KR20200070849A - Method of thermal nitriding of workpiece surface - Google Patents

Abstract

The present invention relates to a thermal oxy-nitriding method on the surface of a workpiece, which performs an oxy-nitriding process on the surface of a material of a component (workpiece) which simultaneously requires strength against impact and high surface hardness, such as a gear, a cam, a clutch, a slide core, an insert, a core pin, and a sleeve that are manufactured on an industrial site, thereby providing surface hardness, wear resistance, and thermal resistance. To this end, the present method comprises: a step of injecting ammonia (NH_3) and nitrogen (N_2) at the ratio of 1:1 for performing a nitriding process on a workpiece; a step of gradually increasing the temperature to 520°C for the first 120 minutes; a step of injecting 0.8 wt% of carbon dioxide (CO_2) with respect to 100 wt% of the total accommodating space of a chamber and then maintaining 520°C for 300 minutes to perform nitriding; a step of, after the nitriding, maintaining 520°C for 300 minutes, supplying gas of nitrogen (N_2) and oxygen (O_2) at the ratio of 8:2, and maintaining 520°C for 20 minutes to perform oxy-nitriding, thereby forming an oxidation thin film (Fe_3O_4) layer; and a step of, after the oxy-nitriding, gradually cooling for 120 minutes to drop the temperature to 100°C or lower and ejecting the workpiece from a nitriding furnace.

Description

{Method of thermal nitriding of workpiece surface}

The present invention is an oxynitriding treatment on the material surface of parts (workpieces) that require high hardness of impact strength and surface at the same time, such as gears, cams, clutches, slide cores, inserts, core pins, sleeves, etc., manufactured in the industrial field. The present invention relates to a method of heat treatment oxynitriding a workpiece surface having surface hardness, abrasion resistance, and heat resistance.

In general, surface heat treatment has been performed on parts requiring high strength against impact and surface hardness, such as gears, cams, clutches, slide cores, inserts, core pins, sleeves, etc., manufactured at industrial sites.

As described above, a method of improving the properties of surface hardness, abrasion resistance, and heat resistance by performing heat treatment on the surface of the material, and increasing the resistance to impact by providing moderate strength is referred to as a surface hardening method.

As one of the surface hardening methods, the nitriding method diffuses nitrogen by heating the nitriding steel in an ammonia stream or a salt bath, and the nitriding steel is iron nitride on the surface of nitriding ( FeN) layer, that is, to form a nitride layer.

Such nitriding methods include gas nitriding, liquid nitriding (or salt bath nitriding), soft nitriding, and ion nitriding. Among them, the liquid nitriding method or the salt bath nitriding method is a method of nitriding at about 570°C using a molten salt bath containing KCN + KCNO + Na2CO3 as a main component, and it is difficult to control wastewater and process due to the use of toxic chemicals. .

In particular, the liquid nitriding method has a slight difference depending on the shape of the product to be heat treated. That is, there is no problem in the case where the outer surface of the product of the object is concise during heat treatment by the liquid nitriding method, but when the outer surface has a complicated shape or when a large number of holes are formed inside, such as the engine cover of a car, the liquid material is injected from the inside of the nitriding furnace. When proceeding in this manner, there is a problem in that the nitride layer is not formed uniformly because a nitride layer is not formed in a gap or a cooling hole having a complicated shape.

Looking at the prior art in this field, the patent registration No. 10-0595000 (registration date: June 22, 2006) "Pressure control free low-temperature/low-pressure gas oxynitriding of ferrous metals" (hereinafter "previous technology" 1"), after evacuating the inside of the chamber (chamber) of the nitrification furnace, nitrogen (N2) gas is introduced, and the primary heating step (10) to raise the temperature to 180 ℃ to 350 ℃; A constant temperature and pre-oxidation step (20) in which an oxidizing gas is introduced into the chamber to form a thin oxide film on an iron-based metal surface; After evacuating the interior of the chamber, ammonia (NH3) gas is introduced into the chamber, and a second heating step 30 of raising the temperature; After evacuating the inside of the chamber, a nitriding step (40) of nitriding by introducing ammonia, nitrogen, and oxidizing gas into the chamber at a predetermined composition ratio so that the internal pressure of the chamber becomes 50 mbar to 1000 mbar; A cooling and oxidation step (50) in which an oxidation treatment is performed using H2O under a normal pressure (1 atm) of the internal pressure of the chamber; Disclosed is a method for oxynitriding an iron-based metal including a cooling step 60 in which nitrogen gas is introduced and cooled to room temperature after evacuating the inside of the chamber.

