EP4190932A1 - Tôles, plaques ou ébauches en alliage d'aluminium de la série 6xxx à formabilité améliorée - Google Patents

Tôles, plaques ou ébauches en alliage d'aluminium de la série 6xxx à formabilité améliorée Download PDF

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Publication number
EP4190932A1
EP4190932A1 EP21211696.6A EP21211696A EP4190932A1 EP 4190932 A1 EP4190932 A1 EP 4190932A1 EP 21211696 A EP21211696 A EP 21211696A EP 4190932 A1 EP4190932 A1 EP 4190932A1
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EP
European Patent Office
Prior art keywords
psi
quenching
temperature
sheet
hours
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.)
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Application number
EP21211696.6A
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German (de)
English (en)
Inventor
Michael LANGILLE
Philip DODGE
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.)
Constellium Neuf Brisach SAS
Constellium Bowling Green LLC
Constellium Muscle Shoals LLC
Original Assignee
Constellium Neuf Brisach SAS
Constellium Bowling Green LLC
Constellium Muscle Shoals LLC
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Application filed by Constellium Neuf Brisach SAS, Constellium Bowling Green LLC, Constellium Muscle Shoals LLC filed Critical Constellium Neuf Brisach SAS
Priority to EP21211696.6A priority Critical patent/EP4190932A1/fr
Priority to PCT/EP2022/083823 priority patent/WO2023099550A1/fr
Priority to CA3239615A priority patent/CA3239615A1/fr
Publication of EP4190932A1 publication Critical patent/EP4190932A1/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Withdrawn legal-status Critical Current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
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
    • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
    • 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
    • C22F1/043—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 of alloys with silicon as the next major constituent
    • 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
    • C22F1/05—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 of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions

Definitions

  • the present invention relates to 6xxx series aluminium alloy sheets, plates or blanks and their method of production, particularly useful for the automotive industry.
  • An application could be a door opening panel (DOP) of a vehicule, for example a car.
  • DOP door opening panel
  • the automotive industry uses more and more aluminium alloys, in particular in view of lighweighting the final vehicle.
  • Various aluminium alloys are used in the form of sheets, plates or blanks for automotive usages.
  • 6xxx series aluminium alloys are the most commonly used.
  • a known alloy could be AA6111-T4, that combines interesting chemical and mechanical properties such as hardness, strength, and formability.
  • the ranges disclosed in the Teal Sheets of the Aluminum Association are as follows: 0.6-1.1% Si ; ⁇ 0.40% Fe ; 0.50-0.9% Cu ; 0.10-0.45% Mn ; 0.50-1.0% Mg ; ⁇ 0.10% Cr ; ⁇ 0.15% Zn ; ⁇ 0.10% Ti.
  • JP3872753 B2 discloses an aluminum alloy having the following composition, in weight percentages: Mg: 0.2 to 1.5%, ; Si: 0.4 to 2.0% ; Fe: 0.001 to 1.0% ; Mn: 0.01 to 2.0% ; Cr: 0.001 to 1.0% ; and the balance Al with inevitable impurities.
  • JP4495623 B2 discloses an aluminium alloy having the following composition, in weight percentages: Si: 0.1 to 2.5% ; Mg: 0.1 to 3.0% ; and the balance Al with inevitable impurities.
  • Still another example may be found in Sergey F.
  • Still another example may be found in Nicholas Robert Kalweit, "Edge Stretch Performance of 6DR1 Aluminum in Typical Automotive Blanking Conditions", A thesis submitted in the University of Michigan-Dearborn, 2017 , that discloses an aluminium alloy having the following composition, in weight percentages: 0.50-1.00% Si ; ⁇ 0.30% Fe ; ⁇ 0.20% Cu ; ⁇ 0.15% Mn ; 0.40-0.80% Mg ; ⁇ 0.10% Cr ; ⁇ 0.10% Zn ; ⁇ 0.10% Ti ; ⁇ 0.05% other elements each ; ⁇ 0.15% other elements in total.
