JPH04202747A - Manufacture of aluminum alloy sheet for forming - Google Patents

Abstract

PURPOSE:To manufacture an Al alloy sheet suitably used for a can material by rolling an Al allay ingot having a specified componental compsn. to rolling in combination with holding at a specified temp. for specified time and hot rolling at a specified amt. of draft. CONSTITUTION:An Al allay ingot contg., by weight, 3.5 to 6% Mg, 0.01 to 0.2% Si, <=1% Mn+Fe, furthermore one or more kinds among Cu, Zn, Cr or the like and the balance Al is rolled to manufacture an Al allay sheet. At this time, this ingot is heated at 500 to 560 deg.C for >=2hr and is thereafter hot- rolled. At the point of time when its draft reaches 40 to 70%, the temp. of the sheet surface is regulated to >=500 deg.C and is held for >=30sec. After that, it is hot-rolled to regulate its thickness to <=8mm and its rolling finishing temp. to <=320 deg.C. Then, the area rate occupied by intermetallmc compound Mg2Si of >=5mum in the full thickness is regulated to <=1%. In this way, the formation of coarse intermetallic compound Mg2Si can be suppressed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing a 5000 series aluminum alloy plate used for forming, particularly for can bodies,
The present invention relates to a method of manufacturing an aluminum alloy plate suitably used for can materials such as can lids.

[Conventional technology]

5000 series aluminum alloy has high strength and good formability such as deep drawability, stretchability, and bending workability, so it is particularly suitable for can bodies that require deep drawability and for applications that require drawing and stretchability. In addition to being used for can materials such as can lids, it is also used in a wide range of fields that require high strength and molding.

Problems to be Solved by the Invention Due to the presence of a trace amount of Si in A1 alloy containing a high Mg content, relatively coarse Mg25i is formed during heat treatment and hot rolling.
intermetallic compounds are formed. However, Sl is an inevitable impurity in Al metal, and it is impossible to reduce the content to 0%. Even if it is reduced as much as possible, high-grade metal must be used, resulting in high costs. This Mg2Si intermetallic compound has hard and extremely brittle properties, and therefore has an adverse effect particularly during molding, such as being more likely to become a starting point for cracks during molding than Al-Mn-based crystallized substances. The object of the present invention is to improve the formability of this alloy system by suppressing the formation of coarse intermetallic compounds of Mg2Si.

[Means to solve the problem]

The present invention, which the inventors have arrived at as a result of intensive research to achieve the above object, is configured as follows. That is, the first claim of the present application is Mg3.5-5 wt%, SiO,O]-0.2wt%
%, Mn + Fe 1wt% or less, and further contains CuO,
05-0.5wt%, Zn 0. 05-0.
5wt%, Cr 0. 0+-0,3w
t%, Zr 0. 01~0. 3wt
%, V 0. In a method of manufacturing an aluminum alloy plate for forming by rolling an aluminum alloy ingot containing one or more of 0 + - 0.3 wt% and the balance consisting of Al and unavoidable impurities according to a conventional method, the ingot After heating the plate at a temperature of 500 to 560°C for 2 hours or more, the plate surface was heated to 500°C at a point in the middle of hot rolling where the ingot was reduced by 40 to 70%.
By holding this state for more than 30 seconds and then continuing hot rolling to finish the plate with a thickness of 8 mm or less and a temperature of 320°C or less after rolling, it is possible to completely observe the parallel cross section of the final plate. Mg2 of 5μm or more in the thickness
A method for producing an aluminum alloy plate for forming processing, characterized in that the area ratio of intermetallic compounds of No. 51 is 1% or less, the second claim is Mg 3.5 to 6 wt%, Si 0.01 to 0.2 wt% ,
Contains 1 wt% or less of Mn+Fe, and further contains CuO,
05-0.5wt%, Zn 0.05-0.5wt%
, Cro, o1~Q, 3wt%, ZrO, OI~0.3
wt%, V O,' 01-0. 3wt%] species or two or more species, and the balance A1 and unavoidable impurities, in a method for producing an aluminum alloy plate for forming processing by rolling according to a conventional method, After heating at a temperature of ℃ for 2 hours or more, the hot rolled ingot has a
% during hot rolling, the temperature of the plate surface was lowered to less than 500°C, and heat treatment was performed by holding the plate at a temperature of 500 to 560°C for 30 seconds or more, and then hot rolling was continued to reduce the temperature to 8 mm. The thickness is as follows and the temperature after rolling is 3.
An aluminum alloy for forming processing, characterized in that by finishing at 20°C or less, the area ratio of Mg25i intermetallic compounds of 5 μm or more in the total thickness is % or less when observed in a parallel cross section of the final plate. A method for manufacturing a board.

