DE60106488T2 - CURABLE ALUMINUM ALLOYS - Google Patents

Abstract

This invention concerns AA5000 series alloys with the addition of Cu that can be retained in a solution treated condition after hot working, for example by hot rolling on a hot mill or by hot extruding. There is described a method of producing an age-hardenable aluminium alloy comprising the steps of: a) casting an alloy of a composition comprising the following expressed in weight percent: Magnesium : 1.0 to 4.0, Cooper : 0.1 to 0.6, Manganese : up to 0.8, Iron : up to 0.5, Silicon : up to 0.3, Chromium : up to 0.15, Titanium : up to 0.15, Balance : Aluminium with incidental impurities b) optionally homogenising the cast alloy, c) hot working the casting at an initial temperature of at least 400 DEG C to form an intermediate product, wherein at least part of the hot working is carried out whilst the casting is at a temperature above the solvus temperature of the alloy, d) cooling the intermediate product either during hot working or in a subsequent step at a rate such that at least a partially recovered or recrystallised structure is formed ant that sufficient copper is retained in solid solution in the alloy to cause an age hardening effect on the alloy if phase precipitation takes place during the alloy's subsequent thermal history, and e) optionally allowing or arranging for phase precipitation to occur in the alloy. The described method is particularly suited to the production of can end stock and sheet for automotive applications.

Description

These Invention relates to alloys of the series AA5000 with the addition of Cu, in a solution-annealed condition can be held after being thermoformed, for example by hot rolling in a hot rolling mill or by extrusion.

To In the prior art, alloys of the AA5000 series are commonly used as not heat treatable considered, i. they are considered non-hardening. The addition of Cu to these alloys makes them hardening, as in EP-A-0 773 303, EP 0 616 044 and EP-A-0 645 655. However, require these known methods also an independent solution annealing.

The Novelty of this invention is the discovery that in certain Cu-containing AA5000 series alloys in hot working, For example, during hot rolling, a sufficient solution annealing takes place, so that the alloy without an extra expensive step the solution annealing is curing. That means a very significant economic advantage, above everything for Consumer Goods such as can lid tape, automotive sheets or extruded products such as Profiles.

EP-A-0 605 947 describes the production of cans tape, with two sequences continuous operations are used. The described additional Steps of uncoiling the hot, coiled sheet, quenching the sheet without intercooling, cold rolling and rewinding are needed but these extra Steps do not become in the process of the present invention needed.

WO-A-99/39019 describes a method for the manufacture of can ends and lugs, but a glow of the Sheet metal is needed as a separate step after hot rolling what in the method of the present invention is not necessary.

WO-A-98/01593 describes a method for the production of aluminum alloy can, but also Here is a separate annealing step required.

JP-A-100121179 describes an aluminum alloy sheet for covers of carbonated cans Beverages, but an independent one Solution annealing is what is not required in the method of the present invention is necessary.

US-A-5 655 593 describes the production of aluminum alloy sheets, being the hot band cooled quickly to minimize the deposition of the alloying elements. This doctrine of fast cooling is contrary to the present invention.

US-A-3 464 866 describes a process for aluminum alloy conductors but in turn teaches fast cooling.

• a)Giessen einer Legierung, die das Folgende in Gewichtsprozent ausgedrückt enthält: Magnesium: 1,0 bis 4,0 Kupfer: 0,1 bis 0,6 Mangan: bis zu 0,8 Eisen: bis zu 0,5 Silizium: bis zu 0,3 Chrom: bis zu 0,15 % Titan: bis zu 0,15 %, vorzugsweise bis zu 0,05 % Bor: von 0 bis 0,05, vorzugsweise bis zu 0,01 Rest: Aluminium mit allfälligen Verunreinigungen.
• (b) wahlweise Homogenisieren der gegossenen Legierung,
• (c) Warmumformen des Gusses mit einer anfänglichen Temperatur von mindestens 400 °C, um ein Zwischenprodukt zu bilden, wobei mindestens ein Teil der Warmbearbeitung ausgeführt wird, während der Guss bei einer Temperatur oberhalb der Lösungstemperatur ist,
• (d) Kühlen des Zwischenprodukts während dem Warmumformen oder in einem darauffolgenden Schritt mit einer Geschwindigkeit von weniger als 5 °C/min, so dass mindestens eine teilweise erholte oder rekristallisierte Struktur gebildet wird, und dass in der festen Lösung in der Legierung genügend Kupfer verbleibt, um einen Aushärtungseffekt bei der Legierung hervorzurufen, wenn während der weiteren thermischen Geschichte der Legierung Phasenabscheidung eintritt, und
• e) wahlweise Zulassen oder Herbeiführen des Eintretens von Phasenabscheidung in der Legierung.

