阅读说明：本技术 成型装置及成型方法 (Molding apparatus and molding method ) 是由 石塚正之 野际公宏 井手章博 上野纪条 于 2020-03-02 设计创作，主要内容包括：本发明的成型装置(成型装置10)使金属管材料(金属管材料14)膨胀从而成型出金属管(金属管100),该成型装置具备：电极(电极17、18),其保持金属管材料并且向金属管材料供给电力来对该金属管材料进行加热；成型模具(成型模具30),其对膨胀的金属管进行淬火成型；及配置于电极与成型模具之间的部件(第1绝缘材料91a、101a；滑动材料92、102),通过调整部件的长度来调整金属管中的未进行淬火的区域。(A forming apparatus (forming apparatus 10) of the present invention is a forming apparatus for forming a metal pipe (metal pipe 100) by expanding a metal pipe material (metal pipe material 14), the forming apparatus including: electrodes (electrodes 17, 18) that hold a metal tube material and supply electric power to the metal tube material to heat the metal tube material; a forming die (forming die 30) for quenching and forming the expanded metal pipe; and members (1 st insulating members 91a, 101 a; sliding members 92, 102) disposed between the electrodes and the molding die, and the length of the members is adjusted to adjust the regions of the metal pipe that are not quenched.)

1. A molding device for molding a metal pipe by expanding a metal pipe material, comprising:

an electrode that holds the metal tube material and supplies electric power to the metal tube material to heat the metal tube material;

a forming die for quenching and forming the expanded metal pipe; and

a member disposed between the electrode and the molding die,

adjusting the length of the component to adjust the area of the metal tube that is not quenched.

2. The molding apparatus according to claim 1,

the member is an insulating material and a sliding material arranged in this order from the electrode side,

the sum of the thickness of the insulating material and the thickness of the sliding material in the direction of arrangement of the insulating material and the sliding material is larger than the contact length of the electrode and the metal tube material in the longitudinal direction of the metal tube material.

3. A molding method of expanding a metal tube material to mold a metal tube, comprising the steps of:

heating the metal pipe material; and

a step of molding the expanded metal tube material using a molding die,

in the heating step, the part whose length has been adjusted is disposed between the electrode and the forming die, and the region of the metal pipe that is not quenched is adjusted.

Technical Field

The present invention relates to a molding apparatus and a molding method.

Background

Conventionally, there has been known a molding apparatus for expanding a metal pipe material and molding the metal pipe with a molding die. For example, patent document 1 discloses a molding apparatus including an electrode, an insulating material, a sliding material, and a molding die. In this molding apparatus, the metal tube material held by the electrode, the insulating material, and the sliding material is electrically heated by power supplied from the electrode, and the metal tube material disposed in the molding die is expanded in a state where the molding die is closed, thereby molding the metal tube.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-

Disclosure of Invention

Technical problem to be solved by the invention

The metal pipe molded by the molding apparatus may be joined to another member. In this case, bolt holes are formed in the ends of the metal pipes, or the ends of the metal pipes are welded to other members to connect the metal pipes to the other members. In this case, if the hardness of the end portion of the metal pipe is too high, it is difficult to drill or weld the end portion. On the other hand, in order to ensure the rigidity of the metal pipe, sufficient hardness is required depending on the portion (the central portion of the metal pipe, etc.).

Accordingly, an object of the present invention is to provide a molding apparatus and a molding method capable of molding a metal pipe in which a portion having low hardness and a portion having high hardness can be adjusted.

Means for solving the technical problem

A forming apparatus according to an embodiment for forming a metal pipe by expanding a metal pipe material includes: an electrode that holds a metal tube material and supplies electric power to the metal tube material to heat the metal tube material; a forming die for quenching and forming the expanded metal pipe; and a member disposed between the electrode and the forming die, wherein the length of the member is adjusted to adjust an area of the metal pipe not to be quenched.

In this embodiment, the member is disposed between the electrode and the molding die. When the metal pipe material is molded, a portion of the metal pipe material corresponding to the molding die is heated to a high temperature and then quench-molded by the molding die, so that the hardness thereof is improved. On the other hand, the portion of the metal pipe material corresponding to the component is not quenched. Here, the length of the member is adjusted to adjust the region of the metal pipe that is not quenched. Therefore, a portion having low hardness and a portion having high hardness can be adjusted.

The member is an insulating material and a sliding material arranged in this order from the electrode side, and a sum of a thickness of the insulating material and a thickness of the sliding material in an arrangement direction of the insulating material and the sliding material may be larger than a contact length of the electrode and the metal pipe material in a longitudinal direction of the metal pipe material. Since the portion of the metal pipe material held by the insulating material and the sliding material is cooled at a low speed and is not easily quenched, the region having low hardness formed at the end portion of the metal pipe can be enlarged by providing the insulating material and the sliding material in a relatively thick thickness.

A forming method according to an embodiment of forming a metal pipe by expanding a metal pipe material includes: heating a metal pipe material; and a step of molding the expanded metal pipe material using a molding die, wherein in the heating step, the length-adjusted member is disposed between the electrode and the molding die, thereby adjusting an area of the metal pipe that is not quenched.

In this embodiment, the same operational effects as those of the molding apparatus described above can be obtained.

Effects of the invention

According to one embodiment of the present invention, a portion having low hardness and a portion having high hardness can be adjusted.

Drawings

Fig. 1 is a schematic configuration diagram showing a molding apparatus according to an embodiment.

Fig. 2 is an enlarged perspective view of the periphery of the electrode.

