US20080289393A1 - Hot forming and in-situ cooling of metallic articles - Google Patents
Hot forming and in-situ cooling of metallic articles Download PDFInfo
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- US20080289393A1 US20080289393A1 US12/125,789 US12578908A US2008289393A1 US 20080289393 A1 US20080289393 A1 US 20080289393A1 US 12578908 A US12578908 A US 12578908A US 2008289393 A1 US2008289393 A1 US 2008289393A1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/02—Stamping using rigid devices or tools
- B21D22/025—Stamping using rigid devices or tools for tubular articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D11/00—Bending not restricted to forms of material mentioned in only one of groups B21D5/00, B21D7/00, B21D9/00; Bending not provided for in groups B21D5/00 - B21D9/00; Twisting
- B21D11/02—Bending by stretching or pulling over a die
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
- B21D37/16—Heating or cooling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
- B21J1/06—Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
- B30B15/34—Heating or cooling presses or parts thereof
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/62—Quenching devices
- C21D1/673—Quenching devices for die quenching
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
- C21D9/085—Cooling or quenching
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Shaping Metal By Deep-Drawing, Or The Like (AREA)
- Heat Treatment Of Articles (AREA)
- Forging (AREA)
Abstract
Disclosed herein is a hot forming method and apparatus that can improve strength of a product via die operation. The hot forming apparatus includes a lower die on which a workpiece is placed, an upper die coupled to the lower die to press the workpiece, a holder disposed between the upper and lower dies to form an inner space of the workpiece, and a cooling unit to cool the workpiece. The hot forming method includes coupling an upper die, a lower die and a holder with a workpiece placed on the lower die, followed by pressing the workpiece to perform a hot forming operation, determining whether or not a preset time has elapsed after pressing the workpiece, and cooling the workpiece by supplying a cooling fluid around the workpiece, if the preset time has elapsed.
Description
- This application claims priority to and the benefit of Korean Patent Application No. 10-2007-0050418, filed May 23, 2007, the disclosure of which is incorporated herein by reference in its entirety.
- 1. Field
- The present disclosure relates to hot forming of metallic articles, and more particularly, to hot forming and cooling in-situ of metallic articles.
- 2. Description of the Related Technology
- Although various kinds of products can be produced by hot forming methods and apparatus, a torsion beam of a rear torsion beam axle suspension for a vehicle will be described herein as one example of the products produced thereby.
- The torsion beam axle suspension is generally constituted by the torsion beam and trailing arms attached to opposite ends of the torsion beam, and serves to maintain a posture of the vehicle with torsion of the torsion beam with respect to a centrifugal force applied to a vehicle body upon cornering of the vehicle. Therefore, the torsion beam is required to have a high torsion and bending rigidity.
- Initially, the torsion beam was formed by bending an iron plate to have a U-shaped or V-shaped cross-section, and provided therein with a torsion bar for reinforcement thereof, with the opposite ends of the torsion beam welded to the trailing arms via a separate reinforcing plate to ensure the high torsion and bending rigidity.
- With such a configuration, although the torsion beam can satisfactorily meet the requirement of the high torsion and bending rigidity by the reinforced strength, it has problems in that the increased number of components, such as the torsion bar and the reinforcing plate, and the increased number of assembling and welding processes result in a significant reduction in productivity, a very high frequency of defective products caused by difficulty in tolerance management in welding, and reduction in fuel efficiency of the vehicle by an increase in weight of the final product.
- The foregoing discussion is to provide general background information, and does not constitute an admission of prior art.
- One aspect of the invention provides a hot forming apparatus comprising: a lower die; an upper die movable relative to the lower die, wherein the lower and upper dies are configured to press a workpiece placed between the lower and upper dies; a holder configured to hold the workpiece while placed between the lower and upper dies; and a cooler configured to cool the pressed workpiece while placed between the lower and upper dies.
- In the foregoing apparatus, the cooler may be configured to cool at least one of the lower die, the upper die, and the holder. The cooler may be configured to quench the workpiece so as to transform at least part of the workpiece from austenite to martensite. The cooler may comprise a cooling path provided in at least one of the lower die, the upper die and the holder so as to flow a cooling fluid therethrough and a pump configured to pump the cooling fluid to the cooling path. The cooling path may comprise a die path defined in the lower or upper die, and a holder path defined in the holder. The holder path may comprise a suction path and an exhaust path surrounding the suction path.
