KR102375231B1 - Process for heat treatment by nitriding of basemetals - Google Patents

Abstract

The present invention relates to a nitrification heat treatment method of a metal base material, the nitrification heat treatment method comprising: a metal base material preparation step (S100) of preparing a metal base material; a metal base material washing step (S200) of washing the prepared metal base material with a cleaning solution to remove foreign substances attached to a surface of the metal base material; a salt bath preparation step (S300) of preparing a salt bath in which the metal base material is to be immersed; a titanium dioxide metal powder dispersion step (S400) of inputting and dispersing titanium dioxide (TiO_2) metal powder in the salt bath; a salt bath heating step (S500) of heating the salt bath in which the titanium dioxide (TiO_2) metal powder is dispersed; a metal base material immersion step (S600) of immersing the metal base material in the heated salt bath; and a surface modification step (S700) of forming a nitrogen nitride layer by thermally treating the surface of the metal base material on which a titanium nitride layer is formed. Accordingly, a metal base material with high hardness and a thick nitride layer can be prepared by nitriding a base material made of metal. Also, a thermally nitrified metal base material capable of improving corrosion resistance and wear resistance of a metal base material can be prepared.

Description

Nitriding heat treatment method of metal base material {PROCESS FOR HEAT TREATMENT BY NITRIDING OF BASEMETALS

The present invention relates to a nitridation heat treatment method of a metal base material, and more particularly, by nitriding the base material made of a metal, a metal base material having a high hardness and a thick nitride layer can be manufactured, and the corrosion resistance and wear resistance of the metal base material can be improved. It relates to a nitridation heat treatment method of a metal base material that can be used.

A hardened nitride layer has been commercially used as a protective hardened layer resistant to corrosion, abrasion and erosion, and titanium nitride has received much attention due to its excellent properties.

A useful cured layer should have good bonding strength between the cured layer and the base material layer. Good adhesion is an important requirement for processing commercially available nitriding heat treatment processes.

Accordingly, a number of nitriding heat treatment processes have been developed, and attempts have been made to improve the interfacial strength between the hardened layer and the base material layer in each of such processes.

Nitriding heat treatment processes currently in use include Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), and Ion Assisted Coating (IAV) and combinations of these processes.

However, such a known heat treatment process has a problem in that contaminants may remain in the interface layer between the base material layer and the cured layer, and these contaminants weaken the bonding force and eventually peel the cured layer. Such heat treatment processes are usually initiated as a cleaning process using ion sputtering to remove contaminating compounds such as sulfides and the like from the surface of the cold base material to be hardened.

However, during the nitriding heat treatment process, the base material is usually heated to 1100~2200 °F, and all sulfur present in the base material diffuses from the bulky base material and segregates on the surface of the base material to form stable sulfides. do. This sulfide interferes with the application of the cured layer and significantly reduces the adhesion of the cured layer.

The conventional nitriding treatment requires nitriding and long-term activation at a high temperature (760° C. or higher) to harden the base material. Other techniques reduce activation and nitridation times, but require high-temperature electrolysis in the presence of a titanium catalyst.

The usefulness of this process is limited in that the base material to be nitrided is warped or distorted at high temperature, and further, electrolysis or long-term activation and nitridation treatment time are unnecessary and inefficient. Therefore, there is a need for an efficient nitriding treatment method that forms a thick and hard nitride layer on various base materials and improves corrosion resistance and wear resistance.

Domestic Registered Patent No. 10-1204509 (Registered on November 19, 2012) Domestic Registered Patent No. 10-1918892 (registered on November 08, 2018)

The present invention is to provide a nitridation heat treatment method of a metal base material capable of manufacturing a metal base material having a high hardness and a thick nitride layer and improving the corrosion resistance and wear resistance of the metal base material by nitriding the base material made of metal.

