EP3896188A1 - Procédé de fabrication d'éléments d'absorption d'énergie constitués de feuilles en alliage d'aluminium durcissables par vieillissement qui facilitent l'assemblage ultérieur - Google Patents

Procédé de fabrication d'éléments d'absorption d'énergie constitués de feuilles en alliage d'aluminium durcissables par vieillissement qui facilitent l'assemblage ultérieur Download PDF

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Publication number
EP3896188A1
EP3896188A1 EP20169730.7A EP20169730A EP3896188A1 EP 3896188 A1 EP3896188 A1 EP 3896188A1 EP 20169730 A EP20169730 A EP 20169730A EP 3896188 A1 EP3896188 A1 EP 3896188A1
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EP
European Patent Office
Prior art keywords
blank
drawpiece
temperature
sht
cooling
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP20169730.7A
Other languages
German (de)
English (en)
Inventor
Pawel Kaczynski
Karol Jaskiewicz
Zbigniew GRONOSTAJSKI
Slawomir Polak
Jakub KRAWCZYK
Mateusz Skwarski
Wladyslaw Chorzepa
Krzysztof Sliz
Slawomir Uzar
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kirchhoff Polska
Politechnika Wroclawska
Original Assignee
Kirchhoff Polska
Politechnika Wroclawska
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kirchhoff Polska, Politechnika Wroclawska filed Critical Kirchhoff Polska
Priority to EP20169730.7A priority Critical patent/EP3896188A1/fr
Publication of EP3896188A1 publication Critical patent/EP3896188A1/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • 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
    • B21D24/00—Special deep-drawing arrangements in, or in connection with, presses
    • B21D24/005—Multi-stage presses
    • 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
    • B21D35/00—Combined processes according to or processes combined with methods covered by groups B21D1/00 - B21D31/00
    • B21D35/002—Processes combined with methods covered by groups B21D1/00 - B21D31/00
    • B21D35/005—Processes combined with methods covered by groups B21D1/00 - B21D31/00 characterized by the material of the blank or the workpiece
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
    • 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

