Classifications

• • 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
  • C22C21/10—Alloys based on aluminium with zinc 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
  • C22F1/053—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 zinc as the next major constituent

Definitions

• the present invention relates to alloys of the Al-Zn-Mg type with high mechanical strength, and more particularly the alloys intended for welded constructions such as the structures used in the field of shipbuilding, automobile bodywork, industrial vehicle and fixed or mobile tanks.
• Alloys of the 5xxx family are usually used in the Hlx (hardened), H2x (hardened and restored), H3x (hardened and stabilized) or O (annealed) states.
• the choice of metallurgical state depends on the compromise between mechanical strength, corrosion resistance and formability which is aimed for a given use.
• the 7xxx alloys (Al-Zn-Mg) are said to be "structurally hardened", which means that they acquire their mechanical properties by precipitation of the addition elements (Zn, Mg).
• Zn, Mg addition elements
• Those skilled in the art know that, to obtain these mechanical properties, the hot transformation by rolling or spinning is followed by dissolving, quenching and income. These operations, carried out in the majority of cases separately, respectively aim to dissolve the alloying elements, to maintain them in the form of a supersaturated solid solution at room temperature, and finally to precipitate them in a controlled manner.
• the alloys of the families 6xxx (Al-Mg-Si) and 7xxx (Al-Zn-Mg) are generally used in the quenched state.
• the tempering giving the maximum mechanical strength is designated T6, when the shaping by rolling or spinning is followed by dissolving and quenching.
• the parameters which govern the choice of the user are essentially the static mechanical characteristics, that is to say the tensile strength Rm, the elastic limit Rpo, 2, and the elongation at break A.
• Other parameters which come into play, depending on the specific needs of the intended application, are the mechanical characteristics of the welded joint, the resistance to corrosion (flaky and under stress) of the sheet and of the joint. welded, resistance to fatigue of the sheet and welded joint, resistance to crack propagation, toughness, dimensional stability after cutting or welding, resistance to abrasion. For each intended use, an appropriate compromise must be found between these different properties.
• the patent GB 1 419 491 (British Aluminum) discloses a weldable alloy containing 3.5 - 5.5% of zinc, 0.7 - 3.0% of magnesium, 0.05 - 0.30% of zirconium, optionally up to 0.05% each of chromium and manganese, up to 0.10% iron, up to 0.075% silicon, and up to 0.25% copper.
• Patent FR 1 501 662 (Veticae Aluminum- Werke Aktiengesellschaft) describes a weldable alloy with a composition
• US Patent 5,061,327 (Aluminum Company of America) describes a process for manufacturing a rolled aluminum alloy product comprising casting a plate, homogenizing, hot rolling, reheating the blank to a temperature between 260 ° C and 582 ° C, its rapid cooling, a precipitation treatment at a temperature between 93 ° C and 288 ° C, then cold or hot rolling at a temperature not exceeding 288 ° C.
• the problem to which the present invention attempts to respond is first of all to improve the compromise of certain properties of Al-Zn-Mg alloys in the form of sheets or strips, namely the compromise between the mechanical characteristics (determined on the metal and on the welded joint), and the resistance to corrosion (leaf corrosion and stress corrosion).
• the first object of the present invention is a process for producing an intermediate laminated product of aluminum alloy of the Al-Zn-Mg type, comprising the following steps: a) a plate containing ( in mass percentages)
• a first hot rolling step is carried out comprising one or more rolling passes on a hot rolling mill, the inlet temperature T 2 being chosen such that (Ti - 60 ° C) ⁇ T 2 ⁇ (Ti - 5 ° C), and the rolling process being carried out so that the outlet temperature T 3 is such that (T ⁇ - 150 ° C) ⁇ T 3 ⁇
• a second object is a product capable of being obtained by the process according to the invention, possibly after additional cold work hardening and / or heat treatment steps, which shows an elastic limit R p o-2 d ' at least 250 MPa, a tensile strength Renfin, of at least 280 MPa, and an elongation at break of at least 8%.
• R p o ⁇ is at least 290 MPa and R m at least 330 MPa
• a third object is the use of the product obtained by the process according to the invention for the manufacture of welded constructions.
