JPH0253745B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing colored magnetic powder for dry magnetic particle flaw detection.

As is well known, dry magnetic particle testing is a method for detecting defects (cracks, pinholes, etc.) that exist on or near the surface of steel products, steel materials, etc.
It is mainly used in the steel products industry.

[Conventional technology]

First, the technical background of the present invention will be described.

As is well known, "magnetic particle testing" is well known as a typical non-destructive testing method for magnetic materials such as steel materials. In this method, when a magnetizable inspection object (for example, a cast product) is magnetized, if a defect such as a minute crack or pinhole exists on or near the surface of the inspection object, the magnetic resistance of the defect By utilizing the phenomenon that magnetic flux becomes larger than other healthy parts, magnetic flux drifts only in the defective part, and leaks into the air. Synthetic resin is coated with white, yellow, red pigments, dyes, or fluorescent substances that emit yellow to yellow-green light when excited by ultraviolet irradiation (hereinafter referred to as "colorants") on the particle-stopping surface of the particles (hereinafter referred to as "colorants"). Powder attached as a binder (hereinafter referred to as
It is called "colored magnetic powder for magnetic particle flaw detection." ) is scattered on the surface of the object to be inspected, and the portion of the leakage magnetic flux on the surface of the object to be inspected,
In other words, the presence of the defective part can be detected non-destructively on the inspected object by causing the magnetic particles to aggregate and adhere to the defective part to form a defective part indicating magnetic particle pattern by the aggregate of the magnetic particles, and by observing the pattern. , is a method of flaw detection. When dispersing colored magnetic particles for magnetic particle flaw detection onto the surface of the object to be inspected, the method in which the magnetic particles are dispersed in the air and scattered onto the surface of the object to be inspected is called the "dry magnetic particle detection method." It is also well known that the method in which the magnetic particles are dispersed in a dispersion medium such as water or kerosene to form a magnetic particle liquid and the magnetic particle liquid is sprayed onto the object to be inspected is called the "wet magnetic particle testing method." By the way.

When carrying out the dry magnetic particle testing method, normally colored magnetic particles for magnetic particle testing are uniformly scattered over the surface of the magnetized inspection object using a magnetic particle spreader using compressed air, and then the defective area is To make it easier to observe the defect-indicating magnetic particle pattern formed in the defect area, the leakage magnetic flux gathers at the defective part by gently vibrating the object to be inspected or by applying a quiet air flow.・After removing anything that is not attached, the presence of the defect is detected by the defect indicator magnetic particle pattern that remains.
A flaw detection method is used.

Therefore, the colored magnetic powder for magnetic particle flaw detection used in the dry magnetic particle flaw detection method is particularly required to have high fluidity.

On the other hand, the oldest and most practical method for manufacturing colored magnetic particles for magnetic particle flaw detection is to disperse or dissolve a coloring material in a solution of a synthetic resin as a binder dissolved in a solvent. The powders are mixed and kneaded to form a paste, and this paste is dried, then ground using a grinder such as a ball mill, and then classified using a sieve or the like to obtain powder with the desired particle size. This is the method. In addition, recently, a method typified by the method disclosed in JP-A No. 58-142253, in which magnetically conductive powder, a hot-melt synthetic resin as a binder, and a coloring material are mixed, and a solvent is used. Powder with the desired particle size is produced by heating to form a paste-like heated molten material, which is then sprayed into the air using a spray gun or rotating disk type atomizer, cooled, and granulated. A method of obtaining it has also been proposed. In this case, the particle size of the granulated material can be adjusted to a desired size by adjusting the spraying conditions.

Regardless of the above-mentioned crushing method or spraying method, the target object, colored magnetic powder for magnetic particle flaw detection, is usually
It is considered to be a fine powder with a maximum particle size of 60 μm or less and an average particle size of about 20 to 10 μm. This is because the larger the particle size of the powder, the lower the flaw detection accuracy (it becomes impossible to detect minute defects);
When implementing the magnetic particle testing method, it is required to be able to detect defects with a depth of 15/100 mm or more in A-type standard test pieces specified in JIS.G.O565, and in order to meet this requirement, This is because the powder must be a fine powder having the particle size as described above.

