JP3145330B2 - Carburizing or nitriding prevention method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to carburizing or nitriding.
Concerning the prevention method (hereinafter referred to as carburizing / nitriding), for example, metal parts such as steel are partially carburized / nitrided to harden the part, and the other parts are left in a non-carburized state or a non-nitrided state. The present invention relates to a method for preventing carburizing and nitriding using a powder used for preventing carburizing and nitriding when the toughness is to be maintained by leaving the above.

[0002]

2. Description of the Related Art Metal mechanical parts such as cams, shafts, pistons, pins, various gears and cutting tools used in automobiles and ships, etc., require toughness as a whole, but are subject to friction. The parts require a high level of wear resistance. As a method of obtaining such a mechanical part having both toughness and wear resistance, there is a method of using a tough steel material and carburizing / nitriding only the part where the wear resistance is required to harden. In this case, a method is employed in which portions other than the portion to be hardened are masked to prevent carburization and nitriding and maintain toughness.

As a masking material of this kind, copper plating or tin plating has been conventionally used. However, since a plating operation for masking is complicated and time-consuming, a paint type which recently forms a gas barrier film is used. Masking materials have been developed and are rapidly spreading. That is, a paint-type masking material is a mixture of a small amount of resin and a solvent with a carburizing / nitriding chemical powder, such as borax, borosilicate or tin powder, prior to heat treatment for carburizing / nitriding. This paint is applied to a specific portion of a steel material. Then, this is placed in a furnace in which a carburizing / nitriding agent is charged or which is kept in a carburizing / nitriding gas atmosphere, and the mixture is placed in a furnace.
When heated to 0 to 1000 ° C., the resin in the paint is thermally decomposed and disappears, and at the same time, the carburizing / nitriding prevention component is baked on the steel material surface to form a carburizing / nitriding prevention film, thereby preventing contact with the carburizing / nitriding component. As a result, carburizing and nitriding of the painted portion are prevented. In this case, if the carburizing / nitriding coating has uneven coating or pinhole defects, the purpose of carburizing / nitriding prevention cannot be fulfilled, so the most important point is to form a defect-free uniform carburizing / nitriding prevention coating. Becomes

[0004] However, in this paint, the amount of the resin component acting as a vehicle component is small (a large amount causes the release of decomposed gas when thermally decomposed, preventing the carburizing / nitriding prevention film from seizing). In order to form a uniform coating film with poor castability, it must be diluted with a solvent and applied repeatedly. Therefore, elaborate work using a brush or a brush is required, and a great deal of manpower and labor is required.

The present inventors have proposed a carburizing / nitriding prevention method whereby a reliable carburizing / nitriding effect can be obtained even when the substrate to be carburized / nitrided is smooth and has a curved surface or unevenness. In Japanese Patent Application No. 8-91436, a boron-based inorganic compound having an action of preventing carburization or nitriding,
A method for fusing a carburizing or nitriding preventing powder containing a heat-fusible resin which thermally decomposes under carburizing or nitriding conditions as an essential component to a site where carburizing and nitriding of a metal to be treated is to be prevented has been disclosed. This carburizing / nitriding prevention method has made it possible to uniformly form a thick film having an excellent carburizing / nitriding preventing effect by simple means regardless of the shape and surface properties of the substrate to be treated. .

[0006]

However, carburizing / nitriding using a carburizing / nitriding agent comprising a substance having an anti-carburizing / nitriding action and a heat-fusible resin as described above.
In the nitridation prevention method, the carburizing / nitriding agent is precisely adhered only to the portion to be carburized / nitriding-treated,
In addition, it is necessary to completely adhere the portion to be subjected to the carburizing and nitriding prevention treatment without any gap. For that, carburizing
Only the part to be subjected to the nitridation treatment must be accurately and sufficiently heated to a temperature higher than the fusion temperature of the heat-fusion resin. An object of the present invention is to precisely adhere and fuse a carburizing / nitriding agent only to a portion to be carburized / nitrided, and to more reliably perform a carburizing / nitriding treatment only to a portion to be carburized / nitrided. Is to provide a way.

