JPH07252614A - Production of aluminum alloy sheet for drawing - Google Patents

Abstract

PURPOSE:To inhibit the precipitation and growth of supersaturated solid solution elements, to increase the strength of a final cold rolled sheet, and to improve drawability by specifying a composition and controlling cooling velocity at the time of continuous casting and after hot rolling. CONSTITUTION:The Al alloy has a composition containing, by weight ratio, 0.4-1.5% Mn, 0.8-2.5% Mg, 0-0.25% Cu, 0-0.25% Zn, 0.1-1.0% Fe, and 0.1-1.0% Si. A molten metal of this Al alloy is cast continuously at >=5 deg.C/sec cooling rate R at the time of solidification, under the condition satisfying inequality. After casting, the resulting cast slab is subjected, without cooling, to holding at a temp. not lower than hot rolling temp., followed by rolling. After hot rolling is finished, the resulting plate is cooled at a rate of >=100 deg.C/min and further cold-rolled into a final product of prescribed thickness. Moreover, it is preferable to regulate hot rolling starting temp. to 350-550 deg.C and also to perform rapid cooling down to about 40-70 deg.C by water atomization after the completion of rolling.

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 Al alloy sheet for draw forming, and particularly to continuous casting and hot rolling using an Al alloy containing Mn and Mg as alloy elements,
A method for producing an Al alloy sheet having excellent drawability by controlling the cooling rate during continuous casting and after hot rolling when producing an Al alloy sheet by further cold rolling Is. The Al alloy sheet obtained by the present invention can be utilized for various forming applications including drinking and eating can materials by utilizing its excellent draw formability.

[0002]

2. Description of the Related Art A conventional method for producing an Al alloy sheet for forming, which is used as, for example, food cans and beverage cans, has been generally practiced so far since it is used for ingots produced by a semi-continuous casting method or the like. This is a method of sequentially performing hot rolling, cold rolling, annealing, etc. after subjecting to cutting treatment and homogenizing heat treatment, and the conventional forming Al alloy plate manufactured through such steps has good draw formability. In addition, it also has a certain level of strength, and satisfies the demands of consumers for the time being.

However, in recent years, the demands of consumers have become more severe, and there is a tendency not only to demand higher strength in order to promote weight reduction, but further improvement in moldability is also desired. The demand for cost reduction by improving productivity is gradually increasing.

As a relatively new Al alloy sheet manufacturing technique that meets these demands, a method of immediately sending a continuously cast moving strip to a rolling step to perform hot rolling and cold rolling (hereinafter referred to as continuous casting / direct rolling method). However, a method of omitting the chamfering and homogenizing heat treatment has been studied (Japanese Patent Laid-Open No. 55-27497, Japanese Patent Publication No. 62-5418).
No. 2). According to this method, it is possible to reduce costs by omitting chamfering and homogenization heat treatment, and to prevent solid-solution elements that are solid-soluted in supersaturation during the casting process from precipitating during homogenization heat treatment. It is possible to obtain an advantage that the strength is enhanced.

The continuous casting method adopted at the time of performing such continuous casting / direct rolling method is currently put into practical use is a water-cooled continuous casting method (formed from a fixed water-cooled continuous casting mold into a plate shape). The continuous cast piece that comes out is directly cooled and solidified with cooling water and continuously cast), a twin roll casting method developed by Hunter Engineering Co., Ltd. (the molten metal is supplied between a pair of rotating cooling rolls, Continuous casting method by cooling and solidifying between rolls), belt-type continuous casting method developed by Hatherley Co., Ltd. (supplying molten metal between two movable belt-shaped cooling members and cooling between the belts) Continuous solid plate casting while solidifying), Block type continuous casting method (movable type 2) developed by Swiss Aluminum Co.
A method of supplying a molten metal between two block-shaped cooling members and continuously casting in a plate shape while cooling and solidifying between the blocks).

