JPH03207840A - Manufacture of aluminum alloy sheet for forming - Google Patents

Abstract

PURPOSE:To manufacture the Al alloy sheet for forming excellent in heat resistance by subjecting an ingot of an Al alloy contg. elements for improving strength, formability or the like to soaking treatment and thereafter executing hot rolling, cold rolling and final cold rolling including process annealing under specified conditions. CONSTITUTION:An ingot of an Al alloy contg., by weight, 0.5 to 5.0% Mg, 0.1 to 1.0% Cu, 0.2 to 1.0% Fe and 0.1 to 1.0% Si and furthermore contg. one or >=2 kinds among 0.6 to 1.8% Mn, <0.3% Cr, <0.3% Zr and <0.3% V is held to >=550 deg.C for >=3hr and is subjected to soaking treatment. Its hot rolling is started at >=450 deg.C and its final finish hot rolling is started at >=400 deg.C and 16 to 65mm sheet thickness as well as the hot rolling is executed in such a manner that the maximum required time between each roll pass is regulated to <=30 sec and the time from the first roll pass to the finish roll pass is regulated to <=100 sec. Furthermore, in the finish rolling, the finishing temp is regulated to >310 deg.C and the finishing sheet thickness to <6mm. Successively, the sheet is cooled to <=100 deg.C, is cold-rolled is subjected to process annealing of heating to 380 to 600 deg.C at >=1 deg.C/sec temp. rising rate and thereafter cooling to <=200 deg.C at <=1 deg.C/sec cooling rate and is subjected to final cold rolling at >=40% draft.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a method for manufacturing an aluminum alloy plate with excellent heat resistance and strength for processing into certain shapes. The present invention relates to a method for producing an aluminum alloy plate for forming processing, which is suitable for various uses.

Conventional technology Aluminum alloy sheets for mold processing, especially aluminum alloy sheets used for can body and can lid materials, have been thinned in recent years in hopes of achieving economical benefits by using thinner sheets with higher strength. Progress is being made to increase the strength of the steel. For this type of application, JIS 3004 alloy hard plate or Its 50
82 alloy hard plate, JIS 5182 alloy hard plate, etc. are mainly used, but 3[104 alloy hard plate in particular has relatively good forming properties even when cold rolled at a high rolling rate to increase strength. It is often used for can body materials because of its properties.

After homogenization heat treatment, this 3004 alloy hard plate is subjected to hot rolling according to a conventional method, then subjected to intermediate annealing after cold rolling or without cold rolling, and then subjected to final cold rolling. Often used as a product board.

Problems to be Solved by the Invention In general, can frame materials are heated to 200°C after forming for can manufacturing.
It is normal to perform a paint baking process for about 20 minutes.
It is known that the pressure resistance performance of a can is correlated with the proof strength of the can body material after being painted and baked. However, 3004 alloy hard plates obtained through conventional conventional processes do not necessarily have sufficient heat resistance strength, and it is desired to further improve the yield strength after paint baking treatment. In addition, recently, continuous annealing has been used as an intermediate annealing in the manufacturing process as described above, instead of the conventional general batch annealing, but the continuous annealing temperature in this case is In order to obtain high-strength materials, high temperatures of around 500°C are required, and continuous annealing at such high temperatures inevitably increases energy costs. It is desired to develop a method that can obtain high-strength materials at lower continuous annealing temperatures.

This invention was made against the background of the above-mentioned circumstances, and aims to produce, at a low cost, an aluminum alloy plate for shape processing that has higher heat resistance strength than conventional 3004 alloy hard plates and can obtain high yield strength after paint baking treatment. The purpose is to provide a method.

Means for Solving the Problems The inventors of the present invention have carried out extensive experiments and studies to solve the above-mentioned problems, and have found that strict regulation of hot rolling conditions, especially finish rolling conditions, will lead to an increase in costs. The present inventors have discovered that an aluminum alloy plate can be obtained which has improved heat resistance and strength compared to conventional ones, and which can have high strength after painting and baking treatment, and has come to form this invention.

