JPH07111421B2 - Manufacturing method of colored magnetic powder for magnetic particle inspection - Google Patents

Description

The present invention relates to a method for producing a colored magnetic powder for magnetic particle flaw detection.

[Conventional technology]

Magnetic particle flaw detection, which is a type of non-destructive inspection method for magnetizable inspected objects such as steel, is standardized in JIS GO 565-1974. Then, in this flaw detection method, the particle surfaces of pure iron particle powder, ferrosoferric oxide particle powder, and stainless steel particle powder (these are referred to as "magnetic particles") that are magnetically conductive particle powders are white, red, or yellow. Those colored with an inorganic or organic dye (such as a "coloring material") such as a pigment or dye exhibiting a color, or a fluorescent dye or the like that is excited by irradiation of ultraviolet rays and emits yellow to yellow-green light. It is well known that "colored magnetic powder" is used.

The colored magnetic powders are roughly classified into those in which a coloring material is fixed to a magnetic powder by using a synthetic resin as a binding material, and those in which the coloring material is directly fixed to a magnetic powder without using a binding material.

The former typical method for producing colored magnetic powder using a binder is the "grinding method", which has been adopted since the oldest and is still in use today.
This is a method called a thermoplastic synthetic resin as a binder, and a coloring material is dispersed or dissolved in a solution of the resin dissolved in a solvent, and magnetic powder is added to this and kneaded to form a paste. In this method, the paste-like material is dried and the solvent is volatilized to form a lump, which is then crushed using a crusher and then classified by a sieve to obtain a colored magnetic powder having a required particle size. is there.

In addition, in the "pulverization method", the coloring material is peeled off together with the binder from the magnetic powder at the time of pulverization, and uncolored magnetic powder and exfoliated substances are mixed in the product, and it is necessary to obtain a product having a required particle size. In view of the disadvantage that the yield is poor as well as being inefficient because it requires classification by a sieve repeatedly, in recent years, the `` spraying method '' represented by the method described in JP-A-60-211358. A method called so far has been proposed, in which a coloring material is dispersed or dissolved in a solution in which a thermoplastic synthetic resin as a binder is dissolved in a solvent, and magnetic particles of a required particle size are added to and mixed with the slurry to form a slurry-like material. Then, the slurry is sprayed using a rotary disk atomizer or a two-fluid nozzle, dried, and made into fine particles to obtain colored magnetic powder having a required particle size. Few, but still It is unavoidable that a considerable amount of uncolored magnetic powder and exfoliated substances are mixed in the product, and the colored magnetic powder that can be produced is limited to those having a relatively large particle size, and the average particle size is about 5 microns or less. It is extremely difficult to obtain the colored magnetic powder.

[Problems to be solved by the invention]

The present invention belongs to a method for producing a colored magnetic powder in which a coloring material is fixed to a magnetic powder by using a synthetic resin as a binder, and an uncolored magnetic powder in a product common to the "crushing method" and the "spraying method" Solving the problem of mixing with exfoliated matter and the problem of poor yield inherent in the "crushing method" and "spraying method"
The technical problem is to solve the problem that it is difficult to obtain colored magnetic powder having an average particle size of about 5 microns or less, which is inherent in the above.

In addition, when magnetic powder flaw detection is performed using colored magnetic powder containing uncolored magnetic powder or exfoliated material, a clear defect indication pattern cannot be obtained, and the flaw detection accuracy may significantly decrease. Well known in the industry.

[Means for solving problems]

The present inventor has achieved the above technical problem by taking the following technical means.

That is, 40 to 90 parts of pure iron particle powder, ferrosoferric oxide particle powder or stainless steel particle powder having an average particle diameter within the range of 1 micron to 10 micron is used as the magnetic powder. Add 5 to 20 parts of thermoplastic synthetic resin particle powder having an average particle size equal to or smaller than the average particle size of the target magnetic powder as a binder, mix both powders in the state of primary particles, and mix the powder Particle velocity in phase 60-16
A film of the binder is formed by a mechanochemical reaction on each particle surface of the target magnetic powder by accelerating the particles to 0 m / sec for 1 to 3 minutes to collide with each other, and further, as a coloring material, Add 5 to 20 parts of an inorganic or organic pigment particle powder having an average particle size smaller than that of the magnetic powder forming the binder coating, and mix both powders in the state of primary particles,
By accelerating the mixed powder in the gas phase to a particle velocity of 60 to 160 m / sec and causing the particles to collide with each other for 1 to 3 minutes, the coloring agent is mechanically attached to each particle surface of the magnetic powder on which the binder coating is formed. It is a method for producing a colored magnetic powder for magnetic particle flaw detection, which comprises fixing by a chemical reaction.

