JPH06104882B2 - Manufacturing method of aluminum alloy sheet for forming - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an aluminum alloy sheet for forming, which has excellent heat resistance strength, and in particular, is baked on a can body material, a can lid material and the like. The present invention relates to a method for producing an aluminum alloy plate for forming, which is suitable for use.

Conventional technology Aluminum alloy sheets for forming, especially aluminum alloy sheets used for can body materials and can lid materials, have recently been reduced in thickness in order to expect economic effects by using thin sheets with higher strength. Higher strength is being promoted. JIS 3004 alloy hard plate and JIS 5082 alloy hard plate,
JIS 5182 alloy hard plate is mainly used,
In particular, the 3004 alloy hard plate exhibits relatively good formability even when cold rolled at a high rolling rate to enhance strength, and is therefore often used as a can body. This 3004 alloy hard plate is subjected to homogenizing heat treatment, hot rolling according to a conventional method, and then subjected to intermediate annealing without being subjected to cold rolling or after cold rolling, and then subjected to final cold rolling. It is often used as a product plate.

Problems to be Solved by the Invention In general, a can body is formed at a temperature of 200 ° C. × 20 after forming for can manufacturing.
It is usual to carry out a baking process for about a minute, and it is known that the pressure resistance of the can correlates with the yield strength of the can body material after the baking process. However, the 3004 alloy hard plate obtained through the conventional conventional process does not always have sufficient heat resistance, and it is desired to further improve the proof stress after the baking treatment. Further, recently, instead of the conventional general batch type annealing as the intermediate annealing in the manufacturing steps as described above, continuous annealing has been applied, but as the temperature of continuous annealing in this case, Requires a high temperature of about 500 ° C to obtain high strength materials, and continuous annealing at such high temperatures inevitably raises the energy cost. It is desired to develop a method capable of obtaining a high-strength material at a lower continuous annealing temperature.

This invention has been made in the background of the above circumstances, the heat resistance strength is higher than the conventional 3004 alloy hard plate, aluminum alloy plate for forming process that can obtain high yield strength after baking treatment, a method for manufacturing at low cost It is intended to provide.

Means for Solving the Problem As a result of intensive experiments and studies conducted by the present inventors in order to solve the above-mentioned problems, hot rolling conditions, in particular, finish rolling conditions are rigorously defined, leading to an increase in cost. Therefore, the inventors have found that an aluminum alloy plate having improved heat resistance strength and higher strength after paint baking can be obtained, and the present invention has been accomplished.

Specifically, the manufacturing method of the aluminum alloy plate for forming according to the present invention includes Mg 0.5 to 5.0 wt%, Cu 0.1 to 1.0 wt% and Fe.
0.2-1.0wt%, Si 0.1-1.0wt%, Mn
0.6-1.8wt%, Cr 0.3wt% or less, Zr 0.3wt% or less, V 0.
An aluminum alloy containing one or more of 3 wt% or less and the balance of Al and unavoidable impurities was used as a raw material, and the ingot was subjected to soaking at a temperature of 550 ° C. or more for 3 hours or more. After that, start hot rolling at a temperature of 450 ° C or higher, and in the final finish rolling in the hot rolling process, set the temperature of the material to be rolled when the finish rolling is started.
400 ℃ or more, the plate thickness is 15 ~ 65 mm, and the maximum required time between each roll pass in the finish rolling is within 30 seconds and the time required from the first roll pass to the final roll pass is within 100 seconds, In addition, the finishing rolling temperature is 310 ℃ or more, and the plate thickness is 6mm or less, then 100 ℃.
Immediately or after cold rolling after cooling to the following, after heating to a temperature in the range of 380 ~ 600 ℃ at a heating rate of 1 ℃ / sec or more and holding immediately or within 10 minutes It is characterized in that an intermediate annealing is carried out at a cooling rate of 1 ° C./sec or more to 200 ° C. or less, and a final cold rolling is further performed at a rolling rate of 40% or more.

