JPS5948856B2 - Aluminum alloy for casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum alloy for casting having high toughness and good corrosion resistance.

BACKGROUND OF THE INVENTION Recently, aluminum alloy castings have been increasingly used in the fields of various industrial machines, vehicle parts, civil engineering and construction materials, etc.

By the way, in some cases, there are parts that are subject to extremely high impact forces, or parts that are brittle and may scatter if broken, resulting in danger, such as movable parts of various machines, studs used for partitioning aisles, and parts on doors. Aluminum alloy castings used for things such as hinges, bicycle cranks, and parapet posts are required to have medium or higher tensile strength, high toughness to withstand impacts, and good corrosion resistance to prevent strength deterioration due to corrosion. There is.

Conventionally, as this type of casting alloy, Al-8i series A
C3A, Al-31-Mg-based AC4C, and A1
-Mg-based AC7A has been used, but these alloys are not satisfactory in terms of toughness, and there has been a desire for an alloy with even better toughness.

The inventors have developed an aluminum alloy for use in non-heat-treated castings, which has medium or higher tensile strength, high toughness, and good corrosion resistance, and contains Mg2.5 as an alloy component by weight percentage. ~3.5%Si0.1% or less, Fed, 20% or less, Ti0005~0.2%,
Bo, 0007~0.01%, CuQ, 1% or less, Na
p, 001% or less, Be00001 to 0.005%, and the Si.

Total impurities excluding Fe, Cu, and Na 0.1% or less,
In addition, we succeeded in imparting the above-mentioned properties appropriately using a non-heat treatment method to a foundry alloy consisting of Ti/B of 30 or less and the balance being AI.

The reasons for the limits on the composition of each component in the alloy of the present invention are as follows.

Mg is an essential element for improving strength without heat treatment as in the present invention, and if it is less than 2.5%, sufficient tensile strength and proof stress cannot be obtained, which is not preferable.

In addition, if it exceeds 3.5%, even if the strength is sufficient, it will elongate and the impact value will drop sharply, so it is necessary to ensure the safety of industrial machinery, vehicle parts, civil engineering and construction materials, etc. This poses a problem as a component.

The most preferred Mg range is 2.7-3.3%.

Ti is used to improve mechanical properties, and if it is less than 0.05%, the effect of adding it will not be sufficient.
If it exceeds 0.2%, it is not preferable because it reduces toughness due to the appearance of giant Ti-Al crystallized substances.

A preferable range of Ti that can sufficiently exhibit impact resistance is 0.10 to 0.15%.

In particular, when B is present in an amount of 0.0007 to 0.01%, the mechanical properties are significantly improved and the substantial strength is increased when a large product is actually cast.

However, if the Ti/B ratio is 30 or more, the improvement effect is attenuated, so the Ti/13 ratio is preferably 30 or less.

Si and Fe both reduce elongation and impact value when their respective upper limits are exceeded;
ed, preferably 20% or less.

In particular, aluminum alloys used for casting items such as rivets that must ensure safety must contain less than 0.05% Sin,
Fed, preferably 15% or less.

If the Cu content exceeds 0.1%, the corrosion resistance will deteriorate rapidly, so it is preferably 0.1% or less.

Na enters from the flux used in the process of melting, melting, or casting aluminum alloys, and when it exceeds 0.001%, it tends to segregate at grain boundaries, causing grain boundaries to become brittle. It is preferably 0.001% or less since it significantly reduces toughness.

Be added to the molten metal reacts with the atmosphere more preferentially than Mg during the melting, melting, and casting processes to form a dense oxide film on the surface of the molten metal. This is to reduce the 0.
If it is less than 0.001%, the effect of the addition will not be sufficient, and if it exceeds 0.005%, the oxidation of Be will become severe, which is not preferable from the viewpoint of the working environment.

The alloy of the present invention can be manufactured by dissolving each component element in molten aluminum according to a conventional method.
The addition of Ti, 13 and Be improves the yield of these elements, so it is better to use these master alloys.

Table 1 shows the composition and mechanical properties of the alloys of the present invention, conventional alloys that have been used to cast products of this type, and comparative alloys.

The aluminum base metal used to manufacture these alloys has a purity of 99.8% AI, 0.01% Cu, 0.05% Si.
, 0.12% Fe, Be is 5% Be-Al master alloy, Ti and B are 5% Ti-1% B-AI master alloy, T
A 10% Ti-Al master alloy was used to adjust i.

Degassing flux 02C is added to the molten metal melted by a conventional method.
160.3% was treated using a phosphorizer at a melt temperature of 760°C.

After cooling, the casting temperature was 720℃ and the mold temperature was 200℃.
A No. I34 test piece was cast in a boat-shaped mold.

The tensile strength, 0.2% proof stress, elongation, and Charpy impact value of these samples were measured using an Amsler type universal testing machine.

Alloy numbers 1 to 4 are alloys of the present invention, numbers 6 to 7 are conventional alloys conventionally used in this type of casting, and numbers 8 to 11 are comparative alloys with different compositions for comparison.

Further, the heat treatment conditions for the alloy No. 6 were that the alloy was held at 525°C for 8 hours, water quenched, and then tempered at 160°C for 6 hours.

From the results in Table 1, conventional alloy 5 A1-8i series AC3A
has low elongation and impact value, compared to conventional alloy 6 Al-81-M.
The heat-treated AC4C of the g series has improved tensile strength and yield strength compared to those without heat treatment, but elongation and impact values are insufficient, and the Al-Mg of conventional alloy 7
It can be seen that the AC7A type has insufficient elongation and impact value, and in both cases, elongation and impact value are low.

On the other hand, as described above, the alloy of the present invention contains Mg and Si.

It can be seen that by limiting the content of Fe, Ti, B, Cu, Na, Be and the value of Ti/B, it is possible to have medium tensile strength and yield strength, as well as high elongation and impact value. .

Furthermore, although Comparative Alloy 8 has a low Mg content, its tensile strength and yield strength are extremely low.

Although Comparative Alloy 10 has a high content of Si, its impact value is extremely low.

Although Comparative Alloy 11 has a high Na content, it can be seen that the tensile strength, yield strength, elongation, and impact value are all extremely low.

Table 2 shows the results of measuring the corrosion resistance of the alloy of the present invention and the conventional alloy.

Alloy number 1 shown in Table 1 was used for the test. 2. 3゜4,
5. 6. A test piece for corrosion resistance measurement (50 mm x 40 mm x 10 m
m) was produced.

These test pieces were then soaked in a 5% NaCl solution (solution temperature 2
8° C.) (10 minute immersion, 50 minute drying performed in a 1 hour cycle), and the corrosion weight loss after 1000 hours was measured.

The corrosion weight loss is the average value of 10 measurements for each alloy.

As can be seen from Table 2, the alloy of the present invention has better corrosion resistance than either of the alloys.

As detailed above, the alloy of the present invention has moderate tensile strength and proof stress, high elongation, and excellent impact value and corrosion resistance, so it can be used for various industrial machine parts,
This invention is expected to be widely used in vehicle parts, civil engineering and construction parts, etc.

Claims (1)

[Claims] I Mg2.5-3.5%, Si0.1% or less, Fe
d, 20% or less, Ti 0.05-0.2%, Bo,
0007~0.01%, Cu0.1% or less, Nap
, 0.001% or less, Be of 0.001 to 0.005% and a total of impurities excluding the aforementioned Si, Fe, Cu, and Na of 0.1% or less, and Ti/B of 30 or less, with the balance being AI. Aluminum alloy for casting.