Method of manufacturing continuous cast aluminium alloy strip of variable width

Abstract

A method of manufacturing an aluminium alloy strip article of variable width by means of continuously casting an aluminium alloy strip article, typically in a gauge range of 3 mm to 40 mm, and including the steps of, providing a first continuously cast aluminium alloy strip article at intermediate gauge and at least a second continuously cast aluminium alloy strip article at intermediate gauge, each of the aluminium alloy strip articles to be welded have the same thickness and are of the same aluminium alloy; welding the first aluminium alloy strip article at intermediate gauge to the second aluminium alloy strip article at intermediate gauge to form a welded aluminium alloy strip article; and rolling in at least one further rolling step of the welded strip article to a final gauge.

Claims

1. A method of manufacturing an aluminium alloy strip article of variable width by means of continuously casting an aluminium alloy strip article, and comprising the steps of, providing a first continuously cast aluminium alloy strip article at intermediate gauge and at least a second continuously cast aluminium alloy strip article at intermediate gauge, wherein each of the aluminium alloy strip articles to be welded have the same thickness, and are of the same aluminium alloy; and welding said first aluminium alloy strip article at intermediate gauge to said second aluminium alloy strip article at intermediate gauge to form a welded aluminium alloy strip article; and rolling in at least one further rolling step of the welded strip article to a final gauge.

2. The method according to claim 1, wherein the welded strip article has been joined utilizing a butt-weld.

3. The method according to claim 1, wherein the welding to form the welded strip article is by friction stir welding or laser beam welding.

4. The method according to claim 1, wherein there is provided a third continuously cast aluminium alloy strip article at intermediate gauge welded to the first aluminium alloy strip article and having the same thickness and the same alloy composition as said first aluminium alloy strip article.

5. The method according to claim 1, wherein each of the aluminium alloy strip articles to be welded are in an as-cast condition.

6. The method according to claim 1, wherein each of the aluminium alloy strip articles to be welded are in a hot-rolled condition.

7. The method according to claim 6, wherein the aluminium alloy strip articles to be welded have a thickness in a range of up to 10 mm.

8. The method according to claim 1, wherein the aluminium alloy is selected from the group consisting of 2xxx, 3xxx, 5xxx, 6xxx, 7xxx, and 8xxx series aluminium alloys.

9. The method according to claim 1, wherein the aluminium alloy is a 3xxx-series aluminium alloy.

10. The method according to claim 1, wherein the aluminium alloy is a 5xxx-series aluminium alloy.

11. The method according to claim 1, wherein the aluminium alloy is a 6xxx-series aluminium alloy.

12. The method according to claim 1, wherein the first aluminium alloy strip article has a width in a range of 1000 mm to 2400 mm, and any further aluminium alloy strip article welded to said first aluminium alloy strip article has a width less than the width of the first aluminium alloy strip article.

13. The method according to claim 1, wherein the welded strip article after the welding step is coiled.

14. The method according to claim 1, wherein the welded strip article is rolled to its final gauge solely by hot rolling.

15. The method according to claim 1, wherein the welded strip article is rolled to its final gauge solely by cold rolling.

16. The method according to claim 1, wherein the welded strip article is rolled to its final gauge by hot rolling followed by cold rolling.

17. The method according to claim 1, wherein the welded strip article is rolled to a final gauge in the range of 0.25 mm to 4.0 mm.

18. The method according to claim 1, wherein the welded strip article after rolling to final gauge is being annealed or solution heat treated.

19. The method according to claim 1, wherein the aluminium alloy strip article is in the form of automotive sheet.

20. The method according to claim 1, wherein the aluminium alloy strip article is subsequently in a forming operation formed into an article of pre-determined shape.

21. A method of using of an aluminium alloy strip article obtained by the method according to claim 1, comprising forming the aluminium alloy strip article into an automotive panel in a forming operation.

22. The method according to claim 1, wherein the aluminium alloy strip article has a gauge range of 3 mm to 40 mm.

23. The method according to claim 6, wherein the aluminium alloy strip articles to be welded have a thickness in a range of 1 mm to 5 mm.

24. The method according to claim 1, wherein the first aluminium alloy strip article has a width in a range of 1000 mm to 1800 mm, and any further aluminium alloy strip article welded to said first aluminium alloy strip article has a width less than the width of the first aluminium alloy strip article.