Definitions

  • a method of forming a metal alloy sheet component taking advantage of SHT is presented in WO2008059242A2 international patent (Process for forming metal alloy sheet components).
  • the method comprises of heating a metal alloy sheet blank to its SHT temperature and maintaining that temperature until SHT is complete, rapid transferring the sheet blank to a set of cold dies, immediate closing the cold dies to form the sheet blank into a shaped component, and holding the formed component in the closed dies during cooling of the formed component.
  • An additional artificial ageing step at the end of the process is added which allows precipitation hardening to occur.
  • the main disadvantage of the described method is that the part is formed in one step. Therefore there is large risk of thinning and cracking in case of forming of part of a complex geometry (i.e. deep drawing operation combined with small radius of the final part).
  • the second disadvantage is that the part after forming must be artificially aged in just a few hours to prevent uncontrolled artificial ageing. Additionally, the joining of the final product follows after artificial ageing, which hardens the final product and increases its strength. This makes the joining process more difficult and increases the wear of joining tools.
  • the main disadvantage is the complexity of the process. It involves two full cycles of heating, holding and rapid cooling and additional age-hardening of the final product after the last stamping phase. It makes the use of this method in the automotive industry unprofitable and practically impossible.
  • the disadvantage of this technology is the lower strength of the final product which is caused by structural changes occurring during stamping in elevated temperature. Additionally, the mentioned technology requires more time to perform two-stage cooling.
  • EP3117019A2 patent A method of forming parts from sheet metal alloy.
  • the method concerns forming parts from sheet metal alloy and comprise the steps of: heating the sheet to a temperature at which SHT of the alloy occurs and so as to achieve SHT, applying at least the critical cooling rate and then placing the sheet between dies to form it into or towards the complex part.
  • the purpose of the invention was to develop a new method of manufacturing of energy-absorbing elements made of aluminum alloy sheets that facilitate further joining.
  • the developed method enables simultaneous production of the drawpieces and solutionizing of the material, which ensures outstanding plastic properties. Additionally, the final product may be cooled down, which allows the so-called “freezing the structure” and prevents natural aging. This results in holding high plastic properties of the drawpiece for a longer period of time.
  • the advantage of this solution is the possibility of using joining methods taking advantage of high plastic properties of the material (such as clinching or riveting) after finishing stamping. At the end of the process, the artificial ageing is performed which restores high strength of the final product. It is also possible to perform artificial ageing during the paint bake cycle of paint layers applied beforehand.
  • the essence of the method is the manufacturing of energy-absorbing elements made of aluminum alloy sheets (specifically 2xxx, 6xxx or 7xxx). It consists of 7 main steps (as depicted in fig. 1 ).
  • the blank is cut out from the rolled sheets of metal. This step is usually done in the punching process by means of the stamp and the die.
  • the blank is heated up to solution heat treatment temperature (T SHT ), so that the strengthening phases dissolve in the solid matrix solution.
  • T SHT solution heat treatment temperature
  • This is preferably done in the type of furnace taking advantage of convection heating, which allows minimizing the time needed to reach SHT temperature.
  • This step is being continued for a period of time that allows to fully dissolve hardening phases into an aluminum-rich solid solution.
  • the third step is performed. It consists of transferring the blank to the stamping station. The transfer time should be minimized in order to prevent an excessive reduction in the temperature of the blank.
  • the blank is formed in two stages ( fourth and fifth step). First, it is preformed, i.e deformed into an intermediate shape between the flat blank and the final geometry of the part. The main goal of this step is to dissipate the blank's heat to the forming tools, which allows the material to be solutionized. Therefore, the deformation level reached in this step is significantly lower than during the second stamping step. In the next forming step, the beforehand solutionized preform is subjected to finishing stamping, which allows obtaining the desired final shape of the drawpiece.
  • the drawpiece is subjected to the sixth step during which the part is being trimmed, in order to remove the excess of the material. This step is usually done in the punching process.
  • the standalone drawpiece or the assembly of the drawpiece with other parts is artificially aged. This is obtained by holding the drawpiece at elevated temperature for a specific amount of time.
  • the artificial ageing may be done during the paint bake cycle or any other process focused on the restoration of high strength properties close to the properties of T6 temper. Additionally, the drawpieces undergoing artificial ageing may be overaged for improvement of the strength stability over time.
  • the main advantage of two-stage stamping is that after the first stamping stage material is solutionized which makes it more susceptible to further stamping operations. In the first stage the larger radius and small strain should be obtained, whereas in the second operation the lager strain and small radius could be performed. This approach is not mentioned in other patents.
  • the large strain and complex shape of the final product may be obtained due to the proper cooling conditions applied in the preforming, i.e. cooling rate larger than 20 °C/s to temperature below 200°C (Fig. 6). The optimal cooling rate equals to 40 °C/s.
  • the part after sixth step may be cooled and stored at a sub-zero temperature, which allows maintaining high plastic properties of the material for a decidedly longer period of time. Without freezing the parts material starts immediately to age naturally. Just after 3 h the material's hardness increases by 22% ( fig. 3 ). The parts cooled to sub-zero temperatures gain only 5% of the strength after 7 days ( fig. 2 ). Therefore, the cooling to sub-zero temperatures allows maintaining the drawpiece in the so-called "soft" state. Thanks to phenomenon the joining process can be postponed and almost no age hardening occurs. Thanks to this, the joining forces can be minimized, and the drawpiece can be assembled easily with other parts.
  • the aluminum alloy sheet of a thickness range from 0.5 mm to 4 mm is used.
  • the cutting out the blank from sheet metal in the first step is done in the process of punching by means of the punch and the die or by laser cutting.
  • the temperature of solution heat treatment (T SHT ) to which the blank is heated up in the second step is in the range of (450 to 550) °C.
  • the T SHT of the blank in second step is maintained for 10 to 60 minutes which allows to fully dissolve hardening phases into an aluminum-rich solid solution.
  • the transfer of the hot blank from a heating station to the preforming station in the third step is done within 30 seconds.
  • the initial temperature of the hot blank at the instant when preforming (fourth step) is started is not lower than (T SHT - 150) °C.
  • the deformation level in preforming step (fourth step) is significantly lower than deformation level in finishing forming step (fifth step).
  • simultaneous preforming and cooling in the fourth step is done by means of tools being cooled by fluid, preferably by water.
  • each radius of the blank after preforming operation (fourth step) is larger than 15 mm.
  • the blank during preforming operation (fourth step) is cooled to a temperature below 200 °C and the cooling rate equals to at least 20 °C/s.
  • the trimming in the sixth step is done in the process of punching by means of the punch and the die.
  • the artificial ageing of the final product which is performed in the seventh step is done in one of four ways: 1) during paint bake cycle (PBC) of the components; 2) in the temperature of 120 °C for 8h; 3) in the following conditions: 4 days of natural ageing ⁇ 170 °C for 25 min. ⁇ 165 °C for 25 min ⁇ 130 °C for 20 min ⁇ final cooling to room temperature; 4) in any other conditions accounting for a significant increase of the material's strength to the value of at least 80% of T6 temper strength.
  • PBC paint bake cycle
  • the optional cooling of the drawpiece to sub-zero temperature is done not later than 3 h after trimming performed in the sixth step.
  • the authors have tested that after this period of time material starts to age naturally itself which results in drastic hardness increase. The results are presented in details in fig. 3 .
  • the temperature range to which the drawpiece is optionally cooled after trimming is in the range of (-60 to -20) °C which successfully prevents natural ageing and precipitation hardening of the final part.
  • the optional holding of the drawpiece in sub-zero temperatures is continued for a period of time equal to 0-7 days.
  • the authors have tested that this period of holding time successfully prevents the material from hardening. This is clearly depicted in fig. 2 .
  • the optional assembling is done by means of a method taking advantage of low strength and high ductility of joined material, for example mechanical clinching or riveting.
  • a method of manufacturing of energy-absorbing elements made of aluminum alloy sheets that facilitates further joining comprising the steps of:
  • the preforming in step d) is done by using only 50% of the total stroke of the press. After using 50% of the stroke the press is stopped and the blank is stretched over the punch, which provides cooling of the material and results in its solutionizing. After 5s the obtained, solutionized preform is being further stamped using the rest of the stroke until the tools are fully closed. After this, the drawpiece has desired final shape and the further operations (trimming, artificial ageing) are performed as in Example 1.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
EP20169730.7A 2020-04-15 2020-04-15 Procédé de fabrication d'éléments d'absorption d'énergie constitués de feuilles en alliage d'aluminium durcissables par vieillissement qui facilitent l'assemblage ultérieur Withdrawn EP3896188A1 (fr)

