JPH07256416A - Production of al alloy sheet for deep drawing - Google Patents

Abstract

PURPOSE:To improve the strength and the formability by solidifying molten Al alloy containing specific contents of Mn, Mg, Cu, Zn, Fe, Si at a specific cooling velocity, hot-rolling in a specific condition and cold-rolling. CONSTITUTION:The Al alloy containing by wt%, 0.4-1.5 Mn, 0.8-2.5 Mg, <=0.25 Cu, <=0.25 Zn, 0.1-1.0 Fe and 0.1-1.0 Si is used. After continuously casting in the conditions satisfying R>=5 and R>=7.5(Fe+Si)+2 (wherein, R: the cooling velocity at the time of solidifying ( deg.C/sec), Fe, Si: alloying ratio of Fe and Si in the Al alloy (%)), the cast slab temp. is kept to the hot-rolling temp. or higher and the hot-rolling is executed and the finishing temp. of the hot rolling is made to be 150-280 deg.C. After hot-rolling, the rolled slab is cooled at >=100 deg.C/min and successively, the cold-rolling is executed.

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 more particularly, to a hot rolling temperature of a moving strip obtained by continuously casting an Al alloy containing Mn and Mg as alloy elements. After holding the above, it is immediately sent to the hot rolling process, or the continuous cast slab is adjusted to the hot rolling temperature and then sent to the hot rolling process to carry out hot rolling, and further cold rolling is carried out to obtain Al. When manufacturing alloy sheets, by controlling the cooling rate during continuous casting, the end temperature during hot rolling, and the cooling rate after hot rolling appropriately, it has excellent drawability and strength. The present invention relates to a method for manufacturing an Al alloy plate. The Al alloy sheet 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 draw formability and strength.

[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 transferring to a rolling process after forming a moving strip by continuous casting (hereinafter, 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 feed rolling method currently in practical use, the finishing temperature in the hot rolling after the continuous casting is high (usually about 300 ° C. or higher),
Coupled with the fact that the component composition of the Al alloy material used is not always appropriate, the alloying elements such as supersaturated Mg and other solid solutions in the continuous casting and hot rolling processes cause recrystallization after hot rolling and the amount of work strain decreases. Continuous annealing (Continuous Annealing Li)
ne), which is an obstacle to an increase in cubic orientation (meaning a crystal orientation in which the rolling surface is parallel to the (100) plane and the rolling direction is parallel to the <100> orientation), and eventually the formability of cold rolled products, especially Ear ratio, which is regarded as important as the evaluation criteria (means the degree of corrugated protrusions that are symmetrically generated during deep drawing due to plate anisotropy, ear ratio = [(average height of peak)-( The average height of the valley)] / (average height of the valley) × 100 (%) The ears (mountains) appearing in the 0 ° and 90 ° directions with respect to the rolling direction are called 0-90 ° ears. , 45 ° to the rolling direction
The problem arises that the ears (mountains) appearing in the direction are called 45 ° ears.

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 keep a moving strip formed by continuously casting an Al alloy at a hot rolling temperature or higher. Immediately to the hot rolling process, or the continuous cast slab is adjusted to the hot rolling temperature and then sent to the hot rolling process for hot rolling,
Further, when cold rolling is performed to produce an Al alloy sheet, the strain amount is increased particularly in the finished state of hot rolling, and the cubic orientation generated during continuous annealing after cold rolling is increased, thereby improving high strength. It is intended to establish a method capable of keeping the formability after the final cold rolling, particularly the earring rate, to a minimum while maintaining the same.

[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 to 1.5% Mg: 0.8 to 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]: The moving strip continuously cast under the condition that the content ratio (%) of Fe and Si in the Al alloy is satisfied is maintained at the hot rolling temperature or higher and immediately sent to the hot rolling step, or Adjusts the continuous cast slab to a temperature equal to or higher than the hot rolling temperature, then sends it to the hot rolling step for hot rolling, and the finishing temperature of the hot rolling is 150 to
The main point is that the temperature is set to 280 ° C., hot rolling is performed, and then cooling is performed at a rate of 100 ° C./min or more, and then cold rolling is performed.

Although the present invention has the above-mentioned configuration as a basic idea,
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 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 is a slab. It is preferable to adjust the timing after the inside temperature has dropped to below the solidus temperature and 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, 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.
After rolling to about 0.1 mm, 0.1 to 0.1 mm by cold rolling.
It is rolled into an Al alloy plate having a wall thickness of about 1 mm. 4. In the cold rolling step performed after hot rolling, it is desirable to perform at least one continuous intermediate annealing, and the preferable temperature during the continuous intermediate annealing is in the range of 470 to solidus temperature. 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 is advantageously applied to the direct-feed rolling method, after continuous casting, it is held once and sent to hot rolling before the slab temperature is substantially lowered to perform hot rolling, and further cold rolling is performed. It can also be applied to the method of doing. 6. In the present invention, it is most common to perform continuous casting, hot rolling, and cold rolling in order, and finally to produce a product in the state of a finished cold rolled sheet, but in some cases, the state of hot rolling as it is It is also possible to commercialize with.

