WO1997047779A1 - Tole laminee en alliage d'aluminium a haute formabilite - Google Patents

Tole laminee en alliage d'aluminium a haute formabilite Download PDF

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Publication number
WO1997047779A1
WO1997047779A1 PCT/US1996/009887 US9609887W WO9747779A1 WO 1997047779 A1 WO1997047779 A1 WO 1997047779A1 US 9609887 W US9609887 W US 9609887W WO 9747779 A1 WO9747779 A1 WO 9747779A1
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Prior art keywords
sheet
aluminum alloy
alloy
copper
manganese
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PCT/US1996/009887
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English (en)
Inventor
Rolf B. Erickson
Shawn J. Murtha
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Aluminum Company Of America
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Priority to PCT/US1996/009887 priority Critical patent/WO1997047779A1/fr
Priority to JP50153198A priority patent/JP2001503473A/ja
Publication of WO1997047779A1 publication Critical patent/WO1997047779A1/fr

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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
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C22C21/14—Alloys based on aluminium with copper as the next major constituent with silicon
    • 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
    • C22C21/12—Alloys based on aluminium with copper as the next major constituent
    • C22C21/16—Alloys based on aluminium with copper as the next major constituent with magnesium
    • 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 an aluminum alloy rolled sheet for forming and a production process therefor. More particularly, the present invention relates to an aluminum alloy rolled sheet for forming which is suitable for applications requiring the combination of excellent formability and good strength and which has been subjected to paint baking, such as in an application for an automobile body. Because of the increasing emphasis on producing lower weight automobiles in order, among other things, to conserve energy, considerable effort has been directed toward developing aluminum alloy products suited to automotive applications. Especially desirable would be a single aluminum alloy product useful in several different automotive applications. Such would offer scrap reclamation advantages in addition to the obvious economies in simplifying metal inventories. Yet, it will be appreciated that different components on the automobile can require different properties in the form used.
  • an aluminum alloy sheet when formed into shaped outside body panels should be capable of attaining high strength which provides resistance to denting as well as being free of Lueders' lines.
  • Lueders' lines are lines or markings appearing on the otherwise smooth surface of metal strained beyond its elastic limit, usually as a result of a non-uniform flow during forming operations, and reflective of metal movement during those operations.
  • the strength and the presence or absence of such lines on aluminum sheet used for inside support panels, normally not visible, is less important. Bumper applications on the other hand require such properties as high strength, resistance to denting, resistance to stress corrosion cracking and exfoliation corrosion.
  • an aluminum alloy product needs to possess excellent forming characteristics to facilitate shaping, drawing, bending and the like, without cracking, tearing, Lueders' lines or excessive wrinkling or press loads, and yet be possessed of adequate strength. Since forming is typically carried out at room temperature, formability at room or low temperatures is often a principal concern. Still another aspect which is considered important in automotive uses is weldability, especially resistance spot weldability. For example, the outside body sheet and inside support sheet of a dual sheet structure such as a hood, door or trunk lid are often joined by spot welding, and it is important that the life of the spot welding electrode is not unduly shortened by reason of the aluminum alloy sheet so as to cause unnecessary interruption of assembly line production, as for electrode replacement.
  • the alloy should have high bending capability without cracking or severe surface roughening, since often the structural products are fastened or joined to each other by hemming or seaming.
  • Heat treatable alloys offer an advantage in that the parts formed from these alloys can be produced at a given lower strength level in the solution treated and quenched temper which can be later increased by artificial aging after the panel is shaped. This offers easier forming at a lower strength level which is thereafter increased for the end use. Further, the thermal treatment to effect artificial aging can sometimes be achieved during a paint bake treatment, so that a separate step for the strengthening treatment is not required.
  • Non-heat treatable alloys are typically strengthened by strain hardening, as by forming and/or cold rolling. These strain or work hardening effects are usually diminished during thermal exposures such as paint bake or cure cycles, which can partially soften or relax the strain hardening effects. Accordingly, it would be advantageous to provide robust sheet materials having a combination of excellent formability and good strength.
  • the primary object of the present invention is to provide a method for producing an aluminum sheet product having a combination of excellent formability and good strength for automotive applications.
  • Another objective of the present invention is to provide a composition that it capable of being produced into an aluminum sheet product which has considerably improved characteristics, particularly in formability and strength.
