KR100998103B1 - Manufacturing Method of High Corrosion Resistant and High Contamination Resistant Iron and Steel Materials - Google Patents

Abstract

Gas Nitriding or Gas Nitrocarburizing is performed on the steel material, followed by Post Oxidation, and then mechanical finish is optionally applied to the surface of the steel material. Apply fingerprint coating or UV coating.

      According to the present invention, there is an effect of providing a steel material having high gloss, high fingerprint resistance, pollution resistance and high corrosion resistance.

Gas Nitriding, Gas Carburization, Corrosion Resistance, Pollution Resistance, Anti-Fluid Coating, UV Coating

Description

Manufacturing Method of High Corrosion Resistant and High Contamination Resistant Iron and Steel Materials

The present invention relates to a method of manufacturing a high corrosion resistance and fouling resistant steel material, and more particularly, high corrosion resistance, beautiful appearance and difficult to adsorb foreign substances such as dust, easy to wash the already attached foreign substances high corrosion resistance And it relates to a method for producing a pollution-resistant steel material.

      As a method for securing high corrosion resistance of automobile and industrial machinery parts, plating processes such as zinc plating, chromium plating, and dark chrome have been conventionally performed. However, these platings are limited in corrosion resistance, and are recently regulated due to environmental problems occurring during the process, and thus new environmentally friendly process development is required.

In order to respond to this, a complex process of nitrification or nitrification followed by post-oxidation was developed. According to this process, an ε-phase compound layer and a Fe ₃ O ₄ oxide layer are sequentially formed from the surface of the material, thereby providing high corrosion resistance and high corrosion resistance. Nitrogen is infiltrated and diffused into the surface of the material while forming a nitrogen diffusion layer to obtain a material having high fatigue strength and excellent low deformation characteristics, and has been widely applied to the surface treatment of automobile and industrial machinery parts.

Such nitriding or nitriding and carburizing processes include salt bath nitriding using a mixed salt melt such as alkali metal cyanide and alkali metal cyanate, depending on the medium of nitrogen and carbon. Plasma nitridation method which injects a process gas such as carbon into an anode, and nitrides or nitrides carburizing with ions generated at this time, and a mixed gas of endothermic gas (Rx Gas) and ammonia or a mixture of ammonia, carbon dioxide and nitrogen Gas nitriding methods using a gas or a mixed gas of ammonia and nitrogen are known.

In the above-mentioned nitriding or nitriding and carburizing methods, the gas nitriding method is generally widely used in consideration of production cost, quality, performance, and environmental impact.

As an example of such a gas nitriding method, Korean Patent No. 0504131 proposed by the present invention performs nitriding or nitriding and carburizing of steel parts at 550 to 600 ° C. in a first furnace using two furnaces, followed by nitriding or nitriding with nitrogen gas. After purging the carburized gas, the steel parts are removed from the furnace, controlled cooling in air for 30 seconds to 1 hour, and then charged into the second furnace at 400 to 540 ° C., which is set to the post-oxidation condition, for 1 minute. After the post-oxidation for ˜5 hours, air cooling or water cooling to disclose a technique consisting of a surface modification method for producing a high corrosion-resistant steel is disclosed.

However, according to the above patent, although it is possible to provide excellent corrosion resistance by forming an oxide of Fe ₃ O ₄ on the compound layer of ε-phase and the compound layer, fine pores are formed in the oxide layer, so that water, dust, oil, dirt, Foreign matters such as fingerprints are easily adsorbed to the pores, so that stains or discolorations are easily generated, and it is difficult to remove the adsorbed foreign matters. In addition, there is a problem in that the appearance is not beautiful, such as black color of opaque color, staining occurs depending on the volatilization of the material on the oxide surface or its thickness.

As another gas nitriding method, U.S. Patent No. 4,881,983 discloses an oxide layer of Fe ₃ O ₄ on top of a compound layer by post-oxidation in the same furnace after purging the gas with inert gas after gas nitriding or gas nitriding. Thereafter, a technique is disclosed in which a color is black to provide corrosion resistance of 200 hours or more during a salt spray test by being removed from a furnace and polished.

However, in US Pat. No. 4,881,983, an oxide layer of Fe ₃ O ₄ remains even after polishing, so foreign matter such as water, dust, oil, and fingerprints is easily adsorbed into the pores during handling, as in Patent No. 0504131. There is still a problem that stains or discoloration are liable to be easily generated, and stains easily due to the adsorption of these foreign substances.

