HK1219075B - Surface treatment method for powdered metal material - Google Patents

Description

Surface treatment method for powdery metal material

Technical Field

The present invention relates to a method for surface treatment of a powdery metal material, and more particularly, to a method for surface treatment of a powdery metal material used as a material for producing a metal product or forming a coating film using a metal powder in powder metallurgy such as sintering or spray coating.

Background

As one of powder metallurgy, "sintering" in which an aggregate of a powdery metal material is heated and solidified at a temperature lower than the melting point to obtain a sintered metal is widely used for manufacturing various machine parts such as gears, and in particular, in recent years, it has been proposed to use a powdery metal material as a molding material in a 3D printer, and it has also been proposed to form a required three-dimensional model from shape data such as CAD by irradiating a laser beam or an electron beam with a specific pattern on the powdery metal material and sintering the powdery metal material directly using the metal material (non-patent document 1).

However, sintered metals obtained by sintering powdery metal materials tend to have lower density and lower strength than those obtained by melt molding due to residual pores, and in this state, they are often not practical as machine parts or the like.

Therefore, in order to remove such residual pores that cause low density and low strength, a process called "sinter forging" is also performed in which the obtained sintered metal is forged, but as described above, if a part manufactured by simple three-dimensional shaping using a 3D printer further requires a process of sinter forging, the advantage of simplicity is lost.

Unlike the post-process of the above-described sinter forging, studies have been made to increase the strength of the sintered metal by devising the composition and structure of the powdery metal material as a raw material for sintering, and as one of them, it has been reported that a high-strength sintered metal can be obtained by subjecting the powdery metal material before sintering to mechanical grinding treatment by stirring with a ball mill to change the internal structure of the material (non-patent documents 2 and 3).

In this method, a powdered metal material having a specific crystal structure as shown in fig. 6 a is subjected to mechanical grinding treatment by a ball mill to intensively subject the powdered metal material to super-strong processing, and as shown in fig. 6B, a region called a shell in which crystal grains are refined (hereinafter, this region is referred to as "fine grain region") is generated in the vicinity of the surface of the powdered metal material, thereby obtaining a powdered metal material having a region called a core (hereinafter, this region is referred to as "coarse grain region") in which the original crystal grain size is maintained and the fine grain region covering the coarse grain region.

Further, as shown in fig. 6(C), the metal obtained by sintering the powdery metal material in which the coarse particle regions and the fine particle regions are formed can be obtained as a metal having a structure called a "coordinated structure" in which a network structure formed by linking the fine particle regions of the powdery metal material and the coarse particle regions in the fine particle regions are arranged in a coordinated manner (in the present invention, such a metal is called a "coordinated structure metal"), and it has been reported that, with regard to such a coordinated structure metal, a strength is greatly improved while maintaining ductility equivalent to that of a sintered metal having a uniform equiaxial particle structure obtained by using a normal powdery metal material which is not subjected to mechanical polishing treatment (non-patent document 2).

In the above description, the method of producing the "coordinated microstructure metal" has been described by taking the case of "sintering" as an example, but in the case where the metal coating is formed on the surface of the base material by "spraying" the powdery metal material having the fine particle region, the metal coating formed may be the "coordinated microstructure metal".

[ non-patent document 1] "TetIto 2-3D Printer | attraction! Chapter | design, manufacturing methods show "diversification of modeling materials such as resin, paper, metal" [ the company "8 th to 68 th pages of" 8 th manufacturing of the luni "(issue date: 2013, 8 th and 1 th) issued by the company" BP, ";

[ non-patent document 2] creation of a novel structural material having both high strength and high ductility, which is obtained by coordinated organization control, in cerealose and customs "[ general community law, japan heat treatment technology association, issue" heat-treated material and surface modification vol.53 No. 12013 "(issue date: 2013, 2/28 days) ];

[ non-patent document 3] "scrap forming and sintering process for recycled brass with hardness 3 times" improved conductivity is practical "[ journal industry newspaper (2013, 4, 30 days) ].

Disclosure of Invention

As described in non-patent documents 2 and 3, when sintering is performed using a powdery metal material that is previously stirred by a ball mill, the sintered metal obtained by sintering becomes a "coordinated structure", and thus a metal having excellent characteristics of both high ductility and high strength is obtained.

