JP2021053688A - Molding device and metal pipe material for blow molding - Google Patents

Abstract

To reduce the possibility that rupture may occur in a metal pipe material.SOLUTION: A molding device according to an embodiment comprises: an electrode that heats a metal pipe material by passing electric currents to the metal pipe material while holding a part to be held of the metal pipe material; a fluid supply part that supplies fluid into the heated metal pipe material to inflate the material; a molding die that has a pair of dies that provide a pair of molding surfaces opposing to each other and molds the part to be processed of the inflated metal pipe material between the pair of dies; and an inflation restricting part, provided between the molding dies and the electrode, which restricts inflation in a radial direction of an intermediate part positioned between the part to be processed and the part to be held in the metal pipe material.SELECTED DRAWING: Figure 8

Description

The present disclosure relates to molding equipment and metal pipe materials for blow molding.

Conventionally, a molding apparatus for molding a metal pipe by heating a metal pipe material and supplying a gas into the heated metal pipe material to expand the metal pipe material is known. For example, Patent Document 1 below describes a molding die having a lower die and an upper die paired with each other, a gas supply unit for supplying gas into a metal pipe material held between the molding dies, and the metal. A molding apparatus including both ends of a pipe material and a pair of electrodes for energizing and heating a metal pipe material is disclosed.

Japanese Unexamined Patent Publication No. 2015-112608

In the conventional molding apparatus as described above, as shown in FIG. 12, a gap 106 is formed between the electrode 101 and the molding die 102 to allow the molding die 102 to move in the vertical direction. Further, in general, in order to suppress a sudden change in the outer diameter of the metal pipe material 110 in the longitudinal direction, the molding surface 103 of the molding die 102 is pressed from the central axis of the metal pipe material 110 as it approaches the electrode 101. A curved surface 105 that curves in the direction away from the surface is formed.

The curved surface 105 and the gap 106 as described above form a space S near the boundary between the electrode 101 of the molding apparatus and the molding die 102. When such a space S exists, as shown in FIG. 12, a part of the metal pipe material 100 enters the space S during blow molding of the metal pipe material 110, and near the boundary between the electrode 101 and the molding die 102. The amount of radial deformation of the metal pipe material 110 increases locally. As a result, the metal pipe material 110 may burst.

Therefore, an object of the present invention is to reduce the possibility of rupture of the metal pipe material.

In one aspect, a molding apparatus is provided that expands and molds a metal pipe material. This molding device holds the held portion of the metal pipe material and heats the metal pipe material by energizing the metal pipe material, and a fluid that supplies fluid into the heated metal pipe material to expand it. Between the mold and the mold, which has a supply unit and a pair of molds that provide a pair of molding surfaces facing each other and that molds the work piece of the metal pipe material that expands between the pair of molds. The metal pipe material is provided with an expansion regulating portion that regulates the radial expansion of the intermediate portion located between the processed portion and the held portion.

In the molding apparatus according to the above embodiment, the expansion regulating portion provided between the molding die and the electrode regulates the radial expansion of the intermediate portion of the metal pipe material, so that the vicinity of the boundary between the electrode and the molding die. The amount of deformation of the metal pipe material in the radial direction can be suppressed. As a result, the metal pipe material can be made less likely to burst.

In one embodiment, the expansion control portion has a pair of contact members arranged between the molding die and the electrode so as to face each other in the opposite direction of the pair of molds, and the pair of contact members is a pair. It can move along the opposite direction together with the mold, and each of the pair of contact members contacts the contact surface of the pair of molds that abuts on the side surface of the corresponding mold and the outer peripheral surface of the intermediate portion during blow molding. It may have a pipe contact surface.

In the molding apparatus according to the above embodiment, since the contact surfaces of the pair of contact members are in contact with the side surfaces of the pair of molds, one of the metal pipe materials is placed between the pair of molds and the pair of contact members. The portion is prevented from expanding and entering. Therefore, it is possible to prevent the metal pipe material from being locally deformed between the pair of molds and the pair of abutting members, and as a result, the possibility of rupture in the intermediate portion of the metal pipe material can be reduced. ..

In one aspect, a metal pipe material for blow molding is provided. This metal pipe material has a processed portion located in the central portion in the longitudinal direction and an outer portion located outside the workpiece in the longitudinal direction and having a shape or characteristic that is less likely to be deformed than the workpiece during blow molding. Has a part.

In the metal pipe material according to the above aspect, since the deformation of the outer portion is suppressed during blow molding, it becomes difficult for the outer portion to enter the space formed near the boundary between the electrode and the molding die. Therefore, the possibility of rupture on the outer side of the metal pipe material can be reduced.

In one embodiment, the outer portion may satisfy at least one of the following conditions (a), (b) and (c).
(A) The wall thickness of the outer portion is thicker than the wall thickness of the processed portion.
(B) The strength of the outer portion is higher than the strength of the workpiece.
(C) The electrical resistance of the outer portion is smaller than the electrical resistance of the workpiece.

In the metal pipe material according to the above embodiment, by increasing the wall thickness of the outer portion, the strength of the pair of slowly changing portions can be increased, and the temperature rise of the outer portion can be suppressed during energization heating. As a result, the outer portion is less likely to be deformed during blow molding of the metal pipe material, so that the outer portion is less likely to enter the space formed near the boundary between the electrode and the molding die. Therefore, the amount of deformation of the outer portion can be reduced, and as a result, the possibility of rupture of the metal pipe material can be reduced. Similarly, when the strength of the outer portion is increased or the electrical resistance of the outer portion is reduced, the outer portion is less likely to be deformed, so that the possibility of rupture of the metal pipe material can be reduced.

In one embodiment, the outer portion comprises a pair of held portions located on both ends in the longitudinal direction and a pair of intermediate portions located between each of the pair of held portions and the workpiece. The wall thickness of the intermediate portion of the above portion may be thicker than the wall thickness of the processed portion, and may be reduced so as to approach the wall thickness of the processed portion as it approaches the processed portion. If the wall thickness changes abruptly in the length direction of the metal pipe material, the metal pipe material may be damaged starting from that portion. In this embodiment, since the wall thickness of the pair of intermediate portions is thinned so as to approach the wall thickness of the processed portion, damage to the metal pipe material can be further suppressed.

In one embodiment, the wall thickness of the pair of held portions may be thicker than the wall thickness of the processed portion.

In the molding apparatus according to another aspect, a pair of held portions located on both end sides in the longitudinal direction, a processed portion located in the central portion in the longitudinal direction, each of the pair of held portions, and the processed portion. A metal pipe material that holds a pair of held parts of a metal pipe material and a metal pipe material that is located between them and has a pair of intermediate parts that are located between them and have a shape or characteristic that is less likely to be deformed than the part to be processed during blow molding. It has an electrode that heats the metal pipe material by energizing the metal pipe material, a fluid supply unit that supplies fluid into the heated metal pipe material to expand it, and a pair of molds that provide a pair of molding surfaces facing each other. An expansion regulation provided between the molding die for molding the workpiece of the metal pipe material expanded between the pair of molds and the molding die and the electrode to regulate the radial expansion of the pair of intermediate portions. It has a part and.

