Priority is claimed to Japanese Patent Application No. 2014-105885, filed May 22, 2014, and International Patent Application No. PCT/JP2015/064479, the entire content of each of which is incorporated herein by reference.
Technical Field
Certain embodiments of the present invention relate to a forming apparatus and a forming method which forma metal pipe.
Description of Related Art
In the related art, a forming apparatus is known which performs forming by expanding a heated metal pipe material by supplying gas into the heated metal pipe material. For example, a forming apparatus as disclosed in the related art is provided with an upper die and a lower die which are paired with each other, a holding unit which holds a metal pipe material between the upper die and the lower die, and a gas supply unit which supplies gas into the metal pipe material held by the holding unit. In this forming apparatus, it is possible to form the metal pipe material into a shape corresponding to the shape of a die by expanding the metal pipe material by supplying gas into the metal pipe material in a state of being held between the upper die and the lower die.
According to an embodiment of the present invention, there is provided a forming apparatus that forms a metal pipe, including: a heating unit which heats a metal pipe material; a gas supply unit which supplies gas into a heated metal pipe material, thereby expanding the metal pipe material; a die which forms the metal pipe by bringing the expanded metal pipe material into contact with the die; a cooling unit which cools the metal pipe after the forming by a cooling medium; and a control unit which controls an operation of the die, the gas supply unit, and the cooling unit, in which the control unit makes cooling of the metal pipe by the cooling medium be performed, by controlling an operation of the die such that the die is opened and controlling the cooling unit such that the cooling unit brings the cooling medium into contact with the metal pipe, subsequently to completion of forming by the die.
According to another embodiment of the present invention, there is provided a forming method that forms a metal pipe, including: a heating step of heating a metal pipe material; a gas supply step of supplying gas into a heated metal pipe material, thereby expanding the metal pipe material; a forming step of forming the metal pipe by bringing the expanded metal pipe material into contact with a die; and a cooling step of cooling the metal pipe after the forming by a cooling medium, in which in the cooling step, cooling of the metal pipe by the cooling medium is performed by opening the die and bringing the cooling medium into contact with the metal pipe, subsequently to completion of the forming by the die.
In the apparatus of the related art described above, after a metal pipe is formed by the die, quenching is performed by cooling the metal pipe by maintaining a state where the metal pipe is brought into contact with the die, for a predetermined time. However, in a case of performing only cooling by contact with the die, due to a cooling rate being too fast, the strength of the metal pipe is increased, and thus there is a case where the metal pipe becomes brittle (toughness is lowered). Therefore, it is required to obtain a forming product having suitable characteristics in accordance with a use of the forming product by controlling strength and toughness according to the use of the forming product.
It is desirable to provide a forming apparatus and a forming method, in which it is possible to obtain a forming product having suitable characteristics.
In the forming apparatus according to an embodiment of the present invention, the control unit makes cooling of the metal pipe by the cooling medium be performed, by controlling an operation of the die such that the die is opened and controlling the cooling unit such that the cooling unit brings the cooling medium into contact with the metal pipe, subsequently to completion of forming by the die. In this manner, by performing the cooling by the contact with the cooling medium, it is possible to slow down a cooling rate, compared to the cooling by the contact with the die, and thus quenching to enhance the toughness of the metal pipe becomes possible. Further, in a case of performing cooling by using the cooling medium, it is possible to easily perform adjustment of hardenability, compared to the cooling by contact with the die. By the above, it becomes possible to control the strength and the toughness of a forming product according to a use, and thus it is possible to obtain a forming product having suitable characteristics.
Further, in the forming apparatus according to an embodiment of the present invention, the control unit may make cooling of the metal pipe by the die be performed, by controlling an operation of the die such that a state where the die and the metal pipe are brought into contact with each other is maintained for a predetermined time, after the completion of the forming, and make cooling of the metal pipe by the cooling medium be performed, after the cooling of the metal pipe by the die. In this manner, by increasing a cooling rate by performing the cooling by the die after the completion of the forming, it is possible to shorten a time after the cooling is started and until the temperature of the metal pipe reaches a martensitic transformation start temperature. Therefore, it becomes possible to secure a longer martensite formation possible time, and thus it becomes possible to easily adjust the cooling rate by the cooling medium according to desired characteristics.
