WO2022234708A1 - プレス成形方法及びプレス成形品の形状評価方法 - Google Patents
プレス成形方法及びプレス成形品の形状評価方法 Download PDFInfo
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- WO2022234708A1 WO2022234708A1 PCT/JP2022/005701 JP2022005701W WO2022234708A1 WO 2022234708 A1 WO2022234708 A1 WO 2022234708A1 JP 2022005701 W JP2022005701 W JP 2022005701W WO 2022234708 A1 WO2022234708 A1 WO 2022234708A1
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- 238000000034 method Methods 0.000 title claims abstract description 83
- 230000008859 change Effects 0.000 claims abstract description 85
- 238000001816 cooling Methods 0.000 claims abstract description 74
- 238000010438 heat treatment Methods 0.000 claims abstract description 74
- 238000000465 moulding Methods 0.000 claims description 90
- 230000008569 process Effects 0.000 claims description 33
- 239000002184 metal Substances 0.000 claims description 30
- 238000005259 measurement Methods 0.000 claims description 9
- 238000004904 shortening Methods 0.000 claims description 7
- 238000011156 evaluation Methods 0.000 claims description 5
- 238000004364 calculation method Methods 0.000 claims description 2
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- 230000000694 effects Effects 0.000 description 3
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- 238000011835 investigation Methods 0.000 description 1
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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
- 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
-
- 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
- B21D22/20—Deep-drawing
- B21D22/30—Deep-drawing to finish articles formed by deep-drawing
-
- 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
- B21D22/022—Stamping using rigid devices or tools by heating the blank or stamping associated with heat treatment
-
- 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
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
- B21D5/01—Bending sheet metal along straight lines, e.g. to form simple curves between rams and anvils or abutments
-
- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted 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
- 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0062—Heat-treating apparatus with a cooling or quenching zone
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Definitions
- the present invention relates to a press forming method and a shape evaluation method for a press forming part, and in particular, to a spring at the moment the die is released from the die.
- the present invention relates to a method for press forming a press-formed product whose shape changes with the passage of time after springback, and a method for evaluating the shape of the press-formed product.
- Press molding is a method that allows metal parts to be manufactured at low cost and in a short time, and is used to manufacture many automotive parts.
- high-strength metal sheets have been used as automotive parts in order to achieve both improved collision safety and weight reduction of automotive bodies. Press molded.
- Springback refers to the residual stress that occurs in the press-formed product when deforming the metal plate using the mold during press-forming, which becomes the driving force, and press-forming is released from the mold. This is a phenomenon in which a product instantly returns to the shape of the metal plate before press forming, like a spring.
- the higher the strength of the metal plate for example, high-tensile steel sheet
- the greater the residual stress in the press-formed product generated by press-forming so the shape change of the press-formed product due to springback is also large. Therefore, the higher the strength of the metal plate, the more difficult it becomes to keep the shape of the press-formed product after springback within the predetermined dimensions. Therefore, techniques have been developed to accurately predict the shape variation of press-formed products due to springback.
- press-forming simulations using the finite element method.
- a procedure for the press-forming simulation first, a press-forming analysis of the process of press-forming a metal plate using a die to the bottom dead center of forming was performed, and the residue generated in the press-formed product was analyzed.
- first stage of stress prediction for example, Patent Document 1
- springback analysis is performed in which the shape of the press-molded product taken out of the mold changes due to springback, and the moment of force and residual stress are analyzed. It is divided into a second stage (for example, Patent Document 2) of predicting the shape of the press-formed product that is balanced.
- FIG. 9 shows an example of how the shape of a press-formed product changes over time.
- a press-formed product 1 having a hat-shaped cross section as shown in FIG. 9(a) as an example causes springback at the moment it is released from the mold, as shown in FIG. 9(b).
- FIG. 9(b) shows a shape change in which the wall opening of the side wall portion 4 increases compared to the molding bottom dead center shape (dotted line in FIG. 9(b)) (FIG. 9(b) Broken line in the middle)
- FIG. 9(b) Broken line in the middle
- the present invention has been made in view of the above problems, and an object of the present invention is to shorten the time required for the shape change of the press-formed product over time after being press-formed and spring-backed, and to shorten the time required for the shape to be changed.
- the press-molding method shortens the time required for the shape change of the press-molded product over time after springback occurs at the moment the press-molded product is released from the mold.
- a heating and holding process in which the molded product is heated to a predetermined temperature A higher than room temperature and held at the predetermined temperature A for a predetermined time of less than 30 minutes; and a cooling process for cooling to (B ⁇ A).
