WO2006098381A1

WO2006098381A1 - Process for producing magnesium alloy

Info

Publication number: WO2006098381A1
Application number: PCT/JP2006/305161
Authority: WO
Inventors: Yasuhiro Aoki; Hitohisa Yamada; Masahiko Muro; Yuuichi Ienaga
Original assignee: The Japan Steel Works, Ltd.; Honda Motor Co., Ltd.
Priority date: 2005-03-15
Filing date: 2006-03-15
Publication date: 2006-09-21
Also published as: EP1859878A1; JP4296158B2; JP2006255713A; EP1859878A4

Abstract

In producing an yttrium-containing magnesium alloy through melting, yttrium segregation is inhibited to obtain an ingot even in chemical composition. An yttrium-containing magnesium alloy is melted and then solidified within a solidification time of 200 seconds to produce an ingot. Desirably, the magnesium alloy melt is stirred and allowed to stand before being subjected to the solidification. The magnesium alloy contains yttrium in an amount of, e.g., 0.5-20 mass%. This process less causes segregation and is effective in producing a magnesium alloy even in chemical composition. Because of this, in producing, e.g., an alloy which considerably changes in performance with ingredient concentration, such as, e.g., a functional material, a high-quality product can be produced in a satisfactory yield. For accomplishing this, the process comprises melting raw materials in a melting furnace, sufficiently stirring the melt after complete melting, allowing the melt to stand, and then casting it into a casting mold designed so as to solidify it within the solidification time shown above. It is also possible to shorten the solidification time by casting into a casting mold sufficiently cooled with water.

Description

Manufacturing method of Mg alloy

Technical field

The present invention relates to a method for producing an Mg alloy containing, for example, an Mg alloy containing 0.5 to 20% by mass of Y while suppressing component segregation.

Background art

[0002] Mg alloys are light and have adequate strength, and are therefore widely used in applications such as automobile parts. This Mg alloy is manufactured by a batch method or a continuous forging method in which a raw material for melting is melted in a melting crucible and poured into a mold. For example, Patent Document 1 discloses a method of pouring into a sand mold, and Patent Document 2 discloses a forging method using die casting.

For Mg alloys, it has been proposed to add various elements for the purpose of improving the properties of the alloy. For example, Patent Documents 3 and 4 disclose Mg alloys to which rare earth elements such as Y are added.

Patent Document 1: Japanese Patent Laid-Open No. 06-279890

Patent Document 2: Japanese Patent Laid-Open No. 2003-305554

Patent Document 3: Japanese Patent Laid-Open No. 05-070880

Patent Document 4: Japanese Unexamined Patent Application Publication No. 2004-099941

Disclosure of the invention

Problems to be solved by the invention

[0003] However, when an Mg alloy containing a large atomic weight such as Y! /, And an element, is formed into a vertical shape, the Y component precipitates downward in the vertical shape, and there is a difference in Y concentration between the upper and lower portions of the ingot. The phenomenon of becoming larger occurs. Recently, requirements for quality have been increasing for applications using Mg alloys, and Mg alloys whose quality has deteriorated due to this component segregation of Y cannot meet the high product quality requirements.

[0004] The present invention has been made against the background of the above circumstances, and when producing an Mg alloy containing Y, an ingot is produced by suppressing component segregation and making the components as uniform as possible. The purpose is to provide a manufacturing method that makes it possible to obtain high-quality Mg products. Means for solving the problem

[0005] That is, in the Mg alloy production method of the present invention, after dissolving the Mg alloy containing Y,

It is characterized by solidifying into an ingot with a solidification time within 200 seconds.

[0006] In addition, the Mg alloy production method of the present invention is characterized in that after molten Mg alloy containing Y is left to stand, it is solidified within a solidification time of 200 seconds or less to form an ingot.

[0007] Further, in the method for producing an Mg alloy of the present invention, the Mg alloy has a soot content of 0.5 to 20% by mass.

% Content.

[0008] Further, the Mg alloy production method of the present invention is characterized in that the solidification time is 10 seconds or more.

