JP2015059236A - Surface treatment method for powder metal material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treatment method which modifies a powder metal material to be used in e.g. powder metallurgy and flame spray, safely and simply in a short time.SOLUTION: A surface treatment method uses a blast processing apparatus which injects an injection powder, together with a compression gas, within a workspace to cause the powder to impinge on a to-be-collided object and is provided with dust collection means of sucking powder dust from the workspace to remove and recover the powder dust. The surface treatment method comprises: carrying out a blast treatment by causing a powder metal material of an average particle size of 10-200 μm and a medium material having a hardness comparable with or higher than the hardness of the powder metal material to collide repeatedly with each other at an injection speed of 100-300 m/s, so as to peel a surface oxide from the powder metal material; and forming fine particle regions having crystal grain sizes smaller than crystal grain sizes in the central part, in the vicinity of the surface of the powder metal material. A sintered metal obtained by the powder metal material subjected to the surface treatment has a harmonious structure in which fine particle regions and coarse grain regions are arranged in a harmonized way and achieves high ductility and high strength at the same time.

Description

  TECHNICAL FIELD The present invention relates to a surface treatment method for a powdered metal material, and more specifically, as a material for manufacturing metal products using metal powder or forming a film, such as powder metallurgy such as sintering or thermal spraying. The present invention relates to a surface treatment method for powdered metal materials.

  As a kind of powder metallurgy, “sintering”, in which an aggregate of powdered metal materials is heated at a temperature lower than the melting point and hardened to obtain a sintered metal, is widely used in the manufacture of various mechanical parts such as gears. In particular, in recent years, it has also been proposed to use a powder metal material as a modeling material in a 3D printer. By applying a laser beam or an electron beam to a powder metal material in a predetermined pattern and sintering it, CAD It has also been proposed that a desired three-dimensional solid model can be directly formed from a metal material from shape data such as (Non-Patent Document 1), and thus produced by sintering a powdered metal material. In the 3D solid model, unlike the resin model manufactured by the conventional 3D printer, it is not only used as a model or sample, but it is a part that is directly incorporated into a machine or the like. It is also expected to be used as.

  However, sintered metal obtained by sintering powdered metal materials tends to have low density and low strength compared to melt molding due to residual pores, etc. In many cases, it cannot be put into practical use as a component.

  Therefore, for the purpose of removing the residual pores that bring about such low density and low strength, a process called “sintering forging” in which the obtained sintered metal is forged is also performed. If parts manufactured by simple three-dimensional modeling using a printer need further sintering forging, the advantage of simplicity is lost.

  Unlike ex-post processing such as sintering forging described above, research to increase the strength of sintered metal has also been promoted by devising the composition and structure of the powder metal material that is the raw material used for sintering. As one of them, high strength sintering is achieved by changing the internal structure of the material by subjecting the powdered metal material before sintering to mechanical milling by stirring with a ball mill. It has also been reported that metals can be obtained (Non-patent Documents 2 and 3).

  In this method, as shown in FIG. 6 (A), the powder metal material having a predetermined crystal structure is subjected to mechanical milling by a ball mill, and the powder metal material is concentrated and subjected to super-strong processing. As shown in FIG. 6 (B), in the vicinity of the surface of the powder metal material, there is a region called a shell (hereinafter referred to as “fine grain region”) formed by refining crystal grains. As a result, a central region called the core that maintains the original crystal grain size (hereinafter referred to as a “coarse grain region”) and the fine grain region that covers the coarse grain region A powdered metal material having the following is obtained.

  The sintered metal obtained by sintering the powdered metal material in which the coarse grain region and the fine grain region are formed in this manner is obtained as shown in FIG. 6C. A metal having a structure called “harmonic structure” in which fine-grained regions are connected to each other and a coarse-grained region is harmoniously arranged in the fine-grained regions (in the present invention, , Such a metal is referred to as “harmonic structure metal”), and with such a harmonic structure metal, a uniform equiaxed grain obtained using a normal powder metal material not subjected to mechanical milling treatment is obtained. It has been reported that significant improvement in strength can be obtained while maintaining ductility equivalent to that of sintered metal in the structure (Non-patent Document 2).