Specifically, the method for producing an aluminum alloy plate for forming according to the present invention includes Mg0.5 to 5.0 wt%, Cu
O. 1-1. Ovl%, F e O. 2-1. Ov
l%, StO. 1=contains 1.0 wt% and further contains M
n0.6-1.8wt%, CrO, 3vt% or less, Zr
O. 3vj% or less, ■O. The material is an aluminum alloy containing one or more of the following: 3vl% or less, with the remainder consisting of AI and unavoidable impurities, and the ingot is subjected to soaking treatment at a temperature of 550°C or more for 3 hours or more. After that, 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 is set to 400°C or higher and the plate thickness is 15°C. ~65+m, and the maximum time required between each roll bath in finish rolling is within 30 seconds, the time required from the first roll bath to the final roll bath is within 100 seconds, and the maximum time required between each roll bath in finish rolling is within 100 seconds, and the maximum time required between each roll bath in finish rolling is within 100 seconds. The temperature was set at 310℃ or higher, the thickness of the plate was set at 6 mm or less, and then 10
After cooling to 0'C or less, immediately or after cold rolling, the temperature is increased from 380 to 600 at a heating rate of 1C/type or more.
After heating to a temperature within the range of °C and holding it immediately or within IO minutes, intermediate annealing is performed by cooling to 20G °C or less at a cooling rate of 1 °C/see or more, and further 40
It is characterized by performing final cold rolling at a rolling reduction of % or more.

Function First, the reason for limiting the number of alloying elements in the method of manufacturing an aluminum alloy plate for certain shapes according to the present invention will be explained.

Mg: Mg coexists with Cu and St. P. Zone → β
'Mg2Si→βMg2Si1 or G. P. Zone → S' A I 2 C u M g + S
It follows a precipitation process similar to that of Al 2 Cu M g, and contributes to strength improvement at the intermediate phase precipitation stage. In the case of can body material, 0. In order to reduce the wall thickness to about 3W, it is desired that the force resistance after the paint baking treatment is about 27 to 29 kg/1 or more, but if excessive Mg is contained, there is a risk of impairing the shapeability. is determined from the harmony of strength and formality. Mg amount is 0. If it is less than 5vt%, it will not be possible to obtain a yield strength of 27kg/- or more after paint baking treatment at a final cold rolling rate of 40% or more even if adjusted with other alloys to some extent, while if it exceeds 5.01% If the Mg content is 0.5, the Mg content becomes easier to work harden, resulting in poor rollability and formability.
It was set within the range of ~5.0 wt%.

Cu; Strength improvement of aluminum alloy plate by the method of this invention,
In particular, age hardening during the paint baking process is actively used to improve the yield strength after the paint baking process, and Cu contributes to the strength improvement due to this age hardening.

Since this effect occurs during the precipitation process of AI-Cu-Mg-based precipitates, it is desirable to maintain a sufficient amount of Cu in solid solution. In the method of the present invention, as will be described later, conditions are adopted to sufficiently maintain the solid solution state of each alloying element in the hot rolling process, and in addition, as an intermediate annealing, Cu is heated until the end of hot rolling. In order to maintain the amount of solid solution, the heating rate is increased to 1℃/8ec or higher, and a temperature of 380℃ or higher is applied to further dissolve fine precipitates.By combining these conditions, C.
The above-mentioned effects due to the addition of u are exhibited. Cu amount is 0.
At less than IWl%, the above effect cannot be obtained; on the other hand, at 1.0w
If it exceeds 1%, age hardening performance will improve, but work hardening will easily occur during molding, impairing moldability.
Cu is 0.1 to l. It was set within the range of Cwt%.

Fe: Fe combines with Mn and Si to form AI-Fe-Mn-
It is effective in promoting Si-based crystallized substances and improving ironing workability, but the effect is small if it is less than 0.2vj%.
1. If it exceeds Owt%, a primary crystal giant compound will be generated together with the addition of Mn, and the moldability will be significantly impaired. Therefore, the amount of Fe is 0.2 to 1. It was set within the range of Owj%.

