JP2022121946A - Method for manufacturing fluorescent magnetic powder for wet magnetic powder flaw detection test - Google Patents

Abstract

To provide fluorescent magnetic powder for wet magnetic powder flaw detection test that is obtained by coating, with water-soluble resin, a surface of a composite particle obtained by attaching fluorescent pigment to a surface of a magnetic powder particle with water-soluble resin therebetween, in which the fluorescent pigment is hardly peeled off and falls off in fluorescent magnetic powder liquid and during a flaw detection test, a background phenomenon hardly occurs, and the fluorescent pigment remains on the surface of the magnetic powder particle at a high ratio, and thus fluorescent magnetic powder liquid can be manufactured which can obtain a clear defect indication pattern with the remarkable difference between a defective part and a part other than the defective part.SOLUTION: A method for manufacturing fluorescent magnetic powder for wet magnetic powder flaw detection test includes: granulating a mixture containing 20 weight%-40 weight% of magnetic powder having a median diameter of 2 μm-7 μm, 5 weight%-12 weight% of water-soluble resin-containing emulsion having a glass transition temperature of 10°C or less, 5 weight%-25 weight% of fluorescent pigment, and water; dispersing 10 weight% or more-55 weight% of the granulated particles in an aqueous solution containing 5 weight-35 weight% of the water-soluble resin-containing emulsion; and subsequently performing granulation again to manufacture the fluorescent magnetic powder for wet magnetic powder flaw detection test.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing fluorescent magnetic particles for wet magnetic particle testing. More specifically, the fluorescent magnetic powder produced by the present invention is a fluorescent magnetic powder obtained by coating the surface of composite particles, in which a fluorescent pigment is attached to the surface of magnetic powder particles via a water-soluble resin, with a water-soluble resin. Since the fluorescent pigment does not easily peel off or fall off in the magnetic powder liquid or during the flaw detection test, the background phenomenon due to the peeled off or fallen off fluorescent pigment hardly occurs, and the ratio of the fluorescent pigment remaining on the surface of the magnetic powder particles is large. Manufacture of fluorescent magnetic powder for wet magnetic particle testing that can produce a fluorescent magnetic powder liquid that can detect fine opening defects and defects directly under the surface without openings with high detection sensitivity because a clear defect indication pattern can be obtained. The method.

As is well known, the wet magnetic particle test method is standardized in JIS-Z-2320, and this test method is used for magnetized inspection objects, such as steel parts such as shafts, magnetic bodies and billets. Magnetic particles for wet-type magnetic particle testing are used on steel materials, magnetic materials, etc. Fluorescent pigments such as Gen Yellow S0790 (manufactured by BASF) and Festa A (manufactured by Swada) have an average particle diameter of 3 to 30 μm (volume distribution, hereinafter the same) and a true specific gravity of 2 to 5 g / cm ³ powder (hereinafter referred to as "magnetic powder") is dispersed in water and applied to the opening defect of the inspection object (fine cracks and pinholes existing on or near the surface of the inspection object). A test method in which magnetic particles dispersed in a liquid are aggregated to form a defect indication pattern, and an opening defect is detected by this defect indication pattern (hereinafter, this test method is referred to as a "wet magnetic particle flaw detection test").

Methods for producing magnetic powder include those called "pulverization method" and "spraying method" among those skilled in the art.

In the pulverization method, an organic solvent-soluble synthetic resin is used as a binder, and a fluorescent pigment is dispersed in a solution in which the binder is dissolved in a volatile organic solvent. In this method, the paste is dried to form lumps, pulverized into fine particles using a pulverizer such as a ball mill, and classified by a sieve or the like to obtain fluorescent magnetic powder having a desired particle size.

The spraying method involves adding a magnetic powder, a fluorescent pigment, and a binder made of a water-dispersible or water-soluble synthetic resin to water to form a paste, and spraying the paste into the air using a spray nozzle or a centrifugal disk. Another method is to obtain spherical fluorescent magnetic powder having a desired particle size in which the magnetic powder and the fluorescent pigment are adhered via a synthetic resin by scattering and drying and granulating.