The present invention is designed to solve the problems of the prior art, the purpose of which is high corrosion resistance, beautiful appearance and difficult to adsorb foreign substances such as dust, high corrosion resistance and pollution resistance that is easy to wash the already attached foreign substances The present invention provides a method for manufacturing a steel material.

Other objects and advantages of the invention will be described below and will be appreciated by the embodiments of the invention.

According to a first aspect of the present invention to achieve the above object, (1) performing a gas nitriding or gas nitriding carburization process in a heat treatment furnace for steel material; (2) performing an oxidation treatment process on the treated material in a heat treatment furnace under an oxidizing gas atmosphere; (3) performing surface finishing on the treated material; And (4) there is provided a method for producing a high corrosion resistance and fouling resistant steel material comprising the step of performing a resin coating or UV coating on the treated material.

In addition, according to a second aspect of the present invention, there is provided a method for manufacturing a steel material, comprising the steps of: (1) performing a gas nitriding or gas nitriding carburizing process in a heat treatment furnace; (2) performing an oxidation treatment process on the treated material in a heat treatment furnace under an oxidizing gas atmosphere; And (3) there is provided a method for producing a high corrosion resistance and fouling resistant steel material comprising the step of performing a rubbing resin coating or UV coating for the treated material.

According to the present invention, after the step (1) may further comprise the step of cooling the treated material in the air.

Further, according to the present invention, the gas nitriding or gas nitriding carburization process or the heat treatment furnace which performs the oxidation treatment process is a fit furnace, a sealed quench furnace, a fluidized bed furnace, a continuous furnace and a vacuum furnace. It is any one selected from.

According to the present invention, surface finishing can be carried out as necessary in consideration of the importance of the appearance of the product, such as buffing, lapping, polishing or shot peening. It can carry out by any one process chosen from among them, The surface roughness obtained by it is good to carry out within the range of 0.5-5 micrometers Ra.

On the other hand, the oxidation treatment step may be carried out in the same furnace in which the gas nitriding or gas nitriding carburization treatment step is performed, or in a furnace different from this.

The oxidizing gas used in the oxidation treatment process according to the present invention may be oxygen, air, carbon dioxide, and steam, for example, and each of these gases or a mixed gas thereof, or nitrogen gas may be further included therein.

The resin constituting the anti-fingerprint coating layer is selected from urethane, acryl or alkyd.

The UV coating is selected from 2-hydroxy benzopinones, 2-high hindered amines, organonickel compounds, silicates, cinnamate diprezocinols, monobenzoates, oxacylidees, and p-hydrobenzobenzoes. It is characterized by using a UV curing paint.

According to the present invention made as described above, it provides the following effects.

First, since it is possible to provide a steel material having high gloss, high anti-fingerprint and pollution resistance that cannot be realized by the conventional method, the handling is easy and the appearance is beautiful.

Second, it is possible to provide a steel material having a higher corrosion resistance than the conventional gas nitriding or nitriding process.

According to the present invention, after performing gas nitriding or gas nitriding on a steel material, an oxidation process is performed, and then surface finishing processing is performed on steel materials as necessary, and a transparent or fingerprint coating, color or fingerprint coating or UV coating is performed. It is composed.

In the gas nitriding or gas nitriding, the process gas may use a mixed gas such as an endothermic gas and ammonia or a mixed gas of ammonia, carbon dioxide and nitrogen, or a mixed gas of ammonia and nitrogen.

The single or carbonitrides are formed, or the amount of the γ'-Fe ₄ N different mixed blend onto each of these nitride single phase nitrides or ε-Fe ₃ (CN) on the ε-Fe ₃ N in accordance with the nitride or nitride carburization step A compound layer composed of a phase may be formed, and the thickness thereof is preferably 15 to 30 µm in consideration of peelability and economical efficiency.

The nitriding or nitriding process is carried out for 30 minutes to 20 hours in a temperature range of 450 to 700 ° C., a mixed gas of endothermic gas (Rx Gas) and ammonia or a mixed gas of ammonia, carbon dioxide and nitrogen, or a mixture of ammonia and nitrogen. Although it can implement in gas atmosphere, such as a gas, if the objective of this invention can be satisfied, the process will not be restrict | limited in particular. More specific techniques related to nitriding or nitriding and carburizing treatment according to the present invention are disclosed in detail in Korean Patent No. 0504131 proposed by the present inventor, and thus description thereof is omitted here.