[Effect]

First, the reason for limiting the components in the aluminum alloy rolled sheet of the present invention will be explained. Mg; Mg coexists with Cu and Si to form G, P,
Sheets, β'Mg2Si, βMg24; i or G, P, Zone, S' Al2CuMg, SA
Although it precipitates through a precipitation process such as 12CuMg, it contributes to improving strength at the intermediate phase precipitation stage. However, high concentration M
In the g-alloy system, the amount of solid solution of Mg25i is small, and giant intermetallic compounds are likely to be formed, which significantly inhibits formability. But M
Since g alone is an element effective in solid solution strengthening, it is essential for high-strength applications and cannot be reduced. M
If Mg is less than 3.5 wt%, strength suitable for this purpose cannot be obtained, and if it is added in excess of 6%, work hardening is likely to occur and hot rollability is significantly deteriorated, so the range of Mg is 3. The content was set at 5 to 6 wt%. It is well known that age hardening can be expected during the precipitation process of Si;Mg2Si compounds. However, in high-concentration Mg alloy systems, the amount of solid solution of Mg2Si is small, and giant intermetallic compounds are likely to be formed, which significantly inhibits formability. Therefore, it is better not to contain Sl, but it is an unavoidable impurity in Al metal, and it is difficult to reduce the content to less than 0.01 wt% for economic reasons.If the S1 content exceeds 0.2 wt%, the present invention However, it is difficult to suppress the formation of giant intermetallic compounds of Mg2Si. Mn and Fe: Mn contributes to improving strength and Fe
Alternatively, in order to form an intermetallic compound of αAl (Mn-Fe)Si, the amount of free Sl that combines with Mg is reduced to form an Mg2Si giant intermetallic compound. It has the ability to suppress its production. Fe forms an intermetallic compound and takes in Sl, so like Mn, free Si that combines with Mg is reduced and Mg25
1. It has the function of suppressing the formation of giant intermetallic compounds. Therefore, it is more convenient for the amount of these two elements to be present if Fe+Mn is less than ]wt%. However, Fe+M
When n is 0.2 wt% or more, the above effect reduces the need for a complicated manufacturing process as in the present invention. The significance of adopting the complicated manufacturing process of the present invention is that Fe+Mn is 0.
．． It is large when it is less than 2wt%. However, Fe+Mn is 1
If it exceeds wt%, the intermetallic compound formed by itself becomes coarse and inhibits formability, so it is set to 1 wt% or less. Cu, Zn, Cr, Zr, V: One or more of these elements contribute to improving strength. Cu-Zn is 0.
05 or more and 0.5wt% or less, Cr-Zr ・V is 0.0
If it is 1 or more and 0.3 wt% or less, the effect of the present invention will not be lost and it will contribute to improving the strength. The remainder of each of the above components may be Al and unavoidable impurities. Note that in ordinary aluminum alloys, small amounts of Ti and B are sometimes added to refine the ingot crystal grains, and the aluminum alloy rolled sheet of the present invention also contains small amounts of Ti and B.
Alternatively, it may contain B. However, when adding T1, the effect cannot be obtained if it is less than 0.01 wt%;
If it exceeds wt%, primary TiAl3 will crystallize and inhibit moldability, so T1 is preferably in the range of 0.01 to 0.2 wt%. Also, when B is added together with Ti, i