  In the above description, the manufacturing method of the “harmonic structure metal” described above has been described by taking the case of “sintering” as an example. However, the above-described powdered metal material having a fine-grain region is Even when a metal film is formed on the surface of the substrate by “thermal spraying”, the formed metal film can be formed as “harmonic structure metal”.

"Special Feature 2-3D Printer | [Design / Manufacturing Solution Exhibition] Report “Diversification of modeling materials such as resin, paper, metal, etc.” [Nikkei BP August issue] (Published date: August 1, 2013) Nos. 64-68 page〕 Satoshi Hatakeyama and Tatsuya Sekiguchi “Creation of Innovative Structural Materials with High Strength and High Ductility by Harmonic Structure Control” [Japan Heat Treatment Technology Association, “Heat Treatment Material and Surface Modification Vol.53 NO.1 2013 "(issue date: February 28, 2013) pages 1-2) “Recycled brass hardness 3 times Cutting scrap forming / sintering Nihon University makes new technology improved conductivity and puts it to practical use” [Nikkan Kogyo Shimbun (April 30, 2013)]

  As introduced in Non-Patent Documents 2 and 3, when sintering is performed using a powdered metal material that has been previously agitated by a ball mill, the sintered metal obtained by sintering becomes a “harmonic structure”. As a result, a metal having excellent properties of achieving both high ductility and high strength can be obtained.

  However, as described in Non-Patent Documents 2 and 3, when processing a powdered metal material with a ball mill, the processing efficiency is extremely poor. As an example, the processing time in Non-Patent Document 2 is 100 hours. The processing time in 3 is 32 hours.

  In addition, the processing of powdered metal materials using a ball mill is extremely dangerous because there is a risk of dust explosion.

  In other words, the powdered metal material used for sintering and the like is generally a fine particle having a particle size of around 100 μm, and this is put into a ball mill and stirred in the presence of air to generate frictional force and impact force. In addition, if an electrostatic discharge occurs due to friction during agitation, a dust explosion occurs.

  Here, a dust explosion occurs when the three elements of presence of oxygen, generation of dust exceeding the lower explosion limit concentration, and presence of an ignition source are combined. However, it is necessary to remove one or more of these conditions, but in order to apply ultra-strong processing to powdered metal materials, the friction from the ball mill that generates frictional force and impact force internally can be a source of ignition. It is impossible to eliminate the occurrence of impact.

  Therefore, when trying to prevent a dust explosion, work in a state where oxygen is excluded by filling the ball mill with an inert gas or so that the amount of powdered metal material input is less than the lower explosion limit concentration. Either coordination or both must be implemented.

However, if the ball mill is filled with an inert gas, the manufacturing cost will increase significantly. The lower explosive concentration of powdered metal (200 mesh (all openings: 74 μm)) is: aluminum in ^{35g / m 3, 45g / m} 3 in the titanium, 120g / m ³ in the iron [ "of arc welding work safety and hygiene (3rd)" the Japan welding Society WE-COM magazine No. 6 ( (Extracted from October 2012)), it is possible to process only a small amount if stirring is performed below the lower explosion limit concentration, and it can be processed for small-scale production at the laboratory level in the laboratory. However, it is impossible to process a large amount of powdered metal material on a commercial basis with a ball mill.

In addition, even if the above-described ball mill treatment can be applied to the treatment of powder metal materials, the powder metal materials treated by this method include surfaces such as oxide scales separated from the surface of the powder metal materials. Oxides are mixed, and this oxide hinders the bonding between powder metal materials during sintering, and impairs the increase in strength.

  In other words, powder metal materials used for sintering and thermal spraying are generally manufactured by the atomizing method. In this atomizing method, the molten metal is atomized by spraying / scattering, and this is rapidly quenched and solidified. Therefore, oxide scale adheres to the surface of the powder metal material.

  In addition, a powdered metal material manufactured by a method other than the atomizing method also forms an oxide film that is a surface oxide by contact with oxygen in the air, although there is a difference in degree.

  Even if such surface oxides such as oxide scales are peeled off from the surface of the powdered metal material due to friction and impact received during stirring in the ball mill, the oxides thus peeled off are peeled off due to the structure of the ball mill. It is mixed in the powder metal material without being removed later.