According to the molding apparatus according to the above aspect, the possibility of rupture of the metal pipe material can be reduced as described above.

According to one aspect of the present invention and various embodiments, the possibility of rupture of the metal pipe material can be reduced.

It is a schematic block diagram which shows the molding apparatus which concerns on 1st Embodiment. It is a schematic side view which shows the heating expansion unit which unitized the component of a holding part, a heating part, and a fluid supply part. It is a flowchart which shows an example of the molding method of a metal pipe material. It is sectional drawing which shows the metal pipe material arranged between the molding dies. It is an enlarged cross-sectional view which shows the metal pipe material and the molding die. It is a flowchart which shows another example of the molding method of a metal pipe material. It is sectional drawing which shows the metal pipe material arranged between the molding dies. It is a schematic block diagram which shows the molding apparatus which concerns on 2nd Embodiment. It is sectional drawing which shows the circumference of the expansion regulation part enlarged. It is a figure which shows the operation of the molding apparatus at the time of blow molding. It is a perspective view which shows the robot arm. It is sectional drawing which shows the part of the conventional molding apparatus enlarged.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each figure, the same parts or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.

(First Embodiment)
FIG. 1 is a schematic view of a molding apparatus 1 according to the first embodiment. The molding apparatus 1 is an apparatus for molding a metal pipe material having a hollow shape by blow molding. In this embodiment, the molding apparatus 1 is installed on a horizontal plane. The molding apparatus 1 includes a molding die (molding mold) 2, a drive mechanism 3, a holding unit 4, a heating unit 5, a fluid supply unit 6, a cooling unit 7, and a control unit 8. In the present specification, the metal pipe refers to a hollow article after the molding is completed by the molding device 1, and the metal pipe material 40 refers to a hollow article before the molding is completed by the molding device 1. The metal pipe material 40 is a hardenable steel type pipe material. Further, among the horizontal directions, the direction in which the metal pipe material 40 extends at the time of molding may be referred to as "longitudinal direction", and the direction orthogonal to the longitudinal direction may be referred to as "width direction".

The molding die 2 is a die for molding a metal pipe material 40 into a metal pipe, and includes a lower die 11 and an upper die 12 facing each other in the vertical direction. The lower mold 11 and the upper mold 12 are composed of, for example, steel blocks, and form a pair of molds. The lower mold 11 and the upper mold 12 have a pair of molding surfaces 11a and 12a, and a recess for accommodating the metal pipe material 40 is formed in a part of each of the molding surfaces 11a and 12a. The lower mold 11 and the upper mold 12 are in close contact with each other (mold closed state), and each recess forms a space having a target shape in which the metal pipe material should be formed. The lower mold 11 is fixed to the base 13 via a die holder or the like. The upper mold 12 is fixed to the slide of the drive mechanism 3 via a die holder or the like.

The drive mechanism 3 is a mechanism for moving at least one of the lower mold 11 and the upper mold 12. In FIG. 1, the drive mechanism 3 has a configuration in which only the upper mold 12 is moved. The drive mechanism 3 lowers the slide 21, the slide 21 that moves the upper mold 12 so that the lower mold 11 and the upper mold 12 are aligned with each other, the pull-back cylinder 22 as an actuator that generates a force for pulling the slide 21 upward, and the slide 21. It includes a main cylinder 23 as a drive source for pressurizing, and a drive source 24 for applying a driving force to the main cylinder 23.

The holding portion 4 is a mechanism for holding the metal pipe material 40 arranged between the lower mold 11 and the upper mold 12. The holding portion 4 includes a lower electrode 26 and an upper electrode 27 that hold the metal pipe material 40 on one end side in the longitudinal direction of the molding die 2, and a metal pipe material on the other end side in the longitudinal direction of the molding die 2. A lower electrode 26 and an upper electrode 27 holding the 40 are provided. The lower electrodes 26 and the upper electrodes 27 on both sides in the longitudinal direction sandwich the pair of ends (pair of held portions) 42 (see FIG. 4) of the metal pipe material 40 from above and below, thereby sandwiching the metal pipe material 40. To hold. Grooves having a shape corresponding to the outer peripheral surface of the metal pipe material 40 are formed on the upper surface of the lower electrode 26 and the lower surface of the upper electrode 27. The lower electrode 26 and the upper electrode 27 are provided with a drive mechanism (not shown), and can move independently in the vertical direction.

The heating unit 5 heats the metal pipe material 40. The heating unit 5 is a mechanism for heating the metal pipe material 40 by energizing the metal pipe material 40. The heating unit 5 heats the metal pipe material 40 in a state where the metal pipe material 40 is separated from the lower mold 11 and the upper mold 12. The heating unit 5 includes the lower electrodes 26 and the upper electrodes 27 on both sides in the longitudinal direction described above, and a power supply 28 for passing an electric current through the electrodes 26 and 27 to the metal pipe material.

The fluid supply unit 6 is a mechanism for supplying a high-pressure fluid into the metal pipe material 40 held between the lower mold 11 and the upper mold 12. The fluid supply unit 6 supplies a high-pressure fluid to the metal pipe material 40 which has become hot due to being heated by the heating unit 5, and expands the metal pipe material 40. The fluid supply unit 6 is provided on both end sides of the molding die 2 in the longitudinal direction. The fluid supply unit 6 moves the nozzle 31 that supplies fluid from the opening of the end 42 of the metal pipe material 40 to the inside of the metal pipe material 40 and the nozzle 31 with respect to the opening of the metal pipe material 40. It includes a drive mechanism 32 and a supply source 33 that supplies a high-pressure fluid into the metal pipe material 40 via the nozzle 31. The drive mechanism 32 brings the nozzle 31 into close contact with the end 42 of the metal pipe material 40 while ensuring the sealing property during fluid supply and exhaust, and separates the nozzle 31 from the end 42 of the metal pipe material 40 at other times. .. The fluid supply unit 6 may supply a gas such as high-pressure air or an inert gas as the fluid.

The cooling unit 7 is a mechanism for cooling the molding die 2. By cooling the molding die 2, the cooling unit 7 can rapidly cool the metal pipe material 40 when the expanded metal pipe material 40 comes into contact with the molding surface of the molding die 2. The cooling unit 7 includes a flow path 36 formed inside the lower die 11 and the upper die 12, and a water circulation mechanism 37 that supplies and circulates cooling water to the flow path 36.

The control unit 8 is a device that controls the entire molding device 1. The control unit 8 controls the drive mechanism 3, the holding unit 4, the heating unit 5, the fluid supply unit 6, and the cooling unit 7. The control unit 8 repeatedly performs an operation of molding the metal pipe material 40 with the molding die 2.

Specifically, the control unit 8 controls a transport means such as a robot arm to arrange the metal pipe material 40 between the lower mold 11 and the upper mold 12 in the open state. Alternatively, the control unit 8 may wait for the operator to manually place the metal pipe material 40 between the lower mold 11 and the upper mold 12. Further, the control unit 8 supports the metal pipe material 40 with the lower electrodes 26 on both sides in the longitudinal direction, and then lowers the upper electrode 27 to sandwich the metal pipe material 40, such as an actuator of the holding unit 4. Control. Further, the control unit 8 controls the heating unit 5 to energize and heat the metal pipe material 40. As a result, an axial current flows through the metal pipe material 40, and the metal pipe material 40 itself generates heat due to Joule heat due to the electrical resistance of the metal pipe material 40 itself.

