KR20190007052A - Surface treatment of metal products and metal products - Google Patents

Abstract

Provided is a surface treatment method capable of continuously forming a uniform nanocrystalline texture along the surface of a metal product of either hard or soft. A substantially spherical sprayed solid having a median diameter of 1 to 20 占 퐉 and a dropping time of 10 sec / m or more in air is sprayed onto the metal product at an injection pressure of 0.05 MPa to 0.5 MPa. As a result, the metal product made of soft material does not have a layered structure, and the average crystal grain size is continuously 300 nm, preferably 100 nm It is possible to form a nanocrystalline texture layer which is finely grained by the following nanocrystals and it is possible to impart a high compressive residual stress of about -180 MPa to a maximum of -1200 MPa and to strengthen the surface of the metal product.

Description

Surface treatment of metal products and metal products

TECHNICAL FIELD The present invention relates to a surface treatment method of a metal product and a metal product surface-treated by the above method, and more particularly to a metal product surface treated by a method of spraying fine particles onto a metal product under predetermined conditions, A surface treatment method for strengthening the surface of a metal product by making the structure into a nanocrystalline structure, and a metal product having a surface strengthened by the above method.

The fact that the strength of the metal material increases in proportion to the reciprocal of the square root of the grain size is known as a Hall-Petch relationship, and the miniaturization of the crystal grain size, which brings about such effects, And the like.

Particularly, it has been reported that a metal product in which the crystal grain size in the vicinity of the surface is miniaturized to the nano level not only remarkably increases the surface hardness but also improves the wear resistance and corrosion resistance.

Successful examples of ball milling, falling weight processing, particle impact machining, and shot peening have been reported as nanocrystallization methods for metal products that enable such surface strengthening. Particularly, Nanocrystallization by shot peening has attracted attention as a low-cost and simple method.

Although the principle of formation of nanocrystalline structure by shot peening has not yet been sufficiently clarified, the following Patent Document 1 and Non-Patent Document 1 disclose that SS400 steel [HV1.20GPa (HV122)], which is a soft material, Shot peening was carried out under the same conditions for an example of surface treatment in which a shot made of a high-speed steel (SKH59) having an average particle diameter of 45 mu m was sprayed at 0.5 MPa for 30 seconds and an SCr420 carburized quartz steel (hardness HV7.55 GPa (HV770) An example of the surface treatment is introduced, and there is a great difference in the structure of the nanocrystal structure formed in both cases (Patent Document 1, Non-Patent Document 1).

In this specification, the conversion between HV (GPa) and HV (negative number) was calculated as "HV (negative number) ≈ HV (GPa) × 102" [Appendix 1 of JIS R 1610 (2003) .

Patent Document 1: JP-A 2007-297651

Non-Patent Document 1: Shinichi Takagi, Masao Kumagani "Surface Nanocrystallization by FPB Treatment" (Journal of Precision Engineering Vol 72. No. 2006: 1079-1082)

As described above, when the surface texture of a metal product is to be nanocrystallized by shot peening, the nanocrystalline texture (layered structure) produced when the metal product to be treated is a soft material and the metal Patent Document 1 and Non-Patent Document 1 mentioned above have reported that there is a remarkable difference in structure in the nanocrystalline structure (without layered processing structure) produced in the product.

Of these, the nanocrystalline structure formed on the surface of the metal product of the hard material (SCr420 carburized quenched steel) is uniformly formed along the surface in a predetermined depth range from the surface and nanocrystalline structure is formed in an ideal state Are reported.

However, in the metal product of the soft material (SS400 steel), as shown in Fig. 1, significant irregularities are formed on the surface due to the collision of the sprayed particles at the initial stage of the shot peening, The protrusions in the concavities and convexities formed by the subsequent collision of the sprayed three-dimensional bodies are folded and infiltrated toward the inside of the material, and furthermore, the formation of the concavities and the folding of the convexities are repeated by the subsequent collision, Layered structure having a layered structure in which layers of the layered structure are stacked in this order, and the transition density is remarkably increased in this layered structure, and nanocrystallization occurs when a grain boundary point is exceeded.

Such a nanocrystalline structure accompanied by the layered structure is not continuously distributed along the surface of the metal product but may be a structure in which the surrounding processing effect area is exposed on the surface or the layered structure (nanocrystalline structure) And it is also possible to form a nonuniform structure in which a widening occurs between the layers which are not sufficiently joined at the time of folding, and a surface portion where no nanocrystalline structure is formed or a portion where a nanometer- And there is also a concern that the fatigue characteristics of the metal product may deteriorate due to nanocrystallization due to shot peening.

As described above, in the case of using a soft material as the object to be processed, nanocrystalline structure accompanied by a layered structure is produced, and it is impossible to perform surface strengthening. In the above-mentioned Patent Document 1, The product is limited to only hard steel having an initial hardness exceeding HV7.0 GPa (HV714), and does not disclose a method of continuously forming a uniform nanocrystalline texture on a surface of a soft material.

Therefore, the present invention has been made in order to solve the drawbacks of the above-mentioned prior art, and a first object of the present invention is to provide a metal product made of a soft material, Which is capable of continuously forming a uniform nanocrystalline structure along the surface of a metal product, without the necessity of producing a uniform surface.

A second object of the present invention is to provide a method for manufacturing a metal product which can be applied commonly to all metal products ranging from a soft material to a hard material regardless of the hardness of the base material of the metal product to be treated, Which can be continuously formed along the surface of a metal product.

In addition, in the cutting process using the cutting tool, the surface of the workpiece is physically deeply cut by the cutting edge of the cutting tool, and a part of the workpiece is divided by dividing, and the cut- A part of the debris is removed by the physical and chemical changes due to the high pressure, large frictional resistance and cutting heat generated between the debris and the cutting surface of the cutting tool, And this adhered debris forms a deposit called " constituent edge (constituent edge) " which is different from the original edge, on the cutting edge of the cutting tool.

The formation of this constituent line is undesirable because it lowers the cutting edge of the cutting tool and invites a reduction in machining accuracy (accuracy).

The adhesion of the material to be processed represented by the constituent cutter is not limited to cutting tools such as drills, end mills, hobs, broaches, phrases and the like as well as punching tools such as pliers, The machining tool can be produced in the full width of the cutting edge of the machining tool.

However, when the inventors of the present invention have applied the surface treatment method of the present invention to the cutting edge of such a machining tool as a test, not only the mechanical properties such as increase in hardness and improvement in abrasion resistance of the cutting edge portion are improved, It was confirmed that the adhesion of the workpiece to the cutting edge portion can be prevented, for example, the generation of the cutting edge is suppressed.

