JPH01208438A - Manufacture of aluminum alloy hard plate for wrapping - Google Patents

Abstract

PURPOSE:To economically manufacture the title hard plate having high strength and high formability with good productivity by executing specific heat treatment and rolling to an Al alloy ingot having specific compsn. consisting of Mg, Mn, Cr, Zn and Al. CONSTITUTION:The Al alloy ingot contg., by weight, 2.0-5.5% Mg, furthermore contg. one or more kinds among <0.7% Mn, <0.5% Cr and 0.05-1.0% Zn and the balance consisting of Al with inevitable impurities is subjected to homogenizing heat treatment at >=450 deg.C. The hot rolling of the ingot is ended to 5mm plate thickness at >=280 deg.C and the ingot is wound into the shape of a coil. The hot rolled coil is thereafter charged to a continuous furnace of 350-600 deg.C and is continuously heated in the state of the coil without lowering the temp. to <=200 deg.C. The coil is allowed to cool or is rapidly cooled to <=150 deg.C at >=100 deg.C/min cooling speed. The coil is thereafter cold-rolled at >=80% cold rolling rate, and if required, is subjected to stabilizing annealing. By this method, the Al alloy hard plate for wrapping which is suitable for a cover to a can can be obtd.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a packaging aluminum alloy hard plate suitable for can lids for beer, carbonated and non-carbonated beverages, and the like. (Prior art and problems to be solved) Conventionally, JIS50 Al, -Mg based alloys have been used as lid materials for beverage cans.
Hard aluminum alloy plates such as 52.5o82.5182 are often used. There are roughly two types of manufacturing methods for this material. One is a method of annealing after hot rolling (after cooling), which has been proposed, for example, in Japanese Patent Publication No. 52-48088. Another method is to perform hot rolling, then cold rolling, and then annealing, which has been proposed, for example, in JP-A No. 60-50141. In both methods, annealing is performed from room temperature, and the reason why annealing is not performed immediately after hot rolling in the former method is due to productivity problems such as the need to arrange a furnace, the need to combine several coils, and the number of coils. This is because when the coils are grouped together, a temperature difference inevitably occurs between the coils, causing stability problems such as changes in retention time, etc. On the other hand, in the latter method, since annealing is performed after cold rolling, the temperature inevitably becomes low. In addition, as an annealing furnace, a batch furnace (coiled and annealed) and a C
There is AL (thread annealing). However, batch furnaces have particular problems in terms of productivity and stability. In addition, CAL is characterized by continuous operation, but in order to achieve continuity, an accumulator is required to connect the coils continuously, and the roll of the accumulator is a rubber roll when the material to be treated is aluminum. Since the heat after hot rolling is used, the heat after hot rolling is released, and in order to maintain the performance of the rubber roll (usually a usable temperature of 150°C or less), it is not possible to maintain the high temperature in the CAL accumulator. There wasn't. As mentioned above, in the conventional aluminum hard plate manufacturing method, the heat during hot rolling is not effectively utilized during annealing, and the time required for cooling after hot rolling is wasted time, and thermal energy is also wasted. It was wasted. The present invention was made under such circumstances, and
The object of the present invention is to provide a method for economically and productively manufacturing aluminum alloy hard plates for packaging that have the required characteristics as a high-strength, high-formability material. (Means for Solving the Problems) In order to achieve the above object, the present inventor has developed a high-strength, high-formability material that has been used in recent years to reduce the weight of cans, particularly from the viewpoint of effective use of heat and reduction of wasted time. The result of intensive research into a method for manufacturing aluminum alloy hard plates with high productivity that can meet the demands of the industry. We have discovered that it is possible to use a continuous furnace by appropriately adjusting the chemical components and regulating the manufacturing process conditions, particularly the conditions of homogenization heat treatment, hot rolling, and continuous heating and cooling. That is, the method for manufacturing an aluminum alloy hard plate for packaging according to the present invention contains Mg: 2, 0 to 5.5%, Mn: less than 0.7%, Cr: 0, less than 5, and Zn.
: An Al alloy ingot containing one or more of 0.05 to 1.0%, the remainder consisting of Al and inevitable impurities, is subjected to homogenization heat treatment at a temperature of 450 ° C. or higher, Hot rolling is completed at a plate thickness of 5 mm or less and a temperature of 280°C or higher, and then rolled up into a coil. After that, the hot-rolled coil is charged into a continuous furnace at a temperature of 350 to 600℃ without lowering the temperature to 200℃ or less, and is continuously heated in the coil state, and the heated coil is then left to cool. Alternatively, it is rapidly cooled to 150°C or less at a cooling rate of 100°C/min or more, and then the cold rolling rate is 8
It is characterized by cold rolling of 0% or more and stabilizing annealing as required. The present invention will be explained in more detail below. First, the reason for limiting the chemical components in the present invention will be explained. Mg is an effective element for improving strength, but if it is less than 2.0%, it will not have sufficient strength as a lid material, and if it exceeds 5.5%, it will have sufficient strength, but it will not work during hot rolling. Cracks may occur, and the formability of the product plate may deteriorate rapidly. Therefore, the amount of Mg is set at 2.0 to 5.5%. Although Lin is an effective element for improving strength, 0.7
%, similar to Mg, cracks may occur during rolling, the strength will become too high, and the formability of the product plate will significantly deteriorate. Therefore, M n fJ is 0.
Regulated to less than 7%. Although Cr is also an effective element for improving strength, 0.5%
If it exceeds the above, the strength will become too high, and in combination with Mn, a huge intermetallic compound will be formed, resulting in a significant decrease in the formability of the product sheet. Therefore, the amount of Cr is 0
．． Regulated to less than 5%. Although Zn has little to do with strength, it is an effective element for improving formability, such as end riveting workability. However, if it is less than 0.05%, the effect is small, and 1.
If it exceeds 0%, the effect is saturated and it becomes uneconomical. Therefore, Zn is in the range of 0.05 to 1.0%. However, it is sufficient to add at least one of the above-mentioned Mn, Cr, and Zn mainly to ensure moldability. Note that although Si, Fe, Cu, Ti, B, and the like may be included as impurities, it is preferable that the amount of impurities be as small as possible. For example, Si is 0.3% or less, preferably 0.1% or less,
