JPH0533107A - Production of hard aluminum alloy sheet excellent in strength and formability - Google Patents

Abstract

PURPOSE:To provide a hard aluminum sheet which is minimal in deterioration in strength even if baking finish is applied to a can body material and also has superior curling characteristic and DI formability in spite of its high strength. CONSTITUTION:An ingot of aluminum alloy having a composition consisting of, by mass, 1.0-1.5% Mn, 1.0-1.5% Mg, 0.10-0.30% Cu, 0.15-0.30% Si, 0.25-0.55% Fe, 0.01-0.04% Ti, 0.0001-0.0010% B, and the balance Al with inevitable impurities is subjected to homogenizing treatment at 600-640 deg.C for 1-10hr. Hot rolling is started at 450-550 deg.C and finished at 280-320 deg.C to <=2.2mm thickness. Then, intermediate heat treatment consisting of holding at 180-230 deg.C for 2hr is performed and final cold rolling is done at 60-90% draft.

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 hard plate mainly used for DI bodies, and particularly to a process for producing a plate material having high strength and excellent ear ratio and formability.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for DI body materials that are thin and have high strength for the purpose of cost reduction of the materials. Therefore, the intermediate heat treatment is performed in a continuous annealing furnace in order to increase the amount of added components and age hardenability. Furthermore, a hard plate that has been subjected to a final cold rolling of 60% or more is used as a DI molding material.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
After molding, a polymer resin is coated and baked (around 200 ° C. for several minutes) for the purpose of improving corrosion resistance. At this time, the material is softened, and in particular, the reduction in the strength of the bottom portion of the can leads to a reduction in the pressure resistance strength of the can body, which causes the above-mentioned reduction in thickness to be impossible. Therefore, for the purpose of improving the material strength,
The amount of added components such as Mg and Mn is increased, and heat treatment in a continuous annealing furnace for imparting age hardening is performed.

However, an increase in Mg causes the work hardening to be too large during the ironing process in the DI molding, and the fracture tends to occur. Further, an increase in Mn facilitates the formation of an Al—Fe—Mn-based coarse intermetallic compound during casting, and this becomes the starting point of fracture during DI molding. There is a problem that the continuous annealed material is further hardened by baking during coating, and cracks easily occur during curling of the flange portion due to insufficient elongation of the material.

[0005]

In the present invention, as a result of intensive studies in view of the above problems, the amount of solute Mn is increased by performing the homogenization treatment at a high temperature, and the end temperature of hot rolling and By controlling the precipitation of alloy components by the combination of the subsequent intermediate heat treatments, it is possible to reduce the decrease in material strength during coating baking treatment (hard to soften) and to achieve high strength. The curling processability was also good.

That is, according to the present invention, Mn: 1.0-1.
5% (mass%, the same below), Mg: 1.0 to 1.5%,
Cu: 0.10 to 0.30%, Si: 0.15 to 0.3
0%, Fe: 0.25 to 0.55%, Ti: 0.01 to
An aluminum alloy ingot containing 0.04% and B: 0.0001 to 0.0010% and the balance Al and unavoidable impurities is homogenized at 600 to 640 ° C. for 1 hour to 10 hours, and 450 to Start hot rolling at 550 ° C,
Finish to a thickness of 2.2 mm or less at 320 ° C. or less and 280 ° C. or more, and then 180 to 230 ° C.
The method for producing an aluminum alloy hard plate having excellent strength and formability is characterized by performing intermediate heat treatment for 2 hours or more and performing final cold rolling in the range of 60% to 90%.

The intermediate heat treatment may be controlled by artificially suppressing the cooling of the material that has been hot-rolled in the preceding stage. Further, after the final cold rolling, a final heat treatment of holding at 120 to 180 ° C. for 1 hour or more may be performed. This final heat treatment may be performed by artificially suppressing the cooling of the material that has been subjected to the final cold rolling at 130 ° C. or higher.

The reasons for limiting the requirements of the present invention will be described below.

