CN110709526A

CN110709526A - Aluminum alloy and aluminum alloy cast product

Info

Publication number: CN110709526A
Application number: CN201780091658.XA
Authority: CN
Inventors: 镝木敦夫; 宫尻聪; 大城直人; 山田毅
Original assignee: Daiki Aluminium Industry Co Ltd
Current assignee: Daiki Aluminium Industry Co Ltd
Priority date: 2017-06-23
Filing date: 2017-06-23
Publication date: 2020-01-17
Also published as: JPWO2018235272A1; WO2018235272A1; PH12019502327A1; JP6267408B1

Abstract

The present invention provides an aluminum alloy which can be economically and sustainably produced using recycled materials such as scrap, and which can well balance mechanical properties, particularly tensile strength, elongation, 0.2% yield strength and hardness, and can also cope with the expansion of uses mainly in general transportation facilities, and an aluminum alloy cast product produced from the aluminum alloy. Specifically, the present invention is an aluminum alloy characterized by containing, in terms of weight%, 0.75% or more and not more than 1.25% of Cu, 7.5% or more and not more than 8.5% of Si, 0.50% or more and not more than 0.80% of Mg, 0.20% or more and not more than 0.50% of Fe, 0.30% or more and not more than 0.50% of Mn, 0.10% or more and not more than 0.30% of Cr, and the balance being Al and unavoidable impurities, and an aluminum alloy cast product thereof.

Description

Aluminum alloy and aluminum alloy cast product

Technical Field

The present invention relates to an aluminum alloy having excellent mechanical properties and an aluminum alloy cast product using the aluminum alloy.

Background

In general transportation equipment such as bicycles and automobiles, weight reduction is required, and the application of aluminum alloy castings is expanding. Conventionally, JIS ADC3 alloy has been used in many of such applications, but applications in which mechanical properties cannot be satisfied with such conventional materials have become remarkable as the applications expand.

Therefore, in order to cope with applications that cannot be dealt with by conventional materials such as JIS ADC3 alloy, for example, patent document 1 (japanese unexamined patent publication No. 2003-27169) discloses an aluminum alloy containing, as an aluminum alloy having improved mechanical strength and toughness, 8.5 to 9.5% of Si, 0.20% or less of Cu, 0.20 to 0.40% of Mg, 0.6% or less of Fe, 0.30 to 0.50% of Mn, 0.05 to 0.15% of Ti, 0.01 to 0.025% of Sr, and 0.15% or less of Zn on a weight basis, with the balance being Al.

According to this technique, it is considered that an aluminum alloy having high strength and high toughness can be provided which is resistant to fracture even in a severe use environment (a use environment of a conventional material).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2003-27169

Disclosure of Invention

Problems to be solved by the invention

However, if Cu is regarded as an impurity and the content of Cu is limited to 0.20% or less as described above in order to maintain the corrosion resistance of the alloy, it is practically impossible to use scrap materials, and an aluminum alloy cannot be economically produced, and it is also an obstacle to the establishment of a recycling society. Further, Cu has an effect of improving mechanical properties such as tensile strength and 0.2% yield strength with respect to an aluminum alloy, but if the content of Cu is limited to 0.20% or less, the effect is also limited.

Accordingly, an object of the present invention is to provide an aluminum alloy which can be economically and sustainably produced using recycled materials such as scrap materials, and which has well-balanced mechanical properties, particularly tensile strength, elongation, 0.2% yield strength, and hardness, and can also cope with applications which are mainly expanded in general transportation facilities; and an aluminum alloy cast product made of the aluminum alloy.

Means for solving the problems

The invention 1 of the present application is an aluminum alloy characterized by comprising, in% by weight, 0.75% to 1.25% of Cu, 7.5% to 8.5% of Si, 0.50% to 0.80% of Mg, 0.20% to 0.50% of Fe, 0.30% to 0.50% of Mn, 0.10% to 0.30% of Cr, and the balance of Al and unavoidable impurities.