  • composition ranges of the aluminium alloy does not seem enough to assure sufficient formability performance in each part of the sheets, plates or blanks, in particular in the area of the sheared edges. It is indeed known that formability of sheared edges decreases after cutting. Formability may for example be evaluated by a stretchability test that is described in the example part.
  • Nan Wang et al. “Mechanism of fractureof aluminum blanks subjected to stretching along the sheared edge", Journal of Materials Processing Technology 233 (2016), pp.142-160 ;
  • the milling step generally done after blanking and prior to stamping a sheet, plate or blank, may be omitted.
  • the shearing process introduces damage to the material and decreases its formability, more specifically, decreases its stretchability, for example illustrated by tensile elongation, compared to a milled edge.
  • the omission of the milling step may allow for cost-savings and increased production speed.
  • An unsuccessful stamp is herein defined by having a split occuring during the stamping process resulting in the obtained piece to be scrapped.
  • the proposed solution uses an alloy having an increased global formability, as well as an improved local formability resulting in an overall increase in the work-hardening capacity, and combines it with a hard quenching step before the shearing step without any milling step.
  • An object of the invention is a process for producing a sheet or a plate or a blank, comprising the following successive steps: (a) casting a 6xxx alloy comprising, in wt.%: Si: 1.25 - 1.45 ; preferably 1.30 - 1.40 Fe: ⁇ 0.30 ; preferably 0.10 - 0.20 Cu: ⁇ 0.15 ; preferably ⁇ 0.09 Mn: 0.01- 0.15 ; preferably 0.05 - 0.10 Mg: 0.25-0.40 ; preferably 0.30-0.35 Cr: ⁇ 0.03 ; preferably ⁇ 0.02 Ni: ⁇ 0.04 ; preferably ⁇ 0.03 Zn: ⁇ 0.15 ; preferably ⁇ 0.10 Ti: 0.01 - 0.10 ; preferably 0.01- 0.04 other elements: ⁇ 0.05 each and ⁇ 0.15 in total rest aluminium; (b) heat treating; (c) hot rolling; (d) cold rolling; (e) optionally inter-annealing between hot rolling and cold rolling and/or during cold rolling and/
  • Another object of the invention is a sheet or plate or blank obtained according to the process of the present invention, characterised in that it has an improved sheared edge stretchability compared to non-milled previous sheets or plates or blanks.
  • Another object of the invention is the use of a sheet or plate or blank of the present invention to produce a vehicle part.
  • Metallurgical tempers referred to are designated using the European standard EN-515.
  • Static tensile mechanical characteristics in other words, the ultimate tensile strength R m (or UTS), the tensile yield strength at 0.2% plastic elongation R p0,2 (or TYS), and elongation A% (or E%), are determined by a tensile test according to NF EN ISO 6892-1.
  • the present invention deals in particular with the notion of "shear” / "shearing”.
  • different equivalent terms may be used when talking about shear/shearing. Some of them are the terms “trim” / “trimming” and “cut” / “cutting”.
  • an ingot is prepared by casting, typically Direct-Chill casting (or DC casting), using 6xxx series aluminium alloys of the invention.
  • the ingot thickness is preferably at least 250 mm, or at least 350 mm and preferentially a very thick gauge ingot with a thickness of at least 400 mm, or even at least 500 mm or 600 mm in order to improve the productivity of the process.
  • the ingot is from 1000 to 3000 mm in width and 2000 to 8000 mm in length.
  • the ingot is scalped.
  • the ingot is heat-treated, generally from 500 to 600°C and up to 35 hours.
  • the heat-treating step may comprise an homogenizing step.
  • the homogenisation of the plate is carried out at a temperature from 500°C to 600°C.
  • the homogenisation temperature is from 520°C to 600°C or 580°C or 560°C.
  • the temperature of the homogenisation is from 540°C to 600°C or 580°C or 560°C.
