JP2008189995A - Method for producing oxide particle dispersion strengthened alloy by casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for mass-producing a high strength oxide dispersion strengthened type alloy in which oxide particles with nanosizes are uniformly dispersed into a base material metal by casting. <P>SOLUTION: The method for producing oxide dispersion strengthened type alloy comprises: a dewatering stage where water molecules stuck to the surfaces of metal oxide particles with the particle diameters of 10 to 80 nm are removed; a melting stage where the metal base material is heated and melted, so as to be stirred; a dispersing stage where the metal oxide particles subjected to the dewatering stage are added to the melted metal base material, and they are stirred and dispersed while being heated; and a casting stage where the melted metal base material into which the metal oxide particles are dispersed is cast using rapid cooling. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for industrially producing an oxide particle dispersion strengthened alloy in which nano-sized metal oxide particles are dispersed.

  In recent years, energy conservation efforts in the transportation equipment industry have become active, and one example is the improvement in fuel efficiency by reducing the weight of transportation equipment. As a material for realizing weight reduction of moving bodies such as automobiles, railways, and airplanes, an oxide dispersion strengthened alloy that is lightweight but has high strength, wear resistance, and heat resistance is useful. The oxide dispersion strengthened alloy is an alloy having an increased strength by uniformly dispersing base metal and inactive fine oxide particles having no solid solubility in an alloy substrate.

  A mechanical alloying method is known as a method for producing an oxide dispersion strengthened alloy. In this method, the base metal powder and the oxide powder are pulverized and mixed to uniformly disperse the oxide particles in the base metal. Patent Document 1 discloses a method for producing an oxide dispersion strengthened chromium-based alloy using a mechanical alloying method. However, since it takes a very long time to produce an oxide dispersion strengthened alloy by the mechanical alloying method, a large productivity cannot be expected. In addition, since this method uses powder processing instead of melting, there is a limit to the size and precision of parts that can be manufactured.

  On the other hand, there is a melt mixing method as a method suitable for industrial production of an oxide dispersion strengthened alloy. This method is a method in which oxide particles are directly added to a molten base metal and mechanically stirred and mixed. Since a general casting method can be used as it is, the size and shape of parts that can be manufactured are wide. However, the molten metal stirring and mixing method has a problem that when the oxide particles become nano-sized, the uniform dispersibility of the particles decreases due to the deterioration of the wettability of the particle surface and the aggregation of the particles. is there.

Japanese Patent Laid-Open No. 10-17958

  An object of the present invention is to provide a method for producing a large amount of a high-strength oxide dispersion strengthened alloy in which nano-sized oxide particles are uniformly dispersed in a base metal by casting.

  In order to achieve the above object, the method for producing an oxide dispersion strengthened alloy according to claim 1 is characterized in that water adhered to the surface of metal oxide particles having a particle diameter of 10 to 80 nm. A dehydration step for removing molecules, a melting step for heating and melting and stirring the metal matrix, and adding the metal oxide particles subjected to the dehydration process to the molten metal matrix and stirring and dispersing while heating And a casting step of casting the molten metal base material in which the metal oxide particles are dispersed using rapid cooling.

  The method for producing an oxide dispersion strengthened alloy according to claim 2 is the method according to claim 1, wherein the metal oxide is at least selected from yttrium oxide, aluminum oxide, titanium dioxide, zirconium dioxide, and magnesium oxide. It is a type. You may use these metal oxides as complex oxide which combined two or more.

  A method for producing an oxide dispersion strengthened alloy according to a third aspect is the method according to the first aspect, wherein the metal base material is aluminum and / or an aluminum alloy.

  The method for producing an oxide dispersion strengthened alloy according to claim 4 is the method according to claim 1, wherein the amount of the metal oxide added is 2 to 5% by weight of the metal base material. And

  The method for producing an oxide dispersion strengthened alloy according to claim 5 is the method according to claim 1, wherein the number of rotations of stirring in the melting step and the dispersing step is 400 rpm to 1200 rpm. To do. If it is slower than this, sufficient stirring effect cannot be obtained. On the other hand, if the speed is higher than this, the metal oxide particles agglomerate during agitation, resulting in non-uniform dispersion.