Various problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The nitridation heat treatment method of a metal base material according to the present invention includes a metal base material preparation step (S100) of preparing a metal base material; a metal base material cleaning step (S200) of washing the prepared metal base material with a cleaning solution to remove foreign substances adhering to the surface of the metal base material; A salt bath manufacturing step of preparing a salt bath (salt bath) in which the metal base material is immersed (S300); A titanium dioxide (TiO 2 ) metal powder dispersing step (S400) of dispersing the titanium dioxide (TiO ₂ ) metal powder in the salt bath; The titanium dioxide (TiO ₂ ) salt bath heating step (S500) of heating a salt bath in which the metal powder is dispersed; A metal base material immersion step (S600) of immersing the metal base material in the heated salt bath; and a surface modification step (S700) of heat-treating the surface of the metal base material on which the titanium nitride layer is formed to form a nitrogen nitride layer.

In the metal base material preparation step (S100), as the metal base material, any one or more metal base materials selected from the group consisting of steel and steel alloys, SUS, carbon steel and carbon steel alloys, aluminum and aluminum alloys, titanium and titanium alloys may be used. .

In the metal base material washing step (S200), the washing solution is 0.1 to 2% by weight of a thiourea compound, 0.1 to 1% by weight of a persulfate, 0.05 to 0.15% by weight of a surfactant, 3 to 7% by weight of hydrochloric acid, 0.5 to 1.5% by weight of nitric acid %, 0.1 to 1% by weight of phosphoric acid, and the balance of deionized water.

In the salt bath preparation step (S300), the salt bath may be included in a weight ratio of 70 to 80% by weight of the phosphate compound and 20 to 30% by weight of sodium dioxide.

The phosphate compound is monobasic sodium phosphate (NaH ₂ PO ₄ ), dibasic sodium phosphate (Na ₂ HPO ₄ ), trisodium phosphate (Na ₃ PO ₄ ), first potassium phosphate (KH ₂ PO ₄ ), second Potassium phosphate (K ₂ HPO ₄ ), ammonium phosphate monobasic ((NH ₄ )H ₂ PO ₄ ), ammonium phosphate dibasic ((NH ₄ ) ₂ HPO ₄ ) and ammonium tertiary ((NH ₄ ) ₃ PO ₄ ), any one or more selected from the group consisting of may be used.

In the titanium dioxide metal powder dispersion step (S400), 5 to 10 parts by weight of titanium dioxide powder may be added to 100 parts by weight of the salt bath.

In the salt bath heating step (S500), the salt bath in which the titanium dioxide (TiO ₂ ) metal powder is dispersed may be heated to a temperature of 600 to 700 °C.

In the metal base material immersion step (S600), the metal base material may be immersed in the heated salt bath for 5 to 10 hours.

Specific details of other embodiments are included in the detailed description.

The nitridation heat treatment method of a metal base material according to the present invention can manufacture a metal base material having a high hardness and a thick nitride layer by nitriding the base material made of a metal, and the nitriding heat treatment metal that can improve the corrosion resistance and wear resistance of the metal base material The base material can be manufactured.

It will be fully understood that embodiments of the technical idea of the present invention may provide various effects not specifically mentioned.

1 is a flowchart for explaining a nitriding heat treatment method of a metal base material according to the present invention.

Advantages and features of the present invention, and methods for achieving them, will become apparent with reference to the embodiments described below in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed subject matter may be thorough and complete, and that the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with the meanings in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

Hereinafter, the nitridation heat treatment method of the metal base material according to the present invention will be described in more detail with reference to the accompanying drawings.

1 is a flowchart for explaining a nitriding heat treatment method of a metal base material according to the present invention.

1, the nitridation heat treatment method of a metal base material according to the present invention comprises a metal base material preparation step (S100), a metal base material washing step (S200), a salt bath preparation step (S300), a titanium dioxide metal powder dispersion step (S400), It includes a salt bath heating step (S500), a metal base material immersion step (S600) and a surface modification step (S700).

1. Metal base material preparation step (S100)

The metal base material preparation step ( S100 ) is a step of preparing a metal base material to be subjected to nitriding heat treatment.

