KR100490760B1 - Al ALLOY MATERIAL FOR BUILDING AND METHOD FOR PRODUCING THE SAME - Google Patents

Abstract

There is provided an Al alloy material for construction and a method for producing the same, which have a low yield strength and are capable of acute bending, even when baking is performed at a high temperature of 260 to 280 ° C. This building Al alloy material is a hot rolled material of A3003 specified in JIS, wherein the structure after baking coating at a temperature of 300 ° C. or less consists of a fiber structure and a recrystallized grain structure having an area ratio of 20% or less. It is manufactured by performing only hot rolling which manages the temperature at the end of rolling to be 290-340 degreeC, with the fall rate of withstand strength being 10% or less.

Description

Aluminum alloy for building and manufacturing method {Al ALLOY MATERIAL FOR BUILDING AND METHOD FOR PRODUCING THE SAME}

The present invention relates to a building Al alloy material and a method for manufacturing the same, and more specifically, Al alloy material actually used as a building material on the premise that baking coating is carried out at a high temperature range of 260 ~ 280 ℃, It also relates to a building Al alloy material having excellent bending workability and a method of manufacturing the same, since the strength reduction is small and the elongation is sufficiently maintained even before and after.

Lightweight Al alloys are used for exterior wall materials, interior materials and curtain wall materials of high-rise buildings.

In this case, as shown, for example, in FIG. 1, the process of bending 90 degree of Al alloy plates 1 is performed. In recent years, as shown in FIG. 2, the bending angle of 90 degree or more is increasing. In such bending processing, the bending part 2 is sharpened and the design is improved. As an example, as shown in FIG. 3, the notch 3 is put in Al alloy material 1, and there exists a method of bending.

Then, prior to performing the above bending process, a coating such as fluorine resin, acrylic resin, urethane resin, etc., is baked on the Al alloy material at a predetermined temperature so as to improve the design and corrosion resistance. do.

Therefore, the following performance is required for the Al alloy material for construction actually used in such an aspect.

First, in terms of building materials, proper strength characteristics are required even after construction. Specifically, for example, in the case of a building exterior wall material, a load capacity of 95 N / mm 2 or more is required even after construction.

Moreover, it has an appropriate elongation characteristic and can bend smoothly, and the bending part becomes sharp.

Conventionally, strength characteristics are important for Al alloy materials for construction, and A3004-H24 materials (3004-H24 specified by ASTM B209) and A3004-H32 materials (3004-H32 specified by ASTM B209), etc., specified in JIS, are used. have.

At the time of manufacture of these materials, the Al alloy material of a predetermined | prescribed specification melt | dissolves first, and the ingot (ingot) is manufactured. Subsequently, a uniform heat treatment for heating the ingot at a predetermined temperature for a predetermined time is performed, and then hot rolling is performed at a predetermined processing rate.

In the process of hot rolling, the cast structure (solidification structure) of the ingot is pressed in the rolling direction and stretched to soften into a fiber structure.

Thereafter, cold rolling is performed to refine the grain size, adjust the thickness, and the like, and then perform annealing to remove the work strain, and then perform cold rolling and heat treatment to remove the work strain at this time.

Further, in the series of manufacturing steps described above, the rolling deformation is accumulated in the rolled material at the time when the hot rolling process and the cold rolling process are completed. Then, after that, when the rolled material is heated to a temperature equal to or higher than the recrystallization temperature, recrystallized particles grow in the structure starting from the strain energy. This recrystallized particle is not a fiber shape but a particle shape of predetermined size normally.

The above materials, such as A3004-H24 ash, are all cold-rolled materials, and the recrystallized grains are fine and the fiber structure may remain, so that sharp 90 ° bending can be performed.

If cracks occur in the bent part by performing acute angle bending of 90 ° or more, weld the part to repair it.

In the Al alloy material used as a building material and used on the premise of baking coating, even after sharpening, the bending strength and the elongation characteristics are appropriate even after baking coating, so that sharp bending or acute bending may be performed. An object of the present invention is to provide an Al alloy material for construction that does not generate cracks and a method of manufacturing the same.