  The method for producing an oxide dispersion strengthened alloy according to claim 6 is the method according to claim 1, wherein the heating temperature in the melting step and the dispersing step is 800 ° C. to 1200 ° C. And When the heating temperature is too low, the viscosity of the metal base material increases and slag is left behind in the manufactured alloy.

  The method for producing an oxide dispersion strengthened alloy according to claim 7 is the method according to claim 1, wherein the stirring time in the dispersion step is 2 minutes to 60 minutes. If it is 2 minutes or less, a sufficient stirring effect cannot be obtained, and the metal oxide particles are not dispersed.

  The method for producing an oxide dispersion strengthened alloy according to an eighth aspect is the method according to the first aspect, wherein the melting step and the dispersing step are performed in an argon atmosphere.

  A method for producing an oxide dispersion strengthened alloy according to a ninth aspect is the method according to the first aspect, wherein the melting step and the dispersing step are performed under vacuum conditions.

  The method for producing an oxide dispersion strengthened alloy according to claim 10 is the method according to claim 1, wherein stirring in the melting step and the dispersing step is performed by a screw-shaped stirring rod. And

  An oxide dispersion strengthened alloy according to an eleventh aspect is manufactured by the method according to any one of the first to tenth aspects.

  In the method for producing an oxide dispersion strengthened alloy according to the present invention, nanosized oxide particles whose surface has been dehydrated are added to a molten metal base material and mechanically stirred. Can be more uniformly dispersed. Therefore, according to the present invention, a higher strength oxide dispersion strengthened alloy can be obtained.

  Moreover, according to the manufacturing method of an oxide dispersion strengthened alloy, a general casting method can be diverted and cast as it is. Therefore, the size and shape of the parts that can be manufactured are wide, and can be manufactured at low cost, and the productivity is high. The oxide dispersion strengthened alloy manufactured by the method of the present invention is used for lightweight structural materials for aerospace, materials for mobile machines such as automobiles, general structural materials, and structural materials for internal combustion engines such as engine blocks and cylinder heads. can do.

Preferred form for carrying out the invention

  Examples of the present invention will be described in detail below, but the scope of the present invention is not limited to these examples.

  As a preferred example of the present invention, a method for producing an aluminum reinforced alloy will be described in detail.

  The manufacturing method of the oxide dispersion strengthened alloy of the present invention utilizes a molten metal stirring and mixing method. First, as pretreatment, dehydration treatment is performed on the surface of oxide particles to be dispersed. An yttrium oxide powder having a purity of 99.99% and a particle diameter of 80 nm is put into acetone and subjected to ultrasonic cleaning for about 15 minutes. Next, the precipitated yttrium oxide is recovered and dried in a vacuum drying furnace, and then powdered again using a ball mill to obtain a dehydrated yttrium oxide powder. The ball milling is performed in an argon atmosphere.

  Nano-sized particles have a high surface area to volume ratio, and in the air, water molecules are chemically adsorbed on the particle surface. When the oxide particles with water molecules attached are used as they are for the production of an oxide dispersion strengthened alloy, the water molecules and the aluminum, which is a molten metal matrix, cause a chemical reaction, and hydrogen gas bubbles are generated on the surface of the oxide particles. And the wettability between the particle surface and the molten aluminum is deteriorated. Further, since the oxide particles are lifted by the buoyancy of the generated hydrogen gas, the oxide particles are not uniformly dispersed in the molten aluminum. Therefore, the dehydration process is indispensable.

  A ceramic crucible containing aluminum having a purity of 99.99%, which is a metal base material, is set in a molten metal stirrer equipped with a stirrer and a heating device, and the temperature is raised to 1000 ° C. to melt the aluminum. After reaching 1000 ° C. and keeping it for 1 minute, a stirring bar is put into the crucible and gradually rotated. At this time, the rotation speed of the stirring rod is preferably 600 rpm, and the distance between the tip of the stirring rod and the crucible bottom is preferably within 5 mm. The melting and stirring of the metal base material may be performed while blowing 10 Nl / min of argon gas into the molten metal stirring device.

