JPH0349962B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Fields> The present invention is used to strengthen plastics, metals, ceramics, etc., to add design to paints, etc. by imparting metallic luster, and to impart corrosion resistance and durability. The present invention relates to a method for producing flat metal raw material powder, which is a raw material for finished flat metal powder suitable for.

<Prior art and its problems> In recent years, in order to improve the durability and corrosion resistance of paints, etc., give them a metallic luster, and enhance the electromagnetic shielding effect, high-quality particles of uniform size and thickness have been developed. Flat metal powder with a high aspect ratio (average major axis/average thickness) is required.

The finished flat metal powder used for the above purpose has a maximum length of 100 μm or less (more preferably
80 μm or less), an average thickness of 1 μm or less (more preferably 0.1 to 0.5 μm), an average major axis of 10 to 90 μm (more preferably 15 to 80 μm), and an aspect ratio of 30 or more (more preferably 100 or more). be.

This is when using a spray gun for paint etc.
If the maximum length exceeds 100 μm, the nozzle may become clogged, and if the average thickness exceeds 1 μm, the average major axis is less than 10 μm, and the aspect ratio is less than 30, sufficient specific surface area may not be obtained, resulting in labyrinth effects and No hiding effect can be obtained, and especially when used in paints, the characteristics of flat metal powders such as rust prevention cannot be exhibited.

Conventionally, methods for producing flat metal powder include a method in which a raw metal is melted and atomized by an atomization method in which water or inert gas is ejected from a nozzle, and then flattened by a ball mill or the like. However, although these methods can produce flat metal powder with a uniform particle size and thickness and a high aspect ratio, they are inefficient and extremely costly.

In addition, for example, in Japanese Patent Application Laid-Open No. 56-98406,
In order to obtain high-grade flat metal powder, thin stainless steel plates and foils are nitrided to increase their hardness and make them easier to pulverize. After pulverization, they are denitrified by heating in a hydrogen stream, and then treated with an aqueous solution of sodium percarbonate. proposed a method for producing stainless steel flat fine powder for paints by decarburizing.

Further, Japanese Patent Application Laid-Open No. 57-67101 proposes a method in which rollable metal powder is supplied to a rolling roll without overlapping each other, and the rolled flat metal powder is scraped off from the roll.

However, through complicated processes such as those described in the above two prior art techniques, it is difficult to efficiently produce flat metal powder with a uniform particle size and thickness and a high aspect ratio at a low cost.

<Object of the Invention> Therefore, the object of the present invention is to obtain a high aspect ratio finished flat metal powder with uniform particle size and thickness suitable for obtaining high aspect ratio finished flat metal powder with uniform particle size and thickness. It is an object of the present invention to provide a method capable of producing flat metal raw material powder through simple steps at an extremely low cost and with a high yield.

<Structure of the Invention> The above object is achieved by the following present invention. That is, the present invention processes a metal material under conditions that form flow-shaped microchips having a shearing sliding surface in a direction substantially perpendicular to the direction of cutting or grinding, and processing these chips along the shearing sliding surface. In order to preferentially promote fineness by peeling off the thin flakes, a crushing means with a large rubbing action is preferably used, such as an attrition mill, a ball mill, a conical ball mill, a cone crusher, a rod mill, a conversion tube mill, a tricone mill, a vibration mill, and a jet mill. , exfoliated and crushed using a Henschel mixer, or an aerofluor mill, etc., with an average thickness of 10 μm or less and an aspect ratio of 5.
As described above, we provide a method for manufacturing flat metal raw material powder suitable for manufacturing ultra-thin metal flakes by crushing and spreading, which is characterized by manufacturing flat fine powder mainly consisting of flat powder, preferably having an aspect ratio of 10 or more. It is something.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

The metal materials used in the present invention include metals such as steel, brass, aluminum, titanium, and stainless steel, or alloys of these metals.

In the present invention, the flatness of the fine powder of the metal material is expressed by the aspect ratio defined as the ratio of the average major axis to the average thickness of the fine powder.