In order to achieve the above object, in the present invention, it is a hot rolled material of A3003 (3003 defined in ASTM B209) specified in JIS, and the structure after baking coating at a temperature of 300 ° C. or less is 20% or less in fiber structure and area ratio. It is made of a recrystallized grain structure of, Al alloy material for building is provided, characterized in that the reduction rate of the strength before and after the baking coating is 10% or less.

In the present invention, the ingot of A3003 (3003 specified in ASTM B209) specified by JIS is subjected to uniform heat treatment, and then only by performing hot rolling at a temperature of 290 to 340 ° C at the end of rolling. Provided is a method for producing an Al alloy material for building, characterized in that it is used.

The Al alloy material of the present invention is a material that is actually used immediately by performing hot rolling only under the conditions described below on A3003 material having excellent strength characteristics. That is, as in the case of the conventional Al alloy material, it is not manufactured through the process of cold rolling-intermediate annealing-cold rolling-heat treatment after hot rolling further.

Specifically, it manufactures as follows.

First, the A3003 ash of a predetermined composition is melt | dissolved and the ingot is manufactured. Subsequently, the ingot is subjected to a uniform heat treatment, followed by hot rolling.

It is preferable to perform uniform heat processing for about 1 to 15 hours in 500-630 degreeC temperature range. If the treatment temperature is lower than 500 DEG C, the amount of the intermetallic compound mainly composed of AlMn decreases and the recrystallized grains grown from the cast structure (coagulation structure) are coarsened. It is easy to occur. In addition, when the treatment temperature is higher than 630 ° C., deformation of the ingot, expansion, or the like occurs, which causes tissue defects during the subsequent process (hot rolling). Preferable treatment temperature is 600-630 degreeC.

In addition, when the treatment time is less than 1 hour, the entire ingot cannot be uniformly heat treated, so that homogeneous hot rolling is difficult. In addition, even if it is longer than 15 hours, the uniform heat treatment effect reaches saturation and consumes heat energy unnecessarily and becomes disadvantageous in cost. Preferable treatment time is 2 to 6 hours.

In this way, the uniformly heat-treated ingot is immediately subjected to hot rolling to grow the cast structure into a fiber structure and to grow a fine secondary structure (subgrain).

In A3003 ash of this invention, said hot rolling is complete | finished and it is actually used as a building material as it is. Therefore, at the time of actual use, the structure of the A3003 material, which is the hot rolled material, is mainly composed of a fiber structure, which is a structure formed by rolling, and a predetermined amount of fine secondary structures is dispersed therein.

This A3003 ash has the following structure, and thus exhibits the following effects.

For example, when an acute bend processing is performed, if the structure is only a fiber structure, cracks and the like occur along the grain boundary of the fiber structure in the bent portion. However, since the fine secondary structure coexists with this material, generation | occurrence | production of the said crack is suppressed. That is, acute angle bending becomes possible.

In the case of this A3003 ash, even if baking coating was performed at a temperature of 300 ° C. or lower, more specifically, at a high temperature range of 260 to 280 ° C., the reduction rate of the A3003 ash strength before and after baking coating was 10% or less. Becomes And even after baking coating, the absolute value of the proof strength is ensured at 95 N / mm <2> or more, and has satisfy | filled the requirements as an exterior wall material of a building. In addition, the elongation is also 27% or more, and good bending can be performed.

The above characteristics, in particular, the fact that the strength reduction rate before and after baking coating becomes 10% or less is an effect caused by the coexistence of the fine secondary structure with the fiber structure. Naturally, this secondary structure grows into recrystallized grain structure at the time of baking coating in a high temperature range, and its particle size becomes large and the amount of precipitation also increases.

However, in the case of the A3003 ash of the present invention, even after baking coating in a high temperature region, the amount of recrystallized grain structure present in the entire structure is controlled to be 20% or less, and the remainder is controlled to be in a fiber structure state, so that baking coating is performed. The strength reduction rate at the front and rear becomes 10% or less.

Such characteristics can be realized by managing the material temperature at the end of rolling at 290 to 340 ° C in the hot rolling.

When the temperature at the end of rolling is higher than 340 ° C., the elongation is about 35%, but the structure becomes almost recrystallized grain structure, resulting in surface roughening of the bent portion during bending processing.

