Classifications

• • 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
• • 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

Definitions

• the invention relates to the field of parts or components of automotive structure also called “white box”, manufactured in particular by stamping aluminum alloy sheets, more particularly alloys of the AA6xxx series according to the designation "Aluminum Association” , intended to absorb energy irreversibly during an impact, and having an excellent compromise between high mechanical strength and good "crash” behavior, such as in particular shock absorbers or “crashboxes", reinforcement pieces, lining, or other body structure parts.
• the invention relates to the manufacture of such components by stamping in a quenched and matured solution state followed by a hardening on part and a treatment of baking paints or "bake hardening".
• the expression 1.4 x Si means that the silicon content expressed in% by weight is multiplied by 1.4.
• the definitions of the metallurgical states are given in the European standard EN 515.
• the static mechanical characteristics in tension in other words the ultimate tensile strength R m , the conventional yield stress at 0.2% elongation Rpo, 2, and the elongation at break A%, are determined by a tensile test according to standard NF EN ISO 6892-1.
• alpha norm The folding angles, called alpha norm, are determined by a 3-point bend test according to the NF EN ISO 7438 standard and the VDA 238-100 and VDA 239-200 procedures.
• Aluminum alloys are increasingly used in the automotive industry to reduce the weight of vehicles and thus reduce fuel consumption and greenhouse gas emissions.
• the aluminum alloy sheets are used in particular for the manufacture of many parts of the "white box” among which are distinguished body skin parts (or outer body panels) such as the front wings, roofs or pavilions, skins bonnet, boot or door, and lining parts or body structure components such as liners or reinforcements door, hood, tailgate, roof, or the rails, aprons, floors of loads, tunnels and feet front, middle and rear, finally the shock absorbers or "crashboxes".
• body skin parts or outer body panels
• lining parts or body structure components such as liners or reinforcements door, hood, tailgate, roof, or the rails, aprons, floors of loads, tunnels and feet front, middle and rear, finally the shock absorbers or "crashboxes”.
• Alloys of the type AA6013 have also been the subject of much work.
• Alcoa in the application US2002039664 published in 2002, an alloy comprising 0.6-1.15% Si; 0.6-1% Cu; 0.8-1.2% Mg; 0.55-0.86% Zn; less than 0.1% Mn; 0.2-0.3%) Cr and about 0.2%> Fe, used in the T6 state, combines good resistance to intergranular corrosion, as well as a Rpo, 2 of 380 MPa.
• the object of the invention is to provide an alloy of the AA6013 type with a reduced Cu level, targeting 355 MPa of Rm in the T6 state and good resistance to intergranular corrosion.
• the composition claimed is as follows: 0.8-1.3%) Si; 0.2-0.45%) Cu; 0.5-1.1%) Mn; 0.45-1.0% Mg.
• EPI 702995 A1 discloses a process for producing an aluminum alloy sheet, which comprises providing a molten aluminum alloy having a chemical composition, in% by weight, Mg: 0.30 to 1 , 00%, Si: 0.30 to 1.20%, Fe: 0.05 to 0.50%, Mn: 0.05 to 0.50%, Ti: 0.005 to 0.10%, optionally one or more among Cu: 0.05 to 0.70%> and Zr: 0.05 to 0.40%>, and the remainder: Al and unavoidable impurities, the casting of the molten alloy in a plate having a thickness of 5 at 15 mm by the double-band casting method with a cooling rate at 1/4 of the plate thickness from 40 to 150 ° C / s, the winding in the form of a coil, a treatment of homogenizing, cooling the resulting coil to a temperature of 250 ° C or less with a cooling rate of 500 ° C / h or more, followed by cold rolling, and then a solution treatment.
• the aim of the invention is to obtain an excellent compromise between T4 formability and high mechanical strength, as well as good riveting and "crash" behavior of the finished component, by proposing a method of manufacturing such components by shaping them at the same time.
• a problem is also to achieve a short and economically advantageous process.
• the subject of the invention is a method for manufacturing a shaped, particularly stamped component, bodywork or body structure, also called a "white body” made of aluminum alloy, comprising the following steps:
• Solution heat treatment quenching and pre-tempering at a temperature generally between 50 and 100 ° C for a period of at least 12 hours, and typically obtained by winding at a temperature of at least 60 ° C followed cooling in the open,
• three-dimensional room means a room for which there is no direction in which the transverse section of said room is constant along said direction.
