JPH059675A - Manufacture of aluminum alloy sheet for forming - Google Patents

Abstract

PURPOSE:To provide an Al alloy sheet excellent in surface quality such as pickups and grain streaks, low in earing ratio in drawing, furthermore small in the dispersion of the above properties in a coil and suitable for forming, particularly for a cap. CONSTITUTION:At the time of manufacturing an Al alloy sheet for forming by subjecting an Al alloy ingot contg., by weight, >0.5 to 2.0% Si and >0.8 to 2.0% Fe as well as <=3% (Si+Fe), contg. <=0.5% Cu, furthermore contg. one or two kinds of <=0.2% Ti and <=0.05% B and the balance substantially Al to homogenizing treatment and thereafter executing hot rolling, cold rolling and annealing, in the hot rolling, the rolling from the sheet thickness of <=120mm is executed by >=8 passes, at least one pass among hot rolling passes executed at the sheet thickness of 30 to 60mm is executed on and after the 5th pass from the sheet thickness of 120mm as well as at >=30% draft, furthermore, the finishing temp. of the hot rolling is regulated to <=280 deg.C and the cold draft to the final product is moreover regulated to 40 to 98%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy sheet for forming, and more specifically, it has excellent surface quality such as pickup and grain streak, has a low earing rate in drawing, and has a high earingling value. The present invention provides a method of manufacturing an aluminum alloy plate for forming which has less variation in the coil, and is particularly suitable for manufacturing an aluminum alloy plate used for a cap.

[0002]

2. Description of the Related Art A pure aluminum alloy plate used for forming a cap is
Usually, it is printed on the surface in the form of a plate, and then press-drawn to form a cap. Therefore, if the ear rate is high, the characters and pictures after molding the cap become messy. Therefore, it is required that the ear rate is low and the surface quality is excellent.

As a method for producing such an aluminum alloy sheet for forming, a DC cast alloy ingot is homogenized, followed by hot rolling, cold rolling and annealing. In order to satisfy the characteristics, the following manufacturing methods are adopted.

First, the pick-up is one in which the roll coating is peeled off and embedded in the plate during hot rolling, or a part of the plate surface locally adheres to the roll and is peeled off. It is a defect that becomes clear. As measures to prevent this, management of rolling oil, driving of brush rolls, and optimization of hot rolling conditions such as not raising the hot rolling temperature have been carried out.

Grain streaks are defects that occur in stripes along the surface after cap formation. This is due to the fact that the fibrous structure produced by hot rolling remains as a texture only by performing annealing, causing recrystallization between hot rolling passes and forming a fibrous structure. It is considered effective to erase them. Specifically, it is achieved by increasing the reduction amount of each pass of hot rolling and raising the rolling temperature.

As for the ear ratio, a low ear material is obtained by optimizing the homogenization treatment conditions, the plate thickness after hot rolling and the final cold rolling ratio.

Although the conditions have been optimized as described above, the following two major problems are currently occurring. The first problem is that manufacturing conditions that completely satisfy all of the above have not been obtained. That is, it is desirable to lower the hot rolling temperature in order to improve the pickup level, but this tends to worsen the grain streak.

The second problem is that differences in characteristics occur in the width direction and the length direction in the same rolled material. Specifically, the ear ratio is remarkably generated, and the product having the ear width of about 0% at the center of the width and length of the product coil may vary from −6% to + 6% at the width and the end of the length. Occur. Furthermore, grain streak occurs only at the edge of the plate width,
The pickup level at the center of the board width may deteriorate. When such variations occur, the yield of products is extremely reduced, which is not preferable in manufacturing. It is considered that this is because the cooling rate during casting is higher at the widthwise end portion and that a temperature difference occurs in the widthwise direction and the longitudinal direction during hot rolling. It is difficult to prevent.

[0009]

The present invention has been made in order to solve the above problems, and has excellent surface quality such as pickup and grain streak, and has a low earing rate in the drawing process and variations in the coil. This is a method for producing an aluminum alloy sheet for forming which has a small amount of defects.