- Further in the foregoing apparatus, the apparatus may further comprise a guide member provided between the lower and upper dies and configured to guide movement of the upper die relative to the lower die. A space may be defined between the holder, the lower die and the upper die. The cooler may be a direct cooling path having an outlet configured to discharge cooling fluid toward the space. The direct cooling path may be formed in at least one of the lower die, the upper die and the holder. The holder may comprise an insert configured to be inserted in the interior space of the workpiece. The holder may comprise a cam.
- Another aspect of the invention provides a hot forming method comprising: providing an apparatus comprising an upper die, a lower die and a holder; holding a workpiece with the holder between the upper die and the lower die; moving the upper die relative to the lower die and pressing the workpiece so as to perform a hot forming operation; maintaining pressing of the workpiece for a predetermined time; and cooling in-situ the pressed workpiece with a cooling fluid.
- In the foregoing method, cooling may comprise quenching the workpiece to transform at least part of the workpiece from austenite to martensite. Cooling may comprise circulating a cooling fluid through a cooling path formed in at least one of the upper die, the lower die and the holder. The holder may comprise an insert which is inserted in the interior space of the workpiece. Cooling may comprise contacting the workpiece with a cooling fluid. The method may further comprise determining that the pressed workpiece reached a predetermined temperature.
- An aspect of the present invention is to provide a hot forming method and apparatus that can produce a product having a bilateral symmetry.
- It is another aspect of the present invention to provide the hot forming method and apparatus that can improve the strength of the product produced by die operation.
- It is yet another aspect of the present invention to provide the hot forming method and apparatus that can reduce occurrence of defective products caused by shape deformation in die operation.
- In accordance with one aspect of the present invention, a hot forming apparatus comprises: a lower die on which a workpiece is placed; an upper die coupled to the lower die to press the workpiece; a holder disposed between the upper and lower dies to form an inner space of the workpiece; and a cooling unit to cool the workpiece.
- Preferably, the cooling unit is provided to at least one of the lower die, the upper die, and the holder. Preferably, the cooling unit is formed in the lower die, the upper die or the holder.
- The cooling unit may comprise a cooling path through which a cooling fluid is supplied to transform structure of the workpiece from austenite to martensite; a pump to supply the cooling fluid into the cooling path; and a cooling pipe connecting the cooling path to the pump. Preferably, the cooling path comprises a die path defined inside the lower and upper dies; and a holder path defined inside the holder. Preferably, the holder path comprises a suction path and an exhaust path surrounding the suction path with an inner wall of the exhaust path separated a predetermined distance from an outer wall of the suction path.
- Preferably, the apparatus further comprises a guide member provided between the lower and upper dies.
- Preferably, a space section is defined between the holder, the lower die and the upper die.
- Preferably, the apparatus further comprises a direct cooling path to supply the cooling fluid to the space section.
- Preferably, the direct cooling path is formed in at least one of the lower die, the upper die and the holder.
- In accordance with another aspect of the present invention, a hot forming method comprises: coupling an upper die, a lower die and a holder with a workpiece placed on the lower die, followed by pressing the workpiece to perform a hot forming operation; determining whether or not a preset time has elapsed after pressing the workpiece; and cooling the workpiece by supplying a cooling fluid around the workpiece, if the preset time has elapsed.
- The cooling step may comprise quenching the workpiece to have a predetermined temperature or less within a predetermined time to transform structure of the workpiece from austenite to martensite.
- The cooling step may comprise circulating the cooling fluid into at least one of the upper die, the lower die and the holder. Preferably, the cooling step comprises circulating the cooling fluid into the lower die, the upper die or the holder. In other words, the present invention can be realized in various modifications, for example, cooling the workpiece by circulating the cooling fluid into at least one of the upper die, the lower die and the holder, and alternatively, cooling the workpiece by sequentially circulating the cooling fluid.
- Preferably, the cooling step comprises supplying the cooling fluid into a path defined between the holder, the upper die and the lower die to make the cooling fluid contact the workpiece.
- The method may further comprise: determining whether or not the workpiece has a predetermined temperature or less after the cooling step; and separating the upper die, the lower die and the holder to eject the workpiece, if the workpiece has the predetermined temperature or less.