Fluorescent magnetic powder is dispersed in a dispersion liquid such as water to prepare a fluorescent magnetic powder solution. Since the fluorescent pigment adheres to the surface of the inspected object other than the defect portion and emits fluorescence, a so-called background phenomenon occurs in which the defect indication pattern becomes difficult to see, resulting in a problem of reduced defect detection sensitivity.

In addition, when the fluorescent pigment peels off or comes off, the amount of the fluorescent pigment covering the surface of the magnetic powder particles is reduced, so that the brightness of the defect indication pattern is lowered, and the detection sensitivity of the defect portion is lowered.

Therefore, the fluorescent pigment strongly adheres to the surface of the magnetic powder particles, and the fluorescent pigment is difficult to peel off or fall off in the fluorescent magnetic powder liquid or during the flaw detection test, so that the background phenomenon does not easily occur, and the surface of the magnetic powder particles is coated. There is a demand for the development of a fluorescent magnetic powder that allows the production of a fluorescent magnetic powder solution that retains a high proportion of the fluorescent pigment and provides a clear defect indication pattern and high detection sensitivity.

JP 2004-101193

In Patent Document 1, magnetically conductive particles, a fluorescent coloring agent, and a binder are dissolved or dispersed in a solvent to form a paste, which is then dried. Fluorescent magnetic powder is described which is produced by spray-drying a paste of a synthetic resin emulsion dispersed in water.

However, if a fluorescent magnetic powder solution is prepared using the fluorescent magnetic powder produced by the production method described in Patent Document 1, the fluorescent pigment on the surface of the magnetic powder particles is likely to peel off or fall off in the fluorescent magnetic powder solution. Since the fluorescent pigment on the surface of the magnetic powder particles tends to peel off or come off, the luminance of the defect indication pattern is low, and the background phenomenon tends to occur, resulting in low detection sensitivity.

The inventors of the present invention made it a technical task to solve the above-mentioned problems, and as a result of repeated trial and error trial production and experiments, 20 weights of magnetic powder with a median system of 2 µm or more and 7 µm or less % or more and 40 wt% or less, the resin content of the water-soluble resin-containing emulsion having a glass transition temperature of 10 ° C. or less is 5 wt% or more and 12 wt% or less, and the fluorescent pigment is 5 wt% or more, and , 25% by weight or less and water are granulated, and an aqueous solution containing 5% by weight or more and 35% by weight or less of the resin content of the water-soluble resin-containing emulsion is added with 10% by weight or more and 55% by weight or less. Fluorescent magnetic powder prepared by re-granulating after dispersing the granulated particles in an amount of 1% by weight or less is a fluorescent magnetic powder in which the fluorescent pigment is firmly adhered to the surface of the magnetic powder particles. Since the fluorescent pigment does not easily peel off or come off during the flaw detection test, the background phenomenon is less likely to occur.In addition, since a high percentage of the fluorescent pigment remains on the surface of the magnetic powder particles, the difference between the defective area and the non-defective area is remarkable. Acquiring a remarkable knowledge that a clear defect indicating pattern can be obtained, the fluorescent magnetic particle liquid can detect open defects and non-opening defects directly under the surface with high detection sensitivity, and the above technical problems have been achieved. It is what I did.

The above technical problems can be solved by the present invention as follows.

The present invention comprises a water-soluble resin-containing emulsion containing 20% by weight or more and 40% by weight or less of magnetic powder having a median system of 2 μm or more and 7 μm or less, and a glass transition temperature of 10° C. or less, and 5 weight percent of the resin content. % or more and 12% by weight or less, 5% by weight or more and 25% by weight or less of a fluorescent pigment, and water are granulated, and the resin content of the water-soluble resin-containing emulsion is 5% by weight. Production of fluorescent magnetic powder for wet magnetic particle testing by dispersing 10% by weight or more and 55% by weight or less of the granulated particles in an aqueous solution containing the above and 35% by weight or less, and then granulating again. The method.

The present invention also provides a method for producing the fluorescent magnetic powder for wet magnetic particle testing, wherein the granulation method is spraying.