The magnetic powder used in the method of the present invention is a pure iron particle powder, a ferrosoferric oxide particle powder or a stainless steel particle powder having an average particle size within the range of 1 to 10 microns. All of these are commonly used for magnetic particle flaw detection, and there are commercial products, and those having a desired average particle size are easily available.

When manufacturing colored magnetic powders used for precise magnetic particle flaw detection, magnetic powders with a required average particle size within the range of average particle size 1 micron to average particle size 5 microns should be selected. When the colored magnetic powder used for the magnetic particle flaw detection is manufactured, the magnetic powder having the required average particle diameter within the range of the average particle diameter of 5 μm to the average particle diameter of 10 μm may be selected.

Using 40 to 90 parts of the above-mentioned magnetic powder means that when performing magnetic powder flaw detection using the obtained colored magnetic powder, if it is less than 40 parts, the ability to collect and adhere to defective parts (magnetic sensitivity) will be small and accurate. This is because it is difficult to obtain a satisfactory flaw detection result, and when it is 90 parts or more, the amounts of the binder and the coloring agent are too small, and sufficient fixing effect and coloring effect cannot be obtained.

The thermoplastic synthetic resin as the binder in the method of the present invention,
Nylon 12, which is commonly used in the production of colored magnetic powder, is a thermoplastic synthetic resin such as polystyrene resin, but its form is required to be in the form of particles, and the average selected from the above target range. It must be a particle powder with an average particle size equal to or smaller than the magnetic powder with a particle size. More specifically, for example, when a magnetic powder having an average particle size of 1 micron is targeted, a thermoplastic synthetic resin particle powder having an average particle size of 1 micron or an average particle size of 1 micron or less is used. When a thermoplastic synthetic resin particle powder having an average particle size larger than that of the target magnetic powder is used, it becomes difficult to form a film by a mechanochemical reaction. The smaller the average particle size of the thermoplastic synthetic resin particle powder is than that of the target magnetic powder, the easier it is to form the thermoplastic synthetic resin coating layer on the surface of each particle of the magnetic powder. It is preferable to select one having an average particle size of 1/5 or less of the average particle size of the target magnetic powder.

Using 5 to 20 parts of the thermoplastic synthetic resin particle powder,
If it is 5 parts or less, it will be difficult to form a film necessary for firmly fixing the coloring material described later, and if 20 parts or more is used, the amount of the magnetic powder and the coloring material which are the essential components of the colored magnetic powder are used. Is less, and colored magnetic powder having a sufficient flaw detection ability cannot be obtained.

Inorganic or organic dye as a coloring material in the method of the present invention,
Titanium white, inorganic pigments such as Benji, which are commonly used in the production of colored magnetic powder, Hansa Yellow 5G (trade name: yellow pigment)
Organic pigments such as Brilliant Carmine 3G (trade name: red pigment) and fluorescent dyes such as Lumogen Brilliant Yellow (trade name: fluorescent dye), but the form thereof is required to be particulate, and , The particle powder should have a smaller average particle size than the average particle size of the magnetic powder with the binder coating. When a magnetic powder having a binder coating and having an average particle size equal to or larger than the average particle size of the magnetic powder is used, it is extremely difficult to fix the particles by a mechanochemical reaction. The smaller the average particle size of the inorganic or organic pigment particle powder is than that of the magnetic powder on which the binder coating is formed, the easier the fixation becomes. It is preferable to select one having an average particle diameter of 1/10 or less of the average particle diameter of the magnetic powder having the binder coating formed thereon.

Using 5 to 20 parts of the inorganic or organic dye particles powder,
If it is 5 parts or less, it is difficult to obtain a sufficient coloring effect, but 5 parts or less
This is because when used up to 20 parts, a practically sufficient coloring effect can be obtained.

