JP3409195B2 - Aluminum alloy hard plate for forming and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy material for forming and processing, and more particularly to an aluminum alloy material suitable for a metal can for beverages, especially for a DI can as a can body, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a beverage can body (DI can) is 300
Hard plate material of 4 alloy is used. There are roughly two types of manufacturing processes for this material. One is a manufacturing process in which the hot-rolled material is annealed (omitted in some cases) and then cold-rolled to make the product sheet thickness. The other process is a manufacturing process in which the hot rolled material is subjected to cold rolling, and then CAL annealing and cold rolling are performed to obtain a product sheet thickness.

In the former manufacturing process as well, there are two types of methods depending on the required strength (pressure resistance after can making), which differs depending on the annealing method. That is, batch type (medium strength material: gradually heated and slowly cooled) and CAL (high strength: Japanese Patent Application No. 1-2226746).
No.). In each case, the earing rate after drawing is small and the yield is excellent. However, it has a larger crystal grain than other manufacturing steps described later and is inferior in moldability (particularly ironing workability).

On the other hand, the latter manufacturing process is a manufacturing process in which a hot rolled material is subjected to cold rolling, and then CAL annealing and cold rolling are performed to obtain a product sheet thickness.
(Cu and Mg are solid-dissolved and strength is increased by baking hard in the can making process), and since annealing is performed after cold rolling, the crystal grains are fine and especially ironing workability, which is the main forming, is excellent. is there.

[0005]

However, in recent years in thinning and lightening the weight, in addition to the bottom of the can, DI molding and painting printing are performed.
Thinning of the neck portion after (baking) is an important issue, and a material that can suppress the occurrence of wrinkles and the occurrence of cracks due to subsequent flange processing is required for thinning the neck portion.

In order to meet this demand, it is important that the bottom of the can has high strength and the necked part has low strength. From this point of view, there is a need for a high-strength material that has a small work hardening and does not cause much bake hard. In response to this, the present inventors have already made some proposals (eg, Japanese Patent Application No. 3-56196). The method is to add C to the hot rolled material described above.
This is a process of performing AL annealing and then cold rolling into a product. However, this material has a problem that it is inferior in ironing workability as compared with a material (grain fine) which is subjected to CAL annealing after cold rolling.

In view of the above problems, it is an object of the present invention to provide an aluminum alloy hard plate having high strength and excellent formability, particularly ironing workability, and a method for producing the same.

[0008]

In order to solve the above-mentioned problems, the inventors of the present invention have made extensive studies on improvement measures that can particularly improve the ironing workability, and developed the present technology here.

That is, according to the present invention, Mn: 0.85-1.
15%, Mg: 0.90 to 1.50%, Fe: 0.35 to 0.5.
55%, Si: 0.15 to 0.30%, Cu: 0.15 to 0.3.
30% and Zn: 0.15 to 1.0% with the balance being Al
And a crystal grain width of 25 to 40 μm in the final cold-rolled sheet state which is composed of unavoidable impurities and is not subjected to finish annealing.
The relationship between tensile strength (TS) and proof stress (YS) is TS / YS = 1.
The gist is an aluminum alloy hard plate for forming, which is characterized by having an elongation of 05 or more and an elongation of 5% or more.

Further, the manufacturing method is as follows. The Al alloy ingot having the above chemical composition is subjected to soaking at 580 to 630 ° C. for 2 hours or more, and then cooled to perform rough hot rolling and finish hot rolling. Hot rolling starting temperature of 450 ~ 52
0 ° C., the temperature before hot rolling is 400 to 450 ° C., and the temperature immediately after hot rolling is 300 to 350 ° C., thereby controlling the crystal grain width in the hot rolled plate to 25 to 40 μm. This hot-rolled sheet is further heated / cooled at 100 ° C /
min or more, continuous annealing within a range of 400 to 600 ° C and a holding time of 10 min or less, and then cold rolling with a heat generation time between passes of 10 min or less, a rolling reduction of 80% or more, and a winding temperature at a final plate thickness of 130 ° C. The feature is that it is performed under the above conditions.

[0011]

The present invention will be described in more detail below. First, the results of the study leading to the knowledge of the present invention will be described.

The present inventors have conducted various studies on ironing workability, and have found that the following improvements are important for improving ironing workability. In other words, refinement of crystal grains: It is important that the crystal grains are uniformly fine in the coil, which leads to reduction in crack susceptibility. Further, even if the material is not as fine as the material subjected to CAL after cold rolling, if it is uniform, the ironing workability is considerably improved. Deterioration of material strength: Deterioration of material strength lowers the deformation resistance during ironing and also reduces crack susceptibility. However, it is necessary to satisfy at least the required strength (can bottom strength: strength after baking).

