JP2001220638A - Aluminum alloy excellent in surface quality and component designing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy satisfying various characteristics to be required and moreover excellent in surface quality and to provide a component designing method therefor. SOLUTION: In a multicomponent aluminum alloy containing Fe, Si and other alloying elements by one or more components, an aluminum alloy in which the solid-liquid coexisting temperature range is 30 deg.C or less, and, in intermetallic compounds of 0.5 μm or more, the ratio of the number of the compounds, in which the content of the above other alloying laments is 50% or more, is 30% or les is excellent in surface quality. For designing the above aluminum alloy, the liquid phase temperature and the solid phase temperature of the above aluminum alloys in variety are measured or calculated, the solid- liquid coexisting temperature range in which the unevenness of etching exceeding an allowable range starts to be generated is investigated, and the respective contents of the above other alloying elements are decided so as to be controlled to this temperature range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy having excellent surface quality and a method for designing its components. More specifically, the present invention relates to an aluminum alloy which is used after being subjected to a surface treatment such as anodic oxidation treatment or etching, and The present invention relates to aluminum alloys suitable for interior and exterior panels for use, heat exchange fins (air conditioners, radiators, etc.), daily necessities, kitchenware, lithographic printing plate supports, electric components, optical devices, and the like, and a method of designing the components thereof.

[0002]

2. Description of the Related Art In recent years, various color tones have been demanded from the viewpoint of designability, and Al has been developed to improve productivity and the like.
The conditions for anodizing and etching of alloys are also diversified, and it is required to quickly design an optimal component system according to the required characteristics of each Al alloy.

In general, when designing the composition of an aluminum alloy, surface treatment properties are important properties to be taken into consideration. However, in consideration of basic properties such as strength, ductility and formability, these properties are comprehensively considered. As a result, the principal component system has been determined.
However, by changing the addition elements and the respective addition amounts in various ways,
When pursuing improvements in properties other than surface treatment properties such as strength, due to the effect of the added alloying element, the content of components that tend to cause unevenness in etching and uneven color tone due to anodic oxidation increases, Even if the basic characteristics are satisfied, there is a problem that the commercial value is lost due to a defect in appearance.

In an aluminum alloy which crystallizes an A1-Fe intermetallic compound, the form of the compound crystallized near or inside the surface of the ingot differs depending on the casting conditions and the size of the ingot. It is known that it affects the anodizing property, etching property unevenness, appearance unevenness, color tone unevenness, etc. of the final product. In particular, there is a problem in that streaky color tone unevenness occurs after processing due to a difference in phase of an intermetallic compound or a fir tree structure generated during ingot casting. Therefore, as a method for preventing the formation of a fir tree-like structure, a method of controlling the amount of components or intermetallic compounds (for example, Japanese Patent Publication No. 58-26421,
JP-A-7-126890, JP-A-5-320839, JP-A-9-235638, JP-A-8-269649, etc.)
And a method of controlling by a casting method (for example,
156487, JP-A-9-141393, Japanese Patent Publication No.
26788, JP-A-1-24590, etc.). However, according to the above component design method and casting method, Cu, Mn, Mg, N
i, Cr, Ti, Zr, Zn, B, V, Be, Ga, S
When a multi-component aluminum alloy to which alloying elements such as n, Ca, Sr, and Co are added is used, the required surface quality cannot be sufficiently satisfied.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an aluminum alloy which satisfies various required characteristics and has excellent surface quality, and a method of designing its components. It is something to offer.

[0006]

The aluminum alloy of the present invention which has solved the above-mentioned problems is a multi-component aluminum alloy containing one or more other alloying elements together with Fe and Si, and has a solid-liquid coexistence temperature. The range is 30 ° C. or less;
When the content of the other alloying element in the intermetallic compound of 5 μm or more is 5 mass% or more, the ratio of the number of the compounds is 3
The gist should be 0% or less.

[0007] In addition, the method of designing a component of an aluminum alloy according to the present invention which solves the above-mentioned problems is as follows: The type and content of the alloying element of a multi-component aluminum alloy containing one or more other alloying elements together with Fe and Si. A method for designing the composition of an aluminum alloy in which the amount is set, wherein the liquidus temperature and the solidus temperature of various aluminum alloys are measured or calculated, and the allowable range (the allowable etching unevenness according to the purpose or application) is determined. The gist is to investigate the solid-liquid coexistence temperature range in which the etching unevenness exceeding the range begins to occur, and to determine the content of each of the other alloying elements so as to be within this temperature range.