• Another object is the welded construction produced with at least two products capable of being obtained by the method according to the invention, characterized in that its elastic limit R p0; 2 in the welded joint between two of said products is at least 200 MPa.
• Figure 1 shows a typical manufacturing range in a time - temperature diagram. The numerical marks correspond to the different process stages:
• Figure 2 shows the test specimens used for the laminating corrosion tests.
• Figure 3 shows the test specimens used for stress corrosion tests. Dimensions are given in millimeters.
• Figure 4 gives the principle of the slow tensile test (stress corrosion).
• FIG. 5 compares the elastic limit in the direction L (black dots connected by the black curve) and the loss of mass during a laminating corrosion test (bars) for an intermediate product according to the invention and five different heat treatments of said intermediate product.
• Figure 6 compares the Vickers microhardness in the welded area for three different welded samples.
• FIG. 7 compares the tear strength Kr as a function of the crack extension ("delta a", which means ⁇ a) for six different sheets.
• FIG. 8 compares the propagation speed of cracks da / dn of a sheet according to the invention with a sheet according to the state of the art.
• the crack propagation speed da / dN is determined according to standard ASTM E647, the damage tolerance K R according to standard ASTM E 561, the resistance to exfoliating corrosion (also called laminating corrosion) is determined according to standard ASTM G34 ( Exco test) or ASTM G85-A3 (Swaat test); for these tests, as well as for even more specific tests, additional information is given below in the description and in the examples.
• the Applicant has surprisingly found that it is possible to manufacture laminated products of 7xxx alloy which show a very good compromise in properties, in particular in the welded state, using a simplified process, in which dissolution, quenching and tempering are carried out during hot transformation by rolling.
• the process according to the invention can be carried out on Al-Zn-Mg alloys in a wide range of chemical composition: Zn 3.0 - 9.0%, Mg 0.5 - 2.0%, the alloy may also contain Mn ⁇ 1.0%, Si ⁇ 0.50%, Fe ⁇ 0.50%, Cu ⁇ 0.50%, Cr ⁇ 0.50%, Ti ⁇ 0.15%, Zr ⁇ 0.20 %, as well as the inevitable impurities.
• the magnesium content must be between 0.5 and 2.0% and preferably between 0.7 and 1.5%. Below 0.5%, mechanical properties are obtained which are not satisfactory for many applications, and above 2.0%, there is a deterioration in the corrosion resistance of the alloy. Furthermore, above 2.0% magnesium, the quenchability of the alloy is no longer satisfactory, which affects the effectiveness of the process according to the invention.
• the manganese content must be less than 1.0% and preferably less than 0.60%, to limit the sensitivity to laminating corrosion and to maintain good quenchability. A content not exceeding 0.20% is preferred.
• the zinc content must be between 3.0 and 9.0%, and preferably between 4.0 and 6.0%. Below 3.0%, the mechanical characteristics are too low to be of technical interest, and above 9.0%, there is a deterioration in the corrosion resistance of the alloy, as well as a degradation of the hardenability.
• the Zn / Mg ratio must be greater than 1.7 to allow it to remain in the composition range which benefits from structural hardening.
• the silicon content must be less than 0.50% in order not to deteriorate the corrosion behavior or the tear resistance.
• the iron content must also be less than 0.50%.
• the copper content must be less than 0.50% and preferably less than 0.25%, which limits the sensitivity to pitting corrosion and maintains good quenchability.
• the chromium content must be less than 0.50%, which makes it possible to limit the sensitivity to leaf corrosion and to maintain good quenchability.
• the titanium content must be less than 0.15% and that of zirconium less than 0.20%, in order to avoid the formation of harmful primary phases; for Zr, it is preferred not to exceed 0.15%.
• Tm ⁇ 0.10% and preferably ⁇ 0.05%
• Lu ⁇ 0.10% and preferably ⁇ 0.05% Hf ⁇ 1.20% and preferably ⁇ 0.50%
• quenchability is understood here to mean the ability of an alloy to be quenched over a fairly wide range of quenching speeds.