- the press-molding method shortens the time required for the shape of the press-molded product to change over time after the press-molded product springs back at the moment it is released from the mold.
- the press-molding method shortens the time required for the shape of the press-molded product to change over time after springback occurs at the moment the press-molded product is released from the mold.
- the press-molding method shortens the time required for the shape of the press-molded product to change over time after springback occurs at the moment the press-molded product is released from the mold.
- a press-molding step of press-molding a metal plate into the press-molded product using the mold, a mold-releasing step of releasing the press-molded press-molded product from the mold, and the mold-releasing step A post-release heating and holding step of heating the press-molded product to a predetermined temperature A higher than room temperature and maintaining it at the predetermined temperature A for a predetermined time of less than 30 minutes; and a cooling step of cooling to A).
- the predetermined temperature A should be 130°C to 150°C, and the predetermined time should be 1 minute or more and 3 minutes or less.
- a method for evaluating the shape of a press-formed product evaluates the shape of a press-formed product that is assembled with other parts after being press-formed.
- a shape determination process shape determination process
- the predetermined temperature A should be 130°C to 150°C, and the predetermined time should be 1 minute or more and 3 minutes or less.
- the time for relaxation of the residual stress in the press-formed product can be shortened compared to the relaxation of the residual stress in the press-formed product only at room temperature. It is possible to shorten the time required for the shape change associated with the molding, and further reduce the shape change after the mold is released again.
- the present invention it is possible to shorten the time required for the shape of the press-formed product to change over time, and efficiently avoid problems in the next process.
- the time constraints in the process can be relaxed, so the productivity of the production and assembly of press-formed products can be improved.
- FIG. 1 is a flow diagram showing the flow of each step of the press molding method according to Embodiment 1 of the present invention.
- FIG. 2 shows an example of the results of measurement of the change over time in the amount of change X k in the wall opening of the vertical wall portion of the press-formed product immediately after springback.
- FIG. 3 shows the result of obtaining the necessary holding time at the predetermined temperature A for the change in the wall opening at room temperature ( ⁇ ) when the press-molded product is heated to the predetermined temperature A ( ⁇ ). is an example.
- FIG. 4 shows the heating time to each predetermined temperature A, the holding time required to sufficiently change the shape at each predetermined temperature A, and cooling time from each predetermined temperature A to room temperature (25° C.).
- FIG. 5 is a flow diagram showing the flow of each step of the press molding method according to another aspect of Embodiment 1 of the present invention.
- FIG. 6 is a flow diagram showing the flow of each step of the press molding method according to Embodiment 2 of the present invention.
- FIG. 7 is a flow diagram showing the flow of each step of the press molding method according to Embodiment 3 of the present invention.
- FIG. 8 is a flow chart showing the flow of each step of the method for evaluating the shape of a press-formed product according to Embodiment 4 of the present invention.
- FIG. 6 is a flow diagram showing the flow of each step of the press molding method according to Embodiment 2 of the present invention.
- FIG. 7 is a flow diagram showing the flow of each step of the press molding method according to Embodiment 3 of the present invention.
- FIG. 8 is a flow chart showing the flow of each step of the method for evaluating the shape of a press-formed product according to Embodiment 4 of the present invention.
- FIG. 9 is a diagram showing a press-formed article having a hat cross-sectional shape targeted in Embodiments 1 to 4 and Examples of the present invention ((a) perspective view, (b) molded bottom dead center shape, shape immediately after springback and shape after the elapse of time).
- the inventors established a method for shortening the time required for the shape change over time of the press-formed product that has been released from the mold and spring back. ), various investigations were carried out on the cause of the change in shape with the lapse of time, targeting the press-formed product 1 having a hat cross-sectional shape shown in FIG.
- the inventors paid attention to the stress relaxation phenomenon in which the stress gradually relaxes and decreases with the passage of time. It was found that the shape of the press-formed product 1 changed so as to balance the moment of the force by gradually relaxing without receiving any external force over time.
- the inventors focused on temperature and studied the effect of temperature on the phenomenon that the residual stress in the press-formed product after springback gradually relaxes over time without receiving external force. rice field.
- a press-formed product 1 having a hat cross-sectional shape as shown in FIG. 9A is used as an example. 3 was locally heated to 50°C, 150°C or 200°C, and the shape change over time of the press-formed product 1 was determined. Compared with shape change.
- the wall opening of the vertical wall portion 4 is targeted, and as shown in FIG.
- the amount of change in the width direction at the position of the distance H s from the top portion 2 in the press forming direction in the vertical wall portion 4 of the product 1 is defined as the amount of change in the wall opening of the vertical wall portion X k It was measured.
