JPH07252615A - Production of aluminum alloy sheet for drawing - Google Patents

Abstract

PURPOSE:To inhibit the precipitation of supersaturated solid solution elements, to increase the strength of a final cold rolled sheet, and to improve curing performance for baking and drawability by specifying a composition and controlling cooling velocity at the time of continuous casting and after hot rolling and also controlling process annealing temp. at the time of cold 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 hot rolling temp., followed by rolling. After hot rolling, the resulting plate is cooled at a rate of >=100 deg.C/min, cold-rolled, continuously process-annealed at a temp. between 500 deg.C and solidus temp., and further cold-rolled, by which the final product of prescribed thickness can be obtained.

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 using an Al alloy containing Mn and Mg as alloying elements, followed by hot rolling and further cold rolling. In producing an Al alloy sheet by rolling, by regulating the cooling rate during continuous casting and after hot rolling, by performing continuous intermediate annealing at an appropriate temperature during the cold rolling step after hot rolling, , Strength, baking paint curability, and draw formability. The Al alloy plate obtained according to the present invention can be utilized for various forming applications including can materials for drinking and eating by taking advantage of its excellent characteristics.

[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 such demands, a method of performing hot rolling and cold rolling by immediately sending to a rolling step after forming a moving strip by continuous casting (hereinafter referred to as continuous casting / direct rolling Method) and omitting chamfering and homogenizing heat treatment (Japanese Patent Laid-Open No. 55-27497, Japanese Patent Publication No. 62-541).
82). 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]

However, in the continuous casting / direct rolling method which has been put into practical use at present, in the cold rolling step performed after continuous casting and hot rolling, 350 to 500 is used in order to prevent work cracking or the like in the cold rolling step. Although intermediate annealing is performed at a relatively low temperature of about C, precipitation of supersaturated solid solution elements occurs in this intermediate annealing step, which causes a problem of hindering the strengthening of the final cold rolled product.

The present invention has been made by paying attention to the problems of the prior art as described above, and the purpose thereof is to keep a moving strip made of an Al alloy continuously cast at a temperature higher than the hot rolling temperature. Immediately or after adjusting the hot rolling temperature and then hot rolling, and then cold rolling to produce an Al alloy sheet, especially continuous casting, hot rolling, cold rolling and intermediate annealing. Let's establish a method that can suppress the precipitation of supersaturated solid solution elements in the series of steps as much as possible, enhance the strength of the final cold-rolled product, and further improve the baking coating hardenability and drawability. It is what

[0008]

[Means for Solving the Problems] The structure of the method for producing a formable Al alloy sheet according to the present invention, which was able to solve the above problems, is as follows: Mn: 0.4-1.5% Mg: 0.8-2 0.5% 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 requirements, the cooling rate during solidification is R ≧ 5 and R ≧ 7.5 ([Fe] + [Si]) + 2, where R is the cooling rate during solidification (° C./sec) [Fe ], [Si]: after continuous casting under conditions satisfying the content ratio (%) of Fe and Si in the Al alloy, the slab is immediately or hot rolled in a state where it is kept at a hot rolling temperature or higher. After hot-rolling after adjusting the temperature above 100 ℃ after hot-rolling
Per minute or more, followed by cold rolling and 500 ° C-
The main point is that continuous intermediate annealing is performed at the solidus temperature and further cold rolling is performed.

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. In continuous casting, a plate-shaped slab with a wall thickness of about 4 to 30 mm is usually continuously produced, and 1 to 1 is obtained by hot rolling.
After rolling to about 5 mm, 0.1 to 1 by cold rolling
It is rolled into an Al alloy plate having a thickness of about mm. 4. INDUSTRIAL APPLICABILITY The present invention is applied to a method in which hot rolling is performed immediately after continuous casting, and subsequently or once wound, and then sent to a cold rolling step. Then, it can be applied to a method in which hot rolling is performed after adjusting the hot rolling temperature or higher, and then sent to the cold rolling step. 5. INDUSTRIAL APPLICABILITY The present invention is advantageous in a so-called continuous casting / direct feed rolling method in which the temperature of a moving strip obtained by continuous casting is maintained and immediately hot-rolled, and subsequently or once wound and then sent to a cold rolling step. Other than the above, the method may be applied to a method in which after continuous casting, the temperature is once held, sent to hot rolling before the slab temperature is substantially lowered, and further cold rolled.