There is no particular problem with the effects of the present invention as long as Fe is 0.5% or less, preferably 0°2% or less, Cu is 0.3% or less, Ti is 0.1% or less, and B is 0.05%. . Next, a method for manufacturing an aluminum alloy hard plate having the above composition will be explained. Aluminum alloys having the above-mentioned chemical components are melted and cast by conventional methods, but the resulting ingots must be subjected to homogenization heat treatment at a specific temperature before hot rolling. That is, if the heating temperature at this time is less than 450° C., the removal of segregation is insufficient and problems such as edge cracking occur due to increased deformation resistance during hot rolling, which is not preferable. Therefore, the homogenization heat treatment temperature is set to 450°C or higher. In the next step of hot rolling, the plate thickness and finishing temperature each affect the strength of the final plate product (after cold rolling) and the edge ratio after deep drawing, so it is necessary to regulate these conditions. That is, when the hot-rolled plate thickness exceeds 5 mm, the strength of the product plate is too high, resulting in a decrease in formability and an increase in the selvage ratio after deep drawing. Furthermore, if the hot rolling end temperature is less than 280° C., the formation of cubic texture (0-90@ direction selvage) is weak even in subsequent annealing, resulting in a cold rolled product having a high 45° selvage. Therefore, when hot rolling, the plate thickness is 5 mm or less, 28
It is necessary to finish at a temperature of 0°C or higher. This hot-rolled plate is wound up into a coil shape and subjected to continuous heating and cooling in the next step, which is the most distinctive feature of the present invention. In other words, conventionally, hot-rolled plates were usually allowed to cool due to the problems described below (productivity, stability, continuity, etc.), and in this case, there was a loss of thermal energy and wasted time until the cooling was completed. It takes time. In contrast, in the present invention, annealing is performed to solve both of these problems, and the hot rolled coil is
From time to time, it is charged in a coiled form into a high-temperature continuous furnace for recrystallization. At that time, if cooling proceeds to 200°C or less, precipitates (for example, M g 2 S l ) are formed, which is difficult to solidify even during subsequent annealing, resulting in insufficient strength and a high edge height. It causes. Therefore, it is necessary to charge the hot-rolled coil into a high-temperature continuous furnace without lowering the temperature to below 200°C. The hot-rolled coil is recrystallized in this high-temperature continuous furnace, but if the furnace temperature is less than 350°C, the time required for recrystallization is longer, and if it exceeds 600°C, the coil is annealed. , problems such as crystal grain growth and burning occur in the etched portion of the coil. Therefore, the furnace temperature of the high-temperature continuous furnace is set in the range of 350 to 600°C. This high-temperature continuous furnace has one inlet and one outlet, and has a mechanism for moving the coil inside the furnace. Further, the heated coil is cooled, and in this case, either natural cooling or forced cooling may be used, but forced cooling is preferable in terms of productivity. However, in the case of forced cooling, in order to further improve solid solution strengthening, it is better to perform cooling at a faster rate and to a lower temperature. Specifically, if the cooling rate is less than 100°C/min, it is insufficient, and if the temperature after cooling exceeds 150°C, further cooling is required before subsequent cold rolling.
This would be a waste of time. Therefore, in the case of forced cooling, at a cooling rate of 100°C/min or more, 150°C
Rapidly cool down to below ℃. Note that cooling methods include air cooling and water cooling, both of which are performed while unwinding the coil. Next, cold rolling is performed at a cold rolling rate of 80% or more until the thickness of the product plate is reached. This is to achieve the desired thickness with high accuracy and to improve strength. However, the cold rolling rate is 80
If it is less than %, sufficient strength cannot be obtained, which is not preferable. Furthermore, stabilization annealing can be performed if necessary. Although the purpose of stabilizing annealing is to suppress the aging characteristic of ArA-Mg alloys, the conditions are not particularly limited. - Numerically treated at a temperature of 100-200°C for several hours. (Example) Next, an example of the present invention will be shown. Example I A l1l-4,5%Mg-0,35%Mn-0,15
An aluminum alloy ingot (50 mm thick) having a chemical composition of %Zn-0,20%Fe-0,09%Si was heated at 500℃.
After homogenization heat treatment for 5 hours, the plate thickness was 4m by hot rolling.
It was set as m. The hot rolling end temperature at this time is 30O℃ and 25
It was manufactured with a temperature of 0°C as the target. The cooling conditions and heat treatment (annealing) conditions after hot rolling were controlled as shown in Table 1 using a programmable high temperature constant temperature bath in order to match the actual manufacturing level. Furthermore, after the heat treatment, it was cold rolled to a thickness of Q, 4 mm. The obtained material was baked at 200°C
In addition to examining the mechanical properties after m1n), the deep drawing selvage ratio and formability (stretchability, riveting workability) were evaluated. The results are shown in Table 2. The deep drawing edge ratio was determined using an Erichsen tester (40φ punch), using mineral oil ('/A slip), and using a wrinkle pressing force of 50.
Under the condition of 0 kg, the difference between the peaks and valleys of a cup with an aperture ratio of 1.67 was calculated as the value (X100) divided by the average height. Stretchability was evaluated by Erichsen test A method. Riveting workability was evaluated by the limit height of multi-stage drawing of 6φ → 4φ → 3.2φ, and the limit height was 1.75mm.
The above items were judged to be good. As is clear from Table 2, the invention examples Nα1 and Nα3
Compared to comparative example Nα5 using the conventional method, the strength is 0,5
~1.0 kgf/mm2 is high, and it can be seen that the riveting processability, which is the main forming of the end, is excellent. In addition, each of the examples of the present invention is charged into a constant temperature furnace without lowering the temperature to 200°C or less after hot rolling, so there is no wasted time and the energy after hot rolling is effectively used, resulting in excellent productivity and energy saving. ing. On the other hand, Comparative Example Ha 2 was not recrystallized due to insufficient heating, and had a high edge and poor moldability. In addition, in Comparative Example Nα4, it takes a long time to cool the plate to a low temperature.
Productivity and energy saving are not much different from Comparative Example Nα5 made by the conventional method. Furthermore, Comparative Example Nα6 has a low end temperature of hot rolling, so the edge height is high.

