Dry magnetic particles for magnetic particle testing and method for manufacturing the dry magnetic particles

Abstract

This invention provides a dry magnetic powder that can be manufactured by a simple method of kneading pure iron powder, resin, and pigment, and because there is no grinding process, it does not contain excessive amounts of fine powder, and because the dry magnetic powder has excellent fluidity, it enables magnetic powder testing with superior accuracy. [Solution] A dry magnetic particle for magnetic particle testing, comprising 0.1 parts by weight or more and 4 parts by weight or less of at least one resin selected from cellulose acetate, cellulose acetate butyrate, alkyl acetalized polyvinyl alcohol, acrylic resin, vinylpyrrolidone-vinyl acetate copolymer, and rosin-modified maleic acid resin; 0.5 parts by weight or more and 25 parts by weight or less of a pigment selected from titanium dioxide, silicon dioxide, Pigment Yellow 101, and β-quinophthalone; and the remainder being pure iron powder with a mode diameter of 90 μm or more and 250 μm or less.

Description

Technical Field

[0001] The present invention relates to dry magnetic powder for magnetic particle inspection tests and a method for manufacturing the dry magnetic powder. Specifically, the dry magnetic powder can be manufactured by a simple method of kneading pure iron powder, resin, and pigment. Since there is no pulverization process, it does not contain excessive fine powder, and because of its excellent fluidity, it is possible to perform a magnetic particle inspection test with excellent inspection accuracy. The present invention relates to dry magnetic powder and a method for manufacturing the dry magnetic powder.

Background Art

[0002] The dry magnetic particle inspection test method is a test method in cold regions and the like, where dry magnetic powder is sprinkled on a magnetized inspection object, and the magnetic powder is aggregated in the opening defect part of the inspection object (fine cracks and pinholes existing on the surface or near the surface of the inspection object) to reveal a defect indication pattern, and the surface opening defect part is inspected by this defect indication pattern.

[0003] Among those skilled in the art, there is a method for manufacturing dry magnetic powder called the "pulverization method".

[0004] The "pulverization method" is a method in which an organic solvent-soluble synthetic resin is used as a binder, a fluorescent pigment is dispersed in a solution obtained by dissolving this in a volatile organic solvent, magnetic powder is mixed and kneaded into a paste-like substance, the paste-like substance is dried into a块状物, and then 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 of a desired particle size.

[0005] In a general pulverization method, since it contains 6% or more of the binder resin, it becomes coarse particles during drying, and a pulverization process is required.

[0006] However, fine powder is generated during the pulverization process.

[0007] The fine powder has problems such as scattering when sprinkled on the inspection object, being inhaled by the tester, or not adhering to the inspection surface, which reduces the inspection accuracy.

[0008] Furthermore, if the dry magnetic particles have poor fluidity, they will not accumulate in the opening defects, which leads to a decrease in the accuracy of the magnetic particle testing.

[0009] One method for attaching magnetic powder to the surface to be inspected is the spray method, in which magnetic powder is dispersed in a dispersion medium and then sprayed onto the surface.

[0010] However, since magnetic powder is made of iron, it settles quickly and is difficult to disperse in a dispersion medium, making it difficult to apply evenly to the surface of the object being inspected.

[0011] Furthermore, if water is used as the dispersion medium, there is a problem in that the sample being tested may rust.

[0012] Therefore, there is a need for the development of dry magnetic powder that can be manufactured using a simple method, produces little fine powder, has excellent fluidity, and enables magnetic particle testing with superior flaw detection accuracy. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 2010-71795 [Overview of the project] [Problems that the invention aims to solve]

[0014] Patent Document 1 describes a magnetic particle for magnetic flaw detection, manufactured by dry stirring a magnetic particle precursor containing magnetic powder, powdered resin, and a coloring material, spraying a solvent in which the powdered resin is soluble to soften the powdered resin, attaching the coloring material to the magnetic powder via the softened resin, and then curing the resin.

[0015] The magnetic powder described in Patent Document 1 does not contain excessive fine powder because it does not involve a grinding process, but the fluidity of the magnetic powder is poor, which may result in low flaw detection accuracy.