Now, colored magnetic particles for magnetic particle flaw detection with a maximum particle size of 60 μm or less and an average particle size of about 20 to 10 μm, which are manufactured by the various methods listed above, do not cause any particular problems when used in wet magnetic particle flaw detection. However, when used in dry magnetic particle testing, there is a problem that the fluidity is insufficient.

That is, the maximum particle size is 60 μm or less, and the average particle size is 20 to 10 μm.
In addition to being very fine, the fluidity is poor due to the use of synthetic resin as a binder.For this reason, when conducting dry magnetic particle testing, a magnetic particle scatterer using compressed air is used to disperse the inspected object. When spraying on the surface, it is difficult to disperse it uniformly, and it is necessary to lightly vibrate the object to be inspected or provide a quiet air flow to remove substances other than those that collect and adhere to the leakage magnetic flux area of the defective part. Even when removing the defective magnetic particles, it is difficult to sufficiently remove the excess without disturbing the defect indicator magnetic particle pattern.

Next, as a means to solve these drawbacks, the following technical means using lubricant powder has been proposed in the art.

One of them is the technique of carrying out a dry magnetic particle detection method using a mixed powder of colored magnetic powder for magnetic particle detection and lubricant powder, as shown in Japanese Patent Publication No. 55-47815. The lubricant powder serves as a dispersion medium for water, kerosene, etc. in wet magnetic particle testing, and the fluidity of colored magnetic powder for magnetic particle testing is hardly a problem. However, since it is necessary to use a large amount of lubricant powder, there are problems in handling and economy.

The second method uses colored magnetic powder for magnetic particle flaw detection, which is obtained by mixing and kneading only three components: magnetically conductive powder, coloring material, and lubricant powder, as disclosed in JP-A-51-73961. In this technology, the amount of lubricant powder used can be 5 to 30% by weight based on the magnetic conductive powder, which is different from the technology shown in the above publication. The disadvantage of using a large amount of lubricant powder has been solved.
In addition to the presence of lubricant powder, since no synthetic resin is used as a binder, the fluidity of the obtained colored magnetic powder for magnetic particle flaw detection is somewhat satisfactory. However, since no synthetic resin is used as the binder, there is a major drawback in that the magnetically conductive powder particles and the coloring material inevitably separate from each other. In addition, if the colored magnetic powder for magnetic particle flaw detection contains a colorant that has peeled off from the magnetically conductive powder, or if the magnetically conductive powder that is not colored by the colorant is mixed in, accurate flaw detection results may not be obtained. It is well known to those skilled in the art that this is not possible. Furthermore, since this technology involves mixing and kneading only the magnetically conductive powder, coloring material, and lubricant powder, it is extremely difficult to achieve a completely homogeneous mixture of the three components, and the lubricant powder is extremely difficult to achieve. There is also a limit to the fluidity improving effect due to the presence of the agent.

[Problem that the invention seeks to solve]

Although the present invention also utilizes lubricant powder as in the case of the above-mentioned prior art, it solves the second problem of the above-mentioned prior art, which is the peeling of the coloring material, and also uses a smaller amount of lubricant powder. The use of lubricant powder brings about a significant improvement in fluidity.

In other words, the present invention has a particle size of 60 μm or less with a maximum particle size of 60 μm or less, which has excellent fluidity, and has minimal peeling of the coloring material and uses a relatively small amount of lubricant powder.
The object of the present invention is to provide colored magnetic powder for dry magnetic particle flaw detection with an average particle size of 25 to 10 μm.

[Means for solving problems]

The present inventor took the following technical means to solve the above problem.

The starting material is colored magnetic powder for magnetic particle flaw detection, which is made by adhering a coloring agent to a magnetically conductive powder using a synthetic resin as a binder.To this, talc, boric acid, silicic acid, magnesia oxide, aluminum oxide, sodium benzoate, stearic acid, and stearin are added. 1 to 10% by weight of a lubricant powder selected from sodium acid, magnesium stearate, and calcium stearate, and a volatile solvent selected from hydrocarbon solvents, halogenated hydrocarbon solvents, alcohol solvents, ketone solvents, and ester solvents. By adding 10 to 40% by weight of a dispersion medium, stirring and mixing, and volatilizing the volatile dispersion medium, the maximum particle size at which the lubricant powder adheres to the particle surface of the colored magnetic powder is determined. This is a technical means (hereinafter referred to as the method of the present invention) which is a method for producing colored magnetic powder for dry magnetic particle testing, which comprises obtaining colored magnetic powder for dry magnetic particle testing with an average particle diameter of 60 μm or less and 25 to 10 μm.

