JPS6315989B2 - - Google Patents

Description

[Detailed description of the invention] The present invention has WC as a main component, a, a,
It is an object of the present invention to provide an even better so-called cemented carbide member, which is made by combining one or more carbides of one or more group A transition metals and mainly an iron group metal, at an industrially low cost.

Generally, the so-called cemented carbide members used in practical use include those in which the WC phase is bonded with Co, and the B-1 in which the WC phase and one or more carbides of the a, a, and a group transition metals are combined. A double carbide with a type crystal structure (hereinafter referred to as the B-1 type hard phase) is
It is bonded with Co. 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 with Co is due to the toughness of WC, the high hardness of the B-1 type hard phase, and the chemical stability against steel. 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. On the contrary, B
-The smaller the content of type 1 hard phase, the better the toughness.
Poor 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 has discovered that the amount of this B-1 type hard phase is different between the surface and the inside of the cemented carbide member.
We thought that if we considered a cemented carbide member with a composite structure, we could provide something better than conventional cemented carbide members. This kind of thinking is
Many proposals have already been made by people other than the inventor, and a cemented carbide member with a significantly larger amount of B-1 type hard phase on the surface than the inside has both surface wear resistance and internal toughness. It has been proposed that it is a better cutting tool.

In all of these proposals, the amount of B-1 type hard phase on the surface of the cemented carbide member is significantly larger than that inside the material, but the inventor has conversely proposed It was thought that a tool in which the amount of B-1 hard phase in the surface portion is smaller than that in the inside may also be excellent as a cutting tool. Generally, in cemented carbide parts, when the amount of B-1 type hard phase decreases, the thermal conductivity of the cemented carbide part increases, so chips due to thermal cracking, such as in milling, dominate tool life. If the surface has a higher thermal conductivity than the inside, the temperature gradient generated on the tool surface will be significantly alleviated.
We thought that because the thermal stress would be reduced, the number of defects caused by thermal cracks would be significantly reduced.

Furthermore, 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 naturally has greater toughness than the inside, making it difficult to chip during cutting. I thought this might be a good thing.

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 the cemented carbide member is significantly lower than that inside the material at an industrially low cost.

Some of the inventors (hereinafter referred to as "partial inventors")
Wettability between the B-1 type hard phase and the liquid phase generated during sintering, equilibrium between the B-1 type hard phase and the sintering atmosphere,
A detailed study was conducted on 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 is
Furthermore, as a result of a more detailed investigation of the previous study, B-
It has been found that, in addition to C and N, which some of the inventors had taken into consideration, O can also be considered as a nonmetallic constituent element of the type 1 hard phase. By the way, the conventional wisdom in the cemented carbide industry is that O is an extremely harmful element, and how to reduce O in raw materials.
Reducing the amount and reducing the chemical potential of O in the sintering atmosphere was even the predominant production technology. This is because O in the raw material or sintering atmosphere reacts with various carbides in the cemented carbide member during the sintering process, converting into gases such as CO and/or _CO2 , and removing C from the cemented carbide member. Go away. 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 inventors have discovered that by incorporating such O as a nonmetallic element in the B-1 type hard phase, which is one of the starting materials, and by carefully adjusting the sintering atmosphere, We have found that this inconvenience can be sufficiently prevented.

Furthermore, based on this knowledge, O
When we manufactured a cemented carbide member containing the following materials, we found that it was an even better cutting tool than conventional cemented carbide members. This is thought to be due to the following reasons.

Firstly, when cutting steel using a cemented carbide member, the surface of the tool cutting edge is covered with a glassy substance based on double oxides such as Ti, Al, Si, Ca, etc. The ability of cemented carbide members to act as a lubricant with the cutting edge is considered to be a major factor in their excellent wear resistance as steel cutting tools. Conversely, if the tool itself contains O in advance,
It is considered preferable for the cutting tool to contain O because it is convenient for such double oxide-based glassy substances such as Ti, Al, Si, and Ca to cover the cutting edge surface of the tool during cutting. .

