EP0121620B1 - Feuillards en alliage d'aluminium durcissant lors de la cuisson du vernis et leur procédé de fabrication - Google Patents
Feuillards en alliage d'aluminium durcissant lors de la cuisson du vernis et leur procédé de fabrication Download PDFInfo
- Publication number
- EP0121620B1 EP0121620B1 EP19830302017 EP83302017A EP0121620B1 EP 0121620 B1 EP0121620 B1 EP 0121620B1 EP 19830302017 EP19830302017 EP 19830302017 EP 83302017 A EP83302017 A EP 83302017A EP 0121620 B1 EP0121620 B1 EP 0121620B1
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- EP
- European Patent Office
- Prior art keywords
- alloy
- aluminium alloy
- bake
- heating
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 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
- C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
Definitions
- This invention relates to a bake-hardenable type aluminium alloy sheets for can bodies, ends and/or tabs and a process for manufacturing same, and more particularly to a process for manufacturing a bake-hardenable type aluminium alloy sheet for can bodies, ends and/or tabs with a fine average grain size, which has excellent formability especially in drawing, ironing, flanging and necking properties and which can be imparted with a high pressure resistance by an outside printing and inside coating stage after formation into can bodies.
- the recent development of ironing techniques has made it possible to produce light can bodies on a large scale.
- the aluminium alloy 3004--H19 is widely used as a can body stock, it is desirable to make the can bodies, ends and/or tabs thinner and lighter from the standpoint of economical use of resources and energy.
- the process for manufacturing such can bodies usually includes the steps of deep drawing, redrawing, ironing, doming, trimming, pickling, washing, chemical conversion, drying, outside printing, baking (for 1 to 10 minutes at about 200°C), inside coating, baking (for 1 to 10 minutes at about 200°C, necking and flanging.
- the thin aluminium alloy sheets for can bodies, which have to undergo such a severe process are generally required to have satisfactory properties in the following respects.
- can body stock should also have satisfactory properties in formability such as drawability, ironing formability, necking formability and flangeability and should not wrinkle in the drawing and necking stages.
- Al-Cu alloy which contains more than 1 % of Cu for precipitation hardening has extremely inferior corrosion resistance and undergoes precipitation hardening before an ironing stage while it is processed through a number of steps, and for a long time, after solution heat treatment, with degradations in formability and resistance to scoring.
- the Al-Mg-Si alloy has a relatively good corrosion resistance but its formability is highly dependent upon the cooling rate after solution treatment (it requires an extremely high cooling rate for good formability) coupled with the drawback that build-up of metal on the dies frequently occurs during the ironing operation due to the Mg content. Further, the AI-Zn-Mg alloy is low in corrosion resistance, owing to the Zn content, and, additionally, has unsatisfactory scoring resistance and is inferior in formability to the other two alloys just mentioned.
- a bake-hardenable aluminium alloy sheet for can bodies, and/or ends and/or tabs containing 0.05 to 0.5% of Cu in solid solution, 0.5 to 2.5% of Mg and 0.5 to 2.0% of Mn, the balance being AI and any impurities, and having an average crystal grain width of smaller than 25 microns after cold rolling.
- a process for producing a bake-hardenable aluminium alloy sheet for can bodies comprising:
- a bake-hardenable type aluminium alloy sheet for can bodies, and/or ends and/or tabs which is satisfactory in the above mentioned properties required for the reduction of the sheet thickness and weight of can bodies, and/or ends and/or tabs, namely, an alloy which has not only a high strength but also properties which supplement any reduction in formability caused by an increase in strength and reduction in thickness, and a process for manufacturing such bake-hardening type aluminium alloy sheets.
- the element Cu should be present, together with Mg since they remain dissolved in solid solution and contribute to hardening in the baking stage by producing fine AI-Cu-Mg precipitates, enhancing the strength of the alloy.