The flat metal raw material powder produced according to the present invention is produced as follows. First, a metal material is processed under conditions that form flow-shaped micro-chips having a shearing sliding surface substantially perpendicular to the direction of cutting or grinding. The cutting depth of the flowing micro chips is set to be as small as possible to 100 μm or less, preferably 50 μm or less (cutting condition on the lower right of broken line a in Fig. 1 described later), and the thickness is several μm to several μm. 10μ
It is desirable to manufacture one with an average length of 100 to 200 μm. Although there may be some parts with a length exceeding 300 μm, mainly 30 μm in length.
It is desirable to adjust the conditions so that the fibers are in the range of ~300 μm and 50 μm or less in thickness.

These flow-shaped micro-chips cannot be identified with the naked eye, but since they have the above-mentioned shedding sliding surface in the cutting direction, they can be easily slid by a crushing method such as a ball mill that has a large rubbing action. It peels along the surface and is crushed into flat powder that looks like slices. Therefore, the short axis of this flat powder (the flat raw material powder of the present invention) approximately corresponds to the thickness of the chips, and the long axis is either the same or slightly larger due to the diagonal cutting. Some of it breaks down into smaller pieces. On the other hand, the thickness depends on the grinding time, but as seen in the examples below, the grinding progresses easily to 10 μm or less, usually several μm, and the aspect ratio is 5 or more, more preferably 10 or more. It is mainly made into flat raw material powder.

By the way, in order to crush the above-mentioned flow-shaped micro chips into flat powder, it is necessary to exfoliate and crush them by using a crushing means that has a large rubbing action to loosen them. Other examples include an attritor mill, a conical ball mill, a cone crusher, a rod mill, a conversion tube mill, a tricone mill, a vibration mill, a jet mill, a Henschel mixer, and an aerofluor mill. On the other hand, crushing means with a small rubbing action such as a geo crusher, a tire retrieval crusher, a roll crusher, an impact crusher, a hammer crusher, a cage mill, or a pan mill, Even if the above-mentioned flow-type micro chips have a thickness of 10 μm or less and an aspect ratio of 5, which is the objective of the present invention,
It becomes difficult to obtain flat fine powder consisting mainly of flat powder.

An important feature of the present invention is that thin flat powder can be easily obtained in such a fine size range. This flat raw material powder is further processed through a dry stamp mill.
By adding a simple crushing and rolling process using a crusher with large pressing and rubbing effects such as a dry ball mill, wet ball mill, vibrating ball mill, or burr mill, a high aspect ratio with uniform grain size and thickness suitable for the purpose of use can be obtained. The completed flat metal powder can be easily produced. If the raw material powder has an aspect ratio of less than 5, the efficiency of producing a finished flat metal powder with a high aspect ratio will be very low, and as disclosed in Japanese Patent Application No. 59-037480, flattening such as intermediate annealing is required. extra steps are required.

The micro chips mentioned earlier are too large, exceeding 300 μm.
In particular, when the number of particles exceeding 500 μm increases, coarse grinding becomes difficult to proceed smoothly, the grinding time becomes longer, and large flat raw material powders are mixed with broken fine particles, resulting in increased dimensional variation. As a result, even when re-pulverizing into ultra-thin flakes, it is likely to cause a decrease in efficiency, inconsistency in product dimensions, decrease in yield, etc., so it is wise to avoid this unless there is a high tolerance for dimensional variations.

For the same reason, it is desirable that the major and minor axes of the flat raw material powder are mainly 90 μm or less, particularly 50 μm or less, and the average diameter is preferably 10 to 20 μm, which is slightly smaller. This dimensional adjustment is mainly performed by adjusting the thickness of the chips.

On the other hand, the finished flat metal powder is less than 10μm, especially 5μm.
m or less, and it is effective to adjust the crushing means and crushing time.