- The above and other aspect, features and advantages of the present invention will become apparent from the following description of exemplary embodiments given in conjunction with the accompanying drawings, in which:
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FIG. 1 is a perspective view of a hot forming apparatus according to one embodiment of the present invention; -
FIG. 2 is a front sectional view illustrating a cooling path of the hot forming apparatus according to one embodiment of the present invention; -
FIG. 3 is a side sectional view illustrating a cooling path of a hot forming apparatus according to one embodiment of the present invention; -
FIG. 4 is a side sectional view illustrating a holder path of the hot forming apparatus according to one embodiment of the present invention; -
FIG. 5 is a flow chart of a hot forming method according to one embodiment of the present invention; and -
FIG. 6 is a perspective view of a torsion beam produced by the hot forming apparatus and method according to one embodiment of the present invention; -
FIG. 7 is a cross-sectional view taken along line A-A ofFIG. 6 ; -
FIG. 8 is a cross-sectional view taken along line B-B ofFIG. 6 ; and -
FIG. 9 is a cross-sectional view taken along line C-C ofFIG. 6 . - Embodiments of the present invention will be described in detail with reference to the accompanying drawings. For descriptive convenience, embodiments will be described based on a method of hot forming a rear torsion beam axle suspension for a vehicle. The drawings may be exaggerated in thickness of lines or size of components for the purpose of descriptive convenience and clarity. Furthermore, terms used herein should be defined in consideration of functions of components of embodiments of the present invention and thus can be changed according to the custom or intention of users or operators. Therefore, definition of such terms should be determined according to overall disclosures set forth herein. Herein, the words “a,” “an,” and “the” are used interchangeably with “at least one” to mean one or more of the elements being described.
- A torsion beam is formed by pressing a cylindrical pipe to have a two-folded U-shaped or V-shaped cross-section at a central region of the torsion beam for ensuring the torsion rigidity and to have a -shaped cross-section at either side thereof for ensuring the bending rigidity and a wide welding area with respect to the trailing arm. With this configuration of the torsion beam, since the torsion beam axle suspension permits reduction in the number of components and processes such as assembling and welding while ensuring sufficient torsion and bending rigidity, it is believed that it can improve the productivity and the fuel efficiency of the vehicle by weight reduction while reducing the frequency of defective products, as compared with the typical torsion beam.
- In forming the torsion beam to have such different cross-sectional shapes at the different portions, since an increase in the number of processes leads to a decrease in productivity and an increase in manufacturing costs resulting in low price competitiveness, it is desirable to obtain the torsion beam with a minimal number of processes.
- As a method and apparatus for producing products having the U-shaped or V-shaped cross-section by pressing the cylindrical pipe, it is known in the art to employ two sets of dies that include lower dies having different shapes, or a single set of dies that includes a single upper die and several lower dies moving to one another.
- The method using the two sets of dies comprises a primary preform process and a secondary precision process, which are performed with the pipe firmly secured by a mandrel at an initial stage. The method using the single set of dies is performed by a lathe-shaped upper die and the lower dies, which are divided into a single middle-set of lower dies and two side-sets of lower dies, which move to one another along a guide plane defined between the lower dies and the upper die or between the lower dies. With these methods and apparatus, it is believed that the product having the overall U-shaped or V-shaped cross-section can be satisfactorily produced. Additionally, when applied to the product having different cross-sectional shapes at different portions as in the torsion beam of the rear torsion beam axle suspension, these methods and apparatus are believed to produce the product with a minimal number of processes.
- However, when forming the product, such as the torsion beam of the torsion beam axle suspension, which has the different cross-sectional shapes formed at the different portions and continuously connected to one another, the method and apparatus as described above may have a problem in that either end or a deformable portion of the product is prone to be deformed or damaged in die operation, since it is difficult to increase the strength of the either end or the deformable portion over a predetermined value.
