JPS5933658B2 - Hard alloys and manufacturing methods - Google Patents

Description

[Detailed description of the invention] T i, Z r * Hf 9 V g N b 9
We want to combine the hard carbides of T a v Cr * Mo g W with iron group metals 4) Cemented carbides are 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.

As for toughness, it has been found through many years of research by the inventors that it can be roughly divided into two types.

These are mechanical strength and thermal fatigue strength.

The relationship between mechanical strength and wear resistance is contradictory in the cemented carbide mentioned above, and the relationship between mechanical strength and wear resistance is contradictory in the above-mentioned cemented carbide.
If the mechanical strength is increased by increasing the abrasion resistance, the wear resistance will decrease.

Changes in thermal fatigue strength are quite complex.

Thermal fatigue strength increases as C4 increases, but Co
If the amount is too large, plastic deformation will occur, leading to a decrease in thermal fatigue strength.

Therefore, there is a limit to the increase in Co content (improvement in thermal fatigue strength).

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

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 also low. Comparatively low.

Therefore, in order to prevent this, a high melting point metal such as ζWl may be used as the bonding metal instead of CO.

In fact, two or three prototype alloys have been made based on this idea, and in Japanese Patent Publication No. 51-47645, TiW
Using the eutectic point of C, (T i , W) C1-x-
It has been proposed that a W alloy be heated to a temperature of around 2500° C. and melted to produce it using a so-called melting method.

Although the wear resistance and plastic deformation resistance at high temperatures of this alloy (hereinafter referred to as cast alloy) are far superior to those of the cemented carbide, the following drawbacks prevent it from being widely used: It didn't work out.

First, the toughness, especially the mechanical strength, is extremely poor.

Although it is an extremely difficult material to grind, since it is made by casting, it is not possible to manufacture products with complex shapes at low cost, such as cemented carbide manufactured by powder metallurgy.

Thirdly, due to the casting temperature, only alloys with low melting points near eutectic compositions can be obtained.

We also proposed an alloy between (Ti, WXC, N)W (%
-9603), but it has not been put into practical use for the same reason.

Therefore, those skilled in the art can readily conceive that the second and third two of the above-mentioned drawbacks can be overcome if the cast alloy composition can be manufactured by powder metallurgy.

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 introducing oxygen into the hard phase, which was conventionally thought to inhibit sintering in hard alloys, sinterability was significantly improved, and roughness also showed an improvement in toughness.

Based on this knowledge, the present invention proposes a high melting point metal binder hard alloy with excellent toughness as a tool to meet the recent demands for high efficiency.

The greatest feature of the present invention is that oxygen and nitrogen are actively introduced into the hard phase, but in this alloy, oxygen is hardly present outside the hard phase;
The composition is 3XC,N,0).

Ml is a metal of group IVaVa of the periodic table T I , Z r
One or more metals selected from gHf,
M2 is one or more metals selected from Vla group metals Cr, Mo, and W; M3 is a Va group metal V
, Nb, and Ta.

This is clear from the X-ray diffraction shown in FIG.

This figure is an X-ray diffraction pattern of an alloy with a composition of W4646 atoms, 24 at% of Ti, 5 at% of Nb, 20 at% of C, 2 att.% of N, and 0.3 atm. 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.

Here, the limiting conditions for the alloy of the present invention will be explained.

First, if the oxygen content, X, is too small, its effect will not be exhibited, and if it is too large, the sinterability will deteriorate.

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.

If the range is 0.05≦X≦0.5, an alloy with high strength 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 (1005≦y≦0.5 is considered to be appropriate).

Regarding the ratio of Ml and M2, if a<0.07, the amount of hard phase is small and the alloy is not suitable as a hard alloy.

On the other hand, when a > 0.7, the high melting point metal phase decreases, making it brittle and impractical.

Furthermore, if the sum of N and 0 1Jif'x + y exceeds the limit, sinterability will be impaired.

Since it is necessary to contain 0.05 or more, it is desirable that the lower limit is also determined and 0.005≦x+y≦0.6.