Si: Since the method of this invention adopts manufacturing conditions that maintain the solid solution amount of St, it is expected that strength will be improved by age hardening even in the Mg2Si crystallization process, but the role of Si is Rather than improving strength, it lies in controlling directionality during molding. Fe is an element that can be actively added to make the recrystallized grains finer, but if Fe is dissolved in the aluminum matrix, 45° ears are likely to occur. It is desirable not to form a solid solution. St promotes the precipitation of Fe,
As a result, it has the effect of reducing the amount of Fe solid solution in the matrix, and therefore the amount of St added is determined depending on the amount of Fe added.

When Si is less than Q, lvl%, the Fe precipitation effect is small, while when St is less than lvl%. If it exceeds 0 wt%, the effect of precipitating Fe will be saturated. Therefore, the amount of St is 0, l ~ l,
It was set within the range of Qvt%.

Mn: Addition of Mn is effective in improving strength and formability.

In particular, Mn in a solid solution state has the effect of delaying softening due to heat, and therefore has the effect of reducing the decrease in strength due to paint baking treatment. Here, M in the final plate
The larger the amount of n solid solution, the better the heat resistance strength, and the decrease in strength due to paint baking treatment can be reduced. In order to fully obtain this effect, the final board should have Mn of 0. 23vt%
It is preferable that the solid solution is more than 100%. Furthermore, in the case of can body materials, which are the main application of the aluminum alloy sheet according to the present invention, the addition of Mn is important for improving shapeability, since severe ironing is usually performed. Normally, emulsion type lubricants are used for ironing aluminum alloy plates, but if there are few Mn-based crystallized substances, emulsion type lubricants alone will not work even if they have the same strength. There is a risk that the lubricating ability will be insufficient, resulting in poor appearance such as scratches and seizures called galling. Mn-based crystallized substances provide a solid lubricant effect during ironing and are effective in preventing appearance defects after ironing, but this effect depends on the size and amount of the crystallized substances,
It is known that it is influenced by the species.

When casting with a high cooling rate using a continuous casting method, it is possible to cast without any particular problem even if Mn is added in excess of 1.8 vt%, and the size of crystallized particles can be adjusted by subsequent heat treatment. In DC casting, which is currently the mainstream, M n
If added in excess of 3 wt%, M n A
/6 primary crystal giant intermetallic compounds are generated, which may significantly impair formability. Therefore, the upper limit of the amount of Mn added is 1.
It was set to 8vt%. The addition of Mn is also effective in improving the tearing and opening properties of the can lid when the alloy of the present invention is used as a can lid material.

If the Mn amount is less than 0.3 vt%, the above-mentioned effect of improving heat resistance strength due to solid solution Mn, the above-mentioned solid lubricating effect due to Mn-based crystallized substances, or the effect of improving can openability cannot be obtained. The lower limit was set to 0.6vt%.

Cr, Zr, V: These are all elements that contribute to improving strength, and one or two of these Cr, Zr, V and the above-mentioned Mn
Contains more than one species. Among these elements, especially Cr, Z
Similar to the above-mentioned Mn, r has the effect of delaying softening due to heat, and is therefore effective in reducing the decrease in strength due to paint baking treatment. However, Cr is 0.3wt%, Zr
is 0.3wt%, ■ is 0. If it exceeds 3vl%, a huge compound will be generated, which is not preferable, so Cr should be 0. 3wt% or less, Zr is 0. 3vt% or less, ■ is limited to 0.3wl% or less.

The remainder of each of the above components may basically be A/ and unavoidable impurities. In addition, in ordinary aluminum alloys, Ti1 or Ti is used to refine the ingot crystal grains.
A trace amount of Ti1 or Ti and B may be added in the case of the present invention. However, when adding Ti, 0. Oiwt
%, the effect of Ti addition cannot be obtained;
If it exceeds 1%, primary TiAJ3 crystals will crystallize and impair the formability. It is preferably within the range of 15vl%. Furthermore, when B is added together with Ti, if B is less than lppI1, the effect of B addition cannot be obtained, whereas if B exceeds 500ppm, coarse particles of T i B 2 will be mixed in, impairing the formability. ~500pp
It is preferable to set it within the range of m. In addition, Be may be added in an amount of 0.02 wt% or less to prevent oxidation of the molten metal during casting.