[0007]

The carburizing / nitriding prevention method according to the present invention, which has solved the above-mentioned problems, is characterized in that only a portion requiring carburizing or nitriding prevention is selectively heated with a laser beam. It has that characteristic. That is,
The present invention relates to a method for preventing a part of a metal to be treated from carburizing or nitriding with a powder for preventing carburizing or nitriding in a carburizing or nitriding treatment of a metal material. After applying the carburizing or nitriding powder to at least the region containing, the portion to be carburized or nitrided is heated to a temperature equal to or higher than the fusion temperature of the carburizing or nitriding powder by laser beam heating, and the portion to be carburized or nitrided is prevented. The present invention also relates to a method for preventing carburization or nitriding, characterized in that the above-mentioned powder for carburizing or nitriding is fused only to the above.

[0008] In particular, the present invention is characterized in that a powder having a carburizing or nitriding preventing action as a powder for preventing carburizing and nitriding and a powder containing a heat-fusible resin which is thermally decomposed under carburizing or nitriding conditions as essential components are used. The present invention relates to the above carburizing / nitriding prevention method.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the carburizing / nitriding prevention method of the present invention, when performing carburizing / nitriding using a powder for carburizing / nitriding prevention, the entire material to be treated or a part to be subjected to carbonitriding / nitriding treatment. Carburizing at least the area containing
An anti-nitriding agent is applied, and then only the portion to be carburized and nitrided is heated by laser irradiation to a temperature higher than the melting temperature at which the powder exhibits thermal fusibility, thereby carburizing only the portion to be carburized and nitrided. -Since the nitridation inhibitor can be fixed, the powder can be easily and reliably adhered only to the portions requiring carbon and nitrogen prevention, regardless of the shape and surface properties of the substrate. The heating temperature at this time may be higher than the temperature according to the melting temperature of the fusion component in the powder, and is usually heated to about 120 to 350 ° C. Since the powder in the non-laser-irradiated portion which does not require the carbon-proofing / nitrification-proofing treatment is not fused to the material to be treated, it is removed by a method such as blowing air after the laser irradiation.

[0010] As the heating means, even if the material to be treated has a curved surface or an uneven shape, and even if the carbon- and nitrogen-proof parts are complicated and fine figures, only necessary parts are required. Which can surely and accurately heat the material is desired. In the present invention, a laser beam heating method is used as such a heating means. After powder coating the material to be treated with a carburizing / nitriding inhibitor, the heating means strictly heats only the portion of the material to be carburized / nitrided to prevent carburizing / nitriding. The powder can be easily and reliably attached. Thus, after the powder is melt-adhered to the carburizing / nitriding site, it is subjected to a carburizing / nitriding process. Since the carburizing / nitriding is usually carried out at a temperature of 500 to 1000 ° C, In the meantime, the resin in the powder undergoes thermal decomposition and disappears, leaving only a substance having an anti-carburizing / nitriding action to form a carbon- and nitric-resistant coating. Will be prevented.

The laser beam heating method used in the present invention uses a scanning type laser beam irradiation apparatus equipped with a scanning head which scans according to a graphic pattern stored in a computer and emits a laser beam only to a portion requiring heating. It is preferred to do so. The graphic to be irradiated with the laser beam may be moved by the laser firing head by a computer or the firing head may be fixed to move the workpiece, but in each case, the graphic tracing is automatically performed. Is preferably controlled.

The width of the laser beam to be emitted is selected according to the size and accuracy of the part to be carburized / nitrided. In order to strictly heat only the portion where carburizing and nitriding are to be prevented, it is preferable that the beam width can be controlled to 1.0 mm, preferably 0.1 mm. The laser output is selected to have a size necessary to quickly heat a required portion of the material to be processed. As the computer-controlled laser generator that can be used to satisfy the above requirements, a commercially available one can be used, and examples thereof include a scanning type laser marker device ML-4140C (manufactured by Miyachi Technos Co., Ltd.).

The specific method for adhering the carburizing / nitriding prevention powder to the material to be treated is not particularly limited, and known methods such as a fluid immersion method, a spray method, and an electrostatic adhesion method may be appropriately modified. Can be applied.

