JPH03193832A - Production of cermet - Google Patents

Abstract

PURPOSE:To produce the cermet which is improved in strength by effective removal of oxygen by reducing mixed raw material powder with hydrogen, then molding the mixture by a hot isotropic pressurization press method at the time of producing the cermet by the hot isotropic pressurization press method. CONSTITUTION:The raw material powder is first compounded at prescribed ratios to form the powder mixture or after this powder mixture is subjected to spray dry pelletization, the pellets are hydrogen-reduced for about >=1 hours at about 1100 to 1250 deg.C in a reducing furnace to remove oxygen in the raw material powder. The raw material powder is then packed in a container and is held for about 2 to 3 hours at about 600 deg.C. The container is vacuum-deaerated to about 10<-2> to 10<-1>Torr and is hermetically closed. The container is then subjected to the hot isotropic pressurization pressing for about 0.5 to 6 hours at about 1280 to 1350 deg.C and about >=1000atm, by which the cermet is produced. The cermet is constituted of the hard dispersion phase which consists essentially of the carbide, nitride or carbonitride of Ti and in which 1 to 70% thereof is substd. with >=1 kinds of the carbide or nitride of group IVa, Va, VIa metals (exclusive of Ti) and a bond phase contg. Ni and Cr.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for producing a cermet with excellent wear resistance, impact resistance, chipping resistance, etc. using a hot isostatic pressing method (hereinafter referred to as HIP). Relating to a method of manufacturing.

[Conventional technology]

Materials used for rolling rolls, dies, punches, etc. are required to have excellent wear resistance and toughness, as well as high impact resistance and high temperature strength. Cast steel and tool steel have traditionally been used as such materials, but in recent years, cemented carbide with better wear resistance, such as WC-Co cemented carbide, has come into use. became. However, W.C.
The specific gravity of Co-based cemented carbide is approximately 15, which is approximately twice as heavy as cast steel or tool steel. Therefore, when applied to rolling rolls, for example, it will generate vibrations and damage the workpiece. There was a problem that the quality of the product was impaired. On the other hand,
The so-called cermet alloy with T1CN as a hard phase is 19
First appeared on the market in 1971, then WC.

Many attempts have been made to replace a part of rVa % Vas Group VIa carbide 1CN such as TaC and NbC, and it currently occupies an important position in the field of rolls and cutting tools. Such cermets are generally T
It is obtained by wet mixing raw material powders such as +C5IIIc and Co to form a mixed powder, molding using a mold press or rubber press, intermediate sintering, molding, and finally vacuum sintering.

By performing vacuum sintering, deoxidation occurs through a reduction reaction with carbon during sintering, so less oxygen remains in the product. However, even with vacuum sintering, it is unavoidable that pores remain, albeit slightly.

In a brittle material such as cermet, stress concentrates in the pores, causing the material to break even under stress that it would normally withstand. Therefore, when used for steel wire rod rolling rolls, plungers, ultra-high pressure anvils, etc., not only will the tools be damaged, but the
It also poses a big problem in terms of safety. Furthermore, if pores exist on the tool surface, they may be transferred to the surface of the workpiece.

For example, pores must not be present in Sendzimir rolls for cold rolling of thin sheets, as this may lead to product defects.

Therefore, various improvements have been made to the process in order to minimize defects, especially pores, in the sintered body.
It has been found that if the cermet is made from old P, the pores can be completely eliminated. The effect was extremely large, and the old P treatment of cermets, especially for large wear-resistant tools, rapidly became popular.

However, when the outer layer of a composite member such as a composite roll is made of cermet and this is manufactured using old P, the raw material mixed powder is sealed in a container made of steel fixed around the core material and then added. Since pressure and heat are applied, sintering is performed in a sealed state, and deoxidation does not occur as in vacuum sintering. Therefore, there was a problem in that the oxygen in the powder remained in the product, making it brittle and reducing its strength.

It is therefore an object of the present invention to provide an improved manufacturing method by HIF in order to increase the strength of cermets.

[Means to solve the problem]

As a result of intensive research in view of the above problems, the present inventor has discovered that 111P
The present invention was completed based on the discovery that the strength of the finished cermet can be improved by reducing the raw material powder with hydrogen before treatment.