• Another object of the invention is a stamped bodywork component or bodywork structure also called “white box” produced by a method according to one of claims 1 to 10, characterized in that its elastic limit, determined according to standard NF EN ISO 6892-1, is Rpo, 2> 270 MPa and preferably> 275 MPa, and in that its "angle of folding three points" abnormal, determined according to standard NF EN ISO 7438 and the procedures VDA 238-100 and VDA 239-200, is> 100 ° and preferably> 105 ° with anorm> - (4/3) * Rp 0 , 2 + 507.
• the invention also encompasses a stamped body component or bodywork structure also called “white box” according to the invention such as in particular a lining or reinforcement door, hood, tailgate, roof, or the side members , aprons, load floors, tunnels and front, middle and rear feet or uprights, as well as shock absorbers or "crashboxes".
• a stamped body component or bodywork structure also called “white box” according to the invention such as in particular a lining or reinforcement door, hood, tailgate, roof, or the side members , aprons, load floors, tunnels and front, middle and rear feet or uprights, as well as shock absorbers or "crashboxes”.
• FIG. 1 shows the device for "three-point folding test" consisting of two rollers R, a punch B of radius r for folding the sheet T of thickness t.
• FIG. 2 shows the sheet T after the "three-point folding" test with the internal angle ⁇ and the external angle, the measured result of the test: a.
• Figure 3 shows the trade-off between the yield strength and the bend angle for a selection of tests.
• the invention is based on the finding made by the Applicant that it is entirely possible, thanks to a composition and a suitable manufacturing process, to obtain sheets having excellent drawability after dissolution, quenching and maturing at ambient temperature, and sufficient mechanical strength in the reclaimed state and after the baking treatment of the paints, typically and respectively for 4 hours and 20 minutes at 205 ° C. and 180 ° C., while guaranteeing a riveting ability and a crash behavior of the finished component very satisfactory.
• the mechanical characteristics reached in this last metallurgical state are a limit of elasticity Rpo, 2> 270 MPa, as well as an anomalous folding angle without crack> 100 ° and preferably> 105 °, with anorm> - (4/3 * Rp 0 , 2 + 507.
• the composition of the alloy according to the invention is the following (% by weight):
• Si 0.60 - 0.85; Fe: 0.05 - 0.25; Cu: 0.05 - 0.30; Mn: 0.05 - 0.30; Mg: 0.50 - 1.00; Ti: 0.02 - 0.10; V: 0.00 - 0.10, with Ti + V ⁇ 0.10 other elements ⁇ 0.05 each and ⁇ 0.15 in total, remaining aluminum, with Mg ⁇ -2.67 x Si + 2.87
• silicon is the first alloying element of aluminum-magnesium-silicon systems (AA6xxx family) to form Mg 2 Si or MgsSie intermetallic compounds that contribute to the structural hardening of these alloys.
• the range of the most advantageous content for silicon is 0.60 to 0.75%.
• Mg Generally, the level of mechanical characteristics of alloys of the AA6xxx family increases with the magnesium content. Combined with silicon to form Mg 2 Si or MgsSie intermetallic compounds, magnesium contributes to the increase of mechanical properties. A minimum content of 0.50% is required to obtain the required level of mechanical characteristics and to form sufficient hardening precipitates. Beyond 1.00%, the Si / Mg ratio obtained is unfavorable to the compromise of properties sought.
• the most advantageous range for magnesium is 0.60 to 0.70%.
• Fe Iron is generally considered an undesirable impurity; the presence of intermetallic compounds containing iron is generally associated with a decrease in formability. Surprisingly, the present inventors have found that a content in excess of 0.05%, and better still 0.10%, improves the ductility and the formability, in particular by delaying the rupture during the deformation after necking. Although they are not related to this hypothesis, the present inventors believe that this surprising effect could come in particular from the substantial decrease in the solubility of solid solution manganese when this element is present and / or the formation of a high density. intermetallic particles guaranteeing good "hardenability" during shaping. In these grades, iron can also contribute to the control of grain size. Above 0.25%), too many intermetallic particles are created with a detrimental effect on ductility and corrosion resistance.
• the most preferred range is 0.05 to 0.20%.
• Mn its content is limited to 0.30%. An addition of manganese above 0.05%) increases the mechanical characteristics by the effect of solid solution, but beyond 0.30% o, it would very strongly decrease the sensitivity to the speed of deformation and therefore the ductility .
• An advantageous range for manganese is 0.10 to 0.15%
• Cu In alloys of the AA6000 family, copper is an effective hardener by participating in hardening precipitation. At a minimum content of 0.05%, its presence makes it possible to obtain higher mechanical characteristics. In the alloy considered, copper above 0.30%> has a negative influence on the resistance to intergranular corrosion. Preferably, the copper content is at most 0.20%.
