JP2006152446A - Production method for alloy powder raw material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an alloy powder raw material which is large in the grain sizes of the powder itself but is fine in the crystal grains of the metal or alloy constituting the substrate of the powder. <P>SOLUTION: By passing the starting raw material powder between a pair of rolls 2a, plastic working is applied to the starting raw material powder, so that the crystal grains of the metal or alloy particles constituting the substrate of the powder after the working is fined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an alloy powder raw material having fine crystal grains and a method for producing the same. In particular, the present invention seeks to refine the magnesium crystal grains constituting the base of the magnesium-based alloy powder as a raw material in order to create a magnesium alloy having both high strength and high toughness.

  Magnesium alloys are expected to have a light weight effect due to their low specific gravity, and are therefore widely used in mobile phone and portable audio equipment casings, automotive parts, mechanical parts, structural materials, and the like. For further lightening effect, it is necessary to increase the strength and toughness of the magnesium alloy. In order to improve such characteristics, it is effective to optimize the composition and components of the magnesium alloy and to refine the magnesium crystal grains constituting the substrate. In particular, for grain refinement of magnesium alloy materials, methods based on plastic working processes such as rolling, extrusion, forging, drawing and ECAE (Equal Channel Angular Extrusion) have been used so far. It was done.

  Japanese Patent Application Laid-Open No. 2001-294966 (Patent Document 1) discloses “magnesium alloy thin plate, method for producing the same, and molded product using the same”. In the method disclosed in this publication, a molten magnesium alloy is formed into a plate-like material by injection molding, the plate-like material is compressed and deformed by roll rolling, and further subjected to heat treatment, thereby recrystallization. Refinement of magnesium crystal grains.

  Japanese Unexamined Patent Publication No. 2000-087199 (Patent Document 2) discloses “a method for manufacturing a magnesium alloy rolled material, a method for pressing a magnesium alloy, and a pressed product”. In the method disclosed in this publication, a magnesium alloy sheet is cold-rolled at a predetermined reduction rate, and then the sheet is subjected to heat treatment at a predetermined temperature range, thereby refining magnesium crystal grains by recrystallization. Is doing.

  In any of the methods disclosed in Japanese Patent Laid-Open Nos. 2001-294966 and 2000-087199, the workpiece is a plate-like material, and what is finally obtained is also a plate material. Therefore, it is extremely difficult to produce a pipe-shaped material, a rod-shaped material, a material having an irregularly shaped cross-section, etc. by the methods disclosed in these publications. In addition, a heat treatment step is required after the rolling process, and there is a problem that the cost of the material is increased in terms of economy.

  Japanese Patent Laying-Open No. 2003-277899 (Patent Document 3) discloses "magnesium alloy member and manufacturing method thereof". In the method disclosed in this publication, the magnesium crystal grains are refined by firstly forging, aging heat treatment, and secondary forging after solution treatment of the magnesium alloy material. Even in this method, it is necessary to repeat forging and heat treatment a plurality of times, resulting in an increase in the cost of the material. Further, in the first forging process, it is indispensable to give a predetermined processing pre-strain to the raw material, so that the product shape is restricted. Furthermore, the method disclosed in this publication is unsuitable for producing a long product such as a rod-shaped material or a pipe-shaped material.

  International Publication No. WO03 / 027342A1 (Patent Document 4) discloses a “magnesium-based composite material”. In the method disclosed in this publication, magnesium alloy powder or magnesium alloy chip is used as a starting material, and this material is put into a mold die and subjected to compression molding and extrusion processing. Further, a high strength magnesium alloy having fine magnesium crystal grains is obtained by subjecting the billet to hot plastic working. According to the method disclosed in this publication, when a large solidified billet is produced, there arises a problem that it is difficult to make the crystal grains finer uniformly in the billet. Further, in order to advance the atomization, it is necessary to remarkably increase the number of compression / extrusion processes described above, which causes a problem that the material cost increases.

  Japanese Patent Laid-Open No. 5-320715 (Patent Document 5) discloses a “manufacturing method of a magnesium alloy member”. In the method disclosed in this gazette, magnesium having a history of plastic working is obtained by compressing and solidifying chips, scraps, wastes, and the like discharged during cutting of a magnesium alloy member and extruding or forging it. We are creating alloy members. At that time, the strength of the magnesium alloy is improved by promoting the refinement of the magnesium crystal grains by plastic working.

  In the case of the above method, the crystal grain size of the magnesium base governing the strength characteristics of the magnesium alloy after extrusion or forging is not only the amount of strain applied to the raw material during plastic processing, but also chips, scrap, There is also a strong relationship with the crystal grain size of waste or cast magnesium. In other words, the refinement of the crystal grains of magnesium constituting the base material of the starting material is extremely effective for increasing the strength of the magnesium alloy material that is the final product. However, in the chips, scraps, wastes, and cast materials used here, the crystal grain size of magnesium is coarser than several hundred microns. Therefore, in a magnesium alloy obtained when a normal magnesium alloy chip, scrap, waste, or cast material is used as a starting material, significant increase in strength and toughness cannot be expected.