If it is less than ppm, there is no effect, and if it exceeds 50ppm, coarse particles of Ti82 will be mixed in, impairing the moldability, so B is preferably in the range of 1 to 500 ppm. Furthermore, in high Mg alloys, Be is added to 1 to prevent oxidation of the molten metal.
~2ooppm may be added, and it is preferable to do so in the present application as well. Next, the manufacturing process in the present invention will be explained. First, an aluminum alloy ingot having the alloy composition described above is produced by the DC9 casting method according to a conventional method. Next, the ingot is soaked and heated at 500° C. or higher in the case of claim 1, or 450° C. or higher and 560° C. or lower for 2 hours or more in the case of claim 2. Basically, the lower limit of the ingot heating temperature is 450°C. Below this temperature, the rollability during hot rolling will decrease significantly, and in high-concentration Mg alloy systems, Mg2Si
The amount of solid solution is small and it is easier to form a solid solution at high temperatures, which is advantageous, but at temperatures above 560°C surface oxidation progresses, and
This temperature range was set because nFe-based intermetallic compounds grow and become coarse. However, in order to promote solid solution, 5
The temperature is preferably 00°C or higher. In addition, in the case of claim 1, 40 to
The lower limit of the ingot heating temperature was set at 500°C because the aim was to create a state in which the temperature when 70% hot rolling was 500°C or higher. After that, hot rolling is applied to the ingot, but if the temperature is 500°C or higher when hot rolling is applied to the ingot by 40 to 70%, the ingot is held in that state for 30 seconds or more, and the Mg2Si Promotes solid solution. (If this is claim 1.) Also,
If the temperature of the ingot is below 500°C when 40 to 70% hot rolling is performed, heat treatment is performed to maintain the humidity at 500 to 560°C for 30 seconds or more to form a solid solution of Mg2Si. promote (This is the case of claim 2.) Since strain is added by hot rolling, Mg25i, which could not be completely dissolved in the ingot at the time of the ingot, becomes easier to dissolve in the solid solution by this treatment. Continue hot rolling to a thickness of 8 mm or less and 32 mm.
Finish to below 0℃. Precipitation of Mg2Si is 330-45
It is most accelerated at 0°C and tends to become coarser between these temperatures. Therefore, the temperature during reheating during hot rolling must be over 450°C, and in the state where it is held at that temperature for the longest time, such as after hot rolling, it is necessary to keep the temperature below 330°C. The following was made. Also, the thickness of the plate after hot rolling is 8
The reason why the thickness is set to be less than mm is merely in consideration of workability during subsequent cold rolling. The rolled plate thus obtained contains Mg
There are only a few large intermetallic compounds of 25 types. Thereafter, cold working, annealing, etc. are performed according to conventional methods to produce the final plate. At this time, when annealing is performed at 330° C. or higher, continuous annealing such as CAL is more effective in preventing coarsening of the Mg2Si intermetallic compound than box annealing. In the aluminum alloy plate for forming obtained by the above manufacturing method, when examining the parallel cross section of the final plate, the area ratio occupied by Mg2Si intermetallic compound of 5 μm or more in the total thickness was 1% or less, and the area ratio was 1% or less, and it was not possible to perform deep drawing. It is a material that suppresses the occurrence of cracks during bending, general stretching, and even local stretching.