In the present invention, Cu is contained in a range of 0.75 wt% to 1.25 wt% inclusive and Mg is contained in a range of more than 0.50 wt% to 0.80 wt% inclusive, so that not only can recycled materials such as scrap be used, but also mechanical properties such as tensile strength, 0.2% yield strength and hardness can be improved. In addition, since the content of Cu that may deteriorate the corrosion resistance is suppressed within the above range and Cr having an effect of improving the corrosion resistance is contained in an amount of 0.10 wt% or more and 0.30 wt% or less, the decrease in corrosion resistance of the aluminum alloy associated with the Cu content can be suppressed to a minimum.

As described above, in the present invention, only by mainly containing the above six element components at predetermined ratios, and utilizing the interaction thereof, it is possible to economically and easily produce an aluminum alloy ingot excellent in castability and mechanical properties using a recycled raw material.

In the aluminum alloy of the present invention, Ti is preferably contained in an amount of 0.30 wt% or less based on the total weight of the alloy. By doing so, the crystal grains of the alloy can be refined to further effectively suppress casting cracks, and the mechanical properties, particularly the elongation, can be improved.

In the aluminum alloy of the present invention, it is preferable that at least one selected from the group consisting of Na, Sr, and Ca is further added in an amount of 30 to 200ppm based on the total weight of the alloy, and Sb is further added in an amount of 0.05 to 0.20 wt% based on the total weight of the alloy. By doing so, the particles of eutectic Si can be made finer, and the toughness and strength of the aluminum alloy can be further improved.

Preferably, B is further added in an amount of 1 to 50ppm based on the total weight of the alloy. By doing so, even when the amount of Si is small or when a casting method with a slow cooling rate is used, the crystal grains of the aluminum alloy can be refined, and as a result, the elongation of the aluminum alloy can be improved.

The invention according to claim 2 is an aluminum alloy cast product produced from the aluminum alloy according to claim 1.

The aluminum alloy cast product produced from the aluminum alloy of the present invention has good castability, can be mass-produced, and can well balance mechanical properties, particularly tensile strength, elongation, 0.2% yield strength, and hardness, and therefore, for example, the aluminum alloy cast product can be suitably used in a new application requiring a lightweight cast product in general transportation facilities in which the application of the aluminum alloy cast product is expanding.

Effects of the invention

According to the present invention, it is possible to provide an aluminum alloy which can be economically and sustainably produced using a recycled material such as scrap and which has well-balanced mechanical properties, particularly tensile strength, elongation, 0.2% yield strength and hardness and can also cope with applications which are mainly expanded in general transportation facilities; and an aluminum alloy cast product made of the aluminum alloy.

Drawings

Fig. 1 is a graph showing the relationship between the content of Cu and the physical properties of an aluminum alloy that has not been heat-treated.

Fig. 2 is a graph showing the relationship between the Cu content and the physical properties of the aluminum alloy treated by T6.

Detailed Description

The following description will discuss embodiments of the present invention, with specific examples being shown.

The aluminum alloy of the present invention is substantially constituted by: the alloy comprises, by weight, Cu of 0.75% to 1.25%, Si of 7.5% to 8.5%, Mg of 0.50% to 0.80%, Fe of 0.20% to 0.50%, Mn of 0.30% to 0.50%, Cr of 0.10% to 0.30%, and Al and inevitable impurities in balance. The characteristics of each element will be described below.

Cu (copper) is an important element for improving wear resistance, mechanical strength and hardness of aluminum alloys.

The content of Cu with respect to the total weight of the aluminum alloy is preferably in the range of 0.75 wt% to 1.25 wt%, as described above. This is because the above-described mechanical property improving effect cannot be obtained when the content of Cu is less than 0.75% by weight, and tensile strength and elongation are insufficient mainly in the T6 treated material (described later) when the content of Cu exceeds 1.25% by weight.

Si (silicon) is an important element for ensuring the fluidity of an aluminum alloy when melted and improving the castability.