  Next, the dehydrated yttrium oxide powder is gradually added to the crucible stirred at 1000 ° C. and 600 rpm over 1 minute. The amount of yttrium oxide powder added is preferably 4% by weight of the molten aluminum. When the addition of yttrium oxide is completed, stirring is continued at 1000 ° C. and 600 rpm for 7 minutes to disperse the yttrium oxide particles in the molten aluminum. Stirring after the addition of yttrium oxide is preferably performed while blowing 10 Nl / min of argon gas into the molten metal stirring apparatus.

  After stirring for 7 minutes, the melt in the crucible is poured into a mold kept at room temperature, and the whole mold is poured into water and rapidly cooled. When the mold is completely cooled, water cooling is stopped, and the alloy in the mold is taken out to obtain an aluminum reinforced alloy in which nano-sized yttrium oxide is dispersed.

The dispersed yttrium oxide is considered to be dispersed in the state of Y ₂ O ₃ and dispersed in the state of AlYO ₃ reacted with aluminum of the metal base material.

  The stirrer comprises a stirrer provided with a free-standing stand that can be freely moved up and down by rotating a handle up and down, and a screw-shaped stir bar having a diameter of 8 mm and a pitch of 10 to 15 mm. A screw-like stirring rod is preferable because the melt in the crucible does not leak out when the stirring rod is pulled up from the crucible. In order to prevent deterioration due to heat, the stirring rod may be coated with a high-temperature heat-resistant functional paint such as a silicone resin paint (for example, Pyrocoat; trade name of Otake Serum Co., Ltd.).

  As the heating device, a high-frequency induction furnace having an electromagnetic stirring effect is used. The heating rate of the high frequency induction furnace is preferably 500 ° C./min. A high frequency induction furnace is a device that performs heating by Joule heat of eddy current generated by electromagnetic induction action of high frequency current flowing in a coil. When a metal is melted using a high frequency induction furnace, a complicated liquid metal flow occurs in the crucible. Since there is a coil around the crucible and a high-frequency current flows through it, a magnetic field is generated through the molten metal in the crucible. On the other hand, in the molten metal, an eddy current is generated in such a direction as to cancel the magnetic field. Joule heat is generated by the electrical resistance between the eddy current and the metal. Here, when a high-frequency magnetic flux is applied, a pinch force is generated toward the center according to Fleming's left-hand rule. This pinch force causes a flow in the molten metal, and the molten metal is agitated.

  Examples in which oxide dispersion strengthened alloys are manufactured using the manufacturing method to which the present invention is applied are shown in Examples 1 to 9.

(Example 1)
1-1 Dehydration of metal oxide particles 5 g of yttrium oxide having a purity of 99.99% and an average particle size of 80 nm is put into 100 mL of acetone, and 45 KHz using an ultrasonic cleaner (AS-ONEULTRA SONIC CLEANER USK 1-R). For 15 minutes. After the yttrium oxide particles were precipitated and the supernatant was removed, the yttrium oxide particles were dried in a vacuum drying furnace (AS ONE VACUUM OVEN AVO-310) at 30 ° C. for 8 hours to obtain lumps of yttrium oxide particles. Using a planetary ball mill (FRITSCH P PLANTARY MONO MILL), the lump of yttrium oxide particles was crushed under the conditions of using a titanium sphere of 10 mm in diameter, argon atmosphere, 100 rpm, crushing time 3 minutes × 2, resting time 1 minute, and yttrium oxide. Particle powder was obtained. The obtained yttrium oxide particle powder was hermetically stored in a desiccator in which silica gel was spread and evacuated.

1-2. Melting of base metal and dispersion of metal oxide particles 45 g of aluminum having a purity of 99.99% was placed in a ceramic crucible and set in a high frequency induction furnace (MU-1700SP1, manufactured by Miwa Seisakusho). In an argon atmosphere, the high-frequency induction path was heated to 1000 ° C. to melt aluminum, and kept at 1000 ° C. for 1 minute.