  • a process for fabricating an aluminum alloy rolled sheet particularly suitable for use for an automotive body comprising: (a) providing a body of an alloy comprising, or preferably consisting essentially of, about 0.8 to about 1.3 wt.% silicon, about 0.2 to about 0.6 wt.% magnesium, about 0.5 to about 1.8 wt.% copper, about 0.01 to about 0.1 wt.% manganese, about 0.01 to about 0.2 wt.% iron, the balance being substantially aluminum and incidental elements and impurities; (b) working the body to produce the sheet; (c) solution heat treating the sheet; and (d) rapidly quenching the sheet.
  • the sheet has an improved formability and strength.
  • the composition includes about 1.0 to about 1.2 wt.% silicon, about 0.2 to about 0.45 wt.% magnesium, about 0.6 to about 1.5 wt.% copper, about 0.04 to about 0.08 wt.% manganese and about 0.05 to about 0.17 wt.% iron.
  • a method for producing an aluminum alloy sheet for forming comprising the steps of: casting an alloy ingot having the composition of the above-mentioned composition by a continuous casting or semicontinuous DC (direct chill) casting; homogenizing the alloy ingot at a temperature of from 450° to 602°C (842° to 1115°F) for a period of from 1 to 48 hours; subsequently rolling until a requisite sheet thickness is obtained; holding the sheet at a temperature of from 450° to 602°C for a period of at least 5 seconds, followed by rapidly quenching; and, aging at room temperature.
  • Figure 1 is a perspective view of the compositional ranges for the Si, Mg and Cu contents of the aluminum alloy sheet according to the present invention.
  • Figure 2 is a graph illustrating the effect of copper content of the alloy of the present invention on tensile yield strength.
  • Figure 3 is a graph illustrating the effect of copper content of the alloy of the present invention on plane strain stretching.
  • Figure 4 is a graph illustrating the effect of copper content of the alloy of the present invention on the material's bending ability.
  • Figure 5 is a graph illustrating the effect of simulated forming and paint baking on yield strength.
  • Formability is used herein to mean the extent to which a sheet material can be deformed in a particular deformation process before the onset of failure. Typically, failure occurs in aluminum alloys by either localized necking of the sheet or ductile fracture. Different measures of formability are known in the art and described in "Formability of Aluminum Sheet Materials” by J.M. Story, Aluminum 62 (1986) 10, pp. 738-742 and 62 (1986) 11, pp. 835-839.
  • sheet as used broadly herein is intended to embrace gauges sometimes referred to as “plate” and “foil” as well as gauges intermediate to plate and foil.
  • ksi shall mean kilopounds (thousand pounds) per square inch.
  • minimum with respect to a property shall mean the property level at which 99% of the product is expected to conform with 95% confidence using standard statistical methods. Properties include, strength and formability.
  • ingot-derived shall mean solidified from liquid metal by known or subsequently developed casting processes rather than through powder metallurgy or similar techniques. The term expressly includes, but shall not be limited to, direct chill (DC) continuous casting, slab casting, block casting, spray casting, electromagnetic continuous (EMC) casting and variations thereof.
  • solution heat treat is used herein to mean that the alloy is heated and maintained at a temperature sufficient to dissolve soluble constituents into solid solution where they are retained in a supersaturated state after quenching.
  • the solution heat treatment of the present invention is such that substantially all soluble second phase particles are dissolved into solid solution.
  • Rapid quench is used herein to mean to cool the material at a rate sufficient that preferably substantially all of the soluble constituents, which were dissolved into solution during solution heat treatment, are retained in a supersaturated state after quenching.
  • the cooling rate can have a substantial effect on the properties of the quenched alloy. Too slow a quench rate, such as that associated with warm water quench or misting water, can cause precipitate particles to prematurely come out of solution. Precipitate particles coming out of solution during a slow quench have a tendency to precipitate heterogenously and have been associated with poor bending performance. Quench rates are considered to be rapid if they do not result in the appreciable precipitation of particles from solution. Rapid quench rates can be achieved by various methods, including cold water quenching, forced air quenching and water spray or water mist quenching.
  • the terms "formed panel” and "vehicular formed panel” as referred to herein in their broadest sense are intended to include bumpers, doors, hoods, trunk lids, fenders, fender wells, floors, wheels and other portions of an automotive or vehicular body.