Fig. 3 is a sectional view taken along the line iii-iii shown in fig. 2.

Fig. 4 is a front view of the electrode.

Fig. 5 is an enlarged view of the periphery of the electrode, in which (a) is a sectional view showing a state where the electrode holds the metal tube material, and (b) is a sectional view showing a state where gas is supplied to the metal tube material.

Fig. 6 is a view showing a manufacturing process of a metal pipe, in which (a) is a view showing a state where a metal pipe material is arranged in a mold, and (b) is a view showing a state where an end portion of the metal pipe material is heated.

Fig. 7 is a diagram showing a state in which blow molding is performed.

Fig. 8 is a sectional view of the molding die, wherein (a) is a view before blow molding and (b) is a view after blow molding.

Fig. 9 is a view showing an example of a finished metal pipe.

Fig. 10 is a graph showing the hardness distribution of the metal pipe according to the example.

Detailed Description

Hereinafter, preferred embodiments of the molding apparatus according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and redundant description thereof is omitted.

< Structure of molding apparatus >

Fig. 1 is a schematic configuration diagram of a molding apparatus according to an embodiment. As shown in fig. 1, a molding apparatus 10 for molding a metal pipe includes: a molding die 13 including an upper die 12 and a lower die 11; a drive mechanism 80 for moving at least one of the upper mold 12 and the lower mold 11; a tube holding mechanism 30 that holds the metal tube material 14 arranged between the upper mold 12 and the lower mold 11; a power supply unit 50 that supplies power for heating the metal tube material 14 held by the tube holding mechanism 30; a gas supply unit 60 for supplying high-pressure gas (gas) into the heated metal tube material 14 held between the upper die 12 and the lower die 11; a pair of gas supply mechanisms 40 for supplying gas from the gas supply unit 60 into the metal tube material 14 held by the tube holding mechanism 30; a water circulation mechanism 72 for forcibly cooling the molding die 13 with water; and a control unit 70 for controlling the driving of the driving mechanism 80, the driving of the tube holding mechanism 30, the driving of the power supply unit 50, and the gas supply of the gas supply unit 60.

In the following description, the finished pipe is referred to as a metal pipe 100 (see fig. 9), and the pipe in the middle of molding before the finished pipe is referred to as a metal pipe material 14. The metal tube material 14 is a hollow cylindrical long steel material having a pair of end portions 14a, 14b on both end sides and a central portion 14c between the pair of end portions 14a, 14b (see fig. 6 (a)). As will be described later, by molding the metal pipe material 14, the pair of end portions 14a and 14b of the metal pipe material 14 become the pair of end portions 100a and 100b of the metal pipe 100, and the central portion 14c of the metal pipe material 14 becomes the central portion 100c of the metal pipe 100.

As shown in fig. 1, a lower mold 11, which is one of the molding dies 13, is fixed to a base 15. The lower mold 11 is made of a large steel block, and has a rectangular cavity (recess) 16 on its upper surface. A cooling water passage 19 is formed in the lower die 11, and a thermocouple 21 inserted from below is provided substantially at the center of the lower die 11. The thermocouple 21 is supported by a spring 22 so as to be movable up and down.

A space 11a is formed near the left and right ends (left and right ends in fig. 1) of the lower mold 11, and movable portions (lower electrodes 17a, 18a, etc., described later) of the tube holding mechanism 30 are disposed in the space 11a so as to be movable up and down. Further, by placing the metal tube material 14 on the lower electrodes 17a, 18a, the lower electrodes 17a, 18a are brought into contact with the metal tube material 14 disposed between the upper mold 12 and the lower mold 11. Thereby, the lower electrodes 17a, 18a are electrically connected to the metal tube material 14.

The upper mold 12, which is the other mold of the molding dies 13, is fixed to a slider 81, which will be described later, constituting the driving mechanism 80. The upper mold 12 is formed of a large steel block, has a cooling water passage 25 formed therein, and has a rectangular cavity (recess) 24 on the lower surface thereof. The cavity 24 is provided at a position facing the cavity 16 of the lower mold 11.

Similarly to the lower mold 11, a space 12a is formed near the left and right ends (left and right ends in fig. 1) of the upper mold 12, and movable portions (i.e., upper electrodes 17b, 18b, etc., described later) of the tube holding mechanism 30 are disposed in the space 12a so as to be movable up and down. In a state where the metal tube material 14 is placed on the lower electrodes 17a and 18a, the upper electrodes 17b and 18b move downward and contact the metal tube material 14 disposed between the upper mold 12 and the lower mold 11. Thereby, the upper electrodes 17b and 18b are electrically connected to the metal tube material 14. In the following, when it is not necessary to distinguish between the lower electrodes 17a, 18a and the upper electrodes 17b, 18b, these are collectively referred to as the electrodes 17, 18.

Fig. 2 is an enlarged perspective view showing the vicinity of the electrode 18, and fig. 3 is a cross-sectional view taken along the line iii-iii shown in fig. 2.

As shown in fig. 2 and 3, between the lower electrode 18a and the lower mold 11, a 1 st insulating material 91a and a sliding material 92 are arranged in this order from the lower electrode 18a side. That is, the 1 st insulating material 91a is provided between the lower electrode 18a and the lower mold 11, and the sliding material 92 is provided between the 1 st insulating material 91a and the lower mold 11. Further, between the upper electrode 18b and the upper mold 12, the 1 st insulating material 101a and the sliding material 102 are arranged in this order from the upper electrode 18b side. That is, the 1 st insulating material 101a is provided between the upper electrode 18b and the upper mold 12, and the sliding material 102 is provided between the 1 st insulating material 101a and the upper mold 12.