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

In the process of this invention, the precipitation of alloying elements, especially transition elements such as Mn, Fe, and Cr, is prevented as much as possible during the hot rolling process, and the solid solution state of the alloying elements is maintained as much as possible by the end of hot rolling. is an important feature, and in this way the solid solution state is maintained until the end of hot rolling.
In addition, the solution effect in the subsequent intermediate annealing allows the elements precipitated up to that point to become solid solutions, which significantly increases the amount of solid solution of alloying elements in the final plate state, which allows the final plate to be painted and baked. By ensuring sufficient age hardening during treatment, a decrease in strength due to paint baking treatment is prevented.

Furthermore, the process of this invention will be specifically explained.

First, an aluminum alloy ingot having the composition as described above is cast by a conventional method such as a DC casting method. Next, the ingot is subjected to soaking treatment (homogenization treatment). This soaking treatment requires a holding temperature of 550°C or higher in order to maintain the solid solution state of transition elements such as Mn and Cr.
Further, if the mixture is held for less than 3 hours, sufficient homogenization cannot be achieved.

Therefore, the soaking conditions were set at 550° C. or higher and held for 3 hours or more.

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

In hot rolling, it is normal 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 conditions for the final finish rolling are strictly defined so that the solid solution state of the alloying elements is maintained as much as possible until the end of the finish rolling. That is, the temperature when the final finish rolling is started is 400°C or higher, and the plate thickness is 15 to 650111.
Regarding the rolling time for finish rolling, the maximum time required between each roll bath shall be 30 seconds or less, and the time required from the first roll bath to the final roll bath shall be 1.
00 seconds or less, and the rising temperature of finish rolling is 310 seconds.
℃ or more, and the top plate thickness is 61 or less.

The reasons for these limitations are as follows.

If the temperature at the start of finish rolling is 400° C. or higher, priority can be given to strain recovery. Once the strain is recovered, precipitation of alloying elements in a short period of time will be reduced, making it easier to maintain the solid solution state of alloying elements. On the other hand, the finish rolling start temperature is 4
If the temperature is lower than 00°C, the recovery of strain is not sufficient, resulting in increased precipitation of alloying elements. If the plate thickness at the start of finish rolling is less than 15 mg, the material to be rolled will cool down before starting finish rolling, making it difficult to obtain the desired temperature (400°C or more), while if it exceeds 65+nm, the number of stands will be large. Otherwise, it will be difficult to reduce the final plate thickness to 6 mm or less in finish rolling.

Regarding the rolling time in finish rolling, the longer the time required between each roll bath and the time required from the first roll bath to the final roll bath (total time),
Precipitation of solid solution elements increases.

If the time required between each roll bath exceeds 30 seconds, precipitation between each roll bath will proceed, and if the total time exceeds 100 seconds, the total amount of precipitation during rolling will increase. Therefore, the time required between each roll bath must be 30 seconds or less, and the total time must be 100 seconds or less.

Note that the time required between each roll bath here means the time from the time when an arbitrary part of the material to be rolled passes through a certain roll to the time when the same part passes through the next roll. Moreover, the total time also means the time from the time when an arbitrary part of the material to be rolled passes through the first roll to the time when the same part passes through the last roll.