Description

DESCRIPTION OF THE DRAWINGS

[0036] The invention shall also be described with reference to the appended drawings, in which:

[0037] FIG. 1 shows schematically the strip article before and after welding process used in the method.

[0038] FIG. 2 shows a flow chart illustrating one embodiment of the process for producing a continuously cast strip article having a variable width.

[0039] In FIG. 1 a first, second and third aluminium alloy strip articles (1,2,3) at intermediate gauge and having respectively a width W1, W2, and W3 are welded together (not shown) to form a single welded strip (4) having a total width of the sum of W1+W2+W3. For example W1 can be selected at about 1200 mm and W2 and W3 each at about 200 mm such that the welded strip width (4) is about 1700 mm and which can be subsequently rolled to final gauge. The rolling direction is in the length direction of the strip article along the weld joint.

[0040] In the embodiment illustrated in FIG. 2 a first and second aluminium alloy strip article of the thickness and the same aluminium alloy composition (and are thus similar and not dissimilar with respect to their alloy composition) are produced separately from each other via continuously casting and typically have a gauge in a range of 3 mm to 40 mm. Once the continuously cast strip articles are removed from the casting apparatus, the continuously cast strip articles may be hot or warm rolled, such as to hot-mill end gauge (typically in a range of up to 10 mm and preferably in a range of 1 mm to 5 mm) or hot-mill intermediate gauge and then edge trimmed to provide strip edges suitable for welding into a butt-weld. At this stage also each alloy strip article is cut into the desired width whereby the first aluminium alloy strip article is preferably wider than the second aluminium alloy strip article. Via a (continuous) welding operation, e.g. FSW, the first and second aluminium alloy strip articles are welded together to form a welded strip, preferably receiving a post-weld surface treatment (not shown), and then coiled. Thereafter the coiled welded strip material is being rolled to its final gauge (preferably in a range of 0.25 mm to 4.0 mm) via one or more hot and/cold rolling steps and if necessary again trimmed. The rolled welded strip article at final gauge is then either annealed followed by suitable quenching and optional coiling or cut-to-length to produce 0 temper products, or solution heat treated, followed by suitable quenching and optional coiling or cut-to-length to produce T temper products, depending on the aluminium alloy used and the temper desired.

[0041] The present invention also relates to the use or to a method of use of the aluminium alloy strip article at a final gauge in a range of 0.25 mm to 4.0 mm as obtained by the method as described herein for forming into automotive panels, more in particular for forming into inner panels or heat shields, or as transportation trailer sheet. Furthermore the strip articles can be used advantageously in the building and construction industry.

[0042] In the following, the invention will be explained further by the following non-limitative examples.

Example 1

[0043] An article of the AA3105 alloy has been manufactured on an industrial scale via continuous casting. The article was in the as-cast condition and had a thickness of 22 mm. From this article two blocks of 60015022 mm were cut to provide two blocks or articles of similar alloy composition and thickness. The two blocks were bud-welded to each other via friction stir welding to widen the width of an article and to provide proof of principle of the present invention. The friction stir welding operation has been done using a 100 kN PTG Powerstir 345 FSW gantry machine, a welding tool of 20 mm has been used applying a rotational speed of 380 rpm, a penetration depth of 19.92 mm and a tilt angle of 3.5, and a welding speed of 50 mm/min. After the welding operation any typical FSW flaw has been removed by milling to obtain a smooth surface. The welded aluminium strip article has been heated to about 440 C. and without any difficulty hot rolled to a thickness of 2 mm using a reduction of about 30% per rolling pass, and subsequently cold rolled in multiple rolling passes to a final gauge of 1 mm.

[0044] Some mechanical properties (yield strength or R.sub.p02, tensile strength or R.sub.m, and the elongation A.sub.50) of both the base material and the welded zone have been determined after hot rolling (HR) and after cold rolled (CR). The results are listed in Table 1. In Table 1 for the welded area the absolute numbers are listed as well as percentage of the base material.