According to the present invention, there is provided a process for producing hardening aluminum alloys comprising the steps of:

• a) casting an alloy containing the following in weight percent: Magnesium: 1.0 to 4.0 Copper: 0.1 to 0.6 Manganese: up to 0.8 Iron: up to 0.5 Silicon: up to 0.3 Chrome: up to 0.15% Titanium: up to 0.15%, preferably up to 0.05% Boron: from 0 to 0.05, preferably up to 0.01 Rest: Aluminum with possible impurities.
• (b) optionally homogenizing the cast alloy,
• (c) hot working the casting at an initial temperature of at least 400 ° C to form an intermediate product, wherein at least a portion of the hot working is carried out while the casting is at a temperature above the solution temperature,
• (d) cooling the intermediate during hot working or in a subsequent step at a rate of less than 5 ° C / min to form at least a partially recovered or recrystallized structure and leaving enough copper in the solid solution in the alloy to cause a hardening effect on the alloy when phase deposition occurs during the further thermal history of the alloy, and
• e) optionally allowing or causing the onset of phase deposition in the alloy.

Preferably After the hot working step, the intermediate usually becomes at a temperature below the solution temperature of the alloy provided that, if the intermediate over the solution temperature the alloy is heated, cooling at a speed of less than 2 ° C / sec. accomplished becomes.

Of the Term "solution temperature the alloy " the temperature below the equilibrium copper through Separation from the solid solution Will get removed. However, it depends the rate of removal of the copper from the reaction kinetics from.

It is believed that the deposited phase, when formed, is an S phase (an Al ₂ CuMg phase), or its metastable precursors.

The Alloy can be continuously cast to form ingots, or be poured continuously, for example in a double-belt caster or a double-roll strip casting machine, to form a sheet.

The cast and preferably homogenized alloy can be extruded, but it is usually hot rolled to make can end band. After casting, the preferred steps are:
optionally homogenizing the cast at a temperature of at least 480 ° C, and preferably 500 to 600 ° C such that substantially all of the magnesium and copper in the cast are in solid solution,
Hot working the casting, optionally reheating the casting above the alloy solution temperature, and preferably at least 450 ° C, to take virtually all magnesium and copper present in the solid solution.

Hot rolling of the casting with an inlet temperature of the casting into the hot rolling mill of at least 400 ° C, and preferably from 450 to 580 ° C,
Continuously rolling the casting to the desired thickness to form a sheet such that at least a portion of the thickness reduction is performed by rolling above the solution temperature of the alloy, and cooling the alloy, either during rolling or thereafter, slowly enough that a at least partially recovered or recrystallized structure, but fast enough to ensure that enough Cu remains in the solid solution to produce a curing effect when a subsequent curing treatment is performed.

Optional Cold rolling the hot rolled sheet, and optionally curing the cold-rolled alloy, preferably after the indispensable Hot rolling step the rolled ingots always at a temperature below their solution temperature is held.