  On the other hand, paying attention to the method of atomizing the magnesium crystal grains in the magnesium alloy powder particles, which is one of the starting materials, there is a rapid solidification process such as a spray method or a single roll method. With these methods, it is possible to produce magnesium-based alloy powder particles having fine crystal grains by suppressing the growth of crystal grains in the process of cooling and solidifying the molten magnesium alloy droplets in a very short time. .

The cooling / solidification rate is governed by the amount of heat removed from the droplet surface. In other words, depending on the specific surface area of the magnesium alloy droplets, the finer the droplets, the higher the solidification rate, and the finer crystal grains that can be solidified in a short time. Therefore, a magnesium-based alloy powder having fine crystal grains can be produced by a rapid solidification method, but on the other hand, the particle size of the powder is small, so that the powder particles are likely to float in the manufacturing process, and dust explosion etc. The risk of increases rapidly. Also, when considering compression solidification by mold press molding, the flowability of fine powder particles is low, so the filling rate into the mold and the formation of local voids, and the frictional force between the powders are large. Therefore, there is a problem that it becomes difficult to harden.
JP 2001-294966 A JP 2000-087199 A JP 2003-277899 A International Publication No. WO03 / 027342A1 JP-A-5-320715

  As described above, in order to increase the toughness of the magnesium alloy, it is effective to refine the magnesium crystal grains in the substrate. To that end, a manufacturing method that does not go through a melting / solidifying process accompanied by grain growth, such as a casting method or a die casting method, is necessary. Specifically, it is a problem to construct a solid phase process in which a powder or a raw material having a geometric shape similar to that is formed and compacted in a temperature range below its melting point.

  Next, it is necessary to refine the crystal grains of the magnesium-based alloy powder used as a raw material at that time. At the same time, it is desirable that the powder is a relatively coarse powder that does not cause dust explosion and has an appropriate size from the viewpoint of press molding.

  An object of the present invention is to provide an alloy powder raw material and a method for producing the same, in which the powder itself has a large particle size, but the crystal grains of the metal or alloy constituting the powder substrate (matrix) are fine.

  The inventors of the present invention have intensively studied the above problems, and have found a means for solving the problems described below by repeating many experiments. Specifically, the material has a maximum crystal grain size of metal or alloy particles constituting the substrate as fine as 30 μm or less, and a relatively coarse alloy powder raw material without a risk of dust explosion and a method for producing the same. It was.

  The present inventors conducted experiments on magnesium-based alloy powder raw materials, but the present invention can also be applied to other material powders such as aluminum-based alloy powder raw materials. In the experiment, it was confirmed that a magnesium alloy obtained by molding and solidifying the above magnesium-based alloy powder raw material has both excellent strength and toughness.

  In the present specification, the terms “metal” and “alloy” are used, but the two are not strictly distinguished. In this specification, the term “metal” or “alloy” should be understood to include both pure metals and alloys.

  The present invention that achieves the above object is as follows.

  The alloy powder raw material according to the present invention has a maximum powder size of 10 mm or less, a minimum powder size of 0.1 mm or more, and a maximum crystal grain size of metal or alloy particles constituting the powder base. 30 μm or less.

  The metal or alloy constituting the powder base is, for example, magnesium or a magnesium alloy. Preferably, the maximum size of the powder is 6 mm or less, and the minimum size of the powder is 0.5 mm or more. More preferably, the maximum crystal grain size of magnesium or magnesium alloy particles constituting the powder base is 15 μm or less.

  In one embodiment, the powder raw material is obtained by subjecting a starting raw material powder having a relatively large crystal grain size to plastic processing to have a relatively small crystal grain size. In another embodiment, the powder raw material is collected from a metal or alloy material having a base having a maximum crystal grain size of 30 μm or less by performing any one of machining, cutting, and grinding. Is.

  In one aspect, the method for producing an alloy powder raw material according to the present invention includes subjecting the starting raw material powder to plastic working, thereby reducing the crystal grain size of the metal or alloy particles constituting the substrate of the starting raw material powder. It is characterized by miniaturization.

  The plastic working is preferably performed until the maximum size of the powder is 10 mm or less, the minimum size is 0.1 mm or more, and the maximum crystal grain size of the metal or alloy particles constituting the powder base is 30 μm or less. Alternatively, when the maximum crystal grain size of the metal or alloy particles constituting the base of the starting raw material powder is 100%, the plastic processing is performed so that the maximum crystal grain size of the metal or alloy particles constituting the powder base after the processing is Continue until 20% or less.

  The plastic working is preferably performed at a temperature of 300 ° C. or lower. Preferably, the starting material powder is heated in an inert gas atmosphere, a non-oxidizing gas atmosphere, or a vacuum atmosphere. The starting material powder is, for example, magnesium or a magnesium alloy powder.