In the metal base material preparation step (S100), various types of base metals may be prepared as the metal base material. For example, as the metal base material, steel and steel alloys, SUS, carbon steel and carbon steel alloys, Any one or more metal base materials selected from the group consisting of aluminum and aluminum alloys, titanium and titanium alloys may be used.

2. Metal base material cleaning step (S200)

The metal base material cleaning step (S200) is a step of removing foreign substances adhering to the surface of the metal base material by washing the prepared metal base material with a cleaning solution.

In the metal base material washing step (S200), the prepared metal base material is immersed in a washing solution or washed with a washing solution to remove foreign substances adhering to the surface, thereby producing a thick, corrosion-resistant, abrasion-resistant metal base material with a nitrided layer formed thereon. The washing solution may be composed of a thiourea compound, a persulfate, a surfactant, hydrochloric acid, nitric acid, phosphoric acid and deionized water.

That is, in the metal base material washing step (S200), the washing solution is 0.1 to 2% by weight of the thiourea compound, 0.1 to 1% by weight of persulfate, 0.05 to 0.15% by weight of surfactant, 3 to 7% by weight of hydrochloric acid, 0.5% by weight of nitric acid to 1.5% by weight, 0.1 to 1% by weight of phosphoric acid and the balance of deionized water.

The thiourea compound may be included so that the washing solution can be stably maintained when the metal base material is washed, and the thiourea compound is thiourea (NH ₂ ) ₂ CS or the general formula (R1R2N)(R3R4N)C It may include a thiourea derivative represented by =S (here, R1, R2, R3, and R4 are each independently any one selected from a hydrogen atom, an ethyl group, or a methyl group).

The persulfate is a material used as an oxidizing agent, and the persulfate may serve to facilitate cleaning. The persulfate is ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ) , sodium persulfate (Na ₂ S ₂ O ₈ ) or potassium persulfate (K ₂ O ₈ S ₂ ) Any one or more selected from may be used.

The surfactant may be added so that the composition constituting the washing solution is uniformly dispersed to improve the stability of the surface of the metal base material and to allow the washing solution to easily flow to the surface of the metal base material. It may include an active agent and a cationic surfactant, and the cationic surfactant may be included in a weight ratio of 1 to 10 parts by weight based on 100 parts by weight of the nonionic surfactant.

In addition, any one or more selected from the group consisting of polyethylene glycol, polyethylene glycol methyl ether, polyethylene glycol monoallyl ether and polyethylene glycol bisphenol-A ether may be used as the nonionic surfactant, and the cationic surfactant may be cetyl Any one or more selected from the group consisting of trimethylammonium chloride, cetyltrimethylammonium bromide, cetylammonium chloride and cetylammonium bromide may be used.

The hydrochloric acid is used as an oxidizing agent, and the nitric acid and phosphoric acid are used as auxiliary oxidizing agents. It can be washed and damaged.

The deionized water is from which ions in water have been removed, and it is preferable to use deionized water having a specific resistance of 18 MΩ·cm or more as the deionized water.

3. Salt bath preparation step (S300)

The salt bath preparation step ( S300 ) is a step of preparing a salt bath in which the metal base material is to be immersed.

In the salt bath preparation step (S300), the salt bath may be prepared by mixing a phosphate compound and sodium dioxide, and the salt bath is 70 to 80% by weight of a phosphate compound and 20 to 30% by weight of sodium dioxide may be included in a weight ratio of

In addition, in the salt bath preparation step (S300), the phosphate compound is monobasic sodium phosphate (NaH ₂ PO ₄ ), second sodium phosphate (Na ₂ HPO ₄ ), third sodium phosphate (Na ₃ PO ₄ ), first phosphoric acid potassium (KH ₂ PO ₄ ), dipotassium phosphate (K ₂ HPO ₄ ), monoammonium phosphate ((NH ₄ )H ₂ PO ₄ ), diammonium phosphate ((NH ₄ ) ₂ HPO ₄ ) and tertiary Any one or more selected from the group consisting of ammonium phosphate ((NH ₄ ) ₃ PO ₄ ) may be used.