Mn: Mn in the present invention contributes to strength in two states. In this type of alloy, about 1 μm of Al—Mn—Si based compound precipitates during the temperature rise during the homogenization treatment, and the amount of dissolved Mn decreases. If it is further heated to 550 ° C. or higher, a part of it is redissolved, and the amount of solute Mn increases. Such solid solution Mn is finely precipitated at the time of baking for coating, and suppresses the movement of dislocations, so that it is difficult to soften. After the hot rolling is completed, if the temperature is kept at 180 to 230 ° C., fine Al—Mn-based compounds of 1 μm or less are deposited,
A cold (rolling) subsequent process provides a processed (dislocation) structure that is not easily blunted. If the added amount is less than 1.0%, the above effect cannot be obtained. If it exceeds 1.5%, Al-Fe- is produced during casting.
Coarse Mn-based crystallized substances tend to be formed, which causes breakage during DI processing, which is not preferable.

Mg: An essential additional element that contributes to strength together with Mn. If the addition amount is less than 1%, it is difficult to achieve high strength, and if it exceeds 1.5%, work hardening becomes too large, and breakage easily occurs during DI molding.

Cu: An element capable of improving the softening resistance of the material. In particular, it is finely precipitated during baking of the coating, and has the effect of suppressing softening of the hard plate. If the addition amount is less than 0.10%, the effect cannot be expected so much, and if the addition amount is more than 0.30%, the effect does not change. Si: From the viewpoint of increasing the amount of solute Mn as much as possible during the homogenization treatment, Si needs to be kept low. Moreover, excessive Si is not preferable for the curling workability of the flange portion. If the added amount is 0.3% or less, there is no practical problem. Also, if less than 0.15%, high purity A
Since l metal is used, the cost will increase. Therefore, from the economical viewpoint, the lower limit of the amount of Si added is set to 0.15%.

Fe: Al-Fe-M formed during casting
The n-type crystallized substance is indispensable for improving the seizure resistance of the material and the tool during DI processing. However, if the amount of Fe added exceeds 0.55%, coarse Al—Fe—Mn-based crystallized substances are formed during casting, which is a cause of fracture, which is not preferable. On the other hand, if it is less than 0.25%, the seizure resistance deteriorates, and since a high-purity Al ingot must be used like Si, the cost increases.

Ti: Effectively works for refining the ingot structure and improving the rollability and the formability of a hard plate. If the added amount is less than 0.01%, the above effect cannot be sufficiently obtained,
If it exceeds 0.04%, a coarse compound with B (TiB ₂ )
, And serious defects such as cracks and pinholes occur.

B: Like Ti, it has the effect of refining the ingot structure. If the addition amount is less than 0.0001%, the effect is not sufficient, and if it exceeds 0.0010%, a coarse compound (TiB ₂ ) with Ti is formed and serious defects such as cracks and pinholes occur.

Further, if the ingot structure is refined by adding Ti and B, the effect of increasing the solid solution amount of Mn by quenching during casting and the effect of accelerating the reinfiltration of the Al-Mn-Si compound during the homogenization treatment are obtained. Be brought.

Homogenizing treatment: The homogenizing treatment is usually carried out to remove solute atom segregation during casting. In the present invention, the temperature is set to 600 ° C. or higher in order to partially re-dissolve the Al—Mn—Si-based compound precipitated during the temperature increase. Although this Al-Mn-Si-based compound shows a solid solution tendency when kept at 550 ° C or higher, it is a compound that exists fairly stably. The re-dissolved Mn finely precipitates in the subsequent intermediate heat treatment and contributes to the strength improvement of the hard material. If the holding temperature is 600 ° C or higher, the holding time may be 1 hour or more and 10 hours or less,
Holding at a lower temperature requires a long time, which is industrially disadvantageous. When the holding temperature exceeds 640 ° C., eutectic melting occurs and the surface quality of the plate surface deteriorates, which is inconvenient. When the holding time is in the range of 600 to 640 ° C., the holding time is at least 1 hour, and the holding time is longer than 10 hours, the same effect is obtained, which is industrially disadvantageous. Hot rolling: If the starting temperature of hot rolling is too high, recrystallized grains tend to become coarse and formability deteriorates. Therefore, in the present invention, the upper limit of the hot rolling start temperature is set to 550 ° C. If the starting temperature is too low, the ending temperature will be too low, and the ear rate will deteriorate in the process of the present invention. Therefore, the lower limit of the hot rolling start temperature was set to 450 ° C.