  • the homogenisation time is at least 1 hour.
  • the maximum homogenization time is at most 48 hours or 46 hours or 44 hours or 43 hours or 42 hours or 41 hours.
  • the homogenisation time is at least 2 hours and at most 48 hours or 46 hours or 44 hours or 43 hours or 42 hours or 41 hours.
  • the homogenisation time is at least 4 hours and at most 48 hours or 46 hours or 44 hours or 43 hours or 42 hours or 41 hours. In another embodiment, the homogenisation time is at least 6 hours and at most 48 hours or 46 hours or 44 hours or 43 hours or 42 hours or 41 hours. In another embodiment, the homogenisation time is at least 8 hours and at most 48 hours or 46 hours or 44 hours or 43 hours or 42 hours or 41 hours. In another embodiment, the homogenisation time is at least 10 hours and at most 48 hours or 46 hours or 44 hours or 43 hours or 42 hours or 41 hours.
  • the homogenizing step may optionally comprise, after the first stage mentioned above, a second stage from 420°C to 550°C of a maximum duration of 4 hours.
  • this second stage has a temperature from 550°C to 440°C or 460°C or 480°C or 500°C or 520°C or 540°C.
  • this second stage has a temperature from 540°C to 440°C or 460°C or 480°C or 500°C or 520°C.
  • said second stage has a temperature from 520°C to 440°C or 460°C or 480°C or 500°C.
  • said second stage has a temperature from 500°C to 440°C or 460°C or 480°C. In another embodiment, this second stage has a temperature from 480°C to 440°C or 460°C. In another embodiment, this second stage has a temperature from 460°C to 440°C.
  • the ingot may then generally either be cooled to room temperature and then reheated to a hot rolling start temperature below the homogenisation temperature or the ingot may be cooled directly from the homogenisation temperature to the hot rolling start temperature.
  • Direct cooling to the hot rolling start temperature is preferably carried out at a direct cooling rate of at least 150°C/h.
  • the direct cooling rate is at most 500°C/h.
  • the ingot is transferred, at the hot rolling start temperature, to the hot rolling mill.
  • the hot rolling start temperature is typically from 360°C to 560°C. In one embodiment, the hot rolling start temperature is at least 360°C and at most 550°C or 540°C or 530°C or 500°C or 450°C or 410°C.
  • the hot rolling start temperature is at least 370°C and at most 560°C or 550°C or 540°C or 530°C or 500°C or 450°C or 410°C In another embodiment, the hot rolling start temperature is at least 380°C and at most 560°C or 550°C or 540°C or 530°C or 500°C or 450°C or 410°C. In another embodiment, the hot rolling start temperature is at least 390°C and at most 560°C or 550°C or 540°C or 530°C or 500°C or 450°C or 410°C.
  • the hot rolling start temperature is at least 480°C and at most 560°C or 550°C or 540°C or 530°C. In another embodiment, the hot rolling start temperature is at least 490°C and at most 560°C or 550°C or 540°C or 530°C. In another embodiment, the hot rolling start temperature is at least 500°C and at most 560°C or 550°C or 540°C or 530°C. In another embodiment, the hot rolling start temperature is at least 510°C and at most 560°C or 550°C or 540°C or 530°C.
  • the hot rolling step is generally done in two successive steps in order to obtain a sheet with a first hot rolling step on a reversible rolling mill also known as roughing mill up to a thickness of typically from 12 to 40 mm and a second hot rolling step on a tandem mill also known as finishing mill up to a thickness of typically from 3 to 12 mm.
  • a tandem mill is a rolling mill in which several cages supporting rolling mill rolls, typically 2, 3, 4 or 5 rolls, act successively ("in tandem").
  • the first step on a reversible mill can be carried out on one or even two reversible mills placed successively.
  • the hot rolling end temperature is from 250°C to 450°C.