However, in the step of subjecting the hot rolled sheet to CAL annealing and then cold rolling, it was very difficult to satisfy the above. This is because the size of the crystal grains is determined by the hot-rolled sheet, and in the subsequent CAL annealing, the crystal grains do not become small even if they become large. Therefore, a detailed investigation was conducted on the components, soaking, and hot rolling with respect to the refinement of crystal grains of the hot rolled sheet. As a result, Fe and Mn, which become nuclei for recrystallized grains,
If the number of grains is increased, the crystal grains become finer, but the compound becomes larger and the formability is lowered. If hot rolling is a method of increasing strain energy (for example, water cooling), although it is effective for refining crystal grains, problems such as poor stability in the coil and poor surface quality have been clarified.

As a solution to such a problem,
The present inventors have clarified detailed tests and mechanisms in the conventional high temperature soaking (often described in existing patent publications at 500 ° C. and 550 ° C. or higher) regions, and the main object of the present invention is to solve the problems. A certain degree of grain refinement was achieved. This is a system in which a continuous heating furnace is used for the homogenization treatment, and the temperature distribution of the ingot is superior to that of the conventional batch system. By using this method, it is possible to heat to the temperature before burning (around 630 ° C), and
The compound of Mn-Fe (-Si) can be made to be an appropriate size and used as the nucleus of recrystallized grains. Further, the variation in the compound size in the coil is reduced, and the crystal grains are homogenized. Furthermore, it is to perform low temperature rolling (introduction of strain amount) during hot rolling,
This increases the nuclei of recrystallized grains. Specifically, it is to control the temperature of hot rolling start by cooling the ingot after soaking at high temperature. Of course, productivity must be taken into consideration, but the temperature range is 450 to 520 ° C.

Next, detailed tests were conducted on the strength reduction of the material, and the following findings were obtained. Reduction of cold rolling rate to product sheet No heat generation between passes in cold rolling to product sheet.

With respect to the above, it is possible to reduce the thickness of the hot-rolled sheet, but the hot-rolling seizure causes a hot-rolled pattern on the surface of the can after painting and printing, which lowers the commercial value. Therefore,
There is currently a limit to the thickness of hot-rolled sheet. In addition, it is difficult to use conventional rolling technology (single rolling mill, mineral oil as coolant). That is, in the conventional technology, the rolling reduction is 50% at maximum, and the thickness of a general hot rolled sheet is 2 mm.
From the above, cold rolling to around 0.3 mm requires 3 or 4 passes, depending on the coil width, but this causes heat generation between passes.

Briefly described below, heat generation between passes gives recovery (reduction in strength) to the material after cold rolling, which seems to be preferable, but when there is a next pass, it is large in subsequent rolling. Shows work hardening and significantly increases strength. As this continues for 3 or 4 passes, of course the increase in strength,
Variations in the time between passes also cause variations among the coils. Therefore, ideally it is to eliminate heat generation between passes. For that purpose, it is necessary to make the rolling conditions capable of high pressure. Specifically, it is a tandem rolling mill using a water-soluble rolling oil, which can be realized by using this rolling mill.

In addition, as a method for increasing the moldability,
The present invention has been completed based on various findings such as CAL conditions for reducing solid solubility (Cu, Mg), reduction ratio for proper strength and cold rolling temperature (rolling temperature). First, the reason for limiting the chemical composition of the Al alloy in the present invention will be described.

Mn: Mn is effective not only for improving the strength but also for improving the ironing workability due to the proper distribution of the compound Al-Mn-Fe-Si (α phase). However, if it is less than 0.85%, all the effects are small, and if it exceeds 1.15%, the size of the compound increases, leading to a decrease in moldability. Therefore, the amount of Mn is 0.85 to 1.15%.

Mg: Mg is a combination of strength increase and Cu.
(Limited to using CAL) is effective in preventing softening due to baking during can making. However, if it is less than 0.90%, there is no effect, and if it exceeds 1.50%, the strength is greatly increased and the formability is lowered. Therefore, Mg
The amount is 0.90 to 1.50%.

Fe: Fe is a refinement of crystal grains and a compound (α
It is effective in improving formability due to the proper distribution of (phase). However, if it is less than 0.35%, it is not effective, and it is 0.55%.
If it exceeds, the moldability is lowered due to the increase in the size of the compound. Therefore, the Fe amount is 0.35 to 0.55.
%.

Si: Si is effective in improving the formability by forming a compound α phase. However, if it is less than 0.15%, its effect is small, and if it exceeds 0.30%, Mg
₂ Strength increase due to Si becomes too large, leading to deterioration of formability. Therefore, the Si amount is 0.15 to 0.30%.