- FIG. 2 shows the measurement results of the amount of change X k in the wall opening of the vertical wall portion 4 from immediately after springback after releasing the mold until two days have passed.
- the amount of change X k immediately after releasing the mold and springing back was 0.05 mm, and the press-formed product 1 was left at room temperature (25°C) without heating.
- the amount of change X k increased at , reaching 0.75 mm after 30 minutes. After that, the amount of change X k gradually increased with the lapse of time, reaching 0.83 mm after two days, and became almost constant.
- the shape change of the press-formed product is more pronounced than when the shape is changed at room temperature (25°C) without heating. occurred in a short time. Furthermore, it was found that the higher the heating temperature, the shorter the shape change occurred.
- the required holding time to reach the amount of change X k when left at room temperature (25°C) for 30 minutes becomes shorter as the heating temperature rises, falling below 5 minutes at 120°C. , it began to saturate around 150°C, and was less than 1 minute above 150°C.
- the heating time for heating the press-formed product to a predetermined temperature A and the cooling from the predetermined temperature A to room temperature (25 ° C) are required.
- the cooling time for heating becomes longer as the predetermined heating temperature A is higher.
- FIG. 4 as an example, when a press-formed product 1 using a steel plate with a thickness of 1.5 mm as a metal plate is charged into a high-temperature furnace with an ambient temperature of 250 ° C and heated, up to each predetermined temperature A , the holding time required for shape change at each predetermined temperature A, and the cooling time from each predetermined temperature A to room temperature (25°C).
- the retention time at each predetermined temperature A was given from the results shown in FIG.
- heating time and cooling time from FIG. It has been found that the preferred range of the predetermined temperature that minimizes the required time (heating time + holding time + cooling time) is 130°C to 150°C.
- the holding time in the predetermined temperature A range of 130°C to 150°C is the longest at 3 minutes at 130°C and the shortest at 150°C for 1 minute. It was found that holding at temperature A for 1 minute or more and 3 minutes or less yields the same shape change as when left at room temperature (25° C.) for 30 minutes or more.
- Embodiments 1 to 4 a hat cross-sectional shape having a top plate portion 2, a vertical wall portion 4, and a flange portion 6 as shown in FIG. 9 as an example, As bend ridges, a shoulder part of a punch 3 connecting the top plate 2 and the vertical wall 4, and a flange portion 6 of the vertical wall 4 and the flange portion 6 A press-formed product 1 having a connecting die shoulder R portion 5 will be described as an example.
- the press-molding method according to Embodiment 1 of the present invention shortens the time required for the shape change over time of the press-molded product 1 (FIG. 9) that springs back at the moment it is released from the mold. , includes a press molding step S1, a mold releasing step S3, a mold fitting step after releasing the mold S5, a heating and holding step S7, and a cooling step S9, as shown in FIG.
- the press-molding step S1 is a step of press-molding a metal plate into a press-molded product 1 using a mold.
- the mold used in the press molding step S1 is not particularly limited as long as it includes a die and a punch, for example, and the die can be relatively moved to the punch side to the bottom dead center of the molding for press molding.
- the mold release step S3 is a step of releasing the press-molded product 1 press-molded in the press-molding step S1 from the mold.
- the press-formed product 1 released from the mold in the mold release step S3 springs back at the moment of release, and the wall opening of the vertical wall portion 4 occurs as indicated by the broken line in FIG. 9(b).
- the press-molded product 1 released from the mold in the mold-releasing step S3 is fitted into the mold used for press molding in the press-molding step S1, and the press-molded product 1 is molded under the mold.
- This is a step of fixing according to the point shape.
- the molding bottom dead center shape refers to the shape of the press-molded product 1 at the molding bottom dead center of the mold used in the press molding step S1 (the same applies hereinafter).
- the heating and holding step S7 is a step of heating the press-molded product 1 fitted in the mold to a predetermined temperature A higher than room temperature and holding it at the predetermined temperature A for a predetermined time of less than 30 minutes.
- the predetermined temperature A for heating the press-molded product 1 is set to 130° C. to 150° C.
- the predetermined time is set to 1 minute or more and 3 minutes or less. is preferred.
- the means for heating the press-formed product 1 in the heating and holding step S7 is not particularly limited. Alternatively, it may be a means for heating the press-molded product 1 fixed to the mold using high frequency induction heating.
- the cooling step S9 is a step of cooling the press-formed product 1 heated and held at the predetermined temperature A in the heating and holding step S7 to room temperature. It should be noted that the temperature of the press-formed product 1 after cooling is not limited to room temperature, and may be set to a predetermined temperature B (B ⁇ A) lower than the predetermined temperature A to be heated.