  • the cooling between the beginning and the end of the hot rolling process is the result of the usual heat exchange of the plate and then the strip or sheet with the air at the ambient temperature of the plant, with the equipment of the hot rolling mill, such as, for example, but not limited to, the rolls or the conveyor rollers, as well as with the usual lubricating or cooling fluids.
  • the hot rolling end temperature is at least 270°C and at most 450°C or 400°C or 380°C or 360°C or 340°C or 320°C or 300°C.
  • the hot rolling end temperature is at least 300°C and at most 450°C or 400°C or 380°C or 360°C or 340°C or 320°C. In another embodiment, the hot rolling end temperature is at least 320°C and at most 450°C or 400°C or 380°C or 360°C or 340°C. In another embodiment, the hot rolling end temperature is at least 340°C and at most 450°C or 400°C or 380°C or 360°C. In another embodiment, the hot rolling end temperature is at least 360°C and at most 450°C or 400°C or 380°C. In another embodiment, the hot rolling end temperature is at least 380°C and at most 450°C or 400°C. In another embodiment, the hot rolling end temperature is at least 400°C and at most 450°C. Controlling this temperature may allow to control the rate of recrystallisation.
  • Cold rolling is done after the hot rolling step to further reduce the thickness of the aluminium sheets.
  • the sheet directly obtained after cold rolling is referred to as the cold rolled sheet.
  • the cold rolled sheet thickness is typically from 0.5 to 2.5 mm and preferably from 0.7 to 2 mm.
  • the cold rolling reduction is at least 40% or at least 50% or at least 60%. Typically, the cold rolling reduction is at most 99% or 98% or 97% or 96% or 95% or 94% or 93% or 92% or 91% or 90%.
  • an inter-annealing step is done between the hot rolling step and the cold rolling step and/or during the cold rolling step and/or after the cold rolling step.
  • the temperature of the inter-annealing step, done between the hot rolling step and the cold rolling step or during the cold rolling step is from 300°C to 500°C or 450°C or 400°C or 380°C.
  • the temperature of the inter-annealing step, done between the hot rolling step and the cold rolling step or during the cold rolling step is from 340°C to 500°C or 450°C or 400°C or 380°C.
  • This inter-annealing step is preferably carried out on the sheet wound into a coil.
  • the cold rolled sheet may be annealed in order to obtain a fully recrystallized microstructure, preferably in a continuous annealing line.
  • the continuous annealing line is operated in such a way that a temperature of at least 310°C, preferably at least 320°C and at most 590°C or preferably at most 580°C is reached by the sheet.
  • the continuous annealing line is operated such that the heating rate of the sheet is at least 10°C/s and the time above 320°C is from 5 s to 25 s.
  • the coiling temperature after annealing is preferably up to 100°C, preferably up to 95°C and more preferably from 80°C to 90°C.
  • the annealing may be carried out by batch annealing at a temperature of at most 590°C.
  • the sheet is then solution heat treated, generally in a continuous furnace and then quenched.
  • the solution temperature is preferably from 500°C to 600°C or 590°C or 580°C or 570°C or 560°C.
  • the solution temperature is at least 520°C and at most 600°C or 590°C or 580°C or 570°C or 560°C.
  • the solution temperature is at least 540°C and at most 600°C or 590°C or 580°C or 570°C or 560°C.
  • the solution temperature is at least 550°C and at most 600°C or 590°C or 580°C or 570°C or 560°C.
  • the solution temperature is at least 560°C and at most 600°C or 590°C or 580°C or 570°C.
  • the solution time is from 10 s to 60 s.
  • Quenching may be done with air or water, preferably with water.
  • air quenching may be done with a strong air flow and water quenching with a water spray (for example flat jets and/or conic jets).
  • the quenching speed is up to 1300°C/s and at least 30°C/s, preferably at least 40°C/s, preferably more than 200°C/s, preferably more than 300°C/s.
  • the temperature of the water used for the quenching step is from 30 to 60°C, preferably from 35 to 50°C.