As another prior art, "One-way clutch bearing of oxynitride-treated fishing reel" (hereinafter referred to as "Prior Art 2") of Registered Utility Model Publication No. 20-0426495 (Registration Date: September 07, 2006) In a silver fishing reel component, a one-way clutch bearing of an oxynitriding fishing reel in which a film layer is formed from the surface of the fishing reel component to a predetermined depth by a conventional oxynitriding heat treatment method has been disclosed. .

Both of the prior arts 1 and 2 are techniques for oxynitriding parts, and in the first heating step, nitrogen (N ₂ ) gas is introduced into the nitriding furnace chamber to raise the temperature first, and then acidification gas is introduced into the chamber again to form an oxide film. After the formation, the ammonia (NH ₃ ) is again introduced into the chamber to heat up a second time, and then ammonia gas, nitrogen, and acidification gas are introduced into the chamber to perform the nitridation step.

That is, in the case of the prior arts 1 and 2, a primary oxidation film is formed at this time by introducing an acidifying gas after first raising the temperature by injecting nitrogen gas. After the oxide film is formed as described above, ammonia gas is introduced into the chamber again, the temperature is raised for a second time, and then vacuum exhausted, followed by injection of ammonia, nitrogen, and acidified gas into the chamber to undergo a nitridation step. Although the oxynitride is formed on the surface, the heat-treated component materials are installed on the site, and when heat of 300° C. or higher is applied, the surface strength gradually decreases.

Republic of Korea Registered Patent Publication No. 10-0595000 Republic of Korea Utility Model Publication No. 20-0426495

The present invention is to solve the problems as described above, gears, cams, clutches, slide cores, inserts, core pins, sleeves, etc. manufactured in the industrial field, and parts that require high strength against impact and high surface hardness at the same time The object is to perform the oxynitriding treatment on the surface of the material of the (processed product) to have surface hardness, abrasion resistance, and heat resistance.

In addition, the present invention is ammonia (NH ₃ ), carbon dioxide (CO ₂ ), nitrogen (N ₂ ), oxygen (O ₂ ) is introduced to form a nitride layer depth of 100 μm to 200 μm, and an oxide layer (Fe ₃ O) on the surface. _It relates to a heat treatment oxynitriding method of a work surface for the purpose of forming ₄ ) and improving corrosion resistance, abrasion resistance and strength by having a surface hardness of Hrc46±1.

The present invention as a means for solving the above object,

Removing oil and foreign substances on the surface of the processed work piece by cleaning and removing the processed chromium film on the surface using sanding;

After removing the processed chromium film on the surface, loading a work piece into a chamber of a nitriding furnace;

Injecting ammonia (NH ₃ ) 1: nitrogen (N ₂ ) 1 into the nitriding chamber loaded with the workpiece;

The ammonia (NH ₃ ) 1: Nitrogen (N ₂ ) 1 After injecting into the nitrifying furnace, gradually raising the temperature to 520°C for the first 120 minutes, and nitriding by maintaining 520°C for 300 minutes;

Raising the temperature to 520° C. and injecting 0.8% by weight of carbon dioxide (CO ₂ ) with respect to 100% by weight of the total receiving space in the nitriding furnace, and then maintaining the temperature at 520°C for 300 minutes to perform nitriding;

After performing the nitridation, after maintaining 300 minutes at 520° C., the gas was supplied at a ratio of nitrogen (N ₂ ) 8: oxygen (O ₂ ) 2 to oxynitride while maintaining at 520° C. for 20 minutes (Fe ₃ O ₄ ) forming a layer;

It is characterized in that it consists of a step of taking the product out of the nitriding furnace after cooling to 100° C. or less by slowly cooling it for 120 minutes after oxynitriding while maintaining 520° C. for 20 minutes.