  Moreover, since the exfoliated oxide is stirred together with the powder metal material in the ball mill, a part of the exfoliated oxide is pressed against the surface of the powder metal material by friction and impact caused by agitation. It is reattached by being embedded.

Therefore, when the powdered metal material processed by the ball mill is taken out as it is and used for sintering, the strength improvement is suppressed by the presence of oxides mixed in the powdered metal material.

  On the other hand, in order to remove oxides mixed in the powder metal material, it is conceivable that the powder metal material after the treatment by the ball mill is subjected to, for example, wind sorting, but in this method, in addition to the treatment by the ball mill, Furthermore, it is necessary to provide a separate step for removing the oxide, and the productivity is further reduced.

  In addition, with this method, even if the oxides mixed in the powder metal material can be removed to some extent, the oxides reattached to the surface of the powder metal material cannot be separated and removed.

  Therefore, if the surface treatment of the powder metal material can be performed by a method that can also remove such a surface oxide film, it is possible to expect higher strength of the resulting harmonic structure metal.

  Therefore, the present invention has been made to solve the above-mentioned drawbacks of the prior art, and is used as a material for obtaining a metal product or a metal film having a harmonized structure by a method such as powder metallurgy such as sintering or thermal spraying. The above-mentioned process for forming fine-grained areas on the surface of a powdered metal material is easy and reliable to remove oxides from the surface and to remove oxides after peeling without worrying about dust explosions. An object of the present invention is to provide a surface treatment method for a powder metal material that can be performed efficiently in a relatively short time.

In order to achieve the above object, a surface treatment method for a powdered metal material of the present invention comprises:
In the method of surface treatment of powdered metal materials used for the production of a harmonic structure metal in which the fine grain region and coarse grain region are arranged harmoniously,
Using a blasting apparatus equipped with dust collecting means for injecting the sprayed powder together with the compressed gas in the working space to collide with the impacted object, and sucking the inside of the working space to remove and collect the dust,
By performing a blasting process in which a powder metal material having an average particle size of 10 to 200 μm and a medium substance having a hardness equal to or higher than that of the powder metal material are repeatedly collided at an injection speed of 100 to 300 m / sec, The surface oxide is exfoliated from the metal material, and a fine grain region having a crystal grain size smaller than the crystal grain size at the center is formed near the surface of the powder metal material. ).

  As the blasting apparatus used for the blasting process, an apparatus in which the dust collecting means includes a cyclone for classifying the dust and the sprayed powder is used.

  Further, in the above blasting apparatus, the collected dust is stored together with non-combustible powder such as calcium carbonate in the dust collecting means (claim 3).

In the surface treatment method of the powder metal material having the above-described configuration,
The powder metal material may be formed with the spray powder, and the medium substance may be used as the collision object (claim 4),
The medium substance may be used as powder to form the spray powder, and the powder metal material may be used as the collision object (Claim 5).
Further, the medium substance is a powder metal material having the same material and the same average particle size as the powder metal material, and both the spray powder and the colliding object are used as the powder metal material. It is good also as a thing (Claim 6).

  The material of the medium substance may be a metal having a hardness equal to or higher than that of the powder metal material, or a ceramic having a hardness equal to or higher than the hardness of the powder metal material after the surface treatment. 7).

  With the configuration of the present invention described above, the following remarkable effects can be obtained according to the surface treatment method for a powder metal material of the present invention.

  By performing a blasting process in which a powder metal material having an average particle size of 10 to 200 μm and a medium substance having a hardness equal to or higher than that of the powder metal material are repeatedly collided at an injection speed of 100 to 300 m / sec, a powder metal The surface oxide of the material is removed, and the rapid temperature rise and cooling that occurs near the surface at the time of collision is repeated, so that the crystal grains near the surface of the powder metal material are refined and the center part A large amount of powdered metal material in which a fine grain region with a crystal grain size smaller than the crystal grain size is formed near the surface can be easily processed in a short time by a relatively simple method called blasting. I was able to.

  Moreover, by performing the blasting process described above with a blasting machine with a dust collecting function, mass production is possible while avoiding the danger of dust explosion, and the surface of oxide scales and the like peeled off from the surface of the powder metal material. By removing and collecting oxides as dust by suction in the work space, a powdered metal material free from surface oxides can be obtained without providing a separate step for removing surface oxides in the subsequent process. I was able to.