[0010]

As described above, in the present invention, the component composition of the Al alloy to be used is defined and the cooling rate at the time of continuous casting is defined. Suppress precipitation of supersaturated solid solution elements by performing hot rolling before lowering, cooling at a specified rate, then cold rolling, continuous intermediate annealing under appropriate temperature conditions, and cold rolling However, even if it precipitates, it is possible to increase the strength of the cold-rolled product by finely and uniformly precipitating it, enhance the proof stress after the subsequent baking coating heat treatment, and further in terms of deep drawing formability, etc. This succeeded in obtaining a more excellent Al alloy plate. Hereinafter, the compositional composition of the Al alloy defined in the present invention and the manufacturing conditions including the intermediate annealing conditions performed in the cold rolling process 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 the effect of enhancing the ironing workability by forming Mn-based or Al-Fe-Mn-based crystallized substances, and at least 0.4% or more must be contained in order to exert these effects effectively. However, if the amount is too large, the formability (drawing, drawing,
Since ironing, overhanging property, flangeability, etc.) tend to worsen, it must be kept below 1.5%. The preferable lower limit of the Mn content is 0.8%, more preferably 1.1%, and the preferable upper limit 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]: After continuous casting under the condition that the content ratios (%) of Fe and Si in the Al alloy are simultaneously satisfied, immediately or in a state in which the slab is kept at a hot rolling temperature or higher, or a hot rolling temperature. After the above adjustment, hot rolling is performed, and after hot rolling, 1
Cool at a rate of 00 ° C / min or more, then cold-roll and 50
The greatest characteristic of the manufacturing method is that continuous intermediate annealing is performed at 0 ° C to the solidus temperature and further cold rolling is performed.

That is, in the conventional example, in order to improve the workability in the cold rolling step after the hot rolling as described above, it is usually 500.
Although intermediate annealing is performed for a short time at a relatively low temperature of less than ℃, in this method, precipitation of supersaturated solid solution elements occurs in the cooling process and intermediate annealing process after continuous casting and hot rolling, and the solid solution strengthening effect Becomes insufficient, which hinders the increase in strength of the final product, and adversely affects the drawability. However, as described above, the cooling rate during the continuous casting and the cooling rate after the hot rolling are specified, and the cooling rate during the cold rolling process is 500%.
~ If you perform continuous intermediate annealing in the range of solidus temperature,
Precipitation of a supersaturated solid solution element during casting and during intermediate annealing is suppressed, the solid solution strengthening effect is effectively exhibited, and high strength is achieved, and the increase in the solid solution element also enhances the baking coating curability. Furthermore, since the cubic orientation also increases, the formability of the final cold-rolled product is improved, and the ear ratio can be significantly reduced.

First, 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 ratios of Fe and Si contained in the Al alloy as parameters. 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 during continuous casting is set so as to satisfy the conditions of the above formulas (1) and (2), the formation of coarse crystallized substances derived from Fe and Si is prevented, and the continuous intermediate during rolling thereafter. Together with the setting of annealing conditions, the above-mentioned characteristics of the final rolled product can be remarkably 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.

Further, hot rolling is carried out immediately after the above continuous casting or before the slab temperature substantially drops.
After this hot rolling, it is necessary to cool at a rate of 100 ° C./min or more. However, if the cooling rate becomes lower than 100 ° C./min, precipitation of a supersaturated solid solution occurs in the cooling process after hot rolling, and the purpose of strengthening by solid solution strengthening cannot be achieved.

