JP2000239824A - Gas nitrosulphurizing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitrosulphurizing method to generate nitrides and sulfides of the surface of steel parts without using any toxic cyanic compound or hydrogen sulfide. SOLUTION: Gas nitriding of gas soft nitriding is applied on steel parts W in a reaction furnace 1 using gaseous ammonium, and then, the reaction furnace 1 is evacuated to discharge the residual gas after nitriding. Then, the gas containing sulfur compounds (CS2) but containing no sulfur gas (S) or hydrogen component is supplied into the reaction furnace 1 to apply the gas sulphurizing on the steel parts W of a work, but H2S is not used. Even if ammonia is decomposed in the nitriding treatment to generate H2, H2 is discharged through evacuation, and no H2S is generated through the reaction with sulfur during the sulphurizing treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment technique for a steel part such as an engine liner, a piston ring, a gear, etc., which requires abrasion resistance and low friction, and in particular, is difficult to handle. The present invention relates to a gas sulfide-nitriding method capable of processing without using or generating highly toxic hydrogen sulfide gas.

[0002]

2. Description of the Related Art Conventionally, methods for sulphinitriding steel products are roughly classified into a salt bath method and a gas method. The former is NaCN or KCN
The steel part is immersed in a salt bath containing a sulfur compound based on a reducing salt composed of a cyanide such as
By holding at 50 to 580 ° C. for 30 to 90 minutes, sulfide (FeS) and nitride (Fe ₃
This is a technique for forming a compound layer with N) and diffusing nitrogen into the base material. The latter is a mixture of ammonia gas (NH ₃ ) and hydrogen sulfide gas (H ₂ S) at a temperature of 540 to 58
This is a technique for generating a compound layer of sulfide and nitride on the surface of a steel part by maintaining the temperature at 0 ° C. for 60 to 180 minutes.

[0003]

However, since the salt bath method uses a highly toxic cyanide compound, it requires a large area and an expensive water treatment apparatus for pollution control of the working environment, especially for water treatment. There's a problem. On the other hand, in the nitrosulphurizing method by the gas method, an exhaust gas treatment device is required because toxic hydrogen sulfide gas is used, but since it is adsorbed and removed by special activated carbon, the management method is difficult and the running cost is high. Problem.

Accordingly, the present invention has been made in view of such problems of the conventional nitrosulphurizing method, and the present invention has been applied to a method of nitriding a steel component surface without using a toxic cyanide compound or hydrogen sulfide. It is an object of the present invention to provide a novel nitrosulphurizing method for producing oxides and sulfides.

[0005]

In order to achieve the above object, the invention of a gas sulfide nitriding method according to the first aspect of the present invention provides a gas nitriding or gas softening method using ammonia gas for steel parts in a reactor. After performing the nitriding treatment, the inside of the furnace is evacuated to remove the residual gas, and thereafter, the sulfur component or the sulfur-containing compound gas containing no hydrogen component is sent into the furnace to perform the gas sulfurizing treatment on the steel part. It is characterized by the following.

Further, according to a second aspect of the present invention, there is provided a gas sulfide-nitriding method.
Ming is a nitriding or nitrocarburizing treatment.
Charging steel parts into the reactor and evacuating the air inside the furnace
And then do not contain sulfur gas or hydrogen components in the furnace
Gas sulfurizing treatment of the steel parts by sending sulfur compound gas
Is performed. Here, used for gas nitriding
Gas, for example, NH_Three+ N_Two+ CO_TwoThere
You. Further, as a gas used in the gas soft nitriding treatment, for example,
NH_ThreeGas + RX gas (H_Two, CO, N_TwoEtc. are included
) Or NH_ThreeGas + decomposition gas of methanol (H _Two, C
O).