The 1 st insulating members 91a and 101a are plates made of a material having heat resistance and insulation properties, and have a function of preventing the electrodes 18 from being electrically connected to the molding die 13. As the 1 st insulating materials 91a, 101a, for example, a ceramic plate made of alumina is used. The 1 st insulating material 91a has a thickness d1 in the arrangement direction of the 1 st insulating material 91a and the sliding material 92, and the 1 st insulating material 101a has a thickness d1 in the arrangement direction of the 1 st insulating material 101a and the sliding material 102.

The sliding materials 92, 102 are plates made of a material having heat resistance. As the sliding material 92, 102, for example, an alloy plate made of lead bronze, gunmetal, brass, phosphor bronze, or white metal is used. The sliding member 92 has a thickness d2 in the arrangement direction of the 1 st insulating member 91a and the sliding member 92, and the sliding member 102 has a thickness d2 in the arrangement direction of the 1 st insulating member 101a and the sliding member 102.

A 2 nd insulating material 91b is fixed to the lower surface of the lower electrode 18 a. The advancing-retreating rod 95 is connected to the 2 nd insulating member 91b, and the actuator is connected to the advancing-retreating rod 95 (see fig. 1). The actuator is used to move the lower electrodes 17a, 18a and the like up and down, and a fixing portion of the actuator is held on the base 15 side together with the lower mold 11.

As shown in fig. 3, the 1 st insulating material 91a and the sliding material 92 are fixed to each other by a fixing mechanism 93 having a bolt 93a and a female screw member 93 b. Specifically, the bolt 93a penetrating the sliding member 92 and entering the opening of the 1 st insulating member 91a is screwed into the female screw member 93b embedded in the opening of the 1 st insulating member 91a, thereby fastening the 1 st insulating member 91a and the sliding member 92 to each other. Further, the lower electrode 18a and the 1 st insulating material 91a are fixed to each other by a fixing mechanism 94. The 2 nd insulating member 91b is fixed to the lower surfaces of the lower electrode 18a and the 1 st insulating member 91 a.

Similarly, a 2 nd insulating material 101b is mounted on the upper surface of the upper electrode 18 b. The advancing-retreating rod 96 is connected to the 2 nd insulating member 101b, and the actuator is connected to the advancing-retreating rod 96. The actuator is used to move the upper electrodes 17b, 18b, etc. up and down, and the fixed portion of the actuator is held on the slider 81 side of the drive mechanism 80 together with the upper mold 12.

The 1 st insulating material 101a and the sliding material 102 are fixed to each other by a fixing mechanism 93 having a bolt 93a and a female screw member 93 b. Specifically, the bolt 93a penetrating the sliding member 102 and entering the opening of the 1 st insulating member 101a is screwed into the female screw member 93b embedded in the opening of the 1 st insulating member 101a, thereby fastening the 1 st insulating member 101a and the sliding member 102 to each other. The upper electrode 18b and the 1 st insulating material 101a are fixed integrally with each other by a fixing mechanism 94. The 2 nd insulating material 101b is fixed to the upper surfaces of the upper electrode 18b and the 1 st insulating material 101 a.

Fig. 4 is a front view of the electrodes 17, 18. As shown in fig. 4, semicircular arc-shaped recesses 20a corresponding to the outer peripheral surface shape of the metal tube material 14 are formed in the surfaces of the lower electrode 18a and the upper electrode 18b facing each other, and the metal tube material 14 can be placed in the recesses 20a and can be fitted to the portions of the recesses 20 a. Further, semicircular arc-shaped grooves are formed in the surfaces of the 1 st insulating material 91a and the 1 st insulating material 101a facing each other and the surfaces of the sliding material 92 and the sliding material 102 facing each other. These grooves have a diameter larger than the diameter of the groove 20 a. Therefore, the 1 st insulating materials 91a, 101a and the sliding materials 92, 102 do not contact the metal tube material 14 while the metal tube material 14 is held between the upper electrode 18b and the lower electrode 18 a. A tapered concave surface 18t is formed on the front surface (surface facing the outside of the mold) of the electrode 18, the periphery of the groove 20a being recessed in a conical shape so as to be inclined toward the groove 20a (see fig. 5 (a) and (b)). Therefore, if the metal tube material 14 is gripped from the up-down direction using the right side portion of the tube holding mechanism 30, it is just possible to tightly surround the entire outer periphery of the end portion 14a of the metal tube material 14 to hold the metal tube material 14.

As shown in fig. 4, a coolant flow field 26 for flowing the coolant R is formed inside the lower electrode 18 a. A pipe 28 is connected to the refrigerant flow path 26, and a refrigerant supply device 32 is connected to the pipe 28. The coolant supply device 32 supplies the coolant R to the coolant flow path 26 via the pipe 28, and collects the coolant R having exchanged heat with the lower electrode 18a from the coolant flow path 26. Similarly, a coolant flow field 27 through which the coolant R flows is formed inside the upper electrode 18 b. The pipe 29 is connected to the refrigerant flow path 27, and the refrigerant supply device 31 is connected to the pipe 29. The coolant supply device 31 supplies the coolant R to the coolant flow path 27 through the pipe 29, and collects the coolant R having exchanged heat with the upper electrode 18b from the coolant flow path 27.