  • a panel can be fashioned from a flat sheet which is stamped between mating dies to provide a three- dimensional contoured shape, often of a generally convex configuration with respect to panels visible from the outside of a vehicle.
  • Other techniques useful for fabricating panels include roll forming, hydroforming and various forming techniques known to the art.
  • Dual or plural panel members comprise two or more formed panels, typically an inside and an outside panel, the individual features of which are as described above.
  • the inner and outer panels can be peripherally joined or connected to provide the dual or plural panel assembly, as shown in U.S. Patent 4,082,578, the teachings of which are incorporated herein by reference.
  • autonomous or “vehicular” as used herein are intended to refer to automobiles, of course, but also to trucks, off-road vehicles and other transport vehicles such as planes, trains and boats.
  • FIG. 1 there is illustrated a perspective view of the range Si, Mg and Cu contents of the aluminum alloy sheet according to the present invention.
  • the cubic area defined by points A-H illustrate the claimed area for the Si, Mg and Cu contents of the claimed alloys.
  • Points A-D are all located on the 0.5 wt.% copper plane.
  • Points E-H are all located on the 1.8 wt.% copper plane.
  • the weight percent of Mg and Si for points A and E, B and F, C and G, and D and H are the same.
  • the alloys of the present invention also include Mn and Fe as essential components of the alloy.
  • Mn and Fe are essential components of the alloy.
  • Each of the essential elements have a role that is performed synergistically as described below.
  • the Si strengthens the alloy due to precipitation hardening of elemental Si and g2Si formed under the co-presence of Mg.
  • Si also effectively enhances the formability, particularly the stretching formability.
  • the Si content is less than about 0.8 wt.%, the strength and formability are unsatisfactory.
  • the Si content exceeds about 1.3 wt.%, the soluble particles cannot always be put into solid solution during heat treatment without melting the alloy. Hence, the formability and mechanical properties of the resulting sheet would be degraded.
  • the Si content is preferably maintained in or about the range of 0.8 wt.% to 1.3 wt.%.
  • Mg is an alloy- strengthening element that works by forming Mg 2 Si under the co-presence of Si. This result is not effectively attained at an Mg content of less than about 0.2 wt.%.
  • Mg is effective in enhancing the strength of aluminum alloys, at higher levels and in amounts exceeding that needed for forming Mg 2 Si, Mg reduces the formability of the alloy.
  • the Mg content is preferably maintained in or about the range of 0.2 to 0.6 wt.%.
  • Cu is an element that enhances the strength and formability of aluminum alloys. It is difficult to attain sufficient strength while maintaining or improving the formability only by the u ⁇ e of Mg and Si. Cu is therefore indispensable. It is desirable to have Cu in the alloy for purposes of strength and formability. When the copper levels are less than about 0.5 wt.%, the resulting product exhibits low strength and low formability (see Figs. 2 and 3) . When the copper levels are greater than 1.8%, the resulting product exhibits a decrease in bending performance (see Fig. 4) .
  • the Cu content is preferably maintained in or about the range of 0.5 to 1.8 wt.%.
  • Fe forms particles which help refine the recrystallized grains and reduce or eliminate the alloy's susceptibility to a surface roughening phenomena known as orange peel. Therefore, Fe is desirable for grain structure control. However, too much Fe decreases the alloy's resistance to necking and/or fracture.
  • the recrystallized grains coarsen at an Fe content of less than about 0.05 wt.%, and the formability is reduced at an Fe content exceeding 0.2 wt.%.
  • the Fe content is preferably maintained in or about the range of 0.05 wt.% to 0.2 wt.%. Preferably, the Fe content is below about 0.17 wt.%.
  • Mn also helps to refine the recrystallized grains.
  • Mn forms dispersoids in the alloy which stabilizes its structure. Low levels of dispersoids can effectively control the grain structure. However, it has been found that when the Mn exceeds 0.1 wt.%, the formability in plane strain stress states is reduced. Consequently, although low levels of Mn are beneficial in preventing roughening during deformation, the amount of Mn in the alloy must be limited to prevent degradations to its plane strain formability. Plane strain formability has been found to be an important characteristic in the fabrication of large formed panels such as those used in automotive applications. For example, it is thought that 80-85% of stamping failures occur in plane strain. It has been found that Mn is desirable up to levels of about 0.1 wt.%. The preferred Mn content is preferably maintained in or about the range of 0.04 to 0.08 wt.%.