In the method of the present invention, colored magnetic powder for magnetic particle flaw detection is used as a starting material, which is prepared by adhering a coloring material to a magnetically conductive powder using a synthetic resin as a binder. This product is manufactured by a well-known method for manufacturing colored magnetic powder for magnetic particle flaw detection, such as the above-mentioned pulverization method or spraying method. still,
It goes without saying that the particle size of the colored magnetic powder for magnetic particle flaw detection used as a starting material must be selected in consideration of the particle size of the target object. In addition, from the viewpoint of improving fluidity, the particle shape is preferably spherical, and particles granulated by a spraying method using a rotating disk type atomizer are particularly suitable.

In view of the adhesiveness of synthetic resin as a binder, the inventor conducted repeated experiments and prototypes in order to attach magnetically conductive powder to magnetically conductive powder without using synthetic resin. We came to the conclusion that we had no choice but to use a synthetic resin as a binder in order to reduce the amount of damage caused by magnetic particles, and after conducting numerous experiments and prototyping, we developed a well-known colored magnetic powder for magnetic particle flaw detection that uses a synthetic resin as a binder. They have completed the method of the present invention, which can impart great fluidity to starting materials.

The above-mentioned lubricant powders used in the method of the present invention are all well-known, and fine powders with an average particle size of about 10 to 100 μm (primary particles) can be selected from commercially available products. good.

The amount used needs to be at least about 1% by weight or more based on the amount of colored magnetic powder for magnetic particle flaw detection used as a starting material.
If less than 1% by weight is used, fluidity cannot be improved. If the amount used is increased, the fluidity will improve in proportion to the increase up to about 10% by weight, but
No significant difference is observed when the amount exceeds about 10% by weight.

The above-mentioned volatile dispersion media used in the method of the present invention are all well known, but to be more specific, hexane and heptane are used as hydrocarbon solvents, and hexane and heptane are used as halogenated hydrocarbon solvents. methylene chloride, trichloroethane, monofluorotrichloromethane, difluorodichloromethane, dichlorofluoromethane; alcohol solvents include methanol, ethanol, and isopropyl alcohol; ketone solvents include acetone, methyl ethyl ketone, and ester solvents. As such, methyl acetate and ethyl acetate may be used, respectively.

The volatile dispersion medium listed above is essential for uniformly adhering each of the lubricant powders listed above to the surface of each particle of colored magnetic powder for magnetic particle flaw detection, which is the starting material. Only by stirring and mixing the colored magnetic powder for flaw detection, the lubricant powder, and the volatile dispersion medium in the coexistence of the three, can the former two be completely mixed in a uniform state.

The amount used needs to be at least about 10% by weight or more based on the amount of colored magnetic powder for magnetic particle flaw detection used as a starting material.
If less than 10% by weight is used, the lubricant powder cannot be sufficiently dispersed and cannot be uniformly adhered to the surface of each particle of colored magnetic powder for magnetic particle flaw detection. Up to about 40% by weight, the dispersion state becomes better in proportion to the increase in amount, but beyond about 40% by weight, no noticeable difference is observed.

In the method of the present invention, predetermined amounts of colored magnetic powder for magnetic particle flaw detection, lubricant powder, and volatile dispersion medium as described above are thoroughly stirred and mixed, and then the volatile dispersion medium is volatilized to obtain a starting material. A lubricant powder is applied uniformly to the surface of each particle of colored magnetic powder for magnetic particle flaw detection.