[0006]

By the way, in the continuous casting / direct feed rolling method which has been put into practical use at present, after continuous casting and direct feed hot rolling, the material is once wound hot and then allowed to cool in the atmosphere. Since the cooling rate at this time, especially the cooling rate on the winding core side is very slow, the composition of the Al alloy used is not necessarily appropriate, and during this period precipitation of a supersaturated solid solution element occurs, and after cold rolling. However, there is a problem of decreasing the strength of.

The present invention has been made by paying attention to the problems of the prior art as described above, and an object thereof is to obtain a moving strip plate continuously cast using molten Al alloy from In the state of holding Al, or when the continuous cast piece is adjusted to a hot rolling temperature or higher and then hot rolled, and further cold rolled to produce an Al alloy sheet, particularly during continuous casting and hot rolling. It is intended to establish a method capable of preventing precipitation of a solid solution element during cooling after hot rolling, increasing the strength of a cold rolled product, and obtaining an Al alloy sheet having good draw formability and the like. .

[0008]

[Means for Solving the Problems] The structure of the method for producing an Al alloy sheet for forming according to the present invention, which has been capable of solving the above-mentioned problems, is as follows. 0.5% or less Cu: 0.25% or less (including 0%) Zn: 0.25% or less (including 0%) Fe: 0.1 to 1.0% Si: 0.1 to 1.0% For an Al alloy satisfying the requirement of, the cooling rate during solidification is R ≧ 5 and R ≧ 7.5 ([Fe] + [Si]) + 2 where R: cooling rate during solidification (° C./sec) [ [Fe], [Si]: after continuous casting under the condition that the content ratio (%) of Fe and Si in the Al alloy is satisfied, immediately after the casting temperature is kept at the hot rolling temperature or more, or the continuous casting The piece is adjusted to a temperature equal to or higher than the hot rolling temperature, hot rolled, cooled at a rate of 100 ° C./min or more after the hot rolling, and further cold rolled. It is those having the spirit in place.

The present invention is based on the above-mentioned structure as a basic idea, and the preferred embodiment or modified embodiment of the present invention will be described in more detail below. 1. As the continuous casting method, a water-cooled continuous casting method, a twin roll type continuous casting method, a belt type continuous casting method, a block type continuous casting method, etc. can be adopted, but the transition time from the continuous casting to the hot rolling step It is preferable to adjust the timing after the inside of the slab has fallen below the solidus temperature and has completely solidified. 2. The starting temperature of hot rolling performed after continuous casting is 35
The range of 0-550 degreeC is preferable. 3. A water spray method is usually used for cooling after hot rolling.
It is rapidly cooled to about 0-70 ° C. 4. In continuous casting, plate-like slabs having a wall thickness of about 4 to 30 mm are usually continuously produced, and hot rolled to obtain 1 to 5 slabs.
mm to 0.1 mm by cold rolling
It is rolled into a thick Al alloy plate. 5. The present invention is a so-called continuous casting in which the temperature of the moving strip obtained by continuous casting is maintained at a hot rolling temperature or higher and immediately hot rolled, and subsequently or once wound and then sent to the cold rolling step. Although it can be advantageously applied to a direct-rolling method, it can also be applied to a method in which after continuous casting, the slab is adjusted to a hot rolling temperature or higher, then hot rolled, and further cold rolled. . 6. In the present invention, it is general that continuous casting, hot rolling, and cold rolling are sequentially performed to finally commercialize the product as a finished cold-rolled sheet, but in some cases, in a state where hot rolling has been completed. It is also possible to commercialize.

[0010]

As described above, in the present invention, the component composition of the Al alloy to be used is defined, the cooling rate at the time of solidification during continuous casting is defined, and the cooling after the hot rolling that is subsequently performed is then defined. By suppressing the precipitation of supersaturated solid solution element by increasing the speed, and even if it precipitates, it is possible to increase the strength of the cold-rolled product by finely and uniformly, and at the same time, after the baking coating heat treatment to be performed thereafter. The present inventors succeeded in obtaining an Al alloy plate having higher yield strength and further excellent deep drawability. Hereinafter, the production conditions including the component composition of the Al alloy defined in the present invention and the cooling rate after hot rolling will be described in detail. First, the reason for defining the component composition of the Al alloy used in the present invention will be described.

