KR20040042330A - Process for preparing an aluminum alloy plate with good formability and high strength - Google Patents

Abstract

PURPOSE: A method for manufacturing an aluminum alloy sheet is provided which obtains ultrafine grain size of the aluminum alloy sheet and substantially improves formability of the sheet by performing warm rolling on an ordinary aluminum alloy sheet and controlling reduction ratio of the warm rolling. CONSTITUTION: The method for manufacturing high strength aluminum alloy sheet having superior formability comprises first heat treatment step of heat treating a commercial aluminum alloy sheet at a temperature of 200 to 300 deg.C; a warm rolling step of performing one cycle of warm rolling on the aluminum alloy sheet passing through the first heat treatment step to a reduction ratio of 60% or more at a temperature of 150 to 250 deg.C; and second heat treatment step of annealing the aluminum alloy sheet passing through the warm rolling step, wherein the method further comprises a cold rolling step of cold rolling a commercial aluminum alloy hot band before the first heat treatment step, wherein the commercial aluminum alloy hot band before the cold rolling step has a thickness of 4 to 7 mm, and the commercial aluminum alloy sheet after the cold rolling step has a thickness of 1 to 4 mm, and wherein the commercial aluminum alloy sheet is an aluminum alloy sheet selected from the group consisting of AA 1000 series aluminum alloy, AA 3000 series aluminum alloy and AA 5000 series non-heat treated aluminum alloy.

Description

Manufacturing method of high strength aluminum alloy plate with excellent moldability {PROCESS FOR PREPARING AN ALUMINUM ALLOY PLATE WITH GOOD FORMABILITY AND HIGH STRENGTH}

The present invention relates to a method for producing a high strength aluminum alloy sheet having excellent moldability, and more particularly, to ultrafine grain size of an aluminum alloy sheet by controlling warm rolling and rolling reduction thereof. The height is related with the manufacturing method of an aluminum alloy plate material.

Grain refinement of metal materials usually depends on three methods.

First, as in the case of low carbon steel, it is quenched at high temperature to refine the particles by inhibiting phase transformation, and second, to control the growth of the matrix particles by adding impurities to the substrate and producing particles by the impurities. The third is to make the nucleation site of the new particles by modifying the tissue by cold rolling, etc., and to make the particles finer by generating a large number of particles during subsequent heat treatment.

Among the above-mentioned methods, grain refinement of the aluminum alloy sheet material, in particular, non-heat treatment type aluminum alloy sheet material has been mainly made by a method of recrystallization heat treatment after cold rolling.

However, it has been difficult to manufacture an aluminum alloy sheet having excellent sheet forming properties and high strength with the existing aluminum alloy sheet manufacturing method including a cold rolling step and a recrystallization heat treatment step.

The reason is that the beta-fiber formed in the matrix due to cold rolling grows into large grains of 30 µm or more by recrystallization heat treatment, so that the strength characteristics are very low, and the cube orientation develops in the recrystallized texture. This is because the plastic workability such as plate material is very poor.

Therefore, studies for overcoming the problems of the conventional aluminum alloy annealed sheet material as described above have been made at various angles, and the present inventors have a plate material having excellent strength and formability by controlling the rolling rate of the hot rolling and thus the warm rolling. To manufacture.

Accordingly, an object of the present invention is to provide a method for producing an aluminum alloy sheet material, in particular, a method for producing a non-heat-treated aluminum alloy sheet material such as AA1000, AA3000, AA5000 series, in which hot rolling is performed at a rolling reduction ratio capable of obtaining a microstructure. After that, by recrystallization heat treatment, to provide a new type of aluminum alloy plate manufacturing method capable of forming within the ultra-fine grains for strength improvement and {111} / / ND structure for improving moldability in itself.

1 is a flow chart schematically showing a method of manufacturing an aluminum alloy sheet according to the present invention.

Figure 2 is a micrograph showing the vertical cross-sectional microstructure formed on the aluminum alloy plate prepared according to Example 1 of the present invention.

Figure 3 is a view showing the texture formed on the aluminum alloy sheet produced according to Example 1 of the present invention.

Figure 4 is an EBSD / GRAIN MAP of the surface layer texture formed on the aluminum alloy plate prepared according to Example 1 of the present invention.