- the Cu content should be greater than 0.05% but no more than 0.5% since a Cu-content in excess of 0.5% will considerably lower the corrosion resistance of the alloy as a can material.
- the preferred range of Cu-content is 0.05 to 0.5%.
- the element Mg needs to be present together with the Cu since it remains dissolved in solid solution with the latter and induces precipitation hardening in a subsequent stage to impart to the alloy a strength required for a can body material.
- the Mg-content does not impair the corrosion resistance as much as the Cu content so that it can be contained in a greater amount for the purpose of increasing the strength to permit reductions of the thickness of the ultimate alloy sheet.
- the Mg-content should be greater than 0.5%.
- Mg-content in excess of 2.5% causes a considerable drop in formability including ironing formability and stretch formability and gives rise to considerable scoring. Consequently, the Mg-content should be in the range of 0.5 to 2.5%.
- the element Mn does not contribute to precipitation hardening but it is as important as Mg for imparting strength to the alloy and prevents scoring by crystallising MnA1 6 together with AI.
- the Mn-content helps to stabilise deep-draw earing by stabilising the recrystallisation texture after a heat treatment. This effect cannot be expected when the Mn-content is less than 0.5%.
- the amount and size of intermetallic compounds are increased with a greater Mn-content, and primary structures are likely to crystallise if its content exceeds 2%, giving rise to pinholes or tear off in the ironing stage. Therefore, the Mn content should be in the range of 0.5 to 2.0%.
- the alloy may further contain up to 0.5% of Si, up to 0.7% of Fe, up to 0.05% of Ti, up to 0.05% of B and up to 0.05% of Cr as impurities.
- an aluminium alloy of the above-mentioned chemical composition is subjected to a soaking treatment at a temperature above 500°C. If the temperature of the soaking treatment is lower than 500°C, a large quantity of very fine MnA1 6 will precipitate, which tends to suppress grain boundary transformation during recrystallisation of the rolled sheet, raising the recrystallisation temperature and coarsening the crystal grains. Also, due to a change in the recrystallisation texture, earing occurs at an angle of 45° with the rolling direction, coupled with the problem of scoring in the ironing stage. Thus, the soaking temperature should be higher than 500°C.
- the hot rolling which follows the soaking treatment involves no control in particular of the hot rolling rate or temperature and may be conducted by an ordinary industrial method.
- the hot-rolled material is then heated (for annealing) as it is or after cold rolling if necessary.
- the heating is effected at a temperature in the range of 400 to 600°C to cause recrystallisation, thereby forming a recrystallisation texture to reduce earing in deep drawing and producing fine and uniform crystal grains, while dissolving Cu in solid solution in order to guarantee the bake-hardening effect by precipitation of AI-Cu-Mg. It is difficult to dissolve Cu in solid solution at a temperature lower than 400°C. Although the temperature in this heating stage should therefore be higher than 400°C, it is preferred to be higher than 430°C in consideration of the Cu content and the heat retention time. However, the growth of recrystallised grains is accelerated at higher temperatures and this tendency becomes pronounced at temperatures above 600°C, making it difficult to control the grain size in a range smaller than 25 microns. Therefore, the heating (annealing) temperature should be in the range of 400°C to 600°C.
- the heating stage it is necessary to raise the temperature quickly in order to produce fine crystal grains and to reduce the time period of the heat treatment in order to suppress production of Mg0 on the surface of the alloy sheet.
- the heating rate should be higher than 100°C/min.
- the control of heat retention time is necessary especially for the purpose of reducing the grain size.
- this can be attained readily in a high temperature treatment even if the retention time is zero, where the treatment employs a relatively low temperature in the above-defined range or for some compositions of the alloy or other conditions of the manufacturing process, the temperature may be retained for a certain time period.
- the retention time should be 10 minutes or less.
