JP2003183747A - Production method of and purification additive for magnesium alloy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing magnesium alloys which can reduce the amount of Fe which is an impurity, without changing the compositions of recycled parent metals, and an additive for purifying magnesium alloys used for this. <P>SOLUTION: In the method for producing magnesium alloys, MnSi particles are heated in an oxidizing atmosphere to form SiO<SB>2</SB>layers on their surfaces and added to a molten magnesium alloy which is subsequently subjected to casting. The additive for purifying magnesium alloys comprises MnSi particles having SiO<SB>2</SB>layers on their surfaces. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnesium alloy and a purifying agent for a magnesium alloy, and more particularly to a method for producing a magnesium alloy containing Fe as an impurity that adversely affects the corrosion resistance of magnesium.

[0002]

2. Description of the Related Art Magnesium (Mg) is the lightest of all practical metal materials and has mechanical properties comparable to aluminum (Al). Therefore, various magnesium alloys can be used as structural members for aircraft and automobiles. Being developed.

For example, a magnesium alloy currently in widespread use is a Mg-Al system (ASTM AM60B,
AM50A, AM20A, etc., mainly for age hardening), M
There are g-Al-Zn type (ASTM AZ91D etc., mainly for casting and age hardening), Mg-Zn type (mainly casting and age hardening), and the like.

The original metal such as a recycled material used as a melting raw material for melting a magnesium alloy inevitably contains various impurities. In particular, Fe is an impurity that deteriorates the corrosion resistance of magnesium alloys, and in that sense, it is contained in the base metal in a non-negligible amount (especially due to the paint of recycled materials, etc.). It is important to reduce as much as possible.

Conventionally, as a means for cleaning such molten metal,
As described in JP-A-8-157981, a method of adding a Mg-Mn alloy as a purifying agent to a molten magnesium alloy or a method of adding an Al-Mn alloy as a purifying agent is performed. By adding these purifying agents, Fe is a compound with Mn ((FeMn) Al _6, etc.)
Is precipitated during the melting process and is removed from the molten metal by precipitation.

However, in the above conventional method, when the magnesium alloy recycled ingot is used, the alloy composition of the ingot to be reused must be changed by the addition of the purifying agent.

That is, since Mn having a function of removing Fe is difficult to dissolve in a molten magnesium alloy by itself, it is added in the form of an alloy with Mg or Al as described above. Generally, as a Mg-Mn purifying agent, An Mg-3.5% Mn alloy is used, and an Al-10% Mn alloy is used as an Al-Mn-based purifying agent. Therefore, when Mn in an amount necessary for the action of removing Fe is actually added, a large amount of Mg (30 times the amount of Mn) or Al (10 times the amount of Mn) is inevitably introduced into the molten metal, and as it is. There was a problem that the composition of the magnesium alloy recycled base metal to be reused with the above composition varied.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a magnesium alloy capable of reducing the content of Fe, which is an impurity, without affecting the composition of recycled metal, and a magnesium alloy purifying agent used therefor. The purpose is to do.

[0009]

In order to achieve the above object, a method for producing a magnesium alloy according to the present invention comprises the following steps: a step of preparing a molten magnesium alloy, a Mn
The Si particles are heat-treated in an oxidizing atmosphere to form S on the surface.
Step of forming iO ₂ layer, M on which the SiO ₂ layer is formed
The method is characterized by including a step of adding nSi particles to the magnesium alloy melt and a step of casting the melt after the addition.

The magnesium alloy purifying agent according to the present invention is a magnesium alloy purifying agent to be added to a molten magnesium alloy, and is characterized by comprising MnSi particles having a SiO ₂ layer on the surface.

[0011]

According to the present invention, since the wettability is improved by reacting SiO ₂ with the molten magnesium alloy in preparation for the surface of MnSi purification agent particles, the fine M
Even nSi particles can be easily added to the molten magnesium alloy. In addition, since MnSi having a high melting point (1275 ° C.) is melted by the heat generated by the above reaction, Mn
Dissolves in magnesium alloy melt. This dissolved Mn
And Fe in the molten metal react with each other to precipitate as a compound, and the Fe is removed by precipitating at the bottom of the molten metal.