Hitherto, it has not been known what kind of raw material powder is suitable for obtaining finished flat metal powder with a high aspect ratio. However, the inventors of the present invention have attempted various methods of pulverizing chips in order to reuse the cutting waste or grinding waste (generally referred to as chips) generated when cutting or grinding metal materials, and as a result, they have found that the Among them, if specific cutting conditions are selected, flat metal powder with uniform grain size and thickness and high aspect ratio can be produced by simple crushing, and furthermore, this flat metal powder can be further processed with a specific crushing method. By doing so, ultrathin flat metal powder with an extremely high aspect ratio, that is, finished flat metal powder, can be efficiently obtained.
A new finding was obtained that the yield of products with the desired dimensions and shapes as described above is extremely high. The present invention was completed based on this new knowledge, which was not previously known, by researching conditions for reproducing it.

As will be exemplified later in Examples, the cutting chips that are the raw material of the present invention may have a cutting depth of several tens of μm, for example.
By maintaining a very small value such as m or several μm, particularly suitable extremely fine short fibers can be obtained. As a result, the length is several tens of μm
At most, it is several hundred micrometers, and the diameter is about several micrometers to several tens of micrometers, so it is a curled several centimeter to several tens of centimeters called cutting chips or grinding chips.
The impression is completely different from the chips that we usually think of when talking about length, and it is exactly like "powder". It would be more appropriate to call it "micro chips." If you actually spill a small amount of it onto a piece of paper and shake it gently, the faint, minute dots will spread out like a thin smudge, like scattered ash. Even if you look closely at it with the naked eye, there are very few things that can be recognized as fibers. However, when this is magnified about 10 times and observed, it clearly has a short fiber shape, and when magnified further 1000 times,
There are many parallel lines in the direction of cutting the fiber into rings. However, in fibers under different cutting or grinding conditions, this kind of cut line is hardly observed even in slightly large short fibers. Even when such unsuitable fibers are pulverized, the fibers are elongated and, although they may be slightly torn, no round-shaped flat powder is produced.

In the case of the present invention, the chips are too small to be separated with the inner eye, but only in the case of micro chips obtained by flow cutting or flow grinding (the above-mentioned micro chips), rubbing is mainly performed. It has been found that by using a crushing method that can be easily transformed into a finer ring-sliced state, it is possible to easily produce flat flakes with dimensions so small that they cannot be easily obtained using normal methods. The essence lies in this. In other words, a fine powder (micro chips) that looks like a faint point that can be seen with the naked eye as a single chip turns into an even finer powder (flat raw material powder). However, the technology of the present invention is based on the knowledge that unexpectedly fine and highly flat powder can be easily obtained only with a specific combination of raw materials and processing methods. That's the point. Furthermore, we have discovered that this flat powder can be easily transformed into ultra-thin flakes with a thickness of 1 μm or less, that is, finished flat metal powder, depending on the subsequent crushing method. This is the first time that its high value as a raw material for ultra-thin flakes has been confirmed.

Therefore, the present inventors investigated the flow-shaped chips that are generated in the cutting or grinding direction when cutting or grinding the metal material mentioned above and have a shear slip in a direction substantially perpendicular to this direction. It has been discovered that flat metal raw material powder can be produced at a low cost by coarsely pulverizing it after removing the particles, etc., to obtain finished flat metal powder with a uniform particle size and thickness and a high aspect ratio at a high yield.

The flow-shaped chips used in the present invention are made by cutting or grinding metal materials, and typically, based on cutting theory,
This will be explained using FIG. c and FIG. 3d.

The shapes of chips generated when cutting the metal material 1, which is the work material, with a cutting tool 2 such as a cutting tool or a milling cutter are shown in FIGS. 3a, 3b, and 3c depending on the cutting conditions.
Flow-type micro chips 3, shear-type chips 31, crack-type chips 32, and fracture-type chips 3 shown in FIGS.
There are 3 types. Cutting conditions that affect the shape of chips include rake angle 4 (measured clockwise from the normal direction of the cutting surface at the angle formed by the normal direction of the cutting surface and the cutting tool) and the depth of cut shown in Fig. 3a. These include depth 5, cutting speed, and properties of the metal material to be cut.