When stirring and mixing the above three components, first, a predetermined amount of colored magnetic powder for magnetic particle detection and a predetermined amount of lubricant powder are placed in a well-known Raikai machine and stirred and mixed for 10 to 15 minutes, and then volatilized. Add a predetermined amount of dispersion medium, and then
It is advisable to stir and mix for 10-15 minutes. Also,
In volatilizing the volatile dispersion medium after stirring and mixing, it is desirable to perform suction for 40 to 0 minutes using a well-known sludge collector to volatilize and dry.

By adopting the technical means described above, the maximum particle size at which the lubricant powder is uniformly adhered to the surface of a single particle of colored magnetic powder for magnetic particle flaw detection as a starting material is obtained.
A powder with an average particle size of 25 to 10 μm is obtained, with a particle diameter of 60 μm or less. This powder, as seen in each example below,
It has high fluidity and is optimal as colored magnetic powder for dry magnetic particle testing.

[Effect]

In the method of the present invention, predetermined amounts of colored magnetic powder for magnetic particle detection, lubricant powder, and volatile dispersion medium are mixed together in a wet state with stirring, so an extremely uniform mixing state can be obtained, especially when mixing. The lubricant powder can be sufficiently dispersed in the system. In this mixed system, the synthetic resin used as a binder on the particle surface of the colored magnetic powder for magnetic particle flaw detection becomes slightly swollen and dissolved, and the lubricant powder is uniformly distributed on the particle surface in such a state. It becomes attached to the .

After thorough stirring and mixing, the volatile dispersion medium is volatilized and dried, and the lubricant powder is uniformly and firmly attached to the surface of each particle of colored magnetic powder for magnetic particle flaw detection used as the starting material. The desired object can be obtained.

All of the above-mentioned volatile dispersion media exhibit the above-mentioned effects, but it is preferable to select a volatile dispersion medium depending on the type of synthetic resin used as a binder for the colored magnetic powder for magnetic particle flaw detection as a starting material. The type should be selected.

For example, if polypropylene or cellulose acetate is the binder, use a hydrocarbon solvent or halogenated hydrocarbon solvent, and if polyethylene is the binder, use a halogenated hydrocarbon solvent, alcohol solvent, ketone solvent, or It is preferable to use an ester solvent.

〔Example〕

Next, examples of the method of the present invention will be given. In addition, "parts" in each example means "parts by weight."

Example 1 First, polyethylene wax (molecular weight 500) 60
Heat and melt the part at about 95℃, and add to it a maximum particle size of 30μm.
Add 25 parts of pure iron powder with an average particle size of 9 μm and 15 parts of Lumogen Brilliant Yellow (yellow-green fluorescence) below.
Stir and mix using a homomixer to obtain a viscosity of 500 cp.
Obtain a melt of (measured using a 95C.B type viscometer).

Next, using a rotating disk type atomizer, the above melt is sprayed with air under the following conditions: temperature near the atomizer inlet is about 110°C, temperature near the rotating disk is about 90°C, temperature near the atomizer outlet is about 20°C, and the rotating disk rotation speed is 26000 rpm. Spray inside and cool naturally to achieve maximum particle size.
Colored magnetic powder for magnetic particle flaw detection with an average particle size of 20μm and less than 55μm
Obtained 98 copies. The flow rate of this material is “JIS Z2502−
1979: An attempt was made to measure the fluidity of metal powder using the "Method for Testing Flow Rate of Metal Powders," but the powder did not fall from the funnel and could not be measured.

95 parts of the above colored magnetic powder for magnetic particle flaw detection and an average particle size of about 20
After stirring and mixing 5 parts of microμm (primary particles) aluminum oxide fine powder in a Raikai machine for 10 minutes,
Add 20 parts of acetone, stir and mix for another 10 minutes, and then vacuum dry for 50 minutes using a dust collector to volatilize the acetone and reduce the maximum particle size to 56 μm or less and the average particle size.
99 parts of 21 μm colored magnetic powder for dry magnetic particle testing were obtained. The fluidity of this material was measured according to "JIS Z2502-1979: Flowability test method for metal powder" and was found to be 35.
sec/50g".

