JPH0513084B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention utilizes hard raw materials such as Ti, Nb, and
The present invention relates to a method for producing composite carbonitride of W. The nitrogen-containing cermet made from composite carbonitride according to the present invention can be effectively used, for example, in cutting tools used under high-speed, high-feed conditions. [Prior art] Nitrogen-containing cermets, in which carbonitrides such as Ti, Nb, and W are bonded with metals such as Ni and Co, have significantly finer dispersed hard phases than conventional cermets that do not contain nitrogen. It is known that the plastic deformation resistance and thermal fatigue resistance of cutting tools are significantly improved (Japanese Patent Publication No. 49-1364). By the way, when producing this type of cermet, if sintering is performed in a vacuum, the carbonitrides contained in the cermet alloy will decompose and a so-called denitrification phenomenon will occur, reducing the effect of nitrogen addition. In addition, the nitrogen gas generated at that time does not escape sufficiently from the sintered body and remains as pores after sintering, both of which significantly reduce the reliability of the nitrogen-containing cermet as a tool. For this reason, the above-mentioned Japanese Patent Publication No. 1364-1984 states that
A technique has been disclosed in which the decomposition of nitrides is suppressed by sintering the cermet in a nitrogen atmosphere rather than in a vacuum. Furthermore, as the amount of nitrogen content increases, the amount of denitrification also increases, so to suppress this, it is necessary to increase the atmospheric nitrogen pressure to 80 Torr.
Although the above is necessary, there is a drawback that degassing from the cermet during sintering is insufficient. As a way to overcome this problem, a method has been proposed in which a composite carbonitride of the metal elements contained in the cermet is produced in advance to lower the nitrogen dissociation pressure and to minimize loss during sintering (for example, −51201, etc.). Furthermore, in order to make the composite carbonitride powder into fine particles, attempts have been made to use an oxide as a starting material, mix carbon powder with it, and heat it in a nitrogen stream (for example, in JP-A-61 −291408, etc.). In addition, conventional methods for producing composite carbonitrides are generally carried out in an open boat-fed continuous furnace, in which the boats are fed one after another while nitrogen is kept flowing. Ta. [Problems to be solved by the invention] However, in the conventional method of producing composite carbonitride by flowing nitrogen through a mixture of oxide and carbon, free carbon and oxygen remain, and the resulting composite carbon There has been a problem in that the sinterability in the sintering process when producing cermets using nitrides as a raw material deteriorates, and as a result, the wear resistance and toughness, which are characteristics of tools, decrease. The present invention solves this problem and uses metal oxide and carbon powder as raw materials to prevent oxygen and free carbon from remaining.
The purpose of this invention is to provide a method for producing a composite carbonitride of Nb and W. [Means and effects for solving the problems] In search of a means for solving the above problems, the present inventors conducted a detailed study on the production process of composite carbonitrides using oxides as starting materials. . As a result, the conventional method of producing composite carbonitride from oxide raw materials using an open boat feeding method with nitrogen flowing in a continuous furnace as described above clearly simplifies the production process, and Since the oxide raw material itself is originally a fine powder, it is effective in that the resulting composite carbonitride powder also becomes fine, but it has been found that the reaction is very complicated. This is because, in addition to the reduction reaction, carbonization and nitridation reactions occur, as well as a solid solution reaction. With heating, the reduction reaction of each oxide progresses as CO gas is generated, followed by nitridation and carbonization. We obtained the knowledge that these events occur in a manner that overlaps with each other. Upon investigation based on this knowledge, it was found that in order to completely remove oxygen, in other words to promote the reduction reaction of the oxide, it is effective to flow hydrogen to create a reducing atmosphere during heating. It can be said that the ideal means is to flow nitrogen after sufficient oxygen has been removed. However, in reality, if nitrogen is not supplied, grain growth will begin at a certain temperature.
The initial objective of atomization cannot be achieved sufficiently. In view of these circumstances, the present inventors have conducted repeated research on a heating method that uses oxides as raw materials and can achieve both oxygen removal, prevention of residual free carbon, and atomization, particularly on atmospheric and temperature conditions. , TiO ₂ ,
After mixing Nb ₂ O ₃ , WO ₃ and carbon powder as starting materials and heating the mixture in a hydrogen atmosphere,
Composite carbon of Ti, Nb, and W, characterized in that it is heated in a nitrogen atmosphere at a temperature of 1200°C or higher and 1500°C or lower, and then maintained at a temperature of 1500°C or higher and 2100°C or lower for reaction in the nitrogen atmosphere. The present invention, which is a method for producing nitrides, has been achieved. The present invention uses Ti, Nb, and W as TiO 2 and TiO ₂ , respectively.
Oxides such as Nb ₂ O ₅ and WO ₃ are supplied, carbon powder is mixed with this, and when this is heat-treated, it is first heated in a hydrogen atmosphere at the low temperature side where the reduction reaction proceeds, and then the temperature is continued to rise. When the temperature reaches a temperature range of 1200°C or higher and lower than 1500°C, switch the atmosphere to nitrogen, and continue to heat the temperature at 1500°C or higher and 2100°C in this nitrogen atmosphere.