- the cooling method in the cooling step S9 may be either natural air cooling or forced air cooling that actively ventilates with a cooling fan or the like, but forced air cooling can shorten the cooling time. preferable.
- the press-molded product 1 which springs back at the moment of releasing the mold, is fitted into the mold and fixed in the shape of the bottom dead center of the molding, and the temperature rises at a predetermined temperature higher than room temperature.
- the residual stress in the press-formed product 1 can be relaxed in a shorter time than at room temperature.
- the press-molded product 1 that is fitted in the mold and held under heat is released again from the mold and springs back, and the change in shape over time is reduced. can do.
- the entire press-formed product 1 is formed into a bottom dead center shape using the mold used for press-molding the press-formed product 1. It was fixed to However, as another aspect of the press molding method according to the first embodiment, instead of the post-mold-releasing mold fitting step S5 and the heating and holding step S7, as shown in FIG. and a heating and holding step S13 may be included.
- a predetermined predetermined shape for example, a target shape (shape defined as a product) of the press molded product 1, or a spring back from the bottom dead center of the molding
- a target shape shape defined as a product
- An intermediate shape between the bottom dead center shape and the target shape, such as the later shape, may be used.
- the shape after springback may be predicted by measuring or calculating the shape of the press-formed product 1 after releasing and springing back. In this case, all or part of the released press-formed product 1 is fitted into a jig capable of retaining the same shape as the shape after releasing and springing back, and all or part of the press-formed product 1 is removed as described above. Fix according to the shape after springback.
- holding the press-formed product 1 in a predetermined shape using a jig may use a jig that holds the entire press-formed product 1 in a predetermined shape, a part of the press-formed product 1, For example, a jig that holds only the punch shoulder R portion 3 in a predetermined shape may be used.
- the press-molded product 1 fitted in the jig in the post-mold jig fitting step S11 is heated to a predetermined temperature A higher than room temperature, and held at the predetermined temperature A for a predetermined time of less than 30 minutes. It is a process to do.
- the predetermined temperature A for heating the press-formed product 1 is set to 130° C. to 150° C.
- the predetermined time is set to 1 minute or more and 3 minutes or less. is preferred.
- the press-molding step S21 and the mold-releasing step S23 are the same as the press-molding step S1 and the mold-releasing step S3 of the first embodiment described above, the description thereof is omitted here.
- the heating and holding step S25 and the cooling step S27 will be described.
- the post-mold heating and holding step S25 is a step of heating the press-molded product 1 released from the mold in the releasing step S23 to a predetermined temperature A higher than room temperature, and holding at the predetermined temperature A for a predetermined time of less than 30 minutes.
- the shape of the press-formed product 1 can be changed by holding at a predetermined temperature A for a predetermined time.
- the predetermined temperature A in the post-release heating and holding step S25 is preferably in the range of 130°C to 150°C, and the predetermined time is preferably 1 minute or more and 3 minutes or less.
- the cooling step S27 is a step of cooling the press-formed product 1, which has been heated and held at the predetermined temperature A for a predetermined time in the post-mold heating and holding step S25, to room temperature.
- the cooling method in the cooling step S27 may be either natural air cooling or forced air cooling by actively ventilating with a cooling blower or the like, but forced air cooling is preferred because it can shorten the cooling time.
- the temperature of the press-formed product after cooling may be set to a predetermined temperature B (B ⁇ A) lower than the predetermined temperature A to be heated, regardless of the room temperature.
- the press-molded product 1 is heated to a predetermined temperature A higher than room temperature and held for a predetermined time.
- the change in shape due to stress relaxation associated with this can occur in a shorter period of time than at room temperature.
- ⁇ Pre-release heating and holding step> In the pre-mold release heating and holding step S33, after the press-molded product 1 is press-molded using the mold in the press-molding step S31, the mold is heated to a predetermined temperature A higher than room temperature at the bottom dead center position of the molding without releasing the mold from the mold. and holding at the predetermined temperature A for a predetermined time of less than 30 minutes.
- the cooling step S35 is a step of cooling the press-formed product 1 heated and held in the pre-release heating and holding step S33 to room temperature.
- the press-molded product 1 is cooled together with the mold for fixing the bottom dead center shape.
- the temperature of the press-formed product 1 after cooling may be set to a predetermined temperature B (B ⁇ A) lower than the predetermined temperature A to be heated, regardless of the room temperature.
- the mold release step S37 is a step of releasing the press-formed product 1 cooled in the cooling step S35 from the mold.
- the press-molded product press-molded to the bottom dead point is fixed in the shape of the bottom dead center without being released from the mold, and the predetermined temperature A higher than room temperature and hold for a specified time of less than 30 minutes.
