CN1997763A - Thin strips or foils of alfesi alloy - Google Patents

Abstract

The invention relates to a thin strip or foil, having a thickness of 6 to 200mum, preferably, of 6 to 50mum, and composed of an alloy containing (in weight %) Si: 1.0 to 1.5, Fe: 1.0 to 1.5, Cu < 0.2, Mn < 0.1, other elements < 0.05 each up to a total < 0.15, the remainder being Al. The annealed thin strip or foil has a tensile strength Rm > 110 MPa for a thickness > 9 mum and > 100 MPa for a thickness of 6 to 9 mum, and an elastic limit R0.2 > 70 MPa. Preferably, said alloy has a silicon content of 1.1 to 1.3 % and an iron content of 1.0 to 1.2 %. The aforementioned thin strips or foils may be used especially for the production of multilayer composites, overcaps for bottles or aluminium wrappings.

Description

Aluminum-iron-silicon alloy thin strip or foil

technical field

The present invention relates to a thin strip or foil having a thickness of less than 200 μm, preferably less than 50 μm, made of an aluminum alloy containing iron and silicon and having a relatively low manganese content. These belts can be obtained by conventional semi-continuous or continuous casting of plates, for example twin-belt casting or twin-roll casting.

Background technique

The trend in the Aluminum Alloy Thin Foil market is towards a continuous reduction in thickness for given applications, while requiring high mechanical properties and good formability.

Alloys with very low manganese content are commonly used for thin foils, such as the Aluminum Association registered 8111 alloy with the following composition (wt %):

Si 0.30-1.1; Fe 0.40-1.0; Cu＜0.10; Mn＜0.10

The lack of manganese makes it easy to achieve recrystallization during the final annealing, but the ultimate tensile strength Rm is insufficient at a thickness of less than 100 μm.

Therefore, there is a need to develop new alloys and/or optimize the transformation process to meet market demands.

Manganese is generally added to improve mechanical strength, such as the 8006 alloy registered by the Aluminum Association with the following composition (weight %):

Si<0.40; Fe: 1.2-2.0; Cu<0.30; Mn: 0.30-1.0; Mg<0.10

The result of adding manganese is to make the material hard. For alloys with the following composition: Si=0.23%; Fe=1.26%; Cu=0.017%; Mn=0.37%; Mg=0.0032%; The mechanical properties obtained during the transformation process are R _m values equal to 103 MPa at a thickness of 6.6 μm.

Mechanical properties can also be improved by adding small amounts of manganese to iron-containing 8000 series alloys. Patent application WO 02/64848 (Alcan international) describes the production by continuous casting of thin strips made of an AlFeSi alloy containing 1.2%-1.7% Fe and 0.35%-0.8% Si. High mechanical strength is obtained by adding 0.07%-0.20% manganese to the alloy. The addition of manganese is considered necessary to obtain a small grain size after the final anneal.

Therefore, manganese appears to be an element capable of improving the mechanical properties of 8000 alloy. However, manganese in solid solution or in finely precipitated form can hinder or delay recrystallization during final annealing. Therefore, the precipitation of the manganese-containing phase needs to be precisely controlled at each step of the process, but this is often difficult. Any deviation in the transformation process has a non-negligible effect on the final annealing effect. Therefore, it would be very useful to develop alloys that do not contain manganese and have high mechanical properties.

U.S. Patent 5 503 689 (Reynolds Metals) describes a method of manufacturing thin strip by continuous casting and cold rolling without intermediate annealing, said thin strip is made of an alloy containing the following composition: 0.30%-1.1% Si and 0.40%- 1.0% Fe, less than 0.25% Cu and less than 0.1% Mn. Preferred levels of iron and silicon are 0.6% and 0.75%.

US Patent 5 725 695 (Reynolds Metals) describes the process of treating the same composition with intermediate annealing at 400°C-440°C (750mm-825mm) and final recrystallization annealing at 288°C (550mm). The ratio of Si and Fe content is greater than or equal to 1. In the embodiment, when the thickness is 46 μm (0.00185′), the obtained maximum ultimate tensile strength is 90 MPa (13.13 ksi), the maximum yield stress is 39.1 MPa (5.68 ksi), and the elongation is 11.37%. These mechanical properties are still low for some applications.