The control unit 8 controls the drive mechanism 3 to lower the upper mold 12 and bring it closer to the lower mold 11 to close the molding die 2. On the other hand, the control unit 8 controls the fluid supply unit 6 to seal the openings at both ends of the metal pipe material 40 with the nozzle 31 and supply the fluid. As a result, the metal pipe material 40 softened by heating expands and comes into contact with the molding surfaces 11a and 12a of the molding die 2. Then, the metal pipe material 40 is molded so as to follow the shapes of the molding surfaces 11a and 12a of the molding die 2. When forming a metal pipe with a flange, a part of the metal pipe material 40 is inserted into the gap between the lower mold 11 and the upper mold 12, and then the mold is further closed to crush the entrance portion. To be the flange part. When the metal pipe material 40 comes into contact with the molding surfaces 11a and 12a, the metal pipe material 40 is quenched by quenching with the molding die 2 cooled by the cooling unit 7.

Next, with reference to FIG. 2, the configurations of the holding unit 4, the heating unit 5, and the fluid supply unit 6 will be described in more detail. FIG. 2 is a schematic side view showing a heating / expanding unit 50 in which the components of the holding unit 4, the heating unit 5, and the fluid supply unit 6 are unitized. Although FIG. 2 shows a heating / expanding unit 50 for one end of the metal pipe material 40 in the longitudinal direction, the heating / expanding unit 50 for the other end also has the same configuration.

As shown in FIG. 2, the heating and expansion unit 50 moves up and down with the above-mentioned lower electrode 26 and upper electrode 27, the electrode mounting unit 51 on which the respective electrodes 26 and 27 are mounted, and the above-mentioned nozzle 31 and drive mechanism 32. It includes a unit 52 and a unit base 53. In the following description, the reference line SL1 will be set at the position of the central axis of the metal pipe material 40 at the positions held by the electrodes 26 and 27. The direction in which the reference line SL1 extends may be referred to as an axial direction. Further, the direction in which the electrodes 26 and 27 are opposed to each other and the direction orthogonal to the axial direction may be referred to as an ascending / descending direction.

The lower electrode 26 and the upper electrode 27 are both rectangular plate-shaped electrodes formed by sandwiching a plate-shaped conductor with an insulating plate. A semicircular groove is formed in each of the central upper end of the lower electrode 26 and the central lower end of the upper electrode 27 so as to vertically penetrate the flat plate surface. Then, when the lower electrode 26 and the upper electrode 27 are arranged on the same plane and the upper end portion of the lower electrode 26 and the lower end portion of the upper electrode 27 are brought into close contact with each other, the semicircular groove portions of each other match. It becomes a circular through hole. The circular through hole has the reference line SL1 as the center line and substantially coincides with the outer diameter of the end portion of the metal pipe material 40. When the metal pipe material 40 is energized, the pair of end portions 42 of the metal pipe material 40 are gripped by the lower electrode 26 and the upper electrode 27 in a state of being fitted into the circular through holes (FIG. 6). See also 4). At this time, the inner peripheral surfaces 26a and 27a of the groove portion of the plate-shaped conductor of the lower electrode 26 and the upper electrode 27 are contact surfaces with respect to the metal pipe material 40 and are energizing surfaces. The outer shape of the pair of end portions 42 of the metal pipe material 40 is not limited to a circle. Therefore, each of the groove portions of the lower electrode 26 and the upper electrode 27 has a shape obtained by dividing the outer shape of the pair of end portions 42 of the metal pipe material 40 by half.

The electrode mounting unit 51 includes an elevating frame 54 in which an elevating unit 52 gives an elevating operation along a direction perpendicular to the upper surface of the unit base 53, and a lower portion provided on the elevating frame 54 to hold the lower electrode 26. A side electrode frame 56 and an upper electrode frame 57 provided above the lower electrode frame 56 and holding the upper electrode 27 are provided. Each of the electrode frames 56 and 57 includes an actuator and a guide mechanism (not shown), and is configured to be slidable in the axial direction and the elevating direction with respect to the unit base 53 while holding the electrodes 26 and 27. Therefore, the electrode frames 56 and 57 function as a part of the drive mechanism 60 for moving the electrodes 26 and 27.

The nozzle 31 is a cylindrical member into which the end portion of the metal pipe material 40 can be inserted. The nozzle 31 is supported by the drive mechanism 32 so that the center line of the nozzle 31 coincides with the reference line SL1. The inner diameter of the end portion (referred to as supply port 31a (see FIG. 4)) of the nozzle 31 on the metal pipe material 40 side substantially matches the outer diameter of the metal pipe material 40 after expansion molding.

The drive mechanism 32 is mounted on the elevating unit 52. Therefore, when the elevating unit 52 moves up and down, the drive mechanism 32 moves up and down integrally with the electrode mounting unit 51. The drive mechanism 32 has a pair of ends 42 of the metal pipe material 40 and a nozzle 31 in a state where the lower electrode 26 and the upper electrode 27 of the electrode mounting unit 51 grip the pair of ends 42 of the metal pipe material 40. The nozzle 31 is supported at a position concentric with and.

The drive mechanism 32 has a hydraulic cylinder mechanism as a nozzle moving actuator that moves the nozzle 31 along the axial direction. This hydraulic cylinder mechanism includes a piston 61 (an example of a support portion) that holds the nozzle 31, and a cylinder 62 that imparts forward / backward movement to the piston 61. The cylinder 62 is fixed to the elevating frame 54 in a direction in which the piston 61 is moved forward and backward in parallel with the axial direction. The cylinder 62 is connected to a hydraulic circuit (not shown), and pressure oil, which is a working fluid, is supplied and discharged inside. In the hydraulic circuit, the supply and discharge of pressure oil to the cylinder 62 is controlled by the control unit 8.

The piston 61 includes a main body portion 61a housed in the cylinder 62, a head portion 61b protruding outward from the left end portion (lower electrode 26 and upper electrode 27 side) of the cylinder 62, and an external portion from the rear end portion of the cylinder 62. It is provided with a tubular portion 61c that protrudes into the. The main body portion 61a, the head portion 61b, and the tubular portion 61c are all cylindrical and are concentrically and integrally formed. The outer diameter of the main body 61a substantially matches the inner diameter of the cylinder 62. Then, in the cylinder 62, flood control is supplied to both sides of the main body portion 61a to move the piston 61 forward and backward. Nozzles 31 are concentrically fixedly mounted on the tip of the head 61b. The nozzle 31 and the piston 61 are formed with a flow path 63 for a compressed gas penetrating over the entire length at the position of the reference line SL1.