The thermoplastic synthetic resin particle powder and the inorganic or organic pigment particle powder may be selected from commercially available products having a required average particle diameter, or a commercially available powdered product may be crushed to a required average particle diameter before use. Good.

The method of the present invention comprises forming a coating film of the thermoplastic synthetic resin particle powder as described above on each particle surface of the magnetic powder as described above, and firmly fixing the inorganic or organic dye particle powder as described above to the coating film. Is. For this purpose, it is first necessary to mix the magnetic powder and the thermoplastic synthetic resin particle powder in a state where one particle and one particle are discrete primary particles and cause the mixed powder to cause a mechanochemical reaction. is there. Since both powders are fine particles in the unit of micron, they are usually in a state of agglomeration, but both powders are circulated at a blade tip peripheral speed of 4-10m / sec and rotation speed by a high-speed stirrer equipped with a rotary blade. 1000-3500 RPM
If the mixture is stirred for 3 to 5 minutes under the above condition, a mixture sufficiently mixed in the state of primary particles can be easily obtained.

A mixture in which magnetic powder and thermoplastic synthetic resin particle powder are mixed in the state of primary particles, using a known high-speed rotating mill or jet mill, the powder is accelerated in the gas phase to a particle velocity of 60 to 160 m / sec. When the particles collide with each other for 1 to 3 minutes, the magnetic powder particles become core particles, the thermoplastic synthetic resin particles become sub-particles, and a uniform film is formed on the surface of the core particles by the mechanochemical reaction, and the heat on the surface is increased. A magnetic powder in which a plastic synthetic resin film is formed and one of which is almost in a scattered state can be obtained.

Next, one piece of the magnetic powder and the inorganic or organic pigment particle powder on which the thermoplastic synthetic resin coating is formed on the above-mentioned surface, one particle is mixed in the state of discrete primary particles, and the mixed powder also It is necessary to cause mechanochemical reaction. Also in this case, both powders are usually in an agglomerated state, but under the same conditions as above, both powders can be easily made into a sufficiently mixed mixture in the state of primary particles.

A mixture of a magnetic powder having a thermoplastic synthetic resin coating formed on its surface and an inorganic or organic pigment particle powder mixed in the state of primary particles, similarly to the above, using a known high-speed rotating mill or jet mill, powder Particle velocity in the gas phase of 60 to 160 m / s
By accelerating to ec and colliding the particles with each other for 1 to 3 minutes, the magnetic powder particles having the thermoplastic synthetic resin coating formed on the surface become core particles, and the inorganic or organic pigment particles become child particles,
By the mechanochemical reaction, the child particles are uniformly and firmly adhered to the surface of the core particles, and a colored magnetic powder in which one particle is in a disjointed state is obtained.

Accelerating the particle velocity to 60-160 m / sec is 60.m / sec or less, but if it is 60.m / sec or less, the mechanical and thermal energy necessary for causing the mechanochemical reaction cannot be obtained. In the case of accelerating to 1, a sufficient film forming effect or a fixing effect due to the mechanochemical reaction is obtained. The higher the particle velocity, the greater these effects, but in practice
Up to 160m / sec is enough.

The time for the particles to collide is 60-160m / sec.
In this case, at least 1 minute or more is required, and a practically sufficient film-forming effect or sticking effect can be obtained with a collision time of 1-3 minutes.

[Action]

As described above, the magnetic powder and the thermoplastic synthetic resin particle powder are used, both powders are mixed in the state of primary particles, and the mixture is accelerated in the gas phase to a particle velocity of 60 to 160 m / sec to make particles 1
When they are collided for ~ 3 minutes, the mechanical and thermal energy generated from the impact force and frictional force at the time of collision causes mechanochemical reaction between the magnetic particles as the core particles and the resin particles as the child particles. A coating of resin particles, which are child particles, is formed on the surface of each magnetic powder particle that is a core particle.

The present inventor has confirmed by microscope observation that a smooth resin coating is formed on the surface of each magnetic powder particle and that the thermoplastic synthetic resin particles used have melted.