  • the pressure of the water used for the quenching step is at most 80 psi or 70 psi or 60 psi or 50 psi or 40 psi or 30 psi or 25 psi. In another embodiment, the pressure of the water used for the quenching step is at least 5 psi and at most 80 psi or 70 psi or 60 psi or 50 psi or 40 psi or 30 psi or 25 psi.
  • the pressure of the water used for the quenching step is at least 10 psi and at most 80 psi or 70 psi or 60 psi or 50 psi or 40 psi or 30 psi or 25 psi. In another embodiment, the pressure of the water used for the quenching step is at least 15 psi and at most 80 psi or 70 psi or 60 psi or 50 psi or 40 psi or 30 psi or 25 psi.
  • the sheet temperature at the beginning of the quenching step is from 480 to 570°C, for example 490°C or 500°C or 510°C or 520°C or 530°C or 540°C or 550°C or 560°C.
  • the sheet temperature at the end of the quenching step is from 50 to 160°C, for example 60°C or 70°C or 80°C or 90°C or 100°C or 110°C or 120°C or 130°C or 140°C or 150°C.
  • the sheet may then be pre-aged.
  • the pre-aging is achieved by coiling the sheet at a temperature from 50°C to 100°C.
  • the pre-aging temperature is at least 60°C and at most 100°C or 95°C or 90°C or 85°C or 80°C or 75°C or 70°C or 65°C.
  • the pre-aging temperature is at least 65°C and at most 100°C or 95°C or 90°C or 85°C or 80°C or 75°C or 70°C.
  • the pre-aging temperature is at least 70°C and at most 100°C or 95°C or 90°C or 85°C or 80°C or 75°C.
  • the pre-aging temperature is at least 75°C and at most 100°C or 95°C or 90°C or 85°C or 80°C. In another embodiment, the pre-aging temperature is at least 80°C and at most 100°C or 95°C or 90°C or 85°C. In another embodiment, the pre-aging temperature is at least 85°C and at most 100°C or 95°C or 90°C. In another embodiment, the pre-aging temperature is at least 90°C and at most 100°C or 95°C. In a further embodiment, the pre-aging temperature is at least 95°C and at most 100°C. The pre-aging takes place during the natural cooling of the coil in the ambient temperature of the workshop for a period of 8 hours to 24 hours.
  • the strip may therefore be in the T4 temper and matures at room temperature from 72 hours to 6 months.
  • a pre-straining step of 0-5% before the bake hardening step in particular in the case of laboratory scale experiments, for example to simulate a stamping step.
  • the sheet After annealing and/or solutionising and/or quenching and/or pre-aging and/or tempering, the sheet is sheared to obtain a plate or a blank, without any milling step before being formed to its final shape by stamping. It could then optionally be painted and bake hardened, for example at 160 to 200°C during 10 to 30 minutes.
  • the inventors have found improved 6xxx aluminium alloy sheets which have an increased global formability as well as an improved local formability, in particular an improved sheared edge stretchability.
  • the quantities and properties of each element of the alloy used according to the present invention are described hereinafter.
  • Si Silicon is, together with magnesium, the main alloying element in aluminium-magnesium-silicon systems (AA6xxx series) to form the hardening precipitates Mg2Si or Mg5Si6, which contribute to the structural hardening of these alloys.
  • the Si content is from 1.25 and 1.45 wt.%. A higher content may degrade the bendability.
  • the minimum Si content is 1.25 wt.% and the maximum is 1.44 wt.% or 1.43 wt.% or 1.42 wt.% or 1.41 wt.% or 1.40 wt.%.
  • the minimum Si content is 1.26 wt.% and the maximum is 1.45 wt.% or 1.44 wt.% or 1.43 wt.% or 1.42 wt.% or 1.41 wt.% or 1.40 wt.%. In another embodiment, the minimum Si content is 1.27 wt.% and the maximum is 1.45 wt.% or 1.44 wt.% or 1.43 wt.% or 1.42 wt.% or 1.41 wt.% or 1.40 wt.%.