Figure 2 shows the cutting speed of mild steel (10 to 100m/
2 is a graph showing the state classification of chips generated depending on the depth of cut and the rake angle when cutting is performed at To explain this using FIG. 2, the flow-shaped microchip used in the present invention (indicated by 3 in FIG. 3a) is produced in the region shown in FIG. This is likely to occur under cutting conditions such as a large rake angle, and as shown in FIG. Shear slip occurs in the metal material 1, and the metal material 1 is continuously cut away. In the flow-type micro chips 3, the shear slip that occurs in a direction substantially perpendicular to the cutting direction is approximately equally spaced, very narrow, and appears continuous, and the thickness of the chips is also approximately constant. For this reason, the flow-shaped chips can be easily divided along the shear sliding surface by coarse pulverization using a pulverizing means with a large rubbing action, such as an attritor mill or a ball mill, and easily have a uniform aspect ratio of particle size and thickness. It becomes a flat metal raw material powder of 5 or more, especially 10 or more.

In the region of Fig. 2, that is, the shear type chips 31 that are likely to occur under cutting conditions such as a small depth of cut and a small rake angle, the shear slip is not uniform as shown in Fig. 3b, and the shear slip occurs at regular intervals. Because sliding failure has occurred, uneven chips with deep constrictions are formed at regular intervals. For this reason, the raw material powder obtained by coarsely pulverizing the sheared chips 31 with a Henshall mixer, attritor mill, plastic pellet pulverizer, ball mill, etc. contains many metal powders with small aspect ratios and uneven particle sizes and thicknesses. Therefore, even if further processing is performed, the yield of "oblate metal powder suitable for the purpose of use" will be low, making it unsuitable as a raw material powder for flat metal.

In addition, crack-shaped chips 32 or fracture-shaped chips 33 that tend to occur under cutting conditions such as a small cutting speed, a large depth of cut, and a small rake angle in the area shown in FIG. 2 are shown in FIGS. 3c and 3c. As shown in Figure 3d, it is caused by a brittle crack that occurs instantaneously, so it does not undergo plastic deformation due to the shear slip seen in the flow type chips 3 and the shear type chips 31, and is in the form of granules. Since it is difficult to flatten by coarse grinding, it is unsuitable as a flat metal raw material powder.

In the case of grinding, in general, in order to obtain flow-shaped micro-chips, the cutting depth and rake angle similar to those shown in Fig. 2 can be achieved. Alternatively, the grain size of the abrasive grains adhered to the grinding belt is not completely uniform but has a distribution, and the adhesion angle of the abrasive grains is also not constant. However, empirically, the effective rake angle in the case of grinding is 0° or less, so the flow-shaped micro chips of the present invention are mainly fibrous grinding powder with a length of 30 to 300 μm and a thickness of 50 μm or less. In order to obtain
It is necessary to use abrasive grains of 600 μm, more preferably 60 to 300 μm.

In addition, for example, a fourth grinder with less abrasive grains mixed in, which does not require extra steps such as separating the abrasive grains and grinding chips,
It has the advantage of being able to grind at high speed with a belt grinder, etc. as shown in the figure, and if the ground pieces are coarsely ground with a grinding means that has a large rubbing action, such as an attritor mill or a ball mill, the same product as above can be obtained. It will be done.

A generally known method can be used for coarsely pulverizing the flow-shaped microchips used in the present invention.
For example, there is a method using an attritor mill or a ball mill. In the present invention, a centrifuge or the like was used as a cleaning treatment to remove oil and moisture etc. attached to the flow-type micro chips, but any device that can effectively separate the chips and oil and moisture etc. For example, a solvent method and other generally known methods can be used.