On the other hand, the higher the rising temperature in finish rolling, the more priority can be given to recovery and the precipitation of alloying elements can be reduced. In this way, by raising the finish rolling temperature of hot rolling to prioritize the recovery of strain after hot rolling and suppressing the precipitation of alloying elements as much as possible, the solution effect of the subsequent intermediate annealing is enhanced, and the paint baking process is improved. In order to increase the strength after treatment more than before, it is effective to set the finish rolling temperature to 310° C. or higher. Note that if the rising temperature of finish rolling is made too high, problems such as roll coating will occur, so it is usually preferable to keep it at about 360° C. or lower. Furthermore, if the finishing plate thickness in finish rolling exceeds 6 m, the number of passes in the subsequent cold rolling process increases and work efficiency decreases, so the finishing plate thickness was set to be 6 W or less.

After finish rolling at a temperature of 310°C or higher as described above, forced cooling is performed by water cooling etc.
It is desirable to rapidly cool to 1[1 G°C or less at a cooling rate of 1°C/sec or more. By rapid cooling immediately after finish rolling, alloying elements, especially Cu,
By reducing the precipitation of Mg, St, etc., the effect of solution treatment during subsequent intermediate annealing can be increased, and as a result, the strength after the paint baking treatment can be further improved.

Thereafter, intermediate annealing is performed after cold rolling, or intermediate annealing is performed immediately without cold rolling.

This intermediate annealing is performed by heating to a temperature within the range of 380 to 600°C at a temperature increase rate of 1°C/see or higher, and then heating to 200°C at a cooling rate of 1°C/sec or higher immediately or after holding for 10 minutes or more. Cool below. The reason why such intermediate annealing conditions were determined is as follows.

That is, the faster the temperature increase rate during intermediate annealing, the less precipitation of alloying elements occurs, making it possible to maintain the solid solution state in the hot-rolled state. This effect has a heating rate of 1°C/sec.
The temperature increase rate was set to be 1'C/see or higher since the temperature is small below 1'C/see. Regarding the temperature of intermediate annealing, in order to maintain the solid solution state of transition elements such as Mn, the optimum temperature is just above the recrystallization end temperature, and for the alloys targeted by this invention, the recrystallization end temperature is is about 380°C, so 380 to 400°C is preferable from the above point of view. However, even if the temperature is higher than this, if the temperature is kept for a short time within IO minutes, precipitation of transition elements such as Mn is small and a solid solution state can be maintained to some extent. On the other hand, the intermediate annealing temperature is 380
If the temperature is higher than 0.degree. C., fine precipitates such as Cu-Mg-St generated immediately after hot rolling or during temperature rise during intermediate annealing will be re-dissolved, resulting in G.I. P.
It is possible to prevent the strength from decreasing by controlling the zone. This effect is 4
If the temperature is 50° C. or higher, it becomes even more noticeable, and solid solution of coarse precipitates of metal elements generated during soaking, heating, and hot rolling is also performed, and the solution effect progresses further, contributing to improvement in strength.

However, in the manufacturing method of the present invention, as mentioned above, a process is applied in which the solid solution state of the alloying elements is maintained as much as possible until the state of hot rolling.
Even if the temperature is not higher than 380°C, high strength can be obtained after the paint baking treatment if the temperature is 380°C or higher. Therefore, the temperature of intermediate annealing was specified to be 380°C or higher. In addition, the cooling rate to a temperature of 200℃ or less after intermediate annealing is 1℃/s.
If the temperature is less than ec, there is a risk that the alloying elements that have been taken into solid solution will re-precipitate.
Temperatures below f°C/see were specified. Note that the heating rate and cooling rate of 1'C/sec or more as described above can be achieved by using a continuous annealing furnace.

After intermediate annealing, final cold rolling is performed at a rolling rate of 40% or more to obtain a predetermined thickness. The rolling ratio of this final cold rolling is 40
If the rolling rate is less than 40%, it will not be possible to obtain a strength comparable to or higher than that of conventional materials, so the rolling rate was set to 40% or more.

After the final cold rolling, it may be used as a final sheet for forming processing, but if shapeliness is particularly important,
Finish annealing (final annealing) may be performed at a temperature in the range of 00 to 200°C for about 0.5 to 5.0 hours. If such final annealing is performed, the aging progresses, so that the decrease in strength after the paint baking treatment will be smaller than in the case of final cold rolling.