In addition, it is generally known that the sliding property of the sliding member is improved by the oil receiving effect of dimples formed by three-dimensional injection and collision. However, in the conventional processing method, the dimples formed by this treatment are caused to push the metal by the collision of the abrasive, and the dimple outer ring rises in a convex shape.

The convex portion of the dimple outer ring is not preferable because it causes the initial friction to be increased with respect to the sliding member, resulting in deterioration of sliding properties such as adhesion of the scraped metal and abrasive wear due to initial friction.

Such a phenomenon is likely to occur in the entire sliding member such as a bearing, a shaft, and a gear.

When the process of the present invention is applied to the sliding member, there is a problem that not only the hardness and the residual stress are given but also the sliding property is improved, and therefore, the treatment method which makes it difficult to cause the dimples of the outer ring of the dimple to increase the initial wear of the sliding member .

Therefore, the present invention provides a surface treatment method for preventing sticking of a workpiece to the cutting edge of a cutting tool of such a machining tool, and a surface treatment method for improving the hardness of the sliding member and imparting residual stress and improving the sliding property As well as the use thereof for the purpose of the invention.

In order to achieve the above object, the present invention provides a method for surface treatment of a metal product, which comprises spraying a substantially spherical sprayed solid having a median diameter d50 of 1 to 20 占 퐉 and a dropping time of 10 sec / A nanocrystal texture layer formed by finely dividing the surface of the metal product into nanocrystals having an average grain size of 300 nm or less in a continuous depth range from the surface along a surface of the metal product, , And a residual compressive stress is applied to the surface of the metal product (Claim 1).

Here, the " median diameter d50 " refers to the cumulative mass of 50% diameter, that is, when the particle group (particle group) is divided into two particles from any particle diameter, Refers to a diameter at which the total amount of particles in the group of particles of the " cumulative height 50% point " is equivalent to that of JIS R 6001 (1987).

In the above-described surface treatment method for a metal product, it is preferable that the injection speed of the sprayed solid is 80 m / sec or more (claim 2).

In this case, it is possible to make the grain size of the nanocrystalline texture layer smaller than 100 nm (claim 3).

Further, the metal product may be a machining tool, and its processing area may be a range of at least 1 mm, more preferably at least 5 mm from its cutting edge (edge) and its vicinity of the cutting edge,

A dimple having a corresponding diameter of 1 to 18 占 퐉, preferably 1 to 12 占 퐉 and a depth of 0.02 to 1.0 占 퐉 or less by injection of the sprayed solid material is applied to the processing region, Or more than 30% of the surface area of the region (Claim 4).

Alternatively, the metal product may be a sliding member used in sliding contact with other members such as a bearing, a shaft, and a gear, at least a sliding portion of the sliding member may be a processing region,

The dimple having an equivalent diameter of 1 to 18 탆, preferably 1 to 12 탆, and a depth of 0.02 to 1.0 탆 or less by injection of the sprayed solid material is applied to the processing region so that the projected area of the dimple is the surface area Or more than 30% of the total thickness (claim 5). In the present invention, " equivalent diameter " refers to a value obtained by converting the projected area of one dimple formed on the treated area (the "projected area" in this specification means the area of the outer periphery of the dimple) Means the diameter of the circle when measured.

The metal product of the present invention is a metal product having a base material hardness of HV714 (HV7.0 GPa) or less and having a uniform depth ranging from the surface along the surface to a nanocrystal having a mean crystal grain size of 300 nm or less And a compressive residual stress is imparted to the surface. (Claim 6) Further, the metal product of the present invention is made of aluminum or an aluminum alloy, and the crystal grain size of the nanocrystalline texture layer is 100 nm or less (claim 7).

Alternatively, the metal product of the present invention may be a machining tool, and the nanocrystalline texture layer may be formed on the surface of the processing region formed by the cutting line and the vicinity of the cutting line, and the equivalent diameter may be 1 to 18 탆, The dimples of 0.02 to 1.0 占 퐉 or less may be formed such that the projected area of the dimples is 30% or more of the surface area of the processing area (claim 8).

Furthermore, the metal product of the present invention is a sliding member, and the nanocrystalline texture layer is formed on the surface of the sliding portion of the sliding member, and the metal product having a diameter of 1 to 18 탆 and a depth of 0.02 to 1.0 탆 The dimple may be formed such that the projected area of the dimple is 30% or more of the surface area of the processing area (claim 9).

With respect to a metal product made of a soft material, which has not been able to form a continuous nanocrystalline texture layer by forming a layered structure and forming a continuous nanocrystalline texture layer by performing the surface treatment using the surface treatment method of the present invention described above, It is possible to form a continuous homogeneous nanocrystalline texture layer and it is possible to impart a high compression residual stress equal to or higher than that in the case of spraying a solid having a relatively large particle size at a high injection pressure.

That is, the sprayed solid having a small median diameter of 1 to 20 占 퐉 and a dropping time of 10 sec / m or more in the air has a small mass and does not reach the deep portion by concentrating the stress near the surface of the metal product, It is possible to cause the surface deformation of the metal product in the spray nozzle to be reduced. On the other hand, such a jetted particle can fly at a speed close to the speed of the airflow because the airflow is easily burned, For example, at a speed of 80 m / sec or higher.

As a result, it is possible to obtain the collision energy necessary for obtaining the nanocrystalline structure even if the injection is performed at a relatively low injection pressure of about 0.05 MPa, and the effect of raising the surface hardness of the metal product at the injection pressure of about 0.1 MPa is almost saturated Thus, even when the injection pressure is higher than 0.1 MPa, hardness increase is hardly observed. Even with a relatively weak injection pressure of 0.5 MPa or less, a nanocrystalline texture layer can be obtained irrespective of the hardness of the base material of the metal product. It was possible to impart a compressive residual stress to the same extent as in the case of spraying a solid object having a size of 50 mu m or more as described above at a high pressure.

In addition, even at 0.05 MPa, compressive residual stress can be ensured at a hardness of about 60% at an injection pressure of 0.1 MPa.

As a result, even in a metal product made of a soft material such as an aluminum alloy, it is possible to form a uniform and continuous nanocrystalline texture layer without forming a layered structure as described with reference to Fig. 1, It is considered possible to form uniform and continuous nanocrystalline texture layers at a spray pressure lower than that shown in the prior art documents.

Furthermore, as described above, it is possible to perform the surface treatment of the metal product under the same processing conditions regardless of the base material of the metal product, and it is possible to carry out the surface treatment of the metal product without any prior art grasp of the hardness of the metal product to be treated, It is also possible to continuously carry out the surface treatment in a conveyance line or the like on which a plurality of kinds of metal products having different materials are conveyed.