In particular, when using a cyclone that classifies the dust and the sprayed powder as dust collecting means for blasting, it is collected in a state where the powdered metal powder and exfoliated surface oxide are mixed. Even in such a case, the surface oxide can be classified and recovered from the spray powder together with the dust, and a powder metal material from which the surface oxide has been removed can be obtained with higher accuracy. It was.

  Furthermore, when the removed dust is stored together with non-combustible powder such as calcium carbonate in the dust collecting means of the above blast processing apparatus, the risk of dust explosion not only in the processing chamber but also in the dust collector can be reduced. did it.

  This blasting may be performed by using a powdered metal material as an injection powder and injecting and colliding with a medium material, or by using a medium material as an injection powder and injecting and colliding with a powdered metal material. Although it is good, when both powder powder and colliding object are made of powder metal material with the same average particle diameter and the same material, powder metal material is jetted and collided with powder metal material. In this case, both the powder metal powder used as the spray powder and the powder metal powder used as the collision object are subjected to surface treatment at the same time, so that the amount of treatment can be doubled. It was.

It is a schematic explanatory drawing of the blast processing apparatus used for the surface treatment method of this invention, (A) is a gravity type, (B) is a direct pressure type. The graph which shows the X-ray-diffraction result of an untreated stainless steel powder (SUS304 equivalent). The graph which shows the X-ray-diffraction result of the stainless steel powder (SUS304 equivalent) processed by the method of Example 1. FIG. The graph which shows the X-ray-diffraction result of an untreated powder high speed tool steel (SKH equivalent article). The graph which shows the X-ray-diffraction result of the powder high speed tool steel (SKH equivalent article) processed by the method of Example 2. FIG. It is explanatory drawing explaining the production | generation of a harmonic structure, (A) is an untreated powder metal material, (B) is a powder metal material after the process by a ball mill, (C) is a powder metal material of (B). The schematic diagram of the harmonic structure | tissue metal obtained by sintering.

  Next, embodiments of the present invention will be described below with reference to the accompanying drawings.

〔overall structure〕
The present invention uses a known blasting apparatus to perform a blasting process in which a powder metal material to be processed and a medium substance colliding with the powder metal material are repeatedly collided at a predetermined injection speed. As a result, surface oxides such as oxide scales that hinder the strength improvement during sintering and thermal spraying are removed from the surface of the powder metal material, and the crystal grain size at the center is near the surface of the powder metal material. It is intended to form a fine grain region having a small crystal grain size.

  In this way, sintering is performed using a powdered metal material in which a coarse grain region having a relatively large crystal grain size is formed in the center and a fine grain region having a small crystal grain size is formed near the surface. For metal products obtained by methods such as powder metallurgy, etc., or metal coatings produced by thermal spraying, coarse grain regions are harmoniously arranged in a network of fine grain structures formed by joining fine grain regions together. It becomes the harmonic structure metal which has the crystal structure (refer FIG.6 (C)) made, and has the outstanding characteristic that high ductility and high intensity | strength are compatible.

[Powdered metal material]
The powder metal material to be treated in the present invention is a powder metal having an average particle size of 10 to 200 μm used as a material for powder metallurgy and thermal spraying such as sintering, and is applied to powder metallurgy and thermal spraying. Any material can be used as long as it is possible, and it may be composed of pure metal or alloy.

  As an example, metals commonly used in powder metallurgy include iron-based, copper-based, stainless-based, titanium-based, and tungsten-based metals. Also, as metals used for thermal spraying, Zinc, aluminum, copper, etc. are common, but in the present invention, any of these can be included in the material of the powder metal material.

  The powder metal materials used can be those produced by various methods, and spray methods represented by the atomization method, which is a method for producing powder metal materials commonly used in powder metallurgy and thermal spraying. In addition, those manufactured by various known methods such as mechanical crushing and electrolytic deposition can be used.

  The shape of the powder may be spherical, but is not limited thereto, and various shapes can be used.