If the temperature at the end of rolling is lower than 290 ° C., the amount of generation of the fine secondary structure is reduced and the elongation is less than 27%, resulting in cracking during acute bending.

In order to manage the temperature at the end of rolling at 290-340 degreeC, in this invention, the temperature at the time of rolling start is set to 350-450 degreeC.

If the temperature is lower than 350 ° C., the temperature at the end of rolling cannot be secured to 290 ° C. or higher, and the strength is high, but the elongation is reduced. Thus, cracking or the like occurs during bending processing.

If the temperature is higher than 450 DEG C, it is difficult to bring the temperature at the end of rolling to 340 DEG C or lower, and in the structure at the end of rolling, coarse recrystallized grain structure is mainly used, and surface roughness of the bent portion at the time of bending is generated. do. And withstand strength becomes smaller than 95 N / mm <2>.

(Example)

Examples 1-16, Comparative Examples 1-9

(1) Al alloy material

The Al alloy material of the following composition was melt | dissolved, and the ingot (thickness 500mm) was manufactured.

A3003 Ash: 0.58 mass% of Si, 0.68 mass% of Fe, 0.18 mass% of Cu, 1.48 mass% of Mn, 0.02 mass% of Mg, 0.09 mass% of Zn, the remainder being Al and unavoidable impurities.

A3004 Ash: 0.58 mass% of Si, 0.68 mass% of Fe, 0.20 mass% of Cu, 1.48 mass% of Mn, 1.01 mass% of Mg, 0.23 mass% of Zn, the remainder being Al and unavoidable impurities.

(2) Manufacture of board

The board | plate material of the plate thickness shown in Table 1 was manufactured by the method provided with the following conditions.

Method (A) of the present invention: After performing a uniform heat treatment for 6 hours in a uniform heat treatment furnace at a temperature of 600 ° C., the temperature at the start of rolling is set to 550 ° C., and the temperature at the end of rolling is shown in Table 1 below. Hot rolling is carried out under temperature control. As it is used as a plate.

Conventional method (B): After performing uniform heat treatment for 6 hours in a uniform heat treatment furnace with a temperature of 600 ° C. on the ingot, hot rolling is performed at a temperature of 550 ° C. at the start of rolling and 310 ° C. at the end of rolling. Cold rolling was performed at a temperature of 80 ° C.

Subsequently, an intermediate annealing was performed at a temperature of 360 ° C. for 3 hours, cold rolling at a temperature of 80 ° C. was further performed, and then heat treatment was performed at a temperature of 230 ° C. for 3 hours. After that, it is used as a plate.

(3) measurement of properties

Strength reduction rate before and after baking coating (%):

The strength (г ₀ ) and the elongation of each plate before baking coating were measured.

Subsequently, the fluororesin coating material was applied to each plate, and baking coating of the temperature shown in Table 1 was performed, and the yield strength and elongation at this time were measured.

_{100 × (г 0 × г)} / calculates the strength decrease rate was set to ₀ г (%) before and after the baking coating. The results are shown in Table 1.

Area ratio of recrystallized grain structure:

The crystal structure was observed by the Barker method.

Specifically, the surface of each plate is ground, the surface is electropolished, an etching treatment using HBF ₄ liquid is performed on the polishing surface, and the area of one recrystallized grain structure is subjected to image processing using polarization. Was integrated. And the ratio (percentage) of the said integrated value in the visual field (5 mm x 5 mm) was calculated | required. The results are shown in Table 1.

Moreover, about the board | plate material of Example 9 and the comparative example 8, the micrograph (magnification x50) of the structure was shown to FIG. 4 and FIG. 5, respectively.

(4) bending test

Bending was performed on each board | plate material after baking coating, and the surface roughness (peeling of a coating) of a bent part, and the presence or absence of a crack were observed visually.

As for surface roughness, as shown in FIG. 6, the direction orthogonal to the rolling direction 4 (the longitudinal direction of a board | plate material), and the direction parallel to the rolling direction 4 (the width direction of a board | plate material) as shown in FIG. The bending angle when surface roughness was observed was carried out in 2 suns.