[0010]

As described above, in the present invention, the component composition of the Al alloy to be used is specified, and the cooling rate during continuous casting and the end temperature and cooling rate in the hot rolling that is subsequently performed are specified within appropriate ranges. To suppress recrystallization, to sufficiently increase the cubic orientation by increasing the amount of processing strain, and to suppress the precipitation of supersaturated solid solution elements during the cooling, or even if it precipitates finely and uniformly. In this way, the strength of the cold-rolled product can be increased, and the yield strength after the subsequent baking / coating heat treatment can be increased to obtain an Al alloy sheet satisfying both formability and strength. Hereinafter, the manufacturing conditions including the component composition of the Al alloy defined in the present invention and the hot rolling finish temperature 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 1.0.
%, And the preferable upper limit value is 1.4%.

Mg: 0.8 to 2.5% 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, the more preferable Cu content is in the range of 0.15 to 0.2%.

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 to 1.0% These elements are effective as elements that further enhance 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]: Finishing temperature of hot rolling performed after continuous casting under the condition that the content ratios (%) of Fe and Si in the Al alloy are simultaneously satisfied is 150 to 280 ° C., and the cooling rate is 10
The most characteristic feature of the manufacturing method is that it is regulated to 0 ° C./min and then cold rolling is performed. Hereinafter, the reasons for defining those conditions will be described in detail.

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 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 during continuous casting is set so that the conditions of the above formulas (1) and (2) are simultaneously satisfied, the formation of coarse crystallized substances derived from Fe and Si is prevented, and the subsequent hot rolling is performed. Combined with the finishing temperature of and the setting of the cooling rate after that,
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.

Further, after the continuous strip is formed into a moving strip, immediately after it is kept at a temperature equal to or higher than the hot rolling temperature, or after the slab is temporarily held and adjusted to a temperature equal to or higher than the hot rolling temperature, hot rolling is performed. In this hot rolling, the finishing temperature is 150 to 280 ° C., more preferably 210 to 26.
It is necessary to set the temperature to 0 ° C. and then cool at a rate of 100 ° C./min or more, more preferably 200 ° C./min or more. Then, the cooling rate after hot rolling is 100 ° C.
This is because when the speed is lower than less than 1 minute, 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.

By the way, in the conventional example, since the finishing temperature of hot rolling is set to a high temperature of 280 ° C. or higher as described above, recrystallization occurs after hot rolling to reduce the amount of work strain, and In the continuous intermediate annealing carried out in the cold rolling step, the increase of the cubic orientation becomes insufficient, and the formability of the cold rolled product, especially the improvement of the earring becomes insufficient. However, if the finishing temperature of the hot rolling is set in the range of 150 to 280 ° C, the recrystallization after the hot rolling is prevented as much as possible, together with the subsequent cooling rate being set to 100 ° C / min or more. Therefore, the cube orientation is sufficiently increased by the increase of the processing strain amount, and the formability including the ear ratio can be remarkably enhanced.

Here, the finishing temperature of hot rolling is 150 to 2
The reason why the temperature is set to 80 ° C. is that when the temperature is lower than 150 ° C., the strength increases too much and rolling cracks easily occur.
This is because at a high temperature exceeding 0 ° C, no significant difference from the conventional hot rolling can be observed. From this viewpoint, a more preferable finishing temperature range is 160 to 270 ° C, and more preferably 200 to 250 ° C.

The present invention has the greatest feature in that the cooling rate at the time of solidification in continuous casting is specified as described above, and the finishing temperature (that is, the end temperature) of hot rolling and the subsequent cooling rate are specified. The other conditions are not particularly limited, but other preferable conditions and the like will be described below.

According to the present invention, the continuously cast moving strip is kept at a temperature equal to or higher than the hot rolling temperature and immediately sent to the hot rolling step, or the continuous cast slab is adjusted to the hot rolling temperature and then hot rolled. It is applied to the method of sending to the rolling process and hot rolling and then continuously, or once winding and sending to the cold rolling process (continuous casting / direct feed rolling method). Compared with the method in which hot rolling is carried out after winding and cooling, the heat loss is small, and it is effective in improving 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.
It is in the range of ° C. In carrying out the present invention,
Usually, a plate-shaped slab having a wall thickness of about 4 to 30 mm is continuously manufactured by continuous casting, and immediately hot-rolled to a wall thickness of 1 to 5 mm, and further cold-rolled to 0.1 mm. An Al alloy product plate having a wall thickness of about 1 mm is manufactured.

