JPH11279670A - Master alloy for regulating content of magnesium to be used at the time of recasting zinc alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and simply add and melt Mg, to enable the regulation of the content of Mg in a Zn alloy and to obtain an Mg-added Zn alloy of high quality by using alloys having a compsn. contg. Mg, furthermore contg. Al and Cu, and the balance An at the time of recasting the Zn alloy. SOLUTION: Alloys having compsns, contg., by weight, 20 to 80% Mg, furthermore contg., at need, <=10% Al and/or <=5% Cu, and the balance Zn with inevitable impurities are used as master alloys for regulating the content of Mg at the time of recasting the Zn alloy. The alloys are small in the difference in the m.p. and specific gravity with the Zn alloy and can easily be melted into the Zn alloy molten metal in a short time. At the time of recasting the Zn alloy, plural master alloys different in the contd. components and contents are prepd., and from the analyzed value of the compsn. of the Zn alloy to be recast and its final objective compsn. after the addition of the master alloys, the kinds and quantity of the master alloys to be required are decided. Moreover, as for the content of Al, its compsn. after the removal of slag is considered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a master alloy for adjusting a magnesium content used in recasting a zinc alloy, and more particularly, to recast and recast a zinc alloy mold for press molding or plastic molding. When remanufacturing and recasting zinc alloy die-cast products and zinc alloy processed products (plates, wires, extruded products, etc.), or recasting zinc alloy ingots to reduce the magnesium content in zinc alloy ingots When it is changed, it relates to a magnesium content adjusting master alloy added to adjust the magnesium content in the zinc alloy at the time of recasting.

[0002]

2. Description of the Related Art When used in the manufacture of molds, zinc alloys have a lower melting point than iron alloys and have good melt flowability, so that they are easy to cast and, furthermore, have a balanced mechanical strength. It has good workability, short delivery time is possible, and the unnecessary mold can be cast and used for low cost. It has been conventionally used as a press molding die for plastics and a plastic molding die. In addition, since zinc alloys have the above characteristics, they are used as die-casting zinc alloys in automobile parts, home electric parts, and other various fields. Usually, the zinc alloys used for them are alloys containing 3% to 7% by weight of aluminum, or aluminum 3%.
An alloy containing 7% by weight to 7% by weight and 4% by weight or less of copper. Magnesium is used in an amount of 0.05% by weight or less to suppress intergranular corrosion.

However, when a conventional zinc alloy is used as a press-forming die, for example, the abrasion resistance of the die is insufficient depending on the processing conditions such as the material, thickness, and processing shape of a work material to be processed. It is said that, even in plastic molding dies, frequent occurrence of pinholes and lack of abrasion resistance have been reported, and that of die-cast parts has been described as lacking creep characteristics. Recently, a zinc alloy has been developed in which abrasion resistance, castability and creep resistance have been improved by adding 1 to 3% by weight of magnesium which has not been conventionally added as an alloy component in addition to aluminum and copper. It has been used as a mold or a die-cast product.

[0004] Instead of newly preparing such a magnesium-containing zinc alloy, a magnesium content of 0.05% was used.
If a zinc alloy having a conventional composition of not more than 10% by weight is cast under operating conditions, magnesium is added at that time to adjust the magnesium content, and if it can be used as a magnesium-added zinc alloy, the cost reduction effect is very large. Regarding the method of adding magnesium, when a magnesium-containing zinc alloy is newly melted, magnesium metal can be used as a magnesium raw material.

[0005]

However, in an attempt to add magnesium metal at the time of recasting a zinc alloy of a conventional composition having a magnesium content of 0.05% by weight or less, the temperature of the molten metal under operating conditions is 430 ° C. 450 ° C, which is 2 times lower than the melting point of 650 ° C of magnesium metal.
While the specific gravity of magnesium metal is 1.74, the specific gravity of molten zinc alloy is, for example, 6.7 for casting alloys and die casting alloys, and the specific gravity difference is large. Since the metal floats on the surface of the molten metal, it dissolves while submerging the magnesium metal in the molten metal, and it takes a long time to dissolve, the magnesium surface is oxidized violently, and it becomes a difficult melting operation, and the alloy composition reaches the target value. Adjustment becomes difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a means for adding magnesium easily and easily without causing the above-mentioned problems when adding magnesium at the time of recasting a zinc alloy. It is an object of the present invention to provide a magnesium content-adjusting master alloy which can be easily melted at a temperature of a molten zinc alloy under the conditions and enables a higher-quality magnesium-added zinc alloy to be prepared.

[0007]

Means for Solving the Problems The present inventors have made intensive studies on the above problems and found that the above problems can be achieved by using a zinc alloy containing a specific amount of magnesium as a master alloy for adjusting the magnesium content. And completed the present invention.