Second, a small amount of O is the so-called hard phase of the cemented carbide member (in this case, both the WC phase and the B-1 type hard phase).
By slightly solid dissolving in a binder phase other than
It is thought that this has the effect of improving the heat resistance of the binder phase and improving the heat resistance of the cemented carbide member as a whole. Therefore, as a cutting tool, it is considered to have excellent plastic deformation resistance at high temperatures.

The advantages of including O in cemented carbide members have been described above.

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

Some inventors have implemented such a method by adjusting the wettability between the B-1 type hard phase and the liquid phase generated during sintering. Specifically, the closer to the surface of the cemented carbide member,
By reducing the nitrogen content of the B-1 type hard phase present during sintering and improving the wettability with the liquid phase generated during sintering, the B-1 type hard phase present near the surface during sintering is reduced. This was achieved by utilizing the phenomenon in which the mold hard phase is flushed into the interior of the cemented carbide. Furthermore, during this sintering, in order to reduce the amount of B-1 type nitrogen content near the surface of the cemented carbide member, the chemical potential of N in the sintering atmosphere should be adjusted to the chemical potential of N in the B-1 type hard phase. If it is made smaller than the equilibrium state, denitrification phenomenon can occur and be achieved. Moreover, such a phenomenon is observed only when the B-1 type hard phase is unstable to a certain extent, and the stability of the B-1 type hard phase depends on the number of outer shell electrons (Valence Electron
Concentration (abbreviated as VEC hereafter)), and it was found that the larger the VEC, the more unstable it is. This time, the inventor continued to study the B-1 type hard phase in more detail, and found that O
We obtained the knowledge that it is also possible. That is, the B-1 type hard phase generally has the molecular formula (M _A , M _B ′, M _C ″) (Cu,
Nv,, Ow) , N in the sintering atmosphere and/or
Or, if the chemical potential of O is lower than the equilibrium value with the chemical potential of N and/or O of the B-1 type hard phase, the denitrification and/or deoxidation phenomenon of the B-1 type hard phase This occurs closer to the surface of the cemented carbide member. This improves wettability with the liquid phase generated during sintering, so B-1 near the surface
It has been found that because the mold hard phase is washed away into the interior, a cemented carbide member can be provided in which the amount of the B-1 hard phase near the surface is significantly smaller than that inside.

When we tried making a cemented carbide member based on the above idea, we obtained a cutting tool that was even better than expected. Regarding the amount of O in the B-1 type hard phase, O has the maximum VEC of 6,
In order to maintain the VEC of type B-1 hard phase at 8.4 or higher,
W is 0.001 considering that the effect is tremendous and that containing O is preferable as a cutting tool.
The above is preferable. When w is 0.001 or less, the effect of containing O is not recognized in the cemented carbide member. or,
If w is 0.5 or more, it is not preferable because it significantly impairs the sinterability of the cemented carbide member. Regarding the amount of N, since N has a VEC of 5, which is also larger than C, it is preferable to keep the VEC at 8.4 or higher. Therefore, like w, v is preferably 0.001 or more. On the other hand, since N has a small VEC compared to O, when v becomes 0.45 or more, w inevitably becomes smaller, which is not preferable. Regarding the amount of C, if it is less than 0.5, the sinterability will be insufficient, and if it is more than 0.95, v and w will become small, which is not preferable. Next, regarding the amount of group a metal, if A is less than 0.2, the wear resistance will be insufficient, and if A is more than 0.8, the VEC will become too small, which is not preferable.

VEC of group a metal is preferably 5, but B is 0.5
If it is more than 0.01, the abrasion resistance will be insufficient, and if it is less than 0.01, the effect of addition will not be recognized, which is not preferable.

Group A metals preferably have a VEC of 6, C
If it is 0.8 or more, the wear resistance will be insufficient, and if it is less than 0.2, the wear resistance will be insufficient.
VEC becomes small, which is not desirable. Regarding x,
x does not indicate the ratio of the metal constituent elements and nonmetallic constituent elements in the B-1 type hard phase, and x cannot be less than 0.6,
The deviation from the so-called stoichiometric value is significant, and B-
The type 1 hard phase itself is not preferred because it significantly reduces the strength. Furthermore, if x is small, VEC will also be small, which is also not desirable.

