EP4444485A1

EP4444485A1 - Hot stamping system and method

Info

Publication number: EP4444485A1
Application number: EP22902555.6A
Authority: EP
Inventors: Kyle Daniel FAIRBARN; David Camil POLSONI
Original assignee: Magna International Inc
Current assignee: Magna International Inc
Priority date: 2021-12-08
Filing date: 2022-12-02
Publication date: 2024-10-16
Also published as: CN118369169A; EP4444485A4; US20250033106A1; WO2023102648A1

Abstract

A method and system for hot stamping components. The method includes forming at least one weld nugget on at least on blank. The method also includes forming at least one pocket in at least one die segment of a die. The method also includes positioning the blank in alignment with the at least one die segment with the at least one weld nugget aligned with the at least one pocket. The method also includes stamping the at least one blank with the at least one die segment, with the at least one weld nugget received in the at least one pocket of the at least one die segment

Description

HOT STAMPING SYSTEM AND METHOD

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This PCT International Patent Application claims the benefit of and priority to U.S. Provisional Patent Application Serial No. 63/287,311, filed on December 8, 2021, and titled “Hot Stamping System and Method,” the entire disclosure of which is hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present disclosure relates to a hot stamping system for forming components from blanks of steel.

BACKGROUND

[0003] Hot stamping, also known as press hardening or hot press forming, is a process of forming blanks, such as those made of ultra-high strength steels, into various shapes. Hot stamped components are used in various industries, such as the automotive industry, for their reduced weight and high rigidity characteristics. According to a conventional hot stamping process, an unformed blank of steel is first heated in a furnace, then shaped in a die while in its hot condition, and then quenched in the die to provide high strength properties.

[0004] An issue with conventional hot stamping systems is that areas of increased thickness on the blanks, such as along spot weld nuggets, can cause die segments to crack and can lead to increased quench times. Accordingly, there remains a need for improvements to hot stamping systems.

SUMMARY OF THE INVENTION

[0005] According to an aspect of the disclosure, a method for hot stamping components includes forming at least one weld nugget on at least one blank. The method also includes forming at least one pocket in at least one die segment of a die. The method also includes positioning the blank in alignment with the at least one die segment with the at least one weld nugget aligned with the at least one pocket. The method also includes stamping the at least one blank with the at least one die segment, with the at least one weld nugget received in the at least one pocket of the at least one die segment.

[0006] According to another aspect of the disclosure, a system for hot stamping components is provided. The system includes at least one die segment. The system also includes a blank for being positioned in alignment with the at least one die segment and for undergoing a stamping operation via engagement with the at least one die segment. The blank presents at least one weld nugget. The at least one die defines at least one pocket in alignment with the at least one weld nugget of the at least one blank such that the at least one weld nugget is received by the at least one pocket during stamping of the blank with the at least one die segment.

[0007] Because the at least one weld nugget is received in the at least one pocket of the at least one die segment, the blanks are advantageously able to be formed and quenched completely to achieve full martensitic properties without an excessive quench time and without applying excessive localized pressure into the die segments at the spot weld nuggets, thereby preventing cracking of the die segments. This occurs without compromising stamping quality.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0009] FIG. l is a schematic diagram of a system for hot stamping; [0010] FIG. 2 is a perspective view of a first example die component including a plurality of pockets for receiving weld nuggets on blanks;

[0011] FIG. 3 is a perspective view of a first example blank including a plurality of weld nuggets;

[0012] FIG. 4 is a perspective view of a second example blank including a plurality of weld nuggets; and

[0013] FIG. 5 is a flow diagram illustrating a method of hot stamping components in accordance with an aspect of the disclosure.

DESCRIPTION OF THE ENABLING EMBODIMENT

[0014] Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a system 10 for hot stamping blanks 12 into components is provided. The system 10 may be used to form various types of components of various shapes, such as automotive components including body pillars, roof rails, rockers, bumpers, and door intrusion beams.

[0015] The system 10 includes one or more blanks 12 that are ultimately formed into the final component. The term “blank” as used herein may include two or more blank segments 12 A, 12B that are connected to one another, such as via a weld. The blank 12 segments may have various shapes and sizes, and may be connected to one another at various locations. The blanks 12 may be of various materials including, but not limited to, ultra-high strength steels such as 22MnB5 boron steel. Prior to hot forming, the blanks 12 may undergo various cold-forming processes, such as trimming and stamping. According to the example embodiment, the blanks 12 undergo at least one welding processes, such as a spot welding process, to secure multiple blank segments 12 A, 12B to one another, thus resulting in one or more weld nuggets 14 on the one or more blanks 12. It should be appreciated that the weld nuggets 14 could be formed via other types of welding processes. FIGS. 1, 3 and 4 illustrate examples of blanks 12 including a plurality of protruding weld nuggets 14. As shown in FIG. 1, the blanks 12 may each include a first side 15 and a second side 17. As illustrated, the first side 15 may be located along a top region of the blank 12 while the bottom side 17 may be located along a bottom region of the blank 12. As shown, the weld nuggets 14 may include any number of first weld nuggets 14A along the first side of the blank 12, and any number of second weld nuggets 14B along the second side of the blank 12. It should be appreciated the weld nuggets 14 can be located along any region of the blank 12 including, but not limited to, top, bottom, sides of the blank 12, and may be located on both flat or angled / irregular surfaces. As part of the process, weld nuggets 14 on sidewalls of the blanks 12 may be tapered out to avoid any die-lock conditions or back draft during stamping.