The end temperature of hot rolling is 280 ° C. or higher and 320
It is necessary to set the temperature to not more than 0 ° C. and to make the recrystallized coarse structure a mixed structure in which some dislocation structure due to processing remains. If the temperature is less than 280 ° C, the 45 ° ear of the final plate becomes too high and the material yield deteriorates. If it exceeds 320 ° C., the dislocation structure remaining in the grains disappears, and the fine precipitation in the intermediate heat treatment performed immediately thereafter does not occur uniformly, which is not preferable. On the other hand, if the thickness of the finished sheet for hot rolling is more than 2.2 mm, the amount of cold rolling increases, and the 45 ° edge of the final sheet becomes too high, deteriorating the material yield.

Intermediate heat treatment: The intermediate heat treatment is performed to precipitate fine Al—Mn-based compounds of 1 μm or less in the grains. Al-M that precipitates when kept at a temperature higher than 250 ° C
The size of the n-based compound becomes large and does not contribute to the strength improvement. If the temperature is lower than 180 ° C, it will be necessary to hold it for a long time.
It is industrially disadvantageous. If the holding temperature is in the range of 180 to 230 ° C., the holding time may be 2 hours or longer. Also, in the cooling process after the hot rolling is completed, the temperature is changed from 230 ° C to 180 ° C.
Similar effects can be obtained by artificially suppressing the cooling of the material so that the cooling time to the temperature becomes 2 hours or more.

In order to obtain the effect of this fine precipitation, it is important that the worked structure (dislocation) remains in the plate after hot rolling and that Mn is sufficiently dissolved as a solid solution. A combination of the homogenization treatment at 600 ° C. or higher, the end of hot rolling at 280 to 320 ° C., and this intermediate heat treatment provides a practical level of effect.

Final cold rolling: Cold rolling is performed to improve the material strength. If the rolling amount is less than 60%, sufficient strength cannot be obtained. On the other hand, if it is more than 90%, the 45 ° ear becomes too high and the material yield deteriorates. From the viewpoint of strength and ear rate, the range of 80 to 85% is more preferable.

Final heat treatment: The elongation and drawability of the material are improved, and the cupping molding can be stabilized more easily. Material strength (proof stress) at temperatures higher than 180 ℃
It is inconvenient because of the large decrease. If the temperature is lower than 120 ° C., it is necessary to hold for a long time to obtain the above effect, which is industrially disadvantageous.

[0022]

EXAMPLES The present invention will be described below with reference to examples and comparative examples.

Example 1 The alloys shown in Table 1 were ingoted by a usual DC casting method to prepare test materials under the conditions shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

A coating baking treatment (210 ° C.) was applied to the obtained test material.
(× 10 minutes) A corresponding heat treatment was performed to examine the mechanical properties, ear ratio and curling moldability. The results are shown in Table 3.

The curling moldability of the neck portion was evaluated by the following method. That is, the obtained test material was further cold-rolled by 40% (corresponding to the reduction of the plate thickness of the neck portion) and subjected to the heat treatment corresponding to the above-mentioned coating baking treatment to obtain a test piece. After making holes and applying wax (Johnson Wax No. 700: water = 1: 1), as shown in FIG. 1, the center of the flat punch 3 having a diameter of 10 mm and the hole 4 made in the test piece 1 were formed on the die 2. The punch 3 is set so as to overlap with the center, the punch 3 is bulged at a speed of 0.2 mm / s, and the hole diameter at the time when the test piece is cracked is measured with an optical microscope. As shown in FIG. 2, the hole diameter is indicated by the average diameter of the diameter a parallel to the rolling direction and the diameter b perpendicular to the rolling direction. The larger the hole diameter, the better the curling processability.