FIG. 1 shows an example of an automatic apparatus incorporating a laser beam heating and a carburizing / nitriding prevention powder coating function suitable for the present invention. According to this figure, the carburizing
The nitriding prevention method will be described. The test piece (6) requiring partial carbon protection and nitrification is moved into the powder coating booth (2) by the 6-axis robot (3). Therefore, a carburizing / nitriding inhibitor is attached to the entire test piece by electrostatic coating. This test piece is YAG laser marker (4) by a 6-axis robot.
To the laser irradiation position, and irradiate the laser only to the part requiring carbon prevention and nitrification, and fuse the carburizing and nitriding inhibitor of the powder to the test piece. In laser irradiation, the laser marker controller (5) can control the X and Y axes of laser irradiation,
The 6-axis robot can control the Z-axis. After that, the robot moves the test piece to the painting booth and scatters the powder except the fused part by air blow.

As the carburizing / nitriding preventing substance constituting the powder for preventing carburizing / nitriding of the present invention, a boron-based inorganic compound or a boron oxide-based amorphous material is preferable. Such a boron-based inorganic compound or a boron oxide-based amorphous body is heated under carburizing and nitriding treatments (normally at 300 to 1000 ° C.).
At about 450 ° C. or higher as a material capable of forming a dense carbon- and nitrogen-proof coating and exerting a function of preventing carburization and nitridation almost at the same time as the burning due to the thermal decomposition of the fusion resin. A boron-based inorganic compound that is melted or fused and seized on the substrate surface to form a dense carbon- and nitrogen-resistant coating is selected.

Specific examples of the boron-based inorganic compound include borax, boron oxide, borosilicate, phenylboronic acid and the like. Among them, boron oxide is particularly preferred.

The boron oxide-based amorphous material used in the present invention is an amorphous material of boron oxide B ₂ O ₃ and another inorganic material. Preferred amorphous materials include boron oxide-silicon oxide, boron oxide-silicon oxide-clay, and boron oxide-silicon oxide-alumina. In the case of boron oxide-silicon oxide amorphous, B ₂
O _3: SiO ₂ (weight ratio) is 65 to 95: 35 to 5, preferably 70 to 90: a 30 to 10.

The boron-based inorganic compound or the boron oxide-based amorphous body has a water content of 10% by weight or less, more preferably 5% by weight or less.
It is desirable to select and use one having a weight percentage of not more than one. If the amount of water in the boron-based inorganic compound or the boron oxide-based amorphous material is too large, regardless of the amount of water adhering or water of crystallization, volatilization of the water during the formation of the carbon- and nitrogen-proof coatings. This causes pinhole defects or the like in the film, making it difficult to form a reliable carbon- and nitrogen-proof coating, or preventing the formation of a carbon- and nitrogen-proof coating at all.

At this time, in order to form a film having a thickness necessary and sufficient for carbon and nitrogen prevention, the content of the boron-based inorganic compound or the boron oxide-based amorphous body in the powder should be 20% on an anhydrous basis. When the content is insufficient, the carbon content after the resin is decomposed and burned is reduced.
The nitrogen barrier film may be thin and non-uniform or may have pinhole defects, making it difficult to obtain a reliable carbon / nitridation effect. Conversely, if the amount is too large, the absolute amount of the resin tends to be insufficient and the powder may be poorly adhered when adhering the powder to the carburizing / nitriding prevention portion of the material to be processed, and may be formed during the carburizing / nitriding process. The adhesion of the carbon-proof and nitrogen-proof film is reduced, and it is difficult to obtain a reliable carbon-proof and nitrogen-proof effect.

On the other hand, the heat-fusible resin acts as an adhesive component when the powder for preventing carburizing and nitriding is adhered to the carbon- and nitriding portions of the material to be treated, and also thermally decomposes under the conditions of carburizing and nitriding. Has the property of disappearing. In other words, in order to prevent carbon and nitrogen, it is necessary to ensure that the powder is first adhered to the carbon and nitrogen portions of the material to be treated. In the present invention, the boron-based inorganic compound or the boron oxide-based compound is used. By containing a predetermined amount of the heat-fusible resin as an essential component together with the amorphous body, the powder can be easily attached to the above carbon- and nitrogen-proof parts. As the heat-fusible resin, a thermoplastic resin and a thermosetting resin can be used, and in the case of a thermoplastic resin, by softening and melting by heat, or in the case of a thermosetting resin, before a curing reaction occurs. Due to the fusibility caused by the plasticization, the powder can be easily attached to the carbon- and nitrogen-proof parts of the material to be treated.

