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
  • C22F1/043—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
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent

Definitions

• alloys Al-Mg-Si that is to say the alloys of the 6000 series.
• alloys 6016 and 6016A with thicknesses of the order of 1 to 1.2 mm, are the most used for this application, because they lead to a better compromise between the various properties required, including ensuring better formability, particularly for crimping, and a better resistance to filiform corrosion than alloys with a content of higher copper such as the 6111 widely used in the United States.
• Alloys of type 6016 are described in particular in the patents FR 2360684 Alusuisse and EP 0259232 of the applicant, while alloys of the type 6111 are described in the patent US 4,614,552 Alcan International Ltd.
• the temperature and the life expectancy for the alloys 6000 are described for example in the article of R. Develay "Heat treatments of aluminum alloys", Engineering Techniques, section M 1290, 1986 , in the article DW Pashley et al. "Delayed aging in aluminum-magnesium silicones alloys: effect on structure and mechanical propperties", Journal of the Institute of Metals, No. 94, 1966, pp. 41-49 , or in the patent EP 0480402 (Sumitomo Light Metal).
• the patent FR 1243877 (Cegedur ) further describes a continuous furnace adapted to perform a prerevenu.
• the object of the present invention is to provide alloy sheets of type 6016 for automobile body skin having a composition suitable for recycling, a sufficient formability for deep drawing and crimping under severe conditions, improved indentation resistance compared to prior art plates of the type 6016, while controlling the springback, good bonding ability, cutting without flaking, and good resistance to filiform corrosion.
• the invention is based on a narrow composition range within the composition of the 6016A recorded at the Aluminum Association, to obtain all the desired properties.
• the silicon content is in the lower part of the 6016A content range, while the magnesium content remains at the center of the range. This lowering of the silicon content contributes to a more complete dissolution of the alloy, favorable to the formability.
• the iron content remains above 0.25%, which allows, unlike the low iron grades such as 6022, the use of recycling metal, and is rather favorable to the surface appearance after stamping.
• the copper content is controlled within very narrow limits: a content of at least 0.1%, a little higher than that of the existing grades of 6016 or 6022, contributes to the mechanical strength, but above 0, 25% the alloy presents a risk of filiform corrosion.
• the alloy must contain at least 0.05% manganese, chromium, vanadium or zirconium to control the grain size, and avoid the appearance of orange peel during severe deformations, such as crimping used for hoods. Conversely, a total content of these elements greater than 0.20% is unfavorable to the formability.
• the method of manufacturing the sheets according to the invention typically comprises the casting of a plate, possibly the scalping of this plate, and its homogenization or a simple reheating at a temperature between 400 and 570 ° C of a duration between 6 and 24 h.
• the hot rolling is preferably at an inlet temperature above 510 ° C, which contributes to improving the mechanical strength with respect to a lower inlet temperature.
• the winding temperature of the hot-rolled strip must be less than 350 ° C., and preferably 300 ° C., to guarantee the mechanical characteristics and to avoid lineal defect.
• the equivalent time is insufficient, the kinetics of hardening when the paints are cooked decreases with the waiting time at ambient temperature. If, on the contrary, the equivalent time is too high, the mechanical characteristics increase too much at the pre-income, and the formability of the sheet is degraded.
• an equivalent time of 1 to 10 hours, and preferably 3 to 6 hours, is well suited.
• the sheet is usually stored at this stage for a longer or shorter time, which leads to a natural maturation which increases the yield strength over time.
• the sheets according to the invention After 3 weeks of maturation, the sheets according to the invention have, at a thickness of the order of 0.9 to 1 mm, a yield strength L of the order of 130 MPa, higher than all variants of 6016, including the high-strength grades DR100 and DR120 described in the article by R. Shahani et al. mentioned above, and only slightly lower than that of 6022. After 6 months of aging, this elastic limit remains below 160 MPa, or 150 MPa, unlike 6022 or 6111 alloys.
• the sheet may be, before shaping, coated with a lubricant, oil or dry lubricant, suitable for stamping, assembly and surface treatment of the part to be produced.
• the sheets according to the invention have a formability, measured by the parameter LDH 0 ("limiting dome height" in plane strain), better than that of the alloys 6111 and 6022, and as good as the grades 6016 with high strength.
• the LDH parameter is widely used for the evaluation of the drawability of sheets with a thickness of 0.5 to 2 mm. It has been the subject of numerous publications, in particular that of R. Thompson, "The LDH Test to Evaluate Sheet Metal Formabiblity - Final Report of the LDH Committee of the North American Deep Drawing Research Group," SAE Conference, Detroit, 1993, SAE Paper No. 930815 .
• the LDH test is a blank stamping test blocked at the periphery by a rod.
• the pressure clamp is controlled to prevent slipping into the rod.
• the blank size 120 x 160 mm, is biased in a mode close to the plane deformation.
• the lubrication between the punch and the sheet is ensured by a plastic film and grease (Shell HDM2 grease).
• the speed of descent of the punch is 50 mm / min.
• the value LDH is the displacement of the punch at break, the limit depth of the stamping. An average of three tests is performed, giving a 95% confidence interval on the measurement of ⁇ 0.2 mm.
• the sheets according to the invention have a crimping ability better than that of alloy sheets 6111 or 6022 and as good as 6016 high strength alloy sheets of the prior art. This crimping ability is evaluated by a laboratory test with a 90 ° bend, a 45 ° pre-crimp and a final flat crimp.
• the sheets according to the invention also have a very weak deformation anisotropy, which can be measured by the difference between the LDH for a main deformation parallel to the rolling direction, and a main deformation. perpendicular to the rolling direction. This difference is less than 1 mm, and preferably 0.6 mm.
• the body skin part is generally made by cutting a blank in the sheet, stamping this blank and clipping the press.
• stamping it is necessary to avoid the appearance of lineage ("roping" or “ridging” in English), which is harmful for the appearance after painting, and can decrease the formability, in particular in case of strong deformation in the perpendicular to the direction of rolling.
• lineage ropeing or "ridging” in English
• Various means have been proposed in this direction, for example the control of the hot rolling outlet temperature between 270 and 340 ° C., as indicated in the patent. EP 0259232 of the plaintiff. It should also avoid the appearance of the stamping "orange peel", which contributes to a visible defect appearance after painting.