Further, in the forming apparatus according to an embodiment of the present invention, the control unit may make the cooling of the metal pipe by the die be performed until the metal pipe reaches a first temperature that is a temperature higher than a martensitic transformation start temperature. In this way, before the metal pipe reaches the first temperature which is a temperature before the martensitic transformation start temperature, it becomes possible to rapidly cool the metal pipe by the die.
Further, in the forming apparatus according to an embodiment of the present invention, the control unit may adjust hardenability of the metal pipe, based on a timing when the cooling of the metal pipe by the cooling medium is started. In this way, it is possible to easily adjust the hardenability of the metal pipe.
Further, in the forming apparatus according to an embodiment of the present invention, the cooling unit may blow gas for cooling as the cooling medium on the metal pipe. Due to using gas as the cooling medium, flow rate adjustment or the like is easy, and therefore, it is possible to easily perform adjustment of hardenability. Further, it is possible to cool the metal pipe without contaminating it.
Further, in the forming apparatus according to an embodiment of the present invention, the cooling unit may be configured of the gas supply unit. In this way, the gas supply unit for expanding the metal pipe can be diverted as the cooling unit, and therefore, it is possible to make the forming apparatus compact.
Further, in the forming apparatus according to an embodiment of the present invention, the cooling unit may blow the gas for cooling on both the inner surface and the outer surface of the metal pipe. In this way, it becomes possible to remove oxide layers stuck to both the inner surface and the outer surface of the metal pipe, and thus it becomes possible to effectively improve the quality of a forming product.
According to the forming method according to another embodiment of the present invention, it is possible to obtain the same operation and effects as those of the forming apparatus described above.
Further, in the forming method according to another embodiment of the present invention, in the cooling step, cooling of the metal pipe by the die may be performed by controlling an operation of the die such that a state where the die and the metal pipe are brought into contact with each other is maintained for a predetermined time, after the completion of the forming, and cooling of the metal pipe by the cooling medium may be performed after the cooling of the metal pipe by the die. In this manner, by increasing a cooling rate by performing the cooling by the die after the completion of the forming, it is possible to shorten a time after the cooling is started and until the temperature of the metal pipe reaches a martensitic transformation start temperature. Therefore, it becomes possible to secure a longer martensite formation possible time, and thus it becomes possible to easily adjust the cooling rate by the cooling medium according to desired characteristics.
Further, in the forming method according to another embodiment of the present invention, in the cooling step, the cooling of the metal pipe by the die may be performed until the metal pipe reaches a first temperature that is a temperature higher than a martensitic transformation start temperature. In this way, before the metal pipe reaches the first temperature which is a temperature before the martensitic transformation start temperature, it becomes possible to rapidly cool the metal pipe by the die.
Further, in the forming method according to another embodiment of the present invention, in the cooling step, hardenability of the metal pipe may be adjusted based on a timing when the cooling of the metal pipe by the cooling medium is started. In this way, it is possible to easily adjust the hardenability of the metal pipe.
Further, in the forming method according to another embodiment of the present invention, in the cooling step, cooling of the metal pipe may be performed by blowing gas for cooling as the cooling medium on the metal pipe. Due to using gas as the cooling medium, flow rate adjustment or the like is easy, and therefore, it is possible to easily perform adjustment of hardenability. Further, it is possible to cool the metal pipe without contaminating it.
Further, in the forming method according to another embodiment of the present invention, in the cooling step, the gas may be blown on both the inner surface and the outer surface of the metal pipe. In this way, the metal pipe is uniformly cooled, and thus occurrence of unevenness in the hardenability of the metal pipe can be suppressed. In addition, it becomes possible to remove oxide layers stuck to both the inner surface and the outer surface of the metal pipe, and thus it becomes possible to effectively improve the quality of a forming product.