[0009] That is, according to the present invention, in a Mg alloy containing Y, solidification is allowed to proceed before the precipitation of Y becomes prominent during ingot production, thereby suppressing the precipitation of Y, thus preventing the segregation of Y components. Thus, an ingot having a uniform component can be obtained. At this time, if the solidification time exceeds 200 seconds, the effect of suppressing Y component segregation cannot be sufficiently obtained, and the quality deterioration due to segregation becomes remarkable. The solidification time within 200 seconds can be solidified according to the segregation allowance, and the solidification time within 200 seconds can be controlled to a segregation rate of 10% or less. Here, the segregation rate is expressed by the following equation. However, when comparing the segregation rates, the absolute values are compared.

Segregation rate (%) = ((Yield)-(Target content)) Z (Target content) * 100 · · · (Formula) Also, if you want to obtain a segregation rate of 5% or less, solidify It is desirable to keep the time within 100 seconds. The solidification time is the time from the release of the molten metal temperature maintenance until the solidification in the mold starts and the solidification ends. In addition, it is desirable to stir the molten Mg alloy before starting cooling to make the components uniform. The stirring method of the molten metal is not particularly limited, and known methods such as stirring blades and electromagnetic stirring can be employed. After stirring the molten metal, it is allowed to stand to start the solidification. The completion of solidification shall mean the time when the solid phase ratio reaches 0.67.

[0010] As a means for achieving the above object, for example, the raw material is melted in a melting furnace, and after the molten metal is melted and sufficiently stirred, the molten metal is solidified within the solidification time as shown above. Plug into the saddle type designed for. It is also possible to shorten the coagulation time by placing it in a well-cooled bowl.

[0011] The content of Y in the Mg alloy is not limited to a specific amount, but it is desirable that the lower limit of the mass ratio of Y is 0.5% and the upper limit is 20%. By containing Y in this range, mechanical strength can be improved. On the other hand, if it is less than 0.5%, the mechanical strength is not improved. If it exceeds 20%, the material becomes brittle, and the prayer at the time of fabrication becomes remarkable. For the same reason, it is more desirable to set the lower limit to 1% and the upper limit to 15%.

[0012] Although the solidification time has an upper limit as described above, the lower limit is not limited to a specific one in the present invention. However, it is desirable to set a solidification time of 10 seconds as the lower limit for the purpose of reducing manufacturing costs when manufacturing large ingots. When the solidification time is below the lower limit, a problem of an increase in production cost tends to occur.

The invention's effect

[0013] As described above, according to the present invention, the Mg alloy containing Y is melted and then solidified in a solidification time of 200 seconds or less to form an ingot. It is effective to obtain a Mg alloy. For this reason, in the production of alloys such as functional materials whose performance varies greatly depending on the component concentration, high quality products can be produced with high yield. Brief Description of Drawings

FIG. 1 is a process diagram in one embodiment of the present invention.

FIG. 2 is a view showing a dissolution test apparatus used in the same example.

FIG. 3 is a drawing-substituting photograph of a test material obtained by a solidification test of an example.

FIG. 4 is a graph showing the relationship between the solidification rate of the test material obtained by the solidification test of the example and the deviation of the Y content.

FIG. 5 is a drawing-substituting photograph of a test material obtained by a solidification test of an example.

FIG. 6 is a graph showing the relationship between the solidification rate of the specimen obtained by the solidification test of the example and the deviation of the Y content.

FIG. 7 is a diagram showing the relationship between the inner diameter of the saddle and the solidification time in the saddle obtained by solidification calculation.

FIG. 8 is a diagram showing the relationship between Y bias and solidification time in an example of the present invention. Explanation of symbols

[0015] 1 melting furnace

2 Mg alloy molten metal

3 Stirrer

4 Vertical

5 Ingot

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] One embodiment of the present invention will be described below.

The Mg alloy used in the present invention contains at least Y, and a preferable content of Y can be 0.5% to 20% by mass ratio. When no other additive elements are contained, the balance is Mg and inevitable impurities. Further, the invention of the present application may contain other additive elements. Illustrative examples of the additive element include, in mass%, Zn: 0.1 to 10%, Zr: 0.1 to 2%, A1: 0.1 to 10%, Ca: 0.1 to 10%, Μη: 0.1-2%, Mm (Misch metal;): 0.1-10%, Sr: 0.001-0.1%, Si: 0.1-2%, Sn: 0.1-10%, Ge: 0.1 to 10%, Ce: 0.1 to 10%, La: 0.1 to 10%, Nd: 0.1 to 10%, Gd: 0.1 to 10%, and the like. The present invention is particularly suitable for suppressing component segregation in Mg alloys containing Zn, rare earth elements, and the like as components.