In this method, a carbonitriding reaction is carried out by heating at a temperature below .degree. C. to obtain a double carbonitride of Ti, Nb, and W.
It is particularly preferable that the nitrogen atmosphere pressure be 30 Torr or more and 10 atmospheres or less. By using oxides as starting materials in this way,
A fine powder is obtained, and the reduction reaction of the oxide can proceed sufficiently in a hydrogen atmosphere, so the oxygen content can be significantly reduced, and the oxygen is replaced by CO2.
Since it escapes as a gas, in addition to the amount of carbon necessary for carbonization, the carbon mixed in for reduction also plays its role. the result,
A high-quality composite carbonitride with extremely low residual oxygen and free carbon can be obtained. Therefore, when a cermet is made using the composite carbonitride of the present invention, a highly reliable alloy with very good sinterability and excellent cutting properties such as wear resistance, toughness, and heat cracking resistance can be obtained. It will be done. The general method and reasons for limitations in the present invention will be described below. (1) Hydrogen atmosphere heating conditions The hydrogen atmosphere pressure should be 10 ^-3 Torr or more and 10 atmospheres or less. If it is less than 10 ^-3 Torr, there is no oxygen removal effect, and even if it exceeds 10 atmospheres, there is no difference in the effect, and it is not preferable because it becomes a high-pressure production facility, which causes waste in terms of equipment. There is no particular restriction on the time to maintain this atmosphere. (2) Temperature increase rate From room temperature (start of heat treatment) to 1500℃ or more to 2100℃
1 to 100 in all temperature ranges up to the following maximum temperatures
C/min is preferred. If it is less than 1°C/min, grains will grow, and if it is more than 100°C/min, oxygen and free carbon cannot be removed sufficiently. (3) Start nitrogen supply at 1200℃ or higher and 1500℃ or lower. If nitrogen is supplied at a temperature lower than 1200°C, oxygen will remain in the composite carbonitride, and if nitrogen is not supplied even if the temperature exceeds 1500°C, grain growth will occur and the hardness of the alloy will decrease, which is not preferable. (4) Nitrogen atmosphere pressure during heat treatment: 30 Torr or more and 10 atmospheres or less. If it is less than 30Torr, the effect of refinement by nitrogen supply cannot be obtained,
Further, even if the pressure exceeds 10 atmospheres, there is no difference in the effect, and it is not preferable because it causes waste in terms of equipment. (5) Reaction temperature The reaction is maintained at 1500°C or higher and 2100°C or lower in a nitrogen atmosphere. If it is less than 1,500°C, solid solution will be insufficient, which is not preferable, while if it exceeds 2,100°C, grain growth will become significant, which is not preferable. (6) Holding time at maximum temperature Preferably 10 minutes or more and 5 hours or less. If the reaction time is less than 10 minutes, the reduction reaction will be insufficient, and if it exceeds 5 hours, grain growth will occur, which is not preferable. [Example] Hereinafter, the present invention will be specifically explained with reference to Examples. Example 1 TiO ₂ powder, Nb ₂ O ₅ powder, WO ₃ powder and C powder were mixed and granulated by water kneading, heated to 1420°C in a hydrogen atmosphere of 1 atm, and then heated in a nitrogen atmosphere of PN ₂ = 300 Torr. The temperature was changed to 1730°C for 1 hour to obtain composite carbonitride A of the present invention. In addition, from the start of heat treatment
The heating rate up to 1730°C was 10°C/min. For comparison, PN ₂ =
Comparative product B was obtained by heating to 1730° C. at a temperature increase rate of 10° C./min in a nitrogen atmosphere of 300 Torr and maintaining this condition for 1 hour. The analysis results for each sample A and B are shown in Table 1. From Table 1, it is clearly seen that although there is almost no difference in particle size between product A of the present invention and comparative product B, the amount of free carbon and oxygen is significantly reduced in product A of the present invention. Ni and Ni were added to the obtained composite carbonitrides A and B, respectively.
Co was added in 8 weight portions and sintered at 1450° C. for 1 hour to produce a cermet alloy. The obtained alloy had almost no cavities in the alloy made from product A of the present invention, whereas the alloy made from comparative product B had AO6 type (Cemented Carbide Tool Association standard).
ClS006B-1983) nests were observed. Example 2 Ti:Nb:W=0.80:0.10:0.10, C:N=
Mix metals, oxides, carbides, and carbonitrides as shown in Table 1 so that the ratio of nonmetallic components/metallic components is 0.60:0.40 and 1.0, and each sample is heated in a hydrogen atmosphere of 400 Torr up to 1350℃. After heating in the chamber, the atmosphere was changed from 1350° C. to nitrogen atmosphere at PN ₂ =1 atm, and maintained at 1700° C. for 1 hour in this atmosphere. From the start of heat treatment
The temperature was raised to 1700°C at a rate of 12°C/min. Table 2 shows the analysis results for the composite carbonitrides of the invention product C and comparative fines D and E obtained. As a result, the product C of the present invention has a much smaller particle size and a reduced amount of free carbon than the comparative product D, which uses metal powder without using oxide raw materials, and also uses carbonitrides and carbides as raw materials. Compared to comparative product E, the amount of free carbon is slightly higher, but the amount of oxygen is about the same.
It can be seen that the particle size is very small. That is, it was recognized that the present invention is the most minute.