• a so-called easily hardenable alloy is therefore an alloy for which the cooling rate during quenching does not have a strong influence on the properties of use (such as mechanical strength or resistance to corrosion).
• the method according to the invention comprises the following steps:
• a second stage of hot rolling of said strip typically using a tandem rolling mill, the inlet temperature T5 being chosen such that T 5 ⁇ T 4 and 200 ° CT 5 ⁇ 300 ° C, and the rolling process being carried out so that the winding temperature T 6 is such that (T 5 - 150 ° C) ⁇ T 6 ⁇ (T 5 - 20 ° C).
• the burn temperature Ts is a quantity known to those skilled in the art, which determines it, for example directly by calorimetry on a raw casting sample, or else by thermodynamic calculation taking into account the phase diagrams.
• the temperatures T 2 and T 5 correspond to the temperature of the surface (most often of the upper surface) of the plate or strip measured just before it enters the hot rolling mill; the execution of this measurement can be done according to methods known to those skilled in the art.
• the temperature T 3 is chosen such that (Ti - 100 ° C) ⁇ T 3 ⁇ (Ti - 30 ° C).
• T 2 is chosen such that (Ti - 30 ° C) ⁇ T 2 ⁇ (Ti - 5 ° C).
• Te is chosen such that (T 5 - 150 ° C) ⁇ T 6 ⁇ (T 5 - 50 ° C).
• the temperature T 3 it is preferable to choose the temperature T 3 so that it is higher than the solvent temperature of the alloy.
• the solvent temperature is determined by a person skilled in the art using differential calorimetry. Maintaining T 3 above the solvent temperature makes it possible to minimize the rough precipitation of the MgZn 2 type phases. It is preferred that these phases are formed in a controlled manner as ends precipitated during winding or after winding. Controlling the temperature T 3 is therefore particularly critical.
• the temperature T 4 is also a critical parameter of the process.
• steps b) and c), c) and d), and d) and e the temperature must not drop below the specified value.
• the temperature of entry to the hot rolling mill during step (e), which is advantageously carried out on a tandem rolling mill is substantially equal to the temperature of the strip after cooling, which requires either a sufficiently rapid transfer of the strip from one rolling mill to the other, or, preferably, an on-line process.
• steps b), c) d) and e) are carried out in line, that is to say that a given volume metal element (in the form of a plate).
• the cooling in step (d) can be done by any means ensuring sufficiently rapid cooling, such as: immersion, spraying, forced convection, or a combination of these means.
• immersion, spraying, forced convection or a combination of these means.
• the passage of the strip through a quenching cell by sprinkling, followed by the passage through a quenching box by natural or forced convection, followed by a passage through a second quenching cell by sprinkling good results.
• cooling by natural convection as the only means is not fast enough, whether in strip or coil. In general, at this stage of the process, the coil cooling does not give satisfactory results.
• the coil can be allowed to cool.
• the product resulting from stage (e) can be subjected to other operations such as cold rolling, tempering, or cutting.
• the intermediate laminated product according to the invention to cold hardening of between 1% and 9%, and / or to a complementary heat treatment comprising one or more bearings at temperatures between 80 ° C and 250 ° C, said additional heat treatment can intervene before, after or during said cold work hardening.
• the method according to the invention is designed so as to be able to carry out three heat treatment operations online which are usually carried out separately: solution dissolving (carried out according to the invention during the first hot rolling step), quenching (carried out according to the invention during cooling of the strip), the income (carried out according to the invention during cooling of the coil). More particularly, the process according to the invention can be carried out so that it is not necessary to reheat the product once it has entered the reversible hot rolling mill, each stage of said process being at a temperature lower than the previous one. This saves energy.
• the intermediate laminated product obtained by the process according to the invention can be used as it is, that is to say without subjecting it to other process steps which modify its metallurgical state; this is preferable. If necessary, it can be subjected to other process steps which modify its metallurgical state, such as cold rolling.
• the process according to the invention can sometimes lead, for a given alloy, to slightly less static mechanical characteristics.
• it leads to an improvement in the tolerance to damage, as well as to an improvement in the resistance to corrosion, especially after welding. This has been observed in particular for a restricted composition domain, as will be explained below.