Furthermore, in the surface treatment method of the present invention, even in the case of a metal product made of aluminum or aluminum alloy having a particularly low hardness among the metal materials, a uniform nanocrystalline texture layer is continuously formed along the surface It is possible to make the crystal grain size of the formed nanocrystalline texture layer to be smaller than 100 nm by treating aluminum or an aluminum alloy and it is possible to obtain a higher surface strengthening effect .

Further, it is preferable that a cutting edge and a vicinity of the cutting edge of a machining tool such as a cutting process are set as a processing region, and the processing region has an equivalent diameter of 1 to 18 mu m, preferably 1 to 18 mu m, 12 μm and a depth of 0.02 to 1.0 μm or less is formed so that the projected area of the dimple is 30% or more of the surface area of the processing area, generation of a constituent edge for the cutting edge is prevented, It is possible not only to strengthen the cutting edge of a machining tool but also to prevent adhesion of the workpiece to the cutting edge.

Also in the sliding member, it is possible to reduce the height of the convex portion of the dimple outer ring formed by the method of the present invention, and to improve the sliding property by preventing abrasive wear and adhesion of abrasion due to reduction in initial wear It was possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a principle of forming a layered structure on a soft material;
FIG. 2 is an explanatory diagram of an application example to a cutting edge of a machining tool, in which (A) is a state before processing, and (B) is a state after processing.
3 is an explanatory diagram of a portion (pressure-receiving surface) to which a compressive force is applied at the time of collision of the sprayed three-dimensional object.
Fig. 4 An analysis image of the von Meisses stress by the FEM (sprayed solid 5 占 퐉).
5 is an analysis image of the von Meisses stress due to the FEM (sprayed solid 10 占 퐉).
FIG. 6 is an analysis image of the von Meister stress due to the FEM (sprayed solid 20 μm).
7 is an analytical image of phoneme-stress due to FEM (sprayed solid 50 m).
FIG. 8 is an analysis image of the von Meisses stress by the FEM (sprayed solid 100 μm).
FIG. 9 is a graph showing the relationship between the particle diameter and the stress of the sprayed three-dimensional body.
10 is a graph showing the relationship between the particle diameter of the sprayed solid and the maximum stress generation depth.
11 is a graph showing the relationship between jet pressure and dynamic hardness.
12 is a SIM image of a preharden steel ("NAK80" manufactured by Daido Steel Industries Co., Ltd.), wherein (A) shows the state before the treatment, and (B) shows the state after the surface treatment of the present invention.
Fig. 13 is a SIM image of the alloy tool steel SKD11, wherein (A) shows the state before the treatment, and (B) shows the state after the surface treatment of the present invention.
14 is a SIM image of an aluminum alloy (A7075), wherein (A) shows the state before the treatment, and (B) shows the state after the surface treatment of the present invention.
15 is a crystal grain size distribution chart of a prehardened steel ("NAK80" manufactured by Daido Steel Co., Ltd.) treated by the method of the present invention.
16 is a crystal grain size distribution diagram of an alloy tool steel (SKD11) treated by the method of the present invention.
17 is a graph showing the results of measurement of the residual stress of free hard steel ("NAK80" made by Datong special steel).
18 is a graph showing the measurement results of the residual stress of the alloy tool steel SKD11.
19 is a graph showing the measurement results of the residual stress of the aluminum alloy (A7075).
20 is a graph showing a change in friction with respect to elapsed time.

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[Target]

The metal product to be treated in the surface treatment method of the present invention can be applied to metal products other than iron-based metals, non-ferrous metals and alloys thereof, if they are made of metal.

The metal product to be treated is not limited in its base material hardness and may be a metal having a relatively soft HV of from about 20 to 400, such as aluminum or an alloy thereof, and a free hard steel (HV400: "NAK80" , SKD11 (HV697), and so on.

Particularly, in the method of the present invention, it is possible to process a metal product made of a soft material, which has been conventionally said to be impossible to form a homogeneous and continuous nanocrystalline texture layer for forming the layered structure described with reference to Fig. 1, It has been confirmed that, in the treatment of metal products made of aluminum and aluminum alloys having a low hardness, among these soft materials, it is possible to obtain extremely fine crystal grain sizes of not more than 100 nm in the crystal grain size of the nanocrystalline structure layer to be formed As a result, it is possible to obtain a large surface strengthening effect.

In addition, the use of the metal product to be treated is not particularly limited, and it can be applied to a metal product for various uses requiring surface strengthening. However, the surface of the present invention can be applied to the cutting edge of a machining tool such as a cutting tool, In the case of applying the treatment method, it is also preferable that not only the cutting edge portion is strengthened but also the adhesion of the workpiece to the cutting edge can be prevented.

In this way, when the cutting edge of the machining tool is to be treated, as shown in Fig. 2, a portion of a cutting edge (edge) serving as a starting point of shearing at the time of cutting or cutting and a portion (A range indicated by a chain double-dashed line in the drawing) in a range of 5 mm, preferably 5 mm, is used as a processing region for spraying / colliding a sprayed solid, which will be described later, And a dimple is formed in this region as shown in Fig. 2 (B).

In the present embodiment, the inclined surfaces on both sides of the cutting edge are set to be processing areas on both sides, but the processing area is provided only on the side where adhesion of the workpiece is obtained, .

Further, when the surface treatment method of the present invention is carried out for the purpose of surface strengthening and improving the sliding property of the sliding member used by sliding it with other members such as a bearing, a shaft, and a gear, Is the machining area described above.

The surface of the metal product to be treated may be a state in which a flash is attached or a state in which a processing mark such as a tool mark is formed, but the surface of the metal product to be processed may have an arithmetic mean roughness (Ra) It is also preferable to perform pre-polishing by polishing with surface roughness.

Such a method of pre-polishing is not particularly limited and may be carried out by manual lapping or buffing. However, such pre-polishing may be performed by blasting using an elastic abrasive.

Here, the elastic abrasive is a material that abrasive grains are carried on an elastic body such as a rubber or an elastomer Such an elastic abrasive can be actuated (slid) on the surface of a metal product by spraying it at an oblique angle, whereby the surface of the metal product can be relatively easily mirror-polished It is possible to perform polishing in a close state.

The abrasive grains dispersed or supported on the elastic body of the elastic abrasive material can be appropriately selected depending on the surface condition of the metal product. For example, silicon carbide or diamond abrasive grains of # 1000 to # 10000 can be used.

[Surface treatment]

In the surface of the above-described metal product, a substantially spherical sprayed solid is sprayed onto the area to be subjected to the surface strengthening to collide with the above-mentioned area.

The sprayed solid, the spraying device, and the spraying conditions used in the surface treatment are shown below as an example.