Further, in the forming method according to another embodiment of the present invention, in the cooling step, oxide layers stuck to the surface of the metal pipe may be removed by blowing the gas on the metal pipe. In this way, the oxide layers stuck to the surface of the metal pipe are removed, and thus it is possible to prevent the oxide layer from remaining on the surface of a forming product. For this reason, the influence on the external appearance and material strength of a forming product can be suppressed, and thus it becomes possible to improve the quality of the forming product.
<Configuration of Forming Apparatus>
As shown in
The lower die 11 is fixed to a large base 15. Further, the lower die 11 is configured of a large steel block and has a cavity (a recessed portion) 16 formed in the upper surface thereof. Further, electrode storage spaces 11a are provided in the vicinity of right and left ends (right and left ends in
Further, a pair of first and second electrodes 17 and 18 which is located on the lower die 11 side also serves as the pipe holding mechanism 30 and can horizontally support the metal pipe material 14 such that the metal pipe material 14 can move up and down between the upper die 12 and the lower die 11. Further, the thermocouple 21 merely illustrates an example of temperature measuring means, and a non-contact type temperature sensor such as a radiation thermometer or an optical thermometer is also acceptable. If the correlation between an energization time and a temperature is obtained, it is also sufficiently possible to make a configuration with the temperature measuring means omitted.
The upper die 12 is a large steel block having a cavity (a recessed portion) 24 in the lower surface thereof and having a cooling water passage 25 formed therein. The upper die 12 is fixed to the slide 82 at an upper end portion thereof. Then, the slide 82 with the upper die 12 fixed thereto is suspended from a pressurizing cylinder 26 and guided by a guide cylinder 27 so as not to laterally oscillate. The drive unit 81 according to this embodiment is provided with a servomotor 83 which generates a driving force for moving the slide 82. The drive unit 81 is configured by a fluid supply section which supplies a fluid that drives the pressurizing cylinder 26 (hydraulic oil in a case where a hydraulic cylinder is adopted as the pressurizing cylinder 26) to the pressurizing cylinder 26. The control unit 70 can control the movement of the slide 82 by controlling the amount of the fluid which is supplied to the pressurizing cylinder 26, by controlling the servomotor 83 of the drive unit 81. Further, the drive unit 81 is not limited to a configuration to apply a driving force to the slide 82 through the pressurizing cylinder 26, as described above, and may have, for example, a configuration to directly or indirectly apply a driving force that is generated by the servomotor 83 to the slide 82 by mechanically connecting the drive unit to the slide 82. Further, in this embodiment, only the upper die 12 moves. However, a configuration is also acceptable in which in addition to the upper die 12 or instead of the upper die 12, the lower die 11 moves. Further, in this embodiment, the drive unit 81 may not be provided with the servomotor 83.
Further, the first electrode 17 and the second electrode 18 configured so as to be able to be advanced and retreated up and down by an actuator (not shown) are provided in electrode storage spaces 12a provided in the vicinity of right and left ends (right and left ends in
The heating mechanism 50 is configured to have a power supply 51, a conducting wire 52 which extends from the power supply 51 and is connected to the first electrode 17 and the second electrode 18, and a switch 53 interposed in the conducting wire 52.
The blowing mechanism 60 is composed of a high-pressure gas source 61, an accumulator 62 which stores high-pressure gas supplied from the high-pressure gas source 61, a first tube 63 which extends from the accumulator 62 to a cylinder unit 42, a pressure control valve 64 and a changeover valve 65 which are interposed in the first tube 63, a second tube 67 which extends from the accumulator 62 to a gas passage 46 formed in a seal member 44, and an ON-OFF valve 68 and a check valve 69 which are interposed in the second tube 67. Further, a leading end of the seal member 44 has a tapered surface 45 formed therein such that the leading end is tapered. The tapered surface 45 is configured in a shape capable of being exactly fitted to and brought into contact with the tapered concave surfaces 17b and 18b of the first and second electrodes (refer to
The pressure control valve 64 plays a role to supply high-pressure gas having an operating pressure adapted to be a pushing force which is required from the seal member 44 side, to the cylinder unit 42. The check valve 69 plays a role to prevent the high-pressure gas from flowing back in the second tube 67. The control unit 70 obtains temperature information from the thermocouple 21 through transmission of information from (A) to (A) and controls the pressurizing cylinder 26, the switch 53, the changeover valve 65, the ON-OFF valve 68, and the like.