[0028]

[Table 3]

The material of the present invention has a proof stress after coating of 270 MPa.
There is above, No. It has higher strength than the conventional material of No. 9. or,
The ear rate is 3% or less, and the characteristics similar to those of conventional materials are obtained even in the hole expanding test. Comparative material No. In No. 4, the homogenization treatment is insufficient, the ear rate is high, and the material yield deteriorates. No. No. 5 has a high earing rate because the hot rolling finish temperature is too low. No. In No. 6, since the finished plate thickness in hot rolling is too thick, the amount of cold rolling is increased and the earring rate is increased. No. In No. 7, the intermediate heat treatment is performed in the continuous annealing furnace. The strength and the ear ratio are good, but the hole expandability (curling processability) is poor. No. No. 8 has a small final cold rolling amount and a low yield strength.
No. Since No. 8 has a different final plate thickness from the other test materials, no comparative investigation was performed in the hole expansion test.

Example 2 The alloys shown in Table 4 were ingoted by a normal DC casting method, and No. 9 or No. A test material was prepared under the conditions of 10. Using the obtained test material, heat treatment equivalent to coating baking (210 ° C. × 10 minutes) was performed in the same manner as in Example 1, and the mechanical properties and the ear rate were examined. Also, with an actual DI molding machine,
(0 can molding), and occurrence of breakage was confirmed. The results are shown in Table 6.

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

The material of the present invention has a proof stress after coating of 270 MPa or more and a good ear rate. It also has excellent DI moldability. Comparative material No. No. 14 has a low Mn content and therefore has low strength. No. In No. 15, since the amount of Mg was too large, the work hardening during ironing was large and the number of fractures was large. 100
Since the number of breaks exceeded 100 cans before forming 0 cans, the test was stopped halfway. No. No. 16 has a large amount of Mn and Fe, and thus coarse crystallized substances exceeding 100 μm are formed during casting.
It became the starting point of cracks during DI processing, and the number of fractures increased. No. In No. 17, a large amount of Ti and B are added, and coarse Ti
The B ₂ compound was formed, and the die forming surface was scratched during DI processing, impairing the properties of the ironing surface, and at the same time, the number of breaks was the starting point of cracking.

[0035]

EFFECTS OF THE INVENTION According to the present invention, even if the body of a can is subjected to a paint baking treatment, its strength is not significantly reduced. Therefore, it is a high-strength aluminum hard plate excellent in curling processability and DI formability. Can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a hole expanding test.

FIG. 2 is an explanatory diagram of a hole diameter measuring method in a hole expanding test. 1 Test piece 2 Dice 3 Flat punch 4 hole

Claims (4)

[Claims] 1. Mn: 1.0 to 1.5% (mass%, the same hereinafter), Mg: 1.0 to 1.5%, Cu: 0.10
0.30%, Si: 0.15 to 0.30%, Fe: 0.
25 to 0.55%, Ti: 0.01 to 0.04%, B:
An aluminum alloy ingot containing 0.0001 to 0.0010% and the balance Al and unavoidable impurities is added to 600 to 6
Homogenize at 40 ° C for 1 hour to 10 hours, 45
Start hot rolling at 0 to 550 ° C., finish to a thickness of 2.2 mm or less at 320 ° C. or less, and finish at 280 ° C. or more, and then perform intermediate heat treatment at 180 to 230 ° C. for 2 hours or more. , Final cold rolling 60% or more 90%
A method for producing an aluminum alloy hard plate excellent in strength and formability, characterized by being applied within. 2. The method for producing an aluminum alloy hard plate excellent in strength and formability according to claim 1, wherein the intermediate heat treatment is controlled by artificially suppressing cooling of the material that has been hot-rolled in the preceding stage. 3. The method for producing an aluminum alloy hard plate excellent in strength and formability according to claim 1 or 2, wherein after the final cold rolling, a final heat treatment of holding at 120 to 180 ° C. for 1 hour or more is performed. 4. The aluminum alloy hard plate excellent in strength and formability according to claim 3, wherein the final heat treatment is performed by artificially suppressing the cooling of the material which has been subjected to the final cold rolling at 130 ° C. or higher. Production method.