4. Titanium dioxide metal powder dispersion step (S400)

The titanium dioxide metal powder dispersing step (S400) is a step of dispersing the titanium dioxide (TiO ₂ ) metal powder after it is added to the salt bath.

In the titanium dioxide metal powder dispersion step (S400), by adding 5 to 10 parts by weight of titanium dioxide powder to 100 parts by weight of the salt bath, the nitride layer formed of titanium later has good bonding strength with the metal base material, It can form a titanium nitride layer that is resistant to corrosion, abrasion and erosion.

5. Salt bath heating step (S500)

The salt bath heating step (S500) is a step of heating the salt bath in which the titanium dioxide (TiO ₂ ) metal powder is dispersed.

In the salt bath heating step (S500), by heating the salt bath in which the titanium dioxide (TiO ₂ ) metal powder is dispersed to a temperature of 600 to 700 ° C., the titanium contained in the titanium dioxide (TiO ₂ ) metal powder is ionic in the salt bath. can be made to exist.

6. Metal base material immersion step (S600)

The metal base material immersion step (S600) is a step of immersing the metal base material in the heated salt bath.

In the metal base material immersion step (S600), by immersing the metal base material in the heated salt bath for 5 to 10 hours, a titanium nitride layer having a thickness of 100 to 200 μm may be formed on the surface of the metal base material.

7. Surface modification step (S700)

The surface modification step (S700) is a step of forming a nitrogen nitride layer to a predetermined thickness by heat-treating the surface of the metal base material on which the titanium nitride layer is formed.

In the surface modification step (S700), a nitrogen nitride layer can be formed by heating a reaction gas made of ammonia (NH ₃ ) to a predetermined temperature and then spraying it onto the titanium nitride layer for a predetermined time period, the surface modification step (S700) ) by using a known reaction chamber to heat a reaction gas made of ammonia (NH ₃ ) to 550 to 650 ° C. A nitrogen nitride layer may be formed.

At this time, the reaction gas made of ammonia (NH ₃ ) undergoes a reaction of 2NH ₃ ⇔ 3H ₂ + 2N, as a result, nitrogen atoms cause a nitridation process on the surface of the titanium nitride layer to form a nitrogen nitride layer with a thickness of 30 to 80 μm By doing so, it is possible to form a thick metal base material with improved corrosion resistance and wear resistance.

Hereinafter, with reference to the accompanying drawings, an embodiment of the nitridation heat treatment method of the metal base material according to the present invention will be described in more detail.

<Example>

First, a carbon steel alloy was prepared as a metal base material, and the carbon steel alloy was prepared by using 1 wt% of a thiourea compound, 0.5 wt% of a persulfate, 0.1 wt% of a surfactant, 5 wt% of hydrochloric acid, 1 wt% of nitric acid, 0.5 wt% of phosphoric acid and It was washed with a washing solution consisting of the remainder of deionized water.

Next, a salt bath (salt bath) mixed with 75 wt% of sodium phosphate (NaH ₂ PO ₄ ) and 25 wt% of sodium dioxide was prepared, and 8 parts by weight of titanium dioxide metal powder was added with respect to 100 parts by weight of the salt bath. After dispersing, it was heated to a temperature of 650°C.

Next, the carbon steel alloy was immersed in the heated salt bath for 8 hours to form a titanium nitride layer on the surface of the carbon steel alloy.

Subsequently, after heating the carbon steel alloy with the titanium nitride layer formed thereon to 600 to 610° C. of a reaction gas made of ammonia (NH ₃ ) using a reaction chamber, the heated reaction gas is titanium nitrided at a spray rate of 900 m/s. A nitrogen nitride layer was formed by spraying over the layer.

1. Nitride layer thickness measurement

The thickness of the nitride layer was measured in the carbon steel alloy in which the nitride layer was formed as in the above example.