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FIG. 1 is a perspective view of a hot forming apparatus according to one embodiment of the present invention, andFIG. 2 is a front sectional view illustrating a cooling path of the hot forming apparatus according to one embodiment of the present invention. - Referring to
FIGS. 1 and 2 , the hot forming apparatus according to one embodiment comprises abase 10, alower die 30 disposed on the base 10 such that a workpiece can be placed on thelower die 30, anupper die 20 movably disposed on thebase 10 and coupled to thelower die 30 for hot forming of the workpiece, holders orside cores 40 movably disposed on thebase 10 and interposed between theupper die 20 and thelower die 30 to form a hollow of the workpiece, and acooling unit 50 provided to thelower die 30, theupper die 20 and theholders 40 to cool the workpiece after hot forming. In one embodiment, the holder has an insert. In another embodiment, the holder has a cam. - The
base 10 comprises alower base 12 disposed on the floor and having thelower die 30 mounted on thelower base 12, and anupper base 14 located above thelower base 12 to be moved by abase cylinder 16 in a perpendicular direction and having theupper die 20 mounted on theupper base 14. - When the
upper base 14 and theupper die 20 are lowered by driving thebase cylinder 16 with a workpiece placed on thelower die 30, theupper die 20 is coupled to thelower die 30, enabling a press operation to be performed by the dies. - The upper and lower dies 20 and 30 are heated to a predetermined temperature or more for hot forming of the workpiece. A heating device (not shown) to heat the dies is well known to those skilled in the art, and detailed description thereof will be omitted hereinafter. Further, since the
base cylinder 16 is a hydraulic cylinder well also known in the art, detailed description of the base cylinder and an operation thereof will be omitted hereinafter. - A
guide member 32 is provided between thelower die 30 and theupper die 20 to assist in precise coupling between the upper and lower dies 20 and 30. - Further, the
guide member 32 serves to ensure the workpiece is correctly placed at the center of thelower die 30, so that a completed product can have a precise bilateral symmetry. - The
guide member 32 is constituted by a guide piece that has a certain size and is placed on an edge of a depression of thelower die 30 where the workpiece will be seated. The guide piece constituting theguide member 32 is coupled to an upper surface of thelower die 30 by means of typical fastening members such as bolts, rivets, etc. - The
holders 40 are respectively provided to a pair ofcylinders 42 disposed horizontally on an upper surface of thelower base 12. - When an arm of each
cylinder 42 is protruded from thecylinder 42, theholder 40 provided to an end of the arm is interposed between the upper and lower dies 20 and 30, and when the arm is inserted into thecylinder 42, theholder 40 is moved outside a space defined between the upper and lower dies 20 and 30. - In the apparatus with such a configuration as described above, when the
cylinders 42 are driven with a pipe-shaped workpiece seated on thelower die 30, theholders 40 are inserted into opposite ends of the workpiece, respectively. - Then, when the
base cylinder 16 is driven, theupper die 20 is lowered and coupled to thelower die 30, followed by hot forming of the workpiece to produce a desired product, that is, atorsion beam 70. - As described above, since the die machine including the
upper die 20,lower die 30, andholder 40 for manufacturing a pipe-shaped beam is well known in the art, an exploded perspective view of theupper die 20,lower die 30, andholders 40 is omitted herein. - The cooling
unit 50 is formed inside at least one of theupper die 20, thelower die 30 and theholders 40. The coolingunit 50 comprises acooling path 52 through which a cooling fluid is supplied, a pump (not shown) to supply the cooling fluid into the cooling path, 52, a coolingpipe 54 connecting the coolingpath 52 to the pump, and a fluid tank (not shown) filled with the cooling fluid and connected to the coolingpipe 54. The coolingpath 52 is disposed to transform the structure of thetorsion beam 70 from austenite formed by the hot forming operation to martensite with the cooling fluid flowing through the coolingpath 52. Preferably, the coolingpath 52 is disposed in thelower die 30, theupper die 20 or theholders 40 to allow quenching of the torsion beam. More preferably, a plurality of coolingpaths 52 are provided into thelower die 30, theupper die 20 or theholders 40. - The cooling
path 52 comprises adie path 52 a defined inside each of the upper and lower dies 20 and 30, and aholder path 52 b defined inside each of theholders 40. - The cooling
pipe 54 comprises diepipes 54 a extending from the tank to the upper and lower dies 20 and 30, andholder pipes 54 b extending from the tank to theholders 40. - The cooling
pipe 54 is provided at a portion extending from the tank with avalve 56, from which thecooling pipe 54 is divided into thedie pipes 54 a and theholder pipes 54 b. - With this configuration, when the pump is driven after the hot forming, the cooling fluid is supplied along the cooling