• the compromise in properties which is obtained with the process according to the invention is at least as interesting as that which is obtained by a conventional manufacturing process, in which dissolution, quenching and tempering are carried out separately. and which leads to state T6.
• the method according to the invention is much simpler and less expensive than the known methods. It advantageously leads to an intermediate product whose thickness is between 3 mm and 12 mm; above 12 mm, the winding becomes technically difficult, and below 3 mm, in addition to the technical difficulties of hot rolling in this thickness zone, the strip is likely to cool too much.
• a preferred composition domain for implementing the method according to the invention is characterized by Zn 4.0 - 6.0, Mg 0.7 - 1.5, Mn ⁇ 0.60 , and preferably Cu ⁇ 0.25. Alloys showing good hardenability are preferred, and among these alloys, alloys 7020, 7003, 7004, 7005, 7008, 7011, 7018, 7022 and 7108 are preferred.
• Al-Zn-Mg alloys according to the invention can be welded by all known welding methods, such as MIG or TIG welding, friction welding, laser welding, electron beam welding. Welding tests were carried out on sheets with an X chamfer, welded by semi-automatic MIG welding in smooth current, with a filler wire of alloy 5183. Welding was carried out in the direction perpendicular to rolling. The mechanical tests on the welded specimens were carried out according to a method recommended by the company Det Norske Veritas (DNV) in their document "Rules for classification of Ships - Newbuildings - Materials and Welding - Part 2 Chapter 3: Welding" of January 1996.
• DNV Det Norske Veritas
• the width of the tensile test piece is 25 mm
• the cord is leveled symmetrically and the useful length of the test piece as well as the length of the extensometer used is given by (W + 2.e) where parameter W designates the width of the bead and parameter e designates the thickness of the test piece.
• the Applicant has found that the MIG welding of the products according to the invention leads to welded joints characterized by a higher elastic limit and a breaking limit than with an alloy produced according to a conventional range. (T6).
• T6 a conventional range.
• the corrosion resistance of the base metal and the welded joints was evaluated using the SWAAT and EXCO tests.
• the SWAAT test allows the evaluation of the corrosion resistance (in particular in the form of laminating corrosion) of aluminum alloys in general. Since the process according to the present invention leads to a product with a strongly fiber-reinforced structure, it is important to make sure that said product resists well to exfoliating corrosion, which develops mainly on products showing a fiber-reinforced structure.
• the SWAAT test is described in appendix A3 to ASTM G85. It is a cyclic test.
• Each cycle consists of a 90-minute humidification phase (98% relative humidity) and a thirty-minute spray period of a solution composed (for one liter) of salt for artificial seawater (see table 1 for the composition, which conforms to standard ASTM Dl 141) and 10 ml of glacial acetic acid.
• the pH of this solution is between 2.8 and 3.0.
• the temperature throughout the duration of a cycle is between 48 ° C and 50 ° C.
• the samples to be tested are tilted 15 ° to 30 ° relative to the vertical. The test was carried out with a duration of 100 cycles.
• Table 1 composition of salt for artificial seawater
• the EXCO test lasting 96 hours, is described in standard ASTM G34. It is mainly intended to establish the resistance to laminating corrosion of aluminum alloys containing copper, but may also be suitable for Al-Zn-Mg alloys (see J. Martinussussen, S. Grjotheim, "Qualification of new aluminum alloys” , 3 rd International Forum on Aluminum Ships, Haugesund, Norway, May 1998).
• rectangular test pieces were used, one side of which was protected by an adhesive aluminum strip (in order to attack only the other side) and whose side to be attacked was either left as it was. , or machined to half thickness on half of the surface of the sample, and left full thickness on the other half.
• FIGS. 2 laminating corrosion
• 3 stress corrosion
• the product according to the invention exhibits a resistance to laminating corrosion equivalent to that which is obtained for the standard product (identical or similar alloy in the T6 state).
• a particularly preferred product according to the invention contains between 4.0 and 6.0% of zinc, between 0.7 and 1.5% of magnesium, less than 0.60%, and even more preferably less than 0.20% manganese, and less than 0.25% copper.