During the Cold rolling usually raises the temperature of the metal to 100-200 ° C while it passed through the rolling mill becomes. Usually the metal is rewound after cold rolling, and the reeled Metal is so massive that it takes a long time to reach room temperature cool. phase deposition and curing can while this cooling time take place without it being absolutely necessary to cool the roll. If necessary, but in addition chilled become. If desired, can be carried out after cold rolling a reheat, if desired, For example, to increase the amount of cold working in the alloy Taxes. This reheating brings the alloy over their solution temperature, and then the cooling will be preferably at a rate of less than 2 ° C / sec to To avoid distortions, or the need for a separate deterrent step to avoid.

As an alternative to discontinuous continuous casting, the alloy could also be cast continuously, for example by double belt casting or twin roll band casting. These techniques allow the production of a thin band
with a low thickness of usually 5mm, sometimes even 2mm. Such thin cast tapes may or may not require homogenization prior to hot rolling because they tend to cool so rapidly that it is likely that the Cu and Mg present remain in solution.

The Cast could be directly or indirectly extruded. Preferably, the Gusstück homogenized as described above and then cooled to room temperature before it for the extrusion is reheated to 400-500 ° C. Optionally, that can Cast directly from its homogenization temperature to the desired extrusion temperature chilled become.

The Pressings are preferably made with stagnant air, or with forced-circulation air cooled. If desired can the compacts are reheated above the solution temperature, and then cooled at a rate of less than 2 ° C / sec. This treatment by reheating may be necessary to control the texture and / or grain size. After being extruded the compacts usually stretched by 1 to 2% and then allowed to cure.

The The present invention is in particular for the production of material for cans applicable, in particular can end-capping tape (CES, can end stock), which has a combination of high strength and formability. The combination of composition and method of the present Overcomes invention many of the manufacturing difficulties of conventional AA5182 sheets, the Can be used at present, and can can lid tape (CES) at lower Cost. It also improves the subsequent performance the can lid, in particular its corrosion resistance at the scribe line. The invention is particularly suitable for the reduction the sheet thickness for making lighter can ends, i. sheet thicknesses down to about 0.150 mm.

For the production of can lid tape, the preferred method is a pig to water, homogenize and roll to about 2 mm to form a strip manufacture. A central aspect of the invention is that the band no additional Work step of the solution annealing needs. Furthermore, even if such is required, the material must not cooled down quickly be, e.g. it does not have to be quenched in water, the cooling takes place generally through the air (possibly with forced circulation) The coil will then be on the final Thick cold rolled and painted.

The range (in weight percent) for the major elements within which the present invention operates is: Magnesium: 1.0-4.0% by weight, preferably 2.0-4.0, in particular 2.5-4.0% Copper: 0.1-0.6% by weight, preferably 0.2-0.5, in particular 0.2-0.4 Manganese: up to 0.8% by weight, preferably up to 0.6, in particular up to 0.5 and most preferably up to 0.4% For some alloys, a minimum Mn content of 0.1% is preferred. Iron: up to 0.5% by weight, preferably up to 0.1-0.3, Silicon: up to 0.3% by weight, preferably up to 0.2%, Chrome: up to 0.15%, preferably traces Titanium: up to 0.15, preferably up to 0.05% Boron: up to 0.05, preferably up to 0.01% Carbon: Up to 0.05, preferably to 0.01%.

For grain refinement of the cast, either TiB ₂ or TiC may be used, but generally not common.

The The present invention will now be described in more detail with Reference to the accompanying drawings, in which:

1 shows a thermodynamic calculation of the solution temperature for the deposition of the S-phase in Al-x% Mg-y% Cu-0.25Mn-0.2Fe-0.12Si,

2 the conductivity changes (% IACS) in the isothermal annealing of an Al-3Mg-0.4Cu-0.25Mn-0.2Fe-0.12Si alloy after solution annealing and quenching with cold water shows,

3 shows the conductivity changes (% IACS) in the isothermal annealing of an Al-3Mg-0.4Cu-0.25Mn-0.2Fe-0.12Si alloy after solution annealing and quenching with cold water and cold rolling,

4 Curves showing the effects of time and temperature on the extent of recrystallization in isothermal annealing of Al-3Mg-0.4Cu-0.25Mn-0.2Fe-0.12Si alloy after solution annealing / quenching with cold water and cold rolling ,

The theoretical basis for the present invention is as follows:
The basic requirement is to select an alloy composition that allows the solutes to be retained in the solid solution on cooling from the temperatures used during hot rolling (say, 250 to 400 ° C). The tape is then processed to effect a phase of setting by precipitation which provides additional strength. This deposition is preferably carried out on the microstructure caused by the cold deformation structures. In the case of Can End Cassette (CES), this cold working is cold rolling, for extrusion it is stretching, and for sheet it is during forming of the sheet when making a part thereof.