In this way, the present invention is made to have surface hardness, abrasion resistance, and heat resistance by subjecting the material surface of a component (workpiece) that requires both strength and high hardness at the same time to an oxynitriding treatment.

The present invention has an effect of smoothly forming oxynitrides in small holes and small inner corners by putting a gaseous material inside the nitriding furnace to proceed with nitriding and at the same time applying a certain pressure during nitriding to form a nitride layer inside the cooling hole. .

1 is a substitute photograph showing a process flow diagram of oxidizing a work piece as an embodiment according to the present invention,
Figure 2 shows the oxynitride layer capability formed by the heat treatment oxynitriding method of the workpiece surface of the present invention,
Figure 3 is an enlarged view of the oxynitriding structure of the workpiece in which the oxynitride layer is formed by the heat treatment oxynitriding method of the workpiece surface of the present invention,
Figure 4 illustrates the oxynitride structure layer formed by the heat treatment oxynitriding method of the workpiece surface of the present invention,
Figure 5 is an exemplary view showing the hardness and depth of the nitride layer of the oxynitride layer of the specimen A formed by the heat treatment oxynitriding method of the workpiece surface of the present invention,
Figure 6 is an exemplary view showing the hardness and depth of the nitride layer of the oxynitride layer of the specimen B formed by the heat treatment oxynitriding method of the workpiece surface of the present invention,
Figure 7 shows the oxynitride layer inside the workpiece hole is oxynitrided by the heat treatment oxynitriding method of the workpiece surface of the present invention,
8 is a graph showing corrosion resistance by exposing the specimen which has been oxynitrided to the salt water by the heat treatment oxynitriding method of the workpiece surface of the present invention,
Figure 9 shows a test graph measuring the corrosion resistance by continuously exposing the specimen to the salt water of the present invention,
Figure 10 shows the results of the corrosion resistance test comparing the corroded state by exposing the specimen oxynitrided by the heat treatment oxynitriding method of the workpiece surface of the present invention and the existing general oxynitride specimen to salt water.

The present invention is used to oxidize a mold for casting in die-casting casting or to provide high strength against impact and surface hardness such as gears, cams, clutches, slide cores, inserts, core pins, sleeves, etc. used in industrial sites. At the same time, it is made to improve the surface hardness, abrasion resistance, and heat resistance by subjecting the surface of the material (workpiece) required to the oxidization treatment.

In the present invention, the nitriding method for increasing the strength and surface hardness of parts of industrial machinery is to diffuse and penetrate nitrogen by heating the steel for nitriding in an ammonia stream or a salt bath. Steel is to make an iron nitride (FeN) layer, that is, a nitride layer, on the surface of the nitriding furnace.

That is, the oxynitridation for forming the nitride layer is a treatment method of oxidizing treatment after soft nitridation and net nitriding treatment, followed by oxynitriding by mixing oxygen with ammonia (NH ₃ ) gas, or by treatment with nitriding treatment followed by water vapor It is a surface heat treatment method that promotes corrosion resistance, abrasion resistance, fatigue resistance, and strength by generating an oxide layer (Fe ₃ O ₄ ) on the surface of water (processed material).

Looking at the principle of oxynitride, the nitridation layer and the oxide layer are first generated by the reaction formula. 2NH ₃ → 3H ₂ +2N The first nitriding heat treatment proceeds and CO+H ₂ → C+H ₂ O reacts to form a penetration process on the surface to diffuse the depth of nitriding, and in the final process, a chemical layer of nitride is formed by 2M+H ₂ O→2MO+2H ₂ /2M+O ₂ →2MO. It is a method of coating to form a kind of ceramic trioxide film (Fe ₃ O ₄ ) on the surface.

After nitriding treatment, the outermost layer of the compound layer is formed on the surface of a porous layer. On the surface, a trioxide film is formed by bonding oxygen and iron atoms in the furnace, and oxygen enters the porous gap to continue to grow the presence of iron oxide to form a ceramic oxide film.

Hereinafter, an embodiment of the present invention will be described in detail.