Further, the present invention is a method for producing the fluorescent magnetic powder for wet magnetic particle testing, wherein the solid content of the magnetic powder, the fluorescent pigment and the water-soluble resin in the mixture is 65% by weight or less.

Further, the present invention is a method for producing the fluorescent magnetic powder for wet magnetic particle testing, wherein the particles granulated from the mixture are composite particles in which a fluorescent pigment is attached to magnetic powder.

The present invention also provides a fluorescent magnetic particle liquid for wet magnetic particle testing, which is obtained by dispersing the fluorescent magnetic particles produced by the above production method.

The fluorescent magnetic powder in the present invention contains 20% to 40% by weight of magnetic powder having a median system of 2 μm to 7 μm, and 5% to 12% by weight of a water-soluble resin-containing emulsion having a glass transition temperature of 10° C. or less. and a mixture containing 5% to 25% by weight of a fluorescent pigment and water is granulated to produce composite particles in which the fluorescent pigment is attached to the surface of the magnetic powder particles via a water-soluble resin, and then the water-soluble After dispersing 10% to 55% by weight of the composite particles in an aqueous solution containing a water-soluble resin-containing emulsion having a resin content of 5% to 35% by weight, the composite particles are granulated again to produce. , the composite particles are coated with a water-soluble resin to form a fluorescent magnetic powder.

Since the fluorescent magnetic powder produced by the manufacturing method of the present invention has a small amount of the fluorescent pigment that peels off or falls off during the fluorescent magnetic powder liquid or during the flaw detection test, the peeled off fluorescent pigment adheres to the surface of the inspected object other than the defective portion and emits fluorescence. It is possible to produce a fluorescent magnetic powder liquid that is less likely to cause a so-called background phenomenon.

In the case of the fluorescent magnetic powder according to the present invention, since the amount of the fluorescent pigment that peels off or falls off in the fluorescent magnetic powder solution is small, a high percentage of the fluorescent pigment remains on the surface of the magnetic powder particles, and the magnetic powder particles can be re-sprayed. Fluorescent pigments that have peeled off from the surface or that have not adhered to the surface of the magnetic powder particles are dispersed in the water-soluble resin-containing emulsion and coat the surface of the composite particles. It is possible to prepare a fluorescent magnetic powder liquid with high detection sensitivity that can detect even an open defect portion or a non-opened defect portion just below the surface.

In particular, if granulation is performed by spraying, fluorescent magnetic powder with a uniform particle size can be produced. It is possible to prepare a fluorescent magnetic powder solution with high detection sensitivity that can detect even

Further, when the total solid content of the magnetic powder, fluorescent pigment and water-soluble resin in the mixture is 65% by weight or less, the mixture is suitable for granulation by spraying.

In the fluorescent magnetic powder liquid in which the fluorescent magnetic powder is dispersed according to the present invention, the background phenomenon hardly occurs and the fluorescent pigment of the fluorescent magnetic powder remains at a high ratio, so that the difference between the defective portion and the non-defective portion is remarkable and the defect indication pattern is clear. Therefore, it is a fluorescent magnetic powder liquid that can detect fine opening defects and non-opening defects just below the surface with high detection sensitivity.

It is a figure which compared peeling water. It is a figure showing the measuring method of exfoliation brightness.

The fluorescent magnetic powder in the present invention is obtained by granulating composite particles from a slurry mixture of a magnetic powder, a water-soluble resin-containing emulsion, a fluorescent pigment, and water, and then adding the composite particles to an aqueous solution containing the water-soluble resin-containing emulsion. Since the particles are dispersed and sprayed again, the composite particles become fluorescent magnetic particles coated with a water-soluble resin.

(Magnetic powder)
The magnetic powder contained in the mixture in the present invention is not particularly limited.
Examples of the magnetic powder include reduced iron powder, electrolytic iron powder, γ-ferric oxide powder, and triiron tetraoxide powder.

The median diameter of the magnetic powder particles is preferably 2 μm to 7 μm, more preferably 3 μm to 5 μm.

If the median system is less than 2 μm, the brightness of the fluorescent magnetic particle liquid may be low and the detection sensitivity of the opening defect portion may be lowered. is.

