JPS594500B2 - Hard alloy containing Mo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Tungsten, which is used in cemented carbide, exists in only a small amount on the earth and is therefore an expensive metal, and its price has soared in recent years as a so-called strategic material.

It has become important to replace tungsten in hard alloys with other materials.

One solution is to use cemented carbide tools or titanium-based cermet tools.

However, these tools have poor toughness and cannot replace cemented carbide in many cases.

Replacement of tungsten carbide in hard alloys with molybdenum carbide has been considered.

The present invention relates to the latter.

Tungsten carbide (We) to molybdenum carbide (MoC)
There has been little consideration in the past to replace it with .

The reason for this is that molybdenum carbide does not stably exist as MoC at room temperature, but exists as Mo2C.

MoC is hard at room temperature (Vickers) is 1800-1500
KP/idL, Kanai.

This is about 2/3 compared to WC's 2400Kf/-.

Furthermore, Mo2C is not often used as an additive in cemented carbide raw materials.

This is because when Mo2C is added, the carbide grain size of the cemented carbide becomes finer, and acicular crystals of Mo2C grow, reducing the alloy strength.

However, when molybdenum carbide forms a solid solution with tungsten carbide, it becomes stable as a monocarbide having a simple hexagonal crystal structure.

If this stable carbide of (Mo, W)C can be easily produced, it is considered possible to replace tungsten with molybdenum.

In order to make this more concrete, development of a stable manufacturing method for (Mo, W)C is also underway.

(JP-A-5L-146306) However, (Mo,
Since the development of cemented carbide using W)C carbide was first reported by W. Dawihl in 1950, several researchers have investigated it, but it seems that it has not yet been successfully developed as a practical alloy. be.

The present invention has been put into practical use by improving the stability and physical properties of carbides in order to significantly improve the practical performance of alloys whose main components are (Mo, W)C.

The feature of the present invention is that 0 Cr is added to the solid solution carbide of (Mo, W)C.
．． (Mo, W,
The reason is that the performance as a monocarbide of Cr)C has been significantly improved.

The present invention provides an alloy that is lightweight, has excellent plastic deformation resistance, and has good wear resistance, chipping resistance, and corrosion resistance, and this alloy is suitable for low-speed cutting.

Specifically, it is suitable for drills, hobs, taps, etc.

Furthermore, the watch frame used as a corrosion alloy has advantages over conventional alloys containing WC-CO as a main component, such as being light and having excellent chipping resistance and corrosion resistance.

In addition, C in the binder phase of the (Mo, W) C-Co alloy
A method of solid solution of r (adding Cr or chromium carbide) is known, but it does not improve the physical properties or stability of the carbide phase, and the improvement is merely an extension of the conventional method.

Hereinafter, Cr was dissolved in (Mo, W)C (Mo, W,
The performance improvement when used in a fine-grained alloy using a Cr)C solid solution will be described.

Attempts have been made for a long time to refine the WC grains of WC-Co cemented carbide to improve the properties of the alloy.

Especially in recent years, ultrafine-grained alloys have suddenly begun to attract attention.

It is becoming clear that this not only improves hardness and toughness by refining the alloy in the high Co region, but also shows very good performance as a cutting alloy in the low-speed cutting region. there were.

The reason for this is that, according to the results of many years of research by some of the present inventors (Sumitomo Electric No. 104, p. 106), the hardness relative to the amount of Co is sufficient as shown in Figure 1, and is 1μ or more than the conventional hardness. This is because fine-grained alloys have advantages such as lower compressive strength as shown in FIG.

The advantage of this alloy is that it is particularly effective in fields where wear resistance is required for drilling tools such as drills and hobs, and where toughness is required more than ever.

If we take advantage of this advantage and make the grain size of the carbide phase finer, it would be possible to further increase the amount of Co, which is a binding metal, but unfortunately, as the amount of Co increases, the yield strength decreases. It has also become clear that there is a limit to the amount of Co added (see Figure 3).

