JPH0146598B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the invention of a method for manufacturing gray-based aluminum wrought materials, and the present invention relates to the invention of a method for manufacturing gray-based aluminum wrought materials, and the present invention relates to an aluminum wrought material having an anodized film with a uniform color tone of light gray to dark gray with a slight bluish tinge. The object of the present invention is to provide a method that can stably and accurately produce a stretched material over multiple charges.

Japanese Patent Publication No. 49-16341, Japanese Patent Application Laid-open No. 55-24944, describes a method of obtaining aluminum materials with anodic oxide films of various tones by anodizing aluminum materials to which color-forming elements have been added.
This method has been known and practiced for a long time, such as in Japanese Patent Application Laid-open No. 53-43016, and in recent years, expanded processed materials obtained by the same method have been widely used for construction and construction materials, and their color tones are also varied. By specifying the manufacturing conditions according to the above-mentioned method, aluminum materials with different hues having different characteristics can be supplied. However, when using such conventional methods, the color tone of the processed material changes due to slight changes in the amount of added elements or casting or processing conditions, and it is necessary to avoid the occurrence of local unevenness in color tone even in the same lot. However, there is a disadvantage in that the color tone changes when such a product is used as a building material or other construction material.

The present invention was devised after repeated studies in view of the above-mentioned circumstances. We succeeded in stably obtaining a uniform coated plate with no color unevenness. That is, in the present invention, Fe: 0.3 to 2.2%, Si: 0.2% or less,
An alloy with a Si/Fe ratio of 0.20 or less with the remainder being Al and unavoidable impurities is produced, and the temperature of the molten metal is
The alloy at a temperature of 690 to 710°C is fed into a water-cooled mold for semi-continuous casting, which has a heat insulating part formed in the upper part and a quenching part in the lower part, and the melt surface height is at least twice the height of the quenching part in the heat insulating part. 35~90mm/ depending on the hot water supply conditions formed in
A cast body is formed at a casting speed of min. min, and the temperature is maintained at 550°C or less even when heating is performed on the cast body, an intermediate in the stretching stage of the cast body, or a processed material after stretching. It is stretched while being stretched, and then anodized in an electrolytic bath containing sulfuric acid to form a light gray to dark gray film.

To explain the method of the present invention more specifically,
The reasons for limiting the composition in the present invention are as follows.

Fe gives a light gray to dark gray oxide film depending on its content; however, if the content is below the lower limit of 0.3%, the oxide film with the unique hue of the present invention cannot be obtained; If it exceeds 2.2%, giant primary crystals are likely to occur, causing defects on the surface of the processed material.

If Si exceeds 0.2%, the unique color tone of the present invention tends to be lost, and the gloss and corrosion resistance also deteriorate, so this is the upper limit.

Even with the above composition, when the Si/Fe ratio is 0.2 or more, the same tendency as described for Si is observed, so this is set as the upper limit.

