JPH07118785A - Mg alloy for casting, non porosity mg alloy casting and their production - Google Patents

Abstract

PURPOSE:To obtain Mg alloy for casting and non porosity Mg alloy casting by adding the specific quantity of Ca in Mg alloy for casting. CONSTITUTION:In producing Mg alloy for casting, Ca not subjecting to dehydrogenizing treatment is mixed in the quantity of 0.5-10wt% of total alloy composition with other alloy components, by melting itself or adding/mixing to molten metal of other alloy components, the molten metal obtained in this way is cast, cooled and solidified. By this method, free hydrogen in Mg alloy is reduced, not requiring degassing treatment at molten metal stage, the casting quality is improved so as to obtain a non porosity (no pinhole) Mg alloy casting.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnesium alloy for casting, a non-porous magnesium alloy casting and a method for producing them, and more specifically, a magnesium alloy for casting which can improve the quality of castings by containing calcium, The present invention relates to a non-porous magnesium alloy casting made of the alloy and a method for producing them.

[0002]

2. Description of the Prior Art Magnesium alloy is the lightest of all practical alloys and has excellent specific strength, so it has been widely used in recent years as a structural material in the fields of automobiles, aircraft, sports, leisure products, etc. Has been done.

Conventionally, magnesium alloy casting is die casting,
The most common method is die casting, but magnesium alloys are likely to combine with hydrogen, and the hydrogen gas dissolved in the molten metal due to the hydrogen becomes bubbles due to the decrease in solubility due to the temperature drop during casting, such as pin poles. Is a cause of casting defects.

When a magnesium alloy casting having such pinholes is used as a structural material, stress concentration occurs in the pinholes, and cracks are generated from the pinholes, resulting in the destruction of the material.

At present, there are attempts to produce pinhole-free magnesium alloy castings by squeeze casting, but so far, no good results have been obtained.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and the object of the present invention is to significantly improve the quality of cast products, and particularly to improve porosity (pinhole). It is an object of the present invention to provide a magnesium alloy for casting, which is capable of improving the quality of cast iron, a non-porous magnesium alloy casting made of the alloy, and a method for producing them.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted various studies in order to solve the above problems, and as a result, the hydrogen storage amount of calcium present in a magnesium alloy is different from that of other general metal elements. On the contrary, paying attention to the fact that it becomes smaller at high temperature but becomes larger at lower temperature, and calcium that has not been subjected to dehydrogenation treatment is added to the molten magnesium alloy consisting of other alloy components or mixed with other alloy components and melted. By this, it was found that the above-mentioned problems can be solved by storing hydrogen released during solidification of the magnesium alloy (that is, when the temperature of the molten metal decreases) in calcium in the magnesium alloy, and the present invention Arrived

That is, the magnesium alloy for casting according to the first aspect of the present invention is characterized by containing 0.5 to 10% by weight of calcium.

The non-porous magnesium alloy casting according to the second aspect of the present invention is characterized by comprising a casting magnesium alloy containing 0.5 to 10% by weight of calcium.

The method for producing a magnesium alloy for casting or a non-porous magnesium alloy casting according to the third aspect of the present invention comprises:
Calcium that has not been subjected to dehydrogenation treatment has a total alloy composition of 0.
It is characterized by being cast after being mixed and melted with other alloy components in an amount of 5 to 10% by weight, or after being added and mixed with the melt of other alloy components.

In the present invention, the magnesium alloy for casting includes all magnesium alloys for casting generally used in sand casting, die casting, die casting and the like, for example M.
g-Al alloys (AM30, AM100, etc.), Mg-A
1-Zn alloy (AZ31, AZ61, AZ63, AZ
91, AZ92, etc.), Mg-Zn-Zr alloy (ZK5
1, ZK61, etc.), Mg-rare earth alloy (EZ3
3, ZE41, QE22, etc.) and magnesium,
Further, an alloying element containing 0.5 to 10% by weight of calcium as an additional alloying component is included, and an example thereof is Mg.
-Ca type alloy, Mg-Al-Ca type alloy, Mg-Al-
Zn-Ca based alloy, Mg-Zn-Zr-Ca based alloy, M
There is a g-rare earth element-Ca alloy.

