GB1566627A

GB1566627A - Can bodies made from light metal blanks

Info

Publication number: GB1566627A
Application number: GB36453/77A
Authority: GB
Original assignee: Alusuisse Holdings AG; Schweizerische Aluminium AG
Current assignee: Alcan Holdings Switzerland AG
Priority date: 1976-09-02
Filing date: 1977-09-01
Publication date: 1980-05-08
Also published as: DE2737232A1; DE2737232C3; CH622031A5; NO772980L; FR2363638A1; NO148154C; DE2737232B2; FR2363638B1; NO148154B; IT1084728B; ES462041A1; ATA628777A; AT362941B

Abstract

For producing cold-extruded and stove-enamelled aluminium cans from annealed blanks, pure aluminium with 0.05 to 0.1% of silicon and 0.1 to 0.25% of iron is used, at least two elements, which inhibit recrystallisation and show peritectic behaviour in aluminium, being added to the pure aluminium in quantities of 0.05 to 0.3% each. In place of the elements showing peritectic behaviour in aluminium, 0.05 to 0.9% of manganese can also be added to the pure aluminium. The elements inhibiting recrystallisation cause a reduction of the decrease in strength of the work-hardened can bodies during stove-enamelling.

Description

(54) CAN BODIES MADE FROM LIGHT METAL BLANKS (71) We, SWISS ALUMINIUM LTD., a Company organised under the laws of Switzerland, of Chippis (Canton of Valais), Switzerland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention concerns stove-lacquered can bodies made out of annealed light metal blanks, and processes for their manufacture.

It is known that annealing conditions have a marked effect on the softening behaviour of can bodies, whether of rolled sheet or impact extruded. Such can bodies are stove lacquered which causes part of the work hardening in the material to be lost due to recovery. With this in mind the inventors set themselves the task of reducing the loss of strength due to the stove lacquering of the can bodies. A consequence of achieving higher strength values in such can bodies is to permit a considerable saving in metal.

According to the present invention, a stovelacquered can body is made from one or more annealed light metal blanks, in which the blanks are pure aluminium alloyed with at least two recrystallisation inhibiting elements, which form peritectic systems with aluminium, each in an amount from 0.05 to 0.3% (by weight).

(All the percentages mentioned in this specification and claims are by weight.) "Pure aluminium" is generally understood to mean non-alloyed aluminium containing from 98 to 99.9% aluminium. Usual impurities are 0.05 to 0.1% silicon and 0.1 to 0.25% iron.

The small additions of recrystallisation inhibiting elements reduce the loss of strength suffered by the cold work-hardened can body during stove lacquering; but the amounts are such that they do not interfere with a rolling or impact extrusion process.

The blanks can be made from sheet manufactured by rotary casting, hot and cold rolling and the usual annealing. Hence there is no need for any new investments in relation to production of the blanks. Likewise, it is possible to carry out the processing of can bodies on blanks made from extruded strip.

It has been found advantageous to use titanium and zirconium as the recrystallisation inhibiting elements, each in an amount from 0.05 to 0.25 %, in particular from 0.08 to 0.12%.

Preferably the amounts of titanium and zirconium are approximately equal, for example about 0.1% each.

Trials were carried out to compare pure aluminium blanks with blanks made from pure aluminium alloyed with 0.1% each of titanium and zirconium. The blanks were made from hot-rolled strip. After a heat treatment which corresponded to stove lacquering, can bodies made from the metal containing titanium and zirconium exhibited 20% higher tensile strength than the can bodies made from pure aluminium. The metal saved in making can bodies in accordance with the invention can amount to about 8%.

Further advantages, features and details of the invention are revealed in the following description of results obtained from tests, and with the aid of the accompanying drawing which shows a graphic representation of the results from four different tests.

Blanks were prepared from 7 mm thick sheets of the compositions listed in the following table and were held in a furnace at 490"C for about ten hours, after a heating-up time of about 40 min.

Sample Si Fe Ti Cr Zr No. % % % % I 0.09 0.25 0.02 - II 0.08 0.25 0.02 - 0.13 III 0.09 0.245 0.02 0.11 0.09 IV 0.09 0.245 0.092 - 0.09 The blanks were cold rolled to 0.5 mm to simulate impact extrusion and, instead of stove lacquering, were annealed in a salt bath at 260"C, for various periods as mentioned below, and then quenched in water.

