KR0182401B1 - Method of manufacturing sintered compact containing tin - Google Patents

Abstract

The present invention relates to a method of sintering a mat containing TiN as a main component for gold color development, and is compact by controlling carbon and other in-house atmospheres and inhibiting decomposition of TiN as a main raw material. The present invention relates to a method for producing a TiN-based sintered compact which exhibits a gold color such as 24K to 14K.

Description

Manufacturing method of TiN type gold expression sintered compact

1 is a photograph showing the microstructure of a sintered body sintered by the method of the present invention.

The present invention relates to a method for producing a TiN-based gold expression sintered body. More specifically, the present invention relates to a method for producing a TiN-based cermet capable of suppressing decomposition of TiN by controlling carbon permeation and sintering atmosphere in the sintered body, which is more reproducible and expresses the color of natural gold (Au).

Natural gold (pure gold), which is widely used in the past, has a very low hardness and strength, so that it is hardly used in everyday life, and it is used as so-called 14K gold or 18K gold by reinforcing the hardness by adding alloys to other metals to make alloys. It is becoming.

However, while 14K or 18K is still very expensive, the hardness is insufficient, and scratches are frequently generated when used in everyday ornaments (eg, watch cases).

As a way of overcoming this, decorative companies (particularly watchmakers) use carbide or other hard metal as their base material, and conduct TiN electroplating (or CVD coating) for pure gold plating or high-quality pure gold color processing. To make ornaments.

However, the plating treatment has a disadvantage in that environmental pollution is severe in the process treatment, and the defective rate generated during the plating treatment is very high. In addition, even if the plating process is perfect, the plated layer is easily discolored or the plated layer is falling over time is a situation that is a major weak point in the production of ornaments (particularly, watch case).

On the other hand, in the case of the watch case, the plating layer is easily discolored in response to sweat from the human body, and the surface of the plating is highly reactive, which causes surface staining to drastically deteriorate the value of luxury goods.

Hereinafter, the present invention will be described in detail.

In the method for producing a TiN-based gold-expressing sintered compact of the present invention, the molded article containing 84 wt% or more of TiN is sintered in a graphite crucible in two stages while being embedded in a TiN powder having the same activity, but the first sintering treatment is performed. It is carried out under a vacuum of 10 ⁻⁵ to 10 ⁻⁶ Torr to a temperature range around 1350 ° C., and is subjected to secondary sintering under N ₂ atmosphere from 1350 ° C. to sintering temperature.

According to one embodiment of the present invention, the charging of the molded body having the main component TiN is embedded in the TiN powder of 10-15㎛ powder particles contained in the graphite crucible, in particular, the molded body having the main component TiN It is preferable to charge BN on the inner surface of the graphite crucible at a thickness equal to or greater than the surface reaction layer, that is, 0.5 mm, and then charge the molded body, and then embed the molded body with the TiN powder.

In the case where the thickness of the BN deviates from 0.5 mm, since the thermal conductivity of the BN plate is lowered and the molded body is bent due to uneven heat transfer, it is most preferable to set the thickness.

Referring to the present invention in more detail as follows.

The present invention is almost similar to gold, so that TiN, which is used as a plating layer for a real watch case, is used as a real base material instead of a plating layer, thereby eliminating unnecessary plating processes and improving hardness (for example, 92.5 or more), as well as color forever. To provide high-quality decorative materials that can be.

However, the TiN-based cermet material is very difficult to densify, and even though the densification is successful, the surface color is very different from the gold intended for the first time. .

In recent years, the development has been attempted in developed countries such as Japan, but the degree of densification is low and the color is less than 14K gold.

In order to overcome this problem, the present invention studies the development of sintering atmosphere, sintering aid, and content to achieve dense [≥94% TD (True Density)] and natural gold (from 14K to 24K). It became.

Conventionally, a vacuum furnace is used by a TiN-based cermet sintering method, wherein the vacuum furnace used is graphite or other non-graphite. Although densification can be obtained to some extent when other vacuum furnaces are used, it is difficult to develop gold. In the case of graphite vacuum furnaces, the prevalent carbon penetrates during the sintering in TiN sintered body to form Ti (CN). The near color is expressed.

In addition, since the solubility of Ti and N in Ni added as a sintering aid during sintering of TiN is different (Ti solubility is greater than N solubility), evaporation of N occurs due to the difference in solubility during liquid phase formation (denitrification phenomenon). . As a result, the sintered compact had a N-deficient structure. Therefore, a compact structure could not be obtained due to the generation of N ₂ gas during sintering.