(1)

The term " roughly spherical " in the substantially spherical sprayed solid used in the surface treatment method of the present invention does not necessarily have to be strictly a sphere, but generally refers to a shape that is used as a " shot " The shape of an ellipse, a bell shape, or the like is included in " substantially spherical sprayed solid " used in the present invention.

As a material of the sprayed three-dimensional body, any of metal and ceramics can be used. As an example of the metal sprayed solid material, alloy steels, cast iron, high speed tool steels (SKH), tungsten (W) (Al ₂ O ₃ ), zirconia (ZrO ₂ ), zirconium (ZrO ₂ ), zirconium (ZrO ₂ ), and the like can be used as the material of the solidified body of the ceramic system. (ZrSiO ₄ ), hard glass, glass, silicon carbide (SiC), and the like.

The particle diameter of the sprayed solid used may be in the range of 1 to 20 占 퐉 in median diameter (d50), 1 to 20 占 퐉, preferably 5 to 20 占 퐉 in median diameter (d50) , A median diameter (d50) of 1 to 20 mu m, preferably 4 to 16 mu m is used.

In addition, with respect to the sprayed solid of the fine powder having a median diameter of 1 to 20 占 퐉, it is possible to impart a long dropping time in the air (floating in the air) by selecting the material density of the sprayed solid, The sprayed three-dimensional object having such a property is easy to burn airflow, and can be made to fly at a speed comparable to the speed of the airflow.

Thereupon, in the surface treatment method of the present invention, the sprayed solid to be used is used in a no-air-blowing air dropping time of 10 sec / m or more, and a speed approximately equal to the speed of the airflow jetted from the jetting nozzle of the blast processing apparatus As shown in FIG.

The drop rate of the iron-based powder having a density of 7.85 was 10.6 sec at a particle size of 20 탆 and 41.7 at a particle diameter of 10 탆 for a powder having a density of 7.85, sec, and the ceramic powder having a density of 3.2 was 26.3 sec at a particle diameter of 20 탆 and 100 sec at a particle diameter of 10 탆.

It is preferable that the sprayed solid used is a sprayed solid of a material having hardness equal to or higher than that of the base material of the metal product to be treated. In the case of using ceramic sprayed solid, almost all of the metal products And the sprayed solid of the ceramic system is low in density and long in the dropping time described above, so that a high-speed spraying speed can be obtained.

(2) Injection device

As the spraying device for spraying the above-mentioned sprayed solid body toward the surface of the treatment area, it is possible to use a known blasting device for spraying the abrasive material together with the compressed gas.

As such a blasting apparatus, there are a section-type blasting apparatus for spraying an abrasive using a negative pressure generated by the injection of a compressed gas, a gravity-type blasting apparatus for spraying the abrasive dropped from the abrasive tank onto a pressurized gas, A direct-blasting type blasting device for introducing the slurry gas into the tank charged with the polishing agent and injecting the abrasive materials from the abrasive tank into the compressor stagnant from a separately supplied compressed gas supply source and injecting the mixture, Blower type blasting apparatus for blowing air into a gas stream generated in a blower unit and the like are commercially available, but any of them can be used for the spraying of the above-described sprayed solid bodies.

(3) Treatment conditions

With respect to the above-described metal products, a sprayed solid of a substantially spherical shape having a median diameter d50 of 1 to 20 占 퐉 and made of the above-described materials and having a falling time in air of 10 sec / m or more is injected at an injection amount of 0.05 MPa or more and 0.5 MPa or less As shown in Fig.

Example

[Confirmation of Optimum Condition]

(1) Particle size of sprayed solid

(1-1) Point of view

As described above, in order to continuously form a uniform nanocrystalline texture layer on the surface of a metal product made of a soft material, it is necessary to suppress generation of a layered structure described with reference to Fig. 1, It is necessary to suppress the deformation of the surface of the metal product which occurs when the projected solid collides with one another in order to suppress the formation of the processed structure.

On the other hand, in order to produce a nanocrystalline structure, it is necessary to give a distortion exceeding a threshold value near the surface of the metal product. In order to impart a distortion exceeding the threshold value, It is thought that it is necessary to give the above.

However, as the impact force applied to the surface of the metal product is increased, the amount of deformation of the surface of the metal product is increased, and the layered structure described with reference to Fig. 1 is likely to be generated. Making it difficult to produce uniform, continuous nanocrystalline texture layers along the surface without accompanying processing tissue.

Thereupon, the inventors of the present invention have found that, while colliding against the surface of a metal product at the time of collision of a sprayed article, the impact force applied to the surface of the metal product is reduced to suppress deformation of the surface of the metal product, The present inventors have studied a processing condition capable of satisfying a contradictory requirement of the present invention.

(1-2) Strain due to collision

The amount of deformation of the surface of the metal product which occurs when the sprayed solid collides is examined.

A median diameter d50 was collided with a three-dimensional object of 20 占 퐉 and 40 占 퐉 and the convex portion volume of the surface of the material was measured by a shape analysis laser microscope and compared with the degree that the convex portion volume was formed by folding. This is because the larger the convex portion volume, the larger the amount of folding when the three-dimensional body collides.

The surface was measured at a magnification of 1000 times using a shape analysis laser microscope (VK-X250, manufactured by KEYENCE CORPORATION).

The measured data was analyzed using a multi-file analysis application (manufactured by KEYENCE CORPORATION).

The multi-file analysis application is software for performing various measurements such as surface roughness, planar measurement, profile measurement, volume and area measurement using data measured by a laser microscope.

In the measurement, first, the reference surface setting is performed using the "image processing" function (in the case of the surface shape being a curved surface, the reference surface setting is performed after correcting the curved surface to the plane using the surface shape correction) The measurement mode was set to the convex portion from the function of " volume / area measurement ", the convex portion to the set " reference plane " was measured, and the average value of the results of the " volume "

The reference plane is calculated from the height data by using the minimum multiplying method.

The following table (Table 1) shows the results. The diameter of the convex portion of the region of the present invention of 20 mu m is reduced by about 70% as compared with the diameter of the conventional technique of 40 mu m.

This extremely small amount of deformation is considered to be a factor of uniform nanocrystal texture formation.

Particle diameter and convex volume of sprayed solid Example Comparative Example Particle size (D50) of sprayed solid ㎛ 20 40 Bulb volume 탆 ³ 932 2738

(1-3) Review of impact force F

The relationship between the impact force F and the particle size of the sprayed solid was reconsidered on the basis of a calculation formula for calculating the impact force F given to the surface of the metal product by the collision of the sprayed solid (one lip).

Here, the mass of the sprayed solid (one lip) is m (kg), the velocity of the jet solid before collision is v1 (m / sec) and the velocity after collision is v2 (m / sec) , The momentum M1 before collision and the momentum M2 after collision of the injected three-

M1 = m · v1 (kgm / sec) ... Equation 1

M2 = m? V2 = -m? V1 (kgm / sec) Equation 2

.

