JPH11229113A - Oxide film removing method, gas nitro-carburizing method, and method for using organic chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely and easily realize the gas-nitrocarburizing treatment free from variance in a nitrided layer which unnecessitates handling harmful matters and low in labor in a short time by completely removing an oxide film on a surface of an alloy steel using an organic chloride. SOLUTION: An ammonium gas or a mixed gas of ammonium and nitrogen is introduced in a nitriding furnace which is a heat treatment furnace. In addition, an organic chloride such as vinylidene chloride or methylene chloride as an oxide film removing agent is poured therein by approximately 10-250 ml/m<3> , an alloy steel is charged in the furnace, and heated to approximately >=250 deg.C. A fine and adhesive oxide film containing chromium oxide on a surface of the alloy steel is completely removed by the effect of the organic chloride. Then, the furnace temperature is raised to approximately 500-600 deg.C. A nitrided layer free from variance is formed on the surface of the alloy steel without any oxide film to prevent penetration of the nitriding gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for removing an oxide film on the surface of an alloy steel material, a gas nitrocarburizing method including the method, and a method for using an organic chloride.

[0002]

2. Description of the Related Art Among alloy steels, those containing a large amount of chromium and nickel, such as stainless steel and heat-resistant steel,
In general, a gas nitrocarburizing treatment is difficult because a dense and adherent oxide film (chromium oxide) on the surface prevents the penetration of nitrogen gas.

Therefore, conventionally, an oxide film is removed by using hydrochloric acid or phosphoric acid, and then a gas nitrocarburizing treatment is performed, or a salt bath nitrocarburizing treatment is performed instead of the gas nitrocarburizing treatment. Was.

[0004]

However, in the method of removing an oxide film using hydrochloric acid or phosphoric acid, the oxide film cannot be completely removed, so that a variation occurs in the nitrided layer in the gas nitrocarburizing treatment. There was a problem.

Further, in order to carry out the salt bath nitrocarburizing treatment, a harmful substance such as cyanide or cyanate had to be used as a main component of the salt. Management was complicated. Furthermore, in order to remove harmful substances attached to the surface, it takes time and effort to wash the treated product after the salt bath treatment, and harmful substances are mixed in the washing water flowing down from the surface of the treated product, There are drawbacks such that the water cannot be drained unless it is removed.

The present invention has been made in view of such circumstances, and a first problem to be solved is to provide a method of removing an oxide film which can completely remove an oxide film on the surface of an alloy steel material. .

A second object of the present invention is to provide a gas nitrocarburizing method which does not cause a variation in a nitride layer.

A third object of the present invention is to provide a gas nitrocarburizing method which does not require handling of harmful substances and can safely and easily obtain a nitrided product with a small number of steps.

A fourth object of the present invention is to provide a gas nitrocarburizing method capable of shortening the time required for a gas nitrocarburizing process which generally takes a long time.

A fifth object of the present invention is to provide a method of using an organic chloride which is effective in solving the above-mentioned problems.

[0011]

Means for Solving the Problems In order to solve the first problem, a method for removing an oxide film according to the present invention is to remove an oxide film on the surface of an alloy steel material using an organic chloride. (Claim 1).

In order to solve the above-mentioned second to fourth problems, a gas nitrocarburizing method according to the present invention uses an organic chloride as an oxide film removing agent for an alloy steel material. Specifically, the oxide film on the surface of the alloy steel material is removed using an organic chloride and gas nitrocarburizing is performed (claim 3). In this case, the gas nitrocarburizing treatment may be performed after removing the oxide film on the surface of the alloy steel using an organic chloride (Claim 4), or the alloy steel and the organic chloride may be placed in a heat treatment furnace. The gas nitrocarburizing treatment may be performed by putting the material together.

More specifically, for example, the object to be treated is placed in a nitriding atmosphere and heated, an oxide film on the surface of the object to be treated is removed using an organic chloride, and then further heated to soften. A nitriding treatment is performed (claim 6).

In order to solve the fifth problem, the method of using an organic chloride according to the present invention uses an organic chloride as an oxide film remover for an alloy steel material.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A nitriding atmosphere is created by flowing ammonia gas or a mixed gas of ammonia and nitrogen into a nitriding furnace which is a heat treatment furnace. An alloy steel material to be treated is put in the nitriding atmosphere and heated to 250 ° C. or higher. Thereafter, 10 to 250 ml / m ^{3 of} vinylidene chloride or methylene chloride as an organic chloride is injected. Then, the oxide film on the surface of the alloy steel material is removed by the action of the injected organic chloride. Then, 5
The temperature is raised to 00 to 600 ° C., and a gas nitrocarburizing treatment is performed for 0.5 to 8 hours.

The organic chloride may be put in the nitrocarburizing atmosphere together with the alloy steel material (by performing gas nitrocarburization following the oxide film removing step).

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment will be described.