Further, the hydrogen component in the gas sulfurization treatment
As sulfur compound gas containing no, for example, carbon disulfide
Elementary (CS_Two) Can be suitably used. Sulfur or disulfide
Although a predetermined amount of carbon may be directly charged into the reactor,
Sulfur generated by putting these into a heated decomposition furnace
May be supplied into the reactor. Gas sulfuration according to the present invention
In the nitriding method, NH 3_ThreeGas and H_TwoS
Nitride and sulfide on the surface of steel parts using a gas mixture of
And nitride formation and sulfide formation without forming
Is performed in a separate process. This is the poisonous H _TwoS
Not only use it, but also do not create it during processing.
It is. That is, first, NH_ThreeGas alone or H_TwoS
Of steel parts in the reactor using a gas mixture with other gases
A nitride is formed on the surface. At this time, H in the mixed gas
_TwoAnd NH_ThreeH generated by decomposition of gas_TwoRemains in the furnace
Then, sulfur gas is flowed into the furnace to perform gas sulfurization.
When reacting with sulfur gas, H_TwoS was generated in the furnace
I will. In order to prevent this, the reaction furnace
The residual gas remaining inside is evacuated and evacuated.
In this way, the formation of nitrides and the formation of sulfides are the same.
Even in the furnace, H_TwoS gas is generated
Never.

[0008] Thus, the formation of nitride and sulfide is
It is not always performed continuously. The gas sulphonitriding method according to claim 2 is a case of a gas sulphonitriding method in which a nitrided steel part which has been subjected to a nitriding treatment or a nitrocarburizing treatment in advance is charged into a reaction furnace and subjected to gas sulfuration. . In this case, a steel part on which a nitride is already formed is subjected to a gas sulfurizing treatment in a reaction furnace. At this time, the air in the furnace is evacuated, and then a sulfur gas or a sulfur compound gas containing no hydrogen component is sent into the furnace to perform a sulfuration treatment.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of a gas oxynitriding furnace as a reaction furnace used for carrying out the gas oxynitriding method of the present invention. Reference numeral 1 in the figure denotes a gas sulfide nitriding furnace main body, and reference numeral 2 denotes a decomposition furnace for producing a sulfur gas. The cracking furnace 2 includes a retort 3 and a heater 4 surrounding the outer periphery thereof.
And the temperature controller T. C1 and is sealed with a lid 5. Through the lid 5, a pipeline 6 for an N ₂ gas supply system that is opened and closed by a valve V1 and a raw material for sulfur gas generation (a sulfur-containing compound or sulfur containing no hydrogen component) that is opened and closed by a valve V2. The supply system pipelines 7 are arranged in a merged manner. Further, a pipeline 8 is provided for taking out a cracked gas (sulfurized gas) obtained by thermally decomposing the supplied raw material for sulfur gas generation in a furnace. Valve 6
The pipeline 8 for taking out the decomposition gas, which is controlled to open and close, is connected to the gas oxynitriding furnace main body 1, and an exhaust port 9 to the outside, which is opened and closed by a valve 9, is provided in the middle of the pipeline.

[0010] The gas sulphonitriding furnace main body 1 includes a retort 11.
, A heater 12 surrounding the periphery thereof, and a temperature controller T. C2 and a stirrer 13 that stirs the inside of the retort 11 are built in. The upper lid 10 is opened and a processed product (work) W can be put in and out of the retort 11. Also, retort 11
, A plurality of pipelines are inserted from the outside of the furnace through the top lid 10. One is a pipeline 8 for taking out a decomposition gas from the decomposition furnace 2. Still other gas supply lines include an NH ₃ gas pipeline 15 controlled to open and close via a valve V3, an N ₂ gas pipeline 16 controlled to open and close via a valve V4, and a CO ₂ gas pipe controlled to open and close via a valve V5. Lines 17 are arranged to join. Further, as an exhaust line for the gas in the retort 11, an exhaust gas pipe 18 controlled to be opened and closed via the valve 7 is provided.
And a vacuum exhaust pipeline 19 connected to a vacuum pump (not shown) via a valve V8.