  Note that the crystal grain size of the powdered metal material before the treatment is directly the crystal grain size of the coarse grain region as described above. Therefore, when the crystal grain size of the coarse grain region is within a predetermined range, it is appropriate. A powder metal material having a crystal grain size is selected. Although not particularly limited, the average crystal grain size in the coarse grain region is, for example, several μm to several tens of μm.

[Medium material]
As the medium substance that collides with the powder metal material, various materials can be used as long as they have a hardness equal to or higher than that of the powder metal material. Things can also be used.

  When using a ceramic medium material that is not work hardened, it is preferable to use a ceramic material having a hardness equal to or greater than the hardness of the powder metal material after the surface treatment of the present invention. Even after the material is work-hardened, the same or higher hardness is maintained.

  Further, the medium substance itself may be composed of the above-described powder metal material, and the above-described ultrafine grain structure may be formed in both powder metal materials by collision between the powder metal materials.

  The shape of the medium substance needs to be configured as a powder when the medium substance side is used as a spray powder. However, when processing the powder metal material described above as a spray powder, It is not necessary to use powder, and for example, it may be configured as a plate or the like.

[Blasting method and blasting apparatus]
The collision between the powdery metal material and the medium substance described above is performed by blasting using a blasting machine.

  In this blasting process, as described above, a powdered metal material may be used as an injection powder, which may be injected toward a medium substance and collided. It is also possible to prepare a substance and inject and collide it as a powder to a powdered metal material. Furthermore, both the powder and the colliding object are made of the same average particle diameter and the same material. It is good also as what consists of a powdery metal material and collides powdery metal materials.

  As the blasting apparatus 1 to be used, a known various configuration is used as long as it is a blasting apparatus with a dust collecting function that sucks the inside of the cabinet 21 and collects the inside of the cabinet 21. Either a direct pressure type or a gravity type blasting apparatus may be used.

  A configuration example of a gravity blasting apparatus 1 used for the surface treatment of the present invention is shown in FIG. 1 (A), and a direct pressure type configuration example is shown in FIG. 1 (B).

  In the following, the surface treatment of the present invention is performed by using the blasting apparatus 1 and using the powdery metal material having the same material and the same average particle diameter for both the spray powder and the colliding object. However, the blasting apparatus 1 used in the surface treatment method of the present invention is not limited to the one shown in the figure.

  A blasting apparatus 1 shown in FIGS. 1A and 1B includes a cabinet 21 serving as a processing chamber that accommodates an injection nozzle 22 and a workpiece and performs blasting, and a dust collector 38 that sucks the inside of the cabinet 21. The cyclone-type recovery tank 23 is provided between the dust collector 38 and the cabinet 21 so that the powder metal material in a state of being mixed with dust collected by sucking the cabinet 21 is recovered. The dust collected in the cyclone-type collection tank 23 can be collected in the dust collector 38.

  And the powdery metal material collect | recovered in the collection tank 23 in this way is comprised so that it can inject from the injection nozzle 22 in the cabinet 21 again.

  Inside the above-described cabinet 21, where the tip of the injection nozzle 22 is directed, a barrel basket 24, which is an upwardly opened container that rotates during injection of the injection powder, is provided. In addition, a powdered metal material to be collided can be introduced.

  In the example shown in FIG. 1 (A), the barrel cage 24 is shown as a wire mesh having a large number of small holes. However, the present invention is not limited to the illustrated example, and the structure does not include such small holes. It's also good.

  Prior to performing the processing using the blast processing apparatus 1 configured as described above, the powder metal material is put into the recovery tank 23 and the powder metal material is also put into the barrel cage 24 provided in the processing chamber. When the injection of the powder metal material is started from the injection nozzle 22 at an injection speed of 100 to 300 m / sec while rotating the barrel cage 24 in this state, the powder metal material injected from the injection nozzle 22 is rotated by the rotating barrel cage. It collides with the powdered metal material in 24.

  The injection pressure may be 100 m / sec or more in the treatment of non-ferrous powder metal materials, but is preferably 150 m / sec or more in the treatment of iron powder metals.

  Thus, by injecting the powder metal material, each of the powder metal material in the barrel cage 24 and the powder metal material injected from the injection nozzle 22 receives the energy at the time of collision with each other and is powdered. The surface oxide, such as oxide scale, formed on the surface of the metal-like metal material is peeled off, and the surface of the collision part rapidly rises in temperature and is cooled, so that the crystal grains on the collision part surface are refined. In the vicinity of the surface of the powder metal material, a fine grain region is formed in which a crystal grain having a small diameter is formed with respect to the crystal grain in the central part.

