JPS5967353A - Hard alloy and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a hard alloy with superior plastic deformation resistance at high temp., superior thermal fatigue resistance and toughness, by carrying out part of a sintering stage for manufacturing a sintered hard alloy consisting of a hard phase made of oxycarbonitride of IVa, VIa and Va group metals and a phase made of a high m.p. metal in an atmosphere under high partial pressure of CO. CONSTITUTION:This sintered hard alloy consists of a hard phase made of oxycarbonitride of IVa, VIa and Va group metals and a phase made of a high m.p. metal, and it has a composition represented by the formula [where M1 is >=1 kind of IVa group metal, M2 is >=1 kind of VIa group metal, M3 is >=1 kind of Va group metal, a+b+c=1, 0.1<=a+c<=0.7, c/(a+c)<=0.3, 0.07<=a<=0.7, 0.3<=b<= 0.9, 0<c<=0.21, 0.05<=x+y<=0.6, 0.05<=x<=0.5, 0.005<=y<=0.5, and 0.1<=z<=0.5]. Powdered starting materials for said constituent components are mixed, die- pressed, and sintered. At the time, part of the temp. raising stage in the sintering is carried out in an atmosphere under >=0.5 Torr partial pressure of CO to enrich the alloy with oxygen. Thus, the desired hard alloy is manufactured.

Description

[Detailed description of the invention] Ti, Zr, Hf, V, Nb, Ta, Crl
Mo1Wc;r) So-called cemented carbide, which is made by bonding hard carbides with iron group metals, is widely used in wear-resistant tools such as cutting tools and roll dies. In recent years, not only carbides but also nitrides and carbonitrides have begun to be used.

It is known that the characteristics required of cemented carbide as a tool are roughly divided into two types. That is, toughness and wear resistance. Regarding toughness, it has been found through many years of research by the inventors that it can be further divided into two types. These are mechanical strength and thermal fatigue strength.

The relationship between mechanical strength and wear resistance is contradictory in cemented carbides.
If the mechanical strength is increased by increasing the wear resistance, the wear resistance will decrease.

Changes in thermal fatigue strength are quite complex. As the amount of Co increases, the thermal fatigue strength increases, but if the amount of Co is too large, plastic deformation occurs instead, leading to a decrease in the thermal fatigue strength. Therefore, there is naturally a limit to the thermal fatigue strength due to an increase in the amount of Co.

On the other hand, in order to improve the efficiency of cutting tools, there is an increasing demand for tools that can withstand heavy cutting with large depths of cut and feed and have high thermal fatigue strength.

Furthermore, in the market for wear-resistant tools, there is a growing demand for tools that can withstand severe thermal cycles for hot plastic working, such as Morgan rolls.

However, as already mentioned, there are limits to the ability of the current cemented carbide to meet these requirements.

The greatest feature of the present invention is that it proposes a tool that has high-temperature plastic deformation resistance and thermal fatigue toughness that cannot be achieved with WC-Co alloys. The idea is described below.

In conventional cemented carbide with Co as a binder phase, the softening temperature of the Co phase is low, so the plastic deformation resistance at high temperatures is already a problem under practical cutting conditions, and the thermal fatigue toughness of the materials described below is low. Comparatively low.

Therefore, in order to prevent this, a high melting point metal such as W may be used as the bonding metal instead of Co. In fact, two to three prototype alloys were produced based on this idea.
Ti-W
Using the eutectic point of -C (Ti, W) C+-x
It has been proposed to produce the alloy by a so-called melting method in which an alloy of -W is heated to a temperature of about 250° C., melted, and then cast.

Although the wear resistance and plastic deformation resistance at high temperatures of this alloy (hereinafter referred to as cast alloy) are far superior to that of cemented carbide, it has the following drawbacks that prevent it from being widely used. There wasn't. First, the toughness, especially the mechanical strength, is extremely poor. Second, although it is an extremely difficult material to grind, it is made by casting, so products with complex shapes cannot be manufactured at low cost compared to cemented carbide manufactured by powder metallurgy. Thirdly, due to the casting temperature, only alloys with low melting points near eutectic compositions can be obtained.

There is also a proposal for a (Ti, W) (CSN)-W casting alloy (Japanese Unexamined Patent Publication No. 47-9603), but it has not been put to practical use for the same reason.

Therefore, those skilled in the art can easily think that if the cast alloy composition can be manufactured by powder metallurgy, the second and third drawbacks mentioned above can be overcome. However, although many attempts have been made to achieve this goal, no superior alloy has actually been created. The reason for this is that since the alloy with this composition is made of carbides and high melting point metals such as Mo and W, its sinterability is extremely poor and sufficient strength cannot be obtained.