Accordingly, the first heat-fusible resin is a thermoplastic resin which is softened and melted by heat and exhibits a fusibility as a first characteristic, or is once softened and shows a fusibility before a thermosetting reaction occurs. And preferably at 350 ° C.
It is desired to select a material exhibiting heat fusibility at a temperature of about 300 ° C. or less, more preferably about 300 ° C. or less. Therefore, the temperature at which the heat fusibility is too high, for example, 350
If the temperature exceeds about ℃, it will be difficult to reliably adhere to the carbon- and nitrogen-resistant parts by the method described below, and as a result, a satisfactory carbon- and nitrogen-resistant effect may not be obtained. is there.

The second characteristic of the fusible resin is that, after the carburizing / nitriding prevention powder is adhered to the carburizing / nitriding prevention site and before the carburizing / nitriding treatment, thermal decomposition occurs. It is necessary to have a property that does not impair the formation of a carbon- and nitrogen-resistant coating consisting solely of the boron-based inorganic compound or the boron-oxide-based amorphous material, and is preferably thermally decomposed in the range of about 400 to 600 ° C. It is desirable to select one that disappears. Therefore, the thermal decomposition temperature is too high, for example, 700 ° C.
If the ratio exceeds 1, thermal decomposition progresses during carburizing and nitriding, causing pinhole defects in the carbon- and nitrogen-proof coatings, making it impossible to obtain a reliable carbon- and nitrogen-proof effect.

Various resins are exemplified as the thermally decomposable resin satisfying the above-mentioned required characteristics. Among them, preferred thermoplastic resins are polyolefin resins such as polyethylene and polypropylene, polyester resins, and the like. Acrylic resins and the like, and thermosetting resins include thermosetting polyester resins and acrylic resins. When a thermosetting resin is used, it is preferable to select a curing agent that blocks the cross-linking reactive functional group, releases the blocking agent after the main agent is heat-plasticized, and shows a curing reaction.

The preferred amount of the heat-fusible resin in the carburizing / nitriding prevention powder according to the present invention is in the range of 20 to 80% by weight, more preferably 40 to 60% by weight.
If the compounding amount of the resin is insufficient, it tends to be difficult to uniformly melt-adhere the powder to the carbon- and nitrogen-proofing sites by a method described later, and conversely if the compounding amount is too large, The absolute amount of the boron-based inorganic compound or the boron oxide-based amorphous body is insufficient, so that it is difficult to form a dense carbon-proof / nitrogen-proof coating.
There is a possibility that the anti-nitrification effect cannot be obtained.

However, when a powder containing the above-mentioned boron-based inorganic compound or boron oxide-based amorphous body and a heat-fusible resin is used, the powder adhered to the surface of the material to be treated will not be heated. (Carbon-proofing / Nitrogen-proofing part) in the heat-fusible resin, due to the adhesive effect associated with the plasticization, it is uniformly fused to the part on the surface of the material to be treated. When exposed to a nitriding atmosphere, the heat-fusible resin disappears due to thermal decomposition, and a sufficient amount of boron oxide-based amorphous material contained in the powder is melted or fused to form a dense carbon / carbon-resistant material. Since the nitrogen coating is formed with good adhesion, it is possible to surely prevent carbon and nitrogen without causing pinhole defects or the like.

The essential components in the carburizing / nitriding prevention powder according to the present invention are the above-mentioned two types, and the other components are water glass, frit, low melting point glass;
It is also effective to add an appropriate amount of a metal powder such as aluminum or zinc, a crushed metal foil, or the like to further enhance the carbon- and carbon-proofing effects. Further, for example, a small amount of titanium oxide, iron oxide, zinc oxide, talc, calcium carbonate, mica, silica (fused silica, aerosil, etc.), alumina, magnesium, silicon carbide, fly ash, graphite, silicic acid, kaolinite, clay, etc. is added. It is also effective to increase the adhesion and denseness of the carbon- and nitrogen-resistant coating to the material to be treated, or to suppress the flow (dripping) of the carbon- and nitrogen-resistant coating during carburizing and nitriding. . It is also desirable to color the powder carburizing / nitriding agent with various pigments in order to increase the laser absorption. The choice of color depends on the heat absorption of the laser light, and green and red are relatively preferred. Colloidal graphite or the like may be applied to the surface of the material to be treated in order to increase the absorption.