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Aluminum alloy ingots having the chemical composition shown in Table 3 (Table 1)
50mm thick) was subjected to homogenization heat treatment at 520°C for 2 hours, and hot rolled (finishing temperature target: 300°C) to a plate thickness of 4mm.
I made it. In the subsequent steps, heat treatment and cold rolling were carried out under the same conditions as in the case of Nα1 (inventive example) in Table 1. The material properties of the obtained material were investigated in the same manner as in Example 1. The results are shown in Table 4. In addition, since edge cracks occurred during hot rolling and cold rolling for alloys with alloy numbers R and E, the desired product plate (plate thickness 4 mm)
could not be obtained, and no investigation of material properties was conducted. As is clear from Table 4, Examples A, B, and F of the present invention all have a small selvage ratio and excellent moldability. In particular, Invention Example A is suitable for can lid materials for non-carbonated beverages such as coffee and fruit juice, and Invention Examples B and F are suitable for internal pressure can lid materials for beer, carbonated beverages, etc. The difference between B and F is It can be seen that the addition of an appropriate amount of Zn leads to an improvement in riveting workability, depending on whether or not Zn is added. On the other hand, Comparative Example C lacks strength due to the small amount of Mg, and it is difficult to make the lid material thinner. It should be noted that if a larger amount of Mg (alloy symbol D) or M n (alloy symbol E) than the range of the present invention is included, there are problems in manufacturing.

