JPS6015691B2 - Cemented carbide parts and their manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is characterized in that the main component is WC, and one or more carbides of one or more group A transition metals such as Na, Va, and bonded mainly with iron group metals. The object of the present invention is to provide a more excellent so-called cemented carbide member at an industrially low cost.

The so-called cemented carbide members generally used in practical use include W.
C phase bonded with Co, WC phase and Wa, V
A double carbide having a B-1 type crystal structure (hereinafter referred to as a B-1 type hard phase) is a carbide of one or more of the group A transition metals of A, and is bonded with Co. The present invention relates to the latter of these. WC phase and B-1
The cemented carbide member, which is bonded to the type hard phase using Co, has excellent wear resistance due to the strength of WC, high hardness of the B-1 type hard phase, and chemical stability against steel. It 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 of the cemented carbide component is and the poorer the flexibility.

Conversely, the higher the content of the B-1 type hard phase is 4.0, the better the toughness and the worse the wear resistance. Therefore, in the conventional cemented carbide industry, a balance between number property and wear resistance has been achieved by adjusting the content of the B-1 type hard phase in the grain hard alloy member. The inventor believes that, considering a cemented carbide member with a composite structure in which the B-1 type hard phase is different on the surface and inside of the cemented carbide member, it is better than conventional cemented carbide members. , I thought it might be possible to offer something even better.

This idea has already been proposed by many people other than the inventor, and the amount of B-1 type hard phase on the surface of a cemented carbide member is significantly larger 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 strength. 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 We thought that a tool with a smaller amount of B-1 type hard phase in the surface area than in the inside would 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 member increases, so damage caused by thermal breakage as in machining reduces 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, and the thermal stress will be reduced, which will significantly reduce the number of chips due to thermal burnout. Thought. Furthermore, if the amount of B-1 type hard phase on the surface of the cemented carbide member is smaller than that on the inside, the surface naturally has greater whipping properties than the inside, making it difficult to chip during cutting. ), so I thought it might be preferable.

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 smaller than that inside the tool at an industrially low cost.

Some of the inventors (hereinafter referred to as "partial inventors") B-1
Leakage between the mold hard phase and the liquid phase generated during condensation, 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, as a result of investigating the previous study in more detail, the inventor found that the nonmetallic constituent elements of the B-1 type hard phase include C and N, which the inventor had taken into consideration, as well as 0. 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 reduce the amount of ○ in the raw material and reduce the chemical potential of ○ in the sintering atmosphere. It was even a technique. This is because the ○ in the raw material or the coagulation atmosphere reacts with various carbides in the cemented carbide member during the scorching process, becoming gases such as CO and/or CO2, and removing C from the cemented carbide member. ,leave. The gas generated at this time significantly impairs the phosphorization of the cemented carbide. Moreover, since the amount of C is also reduced, the cemented carbide member even becomes arms. However, the inventor is
The knowledge that the above-mentioned disadvantages can be sufficiently prevented by including B-1 type hard phase, which is one of the starting materials, as a nonmetallic element and by carefully adjusting the sooting atmosphere. I got it.

Furthermore, when a cemented carbide member containing 0 was actually produced 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. Firstly, when cutting copper using a cemented carbide member, the surface of the tool cutting edge is
The presence of double oxide-based glassy substances such as Ti, AI, Si, and Ca, which acts as a lubricant between copper and the tool cutting edge, makes cemented carbide members excellent as steel cutting tools. It is considered to be a major factor in showing wear resistance.

On the other hand, if the tool itself contains 0 in advance, the mixed oxide-based glassy substances such as Ti, AI, Si, and Ca will odor the cutting edge surface. Since it is particularly convenient, it is considered preferable to contain ○ as a cutting tool. Secondly, the characteristic of 0 is caused by a slight solid solution in the binder phase other than the so-called hard phase of the cemented carbide member (both the WC phase and the B-1 type hard phase in the case of 2).
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, 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 methods for realizing this method have been proposed by the inventors by adjusting the leakage between the B-1 type hard phase and the liquid phase generated during scaling.