  • the minimum Si content is 1.28 wt.% and the maximum is 1.45 wt.% or 1.44 wt.% or 1.43 wt.% or 1.42 wt.% or 1.41 wt.% or 1.40 wt.%. In another embodiment, the minimum Si content is 1.29 wt.% and the maximum is 1.45 wt.% or 1.44 wt.% or 1.43 wt.% or 1.42 wt.% or 1.41 wt.% or 1.40 wt.%.
  • the minimum Si content is 1.30 wt.% and the maximum is 1.45 wt.% or 1.44 wt.% or 1.43 wt.% or 1.42 wt.% or 1.41 wt.% or 1.40 wt.%.
  • Fe Iron is generally considered as an undesirable impurity. The presence of iron-containing intermetallic compounds is generally associated with a decrease in local formability. However, very pure alloys are expensive. According to the present invention, a compromise is a Fe content of up to 0.30 wt.%.. In one embodiment, the Fe content is at least 0.05 wt.% and at most 0.30 wt.% or 0.25 wt.% or 0.24 wt.% or 0.23 wt.% or 0.22 wt.% or 0.21 wt.% or 0.20 wt.%.
  • the Fe content is at least 0.06 wt.% and at most 0.30 wt.% or 0.25% or 0.24 wt.% or 0.23 wt.% or 0.22 wt.% or 0.21 wt.% or 0.20 wt.%. In another embodiment, the Fe content is at least 0.07 wt.% and at most 0.30 wt.% or 0.25 wt.% or 0.24 wt.% or 0.23 wt.% or 0.22 wt.% or 0.21 wt.% or 0.20 wt.%.
  • the Fe content is at least 0.08 wt.% and at most 0.30 wt.% or 0.25 wt.% or 0.24 wt.% or 0.23 wt.% or 0.22 wt.% or 0.21 wt.% or 0.20 wt.%. In another embodiment, the Fe content is at least 0.09 wt.% and at most 0.30 wt.% or 0.25 wt.% or 0.24 wt.% or 0.23 wt.% or 0.22 wt.% or 0.21 wt.% or 0.20 wt.%.
  • the Fe content is at least 0.10 wt.% and at most 0.30 wt.% or 0.25 wt.% or 0.24 wt.% or 0.23 wt.% or 0.22 wt.% or 0.21 wt.% or 0.20 wt.%.
  • Cu In the AA6xxx series alloys, copper is an element participating in the hardening precipitation but it is also known to degrade corrosion resistance. According to the present invention, the copper content is at most 0.15 wt.% or 0.14 wt.% or 0.13 wt.% or 0.12 wt.% or 0.11 wt.% or 0.10 wt% or 0.09 wt.% or 0.05 wt.%. Allowing the presence of copper in the alloy is economically attractive as it allows the recycling of aluminium scrap and waste containing copper. The presence of copper can come from both scrap and waste as such, but can also be introduced accidentally. For example, during the dismantling of an end-of-life vehicle, it is sufficient to inadvertently leave a copper wire with the aluminium parts to pollute a plate obtained with recycled aluminium alloy.
  • Mn Manganese is an effective element for strength improvement, crystal grain refining and structure stabilization.
  • the Mn content is from 0.01 to 0.15 wt.%.
  • the Mn content is under 0.01 wt.%, the aforementioned effects are insufficient.
  • a Mn content exceeding 0.15 wt.% may not only cause a saturation of the above effects but also cause the generation of multiple intermetallic compounds that could have an adverse effect on formability.
  • the Mn content is at least 0.01 wt.% and at most 0.14 wt.% or 0.13 wt.% or 0.12 wt.% or 0.11 wt.% or 0.10 wt.%.
  • the Mn content is at least 0.02 wt.% and at most 0.15 wt.% or 0.14 wt.% or 0.13 wt.% or 0.12 wt.% or 0.11 wt.% or 0.10 wt.%. In one embodiment, the Mn content is at least 0.03 wt.% and at most 0.15 wt.% or 0.14 wt.% or 0.13 wt.% or 0.12 wt.% or 0.11 wt.% or 0.10 wt.%.