【table】

[Table] Example 3 TiO ₂ , Nb ₂ O ₅ , WO ₃ , and C powders were blended as shown in Table 3, heated and reduced in hydrogen at 400 Torr,
Carbonitriding treatment was performed under the conditions shown in Table 3. The temperature increase rate at this time was 10° C./min and PN ₂ was all set to 1 atm. Table 3 also shows the analysis results of the composite carbonitrides of the products F to I of the present invention and comparative products J to O.

[Table] Example 4 Composite carbonitrides A, B, E, obtained in Examples 1 to 3,
H, M, and N are used as raw materials, and Ni and Co are added to these.
Added 10% by weight, mixed and pressed, 1450
A cermet alloy was produced by sintering in a nitrogen atmosphere at PN ₂ =8 Torr for 2 hours. The obtained alloys are designated as P, Q, R, S, T, and V, respectively. Table 4 shows the hardness and transverse rupture strength of each alloy.

[Table] Furthermore, using raw materials E and N, in order to improve the hardness, the amount of Ni and Co added was increased to 7% by weight each.
_Alloy V,
I got a W. The hardness and transverse rupture strength of these alloys are shown in Table 5, and the transverse rupture strength was significantly reduced.

[Table] Next, cutting tests were conducted on the alloys P to W above under the following conditions. The test results are shown in Table 6, and the alloy made from the composite carbonitride of the present invention was superior in all items: flank wear amount, number of chips in interrupted cuts, and number of thermal cracks in interrupted milling cuts. It can be seen that Conditions 1 Continuous cutting workpiece SCM440 (H _B = 290) Cutting speed 200m/min Feed 0.36mm/rev Depth of cut 1.5mm Chip shape SNGN140208 Holder FN11R-44A Cutting time 7 minutes Condition 2 Intermittent cutting workpiece SCM435 ( H _B = 250), 4-groove material cutting speed 120m/min Feed 0.22mm/rev Depth of cut 2.0mm Chip shape SNGN120408 Holder FR11R-44A Cutting time Until breakage. Maximum 2 minutes Conditions 3 Milling cutting Work material SCM435 (H _B = 250) 70mm x 150mm square material Cutting speed 250m/min Feed 0.12mm/blade depth of cut 2.0mm Chip shape SNGN140208 Holder DNF4160R Cutting time 5 minutes

〔Effect of the invention〕

As explained above, the method for producing a composite carbonitride of the present invention has the effect of obtaining a fine powder composite carbonitride of Ti, Nb, and W of high quality with significantly less oxygen and free carbon. . Furthermore, when a cermet is made using the composite carbonitride powder of Ti, Nb, and W according to the present invention, it has very good sinterability and has excellent cutting tool properties such as wear resistance, toughness, and heat cracking resistance. It has the effect of forming an alloy.

Claims (1)

[Claims] 1. Mix TiO ₂ , Nb ₂ O ₅ , WO ₃ and carbon powder as starting materials, heat the mixture in a hydrogen atmosphere, and then heat it in a nitrogen atmosphere at a temperature of 1200°C or more and 1500°C or less. Switch and heat, then continue in the nitrogen atmosphere.
A method for producing a composite carbonitride of Ti, Nb, and W, characterized in that the reaction is carried out while maintaining the temperature at 1500°C or higher and 2100°C or lower. 2.Nitrogen atmosphere pressure during heat treatment is 30Torr or more.
A method for producing a composite carbonitride of Ti, Nb, and W as set forth in claim 1, wherein the pressure is 10 atmospheres or less.