  The refinement of the powder metal material is that when the powder metal material to be processed is less than 100 μm, it is formed on the surface of the powder metal material at a depth of about 20% at maximum with respect to the particle size. It has been empirically confirmed that when the powder metal material to be formed is 100 μm or more, it is formed at a depth of about 10% at the maximum with respect to the particle size. In the surface treatment method of the present invention for treating a metal material, the aforementioned fine grain region is formed in a range of 2 to 20 μm at the maximum from the surface according to the particle size of the powder metal material to be treated.

  The powdered metal material injected from the injection nozzle 22 collides with the powdered metal material in the barrel cage 24 and then accumulates in the barrel cage 24 except for the one ejected out of the barrel cage 24. Agitation is performed with the powdered metal material present in the barrel cage 24.

  Therefore, if the powder metal material is continuously ejected from the spray nozzle 22, the powder metal material in the barrel cage 24 increases, overflows from the barrel cage 24, and falls to the bottom of the cabinet 21.

  The bottom of the cabinet 21 is formed as an inverted trapezoidal hopper, and the lower end of the hopper communicates with the dust collector 38 through the exhaust passage 33 and the recovery tank 23, so that the exhaust air provided in the dust collector 38 is provided. When the inside of the cabinet 21 is sucked by the vessel 39, the powdered metal material or dust that has fallen is sucked together with the air in the cabinet 21 and fed into the cyclone type recovery tank 23, where the dust and the powder metal The material is classified, and the powdered metal material is recovered downward in the recovery tank 23.

  Since surface oxides such as oxide scale generated on the surface of powder metal materials are harder and more brittle than powder metal materials, they are crushed finely when they are peeled off by impact caused by collision between powder metal materials. Therefore, it is not collected in the collection tank 23 but is sent as dust to the dust collector 38 via the pipe 32 connected to the upper portion of the collection tank 23 and collected in the lower part of the dust collector 38, and clean air is discharged. The air is discharged from the fan 39 into the outside air.

  In this way, the processing chamber formed in the cabinet 21 is constantly suctioned to remove dust and powdered metal material floating in the air, and is kept below the lower explosion limit concentration. In terms of form, there is no risk of dust explosion in the cabinet due to the generation of heat or static electricity due to the injection, collision, friction of the powdered metal material.

  On the other hand, the dust classified in the cyclone-type collection tank 23 and collected in the dust collector 38 is incombustible powder such as carbon dioxide so that the concentration of flammable dust in the air in the dust collector 38 is lower than the lower explosion limit concentration. By being accommodated in the dust collector 38 together with the calcium powder, the danger of dust explosion in the dust collector 38 is also avoided.

  The powder metal material recovered in the recovery tank 23 is again injected from the injection nozzle 22 toward the powder metal material in the barrel cage 24, and any of the powder metal materials is obtained by repeating the above-described steps. Surface oxides such as oxide scale are also removed from the surface of the material, and a fine grain region is formed so as to cover the entire surface.

  As described above, a powdered metal material in which a fine grain region is formed in the vicinity of the surface can be obtained by using it as a material for powder metallurgy such as sintering or for forming a metal film such as spraying. In the sintered metal or metal coating obtained, a harmonic structure metal in which coarse grain regions are harmoniously arranged in a network of fine grain structures formed by interconnecting portions of fine grain regions is obtained. With such a harmonic structure metal, excellent properties such as high ductility and high strength can be obtained.

  In particular, in the case of a powdered metal material treated by the method of the present invention, surface oxides such as oxide scale that cause a decrease in strength during sintering and welding can be suitably removed. It is possible to further increase the strength of the sintered metal and the metal coating.

  In the above description, both the spray powder and the colliding object are made of a powdered metal material, and the spray powder and the colliding object are collided in the barrel cage 24 provided in the cabinet 21. As described above, for example, a plate body formed of a material having a hardness equal to or higher than that of the spray powder is accommodated as a medium substance in the cabinet 21 in place of the barrel cage 24 described above, and a powder metal material is accommodated in the plate body. The surface treatment of the present invention may be performed by spraying and colliding as a spray powder.

