JPS5929665B2 - Cemented carbide parts and their manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has WC as a main component, IV a,, VI
The object of the present invention is to provide an even more excellent so-called cemented carbide member in which one or more carbides of one or more group A transition metals are combined with mainly iron group metals at an industrially low cost.

The so-called cemented carbide parts that are generally used in practical use include:
WC phase bonded with Co, WC phase and IV
a,, VI A carbide of one or more group a transition metals, and a double carbide with a B-1 type crystal structure (
Hereinafter referred to as B-1 type hard phase) is C.

It is combined in .

The present invention relates to the latter of these.

A cemented carbide member in which the WC phase and the B-1 type hard phase are bonded by Co'liC is due to the strong toughness of WC and the high hardness and chemical stability against steel of the B-1 type hard phase. It has excellent wear resistance and is widely used as a steel cutting tool.

Generally, in such a cemented carbide member, the higher the content of the B-1 type hard phase in the cemented carbide, the better the wear resistance and the poorer the toughness.

Conversely, the smaller the content of the B-1 type hard phase, the better the toughness and the worse the wear resistance.

Therefore, in the conventional cemented carbide industry, a balance between toughness and wear resistance has been achieved by adjusting the content of the B-1 type hard phase in the cemented carbide member.

The inventor believes that considering a cemented carbide member with a composite structure in which the amount of B-1 type hard phase differs between the surface and the inside of the cemented carbide member, conventional cemented carbide We thought that we could provide something even better than the original parts.

This idea has already been proposed by many people other than the inventor, and it is believed that the amount of B-1 hard phase on the surface of a cemented carbide member is significantly higher than that inside the material, which improves the wear resistance of the surface and the inside. It has been proposed to be a superior cutting tool due to its toughness.

All of these proposals are based on the B-
Although it has only been proposed that the amount of type 1 hard phase is significantly smaller than that of the inside, the inventor has also proposed that the amount of type B-1 hard phase on the surface of the cemented carbide member is smaller than that of the inside. , I thought that it might be excellent as a cutting tool.

Generally speaking, in cemented carbide parts, when the amount of B-19 hard phase decreases, the thermal conductivity of the cemented carbide part decreases, so the tool life is dominated by chipping due to thermal exfoliation, as in machining. In this case, if the surface has a higher thermal conductivity than the inside, the temperature gradient that occurs on the tool surface will be significantly alleviated, which will reduce thermal stress and reduce the number of defects caused by thermal oxidation. .

Additionally, if the amount of B-1 type hard phase on the surface of the cemented carbide member is smaller than on the inside, the surface will naturally be tougher than the inside, making it difficult to chip during cutting. I thought that might be a good idea.

Therefore, the inventor investigated a method of providing a cutting tool in which the amount of B-1 type hard phase on the surface of such a cemented carbide member is significantly smaller than that inside the material at an industrially low cost.

Some of the inventors (hereinafter referred to as "partial inventors") B-1
Wettability between the mold hard phase and the liquid phase generated during sintering, B-1
A detailed study was conducted on the equilibrium between the type hard phase and the sintering atmosphere, and the stability of the B-1 type hard phase.

Furthermore, we obtained the knowledge that the stability of the B-1 type hard phase is the key.

This time, the inventor investigated the previous study in more detail, and found that the nonmetallic constituent elements of the B-1 type hard phase include C and N, which the inventor had taken into consideration. We obtained the knowledge that it can be considered in exactly the same way.

By the way, the conventional wisdom in the cemented carbide industry is that 0 is a completely harmful element, and how to control O in raw materials.
The main production techniques have been developed to reduce the amount and reduce the chemical potential of O in the sintering atmosphere.

This is because carbon dioxide in the raw material or sintering atmosphere reacts with various carbides in the cemented carbide member during the sintering process, becoming CO and/or CO2 gases, and removing carbon from the cemented carbide member. A creeping monkey.

The gas generated at this time significantly impairs the sintering of the cemented carbide member.

Moreover, since the amount of C is also reduced, the cemented carbide member even becomes brittle.

However, the inventor uses \0 as B, which is one of the starting materials.
- By incorporating it as a nonmetallic element in the type 1 hard phase and carefully adjusting the sintering atmosphere,
We have obtained the knowledge that such inconveniences can be sufficiently avoided.