- the residual stress of the press-formed product can be alleviated even if the holding time in the mold is shortened compared to when it is held in the mold at room temperature, and the product springs back when released from the mold. Later shape changes over time can be sufficiently reduced.
- Embodiment 4 In the method for evaluating the shape of a press-formed product according to Embodiment 4 of the present invention, as an example, the shape of a press-formed product 1 that is assembled with other parts after being press-formed, as shown in FIG. This evaluation is performed before the molded product is assembled and processed, and as shown in FIG. It includes a measurement step S49 and a shape determination step S51.
- the press-molding step S41 and the mold-releasing step S43 are the same as the press-molding step S1 and the mold-releasing step S3 in Embodiment 1 described above, and the post-mold-releasing heating and holding step S45 and the cooling step S47 are the same as those in the above-described embodiment. Since it is the same as the post-mold release heating and holding step S25 and the cooling step S27 of Embodiment 2, the shape measuring step S49 and the shape determining step S51 will be described below.
- the shape measurement step S49 is a step of measuring the shape of the press-formed product 1 after cooling in the cooling step S47.
- the reason why the press-formed product 1 is heated and held at the predetermined temperature A for the predetermined time to change the shape and then the shape is measured is that by heating the press-formed product 1 to a predetermined temperature A higher than room temperature, residual This is because the stress is relaxed in a shorter time than at room temperature, and the shape change due to the stress relaxation is caused quickly.
- the shape determination step S51 is a step for determining that the press-formed product 1 is to be assembled if the shape of the press-formed product 1 measured in the shape measurement step S49 is within a predetermined range.
- the predetermined range set in advance in the shape determination step S51 may be appropriately set within a range that does not cause any problems in the assembly process with other parts.
- the press-formed press-formed product 1 is released from the mold, heated to a predetermined temperature A higher than room temperature, and held for a predetermined time, After allowing the shape change due to stress relaxation with the passage of time to be sufficient in a short time from room temperature, it is cooled to a predetermined temperature B (B ⁇ A) and the shape is measured, and the shape of the measured press-formed product 1 is preliminarily If it is within the set predetermined range, it is judged to be supplied to the next step. As a result, it is possible to relax time restrictions in the process, and furthermore, it is possible to prevent problems from occurring in the next process due to shape change in the press-formed product 1 between press-molding and assembly processing. can.
- the press molding method and the method for evaluating the shape of the press-formed product according to the present invention do not particularly limit the shape and type of the metal plate used as the blank or the press-formed product, and the residual stress of the press-formed product is high. It is more effective for automobile parts press-formed using a metal plate of
- the blank has a tensile strength of 440 to 1470 MPa class (MPa-class).
- a metal plate having a tensile strength of less than 440 MPa class has a low residual stress inside the press-formed product, so that the effect of change over time is relatively small.
- parts with low rigidity such as automotive outer panels are susceptible to shape changes due to changes in residual stress. The invention should be applied.
- the metal plate exceeding the 1470 MPa class has poor ductility. In some cases, a fracture may occur at the die shoulder part R (shoulder part of a die) 5, and press molding may not be possible.
- the present invention is not limited to the press-formed product 1 having a hat cross-sectional shape as shown in FIG.
- the present invention is used for press-formed products with a shape having a portion with high residual stress, such as press-formed products with U-shaped cross section, U-shaped cross section, or L-shaped cross section. can be preferably applied.
- Types of press-formed products include outer panel parts such as doors, roofs, and hoods with low rigidity, A pillars and B pillars that use high-strength metal plates, roof rails, side rails, and front side members.
- the present invention is preferably applied to automobile parts such as body frame parts such as rear side members, cross members and the like.
- a press-formed product 1 having a hat cross-sectional shape with The bottom dead center shape of the press-formed product 1 is as follows: the width L T of the top plate portion 2 is 50 mm, the forming height H is 50 mm, the inclination angle ⁇ v of the vertical wall portion 4 is 3°, and the The radius and bending angle were set to 5 mm and 95°, and the curvature radius R and bending angle of the die shoulder R portion 5 were set to 5 mm and 95°.
- the case where the press-formed product 1 that has been released from the mold and springs back is returned to the mold and held at a predetermined temperature A for a predetermined time in the shape of the bottom dead center of the molding, and press-molding to the bottom dead center of the molding.
- Shape change was measured.
- the press-formed product 1 press-formed to the bottom dead center of the molding is released without being held in the mold, and as a comparative example, the press-formed product 1 that is released and springs back.
- the press-formed product 1 that is released and springs back.