In one embodiment, the refrigerant supply devices 31 and 32 are connected to the control unit 70, and thus the flow rate of the cooling medium R supplied from the refrigerant supply devices 31 and 32 to the refrigerant flow paths 26 and 27 can be controlled in accordance with a control signal from the control unit 70.

By circulating the cooling medium R through the refrigerant flow paths 26 and 27 in this manner, the heat of the electrode 18 is taken away by the cooling medium R, and the electrode 18 is cooled. As the cooling medium R, for example, cooling water is used. The cooling medium R is not limited to a liquid, and may be phase change cooling using vaporization heat or gas cooling using gas to cool the electrode 18.

The left side portion of the tube holding mechanism 30 has the same structure as the right side portion of the tube holding mechanism 30 described above. That is, the left side portion of the tube holding mechanism 30 includes the lower electrode 17a and the upper electrode 17b which face each other in the vertical direction, the 1 st insulating members 91a and 101a which face each other in the vertical direction, and the sliding members 92 and 102 which face each other in the vertical direction. More specifically, the 1 st insulating material 91a is disposed between the lower electrode 17a and the lower mold 11, and the sliding material 92 is disposed between the 1 st insulating material 91a and the lower mold 11. The advancing-retreating rod 95 is connected to the 2 nd insulating member 91b, and an actuator for moving the lower electrode 17a and the like up and down is connected to the advancing-retreating rod 95. The 1 st insulating material 101a is provided between the upper electrode 17b and the upper mold 12, and the sliding material 102 is provided between the 1 st insulating material 101a and the upper mold 12. The advancing-retreating rod 96 is connected to the 2 nd insulating member 101b, and an actuator for moving the upper electrode 17b and the like up and down is connected to the advancing-retreating rod 96.

As shown in fig. 4, semicircular arc-shaped concave grooves 20b corresponding to the outer peripheral surface shape of the metal tube material 14 are formed on the opposing surfaces of the lower electrode 17a and the upper electrode 17b on the left side portion of the tube holding mechanism 30, and the metal tube material 14 can be placed on the concave grooves 20b and can be fitted to the portions of the concave grooves 20 b. Further, semicircular arc-shaped grooves are also formed in the surfaces of the 1 st insulating material 91a and the 1 st insulating material 101a facing each other and the surfaces of the sliding material 92 and the sliding material 102 facing each other. These grooves have a diameter larger than that of the grooves 20 b. Therefore, the 1 st insulating materials 91a, 101a and the sliding materials 92, 102 do not contact the metal tube material 14 while the metal tube material 14 is held between the upper electrode 17b and the lower electrode 17 a. A tapered concave surface 17t is formed on the front surface (surface facing the outside of the mold) of the electrode 17, and the periphery of the groove 20b is recessed so as to be inclined in a conical shape toward the groove 20 b. Therefore, if the metal tube material 14 is gripped from the up-down direction using the left side portion of the tube holding mechanism 30, it is possible to closely surround the entire outer periphery of the end portion 14b of the metal tube material 14 to hold the metal tube material 14.

Similarly to the lower electrode 18a and the upper electrode 18b, refrigerant flow paths 26 and 27 are formed in the lower electrode 17a and the upper electrode 17b, respectively. The refrigerant supply devices 31 and 32 are connected to the refrigerant flow paths 26 and 27 via pipes 28 and 29, respectively. The coolant supply devices 31 and 32 circulate and supply the coolant R to the coolant flow paths 26 and 27. By circulating the cooling medium R through the refrigerant flow paths 26 and 27, the heat of the lower electrode 17a and the upper electrode 17b is taken away by the cooling medium R, and the electrode 17 is cooled.

Fig. 5 (a) is a diagram showing a state in which the electrode 18 holds the metal tube material 14. Here, as shown in fig. 5 (a), when a contact length of the electrode 18 in the longitudinal direction of the metal tube material 14 and the metal tube material 14 held on the electrode 18 is taken as L, a sum D of a thickness D1 of the 1 st insulating material 91a and a thickness D2 of the sliding material 92 is set to be greater than the contact length L. Similarly, when a contact length of the electrode 17 in the longitudinal direction of the metal tube material 14 and the metal tube material 14 held on the electrode 17 is taken as L, the sum D of the thickness D1 of the 1 st insulating material 91a and the thickness D2 of the sliding material 92 is set to be larger than the contact length L. By setting the sum D of the thicknesses to be larger than the contact length L, the region formed in the end portions 100a, 100b of the metal pipe 100 having low hardness can be made large.

However, in the above example, the sum D of the thickness D1 of the 1 st insulating materials 91a, 101a and the thickness D2 of the sliding materials 92, 102 is set to be larger than the contact length L between the electrodes 17, 18 and the metal tube material 14, but the sum D of the thicknesses may be equal to or smaller than the contact length L. By increasing the sum D of the thicknesses, the length of the non-solidified portion formed on the end portion side of the metal pipe 100 can be adjusted. That is, the region of the metal pipe 100 not to be quenched is adjusted by adjusting the sum D of the thicknesses. Therefore, the sum D of the thickness D1 of the 1 st insulating materials 91a, 101a and the thickness D2 of the sliding materials 92, 102 can be appropriately adjusted according to the required length of the uncured portion.