The post-oxidation process is carried out for the purpose of forming a compound layer of Fe ₃ O ₄ to improve the corrosion resistance, after performing gas nitriding or gas nitriding, purging the process gas with nitrogen gas, preferably in the same furnace Oxidation process is performed and steel materials are quenched in air-cooled, water-soluble refrigerant or water.

Alternatively, gas nitriding or gas nitriding may be carried out and purged with nitrogen gas, then the steel material may be taken out of the furnace, cooled in air, water-soluble refrigerant or water and subjected to post-oxidation in another furnace. As a method, even after cooling in the air after nitriding or nitriding and nitriding, oxidation occurs while cooling in the air without using a separate furnace, and this case is also included in the post-oxidation process.

At this time, steel materials that require strength can be quenched in water-soluble refrigerants or water after gas nitriding or gas nitriding, and steel materials that do not require strength can be air-cooled, and they can be quenched in water-soluble refrigerants or water to improve productivity even if they do not require strength. can do.

When the post-oxidation process is carried out in the same furnace, a temperature of 500 ° C. to 570 ° C. is preferable. In this case, the oxidation time may be performed for 5 minutes to 1 hour. In order to form a dense Fe ₃ O ₄ compound layer, it is preferable to carry out for 0.3 hours to 5 hours at 250 ℃ to 500 ℃.

At this time, the thickness of the oxide layer is 0.05 to 5㎛, preferably 0.5 to 1㎛ is good, the composition of the oxide layer is most of Fe ₃ O ₄ Phase and small amount of Fe ₂ O ₃ It can be mixed into the phase.

The oxidizing gas used in the post oxidation process may be used alone or in a mixture of all oxidizing gases such as oxygen, air, carbon dioxide, and steam, regardless of the post oxidation process. In addition, the oxidizing gas may include nitrogen gas.

On the other hand, the heat treatment furnace for the gas nitridation treatment, gas nitrate carburizing treatment or post-oxidation treatment may be applied to the fit type, sealed quench furnace, fluidized bed furnace, continuous furnace, etc. If it can satisfy | fill, it is not specifically limited to these furnaces.

Since the surface color of the material after the post-oxidation process is low gloss black, surface finishing such as buffing, lapping, polishing or shot peening of steel materials is performed to increase the surface glossiness. can do.

The surface finishing process is Fe ₃ O ₄ of the surface to improve the appearance characteristics It is preferable to carry out to the extent that an oxide is not removed completely, and the roughness is performed in 0.5-5 micrometers Ra range. If the Fe ₃ O ₄ oxide is completely removed, the adhesion between the steel material and the resin is lowered, which may lower the durability of the resin and the corrosion resistance of the steel material.

Thereafter, the surface of the steel material is coated with a resin such as urethane, acrylic, or alkyd resin, or 2-hydroxy benzopinones, 2-high hindered amines, organic nickel compounds, silicate, cinna UV coating is performed using UV curing paints such as mate diprezocinol, monobenzoate, oxacylide, p-hydrobenzobenzoate and the like.

Anti-fingerprint resin coating is for imparting high gloss, anti-fingerprint and fouling resistance to the surface of the gas-nitrided or gas-nitrided carburized steel and improving corrosion resistance. The coating method is spraying a liquid paint such as urethane, acrylic or alkyd It is composed of 3 ~ 50㎛ thickness on the surface of steel material and drying it at the temperature of 30 ~ 400 ℃ by the method such as coating or dipping or brushing. The fingerprint resin coating layer is formed.

Subsequently, the anti-fingerprint resin coating layer thus formed is dried to improve glossiness and adhesion characteristics. The anti-fingerprint resin coating layer is dried at a temperature range of 30 to 400 ° C. in a pit furnace or a continuous furnace equipped with a transfer device. .

On the other hand, since the color of the steel material subjected to the post-oxidation process is black, when it is necessary to give a color color to the steel material may be carried out color anti-fingerprint coating.

UV coating is a method of coating an object by using a coating cured in a short time by ultraviolet irradiation can improve the hardness, chemical resistance, corrosion resistance and fingerprint resistance compared to the general coating.