For alloys obtained by continuous casting, high temperature heat treatment is usually required to reduce the deleteriousness of segregation by reabsorbing precipitates and homogenizing the structure through the thickness. 8011 alloy (composition 0.71% Fe; 0.77% Si; 0.038% Cu; 0.006% Mn; 98.45% Al) obtained by twin-roll casting at 600 ° C in the article "Centerline Segregation in a Twin -Roll Cast AA8011 Alloy" Aluminum, 74, 1998, pp 318-321 described. The precipitated phase is improved and inhomogeneity is reduced. The reduction of central segregation thus limits the porosity of ultrathin foils and improves their formability.

Limiting the heat treatment temperature is economically attractive. For the 8111 alloy whose composition is 0.7% Fe; 0.7% Si; Mn<0.02, Zn<0.02; Cu<0.02, although it must be annealed at 550°C-580°C in order to obtain a more complete transformation (see "M.Slamova et al. Response of AA8006 and AA8111 Strip-CastRolled Alloys to High Temperature Annealing", ICAA-6, 1998), but at 460°C the onset of phase transition leading to complete recrystallization was observed. Therefore, low-temperature homogenization of alloys that do not contain manganese can be considered.

Also, in the transition to low thickness after homogenization, it is standard practice to add an intermediate annealing step to soften the metal. For manganese alloys, intermediate annealing control usually requires high temperature treatment (above 400°C) to achieve recrystallization.

For manganese-free Type 8000 alloys, it is conceivable to heat treat at temperatures lower than those for Type 8006 alloys.

Patent application WO 99/23269 (Nippon Light Metal and Alcan International) describes a method applicable to AlFeSi alloys containing 0.2%-1% Si and 0.3%-1.2% Fe, and the Si/Fe ratio In this method, the intermediate annealing is carried out in two steps, the first step is carried out at 350°C-450°C, and the second step is carried out at 200°C-330°C. The purpose of this method is to reduce surface defects in the foil. No mention is made of mechanical properties.

The object of the present invention is to obtain, using the most economical industrial manufacturing method possible, a thin strip or foil made of an AlFeSi alloy without addition of manganese and having high mechanical strength while maintaining good formability.

Contents of the invention

The subject of the invention is a thin alloy foil with a thickness of 6-200 μm, preferably 6-50 μm, having the following composition (% by weight):

Si: 1.0-1.5; Fe: 1.0-1.5; Cu<0.2;Mn<0.1; other elements each <0.05 and the total <0.15; the rest is Al, the preferred condition is Si/Fe≥0.95, and the thickness is >9μm when annealed The ultimate tensile strength R _m >110MPa under fire, and R _m >100MPa when the thickness is 6-9μm. Preferably the yield stress R _0.2 of the thin foil is >70 MPa (tested on shear specimens). Ultimate elongation as a function of foil thickness greater than:

Thickness (μm) A(%) is greater than preferably greater than 6-9 3 4 9-15 5 7 15-25 10 15 25-50 18 25 50-200 20 25

The silicon content of the alloy is preferably between 1.1% and 1.3% and its iron content between 1.0% and 1.2%.

Another subject of the invention is a method for the manufacture of thin strips with a thickness of less than 200 μm, made of alloys with the following composition (% by weight): Si: 1.0-1.5; Fe: 1.0-1.5; Cu<0.2; Mn < 0.1; other elements < 0.05 each and in total < 0.15; the rest is Al, the preferred condition Si/Fe ≥ 0.95, the method includes by vertical semi-continuous casting and hot rolling of the plate or by continuous casting that can be followed by hot rolling Preparation of initial strip, which is cold rolled to final thickness, while intermediate annealing may be carried out at a temperature of 250°C-350°C, preferably 280°C-340°C for 2h-20h, and at a temperature of 200°C-370°C Final annealing.

Detailed ways

The thin strip or foil according to the invention is made of 8000 AlSiFe alloy which contains almost no manganese, where the manganese content is usually less than 0.1%. The iron and silicon contents are significantly higher than the manganese-free AlSiFe alloys 8011 and 8111 alloys most commonly used for thin foils. A preferred composition range is an alloy containing 1.1%-1.3% silicon and 1.0%-1.2% iron.