- the cooling rate in order to secure the subsequent precipitation hardening. More particularly, if the cooling rate is too low, precipitation takes place in the cooling stage, so that there is insufficient precipitation hardening in the baking stage. Also, the fine precipitates which are produced in the low temperature range of the cooling stage increase the strength so that the formability of the alloy is lowered prior to the ironing stage. Thus, the cooling rate should be high enough, i.e., higher than 100°C/h, in order to obtain a satisfactory can body material. Although a higher cooling rate may be employed, it is recommended to use air cooling in the case of a coiled material, in view of the surface quality and flatness of the coil. In the cooling stage, the temperature of the alloy has to be lowered below a predetermined level, more particularly, below a temperature level at which precipitation of AI-Cu-Mg takes place, to prevent premature precipitation before the baking stage.
- the alloy should be cooled to a temperature of at least below 150°C and preferably below 100°C where a greater degree of precipitation hardening is desired.
- the average grain size should be smaller than 25 microns to compensate for the decrease in formability of different types which are involved in the course of reductions of thickness of the can body, as well as deterioration in necking property and flangeability due to an increase in strength after the baking stage, and for increasing the effect of precipitation. Smaller grain sizes are normally reflected by improved formability in stretching flanging and ironing properties. There is no problem with regard to the drawability required for the reductions in thickness, but the same may give rise to a problem of wrinkling. However, the wrinkling barely occurs as long as the average grain size is smaller than 25 microns. On the other hand, if the average grain size exceeds 25 microns, it becomes difficult to obtain a thin can body of high strength which is different from the conventional can body material. Thus, the average grain size should be less than 25 microns.
- the crystal grains in the aluminium alloy according to the present invention which is formed into a hard sheet by cold rolling subsequent to the recrystallisation as mentioned hereinbefore, the crystal grains are stretched in the rolling direction and flattened by the cold rolling but the width (average width) of the individual grains as seen on the surface of the rolled sheet remain substantially the same as long as the average grain size at the time of recrystallisation is smaller than 25 microns. This is the reason why the average width of crystal grains on the surface of the rolled alloy sheet is defined as being smaller than 25 microns in the present invention.
- the cold rolling operation subsequent to the above-mentioned heat treatment is necessary to impart a required strength to the alloy as a can body material and is effected at a reduction rate which is determined depending upon the contents of Cu, Mg, and Mn taken in conjunction with the required strength. As a matter of fact, an insufficient effect is produced at a reduction rate smaller than 10%, and it is preferred to be greater than 30%. However, a sufficient reduction of can wall thickness is possible if the reduction rate is in the range of 10% to 30%, depending upon the internal pressure and shape of the can body.
- the alloy material should be maintained at a temperature below 150°C, preferably below 100°C to prevent premature precipitation hardening before the ironing operation. This is also necessary for improving the resistance to scoring since the production of Mg0 on the surface of the alloy sheet from the final cold rolling stage is increased by a heat treatment prior to the ironing operation.
- a bake-hardenable type can body aluminium alloy sheet of excellent properties can be obtained by the process described above, which is also applicable to can lids, tabs or the like, or to other purposes involving a printing or paint-coating operation.
- the bake-hardenable can body aluminium alloy sheet of the present invention is illustrated more particularly by the following examples.
- the workpieces were formed into a 0.34 mm thick sheet in the cases of workpiece (1) and (2) and into a 0.4 mm thick sheet in the cases of workpiece (3) and (4) by final cold rolling.
- the alloy sheets of workpieces (1) and (2) were produced according to the process of the present invention, while the alloy sheets of workpieces (3) and (4) were produced by the conventional process.
- the mechanical properties of aluminium alloy sheets of workpieces (1) to (4) were measured with regard to plain blank sheets and baked specimens which has undergone baking of 200°C x 20 minutes. Further, the plain blank sheets were subjected to baking after ironing and trimming, and to necking and flanging to measure their pressure resistance and column strength. The grain size after annealing and earing of blank sheets in workpieces (1) to (4) were also measured.