Therefore, the change DELTA M of the amount of momentum before and after the collision of the injected three-

? M = M1 - M2 = m? V1 - (? M? V1) = 2m? V1 (kgm / sec) Equation 3

.

Here, the change ΔM of the momentum is equal to the reversal (force product) F Δt (Δt is the inverse time)

F? T =? M ... Equation 4

.

Therefore, the impact force F applied when the sprayed three-dimensional object (one lip) collides with the surface of the metal product is

F =? M /? T = 2mv? 1 /? T (N) ... Equation 5

.

From the formula (5) of the impact force F, the impact force F changes in proportion to the mass m of the sprayed solid, and becomes larger as the particle diameter of the sprayed solid increases.

(1-4) Particle diameter of sprayed solid and pressure side

As described above, the impact force F increases as the particle diameter of the sprayed solid becomes larger. When the particle size of the sprayed three-dimensional body used is large and the impact force F is large, the area (the portion denoted by symbol S in Fig. 3) of the portion that causes deformation of the surface of the metal product Increase.

From this, it was examined how the area (pressure-receiving surface S) of the surface of the metal article, to which the input force is applied, changes with respect to the change in particle size of the sprayed three-dimensional body.

Here, assuming that the surface (circular horizontal surface) of the metal product in which interference with the sprayed solid occurs is the water pressure surface S,

Between the radius a of the hydraulic surface S, the radius r of the sprayed body, and the depth X of the recess,

a ² + (r - X) ² = r ² ... Equation 6

^{a 2 = r 2 - (r} - X) 2 = r 2 - (r 2 - 2rX + X 2) = 2rX - X 2 ... Equation 7

.

Here, assuming that the ratio of the depth X of the recessed portion to the diameter d of the sprayed solid is?

X = 2r? Equation 8

.

Therefore, by substituting Eq. 8 into X in the above-mentioned formula (7)

^{a 2 = 2r (2rα) -} (2rα) 2 ... Equation 8

From 2r = d,

a ² = d ² ? -d ² ? ² = d ² ? (1-?) ... Equation 9

Therefore, the area S (m < 2 >) of the pressure-

^{S = πa 2 = πd 2 α} (1-α) ... Equation 10

And the area of the pressure receiving surface S increases in proportion to the square of the diameter of the sprayed solid.

Here, the layered structure described with reference to Fig. 1 is formed by forming concavo-convexes at the time of collision and folding the convex portions therein, but the convex portions are formed by the concave portions The diagonal line portion) is extruded when the injection solid collides with the base material.

Therefore, it is presumed that the larger the area of the above-described pressure-receiving surface S, the larger the convex portion to be formed, and the easier to form a layered structure.

(1-5) Particle size and injection speed of the sprayed three-

From the above-mentioned expression (5) of the impact force F, the impact force F not only increases with the increase of the mass m of the injection solid but also increases with the increase of the injection speed v1.

Here, how the injection velocity changes with respect to particle size variation of the sprayed solid is described in Ogawa et al., &Quot; Measurement and Analysis of Particle Velocity in Air-Jet Shot Peening " (Transactions of the Japan Society of Mechanical Engineers, Vol. 60, No. 571 , 1994-3), and the injection speed was calculated.

(1-6) Prediction of Optimum Particle Size of Sprayed Solid

The change in the impact condition with respect to the change in particle size of the sprayed solid (density 7.85) made of steel as an example is summarized in Tables 2 and 3 below.

As is apparent from Tables 2 and 3, the larger the particle size of the sprayed solid is, the more the impact force F increases. However, the water pressure area S also increases with the increase in the impact force F, It is considered that a layered processed structure, which is considered to be generated by the folding of the convex portions, is likely to be generated.

In addition, the larger the particle size of the sprayed solid, the larger the value of the impact force F. However, as described above, the area of the water pressure surface S increases in proportion to the square of the diameter d of the sprayed solid, In the case of considering per unit area (impact force F / water pressure area S), the force applied per unit area is small.

When the impact energy of each particle diameter is set to 0.5 MPa in Table 1 and the impact energy of the particle diameter d50 = 50 mu m is 1, d50 = 10 mu m and 20 mu m is about 2 to 3 times larger It is possible to inject energy onto the surface.

From this, it can be seen that the use of a sprayed solid having a large particle diameter makes it easy to deform the surface of the metal product, and not only is it easy to generate the layered structure described with reference to Fig. 1, but also the distortion exceeding the critical value necessary for obtaining the nanocrystalline structure It is expected to be difficult to obtain.

Thereupon, simulation of Von Mises stress is performed by an analysis by a finite element method (FEM) (hereinafter referred to as " FEM analysis ") based on the calculated values shown in Tables 2 and 3 . The results are shown in Tables 4-8.

Fig. 9 is a graph showing the relationship between particle size and stress variation of the sprayed solid obtained from the results of the simulation, and Fig. 10 is a graph showing the relationship between the particle diameter of the sprayed solid and the depth of occurrence of the maximum stress.

Here, FEM analysis is one of the numerical analysis methods. In the case where it is difficult to solve by an analytical method such as a complex shape model, the FEM is divided into fine elements, simple equations are formed on a per element basis, Femap with NX NASTRAN " (manufactured by N.S.T., Ltd.) was used as the analysis software.

The term " von Meister stress " refers to a stress equivalent to a shear strain based on the theory of shear strain energy, expressed as a non-directional scalar value, in a stress field in which the load is complicatedly applied from multiple directions, It is the value projected on tensile or compressive stress.

By referring to the von Meisses stress, it is an index for judging whether or not this material yields, and it is unnecessary to see the stress in the other direction at the time of the comparison with the yield stress, In consideration of the point, this is used to simulate the stress caused by the collision of the sprayed bodies.

According to the simulation results, the relationship between the particle size of the sprayed solid and the depth at which the stress is introduced shows that the smaller the particle size of the sprayed solid is, the stronger the stress is applied to the very low surface layer, and the larger the particle diameter, However, it is judged that this stress is small.

Particularly, in the case where the depth and the intensity of the stress that enter the surface of the metal product change with the particle size of the sprayed solid of 20 占 퐉 as a boundary and the strength exceeds 20 占 퐉, And is becoming clear.

That is, in the contour diagrams shown in Figs. 4 to 8, the center of the portion seen as the hyperdrawn type shows the portion having the greatest stress, and in the simulation with the projected solid of 20 탆 or less, A very strong stress is applied to a part of the resin material. However, when the particle diameter is large, the stress is large and the resin material is dispersed deeply, so that the strength of the stress becomes weak (see Figs. 9 and 10).