The content of the magnetic powder in the mixture is preferably 20% to 40% by weight, more preferably 30% to 37% by weight.

If the content of the magnetic powder is less than 20% by weight, the amount of the fluorescent pigment that does not adhere to the surface of the magnetic powder particles increases, so that the background phenomenon that the fluorescent pigment adheres to the surface of the object to be inspected except for defects and emits fluorescence tends to occur. This is because there is a possibility that the detection sensitivity of the defective portion is lowered.

On the other hand, if the content exceeds 40% by weight, the solid content in the mixture becomes too large, making it difficult to granulate by spraying.

(Emulsion containing water-soluble resin)
The mixture used in the present invention is an emulsion containing a water-soluble resin having a glass transition temperature of 10° C. or less.

This is because if the glass transition temperature exceeds 10° C., the composition is likely to be cured, and there is a risk that fine powder of the water-soluble resin will precipitate after spraying.

A water-soluble resin having a glass transition temperature of 10° C. or lower is not particularly limited.

Examples of water-soluble resin-containing emulsions in the present invention include acrylic acid ester emulsions, styrene-acrylic emulsions, and styrene-butadiene emulsions.

The resin content of the water-soluble resin-containing emulsion contained in the mixture is preferably 5% to 12% by weight, more preferably 6% to 10% by weight.

If the content is less than 5% by weight, the amount of the fluorescent pigment that peels off or falls off from the composite particles increases, and background phenomena tend to occur. This is because there is a possibility that the detection sensitivity may be lowered in both cases.

(Fluorescent pigment)
The mixtures according to the invention contain fluorescent pigments.

Although the fluorescent pigment is not particularly limited, Lumogen Yellow S0790 (manufactured by BASF) and Festa A (manufactured by Swada) can be exemplified.

The content of the fluorescent pigment in the mixture is preferably 5% to 25% by weight, more preferably 10% to 15% by weight.

This is because if the amount is less than 5% by weight, the brightness of the defect indication pattern is low, and thus the detection sensitivity may be lowered.

On the other hand, if the content exceeds 25% by weight, the solid content in the mixture increases and the viscosity becomes too high, making it difficult to granulate by spraying.

The mixture is preferably in the form of slurry with a viscosity of 100 cP or less. This is because it is easily granulated by a spray method.

The solid content of the magnetic powder, fluorescent pigment and water-soluble resin in the mixture is preferably 65% by weight or less.

This is because if the amount exceeds 65% by weight, the viscosity becomes too high and granulation by spraying becomes difficult.

The mixture can be granulated by atomizing it into the air at elevated temperature using a spray dryer to drive off water from the droplets and dry them.

As a result, composite particles in which the fluorescent pigment is attached to the surface of the magnetic powder particles via the water-soluble resin can be obtained.

The fluorescent magnetic powder in the present invention is produced by dispersing the composite particles in an aqueous solution comprising a water-soluble resin-containing emulsion having a glass transition temperature of 10° C. or less and water, and then granulating the dispersion again.

In the aqueous solution containing the water-soluble resin-containing emulsion in which the composite particles are dispersed, the fluorescent pigment that has been peeled off or dropped from the surface of the magnetic powder particles is dispersed. to coat the surface.

The amount of the composite particles dispersed in the aqueous solution containing the water-soluble resin-containing emulsion is preferably 10% to 55% by weight, more preferably 40% to 45% by weight.

If the content of the composite particles is less than 10% by weight, the amount of coating of the surface of the composite particles with the water-soluble resin increases, so there is a risk that the defects may not be sufficiently adsorbed. is increased, the viscosity becomes too high and it becomes difficult to granulate again by the spraying method.

(Aqueous solution containing water-soluble resin-containing emulsion)
The aqueous solution in which the composite particles are dispersed can be prepared by mixing a water-soluble resin-containing emulsion solution with a glass transition temperature of 10° C. or less and water.

This is because if the glass transition temperature exceeds 10° C., the composition is likely to be cured, and there is a risk that fine powder of the water-soluble resin will precipitate after spraying.