However, as mentioned above, molten aluminum containing Fe and Si is cast into a slab or billet shape using a semi-continuous casting method using a water-cooled mold, but in order to produce a uniform color tone according to the present invention, it is necessary to It was found that the coagulation conditions had to be homogeneous. Therefore, the present inventors used a semi-continuous casting mold in which a heat insulating part was formed in the upper part of the quenching part, and in this case, the depth of the quenching part under hot water supply conditions was shorter than that of a normal mold. The above-mentioned method is achieved by forming a hot water supply condition in which the upper part has an adiabatic region having a molten metal depth twice or more than that of the quenching region, and by casting at a specific casting temperature and casting speed. It was confirmed that similar tissues could be obtained. In other words, firstly, during casting, the length of the quenching section is shortened relative to the depth of the molten metal having a heat insulating part, and secondly, the melt supply conditions for the mold having the heat insulating part as described above. As shown in FIG. 1, it is necessary to perform casting under conditions in which the molten metal depth H in the heat insulating part is at least twice the depth in the quenching part, as shown in FIG. To explain this specifically, by setting the length of the quenching section to 25 to 50 mm, preferably 30 to 45 mm, the solidification conditions near the surface of the cast body can be made uniform. In other words, in order to make the structure uniform, the shorter the length of the quenching part in the mold, the better, according to the casting temperature and casting speed as described below, but if it is less than 25 mm, the molten metal in the mold will easily leak from the lower part of the mold. The casting operation becomes unstable. Moreover, if the thickness exceeds 50 mm, a part of the surface of the cast body may be remelted, making it impossible to make the solidification conditions near the surface of the cast body uniform, resulting in uneven color tone. However, the molten metal poured into the mold flows mainly horizontally into the mold through the float and descends below the cast body, but in normal semi-continuous casting, the molten metal poured into the mold flows into the mold wall. As a result, turbulent flow occurs, and the solid-liquid interface (where the molten metal begins to solidify) is rapidly cooled with a considerable temperature distribution, resulting in structural non-uniformity near the surface of the cast body. Even if a heat insulating part is formed above the quenching part, if the depth of the molten metal in the heat insulating part is short, solidification will be completed before the turbulence of the molten metal subsides, so the occurrence of structural inhomogeneity cannot be avoided. In the present invention, by adopting a depth of the molten metal in the heat insulating part that is long enough to suppress the turbulent flow of the molten metal in the mold, it is possible to produce a cast body with almost no structural heterogeneity near the surface as described above. It becomes possible to produce processed materials with uniform hardness and color tone. In other words, the turbulent flow of the molten metal poured into the mold is properly subsided while descending between the depths of the molten metal in the long insulation section, and the temperature distribution at the solid-liquid interface becomes uniform before reaching the quenching section, resulting in an advantageous effect. The solidification conditions near the surface of the cast body can be made uniform.

As for the depth of the molten metal in the heat insulating part above the quenching part, in general, the depth of the molten metal in the heat insulating part should be 2 to 6 times the depth of the quenching part, in terms of the relative relationship with the quenching part. preferable. In other words, the depth of the molten metal in the heat insulating part is less than twice the depth of the quenching part, because the drift of the poured molten metal in the mold cannot be buffered and the solidification conditions near the surface of the cast body cannot be made uniform. This will still cause uneven color tone, and if it is 6 times or more, the static pressure of the molten metal in the mold will increase, making it easy for the molten metal to leak from the lower part of the mold, making stable casting work difficult.

Note that the temperature at which the molten metal is poured into the mold as described above is preferably 690 to 710°C. That is,
If the temperature exceeds 710°C, even if the turbulent flow of the molten metal subsides in the long heat-insulating section, it becomes difficult to obtain a uniform temperature distribution at the solid-liquid interface, and the structure of the cast body tends to become non-uniform, which also causes uneven color tone. Furthermore, when the temperature is below 690°C, primary crystals of aluminum (pure aluminum) tend to occur near the surface of the cast body, which also causes uneven color tone. However, the casting speed in this case is preferably 35 to 90 mm/min, and if the casting speed is less than 35 mm/min, neck-like defects will occur on the surface of the cast object even if the above requirements are satisfied. Stable solidification conditions cannot be obtained, which causes uneven color tone, and conversely, when the flow rate exceeds 90 mm/min, the amount of molten metal flowing into the mold per unit time increases, resulting in stronger turbulence and non-uniform structure. Color tone unevenness tends to occur, and the molten metal in the mold tends to leak from the lower part of the mold, making the casting operation unstable.

The specific mold configuration according to the present invention, taking into consideration the above-mentioned relationships, is as shown in FIGS. 1 to 3.
The figure shows a relatively long water cooling chamber, FIG. 2 shows a standard case, and FIG. 3 shows a relatively short one. That is, in these drawings, 10
are water cooling chambers, and 11 indicates the molten metal surface.The molten metal surface 11 is detected by the float 4, and when it becomes low, the molten metal is rapidly replenished, and as it rises, the molten metal surface 11 is detected. Therefore, the depth of the molten metal in the mold 1 is always maintained at a constant level. However, both 2 and 3 are members having a certain degree of heat insulation, and in particular member 2 is formed into a thin layer suitable for lining the inner surface of the mold 1.
Further, the member 3 is made of a material and strong enough to maintain the molten metal surface inside as a mold. In these mold mechanisms, the quenching part has a height h in the range shown in FIG. The above-mentioned relationship is adopted between the heights h and H. Note that water is poured 7 from the water cooling chamber 10 onto the surface of the cast body 6 pulled out from the quenching section 5,
It is designed for further cooling.