The present inventors have conducted detailed research on these alloys, particularly on the elements that form the hard phase, and have obtained surprising findings.

In other words, they discovered that by adding oxygen to the hard phase, which was conventionally thought to inhibit sintering in hard alloys, sinterability was significantly improved, and toughness was also improved. Based on this knowledge, the present invention proposes a high melting point metal binder hard alloy with excellent toughness as a tool that meets the recent demands for higher efficiency.

The greatest feature of the present invention is that oxygen and nitrogen are actively introduced into the hard phase. However, in this alloy, almost no oxygen is present outside of the hard phase, and the hard phase consists of (Mla,
M2b) has a composition such as (C,N,0)z. M
l is Ti, Zr, Hf, which are group IVa metals in the ringing table;
M2 is one or more metals selected from ■
One or two selected from Cr, Mo, and W for Group A Kanagawa
It is a metal that is more than a species. This is clear from the X-ray diffraction shown in FIG. This figure shows W5050 atom Ti25
This is an X-ray diffraction pattern of an alloy having a composition of 20 at%, C20 at%, and 05 at%, or only W and TiC phases are observed. In the figure, 1 indicates the peak of W, and 2 indicates the peak of the TiC phase. This also applies to alloys containing N.

In this section, the limiting conditions of the alloy of the present invention will be explained.

If the oxygen content, X, is too small, the effect will not be exhibited, and if it is too large, the sinterability will be deteriorated. Generally, the sinterability of mixtures of oxides and metals is poor because of poor wetting of their interfaces, and the same can be considered for the alloys of the present invention.

Within the range of 0.05≦X≦0.5, a high-strength alloy can be obtained without impairing the effect of oxygen addition.

The same thing can be said about nitrogen, but when the lowest wear resistance is required, nitrogen may not be desirable, so 0.005≦y≦0.5 is considered to be appropriate.

Regarding the ratio of Ml and M2, if a is 01, the amount of hard phase is small and it is not suitable as a hard alloy. On the other hand, a>
When it is 0.7, the high melting point metal phase decreases, making it brittle and impractical.

Furthermore, if the sum of N and 0 x 4 - y exceeds the limit, sinterability will be impaired. Since it is necessary to contain 0.05 or more O, the lower limit is also determined: 0.05≦x −) y≦0.6
It is desirable that

When the stoichiometric constant (the molar ratio of the total of C, N, and O to the metal) 2 exceeds 0.5, the hard phase and carbon coexist, which is outside the scope of the present invention. Moreover, if it is less than 041, the hard phase is too small and the hardness is insufficient, so that the purpose of the present invention as a cutting tool or a wear-resistant material is lost. Therefore 0.1
It is required that ≦2≦0.5.

(2) Substituting a part of the group A elements with the group Va elements of VlNb and Ta is effective in improving toughness. However, when added in large amounts, Me (C, N, 0), which is characteristically expressed by the combination of RVA group and VIa group high melting elements,
It becomes easy to deviate from the structure of coexistence of high melting point metal phase and high melting point metal phase.

(Mla, M2b, M3c) (C+-x-y
, Ny, Ox) (however, Ml:IV
aVa group element 2: Via group element, M3: Va group element)a
+C is preferably in the range of <IVaVa group elements as described above, and is between 01 and 0.7, and a-1-τ is 0
It is desirable that it is 3 or less.

Also, a +b -1-c = l, so 0.07
≦a≦07.0.3≦b≦0.9.0<C≦021.

Two methods are possible for producing oxygen-containing alloys such as those of the present invention. One method is to create a Bl type hard phase containing oxygen, mix this with a high melting point metal, and sinter it, and the other method is to introduce oxygen from the atmosphere during sintering.

The former has poor sinterability in the alloy of the present invention, making it difficult to form a strong alloy.Secondly, it is also difficult to precisely control the amount of oxygen contained.

On the other hand, in the latter case, sintering is promoted by the gradual change in the composition of the hard phase due to reaction with the gas phase. Furthermore, since the above reaction can be controlled by adjusting the pressure of the atmosphere, it is also possible to adjust the amount of oxygen contained.

Incidentally, a CO gas atmosphere is the best for introducing oxygen into the hard phase. As a result of detailed research on this matter, the inventors found that when maintained near IQQO'c in a CO gas atmosphere, O infiltrates into the carbides and carbonitrides of the Bl type solid solution. We thought that this reaction could be used to raise the temperature in a CO atmosphere, and when we sintered it using the sintering method shown in the example, we were able to produce a good alloy. At low temperatures, CO gas causes the decomposition reaction of formula (3) to precipitate carbon.