When the stoichiometric constant (molar ratio of the total of C, N, and 0 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 0.1, the hard phase is too small and the hardness is insufficient, which deviates from the purpose of the present invention as a cutting tool or wear-resistant material.

Therefore, it is necessary that 0.1≦2≦0.5.

Substituting the rVaVa group element portion with a Va group element such as V, Nb, or Ta is effective in improving toughness.

However, when added in large amounts, Me(C,N) appears characteristically due to the combination of IVa group and Vla group high melting point elements.

0) and a high melting point metal phase coexist.

(Mla, M2b, M3c) (C1, N O) x-y
yyxz and Table a) (Ml: IVaVa group element A! 2: VIa group phosphorus, M3: Va group element) a+c is preferably in the range of fVaVa group element, and is preferably between 0.1 and 0.7. Yes, -
is preferably 0.3 or less a+C.

Also, a + b + c ”” 1, so 0.0
7≦a≦0.7, 0.3≦b≦0.9.0<c≦0.2
It becomes 1.

It is generally known that the addition of trace amounts of iron group metals, Ag, Pd, Cu, etc. promotes the sinterability of high melting point metals, and this effect is also recognized in the alloy of the present invention.

Even if one or more of these metals are contained, the characteristics of the alloy of the present invention will not be lost.

However, these metals have low melting points, and it is clear that if they are added in multiple amounts, the heat resistance, which is a characteristic of the present alloy, will be reduced.

From this point of view, it is desirable that these metals be added in an amount of 2 atomic % or less.

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 and also making it 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.

Regarding this, the inventor conducted detailed research and found that when maintained at around 1000° C. in a CO gas atmosphere, O intrudes into the carbides and carbonitrides of the Bl type solid solution.

It was thought that this reaction could be utilized to raise the temperature in a CO atmosphere, and when sintering was performed using the sintering method shown in Example 1, a good alloy could be produced.

At low temperatures, CO gas causes the decomposition reaction (3) 2 to precipitate carbon.

2CO+CO2+C (3) Therefore, it is not preferable to create a CO atmosphere from the beginning of the temperature raising process.

It is also a good method to raise the temperature in an atmosphere where N2 partial pressure is applied simultaneously or independently with 00 partial pressure for the purpose of containing nitrogen.

In this case, the raw material is a material containing N (for example, TiN, T
Even if vacuum sintering is performed using i(C,N), etc.), the sinterability will not necessarily deteriorate.

But 0. N is not necessarily introduced only from the gas phase, but also Bl containing oxygen or nitrogen or both.
Using a mold solid solution as a raw material and sintering in an atmosphere using 00 partial pressure, N2 partial pressure, or 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 the following examples that the hard alloy of the present invention exhibits particularly good properties 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 Cr in Group VIa metals cannot necessarily be said to have a high melting point, alloys to which Cr is added exhibit particularly high corrosion resistance, and therefore 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 W82% by weight with an average particle size of 1.5μ and an average particle size of 1μ
TiC 11,0% by weight and TiN 3.5% by weight and T
Weigh out 5.5% by weight of aC, wet mix it in an attritor for 5 hours, and then go through a dry embossing process to form w15°1r17.
A raw material powder having a composition of i25.6 Ta1°8 C21°5 N6 (expressed in atomic units) was prepared.

Samples were prepared using the following two sintering methods.

(5) Vacuum sintering 10-'Torr or less 1850℃X
1 hr (BJ invention room temperature to 1000℃ vacuum 10-” Torr or less 10
0℃~1850℃ CO atmosphere 50Torr1850
℃X 1 hr Vacuum 5×10 Torr or less The temperature increase rate was 10° C./−, and cooling was performed in a vacuum of 10 Torr or less.

The analysis results of carbon, acid, element and nitrogen of the obtained sample are shown in Table 1.

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

(A) W2O"'-Ti 2""-Ta"9-C
2"'-N""-0"' or (Wo, 623 Ti
0.35'raO,027) (Co, soo No
, 19600, QQ4 ) 0.342 (B) p5.2 T 125-2 'l'a1
-OC10・8-N4・7 04.1 or (Wo, 62
2 TiO,352Ta0.026) (C0,69
3NO, 16400, 143) 0.38 nire etc. Commercially available I SOP 30 alloy and W''-T722-Zr
The cutting performance of the four cast alloys having the composition of ``-C26'' was compared.