The elevating unit 52 includes an elevating frame base 64 attached to the upper surface of the unit base 53, and an elevating actuator 66 that imparts an elevating operation to the elevating frame 54 of the electrode mounting unit 51 by the elevating frame base 64. ing. The elevating frame base 64 supports the elevating frame 54 so as to be able to move up and down with respect to the upper surface of the unit base 53 in the elevating direction. The elevating frame base 64 has guide portions 64a and 64b that guide the elevating operation of the elevating frame 54 with respect to the unit base 53. The elevating actuator 66 is a linear actuator that applies a driving force to the unit base 53 to the elevating frame 54, and for example, a hydraulic cylinder or the like can be used. The elevating unit 52 functions as a part of the drive mechanism 60 of the holding unit 4.

The unit base 53 is a rectangular plate-shaped block in a plan view that supports the electrode mounting unit 51 and the drive mechanism 32 on the upper surface via the elevating unit 52. The unit base 53 is attached to the upper surface of the base 13 (see FIG. 1), which is a horizontal surface, by a fixing means such as a bolt, and can be removed. The heating and expansion unit 50 has a plurality of unit bases 53 having different inclination angles on the upper surface, and by exchanging these, the lower electrode 26 and the upper electrode 27, the nozzle 31, the electrode mounting unit 51, the drive mechanism 32, and the elevating mechanism 32 are moved up and down. It is possible to collectively change and adjust the tilt angle of the unit 52. For example, when the center line of the metal pipe material 40 at the end is inclined, the unit base 53 inclines each component so that the reference line SL1 is inclined according to the inclination.

Next, a method of molding the metal pipe material 40 using the molding apparatus 1 will be described, and the metal pipe material 40 blow-molded by the molding apparatus 1 will be described. FIG. 3 is a flowchart showing a molding method MT1 of the metal pipe material 40 according to the first embodiment. In this molding method MT1, first, the metal pipe material 40 to be molded is prepared (step ST1).

FIG. 4 is a cross-sectional view showing a metal pipe material 40 formed by the forming apparatus 1. As shown in FIG. 4, the metal pipe material 40 to be prepared has a pair of end portions 42, a processed portion 44, and a pair of gradual change portions 46. The pair of end portions 42 are located on both end sides of the metal pipe material 40 in the longitudinal direction and are held between the lower electrode 26 and the upper electrode 27. The workpiece 44 is located at a substantially central portion in the longitudinal direction of the metal pipe material 40. The workpiece 44 is formed into a product shape along the shape of the recesses formed on the pair of molding surfaces 11a and 12a when the lower mold 11 and the upper mold 12 are closed. The pair of gradual change portions 46 are provided between one end portion 42 and the processed portion 44 and between the other end portion 42 and the processed portion 44 in the longitudinal direction of the metal pipe material 40, respectively. ing. The pair of gradual change portions 46 form a pair of intermediate portions located between each of the pair of end portions 42 and the portion to be machined 44. The cross-sectional shape of the pair of slowly changing portions 46 changes so as to approach the cross-sectional shape of the portion to be machined 44 as it approaches the portion to be machined 44, and the cross-sectional shape of the pair of end portions 42 as it approaches the pair of end portions 42. It may be changed to approach the shape.

As shown in FIG. 4, the metal pipe material 40 has a uniform outer diameter in the longitudinal direction. On the other hand, the inner diameter of the metal pipe material 40 differs depending on the position in the longitudinal direction. That is, the metal pipe material 40 has a different wall thickness depending on the position in the longitudinal direction. More specifically, the wall thickness of the metal pipe material 40 is increased in the order of the workpiece 44, the pair of gradual change portions 46, and the pair of end portions 42. For example, the pair of end portions 42 has an inner diameter smaller than the inner diameter of the workpiece 44, and the wall thickness TH1 of the pair of end portions 42 is thicker than the wall thickness TH2 of the workpiece 44. .. Further, the wall thickness TH3 of the pair of gradual change portions 46 gradually becomes thinner toward the wall thickness TH2 of the work portion 44 as it approaches the work portion 44, and conversely, the pair as it approaches the pair of end portions 42. It is gradually thickened so as to approach the wall thickness TH1 of the end portion 42 of the. In other words, the inner peripheral surfaces of the pair of slowly changing portions 46 become smaller in inner diameter toward the outside in the longitudinal direction of the metal pipe material 40. That is, the pair of end portions 42 and the pair of gradual change portions 46 form an outer portion located outside in the longitudinal direction of the workpiece 44 of the metal pipe material 40, and this outer portion is larger than the workpiece 44. It has a thick wall thickness.

In the molding method MT1, the pair of end portions 42 of the prepared metal pipe material 40 are held between the lower electrode 26 and the upper electrode 27 (step ST2). For example, the control unit 8 controls the robot arm or the like and arranges the metal pipe material 40 on the lower electrode 26 to put the metal pipe material 40 between the lower mold 11 and the upper mold 12. After that, the control unit 8 lowers the upper electrode 27, so that the pair of end portions 42 of the metal pipe material 40 are held between the lower electrode 26 and the upper electrode 27. At this time, the pair of slowly changing portions 46 of the metal pipe material 40 face the space S formed near the boundary between the lower electrode 26 and the lower mold 11 and near the boundary between the upper electrode 27 and the upper mold 12. It is placed in the position to be.

Next, the heating unit 5 is controlled by the control unit 8, and the metal pipe material 40 is energized and heated (step ST3). In this step ST3, power is supplied from the power source 28 to the lower electrodes 26 and the upper electrodes 27 on both sides in the longitudinal direction. The electric power supplied to the lower electrode 26 and the upper electrode 27 is transmitted to the metal pipe material 40, and the metal pipe material 40 itself generates heat due to Joule heat generated by the electric resistance of the metal pipe material 40.

At this time, since the pair of slowly changing portions 46 have a wall thickness TH3 larger than the wall thickness TH2 of the processed portion 44, the density of the current flowing through the pair of slowly changing portions 46 is higher than that of the processed portion 44. It is smaller than the density of the flowing current. Therefore, when the metal pipe material 40 is energized and heated, the temperature rise of the pair of slowly changing portions 46 is suppressed as compared with the workpiece 44.

Next, the control unit 8 closes the molding die 2 and supplies the fluid to the metal pipe material 40 by the fluid supply unit 6 to perform blow molding (step ST4). In step ST4, the control unit 8 controls the drive mechanism 32 to close the molding die 2 with respect to the heated metal pipe material 40. As a result, as shown in FIG. 5A, the concave portion of the lower mold 11 and the concave portion of the upper mold 12 are combined to form the cavity portion MC, and the workpiece portion of the metal pipe material 40 is formed in the cavity portion MC. 44 is placed.

Further, the control unit 8 controls the fluid supply unit 6 to supply the fluid into the metal pipe material 40. For example, the control unit 8 drives the drive mechanism 32 to move the supply port 31a of the nozzle 31 toward the metal pipe material 40, and fits the supply port 31a of the nozzle 31 to the pair of end portions 42 to fit the metal pipe material. Seal the 40 openings. When the opening of the metal pipe material 40 is sealed, a high-pressure fluid is blown into the metal pipe material 40 from the supply source 33.