  In one embodiment, the plastic working is performed by compressing and deforming the starting material powder through a pair of rolls. As a more specific form, the pair of rolls are arranged in the case, and the above method further includes a raw material charging step of continuously charging the starting raw material powder between the pair of rolls in the case. And a powder discharge step of continuously feeding the powder plastically processed between the pair of rolls to the outside of the case. The powder sent out from the case may be further processed with at least one of a crusher, a pulverizer, and a coarse granulator to obtain a granular powder.

  A plurality of sets of a pair of rolls may be provided, and the raw material powder may be plastically processed by passing between the plurality of sets of rolls. The clearance between the pair of rolls is, for example, 2 mm or less.

  Preferably, the surface temperature of the roll in contact with the starting material powder is 300 ° C. or less. Preferably, the plastic working application region including a pair of rolls is set to one of an inert gas atmosphere, a non-oxidizing gas atmosphere, and a vacuum atmosphere. A roll has a recessed part in the surface, for example.

  In another embodiment, the plastic working is performed by kneading the starting material powder. As a more specific form, the plastic working is performed by putting the starting raw material powder into a case in which a pair of rotating paddles are arranged and kneading. In this case, the above method preferably includes a raw material charging step of continuously charging the starting raw material powder into the case, a kneading step of kneading the starting raw material powder in the case, and the powder after the kneading to the outside of the case. And a powder discharging process for continuously feeding. The powder sent out from the case may be further processed with at least one of a crusher, a pulverizer, and a coarse granulator to obtain a granular powder.

  A plurality of pairs of paddles may be provided, and the starting raw material powder may be kneaded with a plurality of pairs of paddles. The clearance between a pair of paddles is, for example, 2% or less of the paddle diameter, or 20% or less of the size of the starting material powder, or 2 mm or less. The clearance between the paddle and the case is, for example, 2% or less of the paddle diameter, or 20% or less of the size of the starting raw material powder, or 2 mm or less.

  Preferably, the surface temperature of the paddle with which the starting material powder contacts is 300 ° C. or less. Preferably, the temperature of the inner wall surface of the case with which the starting material powder contacts is 300 ° C. or lower. More preferably, the inside of the case is an inert gas atmosphere, a non-oxidizing gas atmosphere, or a vacuum atmosphere.

  In another aspect, the method for producing an alloy powder raw material according to the present invention has any one of a plate shape, a rod shape, a column shape, and a lump shape, and the maximum crystal grain size of the metal or alloy particles constituting the substrate is A process of preparing a material that is 30 μm or less, and machining such as cutting, cutting, and pulverization are performed on the material, and the maximum size is 10 mm or less and the minimum size is 0.1 mm or more. And a step of collecting the powder raw material.

  In the following, embodiments and operational effects of the present invention will be described.

(1) Magnesium-based alloy powder raw material (A) Shape of powder raw material The magnesium-based alloy powder raw material is subjected to continuous plastic working to efficiently promote the refinement of crystal grains of the magnesium base. In order to promote such miniaturization, the starting raw material powder to be used has any one of the shapes of particles, powders, lumps, curls, bands, cutting powders, cutting curls, and chips. Is desirable. These shapes are shown in FIG.

  As plastic processing, compression processing, shearing processing, pulverization processing, kneading processing, etc. are performed, but the powder obtained after processing is a powder similar to the powder used as a starting material or an aggregate thereof, By performing crushing as necessary, the next step, compression molding and solidification, is facilitated.

  Specifically, the magnesium-based alloy powder after plastic processing is required to have appropriate compression moldability and solidification, and when the magnesium-based alloy powder is molded and solidified in a mold die, It is necessary to improve fluidity and filling property in the mold. In order to improve these characteristics, a magnesium-based alloy powder having a particulate, powder, lump, curl, belt, cutting powder, cutting curl, or chip shape is used as a starting material. It is desirable to use it.

(B) Size of powder raw material The magnesium-based alloy powder raw material obtained by the method of the present invention has a maximum powder size of 10 mm or less. Here, the maximum size indicates the largest dimension of the powder, and corresponds to the maximum particle diameter in the case of particles, powders, lumps, and chips. In the case of a strip shape, the dimension in the length direction is the largest when the width, length, and thickness are taken. In the case of a curled shape, it corresponds to the diameter when it is regarded as a circle.

  When the maximum size of the magnesium-based alloy powder of the present invention is 10 mm or less, there is no problem in the above-described compression moldability, solidification property, fluidity, and mold filling property. A more preferable maximum size is 6 mm or less. When the maximum size of the powder exceeds 10 mm, these characteristics are deteriorated, and particularly the compression moldability is deteriorated, so that there is a problem that the solidified billet is cracked or cracked.

  On the other hand, the magnesium-based alloy powder raw material obtained by the method of the present invention has a minimum powder size of 0.1 mm or more. Here, the minimum size indicates the smallest dimension of the powder, and corresponds to the minimum particle diameter in the case of particles, powders, lumps, and chips. In the case of a strip shape, it means the smallest dimension in the thickness direction when the width, length, and thickness are taken. In the case of a curled shape, the dimension of the material having the smaller width or thickness is used.