Although there is a thermodynamic driving force to remove the solutes from the solid solution during hot forming and subsequent cooling, the nucleation and diffusion effects are such that a fair amount of the solutes remain in solution, ie, "the nose of the transformation line is avoided ". The accompanying 1 Figure 12 shows a calculation of the solution temperature for a range of Al-Cu-Mg alloys. This shows that the solutes remain above the stated temperatures in the solid solution. Thus, the solutes can not be separated from the solution until the band is at or below this temperature. It should be noted that even if the solutes begin to be separated from the solid solution, still enough solute remains available to significantly increase strength in further processing.

Conductivity was determined for a 3Mg-0.4Cu-0.25Mn-0.2Fe-0.12Si alloy (wt%) to demonstrate that there is a barrier to nucleation and growth of the deposited substances in this type of alloy which can be exploited commercially to achieve a better compromise between strength and formability. The accompanying 2 Figure 11 shows the effect of isothermal cure on the conductivity of a fully solution annealed and quenched cold water material that isothermal cured. This indicates that at temperatures below the solution temperature, the conductivity increases (indicating that Cu and Mg are precipitated from the solid solution), but that at lower temperatures, deposition becomes difficult. So the solutes can be kept in the solid solution if the belt can be cooled fast enough to these temperatures.

When microstructure dislocations are present, conductivity increases more rapidly because the deposited phase is presumably S phase (an AlCuMg phase), or its metastable precursors known to preferentially nucleate at microstructural dislocations. To demonstrate this, a second series of experiments was performed on isothermal curing on the same alloy but after solution annealing, quenching in cold water and cold rolling. This will be in the accompanying 3 shown. In this case, the drop in conductivity starts after a few seconds. This demonstrates the importance of traversing this temperature range without the presence of a large number of microstructural dislocations because, if the phase nucleates at these high temperatures, it is likely to be relatively coarse and only slightly increase strength. The example shown is an extreme example because the strip was cold rolled to produce a high density of microstructure dislocations before curing. In hot working, the density of microstructure dislocations is lower for a given level of macroscopic stress so that fewer sites are available for nucleation of the deposits.

For the production of can ends, the conditions for hot rolling are selected to ensure that the hot rolled plate recrystallizes during or before coiling, or very shortly thereafter. Preferably, the sheet is completely recrystallized, resulting in a low density of microstructure dislocations. The recrystallization is promoted by setting it so that the minimum temperature of the sheet when leaving the mill is 250 ° C, preferably 270 ° C, especially 300 ° C, and / or the cooling rate of the sheet is low enough to recrystallize the sheet can when reeled or when rewinding. In a conventional mill, the coiling temperature is about the same as when leaving the mill. Where additional means for cooling after the Rolling mill are provided, the minimum temperature during coiling should be in the range of the above minimum temperature when leaving the rolling mill. In practice, it has been found that acceptable cooling rates are on the order of 0.1 and preferably 0.2 to 5 ° C / minute in the temperature range of 400-200 ° C. It is not necessary to unwind the sheet during cooling, for example to quench it.

An indication of the time required for recrystallization was determined for a 3Mg-0.4Cu-0.25Mn-0.2Fe-0.12Si alloy (wt%). This material was solution annealed, quenched with cold water, and 50% cold rolled. Isothermal heat treatments were performed to determine the extent of recrystallization, as in 4 shown. This shows that after this deformation complete recrystallization at temperatures above about 320 ° C within a few minutes is possible. It should be noted that the exact details of the recrystallization kinetics depend on the deformation conditions and the microstructure of the material.