However, in the present invention, the cast body 6 obtained by the above-mentioned installation and method is stretched, but the stretching is carried out at a temperature of 550° C. or lower, as is generally known. In the case where the stretched material is further heat-treated as a final processed material, it is necessary to carry out the heat treatment at a temperature of 550° C. or lower. If the heating temperature exceeds 550°C, it will not be possible to obtain the uniform light gray to dark gray film with a bluish tinge that is unique to the present invention. When the phase or compound of the cast body that is thought to develop the color unique to the present invention when heated _to
It is recognized that this is due to the fact that it is changed into (such as Al ₃ Fe).

The cast body obtained as described above is stretched, and this stretching can be carried out by any suitable method. Specifically, plate materials are produced by rolling to a desired thickness by either hot or cold rolling, or a combination thereof, and in the case of extruded materials, the cast material is rolled through a die having a desired shape. However, in the case of heating during these stretching processes, it is necessary to carry out the heating at the above-mentioned temperature of 55°C or lower.

In the anodizing process, an aqueous solution containing sulfuric acid is used as the electrolyte, and the current density is preferably 3.5 Amp/dm ² or less. That is, this current density is 3.5Amp/d
If it exceeds m ² , the film will become yellowish brown, which is not preferable. The sealing treatment of the film after this anodizing treatment can be carried out appropriately by a conventional method.

When the method of the present invention as described above is used, an aluminum wrought material having a consistently uniform colored film with excellent reproducibility can be obtained. That is, the obtained film exhibits a deep pale color or dark gray color with a bluish tinge, and can be used in a wide range of applications as a material for exterior or interior materials of various buildings, furniture, etc. In particular, it can be used appropriately for wide-width exterior materials that are difficult to use with conventional methods.

Specific examples of the invention are as follows.

Example 1 Al-0.5%Fe-0.05%Si alloy was cast into a slab of 508 x 1060 mm with the height of the quenching section being 40 mm, the depth of the molten metal from the lower end of the insulation above the quenching section being 120 mm, and a casting speed of 65 mm.
mm/min, semi-continuously cast at a molten metal temperature of 690°C, the slab was face cut, soaked and heated at 450°C for 2 hours, and then rolled into a 3mm thick plate by hot and cold rolling. . 15% of the obtained 1000 x 2000 mm board
When anodized in a sulfuric acid bath at 1.5 mm/dm ² × 45 min, the product had no streaks and a uniform light gray film with no uneven color tone.
It was confirmed that even when these 20 sheets were lined up, there was no difference between them.

Example 2 Al-1.8%Fe-0.2%Si alloy was cooled at a height of 35
mm, the depth of the molten metal from the lower end of the insulation on the quenching section is
The slab dimensions were the same as in Example 1 due to the casting conditions of 120 mm, and the molten metal temperature was 700 mm.
℃, casting speed was 60 mm/min. After performing slab surface grinding and soaking treatment in the same manner as in Example 1.
A plate with a thickness of 3 mm was obtained by hot and cold rolling at 450°C, and the plate thus obtained was anodized in a 15% sulfuric acid bath at the same current density and treatment time as in Example 1. It was confirmed that 24 coated plates with a uniform gray color without streaks or color unevenness could be properly obtained in 8 charges, and that there was no difference in color tone even when these 24 plates were observed side by side. It was done.

Comparative Example 1 Al-1.8%Fe-0.08%Si alloy was formed into a 355 x 910 mm slab using a water-cooled mold with a length of 70 mm according to a conventional method, and the molten metal was poured at a temperature of 690°C and a casting speed of 60 mm/min.
Semi-continuous casting was performed at min. The slab was then face-milled, soaked at 450°C for 2 hours, and then hot and cold rolled at 450°C into a 3mm thick plate of 500x1000mm.
The cut plate was heated at 1.5A x dm ² x in a 15% sulfuric acid bath.
When anodic oxidation treatment was performed for 45 minutes, a dark gray coated plate was obtained, but each part had significant color tone unevenness along the rolling direction. Also, some of the coated plates had many thin streaks about 1 to 2 mm wide.