The coordinates in the drawing are such that the duration of the anneal which simulated the stove lacquering is represented in minutes on the horizontal axis, and the subsequent tensile strength in kp/mm2 is represented on the vertical axis.

When the plotted curves are related to the compositions of the materials tested, it is clearly seen that the greater the additions of titanium and zirconium the greater is the strength attained; after an annealing time of eight minutes, the difference in tensile strength amounts to about 4 kp/mm2.

The strength values obtained from actual can bodies have been found to be slightly greater than the values obtained from the blanks; the corresponding curves for can bodies are therefore parallel to those shown here but displaced upwards.

WHAT WE CLAIM IS:- 1. A process for the manufacture of a stovelacquered can body from one or more annealed light metal blanks, in which the blanks are pure aluminium alloyed with at least two recrystallisation inhibiting elements, which form peritectic systems with aluminium, each in an amount from 0.05 to 0.3% (by weight).

2. A process according to claim 1, in which the said elements are two or three of chrom ium, titanium, and zirconium, each in an amount less than 0.2%. ~~~~~~~~~~~~~ 3. A process according to claim 1, in which the said elements are titanium and zirconium, each in an amount from 0.05 to 0.25%.

4. A process according to claim 1, in which the said elements are titanium and zirconium, each in an amount from 0.08 to 0.12 ó.

5. A process according to claim 3 or claim 4, in which the amounts of titanium and zirconium are approximately equal.

6. A process according to claim 1, in which the said elements are approximately 0.1% titanium and approximately 0.1% zirconium.

7. A stove-lacquered can body made from one or more annealed light metal blanks, of pure aluminium alloyed with at least two recrystallisation inhibiting elements, which form peritectic systems with aluminium, each in an amount from 0.05 to 0.3% (by weight).

8. A can body according to claim 7, in which the said elements are two or three of chromium, titanium, and zirconium, each in an amount less than 0.2%.

9. A can body according to claim 7, in which the said elements are titanium and zirconium, each in an amount from 0.05 to 0.25%.

10. A can body according to claim 7, in which the said elements are titanium and zirconium, each in an amount from 0.08 to 0.12%.

11. A can body according to claim 9 or claim 10, in which the amounts of titanium and zirconium are approximately equal.

12. A can body according to claim 7, in which the said elements are approximately 0.1% titanium and approximately 0.1 % zirconium.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Sample Si Fe Ti Cr Zr No. % % % % I 0.09 0.25 0.02 - II 0.08 0.25 0.02 - 0.13 III 0.09 0.245 0.02 0.11 0.09 IV 0.09 0.245 0.092 - 0.09 The blanks were cold rolled to 0.5 mm to simulate impact extrusion and, instead of stove lacquering, were annealed in a salt bath at 260"C, for various periods as mentioned below, and then quenched in water. The coordinates in the drawing are such that the duration of the anneal which simulated the stove lacquering is represented in minutes on the horizontal axis, and the subsequent tensile strength in kp/mm2 is represented on the vertical axis. When the plotted curves are related to the compositions of the materials tested, it is clearly seen that the greater the additions of titanium and zirconium the greater is the strength attained; after an annealing time of eight minutes, the difference in tensile strength amounts to about 4 kp/mm2. The strength values obtained from actual can bodies have been found to be slightly greater than the values obtained from the blanks; the corresponding curves for can bodies are therefore parallel to those shown here but displaced upwards. WHAT WE CLAIM IS:-

1. A process for the manufacture of a stovelacquered can body from one or more annealed light metal blanks, in which the blanks are pure aluminium alloyed with at least two recrystallisation inhibiting elements, which form peritectic systems with aluminium, each in an amount from 0.05 to 0.3% (by weight).

2. A process according to claim 1, in which the said elements are two or three of chrom ium, titanium, and zirconium, each in an amount less than 0.2%. ~~~~~~~~~~~~~

3. A process according to claim 1, in which the said elements are titanium and zirconium, each in an amount from 0.05 to 0.25%.