Since the metal pipe material 40 is heated to a high temperature and softened, the gas supplied into the metal pipe material 40 thermally expands. Therefore, the workpiece 44 of the metal pipe material 40 can be easily expanded by a high-pressure fluid obtained by thermally expanding the metal pipe material 40. As a result, as shown in FIG. 5B, the processed portion 44 of the metal pipe material 40 arranged in the cavity portion MC of the molding die 2 is molded so as to follow the shape of the cavity portion MC.

At this time, the outer peripheral surface of the workpiece 44 expanded by blow molding comes into contact with the surface of the cavity MC of the molding die 2. The workpiece 44 in contact with the surface of the cavity MC is rapidly cooled and quenched. By this quenching, the austenite structure of the processed portion 44 is transformed into a martensite structure. Since the cooling rate decreases in the latter half of cooling, the martensite structure is transformed into troostite, sorbite, etc. by reheating.

At the time of blow molding, the pair of slowly changing portions 46 expand in the radial direction by a high-pressure fluid that has been thermally expanded like the workpiece 44. At this time, since the pair of slowly changing portions 46 have a wall thickness TH3 thicker than the wall thickness TH2 of the processed portion 44, the pair of slowly changing portions 46 have higher strength than the processed portion 44. doing. Further, as described above, when the metal pipe material 40 is energized and heated, the temperature rise of the pair of slowly changing portions 46 is suppressed as compared with that of the workpiece 44. Therefore, the amount of expansion of the pair of slowly changing portions 46 in the radial direction during blow molding is suppressed as compared with the workpiece 44. That is, the pair of slowly changing portions 46 are less likely to be deformed than the workpiece 44. As a result, the pair of slowly changing portions 46 expands so as to enter the space S formed near the boundary between the lower electrode 26 and the lower mold 11 and near the boundary between the upper electrode 27 and the upper mold 12. This is prevented, and as a result, the metal pipe material 40 is prevented from bursting. Even if a part of the pair of slowly changing portions 46 expands so as to enter the space S, since the thickness of the pair of slowly changing portions 46 is large, the pair of slowly changing portions 46 will be expanded at the time of expansion. Can reduce the likelihood of rupture.

Next, the control unit 8 raises the upper mold 12 and separates it from the metal pipe material 40 to open the mold (step ST5). The molded metal pipe material 40 is removed from the molding apparatus 1. A pair of end portions 42 and a pair of gradual change portions 46 are cut off from the metal pipe material 40 removed from the molding apparatus 1, and the molded portion 44 is used as a product.

The operation and effect of the molding method of the metal pipe material 40 of the present embodiment will be described. In the molding method MT1 described above, since the wall thickness of the pair of slowly changing portions 46 is thickened, it is possible to suppress the temperature rise of the pair of slowly changing portions 46 when the metal pipe material 40 is energized and heated, and the pair The strength of the gradual change portion 46 can be increased. Therefore, since the slowly changing portion is hard to be deformed, when the metal pipe material 40 is blow-molded, it is difficult for the pair of slowly changing parts 46 to enter the space S near the boundary between the electrodes 26 and 27 and the molding die 2. Become. As a result, the amount of deformation of the pair of slowly changing portions 46 can be reduced, and the occurrence of rupture of the metal pipe material 40 can be suppressed.

The metal pipe material 40 shown in FIG. 4 has a pair of slowly changing portions 46 having a wall thickness TH3 thicker than the wall thickness TH2 of the processed portion 44, but is more than the processed portion 44 at the time of blow molding. It suffices to have a shape or characteristic that is not easily deformed. For example, in the metal pipe material 40, the pair of slowly changing portions 46 and the portion to be processed 44 are made of different materials, and the strength of the pair of slowly changing portions 46 is formed to be higher than the strength of the portion to be processed 44. It may have been done. By relatively increasing the strength of the pair of slowly changing portions 46, the amount of deformation of the pair of slowly changing portions 46 at the time of blow molding can be reduced. Therefore, as in the above embodiment, the pair of slowly changing portions 46 can be reduced. The possibility of rupture of 46 can be reduced.

Further, in another example, the pair of slowly changing portions 46 and the portion to be processed 44 are made of different materials so that the electric resistance of the pair of slowly changing portions 46 is smaller than the electric resistance of the portion to be processed 44. You may. By reducing the electrical resistance of the pair of slowly changing portions 46, it is possible to suppress the temperature rise of the pair of slowly changing portions 46 due to Joule heat when the metal pipe material 40 is energized and heated. Therefore, as in the above embodiment, it is possible to prevent the pair of slowly changing portions 46 from bursting.

Next, a method for forming the metal pipe material according to another embodiment will be described. FIG. 6 is a flowchart showing a method MT2 for forming a metal pipe material according to another embodiment. Hereinafter, the differences from the molding method MT1 shown in FIG. 3 will be mainly described.

In the molding method MT2, first, the metal pipe material 40A to be molded is prepared (step ST11). As shown in FIG. 7, the metal pipe material 40A prepared in step ST11 includes a pair of end portions 42A, a processed portion 44A, and a pair of slowly changing portions (intermediate portions) 46A. Unlike the metal pipe material 40 described above, in the metal pipe material 40A, the pair of end portions 42A, the processed portion 44A, and the pair of gradual change portions 46A have substantially the same wall thickness.

Next, the pair of ends 42A of the metal pipe material 40 are held between the lower electrode 26 and the upper electrode 27 (step ST12).

Next, the reinforcing member 67 is inserted into the inside of the metal pipe material 40A through the opening of the metal pipe material 40A (step ST13). In step ST13, for example, the control unit 8 controls the robot arm or the like to insert the reinforcing member 67 into the metal pipe material 40A, and the metal pipe material 40A is aligned with the inner peripheral surfaces of the pair of gradual change portions 46A. Place inside. The reinforcing member 67 may be inserted into the metal pipe material 40A by an operator.

Next, the control unit 8 controls the heating unit 5 to energize and heat the metal pipe material 40 (step ST14). Next, the control unit 8 closes the molding die 2 and supplies the fluid to the metal pipe material 40 by the fluid supply unit 6 to perform blow molding (step ST15). By this blow molding, the processed portion 44A of the metal pipe material 40A arranged in the cavity portion MC of the molding die 2 is molded so as to follow the shape of the cavity portion MC.

During this blow molding, the inner peripheral surfaces of the pair of slowly changing portions 46A are covered with the reinforcing member 67, so that the pair of slowly changing portions 46A are not exposed to the high-pressure fluid thermally expanded in the metal pipe material 40A. , Expansion in the width direction is hindered. As a result, the amount of radial deformation of the pair of slowly changing portions 46 is suppressed, so that the possibility of bursting of the pair of slowly changing portions 46A during blow molding of the metal pipe material 40A can be reduced.

Next, the control unit 8 raises the upper mold 12 and separates it from the metal pipe material 40A to open the mold (step ST16). The molded metal pipe material 40A is removed from the molding apparatus 1. A pair of end portions 42A and a pair of gradual change portions 46A are cut off from the metal pipe material 40A removed from the molding apparatus 1, and the molded portion 44A is used as a product.

