JPS5941433A - Aluminum-magnesium alloy for casting - Google Patents

Abstract

PURPOSE:To obtain the titled aluminum-magnesium alloy for casting suited to the structural element of a building, vehicle or the like, by blending the specified amounts of Mg, Si, Zn and Mn in Al. CONSTITUTION:The composition of the casting Al-Mg alloy is made as follows: by wt%, 5-9 Mg, 0.5-1.2 Si, 0.3-1.5 Zn, 0.1-0.6 Mn, and the balance Al and inevitable impurities. Said casting Al-Mg alloy is largely improved in a tendency to stress corrosion cracking which has been considered as the most serious problem in an alloy containing Mg>=5%. Consequently, in cooperation with the excellent mechanical and anodic film-forming properties of the alloy itself, the range of its use is developed as the structural element of a building, vehicle or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum-magnesium alloy for casting.

Aluminum alloys for casting containing magnesium as a main alloying component have excellent mechanical properties and corrosion resistance, and can be anodized, so they are used for ship parts, exterior materials, etc.

As the magnesium content of this type of alloy increases, its strength increases, so it is expected that its use will expand to structural materials in addition to the above-mentioned uses, but on the other hand, it becomes more susceptible to stress corrosion cracking. Therefore, when used under stress, magnesium should not be contained in an amount of 5% or more.

The inventors conducted intensive research on preventing stress corrosion cracking in aluminum alloys for castings containing 5% or more of magnesium, and found that adding appropriate amounts of zinc and silicon to this type of alloy is effective in preventing stress corrosion cracking. thing,! Furthermore, it has been found that when an appropriate amount of manganese is added together with an appropriate amount of zinc and silicon, an excellent effect is exhibited in preventing stress corrosion.

That is, the present invention contains 5.0 to 9.0% magnesium and 0% silicon.
．． 5-1.2%, zinc 0. '5-1.5%, manganese 0
．． This is an aluminum-magnesium alloy for foundry use, containing 1 to 0.6 g of aluminum, with the balance being aluminum and impurities.

The aluminum-magnesium alloy for casting according to the present invention can greatly improve the tendency to stress corrosion cracking, which has been the most problematic problem in alloys containing 5% or more magnesium. Due to its excellent properties, its use as a structural material for buildings, vehicles, etc. is expected to expand.

Next, the reason for determining the composition range of each alloy component in the foundry alloy of the present invention will be described.

Magnesium imparts strength to the alloy and also improves the fluidity of the molten metal. If it is less than 5%, it is not suitable for use in structural materials.

Silicon not only improves die-casting properties, but also has the effect of preventing stress corrosion cracking in combination with the addition of zinc, which will be described later. Silicon 0,
If the content is less than 5%, the effect will not be sufficient, and if it exceeds 1.2%, the mechanical properties will decrease in toughness to 9%, and when an anodic coating is applied, the brightness of the coating will deteriorate.

Zinc improves stress corrosion cracking resistance in combination with the addition of silicon. If it is less than 0.3%, the improvement effect is poor, and 1.
If it exceeds 5%, the corrosion resistance of the alloy will decrease.Manganese coexists with iron, which is present as an impurity in the alloy, and forms aluminum-iron-manganese-based spherical compounds in the alloy structure after casting. The formation of needle-like compounds is suppressed and the mechanical properties and corrosion resistance of the alloy are improved.
It also promotes the effect of suppressing stress corrosion cracking based on the addition of silicon and zinc in the present invention. If it is less than 0.1%, the effect is not sufficient, and if it exceeds 0.6%, an A 13-M n-based compound is produced, which deteriorates the mechanical properties.

Iron contained as an impurity in the alloy forms A4-Fe acicular compounds and deteriorates mechanical properties and corrosion resistance.
It is desirable to keep the length that can be made below to a small amount.

Next, some examples of the alloy of the present invention will be described.

Table 1 shows the chemical composition of the aluminum-magnesium alloy for casting used in this example. However, the stress corrosion cracking tendency of this type of alloy increases even though the stress corrosion cracking tendency increases, so the expansion of industrial applications has been suppressed.The stress corrosion cracking life of this type of alloy has been greatly improved, and the application can be expanded to ceramic materials, etc. Therefore, its industrial effects are great.

Patent applicant: Nippon Light Metal Co., Ltd.

Claims (1)

[Claims] (1) Magnesium 5.0-9.0%, silicon 0.5-1.2%, zinc 0.3-1.5, thimanganese 0.
An aluminum-magnesium alloy for casting, containing 1 to 0.6%, with the balance consisting of aluminum and impurities.