path 54 defined inside thelower die 30, theupper die 20 and theholders 40, quenching thetorsion beam 70 located between thelower die 30, theupper die 20 and theholders 40 to have a predetermined temperature or less. - The
holder path 52 b comprises asuction path 52 c extending from one end, that is, a suction port, of theholder 40 and anexhaust path 52 d surrounding thesuction path 52 c with an inner wall of theexhaust path 52 d separated a predetermined distance from an outer wall of thesuction path 52 c. - Therefore, after being induced into the suction port of the
holder 40, the cooling fluid flows to the other end of theholder 40 along thesuction path 52 c, is discharged from thesuction path 52 c, flows along a space defined between the outer wall of thesuction path 52 c and the inner wall of theexhaust path 52 d, and is finally discharged outside theholder 40. - The
holder 40 has a square cross-sectional outer end, which corresponds to thecylinder 42, and is gradually decreased in cross-sectional area toward an inner center thereof. - The
holder 40 has a V-shaped depression of which cross-sectional area is decreased toward the inner center, so that thetorsion beam 70 can be formed to have a desired shape. -
FIG. 3 is a side sectional view illustrating a cooling path of a hot forming apparatus according to another embodiment of the present invention, andFIG. 4 is a side sectional view illustrating a holder path of the hot forming apparatus according to one embodiment. - Referring to
FIGS. 3 and 4 , the hot forming apparatus according to this embodiment is similar to the above embodiment in that this embodiment also comprises alower die 130, anupper die 120,holders 140, and acooling unit 150. However, thecooling unit 150 of the hot forming apparatus according to this embodiment can be differentiated from the cooling unit of the above embodiment in view of various features. - The
cooling unit 150 comprises aspace section 100 defined between eachholder 140, thelower die 130 and theupper die 120. - According to this embodiment, the hot forming apparatus further comprises a
direct cooling path 110 to supply a cooling fluid into thespace section 100. - Therefore, the cooling fluid supplied along the
direct cooling fluid 110 to cool atorsion beam 70 facilitates cooling of thetorsion beam 70 by a direct contact with thetorsion beam 70 after flowing into thespace section 100. - Such a configuration and operation can facilitate transformation of the microstructure of the
torsion beam 70 from austenite to martensite, allowing more effective reinforcement of thetorsion beam 70. - The
direct cooling path 110 may be formed in at least one of thelower die 130, theupper die 120 and theholder 140. In this embodiment, thedirect cooling path 110 is shown as being formed in theholder 140. - However, the
direct cooling path 110 may be formed in theupper die 120 or thelower die 130. Alternatively, the direct cooling path 11 may be formed by coupling grooves in each of the components. - In the case where the
direct cooling path 110 is formed in theholder 140, preferably, thedirect cooling path 110 extend from an upper surface of theholder 140 into theholder 140 and is bent to extend to thespace section 100 betweenholder paths 152 b such that thedirect cooling path 110 is communicated with thespace section 100. - Next, a hot forming method with the apparatus having the configuration according to one embodiment of the present invention will be described.
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FIG. 5 is a flow chart of the hot forming method according to one embodiment of the present invention,FIG. 6 is a perspective view of a torsion beam produced by the hot forming apparatus and method according to this embodiment,FIG. 7 is a cross-sectional view taken along line A-A ofFIG. 6 ,FIG. 8 is a cross-sectional view taken along line B-B ofFIG. 6 , andFIG. 9 is a cross-sectional view taken along line C-C ofFIG. 6 . - Referring to
FIG. 5 to 9 , the hot forming method of this embodiment comprises coupling theupper die 20, thelower die 30 and theholders 40, with a workpiece placed on thelower die 30, followed by pressing the workpiece to produce atorsion beam 70 by a hot forming operation (hereinafter, pressing operation S10), determining whether or not a preset time has elapsed after the pressing operation S10 (hereinafter, hot forming completion determining operation S20), cooling thetorsion beam 70 by supplying a cooling fluid around the torsion beam 70 (hereinafter, cooling operation S30) if it is determined in the hot forming completion determining operation S20 that the preset time has elapsed, determining whether or not thetorsion beam 70 has a predetermined temperature or less after the cooling operation S30 (hereinafter, temperature determining operation S40), and separating theupper die 20, thelower die 30 and theholders 40 to eject the torsion beam 70 (hereinafter, separating operation S50) if it is determined in the temperature determining operation S40 that thetorsion beam 70 has the predetermined temperature or less. - Hereinafter, the hot forming method of this embodiment will be described in detail.