A high temperature on leaving the mill favors the deposition of S-phase or its precursors as the sheet or roll cools. Faster cooling can counter this and avoid deposition, but if the exit temperature becomes too high, the cooling rate needed is too fast to be of use in practice. To take maximum advantage of the rapid cooling during hot rolling, the upper limit of the outlet temperature from the rolling mill, especially for Cu and Mg-richer alloys, should preferably be below the solution's solution temperature. 1 indicates the solution temperature as a function of Mg and Cu content. Preferably, the maximum exit temperature should be between 340 and 360 ° C, although for some alloys 380 ° C are possible.

It is important to note that the position of the nose of the transformation line during recrystallization varies with the composition of the alloy. For example, the nose lies with the alloy on which 2 refers to a time of about 100 to 1000 seconds. For dilute alloys, the nose is displaced to longer times, while in more concentrated alloys, the nose is shifted to shorter times. In the 2 indicated time compared to times between 1 and 100 seconds for conventional curing systems such as AA7075, AA2017, A6061 and AA6063. For the alloys described in the present invention, this provides longer times below the solution temperature during which the strip is cooled and still the Cu (and Mg) can be held in the solid solution. For this preferred alloy of 2 It has been found that a cooling rate of 5 ° C / min is sufficient to substantially avoid the nose of the transformation line and to ensure a strong curing reaction during further processing. This cooling rate can be achieved, for example, by cooling a coil with forced-circulation air. The prior art solution heat treatment of these Al-Mg-Cu alloys teaches that not only is an independent work step of solution annealing required, but the tape must be quenched at a cooling rate of 2 ° C / second or faster. For the present invention, it has been found that none of these steps must be used, thereby providing a more cost effective production route for these alloys. Likewise, no separate annealing step is required between hot working and before cooling.

These solutes are then used to produce a significant precipitation hardening effect during subsequent thermomechanical processing. During the subsequent cold (or warm) forming of the strip, an increased dislocation density is caused to increase the sites of nucleation of the hardening phase. This transformation need not be necessary for all applications of this invention, since it is known in these compositions that deposition can occur even in the absence of dislocations, albeit at a slower rate. It is believed that the deposited phase is S-phase (Al ₂ CuMg) which can form as needles or rods on the dislocation structures. In the case of Can Lid Tape (CES), this deposition may occur during a separate curing step, or during the thermal history experienced by the material during forming, eg during strip rolling.

As indicated above, it may be important to achieve rapid recrystallization to remove the dislocations from the cooling material. Mn can be added, as a setting element, and to control the grain size, and is therefore best kept as high as possible. However, Mn inhibits recrystallization after hot rolling or annealing, so that under some circumstances it may be necessary for some alloys to limit the Mn content to a maximum of 0.4% in order to achieve complete recrystallization. For many alloys it may be desirable to min at least 0.05 and preferably at least 0.1% Mn in the alloy to help control the grain size in the recrystallized sheet. Recrystallization may also be important in controlling the canister lid crystal (CES) crystallographic texture, but this may not be necessary if the can closing machines are adjusted to account for a significantly greater amount of earing. Control of the crystallographic texture may also be important to the malleability of automotive sheets, another potential application of this invention.

One Another feature of the composition used in the present invention is the importance of low Fe and To have Si contents in the alloy, as this is the presence of an excessive number prevents coarse particles of the alloy components in the sheet. These form during the solidify and can in the homogenization of the pigs are not completely dissolved. Even when rolling Break apart, their presence is disturbing enough to be malleable to impair. Since it has been found that this invention is one over the usual CES (can lid tape) AA5182 offers improved formability the band possibly higher Levels of these elements tolerate, so the cost is reduced become. Tolerating higher Levels of Si and Fe may allow larger amounts of recycled aluminum waste to be used and that is another important aspect of this invention, it can up to be tolerated to 0.5 Fe in the alloy, preferably up to 0.3 % Fe. The minimum content of Fe present is dictated by the cost and less than 0.1 Fe are unlikely to be present. It can up to 0.3% silicon, preferably up to 0.2%.