The content of Si with respect to the total weight of the aluminum alloy is preferably in the range of 7.5 wt% to 8.5 wt%, as described above. This is because, when the content of Si is less than 7.5 wt%, it is difficult to ensure the fluidity of the molten metal, and when it is considered that the molding is performed by a general die casting method which is generally used in many cases, the application to a large-sized member is hindered, and when the content of Si exceeds 8.5 wt%, the castability is improved, but the elongation of the alloy is remarkably lowered.

Mg (magnesium) is mainly in a solid solution state in an Al base material in an aluminum alloy or as Mg₂Si is a component that imparts yield strength and hardness to the aluminum alloy, while at the same time, due to an excessively large content, elongation is significantly reduced and casting properties and corrosion resistance are also adversely affected.

The content of Mg with respect to the total weight of the aluminum alloy is preferably in the range of more than 0.50 wt% and 0.80 wt% or less, as described above. This is because, when the content of Mg is 0.5 wt% or less, it is difficult to ensure 0.2% yield strength and hardness of the alloy regardless of the heat treatment, and when the content of Mg exceeds 0.8 wt%, the elongation of the alloy is significantly reduced.

Fe (iron) is known to have an effect of preventing burning of a mold when casting such as die casting is performed. However, this Fe precipitates needle-like crystals containing Al — Si — Fe, which lowers the toughness (elongation) of the aluminum alloy, and makes it difficult to melt at an appropriate temperature when added in a large amount.

The content of Fe relative to the total weight of the aluminum alloy is preferably 0.20 wt% or more as described above when a recovery raw material such as scrap is used as a part of the raw material from the viewpoint of recovery. On the other hand, when the content of Fe is too high, needle-like crystals containing Al — Si — Fe precipitate as described above, and the elongation of the alloy decreases, so the upper limit thereof is preferably 0.50 wt% or less as described above.

Like Fe, Mn (manganese) is mainly used for preventing seizure between an aluminum alloy and a mold during casting such as die casting. Since it is difficult to melt at an appropriate temperature when Mn is contained in a large amount, as in Fe, the upper limit of the content of Mn with respect to the total weight of the aluminum alloy is limited to 0.50 wt% or less in the present invention.

The lower limit of the Mn content is preferably 0.30 wt% or more as described above in order to exhibit the above-described seizure preventive effect remarkably.

Cr (chromium) is an element which prevents seizure between the aluminum alloy and the mold during casting such as die casting, and has an effect of improving the corrosion resistance of the alloy, similarly to Fe and Mn described above.

The content of Cr with respect to the total weight of the aluminum alloy is preferably in the range of 0.10 wt% to 0.30 wt%, as described above. This is because the above-mentioned effect cannot be sufficiently obtained when the content of Cr is less than 0.10 wt%, and the effect of addition is not improved even when the amount of addition is increased more than 0.30 wt%.

When the content ratios of Cu, Si, Mg, Fe, Mn, and Cr are adjusted in accordance with the above content ratios, an aluminum alloy having well-balanced mechanical properties, particularly tensile strength, elongation, 0.2% yield strength, and hardness can be economically and sustainably produced using recycled materials.

In addition to the above-mentioned element components, Ti (titanium) may be added. This Ti is an element having an effect of refining crystal grains, and is generally capable of suppressing casting cracks and improving mechanical properties, particularly elongation.

The content ratio of Ti with respect to the total weight of the aluminum alloy is preferably 0.30 wt% or less. This is because, when the content of Ti exceeds 0.30 wt%, it is difficult to melt the aluminum alloy, and there is a possibility that a melt residue is generated.

In addition to the above-described respective element components, at least one selected from Na (sodium), Sr (strontium), Ca (calcium), and Sb (antimony) may be added as an improvement treatment material. By adding such an improvement treatment material, the particles of eutectic Si can be made finer, and the toughness and strength of the aluminum alloy can be further improved.