• Such a product shows a mass loss of less than 1 g / dm 2 during the test WAWAAT (100 cycles), and of less than 5.5 g dm 2 during the EXCO test (96 h), before income or after a corresponding income at most at 3 p.m. at 140 ° C.
• ASTM G 129 This test is faster and more discriminating than the methods consisting in determining the stress of the non-breaking threshold in stress corrosion.
• the principle of the slow traction test shown diagrammatically in FIG. 4, consists in comparing the traction properties in an inert medium (laboratory air) and in an aggressive medium. The drop in static mechanical properties in a corrosive environment corresponds to the sensitivity to stress corrosion.
• the most sensitive characteristics of the tensile test are the elongation at break A and the maximum stress (at necking) R m . The elongation at break was used, which is a much more discriminating magnitude than the maximum stress.
• the critical aspects of the slow tensile test concern the choice of the tensile specimen, the strain rate and the corrosive solution.
• the stress rate it is recognized, in particular on Al-Zn-Mg alloys (see the article "Corrosion under stress of Al-5Zn-1.2.2Mg crystals in 30 g / 1 NaCl medium" by T. Magnin and C.
• the hardening precipitates of the MgZn 2 type are clearly coarser in a product according to the invention than in a comparable product according to the prior art.
• the quenching is not as rapid as in a conventional process with dissolution in an oven followed by a separate quenching. It is clear that the method according to the invention does not make it possible to avoid a certain precipitation of coarse phases from the temperature T.
• care must be taken during the execution of the process according to the invention that the quenching speed is sufficiently high, and that precipitation is obtained at a temperature as low as possible. Said phases must not precipitate massively at a temperature between T and T5.
• the grains have a size in the direction of the thickness (cross-short) of less than 30 ⁇ m, preferably less than 15 ⁇ m and even more preferably less than 10 ⁇ m, and a thickness / length ratio of more than 60, and preferably more than 100, whereas for a product comparable according to the state of the art, the grains have a size in the direction of the thickness (cross-short) greater than 60 ⁇ m and a thickness / length ratio significantly less than 40.
• the sheets and strips resulting from the process according to the present invention can be advantageously used for the construction of auto parts, industrial vehicles, road or rail tanks, and for construction in a maritime environment.
• All the sheets and strips resulting from the process according to the present invention lend themselves particularly well to welded construction; they can be welded by any known welding process which is suitable for this type of alloy.
• Sheets according to the invention can be welded together, or with other aluminum or aluminum alloy sheets, using an appropriate filler wire.
• an elastic limit measured as described above
• this value is at least 220 MPa.
• the breaking strength of the welded joint is at least 250 MPa, and in a preferred embodiment at least 280
• a heat affected zone is obtained which shows a hardness of at least 100 NH, preferably at least minus 110 NH, and even more preferably at least 115 NH; this hardness is at least as great as that of the base sheets which has the lowest hardness.
• the Applicant has found that the product obtained by the process according to the invention, in the area of preferential composition (Zn 4.0 - 6.0%, Mg 0.7 - 1.5%, Mn ⁇ 0 , 60%), shows higher resistance to abrasion by sand than comparable products. It notes that this resistance to abrasion does not depend in a simple manner on the mechanical characteristics of the product, nor on its hardness, nor on its ductility. The fiber structure in the TC direction seems to favor resistance to abrasion by sand. For this property of use, the superiority of the product resulting from the process according to the invention is due to the combination between a particular fiber structure, inaccessible with known processes, and the level of mechanical characteristics which its composition gives it.
• the resistance to abrasion by sand of the product capable of being obtained by the process according to the invention expressed in the form of loss of mass during a test described in Example 10 below. , is less than 0.20 g, and preferably less than 0.19 g for an exposed flat surface of dimensions 15 x 10 mm.
• the product according to the invention has good damage tolerance properties. It can be used as a structural element in aeronautical construction.
• the product according to the invention and in particular that which belongs to the restricted composition range defined by Zn 4.0 - 6.0%, Mg 0.7 - 1.5%, Mn ⁇ 0.60%, is thus suitable to be used as a structural element which must meet specific requirements in terms of damage tolerance (toughness, resistance to crack propagation tired).
