JPS62139862A - Method for nitriding surface of titanium - Google Patents

Abstract

PURPOSE:To simply and rapidly nitride the surface of a Ti member to be nitrided by bringing gaseous nitrogen into contact with small Ti pieces before the nitrogen is brought into contact with the Ti member. CONSTITUTION:A Ti member 7 to be nitrided is placed in a hermetically sealed electric furnace and covered small Ti pieces 8. Gaseous nitrogen fed from a cylinder 1 is filled into the furnace and exhausted with a vacuum pump 6 so that a fixed quantity of fresh gaseous nitrogen is always passed through the furnace. The furnace is then worked to keep the treatment part 4 at the required temp. by heating 5. Oxygen and hydrogen in fed gaseous nitrogen are removed by contact with the Ti pieces 8, so fresh gaseous nitrogen comes in contact with the Ti member 7, forming a nitride film on the surface of the member 7 in the heated state.

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 one chamber, nitrogen gas is supplied, and titanium parts are heated from 790°C to 88Q'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. Also, as another method,
Gas nitriding methods exist in which nitrogen gas is brought into contact with the titanium component to be treated under heated conditions.

However, this gas nitriding method requires large and costly equipment to remove the oxygen and hydrogen components present in nitrogen gas, making it difficult to achieve general low cost and general use. It is a cause of obstruction. In particular, when hydrogen and oxygen bones remain in the nitrogen gas, these may react with the pure titanium or α-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.

[Means for solving problems]

The present invention is provided as a solution to these problems, and includes a step of bringing nitrogen gas into contact with small pieces of titanium, and a process of nitriding the nitrogen gas after contacting with the small pieces of titanium in a sealed processing section under heating conditions. It has been found that surface nitriding of titanium can be easily and quickly performed by bringing the titanium material into contact with a titanium member for treatment.

[For production]

In this way, the present invention brings nitrogen gas into contact with small pieces of titanium, for example, small pieces of pure titanium, removes hydrogen and oxygen bones contained in the nitrogen gas, and then heats the nitrogen gas to form a pure nitrogen gas state. A nitride layer is formed on the surface of a titanium member such as pure titanium or a titanium alloy by bringing it into contact with the surface of a titanium member such as pure titanium or a titanium alloy. Here, the titanium pieces must be pure titanium of a size or shape that will not burn when brought into contact with nitrogen gas. Since nitriding usually starts at around 700°C, the size must be such that the titanium pieces will not start burning when they come into contact with the oxygen bones in the nitrogen gas at around this temperature. , its size is 100 meters,
It was about 100 yen. Particles smaller than about 100 meshes, such as small titanium pieces of about 150 meshes or 200 meshes, tended to start burning when they came into contact with nitrogen gas. Therefore, by bringing such small pieces smaller than 100 mesh, that is, such small pieces including powdered and granular pieces, into contact with nitrogen gas at a temperature of about 700°C or higher in the nitriding temperature zone, combustion can be started. This is why small pieces of titanium of this size are removed. It is preferable to use titanium pieces larger than 80 meshes, and in particular, among such small pieces, it is preferable to use plate-like pieces in the form of scraps in addition to those in the form of granules, powder, or granules. By using a substance in this state, even if it comes into contact with nitrogen gas under a heated state, a sufficient state is provided to prevent it from coming into contact with the oxygen and hydrogen components in the nitrogen gas and combusting.

Further, the titanium 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 between the titanium pieces and easily come into contact with the titanium member, it is necessary to keep the titanium pieces as small as possible, that is, to have good air permeability, which will shorten the nitriding time. This is what is desired in the future. In this sense, if a small piece larger than 60 mesh is used, for example a small piece of about 35 mesh, the temperature at the initial stage of nitriding titanium is about 700°C, and the deformation point is about 900°C, so it is difficult to use nitrogen gas. This indicates a situation in which combustion does not start even after contact.

〔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 in which the present surface nitriding method is applied. Nitrogen gas is supplied from the nitrogen gas cylinder shown as 1 in the figure, and by opening the pulp 2, it is passed from the supply path 3 to the titanium treatment section 4. 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 the titanium product is covered with small pieces of titanium 8, for example, chips of titanium material, etc. It is set up. Under this condition, the nitrogen gas supplied from 1 to the nitrogen gas cylinder 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 inside of the furnace, that is, the inside of the processing section 4, is brought to a temperature that requires nitriding, for example, 700"C.
Heating 5 is made possible by the above settings. At this time, before the oxygen and hydrogen content in the nitrogen gas supplied from the nitrogen gas bomb comes into contact with the titanium product, it is brought into contact with the titanium small pieces 8 existing on the outer periphery of the titanium product, that is, its chips, and oxygen and hydrogen are After removing the components, 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 titanium pieces 8 are arranged around the titanium product 70 as shown in FIG. 1, but the titanium product 7 and the titanium pieces 8 are arranged in separate parts. This is what I did. That is, the small 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 small titanium piece 8 is placed on the nitrogen gas inlet side of the electric furnace, and the nitrogen gas is allowed to pass through the inside of the titanium piece 8. , the oxygen and hydrogen in the nitrogen gas are combined with the titanium 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 coated with nitride. It is something to do.