As for the cracks, as shown in Fig. 7, 90 ° bending and 180 ° bending were performed in the direction parallel to the rolling direction (the width direction of the sheet material), respectively, and the presence of cracks was observed.

(Circle) and the case where there is no crack, but the case where there is no problem in practical use were shown as (triangle | delta) and the case where a clear crack generate | occur | produced.

Table 1 shows the following.

(1) As can be seen in comparison with Example 9 and Comparative Example 6, although the material is the same, the temperature at the end of rolling is the same, and the sheet thickness is the same, it is produced through hot rolling followed by cold rolling or intermediate annealing, etc. In the case of Comparative Example 6, although the coating temperature was the same 260 ° C., the proof strength after coating was small compared to Example 9 and less than 95 N / mm 2. And also in a bending test, it becomes easy to produce roughness compared with Example 9. FIG. This is because the structure of the comparative example 6 is a recrystallized grain structure at the time of a series of processes after hot rolling and also baking coating.

From this point of view, the effectiveness of the method of the present invention, which is produced only by hot rolling under conditions in which recrystallized grain structure is not grown even by baking coating, is clear.

(2) The structure after baking coating of Example 9 shown in FIG. 4 is mixed with a fiber structure and a fine secondary structure (subgrain). The yield strength and elongation after baking coating were high at 122 N / mm 2 and 29.5%, respectively, and the yield reduction rate was extremely small at 1.6%. Thus, excellent bending test results have been obtained.

In the structure after baking coating of Comparative Example 8 shown in Fig. 5, no fiber structure was seen, and it was composed of coarse recrystallized grain structure. In addition, although the yield strength after baking coating showed a high value as 160 N / mm <2>, the elongation is small as 15.2%, and a yield reduction rate is very big as 28.9%. As a result, surface roughness and cracks at the time of bending test become very poor.

In this respect, the usefulness of the building Al alloy material of the present invention having the structure in which the fiber structure and the fine secondary structure coexist is clear.

As can be clearly seen from the above description, the hot rolled material of A3003 ash, which manages the temperature at the end of rolling at 290 to 340 ° C., maintains the fiber structure mainly without recrystallized grain structure even after baking coating. The yield reduction rate is 10% or less, and the absolute value of the yield strength is 95 N / mm 2 or more and the elongation rate is 27% or more. Therefore, the Al alloy material of the present invention has a high industrial value as a building material that is excellent in bending workability and does not cause a decrease in yield strength even when baking coating is performed.

In addition, although the said description was performed about the case where the temperature at the time of baking coating is 260-280 degreeC, the building Al alloy material of this invention can be used suitably even if it is 280-300 degreeC, even if the temperature at the time of baking coating is 260 degreeC or less. .

1 is a schematic view showing a 90 ° bending process of a plate.

2 is a schematic view showing an acute angle bending process of a plate.

3 is a schematic view showing a 90 ° bending process with a notch formed.

4 is a micrograph of the sheet structure of Example 9. FIG.

5 is a micrograph of a plate structure of Comparative Example 8. FIG.

6 is a schematic diagram in which a plate is bent in a direction orthogonal to the rolling direction.

7 is a schematic view of bending a plate in a direction parallel to the rolling direction.

Claims (4)

Hot rolled material of (composition) A3003 (3003 specified in ASTM B209) specified in JIS; The structure after baking coating carried out at a temperature of 300 ° C. or lower is composed of a fiber structure and a recrystallized grain structure having an area ratio of 20% or less; And The fall ratio of the yield strength before and after the said baking coating is 10% or less, The building aluminum alloy material characterized by the above-mentioned. The Al alloy material for construction according to claim 1, wherein the yield strength after the baking coating is 95 N / mm 2 or more, and the elongation is 27% or more. The Al alloy material for construction according to claim 1 or 2, wherein the baking coating temperature is 260 to 280 ° C. Uniform heat treatment is performed on the ingot of A3003 (3003 defined in ASTM B209) specified in JIS; next, A method for producing an Al alloy material for building, characterized in that it is actually used only by performing hot rolling at a temperature of 290 to 340 ° C at the end of rolling.