- Table 2 shows the wall opening of the vertical wall portion 4 immediately after press-molding of the press-molded product 1 (immediately after releasing and springing back) and at each elapsed time after releasing from the mold after holding in the mold for a predetermined time.
- the results of measuring the amount of change X k are shown.
- the amount of change X k shown in Table 2 is based on the shape of the press-formed product 1 immediately after being released from the mold and springing back.
- the press-molded product 1 press-molded to the bottom dead center is released from the mold and left at room temperature.
- the amount of change X k of the vertical wall portion 4 was 1.7 mm two days after press molding (immediately after releasing and springing back).
- Comparative Example 1 the press-formed product 1 that was first released and springed back was returned to the mold, held at room temperature, released again, and the press-formed product 1 was returned to the mold repeatedly. It is a thing.
- the pressed product 1 that was first released and spring-backed was returned to the mold, heated to 150 ° C. in 6 minutes in a furnace, held at 150 ° C. for 1 minute, and then removed from the furnace. After cooling to room temperature for 8 minutes, the press-molded product 1 was returned to the mold, and heating, holding, and cooling were repeated.
- the amount of change X k of the vertical wall portion 4 was 0.3 mm 15 minutes after the mold was first released, and 0.5 mm 30 minutes after the first release, and was almost constant.
- the time required after the first release from the mold until the change amount X k of the wall opening becomes 0.3 mm and 0.5 mm is as short as 15 minutes and 30 minutes, respectively, in Invention Example 1, In Comparative Example 1, it was longer, 30 minutes and 2 days, respectively. From this, the press-formed product 1 that has been released and spring-backed is returned to the mold, heated to a predetermined temperature A, and held for a predetermined time of less than 30 minutes. It was shown that it is possible to cause the shape change associated with
- Table 3 shows the results of measuring the amount of change X k in the wall opening after the press-formed product 1 press-formed to the bottom dead center was held in the mold for a predetermined time and then released from the mold.
- the amount of change X k shown in Table 3 is based on the shape of the press-formed product 1 after springback from the bottom dead center of the forming.
- Comparative Example 2 After being press-molded, it was held in a mold at room temperature (25° C.) and then released from the mold.
- the amount of change X k is 0.3 mm immediately after being held in the mold for 15 minutes and immediately after being released from the mold.