• a grain size preferably below 50 microns, which can be obtained by the presence in the alloy of a sufficient amount of manganese, or other elements playing a similar role such as chromium , vanadium or zirconium, by controlling the temperature and duration of dissolution and by a sufficient reduction, typically at least 30%, by cold rolling.
• the edges of the stamped blank have fallen to 90 ° and inserted a stamping lining on which it performs a pre-crimping, and a final crimping flat.
• the sheets according to the invention make it possible to carry out the various operations commonly used for the manufacture of car body skin parts, such as crimping, clinching, riveting, spot welding, laser welding and gluing.
• the parts made from sheets according to the invention also have a good filiform corrosion resistance after painting, better than that of high copper alloys such as 6111.
• the major difficulty lies in the management of the differences in thermal expansion between the two materials during the baking of the paints, especially during cataphoresis firing, which is generally carried out between 160 and 200 ° C. . Indeed, it is essential to limit the residual deformations after cooking to a level acceptable for the appearance of the vehicle.
• the sheets according to the invention make it possible to limit these deformations. Indeed, the applicant has demonstrated that a high yield strength at the firing temperature, for example greater than 140 MPa at a temperature of 160 ° C for the alloy according to the invention, had a favorable effect on the level of deformation, if the assembly is carried out after cooking, of which it is preferable to limit the temperature.
• composition A represents a conventional 6016
• B corresponds to that of the grade DR 100 of the Applicant described in the articles mentioned above
• C and D correspond to an alloy 6111
• E corresponds to an alloy 6022
• F, G, H and I have similar compositions, differing either by Cu (F) or by Mn (G and H) of the composition I according to the invention.
• the plates were scalped, homogenized for 10 h at 570 ° C. and then hot-rolled directly on heat of homogenization, first on a reversible mill and then on a tandem mill.
• the starting temperature of rolling was of the order of 540 ° C, the winding temperature of the hot strip of the order of 310 ° C.
• the hot rolled strip up to 3 mm is then cold rolled to the final thickness of 1 mm.
• An intermediate annealing at the thickness of 2.5 mm was performed, ie a "batch" annealing in a coil, with a rise at 350 ° C. in 10 h, a waiting time of 2 h and a slow cooling, or a "flash" annealing.
• a continuous oven with a rise to 400 ° C in about a minute and immediate cooling.
• Samples taken from the strips are dissolved at a temperature of 570 ° C for less than one minute and then quenched with cold water.
• the yield strength R 0.2 direction L (in MPa) was measured after 3 weeks and 6 months of maturation at room temperature, then after a 30 minute treatment at 165 ° C. or 185 ° C. , simulating the baking treatment of paints.
• the formability was also measured using the parameter LDH (in mm), the main deformation being respectively parallel and perpendicular to the rolling direction.
• the sample I according to the invention has, after maturation of 3 weeks, a yield strength of the same order as that of the conventional 6016 (sample A), and significantly lower than that of the alloys 6111 (C and D). and 6022 (E). After 6 months of maturation, the positioning of the elastic limit of the sample I compared to the samples of the other alloys has not changed.
• the elasticity limit of the sample I after baking the paints when pre-tempered is high, much higher than that of the alloys 6016 and DR100, of the same order as that of the F alloy in copper, and lying between those of the two shades of 6111, which ensures a high resistance to the indentation of the finished part.
• the crimping behavior in the direction parallel to the rolling and in the perpendicular direction, the resistance to filiform corrosion after phosphatation, cataphoresis and painting, as well as the appearance or no flakes or filaments when cutting or trimming after stamping.
• the crimping test is carried out in 3 operations: edge dropping at 90 ° C, pre-crimping at 45 ° and flat crimping on a lining sheet 0.7 mm thick.
• the crimped edges are then classified by visual inspection, as indicated in the article by D. Daniel et al. at IBEC 99.
• the filiform corrosion resistance is assessed according to EN 3665, with 150 x 60 x 1 mm dimensions painted and scratched.
• the test procedure involves activation of HCl corrosion for 1 h followed by wet chamber exposure at 40 ° C for 1000 h.
• the maximum length of the corrosion filaments is measured, with an average of 3 test pieces per case, with the following classification: ⁇ 2 mm: good 2-5 mm: medium> 5 mm: bad.
• the cutting test is described in the article by D. Daniel et al. at IBEC 99 mentioned above. The game was 10% of the thickness and the cutting angle of 0 °.
• Aluminum alloy panels were made of composition indicated in Table 4, with a manufacturing range similar to that of Example 1, with or without pre-tempering and heat treatment after shaping and before assembly, as shown also in Table 4.
• the dimensions of the panels are 1.6 mx 0.9 m.
• Table 4 Ech. Alloy Yes (%) Fe (%) Mg (%) Cu (%) Mn (%) pre-income eq annealing J Inv. 1.05 0.25 0.45 0.19 0.14 5 h 4h-185 ° K Inv. 1.05 0.25 0.45 0.19 0.14 5h No The 6111 0.70 0.25 0.60 0.69 0.21 - No M DR100 1.03 0.26 0.32 0.07 0.11 5 h No NOT 6016 1.03 0.26 0.32 0.07 0.11 - No
• the alloy according to the invention makes it possible to reduce residual deformations after firing.
• the performance of the alloys is well correlated with the yield strength at the baking temperature.
• a heat treatment before assembly and the addition of ribs are beneficial to reduce deformations.
• the dynamic indentation resistance of a sheet of thickness 1 mm elaborated with a manufacturing range of the type of that of Example 1, comprising a pre-income equivalent time of 5 h, and a heat treatment were evaluated. 20 min at different temperatures simulating a baking paints, alloy according to the invention and alloy 6016 DR100, compared with that of a steel sheet of yield strength 290 MPa after baking paints, thickness 0 , 7 mm.
• This value of 290 MPa after baking for the yield strength of a body steel sheet corresponds approximately to the average of the yield strengths of the steel sheets used for the body skins of the most recent recent European cars. .
• a thickness of 1 mm for an aluminum sheet represents an elongation of approximately 50% compared to a 0.7 mm thick steel sheet.
• the device used for the indentation test comprises an indenter with a diameter of 15 mm and a weight of 138 g, dropped from a height of 1 m, at a speed of about 16 km / h, on the flanged sheet sample between two steel plates. The depth of permanent indentation (in mm) is measured. The results are shown in Table 6. Table 6 Températu-re cooking R 0.2 All. inv. R 0.2 DR100 R 0,2 steel Indent. All. inv. Indent. DR100 Indent. steel 170 ° C 193 161 290 1.55 1.80 1.45 185 ° C. 217 189 290 1.45 1.62 1.45 205 ° C 230 290 1.38 1.46 1.45
• the sheet 1 mm thick according to the invention has the same resistance to indentation as the 0.7 mm steel sheet.
• the DR100 alloy this is true only for a paint firing temperature of 205 ° C, higher than the temperatures usually used by car manufacturers.
• a stronger alloy such as 6111 would increase resistance to indentation beyond the needs of the market, but at the expense of formability, especially during crimping.

