JP2003105525A - Nitriding treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of nitriding a metal material, by which the nitriding efficiency can be further enhanced beyond the conventional maximum efficiency hitherto realized by various improvements. SOLUTION: In the method for nitriding the metal material by supplying activated nitrogen to the metal material from a nitriding environment while holding the metal material in the nitriding environment, vibrations by ultrasonic waves are applied to the metal material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of holding a metallic material in a nitriding environment, and nitriding the metallic material by supplying active nitrogen to the metallic material from the nitriding environment.

[0002]

2. Description of the Related Art Conventionally, a nitriding method has been widely used as a surface hardening method for improving the wear resistance and fatigue strength of metal materials represented by steel. As a nitriding method of a metal material, a salt bath nitriding method (for example, a tuftride method), a gas nitriding method, and a plasma (ion) nitriding method are generally performed. Since the nitriding method is generally performed at a relatively low temperature of about 500 to 600 ° C. and does not require heat treatment such as quenching after nitriding, it is a great advantage that thermal strain is extremely small.

The surface hardened layer (nitrided layer) formed by nitriding is composed of an outermost metal nitride layer and a diffusion layer thereunder. In order to improve surface hardening characteristics, productivity and production cost, it is important to form a deeper hardened layer in a shorter time to improve nitriding efficiency. Therefore, various improvements have been made in the above nitriding methods.

However, the improvement of the nitriding efficiency by the conventional improvement has already reached the technical limit, and a new method for further increasing the nitriding efficiency has been demanded.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for nitriding a metal material, which is capable of further increasing the nitriding efficiency beyond the limits of various conventional improvements.

[0006]

According to the present invention, the above object is to hold a metal material in a nitriding environment and to nitride the metal material by supplying active nitrogen from the nitriding environment to the metal material. In the method for treating, a nitriding treatment method is characterized in that ultrasonic vibration is applied to the metal material.

In the present invention, by applying ultrasonic vibration to the metallic material which is the object to be treated during the nitriding treatment, a deep surface hardened layer (nitrided layer) can be obtained in a short time by the following mechanism.

In order to promote the formation of the nitrided layer, in any of salt bath nitriding method, gas nitriding method and plasma nitriding method (ion nitriding method), (1) it exists on the surface of the metal material to be treated. It is important to promote the generation of active nitrogen and (2) promote the diffusion of nitrogen into the material to be treated. These are promoted by the energy of ultrasonic vibration as described below.

(1) Promotion of generation of active nitrogen on the surface of the material to be treated Decomposition of the raw material gas or salt bath on the surface of the material to be treated is promoted, and generation of active nitrogen is promoted. This effect is particularly remarkable for the decomposition of the salt bath in the salt bath nitriding method.

(2) Promotion of diffusion of nitrogen into the material to be treated While promoting diffusion of nitrogen (atoms or ions) inside the material to be treated, at the same time, preventing decrease in diffusion rate due to increase in nitrogen concentration inside the material to be treated. To do.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The ultrasonic vibration used in the present invention means a vibration of 20 kHz or more. As a result, the energy required to generate active nitrogen by the decomposition of the nitrogen gas or the salt bath that constitutes the nitriding environment is supplied. In general,
It is suitable to use ultrasonic vibration of 20 to 30 kHz.

The method of the present invention includes a salt bath nitriding method using a nitrogen-containing salt bath as a nitriding environment, a gas nitriding method using a nitrogen-containing gas, and a plasma (ion) using a nitrogen-containing plasma.
It can be applied to any of the nitriding methods.

The application of ultrasonic vibration to the metallic material to be treated is generally carried out by directly applying it to the metallic material. However, when a salt bath is used as the nitriding environment, ultrasonic vibration is applied. It is also possible to apply directly to the salt bath and indirectly to the metal material via this salt bath.

The metal material treated by the nitriding method of the present invention is typically steel, but the invention is not limited to this, and titanium, titanium alloy, aluminum or aluminum alloy, magnesium or magnesium alloy, etc. are nitrided. Any metal material that can be treated can be used.

[0015]

[Embodiment 1] With reference to FIG. 1, a constitutional example of a nitriding apparatus when the present invention is applied to a salt bath nitriding method will be described.

First, the example shown in FIG. 1 (1) has a structure in which ultrasonic vibration is directly applied to the material to be treated. The illustrated salt bath nitriding apparatus 10 includes a salt bath 11 and an ultrasonic wave application source 12, and an ultrasonic wave application terminal 13 extends from the ultrasonic wave application source 12 into the salt bath 11.

To perform the nitriding treatment, the ultrasonic wave applying terminal 13 is used.
With the material 14 to be treated held at the tip of the ultrasonic bath, the salt bath 11 is filled with a salt bath 15 having a predetermined composition and maintained at a predetermined nitriding temperature, the ultrasonic wave application source 12 is activated, and the ultrasonic wave application terminal 1
Ultrasonic vibration is directly applied to the material to be processed 14 via 3.

The ultrasonic energy transmitted from the material to be treated 14 to the salt bath 15 promotes the generation of active nitrogen due to the decomposition of the nitriding component in the salt bath 15, and the nitrogen in the material to be treated 14 is generated. Diffusion is also facilitated by ultrasonic energy.