The addition ratio of the modifying treatment material to the total weight of the aluminum alloy is preferably in the range of 30 to 200ppm in the case where the modifying treatment material is Na, Sr, and Ca, and 0.05 to 0.20 wt% in the case where the modifying treatment material is Sb. This is because, when the addition ratio of the improvement treatment material is less than 30ppm (less than 0.05 wt% in the case of Sb), it is difficult to refine the particles of the eutectic Si in the aluminum alloy, and when the addition ratio of the improvement treatment material is more than 200ppm (more than 0.20 wt% in the case of Sb), the particles of the eutectic Si in the aluminum alloy are sufficiently refined, and even if the addition amount is increased more than this, the addition effect is not improved.

In addition, B (boron) may be added instead of or together with the above-described modifying material. By adding B in this way, the crystal grains of the aluminum alloy are refined, and the elongation of the alloy can be improved. This effect is particularly remarkable when the amount of Si is small or when a casting method with a slow cooling rate is used.

The ratio of B to the total weight of the aluminum alloy is preferably in the range of 1 to 50 ppm. This is because, when the addition ratio of B is less than 1ppm, it is difficult to refine the crystal grains in the aluminum alloy, and when the addition ratio of B is more than 50ppm, the crystal grains in the aluminum alloy are sufficiently refined, and even if the addition amount is increased more than this, the addition effect is not improved.

In the production of the aluminum alloy of the present invention, first, a raw material containing the respective element components of Al, Cu, Si, Mg, Fe, Mn and Cr at the above-described predetermined ratio is prepared (the above-described Ti, modified material and the like are added as necessary). Next, the raw material is put into a melting furnace such as a melting furnace with a forehearth or a closed melting furnace, and melted. The molten raw material (i.e., molten metal of an aluminum alloy) is subjected to purification treatment such as dehydrogenation treatment and impurity removal treatment as necessary. Then, the purified molten metal is poured into a predetermined mold or the like and solidified, thereby forming molten metal of aluminum alloy into an alloy ingot or the like.

Further, using the aluminum alloy of the present invention, an aluminum alloy casting is cast by various casting methods such as die casting and gravity casting, sand casting or precision casting, and then, as necessary, solution treatment, aging treatment or the like is performed. By thus subjecting the aluminum alloy cast product to solution treatment, aging treatment, or the like, the mechanical properties of the aluminum alloy cast product can be improved.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

The tensile strength, elongation, and 0.2% yield strength among the mechanical properties of the alloys described below were measured by the following methods. That is, a round bar sample piece was prepared by die casting using a general die casting machine (DC 135EL, manufactured by toshiba machine corporation) having a mold clamping force of 135 tons at an injection speed of 1.0 m/sec and a casting pressure of 60MPa in accordance with astm (american Society for testing and material). Then, the tensile strength, elongation and 0.2% proof stress were measured on the round bar specimen in the as-cast state (as-cast) and after the T6 treatment, using a universal testing machine (AG-IS 100kN) manufactured by Shimadzu corporation. Here, the T6 treatment is a heat treatment method in which solution treatment is performed, and then reheating is performed to perform artificial aging treatment. In the present example, as the T6 treatment, the steel sheet was heated at 510 ℃ for 3 hours and then water-cooled (solution treatment), and further heated at 180 ℃ for 3 hours and then air-cooled (artificial aging treatment).

Further, the hardness was evaluated by Rockwell (ロックウェル) hardness test in accordance with JIS G0202. That is, a sample obtained by cutting and polishing the surface of a flat plate sample piece cast under the same conditions as described above by 1mm was tested by a Rockwell tester. The measurement was performed 3 times using this tester, and the average value was defined as the measurement value of the Rockwell hardness test.

Further, the alloy components of the respective alloys were measured using a solid-state emission spectrometer (Thermo Scientific ARL4460, manufactured by サーモフィッシャーサイエンティフィック).

Influence of Cu on physical Properties of aluminum alloy

Table 1 shows the relationship between the composition of the aluminum alloy produced by adjusting the alloy components other than Cu to a certain ratio within the range of the present invention and changing the content ratio of Cu and the mechanical properties (tensile strength, elongation, 0.2% yield strength, and hardness).