That is, according to the present invention, Si of more than 0.5 wt% and 2.0 wt% or less, Fe of more than 0.8 wt% and 2.0 wt% or less and S is added.
Cu containing 0.5 wt% or less, containing i and Fe in a total amount of 3 wt% or less
Containing 0.2% by weight or less of Ti or 0.05% by weight
After homogenizing an Al alloy ingot containing any one or two of the following B and the balance substantially consisting of Al, hot rolling, cold rolling and annealing are performed to form an aluminum alloy sheet for forming. 120mm in hot rolling in the method of manufacturing
Rolling from the following plate thickness in 8 passes or more, and 30 ~ 60
At least one of the hot rolling passes with a plate thickness of mm is performed after the fifth pass from the plate thickness of 120 mm and at a rolling rate of 30% or more, and the end temperature of the hot rolling is set to 280 ° C or less. It is characterized in that the cold rolling rate up to the final product is 40 to 98%.

[0011]

First, the reason why the alloy composition of the present invention is limited as described above will be explained. Si has the function of improving the product strength and further improving the formability such as LDR (limit drawing ratio). However, if the content is 0.5 wt% or less, LD
2.0 wt% because R is too low to be used as cap material
If the content exceeds the above, not only improvement in moldability can be expected, but
Ear ratio increases in the 0-90 ° direction, and A1-Fe-
A Si-based intermetallic compound is generated, which causes a problem of opening the cap such that the cap cannot be normally opened.

Fe has a function of refining recrystallized grains generated during annealing of a product, and is effective in improving moldability and preventing rough skin. However, if the content is less than 0.8 wt%, the effect is not sufficient, and if it exceeds 2.0 wt%, the ear rate increases in the 45 ° direction.

Further, if the total amount of Si and Fe exceeds 3 wt%, work hardening during molding proceeds too much to increase the strength, and the toughness deteriorates to give a brittle product, which causes the problem of opening. Will occur.

Next, Cu reduces variations in ear ratio, and further improves strength and formability.

Ti and B are contained for the purpose of refining the cast structure, but Ti exceeds 0.2 wt% and B is
Even if it exceeds 0.05 wt%, the above effect will be saturated.

Further, in the present invention, in addition to the above elements,
Add 0.5 wt% or less of Mg for the purpose of improving strength,
Even if 0.5 wt% or less of Mn is added for stabilizing the ear ratio, and 0.3 wt% or less of Cr or Zr 0.3 wt% is added for stabilizing the crystal grains, the production method of the present invention. Is not affected at all.

Further, as additive elements other than the above, or as unavoidable impurities, if each is 0.05 wt% or less and a total of 0.15 wt% or less, those elements affect the remarkable characteristics of the present invention. Since it is not used, it may be added.

Next, the manufacturing method will be described. The alloy ingot used in the present invention may be produced by the usual semi-continuous casting method. Conventional casting causes a difference in cooling rate in the width direction, which causes Fe in the width direction,
Although a difference in the amount of solid solution of Si was generated and the characteristics were varied, according to the method of the present invention, the variation caused by this does not occur.

First, the aluminum alloy ingot having the above composition is subjected to a homogenizing treatment. The homogenizing treatment may be performed after the face-cutting and before the hot rolling, or may be separately performed as the homogenizing treatment before the heating in the hot rolling. In addition, if a homogenization treatment is performed in advance, then after chamfering and reheating, and then hot rolling,
The oxide film on the surface of the ingot before rolling is reduced, which is effective for improving the surface quality. Further, the homogenization treatment temperature is preferably 600 ° C or lower, and particularly excellent earing characteristics are exhibited at around 560 ° C.

In the present invention, in hot rolling, rolling with a plate thickness of 120 mm or less is performed with 8 or more passes, and the end temperature of hot rolling is 280 ° C. or less. This is done to improve the pickup level and eliminate variations in the product characteristics within the coil. In this way, by increasing the number of rolling passes, the rolling ratio of each pass is lowered, and the end temperature is lowered below the usual temperature of 300 ° C., so that the pickup level is significantly improved.

Now, the reason why the variation in characteristics within the coil can be prevented by the above hot rolling conditions will be described below. First, regarding the pickup, since it is improved as a whole for the above reasons, it has excellent characteristics at any position in the coil.