  Further, using the blasting apparatus 1 provided with the barrel cage 24 described above, the powdered medium material is used as the spray powder, and the medium material that is the spray powder is used for the powder metal material charged in the barrel cage 24. In this case, the powdered metal material and the medium substance are classified and recovered after the treatment.

  Below, the Example which applied the surface treatment method of this invention with respect to the powdery metal material of various materials is described.

[Example 1]
The surface treatment method of the present invention was performed on stainless steel powder (SUS304 equivalent: # 80) as the powder metal material. The processing conditions are shown in Table 1 below.

  10 kg of stainless steel powder is put into the barrel basket provided in the processing chamber of the blasting machine, and 20 kg of stainless steel powder is put into the collection tank. The treatment was continued for 3 hours.

  As a result of the above treatment, the surface of the treated stainless steel powder was cleaned and the surface was clean, and the hardness of the stainless steel powder from 250 to 350 HV before the treatment increased to 450 to 550 HV after the treatment. This suggests that the crystal grains near the surface are becoming finer.

  In addition, the refinement of the crystal grain size can be evaluated from the increase in the line width of the X-ray analysis peak from the Scherrer (1918) equation. The results of X-ray analysis of untreated stainless steel powder (see Fig. 2) ) On the other hand, the X-ray diffraction results after the processing according to the present application (FIG. 3) show that the peak line width has greatly increased, and the hardness of the powder metal material described above has increased. From the results, it was confirmed that the crystal grain size was reduced on the surface.

[Example 2]
The surface treatment method of the present invention was performed on powder high-speed tool steel (SKH equivalent: # 150) as a powder metal material. The processing conditions are shown in Table 2 below.

  10 kg of powder high-speed tool steel is put into the barrel cage installed in the processing chamber of the blasting machine and 10 kg of powder high-speed tool steel is put into the recovery tank. Under the conditions shown in Table 2 above, the powder high-speed tool steel in the recovery tank is The process of injecting inward was continued for 5 hours.

  As a result, the hardness of the powder high-speed tool steel, which was 650 to 750 HV before the treatment, increased to 900 to 1000 HV after the treatment.

  In addition, the powder high-speed tool steel after the treatment has a clean surface with the oxide scale removed, and the X-ray diffraction results show that the X-ray analysis peak is higher than that of the untreated one (see Fig. 4). The line width increased (see FIG. 5), and it was confirmed that the surface texture was refined by the treatment according to the method of the present invention (see FIGS. 4 and 5).

Example 3
The surface treatment method of the present invention was performed on powder of alloy steel for machine structure (SCM equivalent: # 150) as a powder metal material. The processing conditions are shown in Table 3 below.

  10 kg of machine structural alloy steel powder is put into a barrel basket provided in the processing chamber of the blasting machine, and 10 kg of alloy steel for machine structural use in the recovery tank. The process of spraying from the spray nozzle into the barrel basket was continued for 5 hours.

  As a result, the hardness of the powder of alloy steel for machine structural use, which was 150 to 200 HV before the treatment, increased to 300 to 350 HV after the treatment.

  In addition, the processed alloy steel powder for machine structural use is considered to have a finer structure on the surface due to the above-mentioned increase in hardness as well as the surface being cleaned by removing the oxide scale. .

Example 4
The surface treatment method of the present invention was applied to a copper alloy powder (# 150) as a powder metal material. The processing conditions are shown in Table 4 below.

  20 kg of copper alloy powder is put into the recovery tank, and the copper alloy powder in the recovery tank is turned to a position where the core of 100 mm is shifted from the center of the SKD11 plate (φ400 mm, thickness 20 mm) placed in the processing chamber. The process of spraying from the spray nozzle was continued for 7 hours.

  As a result, the hardness of the copper alloy powder which was 160 to 200 HV before the treatment increased to 220 to 260 HV after the treatment.

  In the copper alloy powder after the treatment, it is considered that the oxide scale is removed and the surface is clean, and a refined structure is formed on the surface due to the increase in hardness described above.