- the amount of change X k in Invention Example 2 was 0.6 mm immediately after heating, holding and cooling in the mold for 15 minutes and then releasing the mold, and then returned to the mold again and heating, holding and cooling for another 15 minutes (metal The total retention time in the mold is 30 minutes), and immediately after releasing from the mold, it is 1.0 mm, and it is returned to the mold again, and finally after being held in the mold at room temperature for 2 days, The amount of change was constant at 1.0 mm.
- the time required for the shape change of the press-formed product with the lapse of time after springback after press-forming is shortened, and the shape change of the press-formed product with the lapse of time after springback is reduced.
- a press-formed product shape evaluation method for evaluating the shape of the press-formed product by shortening the time required for the shape change of the press-formed product before it is assembled with other parts in the next process. can do.
Abstract
Description
本発明の実施の形態1に係るプレス成形方法は、金型から離型した瞬間にスプリングバックしたプレス成形品1(図9)の時間経過に伴う形状変化に要する時間を短縮するものであって、図1に示すように、プレス成形工程S1と、離型工程S3と、離型後金型嵌め込み工程S5と、加熱保持工程S7と、冷却工程S9と、を含む。
プレス成形工程S1は、金型を用いて、金属板をプレス成形品1にプレス成形する工程である。プレス成形工程S1で用いる金型は、例えば、ダイとパンチ(punch)とを備え、ダイをパンチ側に成形下死点まで相対移動させてプレス成形できるものであれば、特に限定はない。
離型工程S3は、プレス成形工程S1においてプレス成形したプレス成形品1を金型から離型する工程である。離型工程S3において金型から離型したプレス成形品1は、離型した瞬間にスプリングバックし、図9(b)の破線に示すような、縦壁部4の壁開きが生じる。
離型後金型嵌め込み工程S5は、離型工程S3において金型から離型したプレス成形品1を、プレス成形工程S1においてプレス成形に用いた金型に嵌め込み、プレス成形品1を成形下死点形状に合わせて固定する工程である。ここで、成形下死点形状とは、プレス成形工程S1で用いた金型の成形下死点におけるプレス成形品1の形状のことをいう(以下、同じ)。
加熱保持工程S7は、金型に嵌め込みしたプレス成形品1を、室温よりも高い所定温度Aまで加熱し、所定温度Aで30分間未満の所定時間保持する工程である。
冷却工程S9は、加熱保持工程S7において所定温度Aで加熱保持したプレス成形品1を室温まで冷却する工程である。なお、冷却後のプレス成形品1の温度は室温にこだわらず、前記の加熱する所定温度Aより低い所定温度B(B<A)とするとよい。冷却工程S9における冷却方式は、自然空冷(natural air cooling)でも、冷却ファン等により積極的に通風させる強制空冷(forced air cooling)のいずれでもよいが、強制空冷の方が冷却時間を短縮できるので好ましい。
離型後治具嵌め込み工程S11は、離型工程S3において離型したプレス成形品1の全部又は一部を、プレス成形工程で用いた金型と同じ形状とする、別の金型を含め予め定めた所定の形状に保持可能な治具に嵌め込み、プレス成形品1の全部又は一部を該所定の形状に合わせて固定する工程である。
加熱保持工程S13は、離型後治具嵌め込み工程S11において治具に嵌め込んだプレス成形品1を、室温よりも高い所定温度Aまで加熱し、該所定温度Aで30分間未満の所定時間保持する工程である。
本発明の実施の形態2に係るプレス成形方法は、一例として図9(a)に示すようなプレス成形品1を金型から離型した瞬間にスプリングバックした後におけるプレス成形品1の時間経過に伴う形状変化に要する時間を短縮するものであって、図6に示すように、プレス成形工程S21と、離型工程S23と、離型後加熱保持工程S25と、冷却工程S27と、を含む。ここで、プレス成形工程S21及び離型工程S23は、前述した実施の形態1のプレス成形工程S1及び離型工程S3と同様であるため、ここではこれらの説明は割愛し、以下、離型後加熱保持工程S25及び冷却工程S27について説明する。
離型後加熱保持工程S25は、離型工程S23において離型したプレス成形品1を室温よりも高い所定温度Aまで加熱し、該所定温度Aで30分間未満の所定時間保持する工程である。
冷却工程S27は、離型後加熱保持工程S25において加熱して所定温度Aで所定時間保持したプレス成形品1を室温まで冷却する工程である。冷却工程S27における冷却方式は、自然空冷でも、冷却ファン(cooling blower)等により積極的に通風させる強制空冷のいずれでもよいが、強制空冷の方が冷却時間を短縮できるので好ましい。なお、冷却後のプレス成形品の温度は、室温にこだわらず、前記の加熱する所定温度Aより低い所定温度B(B<A)とすればよい。