As described above, the present invention has the greatest feature in that the cooling rate during solidification in continuous casting, the finishing temperature (end temperature) during hot rolling, and the cooling rate are specified. In particular, the effect of preventing recrystallization in the cooling process is as described in detail in the section of the prior art described above in continuous casting.
Although it is more effective when the direct rolling method is applied, in addition to this method, after continuous casting, it is temporarily held and adjusted to a temperature equal to or higher than the hot rolling temperature before the hot rolling and cold rolling steps. It can be enjoyed even when applied to the method of sending to.

[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 alloy having the chemical composition shown in Table 1, a casting strip having a thickness of 20 mm was continuously cast at a cooling rate of 12 ° C./sec during solidification to form a moving strip, which was immediately rolled. Temperature 45
Direct hot rolling was performed at 0 ° C. and an end temperature of 250 ° C., and after rolling, it was cooled at a rate of 200 ° C./min 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 plate material having a thickness of 0.3 mm. Obtained.

A deep drawing test (drawing ratio: 40%) was performed on each of the obtained Al alloy plates to measure the ear ratio, and 0.2% proof stress (As proof stress) was measured by the tensile test. In addition, this plate material was subjected to a baking coating heat treatment at 200 ° C. for 20 minutes, and a tensile test was conducted to obtain 0.2% proof stress (A
B proof stress) was measured. 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
Shows a small ear ratio and a high value of both As proof stress and AB proof stress.

On the other hand, comparative examples in which the Al alloy composition deviates from the prescribed requirements of the present invention despite the fact that the cooling rate during continuous casting, the end temperature during hot rolling, and the cooling rate are appropriate are generally It can be seen that those having a large value and a relatively low ear rate have low As proof stress and AB proof stress.

[0031]

[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 at the time of solidification shown in Table 2 to obtain a moving strip plate, which was immediately rolled at a starting temperature. At 450 ° C. and the end temperature of 250 ° C. to perform direct hot rolling, and after rolling, cool at a rate of 200 ° C./min for 3 m
An m-thick hot rolled sheet 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 then cold rolling is performed to obtain an Al plate material having a thickness of 0.3 mm. Obtained.

With respect to each of the obtained Al alloy plates, the average crystal grain size of the insoluble compound was measured by cross-sectional microscopic observation, and the 0.2% proof stress (As proof stress) was also measured by a tensile test. The work amount per unit volume required for tensile rupture was determined and used as an index of toughness. The results are shown in Table 2.
The examples (Nos. 9 to 11) satisfying the requirements of the invention are comparative examples (Nos. 12 to 18).
It is understood that the average particle diameter is smaller than that of No. 1, and that it is an excellent one in which both the As proof stress and the work amount are well balanced.

[0034]

[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.
A continuous strip having a thickness of 0 mm was cast to form a moving strip. Immediately after that, the rolling start temperature was set to 450 ° C. and the end temperature was set to the temperature shown in Table 3 to carry out direct hot rolling to obtain a 3 mm thick hot rolled sheet. It was made. However, No. Regarding No. 27, after continuous casting, it was once cooled and solidified, held at 500 ° C. for 12 minutes, and then hot-rolled under the above conditions. After that, cold rolling is performed to 1 mm, rapid heating is performed, continuous intermediate annealing is performed at 480 ° C. for 1 minute, rapid cooling is performed, and further cold rolling is performed to 0.3.
A cold rolled sheet of mm was obtained.

Ear ratio, As proof stress, AB of each obtained cold-rolled sheet
The yield strength was measured in the same manner as above, and the results shown in Table 3 were obtained together. As is clear from Table 3, the examples (Nos. 19 to 22) satisfying all the requirements of the present invention generally have a smaller ear ratio and As, AB than the comparative examples (Nos. 23 to 27). It can be seen that the yield strength is good and both the strength and the moldability are excellent.

[0037]

[Table 3]

[0038]

The present invention is constituted as described above, and A
Using a molten alloy, the continuously cast moving strip is kept at a hot rolling temperature or higher and immediately sent to the hot rolling process, or the continuous cast slab is adjusted to the hot rolling temperature and then hot rolled. When the aluminum alloy sheet is manufactured by sending it to the rolling step, hot rolling, and cold rolling, the cooling rate during continuous casting, the finishing temperature and the cooling rate during hot rolling, are specified. By increasing the cubic orientation that occurs during continuous annealing after rolling, it is possible to minimize the formability after the final cold rolling, especially the earrings, and to achieve high strength. It has become possible to provide a satisfactory Al alloy plate.

[Brief description of drawings]

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C22F 1/04 C 1/047

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, then the slab temperature is hot-rolled at a hot rolling temperature or higher, and the hot-rolling finishing temperature is set to 150 to 280 ° C. and 100
A method for producing an Al alloy sheet for drawing, which is excellent in strength, characterized by cooling at a rate of ° C / min or more and then performing 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.