2CO-+ CO2+C・・・・・・・・・・・・(3
) Therefore, it is not preferable to set the atmosphere to include CO from the beginning of the heating process.

In addition, for the purpose of containing nitrogen, it is also a good method to raise the temperature in an atmosphere in which a partial pressure of N2 is applied simultaneously or independently with a partial pressure of 00. In this case, the raw material is a material containing N (for example, Ti
Even if vacuum sintering is performed using N, Ti (C, N), etc.), the sinterability does not necessarily deteriorate.

However, it is not necessary to take in O and N only from the gas phase;
Sintering using an l-type solid solution as a raw material in an atmosphere with 00 partial pressure or N2 partial pressure, or using both, produces favorable results because there are no vacancies and oxygen and nitrogen can be precisely controlled. These are shown in Example 2.

Now, it will be clear from Example 1 below that the hard alloy of the present invention shows particularly good results as a cutting tool. It is also within the scope of the present invention to add trace amounts of B, AI, Si, P, etc., which are often used in cemented carbide to adjust grain size and the like.

Furthermore, although it cannot be said that Cr of Group A metals has a high melting point, alloys to which Cr is added exhibit particularly high corrosion resistance, so they are preferable alloys depending on the purpose.

Examples will be shown below, but the scope of the present invention is not limited to the following examples.

Example 1 Commercially available average particle size 1. , 5 II, 85% by weight of W, 11.5% by weight of TiC with an average particle size of 1μ, and 3.5% by weight of TiN were weighed out, wet-mixed in an attritor for 5 hours, and then subjected to a dry embossing process to form W-Tl. A raw material powder having a composition of -CN (expressed in atomic %) was prepared. Samples were prepared using the following two sintering methods.

(A) Vacuum sintering 10 Torr or less 1800”CX1
hr (B) Invention Room temperature to 1000°C Vacuum 10 Torr
Below r1000℃~1800℃Co atmosphere 50 To
rr1800°Cx1hr Vacuum 5X10 Tor
The heating rate below r is 10°C/mix, and the cooling is 1
The test was carried out in a vacuum of 0 Torr or less. The analysis results for carbon and oxygen of the obtained sample are shown in Table 1.

Table 1 Therefore, the final composition can be roughly expressed as follows.

gIl, plf2rr, 'lq4/ (A) W -Ti -C-N -0 or (T
l6331 %7) (C1l, ill+&l N, a
,Q l O<aop)■)W"-Ti'ξ6-Ctg
, 7-N right 0o l 3 or (Tio, i3 + ”q
67) (Ca, &r + Nd, or + Oa,
i) Tests were also conducted with the sintering conditions of the raw material powder above partially changed as follows.

Room temperature to 1000°C Vacuum 10 rorr or less 1000°
C~1800°CCo atmosphere 30 Torr1800°
Cx1hr H2 atmosphere 2 TorrThe final composition of this is expressed as follows.

wra, o-Ti2jT(+-c/iψ-N (4ol
.

These commercially available l5OP 30 alloys and W''-T 1L2-
The four cast alloys having the composition Z r''-C2'
The uJ cutting performance was compared. The cutting conditions were as shown in Table 2.

Table 2 The results of this test are shown in Table 3.

Table 3 The following (*) in the table indicates 12J cutting time of 7 minutes.As is clear from this example, the data on the cutting edge retraction amount S indicates that alloys with W as the interface have excellent plastic deformation resistance. There is. However, commercially available cast alloys that do not contain oxygen can not be used in practice because they cause chipping during interrupted cutting, such as QJ milling.

The conventional product, cemented carbide P30, has significant cutting edge recession and cannot withstand high-efficiency cutting as in Test 1. It is clear that the present invention (B) is a low profile alloy that is good in both turning and milling and has little wear.

Example 2 An alloy having the composition shown in Table 4 was prepared in the same manner as in Example 1. These alloys were cut into the shape of 5PV854, and cutting tests were conducted under the following conditions with a front rake angle of 0° and a side rake angle of 6° to compare the performance.

Work material 845C (HB 240) Speed 80 Horn 1/mm feed rate 1.2 Dragon/rev depth of cut 5-13 mm This work material is a forged product and has severe irregularities, so the depth of cut is 5-13 mm.
It varied between 13 mm. The test was repeated 2 to 4 times in consideration of variations in the work material, and the average lifespan shown in Table 4 was shown.