Next, embodiments of the present invention will be described.

A sintering atmosphere with a chemical potential of N and/or O that is lower than that of the B-1 type hard phase is a sintering atmosphere in which the partial pressure of N and O is sufficiently low for industrial purposes. be. That is, it is sufficient to use a high vacuum of /Torr or less. Therefore, although the degree of vacuum can be sufficiently achieved with a rotary pump, 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+5B+6C+x (4u+5v+6w)≧8.4 A+B+C=1 u+v+w=1 0.8≧A≧0.2 0.50≧B≧0.01 0.8≧C≧0.2 0.50≦u≦0.95 0.001≦ v≦0.45 0.001 ≦w≦0.5 0.6≦x≦1 Even if one or more of the conditions selected from the group consisting of When sintering, by making the chemical potential of N and/or O in the heating atmosphere sufficiently high above 600℃ to the sintering temperature, the B-1 type hard phase after sintering becomes 4A + 5B + 6C + x (4u+5v+6w)≧8.4 A+B+C=1 u+v+w=1 0.8≧A≧0.2 0.50≧B≧0.01 0.8≧C≧0.2 0.50≦u≦0.95 0.001≦v≦0.45 0.001≦w≦0. 5 The three parties 0.6≦x≦1 We found that the requirements can be met.

At first glance, this means that the B-1 type hard phase is 4A+5B+6C+x (4u+5v+6w)≧8.4 A+B+C=1 u+v+w=1 0.8≧A≧0.2 0.50≧B≧0.01 0.8≧C≧0.2 0.50≦u≦0.95 0.001≦ v≦0.45 0.001 This is contradictory to the knowledge that denitrification and/or deoxidation phenomena occur only when the following conditions are satisfied: ≦w≦0.5 0.6≦x≦1. 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. Therefore, such a reaction can occur because there are holes in various places that communicate with the sintering atmosphere, and at the so-called sintering temperature, sintering progresses sufficiently, so such holes do not occur. Since it does not exist at all, 4A+5B+6C+x (4u+5v+6w)≧8.4 A+B+C=1 u+v+w=1 0.8≧A≧0.2 0.50≧B≧0.01 0.8≧C≧0.2 0.50≦u≦0.95 0.001≦v≦0 .45 0.001≦w≦0.5 0.6≦ This is because denitrification and/or deoxidation phenomena are not observed unless x≦1.

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

In addition, when actually applying such a phenomenon industrially, it is sufficient to heat a part or all of it above 600°C to the sintering temperature in an atmosphere with a sufficiently high chemical potential of N and/or C. , it is preferable to use an O atmosphere rather than using a N atmosphere to carry out such a phenomenon because it allows a larger amount of O to be contained in the compact, and industrially it is easier to carry out such a phenomenon than a CO atmosphere. , 1 to 600 Torr is sufficient.
Below 1 Torr, no effect is observed, and above 600 Torr, the effect is saturated, making it industrially meaningless.

Although the product of the present invention can be used as a sufficiently excellent cutting tool as a single unit, it has been found that a, Va,
A so-called coated cemented carbide coated with one or more layers of one or more carbides, nitrides and/or oxides of Group A transition metals and oxides of Al. The parts have both surface wear resistance and internal toughness, and the thin surface layer is certainly extremely wear resistant in cutting tools that are better than conventional cemented carbide parts. Compared to cemented carbide parts, it is extremely brittle and will easily crack when cut. If such a crack penetrates the cemented carbide member, it will lead to damage, but as in the present invention,
It has been found that if a very small portion of the B-1 type hard phase exists on the surface of the cemented carbide, such cracks are stopped at this portion, and the toughness as a whole is significantly improved.

It should be noted that some inventors have obtained the knowledge that it is sufficient to use a material in which 0.01 to 0.50% by weight of free carbon is precipitated as such a coated cemented carbide base material, but the same applies to the present invention. I can say that.

This will be explained in detail in Examples below.