• the term “structural element” or “structural element” of a mechanical construction is used here to mean a mechanical part the failure of which is likely to endanger the safety of said construction, of its users, of its users or of others.
• these structural elements include in particular the elements that make up the fuselage (such as the fuselage skin), the stiffeners or bulkheads, bulkheads, fuselage (circumferential frames)), the wings (such as the wing skin, the stiffeners (stringers or stiffeners), the ribs (ribs) and spars) and the tail section, as well as the profiles of floor beams, seat tracks and doors.
• the present invention relates only to structural elements which can be manufactured from laminated sheets. More particularly, the product according to the invention is suitable for being used as a sheet for fuselage coating, in conventional assembly (in particular riveted) or in welded assembly.
• the method according to the invention therefore makes it possible to obtain a new product endowed with an advantageous combination of properties, such as mechanical resistance, tolerance to damage, weldability, resistance to exfoliating corrosion and to stress corrosion, abrasion resistance, which is particularly suitable for use as a structural element in mechanical construction.
• properties such as mechanical resistance, tolerance to damage, weldability, resistance to exfoliating corrosion and to stress corrosion, abrasion resistance
• it is suitable for use in industrial vehicles, as well as in storage, transport or handling equipment for granular products, such as tippers, tanks or conveyors.
• the method according to the invention is particularly simple and rapid; its operating cost is lower than that of the processes according to the state of the art likely to lead to products having comparable properties of use.
• Examples 1 and 2 belong to the state of the art.
• Examples 3, 4, 8 and 9 correspond to the invention.
• Each of Examples 5, 6, 7, 9 and 10 compares the invention with the state of the art. Examples
• This example corresponds to a transformation range according to the state of the art.
• Two plates A and B were produced by semi-continuous casting. Their composition is indicated in Table 2.
• the chemical analysis of the elements was carried out by X-ray fluorescence (for Zn and Mg elements) and spark spectroscopy (other elements) on a pawn obtained from liquid metal taken from the runner.
• the rolling plates were reheated for 22 hours at 530 ° C. and hot rolled as soon as they had reached, at the outlet of the oven, a temperature of 515 ° C.
• the hot-rolled strips were wound to a thickness of 6 mm, the process being carried out so that the temperature, measured on the edges of the reel after the complete winding (at mid-thickness of the winding) is between 265 ° C and 275 ° C, this value being the average between 2 measurements made on both sides of the coil.
• the coils were cut and a part of the sheets obtained was cold rolled to a thickness of 4 mm.
• the welding was done in the Cross-Long direction, with an X chamfer, by a semi-automatic MIG process in smooth current, with a filler wire of alloy 5183 (Mg 4.81%, Mn 0.651%, Ti 0.120%, Si 0.035%, Fe 0.130%, Zn 0.001%, Cu 0.001%, Cr 0.075%) of diameter 1.2mm, supplied by the company Soudure Auto constitue.
• the tensile test pieces (width 25 mm, symmetrically leveled bead, useful length of the test piece and length of the extensometer equal to (W + 2 e) where W denotes the width of the bead and e the thickness of the test piece) were taken in the long direction, perpendicular to the weld, so that the joint is in the middle.
• the characterization was carried out 19, 31 and 90 days after welding, because a person skilled in the art knows that for this type of alloys, the mechanical properties after welding greatly increase during the first weeks of maturation. Specimens machined to mid-thickness on half of their surface were also subjected to the SWAAT and EXCO tests. The results are presented in Tables 5 (for the properties on the base metal in the T6 state) and 6 (properties on the welded metal).
• a plate C was produced by semicontinuous casting. Its composition is identical to that of plate B from Example 1.
• the plate was hot rolled, after 13 hours reheating at 550 ° C. (time at level) followed by a rolling stage at 540 ° C.
• the first step at the reversible rolling mill, brought the plate to a thickness of 15.5 mm, the exit temperature of the rolling mill being around 490 ° C.