However, as described in non-patent documents 2 and 3, when the powdered metal material is processed by a ball mill, the processing efficiency is extremely poor, and for example, the processing time in non-patent document 2 is 100 hours, and the processing time in non-patent document 3 is 32 hours.

Further, handling of the powdery metal material by the ball mill may cause dust explosion, which is a very dangerous operation.

That is, since the powder metal material used for sintering and the like is usually fine with a particle size of about 100 μm, it is put into a ball mill and stirred in the presence of air to apply a frictional force or an impact force, and if electrostatic discharge is generated by friction during stirring, dust explosion occurs.

Here, dust explosion occurs when three elements of the presence of oxygen, the generation of dust having a lower explosive limit concentration or more, and the presence of an ignition source are oligomeric, so that in the case of preventing the occurrence of dust explosion, it is necessary to remove one or more of these conditions, but in order to perform super-strong processing on a powdery metal material, it is impossible to remove the generation of friction or impact that can become an ignition source from a ball mill that generates friction or impact force inside.

Therefore, when the dust explosion is to be prevented, it is necessary to fill the inside of the ball mill with an inert gas or the like, to perform the operation in a state where oxygen is excluded, to adjust the amount of the powdery metal material to be less than the lower explosion limit concentration, or to perform both of them.

However, when the ball mill is treated in a state in which the inside thereof is filled with an inert gas, the production cost is greatly increased, and it is considered that all the powder metal [200 mesh (74 μm in pore diameter) ] passes through]Has a lower explosive limit concentration of 35g/m in terms of aluminum³Calculated as titanium, 45g/m³Calculated as iron, 120g/m³[ safety and hygiene (3 rd time) selected from "arc welding operation" general society of Law of Japan welding Association WE-COM journal No. 6 (published 10 months 2012)]If the stirring is performed at a concentration lower than the lower explosive limit, only a very small amount can be processed at a time, and even if it can be processed for a small amount of production at the laboratory experimental level, it is impossible to process a large amount of powdery metal material in accordance with the commercial standards by means of a ball mill.

In addition, the treatment by the ball mill can be applied to the treatment of the powdery metal material, and the powdery metal material treated by this method is mixed with surface oxides such as scale peeled off from the surface of the powdery metal material, and the oxides become an obstacle to the bonding of the powdery metal materials to each other at the time of sintering, and prevent the high strength.

That is, a powdery metal material used for sintering or spraying is generally produced by an atomization method in which a molten metal is atomized by spraying and scattering, and is instantaneously quenched and solidified to produce a powdery metal material, and therefore, a scale is adhered to the surface of the powdery metal material.

In addition, although the powder metal material produced by a method other than the atomization method is somewhat inferior, an oxide film as a surface oxide is formed by contact with oxygen in the air.

Even if such surface oxides such as scale are peeled off from the surface of the powdery metal material by friction or impact applied during stirring by the ball mill, such peeled oxides are mixed in the powdery metal material without being removed after the peeling in terms of the structure of the ball mill.

Further, since the exfoliated oxide is stirred together with the powdered metal material in the ball mill thereafter, a part of the exfoliated oxide is pressed against the surface of the powdered metal material by friction or impact caused by the stirring, and is embedded and reattached.

Therefore, when the powdery metal material treated by the ball mill is directly taken out and used for sintering, the improvement of the strength is suppressed by the presence of the oxide mixed in the powdery metal material.

On the other hand, in order to remove oxides mixed in the powdery metal material, it is also conceivable to subject the powdery metal material subjected to the treatment by the ball mill to, for example, air screening, and the like, and in this method, a step for removing the oxides needs to be provided separately from the treatment by the ball mill, and productivity is further lowered.

In addition, in this method, the oxides mixed in the powdery metal material can be removed to some extent, and the oxides adhering to the surface of the powdery metal material again cannot be separated and removed.

Therefore, if the surface treatment of the powdery metal material can be performed by a method capable of removing such a surface oxide film, it is expected that the obtained coordinated structure metal will have further increased strength.