≪ Example 1 >

Pipes made of cold rolled material with an outer diameter of 27.8mmΦ, thickness 0.8mmt and length of 3000mmL were heated at 570 ℃ for 3 hours at a total flow rate of 30㎥, 50% NH ₃ -5% CO ₂ -45% N ₂ % Is the volume%, the same as below) gas nitrate carburizing treatment in a pit furnace of 1200mm Φ 3500mmH, purged with nitrogen gas in the same furnace, and then the temperature was lowered to 540 ℃.

Thereafter, steam was added at this temperature for 30 minutes, oxidation treatment was performed, followed by air cooling, followed by buffing polishing to obtain a surface roughness of 1.3 µm Ra, which was then sprayed onto a pipe having an oxide layer of Fe ₃ O _{4 having} a thickness of 1.0 µm. The urethane type fingerprint coating of 10 micrometers in thickness was performed, and the black high gloss beautiful surface pipe was obtained.

As a result of evaluating corrosion resistance of the pipe by 5% salt spray test, the anti-fingerprint resin-uncoated part partially rusted in less than 120 hours, but the anti-fingerprint resin-coated example of the present example was not found even at 800 hours.

<Example 2>

Pipes made of cold rolled material with an outer diameter of 31.8mmΦ, thickness 1.0mmt and length 2000mmL were heated at 570 ℃ for 3 hours at a total flow rate of 35㎥, 1200mmΦ in a gas atmosphere with 60% NH ₃ -5% CO ₂ -35% N ₂ . Gas nitriding was carried out in a pit furnace of 3,500 mmH, purged with nitrogen gas, and quenched with a water-soluble refrigerant.

Thereafter, the pipe was charged to a separate 1200 mm Φ × 3500 mmH pit furnace maintained at 350 ° C., steam was added for 20 minutes, oxidized, and then cooled by water to form Fe ₃ O ₄ having a thickness of 2.0 μm. A pipe on which the oxide layer was formed was deposited on an alkyd resin to carry out anti-fingerprint coating.

As a result of evaluating the glossiness of this pipe by the Mencell method, the glossiness of the anti-fingerprint resin coated product was 21, but the anti-fingerprint resin coated product of this Example was 70, and the 5% salt spray test result showed 120 hours of the anti-fingerprint coated product. Although fittings and the like were stained at less than, the anti-fingerprint resin coating product of the present example was not rusted even after 600 hours, and no discoloration by ultraviolet rays was detected.

While the invention has been shown and described in connection with the preferred embodiments for illustrating the principles of the invention, the invention is not limited to the construction and operation as shown and described. That is, those skilled in the art will appreciate that many changes and modifications can be made to the present invention without departing from the spirit and scope of the appended claims.

Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

Claims (10)

(1) purging the steel material with nitrogen gas after a gas nitriding or gas nitriding carburization process in a heat treatment furnace; (2) forming a black oxide layer on the surface of the treated material by performing an oxidation treatment process on the treated material in a heat treatment furnace under an oxidizing gas atmosphere; (3) performing a surface finishing process so that the surface of the black oxide layer is uniformly roughened to improve the glossiness while maintaining the black surface color of the treated material as it is; And (4) a method for producing a highly corrosion-resistant and stain-resistant steel material comprising the step of performing a transparent anti-fingerprint resin coating or UV coating to the treated material. delete delete delete The method of claim 1, The surface finishing is performed by any one process selected from buffing, lapping, polishing, or shot peening, and the surface roughness obtained thereby is in the range of 0.5 to 5 탆 Ra. Method for producing a high corrosion resistance and fouling resistant steel material, characterized in that. delete The method of claim 1, The oxidation treatment process is performed for 5 minutes to 5 hours in the temperature range of 250 ℃ to 570 ℃, the oxidizing gas used in the oxidation treatment process used is selected from the group containing oxygen, air, carbon dioxide, and steam. At least one or a method for producing a highly corrosion-resistant and fouling-resistant steel material, characterized in that it further comprises nitrogen gas. The method of claim 1, The transparent anti-fingerprint resin coating is a method of manufacturing a high corrosion resistance and fouling resistant steel material, characterized in that the resin coating layer obtained by using a resin selected from urethane, acrylic or alkyd. delete delete