  When the minimum size of the magnesium-based alloy powder of the present invention is 0.1 mm or more, there is no problem in the above-described compression moldability, solidification property, fluidity, and mold filling property. A more preferable minimum size is 0.5 mm or more. If the minimum size of the powder is less than 0.1 mm, the powder characteristics relating to compression molding and solidification deteriorate, and at the same time, there is a risk that the probability of causing a dust explosion due to floating of the powder increases.

  FIG. 1 shows a maximum size portion and a minimum size portion for each powder shape.

(C) Maximum crystal grain size of magnesium particles constituting the powder base In the magnesium-based alloy powder obtained by the method of the present invention, the maximum crystal grain size of the magnesium particles constituting the base is 30 μm or less. Here, the maximum crystal grain size is a diameter of a circumscribed circle of the crystal grain. Specifically, after the powder is wet-polished with abrasive grains, the largest grain size of the crystal grains observed with an optical microscope or the like is obtained with chemical corrosion (etching) being performed to clarify the grain boundaries. Means.

  In order to improve mechanical properties such as strength and hardness of the powder, it is required not only to reduce the average crystal grain size of the particles constituting the substrate but also to reduce the maximum crystal grain size. Therefore, in the present invention, it has been clarified that a magnesium-based alloy material having both excellent strength and toughness can be created by managing the maximum crystal grain size of magnesium particles within an appropriate range.

  On the other hand, when using a powder raw material such that the maximum crystal grain size of the magnesium particles constituting the substrate exceeds 30 μm, the resulting magnesium-based alloy does not have a balanced strength and toughness, either one, Alternatively, both mechanical properties are degraded. More preferably, the maximum crystal grain size of the magnesium particles in the magnesium-based alloy powder raw material is 15 μm or less.

  The magnesium-based alloy powder raw material having the above configuration is obtained by plastic working or machining on the starting raw material powder. Specifically, in one method, the powder raw material is obtained by subjecting a starting raw material powder having a relatively large crystal grain size to plastic processing to have a small crystal grain size. In another method, the powder raw material is collected from a metal or alloy material having a base having a maximum crystal grain size of 30 μm or less by performing any one of machining processes such as a cutting process, a cutting process, and a crushing process. is there.

  The magnesium-based alloy powder raw material is one embodiment of the alloy powder raw material according to the present invention. The present invention can also be applied to other materials such as aluminum-based alloy powder raw materials. This also applies to the method described later.

(2) Method for Producing Magnesium-Based Alloy Powder Raw Material by Plastic Working FIG. 2 sequentially shows the steps for producing a magnesium-based alloy powder raw material by plastic working.

(A) Raw material heating step In the continuous plastic working of the starting material, the temperature of the raw material during processing is closely related to the refinement of the magnesium crystal grains and must be controlled within an appropriate temperature range. Therefore, it is important to heat and hold the raw material powder at a predetermined temperature before plastic working. For reasons that will be described later, the heating and holding temperature of the powder is desirably 300 ° C. or less, and more preferably 100 to 200 ° C.

  By applying predetermined plastic deformation to the input raw material in the temperature range as described above, the fragmentation and recrystallization of the crystal grains by the high strain processing, which is the driving source for the refinement of the crystal grains, proceeds significantly. Although continuous plastic working is possible even at room temperature, defects such as dislocations introduced into the raw material due to high strain processing increase, and the raw material powder becomes brittle and is pulverized and pulverized in the processing process. Increases the probability of triggering.

  If plastic processing is performed on the starting raw material powder at a temperature range of 100 to 200 ° C, pulverization and pulverization is suppressed while ductility is imparted to the processed powder raw material, and at the same time, the refinement of magnesium crystal grains proceeds. Can be made. On the other hand, if plastic working is performed at a temperature exceeding 300 ° C., seizure / adhesion between the rotating body for plastic working and the raw material occurs in the plastic working process.

  In the heating process of the starting material, it is desirable to heat the starting material powder in an inert gas atmosphere such as nitrogen or argon, a non-oxidizing gas atmosphere, or a vacuum atmosphere from the viewpoint of preventing oxidation of the powder surface. For example, when starting material powder is heated in the atmosphere, oxides are present in the magnesium-based alloy after hot extrusion or forging, which is a subsequent process, due to oxidation of the powder surface, and thereby characteristics such as fatigue strength. This causes problems such as lowering.

(B) Continuous plastic working process of raw material FIGS. 3 and 4 show a roller compactor which is an example of a continuous powder plastic working apparatus, and FIGS. 5 to 7 show other continuous powder plastic working apparatuses. The kneader (kneading machine) which is an example of is shown. First, these device configurations will be briefly described.