Accordingly, the present invention has been made to solve the above-mentioned drawbacks of the background art, and an object of the present invention is to provide a method for surface treatment of a powdery metal material, which is free from the fear of dust explosion, can easily and surely strip an oxide from the surface or remove the stripped oxide, and can efficiently perform a treatment for forming the above-mentioned fine particle region on the surface of the powdery metal material used as a material for obtaining a metal product or a metal coating film having a coordinated structure by powder metallurgy such as sintering or spray coating in a relatively short time.

In order to achieve the above object, a method for surface treatment of a powdered metal material according to the present invention is a method for surface treatment of a powdered metal material used for production of a microstructure metal in which fine particle regions and coarse particle regions are arranged in a coordinated manner, the method comprising:

a blasting machine comprising a dust collecting means for removing and collecting dust by sucking dust in a working space by injecting powder together with compressed gas into the working space and colliding the powder with an object to be collided,

a powder metal material having an average particle diameter of 10 to 200 [ mu ] m and a vehicle substance having a hardness equal to or higher than that of the powder metal material are repeatedly collided at a blast speed of 100 to 300m/sec, thereby peeling off surface oxides from the powder metal material and forming a fine particle region having a crystal particle diameter smaller than that of a central portion in the vicinity of the surface of the powder metal material (claim 1).

The blasting apparatus for the blasting treatment is provided with a cyclone for classifying the dust and the blasting powder by using the dust collecting means (claim 2).

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

In the method for surface treatment of a powdery metal material having the above-described configuration, the blasting treatment may be performed by using the powdery metal material as the blasting powder and the mediator as the collided object (claim 4).

The sprayed powder may be formed by using the medium material as a powder, and the collided object may be formed by using the powdery metal material (claim 5).

Further, the intermediate material may be a powdery metal material having the same material and the same average particle diameter as the powdery metal material, and both the sprayed powder and the collided object may be the powdery metal material (claim 6).

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

According to the above-described configuration of the present invention, the following significant effects can be obtained by the surface treatment method of the powdery metal material of the present invention.

By performing a blasting treatment in which a powdery metal material having an average particle diameter of 10 to 200 μm and a vehicle substance having a hardness equal to or higher than that of the powdery metal material are repeatedly collided at a blasting speed of 100 to 300m/sec, surface oxides of the powdery metal material are removed, and rapid temperature rise and cooling occurring in the vicinity of the surface at the time of collision are repeated, whereby crystal grains in the vicinity of the surface of the powdery metal material are refined, whereby a powdery metal material in which a fine grain region having a crystal particle diameter smaller than that of the central portion is formed in the vicinity of the surface can be mass-treated easily in a short time by a relatively simple method of the blasting treatment.

Further, by performing the blasting using the blasting machine with a dust collecting function, it is possible to prevent the risk of dust explosion and to mass-produce the metal material, and by removing and collecting surface oxides such as scale peeled off from the surface of the powdery metal material as dust by suction in the working space, it is possible to obtain the powdery metal material without separately providing a step of removing the surface oxides in the subsequent step and without mixing the surface oxides.

In particular, when a cyclone separator for classifying the dust and the sprayed powder is used as dust collecting means in the blasting treatment, even when the metal powder is recovered in a state where the metal powder and the surface oxide to be peeled are mixed, the surface oxide and the dust can be classified and recovered from the sprayed powder, and the metal powder material in which the surface oxide is removed with higher accuracy can be obtained.

Further, in the case where the removed dust is stored together with the incombustible powder such as calcium carbonate in the dust collecting means of the blasting machine, the risk of dust explosion in the processing chamber can be reduced, and the risk of dust explosion in the dust collector can also be reduced.

In this blasting process, the powder metal material may be a powder spray to spray the medium material to cause collision, or the medium material may be a powder spray to spray the powder metal material to cause collision, and when the powder metal material is a powder metal material composed of the same average particle size and the same material as both the spray powder and the object to be collided, and the powder metal material is sprayed to the powder metal material to cause collision, both the powder metal powder as the spray powder and the powder metal powder as the object to be collided are subjected to surface treatment simultaneously, so the treatment amount can be doubled.