  Next, a screw-like stirring rod having a diameter of 8.0 mm and a pitch of 10 mm was gently inserted into the molten aluminum in the crucible so that the distance between the tip and the bottom of the crucible was within 5 mm. Using a stirrer (AS-ONE LABORATORY HIGH POWER MIXER), the screw-shaped stir bar was gradually rotated until the rotation speed reached 400 rpm. After stirring the molten aluminum at 400 rpm for 2 minutes while maintaining 1000 ° C., 4% by weight of the yttrium oxide particle powder obtained in 1-1 was added to the molten aluminum over 1 minute, and further under an argon atmosphere. Stir for 2 minutes.

1-3 Casting After the stirring of 1-2 was completed, the crucible was taken out of the high frequency induction furnace, and molten aluminum in which yttrium oxide particles were dispersed was poured into a cylindrical mold having a diameter of 14 mm. This operation was performed in about 15 seconds. The mold was cooled with water, and when the sample was completely cooled, an oxide dispersion strengthened alloy sample was obtained.

(Examples 2-9)
Except that the melting temperature of aluminum in Example 1-2, the number of revolutions of the stirring bar, and the stirring time after adding the yttrium oxide particle powder to the molten aluminum were as shown in Table 1, An oxide dispersion strengthened alloy sample was produced.

  The manufactured oxide dispersion strengthened alloy sample was evaluated as follows.

(Tissue observation)
The oxide dispersion strengthened alloy sample obtained in each Example was cut and polished using a metal cutting machine (Fine Cut, manufactured by Heiwa Kogyo Shoji Co., Ltd.), and the cross section was observed. Observation was performed using a scanning electron microscope (SEM; S-3000, manufactured by Hitachi). For some samples, a field emission scanning electron microscope (FE-SEM; S-5000, manufactured by Hitachi) was used for finer observation. The observation results are shown in FIGS.

(Area fraction measurement)
The area fraction of the region in which the yttrium oxide particles were dispersed was measured on the surface observed during the structure observation. First, with respect to each sample, 30 backscattered electron composition images were continuously photographed from the outer periphery of the sample toward the center at 1K magnification. This photograph was analyzed by computer software “Area Measure”, the area fraction of the yttrium oxide dispersed region in each photograph was measured, and the average value was obtained to obtain the area fraction of the dispersed region of the sample. The measurement results are shown in Table 2.

  First, from Examples 1 to 4, the influence of the rotational speed during stirring on the dispersion of yttrium oxide particles was examined. The SEM photograph of the cut surface of the sample obtained in Example 1 is obtained in FIG. 1 (a), the SEM photograph of the cut surface of the sample obtained in Example 2 is obtained in FIG. An SEM photograph of the cut surface of the sample is shown in FIG. 1C, and an SEM photograph of the cut surface of the sample obtained in Example 4 is shown in FIG. As is apparent from FIG. 1, yttrium oxide dispersion was observed at any rotational speed. Further, as is clear from Table 2, the average area fraction of yttrium oxide showed the highest value for the sample of Example 2 at a rotational speed of 600 rpm, and the lowest value for the sample of Example 1 at 400 rpm.

  Next, from Examples 2, 5, and 6, the influence of the melting temperature of aluminum on the dispersion of yttrium oxide particles was examined. An SEM photograph of the cut surface of the sample obtained in Example 5 is shown in FIG. 2 (e), and an SEM photograph of the cut surface of the sample obtained in Example 6 is shown in FIG. 2 (f). As is clear from FIG. 2, the sample of Example 5 having a melting temperature of 700 ° C. and the sample of Example 6 having a melting temperature of 800 ° C. contained a lot of slag, and almost confirmed dispersion of yttrium oxide particles. could not. On the other hand, dispersion was confirmed in the sample of Example 2 having a melting temperature of 1000 ° C.