First step: Chromium film removal step by cleaning and sanding

After processing and polishing parts such as cams, clutches, slide cores, inserts, core pins, sleeves, etc., which are used as machine parts in industrial sites, oil and foreign substances on the surface are removed by cleaning.

The chromium film formed on the surface of the part is not removed even when the work-polished parts are cleaned as described above, so that the chromium film on the surface is removed by sanding.

Step 2: Loading and gas injection into the nitriding chamber

After removing the chrome film by sanding the surface, the workpiece is loaded into the chamber of the nitriding furnace.

The nitriding treatment gas is injected at a ratio of primary ammonia (NH ₃ ) 1: nitrogen (N ₂ ) 1 into the nitriding chamber loaded with the workpiece (part).

At this time, the nitriding furnace in which the workpiece is loaded forms a chamber inside, and the nitriding furnace body is formed of a jacket having a double wall structure, and a heater is installed to indirectly heat the chamber between the inner and outer walls.

In addition, the gas is injected in stages at a ratio of ammonia (NH ₃ ) 1: nitrogen (N ₂ ) 1 / carbon dioxide (CO ₂ ) 0.1 / nitrogen (N ₂ ) 8: oxygen (O ₂ ) 2. The ratio can be identified through each instrument installed on one side control panel controlling the nitriding furnace, and the system is configured so that each gas mixing ratio can be automatically controlled.

In addition, the electric heater temperature controller and the gas injection time control for heating the nitriding furnace are also regulated on the system, which is performed using a conventional electric and electronic control device.

The gas injected in the present invention is injected at 40% by weight of ammonia and nitrogen evenly mixed with respect to 100% by weight of the space in the chamber.

3rd process: nitriding and forming an oxide layer on the workpiece

After injecting the gas at a ratio of ammonia (NH ₃ ) 1: nitrogen (N ₂ ) 1, gradually raise it to 520°C for the first 120 minutes, and then add 0.8 wt% of carbon dioxide (CO ₂ ) to 100 wt% of the total receiving space in the chamber. After injection, nitriding is performed by maintaining 520°C for 300 minutes.

At this time, after performing the nitridation step, after maintaining 300 minutes at 520°C, the gas was supplied at a ratio of nitrogen (N ₂ ) 8: oxygen (O ₂ ) 2 to oxynitride while maintaining at 520°C for 20 minutes, and the oxide film (Fe ₃ O ₄ ) A layer is formed.

That is, the present invention jilhwaro receiving space 100 compared to nitrogen (N ₂₎ 80% by weight while maintaining a 500 ℃ ~550 ℃ conducted after 300 minutes and nitrided in the step of forming the oxide films (Fe ₃ O ₄₎ layer state: oxygen (O ₂ ) 40% by weight of the mixed gas at 20% by weight is supplied and oxynitrided for 20 minutes to form an oxide film (Fe ₃ O ₄ ) layer.

The temperature at the time of forming the oxide film (Fe ₃ O ₄ ) layer by oxynitriding for 20 minutes is preferably performed for 20 minutes while maintaining 520°C.

After the oxynitriding, the mixture is gradually cooled for 120 minutes, cooled to 100° C. or less, and then removed from the nitriding furnace.

In addition, as another embodiment of the present invention, the oxynitride coating layer step is injected into the nitriding furnace at a ratio of primary ammonia (NH ₃ ) 1: nitrogen (N ₂ ) 1 and gradually raised to 500° C. to 550° C. for 120 minutes, and the secondary nitriding furnace 0.8% by weight of carbon dioxide (CO ₂ ) was injected to 100% by weight of the total receiving space in the interior to perform nitridation while maintaining 500°C to 550°C for 300 minutes, and then performing third nitration to maintain nitrogen for 300 minutes and then nitrogen (N ₂ ) 8: A method of forming a layer of oxide film (Fe ₃ O ₄ ) by supplying a gas at a ratio of oxygen (O ₂ ) and oxidizing while maintaining 500° C. to 550° C. for 20 minutes. Can be implemented.