The water circulation mechanism 72 is composed of a water tank 73 which stores water, a water pump 74 which pumps up and pressurizes the water stored in the water tank 73 and sends the water to the cooling water passage 19 of the lower die 11 and the cooling water passage 25 of the upper die 12, and a pipe 75. Although it is omitted, a cooling tower which lowers a water temperature or a filter which purifies water may be interposed in the pipe 75.
<Operation of Forming Apparatus>
Next, an operation of the forming apparatus 10 will be described.
Subsequently, the control unit 70 controls the heating mechanism 50 such that the heating mechanism 50 heats the metal pipe material 14. Specifically, the control unit 70 switches on the switch 53 of the heating mechanism 50. Then, electric power is supplied from the power supply 51 to the metal pipe material 14, and the metal pipe material 14 itself generates heat (Joule heat) due to resistance which is present in the metal pipe material 14. In this case, the measurement value of the thermocouple 21 is continuously monitored and energization is controlled based on the result.
The metal pipe material 14 is softened by being heated to a high temperature (around 950° C.), and thus the metal pipe material 14 can be blow-formed with relatively low pressure. Specifically, in a case where compressed air having a normal temperature (25° C.) at a pressure of 4 MPa is adopted as the high-pressure gas, as a result, the compressed air is heated to around 950° C. in the hermetically-sealed metal pipe material 14. The compressed air thermally expands and reaches a pressure in a range of about 16 MPa to 17 MPa, based on the Boyle-Charles' Law. That is, it is possible to easily blow-form the metal pipe material 14 having a temperature of 950° C.
Then, the outer peripheral surface of the blow-formed and swelled metal pipe material 14 is rapidly cooled in contact with the cavity 16 of the lower die 11 and at the same time, is rapidly cooled in contact with the cavity 24 of the upper die 12 (since each of the upper die 12 and the lower die 11 has a large heat capacity and is managed to have a low temperature, if the metal pipe material 14 comes into contact therewith, the heat of the surface of the pipe is removed to the die side at once). Such a cooling method is called die contact cooling or die cooling. Thereafter, quenching of the metal pipe 80 is performed by supplying a cooling medium to the metal pipe 80.
(Cooling of Metal Pipe)
Next, cooling of the metal pipe 80 after the forming will be described. The forming apparatus 10 according to this embodiment is provided with the cooling unit 90 which supplies a cooling medium to the metal pipe 80 after the forming, in forming apparatus 10 according to this embodiment, the control unit 70 makes the cooling of the metal pipe 80 by the cooling medium be performed, by controlling the operation of the blow forming die 13 such that the blow forming die 13 is opened and controlling the cooling unit 90 such that the cooling unit 90 brings the cooling medium into contact with the metal pipe 80, after the completion of the forming by the blow forming die 13. The cooling medium is not particularly limited, and gas such as air or inert gas may be applied, liquid such as water or oil may be applied, and solid such as a metal plate or dry ice may be applied. Further, among these cooling mediums, plural types of cooling medium may be used in combination. In the example shown in
The control unit 70 makes the cooling of the metal pipe 80 by the cooling medium be performed, by controlling the operation of the blow forming die 13 such that the blow forming die 13 is opened and controlling the cooling unit 90 such that the cooling unit 90 brings the cooling medium into contact with the metal pipe 80, subsequently to the completion of the forming by the blow forming die 13. Further, the control unit 70 controls the operation of the blow forming die 13 by moving the upper die 12 through the slide 82 by controlling the drive unit 81. Further, the control unit 70 may make the cooling of the metal pipe 80 by the blow forming die 13 be performed, by controlling the operation of the blow forming die 13 such that a state where the blow forming die 13 and the metal pipe 80 are brought into contact with each other is maintained for a predetermined time, after the completion of the forming, and then make the cooling of the metal pipe 80 by the cooling medium be performed. Further, the control unit 70 may make the cooling of the metal pipe 80 by the blow forming die 13 be performed until the metal pipe 80 reaches a first temperature (a temperature T1 of
The relationship between the cooling of the metal pipe 80 and a temperature in this embodiment will be described with reference to the graphs of