That is, the master alloy for adjusting magnesium content of the present invention contains 20 to 80% by weight of magnesium, or further contains one or both of 10% by weight or less of aluminum and 5% by weight or less of copper, and the balance is inevitable. A magnesium content adjusting master alloy used when recasting a zinc alloy, characterized by being made of zinc excluding impurities.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The magnesium alloy master alloy of the present invention (hereinafter simply referred to as "master alloy") is used by adding it to a zinc alloy melt. Zinc alloy molds for press molding, plastic molding, etc., used zinc alloy die-cast products, zinc alloy processed products (plates, wires, extruded products, etc.), and zinc alloy scraps that are melted for recycling. It may be present or may be dissolved to change the magnesium content in an unused zinc alloy ingot. However, the master alloy of the present invention can be particularly preferably used for recycling used zinc alloy molds.

In the master alloy of the present invention, the magnesium content is preferably limited to 20 to 80% by weight. When a master alloy having a magnesium content of less than 20% by weight is used, the required amount of the master alloy increases, and as a result, after the master alloy is added to the molten metal, the master alloy is completely melted and the proper It takes time to reach the molten metal temperature, and the time loss during that time causes a cost increase. In addition, when the master alloy of the present invention is used for recasting a zinc alloy mold, the total weight of the zinc alloy mold increases. For example, when a zinc alloy having a magnesium content of 2% by weight is prepared using a master alloy having a magnesium content of 10% by weight, the total weight of the mold increases by 20% by weight, which increases the stock amount and increases the cost. become.

When the magnesium content exceeds 80% by weight, the melting point of the master alloy exceeds 570 ° C. When a master alloy having such a high melting point is used, at a zinc alloy melt temperature of 430 ° C. to 450 ° C. used in normal operation, the master alloy is added to the melt, and then the master alloy is completely melted to reach an appropriate melt temperature. It takes a long time, and a time loss during that time causes a cost increase, and at the same time, oxidation of the mother alloy proceeds, and a predetermined amount of magnesium cannot be added. As a method of shortening the melting time, it is conceivable to raise the temperature of the molten metal. However, if the temperature of the molten metal is higher than 450 ° C., the oxidation of magnesium proceeds and the melting pot is eroded. Is not preferred. In order to melt at a melt temperature of 430 ° C. to 450 ° C., it is necessary to use a master alloy having a magnesium content of 80% by weight or less. Therefore, the magnesium content of the master alloy is 20 to
It is 80% by weight, preferably 30 to 50% by weight.

When the zinc alloy containing aluminum is cast, a slag containing aluminum slightly higher than the aluminum content in the molten metal is generated and aluminum is removed, so that the amount of aluminum in the molten metal decreases. Therefore, in order to adjust the aluminum content in the molten metal only with the master alloy, the master alloy needs to contain aluminum more than the aluminum content of the zinc alloy before recasting. However, when the aluminum content in the master alloy exceeds 10% by weight, the aluminum content in the molten metal after adjustment when the mother alloy is added so as to have a required magnesium amount may exceed the spec, and the adjustment of the composition of the molten metal may occur. Becomes difficult.
In addition, it takes time from the addition of the master alloy to the molten metal until the mother alloy is completely melted and reaches an appropriate molten metal temperature, and a time loss during that time causes a cost increase. Therefore, the aluminum content of the master alloy used when recasting a zinc alloy containing aluminum is set to 10% by weight or less, preferably 4 to 7% by weight. However, the master alloy used when recasting a zinc alloy containing aluminum does not necessarily need to contain aluminum, and the aluminum content in the molten metal after the addition of a master alloy containing no aluminum is analyzed, and the required amount of aluminum is analyzed. May be added by a separately prepared master alloy for adjusting the aluminum content.

[0013] The change in the composition of copper due to the casting of the zinc alloy is small. Therefore, it is sufficient for the master alloy used for recasting a zinc alloy containing copper to contain approximately the same amount of copper as that contained in the zinc alloy before recasting. The copper content of the zinc alloy is, for example, 0.03% by weight or less for two kinds of zinc alloy blocks for die casting according to JIS H 2201, and 2 to 4% by weight for a general zinc alloy for castings. When the copper content exceeds 5% by weight, the melting point of the master alloy becomes 580 ° C. or higher. At a temperature of 430 ° C. to 450 ° C. of the zinc alloy melt used in a normal operation, the master alloy is completely added after the master alloy is added to the melt. It takes a long time to dissolve in the molten metal and reach an appropriate molten metal temperature, and a time loss during that time causes a cost increase, which is not practical, and also generates ε compounds and τ compounds, which causes segregation. Therefore,
The content of copper in the master alloy used when recasting a zinc alloy containing copper is 5% by weight or less, preferably 4% by weight or less.

As is clear from the above description, regarding the composition of the master alloy of the present invention used at the time of recasting the zinc alloy, the difference between the composition of the recast zinc alloy and the target magnesium-containing zinc alloy composition An optimum composition may be selected within the range of 20 to 80% by weight of magnesium, 0 to 10% by weight of aluminum, and 0 to 5% by weight of copper according to the amount of molten metal.