(Second Embodiment)
Next, the metal pipe material forming apparatus according to the second embodiment will be described with reference to FIGS. 8 and 9. In the following, the differences from the molding apparatus 1 will be mainly described, and duplicate description will be omitted.

FIG. 8 is a cross-sectional view showing a part of the molding apparatus 1A according to the second embodiment. For convenience of explanation, the axial direction of the reference line SL1 will be referred to as the "X direction", the vertical direction will be referred to as the "Z direction", and the direction orthogonal to the X direction and the Z direction will be referred to as the "Y direction".

As shown in FIG. 8, the molding apparatus 1A includes a molding die 2A instead of the molding die 2. The molding die 2A has a lower die 70 and an upper die 71 that are paired with each other. In the present embodiment, the lower die 70 and the upper die 71 are moved by the drive mechanism 3 in the direction toward and away from each other along the Z direction. The lower mold 70 and the upper mold 71 have a pair of molding surfaces 70a and 71a facing each other, respectively.

The molded surface 70a of the lower mold 70 is formed with a curved surface that curves downward as it approaches the end 70b in the X direction. Similarly, the molding surface 71a of the upper mold 71 is formed with a curved surface that curves upward as it approaches the end portion 71b in the X direction. Therefore, the end portions 70b, 71b of the molding surfaces 70a, 71a are arranged at positions separated from the reference line SL1 from the central portion of the molding surfaces 70a, 71a in the X direction.

The lower mold 70 has a pair of side surfaces 70c facing each other in the X direction. The pair of side surfaces 70c are connected to the ends 70b on both sides of the molding surface 70a in the X direction. The upper die 71 has a pair of side surfaces 71c facing each other in the X direction. The pair of side surfaces 71c are connected to the ends 71b on both sides of the molding surface 71a in the X direction.

Next, the side shape of the upper die 71 will be described in more detail with reference to FIG. 9A. Since the side shape of the lower mold 70 is vertically symmetrical with the side shape of the upper mold 71, the description thereof will be omitted. As shown in FIG. 9A, a stepped portion is formed on the upper portion of the side surface 71c of the upper die 71, and the stepped surface 71d, the stepped side surface 71e, and the top surface 71f are further formed. The stepped surface 71d extends horizontally from the upper end of the side surface 71c toward the inside of the upper die 71 in the X direction. The step side surface 71e extends upward from the inner end of the step surface 71d in parallel with the side surface 71c. The top surface 71f extends horizontally from the upper end of the step side surface 71e toward the outside of the upper die 71 in the X direction. In the X direction, the outer end of the top surface 71f is located outward of the side surface 71c.

The molding apparatus 1A further includes an expansion regulating portion 80 that regulates the radial expansion of the pair of slowly changing portions 46A of the metal pipe material 40A (see FIG. 8). The expansion control unit 80 is provided between the molding die 2A and the electrodes 26 and 27 in the X direction. The expansion control unit 80 includes a pair of contact members 82, 83 that face each other in the vertical direction, and a pair of elastic members 85, which slide the pair of contact members 82, 83 with respect to the molding die 2A in the Z direction. Has 86.

The abutting members 82 and 83 are provided between the molding die 2 and the electrodes 26 and 27, and face each other in the Z direction (the direction in which the lower die 70 and the upper die 71 face each other). The abutting members 82 and 83 have, for example, a rectangular flat plate shape, and when the pair of end portions 42A of the metal pipe material 40A are held by the electrodes 26 and 27, they face the pair of gradual change portions 46A. Placed in position.

Semicircular groove portions are formed at the central lower end portion of the abutting member 82 and the central upper end portion of the abutting member 83 so as to penetrate the abutting members 82 and 83 in the X direction, respectively. When the lower end of the abutting member 82 and the upper end of the abutting member 83 are brought into close contact with each other, the semicircular grooves match each other to form a circular through hole. This circular through hole has a reference line SL1 as a center line and has an inner diameter slightly larger than the outer diameter of the gradually changing portion 46A of the metal pipe material 40A. The abutting members 82 and 83 have inner peripheral surfaces 82a and 83a that define the circular through hole. These inner peripheral surfaces 82a and 83a come into contact with the outer peripheral surfaces of the gradual change portion 46A of the metal pipe material 40A during blow molding to regulate the radial expansion of the gradual change portion 46A. That is, the inner peripheral surfaces 82a and 83a function as pipe contact surfaces that come into contact with the outer peripheral surface of the gradual change portion 46A during blow molding.

The contact member 82 will be described in more detail with reference to FIG. 9A. As shown in FIG. 9A, flange portions 82b protruding on both sides in the X direction are formed on the upper portion of the contact member 82. The flange portion 82b has a lower surface 82b1 facing the stepped surface 71d of the upper die 71 and a lower surface 82b2 facing the backing plate 65 provided on the upper electrode 27 in the Z direction. Further, the contact member 82 has a contact surface 82c facing the side surface 71c of the upper die 71. The contact surface 82c extends upward from the end of the inner peripheral surface 82a on the upper die 71 side and is in contact with the side surface 71c of the upper die 71. The length of the contact surface 82c in the Z direction is formed longer than the length of the side surface 71c of the upper mold 71 in the Z direction.

An elastic member 85 is provided between the top surface 71f and the contact member 82. The elastic member 85 is coupled to the top surface 71f and the abutting member 82. Therefore, the contact member 82 and the elastic member 85 can move in the Z direction together with the upper mold 71 as the upper mold 71 moves in the Z direction by the drive mechanism 3. The elastic member 85 is, for example, a gas damper that can expand and contract in the Z direction, and the abutting member 82 is urged toward the reference line SL1 in the Z direction by its elastic force.

When the lower mold 70 and the upper mold 71 are separated from each other, as shown in FIG. 9A, the lower surface 82b1 of the contact member 82 comes into contact with the stepped surface 71d due to the elastic force of the elastic member 85, and Z Pressed in the direction. At this time, since the length of the contact surface 82c of the contact member 82 in the Z direction is longer than the length of the side surface 71c of the upper die 71 in the Z direction, the inner peripheral surface 82a of the contact member 82 is formed in the Z direction. It is arranged at a position closer to the reference line SL1 than the end portion 71b of the surface 71a.

On the other hand, when the lower die 70 and the upper die 71 are closed, as shown in FIG. 9B, the lower die 82b2 of the contact member 82 is brought into contact plate 65 by lowering the upper die 71. Contact the top surface of. When the upper die 71 is further lowered from that state, the elastic member 85 is compressed in the Z direction between the top surface 71f and the contact member 82, and the contact surface 82c of the contact member 82 becomes the side surface 71c of the upper die 71. It slides upward (Z direction) with respect to the lower surface 82b1 of the contact member 82 and is separated from the stepped surface 71d. By sliding the abutting member 82 with respect to the upper mold 71 in this way, at least a part of the inner peripheral surface 82a of the abutting member 82 is a reference line from the end portion 71b of the molding surface 71a in the Z direction. It is located far from SL1. As shown in FIG. 9B, the inner peripheral surface 82a of the contact member 82 may be curved so as to expand upward as it approaches the upper electrode 27. By having such an inner peripheral surface 82a, when the lower mold 70 and the upper mold 71 are closed, the curved surface on the end 70b side of the molding surface 70a and the inner peripheral surface 82a of the contact member 82 And forms a smooth curved surface.