Next, the gas sulphonitriding method of the present invention using the above-mentioned gas sulphonitriding furnace will be described with reference to the flow chart of the process in FIG. A steel part to be subjected to the gas nitrocarburizing process as the work W is previously placed in the retort 11 of the gas oxynitriding furnace main body 1. Step 1: The gas sulfide nitriding furnace main body 1 is opened, and the work W is stored in the retort 11 and hermetically closed.

Step 2: The agitator 13 is driven to start agitation in the retort 11. Step 3: The valves V3, V4, V5, V6 and V7 are closed. By opening the valve V8 and driving a vacuum pump (not shown), the inside of the retort 11 is evacuated via the vacuum exhaust pipeline 19. It is practically preferable to perform the evacuation until the ultimate degree of vacuum in the retort 11 reaches a range of 1 to 5 Torr.

Step 4: The inside of the retort 11 is a predetermined vacuum
The valve V8 is closed, the valve V4 is opened and N _Twogas
N via pipeline 15_TwoSend gas. to this
The air in the retort 11 is N at normal pressure._TwoReplaced by gas
To an inert gas atmosphere. Step 5: N in the retort 11_TwoAfter replacing with gas,
Turn on the heater 12 and start heating the retort 11
You. Temperature controller TC. Heating set temperature by 2 is nitriding temperature
In the range of 500 to 600 ° C. This nitriding temperature
Is maintained until the nitriding of the workpiece W is completed. Nitriding
If the temperature is lower than 500 ° C, nitriding takes too long
Not practical. On the other hand, if the temperature exceeds 600 ° C,
The brittle ε phase formed (white phase visible under a microscope) is not thick
This increases the burden of the grinding and removing operation.

The heating / heating step in step 5 may be performed before the evacuation step in step 3. In this case, since the inside of the retort 11 is heated and evacuated, oxygen and the like adsorbed on the inner wall of the furnace are removed, and contamination in the nitriding treatment described later is prevented. Step 6: After the temperature of the retort 11 reaches a predetermined heating set temperature by the above-mentioned heating (or even during the heating), the valves V3, V4, and V5 are opened, and the NH ₃ gas pipeline 15, the N ₂ gas pipeline 16 , CO ₂ gas pipeline 17 from NH ₃ gas, N ₂ gas, C
O ₂ gas is introduced into the retort 11 and NH ₃ + N ₂ +
A nitriding gas atmosphere formed by mixing CO ₂ is formed.
At the same time, the valve V7 is opened to discharge the in-furnace nitriding atmosphere gas from the exhaust gas pipe 18. As a result, the nitriding process is performed by continuously flowing the nitriding gas at a predetermined flow rate into the retort 11 for a predetermined time. The flow rate of the mixed gas in this nitriding treatment is set to a range of 3 to 15 times / Hr of the internal volume of the retort 11 (furnace internal volume), and is set to an optimum value according to the size, quantity, shape, and the like of the work W. If the flow rate of the nitriding gas is less than 3 times the furnace internal volume / Hr, the nitriding rate is likely to be delayed and the nitriding variation is likely to occur. If the flow rate exceeds 15 times the furnace internal volume / Hr, the cost increases.

The mixing ratio of the mixed gas is N
H ₃ : N ₂ : CO ₂ = 30-100%: 0-80%: 0
The range is preferably in the range of 10% to 10%. Even if N ₂ gas is used instead of NH ₃ gas, nitriding does not occur. Under the above conditions of nitriding temperature, nitriding gas composition and flow rate, 0.5 to 1
A nitriding treatment of 0 hr is performed.