• the laminated plate was then cooled by spraying and by natural convection to a temperature of the order of 260 ° C. At this temperature, it was entered into a tandem rolling mill (3 cages), rolled to the final thickness of 6 mm, and wound.
• the winding temperature of the coil measured as in Example 1, is approximately 150 ° C. Once naturally cooled, the coil was cut into sheets. These have been leveled and have not undergone any other deformation operation.
• the sheets obtained were characterized as gross production (static mechanical characteristics in the Long and Cross-Long direction, laminating and stress corrosion) and after welding (static mechanical characteristics, laminating corrosion) .
• the welding was carried out simultaneously with the welding of Example 2, and according to the same method. Specimens machined to mid-thickness on half of their surface were subjected to the SWAAT and EXCO tests. The results are collated in Tables 7 and 8 (non-welded sheets) and in Table 9 (welded sheets).
• the raw (non-welded) sheet according to the invention has a lower resistance to sheet corrosion than that of BCH sheet, made from the same composition but with a much more complex manufacturing process. On the other hand, its resistance to corrosion under stress is equivalent.
• the sheet according to the invention After welding, the sheet according to the invention has a mechanical resistance very much higher than that of the ACH and BCH sheets produced with a process according to the prior art. Its resistance to laminating corrosion on a welded joint is equivalent. It can be seen that the process according to the invention performs the winding at a temperature of approximately 120 ° C. lower than the process according to the state of the art of Example 1.
• Example 3 The sheet marked “C” from Example 3 was subjected to additional heat treatments of the tempered type at a temperature of 140 ° C. The samples thus obtained were then characterized as in Example 3 (static mechanical characteristics in the L direction and laminating corrosion). The results are collated in Table 10 and in FIG. 5 (the black dots and the black line correspond to the elastic limit, and the bars to the loss of mass during the SWAAT test).
• the microstructure of the ACH, BCH, BFH and C samples of Examples 1, 2 and 3 was characterized by scanning electron microscopy with field emission gun (FEG-SEM, in BSE mode (backscattered electrons), acceleration voltage 15 kN, diaphragm 30 ⁇ m, working distance 10 mm, made on a polished cut in the direction of sampling L-TC with conductive deposition Pt / Pd) and by transmission electron microscopy (TEM, direction of sampling L-TL, preparation of slides by twin jet electrochemical thinning with 30% HNO 3 in methanol at -35 ° C with a potential of 20 V). All samples were taken halfway through the sheet.
• FEG-SEM field emission gun
• BSE mode backscattered electrons
• acceleration voltage 15 kN acceleration voltage
• diaphragm 30 ⁇ m working distance 10 mm
• TEM transmission electron microscopy
• the precipitates of the MgZn 2 type at the grain boundaries have an average size of the order of 30 to 60 nm in the ACH samples, BCH and BFH, whereas they have an average size of between 200 and 400 nm in sample C.
• a welded joint produced with a sheet C shows a significantly higher hardness.
• HZ heat-affected zone
• the heat affected zone has a hardness greater than that of the base metal for the sheet C produced by the process according to the invention, which is completely unusual.
• Plates of alloy 6056 plated on both sides with alloy 1300 were prepared, according to the method described in Example 3 of patent application EP 1 170 118 A1.
• the chemical composition of the core in 6056 is given in Table 12. These products are compared with sheet C of Example 3 of this patent application.
• the thickness of the test pieces is indicated in table 12.
• the test makes it possible to define the curve R of the material, giving the resistance to tearing K R as a function of the extension of the crack ⁇ a.
• the results are collated in Table 13 and in Figure 7.
• the test pieces were cut into the full thickness of the sheets. The results are collated in Figure 8.
• the product according to the invention shows better tenacity under plane stress K R than a known reference product, while the speed of crack propagation da / dN (TL) at high ⁇ K values is substantially comparable.
• SI The essential parameters of the process, here called SI, were:
• T 550 ° C
• T 2 520 ° C
• T 4 267 ° C
• T 5 267 ° C
• T 6 210 ° C
• the temperature Ts was 603 ° C (value obtained by numerical calculation).
• the final thickness of the strip was 6 mm, its width 2400 mm. It is found that the final product does not show any recrystallization.