Furthermore, when a cemented carbide member containing 0 was actually manufactured based on this knowledge, it was found that the cutting tool was even better than conventional cemented carbide members.

This is thought to be due to the following reasons.

First, when cutting steel using a cemented carbide member, the tool cutting edge surface is generally T 1 s A 1 s S 1 s
The presence of double oxide-based glassy substances such as Ca, which act as a lubricant between the steel and the tool cutting edge, is one of the reasons why cemented carbide members exhibit excellent wear resistance as steel cutting tools. It is believed that.

Conversely, if the tool itself contains 0 in advance, Ti, A1. Since double oxide-based glassy substances such as Si and Ca are advantageous in reducing the surface of the cutting edge of the tool during cutting, it is considered preferable to contain O in the cutting tool.

Second, a small amount of O improves the heat resistance of the binder phase by being slightly dissolved in the binder phase other than the so-called hard phase (in this case, both the WC phase and the B-1 type hard phase) of the cemented carbide member. This is thought to have the effect of improving the heat resistance of the cemented carbide member as a whole.

Therefore, it is considered to have excellent plastic deformation resistance at high temperatures as a cutting tool.

The advantages of incorporating 0 into a cemented carbide member have been described above.

Next, an invention will be described regarding a method for realizing the main objective of the present invention, which is a cemented carbide member in which the surface portion has a significantly smaller amount of B-1 type hard phase than the interior.

Some of the inventors have implemented this method by adjusting the wettability between the B-1 type hard phase and the liquid phase generated during sintering.

Specifically, by reducing the amount of nitrogen contained in the B-1 type hard phase that exists during sintering near the surface of the cemented carbide member, and improving wettability with the liquid phase generated during sintering. During sintering, three B-1 type hard phases were flushed into the cemented carbide near the surface! ! This was achieved by utilizing five phenomena.

Furthermore, during this sintering, the area near the surface of the cemented carbide member is B-1.
In order to reduce the amount of nitrogen contained in the mold, the chemical potential of N in the sintering atmosphere is made smaller than the equilibrium state with the chemical potential of N in the B-1 hard phase, and denitrification occurs and is achieved. 5ru.

In addition, such a phenomenon is observed only when the B-1 type hard phase is unstable on 1 u, and the stability of the B-1 type hard phase depends on the number of outer shell electrons (Valence Electron C
It was found that the VEC is more unstable.

This time, the inventor continued to study the B-1 type hard phase in more detail, and as a result, found that 5[0 is also considered to be 5, just like C and N, which were previously considered, as a nonmetal constituent element. Obtained.

That is, the B-1 type hard phase generally has the molecular formula (MA, MC") (
Cu,,Cv,Cw)x, then VEC=4A+6C+x(4u+5v+6w) However, A
10C=1 ju+v+w=1 1>A>0.0.9≧C>0 The B-1 type hard phase with VEC≧8.4 is unstable and cannot be sintered during sintering. If the chemical potential of N and/or O in the atmosphere is lower than the equilibrium value with the chemical potential of N and/or 0 of the B-14iV hard phase, denitrification and/or shredding of the B-1 type hard phase will occur. is the deoxidation phenomenon,
What happens near the surface of the cemented carbide member?

As a result, the wettability with the liquid phase generated during sintering is improved, and the B-1 type fracture layer near the surface is washed away, causing the B-1 type near the surface to be significantly reduced. We have obtained the knowledge that we can provide a cemented carbide member with a smaller amount of hard phase than the inside.

When we tried manufacturing a cemented carbide member based on the above idea, we were able to obtain a cutting tool that was even better than expected.

Regarding the amount of 0 in the Naori-1 type hard phase, 0 has the maximum VEC of 6, and is extremely effective in keeping the VEC of the B-1 type hard phase at 8.4 or higher. Considering that it is preferable for a cutting tool to contain W, W is 0.
001 or more is preferable.

When W is 0.001 or less, the effect of containing 0 is not observed in the cemented carbide member.

Further, if W is 0.5 or more, it is not preferable because it significantly impairs the sinterability of the cemented carbide member.