  A continuous powder plastic working apparatus shown in FIG. 3 includes a case 1, a multistage roll rotating body 2 disposed in the case 1, a crushing device 3, a powder temperature / supply amount control system 4, and a cradle. 5. The multi-stage roll rotating body 2 has three pairs of rolls 2a, 2b, and 2c for rolling the starting material powder. The starting raw material powder undergoes compression deformation when passing between the pair of rolls.

  The starting raw material powder is adjusted to a predetermined temperature and a predetermined amount by the powder temperature / supply amount control system 4 and charged into the case 1. The inside of the case 1 is maintained in an inert gas atmosphere, a non-oxidizing gas atmosphere, or a vacuum atmosphere from the viewpoint of preventing oxidation of the powder surface.

  FIG. 4 shows the third-stage roll pair 2 c and the crushing device 3. The powder delivered from the roll pair 2c is subsequently crushed by the crushing device 3 to become granular powder. The granular powder may be returned to the powder temperature / supply amount control system 4 again, and plastic processing by the multistage roll rotating body 2 may be repeated. The processed granular powder is accommodated in the cradle 5.

  The continuous powder plastic working apparatus shown in FIG. 5 includes a kneading chamber 12 maintained in an inert gas atmosphere, a non-oxidizing gas atmosphere, or a vacuum atmosphere, a supply port 13 for receiving starting raw material powder, A case 11 having a discharge port 14 for delivering powder is provided. In the case 11, two rotating shafts 15 that are rotatably supported by a bearing 16 and are driven to rotate by a driving unit 19 are disposed. A screw 17 for feeding the starting raw material powder charged into the case 11 forward and a paddle 18 for kneading the starting raw material powder are fixed to each rotating shaft 15. In order to heat the case 11, a heater or a jacket capable of supplying a heating medium may be provided to the case 11. Further, in order to heat the rotating shaft 15, a device that can supply a heater or a heating medium to the rotating shaft 15 may be provided.

  The starting raw material powder fed into the kneading chamber 12 by the screw 17 is kneaded when passing through the gap between the pair of rotating paddles 18 and the gap between each paddle 18 and the inner wall surface of the case 11. . This kneading process gives compressive force, shear force, dispersion force, impact force, deformation force, crushing force and the like to the starting raw material powder. A plurality of pairs of rotating paddles 18 are provided.

  In the embodiment shown in FIG. 5, the pair of paddles 18 rotate in the same direction. Each paddle 18 has a shape having three pointed vertices. 6 and 7 show a pair of paddles having a different shape from the paddle 18 of FIG. The pair of paddles 21 and 22 shown in FIG. 6 both have a shape having two pointed vertices and rotate in the same direction. The pair of paddles 31 and 32 shown in FIG. 7 have different shapes, and the rotation direction is also opposite. There are various paddles as described above, and any paddle may be used for kneading.

  Each of the continuous powder plastic working apparatuses shown in FIGS. 3 and 5 has a pair of rotating bodies and is supplied between the rotating bodies or between the rotating body and the case. The raw material powder is subjected to plastic processing such as compression processing, shearing processing, and pulverization processing, and at that time, the refinement of crystal grains by the high strain processing as described above is promoted.

  As described above, since temperature control of the raw material powder at the time of plastic working is important, it is necessary to manage the temperature of the pair of rotating body surfaces in contact with the raw material powder and / or the temperature of the inner wall surface of the case within an appropriate range. is there. The temperature range is desirably 300 ° C. or lower, similar to the heating and holding temperature of the raw material powder, and more preferably 100 to 200 ° C. for the same reason as described above.

  In the continuous powder plastic working apparatus, by arranging a plurality of pairs of rotating bodies, it is possible to give a high strain process to the raw material powder. Another effective method is to repeatedly heat the raw material powder to a predetermined temperature after plastic working and then re-enter the plastic working apparatus to perform plastic working.

  It is desirable that the clearance between the pair of rotating bodies and the clearance between the rotating bodies and the case in the continuous powder plastic working apparatus be set to appropriate values. In the case of the apparatus shown in FIG. 3, the clearance between the pair of rolls is preferably 2 mm or less. In the case of the apparatus shown in FIG. 5, the clearance between a pair of paddles is preferably 2% or less of the paddle diameter, or 20% or less of the size of the starting material powder, or 2 mm or less. Furthermore, the clearance between the paddle and the case is also preferably 2% or less of the paddle diameter, or 20% or less of the maximum size of the starting raw material powder, or 2 mm or less.

  The raw material powder is continuously supplied to the gap portion of the pair of rotating bodies or the gap portion between each rotating body and the case to perform plastic working, but the size of the clearance is preferable as described above. When the value is exceeded, sufficient strong strain processing cannot be applied, and as a result, magnesium crystal grains of 30 μm or less cannot be obtained. The degree of processing varies depending on the size and shape of the raw material powder to be added, but by setting the above clearance to 1/5 or less of the maximum size of the raw material powder, it is possible to continuously refine the magnesium crystal grains stably. .