Incidentally, the above nitriding treatment is performed by NH ₃ , N ₂ ,
Not only gas nitriding using a mixed gas of CO ₂ but also gas nitrocarburizing using a mixed gas of NH ₃ + RX gas may be used. The RX gas is a combustible mixed gas containing N ₂ , H ₂ , and CO as main components, and is originally a kind of atmosphere gas for heat treatment of steel. However, the RX gas is preferably used as a nitriding gas by mixing with ammonia. In this case, the gas ratio is NH ₃ : R
X gas = 30 to 100%: 0 to 50% is preferable.
When this NH ₃ , RX gas mixture is used, NH ₃
The NH ₃ gas is supplied from the gas pipeline 15, and the RX gas is supplied from either the N ₂ gas pipeline 16 or the CO ₂ gas pipeline 17 to the (NH ₃ +
N ₂ + CO ₂ ) may be supplied to the retort 11 at the same gas flow rate as in the case of the mixed gas. At that time, the valve V7 is also opened to discharge the in-furnace nitriding atmosphere gas from the exhaust gas pipe 18. In this case, H ₂ , CO, and the like in the high-temperature exhaust gas are burned and discharged at the outlet of the exhaust gas pipe 18. By this incineration treatment, explosion of a mixed gas such as H ₂ and CO can be prevented.

Thus, the gas nitriding of the work W is completed.
Subsequently, the process proceeds to the next sulfurizing treatment. Here, a description will be given of a preparation step of generating a sulfur gas using the decomposition furnace 2, which is performed simultaneously with the nitriding step. Step 20: First, the heater 4 of the decomposition furnace 2 is turned on, and the retort 3 is heated to 300 to 600 ° C.

Step 21: Next, N into the retort 3
₍₂₎ Open the valve V1 of the gas supply pipeline 6 and the valve V9 of the decomposition gas extraction pipeline 8, and open the valve V2 and the decomposition gas extraction pipeline 8 of the sulfur supply system pipeline 7.
Is closed. As a result, the N ₂ gas is supplied from the pipeline 6 to the retort 3 and is discharged from the external exhaust port 9 of the branch pipe to the outside together with the internal air. Eventually, all the air inside the retort 3 is replaced with N ₂ gas.

Step 22: In the retort 3 previously heated to a predetermined temperature in Steps 20 and 21 and the internal air is replaced with N ₂ gas, the on-off valve V9 of the external exhaust port 9 and the decomposition gas extraction pipeline 8 Valve V6 is closed. Then, open the valve V2 of the pipeline 7,
A sulfur-containing compound (however, a sulfur compound other than H ₂ S, such as CS ₂ or a low-boiling metal sulfide) or powdered sulfur is charged into the retort 3. The input amount varies depending on the number and size of the work W, the thickness of the sulfide layer to be formed, and the like, but is in the range of 1 to 500 g.

If the input amount is less than 1 g, the sulfurization treatment takes too long time, which is impractical. On the other hand, if the input amount exceeds 500 g, unreacted sulfur precipitates at a low temperature part in the furnace, and mechanical troubles are likely to occur. Become. Step 23: The introduced sulfur or the sulfur-containing compound is thermally decomposed in the retort 3 heated to a predetermined temperature to generate sulfur gas.

In parallel with the above-described preparation process for the generation of the sulfur gas, the workpiece W is subjected to the sulfur treatment according to the following procedure. Step 7: After the nitriding treatment in step 6 is completed, the retort 11 is evacuated. That is, the valves V3, V4, V5, V6, and V7 of the gas sulphonitriding furnace main body 1 are closed, and the valve V8 is opened to evacuate the retort 11 through the evacuated pipeline 19 to reach a degree of vacuum of 1 to 5 Torr.
r until the residual gas of the nitriding treatment is completely exhausted. Thus, components of the H ₂ and the like adsorbed to the inner wall of the H ₂ and retort 11 produced by the decomposition of NH ₃ gas used in the nitriding process is also simultaneously eliminates without remaining in the retort 11. Therefore, the danger that these residual H ₂ will react with the sulfur supplied in the next sulfurizing step to generate highly toxic hydrogen sulfide (H ₂ S) is eliminated.
At this time, the temperature in the retort is maintained at the temperature at the time of nitriding.

Step 8: After the inside of the retort 11 reaches a predetermined degree of vacuum (1 to 5 Torr) by evacuation, the valve V8
Is opened to shut off the evacuation pipeline 19 and open the valve V4, so that the N ₂ gas from the N ₂ gas pipeline 16 is opened.
The gas is introduced into the retort 11 in a vacuum state, and the retort 11 is set to an N ₂ gas atmosphere.