Specifically, the closer the surface of the cemented carbide member is, the smaller the amount of nitrogen contained in the B-1 type hard phase that exists during consolidation, and the leakage with the liquid phase that occurs during consolidation is improved. This was achieved by utilizing the phenomenon that the B-1 type hard phase that was present near the surface of the mackerel is washed away into the interior of the cemented carbide. Furthermore, during this competition, in order to reduce the amount of nitrogen contained in the B-1 type near the surface of the cemented carbide, the chemical potential of N in the atmosphere of the grilled mackerel must be adjusted to When the potential is made smaller than the equilibrium state, denitrification phenomenon occurs and can be achieved. Moreover, such a phenomenon is observed only when the B-1 type hard phase is unstable to the extent that it bends, and
The stability of the −1 type hard phase is determined by the number of outer shell electrons (Valence
ElectronCommentration below VE
It was found that the larger the VEC, the more unstable the VEC. This time, the inventor will explain B in more detail.
As a result of continued studies regarding the -1 type hard phase, it was found that 0 can be considered as a non-metallic constituent element in exactly the same way as C and N, which were conventionally considered. That is, the B-1 type hard phase generally has a molecular formula (M^, MB', Mc'') (Cu, Nv, O
W) When expressed as x, VEC = 4A + song + target × (4u
+5v+fence) However, A+B+C=1. u ten v + w = 11
>A>0,1>B>0,0.92C>0, and VEC
The B-1 type hard phase is unstable, and during competition, the chemical potential of N and/or 0 in the competition atmosphere increases the B-1 type hard phase's N and/or Or, if it is lower than the equilibrium value with the chemical potential of 0, the denitrification and/or deoxidation phenomenon of the B-1 type hard phase occurs closer to the surface of the cemented carbide member.

As a result, the leakage with the liquid phase generated during sintering is improved, and the B-1 type hard phase near the surface is washed away to the inside, so the B-1 type hard phase near the surface is significantly reduced. We have obtained the knowledge that it is possible to provide a cemented carbide member with a smaller phase amount 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 ○ in the B-1 type hard phase, 0 has the maximum VEC of 6, and the VEC of the B-1 type hard phase is 8. In order to maintain a good finish, w should be 0.0, which has a great effect and is preferable as a cutting tool to contain 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. Also, lol
If it 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 ○ 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 is 0.
．． 05 or higher is required. Furthermore, if v+w is 0.5 or more, such denitrification and/or deoxidation phenomena are too significant for industrial purposes, impairing the sinterability of the cemented carbide, which is not preferable. Since the present invention uses a B-1 type hard phase, 0.92C>0 must be satisfied. B-1 when C=0 or C>0.9
This is not preferable because it cannot take a type structure. It goes without saying that A and B can take any value under the conditions of VEC≧8.4 and 0.92C>0. Regarding x, x indicates the ratio of metallic constituent elements to non-metallic constituent elements in the B-1 type hard phase, but if x is less than 0.6, the deviation from the so-called stoichiometric value will be significant. , B-1 type hard phase itself is unpreferably reduced 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 is preferably 3% by weight or more and 3% by weight or less from the viewpoint of performance. Next, embodiments of the present invention will be described.

A sintering atmosphere with a chemical potential of N and/or 0 that is lower than the chemical potential of N and/or 0 of the B-1 type hard phase is an adjacent atmosphere in which the partial pressure of N and 0 is sufficiently low for industrial purposes. be.

That is, a high vacuum of less than ITroo is sufficient. 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
44A+$+target+x(4u+5v+6W)Z8.
40.001 miW≦0.5, 0.05Sv1WSO. 5
Even if one or more of the conditions selected from the group consisting of
By making the chemical potential of N and/or O in the heated atmosphere sufficiently high up to the sintering temperature, the B-1 type hard phase after sintering is
+6w) and 8.40.001Sw≦0.5,0.05S
v+wSO. 50.50 miuSO. 95,0<vmi0.
It was found that 45 conditions could be satisfied.

0 At first glance, this means that the B-1 type hard phase is 4A + Madarajuki x (4u + 5v + trace) and 8,40.00
1Sw≦0.5, 0.05Sv+wSO. This is considered to be contrary to the knowledge that denitrification and/or deoxidation phenomena occur only when condition 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 during heating to the sintering temperature. Therefore, such a reaction can occur because there are barrier holes in various places that communicate with the competitive atmosphere, and at so-called false sintering temperatures, sintering progresses sufficiently, so that there are no barrier holes at all. Because it doesn't exist,
Buddha + porridge 10 × (4u + 5v Juro) Z8.40.001
This is because denitrification and/or deoxidation phenomena are not observed unless the following conditions are satisfied: W≦0.5, 0.05Sv+WS0.5. Incidentally, in actuality, the reaction rate is too slow for industrial use and the effect is hard to be observed at 600 qo or less.