[0016] As shown in FIG. 1A, the system 10 further includes a furnace 16 for heating the blanks 12 prior to and/or during stamping. More particularly, according to the example embodiment, the blanks 12 are heated to a high temperature, e.g., exceeding 900 degrees Celsius, to allow subsequent forming in a die 18. Other temperatures may be used based on specific needs. The furnace 16 may be separate from, or may be part of the surrounding structure of the die 18, thus allowing heating of the blanks 12 while they are outside of, or inside the die 18. The die 18 may consist of at least an upper die segment 20 and a lower die segment 22 that are configured to move toward and away from one another in order to stamp the blanks 12 to shape the blanks 12 into their resulting component. It should be appreciated that the die 18 could include any number of segments that are arranged in various manners, e.g., they could close in on one another in a horizontal or angled direction. After stamping, the blanks 12 are quenched to rapidly cool the material to provide desired properties.

[0017] Prior to stamping the blanks 12, one or more pockets 24 are milled or otherwise formed into at least one of the upper and lower die segments 20, 22. FIGS. IB and 2 illustrate examples of die segments 20, 22 including a plurality of pockets 24. The pockets 24 are formed at locations that are aligned with the one or more spot weld nuggets 14 on the blanks 12 when the blanks 12 are received in the die 18 in order to allow the spot weld nuggets 14 to be received in the pockets 24 during the stamping process when the upper and lower die segments 20, 22 are moved toward one another. The diameter, depth and locations of the pockets 24 are selected to provide adequate clearance without compromising surrounding surface area contact. For example, according to the example embodiment, the pockets 24 are defined in alignment with the weld nuggets 13 in a horizontal direction and spaced vertically in a manner such that when the upper and lower die segments 20, 22 are brought toward one another, the weld nuggets 13 are received by the pockets 24. According to the example embodiment, the pockets 24 are dimensioned at between approximately 0.25 mm to 0.50 mm deep and between 7.00 mm to 15.00 mm in diameter. According to the example embodiment, the weld nuggets 14 and pockets 24 have a generally circular shaped cross-section, but could have other shapes without departing from the scope of the subject disclosure. The weld nuggets 14 are approximately the same size, but slightly smaller than the pockets 24 in both the width and height / depth dimensions such that they fit relatively snuggly in the pockets 24 during the stamping process, however, the pockets 24 could be any size as long as the weld nuggets 14 fit in the pockets 24. As illustrated in the example embodiment illustrated in FIG. IB, the pockets may include one or more first pockets 24A on the first die segment 20 and one or more second pockets 24B on the second die segment 22.

[0018] The locations of the pockets 24 and weld nuggets 14 may be determined based on computer aided drawing (CAD) data. More particularly, a control system 26 (schematically shown) may be programmed with electronic drawings of the blanks 12 and die segments 20, 22 prior to stamping. The drawings may include 3-dimensional coordinates of locations of the weld nuggets 14 and their associated pockets 24 on the die segments 20, 22. Furthermore, a milling machine or other appropriate fabricating device may be programmed to mill the pockets 24 in the upper and lower die segments 20, 22 at locations that correlate with the 3 -dimensional data. Likewise, the control system 26 may be configured to automatically or manually guide a welding device to locations of the blanks 12 where the weld nuggets 14 should be created. For example, an automatic welding arm or equivalent device may automatically create welds at the preprogrammed locations based on the CAD data, or the CAD data may be used to assist an operator to guide a welder to specific locations on the blanks 12.

[0019] As presented in FIG. 5, a method 100 for hot stamping components is provided. The method includes 102 forming at least one weld nugget 14 on at least one blank 12. For example, the blank 12 may be comprised of two blank segments 12A, 12B with a spot weld nugget 14 connecting the segments 12A, 12B. The method further includes 104 forming (e.g., milling or otherwise machining) at least one pocket 24 in at least one of the die segments 20, 22 of the die 18. The pockets 24 are located and sized for receiving the at least one spot weld nugget 14. The method further includes 106 heating the at least one blank 12 in a furnace 16. The furnace 16 may heat the at least one blank 12 while located outside of the die 18. In some circumstances, a furnace 15 may heat the dies 18 to delay cooling of the blanks 12 after being formed to provide desired characteristics. For example, this may occur in a Tailor Tempered Properties (TTP) scenario in which it is desired to prevent a phase transformation of pressure hardened steel from achieving martensite and instead ending up in a bainite grain structure which possesses a weaker strength than martensitic grain structure for final stamping. The method also includes 108 positioning the at least one blank 12 in alignment with the die segments 20, 22 with the weld nuggets 14 aligned with the pockets 24. The method further includes 110 stamping the at least one blank 12 in the die with the at least one spot weld nugget 14 received in the at least one pocket 24 of the at least one die segment 20, 22. Finally, the method includes 112 rapidly quenching the at least one blank 12 to provide strengthening characteristics to the resulting component.