Priority Applications (1)

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EP20169730.7A EP3896188A1 (fr) 2020-04-15 2020-04-15 Procédé de fabrication d'éléments d'absorption d'énergie constitués de feuilles en alliage d'aluminium durcissables par vieillissement qui facilitent l'assemblage ultérieur

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EP20169730.7A EP3896188A1 (fr) 2020-04-15 2020-04-15 Procédé de fabrication d'éléments d'absorption d'énergie constitués de feuilles en alliage d'aluminium durcissables par vieillissement qui facilitent l'assemblage ultérieur

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EP3896188A1 true EP3896188A1 (fr) 2021-10-20

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008059242A2 (fr) 2006-11-14 2008-05-22 The University Of Birmingham Procédé pour former des composants de feuilles d'alliage métallique
US20120186706A1 (en) 2011-01-24 2012-07-26 GM Global Technology Operations LLC Stamping of age-hardenable aluminum alloy sheets
US8613820B2 (en) 2009-06-12 2013-12-24 Aleris Aluminum Duffel Bvba Structural automotive part made from an Al—Zn—Mg—Cu alloy product and method of its manufacture
EP3117019A2 (fr) 2014-03-14 2017-01-18 Imperial Innovations Limited Procédé de formation de pièces à partir d'un alliage métallique en feuille
CN107740014A (zh) * 2017-10-30 2018-02-27 中南大学 一种抑制铝合金汽车板自然时效的深冷处理方法
US10029624B2 (en) 2010-08-02 2018-07-24 Benteler Automobiltechnik Gmbh Sheet metal molding for motor vehicles and process for producing a sheet metal molding for motor vehicles
US20190070652A1 (en) * 2016-05-10 2019-03-07 Bayerische Motoren Werke Aktiengesellschaft Method for Manufacturing a Component
EP3467138A1 (fr) 2017-10-04 2019-04-10 Automation, Press and Tooling, A.P. & T AB Procédé et système de formation d'ébauche d'alliage d'aluminium

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008059242A2 (fr) 2006-11-14 2008-05-22 The University Of Birmingham Procédé pour former des composants de feuilles d'alliage métallique
US8613820B2 (en) 2009-06-12 2013-12-24 Aleris Aluminum Duffel Bvba Structural automotive part made from an Al—Zn—Mg—Cu alloy product and method of its manufacture
US10029624B2 (en) 2010-08-02 2018-07-24 Benteler Automobiltechnik Gmbh Sheet metal molding for motor vehicles and process for producing a sheet metal molding for motor vehicles
US20120186706A1 (en) 2011-01-24 2012-07-26 GM Global Technology Operations LLC Stamping of age-hardenable aluminum alloy sheets
EP3117019A2 (fr) 2014-03-14 2017-01-18 Imperial Innovations Limited Procédé de formation de pièces à partir d'un alliage métallique en feuille
US20190070652A1 (en) * 2016-05-10 2019-03-07 Bayerische Motoren Werke Aktiengesellschaft Method for Manufacturing a Component
EP3467138A1 (fr) 2017-10-04 2019-04-10 Automation, Press and Tooling, A.P. & T AB Procédé et système de formation d'ébauche d'alliage d'aluminium
CN107740014A (zh) * 2017-10-30 2018-02-27 中南大学 一种抑制铝合金汽车板自然时效的深冷处理方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JAE-YEOL JEON ET AL: "Two-Step Die Motion for Die Quenching of AA2024 Aluminum Alloy Billet on Servo Press", MATERIALS TRANSACTIONS, THE JAPANESE INSTITUTE OF METALS AND MATERIALS, JP, vol. 55, no. 5, 11 April 2014 (2014-04-11), pages 818 - 826, XP002745093, ISSN: 1345-9678, DOI: 10.2320/MATERTRANS.L-M2014806 *

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