Below, flow-shaped chips are formed based on Fig. 1, and the obtained flow-shaped micro-chips are coarsely pulverized using means with a strong rubbing action, and contain 70% or more of particles with an aspect ratio of 5 or more. We will explain the cutting conditions that will yield a good finished flat metal powder with an aspect ratio of 30 or more with a yield of 90% or more when used as a flat raw material powder.

The inventors used an experimental high-speed milling machine to
Stainless steel, nickel, chromium, titanium, and their alloys were cut at a high cutting speed of 1200 to 1500 m/min, and tests were conducted while changing the cutting depth and rake angle of the cutter, and the results shown in Figure 1 were obtained. Obtained. 1st
In the figure, the a curve indicates that flat raw material powder containing 70% or more of particles with an aspect ratio of 5 or more can be easily obtained, and by further crushing and spreading using means with strong pressing and rubbing action, the aspect ratio can be increased to 30 or more. This is the borderline of flow-shaped chips that can yield more than 90% of finished flat stainless steel powder as a finished product. Curve b indicates that flat raw material powder containing 30% or more of particles with an aspect ratio of 5 or more can be easily obtained, and by further crushing and rolling it using means with strong pressing and rubbing action, a finished flat stainless steel with an aspect ratio of 30 or more can be obtained. It is the boundary line where 60% or more of the powder can be obtained as a finished product, and the c curve is the boundary line between sheared chips and cracked chips or fractured chips.

From this, it is clear that when cutting under the conditions (depth of cut, rake angle) below curve a in Figure 1, flat finished metal powder as described above can be obtained at a high yield (for example, 90% or more). It became.

Although it is possible to obtain the micro chips of the present invention under conditions between both curves a and b in FIG.
Since it is inferior to the conditions below curve a in various aspects such as dimensional uniformity and yield, it cannot be positively recommended.

In the case of grinding, it is best to use a grinding cloth (abrasive cloth) or a grinding belt (abrasive belt) to which abrasive grains of uniform particle size are attached in order to obtain flow-shaped microchips with a uniform average length and thickness. Preferably, as mentioned above, the adhesion angle of the abrasive grains in such a grinding cloth or belt is not constant. but,
In this case, empirically the effective rake angle is −50
It was found that this is considered to be equivalent to approximately 0°. Correspondingly, in order to secure the cutting depth for obtaining the flow-shaped micro-chips of the present invention that belong to the shaded area in FIG. 1, the belt speed of the belt grinder shown in FIG. 1500m/min
In the case of , grinding (polishing) using abrasive grains with particle size numbers #30 (mainly abrasive grains of 500 to 600 μm) to #180 (mainly abrasive grains of 50 to 65 μm) with cloth numbers #30 to #180 ( polish)
Preferably, cloth is used. If the particle size number is smaller than #30, that is, the particle size distribution of mainly abrasive grains is 500~
If it is coarser than 600 μm, the flow-shaped micro chips of the present invention cannot be sufficiently obtained. On the other hand, if the particle size number is larger than #180, that is, if the particle size distribution of mainly abrasive grains is finer than 50 to 65 μm, the cutting efficiency will be extremely reduced, which is undesirable.

<Example> Next, the present invention will be specifically explained using examples.

Example 1 Stainless steel was cut under the following conditions to obtain flow-shaped micro chips.

Rake angle: Approximately -20° Depth of cut: 10μm Cutting speed: 1300m/min The oil and moisture adhering to these chips are removed using a centrifuge.
The mixture was coarsely pulverized in an attritor mill for 2 hours to obtain flat stainless steel raw material powder.

Long diameter: 5 to 30 μm Short diameter: 2 to 15 μm Thickness: 1 to 3 μm More than 90% of the samples had an aspect ratio of 5 or more. 80 for sizes with an aspect ratio of 10 or more
% or more. When the obtained raw material powder was further processed in a ball mill for 7 hours, the major diameter was 5 to 80μ.
90% or more of ultra-thin flat stainless steel flakes with a thickness of 0.1 to 0.5 μm and an aspect ratio of 30 or more were obtained.

Example 2 A titanium plate was cut under the following conditions to obtain flow-shaped micro chips.