TABLE 1

TABLE 1 relationship between changes in Cu content and physical properties of aluminum alloys

T6 treatment conditions: water cooling at 510 deg.C for 3 hr, water cooling at 180 deg.C for 3 hr

As shown in table 1 and fig. 1 and 2, it was observed that: when the Cu content of the aluminum alloy is 0.75 wt% or more, a sufficient tensile strength can be obtained for well balancing the mechanical properties, particularly the tensile strength, elongation, 0.2% yield strength and hardness, and when the Cu content is up to 1.25 wt%, both the non-heat-treated material and the T6-treated material increase in tensile strength as the Cu content increases. When the content of Cu in the treated material of T6 exceeds 1.25 wt%, the tensile strength is lowered. This tendency is also seen in 0.2% yield strength and hardness.

On the other hand, the elongation of the alloy gradually decreases as the content of Cu increases, and particularly in the T6-treated material, when the content of Cu exceeds 1.25 wt%, the elongation is less than 5.0%, and it is difficult to say that the elongation is excellent.

Therefore, in the aluminum alloy of the present invention, the content ratio of Cu is defined to be in the range of 0.75 wt% or more and 1.25 wt% or less.

In table 1, alloys 1 and 2 are example alloys having alloy compositions within the scope of the present invention, and alloy 9 is JIS ADC3 alloy representing a conventional material.

Influence of Mg on physical Properties of aluminum alloys

Table 2 shows the relationship between the composition of the aluminum alloy produced by adjusting the alloy components other than Mg to a certain ratio within the range of the present invention and the mechanical properties (tensile strength, elongation, 0.2% yield strength, and hardness) by changing the content ratio of Mg.

TABLE 2

TABLE 2 relationship between the change in Mg content ratio and the physical Properties of aluminum alloys

As shown in table 2, when alloy 10 having an Mg content of 0.29 wt% in the aluminum alloy is compared with alloys 1 and 2 having an Mg content of 0.66 wt%, the 0.2% yield strength and hardness of the alloy increase and the elongation decreases when the Mg content is large. Therefore, in the aluminum alloy of the present invention, as described above, the content ratio of Mg is defined to be in a range of more than 0.50 wt% and 0.80 wt% or less in consideration of balance with other element components.

In table 2, alloys 1 and 2 are the alloy compositions in the present invention, i.e., the example alloys.

According to the aluminum alloy of the present embodiment, Cu is contained in a range of 0.75 wt% to 1.25 wt% inclusive and Mg is contained in a range of more than 0.50 wt% to 0.80 wt% inclusive, so that not only can the recycled materials such as scrap be used, but also the mechanical properties such as tensile strength, 0.2% yield strength and hardness can be improved. In addition, since the content of Cu that may deteriorate the corrosion resistance is suppressed within the above range and Cr having an effect of improving the corrosion resistance is contained in an amount of 0.10 wt% or more and 0.30 wt% or less, the decrease in corrosion resistance of the aluminum alloy associated with the Cu content can be suppressed to a minimum.

Claims

1. An aluminum alloy characterized by containing, in wt%, 0.75% or more and 1.25% or less of Cu, 7.5% or more and 8.5% or less of Si, 0.50% or more and 0.80% or less of Mg, 0.20% or more and 0.50% or less of Fe, 0.30% or more and 0.50% or less of Mn, 0.10% or more and 0.30% or less of Cr, and the balance of Al and inevitable impurities.

2. The aluminum alloy according to claim 1, further comprising 0.30 wt.% or less of Ti relative to the total weight of the alloy.

3. The aluminum alloy according to claim 1 or 2, further comprising at least one element selected from the group consisting of Na, Sr and Ca in an amount of 30 to 200ppm based on the total weight of the alloy.

4. The aluminum alloy according to any one of claims 1 to 3, wherein Sb is further added in an amount of 0.05 to 0.20 wt.% based on the total weight of the alloy.

5. The aluminum alloy according to any one of claims 1 to 4, wherein B is further added in an amount of 1 to 50ppm based on the total weight of the alloy.

6. An aluminum alloy casting produced from the aluminum alloy according to any one of claims 1 to 5.