• the most favorable range for copper is 0.08 to 0.15%.
• V and Ti each of these elements, for Ti at a content of at least 0.02%, can promote a solid solution hardening leading to the required mechanical characteristics and each of these elements has a favorable effect on the ductility in service and resistance to corrosion.
• a maximum content of 0.10% for Ti as for V, and a sum of the Ti and V Ti + V contents ⁇ 0.10%) are required in particular to avoid the conditions of formation of the primary phases during the vertical casting and improve formability performance.
• the most preferred range is 0.03 to 0.10% for Ti.
• a range of V from 0.03 to 0.08% is preferred, however in another advantageous embodiment for recycling problems, the V content is maintained at at most 0, 03%.
• the other elements are typically impurities whose content is kept below 0.05%; the rest is aluminum.
• impurities that may be mentioned for example Cr, Ni, Zn, Zr and Pb.
• certain impurities are maintained at even lower contents.
• the content of Ni and Zr is advantageously kept below 0.03% and the Pb content is advantageously kept below 0.02%.
• the method of manufacturing the sheets according to the invention typically comprises the casting of a plate, the scalping of this plate, followed by its homogenization advantageously with a temperature rise rate of at least 30 ° C / h to a maximum of temperature of 530 to 570 ° C with a maintenance between 2 and 12 h, preferably between 4 and 6 h, followed by cooling, either up to room temperature or up to hot rolling start temperature.
• the hot rolling of the plate in a strip of thickness between 3.5 and 10 mm the cold rolling to the final thickness typically between 1 and 3.5 mm, the dissolution of the rolled strip at a temperature above the solvus temperature of the alloy, while avoiding a local melting or burning, or between 540 and 570 ° C for 10 s to 30 min, quenching at a rate of more than 30 ° C / sec and more preferably at least 100 ° C / sec.
• a pre-income that is to say a treatment at a temperature of between 50 and 100 ° C. for a duration of at least 12 hours, typically occurs. obtained by winding at a temperature of at least 60 ° C followed by cooling in the open air, then maturation at room temperature for 72 hours to 6 months.
• the sheets according to the invention have a very good stamping ability.
• T is the instantaneous temperature expressed in Kelvin, which evolves with the time t and T eq is the reference temperature of 205 ° C (478 K), and Teq is the equivalent time.
• the components thus manufactured have, in use, after forming, optimized income on the part, assembly and baking of the paints, properties high mechanical characteristics, very good crash behavior and good corrosion resistance.
• a stamped bodywork component or bodywork structure also called a “blank body” produced by a method of the invention, is characterized in that its elastic limit, determined according to the NF EN ISO 6892-1 standard, is Rpo, 2> 270 MPa and preferably> 275 MPa, and in that its abnormal "angle of folding three points", determined according to the standard NF EN ISO 7438 and the procedures VDA 238-100 and VDA 239-200, is > 100 ° and preferably> 105 ° with anorm> - (4/3) * Rpo, 2 + 507.
• a stamped bodywork component or bodywork structure also known as a "white body”, according to the invention, is chosen from the group containing, in particular, liners or reinforcements for doors, bonnets, tailgate or roof, or the spars, aprons, load floors, tunnels and front, middle and rear feet, as well as shock absorbers or "crashboxes".
• Table 1 summarizes the nominal chemical compositions (% by weight) of the alloys used in the tests. The content of the other elements was ⁇ 0.05.
• the rolling plates of these different alloys were obtained by vertical semi-continuous casting. After scalping, these different plates have undergone a heat treatment homogenization and / or reheating whose temperatures are given in Table 2.
• the plates of composition 1, 2, 7 and 8 underwent a homogenization treatment at 530 ° C. consisting of a temperature rise at a speed of 30 ° C./h up to 530 ° C. and a maintenance of the order 3 hours at this temperature.
• This homogenization step is directly followed by a hot rolling step.
• the plates of composition 3, 31 and 9 have undergone a homogenization treatment at 540 ° C. consisting of a temperature rise at a speed of 30 ° C./h up to 540 ° C., a maintenance of the order of 5 hours at this temperature directly followed by hot rolling.
• composition 4, 5 and 6 were homogenized consisting of a rise at 570 ° C. with a minimum hold of 2 hours at this temperature, directly followed by hot rolling.
• the composition plate 10 has undergone a homogenization treatment at 550 ° C consisting of a temperature rise at a rate of 30 ° C / h to 550 ° C, a maintenance of about 4 hours at this temperature .