Refer back to fig. 1. As shown in fig. 1, the drive mechanism 80 includes: a slider 81 which moves the upper mold 12 in a direction in which the upper mold 12 and the lower mold 11 are closed to each other; a shaft 82 that generates a driving force for moving the slider 81; and a link 83 for transmitting the driving force generated by the shaft 82 to the slider 81. The shaft 82 extends in the left-right direction above the slider 81 and is rotatably supported. The eccentric crank 82a is coupled to a rotary shaft 81a provided on the upper portion of the slider 81 and extending in the left-right direction via a connecting rod 83. In the drive mechanism 80, the control section 70 controls the rotation of the shaft 82 to change the height of the eccentric crank 82a in the vertical direction, and the change in the position of the eccentric crank 82a is transmitted to the slider 81 via the connecting rod 83, thereby enabling the vertical movement of the slider 81 to be controlled. Here, the swing (rotational motion) of the link 83 generated when the position change of the eccentric crank 82a is transmitted to the slider 81 is absorbed by the rotary shaft 81 a. The shaft 82 is rotated or stopped by driving of a motor or the like controlled by the control unit 70.

The power supply unit 50 includes a power source 51, a bus bar 52 connecting the power source 51 and the lower electrodes 17 and 18, and a switch 53 provided on the bus bar 52. The power supply unit 50 supplies electric power for electrically heating the metal tube material 14 to the electrodes 17 and 18. Specifically, the power supply portion 50 is controlled to heat the metal tube material 14 to the quenching temperature (AC3 transformation point temperature or more) in accordance with a control signal from the control portion 70. The power supply portion 50 constitutes a heating portion that heats the metal tube material 14 together with the electrodes 17 and 18.

The pair of gas supply mechanisms 40 each include: a cylinder unit 42; a piston rod 43 that moves forward and backward in accordance with the operation of the cylinder unit 42; and a seal member 44 connected to the end of the piston rod 43 on the tube holding mechanism 30 side. The cylinder unit 42 is supported on the block 41. A tapered surface 45 that tapers toward the tip is formed at the tip of the sealing member 44, and the tapered surface 45 is configured to fit into and abut against the tapered concave surfaces 17t and 18t of the electrodes 17 and 18 (see fig. 5 (b)). The seal member 44 is coupled to the cylinder unit 42 via the piston rod 43 and can move forward and backward according to the operation of the cylinder unit 42. The cylinder unit 42 is mounted on and fixed to the base 15 via the block 41. The seal member 44 is provided with a gas passage 46 through which high-pressure gas supplied from the gas supply unit 60 flows. The gas passage 46 is open at the distal end of the sealing member 44, and the gas flowing through the gas passage 46 is ejected from the opening.

The gas supply unit 60 includes a gas source 61, a gas tank 62 for storing gas supplied from the gas source 61, a 1 st pipe 63 extending from the gas tank 62 to the cylinder unit 42 of the gas supply mechanism 40, a pressure control valve 64 and a switching valve 65 provided in the 1 st pipe 63, a 2 nd pipe 67 connecting the gas tank 62 and the gas passage 46, and a pressure control valve 68 and a check valve 69 provided in the 2 nd pipe 67. The pressure control valve 64 supplies high-pressure gas for pressing the sealing member 44 against the metal tube material 14 to the cylinder unit 42. The check valve 69 prevents the high-pressure gas from flowing backward in the 2 nd pipe 67.

The pressure control valve 68 supplies gas having a working pressure for expanding the metal tube material 14 to the gas passage 46. The control unit 70 is connected to the pressure control valve 68, and the control unit 70 controls the opening degree of the pressure control valve 68 of the gas supply unit 60 so that gas of a desired working pressure can be supplied into the metal tube material 14.

The control unit 70 receives the information transmitted from (a) shown in fig. 1, acquires temperature information from the thermocouple 21, and controls the driving mechanism 80, the power supply unit 55, and the like. The water circulation mechanism 72 includes: a water tank 73 for storing water; a water pump 74 for pumping up the water accumulated in the water tank 73 and pressurizing the water to send the water to the cooling water passage 19 of the lower mold 11 and the cooling water passage 25 of the upper mold 12; and a pipe 75. Although not shown here, the pipe 75 may be provided with a cooling tower for reducing the temperature of water or a filter for purifying water.

< method for Forming Metal tube Using Forming device >

Next, a method of forming a metal pipe using the forming apparatus 10 will be described. Fig. 6 shows a tube feeding step of feeding the metal tube material 14 as a material to an energization heating step of energizing and heating the metal tube material 14. First, a cylindrical metal pipe material 14 of quenchable steel is prepared. As shown in fig. 6 (a), the metal tube material 14 is placed (thrown) on the electrodes 17 and 18 provided on the lower mold 11 side by, for example, a robot arm or the like. Since the grooves 20a, 20b are formed on the electrodes 17, 18, the metal tube material 14 is positioned by the grooves 20a, 20 b.

Next, the control unit 70 controls the driving mechanism 80 and the tube holding mechanism 30 such that the tube holding mechanism 30 holds the end portions 14a and 14b of the metal tube material 14. Specifically, as shown in fig. 6 (b), the controller 70 operates an actuator (not shown) capable of driving the tube holding mechanism 30 to move forward and backward, and moves the advancing-retreating levers 95, 96 up and down. During the vertical movement, the sliding member 92 and the sliding member 102 slide with respect to the lower mold 11 and the upper mold 12, respectively. By this vertical movement, the end portions 14a and 14b of the metal tube material 14 are sandwiched by the tube holding mechanism 30 from the vertical direction. Since the grooves 20a and 20b formed in the electrodes 17 and 18 and the grooves formed in the 1 st insulating materials 91a and 101a and the sliding materials 92 and 102 are present in this clamping, the electrodes 17 and 18 clamp the metal tube material 14 so as to be in close contact with the entire circumference in the vicinity of both side ends of the metal tube material 14. The electrodes 17 and 18 may be configured to abut against a part of the metal tube material 14 in the circumferential direction, instead of being configured to abut against the entire circumference of the metal tube material 14.