Action First, the reasons for limiting the components of alloying elements in the method for producing an aluminum alloy sheet for forming according to the present invention will be described.

Mg: Mg coexists with Cu and Si GP zone → β′Mg ₂ Si → βMg
_It follows the precipitation process such as ₂ Si or GP zone → S'Al ₂ CuMg → SAl ₂ CuMg and contributes to the strength improvement at the precipitation stage of the intermediate phase. In the case of can body materials, in order to reduce the wall thickness to about 0.3 mm, it is desirable that the proof stress after painting and baking treatment is 27 to 29 kg / mm ² or more, but if Mg is contained excessively, the formability may be impaired. Therefore, the amount of Mg is determined by the balance between strength and formability. If the amount of Mg is less than 0.5 wt%, it is not possible to obtain a yield strength of 27 kg / mm ² or more after paint baking at a final cold rolling rate of 40% or more, even if adjusted with other alloy components,
On the other hand, if it exceeds 5.0 wt%, work hardening tends to occur, and the rollability and formability deteriorate, so the Mg content was made within the range of 0.5 to 5.0 wt%.

Cu: Strengthening of the aluminum alloy plate by the method of the present invention,
In particular, in order to improve the yield strength after paint baking, age hardening during paint baking is actively used, and Cu contributes to the improvement of strength by this age hardening. Since this effect occurs during the precipitation process of Al-Cu-Mg-based precipitates, it is desirable that Cu maintain a sufficient solid solution amount. In the method of the present invention, as will be described later, the conditions for sufficiently maintaining the solid solution state of each alloying element in the hot rolling step are adopted, and as the intermediate annealing, Cu of until the end of hot rolling is adopted. In order to maintain the amount of solid solution, the heating rate is increased to 1 ° C / sec or more, and the temperature of 380 ° C or more is applied to further solid-dissolve fine precipitates. By combining these conditions, Cu The above-mentioned effect is exerted by the addition of. If the amount of Cu is less than 0.1 wt%, the above-mentioned effect cannot be obtained. On the other hand, if it exceeds 1.0 wt%, age hardening performance is improved, but work hardening easily occurs during molding, which impairs formability. It was set within the range of 0.1 to 1.0 wt%.

Fe: Fe combines with Mn and Si to form an Al-Fe-Mn-Si-based crystallized substance, which is effective in improving ironing workability, but 0.2w
If it is less than t%, its effect is small, and if it exceeds 1.0% by weight, along with the addition of Mn, a primary crystal giant compound is generated and formability is significantly impaired. Therefore, the Fe content is 0.2-1.0 wt%
Within the range of.

Si: In the method of the present invention, since the manufacturing conditions that maintain the solid solution amount of Si are adopted, strength improvement due to age hardening can be expected even in the crystallization process of Mg ₂ Si system, but as the role of Si Is to control the directionality during the molding process rather than to improve the strength. Fe is an element that can be positively added in order to make the recrystallized grains finer, but when Fe is solid-dissolved in the aluminum matrix, 45 ° ears are likely to occur, so it is easy to generate in the aluminum matrix. It is desirable not to form a solid solution. Si has the effect of promoting the precipitation of Fe and consequently reducing the amount of solid solution of Fe in the matrix.
The amount of Si added depends on the amount of Fe added. Si is 0.1wt%
If it is less than 1.0, the effect of precipitating Fe is small, while if Si exceeds 1.0 wt%, the effect of precipitating Fe is saturated. Therefore
The amount of Si was set within the range of 0.1 to 1.0 wt%.

