JPS62196365A - Surface nitriding method for titanium - Google Patents

Abstract

PURPOSE:To quickly form a good nitride film with a simple device by bringing the gaseous nitrogen after contact with sponge Ti into contact with a Ti member for a nitriding treatment. CONSTITUTION:The above-mentioned Ti member 7 is disposed in an electric furnace, i.e, Ti treatment part 4 and a small sponge Ti piece 8 is provided around said member to enclose the member. The gaseous nitrogen from a cylinder 1 is filled in the treatment part 4 and is evacuated by a vacuum pump 6 from the other side. An adequate temp. is maintained in the treatment part 4 and the gaseous nitrogen after the removal of the oxygen and hydrogen components in the gaseous nitrogen from the above-mentioned cylinder 1 by first bringing said gas with the small Ti piece 8 is brought into contact with the above-mentioned member 7 and the film of the nitride is formed on the surface of the member 7. The small Ti piece 8 is preferably of about 100 mesh and more preferably 80 mesh or larger. The small ti piece 8 is preferably disposed in the mid-way of the gaseous nitrogen supply path separately from the member 7 in such a manner that said piece can contact the gaseous nitrogen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for surface nitriding titanium members such as dental products.

[Conventional technology]

Conventionally, methods for nitriding the surface of titanium members include:
For example, there is a method for nitriding the surface of pure titanium or α-titanium alloy, as typified by Japanese Patent Publication No. 56-44148. In this surface nitriding method, titanium nitride powder and pure titanium or α-titanium alloy are brought into contact with each other in the form of a rod, and nitrogen gas is supplied to the titanium member while heating it from 790°C to 880°C. The surface of pure titanium or the like to be treated is nitrided using titanium nitride powder present around the titanium nitride. However, this method has a disadvantage in that it takes a long time to process because titanium nitride is used to form nitride on the surface of pure titanium or α-titanium alloy by mutual reaction. Further, as another method, there is a gas nitriding method in which nitrogen gas is brought into contact with the titanium member to be treated under a heated state.

However, this gas nitriding method requires large and costly equipment to remove oxygen and hydrogen present in the nitrogen gas, making it difficult to reduce the cost and make it more versatile. It is a cause of obstruction. In particular, when hydrogen and oxygen components remain in the nitrogen gas, these may react with the pure titanium or alpha titanium alloy surface to be treated, changing the surface strength or changing the color from the desired color to another color. There is a tendency to change to

[Problem that the invention seeks to solve]

The present invention aims to simplify the conventional method for surface nitriding of titanium members such as pure titanium and titanium alloys, which requires expensive and complicated equipment, and also to shorten the processing time. The present invention aims to provide a method for surface nitriding a titanium member.

[Failure to solve the problem]

The present invention is provided as a solution to these problems, and includes a step of bringing nitrogen gas into contact with a small piece of titanium sponge, and a treatment in which the nitrogen gas is suspended and sealed in a heated state after contacting with the small piece of titanium sponge. It has been found that the surface nitriding of titanium can be performed simply and quickly at low cost by bringing the titanium material into contact with a titanium member for nitriding treatment within the unit.

[For production]

The present invention is thus a method for surface nitriding titanium using sponge titanium, which is relatively low cost, easy to obtain, and relatively porous, so it is good as a deoxidizing and hydrogen material. For example, after contacting a piece of pure titanium sponge to remove the hydrogen and oxygen contained in the nitrogen gas, the nitrogen gas is heated to form a pure nitrogen gas state and then heated to form a pure titanium or titanium material. It is brought into contact with the surface of a titanium member such as an alloy to form a nitride layer on the surface. Here, the titanium sponge pieces must be pure titanium of a size or shape that will not burn when brought into contact with nitrogen gas. For this size, nitriding is usually 700℃.
Since the titanium sponge pieces start at about this temperature, they need to be of a size that does not start combustion when they come into contact with oxygen in nitrogen gas, etc., and the size is about 100 mesh. Ta. Particles smaller than about 100 meshes, such as 150 meshes or 200 meshes.
Small mesh titanium pieces tended to start burning each time they came into contact with nitrogen gas. Therefore,
By bringing such small pieces smaller than 100 meshes, including powdery and granular pieces, into contact with nitrogen gas at a temperature higher than the nitriding temperature, that is, about 700°C, combustion can be started. Therefore, small pieces of titanium of this size are removed. Preferably,
It can be said that it is preferable to use a small piece of sponge titanium larger than 80 mesh. By using a product in this state, even if it comes into contact with nitrogen gas under heating,
This provides conditions sufficient to inhibit combustion upon contact with the oxygen and hydrogen components in the nitrogen gas.