The liquidus temperature is the temperature at which a solid phase appears in the liquid phase during the cooling process of the liquid phase.
The temperature at which all liquid phases change to solid phases. The solid-liquid coexisting temperature range is a temperature range in which a solid phase and a liquid phase coexist,
In other words, it is the temperature difference between the liquid phase temperature and the solid phase temperature.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to obtain an Al alloy plate having excellent surface quality, it is essential to prevent etching unevenness. The reason for this uneven etching is that
This is because the etching properties, etching rates, etc., differ depending on the difference in the form of the intermetallic compound in the material. This is caused by various changes to a metastable phase and a stable phase on the equilibrium diagram. For example, A1-Fe-based crystallized substances, with the components and casting _{conditions, A1 3 Fe, A1 6 Fe} , A1 m Fe of other alpha-A
1FeSi, β-A1FeSi, etc.

[0010] Furthermore, the state of these ingots at the time of ingot or the solid solution state is liable to fluctuate, which affects the precipitation behavior in the subsequent soaking step or hot working step. ing.

In any of the alloy types, components other than Fe and Si contribute to the improvement of surface treatment properties, anodic oxidation treatment properties, mechanical properties (strength, ductility, toughness, hardness, etc.), formability, corrosion resistance, etc. Alloying elements are selected and added.
The alloying elements include Cu, Mn, Mg, Ni, C
r, Ti, Zr, Zn, B, V, Be, Ga, Sn, C
Although there are a, Sr, Co, etc., the morphology of the crystallized material was greatly changed by the influence of these alloying elements, and the surface quality was varied. Further, the above-mentioned A1-Fe system and A1
-When the crystallization form in the Fe-Si system is a metastable phase, the alloying element is easily dissolved or replaced, and the crystallization form is variously changed to change the surface quality and the etching property. Is what it is.

[0012] In addition, depending on the steps of soaking, hot working, cold working, annealing, and the like (some products include an intermediate annealing step) after casting, which are ordinary manufacturing steps, there are crystallized forms during casting. The variation is caused by A1-Fe-based precipitates and A1-Fe during the process.
-Affects Si-based precipitates, single-Si precipitation, etc., and affects variations in surface quality.

The present inventors have conducted intensive studies on a method for controlling the surface quality in a multi-component system that changes in a complex manner.
It has been found that the content of alloying elements other than Fe and Si in the A1-Fe-Si based intermetallic compound and the solid-liquid coexistence temperature range of the Al alloy are closely related to the surface quality. That is, the surface quality can be improved by controlling the temperature range in which the liquid phase exists, and it is ascertained that the component design of an Al alloy having excellent surface quality is possible even in a multi-component system,
The present invention has been made.

First, the reason for setting the solid-liquid coexistence temperature range (hereinafter sometimes referred to as ΔT) to 30 ° C. or lower in the present invention is as follows.

A component system having a larger solid-liquid coexistence temperature range ΔT is more susceptible to fluctuations in the crystallized phase depending on casting conditions, and its form is more likely to vary at the surface of the ingot. Therefore, the phase of the intermetallic compound tends to fluctuate, and a fir tree structure of the ingot tends to occur. As shown in FIG. 1, when the liquid phase alloy is cooled, after the liquidus temperature, a solid phase also starts to appear, and as a compound, an Al—Fe-based compound is generated,
Next, a metastable Al-Fe phase is formed, and all of the remaining liquid phase becomes a solid phase at the solid phase temperature. The liquid phase, aluminum matrix (solid phase) and A1-Fe
The wider the temperature range in which the system compounds coexist, the more component systems
Depending on the conditions in the solidification / cooling process at the time of casting, the variation in the formation of the A1-Fe-based stable phase and the metastable phase tends to increase. That is, a component system having a wider solid-liquid coexistence temperature range tends to have a more variable surface quality, and a narrower range allows component design without deteriorating the surface quality. Therefore, ΔT should be less than 30 ° C.
It is preferable that the temperature is 8 ° C or lower. It should be noted that ΔT should be limited to a smaller value for an aluminum alloy applied to a field where the demand for surface quality is strict (for example, 15T).
C. or lower, 10 ° C. or lower, 5 ° C. or lower). The temperature of 30 ° C. or lower specified in the present invention is a value in the case where only the surface quality is improved compared to the conventional one without considering the relationship with other applications. Also,
As a general tendency of each component, the solid-liquid coexistence temperature range of Fe tends to narrow with an increase in the addition amount, and the solid-liquid coexistence temperature range increases with an increase in the addition amount of an element other than Fe in the case of an element other than Fe. There is a tendency. However, the degree of influence differs depending on the type of alloying element, and in a multi-component system, the solid-liquid coexistence temperature range also changes due to the interaction of each component.
Further, the temperature range that exceeds the range of allowable etching unevenness varies depending on the purpose and application.