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. A method is employed in which nitrogen gas is introduced into the furnace under a vacuum state, or nitrogen gas is introduced and passed through the furnace at the beginning of the reaction to create a nitrogen gas atmosphere inside the furnace. In addition, heating can be done after creating a nitrogen gas atmosphere inside the furnace, or by raising the temperature inside the electric furnace and inserting the titanium product as a processing member into this state, and then introducing nitrogen gas. It is also a matter of discretion to supply them.

[Experimental Example 1] Table 1 shows that small pieces of various sizes were used as small titanium pieces,
We then looked at the conditions under which the titanium particles started to ignite, or burn, at each temperature. This experiment also shows that, for example, 100 mesh pieces can be used as titanium pieces in the method of the 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.

However, even with 100 mesh products, when the temperature was raised to 800°C, the small pieces sometimes started to burn. In this case, a surface nitrided layer with a thickness of 2.5 μm was obtained in 4 hours. Therefore, it was found that a small piece of 100 mesh could not be used at temperatures above 800°C.

Next, with 80 mesh, it can be used at 850'C, but when the temperature reaches 900'C, the pH sometimes changes.
It has started baking and is no longer usable. This 9
At around 00°C, the deformation point of titanium is about 882°C, so it was found that it could only be used in items larger than a 60-mesh titanium piece. Therefore, connoisseur? δ, the temperature for nitriding treatment is 700'C ~ 8
Since the temperature is about 80°C, it was found that titanium pieces of 60 mesh or more could be used. In addition, as for such small titanium pieces, if we use plate-shaped titanium pieces in the form of chips compared to those in the form of hananaruwa), grains, or granules, and if these are placed around the titanium member, the air permeability will be lowered. It can be said that small pieces of titanium are preferable for obtaining a good nitride film because they have good properties and can easily combine with oxygen and hydrogen in nitrogen gas.

Table 1 [Experimental Example 2] Next, Table 2 shows the nitriding conditions at a temperature of 800°C and a treatment time of 4.
The results of the present invention using various titanium pieces according to the method of the embodiment shown in FIG. 1 were as shown in the right column of the figure. According to this, small titanium pieces of 200 mesh or 325 mesh cause an ignition phenomenon and cannot withstand actual use. However, although 100-mesh titanium pieces sometimes catch fire, it has been found that this is the limit size for use. In addition, the 35 mesh type is in a usable condition, and it is ranked No. 5 as a small titanium piece.
Good nitriding was possible when the chips had a length of 2 to 4 mm and a thickness of 1 to 2 mm. It should be noted that even when titanium pieces of sizes No. 6 and 7 are used instead of these chips, they are still 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 involves bringing nitrogen gas into contact with small pieces of titanium to remove oxygen and hydrogen from the nitrogen gas, and applying pure nitrogen gas to the titanium member as the workpiece. This makes it possible to form a good nitride film in a short time using a simple device.

[Brief explanation of drawings]

1 and 2 are flowcharts showing two embodiments of the present invention. [: To nitrogen gas cylinder, 2: Harb, 3: Supply path,
4: Titanium treatment part, 5; Heating, 6
; Vacuum pump, 7: Titanium member, 8: Titanium piece, patent applicant OHARA Co., Ltd. Figure 1

Claims (7)

[Claims] (1) Surface nitriding of titanium, comprising: a step of bringing nitrogen gas into contact with the titanium pieces; and a step of bringing the nitrogen gas that has been in contact with the titanium pieces into contact with a titanium member for nitriding treatment in a sealed processing section under heated conditions. Method. (2) A method for surface nitriding titanium according to claim 1, wherein a small piece of titanium 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 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 titanium pieces larger than 100 mesh as the titanium pieces. (5) A method for surface nitriding titanium according to claim 1, 2, or 3, using titanium pieces larger than 80 mesh as the titanium pieces. (6) A method for surface nitriding titanium according to claim 1, 2, 3, 4, or 5, in which a small titanium plate-like piece is used as the titanium piece. (7) A method for surface nitriding titanium according to claim 1 or 2 or 3 or 4 or 5 or 6, which uses titanium chips as the titanium pieces.