That is, the method of the present invention is a method for manufacturing cermet by hot isostatic pressing, in which mixed raw material powder is reduced with hydrogen, or mixed raw material powder is spray-dried and granulated, and then hydrogen It is characterized in that it is reduced with water and then molded by hot isostatic pressing.

Further, the cermet produced by the above method has Ti carbide, nitride, or carbonitride as a main component, and
A hard dispersed phase consisting of 70 mol% substituted with one or more carbides and nitrides of group VIa metals (excluding T1) is bonded with a binder phase containing Ni and Cr. It is desirable that it be done.

The present invention will be explained in detail below.

In the method of the present invention, cermet is manufactured using old P, and the pre-processes include (a) mixing of raw material powder, (b) granulation as necessary, (C) classification, and (d) Perform hydrogen reduction, (e) canning, and (f) vacuum degassing.

(a) In the step of mixing raw material powders, a predetermined amount of raw material powders are blended, and dry or wet mixing is performed using a ball mill or the like to obtain a mixed powder. Then, c) if necessary, the mixture is granulated to a predetermined particle size by spray drying.

The particle size of the granulated powder is preferably about 30 to 150 particles. As a granulating device, a conventional one such as a cyclone type, horizontal type, or vertical cylindrical type can be used. When granulated, spherical calcined powder with good filling properties and an appropriate size can be obtained by hydrogen reduction, so the pulverization process required in normal sintering to make the powder fine after calcining is omitted. be able to. Next, (C) sieve to make the particle size uniform.

Next, (d) hydrogen reduction is carried out in a reduction furnace between 1100 and 125
The test is carried out for at least 1 hour at a temperature of 0°C. Hydrogen reduction temperature is 1100
If the temperature is less than 1250°C, reduction may not be sufficient, and if the temperature exceeds 1250°C, there is a risk that nitrides or carbonitrides will be decomposed. In addition, the reduction time varies slightly depending on the temperature, but the reduction time is 1
The time is preferably at least 1 hour, particularly preferably 2 to 4 hours. By this hydrogen reduction step, oxygen in the raw material powder is almost completely removed, and no oxygen remains even after HIP.

(e) The canning is usually made of steel or the like and has a thickness of 5
~ Use a container with a diameter of about 12 mm, and add 50% of the raw powder into it.
Press and fill to achieve the above density. As the canning container, heat-resistant metal such as nickel can be used in addition to steel.

Next, the container filled with the raw material powder is kept at about 600° C. for 2 to 3 hours, and vacuum degassed so that the inside becomes 10 −2 to IQ −’ torr (step (f)).

Next, after sealing the deaeration port of the container by welding, the old P is performed. ) IIP is a temperature of 1280-1350°C, 110
It is carried out for 0.5 to 6 hours at a pressure of 00at or more.

The reason for performing hydrogen reduction before HIP is as follows. In normal sintering methods including vacuum sintering, a reduction reaction occurs with carbon in the raw material powder during sintering and deoxidization occurs, so there is no need to perform a reduction treatment in advance. However, in HIP sintering for manufacturing composite members and the like, the raw material mixed powder is sealed in a container and pressurized and heated, so reduction reactions are unlikely to occur.

For these reasons, it is necessary to perform hydrogen reduction before the old P.

The cermet to which the above method is applied is mainly composed of Ti carbides, nitrides, or carbonitrides, and
A hard dispersed phase consisting of one or more carbides and nitrides of group IVa, Va, and VIa metals (excluding Ti) substituted with 0 mol% is a binder phase containing Ni and Cr. Preferably combined. Hydrogen reduction removes oxygen from oxides such as TlO□, yielding a cermet with high strength.

The reason for replacing 1 to 70 mol% of the main component consisting of titanium carbides, nitrides, or carbonitrides with carbides or nitrides of groups ■a SVa and VIa of the periodic table is that the main components such as carbonitrides themselves This is to improve the toughness of carbonitride and the wettability between the carbonitride and the binder phase, as well as to improve the high temperature strength. If it is less than 1 mol %, the effect will not be exhibited, and if it exceeds 70 mol %, wear resistance and oxidation resistance will deteriorate, which is not preferable.