TABLE-US-00001 TABLE 1 Mechanical properties of the welded article both in the base material and in the welded area during various phases of the production process. Base material Welded area R.sub.p0.2 R.sub.m A.sub.50 R.sub.p0.2 R.sub.m A.sub.50 R.sub.p0.2 R.sub.m A.sub.50 [MPa] [MPa] [%] [MPa] [MPa] [%] [MPa] [MPa] [%] As percentage of the base material HR 220 248 3.2 215 240 5.7 98% 97% 177% CR 242 287 1.8 269 283 3.4 111% 99% 186%

[0045] This example shows that the welded article can be successfully hot rolled and cold rolled to final gauge. From the results listed in Table 1 it can be seen that as expected the mechanical strength increases after the cold rolling operation, both for the base material and the welded area. Following the cold rolling operation the properties of the welded area are similar or exceed those of the base material. It is believed that the FSW operation may have created a favourable grain structure in the welded area and which is to some extent retained following further processing by means of rolling.

From this example it can be seen that the width of a continuous cast article can be increased by welding together, in this case by means of FSW, another article of similar composition and thickness. The welded article can be further processed by means rolling to final gauge such that the mechanical properties of the welded area are close to or exceed those of the base material. Such a welded article may be used in a subsequent forming or stamping operation to produce a shaped article of pre-determined shape. The width of the welded article can be varied dependent on requirements.

Example 2

[0046] An article of the AA5182 alloy has been manufactured on an industrial scale via continuous casting to a thickness of 22 mm and hot rolled to an intermediate gauge of 3.4 mm. From this hot-rolled article two blocks of 60030003.4 mm were cut and the two blocks were bud-welded to each other via laser beam welding to increase the width of an article. The welding has been done using a Trumpf TruDisk 16002 disk-laser with a fibre diameter of 300 m, the collimation length was 200 mm with a focus length of 400 mm and a focus diameter of 0.6 mm. The joint length was 300 mm obtained at a speed of 3 m/min under Argon atmosphere.

[0047] The welded aluminium strip article has been solely cold rolled without any difficulty from 3.4 mm to 1.2 mm using multiple rolling passes and then annealed at 350 C.

[0048] Some mechanical properties (yield strength or R.sub.p0.2, tensile strength or Rm, and elongation A.sub.50) of both the base material and the welded zone have been determined in the as-welded condition (AW), in the cold rolled condition (CR) and in the annealed condition (AN). The results are listed in Table 2. In Table 2 for the welded area the absolute numbers are listed as well as percentage of the base material.

TABLE-US-00002 TABLE 2 Mechanical properties of the welded article both in the base material and in the welded area during various phases of the production process. Base material Welded area R.sub.p0.2 R.sub.m A.sub.50 R.sub.p0.2 R.sub.m A.sub.50 R.sub.p0.2 R.sub.m A.sub.50 [MPa] [MPa] [%] [MPa] [MPa] [%] [MPa] [MPa] [%] As percentage of the base material AW 208 237 7.6 167 216 2.5 80% 91% 32% CR 351 401 5.5 345 382 3.1 98% 98% 57% AN 146 265 21.9 143 261 21.7 98% 98% 99%

[0049] From the results of Table 2 it can be seen that in the as-welded condition the mechanical properties of the welded area are significantly lower than of the base material. However, the welded article can still be successfully cold rolled using a total cold rolling reduction of about 65%. Following the cold rolling operation the yield strength and the tensile strength of the welded area approach the properties of the base material, whereas the elongation is still falling short. However, after annealing the properties of the welded area are within measurement accuracy the same as those of the base material.

From this example it can be seen that the width of a continuous cast article can be increased by welding together, in this case by means of laser beam welding, another article of similar composition and thickness. The welded article can be further processed by means rolling to final gauge such that the mechanical properties of the welded area are close of those of the base material. Such a welded article may be used in a subsequent forming or stamping operation to produce a shaped article of pre-determined shape. The width of the welded article can be varied dependent on requirements or needs without a capital investment for a continuous caster having an increased nozzle width.

[0050] Where is Example 1 and Example 2 materials has been taken from one and the same continuously cast strip material, as set out with reference to FIG. 2 it will be evident for the skilled person that on a larger scale a first article is being continuously cast having a certain width limited by the nozzle width of the casting apparatus and that the width of said first article can be increased by welding a strip thereto of similar composition and thickness taken from a separately continuously cast second article and optionally a third article.

[0051] The invention is not limited to the embodiments described before, which may be varied widely within the scope of the invention as defined by the appending claims.