Drawings

Fig. 1 is a schematic explanatory view of a blasting apparatus used in the surface treatment method of the present invention, in which (a) is a gravity type and (B) is a direct pressure type.

FIG. 2 is a graph showing the X-ray diffraction results of an untreated stainless steel powder (a product corresponding to SUS 304).

FIG. 3 is a graph showing the X-ray diffraction results of the stainless steel powder (corresponding to SUS304) treated by the method of example 1.

FIG. 4 is a graph showing the X-ray diffraction results of untreated powder high-speed tool steel (product corresponding to SKH).

FIG. 5 is a graph showing the X-ray diffraction results of the powder high-speed tool steel (product corresponding to SKH) treated by the method of example 2.

Fig. 6 is an explanatory view for explaining generation of a coordinated structure, where (a) is an unprocessed powdery metal material, (B) is a powdery metal material processed by a ball mill, and (C) is a schematic view of a coordinated structure metal obtained by sintering the powdery metal material of (B).

Detailed Description

Next, an embodiment of the present invention will be described below with reference to the drawings.

[ integral constitution ]

The invention is as follows: by performing a blasting process in which a powdery metal material to be processed and a mediator substance that collides with the powdery metal material are repeatedly collided at a specific blasting velocity using a known blasting apparatus, surface oxides such as scale that inhibit strength improvement during sintering or spraying are removed from the surface of the powdery metal material, and a fine particle region having a crystal particle diameter smaller than that of the central portion is formed in the vicinity of the surface of the powdery metal material.

In this way, a metal product obtained by powder metallurgy or the like such as sintering or a metal film produced by melting and using a powdered metal material having a coarse particle region having a large crystal particle diameter in the center and a fine particle region having a small crystal particle diameter relative to the coarse particle region in the vicinity of the surface has a crystal structure in which the coarse particle regions are arranged in a coordinated manner in a network of fine particle structures formed by bonding the fine particle regions to each other [ see fig. 6(C) ], and becomes a coordinated structure metal having excellent properties of both high ductility and high strength.

[ powdered metal Material ]

The powdery metal material to be processed in the present invention is a powdery metal having an average particle size of 10 to 200 μm used in powder metallurgy such as sintering or in spray coating, and any of various materials can be used as long as it is a material applicable to powder metallurgy or spray coating, and it can be composed of any of pure metals and alloys.

Examples of the metal generally used in powder metallurgy include iron-based, copper-based, stainless steel-based, titanium-based, and tungsten-based metals, and the metal used in meltallizing is generally zinc, aluminum, copper, or the like.

The powdery metal material to be used can be produced by various methods, and can be produced by various known methods such as mechanical crushing, electrolytic precipitation, etc., in addition to a spraying method represented by an atomization method which is a method for producing a powdery metal material generally used in powder metallurgy or spray coating.

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

Further, since the crystal grain size of the powdery metal material before the treatment is directly the crystal grain size of the coarse particle region, when the crystal grain size of the coarse particle region is within a specific range, the powdery metal material having the corresponding crystal grain size is selected. Although not particularly limited, the average crystal grain size of the coarse particle region is, for example, several μm to several tens μm.

[ Medium substance ]

As the medium substance with which the powder metal material collides, various substances can be used as long as the medium substance has a hardness equal to or higher than that of the powder metal material, and not only those made of metal but also those made of ceramic can be used.

In the case of using a ceramic intermediate material that is not work hardened, it is preferable to use a ceramic having a hardness equal to or higher than the hardness of the powdered metal material after the surface treatment of the present invention so that the powdered metal material maintains the same or higher hardness even after the work hardening.

Further, the medium substance itself may be formed of the powdery metal material, and the superfine grain structure may be formed on the powdery metal materials by collision of the powdery metal materials with each other.

In the case where the powder-like metal material is treated as the sprayed powder, the intermediate material does not need to be made into powder, and may be formed into a plate or the like, for example.

[ peening method and peening apparatus ]

The collision between the powdery metal material and the intermediary material described above is performed by peening using an peening device.

As described above, the blasting may be performed by ejecting the powder metal material as the blasting powder and colliding the powder metal material with the medium material, or conversely, by preparing the powder medium material as the blasting powder and colliding the powder metal material with the blasting powder, or by making both the blasting powder and the collided object of the powder metal material having the same average particle diameter and the same material and colliding the powder metal materials with each other.