  • the aluminum alloy ingot having a composition in the above-identified ranges is formed by an ordinary continuous casting or a semicontinuous DC casting method.
  • the aluminum alloy ingot is subjected to homogenization to completely dissolve soluble constituent particles and to develop and refine secondary phase particles to assist in grain structure control during subsequent processing.
  • the effects of homogenizing are not properly attained when the heating temperature is less than 450°C (842°F) .
  • the homogenizing temperature exceeds 602°C (1115°F) , melting may occur.
  • Homogenization temperatures must be maintained for a sufficient period of time to insure that the ingot has been homogenized.
  • the ingot After the ingot has been homogenized, it is brought to the proper rolling temperature and then rolled by an ordinary method to a final gauge. Alternatively, the ingot may be brought to room temperature following homogenization and then reheated to a proper rolling temperature prior to hot rolling.
  • the rolling may be exclusively hot rolling or may be a combined hot rolling and subsequent cold rolling. Cold rolling is desired to provide the surface finish desired for autobody panels.
  • the rolled sheet is subjected to the solution heat treatment at a temperature of from 450° to 602°C (842° to 1115°F), followed by rapid cooling (quenching) .
  • the solution heat treatment temperature is less than 450°C (842°F) , the solution effect can be unsatisfactory, and satisfactory formability and strength are not obtained.
  • the solution treatment is more than 602°C (1115°F) , melting may occur.
  • a holding of at least 5 seconds is necessary for completing solutionizing.
  • a holding of 30 seconds or longer is preferred.
  • the rapid cooling after the holding at a solution temperature may be such that the cooling speed is at least equal to the forced air cooling, specifically 300°C/min. or higher.
  • the solution heat treatment is preferably carried out in a continuous solution heat treatment furnace and under the following conditions: heating at a rate of 2°C/sec or more; holding for 5 to 180 seconds or longer, and cooling at a rate of 300°C/min. or more.
  • the heating at a rate of 2°C/sec or more is advantageous for refining the grains that recrystallize during solution heat treatment.
  • a continuous solution heat treatment furnace is most appropriate for subjecting the sheet, which is mass produced in the form of a coil, to the solution heat treatment and rapid cooling.
  • the holding time of 180 seconds or less is desirable for attaining a high productivity.
  • the slower cooling rate is more advisable for providing a better flatness and smaller sheet distortion.
  • the higher cooling speed (>300°C/min. ) is more advisable for providing better formability and a higher strength.
  • a forced air cooling at a cooling speed of 5°C/sec to 300°C/ ⁇ ec is preferable.
  • an intermediate annealing treatment followed by cold rolling may be carried out to help control final grain size, crystallographic texture and/or facilitate cold rolling.
  • the holding temperature is preferably from 316° to 554°C, more preferably from 343° to 454°C, and the holding time is preferably from 0.5 to 10 hours for the intermediate annealing.
  • the intermediate annealed sheet of aluminum alloy is preferably cold rolled at a reduction rate of at least 30%, and is then solution heat treated and rapidly quenched.
  • the temperature of the intermediate annealing is less than 316°C, the recrystallization may not be complete.
  • the temperature of the intermediate annealing is greater than 554 ⁇ C, grain growth and discoloration of the sheet surface may occur.
  • the intermediate annealing time is less than 0.5 hour, a homogeneous annealing of coils in large amounts becomes difficult in a box-type annealing furnace.
  • an intermediate annealing of longer than 10 hours tends to make the process not economically viable.
  • the intermediate annealing temperature is preferably from 343° to 454°C.
  • a cold-rolling at a reduction of at least 30% preferably should be interposed between the intermediate annealing and solution heat treatment to prevent or reduce grain growth during the solution heat treatment.
  • the painting and baking or artificial aging treatment may be carried out.
  • the baking temperature is ordinarily from approximately 150° to 250°C.
  • the aluminum alloy rolled sheet according to the present invention is most appropriate for application as. inner hang-on panels on an automobile body and can also exhibit excellent characteristics when used for other automobile parts, such as a heat shield, an instrument panel and other so-called “body- in-white” parts.