【Example】

] A 400 mm thick DC ingot with the alloy components shown in the table,
As shown in Table 2, heating and hot rolling were performed, intermediate annealing was performed as CAL, and then cold rolling was performed to obtain the final plate thickness. Thereafter, only sample material B was subjected to final annealing. Since the typical use of this material is as a can lid material, it was subjected to a heat treatment equivalent to baking paint for can lids (270°C x 20 seconds) and its performance was evaluated as shown in Table 1. Alloy composition (unit: wt%) ) Table 2 (margin below) Manufacturing conditions and metallographic structure Note) "85 minutes" on the hot-rolled heating holding rack means that the hot-rolled A was held for 5 minutes without being heated. Below is the margin table 3.Performance table below is the margin survey and shown in Table 3. Also, at this time, Mg2S of 5 μm or more
The area ratio of i was measured and shown in Table 2. B and E are examples of the invention according to claim 1, and D and F are examples of the invention according to claim 2. G is a case where the generally used S1 content is high, and C is a case where the final hot-rolling finish (referred to as "hot-rolling B finish" in the table) temperature is as high as 330°C, and each was used as a comparative example. . Further, A was used as a conventional example in which holding or heating was not performed during hot rolling. Comparing the performance in Table 3, even though the yield strength values are almost the same,
The material obtained by the manufacturing method according to the present invention has Mg of 5 μm or more.
The area ratio of 25l is reduced, and the overhang property (Eriksen,
It can be seen that the material has excellent local extrusion properties) and bendability. However, when the Si content is high as in G, even if heating is performed during hot rolling, the area ratio of Mg2Si of 5 μm or more does not decrease, resulting in poor formability. In the invention example &
The properties are the best when final annealing of H is applied. This is because as a result of promoting age hardening during final annealing, the cold rolling rate after intermediate annealing can be reduced, resulting in improved formability. By performing the final annealing at low humidity (250°C or less) in this way, it is possible to promote the precipitation of ^]-Cu-Mg and Mg-5i-based precipitates finer than 5 μm, and to recover appropriate strain. By achieving this, the properties after baking may be improved. Furthermore, even if the intermediate annealing is performed as a batch type, as long as the temperature is 320° C. or lower, the material obtained by the present invention has better performance than the material obtained by the conventional Nokunotitaib manufacturing method. That is, in the case where only the intermediate annealing was done in a batch type at 315°C for 2 hours, and the manufacturing code was the same as in E, the area ratio of M g 251 with a diameter of 5 μm or more was 0°7 and 0.7 μm, respectively. 6%, and has good local stretchability and bendability. However, the tensile strength is lower by about I Kgf/am2 compared to when intermediate annealing is CAL.

【Effect of the invention】

According to the present invention, it is possible to suppress the formation of coarse intermetallic compounds of Mg2Si that have a particularly negative effect on molding, such as being likely to become a starting point for cracks during molding. Therefore, it can be suitably used for can materials such as can bodies and can lids, which are thinner and require stricter formability. that's all

Claims (1)

[Claims] 1. Mg 3.5-6 wt%, Si 0.01-0.2 wt%
%, Mn+Fe 1wt% or less, and Cu0.
05-0.5wt%, Zn0.05-0.5wt%, C
r0.01~0.3wt%, Zr0.01~0.3wt
%, V0.01 to 0.3 wt%, and the remainder is Al and unavoidable impurities. After heating the ingot at a temperature of 500 to 560 °C for 2 hours or more, the ingot was hot rolled and the ingot was rolled down by 40 to 70%.The temperature of the plate surface was determined during hot rolling. The temperature was raised to 500°C or higher and held in this state for 30 seconds or more, and then hot rolling was continued to achieve a thickness of 8mm or less and a temperature at the end of rolling of 30 seconds.
An aluminum alloy for forming processing, characterized in that by finishing at 20°C or less, the area ratio of Mg_2Si intermetallic compounds of 5 μm or more in the total thickness is 1% or less when observed in a parallel cross section of the final plate. Method of manufacturing the board. 2. Mg3.5-6wt%, Si0.01-0.2wt
%, Mn+Fe 1wt% or less, and Cu0.
05-0.5wt%, %n0.05-0.5wt%, C
r0.01~0.3wt%, Zr0.01~0.3wt
%, V0.01 to 0.3 wt%, and the remainder is Al and unavoidable impurities. After heating the ingot at a temperature of 450 to 560°C for 2 hours or more, the ingot was hot rolled and the ingot was rolled down by 40 to 70%.At a point in the middle of hot rolling, the temperature of the plate surface was determined. By performing heat treatment to lower the temperature to less than 500°C and holding it at a temperature of 500 to 560°C for 30 seconds or more, and then continuing hot rolling to finish the product with a thickness of 8 mm or less and a finished rolling temperature of 320°C or less, A method for producing an aluminum alloy plate for forming, characterized in that when observing a parallel cross section of the final plate, the area ratio of Mg_2Si intermetallic compounds of 5 μm or more in the total thickness is 1% or less.