As the blasting machine 1 used, a blasting machine having a cabinet 21 serving as a processing chamber and a dust collecting function for sucking and collecting dust in the cabinet 21 can be used, and any of direct pressure type and gravity type blasting machines can be used.

Fig. 1(a) shows a configuration example of a gravity-type blasting machine 1 used for the surface treatment of the present invention, and fig. 1(B) shows a configuration example of a direct-pressure type.

Hereinafter, an example will be described in which the surface treatment of the present invention is performed using these blasting apparatuses 1 and using both the blasting powder and the collided object as the powder metal materials having the same material and the same average particle size, but the blasting apparatus 1 used in the surface treatment method of the present invention is not limited to the illustrated configuration.

The peening device 1 shown in fig. 1(a) and (B) includes: a machine cabinet 21 serving as a processing chamber for storing a spray nozzle 22 and a workpiece to be processed and performing spray processing and a dust collector 38 for sucking the inside of the machine cabinet 21 are provided with a cyclone type recovery tank 23 between the dust collector 38 and the machine cabinet 21, so that a powdery metal material in a state of being mixed with dust and being recovered by sucking the inside of the machine cabinet 21 is recovered in the recovery tank 23, and dust separated from the powdery metal material in the cyclone type recovery tank 23 can be recovered in the dust collector 38.

The powdery metal material thus recovered in the recovery tank 23 is configured so as to be ejected again from the spray nozzle 22 in the cabinet 21.

A cage (バレルカゴ)24, which is an upwardly open container that rotates during the spraying of the sprayed powder, is provided in the front of the spray nozzle 22 facing the front end inside the cabinet 21, and is formed so that a powder-like metal material that is a collision target can be put therein.

In the example shown in fig. 1(a), the cage 24 is a metal wire mesh formed with a plurality of small holes, but the present invention is not limited to the example shown in the drawing, and may be configured without such small holes.

Before the treatment using the blasting machine 1 configured as described above, the powdery metal material is charged into the recovery tank 23, and the powdery metal material is also charged into the hopper 24 provided in the processing chamber, and the spraying of the powdery metal material is started from the spray nozzle 22 at a spraying speed of 100 to 300m/sec while the hopper 24 is rotated in this state, so that the powdery metal material sprayed from the spray nozzle 22 collides with the powdery metal material in the rotating hopper 24.

The injection pressure may be 100m/sec or more in the treatment of the nonferrous powdery metal material, and preferably 150m/sec or more in the treatment of the iron powdery metal material.

By the injection of the powdery metal material in this manner, the powdery metal material in the cage 24 and the powdery metal material injected from the injection nozzle 22 receive energy at the time of collision, respectively, and the surface oxide such as scale formed on the surface of the powdery metal material is peeled off, and the temperature is abruptly raised and cooled on the surface of the collision portion, whereby crystal grains on the surface of the collision portion are refined, and a fine grain region in which crystal grains having a smaller diameter than those in the central portion are formed in the vicinity of the surface of the powdery metal material is formed.

In the surface treatment method of the present invention, which is a treatment target of a powdery metal material having an average particle diameter of 10 to 200 μm, the fine particle region is formed in a range of 2 to 20 μm at the maximum from the surface, based on the particle diameter of the powdery metal material to be treated, because it is empirically confirmed that the surface of the powdery metal material is formed at a depth of at most 20% with respect to the particle diameter when the powdery metal material to be treated is less than 100 μm, and at a depth of at most 10% with respect to the particle diameter when the powdery metal material to be treated is 100 μm or more.

The powdery metal material sprayed from the spray nozzle 22 collides with the powdery metal material in the material cage 24, and then is ejected to the outside of the material cage 24, and remains in the material cage 24, and is stirred together with the powdery metal material originally present in the material cage 24 along with the rotation of the material cage 24.

Therefore, if the spraying of the powdery metal material is continued from the spraying nozzle 22, the powdery metal material in the material cage 24 increases, overflows from the material cage 24, and falls to the bottom of the cabinet 21.