Next, in the present invention, a compound having a content of alloying elements other than Fe and Si of at least 5% by mass, which is an intermetallic compound having a size of at least 0.5 μm, is added in an amount of 30% by number.
The reason for the following is as follows.

Alloying elements other than Fe and Si are dissolved or substituted in the A1-Fe-based and A1-Fe-Si-based compounds to change the crystallized form in various ways, thereby reducing the surface quality and etching property. It has been changed, but especially the size is 0.
The compound phase of 5 μm or more has a bad influence on the surface quality, the appearance deterioration and the etching property, and particularly when the content of alloying elements other than Fe and Si is 5% by mass or more, the bad influence is large. From the viewpoint of improving the surface quality, the mass ratio in the alloying elements other than Fe and Si and the intermetallic compound is preferably small, and more preferably 4% by mass or less.

Actually, the amount of the intermetallic compound is effective. Specifically, a compound in which the content of alloying elements other than Fe and Si is 5% by mass or more is 30% by number. If it exceeds, the surface quality deteriorates. It is desirable that the number ratio of the above compound is small, more preferably 25% or less.

The casting conditions for producing the Al alloy according to the present invention include semi-continuous casting and continuous casting in the casting method, and depend on the mold size and the capacity of each equipment. Although it cannot be specified, in the case of a component system having a large ΔT, the effect of the added element on the etching property is large and crystallized matters are likely to be uneven. Therefore, it is preferable to control the cooling rate at a lower cooling rate with the minimum amount of cooling water that can be cast. , △ T
In a component system having a small value, the effect of the added element on the etching property is small, and it is difficult to cause unevenness of crystallized substances. Therefore, the cooling rate may be controlled at a high speed.

When designing the composition of a multi-component Al alloy, the main component is usually determined from the viewpoints of surface treatment properties, strength, ductility, formability, etc., but the present invention satisfies these properties. In addition, the present invention provides a method for designing a multi-component system alloy with good surface quality, and controls the solid-liquid coexistence temperature range to design a component of a multi-component Al alloy.

FIG. 2A shows that Fe: 0.36%, Si:
Al alloy A containing 0.05% and Cu: 0.016%
FIG. 2B is a graph showing the liquid phase temperature and the solid phase temperature depending on the amount of Fe added and the temperature.
Si: 0.05%, Cu: 0.005%, Ni: 0.0
3 is a graph showing a liquid phase temperature, a solid phase temperature, and the like depending on the amount and temperature of Fe added to an Al alloy B containing 3%. Alloy A
Comparing the solid-liquid coexisting temperature range of the alloy B and the alloy B, it can be seen that the solid-liquid coexisting temperature range is widened by the addition of Ni.

In designing the components, the liquid phase temperature and the solid phase temperature of an Al alloy having a reference composition satisfying the main characteristics such as strength are measured or calculated, and are allowed according to the purpose and application. Investigate the upper limit solid-liquid coexistence temperature range where surface quality unevenness beyond the range of surface quality unevenness starts to occur,
This can be performed by determining the multi-component elements (alloying elements) of the aluminum alloy and the amounts of the respective alloying elements to be added within this temperature range.

In the component designing method according to the present invention, it is necessary to previously measure or calculate the liquidus temperature and the solidus temperature with various compositions and addition amounts. If it is systemized, it is possible to quickly design components of a multi-component system. A thermodynamic equilibrium diagram calculation can be cited as a method of calculating the liquidus temperature and the solidus temperature.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples do not limit the present invention, and any design change based on the above and following gist is not limited to the examples. It is within the technical scope of the invention.

[0025]

EXAMPLES As shown in Example 1 in Table 1, the conventional DC casting an aluminum alloy having the composition of changing solid-liquid coexistence temperature range in a variety,
An ingot having a thickness of 500 mm and a width of 1500 mm was cast. Then, after the homogenization treatment, the surface was cut, or the surface was subjected to the homogenization treatment, followed by heating or furnace cooling, hot working and cold working to prepare a plate material. Using these plates,
A solid-liquid coexistence temperature range is determined as follows,
Intermetallic compounds were analyzed and surface quality was investigated.
Furthermore, the variation of each characteristic value was also evaluated.

(1) Calculation of the solid-liquid coexisting temperature range The liquid phase temperature and the solid phase temperature were measured by differential thermal analysis, and the temperature range of the solid-liquid coexisting region was calculated.

(2) Content of alloying component in intermetallic compound of 0.5 μm or more EDS by TEM, FE-TEM or FE-SEM
The size of the intermetallic compound and the content of each component in the intermetallic compound were measured by (EDX). The number of intermetallic compounds measured was 200 or more, and the number ratio of compounds in which each component other than Fe and Si exceeded 5% by mass was calculated.