Si released by the dissolution of MnSi is F
The amount is the same as the amount of Mn required to remove e, and does not substantially affect the properties of the alloy. A part of Si reacts with Mg to form Mg ₂ Si or the like, but rather, this exerts a preferable action in improving the heat resistance of the alloy.

Further, SiO provided on the surface of MnSi particles
_Although MgO is produced by the reaction between the oxygen derived from ₂ and the molten metal, this is floated and separated as slag.

In this way, Fe can be removed without substantially affecting the alloy composition of the base metal.

[0015]

EXAMPLE A magnesium alloy was produced by the method of the present invention by the following procedure.

Commercially available ASTM AZ9 is used as a starting material.
Three lots of 1D magnesium alloy recycled metal were prepared. The chemical composition analysis values for each commercial lot are shown in Table 1 together with the standard values.

Larger MnSi particles (average particle size 30 μm)
Heat treatment was performed by heating in air at 1000 ° C. for 1 hour.
As a result, on the surface of the MnSi particles, S having a thickness of about 30 μm is formed.
iO _TwoThe formation of the layer was confirmed by X-ray diffraction (XRD).
I confirmed.

For each lot, 1 kg of reclaimed magnesium alloy ingot was melted at 750 ° C., and 2 g of MnSi particles after the above heat treatment were added to the obtained molten magnesium alloy.

After the addition, the molten metal was stirred for 5 minutes and then cast in a mold (φ50 mm, h30 mm).

As a comparative example, melting, stirring, addition and casting were performed by the same procedure as above except that the MnSi particles were not heat treated.

Table 1 shows the result of analysis of the chemical composition of the cast product for each lot.

[0022]

[Table 1]

As shown in Table 1, the lots 1, 2, and 3 of the commercial recycled ingots have Fe contents of 0.014% and 0.00, respectively.
The values were 17% and 0.016%, which greatly exceeded the standard upper limit value of 0.004%.

Mn without heat treatment for each gold lot
In Comparative Examples 1, 2, and 3 in which Si particles were added, F
The e content was 0.013%, 0.016%, and 0.015%, and almost no reduction effect was recognized. The components other than Fe did not substantially change with respect to the composition of the ingot.

On the other hand, in Invention Examples 1, 2, and 3 in which MnSi particles having a surface SiO ₂ layer formed by heat treatment according to the present invention were added, the Fe content was 0.003.
%, 0.004%, 0.004%, which is within the standard range. The components other than Fe did not substantially change with respect to the metal composition.

This is the MnS with SiO ₂ surface layer of the present invention.
It is considered that the i particles react with the molten Mg alloy as follows.

First step: SiO on the surface of MnSi particles
Reaction of ₂ with Mg SiO ₂ (s) + 4Mg (l) → Mg ₂ Si (s) ↓ + 2MgO
(s) ↑ Second step: MnSi is melted by heat generated by the above reaction MnSi (s) → MnSi (l) Third step: Molten MnSi is Fe, Al in the molten metal
Reaction with Fe (l) + 6Al (l) + MnSi (l) → (FeMn) Al
₆ (s) ↓ + Si (l) Si (l) + 2Mg (l) → Mg ₂ Si (s) ↓ In the above reaction formulas, symbols are s: solid,
l: liquid, ↑: floating, ↓: precipitation.

FIG. 1 shows the above results collectively.

The recycled metal used was A for each lot.
The Mn content was lower than the standard composition of Z91D, but this does not affect the Fe reduction effect according to the present invention, and the Mn content as an alloy component may be adjusted during melting as necessary.

[0030]

As described above, according to the present invention,
Fe, which is an impurity, does not affect the composition of recycled metal
Provided is a method for producing a magnesium alloy capable of reducing the content of magnesium and a magnesium alloy purifying agent used for the method.

[Brief description of drawings]

FIG. 1 is a graph showing the Fe content reduction effect according to the present invention.

Claims (2)

[Claims] 1. A following steps: preparing a magnesium alloy melt, by heat-treating MnSi particles in an oxidizing atmosphere to form a SiO ₂ layer on the surface thereof, a MnSi particles forming the SiO ₂ layer And a step of adding the molten metal to the magnesium alloy, and a step of casting the molten metal after the addition. 2. A magnesium alloy purifying agent for adding to a magnesium alloy melt, comprising a MnSi particle having a SiO ₂ layer on the surface thereof.