  Next, from Examples 2, 7, 8, and 9, the influence of the stirring time after the addition of yttrium oxide particles on the dispersion of yttrium oxide particles was examined. The SEM photograph of the cut surface of the sample obtained in Example 7 is obtained in FIG. 3 (g), the SEM photograph of the cut surface of the sample obtained in Example 8 is obtained in FIG. The SEM photograph of the cut surface of each sample is shown in FIG. As apparent from FIG. 3, the dispersion region of the yttrium oxide particles increased as the stirring time increased. In the sample with a stirring time of 8 minutes (see FIG. 3 (i)), it was observed that many yttrium oxide particles were dispersed along the grain boundary. The average area fraction of yttrium oxide particles was highest for the sample of Example 9 with a stirring time of 8 minutes, and the lowest value for the sample of Example 2 with a stirring time of 2 minutes.

(Hardness measurement)
The hardness of the alloy sample of Example 9 having the largest dispersion amount among the oxide dispersion strengthened alloy samples obtained in each Example was measured.

  The alloy sample obtained in Example 9 was set in a micro Vickers hardness tester (manufactured by AKASHI), the hardness was measured under the conditions of a test load of 500 g and a holding time of 15 seconds, and an average of 10 points excluding the maximum and minimum values. Asked. For comparison, the hardness of the comparative sample prepared in the same manner as in Example 9 except that the yttrium oxide particles were not added was measured by the same method.

  As a result of the hardness measurement, the alloy sample of Example 9 was 37.6 Hv, while the comparative sample was 16.6 Hv. From this, it was confirmed that the hardness of the alloy of the example was remarkably increased as compared with the conventional aluminum.

(Transmission electron microscope (TEM) observation)
The grain boundary portion of the alloy sample obtained in Example 7 was observed with a transmission electron microscope. The results are shown in FIG. As shown in FIG. 4, a dispersion of 100 nm or less was observed by TEM.

  From the above results, it was revealed that nano-sized yttrium oxide was dispersed in the alloy samples obtained in the examples.

Scanning electron microscope of the cut surface of each oxide dispersion strengthened alloy obtained in Example 1 (a), Example 2 (b), Example 3 (c), and Example 4 (d) to which the present invention is applied It is a photograph. It is a scanning electron micrograph of the cut surface of each oxide dispersion strengthen type alloy obtained in Example 2 (b), Example 5 (e), and Example 6 (f) to which the present invention is applied. Scanning electron microscope of cut surface of each oxide dispersion strengthened alloy obtained in Example 2 (b), Example 7 (g), Example 8 (h), and Example 9 (i) to which the present invention is applied It is a photograph. It is a transmission electron micrograph of the oxide dispersion strengthened type alloy obtained in Example 7 which applies this invention.

Claims (11)

  A dehydration step for removing water molecules adhering to the surface of the metal oxide particles having a particle diameter of 10 to 80 nm, a melting step for heating and melting and stirring the metal base material, and the dehydration step for the molten metal base material. A dispersion step in which the metal oxide particles are added and stirred and dispersed while heating, and a casting step in which the molten metal base material in which the metal oxide particles are dispersed is cast using rapid cooling. A method for producing an oxide dispersion strengthened alloy.   The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein the metal oxide is at least one selected from yttrium oxide, aluminum oxide, titanium dioxide, zirconium dioxide, and magnesium oxide.   2. The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein the metal base material is aluminum and / or an aluminum alloy.   The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein the amount of the metal oxide added is 2 to 5% by weight of the metal base material.   2. The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein a rotation speed of stirring in the melting step and the dispersing step is 400 rpm to 1200 rpm.   2. The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein the heating temperature in the melting step and the dispersing step is 800 ° C. to 1200 ° C. 3.   The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein the stirring time in the dispersion step is 2 minutes to 60 minutes.   The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein the melting step and the dispersing step are performed in an argon atmosphere.   The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein the melting step and the dispersing step are performed under vacuum conditions.   The method for producing an oxide dispersion strengthened alloy according to claim 1, wherein the stirring in the melting step and the dispersing step is performed by a screw-shaped stirring rod.   An oxide dispersion strengthened alloy manufactured by the method according to claim 1.

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