JPS6140300B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum alloy for casting, which is free from coloring during heat treatment and generates significantly less oxide film (ie, slag) during melting of the alloy. Conventionally, A-Si-Mg alloys containing Sb (JISAC4C, AC4A, etc.) have been widely used in various industrial parts because they have good castability and improvement sustainability, and show excellent toughness and strength when heat treated. ing. However, when this alloy is heat-treated in a high-temperature oxidizing atmosphere, the cast surface becomes oxidized and turns black, compared to ordinary A--Si--Mg alloys that do not contain Sb. Another disadvantage is that metal loss is large due to the large amount of oxide film formed during melting. The present invention solves the above-mentioned problems, and includes Si6 to 10%, Mg0.2 to 0.8%, Sb0.08 to 0.2%,
Aluminum alloy for casting consisting of Be0.002~0.010%, Ca0.01~0.07%, balance aluminum and unavoidable impurities, and the above alloy further includes Mn0.1~0.07%.
The purpose is to provide an aluminum alloy for casting with 0.5% addition. The reason for limiting the composition of each component in the alloy of the present invention is as follows. Good results can be obtained when Si is added in an amount of 6% or more to improve fluidity, but if it exceeds 10%, the toughness decreases, so 6 to 10% is appropriate. Mg has the effect of precipitating Mg ₂ Si by heat treatment and increasing strength, and for this purpose it is added at 0.2% or more, but if it exceeds 0.8%, toughness decreases, so 0.2
~0.8% is preferred. Sb has the property of refining the eutectic Si in the alloy, and if it is less than 0.08%, the effect is insufficient, and if it is added in an amount more than 0.2%, no improvement in the effect can be expected, but rather mechanical Since properties and corrosion resistance deteriorate, 0.08 to 0.2% is suitable. Be has a remarkable effect on suppressing molten metal oxidation. If it is less than 0.002%, the effect is insufficient, and if it is added in an amount greater than 0.010%, the effect cannot be improved much, so 0.002 to 0.010% is appropriate. Ca coexists with Be in the above composition range, resulting in Sb-containing A-Si-Mg alloys (JISAC4A,
AC4A, etc.) suppresses coloration during heat treatment and gives it a metallic luster. If it is less than 0.01%, the effect is insufficient, and if it is more than 0.07%, metallic luster cannot be obtained, so 0.01 to 0.07% is appropriate. If Ca or Be in the above composition range is added alone to an A-Si-Mg alloy, coloring during heat treatment cannot be suppressed. When Ca is added alone, metallic luster cannot be obtained after heat treatment, and when Be is added alone, the casting surface becomes colored after casting. Mn has the effect of further improving the castability of the alloy described in claim 1. If it is less than 0.1%, the effect is insufficient, and if it is added more than 0.5%, the toughness decreases, so 0.1 to 0.5
% is appropriate. In the case of large castings or castings with complicated shapes (castings with uneven thickness), the solidification rate is slow, so the crystal grains of the casting after solidification are coarse. It is beneficial to add 0.05-0.20% Ti to refine the grains. On the other hand, in the case of small castings or thin castings, even without the addition of Ti, ultrafine particles are generated one after another in the molten metal because the cooling rate of the molten metal is fast, and crystallization occurs with these ultrafine particles as nuclei. grows, resulting in a casting with fine grains and satisfactory mechanical properties and shrinkage test results. Fe is a component that is inevitably contained as an impurity in aluminum. Next, examples of the present invention will be shown. Example 1 Table 1 shows the color of the casting surface after casting and after heat treatment. Alloys of various compositions were cast at 750°C by heating a mold coated with a release agent to 300°C. The heat treatment was performed at 530° C. for 8 hours in a tempering furnace in an air atmosphere.
The coloring of the cast surface was evaluated on an 8-level scale. In conventional alloy-2 and -3, conventional alloy-1
Unlike, after heat treatment, the casting surface becomes colored. Alloys-1 to -4 of the present invention exhibit metallic luster even after casting and heat treatment. The comparative alloys, except for -2, after casting,
Colors both or after heat treatment.

【table】

[Table] Example 2 Figure 1 shows the weight increase due to oxidation when the alloys having the compositions shown in Table 2 were melted and held. Among the conventional alloys, Alloys-5 and -6 containing Sb have a large weight increase, but it can be seen that the oxidation of the molten metal is significantly suppressed in the present invention Alloy-5. The test was conducted using a thermobalance.

[Table] Example 3 An alloy with the composition shown in Table 3 was subjected to T6 treatment (solution treatment at 530°C for 8 hours, water quenched, and then heated at room temperature).
Figure 2 shows the mechanical properties after heat treatment (heat treatment of leaving for 15 hours and tempering at 140°C for 6 hours). Inventive alloy-6, with changes in Ca content,
The tensile strength and proof stress hardly change, but the elongation and impact value show minimum values around 0.04% Ca. However, this minimum value is comparable to comparative alloys -11 and -12 which were treated with Na or Ca. Furthermore, as a result of investigating the coexistence effect of Sb and Ca on the microstructure of the A-7%Si-0.33%Mg alloy, the changes in elongation and impact value were found to be due to the degree of refinement of the eutectic Si. it is conceivable that.

[Table] Example 4 The alloys having the compositions shown in Table 4 were subjected to a shrinkage test using a Tatur mold, and the results are shown in Table 5. By the way, the Tater mold method is a measurement method proposed by A. Tatur, which measures the shrinkage of the Tater sample shown in Figure 4, which was cast using a Tater mold with the dimensions (unit: mm) shown in Figure 3. do. Referring to FIG. 5, the state of occurrence of porosity inside the sample shows that conventional alloy-7 shows a concentrated type of shrinkage cavities, but alloy-7 of the present invention shows a dispersed type of shrinkage cavities. The present invention alloy-8, which is obtained by adding Mn to the present invention alloy-7, exhibits concentrated shrinkage cavities.

【table】

[Table] The advantages of the alloy of the present invention are as follows. (i) Significantly less oxide film is formed during alloy melting. (ii) normal
A--Si--Mg alloys containing Sb turn black after heat treatment, but the alloy of the present invention maintains metallic luster even after heat treatment and provides a good appearance. (iii) Has excellent strength and elongation. Since the alloy of the present invention has the above-mentioned advantages, it can be used for various industrial parts, and is suitable as a material for wheels and steering wheel crowns, for example.

[Brief explanation of the drawing]

Figure 1 is a graph showing the weight increase due to oxidation when alloys having the composition shown in Table 2 are melted and held.
The figure is a graph showing the mechanical properties of an alloy having the composition shown in Table 3 after T6 treatment, FIG. 3 is a cross-sectional view of a Teter mold, and FIG. 4 is a schematic diagram of a Teter sample.

Claims (1)

[Claims] 1 Si6-10%, Mg0.2-0.8%, Sb0.08-0.2%,
Aluminum alloy for castings consisting of 0.002~0.010% Be, 0.01~0.07% Ca, and the balance being aluminum and unavoidable impurities. 2 Si6~10%, Mg0.2~0.8%, Sb0.08~0.2%,
Be0.002~0.010%, Ca0.01~0.07%, Mn0.1~0.5
%, an aluminum alloy for castings consisting of the balance aluminum and unavoidable impurities.