Mn: Addition of Mn is effective in improving strength and moldability. In addition, Mn in a solid solution state has an effect of delaying softening due to heat, and therefore has an effect of reducing a decrease in strength due to coating baking treatment. Here, the larger the amount of Mn solid solution in the final plate is, the more excellent the heat resistance is, and it is possible to reduce the strength reduction due to the coating baking treatment. In order to sufficiently obtain the effect, Mn is 0.23 wt% or more in the final plate. It is desirable that it is melted. Further, in the case of a can body, which is the main use of the aluminum alloy sheet according to the present invention, it is usual to perform severe ironing, and therefore addition of Mn is important for improving formability. Emulsion type lubricants are usually used in ironing of aluminum alloy sheets, but if the amount of Mn-based crystallized substances is small, even if they have similar strength, they can be lubricated only with emulsion type lubricants. There is a risk of poor appearance and poor appearance such as scratches and seizure called "goring". Mn-based crystallized substances have a solid lubricating effect during ironing and are effective in preventing appearance defects after ironing, but the effect depends on the size, amount, and type of crystallized substances. Known to be affected. When performing casting with a high cooling rate using the continuous casting method, it is possible to cast Mn in excess of 1.8 wt% without any problem, and the crystallized substance size can be adjusted by subsequent heat treatment. In DC casting, which is the mainstream, Mn 1.8
If it is added in excess of wt%, primary crystal giant intermetallic compounds of MnAl ₆ will be generated, and the formability may be significantly impaired. Therefore, the upper limit of the amount of Mn added is set to 1.8 wt%. Further, the addition of Mn is also effective for improving the tearability and can openability of the can lid when the alloy of the present invention is used as a can lid material. Mn amount is 0.
If it is less than 3 wt%, the effect of improving the heat resistance by the solid solution Mn as described above, the effect of the solid solution lubrication by the Mn-based crystallized product, or the effect of improving the can openability cannot be obtained.
It was set to 0.6 wt%.

Cr, Zr, V: All of these are elements that contribute to the improvement of strength, and one or more of these Cr, Zr, V and the above Mn are contained. Among these elements, especially Cr and Zr are Mn
Similar to the above, it has the effect of delaying softening due to heat, and is therefore effective in reducing the decrease in strength due to paint baking. However, Cr is 0.3 wt%, Zr is 0.3 wt%, V is 0.3 wt%
If it exceeds, a huge compound will be generated, which is not preferable,
Cr is 0.3 wt% or less, Zr is 0.3 wt% or less, and V is 0.3 w
Limited to t% or less.

The balance of the above components may basically be Al and inevitable impurities. In addition, in a usual aluminum alloy, a small amount of Ti or Ti and B may be added for refining the ingot crystal grains. Even in the case of the present invention, a small amount of Ti or Ti and B is contained. Is also good. However, when Ti is added, the effect of Ti addition will not be obtained if it is less than 0.01 wt%, while primary TiAl ₃
However, Ti is preferable to be in the range of 0.01 to 0.15 wt%. When B is added together with Ti, the effect of B addition cannot be obtained if B is less than 1 ppm.
On the other hand, if B exceeds 500 ppm, coarse particles of TiB ₂ are mixed and impair the moldability, so B is preferably in the range of 1 to 500 ppm. In addition, to prevent molten metal oxidation during casting
Be may be added in the range of 0.02 wt% or less.

Next, the manufacturing process conditions in the method for manufacturing an aluminum alloy sheet for forming according to the present invention will be described.

In the process of the present invention, in the hot rolling step, it is possible to prevent the precipitation of alloying elements, in particular, transition elements such as Mn, Fe, and Cr, and to maintain the solid solution state of the alloying elements as much as possible by the end of hot rolling. Is an important feature, thus maintaining the solid solution state until the end of hot rolling, and by further solubilizing the elements that have been precipitated by the liquefaction effect in the subsequent intermediate annealing, The solid solution amount of the alloy element in the state of the final plate is remarkably increased, whereby the age hardening during the paint baking treatment for the final plate is sufficiently achieved and the strength reduction due to the paint baking treatment is prevented.

Further, the process of the present invention will be specifically described.