  In the continuous powder plastic working apparatus, the surface properties of a pair of roll rotating bodies in contact with the raw material powder may be improved. Specifically, a recess is formed on the surface of the roll rotator. One or a plurality of concave grooves or concave slits may be considered as the concave portions, but they extend in a direction perpendicular to the rotation direction, a parallel direction, or a direction intersecting at an angle with an angle. Accordingly, the raw material powder can be efficiently drawn between the roll rotating bodies due to the wedge effect, and at the same time, the high strain processing can be forcibly performed. However, it is not essential to provide a concave portion, and even a roll rotating body having a surface not provided with such a concave groove or a concave slit can refine crystal grains by plastic working.

  In order to suppress oxidation of the raw material powder during plastic processing, a part or the whole including the rotating body is covered with a glow box etc. in a continuous powder plastic processing apparatus, and the atmosphere is inert gas atmosphere, non-oxidizing gas atmosphere Manage in a vacuum atmosphere.

  By subjecting the starting raw material powder to the plastic processing as described above, the alloy powder raw material after processing has the following characteristics. That is, the alloy powder raw material has a maximum crystal grain size of 30 μm or less of alloy particles constituting the powder base. Alternatively, when the maximum crystal grain size of the alloy particles constituting the base of the starting raw material powder is 100%, the plastic working is performed such that the maximum crystal grain size of the alloy particles constituting the base of the powder after processing is 20% or less. Do until it becomes. If such crystal grain refinement cannot be realized, it is difficult to achieve both excellent strength and toughness in a magnesium-based alloy material produced by molding and solidifying the obtained powder.

(C) Powder transfer / discharge process The powder subjected to plastic working is continuously discharged from the case. When a plurality of plastic workings are required, the powder is again supplied to the heating process and the continuous plastic working is performed. When the discharged powder is large, it is crushed or granulated to an appropriate size and shape and then supplied to the heating process.

(D) Crushing / Roughening / Granulating Step As described above, the magnesium-based alloy powder raw material according to the present invention is compression-molded and solidified later. Therefore, appropriate compression moldability, solidification property, fluidity, and mold filling property are required. Since these characteristics are due to the size and shape of the powder, it is preferable to use a crusher, crusher, coarse grain machine, etc. for the powder discharged from the apparatus after continuous plastic working. Crushing treatment, coarse graining treatment, and granulating treatment to make the dimensions (particle diameter) and shape uniform. From the viewpoint of pulverization processability, it is desirable that the temperature of the powder at that time is room temperature. The alloy powder raw material finally obtained has a maximum powder size of 10 mm or less and a minimum powder size of 0.1 mm or more. The shape of the powder is, for example, a granular powder.

(3) Method for Producing Magnesium-Based Alloy Powder Raw Material by Machining The magnesium-based alloy powder raw material according to the present invention can be produced by machining instead of plastic working as described above.

  In this method, first, a material having any one of a plate shape, a rod shape, a column shape, and a lump shape and having a maximum crystal grain size of magnesium alloy particles constituting the substrate of 30 μm or less is prepared. Such materials are subjected to hot or warm plastic processing such as rolling, extruding, forging, etc. on the starting material, plate-like, rod-like, plate-like, or massive magnesium-based alloy material, and high strain processing Is obtained. In this way, the maximum crystal grain size of the magnesium alloy particles constituting the material base is refined to 30 μm or less. Preferably, the magnesium alloy particles are refined until the maximum crystal grain size of the magnesium alloy particles is 15 μm or less.

  Next, the magnesium alloy material with refined crystal grains is subjected to machining such as cutting, cutting, and pulverization. From this material, the maximum size of the powder is 10 mm or less, and the minimum size of the powder A powder raw material having a diameter of 0.1 mm or more is collected. The maximum crystal grain size of the magnesium alloy particles constituting the base of the collected powder is 30 μm or less, preferably 15 μm or less. The size of the powder can be dealt with by adjusting the machining conditions described above, for example, adjusting the cutting speed, selecting the material and shape of the tool, and adjusting the processing time when grinding with a ball mill.

  AM60 (nominal composition: Mg-6% Al-0.5% Mn / weight basis) alloy chip (length 3.5mm, width 1.5mm, thickness 1.2mm as the starting material, maximum crystal of magnesium on the base A particle size of 350 μm and an average Vickers hardness of 65.4 Hv) were prepared. A roller compactor having a pair of roll rotating bodies (roll diameter 66 mmφ, roll width 60 mm, clearance between rolls 0.4 mm) was used as a continuous powder plastic working apparatus. The AM60 chip was held at each temperature shown in Table 1 in a heating furnace controlled in a nitrogen gas atmosphere, and then supplied to the processing apparatus to give the chip a compressive deformation. After the sample discharged from the apparatus was pulverized and granulated by a batch apparatus, as shown in Table 1, it was again heated and held at a predetermined temperature, and then continuously subjected to compressive deformation by the processing apparatus.