However, in terms of color development, although some degree of carbon penetration is red, it is a very essential item for gold expression, and therefore, proper in-house atmosphere control is a very important technology. In the present invention, in order to properly suppress the penetration of carbon during sintering, a TiN molded body containing 85% by weight or more of TiN is embedded in a TiN powder having the same activity as that of the molded body and having powder particles of 10 to 15 µm, and the sintering conditions are also premature. 3 SLPM (liter per minute: unit indicating the amount of gas flow) in the temperature range around 1350 ° C, for example, 1100 ° C to 1350 ° C, in a vacuum from 1350 ° C to 1700 ° C In order to minimize the decomposition of TiN by sintering while flowing.

When the size of the TiN powder particles is less than 10 μm, it is not preferable because the powder to be embedded with the liquid in the TiN molded body reacts. On the contrary, when the size of the TiN powder particles exceeds 15 μm, scratches may occur in the molded body due to the load of the embedded powder. There is a problem.

In addition, when the primary sintering temperature exceeds 1350 ℃ TiN is severely volatilized and the sinterability is sharply lowered, it is preferable to carry out in the above temperature range to obtain a sintered body without open pores. In the case of secondary sintering in the above temperature range under N ₂ atmosphere conditions, the sintered compact which prevents decomposition of TiN and removes internal pores can be manufactured. In other words, the sintered body primarily sintered at 1350 ° C. or less has an effect that densification proceeds to a certain degree and that the decomposition of TiN is not severe even at a temperature higher than that.

On the other hand, a colorimeter was used to quantitatively indicate the color of the sintered compact, and the sintered compact according to the present invention had a smaller red color value and a higher yellow value than the conventional sintering method. I could confirm it. Table 1 shows the results.

(a *: + → red,-→ green)

(b *: + → yellow,-→ blue)

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

TiN (84.5 wt%), iN (3 wt%), Co (3 wt%), NbC (8 wt%) and MoC (1.5 wt%) powders used in the present invention for 120 hours using alcohol as a mixed solvent. Mix and grind in Sus. Jar Ball Mill. The mixed slurry is sufficiently dried and then re-divided to be shaped and sintered in a graphite vacuum furnace.

At this time, the sintering process used a two-step atmosphere conversion to control the sintering atmosphere. First up to 1350 ℃ at room temperature 10 To 10 Vacuum sintering was carried out, and then the atmosphere was changed to N, and the N partial pressure was adjusted to 0.5 to 1 atm while sintering while flowing N at 3 SLPM. Charging of the molded body is first performed by applying BN to the inner surface of the graphite crucible at a thickness of 0.5 mm or more, which is equal to or greater than the surface reaction layer, and then charging the molded body, and then embedding the TiN powder having a large particle size of about 10 to 15 µm to perform sintering.

In the case of landfill sintering, the liquid phase flows out through only the N atmosphere sintering alone and reacts with the landfill powder.

After sintering, the microstructure was examined for porosity measurement by optical microscope after polishing. In addition, chromaticity was quantified using a color difference meter. The color difference measurement results at this time were as shown in Table 1, the density measurement results were 94% TD or more when sintered under the sintering conditions of the present invention.

The photograph of FIG. 1 of the accompanying drawings shows the microstructure of the sintered compact sintered by the said method.

In the photograph of FIG. 1 of the accompanying drawings, it can be seen that the pores are smaller than the conventional single atmosphere sintering, and the distribution is also uniform. As a result, it can be seen that the color, density, and microstructure are superior to those of the sintering method of the present invention.

Claims (3)

BN is coated on the inner surface of the graphite crucible with a thickness of at least a surface reaction layer and charged with a molded body consisting of 84.5 wt% TiN, 3 wt% Ni, 3 wt% Co, 8 wt% NbC, and 1.5 wt% Mo ₂ C, Sintering was carried out in two stages in the graphite crucible in a state buried in TiN powder having the same activity as above, but the first sintering was carried out under a vacuum of 10 ^-5 to 10 ^-6 Torr to a temperature of 1100 ° C to 1350 ° C. And a sintering temperature of 1350 ° C. to 1700 ° C. in a N ₂ atmosphere of 0.5 to 1 atm, followed by secondary sintering. The method for producing a TiN-based gold-expressing sintered compact according to claim 1, wherein the molded article containing TiN as a main component is embedded in a TiN powder having a particle size of 10 to 15 µm embedded in the graphite crucible. The method for producing a TiN-based gold-expressing sintered compact according to claim 1, wherein the thickness is 0.5 mm.