Since the bottom of the cabinet 21 is formed as a hopper of an inverted trapezoid shape and the lower end of the hopper communicates with the dust collector 38 via the exhaust passage 33 and the recovery tank 23, when the inside of the cabinet 21 is sucked by the exhaust fan 39 provided in the dust collector 38, the falling powdery metal material or dust is sucked together with the air in the cabinet 21 and is fed into the cyclone-type recovery tank 23, the dust and the powdery metal material are classified in the recovery tank 23, and the powdery metal material is recovered to the lower side in the recovery tank 23.

Since surface oxides such as scale generated on the surface of the powdery metal material are brittle and have higher hardness than the powdery metal material, they are broken into fine particles when peeled off by an impact caused by collision of the powdery metal materials with each other, and therefore, they are not collected in the collection tank 23, but sent as dust to the dust collector 38 through the pipe 32 connected to the upper part of the collection tank 23, collected in the lower part of the dust collector 38, and discharged from the air discharger 39 into the outside atmosphere.

In this way, since the processing chamber formed in the cabinet 21 is always sucked to remove the dust or the powdery metal material floating in the air and suppress the dust or the powdery metal material to the lower explosion limit concentration or less, there is no fear of dust explosion occurring in the cabinet even if heat or static electricity is generated due to ejection, collision, or friction of the ejection powder as the powdery metal material in the present embodiment.

On the other hand, the dust collected into the dust collector 38 by classification in the cyclone type collection tank 23 is stored in the dust collector 38 together with powder of incombustible powder such as calcium carbonate so that the concentration of combustible dust in the air in the dust collector 38 becomes equal to or lower than the lower explosive limit concentration, thereby also avoiding the risk of dust explosion in the dust collector 38.

Then, the powdery metal material recovered in the recovery tank 23 is sprayed again from the spray nozzle 22 to the powdery metal material in the material cage 24, and the above steps are repeated to remove surface oxides such as scale from the surface of any one of the powdery metal materials and form a fine particle region so as to cover the entire vicinity of the surface.

As described above, when the powder metal material having the fine particle regions formed in the vicinity of the surface is used as a material for powder metallurgy such as sintering or for forming a metal film such as spray coating, the sintered metal or the metal film obtained can be obtained as a coordinated structure metal in which coarse particle regions are coordinated and arranged in a network of fine particle structures formed by linking portions of the fine particle regions to each other. Such a metal having a coordinated structure can achieve excellent properties of high ductility and high strength.

In particular, in the powdery metal material treated by the method of the present invention, since surface oxides such as scale, which cause a decrease in strength at the time of sintering or welding, can be preferably removed, the sintered metal or the metal coating film obtained can be further enhanced in strength.

In the above description, the configuration in which the sprayed powder and the collided object are both powdery metal materials and the sprayed powder collides with the collided object in the material cage 24 provided in the cabinet 21 has been described, but the surface treatment of the present invention may be performed by, for example, storing a plate body formed of a material having a hardness equal to or higher than that of the sprayed powder as a medium material in the cabinet 21 instead of the material cage 24, spraying the plate body with the powdery metal material as the sprayed powder, and colliding the sprayed powder.

In addition, in the case where the blasting apparatus 1 having the cage 24 is used, the powdery medium material may be used as the blasting powder, and the powdery metal material charged into the cage 24 may be sprayed with the medium material as the blasting powder, and in this case, the powdery metal material and the medium material may be classified and collected after the treatment.

[ examples ]

Hereinafter, examples in which the surface treatment method of the present invention is applied to powdery metal materials of various materials will be described.

[ example 1]

The surface treatment method of the present invention was carried out on a stainless steel powder (product corresponding to SUS 304: #80) as a powdery metal material. The treatment conditions are shown in table 1 below.

[ Table 1]

Processing conditions in example 1(SUS304)

A treatment of spraying stainless powder in the recovery tank from the spray nozzle into the material cage was continuously performed for 3 hours under the conditions shown in Table 1, in which 10kg of stainless powder was put into the material cage provided in the processing chamber of the blasting processing apparatus and 20kg of stainless powder was put into the recovery tank.