Heat-resistant steel (SUH3
5) A bar was prepared and placed in a nitriding furnace. The nitriding atmosphere in the nitriding furnace was set to 50% in an ammonia gas furnace and 50% in a nitrogen gas furnace, and heated to 500 ° C. Thereafter, 125 ml / m ^{3 of} vinylidene chloride was injected into the nitriding furnace. Then, while keeping the temperature in the nitriding furnace at 500 ° C., a gas soft nitriding treatment was performed for 8 hours, and the heat-resistant steel bar was taken out of the nitriding furnace. A uniform nitrided layer of 35 μm was formed on the surface of the heat-resistant steel bar.

A second embodiment will be described.

As an object to be nitrided, stainless steel (S
US304) A material was prepared and placed in a nitriding furnace. The nitriding atmosphere in the nitriding furnace was set to 40%
The furnace was heated to 570 ° C. with nitrogen gas at 60% in furnace. Thereafter, 250 ml / m of vinylidene chloride was introduced into the nitriding furnace.
^Three injections were made. Then, while the temperature in the nitriding furnace was maintained at 570 ° C., a gas soft nitriding treatment was performed for one hour, and the stainless steel material was taken out of the nitriding furnace. A uniform nitride layer of 40 μm was formed on the surface of the stainless steel material.

A third embodiment will be described.

As an object to be nitrided, stainless steel (S
US316) materials were prepared. The inside of the nitriding furnace is a nitriding atmosphere of 50% of furnace gas in ammonia gas and 50% of furnace gas in nitrogen gas.
It was kept at 300 ° C. The stainless steel material was put into the nitriding furnace in this state together with 12.5 ml / m ^{3 of} vinylidene chloride, and the temperature was raised to 570 ° C. The gas soft nitriding treatment was performed for 2 hours, and the stainless steel material was taken out of the nitriding furnace. On the surface of the stainless steel material, 45
A uniform nitride layer of μm was formed.

A fourth embodiment will be described.

As an object to be nitrided, stainless steel (S
US304) A material was prepared and placed in a nitriding furnace. The nitriding atmosphere in the nitriding furnace was set to 40% in an ammonia gas furnace and 60% in a nitrogen gas furnace, and heated to 570 ° C. Thereafter, 90 ml / m ^{3 of} methylene chloride was introduced into the nitriding furnace.
Injected. Then, while the temperature in the nitriding furnace was maintained at 570 ° C., a gas soft nitriding treatment was performed for one hour, and the stainless steel material was taken out of the nitriding furnace. A uniform nitride layer of 45 μm was formed on the surface of the stainless steel material.

A fifth embodiment will be described.

Heat-resistant steel (SUH3
5) A bar was prepared and placed in a nitriding furnace. The nitriding atmosphere in the nitriding furnace was set to 50% in an ammonia gas furnace and 50% in a nitrogen gas furnace, and heated to 570 ° C. Thereafter, 45 ml / m ^{3 of} methylene chloride was injected into the nitriding furnace. Then, while keeping the temperature in the nitriding furnace at 570 ° C., gas nitrocarburizing treatment was performed for one hour, and the heat-resistant steel bar was taken out of the nitriding furnace. On the surface of the heat-resistant steel bar,
A uniform nitride layer of 40 μm was formed.

A sixth embodiment will be described.

As the nitriding object, tool steel (SKD6)
1) A bar was prepared and placed in a nitriding furnace. The nitriding atmosphere in the nitriding furnace was set to 45% in an ammonia gas furnace and 55% in a nitrogen gas furnace, and heated to 570 ° C. Thereafter, 90 ml / m ^{3 of} methylene chloride was injected into the nitriding furnace. Then, while the temperature in the nitriding furnace was maintained at 570 ° C., gas soft nitriding was performed for 1 hour, and the tool steel bar was taken out of the nitriding furnace. On the surface of the tool steel bar,
A uniform nitride layer having a thickness of 100 μm was formed.

[0029]

According to the present invention, the oxide film on the surface of the alloy steel material can be completely removed by the action of the organic chloride.

According to the present invention, a uniform nitrided layer can be obtained on the surface of the alloy steel material. Further, unlike the salt bath treatment which has been conventionally employed because gas nitrocarburizing treatment is difficult, it is not necessary to handle harmful substances, so that a nitrided product can be obtained safely and easily with a small number of steps. Furthermore, the time of the gas nitrocarburizing process, which generally takes a long time, is reduced.

Claims (7)

[Claims] 1. A method for removing an oxide film, comprising removing an oxide film on the surface of an alloy steel material using an organic chloride. 2. A gas nitrocarburizing method comprising using an organic chloride as an oxide film remover for an alloy steel material. 3. A gas nitrocarburizing method comprising removing an oxide film on the surface of an alloy steel material using an organic chloride and performing a gas nitrocarburizing process. 4. A gas nitrocarburizing method comprising removing an oxide film on the surface of an alloy steel material using an organic chloride and then performing a gas nitrocarburizing process. 5. A gas nitrocarburizing method comprising the steps of: introducing an alloy steel material and an organic chloride into a heat treatment furnace and performing a gas nitrocarburizing process. 6. An object to be treated is placed in a nitriding atmosphere and heated, an oxide film on the surface of the object to be treated is removed using an organic chloride, and thereafter, a nitriding treatment is performed by further heating. Gas nitrocarburizing treatment method. 7. A method for using an organic chloride, wherein the organic chloride is used as an oxide film remover for an alloy steel material.