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

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• 2002
  • 2002-02-05 FR FR0201346A patent/FR2835533B1/fr not_active Expired - Fee Related
• 2003
  • 2003-02-03 WO PCT/FR2003/000318 patent/WO2003066919A2/fr active Application Filing
  • 2003-02-03 DE DE03712292T patent/DE03712292T1/de active Pending
  • 2003-02-03 EP EP03712292A patent/EP1472380B1/fr not_active Revoked
  • 2003-02-03 KR KR1020047012157A patent/KR100964855B1/ko not_active IP Right Cessation
  • 2003-02-03 ES ES03712292T patent/ES2316738T3/es not_active Expired - Lifetime
  • 2003-02-03 AT AT03712292T patent/ATE413476T1/de not_active IP Right Cessation
  • 2003-02-03 DE DE60324526T patent/DE60324526D1/de not_active Expired - Lifetime
  • 2003-02-03 AU AU2003216971A patent/AU2003216971A1/en not_active Abandoned
  • 2003-02-03 CA CA2471501A patent/CA2471501C/fr not_active Expired - Fee Related
  • 2003-02-03 JP JP2003566264A patent/JP2005525462A/ja active Pending
  • 2003-02-03 US US10/502,659 patent/US20050028894A1/en not_active Abandoned
• 2008
  • 2008-12-09 JP JP2008312816A patent/JP2009133006A/ja active Pending

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