Next, the control portion 70 controls the power supply portion 50 to heat the metal tube material 14. Specifically, when the switch 53 is turned on based on a control signal from the control unit 70, electric power from the power supply 51 is supplied to the electrodes 17 and 18 via the bus 52. The electric power supplied to the electrodes 17, 18 is transmitted to the metal tube material 14, and the metal tube material 14 itself generates heat (joule heat) based on the resistance of the metal tube material 14 itself.

Here, the current has a property of selectively flowing to a portion having a low resistance, and therefore, as shown in (a) of fig. 5, the current C supplied from the electrode 18 does not uniformly flow over the entire length of the metal tube material 14, and mainly flows into the metal tube material 14 from the vicinity of the boundary of the electrode 18 and the 1 st insulating materials 91a, 101 a. That is, in the boundary surfaces between the electrodes 18a and 18b and the metal tube material 14, the region on the 1 st insulating material 91a or 101a side is a region in which more current flows than the region on the end portion 14a side. Therefore, when the metal tube material 14 is electrically heated, a smaller current flows through the end portions 14a and 14b of the metal tube material 14 than through the central portion 14c of the metal tube material 14. In fig. 5 (a), only the main flow of the current C is shown by arrows, but the current also flows near the end 14 a. Thus, the metal tube material 14 has a temperature distribution in which the temperature of the end portions 14a, 14b is lower than the temperature of the central portion 14c of the metal tube material 14. More specifically, the metal tube material 14 is heated such that the temperature of the end portion 14a is lower than the quenching temperature of the metal tube material 14, and the temperature of the central portion 14c is higher than the quenching temperature of the metal tube material 14.

In particular, since the electrodes 17 and 18 are controlled to have a low temperature by the cooling medium R flowing through the coolant flow path 26, the temperature rise of the end portions 14a and 14b of the metal pipe material 14 is suppressed. On the other hand, the thermocouple 21 constantly measures the temperature of the central portion 14c of the metal tube material 14, and controls the power supplied to the electrodes 17, 18 based on the measurement result.

Next, as shown in fig. 7, the control section 70 controls the drive mechanism 80 to close the forming die 13 with respect to the heated metal tube material 14. Thereby, the cavity 16 of the lower mold 11 and the cavity 24 of the upper mold 12 are combined with each other, and the metal tube material 14 is arranged and sealed in the cavity portion MC between the lower mold 11 and the upper mold 12. At this mold closing time, the slide material 92 slides with respect to the lower mold 11, and the slide material 102 slides with respect to the upper mold 12.

Then, the cylinder unit 42 of the gas supply mechanism 40 is operated to advance the sealing member 44, thereby sealing both ends of the metal tube material 14 (refer to fig. 5 (b) as well). After the sealing is completed, the pressure control valve 68 is opened, so that high-pressure gas from the gas tank 62 is blown into the metal tube material 14 via the gas passage 46.

Since the central portion 14c of the metal tube material 14 is heated to a high temperature (about 950 ℃) and softened, the gas supplied into the metal tube material 14 thermally expands. Therefore, for example, compressed air is used as the supply gas, and the central portion 14c of the 950 ℃. As a result, as shown in fig. 8 (a) and (b), the central portion 14c of the metal tube material 14 disposed in the cavity MC of the molding die 13 is molded into the same shape as the cavity MC.

The outer peripheral surface of the central portion 14c of the metal tube material 14 expanded by blow molding is rapidly cooled when it comes into contact with the cavity 16 of the lower mold 11 and the cavity 24 of the upper mold 12 (since the upper mold 12 and the lower mold 11 have a large heat capacity and are controlled to have a low temperature, the heat of the tube surface is immediately taken away by the mold side as long as the metal tube material 14 comes into contact with the upper mold 12 or the lower mold 11), and quenching is performed. This cooling method is called mold contact cooling or mold cooling. Immediately after being rapidly cooled, austenite is transformed into martensite (hereinafter, a phenomenon in which austenite is transformed into martensite is referred to as martensite transformation). Since the cooling speed becomes slow at the latter stage of cooling, martensite is transformed into another structure (troostite, sorbite, etc.) by regenerative heating. Therefore, a separate tempering treatment is not required. In the present embodiment, instead of the mold cooling, for example, a cooling medium may be supplied into the cavity 24 to perform the cooling, or in addition to the mold cooling, for example, a cooling medium may be supplied into the cavity 24 to perform the cooling. For example, the metal tube material 14 may be cooled by being brought into contact with the dies (the upper die 12 and the lower die 11) up to the start temperature of the martensitic transformation, and then the dies may be opened and a cooling medium (cooling gas) may be blown into the metal tube material 14 to cause the martensitic transformation.