- First, when the
cylinders 42 are driven with a pipe-shaped workpiece of metal seated on thelower die 30, theholders 40 are inserted into the opposite ends of the workpiece. - As the
base cylinder 16 is driven, theupper die 20 is coupled to thelower die 30, followed by performing the pressing operation S10 to produce thetorsion beam 70. - At this time, the
upper die 20,lower die 30 andholders 40 are heated at 600˜900° C. for the hot forming operation. - The hot forming completion determining operation S20 is a process to measure time for which hot forming is performed, and can be performed by means of a typical time measuring device such as a timer.
- If it is determined in the hot forming completion determining operation S20 that the preset time has elapsed, the pump is driven to allow a cooling fluid to be supplied into the
lower die 30, theupper die 20 and theholders 40 along the coolingpipes 54 and the coolingpath 52, so that the cooling operation S30 can be performed for quenching thetorsion beam 70. - Additionally, after being induced into the
holders 40 through theholder pipes 54 b, the cooling fluid flows to an inner end of each of theholders 40 along thesuction path 52 c, is discharged from thesuction path 52 c, flows along a space defined between thesuction path 52 c and theexhaust path 52 d, and is finally discharged outside theholder 40. - In this manner, the
torsion beam 70 is subjected to quenching to have a temperature of 100˜350° C. within about 1 second. - By such a cooling operation S30, the temperature of the
torsion beam 70 is lowered below a predetermined temperature or less within a preset time to transform the structure of thetorsion beam 70 from austenite to martensite, thereby improving the strength of thetorsion beam 70. - At this time, the cooling fluid cools the
torsion beam 70 while circulating through thelower die 30,upper die 20 andholders 40. - Alternatively, the cooling operation S30 can be performed by circulating the cooling fluid only into the lower and upper dies 30 and 20 or only into the
lower die 30. - Additionally, the cooling operation S30 may further comprise direct supplying the cooling fluid to the
torsion beam 70 to accelerate the cooling rate to further facilitate transformation of the workpiece to the martensite structure. - For this purpose, the hot forming method may be performed using the hot forming apparatus according to the embodiment as shown in
FIGS. 3 and 4 . - In this method, when the cooling step S30 is started, a cooling fluid is simultaneously supplied to the cooling path 152 and to the
space section 100 along thedirect cooling path 110. - Therefore, as the
upper die 120,lower die 130 andholders 140 are cooled, thetorsion beam 70 in contact with theupper die 120,lower die 130 andholders 140 is rapidly cooled. Here, the cooling fluid supplied into thespace section 100 is brought into contact with thetorsion beam 70 and accelerates cooling of thetorsion beam 70, so that a more effective cooling operation can be obtained. - The temperature determining operation S40 is a process to measure time for which the cooling fluid is supplied, and can be performed using the typical time measuring device as in the hot forming completion determining operation S20. If it is determined in the temperature determining operation S40 that a preset time has elapsed, manufacture of the
torsion beam 70 is completed by completing the cooling operation S30. - Then, the separating operation S50 is performed in such a fashion that the
base cylinder 16 and thecylinders 42 are driven in the counterclockwise direction to separate theupper die 20 and thelower die 30 while theholders 40 are separated from the opposite ends of thetorsion beam 70. - With such a configuration and operation of the apparatus as described above, the
torsion beam 70 is formed to have a square-shaped cross-section at eitherend 74, a V-shaped cross-section at amiddle region 72 with upper and lower surfaces brought into close contact with each other, and a combination of the square-shaped cross-section and a V-shaped groove at aconnection region 76 between themiddle region 72 and either end 74 in which the V-shaped groove of theconnection region 76 is formed on an upper center thereof. - As apparent from the above description, the hot forming apparatus of one embodiment is provided with a guide member to ensure a workpiece is seated on the center of a lower die and to prevent the workpiece from being deviated from the center when the upper die is coupled to the lower die, thereby providing a torsion beam with a bilateral symmetry.
- Further, for the hot forming apparatus and method of one embodiment, a cooling unit is located in the hot forming apparatus for quenching the hot formed torsion beam to facilitate transformation of the torsion beam from austenite structure, which is stable at high temperatures, into martensite structure, which is stable at low temperatures and enhances the strength of the workpiece, thereby effectively preventing deformation and damage of the torsion beam.