Mn: 0.4-1.5% Mn is not only an element which is indispensable for enhancing the strength of the Al alloy plate as a solid solution strengthening element, but also Al-
It also has an action of enhancing ironing workability by forming Fe-Mn-based crystallized substances, and at least 0.4% or more must be contained in order to effectively exhibit these actions. However, if the amount becomes too large, M will not be dissolved completely.
Formability (drawing, ironing, overhanging,
Since there is a tendency for the flanging property) to worsen, it must be kept to 1.5% or less. The lower limit of the Mn content is preferably 0.8%, more preferably 1.1.
%, And the preferable upper limit value is 1.4%.

Mg: 0.8 to 2.5% or less Mg also acts as a solid solution strengthening element, and Al-M
It has the effect of increasing the strength by forming g-type or Al-Mg-Cu-type crystallized substances, and must be contained in an amount of 0.8% or more in order to secure the level of strength intended in the present invention. However, if the content is too large, the formability deteriorates due to an increase in the amount of Mg that is not completely dissolved, as in the case of Mn, so it must be suppressed to 2.5% or less. The preferable lower limit of the Mg content is 1.3%, more preferably 1.6%, and the preferable upper limit thereof is 2.4%.

Cu: 0.25% or less Cu is not always essential, but Al-Mg
Since it has the effect of increasing the strength by the formation of the Cu-based crystallized substance, it is desirable to positively add it when the demand for the strength is high. However, if it is too large, the formability is adversely affected, so it must be suppressed to 0.25% or less. Considering the balance between strength and formability, a more preferable Cu content is in the range of 0.15 to 0.20%.

Zn: 0.25% or less Zn is not an essential component, but it has an effect of enhancing the formability such as drawing and ironing by containing an appropriate amount, and is particularly suitable for applications where severe molding conditions are added. When used, it is preferably contained in a small amount. However, if the amount is too large, not only the moldability tends to deteriorate, but it is also disadvantageous in terms of cost.
% Must be kept below. The more preferable content rate of Zn is 0.16 to 0.22%.

Fe: 0.1 to 1.0%, Si: 0.1
1.0% These elements are effective as elements that further improve the formability and strength. That is, Fe has an effect of forming an Al—Mn—Fe-based crystallized substance to prevent rough skin during molding and also has an effect of enhancing ironing workability, and it is necessary to contain 0.1% or more. However, if it is too large, coarse crystallized substances are formed during casting to deteriorate the formability, so 1.0% is made the upper limit. Further, Si forms fine Mg ₂ Si-based precipitates and contributes to strengthening, and it must be contained at least 0.1% or more, but if it is too much, Si precipitates as a simple substance. 1.0 because the formability is adversely affected
% Is the upper limit. Considering these advantages and disadvantages, the more preferable Fe content is 0.1 to 0.8%, and the more preferable Si content is 0.1 to 0.6%.

The balance component of the Al alloy in the present invention is Al
And unavoidable impurities such as Ni, Cr, V, Ti, Zr, Li, etc., but as long as the amount is an unavoidable impurity, it is necessary to ensure the performance intended in the present invention. It doesn't hinder you.
Next, each condition such as continuous casting using the above Al alloy, hot rolling, cold rolling will be described.

In the present invention, an Al alloy satisfying the above-mentioned compositional requirements is used, and the cooling rate at the time of solidification is (1)
(2) Formula R ≧ 7.5 ([Fe] + [Si]) + 2 (1) R ≧ 5 (2) where R: cooling rate during solidification (° C./sec) [Fe], [Si]: Continuous casting is performed under the condition that the contents (%) of Fe and Si in the Al alloy are simultaneously satisfied.