[Left below]

(Effects of the Invention) As detailed above, according to the present invention, since the chemical components are appropriately adjusted and the manufacturing process conditions are regulated, it is possible to provide a high-strength, high-formability end material that can meet the recent trend toward thinner walls and lighter weights. In addition, it has remarkable productivity and energy saving effects, and will greatly contribute to the spread of aluminum cans in this type of field. Note that the heat treatment step in the method of the present invention may be performed on other materials, such as cap materials, equipment materials, and even heat treatment materials (Al-M
g-3i series, Al-Zn-Mg series), etc., and the ripple effect is also significant. Patent applicant Hisashi Nakamura, patent attorney representing Kobe Steel, Ltd.

Claims (2)

[Claims] (1) In weight% (the same applies hereinafter), Mg: 2.0 to 5.5
%, further Mn: less than 0.7%, Cr: 0.5%
and Zn: one or two of 0.05 to 1.0%
An Al alloy ingot containing at least 5 mm of aluminum with the remainder consisting of Al and unavoidable impurities is subjected to homogenization heat treatment at a temperature of 450°C or higher, and hot rolling is completed at a plate thickness of 5 mm or less at a temperature of 280°C or higher. The hot-rolled coil is then rolled up into a coil for 3 hours without lowering the temperature below 200°C.
The coil is charged into a continuous furnace at a temperature of 50 to 600°C and continuously heated in the form of a coil, and the heated coil is then left to cool or rapidly cooled to 150°C or less at a cooling rate of 100°C/min or more, A method for producing an aluminum alloy hard plate for packaging, which comprises thereafter performing cold rolling at a cold rolling rate of 80% or more. (2) Contains Mg: 2.0 to 5.5%, and further contains Mn: 0
．． Less than 7%, Cr: less than 0.5% and Zn: 0.05~
Contains one or more of 1.0% and the remainder is A.
4 for an Al alloy ingot consisting of l and inevitable impurities.
Applying homogenization heat treatment at a temperature of 50°C or higher, finishing hot rolling at a plate thickness of 5 mm or less and a temperature of 280°C or higher, winding it into a coil, and then lowering the hot rolled coil to a temperature of 200°C or lower. Without heating, the coil is charged into a continuous furnace at a temperature of 350 to 600℃ and heated continuously, and the heated coil is then left to cool or at a cooling rate of 100℃/m.
It is rapidly cooled to 150°C or less at a temperature of in or more, and then,
A method for manufacturing an aluminum alloy hard plate for packaging, characterized by cold rolling at a cold rolling rate of 80% or more and stabilizing annealing.