- the aluminium alloy sheets of workpieces nos. 1 and 2 have a higher after-baking (AB) strength as compared with the alloys sheets of workpieces 3 and 4 due to differences in heating conditions and cooling speed. It will be seen that higher heating temperatures and cooling rates give better results.
- the alloy sheets of workpieces nos. 3 and 4 exhibit a drop in strength upon baking owing to the use of deficient cooling rate and heating temperature.
- Table 2 shows the properties of ironed cans, from which it will be understood that the thin blank sheets of workpieces nos. 1 and 2 according to the process of the present invention, especially, the blank sheet in workpiece 1 has properties comparable to the 0.4 mm thick alloy sheets of workpieces nos. 3 and 4 in can formability as well as in pressure proofing and buckling strength in spite of its reduced thickness.
- the improvement of the can formability is attributable to a finer crystal grain size, while the improvements in pressure resistance and buckling strength are ascribed to the improvement of strength after baking.
- the annealing time periods for the alloy sheets nos. 1 to 4 are shorter than in the batch system, and above all the alloy sheets nos. 1 and 2 give good results with only an extremely small amount of scoring on the can walls notwithstanding the heating, heat retention and the short time periods of cooling.
- 400 mm thick ingots were prepared by smelting and casting (1) an aluminium alloy consisting of 0.15% of Cu, 1.05% of Mn, 1.13% of Mg and the balance of aluminium and impurities (in the range of the present invention), and (2) an aluminium alloy consisting of 0.03% of Cu, 1.0% of Mn, 1.2% of Mg and the balance of aluminium and impurities (outside the range of the present invention).
- the ingots of aluminium alloy thus obtained were hot-rolled into a thickness of 4 mm after a soaking treatment at 540°C, and then cold-rolled into a 1.0 mm thick sheet, followed by a heat treatment employing a heating rate of either
- the aluminium alloy sheet no. 1-B according to the present invention provides good can formability along with high pressure resistance and column strength.
- An aluminium alloy containing 0.20% of Cu, 1.0% of Mn and the balance of aluminium and impurities (outside the range of the present invention), and (2) an aluminium alloy containing 0.17% of Cu, 0.95% of Mn, 1.1% of Mg and the balance of aluminium and impurities (in the range of the present invention) were smelted and cast into 500 mm thick ingots. Each ingot was hot-rolled to a thickness of 3 mm after a soaking treatment at 590°C and then cold-rolled into a 1 mm thick sheet.
- the alloy sheet After heating to 515°C at a heating speed of 500°C/min, the alloy sheet was immediately cooled to 90°C at a cooling rate of 500°C/ min and cold-rolled into a thickness of 0.4 mm, followed by the same measurements and forming tests as in the foregoing examples.
- alloy sheet no. 2 according to the process of the present invention is far superior to the sheet no. 1 in overall properties.
- Example 1 was cold-rolled into (A) a 0.8 mm thick sheet and (B) a 0.67 mm thick sheet, followed by a heat treatment in which, immediately after heating to 500°C at a heating rate of 500°C/min, the respective sheets were air-cooled to 90°C at a cooling rate of 500°C/min.
- the aluminium alloy of no. 2 was reduced to a thickness of 4 mm and then cold-rolled to a thickness of 1 mm and annealed by the conventional batch system, heating the alloy sheet to 360°C with heating and cooling rates of 40°C/h. Thereafter, the alloy sheets nos. 1 and 2 were cold-rolled to a thickness of 0.4 mm, followed by the same measurements and forming tests as in Example 1 except for the baking at 230°C for 10 minutes.
- the aluminium alloy sheets nos. 1-A and 1-B according to the process of the present invention were produced with smaller reduction rates in cold rolling (ie with reduction rates of 50% and 40%, respectively, as compared with 60% in Examples 1 to 3 and a higher baking temperature.
- the blank sheet 2 had a strength intermediate between the sheets nos. 1-A and 1-B but exhibited an after-baking (AB) strength far lower than the sheets nos. 1-A and 1-B, with inferior formability due to a greater grain size.