Further, as described above, using a magnetic powder having a thermoplastic synthetic resin coating formed on the surface and an inorganic or organic pigment particle powder, both powders are mixed in the state of primary particles, and the mixture has a particle velocity of 60 in the gas phase. When the particles are collided with each other for 1 to 3 minutes by accelerating to ~ 160 m / sec, the magnetic powder particles and the child particles, which become the core particles by the mechanical / thermal energy generated from the impact force and the frictional force at the time of collision, A mechanochemical reaction occurs with the dye particles, and the dye particles, which are the child particles, firmly adhere to the surfaces of the magnetic powder particles, which are the core particles.

The present inventor, by microscopic observation, the inorganic or organic pigment particles adhere to the surface of each of the magnetic powder particles in the form of a film having fine irregularities, and the irregularities are compared with the case where the inorganic pigment particles are used. Then, it was confirmed that when organic dye particles were used, finer irregularities were formed. This result shows that the inorganic pigment particles are embedded in the surface of the resin coating, and the organic pigment particles are embedded in the surface of the resin coating, and a part thereof is melted.

〔Example〕

The method of the present invention will be described in more detail with reference to examples. still,
"Parts" means "parts by weight".

Example 1. Pure iron particle powder 90 having an average particle diameter of 5 microns commercially available as magnetic powder 90
Commercially available nylon with an average particle size of 5 microns
12 parts (heat distortion temperature 150 ° C) and 5 parts, using a high-speed stirring mixer, 4 at a stirring blade tip speed of 8 m / sec and a rotation speed of 1200 RPM.
Mixing for minutes gave a mixed powder.

Next, the mixed powder was accelerated to a particle velocity of 120 m / sec using a high-speed rotating mill, and the particles were collided with each other for 3 minutes to obtain 93 parts of granulated particles having an average particle diameter of 7 microns.

Furthermore, 93 parts of the above granulated particles and a commercially available average particle size as a coloring material
5 parts of 0.2 micron titanium white was mixed under the same conditions as above using a high-speed stirring mixer to obtain a mixed powder.

Next, the above mixed powder was made to collide with each other under the same conditions as above using a high-speed rotary mill to obtain 96 parts of colored magnetic powder having an average particle diameter of 8 microns.

The colored magnetic powder was taken out from the high-speed rotary mill and used as it was for the following magnetic particle flaw detection.

The surface of a 80 mm square billet in which 2 g of the above-mentioned colored magnetic powder per 1 water is dispersed with a dispersant (use 20 ml of surfactant per 1 water), and a magnetic powder liquid is electrified (DC-1000A) by the axial electrification method. By observing the sprayed surface under visible light, it can be confirmed that the defect portion with a depth of 0.15 mm existing on the surface of the square billet is clearly indicated by the white defect instruction pattern. It was This flaw detection result shows that the peeling and dropping of the coloring material hardly occurred.

Example 2. Pure iron particle powder 90 having an average particle diameter of 3 microns, which is commercially available as magnetic powder
Parts and 5 parts of a commercially available polystyrene resin having an average particle size of 3 microns (heat distortion temperature 80 to 90 ° C) as a binder, using a high-speed stirring mixer, a stirring blade tip speed of 9 m / sec, a rotation speed of 1400.
Mixed by RPM for 4 minutes to obtain a mixed powder.

Next, the mixed powder was accelerated to a particle velocity of 120 m / sec using a high-speed rotary mill, and the particles were collided with each other for 5 minutes to obtain 93 parts of granulated particles having an average particle diameter of 4 microns.

Furthermore, 93 parts of the above granulated particles and a commercially available average particle size as a coloring material
5 parts of 0.2 micron brilliant carmine 3G (trade name: red pigment) was mixed under the same conditions as above using a high-speed stirring mixer to obtain a mixed powder.

Next, the mixed powder was made to collide with each other under the same conditions as above using a high-speed rotary mill to obtain 96 parts of colored magnetic powder having an average particle diameter of 5 microns.

The colored magnetic powder was taken out from the high-speed rotary mill and used as it was for the following magnetic particle flaw detection.

A magnetic powder solution prepared by dispersing 2 g of the above-mentioned colored magnetic powder per water with a dispersant (using 20 ml of surfactant per 1 water) was applied to the surface of an 80 mm square billet which was energized (DC-1000A) by the axial energization method. When sprayed and the sprayed surface was observed under visible light, it was confirmed that the defect portion having a depth of 0.15 mm existing on the surface of the square billet was clearly indicated by the defect indicating pattern showing red. This flaw detection result shows that the peeling and dropping of the coloring material hardly occurred.