As mentioned above, by reducing the particle size of carbides in cemented carbide whose main component is WC, it can achieve excellent performance as an alloy for use in drills, hobs, taps, etc. up to 15% by weight. There was a problem that alloys containing metals were not effective at all.

In particular, with alloys for low-speed cutting such as drills, the temperature of the cutting edge increases due to frictional heat and deforms, rendering it useless.

The researchers conducted further research to develop an alloy with higher wear resistance and toughness and discovered the following.

That is, it has been found that if WC is made into a carbide composed of a solid solution of three elements, Mo, W, and Cr, deformation at high temperatures is significantly improved.

That is, compared to We-Co alloy, (Mo, W)C
-C.

The alloy has high high-temperature hardness, and when Cr is dissolved in this carbide, the hardness is further improved and the high-temperature hardness is also improved, so it is possible to solve the shortcomings of conventional WC-Co alloys at once. It became clear.

(See Figure 4) 0 The present invention is characterized in that the carbide phase is (Mo, W
, Cr) It is a solid solution of C.

It was also found that when Cr is dissolved in a solid solution of (Mo, W)C, it is possible to make carbide particles finer and that it becomes stable as a monocarbide of (Mo,W,'Cr)C.

This is because the known method of simply adding Cr to the binder phase has the disadvantage that it is impossible to refine the carbide, and that monocarbide, in which the carbide phase is a solid solution of (Mo, W, and Cr), cannot be stably produced. Yes, but not valid.

Note that the amount of Cr added to the solid solution carbide of (Mo, W)C must be 0.3% or more and 10% or less.

If Cr is less than 0.3%, carbides cannot be refined, and if it is more than 10%, Cr3C2 will separate and Cr carbide will precipitate in the alloy.

Further, a decrease in hardness also occurred, which was not preferable.

The amount of W is preferably 1 to 9% ON.

If it is less than 1% by weight, the monocarbide will not be stable, which is not preferable.

If W is 90% by weight or more, it is still not preferable from the purpose of the present invention, which is to replace tungsten resources with molybdenum.

A second feature of the alloy of the present invention is that a part of the carbon in the (Mo, W, Cr)C solid solution carbide is replaced with nitrogen, oxygen, or hydrogen.

In other words, if the carbon contained in (M6, W, Cr)C is added as a solid and reacted to form a compound with a 100% reaction rate, it is easy to think that the crystal will be stable, but it is not necessarily the case that only carbon Instead, if nitrogen is included (Mo
, W, Cr) (CN) can be stabilized, and oxygen and hydrogen can be dissolved in it (M
o, W, Cr) (CaNbOcHd) [a + b
10c 10d = 1], the carbide was found to be more stable.

This is because if there are defects in the carbide, the carbide becomes unstable during sintering, and M2C type composite carbides precipitate in the form of needles, resulting in defects such as reduced strength.

Note that the amount of carbon substitution is preferably 0.02 to 50% by weight in the nonmetallic elements of the carbide phase structure.

If it is less than 0.02% by weight, no effect will be observed, and if it is more than 50% by weight, the monocarbide phase will not be stable, which is not preferable.

As for the application of this alloy, by limiting the amount of Cr in (Mo, W, Cr)C to 0.3% to 10%, finer carbides can be obtained, and iron group such as Fe, Ni, Co, etc. If one or more metals are added in an amount of 15 to 30% by weight as a binder phase, it becomes a super-tall metal for low-speed cutting.

For example, it can provide excellent performance in drills, taps, and hobs.

Further, when the binding metal is 3 to 15% by weight, it is sufficiently effective as a corrosion-resistant alloy.

This alloy exhibited good performance in applications such as corrosion-resistant seal rings, watch frames, caliper tips, )-J-) nical seals, etc.

In addition, in the composition of this alloy, some of these carbides 3
T i , Z r , Hf , V , N
b.

A cemented carbide with high toughness can be obtained at low cost by substituting various compounds with nonmetallic elements including Ta+Cr, Mo, and W, such as Bl type solid solution and M2C type solid solution.

In addition, when iron group metals become a binder phase, IV a-r V
a.