Next, regarding the sum of O and N, since the present invention utilizes the denitrification and/or deoxidation phenomenon of the B-1 type hard phase,
It is essential, and V + W of 0.05 or more is required.

On the other hand, if V + W is 0.5 or more, such denitrification and/or deoxidation phenomena are too significant industrially, impairing the sinterability of the cemented carbide member, which is not preferable.

Since the present invention uses a B-1 type hard phase, 0.9≧C>0 must be satisfied.

When c=o, b or C>0.9, a B-1 type structure cannot be obtained, which is not preferable.

A. Regarding CK, VEC≧8. Under the condition that j, 0.9≧C>O, it is unlikely that any value can be taken.

With regard to ,B-
The type 1 hard phase itself is not preferred because it causes a significant decrease in strength.

Moreover, if X is small, VEC will also be small, which is also not preferable.

In addition, the iron group metal that binds the above-mentioned hard phase preferably has a weight ratio of 3 or more and 30 or less by weight in terms of performance.

Next, embodiments of the present invention will be described.

A sintering atmosphere with a chemical potential of N and/or O lower than the chemical potential of N and/or O of the B-1 type hard phase is a sintering atmosphere with a sufficiently low partial pressure of KN and O for industrial purposes. .

That is, a high vacuum of I Torr or less is sufficient, and therefore, a degree of vacuum sufficiently attainable by a rotary pump is sufficient, but it is more preferable to use a mechanical booster, an oil diffusion pump, etc. in combination.

Next, the B-1 type hard phase, which is the starting material, is 4A + 6C + x (4u + 5v + 6w) ≧ 8.40.00
Even if one or more of the conditions selected from the group consisting of 1≦W≦0.5 jo, 05≦v+w≦0.5 is not satisfied, using the raw materials listed above and using the normal powder metallurgy method When sintering the produced green compact, the chemical potential of N and/or O in the heating atmosphere is made sufficiently high to 600"C or higher, up to the sintering temperature, so that the B after sintering is
-IQ hard phase is 4A+6C+x(4u+5v+6w)≧8.40.00
1≦W≦0.5, 0.05≦v + w≦0.50.5
It was found that the following conditions could be satisfied: 0≦U≦0.95 jO<v≦0.45.

At first glance, this means that the B-1 type hard phase is 4A+6C+x(4u+5v+6w)≧8.40.00
1≦W≦0.5 jo, 05≦v 10 This is considered to be contrary to the knowledge that denitrification and/or deoxidation phenomena occur only when w≦0.5 is satisfied.

However, this fact means that when the green compact is sintered, each powder particle is not completely sintered because the green compact is not completely sintered while being heated to the sintering temperature. Because there are no pores in various places that communicate with the sintering atmosphere, such reactions occur. does not exist at all, 4A+, 6C+x (4u+5v+6w)≧8.40.
This is because denitrification and/or deoxidation phenomena are not observed unless 001≦W≦0.5j0.05≦v+w≦0.5 is satisfied.

In fact, when the above phenomenon occurs, the reaction rate is too slow for industrial purposes at temperatures below 600°C, making it difficult to recognize the effect.

In addition, when this phenomenon is actually applied industrially, 600
℃ or higher up to the sintering temperature, N and/or
Alternatively, heating may be performed in an atmosphere where the chemical potential of C is sufficiently high, but it is better to use a 0 atmosphere than to perform the heating phenomenon using a N atmosphere. It is preferable because it contains CO, and industrially it is easy to create a CO atmosphere, and the pressure may be 1 to 600 Torr.

No effect was observed under ITorr Iu and 600 Torr.
On rJ4, the effect is saturated, so it is industrially meaningless.

The product of the present invention can be a sufficiently excellent cutting tool when used alone, but it is also excellent as a base material for coated cemented carbide.

This method has become particularly widely used in recent years, and is known to cause damage to the surface of cemented carbide members.

one or more carbides, nitrides and/or oxides of Group VIa transition metals, oxides of AI and/or Zr;
So-called coated cemented carbide parts coated with a layer or more have both surface wear resistance and internal toughness, and are superior to conventional cemented carbide parts in cutting tools. It is true that it is extremely wear resistant, but compared to cemented carbide parts, it is extremely brittle, so it gets scorched when cut.