[0016] The inventors of this invention made solving the aforementioned problems their technical challenge. As a result of numerous trial-and-error prototypes and experiments, they obtained the remarkable finding that a dry magnetic particle for magnetic particle testing, comprising 0.1 parts by weight or more and 4 parts by weight or less of at least one resin selected from cellulose acetate, cellulose acetate butyrate, alkyl acetalized polyvinyl alcohol, acrylic resin, vinylpyrrolidone-vinyl acetate copolymer, and rosin-modified maleic acid resin, 0.5 parts by weight or more and 25 parts by weight or less of a pigment selected from titanium dioxide, silicon dioxide, Pigment Yellow 101, and β-quinophthalone, with the remainder being pure iron powder having a mode diameter of 90 μm or more and 250 μm or less, can be manufactured by a simple method of kneading the pure iron powder, resin, and pigment. Since there is no grinding process, it does not contain excessive fine powder and has excellent fluidity, allowing for highly accurate magnetic particle testing. Thus, the inventors have achieved the aforementioned technical challenge. [Means for solving the problem]

[0017] The aforementioned technical problems can be solved by the present invention as follows.

[0018] The present invention relates to a dry magnetic particle for magnetic particle testing, comprising 0.1 parts by weight or more and 4 parts by weight or less of at least one resin selected from group A below, 0.5 parts by weight or more and 25 parts by weight or less of a pigment selected from group B below, and the remainder being pure iron powder with a mode diameter of 90 μm or more and 250 μm or less. Group A: Cellulose acetate, cellulose acetate butyrate, alkylacetalized polyvinyl alcohol, acrylic resin, vinylpyrrolidone / vinyl acetate copolymer, rosin-modified maleic acid resin Group B: Titanium dioxide, silicon dioxide, Pigment Yellow 101, β-quinophthalone

[0019] The present invention also relates to a method for producing dry magnetic powder for magnetic particle testing, which is manufactured by kneading the pure iron powder, resin, and pigment.

[0020] Furthermore, the present invention relates to a magnetic particle testing method using the dry magnetic powder described above. [Effects of the Invention]

[0021] The dry magnetic powder in the present invention can be produced by a simple method of kneading pure iron powder, resin, and pigment, and since there is no pulverization process, it does not contain an excessive amount of fine powder.

[0022] In addition, since the mode diameter of the pure iron powder in the present invention is 90 μm to 250 μm, it becomes a dry magnetic powder with high fluidity.

[0023] Therefore, for the dry magnetic powder in the present invention, a magnetic particle inspection test with excellent inspection accuracy can be carried out.

Mode for Carrying Out the Invention

[0024] The dry magnetic powder in the present invention consists of pure iron powder (magnetic powder), resin, and pigment.

[0025] As long as the magnetic powder is pure iron powder, either reduced iron powder or electrolytic iron powder may be used.

[0026] The mode diameter of the pure iron powder is preferably 90 μm to 250 μm, more preferably 125 μm to 250 μm.

[0027] If the mode diameter is less than 90 μm, the amount of scattering when sprinkling on the detected object increases, and there is a risk that the visibility decreases due to adhesion to parts other than the open defect part. Also, if it exceeds 250 μm, there is a risk that it will not be crushed into primary particles and will form lumps.

[0028] The mode diameter can be measured by performing a particle size distribution measurement by the laser diffraction method or a sieving test by a vibrating sieve and calculating the particle size distribution.

[0029] The content of pure iron powder in the dry magnetic powder is preferably 74 parts by weight to 98.5 parts by weight, more preferably 80 parts by weight to 98.5 parts by weight.

[0030] If the pure iron powder content is less than 74 parts by weight, the amount of fine powder may increase and the fluidity may deteriorate. If the content exceeds 98.5 parts by weight, the brightness of the magnetic powder adhering to the opening defects may decrease and the visibility may deteriorate.

[0031] The dry magnetic powder in this invention contains one or more of the following: cellulose acetate, cellulose acetate lactate, alkylacetalized polyvinyl alcohol, acrylic resin, vinylpyrrolidone-vinyl acetate copolymer, and rosin-modified maleic acid resin.

[0032] The resin content in the dry magnetic powder is preferably 0.1 to 4 parts by weight, and more preferably 0.1 to 1.0 part by weight.

[0033] If the resin content is less than 0.1 parts by weight, there is a risk that the pigment will peel off from the pure iron powder, and if it exceeds 4 parts by weight, there is a risk that the primary particles will not be broken down and will form clumps.

[0034] The pigments used in this invention are titanium dioxide, silicon dioxide, Pigment Yellow 101, and β-quinophthalone.