The water-soluble resin-containing emulsion having a glass transition temperature of 10° C. or less is not particularly limited, and may be exemplified by an acrylic acid ester emulsion, a styrene-acrylic emulsion, and a styrene-butadiene emulsion.

The resin content of the water-soluble resin-containing emulsion in the aqueous solution is preferably 5% to 35% by weight.

This is because if the proportion of the resin in the aqueous solution is less than 5% by weight, the effect of the coating is weak, and there is a risk that peeling or falling off of the fluorescent pigment cannot be suppressed.

On the other hand, if the content exceeds 35% by weight, the viscosity increases due to the excessive solid content, which may make it difficult to granulate by spraying.

(fluorescent magnetic powder liquid)
A fluorescent magnetic powder solution can be prepared by dispersing the produced fluorescent magnetic powder in an organic solvent such as water or white kerosene.

The fluorescent magnetic powder contained in the fluorescent magnetic powder liquid is preferably 0.3 g/L to 2.0 g/L.
This is because fine defect portions can be detected with high detection sensitivity.

In order to enhance the dispersibility of the fluorescent magnetic particles, a commercially available magnetic particle dispersant for wet magnetic particle flaw detection tests may be added to the fluorescent magnetic particle liquid of the present invention.

(Wet magnetic particle testing method)
1 shows one aspect of a wet magnetic particle flaw detection test using a fluorescent magnetic particle liquid in which fluorescent magnetic particles are dispersed according to the present invention.

After magnetizing the object to be inspected by the axial current method according to the usual method, fluorescent magnetic powder solution is applied, and the defect indication pattern is observed by irradiating the ultraviolet light in a dark place, and the number and size of the defect part etc. are observed. to measure.

The fluorescent magnetic powder solution of the present invention can be suitably used to detect an open defect having a width of 0.02 mm or more and a ketos No. 7 defect directly below the surface that is not open.

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these.

As shown in the table, a slurry-like mixture was prepared by mixing triiron tetraoxide powder, an acrylic acid ester emulsion, a melamine-based fluorescent pigment (Shinroihi Color 5005/manufactured by Shinroihi Co., Ltd.), and water.

The "water-soluble resin" column in each table shows the glass transition temperature (Tg) of the acrylic acid ester resin in the mixture or aqueous solution and the content (% by weight) of the resin.

The prepared mixture was atomized into the air at a high temperature with a spray dryer, dried by removing water from the droplets, and granulated.

The obtained composite particles were divided into those which were not sprayed again and those which were sprayed again.

An aqueous solution containing an acrylate emulsion was prepared by dissolving the acrylate emulsion in water.

After the composite particles to be re-sprayed were dispersed in the prepared acrylic acid ester emulsion-containing aqueous solution, they were again granulated with a spray dryer to obtain re-sprayed fluorescent magnetic powder.

Hereinafter, those not re-sprayed will be referred to as composite particles, and those that have been re-sprayed will be referred to as re-sprayed fluorescent magnetic powders.

(Sprayability)
Those that could be sprayed with a spray gun during re-spraying were evaluated as ◯, and those that could not be dispersed in the aqueous solution containing the water-soluble resin-containing emulsion and could not be sprayed were evaluated as x.

(Detection sensitivity)
A type A test piece specified in JIS Z 2320 was attached to a square steel material of No. 60, and a magnetic powder solution was applied while magnetizing it by the axial current method, and the detection state of artificial defects in the A type test piece was visually observed. evaluated.

When the detection sensitivity of the fluorescent magnetic powder liquid in which the re-sprayed fluorescent magnetic particles were dispersed was equal to or higher than that of the fluorescent magnetic powder liquid in which the composite particles were dispersed, it was evaluated as ◯, and when it decreased, it was evaluated as x.

(Peeling brightness)
0.5 g each of the re-sprayed fluorescent magnetic powder and the composite particles of Examples and Comparative Examples were dispersed in 1 L of water by adding a dispersant (Eco-Magna Dispersant EC-4/manufactured by Marktec Co., Ltd.).