Since the contact member 83 and the elastic member 86 are vertically symmetrical with the contact member 82 and the elastic member 85, the description thereof will be omitted.

Next, a method of molding the metal pipe material 40A using the molding apparatus 1A will be described with reference to FIGS. 8 and 10. FIG. 8 shows an energization heating step of the metal pipe material 40A. First, the metal pipe material 40A to be molded is prepared. In the metal pipe material 40A shown in FIG. 8, a pair of end portions 42A, a processed portion 44A, and a pair of slowly changing portions (intermediate portions) 46A have substantially the same wall thickness. Next, the control unit 8 arranges the pair of end portions 42A of the metal pipe material 40A between the lower electrode 26 and the upper electrode 27 by using, for example, a robot arm or the like. At this time, the pair of slowly changing portions 46A of the metal pipe material 40A are arranged between the abutting members 82 and 83. Next, the control unit 8 controls the heating unit 5 to energize and heat the metal pipe material 40A.

Next, primary blow molding is performed. As shown in FIG. 10A, in the primary blow molding step, the fluid is supplied from the fluid supply unit 6 to the inside of the metal pipe material 40A in a state where the lower mold 70 and the upper mold 71 are separated from each other. In the primary blow molding step, the lower mold 70 and the upper mold 71 are separated from each other. Therefore, as shown in FIG. 9A, the lower surface 82b1 of the contact member 82 and the stepped surface 71d of the upper mold 71 are in contact with each other. The contact member 82 is arranged at the contacting position. Therefore, the inner peripheral surfaces 82a and 83a of the contact member 82 have a diameter of the gradually changing portion 46A of the metal pipe material 40A at a position closer to the reference line SL1 than the ends 70b and 71b of the molded surfaces 70a and 71a in the Z direction. Arranged so as to surround from the outside in the direction.

Therefore, the pair of gradual change portions 46A expanded in the radial direction by the high-pressure fluid thermally expanded in the metal pipe material 40A come into contact with the inner peripheral surfaces 82a and 83a of the contact member 82, and the expansion in the radial direction is hindered. Be done. As described above, at the time of primary blow molding, since the inner peripheral surfaces 82a and 83a of the contact member 82 are arranged at positions close to the reference line SL1, the amount of expansion of the pair of gradual change portions 46A in the radial direction is small. Is regulated to be.

Next, secondary blow molding is performed. As shown in FIG. 10B, in the secondary blow molding step, the fluid is supplied from the fluid supply unit 6 to the inside of the metal pipe material 40A in a state where the lower mold 70 and the upper mold 71 are closed. .. In the secondary blow molding step, the lower mold 70 and the upper mold 71 are molded closed, so that the elastic member 85 is in the Z direction between the top surface 71f and the contact member 82 as shown in FIG. 9B. The contact member 82 is slid upward with respect to the upper mold 71. As a result, at least a part of the inner peripheral surfaces 82a, 83a of the contact members 82, 83 is arranged at a position farther from the reference line SL1 than the ends 70b, 71b of the molded surfaces 70a, 71a in the Z direction. At this time, the inner peripheral surfaces 82a and 83a may be arranged so that the curved surface on the end 70b side of the molding surface 70a and the inner peripheral surface 82a of the contact member 82 form a smooth curved surface. By this secondary blow molding, the workpiece 44A of the metal pipe material 40A is formed so as to follow the shape of the cavity MC, and the outer diameter of the metal pipe material 40A changes smoothly in the longitudinal direction. The gradual change portion 46A is formed.

After that, the lower mold 70 and the upper mold 71 are opened, and the metal pipe material 40A after molding is removed from the molding apparatus 1A. A pair of end portions 42A and a pair of gradual change portions 46A are cut off from the metal pipe material 40A removed from the molding apparatus 1, and the molded portion 44A is used as a product.

In the molding apparatus 1A described above, the expansion regulating portion 80 provided between the molding die 2A and the electrodes 26 and 27 regulates the radial expansion of the pair of slowly changing portions 46A of the metal pipe material 40A. Therefore, the amount of deformation of the metal pipe material 40A between the molding die 2A and the electrodes 26 and 27 can be reduced. As a result, the metal pipe material 40A can be made less likely to burst.

Although the molding apparatus according to the various embodiments has been described above, various modifications can be configured without changing the gist of the invention without being limited to the above-described embodiment.

For example, in the above-described embodiment, the metal pipe materials 40 and 40A are straight pipes extending straight in the longitudinal direction, but a two-dimensionally bent pipe or a three-dimensionally bent pipe is adopted. May be good. The outer shape of the cross section of the metal pipe material is circular, but the shape is not particularly limited, and may be an ellipse, a flat shape, or a polygonal shape. By restricting the radial expansion of the pair of slowly changing portions 46, 46A, it is possible to prevent the metal pipe materials 40, 40A from bursting.

Further, in the molding apparatus 1A described above, the metal pipe material 40A having a uniform wall thickness in the longitudinal direction is used as the metal pipe material to be molded, but the metal having a different wall thickness depending on the position in the longitudinal direction. The pipe material 40 may be used as a molding object. That is, as shown in FIG. 4, the molding apparatus 1A may mold the metal pipe material 40 having a thick wall thickness in the order of the workpiece 44, the pair of gradual change portions 46, and the pair of end portions 42. In this case, since the expansion regulating portion 80 regulates the expansion of the pair of slowly changing portions 46, which are thicker than the workpiece 44, in the radial direction, the possibility that the metal pipe material 40 may burst is increased. Can be lowered. The molding devices 1, 1A may include the metal pipe materials 40, 40A, which is the object to be molded, as a part of the constituent elements.

Further, as shown in FIG. 11, the holding portion 4 may have a robot arm 130 that moves the metal pipe material 40 from the outside of the molding die 2 between the lower die 11 and the upper die 12. Further, the robot arm 130 may have a heating unit 5 for heating the metal pipe material 40 while holding the metal pipe material 40. The robot arm 130 includes an upper electrode 131 and a lower electrode 132 at its tip. The robot arm 130 holds the pair of ends 42 of the metal pipe material 40 sandwiched between the electrodes 131 and 132, and can energize and heat the metal pipe material 40 by the electric power from the power supply cable 133. As a result, the robot arm 130 can perform energization heating at the same time as arranging the metal pipe material 40 between the lower mold 11 and the upper mold 12.

In the above-described embodiment, the fluid supply unit 6 supplies gas as a fluid, but a liquid may be supplied.

In the above-described embodiment, the molding die 2 is composed of the lower die 11 and the upper die 12, but may further include a die from the side. Further, the longitudinal direction of the molding die 2 is the horizontal direction, but it is not particularly limited, and those whose longitudinal direction is inclined with respect to the horizontal direction or those in the vertical direction may be adopted.