[0017] As shown in FIG. 1 (a), the Mg alloy whose components have been adjusted is melted by heating in, for example, a melting furnace 1 to obtain a molten Mg alloy 2. The melting method of the Mg alloy is not particularly limited as the present invention, and for example, it can be carried out using a known melting furnace by a conventional method. The molten Mg alloy is preferably stirred and mixed. The method and means for stirring and mixing are not particularly limited, and appropriate methods can be adopted. For example, as shown in FIG. 1 (b), the molten Mg alloy 2 is stirred by the stirring blade 3.

[0018] As shown in Fig. 1 (c), the molten Mg alloy 2 is usually solidified in the mold 4 in a stationary state after being poured into the mold 4. At this time, the solidification rate and solidification of the molten metal are caused by the components of the Mg alloy (the freezing point varies depending on the components), the temperature of the molten Mg alloy, the cooling capacity of the vertical mold, the mass effect of the Mg alloy, etc. Time, that is, the coagulation time is determined. Since the component segregation rate of Y greatly depends on this solidification time, it matches the desired component segregation rate. The longest coagulation time is determined. If the segregation rate is 10% or less, set the solidification time within 200 seconds. If the segregation rate is within 5%, set the solidification time within 100 seconds. It is necessary to determine the material and size of the bowl, the temperature of the molten metal, the presence or absence of forced cooling of the bowl, and the method so that it is within this solidification time.

[0019] After these conditions are determined, the ingot 5 is obtained by solidifying the molten Mg alloy 2 within a predetermined solidification time. This ingot has a segregation rate power of Y that is equal to or lower than a predetermined segregation rate, and an ingot in which the components are homogeneous can be obtained. By producing Mg products using this ingot as a raw material, it is possible to obtain an excellent quality product with little component prayer. It should be noted that the process up to obtaining the Mg product using the ingot as a starting material is not particularly limited as the present invention, and a known processing method can be employed.

Example 1

[0020] Examples of the present invention will be described below.

In order to reproduce the segregation of the Y component, a small dissolution test apparatus 10 as shown in Fig. 2 was prepared. The melting test apparatus 10 is made of a heat-resistant material, and a furnace body 11 having a cylindrical inner space inside is vertically arranged with the axis being vertical, and a cylindrical heating element 12 is placed in the furnace body 11. Is disposed, and a core tube 13 is concentrically disposed inside the heating element 12. A crucible 14 is disposed as a melting furnace in the core tube 13, and the crucible 14 is placed on a support 13 a installed in the core tube 13. The temperature of the crucible 14 is raised by operating the heating element 12 to heat the core tube 13.

In addition, the upper and lower ends of the core tube 13 project outside the furnace body 11 and are closed by water cooling caps 15 and 16. The water cooling caps 15 and 16 are provided with cooling water introduction pipes 15a and 16a and cooling water discharge pipes 15b and 16b, respectively. Cooling water introduced from the cooling water introduction pipes 15a and 16a passes through the water cooling cap. Water is discharged and discharged from the cooling water discharge pipes 15b and 16b. The cooling water is passed during heating to prevent damage to the members in the water cooling caps 15 and 16.

[0022] The water cooling cap 16 is provided with an Ar gas introduction pipe 17a, and the Ar gas introduction pipe 17a communicates with the reactor core pipe 13. The water cooling cap 15 has an Ar gas discharge pipe 17b. The Ar gas discharge pipe 17b is also communicated with the reactor core pipe 13.

By introducing Ar gas into the reactor core tube 13 through the Ar gas introduction tube 17a, the atmosphere in the reactor core tube 13 can be changed to an Ar gas atmosphere. When the Mg alloy is melted by the crucible 14, the alloy is oxidized. To prevent.

The furnace body 11 is provided with a furnace control thermometer 18 for measuring the temperature of the furnace body space, and the water cooling cap 15 is provided with a thermocouple 19 for measuring the temperature of the molten metal in the crucible 14.

[0023] In the small dissolution test apparatus 10 described above, 90 g of Mg alloy containing 6.7% Y as a melting base material is inserted into the crucible 14 and heated to 750 ° C to be melted and solidified in a solidification time of 1000 seconds. Then, when the sample was cut longitudinally and the cross-sectional structure was observed (EPMA method), a phenomenon of thickening at the bottom of the Y component force ingot was observed as shown in Fig. 3.