The present invention made in this way briefly looks at the process for nitriding and oxynitriding the workpiece,

① Primary ammonia (NH ₃ ) 1: Nitrogen (N ₂ ) 1 The gas is injected at a rate of 1 minute and then gradually raised to 520°C for 120 minutes.

② After raising to 520°C, 0.8% by weight of carbon dioxide (CO ₂ ) is injected to 100% by weight of the total receiving space of the chamber, and then maintained at 520°C for 300 minutes.

③ After nitriding at 520° C. for 300 minutes, the gas is supplied at a rate of nitrogen (N ₂ ) 8: oxygen (O ₂ ) 2 to oxynitride while maintaining 520° C. for 20 minutes, and the oxide film (Fe ₃ O ₄ ) layer To form.

④ After 20 minutes of oxynitriding, it is gradually cooled for 120 minutes, cooled to below 100℃, and then the work is taken out of the nitriding furnace.

In the present invention, as the gas material is put into the nitriding furnace, nitridation proceeds, so that a certain pressure is applied during the nitriding, so that it is formed in the nitriding layer inside the cooling hole, and oxynitridation occurs.

In addition, in the present invention, the nitriding layer depth of the oxynitrided component (workpiece) is 200 µm to 400 µm, the oxidizing layer depth is 2 µm to 3 µm, and the compound layer depth is performed by nitriding by gas in the nitriding furnace. Is formed from 8 μm to 10 μm.

Looking at the inspection results of each component oxynitride specimen carried out by the oxynitriding method of the present invention, it can be seen that the results are shown in Table 1 below.

As can be seen from Table 1, all specimens had a base material hardness of Hrc46±1, a surface hardness of Hv1000 or higher, an oxide layer depth of 1.5 µm or higher, a compound layer depth of 8 µm or higher, and a nitride layer depth of 100 µm or higher.

Hereinafter, with reference to the accompanying drawings of the present invention will be described.

1 is an exemplary embodiment according to the present invention, showing a process flow diagram of oxynitriding a workpiece, ① a workpiece preparation step, polishing the outer surface of the workpiece to be oxynitrided to complete the processing of the workpiece.

② In the cleaning step, the finished work is cleaned of foreign matter such as oil on the outer surface, so it is cleaned to completely remove the oil and foreign matter on the outer surface.

③ Sanding step, by removing the chromium film formed on the processing surface of the workpiece by sanding, the nitride layer is uniformly formed by uniformly entering the nitriding gas.

④ Product loading step in nitriding furnace and charging step in nitriding furnace, in order to oxidize the workpiece with the chromium film removed from the above, it is placed on the processing base of the nitriding furnace, charged into the nitriding furnace, and then injected with gas for nitriding, while operating the heater to heat the nitriding furnace do.

⑤ After forming the oxynitride layer and extracting the processed product (product), after loading the processed product, the nitriding furnace is heated with a heater and gas for nitriding is injected into the nitriding furnace. Primary ammonia (NH ₃ ) 1: Nitrogen (N ₂ ) After injecting at a ratio of 1, and then gradually raising it to 520°C for the first 120 minutes as the _{second time} , 0.8% by weight of carbon dioxide (CO ₂ ) was injected to 100% by weight of the total space in the chamber, and maintained at 520°C for 300 minutes. After nitriding and maintaining 300 minutes at 520°C for the third time, the gas was supplied at a rate of nitrogen (N ₂ ) 8: oxygen (O ₂ ) 2 to oxynitride while maintaining at 520°C for 20 minutes. After forming the Fe ₃ O ₄ ) layer, the oxynitride-finished workpiece is completed in a nitriding furnace and extracted from the nitriding furnace.

Figure 2 shows the oxynitride layer formed by the heat treatment oxynitriding method of the workpiece surface of the present invention, as can be seen in Figure 2, the nitride layer depth is 200㎛ to 400㎛, the oxide layer depth is 2㎛ to 3 It is found that the thickness of the compound layer is 8 μm to 10 μm.

When the oxynitride layer is formed as shown in FIG. 2, it can be applied to a hot forging mold, sleeve, TIP, cylinder, screw, etc. because of improved corrosion resistance, abrasion resistance, and moisture resistance.