Next, the example shown in FIG. 1 (2) has a structure in which ultrasonic vibration is applied to the material to be treated through a salt bath. The illustrated salt bath nitriding device 20 includes a salt bath 21 and an ultrasonic wave application source 2
2 and the tip of the ultrasonic wave application terminal 23 extending from the ultrasonic wave application source 22 is connected to the outer wall of the salt bath 21.

To perform the nitriding treatment, the material to be treated 24 is held at a predetermined position in the salt bath 21, and the salt bath 21 is filled with a salt bath 25 having a predetermined composition and maintained at a predetermined nitriding temperature. The ultrasonic wave application source 22 is activated to apply ultrasonic vibration to the salt bath 25 via the ultrasonic wave application terminal 23 and the salt bath 21.

The ultrasonic energy applied to the salt bath 25 promotes the generation of active nitrogen due to the decomposition of the nitriding component in the salt bath 25, and at the same time, the material 24 to be treated from the salt bath 25.
Diffusion of nitrogen inside the material 14 to be processed is also promoted by the ultrasonic energy transmitted to the material 14.

[Embodiment 2] With reference to FIG. 2, a structural example of a nitriding apparatus when the present invention is applied to a gas nitriding method or a plasma (ion) nitriding method will be described.

The illustrated nitriding apparatus 30 includes a nitriding chamber 31 and an ultrasonic wave application source 32, and the ultrasonic wave application terminal 3 extends from the ultrasonic wave application source 32 into the chamber 31.
3 is extended.

To perform the nitriding treatment, the ultrasonic wave applying terminal 33 is used.
With the material 34 to be processed held at the tip of the chamber 31 and the inside of the chamber 31 being maintained at a predetermined nitriding atmosphere 35 and a predetermined nitriding treatment temperature, the ultrasonic wave application source 32 is activated and the ultrasonic wave application terminal 33 is used. Ultrasonic vibration is directly applied to the material 34 to be processed.

The nitriding atmosphere 35 is generated by the ultrasonic energy transmitted from the material 34 to be treated into the nitriding atmosphere 35.
The generation of active nitrogen by the decomposition of the nitriding component in the inside is promoted, and the diffusion of nitrogen inside the material to be treated 34 is also promoted by the ultrasonic energy.

FIG. 3 schematically shows the cross-sectional structure of the surface layer of the material to be treated after the nitriding treatment. In the material S to be treated, a nitride layer C made of a metal nitride is formed on the outermost surface, and a diffusion layer D in a solid solution state in which nitrogen is diffused is formed inside the material. It is made of the original metal material M that is not affected by the upper nitriding treatment. The nitride layer C and the diffusion layer D form a surface hardened layer (for convenience, referred to as a “nitrided layer”).

When ultrasonic vibrations are applied according to the present invention, the growth of the active nitrogen potential on the surface of the material to be treated promotes the growth of the outermost nitride layer C and the diffusion layer D inside the outermost layer, so that the growth time is short. Forms a deep nitride layer. In particular, since the diffusion of nitrogen inside the material S to be processed is promoted, the growth of the diffusion layer D is significantly promoted.

[0028]

According to the present invention, there is provided a method for nitriding a metal material, which is capable of further increasing the nitriding efficiency, overcoming the limits of various conventional improvements.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a nitriding apparatus when the present invention is applied to a salt bath nitriding method. (1) shows the case where ultrasonic vibration is directly applied to the material to be treated from the ultrasonic wave application source, and (2) shows the case where ultrasonic vibration is applied to the material to be treated from the ultrasonic wave application source through the salt bath.

FIG. 2 is a sectional view showing a configuration example of a nitriding apparatus when the present invention is applied to a gas nitriding method or a plasma (ion) nitriding method.

FIG. 3 is a cross-sectional view schematically showing a cross-sectional structure of a surface layer portion of a material to be treated after nitriding treatment.

[Explanation of symbols]

10, 20 ... Salt bath nitriding equipment 11, 21 ... Salt bath 12, 22 ... Ultrasonic wave application source 13, 23 ... Ultrasonic wave application terminal 14, 24 ... Material to be treated 15, 25 ... salt bath 30 ... Gas nitriding device or plasma (ion) nitriding device 31 ... Nitriding chamber 32 ... Ultrasonic wave application source 33 ... Ultrasonic wave application terminal 34 ... Material to be treated 35 ... Nitriding atmosphere S: Material to be treated C ... Nitride layer D ... Diffusion layer M: Core (metal material)

Claims (3)

[Claims] 1. A method of holding a metal material in a nitriding environment and nitriding the metal material by supplying active nitrogen from the nitriding environment to the metal material, wherein ultrasonic vibration is applied to the metal material. A nitriding method characterized by the above. 2. The nitriding environment comprises a nitrogen-containing salt bath, a nitrogen-containing gas, or a nitrogen-containing plasma, and the ultrasonic vibration is directly applied to the metallic material.
The method described. 3. The method of claim 1, wherein the nitriding environment comprises a salt bath and the ultrasonic vibrations are applied to the metallic material through the salt bath.