The carburizing / nitriding prevention powder of the present invention is obtained by uniformly mixing the above-mentioned components, and the production method thereof is not limited at all. For example, a powdered boron oxide-based amorphous material and a powdered The heat-fusible resin, and furthermore, if necessary, can be obtained by blending and uniformly mixing other auxiliary additives, but preferably, the heat-fusible resin is heated and softened. Is a method of uniformly dispersing a boron oxide-based amorphous powder and other auxiliary additive powders, cooling, solidifying, and then freeze-pulverizing. In this method, individual components are separated. It is preferable because a powder having a homogeneous component composition can be easily obtained. As a method similar to this method, a heat-fusible resin is dissolved in an appropriate solvent, and a boron oxide-based amorphous powder and other auxiliary additive powders are uniformly mixed with this, followed by spray drying. A method of drying by, for example, is also exemplified as a preferable method.

The powder for preventing carburizing and nitriding is treated with a carbon
In order to allow the powder to adhere uniformly to the nitrogen-proofing site, the average particle diameter of the powder is 10 to 250 μm, more preferably 50 to 2 μm.
It is desirable to adjust the particle size to a range of 00 μm. However, if the powder is too coarse, it tends to be difficult to form a uniform carbon- and nitrogen-proof coating. Conversely, if the powder is too fine, it is difficult to form a thick carbon- and nitrogen-proof coating, which is satisfactory. This is because there is a tendency that a high carbon-prevention / nitrification-prevention effect is hardly exhibited.

The preferred content of the boron-based inorganic compound or the boron oxide-based amorphous substance having a carburizing or nitriding-preventing action in the carburizing or nitriding-preventing powder is from 20 to 80% by weight on an anhydrous basis. Preferably 40
And the preferred content of the heat-fusible resin that thermally decomposes under carburizing or nitriding conditions is 20% by weight.
To 80% by weight, more preferably 40 to 60% by weight.

The above-mentioned boron-based inorganic compound or boron oxide-based amorphous body is particularly preferable because it has a water content of 10%.
% By weight or less, more preferably 5% by weight or less, respectively, of boron oxide or boron oxide-silicon oxide amorphous material. Preferred as the heat-fusible resin are polyolefin resins,
One of polyester-based resins and acrylic-based resins or a mixed resin thereof.

Examples of the material to be treated according to the present invention include various metal materials whose surface is hardened by partial carburizing and nitriding treatment. Among them, steel materials and alloy steels are the most common. For parts that are subject to strong friction or wear, such as shafts and bearings or grinding and grinding members, are hardened by carburizing and nitriding, and other parts are required to suppress carburizing and nitriding to maintain high toughness. By applying the present invention to the carbon- and nitrogen-proof parts at the time of obtaining, it is possible to harden only the non-adhered parts by carburizing and nitriding while maintaining the toughness of the carbon- and nitrogen-proof parts.

[0032]

EXAMPLES Hereinafter, the structure and operation and effect of the present invention will be described specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples, and the purpose of the present invention is described below. It is, of course, possible to carry out the present invention with appropriate modifications as far as it is applicable, and all of them are included in the technical scope of the present invention.

Example 1 As a test piece for carburizing treatment, a cylindrical (semi-cylindrical) type in which a cylindrical steel material having a diameter of 22 mm and a length of 70 mm was bisected in a vertical direction was used. The test piece was transferred to the coating booth (2) by the six-axis robot shown in FIG. 1, and the entire test piece was electrostatically coated by 90% by weight of boron oxide and 10% by weight of silicon oxide.
An anti-carburizing / nitriding agent powder (average particle size: 100 μm) consisting of 55% by weight of a boron oxide-silicon oxide-based amorphous body powder made of and 55% by weight of a polyethylene powder was applied. Next, the test piece is moved to the laser irradiation position of the YAG laser marker (4) by a 6-axis robot, and the flat portion of the test piece (the bottom portion of the Kamaboko shape) is controlled by a computer.
Laser irradiation was performed so that a square pattern with a side of 5 mm could be drawn on the upper side. The test piece after the laser irradiation was transferred again to the painting booth (2) by a six-axis robot, and air blown to blow off the carburizing / nitriding inhibitor on the test piece. An anti-carburizing / nitriding agent was fused on the test piece with an accuracy of ± 0.5 mm. Next, this test piece was put into a heating furnace for carburizing treatment, and carburizing treatment was performed by gas carburizing. After the treatment, the specimen was evaluated by microscopic observation and hardness measurement, and it was found that only the part intended to improve the wear resistance by carburizing treatment showed an accurate increase in hardness, and the part protected by the carburizing and nitriding agent was completely The carburizing action was protected from.