  In Table 1, the number of passes indicates the number of times AM60 chips are supplied to the roller compactor. Table 1 shows the shape and dimensional measurement results of the obtained powder sample, and Table 2 shows the measurement results of the maximum crystal grain size and Vickers hardness by observation with an optical microscope after polishing and chemical corrosion.

  In Sample Nos. 1 to 5, which are examples of the present invention, the maximum crystal grain size of the substrate is refined to 30 μm or less as compared with the AM60 chip as the input material, and 15 μm can be obtained by optimizing the temperature condition. Further refinement is possible to the following. It is also recognized that the Vickers hardness is increased by the high strain processing.

  In Sample No. 6, which is a comparative example, the temperature of the input sample AM60 tip exceeded 330 ° C. and the appropriate range, so that a problem that the sample tip adhered to the roll surface during the plastic working process occurred.

FIG. 8 shows the structure observation results of the samples Nos. 1 and 4 which are examples of the present invention shown in Tables 1 and 2 by the optical microscope and the structure observation results of the input material AM60 chip by the optical microscope.

  (A) of FIG. 8 shows the sample of sample number 1, the maximum crystal grain size of the magnesium particles constituting the substrate is 26 μm, and the average crystal grain size is as fine as 14.3 μm according to the result of image analysis. Granulated.

  FIG. 8 (b) shows the sample of sample number 4, the maximum crystal grain size of the magnesium particles constituting the substrate is as small as 11 μm, and the average crystal grain size is as fine as 7.8 μm according to the result of image analysis. Granulated.

  (C) of FIG. 8 shows AM60 chip as an input material, and the maximum crystal grain size of the magnesium particles constituting the substrate is 350 μm, the minimum crystal grain size is 123 μm, and the average crystal grain size is 218 μm (both images) Analysis results).

  As is clear from the above results, it is possible to produce a coarse magnesium-based alloy powder having fine magnesium crystal grains of 30 μm or less by continuous powder plastic working according to the present invention.

  AM60 (nominal composition: Mg-6% Al-0.5% Mn / weight basis) alloy chip (length 3.5mm, width 1.5mm, thickness 1.2mm as the starting material, maximum crystal of magnesium on the base A particle size of 350 μm and an average Vickers hardness of 65.4 Hv) were prepared. A roller compactor having a pair of roll rotating bodies (roll diameter 100 mmφ, roll width 80 mm, clearance between rolls 0.5 mm) was used as a continuous powder plastic working apparatus. The AM60 chip was heated and held at 200 ° C. in a heating furnace controlled in a nitrogen gas atmosphere, and then supplied to a processing apparatus to give the chip a compressive deformation. After the sample discharged from the apparatus was pulverized and granulated by a batch apparatus, it was again heated and held at a predetermined temperature, and then continuously compressed and deformed by the same processing apparatus.

  Here, the number of passes indicates the number of times of supplying AM60 chips to the roller compactor. Table 3 shows the measurement results of the maximum crystal grain size and Vickers hardness of the obtained powder sample by observation with an optical microscope after polishing and chemical corrosion.

  In Sample Nos. 11 to 16, which are examples of the present invention, the maximum crystal grain size of the substrate is refined to 30 μm or less as compared with the AM60 chip as the input material. It is recognized that further reduction of the particle size to 15 μm or less is possible. At the same time, the Vickers hardness increases due to the accumulation of high strain processing. All samples subjected to batch processing after being subjected to continuous plastic working are mixed powders of plate-like samples and granular samples, and the size is 0.3 to 4.5 mm. This satisfies the proper size range.

  Samples Nos. 12 and 16 shown in Table 3 and the input raw material AM60 chip were used as starting materials, and each powder was solidified at room temperature to produce a compacted body having a diameter of 35 mmφ and a height of 18 mm. After heating in a nitrogen gas atmosphere at a temperature of 400 ° C. and a holding time of 5 minutes, hot extrusion (extrusion ratio 25, die temperature 400 ° C.) was immediately performed to prepare a dense magnesium-based alloy rod (diameter 7 mmφ). Tensile test pieces (parallel portion 15 mm, diameter 3.5 mmφ) were prepared from the obtained extruded materials, and tensile strength characteristics (tensile strength, yield stress, elongation at break) were evaluated at room temperature. The results are shown in Table 4.

  Tensile strength, yield stress and elongation at break of extruded material produced using AM60 magnesium-based alloy powder having a fine structure with a maximum magnesium crystal grain size of 15 μm or less produced by continuous powder plastic working of the present invention Is significantly improved as compared with the case of using the input raw material AM60 chip that is not subjected to plastic processing. As is apparent from this result, it is recognized that the magnesium base alloy can be made to have both high strength and high toughness by refining magnesium crystal grains using the plastic working method proposed by the present invention.