First, an aluminum alloy ingot having the above-described composition is cast by a DC casting method or the like according to a conventional method. Then, the ingot is subjected to soaking treatment (homogenization treatment). This soaking is required to maintain a holding temperature of 550 ° C. or higher in order to maintain the solid solution state of transition elements such as Mn and Cr, and sufficient homogenization cannot be achieved by holding for less than 3 hours. Therefore, the conditions for soaking were set to 550 ° C. or higher and held for 3 hours or longer.

After soaking, hot rolling is performed. In this case, the hot rolling start temperature may be 450 ° C or higher, but immediately after soaking
Hot rolling may be performed at a temperature of 50 ° C. or higher, or preheating for hot rolling may be performed again after soaking and then hot rolling may be started at 450 ° C. or higher.

In hot rolling, it is usual to first perform rough rolling and then finish rolling, or to perform rough rolling and then intermediate rolling (intermediate finish rolling), and then finish rolling. The present invention is characterized in that the final finish rolling is rigorously defined as a condition so that the solid solution state of the alloy elements is maintained as much as possible until the end of the finish rolling. That is, the temperature at the time when the final finish rolling is started is 400 ° C., the plate thickness is 15 to 65 mm, and the rolling time of the finish rolling, the maximum required time between each roll pass is 30 seconds or less and the first The time required from the roll pass to the final roll pass should be 100 seconds or less, and the finishing rolling rise temperature should be 310 ° C or higher and the rise plate thickness should be 6 mm or less. The reasons for these limitations are as follows.

If the temperature at the start of finish rolling is 400 ° C or higher, strain recovery can be prioritized. When the strain is recovered, precipitation of alloying elements in a short time is reduced, and it becomes easy to maintain the solid solution state of the alloying elements. On the other hand, the finish rolling start temperature is 400
If the temperature is lower than ° C, the recovery of strain is not sufficient, so that the precipitation of alloying elements increases. The plate thickness at the start of finish rolling is 15
If it is less than mm, the material to be rolled will be cooled before starting the finish rolling, and it will be difficult to obtain the desired temperature (400 ° C or higher).
If it exceeds 5 mm, it will be difficult to make the final plate thickness 6 mm or less by finish rolling unless the number of stands is very large.

Regarding the rolling time in finish rolling, the longer the time required between each roll pass and the time required from the first roll pass to the last roll pass (total time),
Precipitation of solid solution elements increases. If the time required for each roll pass exceeds 30 seconds, precipitation will progress between roll passes, and if the total time exceeds 100 seconds, the total amount of precipitation during rolling will increase. Therefore, the time required for each roll pass should be 30 seconds or less, and the total time should be 100 seconds or less. Here, the time required between each roll pass means the time from the time when an arbitrary part of the material to be rolled passes a certain roll to the time when the same part passes the next roll. The total time also means the time from the time when any part of the material to be rolled passes the first roll to the time when the same part passes the last roll.

On the other hand, if the rising temperature of finish rolling is higher, recovery can be prioritized and precipitation of alloying elements can be reduced. In this way, the finish rolling rise temperature of hot rolling is raised to prioritize the recovery of strain after hot rolling and the precipitation of alloying elements is suppressed as much as possible to enhance the solution treatment effect by the subsequent intermediate annealing, and the coating baking. In order to increase the strength after the treatment as compared with the conventional method, it is effective to set the rising temperature of finish rolling to 310 ° C or higher. If the rising temperature of finish rolling is too high, problems such as roll coating will occur. Therefore, it is usually preferable to set the temperature to about 360 ° C or lower. Also, if the finish rolling thickness exceeds 6 mm, the number of passes in the subsequent cold rolling process will increase and work efficiency will decrease,
The ascending plate thickness was 6 mm or less.