That is, the inventors of the present invention have confirmed that the strength and drawability of the final rolled product are well controlled by controlling the cooling rate during continuous casting with the content ratio of Fe and Si contained in the Al alloy as a parameter. The cooling rate during solidification is significantly increased by the above (1)
I learned that it is important to set so that the formula and the formula (2) are satisfied at the same time. However, the above properties of the final rolled product are affected by the continuous casting step and the subsequent rolling and intermediate annealing conditions. Especially, Fe and Si in the Al alloy cause coarse crystallized substances during continuous casting, and they are The above-mentioned properties of the final rolled product are adversely affected. However,
If the cooling rate at the time of continuous casting is set so as to satisfy the conditions of the formulas (1) and (2), the formation of coarse crystallized substances derived from Fe and Si is prevented, and hot rolling is performed thereafter. Together with the subsequent setting of the cooling rate, the properties of the final rolled product can be significantly enhanced.

The recommended range represented by the conditional expressions (1) and (2) is [Fe] + [Si] as shown in FIG.
When the value of is more than 0.4%, it is calculated by the formula (1), and [F
When the value of e] + [Si] is 0.4% or less, it means that it is defined by the equation (2). By the way, if the cooling rate during solidification deviates from the above requirements, coarse crystallized substances derived from Fe and Si are generated in the continuous casting structure, and they remain in the subsequent rolling and continuous intermediate annealing steps to improve the strength. And workability will be adversely affected.

In the present invention, hot rolling is carried out immediately after forming a moving strip by continuous casting, or while it is once held and before the slab temperature substantially drops, and after hot rolling is completed, 1
It is an essential requirement to carry out cold rolling after cooling at a rate of 00 ° C / min or more. That is, in the conventional example, as described above, a method of once winding after hot rolling and then allowing to cool in the atmosphere is adopted. In this method, the cooling rate after hot rolling, especially the core portion, is adopted. Since the cooling rate in the steel sheet becomes extremely slow, precipitation of supersaturated solid solution elements such as Mn and Mg does not occur during the subsequent cold rolling process, which hinders the strengthening of the final product. In addition, the drawability is adversely affected. However, if the cooling rate after hot rolling is increased to 100 ° C./min or more as described above, the precipitation of the supersaturated solid solution element as described above does not occur, and even if it precipitates, it precipitates finely and uniformly. Therefore, the strength of the final cold-rolled Al plate is remarkably increased, and at the same time, it is possible to obtain a very good formability such as drawing and ironing.

Here, the cooling rate is set to 100 ° C./min or more, and a cooling rate lower than 100 ° C./min has a significant effect of suppressing the precipitation of the supersaturated solid solution element as compared with the conventional cooling rate by winding and cooling. This is because it is not possible to obtain the desired effect of the present invention.

As a concrete means for obtaining such a cooling rate, there is exemplified a method of quenching after hot rolling by spraying a coolant such as water mist, a method of immersing in a cooling medium and quenching. However, of course, the cooling means itself is not particularly limited, and any means may be adopted as long as it is a cooling method that can satisfy the cooling rate requirement defined above. A more preferable cooling rate is 150 ° C./minute or more, and more preferably 200 ° C./minute or more, in order to effectively exhibit the above-mentioned effects by the rapid cooling. The preferred ultimate temperature during the cooling is 40 to 70 ° C. In the present invention, the maximum feature is that the cooling rate after continuous casting and after hot rolling is specified as described above, and there are no particular restrictions on other conditions, but other preferable conditions, etc. The explanation is as follows.

According to the present invention, after continuous casting, the temperature of the moving strip is maintained at a hot rolling temperature or higher and immediately hot rolled, or the continuous cast piece is adjusted to a hot rolling temperature or higher and then hot rolled. Rolling,
It is applied to the method of continuously or once winding and then sending it to the cold rolling process, whereby heat loss is reduced as compared with the method of winding once after continuous casting, cooling and then hot rolling. It is also effective in increasing productivity. The continuous casting method adopted here is as follows:
The water-cooled continuous casting method, twin roll continuous casting method, belt continuous casting method, block continuous casting method and the like as described above can be appropriately selected and employed.