- AB after-baking
- Figure 1 Plotted in Figure 1 are softening curves of the alloy sheets 1-A and 2, showing the baking temperature in relation with the tensile strength 03 and yield strength °0 . 2 , in which the alloy sheets no. 1-A (0.4 mm thick) and no. 2 (0.4 mm thick) are indicated by "0" and "A", respectively.
- an aluminium alloy sheet which is produced according to the above-described process of the present invention has improved formability in stretching, ironing and flanging properties and the like owing to the fine grain size and provides a high pressure resistance by hardening in a printing and coating stage subsequent to the drawing and ironing operations.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Metal Rolling (AREA)
Claims (6)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE8383302017T DE3364258D1 (en) | 1983-04-11 | 1983-04-11 | Bake-hardenable aluminium alloy sheets and process for manufacturing same |
EP19830302017 EP0121620B1 (fr) | 1983-04-11 | 1983-04-11 | Feuillards en alliage d'aluminium durcissant lors de la cuisson du vernis et leur procédé de fabrication |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP19830302017 EP0121620B1 (fr) | 1983-04-11 | 1983-04-11 | Feuillards en alliage d'aluminium durcissant lors de la cuisson du vernis et leur procédé de fabrication |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0121620A1 EP0121620A1 (fr) | 1984-10-17 |
EP0121620B1 true EP0121620B1 (fr) | 1986-06-25 |
Family
ID=8191116
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19830302017 Expired EP0121620B1 (fr) | 1983-04-11 | 1983-04-11 | Feuillards en alliage d'aluminium durcissant lors de la cuisson du vernis et leur procédé de fabrication |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0121620B1 (fr) |
DE (1) | DE3364258D1 (fr) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60187656A (ja) * | 1984-03-05 | 1985-09-25 | Sumitomo Light Metal Ind Ltd | 耐食性に優れた包装用アルミニウム合金板及びその製造方法 |
JPS60248859A (ja) * | 1984-05-25 | 1985-12-09 | Sumitomo Light Metal Ind Ltd | 超高圧用プレ−トフイン型熱交換器のフイン材 |
US5192378A (en) * | 1990-11-13 | 1993-03-09 | Aluminum Company Of America | Aluminum alloy sheet for food and beverage containers |
EP0666330A3 (fr) * | 1991-03-14 | 1996-07-17 | Pechiney Rhenalu | Alliages d'al pour embouttissage-étirage résistants, formables et isotropes. |
US5362341A (en) * | 1993-01-13 | 1994-11-08 | Aluminum Company Of America | Method of producing aluminum can sheet having high strength and low earing characteristics |
US5362340A (en) * | 1993-03-26 | 1994-11-08 | Aluminum Company Of America | Method of producing aluminum can sheet having low earing characteristics |
CN107723632B (zh) | 2014-04-30 | 2021-03-19 | 美铝美国公司 | 具有高可成形性的铝板和所述铝板制成的铝容器 |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3787248A (en) * | 1972-09-25 | 1974-01-22 | H Cheskis | Process for preparing aluminum alloys |
US4235646A (en) * | 1978-08-04 | 1980-11-25 | Swiss Aluminium Ltd. | Continuous strip casting of aluminum alloy from scrap aluminum for container components |
DE2929724C2 (de) * | 1978-08-04 | 1985-12-05 | Coors Container Co., Golden, Col. | Verfahren zum Herstellen eines Bandes aus einer Aluminiumlegierung für Dosen und Deckel |
-
1983
- 1983-04-11 EP EP19830302017 patent/EP0121620B1/fr not_active Expired
- 1983-04-11 DE DE8383302017T patent/DE3364258D1/de not_active Expired
Also Published As
Publication number | Publication date |
---|---|
EP0121620A1 (fr) | 1984-10-17 |
DE3364258D1 (en) | 1986-07-31 |
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