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

EXAMPLE Aluminum alloys having the composition range of the present invention shown in Table 1 were cast by DC casting according to a conventional method. After face cutting both sides of the obtained ingot to a thickness of 500 mm,
Soaking treatment was carried out at 0°C for 6 hours, and then hot rolling was started at 480°C. In the example of the present invention, this hot rolling was performed using a single reverse rolling mill and a 5-stand rolling mill, with rough rolling and intermediate rolling performed using the single reverse, and then finishing rolling performed using the 5-stand rolling mill. In addition, all comparative examples were hot rolled by single reverse. Here, in the finish rolling, the plate thickness at the entry side was 4 hm, and the plate thickness was 3 mm under various conditions as shown in Table 2. It was rolled to Oaa. After the hot-rolled sheets thus obtained were cold-rolled to a thickness of 1 mm, intermediate annealing was performed using a continuous annealing furnace or a box annealing furnace under the conditions shown in Table 1. After that, final cold rolling is performed to achieve a plate thickness of 0. A rolled plate of 3 m+* was obtained and further subjected to finish annealing under the conditions shown in Table 1.

Regarding the final plate obtained as described above, the amount of solid solution of Mn was examined, and the yield strength and elongation before the paint baking treatment were also examined. Further, the final board was subjected to a paint baking treatment at 200°C for 20 minutes, and the yield strength and elongation after the paint baking treatment were examined. In addition, the formability (redrawability and ironability) before the paint baking treatment was also investigated. The results are shown in Table 3.

Table 1: Component composition of sample alloy (unit: vl%) As is clear from Table 3, the rolled plates obtained by the method of the present invention (condition codes 1 to 3) have a yield strength of It is clear that the strength is high and that there is little decrease in strength due to the paint baking treatment, and it is also clear that the formability is no different from that of the conventional method.

Effects of the Invention According to the method of the present invention, by strictly specifying the hot rolling conditions, especially the finish rolling conditions, the solid solution state of the alloying elements is maintained as much as possible until the hot rolled state,
Furthermore, by achieving solution treatment in the subsequent intermediate annealing,
It is now possible to obtain an aluminum alloy plate for forming that has a yield strength of 0.5 kg/1 or more in terms of yield strength after paint baking treatment, which is higher than that of conventional materials, without reducing formability. Furthermore, it is ideal for producing materials for molding that require high strength. Further, according to the method of this invention, when continuous annealing is applied as intermediate annealing,
Sufficient strength can be obtained even at a relatively low temperature of about 400° C. Therefore, in this case, it is possible to save energy in continuous annealing.

Claims (1)

[Claims] Mg0.5-5.0wt%, Cu0.1-1.0wt%
, Fe0.2-1.0wt%, Si0.1-1.0wt
%, and further contains Mn0.6-1.8wt%, Cr0
．． 3wt% or less, Zr0.3wt% or less, V0.3wt
% or less, and the remainder is A.
The ingot is made of an aluminum alloy consisting of l and inevitable impurities, and after soaking the ingot at a temperature of 550°C or higher for 3 hours or more, hot rolling is started at a temperature of 450°C or higher, and the In the final finish rolling in the inter-rolling process, the temperature of the rolled material at the start of finish rolling should be 400°C or higher, the plate thickness should be 15 to 65 mm, and the maximum required distance between each roll bath in the finish rolling should be 3 hours
0 seconds or less, the time required from the first roll bath to the final roll bath is within 100 seconds, and the rising temperature of finish rolling is 310°C or higher, the rising plate thickness is 6mm or less, and then cooling to 100°C or lower. After that, immediately or after cold rolling, heat to a temperature within the range of 380 to 600 °C at a temperature increase rate of 1 °C / sec or more and hold it for 10 minutes or less, then 1 °C / se
A method for manufacturing an aluminum alloy rolled sheet for forming work, comprising performing intermediate annealing by cooling to 200° C. or less at a cooling rate of c or more, and further performing final cold rolling at a rolling rate of 40% or more.