The starting temperature of hot rolling performed after continuous casting is 350 to 550 ° C., more preferably 400 to 500.
And the hot rolling finish temperature is 150 to 33.
The temperature is 0 ° C, and more preferably 180 to 300 ° C.
Further, in carrying out the present invention, a plate-shaped slab having a wall thickness of about 4 to 30 mm is usually continuously produced by continuous casting, and immediately hot-rolled to obtain a wall thickness of 1 to 5
mm to 0.1 to 1 m by cold rolling.
An Al alloy product plate having a wall thickness of about m is manufactured.

As described above, the present invention has the greatest feature in that the cooling rate during continuous casting and after hot rolling is defined, and that feature, particularly the effect of preventing the precipitation of saturated solid solution elements, is , Continuous casting as detailed in the section of the prior art
Although it is more effectively exhibited when the direct rolling method is applied, in addition to this, after continuous casting, it is temporarily held and sent to the hot rolling step before the slab temperature substantially drops, and then cold rolling is performed. It can be enjoyed even when applied to the method.

[0026]

EXAMPLES Next, examples of the present invention will be shown, but the present invention is not limited by the following examples, and may be carried out with appropriate modifications within a range compatible with the gist of the preceding and following description. Of course, it is possible, and all of them are included in the technical scope of the present invention.

Example After melting an Al alloy having the chemical composition shown in Table 1, continuous casting was performed as a moving strip having a plate thickness of 20 mm at a cooling rate of 12 ° C./sec at the time of solidification. Four
Direct hot rolling was carried out at 50 ° C. and an end temperature of 300 ° C., and immediately cooled at a rate of 200 ° C./min.
A hot rolled sheet having a thickness of mm was produced. Water mist spray was used for cooling after hot rolling. After that, cold rolling is performed to 1 mm, the temperature is raised to 480 ° C. by rapid heating, continuous intermediate annealing is performed for 1 minute, rapid cooling is performed, and further cold rolling is performed to obtain an Al alloy sheet material having a thickness of 0.3 mm. It was

For each of the obtained Al alloy plates, the As proof stress was measured by a tensile test, and a deep drawing test was performed to measure a limiting drawing ratio. In addition, 200 ℃ ×
A baking coating heat treatment was performed for 20 minutes, and a tensile test was performed to measure 0.2% proof stress (AB proof stress). 0.2% proof stress measurement method: based on JIS Z 2241 The results are as shown in Table 1, and examples (No. 1 to 3) in which the component composition of the Al alloy meets the specified requirements of the present invention
In both cases, the As proof stress and the AB proof stress are high, and excellent results are obtained even in the limiting drawing ratio.

On the other hand, comparative examples (No. 4 to No. 4) in which the Al alloy composition deviates from the specified requirements of the present invention, although the cooling rate during continuous casting and the cooling rate after completion of hot rolling are appropriate.
In 12), it can be seen that the limit drawing ratio is generally low, and that the high limit drawing ratio has low As proof stress and AB proof stress.

[0030]

[Table 1]

Next, the Al alloy having the chemical composition shown in Table 2 was melted, and then continuously cast at a plate thickness of 20 mm at a cooling rate during solidification shown in Table 2 to form a moving strip plate, which was immediately rolled at a starting temperature. At 450 ° C. and the end temperature of 300 ° C. to perform direct hot rolling, and immediately cool at a rate of 200 ° C./minute to produce a hot-rolled sheet having a thickness of 3 mm. Water mist spray was used for cooling after hot rolling. After that, cold rolling is performed to 1 mm, the temperature is raised to 480 ° C. by rapid heating, continuous intermediate annealing is performed for 1 minute, rapid cooling is performed, and further cold rolling is performed to obtain an Al alloy sheet material having a thickness of 0.3 mm. Obtained.