- Moreover, according to one embodiment of the present invention, hot forming and quenching are performed in a single process, and, the hot formed product is subjected to quenching with an elapse of a preset time after the hot forming, thereby simplifying the process and reducing a frequency of defective products in die operation.
- Although embodiments of the present invention has been described with reference to the accompanying drawings, these embodiments are provided for the illustrative purpose, and it will be apparent to those skilled in the art that various modifications and equivalent embodiments can be made from these embodiments disclosed herein.
- Furthermore, although embodiment so the present invention has been described based on the torsion beam of the rear torsion beam axle suspension for the vehicle as one example, embodiments of the present invention can be applied to torsion beams of other applications without being limited to the vehicle. Therefore, the scope of the present invention should be limited only by the accompanying claims as follows.
Claims (18)
1. A hot forming apparatus comprising:
a lower die;
an upper die movable relative to the lower die, wherein the lower and upper dies are configured to press a workpiece placed between the lower and upper dies;
a holder configured to hold the workpiece while placed between the lower and upper dies; and
a cooler configured to cool the pressed workpiece while placed between the lower and upper dies.
2. The apparatus according to claim 1 , wherein the cooler is configured to cool at least one of the lower die, the upper die, and the holder.
3. The apparatus of claim 1 , wherein the cooler is configured to quench the workpiece so as to transform at least part of the workpiece from austenite to martensite.
4. The apparatus according to claim 1 , wherein the cooler comprises:
a cooling path provided in at least one of the lower die, the upper die and the holder so as to flow a cooling fluid therethrough; and
a pump configured to pump the cooling fluid to the cooling path.
5. The apparatus according to claim 4 , wherein the cooling path comprises a die path defined in the lower or upper die, and a holder path defined in the holder.
6. The apparatus according to claim 5 , wherein the holder path comprises a suction path and an exhaust path surrounding the suction path.
7. The apparatus according to claim 1 , further comprising a guide member provided between the lower and upper dies and configured to guide movement of the upper die relative to the lower die.
8. The apparatus according to claim 1 , wherein a space is defined between the holder, the lower die and the upper die.
9. The apparatus according to claim 8 , wherein the cooler comprises a direct cooling path having an outlet configured to discharge cooling fluid toward the space.
10. The apparatus according to claim 9 , wherein the direct cooling path is formed in at least one of the lower die, the upper die and the holder.
11. The apparatus of claim 1 , wherein the holder comprises an insert configured to be inserted in the interior space of the workpiece.
12. The apparatus of claim 1 , wherein the holder comprises a cam.
13. A hot forming method comprising:
providing an apparatus comprising an upper die, a lower die and a holder;
holding a workpiece with the holder between the upper die and the lower die;
moving the upper die relative to the lower die and pressing the workpiece so as to perform a hot forming operation;
maintaining pressing of the workpiece for a predetermined time; and
cooling in-situ the pressed workpiece with a cooling fluid.
14. The method according to claim 13 , wherein cooling comprises quenching the workpiece to transform at least part of the workpiece from austenite to martensite.
15. The method according to claim 13 , wherein cooling comprises circulating a cooling fluid through a cooling path formed in at least one of the upper die, the lower die and the holder.
16. The method of claim 13 , wherein the holder comprises an insert which is inserted in the interior space of the workpiece.
17. The method according to claim 13 , wherein cooling comprises contacting the workpiece with a cooling fluid.
18. The method according to claim 13 , further comprising determining that the pressed workpiece reached a predetermined temperature.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR10-2007-0050418 | 2007-05-23 | ||
KR1020070050418A KR100907225B1 (en) | 2007-05-23 | 2007-05-23 | Hot forming apparatus and hot forming method |
Publications (1)
Publication Number | Publication Date |
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US20080289393A1 true US20080289393A1 (en) | 2008-11-27 |
Family
ID=40071141
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/125,789 Abandoned US20080289393A1 (en) | 2007-05-23 | 2008-05-22 | Hot forming and in-situ cooling of metallic articles |
Country Status (3)
Country | Link |
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US (1) | US20080289393A1 (en) |
KR (1) | KR100907225B1 (en) |
CN (1) | CN101342559B (en) |
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Also Published As
Publication number | Publication date |
---|---|
CN101342559B (en) | 2010-09-01 |
KR20080103300A (en) | 2008-11-27 |
CN101342559A (en) | 2009-01-14 |
KR100907225B1 (en) | 2009-07-10 |
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