Further, these small titanium sponge pieces may be placed closely around the outer periphery of the titanium member in a processing section serving as a processing space in which the titanium member is arranged. In such a case, in order for the nitrogen gas to pass through the titanium sponge and easily come into contact with the titanium parts, it is said that the nitriding time will be shortened if the titanium sponge is not as small as possible, that is, if the air permeability is good. This is what is desired above. In this sense, a piece larger than 60 meshes, e.g.
If a small piece of about 5 mesh size is used, the temperature at the initial stage of nitriding titanium is about 700°C, and the deformation point is just under 900°C, so it is known that combustion does not start even when it comes into contact with nitrogen gas. It is.

〔Example〕

The process will be explained based on a flow sheet further illustrating the details of the present invention. What is shown in FIG. 1 is an example to which this surface nitriding method is applied. Nitrogen gas is supplied from the nitrogen gas cylinder shown as 1 in the figure, and by opening the valve 2, the titanium treatment section 4 is supplied from the supply path 3. Nitrogen gas can be supplied into the electric furnace. This electric furnace enables heating 5 for the nitriding process and at the same time provides a hermetically sealed chamber that can create a nitriding atmosphere inside the furnace. Gas inside the processing section 4 can be sucked from one section 4 to the other by a vacuum pump 6. That is, a flow path is formed that allows new gas to be supplied from the nitrogen gas cylinder 1. Inside this electric furnace, a titanium product such as pure titanium or a titanium alloy is placed as a titanium member 7 to be processed, and small pieces of sponge titanium 8 are provided around the titanium product to cover the outside. Under this condition, the nitrogen gas supplied from the nitrogen gas cylinder 1 fills the furnace, and is then drawn from the other side by the vacuum pump 6, so that a constant amount of fresh nitrogen gas always passes through the furnace. Become.

Next, by operating the electric furnace under this condition,
The temperature inside the furnace, that is, inside the processing section 4, is at a temperature of, for example, 70°C, which requires nitriding.
The temperature is set to 0° C. or higher to enable heating 5. At this time, before the oxygen and hydrogen bones in the nitrogen gas supplied from the nitrogen gas cylinder came into contact with the titanium product, they were brought into contact with the sponge titanium pieces 8 existing on the outer periphery of the titanium product to remove the oxygen and hydrogen bones. Thereafter, fresh nitrogen gas is brought into contact with the titanium product under heating conditions to form a nitride film on the surface of the titanium product. Then, such a state is repeated one after another to form a nitride layer with a desired thickness.

Next, what is shown in Fig. 2 is not the method in which the sponge titanium pieces 8 are arranged around the titanium product 7 shown in Fig. 1, but the titanium product 7 and the sponge titanium pieces 8 are separated into separate parts. It is arranged according to the condition. That is, the sponge titanium piece 8 is placed at a suitable place in the nitrogen gas supply path 3 from the nitrogen gas cylinder 1, for example, in the example shown, the sponge titanium piece 8 is placed on the nitrogen gas inlet side of the electric furnace, and the inside of the titanium sponge piece 8 is filled with nitrogen gas. The oxygen and hydrogen bones in the nitrogen gas are combined with the small titanium sponge pieces 8, and the pure nitrogen gas, with impurities in the gas removed, is brought into contact with the titanium product 7 on the right side of the figure, and its surface is It is made of nitride. Even under such conditions, a titanium product with the desired surface nitridation can be obtained by sequentially suctioning the gas in the electric furnace with the vacuum pump 6 and discharging the gas to the right in the figure, as in Figure 1. It is something that can be done. Furthermore, if the nitrogen gas pressure inside the furnace is maintained at a state slightly higher than atmospheric pressure, it will be easier to maintain the airtight state. Methods such as introducing nitrogen gas in a vacuum state, or creating a nitrogen gas atmosphere in the furnace by introducing and passing nitrogen gas at the beginning of the reaction are employed.