On the other hand, when the metal tube material 14 is heated by energization, the end portions 14a and 14b of the metal tube material 14 are heated to a temperature lower than the quenching temperature, and therefore the end portion 14a is not quenched. In particular, since the electrodes 17 and 18 are controlled to have a low temperature by the cooling medium R flowing through the refrigerant flow path 26, the temperature rise of the end portions 14a and 14b of the metal pipe material 14 is further suppressed when the metal pipe material is heated by energization, and quenching of the end portions 14a and 14b of the metal pipe material 14 is suppressed. Further, the portion of the metal tube material 14 held between the 1 st insulating materials 91a, 101a and the sliding materials 92, 102 is not in contact with the molding die 13, and therefore the cooling rate is slower than the central portion 14c of the metal tube material 14. Thus, the portion of the metal tube material 14 is also not easily quenched. Thus, the regions of the metal pipe corresponding to the electrodes 17 and 18, the insulating materials 91a and 101a, and the sliding materials 92 and 102 during molding are regions that are not quenched.

As described above, the metal pipe material 14 is blow molded, cooled, and then opened to obtain the metal pipe 100 having a substantially rectangular cylindrical body portion. When the mold is opened, the slide member 92 also slides with respect to the lower mold 11, and the slide member 102 also slides with respect to the upper mold 12.

Fig. 9 is a view showing a finished metal pipe 100. As shown in fig. 9, the metal pipe 100 of the molded article has a pair of end portions 100a and 100b and a central portion 100 c. The pair of end portions 100a, 100b are formed by molding the pair of end portions 14a, 14b of the metal tube material 14, and the central portion 100c is formed by molding the central portion 14c of the metal tube material 14. As described above, since the pair of end portions 100a and 100b are not quenched, the pair of end portions 100a and 100b become non-solidified portions having relatively low hardness. In contrast, since the central portion 100c is quenched, the central portion 100c becomes a solidified portion having a hardness higher than the hardness of the end portions 100a, 100 b. Therefore, by molding the metal tube material 14 using the molding apparatus 10, the metal tube 100 having the low hardness of the pair of end portions 100a, 100b and the high hardness of the central portion 100c can be molded.

In one embodiment, the metal pipe 100 having the vickers hardnesses of the pair of end portions 100a and 100b of less than 300HV and the center portion 100c of 300HV or more can be molded by controlling the temperature distribution of the metal pipe material 14, the temperatures of the electrodes 17 and 18, the temperature of the molding die 13, and the like at the time of molding. By setting the vickers hardness of the pair of end portions 100a, 100b to less than 300HV, the pair of end portions 100a, 100b can be subjected to machining such as drilling and welding.

Further, according to the molding apparatus 10, when the driving mechanism 80 moves the molding die 13, the sliding members 92 and 102 are present between the lower mold 11 and the 1 st insulating member 91a and between the upper mold 12 and the 1 st insulating member 101a, so that the molding die 13 does not contact the 1 st insulating members 91a and 101 a. Therefore, the 1 st insulating materials 91a and 101a can be suppressed from being worn.

As described above, the molding apparatus 10 is a molding apparatus 10 for molding the metal pipe 100 by expanding the metal pipe material 14, and the molding apparatus 10 includes: electrodes 17, 18 that hold the metal tube material 14 and supply electric power to the metal tube material 14 to heat the metal tube material 14; a forming die 13 for quench-forming the expanded metal pipe 100; and sliding members 92 and 102 and insulating members 91a, 91b, 101a, and 101b disposed between the electrodes 17 and 18 and the molding die 13, and the length of the sliding members 92 and 102 and the insulating members 91a, 91b, 101a, and 101b is adjusted to adjust the region of the metal pipe 100 that is not quenched.

In this embodiment, the sliding members 92 and 102 and the insulating members 91a, 91b, 101a, and 101b are disposed between the electrodes 17 and 18 and the molding die 13. In the molding of the metal tube material 14, the portion of the metal tube material 14 corresponding to the molding die 13 is heated to a high temperature, and then is subjected to quenching molding by the molding die 13, so that the hardness thereof is increased. On the other hand, the portions of the metal tube material 14 corresponding to the sliding members 92 and 102 and the insulating members 91a, 91b, 101a, and 101b are portions that are not quenched. Here, the length of the sliding members 92 and 102 and the insulating members 91a, 91b, 101a, and 101b is adjusted to adjust the region of the metal pipe 100 that is not quenched. Therefore, a portion having low hardness and a portion having high hardness can be adjusted.

The forming method is a method of expanding the metal tube material 14 to form the metal tube 100, and includes the steps of: a step of heating the metal tube material 14; and a step of molding the expanded metal pipe material 14 using the molding die 13, wherein in the heating step, the sliding members 92 and 102 and the insulating members 91a, 91b, 101a, and 101b, the lengths of which have been adjusted, are arranged between the electrodes 17 and 18 and the molding die 13, thereby adjusting the regions of the metal pipe 100 that are not quenched.

In this embodiment, the same operational effects as those of the molding apparatus described above can be obtained.

The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

Fig. 10 is a graph showing the hardness distribution of the metal pipe according to the example. The metal pipe is obtained by molding a metal pipe material using the molding apparatus 10 described above.

The metal pipe according to the example thus formed had a hardness distribution as shown in fig. 10. Specifically, the metal pipe according to the example has a vickers hardness of less than 300HV in a range of 0mm to 55mm from one end, and has a vickers hardness of about 500HV in a range of 65mm to 150mm from one end. According to this example, it was confirmed that a metal pipe having a low hardness at the end portion and a high hardness at the central portion can be molded by molding a metal pipe material using the molding device 10.

The molding apparatus 10 according to the various embodiments has been described above, but the present invention is not limited to the above embodiments, and various modifications are possible without departing from the scope of the invention.