[0024] Further, using the small dissolution test apparatus 10, the γ component analysis of the ingot center of the sample coagulated at various coagulation times was performed, and the correlation between the coagulation time and Y bias was examined. The results are shown in Fig. 4. As shown in Fig. 4, if the solidification time is long, the Y component settles downward, and the Y component value in the center of the ingot becomes lower than the ladle value (molten component value). It is becoming clear that the degree tends to increase. On the other hand, when the solidification time was shortened to lOsec, it was found that the prejudice of the Y component could be suppressed as shown in Fig. 5.

[0025] Next, using a large melting furnace, a raw material of 167 kg of Mg containing 6.7% Y (Y6.7 wt%, Zr4.9 wt%, Lai. Owt%, remaining Mg) was inserted into the crucible, After pouring, the molten metal was poured into a square mold (320 X 490 X 440mm), and the relationship between the Y component prayer and the solidification time was investigated. Figure 6 shows the relationship between the component prayer for Y in each part of the ingot and the solidification time. The solidification time is calculated based on the distance of the ingot bottom force. Therefore, there is a one-to-one correspondence between the solidification time and the ingot bottom force distance. Even in the mold brazing material, as the solidification time becomes longer, the Y component force settles to the bottom of the ingot, so the Y concentration increases at a position 20 mm from the bottom of the ingot, and conversely at the sampling position at the top of the ingot. Y component value tended to decrease. The rate of decrease was found to be 5% for lOOsec, 10% for 200 sec, and 15% for 400 sec. [0026] Next, in order to produce an ingot in which the component segregation of Y was suppressed to within 10%, the solidification time was judged from Fig. 6, and the saddle shape was designed so that the solidification time was within 200 seconds. The solidification time of a cylindrical bowl of 20 mm thickness correlates with the inner diameter of the solidification calculation force, and from Fig. 7, it was determined that it should be φ230 mm or less for an air-cooled bowl. Based on this result, a φ200mm bowl was produced.

Using a large melting furnace, a raw material of Mg alloy containing 6.7% Y was inserted into the crucible, and after melting, about 60 kg of molten metal was inserted into a cylindrical bowl of φ200mm X H650mm. Figure 8 shows the relationship between the Y component prayer and the solidification time of each part of the ingot. The component segregation ratio of Y was suppressed to 10% or less, and a uniform ingot could be produced.

[0027] When producing an ingot in which the component segregation of Y is suppressed to within 10%, a water cooling pipe is welded to the side surface of the saddle in order to make the saddle inner diameter larger than in the above examples, and water is allowed to flow. Prepare a water-cooled mold that can cool the mold sufficiently. From the calculation results shown in Fig. 7, it was found that the inner diameter of the cylindrical saddle that can be solidified within 200 seconds is expanded to 350 mm or less in the water-cooled vertical mold. Using a large melting furnace, insert a raw material of Mg alloy containing 6.7% Y into the crucible, and after pouring about 180 kg of molten metal into a cylindrical bowl of φ 350 mm X H 650 mm, the component segregation ratio of Y Is less than 10%, and a uniform ingot can be produced.

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

This application is based on a Japanese patent application filed on March 15, 2005 (Japanese Patent Application No. 2005-072308), the contents of which are incorporated herein by reference.

Industrial applicability

[0028] In the present invention, after the Mg alloy containing Y is melted, it is solidified within a solidification time of 200 seconds or less to form an ingot. As a result, high-quality products can be manufactured with high yield in the production of alloys such as functional materials whose performance varies greatly depending on the component concentration.

Claims

The scope of the claims

[1] A method for producing an Mg alloy, comprising melting an Mg alloy containing Y and then solidifying it in a solidification time within 200 seconds to form an ingot.

[2] A method for producing an Mg alloy, characterized in that the molten Mg alloy containing Y is left to stir and then solidified within a solidification time of 200 seconds or less to form an ingot.

[3] The method for producing an Mg alloy according to [1] or [2], wherein the Mg alloy contains 0.5 to 20% by mass%.

[4] The method for producing an Mg alloy according to any one of claims 1 to 3, wherein the solidification time is 10 seconds or more.