Cu: Cu is a combination of strength increase and Mg (C
It is effective in preventing softening due to baking during can making. However, if it is less than 0.15%, there is no effect, and if it exceeds 0.30%, the strength is greatly increased and the formability is lowered. Therefore, the amount of Cu is 0.15 to 0.30%.

Zn: Zn is effective in improving the moldability by uniformly refining the compound, but if it is less than 0.1%, the effect is small, and if it exceeds 1.0%, the effect is saturated. . Therefore, the amount of Zn is 0.1 to 1.0%.

Other unavoidable impurities include T
The effect of the present invention is not hindered as long as the impurity level is such that i is 0.1% or less and B is 0.05% or less.

Next, the manufacturing process of the present invention will be described. The Al alloy ingot cast by the normal method is face-cut (5 mm or more) and then subjected to soaking treatment which is the point of the present invention.
As mentioned above, soaking affects the refinement of crystal grains in the hot rolled sheet. In this respect, it is generally less than 600 ° C. under the conventional conditions. That is, in the conventional pit furnace (batch furnace), there is a difference in the heating temperature of the ingot, and there is a risk of burning in the high temperature part, so there is no further heating, and since it is still high temperature (Al -54 for Mg alloy
This is because the effect of soaking at a higher temperature was not clear. On the other hand, in the present invention, the soaking temperature is set to 580 to 630 ° C. If the temperature is lower than 580 ° C, nucleation of recrystallized grains by the compound is small and the effect is small. If the temperature exceeds 630 ° C, burning may occur. More preferably, it is in the range of 600 to 620 ° C. This high temperature soaking is possible by using a continuous heating furnace which is excellent in the uniform temperature distribution of the steel ingot.

Subsequently, hot rolling (rough hot rolling, finish hot rolling) by low-temperature rolling is performed after soaking, and strain is positively introduced during hot rolling. The introduction of strain during hot rolling can further refine the crystal grains in the hot rolled sheet. For that purpose, the ingot is cooled before the start of hot rolling, and hot rolling is started within a predetermined temperature range. The effect of starting hot rolling at a temperature above 520 ° C is small, and 4
If the temperature is lower than 50 ° C, the effect is obtained, but the productivity (time until cooling) is poor. Therefore, the hot rolling start temperature is 450 to 5
Set to 20 ° C. In addition, in order to adjust the starting temperature, a method of cooling inside the furnace and cooling to room temperature after soaking (cooling or forced air cooling),
There is a method of heating to the hot rolling temperature. The former is more productive.

Hot rolling is performed by reverse type rough rolling and tandem finish rolling, and in order to make the crystal grains of the hot rolled sheet fine, it is necessary to control the temperature at the time of finishing rolling. The inlet temperature should be low, but the inlet temperature should be 400-450 to control the outlet temperature within the proper temperature range.
Must be ℃. Also, the outlet temperature is 300 to 3
It needs to be 50 ° C. If the outlet temperature is less than 300 ° C, the entire hot rolled coil cannot be recrystallized, and 350 ° C
If it exceeds the limit, recrystallization will occur, but the crystal grains will become coarse.
(Growth of crystal grains) is caused. The reason for recrystallizing the entire coil after hot rolling is to obtain fine recrystallized grains,
This is because if the remaining partially unrecrystallized grains are recrystallized by subsequent annealing, the crystal grains become coarse.

The crystal grain width of the hot rolled sheet obtained under the above conditions is 25 to 45 μm. However, in this range, the crystal grain changes depending on the thickness of the hot-rolled sheet, and becomes larger as the sheet thickness of the hot-rolled sheet increases. Although the thickness of the hot rolled sheet is not regulated in the present invention, it is generally 1.5 to 3.0 mm considering the sheet thickness of the product and the required strength.

The hot rolled sheet (coil) was then subjected to continuous annealing (CA
L) is applied. This is to obtain appropriate strength and moldability, and among the chemical components of the present invention, it is particularly important to control the amounts of Cu and Mg. If it is less than 400 ° C, the solid solution amount of Cu and Mg is small, and the baking strength at the time of can making cannot be obtained.
On the other hand, when the temperature exceeds 600 ° C, the solid solution increases,
Although the strength can be secured, it leads to deterioration of moldability. Therefore, the heating temperature is set to 400 to 600 ° C. Also,
If the heating / cooling rate is slow, the amount of solid solution decreases, and the strength also becomes insufficient. Therefore, the heating / cooling rate is 100 ° C / min.
That is all. The holding time for heating varies depending on the heating temperature, but 10 minutes or less is appropriate.