  • Examples 1-5 To demonstrate the practice of the present invention and the advantages thereof, aluminum alloy products were made having the compositions shown in Table 1, the remainder aluminum and elements and impurities. Four of the alloys fall within the composition box shown in Figure 1. The alloys were cast to obtain ingot and fabricated by conventional methods to sheet gauges. The ingots were homogenized between 1000° and 1050°F for at least 4 hours and hot rolled directly thereafter to a thickness of 0.125 inch, allowed to cool to room temperature, intermediate annealed and then cold rolled to a final gauge of 0.036 inch (1 mm) . The sheet was examined prior to solution heat treatment, and significant amounts of soluble second phase particles were found to be present.
  • Coils were solution heat treated in the range of 1000 to 1050°F and rapidly quenched. The sheets were then naturally aged at room temperature for a period of at least two weeks. The alloys were examined, and it was found that substantially all of the second phase particles remained in the solid solution in a supersaturated state.
  • Example 6 For comparison purposes, an AA2008 alloy sheet having the composition of Alloy Example 6 is shown in Table 1.
  • the AA2008 sheet is heat treatable aluminum which is used commercially for automotive applications.
  • AA2008 is the current benchmark for the combination of excellent formability and good strength.
  • AA2008 is used for inner panels on automobiles.
  • Examples 7-12 Ingot-derived sheets of Examples 1-6 were aged naturally at room temperature (T4 temper) . After at least two weeks of natural aging, the materials were tested to determine the mechanical properties. The mechanical tests were performed in three orientations: 0°, 45° and 90° to the rolling direction. The results are shown in Table 2. For purposes of comparison, some of the data is repeated in Table 3.
  • a minimum value of 15 ksi is desirable for yield strength. It is believed that the material needs to have at least this minimum value to resist damage of the naturally aged material (T4 temper) during handling and assembly. All of the experimental alloys of the present invention (Examples 1, 2, 4 and 5) exhibited yield strengths above the minimum. The alloys of Examples 2 and 5 exhibited yield strengths greater than 20 ksi. However, as will be seen below, even though these materials exhibit high strengths, the materials of Examples 2 and 5 also, are highly formable.
  • Figure 2 is a graph illustrating the relationship of copper content of the alloy of the present invention to its transverse yield strengths. As the copper content increases, the transverse yield strength also increases (see Fig. 2) .
  • Sheet formed from alloys with the lower copper contents did not have adequate yield strengths, i.e., greater or equal to the commercially available AA2008.
  • the alloy To meet or exceed the AA2008 benchmark, the alloy must have a minimum copper level greater than 0.5 wt.% (see Table 2) .
  • the tensile elongation of the alloys of Examples 1-6 were also measured. Tensile elongation is considered to be an indirect measurement of formability.
  • AA2008 which is one of the most formable heat treatable alloys in use today, exhibits T4 tensile total elongation values between 25% to 30%. All of the alloys of the present invention exhibited a T4 tensile total elongation greater than or equal to about 28%. Therefore, all of these alloys appear to have better tensile elongations than AA2008.
  • the materials of Examples 1, 2, 4 and 5 meet or exceed all criterion for formability.
  • the uniform elongation of the alloys of Examples 1-6 were also measured.
  • Uniform elongation is a measure of a material's ability to deform uniformly prior to local deformation. It is a measurement of the - 16 - maximum strain that a material can withstand prior to necking. Therefore, it is an indication of a material's resistance to necking. It is desirable to have uniform elongations greater than commercially available AA2008 (Table 2) . All of the materials of the present invention exhibited a uniform elongation of 26.0% or greater. AA2008 in its T4 condition typically exhibits uniform elongations values in the range of about 22% to about 25%. Therefore, the alloys of the present invention will perform better than the current benchmark, AA2008. The variation in uniform elongation, with respect to rolling direction, was insignificant.
  • strain hardening exponent of the alloys of Examples 1-6 was calculated.
  • the strain hardening exponent is derived by measuring the slope of the true stress/strain curve within a specified strain range. Like uniform elongation, strain hardening exponent is a measure of a material's ability to deform uniformly prior to local deformation. It is desirable to have strain hardening exponent values greater than the commercial benchmark, AA2008. All of the materials of the present invention exhibited a strain hardening exponent 0.25 or greater. AA2008 in its -T4 temper typically exhibits strain hardening exponent values in the range of 0.23-0.26. Therefore, it is expected that the alloys of the present invention will perform better than the current benchmark, AA2008.