Example 5
The surface treatment method of the present invention was performed on an aluminum alloy powder (AC8A: # 80) as a powder metal material. The processing conditions are shown in Table 5 below.

  A barrel basket with a number of holes of 1 mm diameter is installed in the processing chamber, and 10 kg of aluminum alloy (AC8A) powder is put into the barrel basket, and the high-speed steel shot put into the collection tank is directed into the barrel basket. The spraying process was continued for 7 hours.

  As a result of the above treatment, the hardness of the aluminum alloy powder, which was 120 to 140 HV before the treatment, increased to 200 to 250 HV after the treatment.

  In addition, the treated aluminum alloy powder has a clean surface with oxide scale removed, and due to the above-mentioned increase in hardness, the medium material, high-speed steel, diffuses and penetrates into the aluminum alloy powder surface. In addition, it is considered that a fine structure is formed on the surface.

[Sintering test results]
As described above, the discharge plasma sintering was performed using the powdered metal material treated by the surface treatment method of the present invention described as Examples 1 to 5.

  As a result, in the sintered metal obtained by sintering any powdered metal material of Examples 1 to 5, the coarse grain structure is harmonized in the network formed by interconnecting the fine grain regions. The surface treatment method of the present invention is capable of treating powder metal materials used for the production of a harmonic structure metal simply, in large quantities, and safely. The method was confirmed.

1 Blasting device 21 Cabinet 22 Injection nozzle 23 Collection tank (Cyclone type)
24 barrel basket 32 tube 33 air exhaust path 38 dust collector 39 air exhaust

In order to achieve the above object, a surface treatment method for a powdered metal material of the present invention comprises:
In the surface treatment method of a powder metal material used as a production material of a harmonic structure metal in which a fine grain region and a coarse grain region are arranged harmoniously,
Using a blasting apparatus equipped with dust collecting means for injecting the sprayed powder together with the compressed gas in the working space to collide with the impacted object, and sucking the inside of the working space to remove and collect the dust,
By performing a blasting process in which a powder metal material having an average particle size of 10 to 200 μm and a medium substance having a hardness equal to or higher than that of the powder metal material are repeatedly collided at an injection speed of 100 to 300 m / sec, The surface oxide is exfoliated from the metal material, and a fine grain region having a crystal grain size smaller than the crystal grain size at the center is formed near the surface of the powder metal material. ).

Claims (7)

In the method of surface treatment of powdered metal materials used for the production of a harmonic structure metal in which the fine grain region and coarse grain region are arranged harmoniously,
Using a blasting apparatus equipped with dust collecting means for injecting the sprayed powder together with the compressed gas in the working space to collide with the impacted object, and sucking the inside of the working space to remove and collect the dust,
By performing a blasting process in which a powder metal material having an average particle size of 10 to 200 μm and a medium substance having a hardness equal to or higher than that of the powder metal material are repeatedly collided at an injection speed of 100 to 300 m / sec, A powdered metal characterized by exfoliating a surface oxide from a metal material and forming a fine grain region having a crystal grain size smaller than the crystal grain size of a central part near the surface of the powdery metal material Material surface treatment method.   2. The surface treatment method for a powdered metal material according to claim 1, wherein the dust collecting means of the blast processing apparatus includes a cyclone for classifying the dust and the spray powder.   The method for treating a surface of a powdered metal material according to claim 1 or 2, wherein the dust collecting means of the blasting apparatus stores the collected dust together with non-combustible powder.   The surface of the powder metal material according to any one of claims 1 to 3, wherein the powder metal material is formed with the spray powder and the blast treatment is performed using the medium substance as the collision object. Processing method.   The powder metal according to any one of claims 1 to 3, wherein the blast treatment is performed by using the medium material as powder and the spray powder, and using the powder metal material as the collision object. Material surface treatment method.   The medium substance is a powder metal material having the same material and the same average particle diameter as the powder metal material, and both the spray powder and the colliding object are the powder metal material. The surface treatment method of the powdery metal material according to any one of claims 1 to 3. The material of the medium substance is a metal having a hardness equal to or higher than that of the powder metal material or a ceramic having a hardness equal to or higher than the hardness of the powder metal material after the surface treatment. Item 6. A surface treatment method for a powdery metal material according to any one of Items 1 to 5.

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