The above-mentioned colored magnetic powder for dry magnetic particle flaw detection is applied to an alternating current magnetized pole-to-pole type magnetizer (Bead Magna, product name: Tokushu Toyo Co., Ltd.).
manufactured by JIS.G.), magnetized by applying electricity for about 3 seconds.
The surface of O565 type A standard test piece was sprayed using a well-known magnetic powder spreader using compressed air, and after giving a quiet air flow to the sprayed surface, it was observed under ultraviolet light (black light) irradiation. , 15/100 of the test flat
It can be seen with the naked eye that defective areas with a depth of mm or more are clearly indicated by the yellow-green fluorescent defect indicator magnetic particle pattern, and remaining in healthy areas other than the defect indicator magnetic particle pattern. No colored magnetic particles were observed.

Example 2 First, atactic polypropylene (molecular weight
400) Heat and melt 40 parts at about 150℃, add 50 parts of stainless steel powder with a maximum particle size of 40 μm or less and an average particle size of 20 μm, and 10 parts of titanium white (white), and stir and mix using a homomixer. and the viscosity is 750 cp (150
℃, measured using a B-type viscometer) is obtained.

Next, using a rotating disk type atomizer, the above molten material is atomized with air under the following conditions: temperature near the atomizer inlet is about 170°C, temperature near the rotating disk is about 150°C, temperature near the atomizer outlet is about 35°C, and rotating disk rotation speed is 30,000 rpm. Spray inside and cool naturally to achieve maximum particle size.
Colored magnetic powder for magnetic particle flaw detection with an average particle size of 24 μm and less than 58 μm
Got 99 copies. An attempt was made to measure the fluidity of this material in the same manner as in Example 1, but it did not fall from the funnel and could not be measured.

98 parts of the above colored magnetic powder for magnetic particle flaw detection and an average particle size of about 12
After stirring and mixing 2 parts of micro μm (primary particles) silicic acid powder for 10 minutes using a Raikai machine, 10 parts of difluorodichloromethane was added, stirring and mixing for another 10 minutes, and then suction drying for 40 minutes using a dust collector. to volatilize difluorodichloromethane and reduce the maximum particle size.
99 parts of colored magnetic powder for dry magnetic particle flaw detection with an average particle size of 25 μm and 59 μm or less was obtained. The fluidity of this product was measured in the same manner as in Example 1 and was found to be "33 sec/50 g".

A defect indicating magnetic particle pattern was formed under the same conditions as in Example 1 using the above colored magnetic powder for dry magnetic particle flaw detection, and when observed under a white light, it was found that 15/100mm of the test piece
It can be confirmed with the naked eye that defective areas with depths above are clearly indicated by the white defect indicator magnetic particle pattern, and colored magnetic particles remaining in healthy areas other than the defect indicator magnetic particle pattern can be seen. I couldn't help it.

Example 3 First, polyethylene wax (molecular weight 400) 80
10 parts of γ-Fe ₂ O ₃ powder with a maximum particle size of 5 μm or less and an average particle size of 1 μm and 10 parts of α-Fe ₂ O ₃ powder (red) with the same particle size. and stirred using a homomixer to obtain a viscosity of 300 cp (90℃,
Obtain a melt (measured using a B-type viscometer).

Next, using a rotating disk type atomizer, the above melt is sprayed with air under the following conditions: temperature near the atomizer inlet is about 100 degrees Celsius, temperature near the rotating disk is about 80 degrees Celsius, temperature near the atomizer outlet is about 17 degrees Celsius, and rotation speed of the rotating disk is 32,000 rpm. Spray inside and cool naturally to achieve maximum particle size.
Colored magnetic powder for magnetic particle flaw detection with an average particle size of 17μm and less than 50μm
Obtained 98 copies. An attempt was made to measure the fluidity of this product in the same chamber as in Example 1, but it did not fall from the funnel and could not be measured.

90 parts of the above colored magnetic powder for magnetic particle flaw detection and 10 parts of aluminum oxide powder of about 20 microμm (primary particles) were stirred and mixed in a Raikai machine for 10 minutes, and then mixed with ethanol.
Add 40 parts and stir and mix for another 10 minutes, then suction dry for 60 minutes using a dust collector to volatilize the ethanol to obtain 99 parts of colored magnetic powder for dry magnetic particle testing with a maximum particle size of 52 μm or less and an average particle size of 19 μm. Obtained. The fluidity of this product was measured in the same manner as in Example 1 and was found to be "34 sec/50 g".