Further, the control unit 70 may make the cooling of the metal pipe 80 by the blow forming die 13 be performed, by controlling the operation of the blow forming die such that a state where the blow forming die 13 and the metal pipe 80 are brought into contact with each other is maintained for a predetermined time, after the completion of the forming, and then make the cooling of the metal pipe 80 by the cooling medium be performed, by controlling the cooling unit 90. The control unit 70 makes the cooling of the metal pipe 80 by the blow forming die 13 be performed until the metal pipe 80 reaches the first temperature (the temperature T1 in
The control unit 70 adjusts the hardenability of the metal pipe 80, based on a timing (the starting point P1) when the cooling of the metal pipe 80 by the cooling medium is started. That is, the control unit 70 adjusts the starting point P1 so as to extend a quenching time by the cooling medium, whereby it is possible to improve stretchability, although strength is reduced. Alternatively, the control unit 70 shortens the quenching time by the cooling medium, whereby it is possible to improve strength. The control unit 70 makes cooling be performed on a preset cooling condition, based on characteristics which are required in accordance with a use or the like of the metal pipe 80 that is a forming target.
Next, an example of a process of the cooling (quenching) of the metal pipe 80 after the completion of the forming will be described with reference to
First, as shown in
Next, as shown in
Next, the operation and effects of the forming apparatus 10 according to this embodiment will be described.
In the forming apparatus 10 according to this embodiment, the control unit 70 makes the cooling (quenching) of the metal pipe 80 by the cooling medium be performed, by controlling the operation of the blow forming die 13 such that the blow forming die 13 is opened and controlling the cooling unit 90 such that the cooling unit 90 brings the cooling medium into contact with the metal pipe 80, subsequently to the completion of the forming by the blow forming die 13. In this manner, by performing the cooling by the contact with the cooling medium, it is possible to slow down a cooling rate, compared to the cooling by the contact with the blow forming die 13, and thus quenching to enhance the toughness of the metal pipe 80 becomes possible. For example, as shown in
Further, in the forming apparatus 10 according to this embodiment, the control unit 70 makes the cooling of the metal pipe 80 by the blow forming die 13 be performed, by controlling the operation of the blow forming die 13 such that a state where the blow forming die 13 and the metal pipe 80 are brought into contact with each other is maintained for a predetermined time, after the completion of the forming, and makes the cooling of the metal pipe 80 by the cooling medium be performed, after the cooling of the metal pipe 80 by the blow forming die 13. The blow forming die 13 has high thermal conductivity and high heat capacity, and therefore, by bringing the blow forming die 13 into contact with the metal pipe 80, it is possible to rapidly cool the metal pipe 80. In this manner, by increasing the cooling rate by performing the cooling by the blow forming die 13 immediately after the completion of the forming, it is possible to shorten a time after the cooling is started and until the temperature of the metal pipe 80 reaches the martensitic transformation start temperature. As shown in
Further, in the forming apparatus 10 according to this embodiment, the control unit 70 makes the cooling of the metal pipe 80 by the blow forming die 13 be performed until the metal pipe 80 reaches the first temperature T1 which is a temperature higher than the martensitic transformation start temperature TS, by controlling the operation of the blow forming die 13. In this way, before the metal pipe 80 reaches the first temperature T1 which is a temperature before the martensitic transformation start temperature TS, it becomes possible to rapidly cool the metal pipe 80 by the blow forming die 13. In this way, it is possible to lengthen the martensite formation possible time.
Further, in the forming apparatus 10 according to this embodiment, the control unit 70 adjusts the hardenability of the metal pipe 80, based on a timing (the starting point P1 of
Further, in the forming apparatus 10 according to this embodiment, the cooling unit 90 blows gas for cooling as the cooling medium on the metal pipe 80. Due to using gas as the cooling medium, flow rate adjustment or the like is easy, and therefore, it is possible to easily perform adjustment of hardenability. Further, it is possible to cool the metal pipe 80 without contaminating it, compared to a case of using liquid as the cooling medium.