[0034]

According to the method of the present invention, the carburizing / nitriding preventive agent can be attached with high precision only to the portion of the metal material to be carburized / nitrided where the carburizing / nitriding treatment is desired.

[Brief description of the drawings]

FIG. 1 is a side view of an example of an apparatus for performing a carburizing / nitriding prevention treatment of the present invention.

[Explanation of symbols]

 1: powder electrostatic coating device, 2: painting booth, 3: 6-axis robot, 4: YAS laser marker: 5: laser marker controller, 6: test specimen.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Toi 2-6-1 Nishi-Nagasu-cho, Amagasaki-shi, Hyogo Inside Nard Research Institute Co., Ltd. (72) Inventor Yoshimi Ishigaki 2-6-Nishi-Nagasu-cho, Amagasaki-shi, Hyogo No. 1 Nard Research Laboratories Co., Ltd. (72) Inventor Katsuya Akamatsu 1-23-13 Midorigaoka, Toyonaka-shi, Osaka (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 8 / 02,8 / 04 C23C 8 / 20,8 / 24 C21D 1 / 09,1 / 34,1 / 70

Claims (9)

(57) [Claims] 1. A method for preventing a part of a metal to be treated from being carburized or nitrided by a carburizing or nitriding powder in a carburizing or nitriding treatment of a metal material, wherein the whole metal material to be treated or a carburizing or nitriding preventing treatment is performed. After applying the carburizing or nitriding preventing powder to at least the region including the portion to be carburized, the portion to be carburized or nitriding is heated by laser beam heating to a temperature equal to or higher than the fusion temperature of the carburizing or nitriding preventing powder to prevent carburizing or nitriding. A method for preventing carburization or nitriding, wherein the powder for preventing carburizing or nitriding is fused only to a part to be carburized. 2. The laser beam heating automatically controls the movement of a laser beam emitting device and a scanning head that emits a laser beam so that the laser beam is applied only to a portion of the material to be treated that is to be carbon or nitrogen resistant. The method for preventing carburization or nitriding according to claim 1, wherein the method is performed by a laser beam emitted from a device including a computer that is controlled and driven. 3. The method for preventing carburization or nitriding according to claim 2, wherein the scanning in the X and Y axes directions (two orthogonal horizontal axis directions) is controlled by a computer so that a laser beam moves and the vertical scanning is performed by a robot. . 4. The carburizing or nitriding preventing powder comprises a powder containing, as essential components, a substance having a carburizing or nitriding preventing effect and a heat-fusible resin thermally decomposed under carburizing or nitriding conditions. 4. The method for preventing carburization or nitriding according to any one of 2 and 3. 5. The carburizing or nitriding preventing method according to claim 4, wherein the substance having a carburizing or nitriding preventing action is a boron-based inorganic compound or a boron oxide-based amorphous substance. 6. The carburizing or nitriding condition wherein the boron-based inorganic compound or the boron oxide-based amorphous material having a carburizing or nitriding preventing action in a powder for carburizing or nitriding has an anhydrous content of 20 to 80% by weight, The method for preventing carburization or nitriding according to claim 4 or 5, wherein the content of the heat-fusible resin which thermally decomposes below is 20 to 80% by weight. 7. The method for preventing carburization or nitriding according to claim 5, wherein the boron-based inorganic compound is boron oxide having a water content of 10% or less. 8. The boron oxide-based amorphous material has a B ₂ O ₃ content of 65 to 65.
95 consists wt% and 35-5 wt% of SiO _2, carburizing or Act nitride according to claim 5 or 6 water content is 10 wt% or less. 9. The heat-fusible resin is at least one resin selected from the group consisting of polyolefin resins, polyester resins, and acrylic resins.
The method for preventing carburization or nitriding according to any one of the above.