Comparative Example 2 Using the same alloy and mold as in Example 2, casting was carried out at a molten metal temperature of 720° C. and a casting speed of 65 mm/min. After carrying out the slab facing and soaking treatment in the same manner as in Example 1, a plate with a thickness of 3 mm was obtained by hot and cold rolling at 450°C, and this plate was heated in a 15% sulfuric acid bath at the same current as in Example 1. When the anodic oxidation treatment was carried out depending on the density and treatment time, narrow and sharp color tone unevenness slightly occurred along the rolling direction.

Comparative Example 3 Using the same alloy and mold as in Example 2, casting was carried out at a molten metal temperature of 680° C. and a casting speed of 65 mm/min. After carrying out the slab facing and soaking treatment in the same manner as in Example 1, a plate with a thickness of 3 mm was obtained by hot and cold rolling at 450°C, and this plate was heated in a 15% sulfuric acid bath at the same current as in Example 1. When anodic oxidation treatment was carried out depending on the density and treatment time, it was found that there was a slight unevenness in color tone in the form of an indistinct band with wide boundaries along the rolling direction.

Comparative Example 4 Using the same alloy and mold as in Example 2, casting was carried out at a molten metal temperature of 710° C. and a casting speed of 30 mm/min. After carrying out the slab facing and soaking treatment in the same manner as in Example 1, a plate with a thickness of 3 mm was obtained by rolling at 450°C and cold rolling, and this plate was placed in a 15% sulfuric acid bath at the same current density as in Example 1. When anodic oxidation treatment was carried out for a treatment time of 200 mL, it was found that there was an indistinct band-like color tone unevenness with wide boundaries along the rolling direction.

Comparative Example 5 Using the same alloy and mold as in Example 2, casting was carried out at a molten metal temperature of 690° C. and a casting speed of 100 mm/min. After carrying out the slab facing and soaking treatment in the same manner as in Example 1, a plate with a thickness of 3 mm was obtained by hot and cold rolling at 450°C, and this plate was heated in a 15% sulfuric acid bath at the same current as in Example 1. When the anodic oxidation treatment was carried out depending on the density and treatment time, there was severe narrow and sharp color tone unevenness along the rolling direction.

Comparative Example 6 The same alloy and mold as in Example 2 were used, but the casting conditions were such that the depth of the molten metal from the lower end of the insulation provided on the quenching section with a height of 35 mm was 50 mm, and the molten metal temperature was 700°C. , casting speed of 60 mm/min were the same as in Example 2, slab facing, soaking treatment, hot rolling and cold rolling were carried out in the same manner, and anodizing treatment was carried out in the same manner. It was confirmed that indistinct color tone unevenness with a wide border occurred along the direction.

According to the present invention as described above, it is possible to appropriately clarify the cause of uneven color tone and accurately produce a stretched aluminum material having a stable and uniform color tone over multiple charges. This is an invention with great industrial effects.

[Brief explanation of drawings]

The drawings illustrate embodiments of the invention,
1 to 3 are partial cross-sectional views showing some examples of molds for carrying out the method of the present invention. However, in these drawings, 1 is a mold, 2,
3 are members each having heat insulating properties, 4 is a float, and 5
6 is a quenching section, 6 is a cast body, 7 is a water injection chamber, 10 is a water cooling chamber, and 11 is a molten metal surface.

Claims (1)

[Claims] 1 Contains Fe: 0.3 to 2.2%, Si: 0.2% or less,
An alloy with a Si/Fe ratio of 0.20 or less with the remainder being Al and unavoidable impurities is produced, and the temperature of the molten metal is
The alloy at a temperature of 690 to 710°C is fed into a water-cooled mold for semi-continuous casting, which has a heat insulating part formed in the upper part and a quenching part in the lower part, and the melt surface height is at least twice the height of the quenching part in the heat insulating part. 35~90mm/ depending on the hot water supply conditions formed in
A cast body is formed at a casting speed of min. min, and the temperature is maintained at 550°C or less even when heating is performed on the cast body, an intermediate in the stretching stage of the cast body, or a processed material after stretching. 1. A method for producing a gray aluminum wrought material, which comprises stretching it while tightening it, and then anodizing it in an electrolytic bath containing sulfuric acid to form a light gray to dark gray film.