Example 1 23.4% by weight of commercially available TiC powder and 23.4% by weight of commercially available TiC powder
A mixed powder consisting of 76.6% by weight of WC was prepared under vacuum (2
×10 ^-2 Torr) using carbon mold, 1900
After hot pressing for 1 hour at a temperature of 100 Kg/cm ² at a pressure of 100 Kg/cm 2 , the resulting double carbide was ground in a ball mill to produce (Ti _0.5 W _0.5 ) C _1.0 .

This (Ti _0.5 W _0.5 )C _1.0 4% by weight, WC 85.5% by weight, NbC 5% by weight, Co 5.5% by weight were weighed, ethanol was added, and wet mixing was performed using a stainless steel ball mill using a carbide ball. . Camphor was added in an amount of 3% by weight to this mixed powder, and an embossed green compact (model number TNMG432ENZ) was produced under a pressure of 2 t/cm ² .

The compacted powder is sintered in vacuum at 10 ^-3 Torr and ¹⁴⁵⁰ °C.
C. to 1450.degree. C. in a CO atmosphere at _P.sub.CO =300 Torr, and then sintered at 1450.degree. C. and 10 Torr for 1 hour. C and D were coated with 6μ of TiC using a known chemical vapor deposition method.

The composition of the B-1 type hard phase of C is (Ti _0.09
The composition of D is ( _{Ti 0.12 Nb 0.38} W _0.50 ) _{( C 0.80 N 0.002}
O _0.198 ) was _0.95 .

A cutting test was conducted on C and D under the following conditions.

Work material S55C forged material φ50mm x 2300mm Cutting speed 150m/min Feed 0.50mm/rev Depth of cut 1~5mm No cutting oil used Compared to the D chip of the present invention, which could process 48 pieces, Only 31 pieces of C could be processed.

Example 2 WC-(Ti,
Ta, W) (C, N, O)-Co alloy, however, WC is 85
Weight%, Co5% by weight, balance (Ti, Ta, W) (C,
N, O) composition in atomic ratio (Ti _0.4 Ta _0.1 W _0.5 )
(C _0.99 N _0.005 O _0.005 ) _0.92 cemented carbide (model number
CNMG432ENZ) was created.

TiC is applied to this chip using a known chemical vapor deposition method.
Chips coated with 3μ Al ₂ O ₃ are E, TiC.
A cutting test was carried out under the following conditions: F was a chip coated with 1.5μ of TiN, 1.5μ of TiN, and 3μ of Al ₂ O ₃ was designated as F, and G was a chip coated with 3μ of TiC and 3μ of ZrN.

Work material SCM435 forged material (φ50mm x l200mm) Cutting speed 100m/min Feed 0.50mm/rev Depth of cut 1~5mm No cutting oil used Chips E of the present invention are 125, F is 139, and G is 69.
While the main cutting was successful, TiC was applied to the cemented carbide base material using the same manufacturing method as D in Example 1 using the chemical vapor deposition method.
A chip coated with 3μ and 3μ of Al ₂ O ₃ broke off after cutting 12 chips and could not be cut any further.

Claims (1)

[Claims] 1. The molecular formula is generally (M _A , M _B ′, M _C ″) (Cu,
Nv, Ow) Nitrogen and O indicate oxygen, A, B, C, u, v, w are their respective atomic ratios,
x indicates the ratio of the nonmetallic constituent elements to the constituent elements. It is a cemented carbide member that contains W as a constituent element and has two hard phases: a solid solution phase with a B-1 crystal structure and a WC phase, and is bonded with an iron group metal. WC is 5% by weight or more and 95% by weight or less, iron group metal is 3% by weight or more and 40% by weight or less, and the remainder is the B-1 type hard phase, A, B,
4A+5B+6C+x (4u+5v+6w)≧8.4 between C, u, v, w, and x ≦0.45 0.001≦w≦0.5 0.6≦x≦1, and the surface part of the base material is made of a cemented carbide member whose B-1 type hard mass is significantly less than the inside. Group a transition carbides, nitrides and/or oxides and
A coated cemented carbide member characterized in that it is coated with one or more thin layers of 0.1 to 20μ of one or more selected from the group consisting of oxides of Al.