  • Example 13-30 The alloys of Examples 1-6 were artificially aged by three practices to investigate the change in mechanical properties of the sheet material.
  • the first artificial aging practice was performed by heating the material for 30 minutes at 350°F. This artificial aging practice was intended to simulate a paint bake response that the material would exhibit in commercial automotive production.
  • the second artificial aging practice was similar to the first practice in that the sheet material was heated for 30 minutes at 350°F. However the material was subjected to a 2% stretch prior to heating.
  • This artificial aging practice simulates the development of properties obtainable in a typical commercial application; namely, the strain induced into the material during part forming operations followed by painting and then paint baking.
  • the third artificial aging practice the material was heated for 60 minutes at 400°F. This artificial aging practice was intended to determine the anticipated peak strength obtainable in a paint bake cycle in commercial production.
  • the results of the three artificial aging practices are shown in Table 3. For purposes of comparison, the corresponding properties of the naturally aged material (T4 temper) are repeated in Table 3.
  • the Limiting Dome Height (LDH) test is a method used to measure a material's plane strain stretching ability (strain hardening characteristics and limiting strain capabilities) .
  • LDH Limiting Dome Height
  • standard LDH test rectangular blanks of various widths are cut so that longest sides of the rectangular blanks correspond to the longitudinal rolling direction. The rectangular blanks are rigidly clamped and then stretched by a four-inch hemispherical punch.
  • L H Q is the minimum punch height observed over the range of specimen widths evaluated. This is assumed to be at or near plane strain.
  • additional samples were tested in which the longest side of the rectangular blanks corresponded to the transverse rolling direction. The transverse samples were tested using one width; namely, the same specimen width which LDH 0 was measured in the longitudinal direction. The results of the LDH tests are set forth in Table 4.
  • alloys of the present invention (Alloys 1, 2, 4 and 5) exhibited an improvement in longitudinal LDH of 0.052"-0.069" over AA2008 and an improvement of 0.212"-0.234" over AA2008 in transverse LDH.
  • the 90° GBT is essentially a frictionless downflange test to predict a material's bending performance.
  • the GBT can be used to predict if an alloy can be flat hemmed.
  • a pre-stretched (10%) strip is rigidly clamped and then forced to bend 90° over a die radius by a roller. The test is repeated with progressively smaller die radii until fracture occurs. The smallest die radius (R) resulting in a bend without fracture is divided by the original sheet thickness (t) to determine the minimum R/t ratio.
  • Materials which exhibit minimum R/t values less than about 0.5 are generally considered to be flat hem capable. Tho ⁇ e exhibiting minimum R/t values in the range of about 0.5 to about 1.0 are considered to be marginal, and materials with minimum R/t values greater than about 1.0 are not "flat-hem capable".
  • AA2008 is considered to be one of the best forming heat-treatable alloys commercially available for automotive applications. Consequently, alloys which exhibit a better combination of excellent formability and good strength, such as those of Examples 1, 2, 4 and 5, can be used in the fabrication of formed panels having more demanding shapes and still provide adequate resistance to handling damage. Examples 43-46
  • the sheet products were tested to determine the mechanical properties and formability as measured by LDH, Guided Bend, Stretch Bend and Bulge tests.
  • the LDH and Guided Bend tests were conducted as described previously.
  • the Stretch Bend test is a recognized forming test which is used to measure formability in the bending-under-tension mode. The test is conducted by rigidly clamping a rectangular blank at its ends and then deforming the blank by a punch until fracture occurs. The value reported (H/t) is the distance the punch has traveled at peak load divided by the sheet thickness.
  • the Bulge test is a recognized forming test used to measure a material's ability to deform after large strains in bi-axial stress states.
  • the test is conducted by deforming a rigidly clamped square blank with pressurized hydraulic fluid.
  • the pressurized fluid generates a frictionless force which deforms the material.
  • One parameter used to measure a material's performance during the Bulge test is the maximum distance the material has deformed (Bulge Height) prior to failure.
  • Example 45 exhibited inferior formability values compared to similar alloys with lower amounts of Fe (Example 46) .