As a result of the above treatment, the scale of the stainless steel powder after the treatment is removed, the surface is cleaned, and the hardness of the stainless steel powder of 250 to 350HV before the treatment is increased to 450 to 550HV after the treatment, whereby it is predicted that the crystal grains near the surface are refined.

Further, the refinement of the crystal grain size was evaluated from the increase in the line width of the X-ray diffraction peak by Scherrer (1918) formula, and as a result, the line width of the peak was greatly increased in the X-ray diffraction result after the treatment (fig. 3) of the present application, and the hardness of the powdery metal material was increased, and the refinement of the crystal grain size on the surface was also confirmed from the X-ray diffraction result, as compared with the X-ray diffraction result of the untreated stainless steel powder (see fig. 2).

[ example 2]

The surface treatment method of the present invention was carried out on powder high-speed tool steel (product corresponding to SKH: #150) as a powder metal material. The treatment conditions are shown in table 2 below.

[ Table 2]

Example 2 (powder high speed tool Steel: SKH equivalent article)

A10 kg of powder high-speed tool steel was charged into a cage provided in a processing chamber of a blasting apparatus, and a 10kg of powder high-speed tool steel was charged into a recovery tank, and the powder high-speed tool steel in the recovery tank was continuously sprayed into the cage from a spray nozzle for 5 hours under the conditions shown in Table 2.

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

Further, it was confirmed that the surface structure was refined by the treatment according to the method of the present invention (see fig. 4 and 5) by removing the scale from the treated powder high-speed tool steel to clean the surface and increasing the line width of the X-ray diffraction peak from the untreated one (see fig. 4) according to the X-ray diffraction result (see fig. 5).

[ example 3]

The surface treatment method of the present invention was performed on a powder of alloy steel for machine structural use (product #150 corresponding to SCM) as a powdery metal material. The treatment conditions are shown in table 3 below.

[ Table 3]

Example 3 treatment conditions for powder of alloy steel for machine structural use (SCM-equivalent product)

Powder of 10kg of alloy steel for machine structural use was charged into a cage provided in a processing chamber of a blasting processing apparatus, and powder of 10kg of alloy steel for machine structural use was charged into a recovery tank, and the treatment of ejecting the powder of alloy steel for machine structural use in the recovery tank from an ejection nozzle into the cage was continuously performed for 5 hours under the conditions shown in table 3.

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

Further, it is considered that the surface of the alloy steel for machine structural use after the treatment is cleaned by removing the scale from the powder, and the surface is formed with a finer structure by the increase in hardness.

[ example 4]

The surface treatment method of the present invention was performed on a copper alloy powder (#150) as a powdery metal material. The treatment conditions are shown in table 4 below.

[ Table 4]

Example 4 (copper alloy) treatment conditions

20kg of copper alloy powder was charged into the recovery vessel, and the following treatments were continuously carried out for 7 hours: the copper alloy powder in the recovery tank was sprayed from the spray nozzle toward a position where the core was shifted by 100mm toward the center of a plate (400 mm in diameter, 20mm in thickness) made of SKD11 placed in the processing chamber.

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

Further, it is considered that the scale of the treated copper alloy powder is removed to clean the surface, and the surface is formed with a finer structure by the increase in hardness.

[ example 5]

The surface treatment method of the present invention was performed on a powder of an aluminum alloy (AC 8A: #80) as a powdery metal material. The treatment conditions are shown in table 5 below.

[ Table 5]

Example 5 treatment conditions in aluminum alloy (AC8A)

A cage having a large number of holes with a diameter of 1mm formed therein was set in a processing chamber, 10kg of aluminum alloy (AC8A) powder was charged into the cage, and a treatment of ejecting a high-speed steel jet charged into a recovery tank into the cage was continuously performed for 7 hours.

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

Further, it is considered that the surface of the treated aluminum alloy powder is cleaned by removing the scale, and the high-speed steel as the mediator diffuses and permeates through the surface of the aluminum alloy powder by the increase in hardness, and a structure is formed on the surface of the aluminum alloy powder in a refined state.

[ 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 in examples 1 to 5.