* Thickness of titanium nitride layer: 162㎛

* Thickness of nitrogen nitride layer: 60㎛

2. Surface hardness and water resistance evaluation

(1) Surface hardness evaluation

Pencil hardness was measured according to KS D 6711.

(2) Water resistance evaluation

The time for continuous surface deformation (cracks, blisters, etc.) to occur in hot water at 90°C was measured.

The evaluation results are shown in [Table 1].

division Example surface hardness 4H water resistance 820hr

Referring to [Table 1], it can be confirmed that the metal base material having the nitride layer formed according to the embodiment is thick, has excellent surface hardness, and has excellent durability.

As described above, a preferred embodiment of the present invention has been described, but those of ordinary skill in the art to which the present invention pertains will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential features thereof. will be able Therefore, it should be understood that the embodiment described above is illustrative in all respects and not restrictive.

Claims (5)

A metal base material preparation step of preparing a metal base material (S100);
a metal base material cleaning step (S200) of washing the prepared metal base material with a cleaning solution to remove foreign substances adhering to the surface of the metal base material;
A salt bath manufacturing step of preparing a salt bath (salt bath) in which the metal base material is immersed (S300);
A titanium dioxide (TiO 2 ) metal powder dispersing step (S400) of dispersing the titanium dioxide (TiO ₂ ) metal powder in the salt bath;
The titanium dioxide (TiO ₂ ) salt bath heating step (S500) of heating a salt bath in which the metal powder is dispersed;
A metal base material immersion step (S600) of immersing the metal base material in the heated salt bath to form a titanium nitride layer on the surface of the metal base material; and
and a surface modification step (S700) of heat-treating the surface of the metal base material on which the titanium nitride layer is formed to form a nitrogen nitride layer,
In the salt bath preparation step (S300), the salt bath is included in a weight ratio of 70 to 80% by weight of the phosphate compound and 20 to 30% by weight of sodium dioxide,
The phosphate compound is monobasic sodium phosphate (NaH ₂ PO ₄ ), dibasic sodium phosphate (Na ₂ HPO ₄ ), trisodium phosphate (Na ₃ PO ₄ ), first potassium phosphate (KH ₂ PO ₄ ), second Potassium phosphate (K ₂ HPO ₄ ), ammonium phosphate monobasic ((NH ₄ )H ₂ PO ₄ ), ammonium phosphate dibasic ((NH ₄ ) ₂ HPO ₄ ) and ammonium tertiary phosphate ((NH ₄ ) ₃ PO ₄ ) nitriding heat treatment method of a metal base material, characterized in that any one or more selected from the group consisting of is used. The method of claim 1,
In the metal base material preparation step (S100), as the metal base material, any one or more metal base materials selected from the group consisting of steel and steel alloys, SUS, carbon steel and carbon steel alloys, aluminum and aluminum alloys, and titanium and titanium alloys are used. A method of nitriding heat treatment of a metal base material. 3. The method of claim 2,
In the metal base material washing step (S200), the washing solution is 0.1 to 2% by weight of a thiourea compound, 0.1 to 1% by weight of a persulfate, 0.05 to 0.15% by weight of a surfactant, 3 to 7% by weight of hydrochloric acid, 0.5 to 1.5% by weight of nitric acid %, phosphoric acid 0.1 to 1% by weight, and nitridation heat treatment method of a metal base material comprising the remaining amount of deionized water. delete 4. The method of claim 3,
In the titanium dioxide metal powder dispersion step (S400), it is added in a weight ratio of 5 to 10 parts by weight of titanium dioxide metal powder with respect to 100 parts by weight of the salt bath,
In the salt bath heating step (S500), the titanium dioxide (TiO ₂ ) The salt bath in which the metal powder is dispersed is heated to a temperature of 600 to 700 ℃,
In the metal base material immersion step (S600), a nitridation heat treatment method of a metal base material, characterized in that immersing the metal base material in the heated salt bath for 5 to 10 hours.

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