One another advantage over the conventional one Can lid tape (CES) AA5182 is that the lower magnesium content the can lid less vulnerable for stress corrosion cracks (SRK), which leads to catastrophic failure of the can lid in the Tension condition as encountered by a pressurized can is, lead can. The invention described herein makes the lid against them Conditions less sensitive, since the lower Mg content, the deposition Beta phase associated with SRK decreased. Avoiding SRK is also common in many other applications, including sheet metal for car bodies important.

Can end (CES) is currently made from AA5182 and gets its strength mainly from a combination of solution hardening and Strain hardening. This makes it difficult to roll and leads to relatively high production costs.

The Alloy used in the present invention has during the Rolling process a lower strength, but develops its strength while the subsequent thermal exposure during the Production. So there is the advantage, a less solid sheet to roll, and still in the end the desired properties of the sheet to reach. It is also possible, To produce a stronger sheet, which is suitable for reducing the thickness is more difficult without reducing the rolling capacity (higher rolling pressures) the implementation the rolling process), as with alloys with a higher Mg content how to find AA5182 and AA5019A.

The present invention is also for the production cost-effective Bracket applicable where the material used in hot rolled condition could be (direct hot rolling on thickness), potentially increasing the need the solution annealing of Sheet metal is avoided. Optionally, the sheet could be as for can lid tape (CES) to the desired Thickness hot rolled, with final continuous annealing to him the for needed this application Formability, and the solutes in solution too bring - that Cool after the glow should be done quickly enough to remove essentially all solutes n the solution to keep. The curing can be done in a separate operation before or after molding, for example while the baking of the paint of the auto part.

Some embodiments The present invention will now be described by way of example.

example 1

An alloy of the following composition was cast as a 225 mm × 75 mm cross-section ingot: magnesium 3.0% by weight copper 0.4% by weight manganese 0.25% by weight iron 0.20% by weight silicon 0.12% by weight rest Aluminum with possible impurities

The Massel was watering not treated for grain refining and therefore the Ti content was 0.0018 % and B less than 0.0001%.

This was 2 hours at 540 ° C (Heating rate 50 ° C / h) homogenized, followed by hot rolling in the laboratory to 6 mm. During the Rolling temperatures were only about 100-200 ° C, so the tape was still sometimes solution treated to complete recrystallization to reach, and the dissolved substances back into the solid solution bring to. This reproduces levels of solutes that more closely match those to find when rolling on an industrial hot rolling mill would be (before rewinding).

Various heat treatments were then applied to this sheet. The tape was either solution annealed (SHT) (5 minutes at 550 ° C) and quenched with cold water (CWQ), or it was solution treated, and then air cooled to temperatures in the range of 300 to 400 ° C, and then cooled at 1 ° C / min. The conductivity was measured at this step to determine how much solute in the solid solution remain. These conditions were selected to match the conditions simulate that one while the commercial application of this invention. To the strip temperature below the solution temperature the alloy falls, the S-phase contained therein can not be separated, and that's why the Cu (and Mg) essentially in the solid solution. The tape could then quenched at the end of hot rolling or, preferably, cooled after being coiled become. During this Procedure could the initial temperature may be in the range of 300 to 340 ° C and the typical initial cooling would be 1 ° C / min. Of the Temperature range between the solution temperature (about 390 ° C for the Alloy) and the temperature during coiling becomes very fast drive through, as this is the period of time during which the band typically in the tandem hot rolling mill is, and therefore lubricant is applied as a coolant acts. This phase was performed using air cooling of the solution annealing temperature simulated.

The Ribbon was then cold rolled to 0.24 mm, and allowed to cool in Coil of 150 ° C to ambient temperature at a cooling rate of 0.4 ° C / min. Then a paint bake cycle was simulated with 3 minutes at 205 ° C.

at Tensile tests were performed on each treatment step, and the results with those of conventional can lid tape AA5182 processed in the laboratory compared.