Furthermore, the reason why the continuous intermediate annealing temperature performed during the subsequent cold rolling is set in the range of 500 ° C. to the solidus temperature is that the precipitation of the saturated solid solution element is sufficiently prevented at a low temperature of less than 500 ° C. This is because not only cannot it be achieved but high strength cannot be achieved, but also the curing property for baking coating and the moldability cannot be sufficiently improved. After this continuous intermediate annealing,
It is preferable to cool to about 50 to 100 ° C. at a cooling rate of 100 ° C./minute or more.

In the present invention, the cooling rate during continuous casting and after hot rolling is specified as described above, and the maximum value is set when the continuous intermediate annealing temperature during cold rolling performed after hot rolling is set higher. Other conditions are not particularly limited, but other preferable conditions and the like will be described below.

According to the present invention, after continuous casting, hot rolling is performed immediately while maintaining the temperature of the moving strip at a temperature equal to or higher than the hot rolling temperature.
Alternatively, it is applied to a method (continuous casting / direct feed rolling method) in which the continuous cast slab is adjusted to a hot rolling temperature or higher and then hot rolled, and subsequently or once wound and then sent to a cold rolling step. Therefore, after continuous casting, once wound up,
Compared with the method of performing hot rolling after cooling, it has less heat loss, and is also effective in increasing productivity. As the continuous casting method adopted here, a water-cooled continuous casting method, a twin roll continuous casting method, a belt continuous casting method, a block continuous casting method or the like as described above may be appropriately selected and used. You can

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 28
It is 0 ° C., and more preferably 210 to 260 ° 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, in the present invention, the cooling rate during continuous casting and after hot rolling is regulated, and continuous intermediate annealing is performed under appropriate temperature conditions during cold rolling performed after hot rolling. It has the greatest feature as, that is, the effect of preventing the precipitation of the saturated solid solution element by setting the intermediate annealing temperature to a high value is continuous casting as described in detail in the section of the prior art.・ It is more effective when the direct rolling method is applied.
It can also be enjoyed when applied to a method in which after continuous casting, the temperature is once held and sent to the hot rolling and cold rolling steps before the slab temperature substantially drops.

[0027]

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, a continuous strip was cast at a plate thickness of 20 mm at a cooling rate of 12 ° C./sec at the time of solidification to form a moving strip, and immediately thereafter, rolling was started. Direct feed hot rolling was performed at a temperature of 450 ° C. and an end temperature of 260 ° C. to produce a hot rolled sheet having a thickness of 3 mm. Incidentally, water mist spraying was adopted for cooling after hot rolling to secure a cooling rate of 200 ° C./min. After that, cold rolling is performed to 1 mm, the temperature is raised to 530 ° C. by rapid heating, 1 minute of continuous intermediate annealing is performed, and then rapid cooling is performed, and further cold rolling is performed to perform cold rolling of 0.3 mm thick Al. I got a plate.

A deep drawing test (drawing ratio: 40%) was performed on each of the obtained Al alloy cold-rolled sheets to measure the ear ratio.
Further, a tensile test was conducted on the cold finished material and the heat-treated material for baking and coating at 200 ° C. for 20 minutes.

Ear ratio: The degree of corrugated protrusions that are symmetrically produced during deep drawing due to plate anisotropy [(average height of peaks)-(average height of valleys)] / (valleys It is expressed by the average height of 100 × 100%. If there are ears (mountains) in the 0 to 90 ° direction to the rolling direction, 0 to 90 ° ears, 4 to the rolling direction
When there is an ear (mountain) in the 5 ° direction, it is called a 45 ° ear. 0.2% yield strength (As yield strength and AB yield strength): JIS Z
2241 compliant

The results are shown in Table 1 together, and the results are shown in Examples (N) in which the component composition of the Al alloy meets the specified requirements of the present invention.
o. All of 1 to 3) have small ear ratios and good results are obtained in both As proof stress and AB proof stress. On the other hand, although the cooling rate at the time of continuous casting and the continuous intermediate annealing performed in the cold rolling process are proper, the Al alloy composition is out of the prescribed requirements of the present invention (Nos. 4 to 8). It can be seen that generally has a high 45 [deg.] Ear rate, and those with a relatively low ear rate have low As proof stress and AB proof stress.