From the above results, it can be seen from the above results that it is difficult to form irregularities (particularly convex portions) which are the cause of formation of layered structures on the surface of metal products as described with reference to Fig. 1, It is believed that there is an effect of concentrating compositional distortions exceeding the critical value necessary for creating the tissue near the surface of the metal product.

(2) Determination of injection pressure

Of an iron alloy having a median diameter d50 of 20 占 퐉 in an area of 6 mm x 5 mm in a specimen made of an alloy tool steel SKD11, a free hard steel (NAK80 manufactured by Daido Steel Industries Co., Ltd.) and an aluminum alloy (A7075) And the change of the surface hardness (dynamic hardness) of each test piece was measured.

In order to obtain a jet pressure applicable to both hard materials and soft materials, specimens processed with different jetting pressures were prepared for each material, and densities of 30 points in a region of 6 mm x 5 mm The hardness obtained by measuring the hardness was defined as the surface hardness (dynamic hardness) of each test piece.

Fig. 11 shows a graph of the measurement results.

The dynamic hardness (DHT) was determined by measuring the hardness by pushing in an indenter, and the measurement was carried out under the following conditions.

Equipment used: DUH-W210 dynamic micro-hardness tester manufactured by Shimazu Seisakusho

3 kgf (A7075), 5 gf (" NAK80 "), 10 gf (SKD11)

Holding time: 5 seconds

Indenter shape: triangular diamond indenter (115 °)

Calculation method: DHT = α × P (D ² )

In the above equation, DHT is the dynamic hardness,? Is the indenter shape coefficient (3.8584), P is the indentation load (mN), and D is the indentation depth.

Conventionally, in the case where strong stress is applied to the surface of a metal product by shot peening, it is considered effective to increase the injection pressure.

However, from the measurement results of the dynamic hardness (DHT) shown in Fig. 11, even in the case of the sprayed solid having a median diameter of 20 mu m or less used in the present invention, when the injection pressure is in the range of 0 to 0.1 MPa, It has been confirmed that the surface hardness (dynamic hardness) of the product is increased. However, when it exceeds 0.1 MPa, the surface hardness is not further increased even for the test piece made of any material having high hardness and low hardness, , It was confirmed that the effect of improving the hardness was saturated.

Therefore, in the method of the present invention, it is considered that if the injection pressure is 0.05 MPa or more, energy necessary for raising the hardness (and thus making the nanocrystallization) be imparted to the surface of the metal product to be treated, It was confirmed that it is possible to perform surface treatment on both the hard material and the soft material by the relatively low injection pressure below.

In addition, by using such a minute sprayed solid material, machining can be performed at a relatively low injection pressure, even when a metal product made of a soft material is to be treated, deformation of the surface of the metal product is minimized, It is considered that it is possible to suppress the generation of the layered structure described with reference to Fig.

As described above, in the method of the present invention, low ejection pressure can be applied because, when particles are gravity settled in the air, when the particle diameter is large, the particles fall due to gravity (external force) It is considered to be due to the property that it is difficult to precipitate because it is easy to burn.

That is, since the mass is small and the influence of the inertial force is small in such a small particle size, the large force is not required to move it, and even if the pressure of the carrier gas is low, the jet three- Can be made close to the speed of the compressed gas injected from the injection nozzle easily.

As a result, by using the sprayed three-dimensional body which easily rides on the airflow as described above, there is no large difference in the injection speed of the sprayed solid when the injection pressure is 0.1 MPa or 0.5 MPa and the injection pressure is 0.1 MPa , It is considered that the hardness increase as in the case of 0.5 MPa is obtained.

Also, even at a pressure of 0.05 MPa, the hardness thereof can be made to be 60% or more at 0.1 MPa.

However, even in the case of a jet powder having a median diameter of 20 μm or less, a large mass is liable to be influenced by an inertia force, and it is difficult to burn airflow and reaches a surface of a metal product before reaching a maximum velocity.

Here, the iron-based sprayed solid having a median diameter of 20 占 퐉 used in the above test was 10.6 (sec / m) in fall time in air (the reciprocal of the termination speed in the Stokes equation) In the test, good surface hardness (dynamic hardness) was improved in any of the ranges of the injection pressure of 0.05 MPa or more and 0.5 MPa or less.

Therefore, it is considered that, if the dropping time in the air is long and the airflow is easily generated even by the sprayed solid, the necessary jetting speed can be obtained and the surface of the metal product can be made nanocrystalline.

According to the above results, the sprayed solid used in the method of the present invention was determined to have a median diameter of 20 占 퐉 or less and a dropping time of 10 sec / m or more in air.

The spraying speed of the above-mentioned iron-based spray powder having a particle diameter of 20 占 퐉 is 80 m / sec or more from Tables 2 and 3, and in the surface treatment method of the present invention, it is preferable to spray the sprayed solid at an injection speed of 80 m / sec or more Do.

[Effect confirmation test]

(1) Purpose of examination

By performing shot peening under the processing conditions obtained as a result of the test and simulation for deriving the above-described treatment conditions, it is possible to obtain uniform nanocrystalline texture layers on both surfaces of metal products made of hard materials and soft materials It is possible to form the metal product continuously, and it is confirmed that a high residual stress can be imparted to the surface of the metal product.

(2) Test method

The surface treatment was carried out on the test specimens of Freihadang (NAK80 made by Daido Steel Co., Ltd.), alloy tool steel (SKD11) and aluminum alloy (A7075) by the method of the present invention.

The surface treatment conditions are shown in Table 4 below.

Exam conditions NAK 80 SKD 11 A 7075 table
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Lee Injection method SF SF SF Injection Density Material Median Diameter d50 (㎛) Iron alloy 20㎛ Iron alloy 20㎛ Iron alloy 20㎛ Injection pressure (MPa) 0.5 0.5 0.5 Nozzle Diameter (mm) φ7 φ7 φ7 Spray time (sec) 30 30 30

(3) Observation method

Each test piece subjected to the surface treatment under the above conditions was observed in the following manner.

(3-1) Observation by SIM

Using a scanning ion microscope ("SMI3050SE" manufactured by SIM Hitachi High-Tech Science Co., Ltd.), a change in the crystal structure near the surface of each test piece was observed.

(3-2) Observation by EBSD

The crystal grain size and the crystal grain distribution in the crystal structure near the surface of each test piece were observed by back scattering electronic analysis (Electron Back Scatter Diffraction TSL Solutions).

(3-3) Residual stress measurement

Residual stress on the outermost surface of each test piece was measured using a portable X-ray residual stress measuring device (" μ-X360 "

(4) Test results

(4-1) Observation result by SIM

The SIM images of each test piece are shown in Figs. Fig. 12 shows the SIM image of the free hard steel (NAK80), Fig. 13 shows the alloy tool steel SKD11 and Fig. 14 shows the aluminum alloy A7075. In each figure, It is.