(3) Surface quality investigation Alkali etching 10% NaOH aqueous solution at 60 ° C.
After etching for 3 minutes, washing with water and desmutting with nitric acid, the unevenness of etching was evaluated visually and with a roughness meter according to the following criteria. ◎: good ○: acceptable △: bad ×: very bad

(4) Evaluation of Characteristics Variation Strength Using a JIS No. 5 tensile test piece, a tensile test was performed at a tensile speed of 5 mm / min up to a 0.2% proof stress, and at a tensile speed of 20 mm / min thereafter. The proof stress was measured.

LDH (Limiting Tensile Height) A ball-overhanging punch having a diameter of 101.6 mm was used to obtain a length of 18 mm.
A wrinkle holding pressure of 2 on a test piece having a width of 0 mm and a width of 110 mm
Molding was performed using a lubricating oil for copper plates (“R-303P” manufactured by Sugimura Chemical Industry Co., Ltd.) under the conditions of 00 KN and a punch speed of 4 mm / s, and the LDH was measured.

In the above test, the characteristic variation was evaluated by repeating the test three times and varying the characteristic value at a total of six locations in the coil, that is, a front end, a center, a rear end, and a center and an end in the width direction. Ratio [= [("maximum value"
− “Minimum value”) / “average value”] × 100%].

Ear ratio Blank diameter 80 mm, punch diameter 40 mm, drawing ratio 50%
A cup squeezing test was performed, and the ear ratio was determined by the following formula. Ear ratio = [[((45 ° − “average height in four directions”) − (0,
90 ° − “average height in four directions”)] / “average height in eight directions”] × 100 (%) (here, 45 ° means ears in the rolling direction of 45 °). To evaluate the variation of the rate, the test was repeated three times, and the width of the characteristic value variation (= “maximum value”) −
"Minimum value").

[0033]

[Table 1]

[0034]

[Table 2]

No. Nos. 1 to 8 are examples of the present invention, in which the surface quality was good without etching unevenness, and the dispersion of various characteristic values was small.

On the other hand, no. 9 to 11, the ratio of the number of compounds in which the solid-liquid coexistence temperature range exceeds 30 ° C. and the content of alloying elements other than Fe and Si is 5% by mass or more in the intermetallic compound of 0.5 μm or more. This is a comparative example in which it exceeds 30%, in which etching unevenness was observed and the variation in characteristics was large.

Example 2 No. 3 in Table 3 No. B-1 is assumed to be designed based on the alloy No. B-1. The alloy No. B-1 was used as a base, and the solid-liquid coexistence temperature range was variously changed. B-2
Alloys Nos. B-9 were manufactured in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.

[0038]

[Table 3]

[0039]

[Table 4]

No. Nos. B-1 to B-9 satisfy the condition of claim 1 of the present invention and have good surface quality without etching unevenness. B-2 to B-6
No. is a base alloy. The surface quality is equal to or higher than that of B-1. B-1
Than was better. On the other hand, no. B-7 to B
In the case of -9, the surface quality is inferior to that of B-1, and the quality characteristics also vary widely. Therefore, as described above, B
Assuming a situation in which the component design is performed on the basis of the -1 alloy, the design may be performed with the target of an alloy such as B-2 to B-6. In this case, it is understood that it is preferable to design the components by setting the allowable temperature range of the surface quality unevenness to 15 ° C. or less.

[0041]

As described above, according to the present invention, it is possible to provide an aluminum alloy which satisfies various required characteristics and has an excellent surface quality, and a method for designing its components.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a solid-liquid coexisting temperature range.

FIG. 2 is a graph showing a relationship between an alloying element and a solid-liquid coexistence temperature range.

Claims (2)

[Claims] 1. The method according to claim 1, further comprising adding another alloying element together with Fe and Si.
A multi-component aluminum alloy containing at least one component, the solid-liquid coexistence temperature range is 30 ° C. or less, and the content of the other alloying element in the intermetallic compound of 0.5 μm or more is 5% by mass or more. An aluminum alloy having excellent surface quality, wherein the ratio of the number of compounds is 30% or less. 2. An alloying element together with Fe and Si,
An aluminum alloy component design method for setting the type and content of alloying elements of a multi-component aluminum alloy containing at least one component, wherein the liquid phase temperature and solid phase temperature of various aluminum alloys are measured or calculated. Investigate the solid-liquid coexistence temperature range at which etching unevenness exceeding the allowable range begins to occur, and determine the content of each of the other alloying elements so as to be within this temperature range.Excellent surface quality. Aluminum alloy composition design method.