Of the Effect of strength development was also at different stages the laboratory simulation of the can lids tape production route. Below is an example for this Alloy annealed at 2 mm solution, and rolled to a thickness of 0.2 mm.

This is compared to laboratory rolled AA5182, where a simulation the commercial production route of this alloy was used. The 0.2% yield strength is shown in Table 1 below. The strength in the rolling condition was lower than that of AA5182, which easier rolling means, and the strength drop in the simulated Coiling and paint bake was lower, showing the advantages of deposit cure. additionally is the softest direction for can lid tape (CES) from AA5182 mostly about 45 ° off the rolling direction of the sheet (about 10-20MPa softer) and you take that this controls the beeing pressure of the sheet. In the present Invention becomes less to produce the desired strength Work hardening needed, so the weakest Direction is likely this value in the longitudinal direction. That's why in the cheapest Case the combination of composition and processing of the present invention a strength value of about 45 MPa stronger as conventional Create AA5182.

Table 1: Comparison of properties with conventional can band

The results for the conductivity are shown in Table 2 below. They show that the conductivity in the solution annealing step can be increased from 33.1 to 35, if the solutes can be separated, but that when the material is cooled from room temperature of 1 ° C / min to 300 ° C, the conductivity is only about a fraction of this increase is increasing. (0.3% vs. 1.9%). This means that a significant portion of the solutes remain in solid solution even at these cooling rates. Table 2: Conductivity after different heat treatments at 2 mm thickness Status Conductivity (% IACS) Solution annealed and quenched with cold water 33.1 Solution annealed and cooled with fast circulating air 33.1 Solution annealed and cooled from 340 ° C 33.9 Solution annealed and cooled from 320 ° C 33.8 Solution annealed and cooled from 300 ° C from 33.4 Solution annealed, cold worked and cured at 320 ° C for 14 hours 35.0

The final can lid tape strength developed by these materials after baking the paint is shown in Table 3. In this case, the sheet was rolled to 0.24 mm. This shows that enough solutes still remain in the solid solution to produce a can end band of noticeable strength. Bending tests were also carried out; they show an improvement in the pre-failure bending potential compared to the conventional can lid tape AA5182. Table 3: Strength which developed after processing to 0.24 mm and various thermal treatments at 2 mm hot strip thickness. Status Test voltage at 0.2% (MPa) Solution annealed and quenched with cold water 350 MPa Solution annealed and cooled from 340 ° C 327 MPa Solution annealed and cooled from 320 ° C 329 MPa

Example 2

An alloy of the following composition was continuously cast for processing in an industrial plant: magnesium 2.9% by weight copper 0.4% by weight manganese 0.1% by weight iron 0.20% by weight silicon 0.08% by weight rest Aluminum with possible impurities.

The Masses were with additional Grain refiners poured.

The pigs were homogenized at 540 ° C and on a reversing mill with a scaffold on hot rolled to a thickness of 38 mm, the temperature being 480 ° C. The tape was then hot rolled to a thickness of 2.5 mm in a three-stand tandem mill train. The conditions were adjusted to achieve different cooling rates to show the effects of the opposite extremes of this invention. In both cases, the coils were cooled with forced-circulation air, causing a cooling rate determined at the outer layers of the coil to be approximately 0.7 ° C / min.

Of the cooler Coil was further processed to obtain a sidewall temperature of 280-290 ° C. In In this case, the microstructure was essentially unrecrystallized. That's why they were solved Substances on the existing dislocation structure from hot forming easily from the solid solution excreted. The conductivity of the band is shown in Table 4, it can be seen that the% IACS values are similar like those of material in which the deposition is completely permitted has been. Table 4 also shows the conductivities listed under cooling of ribbons with 2.5 mm thick metal with stagnant air (about 60 ° C per minute) at the end of the hot rolling, they show that in these cooling rates a significant proportion of the dissolved Substances in the solid solution can be held.