It is natural to form a solid solution with group VIa metals, and Al.

The effects of the present invention are not lost even by adding elements such as Si, Ca, Ag, etc., which have a solid solution layer with them.

Example 1 1μ WC powder 527F, 2μ Mo2C 430g 1
13.9 μ of Cr3C2 was mixed, 5I of Co powder was added as a diffusion aid, and 279 of carpop plaque was added as a carbon deficiency, and the mixture was mixed in a dry ball mill for about 30 hours.

This mixed powder was heated for about 40 minutes in a Tammann furnace maintained at 1900°C.

When the reaction product was measured using X-rays, a large amount of Mo 2 C was detected, so it was ground in a ball mill for 30 minutes to give strain to the powder, and then reacted for 30 minutes at 1400°C in a nitrogen stream. Ta.

Analysis of the obtained powder showed the results shown in Table 1.

That is, this carbide is (Mo□, 6W□, 38CrO,0
2) It was found that it is a monocarbide calculated as C.

16% by weight of Co powder was added to this carbide, mixed in a wet solvent in a ball mill for 150 hours, dried, stamped, and then sintered at 1400°C for 1 hour to form an alloy. The performance of the WC-Co alloys was compared using an end mill.

The cutting test conditions were as follows.

Cutting material; SCM3, HRC8~13, length 385
mm end mill; 8φ, 2-flute, right blade right helix 25°,
Solid cutting method: Cutting a groove with a depth of 5 mm in the above-mentioned workpiece The life judgment is VB = 0.3 mm or the point at which chipping occurs,
Comparison of the cutting length at that time Machine: No. 4 milling machine Cutting conditions: V = 26.5 m/m1n f = 0.0285 mm 1 blade Water-insoluble cutting fluid was used The results obtained were as follows.

*The alloy of the present invention showed superior performance in terms of wear resistance and chipping resistance compared to fine-grained alloys whose main raw material is WC and vices.

This is because this alloy has high high-temperature hardness, so even if the amount of binder phase was increased, the wear resistance would not decrease and the toughness could be further improved.

Example 2 A mixed powder mixed in the same manner as in Example 1 was heated to 2000 ml in a H2 gas stream.
After sufficiently crushing the primary carbide obtained by reacting at ℃,
Secondary carbonization was performed.

In the secondary carbonization, the carbon in the carbide of (Mo, W, Cr)C was partially replaced with oxygen, nitrogen, and hydrogen, and the reaction was carried out again under the following conditions in order to further stabilize it.

A) 14°C in NH3 stream for 1 hour B) 100°C x 2 hours in Co air flow C) 1500°C x 1 hour in H2 stream D) 1590℃×1 hour in vacuum The reaction was carried out under the above conditions to obtain various carbides.

Table 3 shows the analytical values of each carbide.

In addition, Table 3 also shows the weight ratios of oxygen, nitrogen, and hydrogen to the nonmetallic elements constituting each carbide of A, B, C, and D.

All of the carbides obtained by heating in a gas atmosphere became monocarbide, but the carbides heated in vacuum left a lot of free carbon, and when the carbides were measured with X-rays, Mo2C was precipitated. Ta.

On the other hand, Mo2C was not detected in the carbide obtained in a gas atmosphere even though the amount of carbon was slightly insufficient.

<C as in Example 1 for the carbides of A-D.

An alloy was prepared by adding 16% by weight of powder.

After that, a cutting test was conducted under the same conditions as in Example 1, and A had a cutting length of 37.2 ms and a number of cutting grooves of 96.6.
In this case, B has a cutting length of 34.2ms and a number of cutting grooves of 88.8, and C
In D, the cutting length was 29.8 ms and the number of cutting grooves was 77.4, which was superior to the conventional fine grain W C-Co, whereas in D, the cutting length was 11.8 ms and the number of cutting grooves was only 30.6. .

Example 3 (Mo, W, Cr)C obtained by the method of Example 1
10% by weight of co powder was added to the solid solution carbide, and wet ball milling was performed in an organic solvent for 100 hours to obtain sufficient mixing.