Further, in the forming apparatus 10 according to this embodiment, the cooling unit 90 is configured of the blowing mechanism 60 which is a gas supply unit. In this way, the gas supply unit for expanding the metal pipe 80 can be diverted as the cooling unit, and therefore, it is possible to make the forming apparatus 10 compact.
Further, in the forming apparatus 10 according to this embodiment, the cooling unit 90 may blow gas for cooling on both the inner surface and the outer surface of the metal pipe 80. In this way, it becomes possible to remove scales (oxide layers) (described later) or the like, stuck to both the inner surface and the outer surface of the metal pipe 80, and thus it becomes possible to effectively improve the quality of a forming product.
The forming method according to this embodiment includes: a heating step of heating the metal pipe material 14; a gas supply step of supplying gas into a heated metal pipe material 14, thereby expanding the metal pipe material 14; a forming step of forming the metal pipe 80 by bringing the expanded metal pipe material 14 into contact with the blow forming die 13; and a cooling step of cooling the metal pipe 80 after the forming by a cooling medium. Further, in the cooling step, the cooling of the metal pipe 80 by the cooling medium is performed by opening the blow forming die 13 and bringing the cooling medium into contact with the metal pipe 80, subsequently to the completion of the forming by the blow forming die 13. According to the forming method according to this embodiment, it is possible to obtain the same operation and effects as those of the forming apparatus 10 described above.
The present invention is not limited to the embodiment described above.
For example, as shown in
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Further, the forming apparatus 10 described above is provided with the heating mechanism 50 capable of performing heating treatment between the upper and lower dies, and the heating mechanism 50 heats the metal pipe material 14 by using Joule heat by energization. However, there is no limitation thereto. For example, a configuration is also acceptable in which heating treatment is performed at a place other than the place between the upper and lower dies and a metallic pipe after the heating is transported into an area between the dies. Further, in addition to the use of Joule heat by energization, radiation heat of a heater or the like may be used, and it is also possible to perform heating by using a high-frequency induction current.
As the high-pressure gas, a non-oxidizing gas or an inert gas such as nitrogen gas or argon gas can be adopted mainly. However, although these gases can make generation of an oxidized scale in a metal pipe difficult, these gases are expensive. In this regard, in the case of compressed air, as long as a major problem due to the generation of an oxidized scale is not caused, it is inexpensive, and even if it leaks into the atmosphere, there is no actual harm, and handling is very easy. Therefore, it is possible to smoothly carry out a blowing process.
The blow forming die may be either of a non-water-cooled die or a water-cooled die. However, the non-water-cooled die needs a long time when reducing the temperature of the die to a temperature near an ordinary temperature after the end of blow forming. In this regard, in the case of the water-cooled die, cooling is completed in a short time. Therefore, from the viewpoint of improvement in productivity, the water-cooled die is preferable.
Further, in the forming apparatus 10 described above, the cooling of the metal pipe 80 by the blow forming die 13 is performed until the metal pipe 80 reaches the first temperature (the temperature T1 in
The forming apparatus and the forming method according to embodiments of the present invention can be used as a forming apparatus and a forming method, in which strength and toughness are controlled according to, for example, a use, and thus a forming product having suitable characteristics is provided.
It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.
Number | Date | Country | Kind |
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2014-105885 | May 2014 | JP | national |
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2003-154415 | May 2003 | JP |
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Entry |
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International Search Report dated Aug. 11, 2015 corresponding to International Patent Application No. PCT/JP2015/064479. |
International Preliminary Report on Patentability International application No. PCT/JP2015/064479 dated Nov. 22, 2016. |
Number | Date | Country | |
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20170066028 A1 | Mar 2017 | US |
Number | Date | Country | |
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Parent | PCT/JP2015/064479 | May 2015 | US |
Child | 15355283 | US |