[0032]

[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 obtain a moving strip plate, which was immediately hot rolled. Direct temperature hot rolling was performed by setting the starting temperature to 450 ° C and the ending temperature to 260 ° C, and cooling at a rate of 200 ° C / min.
A hot rolled sheet having a thickness of mm was produced. Then, it was cold-rolled to 1 mm, rapidly heated and held at 530 ° C. for 1 minute, then rapidly cooled, and further cold-rolled to obtain a 0.3 mm cold-rolled sheet. The average particle size of the insoluble compound was measured by observing the plate with a cross-section microscope, the As proof stress was measured in the same manner as above, and the work per unit volume required for tensile rupture was determined from the stress-strain curve to determine the toughness. It was used as an index. The results are shown in Table 2 together. In Examples (Nos. 9 to 11) satisfying the requirements of the invention, the insoluble compound was fine, and good results were obtained in both the As yield strength and the work amount. Has been obtained. On the other hand, in Comparative Examples (No. 12 to 18) lacking any of the requirements defined in the present invention, the average particle size is coarse, the value of the work amount is small, the toughness is poor, or the As proof stress is insufficient. It turns out that

[0034]

[Table 2]

After melting the Al alloys having the chemical compositions shown in Table 3, continuous casting was performed to a plate thickness of 20 mm at a cooling rate of 12 ° C./sec at the time of solidification, and immediately thereafter, the rolling start temperature was 450 ° C. Direct-feed hot rolling was performed at an end temperature of 260 ° C., and immediately thereafter, cooling was performed at the cooling rate shown in Table 3 to produce a hot-rolled sheet having a thickness of 3 mm. Water mist spray was used for cooling after hot rolling. However, No. Regarding No. 27, after continuous casting, it was once cooled and solidified, reheated and held at 500 ° C. for 12 minutes, and then hot rolled. Then, it was cold-rolled to 1 mm, rapidly heated, held at the temperature shown in Table 3 for 1 minute, then rapidly cooled, and further cold-rolled to obtain an Al alloy cold-rolled sheet having a thickness of 0.3 mm. The earring rate, As yield strength and AB yield strength of the obtained cold rolled sheet were measured in the same manner as above, and the results shown in Table 3 were obtained together.

[0036]

[Table 3]

As is clear from Table 3, the examples (Nos. 19 to 22) satisfying all the requirements of the present invention are:
Good results were obtained in all of the As proof stress, AB proof stress, and ear rate as compared with the comparative example.

[0038]

EFFECTS OF THE INVENTION The present invention is configured as described above, and after continuously casting an Al alloy having a specified component composition, the cast slab is immediately or after being hot-rolled at a temperature higher than the hot rolling temperature. When an Al alloy sheet is manufactured by performing hot rolling after adjusting to the hot rolling temperature and then performing cold rolling, the cooling rate is particularly specified during continuous casting and after direct hot rolling, and the cold rolling step is performed. The precipitation of supersaturated solid solution elements during the intermediate annealing carried out in (4) is suppressed as much as possible, the strength of the final cold rolled product is increased, and the baking coating hardenability and drawability are also improved, and both strength and formability are improved. It has become possible to manufacture an Al alloy plate satisfying the characteristics.

[Brief description of drawings]

FIG. 1 is a graph showing preferable cooling rate conditions during continuous casting carried out 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 the slab temperature is hot-rolled at a temperature not lower than the hot-rolling temperature.
Per minute or more, followed by cold rolling and 500 ° C-
A method for producing an Al alloy sheet for draw forming having excellent strength, which comprises performing continuous intermediate annealing at a solidus temperature 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.