Regarding grain streak, these characteristics are extremely deteriorated only by the number of passes and the end temperature of the hot rolling conditions. This is because the conditions for hot rolling in the present invention are such that recrystallization does not occur near the final pass of hot rolling. Therefore, in the present invention, at least one of the number of rolling passes of hot rolling carried out with a plate thickness of 30 to 60 mm is used.
The condition is added that the pass is performed after the fifth pass after counting the plate thickness of 120 mm or less and the rolling rate is 30% or more. According to such a rolling pass, fine recrystallization occurs only in the extreme surface layer portion of the plate, and grain streak is improved. This pass is performed after the 5th pass counting below 120 mm as described above. However, if this pass is performed below the 5th pass, the effect of strain accumulation due to the rolling passes up to that point is not sufficient, so recrystallization is sufficient. It does not occur and grain streak does not improve. Also, when the rolling ratio is less than 30%, the recrystallization does not proceed sufficiently and the grain streak is not improved.

Next, regarding the ear rate, by performing the hot rolling conditions of the present invention, it is possible to eliminate variations in the ear rate in the width and longitudinal direction of the coil. That is, conventionally, it has been considered that the ear ratio can be lowered by cold rolling and annealing conditions, and the hot rough rolling condition has been determined by pickup, grain streak and productivity. By doing so, it is possible to surely reduce the ear rate at the center of the width and the longitudinal direction, but there was a difference in the ear rate values in the coil. Therefore, when the inventors conducted a detailed study on the mechanism of occurrence of the variation in the ear rate, the causes of the variation were 1 recrystallization behavior and 2 precipitation in a pass near the final rolling pass in hot rolling. It turned out to be in behavior. That is, in hot rolling, dynamic recovery occurs during the rolling pass, and the amount of strain accumulated in the sheet material before the start of recrystallization is small.Therefore, the recrystallization behavior that occurs between rolling passes Is very susceptible to the temperature of the plate during recrystallization and the solid solution / precipitation state. Therefore, there is a difference in the recrystallization behavior due to the variation in the amount of solid solution elements in the width direction caused by casting, the difference in the width during hot rolling, and the temperature difference in the longitudinal direction, which causes variations in the ear rate.

The above 1 will be described in more detail.
Generating recrystallization in the vicinity of the final pass of hot rolling is generally performed to improve grain streak, but the temperature at the edge of the strip width is lower than at the center, so there is a difference between the rolling pass and the pass. In some cases, the recrystallization that occurs between the ends is not completely completed. In such a case, a large amount of rolling texture remains at the end portion as compared with the center portion of the plate width in which recrystallization is completely completed, so that 45 ° ears are strongly generated. Even if the plate temperature is high overall and recrystallization occurs on the entire surface of the plate in the vicinity of the final pass of the hot rough rolling, if there is a difference in temperature in the plate material or in the solid solution / precipitation state, The recrystallized structure at the width end includes many cubic orientations, but in this case, the ear rate at the plate end is 0-90 °. And, once such a difference in ear ratio occurs, it is not easy to eliminate the difference in a subsequent process.

As described above, in addition to the variation in the earrings occurring during hot rolling and remaining in the final product, the recrystallization texture produced during final annealing is affected by the amount of solid solution and the precipitation state before annealing. The susceptibility to noise is also a cause of increasing the variation of the ear rate in the coil. This phenomenon is remarkable when recrystallization occurs in the plate thickness near the final pass of hot rolling (a recrystallization texture is formed in the final pass, from the plate thickness there to the plate thickness during annealing). Since the amount of work is small, annealing is performed in a state where the rolling texture is not fully developed, so it is easily affected.) If hot rolling cannot eliminate the difference between the solid solution and precipitation states of the sheet, it will be formed during annealing. The recrystallized texture that occurs is greatly changed.

The hot rolling conditions of the present invention have been determined based on the above-mentioned investigations. By increasing the number of rolling passes, rolling at a plate thickness of at least 120 mm or less is less likely to cause recrystallization, and rolling is performed. By increasing the amount of precipitation, the difference in the ear ratio in the width direction is eliminated. That is, if recrystallization does not occur during hot rolling, no difference in earrings occurs during hot rolling, and by further preventing recrystallization, the rolling texture is strongly integrated, and the hot rolling sheet By eliminating the difference in the precipitation state, it is possible to eliminate the variation in the ear rate that occurs during annealing due to the solid solution / precipitation state.