For each of the obtained Al alloy plates, the average particle size of the insoluble compound was measured by cross-sectional microscopic observation, and the As proof stress by the tensile test and the work per unit volume required for tensile rupture from the stress-strain curve were determined. It was obtained and used as an index of toughness. Further, a deep drawing test was conducted to measure the limiting drawing ratio. The results are shown in Table 2 together, and the examples (Nos. 13 to 15) satisfying all the specified requirements of the present invention are:
Compared with the comparative examples (Nos. 16 to 18), the crystal grain size of the insoluble substance was smaller, and a well-balanced and good value was obtained in all of the yield strength, toughness, and limiting drawing ratio.

[0033]

[Table 2]

Next, after the Al alloy having the chemical composition shown in Table 3 was melted, the cooling rate during solidification was set to 12 ° C./sec, and 2
A continuous strip having a thickness of 0 mm is cast to form a moving strip, which is immediately set to a rolling start temperature of 450 ° C. and an end temperature of 300 ° C. and subjected to direct hot rolling to a thickness of 3 mm. Cooled at rate. However, No. Regarding No. 25, after continuous casting, it was once cooled and solidified, held at 500 ° C. for 12 minutes, and then hot rolled under the above conditions. Then 1 mm
Cold rolling, rapid heating, continuous intermediate annealing at 480 ° C. for 1 minute, rapid cooling, and cold rolling to obtain a 0.3 mm cold rolled sheet.

The limiting drawing ratio, As proof stress, and AB proof stress of each of the obtained cold-rolled sheets were measured in the same manner as above, and the results shown in Table 3 are obtained together. As is clear from Table 3, Examples (Nos. 19 to 21) satisfying all the requirements of the present invention are:
All have excellent As proof stress, AB proof stress, and critical drawing ratio, and are good in both strength and formability. On the other hand, even if the Al alloy composition is appropriate, the cooling rate after hot rolling is completed. Comparative example (No. 22 to 24) that is out of the specified requirements
It can be seen that, although the limiting drawing ratio is considerably good, the As proof stress and the AB proof stress are low, and there is a problem in strength.

[0036]

[Table 3]

[0037]

EFFECTS OF THE INVENTION The present invention is configured as described above. After continuous casting of an Al alloy having a specified component composition, hot rolling is performed while maintaining the slab temperature, and further cold rolling is performed. A
In the production of 1-alloy sheet, the cooling rate during continuous casting is specified by using the Fe and Si contents as parameters, and the precipitation of solid solution elements during cooling is prevented by increasing the cooling rate after hot rolling. However, the strength of the cold-rolled product can be increased, and an Al alloy sheet having good draw formability can be provided.

[Brief description of drawings]

FIG. 1 is a graph showing preferable cooling conditions during continuous casting adopted in the present invention.

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Claims (3)

[Claims] 1. Mn: 0.4 to 1.5% (meaning weight%; the same applies hereinafter) Mg: 0.8 to 2.5% Cu: 0.25% or less (including 0%) Zn: 0.25% or less (including 0%) Fe: 0.1-1.0% Si: 0.1-1.0% Al alloy satisfying the requirements, the cooling rate during solidification is R ≧ 5, And R ≧ 7.5 ([Fe] + [Si]) + 2, where R: cooling rate during solidification (° C./sec) [Fe], [Si]: Fe and Si content in Al alloy (%) ) Is continuously cast, and then the slab temperature is hot-rolled at a temperature equal to or higher than the hot-rolling temperature, and hot-rolling is performed.
A method for producing an Al alloy sheet for drawing, which comprises cooling at a rate of 0 ° C./minute or more and further cold rolling. 2. The manufacturing method according to claim 1, wherein the continuously cast moving strip is immediately sent to the hot rolling step. 3. The manufacturing method according to claim 1, wherein the continuously cast slab is adjusted to a hot rolling temperature or higher and sent to a hot rolling step.