  • the superior formability values of Example 46 are indicated by higher average N values, longitudinal uniform elongation values, transverse stretch bend and bulge height measurements.
  • the ASTM grain size and number of grains per mm was optically determined. The values are listed in
  • Example 47 which contained no manganese, had less than 25% of the number of grains per mm 3 than Example 48. Since coarser grain sizes typically can cause orange peel or Lueders' lines to occur during deformation, it is desirable to maintain some low level of Mn in the material. What is believed to be the best mode of the invention has been described above. However, it will be apparent to those skilled in the art that numerous variations of the type described could be made to the present invention without departing from the spirit of the invention. The scope of the present invention is defined by the broad general meaning of the terms in which the claims are expressed.

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Abstract

Cette invention se rapporte à un procédé pour fabriquer une tôle laminée en alliage d'aluminium particulièrement appropriée pour être utilisée dans des carrosseries d'automobiles. Ce procédé consiste: (a) à fournir un corps d'un alliage comprenant environ 0,8 à environ 1,3 % en poids de silicium, environ 0,2 à environ 0,6 % en poids de magnésium, environ 0,5 à environ 1,8 % en poids de cuivre, environ 0,01 à environ 0,1 % en poids de manganèse, environ 0,01 à environ 0,2 % en poids de fer, le reste étant constitué essentiellement par de l'aluminium et des éléments et impuretés accidentels; (b) à usiner ledit corps pour en faire une tôle; (c) à appliquer à ladite tôle un traitement thermique de mise en solution; et (d) à soumettre ladite tôle à une hypertrempe. Dans un mode de réalisation préféré, le traitement thermique en solution est effectué à une température supérieure à 840 °F et la tôle est soumise à une hypertrempe. La tôle qui en résulte possède une combinaison améliorée de formabilité excellente et de bonne résistance.
PCT/US1996/009887 1996-06-14 1996-06-14 Tole laminee en alliage d'aluminium a haute formabilite WO1997047779A1 (fr)

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PCT/US1996/009887 WO1997047779A1 (fr) 1996-06-14 1996-06-14 Tole laminee en alliage d'aluminium a haute formabilite
JP50153198A JP2001503473A (ja) 1996-06-14 1996-06-14 成形性の高いアルミニウム合金製圧延シート

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WO1998059086A1 (fr) * 1997-06-20 1998-12-30 Alcan International Limited Procede de production d'une feuille en alliage d'aluminium apte au traitement thermique
NL1010186C2 (nl) * 1998-09-25 1999-06-29 Hoogovens Aluminium Nv Werkwijze voor het vervaardigen van een goed felsbare aluminiumplaat vrij van roping.
WO2011000635A1 (fr) * 2009-06-30 2011-01-06 Hydro Aluminium Deutschland Gmbh Bande en almgsi pour applications à exigences élevées de déformation
CN113695538A (zh) * 2021-09-03 2021-11-26 中铝河南洛阳铝加工有限公司 一种高成形性镜面铝板带材的制备方法及镜面铝板带材

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998059086A1 (fr) * 1997-06-20 1998-12-30 Alcan International Limited Procede de production d'une feuille en alliage d'aluminium apte au traitement thermique
NL1010186C2 (nl) * 1998-09-25 1999-06-29 Hoogovens Aluminium Nv Werkwijze voor het vervaardigen van een goed felsbare aluminiumplaat vrij van roping.
WO2011000635A1 (fr) * 2009-06-30 2011-01-06 Hydro Aluminium Deutschland Gmbh Bande en almgsi pour applications à exigences élevées de déformation
US10047422B2 (en) 2009-06-30 2018-08-14 Hydro Aluminium Deutschland Gmbh AlMgSi strip for applications having high formability requirements
US10612115B2 (en) 2009-06-30 2020-04-07 Hydro Aluminium Deutschland Gmbh AlMgSi strip for applications having high formability requirements
CN113695538A (zh) * 2021-09-03 2021-11-26 中铝河南洛阳铝加工有限公司 一种高成形性镜面铝板带材的制备方法及镜面铝板带材
CN113695538B (zh) * 2021-09-03 2023-07-25 中铝河南洛阳铝加工有限公司 一种高成形性镜面铝板带材的制备方法及镜面铝板带材

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