As for the test piece made of any material, it can be confirmed that the surface of the test piece after the surface treatment by the method of the present invention is clearly finer in the metal structure in the region of about 3 탆 from the surface layer. . ≪ / RTI >

It was confirmed that the nanocrystalline structure was formed continuously along the surface of the test piece in the visual field (about 10 mu m) on the SIM, and a continuous nanocrystal structure layer was formed.

This nanocrystalline structure can be obtained even in the case of a test piece to be treated with an aluminum alloy (A7075) which is a soft material, without involving the layered structure described with reference to Fig. 1, It was confirmed that a uniform nanocrystal structure was formed.

Further, in these test pieces, although a region in which microcrystallization (nanocrystallization) was remarkable in the range of 3 mu m from the surface layer was confirmed, the crystal became finer even in a region where the depth from the surface layer was deeper, And the microfabrication is remarkable.

Thus, from the observation results by SIM, in the surface treatment method of the present invention, in both the test piece made of the hard material and the test piece made of the soft material, in the range of the predetermined depth (about 3 m) from the surface, It is confirmed that a uniform nanocrystalline texture layer can be continuously formed along the surface of the substrate.

11, the surface hardness (dynamic hardness) of the test piece having the nanocrystalline texture layer formed in the vicinity of the surface thereof is about 100 to 200 (hardness) as compared with the untreated (injection pressure of 0 MPa in FIG. 11) Has been ascertained to be effective as a surface strengthening method for a metal product formed of all materials from a soft material to a hard material.

(4-2) Observations by EBSD

Fig. 15 shows the grain size distribution of the grain near the surface of the Freeharden steel (NAK80) test piece obtained as a result of the analysis by EBSD, and Fig. 16 shows the grain size distribution of the grain near the surface of the alloy tool steel (SKD11) Respectively.

From the results of observation by the EBSD, it was confirmed that the crystal grain size of the nanocrystalline texture layer was in the range of 100 to 500 nm in the free hard steel (NAK80), and from the crystal grain distribution (see Fig. 15) The average crystal grain size was 240 nm.

In the alloy tool steel SKD11, it can be confirmed that the average crystal grain size of the nanocrystalline texture layer is in the range of 100 to 500 nm. From the crystal grain distribution (see Fig. 16), the average crystal grain size of the nano- Nm.

Further, in the aluminum alloy (A7075) test piece, crystal grain size produced is considerably small compared with the resolution of EBSD, so it was not possible to perform crystal analysis by EBSD. However, the maximum resolution of EBSD was 30 nm, The finest crystal grains among the test specimens are observed from the SIM phase. Therefore, it is reasonable to speculate that many of the crystal grains in the nanocrystal structure layer formed on the surface of the aluminum alloy (A7075) are smaller than 30 nm, which is the highest resolution of EBSD Therefore, it is considered that the grain size of the nanocrystalline texture layer formed on the surface of the aluminum alloy (A7075) is 100 nm or less.

(4-3) Measurement results of residual stress

17 to 19 show the results of measurement of the residual stress on the outermost surface of each test piece.

In any of the test pieces, the residual stress, which was a value of + (tensile stress) in the raw state, is changed to a value of - (compressive stress). By performing the surface treatment method of the present invention, a high compressive residual stress It is possible to confirm that it can be given.

Among them, the stress of the free hardened steel (NAK80) shown in Fig. 17 and the stress of the aluminum alloy A7075 shown in Fig. 19 hardly show a change in the change of the injection pressure. As described above, , It was confirmed that it is possible to impart a sufficient compressive residual stress even in the case of spraying at a relatively low injection pressure of 0.5 MPa or less.

19 showing the residual stress of the aluminum alloy (A7075), the graph shown as a comparative example is a graph showing the residual stress of the aluminum alloy (A7075) when the sprayed solid having a median diameter of 40 mu m larger than the range of the present invention is injected at an injection pressure of 0.5 MPa And the result of measurement of the residual stress is shown.

As described above, residual compressive stress can be imparted in the example (comparative example) using the sprayed solid having a larger particle size as compared with the sprayed solid used in the present invention. However, the residual stress imparted by the method of the present invention is 1/5 Or less of the residual stress, and when the surface treatment is carried out by the method of the present invention, a higher surface strengthening effect is obtained.

18), the residual stress was increased with the increase of the injection pressure. However, even when the injection was performed at the lowest injection pressure (0.1 MPa), sufficient residual stress was given to the alloy tool steel (SKD11) .

In the example in which the surface treatment of the present invention was carried out at the injection pressure of 0.1 MPa, the residual stress was slightly lower than that of the comparative example (median diameter of the spray solid: 40 mu m, injection pressure: 0.5 MPa) In MPa, residual stress equal to or higher than that in the comparative example is applied.

[Application of machining tool to cutting edge]

(1) Test method

(Examples 1 and 2) made of SKD11, the untreated SKD11 punching tool (untreated product), and the surface treatment of the present invention, (Comparative Example 1) was used for punch press processing, and the state of the cutting edge after the processing was observed.

(2) Surface treatment conditions

Surface treatments were carried out on the cutting edge punches (length 3 cm, diameter 0.5 cm) made of SKD 11 under the conditions shown in Table 5 below.

Surface treatment conditions for punch for punching Example 1 Example 2 Example 3 table
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Lee Injection method SF SF SF Injection Density Material Median Diameter d50 (㎛) 15 (High) 16 (alumina) 80 (High) Injection pressure (MPa) 0.3 0.05 0.3 Nozzle Diameter (mm) 7 7 7 Spray time (sec) 30 30 30

In Table 5, " SF " in the " spraying method " indicates the section spraying method. In this test example, " SFK-2 "

(3) Punching conditions and observation method

Punches subjected to the surface treatment in each of the methods of Examples 1, 2, and Comparative Example 1, and untreated products were subjected to punch press processing for 9,000 consecutive times on the workpieces made of SS steel material, The state of the surface of each punch after the punch press processing was observed and the state of consumption was observed by a microscope.

(4) Observations

The surface condition of each punch after the punch press processing is as shown in Table 6 below.

Surface condition of punch after press-forming Treatment condition Surface condition Example 1 The damage is almost invisible.
And there is no adhesion of the material to be processed. Example 2 The damage is almost invisible.
No occurrence of adhesion Comparative Example 1 Identify a number of muscle wounds in the longitudinal direction
In the adhesion of the material to be processed Untreated goods Ineffective at 1,800 times

(5) Consideration

In the present invention, by performing the surface treatment of the present invention on the punch made of SKD11, the hardness after the surface treatment is raised to about 950 Hv in the treatment of Example 1, Of the hardness was increased.