The starting temperature of the hot rolling is 480 ° C or lower and 38
0 ° C or higher is desirable. This is because the condition of 480 ° C or lower is for improving the pickup level, and the condition of 380 ° C or higher is for producing fine recrystallized grains in the surface layer portion with a plate thickness of 30 to 60 mm. And a temperature of 430 ° C. or less is most recommended. This is because if the hot rolling start temperature is 430 ° C or lower, recrystallization in the initial pass of hot rolling can be prevented,
This is because the rolling texture is formed from a sheet thickness thicker than 120 mm, so that the rolling texture before annealing is strongly integrated, and the variation in ear ratio is further reduced.

In the present invention, the number of rolling passes for rolling with a plate thickness of 120 mm or less is set to 8 or more. The 120mm referred to here
Is the starting plate thickness of the rolling pass. Conventionally, it is usually carried out in 5 passes or 6 passes. However, when the number of passes is less than 8 in this way, the rolling rate for each rolling pass increases and the temperature decrease to the final pass is insufficient, so that hot rolling In the vicinity of the final pass, the whole plate is likely to be recrystallized, resulting in uneven earing rate. Furthermore, since the number of rolling passes is small and the amount of precipitation is small, the effect of eliminating the difference in the amount of precipitation in width and length is insufficient due to the progress of precipitation, and the recrystallization behavior is different in the annealing after cold rolling, resulting in variation in ear ratio. It will be.

Although the rolling reduction of each pass is not specified here,
When the rolling reduction is 40% or less, recrystallization due to rolling is prevented and more stable properties are obtained. The reduction ratio of each rolling pass is tn, t which is the thickness before and after one rolling pass.
If n + 1, {(tn-tn + 1) / tn} × 100
(%).

In the present invention, rolling conditions up to a plate thickness of 120 mm are not particularly specified, but even when rolling with a plate thickness exceeding 120 mm, if the rolling ratio of each pass is 40% or less, rolling from a plate thickness greater than 120 mm is performed. Since the texture is formed, the rolling texture before annealing is strongly accumulated, which is more effective in reducing the variation in the ear rate.

Further, in the present invention, it is recommended that the rolling temperature at a sheet thickness of 120 mm or less is 430 ° C. or less. This is for improving the pickup level and stabilizing the earring rate, and for the latter, it is for preventing recrystallization from progressing between the passes of each rolling pass. When rolling at a temperature above 430 ° C, it is recommended that the rolling amount of each rolling pass be 30% or less and the time between passes be within 5 minutes.

In the present invention, rolling with a plate thickness of 120 mm or less is specified, but especially when rolling with a plate thickness of 30 mm or more and 60 mm or less and a rolling rate of 30% or more, the rolling end temperature of the pass is 330 ° C.
Above 400 ℃ is desirable. This is because if the temperature is lower than 330 ° C, recrystallization may not proceed sufficiently, and if the temperature exceeds 400 ° C, the recrystallized grains may become coarse and grain streak may decrease.

Regarding the above-mentioned ear ratio, the state in which recrystallization has not occurred in hot rolling means a state in which the recrystallization rate is 40% or less. The reason for recrystallization in hot rolling is that the accumulation of rolling texture is reduced by recrystallization, but when the recrystallization rate is 40% or less, most of the recrystallized grains are Is a recrystallized grain having the same orientation as that of the rolling texture, so that the accumulation of rolling texture hardly decreases. Therefore, in hot rolling, even if at least one of the rolling passes with a plate thickness of 30 to 60 mm is performed after the fifth pass of the passes counting from a plate thickness of 120 mm or less and the rolling rate is 30% or more, in this case, the maximum Since it recrystallized from the surface only about 20%, there is no problem in reducing the variation in the ear ratio, on the contrary, prevents the rolling texture at the end of hot rolling from excessively developing,
It has the function of lowering the ear rate of the final product.

In the present invention, hot rolling is carried out so that the end temperature is 280 ° C or lower. This is because when the rolling is completed at a temperature higher than 280 ° C, recrystallization occurs in the central portion where the coil is hard to be cooled during cooling, which causes variations in the ear rate within the coil. Further, the final plate thickness of the hot rolling is determined by the product plate thickness, but may be any plate thickness that can carry out the cold rolling conditions of the present invention, usually 3 to 12 mm, and the applicable product plate thickness is 0.1 to 0.5. It is about mm.