[0035] The dry magnetic powder in this invention may be mixed with plasticizers, rust inhibitors, flow improvers, etc., as needed.

[0036] Examples include tributyl acetylcitrate as a plasticizer, sodium 4-(1,1-dimethylethyl)benzoate as a rust inhibitor, and silica as a flow improver.

[0037] The dry magnetic powder in this invention can be manufactured by first placing pure iron powder, resin, and pigment into a container and mixing them together using only the powders to create a uniform state, then adding an organic solvent to dissolve the resin and kneading until primary particles are formed, and finally evaporating the organic solvent.

[0038] The dry magnetic powder used in this invention can be manufactured by a simple kneading method, and since there is no grinding process, it does not contain excessive fine powder, thus enabling magnetic particle testing with superior flaw detection accuracy.

[0039] The organic solvent used to dissolve the resin is not particularly limited, but acetone and butyl acetate are examples. [Examples]

[0040] 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.

[0041] The pure iron powder listed in Table 1 was used.

[0042] [Table 1]

[0043] The resins listed in Table 2 were used.

[0044] [Table 2]

[0045] The pigments listed in Table 3 and Pigment Yellow 101 were used.

[0046] [Table 3]

[0047] The plasticizer used was tributyl acetyl citrate (manufactured by Morimura Shoji Co., Ltd.), the rust inhibitor was sodium 4-(1,1-dimethylethyl)benzoate (manufactured by Fuso Chemical Industry Co., Ltd.), and the fluidity improver was silica (manufactured by Tokuyama Corporation).

[0048] Each ingredient was mixed as shown in Tables 4 to 8.

[0049] (Particle state) After taking a predetermined amount of each ingredient and mixing them with a spatula, the mixture was dried at 80°C for 60 minutes.

[0050] The appearance of the dried magnetic powders of the examples and comparative examples was observed, and those that were mostly particulate were evaluated as ○, those that were about half coarse particles as △, and those that formed large clumps as ×.

[0051] (Detection capability) Two g of each dry magnetic powder from the examples and comparative examples was sprinkled onto a Type 1 test specimen. After tilting the specimen to remove excess magnetic powder, the defect indication pattern was visually inspected. A good defect indication pattern was marked with ○, and no defect indication pattern was observed was marked with ×.

[0052] (Liquidity) A funnel-shaped fluidity measuring cup made of non-magnetic metal material with an opening of Φ50.8 mm, a height of Φ60 mm, and a Φ2.5 mm hole was held horizontally on a stand. 50 g of magnetic powder was passed through the cup, and a score of ○ was given if the entire amount passed smoothly. A score of × was given if it took 60 seconds or more for the entire amount to pass through, or if a blockage occurred midway.

[0053] Tables 4 to 8 show the composition (parts by weight) and evaluation of the dry magnetic powders used in the examples and comparative examples.

[0054] [Table 4]

[0055] [Table 5]

[0056] [Table 6]

[0057] [Table 7]

[0058] [Table 8]

[0059] The dry magnetic powder according to the present invention can be manufactured by a simple method and has excellent fluidity, thus demonstrating that it enables magnetic particle testing with superior accuracy. [Industrial applicability]

[0060] The present invention provides a dry magnetic particle for magnetic particle testing that can be manufactured by a simple method of kneading pure iron powder, resin, and pigment, does not contain excessive fine powder because there is no grinding process, and has excellent fluidity for dry magnetic particles, enabling magnetic particle testing with superior inspection accuracy. Therefore, the industrial applicability of this invention is high.

Claims

1. A dry magnetic particle for magnetic particle testing, comprising 0.1 parts by weight or more and 4 parts by weight or less of at least one resin selected from group A below, 0.5 parts by weight or more and 25 parts by weight or less of a pigment selected from group B below, and the remainder being pure iron powder with a mode diameter of 90 μm or more and 250 μm or less. Group A: Cellulose acetate, cellulose acetate butyrate, alkyl acetalized polyvinyl alcohol, acrylic resin, vinylpyrrolidone / vinyl acetate copolymer, rosin-modified maleic acid resin Group B: Titanium dioxide, silicon dioxide, Pigment Yellow 101, β-Quinophthalone

2. A method for producing dry magnetic powder for magnetic particle testing according to claim 1, comprising kneading the aforementioned pure iron powder, resin, and pigment.

3. A method for testing magnetic particle defects using dry magnetic powder as described in claim 1.

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