Further, in the above-described embodiment, the end portions 42, 42A of the metal pipe materials 40, 40A form a held portion held by the lower electrode 26 and the upper electrode 27, but the metal pipe materials 40, 40A The held portion does not necessarily have to be the end portion of the metal pipe materials 40 and 40A. Further, the molding dies 2 and 2A may be molds made of a material other than metal.

The wall thickness of the pair of gradually changing portions 46 of the metal pipe material 40 described above is formed so as to gradually become thinner as it approaches the work portion 44 so as to approach the wall thickness of the work portion 44. The gradual change portion 46 may have a constant wall thickness in the longitudinal direction. Further, the wall thickness of the pair of slowly changing portions 46 and the pair of end portions 42 may be gradually increased toward both ends of the metal pipe material 40.

Further, in the examples shown in FIGS. 10A and 10B, a fluid is supplied to the inside of the metal pipe material 40A with the lower mold 70 and the upper mold 71 separated from each other during the primary blow molding, and the secondary blow is performed. The fluid is supplied to the inside of the metal pipe material 40A with the lower mold 70 and the upper mold 71 closed at the time of molding, but in one embodiment, the secondary blow molding is not performed and the primary blow molding is performed. The metal pipe material 40A may be molded by supplying a fluid to the inside of the metal pipe material 40A in a state where the lower mold 70 and the upper mold 71 are closed.

All or part of the method for forming a metal pipe material described above can be expressed by the following description, but is not limited to the following description.
[Embodiment 1]
A method for molding a metal pipe material using a molding device having a pair of electrodes, a fluid supply unit, and a molding die.
A step of preparing the metal pipe material, wherein the metal pipe material has a pair of ends located on both ends in the longitudinal direction of the metal pipe material and a cover located at the center of the metal pipe material in the longitudinal direction. A process having a machined portion, a pair of slowly changing portions located between each of the paired end portions and the workpiece portion, and the process.
The step of holding the pair of ends by the pair of electrodes, and
A step of supplying electric power from the pair of electrodes to heat the metal pipe material, and
A molding step of forming the processed portion of the metal pipe material by supplying a fluid from the fluid supply portion into the metal pipe material and expanding the molding mold in a closed state.
Including
The metal pipe material to be prepared is a molding method that satisfies at least one of the following (a), (b) and (c).
(A) The wall thickness of the pair of gradually changing portions is thicker than the wall thickness of the processed portion.
(B) The strength of the pair of slowly changing portions is higher than the strength of the workpiece.
(C) The electrical resistance of the pair of slowly changing portions is smaller than the electrical resistance of the workpiece.
[Embodiment 2]
The first embodiment, wherein the wall thickness of the pair of slowly changing portions is thicker than the wall thickness of the work portion and becomes thinner so as to approach the wall thickness of the work portion as it approaches the work portion. Molding method.
[Embodiment 3]
The molding method according to the second embodiment, wherein the thickness of the pair of ends is thicker than the thickness of the portion to be processed.
[Embodiment 4]
A method for molding a metal pipe material using a molding device having a pair of electrodes, a fluid supply unit, and a molding die.
A step of preparing the metal pipe material, wherein the metal pipe material has a pair of ends located on both ends in the longitudinal direction of the metal pipe material and a cover located at the center of the metal pipe material in the longitudinal direction. A process having a machined portion, a pair of slowly changing portions located between each of the paired end portions and the workpiece portion, and the process.
The step of holding the pair of ends by the pair of electrodes and
A step of arranging a cylindrical reinforcing member along the inner peripheral surface of the pair of slowly changing portions, and
After arranging the reinforcing member, a step of supplying electric power from the pair of electrodes to heat the metal pipe material, and
A molding step of forming the processed portion of the metal pipe material by supplying a fluid from the fluid supply portion into the metal pipe material and expanding the molding mold in a closed state.
Molding method, including.

1,1A ... Molding device, 2,2A ... Molding mold (molding mold), 6 ... Fluid supply part, 40,40A ... Metal pipe material, 42,42A ... End part (held part), 44 ... Processed part , 46, 46A ... Slow change part, 70c, 71c ... Side surface, 70a, 71a ... Molding surface, 70b, 71b ... End part, 80 ... Expansion control part, 82, 83 ... Contact member, 82a, 83a ... Inner peripheral surface (Pipe contact surface), 82c ... Contact surface, 85, 86 ... Elastic member.

Claims (7)

A molding device that expands and molds metal pipe materials.
An electrode that holds the held portion of the metal pipe material and heats the metal pipe material by energizing the metal pipe material.
A fluid supply unit that supplies fluid into the heated metal pipe material to expand it,
A molding die having a pair of molds providing a pair of molding surfaces facing each other and molding a workpiece of the metal pipe material expanded between the pair of molds.
An expansion regulating portion provided between the molding die and the electrode and restricting radial expansion of an intermediate portion of the metal pipe material located between the processed portion and the held portion.
A molding device. The expansion regulating portion has a pair of contact members arranged between the molding die and the electrode so as to face each other in the opposite direction of the pair of molds, and the pair of contact members is the pair. Can move along the opposite direction with the mold of
Each of the pair of abutting members has an abutting surface that abuts on the side surface of the corresponding mold of the pair of molds, and at the time of blow molding in which the fluid is supplied into the metal pipe material from the fluid supply unit. The molding apparatus according to claim 1, further comprising a pipe contact surface that contacts the outer peripheral surface of the intermediate portion. A metal pipe material for blow molding
A portion to be machined located in the central portion in the longitudinal direction and an outer portion located outside the portion to be machined in the longitudinal direction and having a shape or characteristic that is less likely to be deformed than the portion to be machined during blow molding. Have metal pipe material. The metal pipe material according to claim 3, wherein the outer portion satisfies at least one of the following (a), (b) and (c).
(A) The wall thickness of the outer portion is thicker than the wall thickness of the work portion.
(B) The strength of the outer portion is higher than the strength of the workpiece.
(C) The electrical resistance of the outer portion is smaller than the electrical resistance of the workpiece. The outer portion includes a pair of held portions located on both end sides in the longitudinal direction, and a pair of intermediate portions located between each of the pair of held portions and the processed portion.
According to claim 3 or 4, the wall thickness of the pair of intermediate portions is thicker than the wall thickness of the work portion and becomes thinner so as to approach the wall thickness of the work portion as it approaches the work portion. Described metal pipe material. The metal pipe material according to claim 5, wherein the wall thickness of the pair of held portions is thicker than the wall thickness of the processed portion. A pair of held portions located on both ends in the longitudinal direction, a processed portion located in the central portion in the longitudinal direction, and a blow located between each of the pair of held portions and the processed portion. A metal pipe material having a pair of intermediate portions having a shape or characteristic that is less likely to be deformed than the workpiece during molding.
An electrode that holds the pair of held portions of the metal pipe material and heats the metal pipe material by energizing the metal pipe material.
A fluid supply unit that supplies fluid into the heated metal pipe material to expand it,
A molding die having a pair of molds providing a pair of molding surfaces facing each other and molding a workpiece of the metal pipe material expanded between the pair of molds.
An expansion regulating portion provided between the molding die and the electrode to regulate the radial expansion of the pair of intermediate portions, and an expansion regulating portion.
A molding device.

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