Fig. 3 is an enlarged view of the oxynitriding structure of a workpiece in which the oxynitride layer is formed by the heat treatment oxynitriding method of the workpiece surface of the present invention, and Fig. 4 illustrates the oxynitriding tissue layer formed by the heat treatment oxynitriding method of the workpiece surface of the present invention As can be seen in Figure 3, it can be seen that the oxynitride is formed of an oxide film (Fe ₃ O ₄ ), a porous layer, a white layer, and a matrix in the tissue.

As shown in FIG. 4, the structure formed in the workpiece is an oxide layer (Fe ₃ O ₄ C) formed of ① 2 to ₃ μm, and a carbon oxide film is formed to improve corrosion resistance and seizure resistance. Phosphorus layer (Fe ₃ O ₄ ) is formed to improve lubricity and corrosion resistance, and a nitride is formed with a white layer (Fe _2.3 N) of 6 to 10 µm to improve wear resistance, seizure resistance, and corrosion resistance. Diffusion layer (Fe ₄ N) is formed to increase the strength against fatigue and improve wear resistance by forming compressive residual stress and increasing hardness, and it can be seen that the inherent strength, toughness, and ductility of the base material are maintained due to the base material of 350 µm or less. .

Figure 5 is an exemplary view showing the hardness and depth of the nitride layer of the oxynitride layer of the specimen A formed by the heat treatment oxynitriding method of the workpiece surface of the present invention, Figure 5 is an embodiment of the mechanical sleeve treated with the oxynitriding method of the present invention For example, since the depth of the nitride layer is 200 µm to 400 µm, when the nitridation is applied after pure nitridation, the nitride layer is deep and a coating film is formed on the surface to increase the wear resistance to improve the life of the workpiece.

Figure 6 is an exemplary view showing the hardness and depth of the nitride layer of the oxynitride layer of the specimen B formed by the heat treatment oxynitriding method of the workpiece surface of the present invention, Figure 6 is the nitriding surface hardness by oxynitriding the mold sleeve of the present invention It shows that Hv100g900 or more and diffusion layer depth of 100 μm or more are shown.

Figure 7 shows the oxynitriding layer inside the workpiece hole where the oxynitridation is performed by the heat treatment oxynitriding method of the workpiece surface of the present invention, Figure 7 is a test of the formation of oxynitride in the arc of the workpiece by 400m section hole size The oxynitride was tested.

This confirms whether or not an oxynitride layer is formed inside the hole during the oxynitride treatment, and it can be seen that the oxynitride layer formed in the hole of the workpiece is formed up to the inside of the hole regardless of the hole size.

It can be seen that the oxynitriding treatment of the present invention results in high-quality oxynitridation of not only the surface of the workpiece, but also the hole, as the gas penetrates to a minute portion compared to the liquid by oxynitriding treatment using gas.

8 is a graph showing the corrosion resistance by exposing the specimen oxynitrided to the salt water by the heat treatment oxynitriding method of the workpiece surface of the present invention, when the workpiece is oxidized in a nitriding furnace, the gas is first ammonia (NH ₃ ) 1: After injecting with nitrogen (N ₂ ) 1, the temperature was gradually raised to 520°C for the first 120 minutes, and then 0.8520% of carbon dioxide (CO ₂ ) was injected for 100% by weight of the total receiving space in the chamber, followed by 520°C for 300 minutes. After maintaining, nitridation is performed, and then, after holding for 300 minutes at 520° C., the gas is supplied at a rate of nitrogen (N ₂ ) 8: oxygen (O ₂ ) 2 to oxynitride while maintaining at 520° C. for 20 minutes. The process of forming a (Fe ₃ O ₄ ) layer, slowly cooling for 120 minutes after oxynitriding, and cooling to 100° C. or less is shown graphically.

9 shows a test graph measuring corrosion resistance by continuously exposing the specimen to the salt water of the present invention, and FIG. 10 shows the specimen oxynitrided by the heat treatment oxynitriding method of the workpiece surface of the present invention and the conventional general oxynitride It shows the results of anti-corrosion performance test comparing the corroded condition by exposing the specimen to salt water.