In the above embodiment, the sum of the thickness of the 1 st insulating material 91a and the thickness of the sliding member 92 is set to be the same as the sum of the thickness of the 1 st insulating material 101a and the thickness of the sliding member 102, but the sum of these thicknesses may be different from each other. In this case, the length of the non-solidified portion can be made different between the upper side and the lower side of the metal pipe 100.

Further, in the above embodiment, the 1 st insulating members 91a, 101a and the sliding members 92, 102 are configured as separate members, but the 1 st insulating members 91a, 101a and the sliding members 92, 102 may be integrally formed by thermally spraying the sliding members 92, 102 onto the 1 st insulating members 91a, 101a, respectively. In this case, since the 1 st insulating members 91a and 101a and the sliding members 92 and 102 can be fixed without using the fixing mechanism 93, the number of components can be reduced and the cost can be reduced.

Further, in the above embodiment, the sliding members 92 and 102 are fixed to the 1 st insulating members 91a and 101a, respectively, but the sliding member 92 may be fixed to the lower mold 11, and the sliding member 102 may be fixed to the upper mold 12. Even in this case, the molding die 13 and the 1 st insulating members 91a and 101a do not contact each other, and therefore the 1 st insulating members 91a and 101a can be suppressed from being worn.

Further, although the drive mechanism 80 according to the above embodiment moves only the upper mold 12, it may be configured to move the lower mold 11 in addition to the upper mold 12, or to move only the lower mold 11 instead of the upper mold 12. When the lower mold 11 is moved, the lower mold 11 is not fixed to the base 15, and is attached to, for example, the slider 81 of the drive mechanism 80.

The metal pipe 100 according to the above embodiment may have one or more flange portions. At this time, one or more sub-cavity portions communicating with the cavity portion MC when the upper mold 12 and the lower mold 11 are fitted to each other are formed in the molding die 13.

In the drive mechanism 80 according to the above embodiment, for example, a booster cylinder, a guide cylinder, and a servomotor may be used instead of the shaft 82. At this time, slide member 81 is lifted by the pressure cylinder and guided by the guide cylinder so as not to laterally oscillate. The servo motor functions as a fluid supply unit that supplies fluid (hydraulic oil in the case where the hydraulic cylinder is used as the pressure cylinder) for driving the pressure cylinder to the pressure cylinder.

Metal pipes formed by a forming apparatus are sometimes joined to other parts. In this case, bolt holes are formed in the ends of the metal pipes, or the ends of the metal pipes are welded to other members to connect the metal pipes to the other members. In this case, if the hardness of the end portion of the metal pipe is too high, it is difficult to drill or weld the end portion. On the other hand, in order to ensure the rigidity of the metal pipe, the central portion of the metal pipe is required to have sufficient hardness.

Therefore, in one embodiment, it is required to provide a molding apparatus and a molding method capable of molding a metal pipe having a low hardness at an end portion and a high hardness at a central portion.

In one embodiment, a forming device is provided for expanding a metal tube material to form a metal tube. The molding device is provided with: an electrode that holds an end portion of the metal tube material and supplies electric power to the metal tube material to heat the metal tube material; a gas supply unit for supplying gas into the heated metal tube material to expand the metal tube material; and a molding die for molding the expanded metal pipe. The electrode heats the metal tube material to a temperature lower at the end portion of the metal tube material than at the central portion of the metal tube material.

In this embodiment, the metal tube material is heated such that the end portions of the metal tube material have a lower temperature than the central portion of the metal tube material. When the temperature rise of the end portion of the metal pipe material is suppressed at the time of molding the metal pipe material, the end portion of the metal pipe material is less likely to be quenched, and thus the hardness increase thereof is suppressed. On the other hand, since the central portion of the metal pipe is heated to a high temperature, quenching is performed by subsequent cooling, so that the hardness thereof is improved. Therefore, according to the molding apparatus of the above embodiment, the metal pipe having low hardness at the end portion and high hardness at the central portion can be molded.

The electrode may be provided with a coolant flow path through which a coolant flows. By flowing the cooling medium through the coolant flow channel, it is possible to suppress a temperature increase at the end of the metal tube material when power is supplied from the electrode. Therefore, the end portion of the metal pipe material held by the electrode is less likely to be quenched, and the metal pipe having a low hardness at the end portion can be formed more reliably.

Between the electrode and the molding die, an insulating material and a sliding material are arranged in this order from the electrode side, and the sum of the thickness of the insulating material and the thickness of the sliding material in the arrangement direction of the insulating material and the sliding material may be larger than the contact length between the electrode and the metal pipe material in the longitudinal direction of the metal pipe material. Since the portion of the metal pipe material held by the insulating material and the sliding material is cooled at a low speed and is not easily quenched, the region having low hardness formed at the end portion of the metal pipe can be enlarged by providing the insulating material and the sliding material in a relatively thick thickness.

According to one embodiment, a metal pipe having a low hardness at the end portion and a high hardness at the central portion can be molded.

Description of the symbols

10-forming means, 11-lower, 12-upper, 13-forming die, 14-metal tube material, 14a, 14 b-end, 14 c-center, 17, 18-electrode, 26, 27-refrigerant flow path, 30-tube holding means, 31, 32-refrigerant supply means, 40-gas supply means, 50-power supply means, 60-gas supply means, 70-control means, 91a, 101 a-1 st insulating material (part), 91b, 101 b-2 nd insulating material (part), 92, 102-sliding material (part), 100-metal tube, 100a, 100 b-end, 100 c-center, D-sum of thickness, L-contact length, MC-cavity, R-cooling medium.