  • the Mn content is at least 0.04 wt.% and at most 0.15 wt.% or 0.14 wt.% or 0.13 wt.% or 0.12 wt.% or 0.11 wt.% or 0.10 wt.%. In one embodiment, the Mn content is at least 0.05 wt.% and at most 0.15 wt.% or 0.14 wt.% or 0.13 wt.% or 0.12 wt.% or 0.11 wt.% or 0.10 wt.%.
  • Mg Magnesium is one of the main alloying elements of the 6xxx series alloys and it contributes to strength improvement by combination with silicon to form the hardening precipitates Mg2Si or Mg5Si6.
  • the Mg content is from 0.25 to 0.40 wt.%. When the Mg content is under 0.25 wt.%, strength improvement may be insufficient. On the other hand, a content exceeding 0.40 wt.% may result in a strength detrimental to formability.
  • the Mg content is at least 0.25 wt.% and at most 0.39 wt.% or 0.38 wt.% or 0.37 wt.% or 0.36 wt.% or 0.35 wt.%.
  • the Mg content is at least 0.26 wt.% and at most 0.40 wt.% or 0.39 wt.% or 0.38 wt.% or 0.37 wt.% or 0.36 wt.% or 0.35 wt.%. In one embodiment, the Mg content is at least 0.27 wt.% and at most 0.40 wt.% or 0.39 wt.% or 0.38 wt.% or 0.37 wt.% or 0.36 wt.% or 0.35 wt.%.
  • the Mg content is at least 0.28 wt.% and at most 0.40 wt.% or 0.39 wt.% or 0.38 wt.% or 0.37 wt.% or 0.36 wt.% or 0.35 wt.%. In one embodiment, the Mg content is at least 0.29 wt.% and at most 0.40 wt.% or 0.39 wt.% or 0.38 wt.% or 0.37 wt.% or 0.36 wt.% or 0.35 wt.%.
  • the Mg content is at least 0.30 wt.% and at most 0.40 wt.% or 0.39 wt.% or 0.38 wt.% or 0.37 wt.% or 0.36 wt.% or 0.35 wt.%.
  • Chromium may be added for strength improvement, crystal grain refining and structure stabilization. According to the present invention, the Cr content is at most or less than 0.03 wt%, preferably at most or less than 0.02 wt.%.
  • Ni Nickel may be introduced by the way of recycled content. According to the present invention, the Ni content is at most, or less than, 0.04 wt%, preferably at most, or less than, 0.03 wt.%.
  • Zn As zinc is an addition element in aluminium alloys, it is interesting to have some in the alloy of the present invention for the purpose of recycling aluminium scrap and waste, in particular from end-of-life vehicles. Indeed, Zn is used in some alloys in some components such as heat exchangers. According to the present invention, the Zn content is at most, or less than, 0.15 wt.%, preferably at most, or less than, 0.10 wt.%. The inventors have found that the invention alloy can tolerate such content of Zn without adversely affecting the properties, which is beneficial for recycling purposes.
  • Titanium is added to control the as-cast grain structure. It is known as a grain refiner. This element can also promote solid solution hardening leading to the required level of mechanical properties and it also has a favourable effect on service ductility and corrosion resistance.
  • a maximum content of 0.10 wt.% of Ti is required to avoid the conditions of primary phase formation during vertical casting, which have a detrimental effect on the overall properties.
  • the Ti content is from 0.01 to 0.10 wt.% or to 0.09 wt.% or to 0.08 wt.% or to 0.07 wt.% or to 0.06 wt.% or to 0.05 wt.% or to 0.04 wt.%.
  • the content of other elements is less than 0.05 wt.% each and less than 0.15 wt.% in total.