  AM60 (nominal composition: Mg-6% Al-0.5% Mn / weight basis) alloy chip (length 3.5mm, width 1.5mm, thickness 1.2mm as the starting material, maximum crystal of magnesium on the base A particle size of 350 μm and an average Vickers hardness of 65.4 Hv) were prepared. A kneader (kneading machine) having a pair of rotating paddles (a clearance between the pair of paddles of 0.3 mm and a clearance between the paddle and the case of 0.3 mm) was used as a continuous powder plastic working apparatus. After holding the AM60 chip at each temperature shown in Table 5 in a heating furnace controlled in a nitrogen gas atmosphere, the chip was supplied to a processing apparatus and subjected to compressive deformation and shearing. The sample discharged from the apparatus was pulverized and granulated with a batch apparatus. Table 5 shows the shape and dimensional measurement results of the obtained powder sample, and Table 6 shows the measurement results of the maximum crystal grain size and Vickers hardness by observation with an optical microscope after polishing and chemical corrosion.

  In sample numbers 21 to 25, which are examples of the present invention, the maximum crystal grain size of the substrate is refined to 30 μm or less as compared with the AM60 chip as the input material, and 15 μm can be achieved by optimizing the temperature conditions. It can be seen that further refinement is possible to: It is also recognized that the Vickers hardness is increased by the high strain processing.

  In Sample No. 26, which is a comparative example, the temperature of the input sample AM60 tip exceeded 350 ° C. and the appropriate range, so that there was a problem that the sample tip adhered to the paddle and the case inner wall surface during the plastic working process.

FIG. 9 shows the structure observation results of the samples Nos. 23 and 24, which are examples of the present invention shown in Tables 5 and 6, using an optical microscope. In any magnesium-based alloy powder, the maximum crystal grain size of magnesium is as small as 15 μm or less, and a coarse magnesium-based alloy powder having fine magnesium crystal grains is produced by continuous powder plastic working according to the present invention. It is recognized that this is possible.

  AM60 (nominal composition: Mg-6% Al-0.5% Mn / weight basis) alloy chip (length 3.5mm, width 1.5mm, thickness 1.2mm as the starting material, maximum crystal of magnesium on the base A particle size of 350 μm and an average Vickers hardness of 65.4 Hv) were prepared. A roller compactor (roller shaft is cantilevered) having a pair of roll rotating bodies (roll diameter 66 mmφ, roll width 60 mm, clearance between rolls 0 mm) was used as a continuous powder plastic working apparatus.

  The temperature of the sample supply port was 170 ° C., and the AM60 chip was held at 200 ° C. in a heating furnace controlled in a nitrogen gas atmosphere, and then supplied to the processing apparatus to give the chip a compressive deformation. After the sample discharged from the apparatus was pulverized and granulated by a batch apparatus, it was again heated and held at 200 ° C. and then continuously subjected to compressive deformation by the same processing apparatus.

  Here, the number of passes indicates the number of times of supplying AM60 chips to the roller compactor. Table 7 shows the shape and size measurement results of the obtained powder sample, and Table 8 shows the measurement results of the maximum crystal grain size and Vickers hardness by optical microscope observation after polishing and chemical corrosion.

  In the samples of Sample Nos. 31 to 36, which are examples of the present invention, the maximum crystal grain size is reduced to 15 μm or less as compared with the AM60 chip as the input material, and rolls can be made by optimizing the temperature conditions. It can be seen that the AM60 chip can be made finer without the material adhering to the surface. It is also recognized that the Vickers hardness is increased by the high strain processing.

  The present invention can be advantageously used as an alloy powder raw material for obtaining an alloy having both high strength and high toughness and a method for producing the same.

It is a figure which shows the various shapes of a powder raw material. It is a figure which shows the manufacturing process of the method according to this invention in order. It is an illustration figure of the roller compactor as an example of a continuous type powder plastic processing apparatus. FIG. 4 is a diagram showing a third-stage roll pair and a crushing device in the continuous powder plastic working device shown in FIG. 3. It is a figure which shows the kneading machine as another example of a continuous type powder plastic processing apparatus. FIG. 6 is a view showing another example of a pair of paddles in the continuous powder plastic working apparatus shown in FIG. 5. FIG. 6 is a view showing still another example of a pair of paddles in the continuous powder plastic working apparatus shown in FIG. 5. It is the optical microscope photograph of the sample of the sample numbers 1 and 4 of Table 1 and Table 2, and the optical microscope photograph of input raw material AM60 chip | tip. It is an optical micrograph of the sample of the sample numbers 23 and 24 of Table 5 and Table 6. FIG.

Explanation of symbols

  1 case, 2 multi-stage roll rotating body, 2a, 2b, 2c roll pair, 3 crushing device, 4 powder temperature and supply control system, 5 cradle, 11 case, 12 kneading chamber, 13 supply port, 14 discharge port, 15 rotating shafts, 16 bearings, 17 screws, 18 paddles, 19 drive units, 21, 22, 31, 32 paddles.

Claims (1)

A method for producing an alloy powder raw material, comprising subjecting the starting raw material powder to plastic working to refine the crystal grain size of metal or alloy particles constituting the substrate of the starting raw material powder.