本発明の実施の形態3に係るプレス成形方法は、一例として図9(a)に示すようなプレス成形品1を金型から離型した瞬間にスプリングバックした後におけるプレス成形品1の時間経過に伴う形状変化に要する時間を短縮するものであって、図7に示すように、プレス成形工程S31と、離型前加熱保持工程S33と、冷却工程S35と、離型工程S37と、を含む。なお、プレス成形工程S31は、前述した実施の形態1のプレス成形工程S1、と同様であるため、以下、離型前加熱保持工程S33、冷却工程S35及び離型工程S37と、について説明する。
離型前加熱保持工程S33は、プレス成形工程S31において金型を用いてプレス成形品1をプレス成形した後、金型から離型せずに成形下死点位置で室温よりも高い所定温度Aに加熱し、該所定温度Aで30分間未満の所定時間保持する工程である。
冷却工程S35は、離型前加熱保持工程S33において加熱保持したプレス成形品1を、室温まで冷却する工程である。冷却工程S35においては、プレス成形品1を成形下死点形状に固定する金型ごと冷却する。なお、冷却後のプレス成形品1の温度は、室温にこだわらず、前記の加熱する所定温度Aより低い所定温度B(B<A)とすればよい。
離型工程S37は、冷却工程S35において冷却したプレス成形品1を金型から離型する工程である。
本発明の実施の形態4に係るプレス成形品の形状評価方法は、一例として図9(a)に示したような、プレス成形した後に他部品と組み立て加工されるプレス成形品1の形状をプレス成形品の組み立て加工に供する前に評価するものであって、図8に示すように、プレス成形工程S41と、離型工程S43と、離型後加熱保持工程S45と、冷却工程S47と、形状測定工程S49と、形状判定工程S51と、を含む。
形状測定工程S49は、冷却工程S47において冷却した後のプレス成形品1の形状を測定する工程である。
形状判定工程S51は、形状測定工程S49において測定したプレス成形品1の形状が予め設定した所定の範囲内であれば、プレス成形品1を組み立て加工に供すると判定する工程である。
2 天板部
3 パンチ肩R部
4 縦壁部
5 ダイ肩R部
6 フランジ部
Claims (7)
- プレス成形品を金型から離型した瞬間にスプリングバックした後における前記プレス成形品の時間経過に伴う形状変化に要する時間を短縮するプレス成形方法であって、
前記金型を用いて、金属板を前記プレス成形品にプレス成形するプレス成形工程と、
プレス成形した前記プレス成形品を前記金型から離型する離型工程と、
離型した前記プレス成形品を前記金型に嵌め込み、該プレス成形品を成形下死点形状に合わせて固定する離型後金型嵌め込み工程と、
前記金型に嵌め込みした前記プレス成形品を、室温よりも高い所定温度Aまで加熱し、該所定温度Aで30分間未満の所定時間保持する加熱保持工程と、
加熱保持した前記プレス成形品を所定温度B(B<A)まで冷却する冷却工程と、
を含む、プレス成形方法。 - プレス成形品を金型から離型した瞬間にスプリングバックした後における前記プレス成形品の時間経過に伴う形状変化に要する時間を短縮するプレス成形方法であって、
前記金型を用いて、金属板を前記プレス成形品にプレス成形するプレス成形工程と、
該プレス成形したプレス成形品を前記金型から離型する離型工程と、
該離型したプレス成形品の全部又は一部を、前記金型と同じ形状の別の金型を含め、予め定めた所定の形状に保持可能な治具に嵌め込み、該プレス成形品の全部又は一部を該所定の形状に合わせて固定する離型後治具嵌め込み工程と、
該治具に嵌め込んだプレス成形品を、室温よりも高い所定温度Aまで加熱し、該所定温度Aで30分間未満の所定時間保持する加熱保持工程と、
該加熱保持したプレス成形品を所定温度B(B<A)まで冷却する冷却工程と、
を含む、プレス成形方法。 - プレス成形品を金型から離型した瞬間にスプリングバックした後における前記プレス成形品の時間経過に伴う形状変化に要する時間を短縮するプレス成形方法であって、
前記金型を用いて、金属板を前記プレス成形品にプレス成形するプレス成形工程と、
該プレス成形したプレス成形品を前記金型から離型する離型工程と、
該離型しスプリングバックした後の形状を測定または計算により予測し、前記離型したプレス成形品の全部又は一部を、前記離型しスプリングバックした後の形状と同じ形状に保持可能な治具に嵌め込み、該プレス成形品の全部又は一部を前記スプリングバックした後の形状に合わせて固定する離型後治具嵌め込み工程と、
該治具に嵌め込んだプレス成形品を、室温よりも高い所定温度Aまで加熱し、該所定温度Aで30分間未満の所定時間保持する加熱保持工程と、
該加熱保持したプレス成形品を所定温度B(B<A)まで冷却する冷却工程と、
を含む、プレス成形方法。 - プレス成形品を金型から離型した瞬間にスプリングバックした後における前記プレス成形品の時間経過に伴う形状変化に要する時間を短縮するプレス成形方法であって、
前記金型を用いて、金属板を前記プレス成形品にプレス成形するプレス成形工程と、
該プレス成形したプレス成形品を前記金型から離型する離型工程と、
該離型したプレス成形品を室温よりも高い所定温度Aまで加熱し、該所定温度Aで30分間未満の所定時間保持する離型後加熱保持工程と、
該加熱保持したプレス成形品を所定温度B(B<A)まで冷却する冷却工程と、
を含む、プレス成形方法。 - 前記所定温度Aを130℃~150℃とし、かつ、前記所定時間を1分間以上3分間以下とすることを特徴とする請求項1乃至4のうち、いずれか一項に記載のプレス成形方法。
- プレス成形した後に他部品と組み立て加工されるプレス成形品の形状を評価するプレス成形品の形状評価方法であって、
金型を用いて、金属板を前記プレス成形品にプレスするプレス成形工程と、
該プレス成形したプレス成形品を前記金型から離型する離型工程と、
該離型したプレス成形品を室温よりも高い所定温度Aまで加熱し、該所定温度Aで30分間未満の所定時間保持する離型後加熱保持工程と、
該加熱保持したプレス成形品を所定温度B(B<A)まで冷却する冷却工程と、
該冷却後のプレス成形品の形状を測定する形状測定工程と、
該測定したプレス成形品の形状が予め設定した所定の範囲内であれば、該プレス成形品を前記組み立て加工に供すると判定する形状判定工程と、
を含む、プレス成形品の形状評価方法。 - 前記所定温度Aを130℃~150℃とし、かつ、前記所定時間を1分間以上3分間以下とすることを特徴とする請求項6に記載のプレス成形品の形状評価方法。
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