The alloy according to the invention preferably has a composition such that the ratio of silicon and iron contents is Si/Fe≧0.95. For alloys with this composition, their mechanical strength under annealing and tempering (O tempering) is excellent, i.e. ultimate tensile strength _Rm > 110Mpa or even 115Mpa for thickness > 9μm, _Rm for thickness 6-9μm >100 MPa, normal yield stress R _0.2 >70 MPa at 0.2%. This high mechanical strength is not obtained at the expense of formability since the elongation is at least as high as the 8011 and 8111 alloys and the bursting pressure is higher.

These high mechanical properties obtained are as good as strips produced from plates obtained by conventional vertical semi-continuous casting and hot rolling, and strips obtained from continuous casting by strip casting or twin-roll casting. Continuous strip casting is also followed by hot rolling.

Hot-rolled or as-cast strip obtained by continuous twin-roll casting can be homogenized at low temperature (between 450°C and 500°C) to reduce center segregation, which reduces formability, to achieve final thickness. This low temperature heat treatment is sufficient to resorb any center segregation in these manganese-free alloys. The strip is then cold rolled to a final gauge or to an intermediate gauge of 0.5mm-5mm, at which point an intermediate anneal is performed. Unlike alloys containing manganese, this intermediate annealing can be carried out for more than 2 hours at a lower temperature of 250°C-350°C, preferably 280°C-340°C. Although this temperature range is described in the literature, especially in the above-mentioned patent application WO 02/64848, it is lower than the normal range kept above 400°C.

The applicant has found that the low-temperature heat treatment of AlFeSi alloys, more specifically AlFeSi alloys with a composition Si/Fe > 0.95, can eliminate, where technically possible, intermediate annealing, resulting in mechanical strengths significantly higher than normal The mechanical strength obtainable by intermediate annealing is at least 15% higher. Higher mechanical strength is obtained while improving formability as measured by burst pressure or dome height according to ISO standard 2758.

The final annealing is carried out at a temperature of 220°C-370°C for 1h-72h. The annealing time depends on the degreasing quality of the foil. After annealing a fine grain structure is obtained, with an average grain size of less than 3 μm as measured by image analysis with a scanning electron microscope.

The combination of low-temperature homogenization or complete heterogeneity with low-temperature intermediate annealing or no intermediate annealing at all is economically advantageous and also contributes to a fine grain size. The grain size is about 30% smaller than achievable with high temperature heat treatment, thus improving the mechanical properties R _0.2 and R _m , which are related to the number of grain joints for small thicknesses. The increase in mechanical properties is not achieved at the expense of elongation, since the increased number of grains through the thickness also limits the risk of local failure of one or two single grains through the thickness of the foil.

The thin foils according to the invention are particularly suitable for applications requiring good mechanical strength and high formability, such as the production of multilayer composites, especially lids, closures or aluminum packaging materials for packaging fresh products.

Example

Example 1

Two 6.1 mm thick strips made of alloy A according to the invention and alloy B of the 8111 type were produced by continuous twin roll casting to demonstrate the effect of alloy composition, the compositions of alloy A and alloy B are shown in Table 1 (wt. %):

Table 1

Alloy Si Fe Fe Cu Mn Mg Cr Ti B A 1.17 1.11 0.001 0.003 0.0004 0.0007 0.006 0.0005 B 0.7 0.7 0.001 0.003 0.0005 0.001 0.007 0.0005

The strip was cold rolled to a thickness of 2 mm and then intermediate annealed at 320° C. for 5 hours. These strips were then cold rolled several times to a final thickness of 38 μm. They were then subjected to a final anneal at 270°C for 40 hours.