After finishing rolling at a rising temperature of 310 ° C or higher as described above, forced cooling is performed by water cooling or the like to obtain 1 ° C.
Rapid cooling to 100 ° C or less at a cooling rate of / sec or more is desirable. By rapid cooling immediately after finish rolling in this way, precipitation of alloying elements, especially Cu, Mg, Si, etc., can be reduced, and the effect of solution treatment during the subsequent intermediate annealing can be increased. The strength after the treatment can be further improved.

After that, cold rolling is performed and then intermediate annealing is performed, or intermediate annealing is immediately performed without performing cold rolling.
This intermediate annealing is performed at a temperature rising rate of 1 ° C / sec or more and 380 to 6
200 ℃ at a cooling rate of 1 ℃ / sec or more after heating to a temperature within the range of 00 ℃ and holding immediately or within 10 minutes
Cool to: The reason for defining the conditions for such intermediate annealing is as follows.

That is, as the rate of temperature rise during intermediate annealing is higher, the precipitation of alloying elements is less, and it becomes possible to maintain the solid solution state in the hot rolled state. Since this effect is small when the heating rate is 1 ° C./sec or less, the heating rate is set to 1 ° C./sec or more. Regarding the temperature of the intermediate annealing, the temperature immediately above the recrystallization end temperature is optimal in order to maintain the solid solution state of the transition element such as Mn, and in the alloy of the system targeted by the present invention, the recrystallization end temperature. Is about 380 ° C, so 380
~ 400 ° C is preferred. However, even if the temperature is higher than this, 1
If it is held for a short time of 0 minutes or less, the precipitation of transition elements such as Mn is small and the solid solution state can be maintained to some extent.
On the other hand, if the intermediate annealing temperature is 380 ° C or higher, fine precipitates such as Cu-Mg-Si generated immediately after hot rolling or during the temperature increase of intermediate annealing are re-dissolved, resulting in the final plate. A GP zone can be formed after the paint baking treatment of to prevent the strength from decreasing.
This effect becomes more remarkable if the temperature is 450 ° C. or higher, and the precipitate of the coarse metal element generated during soaking-heating-hot rolling is also solid-solved, and the solution effect further advances and contributes to strength improvement. To do. However, in the manufacturing method of the present invention, as described above, since a process that maintains the solid solution state of the alloying elements as much as possible up to the state of hot rolling is applied, a high temperature of 450 ° C. or higher is not always required. However, if the temperature is 380 ° C. or higher, high strength after paint baking can be obtained. Therefore, the temperature of the intermediate annealing was specified as 380 ° C or higher. Further, if the cooling rate to the temperature of 200 ° C or lower after the intermediate annealing is less than 1 ° C / sec, the alloy elements dissolved in solid solution may be reprecipitated. Therefore, the cooling after the intermediate annealing is performed at the temperature of 200 ° C or lower. Up to 1 ℃ / sec. In addition, 1 ℃ as above
The temperature rising rate and cooling rate of not less than / sec can be achieved by using a continuous annealing furnace.

After the intermediate annealing, perform a final cold at a rolling rate of 40% or more,
It has a predetermined plate thickness. If the rolling ratio of this final cold rolling is less than 40%, the strength equal to or higher than that of the conventional material cannot be obtained.
The rolling rate was set to at least%.

After the final cold rolling, it may be used as it is as the final plate for forming work, but if the formability is particularly important, it is 10
Finish annealing (final annealing) may be performed at a temperature within the range of 0 to 200 ° C for about 0.5 to 5.0 hours. When such finish annealing is performed, the deterioration of the strength after the coating baking treatment is further reduced as compared with the case of the final cold rolling as it is because the aging progresses.

In the method of the present invention, as a rolling mill used for finish rolling in the hot rolling step, any rolling mill can be used as long as the above-mentioned finish rolling conditions are satisfied, and a single reverse rolling mill or a continuous rolling mill. Any of (3 tandem rolling mill, 5 tandem rolling mill, etc.) can be used.