Figure 5 is a micrograph showing the vertical cross-sectional microstructure formed on the aluminum alloy plate prepared according to Example 3 of the present invention.

Figure 6 is a view showing a surface layer aggregate structure formed on the aluminum alloy sheet produced according to Example 3 of the present invention.

Figure 7 is a graph showing the R-value showing the moldability of each of the aluminum alloy sheet material prepared according to Example 3 and Comparative Example 2 of the present invention.

Figure 8 is a view showing the development of the texture of the aluminum alloy sheet produced according to Example 3 of the present invention.

In order to achieve the above object, the present invention comprises a first heat treatment step (S10) for heat-treating a commercial aluminum alloy plate at a temperature of 200 ~ 300 ℃; A warm rolling step (S20) of first heating the aluminum alloy plate material subjected to the first heat treatment step (S10) at a rolling reduction ratio of 60% or more at a temperature of 150 to 250 ° C; It provides a method of manufacturing a high strength aluminum alloy plate material having excellent formability, characterized in that it comprises a second heat treatment step (S30) for annealing heat treatment of the alloy plate material subjected to the warm rolling step (S20).

The first heat treatment step (S10), for the warm rolling to be described below, is to make the alloy plate structure in a state where recovery (recovery) is completed and recrystallization partially, the temperature range of 200 ~ 300 ℃ It was found that tissues in the same state were obtained. In particular, when the heat treatment over the temperature of 300 ℃, recrystallization is too rapid, it can be seen that it is difficult to obtain the structure in the above state.

Thereafter, the aluminum alloy sheet material subjected to the first heat treatment step S10 is warm-rolled, whereby grain refinement is achieved and {111} // ND texture is obtained.

In addition, the aluminum alloy sheet material that has passed through the first heat treatment step S10 is further formed to have a formability such as deep drawing property by the subsequent annealing heat treatment.

Here, it is preferable that recrystallization annealing temperature is performed in about 300 degreeC.

On the other hand, when the thickness of the prepared aluminum alloy, more specifically, the aluminum alloy hot band is too large, for the warm rolling step (S20) to be performed later, by cold rolling before the first heat treatment step (S10) to reduce the thickness It is desirable to give.

That is, in order to prepare as a workpiece (aluminum alloy sheet material before hot rolling) about 1 to 4 mm using an aluminum alloy hot band larger than about 4 mm thick, a predetermined reduction ratio before the first heat treatment step (S10) described above. Cold rolling is preferable.

At this time, it is most preferable that the first heat treatment step performed between cold rolling and warm rolling is performed for about 1 hour at a temperature of about 250 ° C.

By the heat treatment in the first heat treatment step, the texture and hardness of the aluminum alloy sheet material are preferably controlled.

In the above description, the commercial aluminum alloy sheet is preferably a non-heat treatment aluminum alloy selected from the group consisting of AA1000 series, AA3000 series, AA5000 series, the AA1000 series has an Al component of at least 99.0% by weight, AA3000 series Mn is the main alloying element, and AA5000 series has Mg as the main alloying element.

Table 1 shows the components of the alloying elements included in addition to aluminum for each of the above non-heat treatment alloys.

division Si Fe Cu Mn Mg Cr Zn Remainder AA1000 (based on Al 1100) ~ 1.0 0.05-0.2 ~ 0.05 * * ~ 0.1 ~ 0.15 AA3000 (based on Al 3004) ~ 0.3 ~ 0.7 ~ 0.25 1.0-1.5 0.8 ~ 1.3 * ~ 0.25 ~ 0.15 AA5000 (based on Al 5052) ~ 0.25 ~ 0.4 ~ 0.1 ~ 0.1 2.2 to 2.8 0.15-0.35 ~ 0.1 ~ 0.15

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart illustrating a method of manufacturing an aluminum alloy sheet, in particular, a non-heat treated aluminum alloy sheet according to the present invention.

As shown in FIG. 1, the method for manufacturing an aluminum alloy sheet according to the present invention includes a first heat treatment step (S10) of heat treating a commercial aluminum alloy plate material at a temperature of 200 to 300 ° C., and the first heat treatment step (S10). A second heat treatment for annealing the aluminum alloy sheet having a rough rolling step at a temperature of 150 to 250 ° C. with a rolling reduction ratio of 60% or more, and annealing and heat treatment of the alloy sheet having undergone the warm rolling step (S20). Step S30 is included.