Mechanical properties were measured in each case. The measured values are the ultimate tensile strength R _m (in MPa) according to NF-EN standard 546-2, the normal yield stress R _0.2 at 0.2% and the ultimate elongation A (in %), measured according to ISO standard 2758 The burst pressure Pe (in kPa) and the dome height Hd (in mm). The results are given in Table 2:

Table 2

Alloy R _m (MPa) R _0.2 (MPa) A(%) Pe(kPA) Hd A 123 76 30 394 9.2 B 104 54 15.8 284 6.6

It was found that, unlike alloy B of the 8111 type, the ultimate strength of the alloy A ribbon was much greater than 110 MPa, and the yield stress was greater than 70 MPa. The burst pressure and elongation are also higher, so the alloy is stronger and more formable.

Example 2

A 6.1 mm thick strip made of alloy A as described in Example 1 was produced by continuous twin roll casting. The strip was then cold rolled to a thickness of 2 mm, and a portion of the strip was then subjected to the normal intermediate annealing for this type of alloy at 500° C. for 5 hours. The remainder of the tape was intermediate annealed at 320° C. for 5 hours according to the invention. These two parts of the strip were then cold rolled several times to a final thickness of 10.5 μm. They were then subjected to final annealing at 270°C for 40 hours.

Performance is identical with embodiment 1, and numerical value is shown in table 3:

table 3

Intermediate annealing R _m (MPa) R _0.2 (MPa) A(%) Pe(kPa) Hd(mm) 470°C 99 63 7.3 71 5.1 320℃ 117 84 8.1 92 5.7

It was found that lower intermediate annealing temperatures improved mechanical strength, elongation, burst strength and formability. The average grain size measured by SEM image analysis was 3.6 μm at 470° C. annealing and 2.3 μm at 320° C. annealing. Therefore, the enhancement of mechanical properties by low-temperature annealing is related to the reduction in grain size obtained after final annealing.

Claims (10)

1. alloy thin band or paper tinsel, its thickness is 6-200 μ m, preferred 6-50 μ m, described alloy has following composition (weight %):

Si:1.0-1.5; Fe:1.0-1.5; Cu＜0.2; Mn＜0.1; Other element separately＜0.05 and amount to＜0.15, residue is Al, the ultimate tensile strength R during thickness＞9 μ m under the annealing tempering _mR when＞110MPa, thickness are 6-9 μ m _m＞100MPa.

2. according to the strip or the paper tinsel of claim 1, it is characterized in that described strip or the paper tinsel ultimate tensile strength R under the annealing tempering when thickness＞9 μ m _m＞115MPa.

3. according to the strip or the paper tinsel of claim 1 or 2, it is characterized in that the yielding stress R of described strip or paper tinsel _0.2＞70MPa.

4. according to strip any among the claim 1-3 or paper tinsel, the elongation limit A that it is characterized in that described strip or paper tinsel is the function of thickness, and is as follows:

Thickness (μ m) A (%) greater than Be preferably greater than 6-9 3 4 9-15 5 7 15-25 10 15 25-50 18 25 50-200 20 25

5. according to strip any among the claim 1-4 or paper tinsel, what it is characterized in that described alloy consists of Si/Fe 〉=0.95.

6. according to strip any among the claim 1-5 or paper tinsel, the silicone content that it is characterized in that described alloy is that 1.1%-1.3% and its iron level are 1.0%-1.2%.

7. the manufacture method of strip, described strip thickness is made less than 200 μ m and by the Al-Fe-Si alloy with following composition (weight %):

Si:1.0-1.5; Fe:1.0-1.5; Cu＜0.2; Mn＜0.1; Other element separately＜0.05 and amount to＜0.15; Remaining is Al,

Described method comprises by the vertical D.C.casting of sheet material and hot rolling or by hot rolled continuous casting subsequently and prepares initial strip, this initial strip is cold-rolled to final thickness, simultaneously can under 250 ℃-350 ℃, preferred 280 ℃-340 ℃ temperature, carry out process annealing, and under 200 ℃-370 ℃ temperature, carry out final annealing.

8. according to the method for claim 7, what it is characterized in that described alloy consists of Si/Fe 〉=0.95.

9. according to the method for claim 7 or 8, it is characterized in that described initial strip being homogenized before cold rolling under 450 ℃ of-500 ℃ of temperature.

10. according to method any among the claim 7-9, it is characterized in that described band is by continuous double-roller casting preparation.