[0020] In view of the foregoing, the pockets 24 advantageously allow the blanks 12 to be formed and quenched completely to achieve full martensitic properties without an excessive quench time and without applying excessive localized pressure into the die segments 20, 22 at the spot weld nuggets, thereby preventing cracking of the die segments 20, 22. The arrangement provides pressure point relief for swollen spot weld thickness without comprising stamping quality.

[0021] Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims. These antecedent recitations should be interpreted to cover any combination in which the inventive novelty exercises its utility. It should be appreciated that features of the various embodiments discussed herein may be combined with one another.

Claims

CLAIMS What is claimed is:

1. A method for hot stamping components, comprising: forming at least one weld nugget on at least one blank; forming at least one pocket in at least one die segment of a die; positioning the blank in alignment with the at least one die segment with the at least one weld nugget aligned with the at least one pocket; and stamping the at least one blank with the at least one die segment, with the at least one weld nugget received in the at least one pocket of the at least one die segment.

2. The method as set forth in claim 1, wherein the at least one weld nugget is substantially the same size as the at least one pocket.

3. The method as set forth in claim 2, wherein the at least one weld nugget has a height, the at least one pocket has a depth, and wherein the height of the at least one weld nugget is at least a size of the depth of the at least one pocket.

4. The method as set forth in claim 3, wherein the height of the at least one weld nugget is in the range of approximately 0.25 to 0.50 mm, and wherein the depth of the at least one pocket is in the range of approximately 0.25 to 0.50 mm deep.

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5. The method as set forth in claim 2, wherein the at least one weld nugget has a width, wherein the at least one pocket has a width, and wherein the width of the at least one weld pocket is at least a size of the width of the at least one weld nugget.

6. The method as set forth in claim 5, wherein the at least one weld nugget has a diameter in the range of approximately 7 to 15 mm, and wherein the at least one pocket has a diameter in the range of approximately 7 to 15 mm.

7. The method as set forth in claim 1, wherein the at least one die segment includes a first die segment and a second die segment overlying one another, and wherein the at least one blank is positioned between the first and second die segments.

8. The method as set forth in claim 7, wherein the at least one blank has a first side facing the first die segment and a second side facing the second die segment, wherein the at least one spot weld includes at least one first spot weld on the first side of the blank and at least one second spot weld on the second side of the blank, wherein the first die segment has at least one first pocket aligned with the at least one first spot weld for receiving the at least one first spot weld, and wherein the second die segment has at least one second pocket aligned with the at least one second spot weld for receiving the at least one second spot weld.

9. The method as set forth in claim 8, wherein the at least one first spot weld includes a plurality of first spot welds on the first side of the blank, the at least one second spot weld includes a plurality of second spot welds on the second side of the blank, wherein the at

9 least one first pocket includes a plurality of first pockets defined by the first die segment each for receiving one of the plurality of first spot welds, and wherein the at least one second pocket includes a plurality of second pockets defined by the second die segment each for receiving one of the plurality of second spot welds.

10. The method as set forth in claim 1, further including determining a location of the at least one pocket on the at least one die based on computer aided design data, and wherein forming the at least one pocket includes milling the at least one pocket into the at least one die at the determined location of the at least one pocket.

11. The method as set forth in claim 1, further including determining a location of the at least one weld nugget on the at least one blank based on computer aided design data, and wherein forming the at least one weld nugget includes spot welding the at least one weld nugget at the determined location of the at least one weld nugget.

12. The method as set forth in claim 1, wherein the at least one blank is made of a 22 MnB5 boron steel.

13. The method as set forth in claim 1, further including heating the at least one blank in a furnace prior to stamping the at least one blank in the die.

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14. The method as set forth in claim 13, wherein the at least one blank is heated to a temperature that exceeds 900 degrees Fahrenheit during the step of heating the at least one blank in the furnace.

15. The method as set forth in claim 1, further including cold forming the at least one blank prior to stamping the at least one blank.

16. The method as set forth in claim 1, further including quenching the at least one blank after stamping.

17. A system for hot stamping components, comprising: at least one die segment; a blank for being positioned in alignment with the at least one die segment and for undergoing a stamping operation via engagement with the at least one die segment; the blank presenting at least one weld nugget; and the at least one die defining at least one pocket in alignment with the at least one weld nugget of the at least one blank such that the at least one weld nugget is received by the at least one pocket during stamping of the blank with the at least one die segment.

18. The system as set forth in claim 17, wherein the at least one weld nugget has a height, the at least one pocket has a depth, and wherein the depth of the at least one pocket is at least the height of the at least one weld nugget.

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19. The system as set forth in claim 18, wherein the height of the at least one weld nugget is between approximately 0.25 to 0.50 mm deep, and wherein the depth of the at least one pocket is between approximately 0.25 to 0.50 mm deep.

20. The system as set forth in claim 17, wherein the at least one weld nugget has a width, wherein the at least one pocket has a width, and wherein the width of the at least one pocket is at least as large as the width of the at least one weld nugget.

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