Calcium, when contained in a magnesium alloy, has the property of imparting excellent hydrogen storage properties to the magnesium alloy. This characteristic becomes clear when the calcium content is 0.5% by weight or more. However, if the calcium content exceeds 10% by weight, the mechanical properties of the magnesium alloy deteriorate and the cost increases. Therefore, in the present invention, the calcium content should be selected within the range of 0.5 to 10% by weight.

In the production of the magnesium alloy for castings or the non-porous magnesium alloy casting of the present invention, calcium which has not been subjected to dehydrogenation treatment is added to the total alloy composition of 0.5 to 10.
The alloy is mixed with the other alloy components in an amount of weight% and melted, or added to and mixed with the melt of the other alloy components. When the molten metal obtained in this way is cast, cooled, and solidified, the hydrogen occluded in magnesium is released at this time, but this hydrogen is occluded by the added calcium, and in the magnesium alloy, Less free hydrogen,
As a result, the quality of the cast product of the magnesium alloy or the magnesium alloy casting is remarkably improved, and in particular, the non-porosity (no pinhole) is improved. Therefore, in manufacturing a cast product, it is not necessary to perform degassing treatment at the time of molten metal, so that work efficiency can be improved.

[0014]

[Example] Using calcium that has not been subjected to dehydrogenation treatment,
The alloy component materials were blended so as to have the alloy compositions shown in Table 1, respectively, and these alloy composition blends were mixed in a graphite crucible to about 7%.
It melt | dissolved in air at 00-750 degreeC, and performed the pinhole test.

In the pinhole test for each alloy, an iron crucible (about 10 cc) was preheated to 100 ° C., a part of each molten alloy was cast into the crucible at a casting temperature of 700 ° C., and solidified in a vacuum suction atmosphere. . In this solidification process,
Traces of gas generation such as bubbles appear in the solidified casting depending on the amount of gas dissolved in the molten metal.

FIG. 1 is a photograph of a cross section of a cast product obtained from each alloy having the composition shown in Table 1. As is clear from FIG. 1, 1% by weight, 3% by weight or 5% by weight of calcium was added to each alloy. By doing so, the cracks and cavities in the cross section were remarkably improved.

Further, by measuring the density of the obtained casting, the degree of the amount of gas dissolved in the molten metal (the amount of porosity) can be qualitatively expressed by the following formula: amount of porosity = (1 / ρ'-1 / ρ) × 100 [cc
/ 100g] ρ ': Measured density ρ: Theoretical density (calculated from the components in the table) Table 2 shows theoretical specific gravity, measured specific gravity and porosity amount of cast products obtained from each alloy having the composition shown in Table 1. As is clear from Table 2, the specific gravity measured by adding calcium is close to the theoretical specific gravity, and the porosity amount is remarkably reduced.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

In the magnesium alloy for casting according to the present invention, the hydrogen storage amount of calcium present in the magnesium alloy is small at high temperature but becomes large at low temperature, so that hydrogen released when the molten magnesium alloy solidifies. Is occluded by the calcium in the magnesium alloy, so that pinholes do not occur in the cast product and it can be an excellent magnesium structural material. Further, in the production of the cast product, it is not necessary to perform degassing treatment at the time of molten metal, so that work efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional photograph of a cast product obtained from each alloy having the composition shown in the example.

Claims (3)

[Claims] 1. A magnesium alloy for casting, which contains 0.5 to 10% by weight of calcium in the magnesium alloy for casting. 2. A non-porous magnesium alloy casting comprising a magnesium alloy for casting containing 0.5 to 10% by weight of calcium. 3. A molten metal containing calcium which has not been subjected to dehydrogenation treatment after being mixed and melted with other alloy components in an amount of 0.5 to 10% by weight of the total alloy composition. A method for producing a magnesium alloy for casting or a non-porous magnesium alloy casting, which comprises adding and mixing to, and casting.