JP2001181774A - EXTRUDED PRODUCT MADE OF Mg ALLOY AND PRODUCING METHOD THEREFOR - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Mg alloy extruded product excellent in mechanical properties, corrosion resistance and formability. SOLUTION: This extruded product made of an Mg alloy is formed of an Mg alloy containing, by weight, 4.5 to 6.5% Zn and 0.2 to 2.0% Zr, and the balance Mg. The maximum crystal grain size is controlled to <=60 μm, and the ratio of the crystal grains with the crystal grain size of <=10 μm is controlled to >=60% of the whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruded product made of an Mg alloy and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, M
The g alloy is attracting attention as a substitute for plastic parts, such as automobile parts and home electric parts, which need to be reduced in weight, and is increasingly used for casting, semi-solid molding, and the like.

[0003] By the way, the working of the Mg alloy is performed by warm working at around 300 ° C.
Poor workability due to structural metal. Further, the Mg alloy has a hcp structure and thus has poor corrosion resistance, and at present, a surface treatment technique for obtaining an anticorrosion effect has not been sufficiently developed.

The present invention has been made in view of the above circumstances, and has as its object to provide an extruded Mg alloy having excellent mechanical properties, corrosion resistance and formability.

[0005]

According to the first aspect of the present invention, M
g alloy extrudate contains 4.5-6.5 wt% Zn and Zr
It is made of an Mg alloy containing 0.2 to 2.0% by weight, with the balance being Mg, and the maximum crystal grain size is 60 μm or less, and the crystal grains having a crystal grain size of 10 μm or less constitute 60% or more of the whole. Things.

In the first aspect of the present invention, the reasons for containing each alloy component and the reasons for limiting the content are as follows.

Zn: 4.5 to 6.5% by weight Zn is contained in a Mg alloy to enhance the mechanical properties of an extruded Mg alloy and to cast a billet for forming the extruded product. It has the property of improving fluidity and improving castability. Zn content of 2.0 to
If the content exceeds 3.0% by weight, the elongation is reduced, the moldability is deteriorated, and the castability of the billet may be reduced. However, the strength increases with an increase in the Zn content. However, when the Zn content exceeds 6.5% by weight, the effect of improving the strength with respect to the increase in the content is reduced. Therefore, Zn
The content of is 4.5 to 6.5% by weight mainly for the purpose of improving strength and taking into account the balance between castability and formability.
Should be within the range.

[0008] Zr 0.2 to 2.0 wt% Zr has an effect of making crystal grains of an extruded billet used for forming an extruded Mg alloy product fine by containing Zr in an Mg alloy. That is, there is a crystal grain refinement effect due to a peritectic reaction during solidification during casting, and primary Zr crystallized near the peritectic temperature contributes to crystal grain refinement. There are reports that the remaining Zr can also be a recrystallization nucleus generation site. However, the effect is small when the Zr content is less than 0.2% by weight,
The effect does not increase any more even if it exceeds% by weight.
Therefore, the content of Zr should be in the range of 0.2 to 2.0% by weight. In particular, since the solubility limit of Zr at the peritectic temperature is about 0.6% by weight, the Zr content is preferably about 0.6% by weight in order to refine crystal grains.

Further, in the invention of claim 1, the reason why the maximum crystal grain size is 60 μm or less and the crystal grains having a crystal grain size of 10 μm or less are limited to 60% or more of the whole is that tensile strength, proof stress,
This is for improving mechanical properties such as elongation. here,
The reason for specifying the amount of crystal grains having a crystal grain size of 10 μm or less instead of the average particle size is that in this extruded product, the ratio of crystal grains is large, and it is difficult to calculate the average particle size.

The extruded Mg alloy product according to the first aspect of the present invention may be a final product, or may be formed by cutting,
In some cases, it is a work for performing processing such as forging and rolling.
Further, the Mg alloy extruded product according to the first aspect of the present invention may contain unavoidable impurities. In this case, the content of inevitable impurities is preferably not more than 0.3% by weight in total.

According to the Mg alloy extruded product of the present invention, mechanical properties, corrosion resistance and formability can be improved, and castability of an extruded billet for forming an extruded product is improved. be able to.

The method for producing an extruded Mg alloy according to the second aspect of the present invention is characterized in that 4.5 to 6.5% by weight of Zn and 0.2% of Zr 0.2
An extruded billet formed of an Mg alloy containing up to 2.0% by weight, the balance being Mg, is heated to 200 to 400 ° C. and hot extruded at a maximum product speed of 5 m / min. .

In the second aspect of the present invention, the heating temperature of the extruded billet during the hot extrusion is limited to 200 to 400 ° C., if the heating temperature is lower than 200 ° C. Extrusion molding becomes difficult due to increased resistance. If the temperature exceeds 400 ° C., surface defects occur due to oxidation of extruded billets and an increase in product temperature, and crystal grains become coarse and the maximum crystal grain size becomes 60 μm or less. Diameter 1
This is because crystal grains having a size of 0 μm or less cannot be made to be 60% or more of the whole. After heating to the above temperature, the heating may be terminated immediately, or a maximum of 2 hours.
Heating may be continued for up to an hour.

In the invention of claim 2, the product speed during hot extrusion is limited to a maximum of 5 m / min because when the product speed exceeds 5 m / min, cracks or the like are formed on the surface of the extruded product obtained. This is because a defect may occur. Note that the lower limit of the product speed is preferably about 0.65 m / min.

According to the method for manufacturing an Mg alloy extruded product according to the second aspect of the present invention, the Mg alloy extruded product according to the first aspect of the present invention can be manufactured without producing defects on the surface and with high productivity. Can be.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Examples 1 to 3 Zn 6% by weight, Zr 5.59% by weight and Mn 0.00
Mg alloy containing 7% by weight and the balance being Mg
A 2 mm extruded billet was made, and a round bar was extruded under various conditions using the extruded billet. Then, the crystal state of the surface layer and the center of the round bar was observed. as a result,
In the extruded billet, small recrystallized grains and coarse crystal grains of several hundred μm extending in the length direction were present. Further, all or most of the round bars had an equiaxed recrystallized structure. Table 1 shows the relationship between the extrusion conditions and the crystal grains in Examples 1 to 3.

[0018]

[Table 1]

[0019]

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 624 C22F 1/00 624 630 630A 630K 691 691B 694 694A 694B (72) Inventor Hiroyuki Kawabata Sakai City 6,224, Kaiyamacho, Showa Aluminum Co., Ltd. (72) Inventor Kazuhiko Minami 6,224, Kaiyamacho, Sakai City, F Showa, Showa Aluminum Co., Ltd. 4E029 AA07 TA02

Claims (2)

[Claims] 1. 4.5 to 6.5% by weight of Zn and Zr
It is made of an Mg alloy containing 0.2 to 2.0% by weight, with the balance being Mg, and the maximum crystal grain size is 60 μm or less, and the crystal grains having a crystal grain size of 10 μm or less constitute 60% or more of the whole. Extruded product made of Mg alloy. 2. 4.5 to 6.5% by weight of Zn and Zr
An extruded billet containing 0.2 to 2.0% by weight and formed of a Mg alloy consisting of the balance of Mg
2. A method for producing an extruded product of an Mg alloy according to claim 1, wherein the extruded product is heated at a maximum product speed of 5 m / min.