Next, cold rolling is performed, which is the second point of the present invention. The annealed hot rolled sheet is cold rolled into a product. Cold rolling is carried out several times depending on the relationship between the hot rolled sheet thickness and the product sheet thickness. In this case, recovery occurs due to self-heating (about 100 ° C. in normal cold rolling) during the cold rolling. This recovery causes an increase in strength due to large work hardening in the subsequent cold rolling, and a considerable increase in strength can be obtained by repeating this, but it is not possible to maintain constant recovery (heat generation between passes) due to self-heating in production. difficult. Therefore, the variation becomes large, and when the strength is high, the formability is deteriorated. If the strength is low, the strength of the can is insufficient. In the present invention, the variation in strength during cold rolling is significantly reduced, so the heat generation between passes is extremely reduced. There is no problem if the heat generation time between passes (time between rolling and the next rolling: usually 10 hours to several days) is within 1 hr, but in the present invention, the heat generation time between passes (from hot rolled sheet to product sheet) is 10 min. Within

Further, in order to secure the strength, it is necessary to set the total rolling reduction to 80% or more. Furthermore, DI can molding
Strength improvement (TS / YS = 1.05 or more) and appropriate ductility (elongation rate of 5% or more) are required to improve performance in (drawing-ironing, overhanging, etc.), and winding at the final plate thickness Temperature less than 130 ℃, tensile strength (TS) and yield strength
If the relationship of (YS) is less than TS / YS = 1.05 and the elongation is less than 5%, the effect cannot be obtained. Therefore, the winding temperature at the final plate thickness is 130 ° C. or higher.

Only cold rolling is required to improve formability.
It is necessary to show excellent properties when the material is recovered (without finish annealing). According to the present invention, the crystal grain width is 25 to 40 μm and the relationship between the tensile strength (TS) and the proof stress (YS) is TS / YS =
An elongation rate of 1.05 or more and an elongation rate of 5% or more can be obtained. If the crystal grain width is less than 25 μm, the ear ratio at the time of manufacturing the cup becomes very high, and there is a risk of cutting the edges during DI processing.
If it exceeds μm, workability (drawability, ironing property) is deteriorated, which is not preferable. On the other hand, if the TS / YS ratio is less than 1.05, the difference between the start of plastic deformation and the fracture is too small, resulting in a decrease in workability (drawability, ironing property). Further, if the elongation is less than 5%, wrinkles occur at the cup mouth during cup molding,
Flange cracking of the DI can due to the wrinkles is likely to occur during neck flange molding, and can bottom wrinkles are likely to occur during DI processing. If the wrinkle pressing force is increased in order to prevent wrinkles on the bottom of the can, the processing becomes very strict and defects such as cracking of the can body or pinholes in the can body occur, which is not preferable.

Next, examples of the present invention will be described.

[0035]

Example 1 A cold-rolled sheet was manufactured from an Al alloy ingot having the chemical composition shown in Table 1 by the manufacturing process shown in Table 2. Table 3 shows the mechanical properties, formability and can strength after cold rolling and baking.
It shows in Table 4. The evaluation of the formability of the product plate for can manufacturing and the investigation of the can strength were carried out as follows.

The limit drawing ratio (LDR) is the drawing ratio that can be formed by changing the blank diameter using an Erichsen tester.
It was calculated by (blank diameter / punch diameter). Punch diameter is 33mm
φ, using Dydro-N as lubricating oil, and wrinkle holding force is 5
It is 00 kgf. The overhang property (Erichsen value) was evaluated by the Erichsen test B method of JIS. For ironing workability, using a squeeze cup manufactured with a blank diameter of 140 mmφ and a punch diameter of 90 mmφ, the final ironing rate was 4 with a DI processing machine.
A can-making test of about 50,000 cans was conducted with 1%, and the tear-off rate at that time was evaluated. The can size was 350 cc, and the lubricating oil used was a water-soluble lubricating oil.

Regarding the formability after baking, the obtained DI can was baked at 200 ° C. and subjected to 4-step necking. The processing distribution is 2 mm / step. It was evaluated by the success rate (neck success rate) in which a 4-step neck was formed. Furthermore, 4
The hole of the flange portion was expanded (expanded) with a punch with a 90 ° cross angle to the stepped neck can, and the flange ratio was 12% (flange diameter 65 m
The success rate (flange success rate) at mφ and neck diameter of 58 mmφ was evaluated. Further, the pressure resistance and buckling strength, which are can strength, were determined by hydraulic load and axial compression.