Example 3. Pure iron particle powder 90 having an average particle size of 5 microns, which is commercially available as magnetic powder
Parts and 5 parts of a commercially available polystyrene resin having an average particle size of 3 microns (heat deformation temperature of 80 to 90 ° C) as a binder, using a high-speed stirring mixer, a stirring blade tip speed of 8 m / sec, a rotation speed of 1200
Mixed by RPM for 4 minutes to obtain a mixed powder.

Next, the mixed powder was accelerated to a particle velocity of 120 m / sec using a high-speed rotating mill, and the particles were collided with each other for 3 minutes to obtain 93 parts of granulated particles having an average particle diameter of 7 microns.

Furthermore, 93 parts of the above granulated particles and a commercially available average particle size as a coloring material
5 parts of 0.5 micron Lumogen Brilliant Yellow (trade name: Fluorescent dye) and a high-speed stirring type mixer,
Mixed under the same conditions as above to obtain a mixed powder.

Next, the mixed powder is made to collide with each other under the same conditions as above using a high-speed rotating mill to give a colored magnetic powder having an average particle diameter of 8 microns (which is called "fluorescent magnetic powder" in the art). ) 96 parts were obtained.

The colored magnetic powder was taken out from the high-speed rotary mill and used as it was for the following magnetic particle flaw detection.

A magnetic powder liquid prepared by dispersing 0.5 g of the above-mentioned colored magnetic powder per 1 water using a dispersant (using 20 ml of surfactant per 1 water) was electrified (DC-1000A) by an axial electrification method to obtain an 80 mm square billet. When sprayed on the surface and irradiated with ultraviolet light using a black light on the sprayed surface and observed in a dark place, the defect part with a depth of 0.15 mm present on the surface of the square billet has a defect indicator pattern showing yellow-green fluorescence. It was confirmed that it was clearly instructed. This flaw detection result shows that the peeling and dropping of the coloring material hardly occurred.

〔effect〕

According to the present invention, a colored magnetic powder in which a coloring material is firmly fixed to a magnetic powder by using a synthetic resin as a binder can be produced with high efficiency and high yield.

In particular, according to the present invention, the coloring material hardly peels off together with the binder from the magnetic powder during the manufacturing process, and therefore, the uncolored magnetic powder and the peeled material almost never enter the product. Absent.

Further, according to the present invention, the average particle size of the target magnetic powder can be freely selected from a relatively small one to a relatively large one, and the binder and the coloring material are uniformly fixed to each magnetic powder particle. There is one and one colored magnetic powder in a disjointed state is obtained without crushing and sieving steps,
Since the obtained colored magnetic powder is proportional to the average particle size of the target magnetic powder, colored magnetic powder having a required average particle size can be easily manufactured.

Claims (1)

[Claims] 1. As magnetic powder, 40 to 90 parts of pure iron particle powder, ferrosoferric oxide particle powder or stainless steel particle powder having an average particle size of 1 micron to 10 micron. 5 to 20 parts of a thermoplastic synthetic resin particle powder having an average particle diameter equal to or smaller than the average particle diameter of the target magnetic powder as a binder is added thereto, and both powders are mixed in the state of primary particles, Particle velocity of mixed powder in gas phase
The coating of the binder is formed on the surface of each particle of the magnetic powder by colliding the particles with each other for 1 to 3 minutes by accelerating to 60 to 160 m / sec by a mechanochemical reaction, and further,
5 to 20 parts of an inorganic or organic pigment particle powder having an average particle diameter smaller than that of the magnetic powder having the binder coating formed thereon as a coloring material is added thereto, and both powders are mixed in a primary particle state, By accelerating the mixed powder in a gas phase to a particle velocity of 60 to 160 m / sec and causing the particles to collide with each other for 1 to 3 minutes, the coloring agent is mechanically attached to each particle surface of the magnetic powder on which the binder coating is formed. A method for producing a colored magnetic powder for magnetic particle flaw detection, which is characterized in that it is fixed by a chemical reaction.