Further, in titanium carbonitride, it is desirable that the atomic ratio of nitrogen to carbon be 0.05/1 to 5/l.

If it is less than 0.05/1, the hard phase particles will become coarse and the toughness will be significantly reduced, and if it exceeds 5/l, carbonitrides will decompose and N2 gas will be generated, micropores will be created, and carbonitrides will be The wettability of the binder phase deteriorates, and the transverse rupture strength decreases.

If the total weight of the hard phase is less than 30%, the wear resistance will be poor, while if the total weight is more than 70%, the binder phase will decrease and the toughness will deteriorate significantly, so the amount of the hard phase should be 30 to 70%.
It is best to set it within the range of .

On the other hand, the binder phase is an alloy containing Ni and Cr, preferably 20 to 50% by weight of Nl and 5 to 30% by weight of Cr. Furthermore, if the weight ratio of Cr to the total amount of Ni and Cr is less than 2/100, the effect of containing these components will not be sufficiently exhibited, and if it exceeds 40/100, too much Cr carbide will precipitate, resulting in a decrease in toughness. Therefore, Ni and Cr
The weight ratio of Cr to the total amount is 2/100 to 40/1.
00 is desirable. In some cases, Fe
The inclusion of CO and/or CO does not affect the properties of the cermet of the present invention.

〔Example〕

The present invention will be explained in more detail by the following specific examples.

Examples 1 to 4 The main component was T1CN powder with an average particle size of 1 to 6ρ as the raw material powder, and MO2C powder, WC powder, and Ni and Cr powder were blended in the proportions shown in Table 1, and a cemented carbide ball was used. The mixture was wet mixed for about 48 hours in a high speed rotating mill and then dry granulated in a cyclone dryer to an average particle size of 30-100 Am.

Next, after passing the granulated powder through a 60-mesh sieve,
The mixture was placed in a steel can and subjected to hydrogen reduction at 1200° C. for 3 hours in a reduction furnace. Next, the inside of the can was vacuum degassed to 10-"torr while maintaining it at 600 °C for 2.5 hours, and finally IllP
HIP sintering was performed for 4 hours at 1300° C. and 11000 at.

The compositions of the various cermets obtained in this way were
Examples 1 to 4 are shown in the table. Furthermore, the transverse rupture strength, fracture toughness value, and hardness of each of these alloys were measured. The results are shown in Table 2.

Comparative Examples 1 to 4 In the same manner as in the above Examples, various raw material powders were blended in the proportions shown in Table 1, mixed, dried and granulated. Sintered.

The compositions of the various cermets thus obtained are shown in Table 1 as Comparative Examples 1 to 4. Further, the transverse rupture strength, fracture toughness value, and hardness of each of these alloys were measured. Second result
Shown in the table.

As shown in the measurement results in Table 1, deoxidation was performed in each example in which hydrogen reduction was performed, and the transverse rupture strength and fracture toughness values were higher on average than in the comparative examples. Ta.

〔Effect of the invention〕

As explained above, according to the manufacturing method of the present invention, in the old P sintered body of cermet, which is composed of a hard dispersed phase and a binder phase and has inherently excellent strength, toughness, wear resistance, impact resistance, etc. Since oxygen can be effectively removed, the strength is further improved.

In addition, HIP allows for compounding with steel materials, etc.
Can be widely used for various composite rolls, etc.

Claims (3)

[Claims] (1) A method for producing a cermet by a hot isostatic pressing method, which comprises reducing mixed raw material powder with hydrogen and then molding it by a hot isostatic pressing method. (2) In the method of manufacturing cermet by hot isostatic pressing, the mixed raw material powder is granulated by spray drying, reduced with hydrogen, and then molded by hot isostatic pressing. Characteristic cermet manufacturing method. (3) In the method according to claim 1 or 2, the cermet has Ti carbide, nitride, or carbonitride as a main component, and 1 to 70 mol% of Ti carbide, Va, or VIa group metal (but , excluding Ti) substituted with one or more of carbides and nitrides;
A method for producing a cermet, comprising a binder phase containing Ni and Cr.