As shown in Tables 3 and 4, Nos.
Nos. 1 to 4 are Nos. 5, No. 6, and Nos. 10 to N of the comparative examples.
Compared to No. 15, it has excellent ironing formability (tear-off rate), and has substantially the same formability as No. 7 to No. 9 of Comparative Example, but in can strength. Are better.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

Example 2 A cold-rolled sheet was manufactured from the Al alloy ingot having the chemical composition shown in Table 5 by the manufacturing process shown in Table 6. Note that step A is the step of the present invention, and step B is the step of the comparative example. Tables 7 and 8 show the mechanical properties, moldability and can strength of the cold-rolled sheet and after baking. The material obtained in Process A of the present invention has an appropriate crystal grain width, and is clearly superior to Process B in moldability (particularly tear-off rate).

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

[Table 8]

[0048]

Example 3 From the Al alloy having the chemical composition shown in Table 9, Table 10
A cold-rolled sheet was manufactured by the manufacturing process shown in. The process C is the process of the present patent, and the process D is the process of the comparative example, and the time between passes in cold rolling is different. Tables 11 and 12 show the mechanical properties, formability and can strength after cold rolling and baking. Compared to the strength of the base plate of the material produced by process D is too high,
The material according to the process C of the present invention is obviously superior in moldability (particularly the tear-off rate).

[0049]

[Table 9]

[0050]

[Table 10]

[0051]

[Table 11]

[0052]

[Table 12]

[0053]

Example 4 From the Al alloys having the chemical components shown in Table 13, Table 1
A cold rolled sheet was manufactured by the manufacturing process shown in FIG. Step E is the step of the present invention, and step F is the step of the comparative example, and the winding temperature in cold rolling is different. Tables 15 and 16 show the mechanical properties, formability and can strength of the cold-rolled sheet and after baking.
Proper strength balance (TS /
While the YS ratio) is broken, the material according to the process E of the present invention is obviously superior in moldability (particularly the tear-off rate).

[0054]

[Table 13]

[0055]

[Table 14]

[0056]

[Table 15]

[0057]

[Table 16]

[0058]

As described in detail above, according to the present invention,
Since it has a predetermined high strength and is excellent in moldability, especially ironing workability, the effect of enabling the material of the aluminum can to be thin is extremely remarkable.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masatoshi Koide               15 Kinugaoka, Moka City, Tochigi Prefecture God Inc.               Inside the Tooka Works Moka Works                (56) Reference JP-A-4-272151 (JP, A)                 JP-A-2-270930 (JP, A)                 JP-A-1-96346 (JP, A)                 JP-A-56-139646 (JP, A)

Claims (3)

(57) [Claims] 1. Mn: 0.8 by weight% (hereinafter the same)
5 to 1.15%, Mg: 0.90 to 1.50%, Fe:
0.35-0.55%, Si: 0.15-0.30%,
Cu: 0.15 to 0.30%, Zn: 0.10 to 1.0
%, The balance consists of Al and unavoidable impurities,
In the final cold-rolled sheet state without finish annealing, the crystal grain width is 25 to 40 μm, the tensile strength (TS) and the yield strength (Y
The aluminum alloy hard plate for forming DI cans, wherein the relationship S) is TS / YS = 1.05 or more and the elongation is 5% or more. 2. Mn: 0.85 to 1.15%, Mg:
0.90 to 1.50%, Fe: 0.35 to 0.55%,
Si: 0.15 to 0.30%, Cu: 0.15 to 0.3
0%, Zn: 0.10 to 1.0%, balance Al
580 to an Al alloy ingot containing inevitable impurities
A soaking treatment is performed at 630 ° C. for 2 hours or more, followed by cooling to perform hot rolling including rough hot rolling and finish hot rolling. The hot rolling start temperature is 450 to 520 ° C., and the temperature before finish hot rolling is 40.
0-450 ℃, the temperature immediately after hot rolling is 300-350
The temperature of the crystal grain width in the hot-rolled sheet is controlled to 25 to 40 μm by carrying out under the condition of 0 ° C., and this hot-rolled sheet is further kept at a heating / cooling rate of 100 ° C./min or more and a temperature of 400 to 600 ° C. within 10 minutes. Continuous annealing, and then cold rolling, the heat generation time between passes is within 10 min, the rolling reduction is 80% or more, and the winding temperature at the final plate thickness is 130 ° C.
It is characterized in that it is carried out under the above conditions, the grain width is 25 to 40 μm, and the relationship between the tensile strength (TS) and the proof stress (YS) is TS / YS =
A method of manufacturing an aluminum alloy hard plate for forming, which has a elongation of 1.05 or more and an elongation of 5% or more. 3. The method according to claim 2, wherein a continuous heating furnace is used for soaking.