The addition of a master alloy used when recasting a zinc alloy is performed as follows. Plurality of master alloys with different components and contents (for example, those that do not contain aluminum and copper, those that contain one or both of aluminum and copper, those that have high, medium, and low magnesium contents, etc. ) Is prepared. First, the composition of the zinc alloy to be cast is analyzed and used as the basis for calculating the amount of the master alloy to be added. When the aluminum content is readjusted as described below, the value after the readjustment is adopted. Further, the final target composition after addition of the master alloy is determined. Thereafter, under the same operating conditions as in the prior art, the slag is removed neatly, and if necessary, the aluminum content of the zinc alloy melt is reduced, for example, as disclosed in JP-A-5-33.
Just before the furnace is analyzed immediately before the furnace according to the pre-furnace analysis method for zinc alloys as described in US Pat. No. 2961, and the shortage aluminum is readjusted by the addition of a master alloy for aluminum content adjustment. Next, a master alloy to be used is selected based on the difference between the final target composition and the composition of the zinc alloy to be cast, and the difference between the composition of the final target composition and the composition of the zinc alloy to be cast. Then, the addition ratio of the mother alloy to be used is calculated based on the amount of molten zinc alloy to be cast. This calculated amount of the master alloy is added to the molten zinc alloy to be cast.

[0016]

The present invention will be described below based on examples and comparative examples. Examples 1 to 7 and Comparative Examples 1 to 4 Unused zinc alloy ingots (described as alloys in Table 1), used zinc alloy dies for press forming ( In Table 1, it was described as a mold) and a used zinc alloy die-cast product (in Table 1, it was described as DC material). Each zinc alloy was melted and their composition was analyzed. The results are as shown in Table 1. The analytical values of the magnesium content were all 0.03 to 0.04% by weight. From the previously prepared master alloys of various compositions, the magnesium content in the zinc alloy after addition of the master alloy was set to about 2% by weight, and the aluminum content and the copper content were almost the same as those in the zinc alloy before recasting. Was selected.
The molten metal temperature of each zinc alloy is controlled to 430 ° C., a predetermined amount of a selected amount of a mother alloy having the composition shown in Table 1 is added to the molten metal, and the molten metal is stirred to completely melt the mother alloy to an appropriate molten metal temperature. The time until becoming was measured. The alloy composition of the molten metal after the addition of the mother alloy was analyzed and compared with a target value. The measured and analyzed values were as shown in Table 1.

[0017]

[Table 1]

As is apparent from the data of Examples 1 to 7 in Table 1, when the master alloy of the present invention was used at the time of recasting a zinc alloy, the temperature of the zinc alloy melt under the conventional operating conditions was Melting can be performed in a short time, magnesium can be added while suppressing an increase in the total amount of molten zinc alloy within 10% by weight, and a high-quality zinc alloy can be regenerated. However, as is apparent from the data of Comparative Example 1, when a master alloy having a magnesium content exceeding 80% by weight was used,
The oxidation of the surface of the mother alloy was so severe that the deviation from the target value was large. Further, from the data of Comparative Examples 2 to 4, when a master alloy having a magnesium content of less than 10% by weight was used, when a master alloy having an aluminum content exceeding 10% by weight was used,
When a master alloy having a copper content of more than 5% by weight is used, the required amount of the master alloy increases and the melting point increases, so that the master alloy is completely melted after the master alloy is added to the molten metal. It takes a long time to reach an appropriate molten metal temperature, and the time loss during that time causes a cost increase and a cost increase such as an increase in the total amount of zinc alloy, and a master alloy having an aluminum content exceeding 10% by weight. When used, the aluminum content in the melt exceeded the spec.

[0019]

The master alloy of the present invention can be melted at the temperature of the molten zinc alloy under the conventional operating conditions when used when recasting a zinc alloy, and the total zinc alloy melt can be increased by up to 10% by weight. To enable the regeneration of high quality zinc alloy.

Continued on the front page (72) Inventor Fuminori Matsuda 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (5)

[Claims] 1. A master alloy for adjusting a magnesium content for use in recasting a zinc alloy, comprising 20 to 80% by weight of magnesium and the remainder being made of zinc excluding unavoidable impurities. 2. A master alloy for adjusting a magnesium content used in recasting a zinc alloy, comprising 20 to 80% by weight of magnesium and 10% by weight or less of aluminum, and the balance being made of zinc excluding unavoidable impurities. . 3. A master alloy for adjusting a magnesium content used in recasting a zinc alloy, comprising 20 to 80% by weight of magnesium and 5% by weight or less of copper, and the balance being made of zinc excluding unavoidable impurities. . 4. It is characterized in that it contains 20 to 80% by weight of magnesium, 10% by weight or less of aluminum and 5% by weight or less of copper, and the balance consists of zinc excluding unavoidable impurities.
A master alloy for magnesium content adjustment used when casting zinc alloys. 5. The master alloy for adjusting magnesium content according to claim 1, which is used at the time of recasting a zinc alloy mold.