In addition, heating can be done after creating a nitrogen gas atmosphere in the furnace, or by raising the temperature in the electric furnace to begin with.
It is optional to insert a titanium product as a processing member in this state and to supply nitrogen gas.

[Experimental Example 1] Table 1 shows the results of using various thicknesses of titanium sponge pieces and looking at the state in which the titanium pieces start to ignite, that is, burn, at each temperature. . This experiment also shows that, for example, a 100-mesh piece can be used as a sponge titanium piece in the method of the present invention under heating conditions of 700°C. For example, a surface nitrided layer with a thickness of 1 μm could be obtained in 4 hours. Even a small piece of 100 pieces is 8
Under conditions of elevated temperature to 00°C, the pieces sometimes started to burn. In this case, the film thickness was 2.5μ in 4 hours.
A surface nitrided layer was obtained. Therefore, it was found that a small piece of 100 mesh could not be used at temperatures above 800°C.

Next, the 80-mesh type can be used at 850°C, but when the temperature reaches 900°C, it sometimes starts to burn and becomes unusable. This 900℃
In the vicinity, the deformation point of titanium is around 882 degrees Celsius, so
In things larger than 60 mesh titanium pieces,
It was discovered for the first time that it was usable. therefore,
Since the temperature for nitriding treatment is usually about 700° C. to 880° C., it has been found that titanium sponge pieces of 60 mesh or more can be used.

[Experimental Example 2] Next, Table 2 shows the nitriding conditions at a temperature of 800°C and a treatment time of 4.
According to the experimental results of the present invention using various titanium sponge pieces according to the method of the embodiment shown in FIG.
It was as shown in the right column of the figure. According to this, 200
Menshi and small 325 mesh titanium sponge pieces cause ignition and are in a state where they cannot withstand actual use. However, 100 mesh titanium sponge pieces sometimes catch fire.
It was found that this was the critical size that could be used.

In addition, the 35 mesh one is in a usable condition, and the No. 50 titanium sponge piece is in good condition.
Good nitriding was possible with the 2mIII square one. Incidentally, even when sponge titanium pieces of sizes No. 6 and 7 are used instead of this 2111m, the condition is usable. The degree of coloration of the surface of each of these nitrides in a usable state was such that the desired nitride color was exhibited.

〔Effect of the invention〕

As described above, the titanium surface nitriding method according to the present invention uses small pieces of titanium sponge, which is relatively porous and good as a deoxidizing and hydrogen material, and is relatively low cost. Nitrogen gas is brought into contact with the small piece of titanium sponge. The oxygen and hydrogen content in the nitrogen gas is removed, and the pure nitrogen gas is brought into contact with the titanium material to be treated, so a good nitride film can be formed in a short time with a low-cost and simple device. This made it possible to form.

[Brief explanation of drawings]

1 and 2 are flowcharts showing two embodiments of the present invention. Nitrogen gas cylinder, 2: Valve, 3: Supply path, 4: Titanium treatment section, 5: Heating,
6: Vacuum pump, 7: Titanium member, 8: Sponge titanium piece, Patent applicant OHARA Co., Ltd. Agent Patent attorney Takashi Yanagino ML Diagram

Claims (5)

[Claims] (1) A step of bringing nitrogen gas into contact with a small piece of titanium sponge, and a step of bringing the nitrogen gas that has been in contact with the small piece of titanium sponge into contact with a titanium member for nitriding treatment in a sealed processing section under heated conditions. Surface nitriding method. (2) A method for surface nitriding titanium according to claim 1, wherein a small piece of titanium sponge is placed in the nitrogen gas supply path separately from the titanium member so as to be able to come into contact with the nitrogen gas. (3) A method for surface nitriding titanium according to claim 1, wherein small pieces of titanium sponge are arranged around a titanium member arranged in the processing section. (4) The method for surface nitriding titanium according to claim 1, 2, or 3, using a sponge titanium piece larger than 100 mesh as the sponge titanium piece. (5) The method for surface nitriding titanium according to claim 1, 2, or 3, using a sponge titanium piece with a size larger than 80 mesh as the sponge titanium piece.