Of the warmer Coil was further processed to obtain a sidewall temperature of 330-340 ° C. Table 4 shows that in this case cooling with forced-circulation air more solved Substances in the solid solution holds, as Follow the whole recrystallized grain structure, due to the higher temperature during coiling was achieved. The amount of dissolved Substances in the solid solution with the faster cooling is even higher, and approaching the conventional Materials that solution heat treated and with cold water were quenched. That shows that a cooling rate of 0.7 ° C / min is capable to keep part of the copper in the solid solution, but that one faster cooling more copper in the solid solution stops, and the material is still completely recrystallized. The cooling of the coil with forcibly recirculated air from a temperature below 330 ° C achieved a similar Effect (i.e., more dissolved Substances in the solid solution), because the conversion curve is also essentially missed in this case becomes. The forced-circulation Air cooled Coil was rolled to 0.216 mm, and the tensile strength after the Rolls measured at 347 MPa.

Between these two limits of the cooling temperature At the end of hot rolling, more solutes will be in solid solution so that sheet metal with even higher Strength can be produced.

Table 4: Conductivity after various thermomechanical treatments in an industrial plant

Claims (13)

A method of producing hardening aluminum alloys, comprising the steps of: a) casting an alloy containing the following in weight percent: magnesium 1.0 to 4.0 copper 0.1 to 0.6 manganese up to 0.8 iron up to 0.5 silicon up to 0.3 chrome up to 0.15 titanium up to 0.15 rest Aluminum with possible impurities b) optionally homogenizing the cast alloy c) hot working the casting at an initial temperature of at least 400 ° C to obtain an intermediate product wherein at least a portion of the hot working is performed while the casting is at a temperature above the solution temperature of the alloy, i Cooling the intermediate either during hot working or in a subsequent step at a rate of less than 5 ° C / min to form at least a partially recovered or recrystallized structure and leaving enough copper in the solid solution in the alloy. to cause a hardening effect on the alloy when phase crystallization occurs during the further thermal history of the alloy, and e) optionally allowing or inducing the onset of phase crystallization in the alloy. The method of claim 1, wherein the alloy has the following composition, expressed in weight percent: Magnesium: 1.0 to 4.0 Copper: 0.2 to 0.5 Manganese: up to 0.6, preferably up to 0.5 Iron: 0.1 to 0.3 Silicon: up to 0.2 Chrome: up to 0.15 Tinat: up to 0.15 Boron or carbon: up to 0.01 Rest: Aluminum with possible impurities The method of claim 2, wherein the magnesium content 2.5 to 4% is. Method according to one of claims 1 to 3, wherein the intermediate a practically complete recovered or recrystallized structure has. Method according to one of the preceding claims, wherein the casting before hot working at a temperature of at least 480 ° C, preferably 500 to 600 ° C is homogenized, leaving virtually everything copper and magnesium in the casting in solid solution are. Method according to one of the preceding claims, wherein the casting is thermoformed, optionally with reheating the casting over the solution temperature of the alloy, and preferably at least 450 ° C, to be practical Add all magnesium and copper to the solid solution to take. Method according to one of the preceding claims, wherein the hot forming step is performed when the casting is a initial Temperature of 450 ° C up to 580 ° C Has. Method according to one of the preceding claims, wherein the alloy is continuously cast. Method according to one of the preceding claims, which the step of cold rolling the hot formed casting, optionally with winding, includes. Method according to one of claims 1 to 9, wherein the hot forming by extrusion through to be led. Method according to one of claims 1 to 9, wherein the hot working performed by hot rolling becomes. Method according to one of the preceding claims, wherein the hot-formed casting is cooled at a rate of less than 1 ° C / min. Method according to one of the preceding claims, wherein if, after the hot forming step, the temperature of the intermediate the solution temperature exceeds the alloy, cooling the Intermediate below the solution temperature at a rate of less than 2 ° C / sec.