As a result, it was confirmed that the sintered metal obtained by sintering any of the powder metal materials of examples 1 to 5 has a "harmonized structure" in which coarse-grained structures are harmonized and arranged in a mesh formed by interlinking fine-grained regions, and the surface treatment method of the present invention is a surface treatment method capable of easily, massively and safely treating the powder metal material for producing a harmonized structure metal.

Description of the symbols

1: spray-impact processing device

21: machine cabinet

22: spray nozzle

23: recovery tank (cyclone separator type)

24: material cage

32: pipe

33: air exhaust path

38: dust collector

39: an air exhauster.

Claims (15)

1. A method for surface treatment of a powdery metal material used as a material for producing a metal having a fine structure in which fine particle regions and coarse particle regions are arranged in a coordinated manner,

a blasting machine having a dust collecting means for removing and collecting dust by sucking dust in a working space by injecting powder together with compressed gas into the working space and colliding the powder with an object to be collided,

a powder metal material having an average particle diameter of 10 to 200 [ mu ] m and a vehicle substance having a hardness equal to or higher than that of the powder metal material are repeatedly subjected to a blasting treatment at a blasting speed of 100 to 300m/sec, thereby peeling off surface oxides from the powder metal material and forming a fine particle region having a crystal particle diameter smaller than that of the central portion in the vicinity of the surface of the powder metal material.

2. The surface treatment method for a powdery metal material according to claim 1, wherein the dust collecting means of the blasting apparatus comprises a cyclone for classifying the dust and the sprayed powder.

3. The method for surface treatment of a powdery metal material according to claim 1 or 2, wherein the dust collecting means of the blasting apparatus stores the collected dust together with a noncombustible powder.

4. The surface treatment method for a powdery metal material according to claim 1 or 2, wherein the blasting is performed with the powdery metal material as the blasting powder and the intermediary substance as the collided object.

5. The surface treatment method for a powdery metal material according to claim 3, wherein the blasting is performed with the powdery metal material as the blasting powder and the intermediary substance as the collided object.

6. The surface treatment method for a powdery metal material according to claim 1 or 2, wherein the blasting is performed with the intermediary substance as a powder and the powdery metal material as the collided object.

7. The surface treatment method for a powdery metal material according to claim 3, wherein the blasting is performed with the intermediary substance as a powder and the powdery metal material as the collided object.

8. The surface treatment method for a powdery metal material according to claim 1 or 2, wherein the intermediate material is a powdery metal material having the same material and the same average particle diameter as those of the powdery metal material, and both the sprayed powder and the collided object are the powdery metal material.

9. The method for surface treatment of a powdery metal material according to claim 3, wherein the intermediate material is a powdery metal material having the same material and the same average particle diameter as those of the powdery metal material, and both the sprayed powder and the collided object are the powdery metal material.

10. The surface treatment method for a powdered metal material according to claim 1 or 2, wherein the material of the intermediate material is a metal having a hardness equal to or higher than that of the powdered metal material, or a ceramic having a hardness equal to or higher than that of the powdered metal material after the surface treatment.

11. The method for surface treatment of a powdery metal material according to claim 3, wherein the material of the intermediate substance is a metal having a hardness equal to or higher than that of the powdery metal material, or a ceramic having a hardness equal to or higher than that of the powdery metal material after the surface treatment.

12. The method for surface treatment of a powdery metal material according to claim 4, wherein the material of the intermediate substance is a metal having a hardness equal to or higher than that of the powdery metal material, or a ceramic having a hardness equal to or higher than that of the powdery metal material after the surface treatment.

13. The method for surface treatment of a powdery metal material according to claim 5, wherein the material of the intermediate substance is a metal having a hardness equal to or higher than that of the powdery metal material, or a ceramic having a hardness equal to or higher than that of the powdery metal material after the surface treatment.

14. The method for surface treatment of a powdery metal material according to claim 6, wherein the material of the intermediate substance is a metal having a hardness equal to or higher than that of the powdery metal material, or a ceramic having a hardness equal to or higher than that of the powdery metal material after the surface treatment.

15. The method for surface treatment of a powdery metal material according to claim 7, wherein the material of the intermediate substance is a metal having a hardness equal to or higher than that of the powdery metal material, or a ceramic having a hardness equal to or higher than that of the powdery metal material after the surface treatment.