Example An aluminum alloy within the compositional range of the present invention shown in Table 1 was DC cast according to a conventional method. Both sides of the obtained ingot were chamfered to a thickness of 500 mm, soaking was performed at 600 ° C. for 6 hours, and then hot rolling was started at 480 ° C. In the hot rolling of the present invention, a single reverse rolling mill and a 5-stand rolling mill were used, rough rolling and intermediate rolling were performed by single reverse rolling, and then finish rolling was performed by 5 stands. Further, in all the comparative examples, hot rolling was performed by single reverse. Here, finish rolling is the entry side plate thickness
40mm, thickness 3.0m under various conditions as shown in Table 2.
Rolled to m. The hot-rolled sheet thus obtained had a thickness of 1
After cold rolling to mm, an intermediate annealing was carried out using a continuous annealing furnace or a box annealing furnace under the conditions shown in Table 1. After that, final cold rolling was performed to obtain a rolled plate having a plate thickness of 0.3 mm, and further finish annealing was performed under the conditions shown in Table 1.

With respect to the final plate obtained as described above, the amount of Mn solid solution was examined, and the yield strength and elongation before the baking treatment were examined. The final plate was subjected to paint baking treatment at 200 ° C for 20 minutes, and the yield strength and elongation after the paint baking treatment were examined. At the same time, the formability (redrawability and ironing property) before the paint baking treatment was also examined. The result is the third
Shown in the table.

As is clear from Table 3, it is clear that the rolled plate obtained by the method of the present invention (conditions 1 to 3) has a high yield strength after the paint baking treatment and a small decrease in strength due to the paint baking treatment. It is also clear that the moldability is no different from that of the conventional method.

Effects of the Invention According to the method of the present invention, by strictly defining the hot rolling conditions, especially the finish rolling conditions, the solid solution state of the alloy elements is maintained as much as possible until the state of hot rolling,
Furthermore, by performing solution treatment in the subsequent intermediate annealing,
It is possible to obtain an aluminum alloy plate for forming that has a strength after coating baking treatment of 0.5 kg / mm ² or higher and a yield strength higher than that of conventional materials without lowering the formability. Moreover, it is optimal for the production of molding materials that require high strength. Further, according to the method of the present invention, when continuous annealing is applied as the intermediate annealing,
Sufficient strength can be obtained even at a relatively low temperature of about 0 ° C. Therefore, in this case, energy saving in continuous annealing can be achieved.

Claims (1)

[Claims] 1. Mg 0.5-5.0 wt%, Cu 0.1-1.0 wt%, Fe
0.2-1.0 wt%, Si 0.1-1.0 wt%, Mn 0.
6-1.8wt%, Cr 0.3wt% or less, Zr 0.3wt% or less, V 0.3w
Contains 1 or 2 or more of t% or less, and the balance is A
Aluminum alloy consisting of l and unavoidable impurities is used as a raw material, and the ingot is subjected to soaking at a temperature of 550 ° C or higher for 3 hours or more, then hot rolling is started at a temperature of 450 ° C or higher, and In the final finish rolling in the hot rolling process, the temperature of the material to be rolled when the finish rolling is started is set to 40
0 ℃ or more, the plate thickness is 15 ~ 65 mm, and the maximum required time between each roll pass in the finish rolling is within 30 seconds and the time required from the first roll pass to the final roll pass is within 100 seconds, And finish rolling up temperature 3
After cooling to 10 ° C or more and the ascending plate thickness of 6 mm or less, and then cooling to 100 ° C or less, immediately or after cold rolling,
Heating to a temperature in the range of 380 to 600 ° C at a heating rate of 1 ° C / sec or more and holding immediately or within 10 minutes, then cooling to 200 ° C or less at a cooling rate of 1 ° C / sec or more A method for producing a rolled aluminum alloy sheet for forming, which comprises performing intermediate annealing and further performing final cold rolling at a rolling rate of 40% or more.