• a fiber-reinforced microstructure is observed at mid-thickness, with a grain thickness of the order of 10 ⁇ m.
• the corrosion resistance evaluated by the EXCO test, was EA at the surface and at mid-thickness.
• the temperature Ts for the alloy U was 600 ° C. (value obtained by numerical calculation).
• the thickness of the strips U3 and U4 was 6 mm, that of the strips Ul, U2 and S2 of 8 mm.
• the material 7108 T6 had the composition of the alloy B of Example 2, and was close to the material BCH.
• the material 7108 F7 has the same composition B of Example 2.
• Abrasion resistance has been characterized using an original device which reproduces the conditions such as they may arise, for example when loading, transporting and unloading sand in a bucket.
• This test consists in measuring the loss of mass of a sample subjected to a vertical movement back and forth in a tank filled with sand.
• the diameter of the tank is about 30 cm, the height of the sand about 30 cm.
• the sample holder is fixed on a vertical rod connected to a double-acting cylinder which ensures the vertical movement back and forth of the rod.
• the sample holder is in the form of a pyramid with an angle of 45 °. It is the tip of the pyramid that plunges into the sand.
• the samples to be tested are embedded in the faces of the pyramid so that their surface is tangent to that of the corresponding face of the pyramid; it is the face corresponding to the L-TL plane (dimension 15 x 10 mm) which is exposed to the sand.
• the depth of penetration of the sample into the sand was 200 mm.
• the same procedure was used for all samples. It involves degreasing the sample with acetone, filling the tank with the same amount of the same standardized sand (sand according to NF EN 196-1), stopping the machine every 1000 cycles and replacing the used sand. using new sand, weighing the samples every 2000 cycles (preceded by cleaning with acetone and compressed air), stopping the test after 10,000 cycles.
• Table 20 The results are given in table 20:
• the mass loss values indicated are the average between three tests; the confidence interval is of the order of ⁇ 0.01 to 0.02 g; this underlines the good repeatability of this test.
• Table 19 shows the very specific microstructure of the product obtained by the process according to the present invention, by comparing the two products in alloy 7108, one (reference T6) obtained according to a known process, the other (reference F7) according to the process which is the subject of the present invention.
• Table 20 shows the effect of this microstructure on abrasion resistance. We can immediately see that the product according to the invention is more resistant to abrasion than the standard product 5086 H24. This underlines its good suitability for use in industrial vehicles, as well as in storage and handling equipment for granular products, such as skips, tanks, or conveyors.

Landscapes

• 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)
• Metal Rolling (AREA)
• Powder Metallurgy (AREA)
• Heat Treatment Of Sheet Steel (AREA)
• Laminated Bodies (AREA)
• Heat Treatment Of Steel (AREA)
• Manufacture And Refinement Of Metals (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=32104485

Family Applications (1)

Country Status (11)

Families Citing this family (45)

Family Cites Families (21)

• 2002
  • 2002-11-06 FR FR0213859A patent/FR2846669B1/fr not_active Expired - Fee Related
• 2003
  • 2003-11-06 ES ES03767916T patent/ES2314255T3/es not_active Expired - Lifetime
  • 2003-11-06 DE DE60324581T patent/DE60324581D1/de not_active Expired - Lifetime
  • 2003-11-06 JP JP2004550747A patent/JP2006505695A/ja active Pending
  • 2003-11-06 EP EP03767916A patent/EP1558778B1/de not_active Expired - Lifetime
  • 2003-11-06 AT AT03767916T patent/ATE413477T1/de not_active IP Right Cessation
  • 2003-11-06 AU AU2003292348A patent/AU2003292348A1/en not_active Abandoned
  • 2003-11-06 CA CA2504931A patent/CA2504931C/fr not_active Expired - Fee Related
  • 2003-11-06 RU RU2005117168/02A patent/RU2326182C2/ru not_active IP Right Cessation
  • 2003-11-06 WO PCT/FR2003/003312 patent/WO2004044256A1/fr not_active Ceased
  • 2003-11-06 US US10/534,006 patent/US7780802B2/en not_active Expired - Lifetime

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events