The hot rolling may be carried out by different rolling mills for hot rough rolling and finish rolling, or may be carried out by one rolling mill.

The coil which has been hot-rolled is cold-rolled and annealed. In the present invention, the cold-rolling rate up to the final product sheet thickness is 40% or more and 98% or less. In this way, the cold rolling rate
The reason for setting 40 to 98% is to reduce the ear rate. However, if the cold rolling rate is less than 40%, the working texture is insufficient and the ears become large at 0-90 °. On the other hand, if the cold rolling rate exceeds 98%, even if annealing is performed in the intermediate step, it will be 45 °. This is because the ears cannot be made smaller.

Next, the annealing condition is not particularly specified as long as it is a condition that completely recrystallizes. Generally, batch annealing is performed at 300 ° C to 450 ° C for 0.5 to 6 hours, and continuous annealing is 430 ° C to 580 ° C at 0.5 to 6 hours.
It should be about 60 seconds.

[0038]

The present invention will be described in detail below based on examples. Aluminum alloys (A to F) having the compositions shown in Table 1 were each cast into ingots each having a thickness of 500 mm and a width of 1000 mm by ordinary DC casting.
~ 6 types were cast.

[0039]

[Table 1]

Further, as shown in Table 2, conditions of homogenizing treatment, chamfering, and hot rolling to be applied to the alloy ingot are set up to. Then, these alloys and these rolling conditions are combined as shown in Tables 3 and 4, homogenization treatment, chamfering and hot rolling are performed, and then cold rolling and annealing are performed under the conditions shown in Tables 3 and 4. Inventive method No. 1 to 5 and comparative method No. 6 to 14
Manufactured rolled coil.

For each coil thus obtained, the pickup, grain streak, and ear ratio were examined at six positions in the widthwise end and center at the front, center, and rear in the longitudinal direction, and the results were obtained. The results are shown in Tables 3 and 4. Here, the pickup visually inspects the plate surface, and the grain streak is visually inspected after etching the plate with aqua regia, and as a result, ◎ when these are superior to the normal material, ○ when they are equivalent, poor, When it is shown, it is indicated by x. Regarding the ear rate, the blank diameter was 61 mm, the punch diameter was 33 mm, and the cup was squeezed to 0.
The same is shown in Tables 3 and 4 with the −90 ° ear as the + ear and the 45 ° ear as the − ear.

Further, cap products were prepared from 6 positions of each of the above-mentioned rolling coils, and the cap opening torque values of the caps were measured, and the cap values were compared with the torque values of ordinary materials to obtain good results. Is shown in Table 3, with ⊚ in place, ○ in equivalent, and X in inferior.

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

According to Tables 3 and 4, the rolled coils produced by the method of the present invention are both excellent in pick-up and grain streak, have a low earing rate in drawing, and have little variation in their characteristics within the coil. It can be seen that the plugging property is also good.

[0047]

As described above, according to the present invention, the surface quality of the aluminum alloy plate material for forming is excellent, the earring ratio is low in the drawing process, and the variations thereof are small. Since the plugging property is good, a remarkable effect such as obtaining a particularly excellent plate material for a cap can be obtained.

Claims (1)

Claims: 1. More than 0.5 wt% and less than 2.0 wt% Si, 0.8
Fe of more than 2.0 wt% and less than 2.0 wt%, containing Si and Fe in a total amount of 3 wt% or less, containing Cu of 0.5 wt% or less, and further containing Ti of 0.2 wt% or less or B of 0.05 wt% or less. In a method of producing an aluminum alloy sheet for forming by performing homogenization treatment on an Al alloy ingot containing 1 type or 2 types and the balance being substantially Al, performing hot rolling, cold rolling and annealing. In hot rolling, rolling from a sheet thickness of 120 mm or less is performed in 8 passes or more, and at least one of hot rolling passes performed in a sheet thickness of 30 to 60 mm is the 5th pass or more after counting from a sheet thickness of 120 mm and A method for producing an aluminum alloy sheet for forming, characterized in that the rolling rate is 30% or more, the end temperature of hot rolling is 280 ° C or less, and the cold rolling rate until the final product is 40 to 98%. ..