Step 9: Sulfur gas is introduced into the retort 11 in the N ₂ gas atmosphere, and the sulfur treatment of the work W is started. The sulfur gas is obtained by pyrolyzing solid sulfur or carbon disulfide (CS ₂ ) in the decomposition furnace 2. That is, the valve V6 of the decomposition gas extraction pipeline 8 is opened, and the valve V7 of the exhaust gas pipe 18 of the retort 11 is opened. This allows retort 1
The replacement N ₂ gas filled in 1 is discharged to the outside, and sulfur gas is introduced from the decomposition furnace 2 to start the sulfuration treatment. The sulfurizing time is in the range of 10 to 120 minutes, and is appropriately set according to the size, shape, required characteristics, sulfurizing temperature, and the like of the work W. Further, the temperature of the sulfurizing treatment is in the range of 400 to 600 ° C. If the temperature is lower than 400 ° C., the sulfuration rate is low, while if it exceeds 600 ° C., the surface of the work is roughened.

Step 10: When the sulfurizing treatment subsequent to the nitriding treatment is completed, the valves V6 and V7 are closed and the valve V8 is opened to evacuate the inside of the retort 11 to remove the remaining sulfur gas. Step 11: Thereafter, the valve V8 is closed, the valve V4 is opened, and N ₂ gas is introduced into the retort 11 to perform replacement.

Step 12: After the gas oxynitriding furnace main body 1 replaced with N ₂ gas is cooled and cooled, the processed work W is taken out from the furnace. In the above embodiment, the case where the first-stage nitriding treatment and the second-stage sulfurizing treatment are continuously performed by the same apparatus has been described. However, the gas-sulfurizing / nitriding method of the present invention is not limited to this. For example, the pre-nitriding process is separately and independently performed in advance in another apparatus or another place, and the nitriding-treated steel part may be subjected to the sulfurizing treatment of the present invention. It is possible. In such a case, the former stage nitriding treatment is not necessarily limited to the gas nitriding method or the gas nitrocarburizing method when a purchased product is used, and may be applied to a nitriding treatment by a salt bath method.

In the above embodiment, the sulfur gas obtained by thermally decomposing a sulfur-containing compound containing no sulfur or a hydrogen component in a decomposition furnace as a gas for sulfuration is introduced into a reaction furnace to perform a sulfuration treatment. However, the present invention is not limited to this, and the sulfur-containing compound may be directly introduced into the reaction furnace and subjected to the sulfurizing treatment.

[0027]

As described above, according to the gas sulfide nitriding method of the present invention, highly toxic hydrogen sulfide gas (H ₂ S) is used.
Sulphonitriding can be carried out without using or generating cyanide, and without the need for expensive water treatment equipment or exhaust gas treatment equipment. To play.

[Brief description of the drawings]

FIG. 1 is a schematic view of a gas oxynitriding furnace for performing a gas oxynitriding method of the present invention.

FIG. 2 is a flowchart of the gas sulphiditriding process of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactor 7 Sulfur-containing compound supply line 12 Heater 15 Ammonia gas supply line 19 Vacuum exhaust line W Steel parts

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16J 10/04 F16J 10/04

Claims (2)

[Claims] 1. A steel part in a reactor is subjected to gas nitriding or gas nitrocarburizing treatment using ammonia gas, and then the furnace is evacuated to remove residual gas. A method for gas-sulfur-nitriding, wherein a sulfur-containing compound gas containing no hydrogen component is sent to subject the steel component to gas-sulfurization. 2. A part made of a nitrided steel, which has been subjected to a nitriding treatment or a nitrocarburizing treatment in advance, is charged into a reaction furnace, the air in the furnace is evacuated, and then the sulfur gas or sulfur containing no hydrogen component is contained in the furnace. A gas sulfide nitriding method, wherein a compound gas is sent to perform a gas sulfide treatment on the steel part.