In general, the method for producing an aluminum alloy sheet according to the present invention can be used as a work piece of a commercial aluminum alloy plate of various thickness in an environment that is allowed to 60% or more warm rolling, among them, commercial aluminum alloy of 1 ~ 4mm thickness It is most preferable to warm the sheet using a sheet, and therefore, when the workpiece, i.e. the initial aluminum alloy sheet or aluminum alloy hot band, has a thickness greater than 4 mm, the workpiece is cold rolled before the first heat treatment step mentioned above. It is desirable to control the thickness through.

The aluminum alloy sheet manufacturing method according to the following embodiments includes a cold rolling step, a first heat treatment step, a warm rolling step, a second heat treatment step, and the cold rolling step serves to control the thickness of the workpiece The cold rolling step may be optionally included in the method of the present invention.

<Example 1>

Cold rolled 4mm thick sheet was subjected to intermediate heat treatment at 260 ° C. for 1 hour after making a thickness of 4 mm by rolling the AA1100 hot band having a thickness of 6.2 mm to 36%.

The aluminum sheet thus prepared was warm rolled once (1 pass) to a thickness of 1 mm at a temperature of 150 캜 according to the present invention, and the warm rolled aluminum sheet was subjected to recrystallization annealing at 300 캜.

Figure 2 is a micrograph showing the longitudinal cross-sectional microstructure of the non-heat treatment aluminum alloy plate prepared in Example 1.

As can be seen from the micrograph of Figure 2, the aluminum alloy plate material prepared in Example 1 is formed ultrafine grains in all the thickness layer except the center layer.

In addition, Figure 3 is a view showing the aggregate structure of the surface layer formed on the alloy plate material prepared in Example 1, referring to Figure 3, the surface layer of the alloy plate material observed in the conventional non-heat treatment aluminum annealing plate material { It can be seen that the shear aggregate tissue {001} <110> and {111} // ND are formed rather than the 001} <100> cube tissue.

This {111} // ND orientation is an aggregate formed in the IF steel, and exhibits high sheet formability and exhibits a high R-value.

In addition, Figure 4 is a view showing the results of observing the GRAIN MAP of the EBS (electron backscattered diffraction) of the microstructure formed on the alloy plate prepared in Example 1, Figure 4 is about 1.0㎛ in the microstructure of the alloy plate It was observed that ultrafine grains of were formed.

Therefore, the non-heat treatment aluminum alloy plate material prepared according to Example 1 has a very high hardness as compared to the non-heat treatment aluminum alloy plate material produced only by cold rolling without warm rolling, as described in detail below.

<Example 2>

All the conditions were the same as in Example 1, except that the non-heat treatment aluminum alloy sheet was manufactured at a warm rolling temperature of 250 ° C.

Comparative Example 1

All conditions were the same as in Example 1 and Example 2, but instead of warm rolling, only 1 mm thick non-heat treatment aluminum alloy plate was manufactured.

Table 2 below shows the hardness values of Examples 1 and 2 and Comparative Example 1 according to the present invention.

division Hardness (Hv) Example 1 70.50 Example 2 70.26 Comparative Example 1 55.42

As can be seen from Table 1, the non-heat treatment aluminum alloy sheet prepared according to Example 1 and Example 2 of the present invention is a non-heat treatment aluminum prepared by the conventional aluminum alloy sheet manufacturing method as in Comparative Example 1 It can be seen that the hardness value is significantly larger than that of the alloy plate.

<Example 3>

After cold rolling the AA3004 hot band having a thickness of 6.2 mm to 1.5 mm, the cold rolled 1.5 mm thick plate was subjected to intermediate heat treatment at 250 ° C. for 1 hour.

The aluminum sheet thus prepared was warm rolled once (1 pass) to a thickness of 0.6 mm while being maintained at 250 ° C. for 20 minutes in accordance with the present invention, and the warm rolled aluminum sheet was subjected to recrystallization annealing heat treatment at 300 ° C. temperature.

5 is a micrograph showing a vertical cross-sectional microstructure of a non-heat treatment aluminum alloy sheet prepared in Example 3. FIG.