The cutting conditions were as shown in Table 2.

The results of this test are shown in Table 3.

As is clear from this example, the alloy containing W as a binder has excellent plastic deformation resistance as shown by the data on the amount of cutting edge recession.

However, oxygen-free alloys and commercially available cast alloys cannot be used practically because they chip when subjected to interrupted cutting such as milling.

The conventional product, cemented carbide P30, had a significant amount of cutting edge retraction and could not withstand high-efficiency cutting as in Test 1 C).

It is clear that the present invention (B) is an excellent 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 finished in the shape of SPV 854, and a cutting test was conducted under the following conditions with a front rake angle of 0° and an initial rake angle of 6° to compare the performance.

Work material S 45 C(, I-(B 240 > speed
degree 80m/groove
It varied between 13 and 13.

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 obtained.

The product of the present invention has 3 to 5 times higher performance than conventional cemented carbide.

In addition, they often have compositions that have better properties than commercially available cast 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.

Example 3 An alloy prepared by straining in the same manner as in Examples 1 and 2 was milled and compared.

In this case, the tool form is chamfer honing Q, 4
Wet milling was performed using a 10-inch cutter with an axial rake of +8° and a radial rake of O0, using a tip with ttzx

Cutting target 555C (HB270) Speed 1st 120m/1m Feedback: 0.5 mm/blade Cut lQmi Table 5 shows the results of this test.

The present invention exhibits twice the performance as the conventional product ISOP 30.

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 and 3 that the present invention has wide versatility.

In the above example, TiC, TiN, and W are used as raw materials, but similar results can also be obtained by using powders of oxides such as Tic, and compounds made of carbides, nitrides, and oxides. Ta.

[Brief explanation of drawings]

Ig I Figure Cv6-Ti” Nb”-C20-N2
-03 (shows the X-ray diffraction pattern of the present invention alloy with 7Jfi formation. 1... W peak, 2... Ti (m peak.

Claims (1)

[Claims] 1. Consists of a hard phase consisting of carbonate nitrides of metals from groups IVa, VIa, and Va of the periodic table and a high melting point metal phase, and the high melting point metal phase is a high melting point metal or a high melting point metal containing an iron group metal and a high melting point metal. One or more metals selected from Ag, Cu, and Pd contain O~2 (not including 0) atomic percent, and the entire composition of the alloy is represented by formula (1). hard alloy. (Mla, M2b, M3c) (C, N,
O)
is one or more types of Vla group metals, M3 is one or more types of Va group metals V, Nb, Ta, and a
+b+c21, 0.1≦a+C≦0. -7. −<0.3, 0.07≦a≦0.7, 0.3≦b≦0
．． 9゜a+C- 0<c≦0.21, and further 0.05≦x+y≦0
．． 6゜0.05≦X≦0.5, 0.005≦y≦0.5
, 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. Consists of a hard phase consisting of carbonitrides of metals of groups IVa, Via, and V of the periodic table and a high melting point metal phase, and the high melting point metal phase is a high melting point metal or a high melting point metal containing an iron group metal and Ag,
One or more metals selected from Cu and Pd are O~
2 (not including 0), and the total composition of the alloy is represented by formula (2), (Mlz9M2b9M3c)(C1-NO)x
yt yv x z ・・・・・・・・・(2) However, Ml is an IVaVa group metal species or two or more kinds, M2
is one or more Via group metals, M3 is one or more Va group metals V, Nb, Ta, a+b+c=1, 0.1≦a+c≦0, 7, - <
0.3, 0.07≦a≦0.7, 0.3≦ba+C-≦0.9.0<c≦0.21, and 0.05≦X
+y≦0.6, 0.05≦X≦0.5, 0.005
≦y≦0.5, 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. 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 In claim 2, there is also the production of a hard alloy characterized in that part or all of the temperature raising process is performed in an atmosphere with a nitrogen partial pressure ITorr or higher.