9 and 10 are experiments using the oxynitride-treated workpiece using salt water (salt water), and 9 is a measurement of corrosion resistance by continuously exposing the specimen to a concentration of 35% salt water. (Shingi oxynitride) was found to have a significant difference in the general oxynitride-treated specimens of 200 hours, while corrosion resistance was not affected by salt water at a concentration of 35% for up to 800 hours.

In order to examine this in more detail, as shown in FIG. 10, when the oxynitride-treated specimen of the present invention and the general oxynitride-treated specimen were exposed to salt water, the specimen of the present invention did not change until 45 days, but the general acid It can be seen that the nitridated specimen started to rust from the 7th day, and the rusting was significantly started from the 8th day.

As described above, by using a gas composed of ammonia (NH ₃ ), nitrogen (N ₂ ), carbon dioxide (CO ₂ ), and nitrogen (N ₂ ) of the present invention, nitriding treatment is used to improve the corrosion resistance, abrasion resistance, moisture resistance, and seizure resistance of the workpiece. Since it has improved friction and surface hardness, it is applied to parts of machine sleeves, slide cores, movable dies, slider hold, curank inserts, inserts, and core pins, and it is a work piece that requires high strength against impact and high hardness of the surface at the same time. It has the effect of prolonging the lifespan and having economic benefits.

Claims (3)

Removing oil and foreign substances on the surface of the processed workpiece by cleaning and removing the processed chromium film on the surface using sanding;
After removing the processed chromium film on the surface, loading the workpiece into the chamber of the nitriding furnace;
Injecting ammonia (NH ₃ ) 1: nitrogen (N ₂ ) 1 into the nitriding chamber loaded with the workpiece;
The ammonia (NH ₃ ) 1: Nitrogen (N ₂ ) 1 After injecting into the nitrifying furnace, gradually raising the temperature to 520°C for the first 120 minutes, and nitriding by maintaining 520°C for 300 minutes;
Raising the temperature to 520° C. and injecting 0.8% by weight of carbon dioxide (CO ₂ ) relative to 100% by weight of the total receiving space in the nitriding furnace, and then maintaining 520°C for 300 minutes to perform nitriding;
After performing the nitridation, after maintaining 300 minutes at 520° C., the gas was supplied at a ratio of nitrogen (N ₂ ) 8: oxygen (O ₂ ) 2 to oxynitride while maintaining at 520° C. for 20 minutes, and the oxide film (Fe ₃ O ₄ ) forming a layer;
The method of heat treatment oxynitriding of the surface of a workpiece is characterized in that it consists of a step of taking oxynitride while maintaining at 520°C for 20 minutes, gradually cooling for 120 minutes, cooling to 100°C or less, and then taking the workpiece out of the nitriding furnace.
According to claim 1,
In the step of forming the oxide layer, nitriding is performed for 300 minutes and then maintained at 500° C. to 550° C. to 80% by weight of nitrogen (N ₂ ) compared to 100% by weight of the nitriding furnace space: 20% by weight of oxygen (O ₂ ) A method of heat-treating oxynitride on a surface of a workpiece characterized by forming an oxide film (Fe ₃ O ₄ ) layer by supplying 40% by weight of a mixed gas and oxynitriding for 20 minutes.
According to claim 1,
The step of the oxynitride coating layer is injected into the nitrification furnace at a ratio of primary ammonia (NH ₃ ) 1: nitrogen (N ₂ ) 1 and gradually raised to 500° C. to 550° C. for 120 minutes, to 100 wt% of the total receiving space in the secondary nitrification furnace. With respect to carbon dioxide (CO ₂ ), 0.8% by weight is injected to perform nitridation while maintaining 500° C. to 550° C. for 300 minutes, followed by tertiary nitration to maintain 300 minutes, followed by nitrogen (N ₂ ) 8: oxygen (O ₂ ) A method of heat-treating oxynitriding of a surface of a workpiece, characterized by forming an oxide film (Fe ₃ O ₄ ) layer by supplying a gas at a ratio of 2 to oxynitride while maintaining 500° C. to 550° C. for 20 minutes.

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