• This homogenization step is directly followed by a hot rolling step.
• the next hot rolling step is carried out on a reversible rolling mill followed according to the case of a hot tandem rolling mill with 4 stands up to a thickness of between 3.5 and 10 mm.
• the hot rolling output thicknesses of the tested cases are given in Table 2. It is followed by a cold rolling step which makes it possible to obtain sheets of thickness between 2.0 and 2.5 mm.
• the cold rolling output thicknesses of the tested cases are given in Table 2 below.
• the rolling steps are followed by a solution heat treatment step and quenching.
• the dissolution is done at a temperature above the solvus temperature of the alloy, while avoiding burning.
• the dissolved sheet is then quenched at a minimum speed of 30 ° C / s. For tests 18 to 21 a minimum speed of 100 ° C / s was used.
• this step is carried out in a passing furnace by raising the temperature of the metal to the dissolution temperature in less than about one minute directly followed by a tempering.
• the dissolution is done in an air oven with introduction in hot furnace, reached the dissolution temperature in less than 20 minutes and maintained at this temperature for 30 minutes.
• This dissolution step is followed by immersion quenching in water at 85 ° C.
• the quenching is followed by a pre-tempered heat treatment, intended to improve the curing performance during the baking of the paints.
• this step is performed by winding at a temperature of at least 60 ° C followed by cooling in the open air.
• the pre-income is obtained by immersing and keeping the sheets in water at 85 ° C for 8 hours.
• a maturation at a temperature of at least 72 hours was then carried out.
• the protocols recommend for the pieces shaped to the metallurgical state T4 then undergoing the baking treatment of the paints, to achieve between the maturation and the baking of the paintings a pre-deformation in controlled tension of 2%, to simulate the setting form by stamping.
• the crash behavior can be estimated by a "three-point folding test" according to the NF EN ISO 7438 standard and the VDA 238-100 and VDA 239-200 procedures.
• the folding device is as shown in FIG.
• the rollers have a diameter of 30 mm and the distance between the axes of the rollers is equal to 30 + 2t mm, t being the thickness of the sheet tested T.
• the punch is brought into contact with the sheet with a pre-force of 30 Newtons. Once the contact is established, the displacement of the punch is indexed to zero. The test then consists in moving the punch so as to perform the "three-point folding" of the sheet.
• the test stops when a micro-cracking of the sheet leads to a force drop on the punch of at least 30 Newtons, or when the punch has moved 14.2 mm, which corresponds to the stroke maximum allowed.
• the sheet sample is thus folded as shown in Figure 2.
• the ductility in service is then evaluated by measuring the bending angle a.
• the higher the angle a the better the ability to crash or bend the sheet.
• all the angles measured for different sheet thicknesses are brought back to the anormal value, according to the formula below, as described in the VDA 239-200 standard:
• the protocols recommend for the pieces shaped to the metallurgical state T4 and then undergoing the baking treatment of the paints, to achieve between the maturation and the baking of the paintings a pre-deformation in tensile control of 10%, to simulate the setting form by stamping.
• this pre-deformation has no very significant effect on the characteristics of the final component.
• Table 4 By combining the preferred income and the compositions according to the invention, according to tests 19, 20 and 21, a remarkable compromise of property is reached, namely a yield strength Rpo, 2> 270 MPa and preferably> 275 MPa, and that an anomalous folding angle without crack> 100 ° and preferably> 105 ° and anorm> - (4/3) * Rpo, 2 + 507, which is illustrated by FIG. 3.
• examples 4 and 7 allow to obtain a limit of elasticity Rpo, 2> 270 MPa and an angle of folding without crack> 100 ° but do not allow to obtain and that an angle of folding without abnormal cracks> - (4 / 3) * Rp 0 , 2 + 507.

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• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Heat Treatment Of Articles (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Shaping Metal By Deep-Drawing, Or The Like (AREA)
• Body Structure For Vehicles (AREA)

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• 2017
  • 2017-04-06 FR FR1753018A patent/FR3065013B1/fr active Active
• 2018
  • 2018-04-03 EP EP18718608.5A patent/EP3607104A1/de active Pending
  • 2018-04-03 CA CA3057728A patent/CA3057728A1/fr active Pending
  • 2018-04-03 DE DE18718608.5T patent/DE18718608T1/de active Pending
  • 2018-04-03 WO PCT/FR2018/050829 patent/WO2018185425A1/fr unknown
  • 2018-04-03 CN CN201880023671.6A patent/CN110494578B/zh active Active
  • 2018-04-03 US US16/500,724 patent/US11649536B2/en active Active

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