Rake angle: Approximately -40° Depth of cut: 3 μm Cutting speed: 1000 m/min The microchips were centrifuged to separate the oil and moisture attached, and ground in a ball mill for 1 hour to obtain flat titanium raw material powder. .

Long diameter: 6 to 30 μm Short diameter: 2.5 to 16 μm Thickness: 1 to 2.8 μm Over 85% had an aspect ratio of 5 or more, and over 80% had an aspect ratio of 10 or more. When the obtained raw material powder was further processed in a ball mill for 6 hours, 80% or more of ultra-thin flat titanium flakes having a major axis of 5 to 80 μm, a thickness of 0.1 to 0.5 μm, and an aspect ratio of 30 or more were obtained.

Example 3 SUS304 stainless steel was ground using a belt grinder (belt grinding machine) shown in FIG. 4 under the following conditions. In the figure, 10 is a belt grinder;
1 is a belt (grinding cloth), 12 and 13 are pulleys with a diameter of 300 mm, 14 is a material to be ground, and the material to be ground 14 is reciprocated in a direction perpendicular to the parallel part of the belt 11 (grinding direction).

Grinding cloth R/R cross belt #80 (main particle size 150~
180 μm) Belt speed: 1200 m/min Moving speed of material to be ground: 10 m/min The obtained microchips exhibit a curled fibrous shape, and the attached oil and moisture are removed using a centrifugal separator. It was pulverized to obtain flat stainless steel raw material powder.

Long diameter: 6 to 40 μm Short diameter: 6 to 20 μm Thickness: 0.9 to 2.8 μm Over 95% of the samples had an aspect ratio of 5 or more. 80 for sizes with an aspect ratio of 10 or more
% or more. When the obtained raw material powder was further ball milled for 6 and a half hours, the major diameter was 5 to 80μ.
90% or more of ultra-thin flat stainless steel flakes with a thickness of 0.1 to 0.5 μm and an aspect ratio of 30 or more were obtained.

Example 4 SUS304 stainless steel was ground using a belt grinder under the following conditions.

Grinding cloth R/R cross belt #120 (main particle size 90~
110 μm) Belt speed: 1200 m/min Moving speed of material to be ground: 10 m/min The obtained micro-chips exhibit a curled fibrous shape, and the attached oil and moisture are removed using a centrifuge, and then coarsely ground for 1 hour using a rod mill. A flat stainless steel raw material powder was obtained.

Long diameter: 6 to 25 μm Short diameter: 6 to 15 μm Thickness: 0.5 to 1.5 μm Over 95% had an aspect ratio of 5 or more, and over 87% had an aspect ratio of 10 or more.

When the obtained raw material powder was further processed in a ball mill, ultra-thin flat stainless steel flakes with a long diameter of 5 to 53 μm, a thickness of 0.1 to 0.3 μm, and an aspect ratio of 30 or more were obtained.
Obtained 94%.

Example 5 SUS316 stainless steel was ground using a belt grinder under the following conditions.

Grinding cloth R/R cross belt #60 (main particle size 210~
250μm) Belt speed: 1200m/min Moving speed of material to be ground: 10m/min The obtained micro-chips exhibit a curled fibrous shape, and the attached oil and moisture are removed using a centrifuge, and coarsely ground for 1 hour using a conical ball mill. A flat stainless steel raw material powder was obtained.

Long diameter: 8 to 60 μm Short diameter: 8 to 35 μm Thickness: 0.5 to 4 μm Over 95% had an aspect ratio of 5 or more, and over 72% had an aspect ratio of 10 or more.

When the obtained raw material powder was further processed in a ball mill, 90% or more of ultra-thin flat stainless steel flakes having a major axis of 5 to 104 μm, a thickness of 0.1 to 0.6 μm, and an aspect ratio of 30 or more were obtained.

