described above, according to the bulging method of the present invention, the internal pressure at the time of the initial molding of the bulging portion can be reduced, so that the metal pipe P can be cracked, wrinkled and uneven thickness. In addition, it is possible to overhang and form the branch pipe.
Moreover, the present invention can be applied not only to the case where the number of branch pipes is one, but also to the case where there are two or more branch pipes.

That is, as shown in FIGS. 7 to 9, even when the number of overhanging cavities 15 and the number of the bent portions 20 in a U-shape are plural, both ends of the metal tube P are connected in the same manner as described above. By compressing with a pair of shaft pressing shaft molds 12, a plurality of branch pipes can be simultaneously bulge-extended. In this case, a fixed mold 17 is provided at the center of the molds 13 and 14 forming the overhanging cavity portion 15, and the molds 13 and 14 on both sides are moved toward the fixed mold 17 to form the projecting cavity 15. The width of the cavity 15 is reduced. Each counter mold 16 must always be moved so as to be at the center of each overhanging cavity 15, but the other points are the same as those shown in FIGS. 1 to 5.

When the moving speed of the dies 13 and 14 with respect to the fixed mold 17 is V, the moving speed of the counter mold 16 may be V / 2. When the mold 13 is fixed and the mold 14 is moved at the moving speed V, the mold 13
The moving speed of the counter mold 16 closer to the mold 14 is V / 4, and the moving speed of the counter mold 16 closer to the mold 14 is 3V / 4.
And it is sufficient. In this case, the fixed mold 17 is also moved toward the mold 13 at a moving speed of V / 2. Even when the number of branch pipes is three or more, molding can be performed by setting based on the same concept.

[0019]

Examples of the present invention will be described below. First, the outside diameter (d) is 70 mm and the wall thickness is 2 m inside the mold shown in the embodiment.
A metal tube (material: STKM11A) having a length of 500 mm and a length of 500 mm was set, and a shaft pressing die was moved to apply a shaft pressing force of 20,000 N to seal the tube end. Next, the width of the overhanging cavity was set to four times (4d) the diameter of the metal tube, and the counter mold was fixed at a height of 1.5d. Then, the axial pressing die was moved while applying an internal pressure of 20 MPa to the inside of the metal tube through the axial pressing die, and the metal pipe was bent into a dogleg shape to obtain the state shown in FIG. Next, the internal pressure was increased to 35 MPa, and the bent portion of the metal tube was swelled into the projecting cavity as shown in FIG. (Primary molding)

Next, a molding pressure is introduced into a cylinder for driving the counter mold, and the center of the bulging portion is pressed with a force synchronized with the molding pressure, while forming a shaft pushing die and a mold for forming a projecting cavity. And were moved at the same speed. The molding pressure is 35MP
a was maintained at a constant value. As a result of moving the axial pressing die and the die forming the overhanging cavity by 1.5d on each side until the width of the overhanging cavity becomes d, as shown in FIG. 10, the T-shape is increased to a height of 3d. Bulge bulging molding (secondary molding). Part A shown in FIG. 10 (the side opposite to the bulging part)
The thicknesses of the part B (bulging part) and the part C (bulging branch part) are as shown in Table 1, and it was confirmed that a molded article with less uneven thickness can be obtained by the method of the present invention. .

[0021]

[Table 1]

[0022]

As described above, according to the present invention, it is possible to bulge a branch pipe much higher than before without causing cracks and wrinkles, and to form two or more branch pipes. Can be simultaneously bulged.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state at the start of molding according to the present invention.

FIG. 2 is a perspective view of a mold.

FIG. 3 is a cross-sectional view showing a state in which a bent portion is bulged into a projecting cavity.

FIG. 4 is a cross-sectional view showing a state where the width of the overhanging cavity is reduced.

FIG. 5 is a cross-sectional view showing a state at the time of completion of bulge overhang forming.

FIG. 6 is a process explanatory view showing another embodiment.

FIG. 7 is a cross-sectional view showing an initial step of simultaneously bulging and forming two T-shaped branches.

FIG. 8 is a cross-sectional view showing a state in which a bent portion is swelled in a projecting cavity.

FIG. 9 is a cross-sectional view showing a state where two branch pipes are simultaneously bulge-extended.

FIG. 10 is a front view of a molded product according to an example.

FIG. 11 is a perspective view showing a conventional technique.

[Explanation of symbols]

 P Metal tube 1 Overhanging cavity in prior art 2 Mold for bulging in prior art 3 Axle pressing mold in prior art 10 Mold for bulging 11 Cavity 12 Axial pressing mold 13 Overhanging cavity Mold to be formed 14 Mold to form overhanging cavity 15 Overhanging cavity 16 Counter mold 17 Fixed mold 20 Lenticular bent part 21 Opposite surface of bent part 22 Swelling part

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Itsuro Hiroshige 5-3 Tokai-cho, Tokai-city, Aichi Prefecture Inside Nagoya Works, Nippon Steel Corporation (72) Inventor Koichi Hiramatsu 1st Toyota Town, Toyota-shi, Aichi Prefecture Toyota (72) Inventor Kyoichi Mano 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F-term (reference) 4E063 AA04 BA20

Claims (8)

[Claims] An internal pressure is applied to a metal tube having a bent or curved bent portion in a bulge-forming mold having a projecting hollow portion on one side, and the bent portion is used for projecting. The metal tube that expands into the cavity, and then moves the mold that forms the cavity for overhanging, reduces the width of the cavity for overhanging, applies axial compression to the metal tube with the axial pressing die, and stretches the metal tube. A bulge processing method, comprising: forming a bulge in an outlet cavity. 2. The bulge according to claim 1, wherein the bulge is formed by bringing a counter mold provided in the overhanging cavity into contact with the apex of the bulging portion of the metal tube and pressing the bulge with a predetermined pressure. Processing method. 3. The bulging method according to claim 1, wherein the mold forming the overhanging cave is moved in conjunction with the axial pushing die. 4. The bulge forming method according to claim 1, wherein the bent or curved bent portion is formed in a bulging die. 5. The bulging method according to claim 1, wherein the bent or bent portion is formed outside a bulging die in advance. 6. The bulge forming method according to claim 1, wherein the bent or bent portion is formed outside a bulging mold in advance, and further formed in the bulging mold. 7. A plurality of branch pipes are simultaneously bulge-extended and formed by axially compressing both ends of the metal pipe with a plurality of projecting cavities of the mold and bending sections of the metal pipe.
7. The bulge processing method according to any one of claims 6 to 6. 8. The bulge according to claim 7, wherein the moving speed of the mold forming the overhanging cave portion is V and the moving speed of the counter mold is V / 2, and the two branch pipes are simultaneously bulge-bulged. Processing method.