In the treatment of Example 2, the hardness was increased to about 870 Hv, and the hardness was increased by about 16%.

This increase in hardness is thought to be caused by the formation of the nanocrystalline texture layer described above.

Further, in the punches (Examples 1 and 2) subjected to the surface treatment by the method of the present invention, it is possible to prevent adhesion of the workpiece to the cutting edge as described above. It is considered to be one factor for improving the life of the punch.

The principle of obtaining such an effect that the adhesion of the workpiece is prevented is not necessarily clear, but the surface of the metal product subjected to the surface treatment by the method of the present invention has a diameter of 1 to 18 mu m and a depth of 0.02 to 1.0 mu m or less (See Fig. 2 (B)), the projected area of the dimple is 30% or more of the surface area of the treated region, and the dimple serves as an oil pan to obtain the effect of preventing adhesion of the workpiece .

The diameters (equivalent diameters) and depths of the dimples were measured using a shape analysis laser microscope ("VK-X250", manufactured by KEYENCE CORPORATION). If the surface of the metal product can be directly measured, , Methyl acetate was added dropwise to the acetyl cellulose film and fused to the surface of the metal product, dried, peeled off, and measured on the basis of the dimples transferred in reverse on the acetyl cellulose film. (Image data obtained by reversing the photographed image in the measurement of image data (in the case of measurement using an acetylcellulose film)) was analyzed by using a " multi-file analysis application (VK-H1XM made by KYENCE Corporation) ".

Here, the " multi-file analysis application " is an application for analyzing surface roughness, line roughness, height and width, measurement of circle equivalent diameter and depth, It is an application that can perform processing.

In the measurement, first, the reference plane is set using the " image processing " function (if the surface shape is a curved surface, the reference plane is set after correcting the curved surface to the plane using the surface shape correction) The measurement mode is set to the concave portion from the function of the "volume and area gain" to measure the concave portion with respect to the set "reference plane", and the average value of the results of the "average depth" and "circle equivalent diameter" The depth of dimples, and the equivalent diameter.

The above-mentioned reference plane was calculated from the height data using the least squares method.

The above-mentioned " circle equivalent diameter " or " equivalent diameter " was measured as the diameter of the circular shape measured by converting the projection area measured as a dimple into a circular projection area.

The above-mentioned " reference plane " refers to a plane having a measurement zero point (reference) among the height data, and is mainly used for measurement in the vertical direction such as a depth and a height.

[Application to sliding members]

(1) Test method

(Example 3), a mirror surface state untreated (Comparative Example 2), and a conventional technique (Comparative Example 3) were prepared on an SUS304 plate of 40 mm x 40 mm and a thickness of 2 mm, And a sliding property evaluation was carried out.

Surface treatment conditions Example 3 Comparative Example 3 Injection method SF SF Injection solid median diameter d50 (占 퐉) 20 (iron alloy) 40 (High) Injection pressure (MPa) 0.1 0.3 Nozzle Diameter (mm) 7 7 Spray time (sec) 20 20

(2) Evaluation method

After machining under the above conditions, a ball-on-disk test was performed on the SUS304 plate until the friction coefficient reached 2.0, and the sliding time was compared to evaluate the sliding properties.

Friction and wear test conditions Testing machine FPR-2000 Load g 10 Rotation diameter mm 4 Rpm 200 Lubrication none rater 3/16 inch
SUS304 ball

A ball-on-disc type friction and wear tester was used. The ball diameter was 3/16 inches, made of SUS304.

(3) Evaluation results

20 is a graph showing a change in friction with respect to elapsed time.

As can be seen from the measurement results, the treatment under the conditions of Example 3 had about three times durability as compared with the treatments under the conditions of untreated (Comparative Example 2) and Comparative Example 3.

(4) Consideration

It can be inferred that the durability of about 5 times that of Comparative Example 2 and about 3 times of the durability of Comparative Example 3 were obtained only by the low friction test. Therefore, it is considered that about three times the sliding property is obtained by carrying out the treatment of the present invention.

Claims (9)

Spraying a substantially spherical sprayed solid having a median diameter d50 of 1 to 20 占 퐉 and a dropping time of 10 sec / m or more in the air at an injection pressure of 0.05 MPa to 0.5 MPa on the metal product, Characterized in that a nanocrystalline texture layer in which a nanocrystal having an average crystal grain size of 300 nm or less is finely and continuously formed in the range of a predetermined depth from the surface and a compression residual stress is applied to the surface of the metal product / RTI > The method according to claim 1,
Wherein the spraying speed of the sprayed solid is set to 80 m / sec or more. 3. The method according to claim 1 or 2,
Wherein the material of the metal product is aluminum or an aluminum alloy and the crystal grain size of the nanocrystalline texture layer is made smaller than 100 nm. 3. The method according to claim 1 or 2,
Wherein the metal product is a machining tool, a cutting edge of the machining tool and a vicinity of the cutting edge are used as a processing region,
A dimple having a diameter of 1 to 18 mu m and a depth of 0.02 to 1.0 mu m or less by injection of the sprayed solid is formed in the processing region such that the projected area of the dimple is 30% or more of the surface area of the processing region ≪ / RTI > 3. The method according to claim 1 or 2,
Wherein the metal product is a sliding member, at least a sliding portion of the sliding member is a processing region,
A dimple having a diameter of 1 to 18 mu m and a depth of 0.02 to 1.0 mu m or less by injection of the sprayed solid is formed in the processing region such that the projected area of the dimple is 30% or more of the surface area of the processing region ≪ / RTI > A core material hardness of HV714 or less, a nanocrystalline texture layer in which the average crystal grain size is uniformly reduced to nanocrystals continuously in the range of a certain depth from the surface along the surface, and a compressive residual stress is applied to the surface Wherein the metal product is a metal product. The method according to claim 6,
Aluminum or an aluminum alloy, and the crystal grain size of the nanocrystalline texture layer is 100 nm or less. The method according to claim 6,
Wherein the nanocrystalline texture layer is formed on the surface of the processing region formed by the cutting line and the vicinity of the cutting line and the dimple whose equivalent diameter is 1 to 18 mu m and the depth is 0.02 to 1.0 mu m or less, A metal product which is a machining tool formed to be at least 30% of the surface area of the area. The method according to claim 6,
The dimpled texture layer is formed on the surface of the sliding portion which is brought into sliding contact with the other member and the dimple whose equivalent diameter is 1 to 18 mu m and the depth is 0.02 to 1.0 mu m or less, Wherein the sliding member is formed to be at least 30% of the surface area of the region.

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