As can be seen from the micrograph of Figure 5, the aluminum alloy plate material prepared in Example 3 can be seen that the ultra-fine grains are formed in all thickness layers except the center layer.

In addition, Figure 6 is a view showing the aggregate structure of the surface layer formed on the alloy plate material prepared in Example 3, referring to Figure 6, the surface layer of the alloy plate material is observed { It can be seen that the shear aggregate tissue {001} <110> and {111} // ND are formed rather than the 001} <100> cube tissue.

This {111} // ND orientation is a structure formed in the IF steel and exhibits high sheet formability and thus exhibits a high R-value.

Comparative Example 2

All of the same conditions as in Example 3, but instead of hot rolling, a non-heat treatment aluminum alloy plate material having a thickness of 0.6 mm was manufactured by cold rolling alone.

FIG. 7 shows a diagram showing the R-values of the non-heat treatment aluminum alloy plate material prepared by Example 3 and labeled HWR and the non-heat treatment aluminum alloy plate material prepared by Comparative Example 2 and labeled HCR. .

As shown in FIG. 7, the non-heat treatment aluminum alloy plate material prepared by Example 3 has a higher R-value than the non-heat treatment aluminum alloy plate material prepared by 2 in comparison, and accordingly, It can be seen that it has a far superior sheet formability.

Table 3 below shows the hardness test results of the non-thermal treatment aluminum alloy sheet produced by Example 3 and Comparative Example 2.

division Hardness (Hv) Example 3 110.16 Comparative Example 2 87.16

<Example 4>

The cold rolled 4mm thick plate was subjected to intermediate heat treatment at 260 ° C. for 1 hour.

The aluminum sheet thus prepared is warm rolled once to a temperature of 200 to 300 ° C., preferably at 250 ° C., to a thickness of 1 mm according to the present invention, and the warm rolled aluminum sheet is subjected to recrystallization annealing at 300 ° C. It was.

The structure of the non-heat treatment aluminum alloy sheet material produced by Example 4 is shown in FIG. 8, which shows the texture of the surface layer.

As can be seen from Fig. 8, in the aluminum alloy sheet produced in Example 4, {001} <110> rotated cubes and {111} <uvw> γ which cannot be obtained by a conventional rolling method. Fine tissue comprising fibers was obtained.

Finally, in order to see the effect of the first heat treatment performed before warm rolling according to the present invention, the aluminum alloy sheet products are manufactured by varying only the first heat treatment step with all the conditions as in Example 2 described above. Table 4 shows the hardness values according to the refinement of these particles.

division Hardness (Hv) Heat-free treatment 106.8 First Heat Treatment at 250 ° C. (Example 3) 110.6 First heat treatment at 300 ° C 111.4

As can be seen from Table 4, it can be seen that the particles are further refined by the first heat treatment to increase the hardness value.

The present invention enables the production of non-heat treatment aluminum alloy plate having excellent sheet forming properties and high strength, and can be applied to the field of manufacturing non-heat treatment aluminum can materials and automobile exterior plate materials with improved weight and strength, It is very suitable for mass production.

Claims (3)

A first heat treatment step (S10) of heat treating the commercial aluminum alloy sheet at a temperature of 200 ° C. to 300 ° C .; A warm rolling step (S20) of first heating the aluminum alloy plate material subjected to the first heat treatment step (S10) at a rolling reduction ratio of 60% or more at a temperature of 150 to 250 ° C; Method for producing a high strength aluminum alloy plate material having excellent formability, characterized in that it comprises a second heat treatment step (S30) for annealing heat treatment of the alloy plate material undergoing the warm rolling step (S20). The method of claim 1, further comprising a cold rolling step of cold rolling a commercial aluminum alloy hot band before the first heat treatment step (S10), The thickness of the commercial aluminum alloy hot band before the cold rolling step is 4 ~ 7mm, the thickness of the commercial aluminum alloy plate reduced in thickness after the cold rolling step is 1 ~ 4mm high strength aluminum alloy excellent in formability Method of manufacturing plate. The non-heat treatment system according to claim 1 or 2, wherein the commercial aluminum alloy plate is one selected from the group consisting of AA1000 series aluminum alloys, AA 3000 series aluminum alloys, and AA 5000 series non-thermal treatment aluminum alloys. Aluminum alloy sheet manufacturing method.