Comparative example Water atomized powder of SUS304 steel (average particle size 60μm)
When the material was pulverized in a ball mill, 55% of the flakes were finished as ultra-thin metal flakes with a long diameter of 5 to 80 μm, a thickness of 0.1 to 0.5 μm, and an aspect ratio of 30 or more after 18 hours of processing.

As described above, even though it took several times as long as in Example 3, the yield of finished ultra-thin metal flakes was still very poor.

<Effects of the Invention> According to the method of the present invention, when cutting or grinding a metal material, cutting speed, depth of cut, rake angle, speed of the grinding cloth or grinding belt, particle size distribution of the grinding cloth or the grinding belt, etc. By appropriately selecting the cutting or grinding conditions, it is possible to obtain uniform grain size and thickness simply by coarsely pulverizing flow-shaped micro-chips that occur in the cutting or grinding direction and have shear slip in a direction approximately perpendicular to this direction. Flat metal raw material powder with an aspect ratio of 5 or more can be produced in high yield and at low cost.

The flat metal raw material powder produced by the method of the present invention has a uniform particle size and thickness, and the aspect ratio is about 90% with an aspect ratio of 5 or more, and more than 80% with an aspect ratio of 10 or more. If you add
High aspect ratio (30 or more, preferably 100 or more) with uniform grain size and thickness suitable for the intended use
Because ultra-thin metal flakes can be easily produced, the yield of ultra-thin metal flakes has been greatly improved and the manufacturing cost has been greatly reduced.

[Brief explanation of drawings]

Figure 1 shows the amount of chips generated depending on the depth of cut and rake angle when cutting stainless steel, nickel, chromium, titanium, and their alloys at a cutting speed of 1200 to 1500 m/min using a high-speed experimental milling machine. It is a graph showing the relationship between the shape and the flat metal raw material powder produced from the chips. FIG. 2 is a graph showing the form of chips generated depending on the depth of cut and rake angle when mild steel is cut at a common cutting speed (10 to 100 m/min). Figures 3a, 3b, 3c and 3d are diagrams showing the morphology of micro flow chips, shear chips, crack chips and fracture chips, respectively. FIG. 4 is a schematic diagram of an example of a belt grinder used for grinding according to the present invention. Explanation of symbols, ...area where flow-shaped micro chips are formed, ...area where shear-type chips are formed, ...
Area where crack-shaped chips or fracture-shaped chips occur, 1...
...Workpiece metal material, 2...Cutting tool, 3...Flow-shaped micro chips, 4...Rake angle, 5...Depth of cut,
31...Shear-shaped chips, 32...Crack-shaped chips, 3
3... Fracture-shaped chips, A... Cutting direction (relative direction of movement of the cutting tool), a... Boundary of flow-shaped micro chips that can yield 90% or more of flat stainless steel powder with an aspect ratio of 30 or more. Line, b...aspect ratio 30
The boundary line where 60% or more of the above flat stainless steel powder can be obtained, c... The boundary line between sheared chips and cracked chips or fractured chips.

Claims (1)

[Scope of Claims] 1. A metal material is processed under conditions to form flow-shaped micro-chips having a shearing sliding surface in a direction substantially perpendicular to the direction of cutting or grinding, and the chips are processed on the said shedding sliding surface. In order to preferentially promote micronization by exfoliating flakes along the lines, exfoliation and pulverization is performed using a pulverizing means with a large rubbing action to loosen the flakes, producing flat fine powder mainly consisting of flat powder with an average thickness of 10 μm or less and an aspect ratio of 5 or more. A method for producing flat metal raw material powder suitable for producing ultra-thin metal flakes by crushing and spreading. 2. The grinding means having a large rubbing action is an attritor mill, a ball mill, a conical ball mill, a cone crusher, a rod mill, a conversion tube mill, a tricone mill, a vibration mill, a jet mill, a Henschel mixer, or an aerodynamic mill. A method for producing a flat metal raw material powder according to claim 1. 3. The method for producing flat metal raw material powder according to claim 1 or 2, wherein the main flat powder in the flat fine powder has an aspect ratio of 10 or more.