After that, as shown in FIG. 2, the water from which the fluorescent magnetic powder was removed with a magnet (hereinafter referred to as “separation water”) was passed through a transparent Teflon (registered trademark) tube with a diameter of 6 mm, and the outer surface of the Teflon (registered trademark) tube was irradiated with ultraviolet rays. , the emitted light was read by a photosensor.

In the specification of the present application, the luminance of the stripping water read by the photosensor by the above-described method is referred to as stripping brightness.

The exfoliation brightness of the composite particles before re-spraying in Example 1 was 0.714, and the exfoliation brightness of the re-spraying fluorescent magnetic powder after re-spraying was 0.155 (Fig. 1).

The rate of decrease in peeling luminance was determined by the following formula.
(Formula) 0.155/0.714 x 100 = 21.7%

Similarly, re-sprayed fluorescent magnetic particles with a reduction rate of 50% or less in peeling brightness compared to the peeling water of the fluorescent magnetic powder liquid in which the composite particles are dispersed before re-sprayed are evaluated as ◯, and those exceeding 50%. was evaluated as ×.

The results are shown in Tables 1 and 2.
"Resin deposition" in the table means that fine powder of water-soluble resin was generated after spraying.

A comparison of the release water of the composite particles and the resprayed fluorescent magnetic powder is shown in FIG.

As shown in Tables 1 to 3, even when the re-sprayed fluorescent magnetic powder of the present invention is dispersed in water, the fluorescent pigment hardly peels off or comes off.

Therefore, it was proved that the fluorescent magnetic particle liquid in which the fluorescent magnetic particles according to the present invention are dispersed provides a clear defect indication pattern and is a fluorescent magnetic particle liquid with high detection sensitivity.

The fluorescent magnetic powder according to the present invention is a fluorescent magnetic powder obtained by coating composite particles, in which a fluorescent pigment is attached to the surface of magnetic powder particles via a water-soluble resin, with a water-soluble resin, and the fluorescent pigment is firmly attached to the surface of the magnetic powder particles. Therefore, since the fluorescent pigment is less likely to peel off or come off in the fluorescent magnetic particle liquid or during the flaw detection test, the fluorescent magnetic particle liquid can be produced in which the background phenomenon is less likely to occur.
In addition, since the fluorescent pigment is less likely to peel off or fall off, a large proportion of the fluorescent pigment remains on the surface of the magnetic powder particles. Since the surface is coated with the water-soluble resin in which the detached fluorescent pigment is dispersed during re-spraying, it is possible to produce a fluorescent magnetic powder liquid that provides a clear defect indication pattern.
Therefore, the fluorescent magnetic particle liquid in which the fluorescent magnetic particles are dispersed according to the present invention can detect fine opening defects and non-opening defects just below the surface with high detection sensitivity.
Therefore, the industrial applicability of the present invention is high.

Claims (5)

20% by weight or more and 40% by weight or less of magnetic powder having a median system of 2 μm or more and 7 μm or less, and 5% by weight or more of the resin content of the water-soluble resin-containing emulsion having a glass transition temperature of 10° C. or less, and , 12% by weight or less, 5% by weight or more of a fluorescent pigment, 25% by weight or less and water are granulated, and the resin content of the water-soluble resin-containing emulsion is 5% by weight or more, and A method for producing fluorescent magnetic powder for wet magnetic particle testing, comprising dispersing 10% by weight or more and 55% by weight or less of the granulated particles in an aqueous solution containing 35% by weight or less, and then granulating again. 2. The method for producing fluorescent magnetic particles for wet magnetic particle testing according to claim 1, wherein the granulation method is spraying. 3. The method for producing fluorescent magnetic powder for wet magnetic particle testing according to claim 1, wherein the solid content of said magnetic powder, said fluorescent pigment and said water-soluble resin in said mixture is 65% by weight or less. 4. The method for producing a fluorescent magnetic powder for wet magnetic particle testing according to any one of claims 1 to 3, wherein the particles granulated from the mixture are composite particles in which a fluorescent pigment is attached to the surface of the magnetic powder particles. Fluorescent magnetic powder liquid for wet magnetic particle flaw detection test, in which the fluorescent magnetic powder produced by the production method according to any one of claims 1 to 4 is dispersed.

Images