The product of the present invention is 3 to 5 times smaller than conventional cemented carbide. It has twice the performance. In addition, they often have compositions that have better properties than commercially available forged alloys, and the best ones show about a 60% improvement in performance.

Further, the broader applicability of the invention is illustrated in the following examples.

Table 4 10. 22 2 *Composition is W -T+ -Zr -C'' Example 3 An alloy prepared in the same manner as in Example 1.2 was milled and compared.
Wet milling was performed using a 10-inch cutter with an axial rake of +8° and a radial rake of 0° using a tip equipped with Honing Q, 4717WX-75°.

Work material 555C (HB270) Speed 120772/mix feed Reo, 5mm 7 blades depth of cut 10M Table 5 shows the results of this test.

Table 5 The present invention shows twice the performance as the conventional product 15OP30. This tool can fully meet the demands for high feed rates in milling, where commercially available cast alloys cannot be used at all.

It is also clear from Examples 2.3 that the present invention has wide versatility.

In the first embodiment, Tic, TjN, and W are used as raw materials, but similar results can be obtained by using powders of oxides such as TiO, and compounds made of carbides, nitrides, and oxides. Obtained.

[Brief explanation of the drawing]

Figure 1 shows the X-ray diffraction pattern of the alloy of the present invention having the composition W -T+ -C-0. 1... W peak, 2... TiO phase peak Procedural amendment C method) July 7, 1955 Commissioner of the Japan Patent Office Kazuo Wakasugi Indication of the Tono case Showa Sg year patent application No. 1 istt No. 2, Name of the invention: Hard alloy and manufacturing method; Relationship with the amended case; Patent applicant address: 15 J-chome, Kitahama, Higashi-ku, Osaka @ Place name (, 2/3) Sumitomo Electric Industries, Ltd. Representative: President Satoshi Yogami Part 4, Agent Address 5 Otsu 0 2-chome, Hotaike Kitamachi, Toyonaka City, Osaka Prefecture Contents of Amendment to Specification No. Z The handwritten specification at the time of issuance is type-printed as shown in the attached sheet.

Claims (1)

[Claims] 1. The alloy is composed of a hard phase consisting of a carbonate nitride of a metal in Groups ■a and ■a of the periodic table, and a high melting point metal phase, and that the entire composition of the alloy is expressed by the formula (1). Hard alloy with special features. (Mla, M2b, M3c) (C+-x-
y, Ny, Ox) z−−−=−−−−(1)
However, Ml is one or more group IVa metals, M2
is one or more types of VIIa group metals, M3 is one or more types of Va group metals (V, Nl), Ta, a + b + c = 1, 0.1≦a 4- ,
c≦o, 7, TT≦0.3.0.07≦a≦0.70
3≦b≦0.9, O (c≦0.21, and further 005
≦x y≦0.6.0.05≦X≦05.0.005
≦y≦05.0.1≦2≦0.5. Further, a, b, c, x, and y are mole fractions, and 2 is the total molar ratio of C, N, and 0 to the metal. 2. When manufacturing a hard alloy consisting of a hard phase consisting of carbonitrides of metals in Groups a, VIa, and Va of the periodic table and a high-melting point metal phase, the total composition of the alloy is represented by formula (2), (M1a1M2b1M3c) (C+-x-ylNy
, Ox) z...42) However, Ml is IV
One or more group a metals -4-1 M2 is one or more group VIa metals, M3 is a group II metal V,
one or more of Nb and Ta, a-1-b
10c = 1, 01≦a+C≦0.7, TTT≦0
．． 3.0.07≦a≦0.7.0.3≦b≦0.9, o
<c≦0.21, and further 005≦x+y≦06.0
．． 05≦X≦0.5.0.005≦y≦0.5.0.1
≦2≦0.5. Further, a, b, c, and xly are mole fractions, and 2 is the total molar ratio of C, N, and 0 to the metal. The powdered raw materials of high-melting point metals, carbides, nitrides, oxides, and these compounds, which are the constituent components of formula (2), are manufactured by a so-called powder metallurgy method consisting of mixing, embossing, and sintering. Part of the heating process is carried out at a carbon monoxide partial pressure of 0.5 To
A method for producing a hard alloy, characterized by enriching the alloy with oxygen by creating an atmosphere of rr or more. 3. A method for manufacturing a hard alloy according to claim 2, characterized in that part or all of the temperature raising process is performed in an atmosphere with a nitrogen partial pressure of I Torr or higher.