  • the other elements are typically unavoidable impurities or incidental elements added in very small quantity such as boron which can be typically added together with Ti in the form of TiB 2 .
  • the rest of the alloy is composed of aluminium.
  • the use of the 6xxx series aluminium sheets or plates or blanks according to the invention for automobile manufacturing is advantageous, in particular for the manufacture of a vehicle part, for example a body-in-white (BIW) part like a door or a bonnet.
  • the method of manufacturing the BIW part therefore comprises the following successive steps:
  • the target of the material according to the present invention is to fulfil the specifications as shown in Table 1 hereinafter while having a sheared edge stretchability without any milling step that is improved over the current products.
  • Table 1 Property Specification Rp0.2 (30 days) (MPa) > 97 UTS (MPa) > 200 UE (%) > 19% TE (%) > 22.5 r avg > 0.50 r 10 45° ⁇ 0.3 Rp0.2 (180°C ; 20 min) (MPa) > 155
  • Example 1 Composition of the alloy
  • the sheared edge stretchability is defined as the elongation at 95% of the maximum force after the UTS whereby the width of half-dog-bone samples (see Figure 1 ) have been sheared using a 30% clearance (30% of the sheet thickness, eg: a 1mm thick sheet would yield a 0.3mm clearance) between upper and lower shearing tools (see reference numbers 3, 4 and 5 in Figure 2 ).
  • the die used according to the present examples to shear the half-dog bone sample 6 consisted of a fixed lower shearing tool 3, a pad 2 to fix the sample 6, and a upper shearing tool 4 that translate up and down to shear the sample 6.
  • the shearing of a metal sheet consists in 3 stages A, B and C as illustrated in Figure 2 :
  • the upper shearing tool 4 edge shape (sharpness), the lower shearing tool 3 edge shape (sharpness) and the clearance ( (gap) between the lower shearing tool 3 and the upper shearing tool 4 influence the shearing process and ultimately affect the shearing edge quality.
  • E SE is thus done via a tensile test in the presence of a sheared edge on a half-dog bone sample to evaluate the degredation in its ductility/formability due to the shearing process.
  • the half-dog bone samples are single-sided tensile samples that are sheared on one side along the shear line 1 as illustrated in Figure 1 , with the shearing die as illustrated in Figure 2 . In the present examples, the clearance was 30% of the sample thickness. The side that was sheared is called the sheared edge.
  • the reference number 11 is the point of the curve corresponding to 95% of the maximum force after the UTS, as discussed in the definition of E SE hereinabove, or to a 5% drop in the maximum force.
  • E SE 9 is the elongation corresponding to point 11 in the tensile test curve as shown in Figure 3 .
  • 10 to 30 samples were tested, in each direction (rolling direction RD, transverse direction TD and 45° from rolling direction) when applicable, in order to obtain a statistically significant standard deviation ( ⁇ ) and an average sheared edge stretchability (E SE ). ⁇ thus corresponds to the standard deviation obtained with 10 to 30 repetitions.
  • the half-dog bone samples were obtained by the following process:
  • TD transverse direction
  • RD rolling direction and 45° is the angle compared to the rolling direction.

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  • Organic Chemistry (AREA)
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EP21211696.6A 2021-12-01 2021-12-01 Tôles, plaques ou ébauches en alliage d'aluminium de la série 6xxx à formabilité améliorée Withdrawn EP4190932A1 (fr)

Priority Applications (3)

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EP21211696.6A EP4190932A1 (fr) 2021-12-01 2021-12-01 Tôles, plaques ou ébauches en alliage d'aluminium de la série 6xxx à formabilité améliorée
PCT/EP2022/083823 WO2023099550A1 (fr) 2021-12-01 2022-11-30 Feuilles ou flans d'alliage d'aluminium série 6xxx à formabilité améliorée
CA3239615A CA3239615A1 (fr) 2021-12-01 2022-11-30 Feuilles ou flans d'alliage d'aluminium serie 6xxx a formabilite amelioree

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