If such chips penetrate the cemented carbide member, it will lead to defects, but if there is an extremely small portion of the B-1 type hard phase on the surface of the cemented carbide, as in the present invention, such chips will penetrate the cemented carbide member. It was found that the toughness as a whole was significantly improved because it was stopped at a certain portion.

In addition, some inventors have obtained the knowledge that it is sufficient to use a coated cemented carbide base material in which 0.01 to 0.50 weight percent of free carbon has been precipitated. The same can be said for inventions.

This will be explained in detail in an example below.

Example 1 TiCj TiN and WC were used as raw materials in hot spring v7 (T i 0.75W0.25 ) (CoBs N
o, 2900.03) 1. .

It was created.

This B-1 type hard phase was measured by weight of 4.0, WC by weight by 90.5, and Co by weight by 5.5. Ethanol was added and wet mixing was performed using a stainless steel ball mill using a carbide ball. Ta.

3 weight percent of camphor was added to this mixed powder to make 2 tons.
After stamping with a pressure of /cat (model number 5NU432
), A is sintered at 1450℃, 10″″3 Torr,
B was sintered at 1450° C. in an N2 atmosphere of 100 Torr.

When the obtained alloy was examined under a microscope, it was found that A was 2 from the surface.
Completely down to 0μ [The B-1 type hard phase had disappeared, whereas in B, only the B-1 type hard phase was observed from the surface to 3μ.

A cutting test was conducted on these A and B under the following cutting conditions.

Work material SCM3 (HB=280) Cutting speed 108 m/rrin Feed rate 0.15 mm/blade depth of cut 2.0 mm Cocker body NLFO6R Cutting tests were conducted for 5 passes each under the following conditions. In A, only 8 heat burns were observed on the cutting edge, whereas in B, the cut edge was damaged due to heat burn in the 4th pass.

Example 2 In the same process as Example 1, the following alloys shown in Table 1 were produced as prototypes.

In both alloys, WC is 85.5% by weight, Co is 5.5% by weight, and the remainder is B-1 type hard phase, and the model number is 5NU432.

A cutting test was conducted on these chips under the same conditions as in Example 1.

The results were as shown below in Table 1.

Claims (1)

[Claims] 1. The molecular formula is general [(MA,, Mc“)(CujNv,
. Ow) w is the respective atomic ratio, and X is the ratio of the nonmetallic constituent element to the metallic constituent element. A B C, u g V
A+C=1 between 4 wj
8.40.05≦v10w≦0.5 jo, 001≦W≦
0.5゜0.6≦X≦1, 1>A>0, 0.9≧C
〉0゜0.50≦U≦O-95s O< v≦0.45
B-1 of the surface part of the cemented carbide member
A cemented carbide member characterized in that the mold hard phase is less than its interior. 2 The molecular formula is generally (MA, e Mc“) (Ou
, @Nv. Ow) X indicates the ratio of the non-metallic constituent elements to the metallic constituent elements.The solid solution phase, which contains W as a constituent element and has a B-1 crystal structure, and the WC phase are hard AjC,, u, v, w, x
Between A+C=I Qu+v+w=1 4A+6C+x(4u+5v+6w)≧8.40.05
≦v 10w≦0゜5,0.001≦W≦0,5゜0.6
≦X≦1, 1>A>0, s O99≧C>00.5
0≦U≦0.95 jO<v≦0.45, and when manufacturing a cemented carbide member characterized by having less B-1 type hard phase on the surface than in the inside, When a green compact is sintered according to a normal powder metallurgy method, N and/or O of the B-1 type solid solution phase present in the green compact are
A method for manufacturing a cemented carbide member characterized by sintering in a sintering atmosphere lower than the equilibrium value with the chemical potential of ゎ3
A method for manufacturing a cemented carbide member according to claim 2, characterized in that the sintering atmosphere is kept at I Torr or less. 4. In the method for manufacturing a cemented carbide member as set forth in claim 2, part or all of the atmosphere up to the sintering temperature of 600°C is made into a 1 to 600 TorrCO atmosphere, and then Q at the sintering temperature is , in a high vacuum of l'l'orr or higher,
A method for producing a cemented carbide member, characterized by sintering for 1 minute or more.