The obtained mixed powder was stamped at 1 ton/CIi and 140
It was made into an alloy at 0°C.

This alloy was lapped with diamond paste until a mirror surface appeared.

As shown in Table 4, the physical properties of this alloy are low in specific gravity, have sufficient toughness, and exhibited better properties than conventional WCT-Co alloys in corrosion resistance tests in artificial sweat.

When we created a watch frame using this alloy and actually put it in a watch to compare its performance, we found that the alloy of the present invention was lightweight, resistant to scratches, and did not discolor due to sweat. .

Example 4 15% by weight of commercially available (Ti, W)C and Ta were added to the solid solution carbide of (Mo, W, Cr)C obtained by the method of Example 1.
An alloy was prepared by adding 10% by weight of C and 15% by weight of Co.

An end mill was made from this alloy and a cutting test was conducted under the following conditions.

Workpiece material: 5S41 End mill: 25 mm φ, 3 blades, helix 300 Cutting conditions: V = 80 m/m1n f = o, 03 mm/blade d = 5.0 mm Machine using water-insoluble cutting fluid: Vertical machining center One piece of alloy is 8.2m until it becomes unusable due to chipping.
Compared to commercially available 110 cemented carbide, 43 (m)
Even with 120 cemented carbide, it broke at 63cIIL and could not be cut.

Also, even with commercially available P-40 cemented carbide, it is 2.3 m due to wear.
L, I couldn't cut it.

[Brief explanation of drawings]

Figure 1 is a chart showing the hardness of ultrafine-grained alloys whose main component is WC.
Conventional alloy with C grain size of 2μ. Figure 2 is a chart showing the relationship between compressive strength and strain of ultrafine-grained alloys, and A and B in the figure are the same as A and B in Figure 1. Figure 3 is a chart showing the compressive strength and yield strength of ultrafine grained alloys, and A in the diagram. B is the same as A and B in Figure 1. Figure 4 shows a conventional WC-C. alloy and the present invention (Mo-W
-Cr) This is a chart showing a comparison of the high temperature hardness of C-Co alloys, where A is WC-10%Co and B is (Mo, W, Cr
)C-(9%Co 1,500%Ni), C is WC-15%C
o and D represent (Mo, W-Cr)C-15%Co.

Claims (1)

[Scope of Claims] 1. A carbide phase of one or more metals of group IVa, Va, and VIa of the periodic table is used as a hard phase, and one or more of the carbide phases as the hard phase are composed of Mo, W, and Cr. It is composed of a solid solution, and the amount of Cr contained in the solid solution is 0.3 to 10% by weight among the solid solution metal constituent elements, and the amount of W is 1 to 10% by weight.
90% by weight, remainder M. and the crystal structure of the carbide phase of 70% by weight or more is monocarbide type simple hexagonal, and the binder phase is composed of 3 to 50% by weight of an iron group metal. . Hard alloys including. 2. The alloy according to claim 1, which is composed of a solid solution of Mo, W, and Cr in which the grain size of the carbide phase is 1 μ or less, and the amount of Cr contained in the solid solution is 0.3 to 2% by weight. A hard alloy containing Mo for low-speed cutting, characterized in that the binder phase is composed of 3 to 30% by weight of an iron group metal. 3 I Va + Va of the periodic table, one or more metal carbide phases of group VIa transition metals are used as a hard phase, one or more of the carbide phases as the hard phase are composed of a solid solution of Mo, W and Cr, and a solid solution Cr contained in
The amount of W is 0.3 to 10% by weight in the solid solution metal constituent elements, W
1 to 90% by weight, the balance being Mo, 0.02 to 50% by weight of the carbon in the carbide phase is replaced by one or more of oxygen, nitrogen, and hydrogen, and 70% by weight or more of the carbon in the carbide phase A hard alloy containing Mo, characterized in that its crystal structure is a monocarbide type simple hexagonal, and its binder phase is composed of 3 to 50% by weight of an iron group metal.