A defect indicating magnetic particle pattern was formed under the same conditions as in Example 1 using the above-mentioned colored magnetic powder for dry magnetic particle flaw detection, and when observed under a white light, it was found that 15/100mm of the specimen
It can be confirmed with the naked eye that defective areas with depths above are clearly indicated by the red defect indicator magnetic particle pattern, and colored magnetic particles remaining in healthy areas other than the defect indicator magnetic particle pattern are visible. I couldn't help it.

Example 4 First, 10 parts of cellulose acetate was dissolved in 20 parts of acetone, and the average particle size was added to this solution with a maximum particle size of 5 μm or less.
Add 70 parts of 1 μm triiron tetroxide powder (black) and knead for 60 minutes to form a paste, and dry this paste to obtain a lump.

Next, the above lump was crushed using a ball mill, and the crushed material was passed through a 325 mesh (44μ) sieve to obtain 97 parts of colored magnetic powder for magnetic particle flaw detection having a maximum particle size of 44μm or less and an average particle size of 10μm. An attempt was made to measure the fluidity of this product in the same manner as in Example 1, but it did not fall from the funnel and could not be measured. (In this example, only the triiron tetroxide powder is used to serve the dual roles of "magnetic conductive powder" and "coloring material" in the present invention.) After stirring and mixing 7 parts of silicic acid powder with an average particle size of approximately 50 μm (primary particles) in a Raikai machine for 10 minutes, heptane
Add 30 parts and stir and mix for another 10 minutes, then suction dry for 50 minutes using a dust collector to volatilize the heptane to obtain 99 parts of colored magnetic powder for dry magnetic particle testing with a maximum particle size of 46 μm or less and an average particle size of 11 μm. Obtained. The fluidity of this product was measured in the same manner as in Example 1 and was found to be "38 sec/50 g".

A defect indicating magnetic particle pattern was formed under the same conditions as in Example 1 using the above-mentioned colored magnetic powder for dry magnetic particle flaw detection, and when observed under a white light, it was found that 15/100mm of the specimen
It was confirmed with the naked eye that the defective portions with the above depth were indicated by the black defect indicator magnetic particle pattern.
Further, there was an extremely small amount of colored magnetic powder remaining in the healthy area other than the area with the defect indicator magnetic particle pattern.

Incidentally, the fact that clear defect indications were obtained in each example indicates that peeling and falling off of the coloring material, etc., hardly occurred.

〔effect〕

According to the method of the present invention, colored magnetic powder for dry magnetic particle flaw detection having practically sufficient fluidity can be easily obtained at a high yield, as seen in each of the Examples.

Furthermore, the colored magnetic powder for dry magnetic particle flaw detection obtained by the method of the present invention has a flaw detection accuracy sufficient for practical use.

Claims (1)

[Claims] 1. Starting material is colored magnetic powder for magnetic particle flaw detection, which is made by adhering a coloring agent to magnetically conductive powder using a synthetic resin as a binder. 1 to 10% by weight of lubricant powder selected from sodium acid, stearic acid, sodium stearate, magnesium stearate, and calcium stearate, hydrocarbon solvent, halogenated hydrocarbon solvent, alcohol solvent, ketone solvent, and ester. After adding 10 to 40% by weight of a volatile dispersion medium selected from system solvents and stirring and mixing, the lubricant powder is applied to the particle surface of the colored magnetic powder by volatilizing the volatile dispersion medium. Maximum attached particle size 60μm or less, average
A method for producing colored magnetic powder for dry magnetic particle flaw detection, characterized by obtaining colored magnetic powder for dry magnetic particle flaw detection of 25 to 10 μm. 2. Colored magnetic powder for magnetic particle flaw detection as a starting material is produced by spraying and granulating a heated melt of magnetically conductive powder, a hot melt type synthetic resin as a binder, and a coloring material into the air. A method for producing colored magnetic powder for dry magnetic particle flaw detection according to item 1, which is colored magnetic powder for use in dry magnetic particle flaw detection.