In addition, when the above phenomenon is actually applied industrially, 600
It is sufficient to flood part or all of the temperature from qo to the dawning temperature in an atmosphere with a sufficiently high chemical potential of N and/or C. It is preferable to use an atmosphere because it allows more ○ to be contained in the green compact, and industrially, CO
The easiest atmosphere is 1 to 600rmo. No effect was observed below ITroo and 60mroo
Above this, the effect is saturated and there is no industrial meaning. In addition,
Although the product of the present invention has a strong cutting odor when used alone, it is also excellent as a base material for coated cemented carbide.

This has become particularly widely used in recent years, and involves coating the surface of cemented carbide components with carbides, nitrides and/or oxides of one or more Group A transition metals such as Wa, Va, AI and A so-called coated cemented carbide member, which is coated with one or more layers of one or more selected from the group consisting of Zr oxides, has both surface wear resistance and internal toughness, In cutting tools that are better than conventional cemented carbide parts, the thin surface layer is certainly very wear resistant), and compared to cemented carbide parts, it is very resistant to cutting, and it is very hard to cut when cutting. I get angry. If such a crack penetrates through the cemented carbide member, it will lead to a chipping, but if a significantly small part of the B-1 type hard phase exists on the surface of the cemented carbide as in the present invention, such a crack will occur. It was found that because the material stopped at only one part, the overall toughness was significantly improved. In addition, some inventors have proposed that the coated cemented carbide member has a free carbon content of 0.0
It has been found that it is sufficient to use a material precipitated in an amount of 1 to 0.5% by weight, and the same can be said of the present invention. This will be explained in detail in Examples below.

Example 1 Using commercially available oxygen-containing TIC, TIN and WC as raw materials, they were heated in a hot press in a nitrogen atmosphere for 2000 min.
React at the temperature and pressure of 0,200k9/carp (Tj Elementary School 75 Wo.25) (C Elementary School 68 NO.Ko○o.),. o
It was created.

4.0% by weight of this B-1 type hard phase, 85.5% by weight of WC, and 5% of (Tao.75N wide.25)C. Weight % of C
5.5% by weight of o was weighed out, ethanol was added, and green mixing was performed in a stainless steel ball mill using a cemented carbide ball. After adding 3% by weight of camphor to this mixed powder and stamping it at a pressure of small n/m (model number SNU432), A was sintered to 145,000 and 10-3 Troo, and B was sintered to 1450.
00, 100 Troo in an N2 atmosphere.

When the obtained alloy was examined under a microscope, it was found that A was 2 from the surface.
The B-1 type hard phase completely disappeared up to 0 mm, whereas in B, almost only the B-1 type hard phase was observed from the surface to 3 mm. A cutting test was conducted on these A and B under the following cutting conditions.

Workpiece village SCM3 (HB=280) Cutting speed 108m/mjn feed
0.15 leg/blade depth of cut
2. Overboard cutter poday
When we conducted a cutting test (5 passes each) under the conditions of NLFOaR (NLFOaR), only 6 thermal cracks were observed on the cutting edge in A, while in B there were no chips due to thermal cracks on the 5th pass. have done.

Example 2 In the same process as in Example 1, alloys shown in Table 1 shown on the next page 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 SNU432.

A cutting test was conducted on these chips under the same conditions as in Example 1. The results were as shown below Table 1 on the next page. In the table, A has a VEC of 8.36, which is outside the product of the present invention, and C has a sintering atmosphere of PN2 = 10rroo, and when sintered under these conditions instead of the method of the present invention, the B-1 type hard phase moves from the inside to the surface. This is outside the scope of the present invention. Also, G
VEC of alloy only is 8. Although it was the Buddha's death (9.12),
This is an alloy that has been deoxidized for 1 hour at 1600°C in two air streams on a normal day, and the oxygen content is extremely low by 4. The other products B, D, E, and F are products of the present invention. Table 1 A...Defected in 3 passes B.・．． 8 sharps on the cutting edge during 5-pass cutting C...Defected in 1st pass D-...Defected in 3rd pass E...5 sharps on the cutting edge during 5-pass cutting F...During 5th pass cutting Cutting edge K6 sharp G...Example of loss during 5 pass cutting 3 Commercially available TIC and TIN containing normal oxygen content as an impurity
, Z, ZrN, TaC, TaN, Mo2C, WC powder was mixed, heated in a nitrogen stream at 2000o○ for 1 hour to 1 feeding time, and then ground to form B of H to L with the composition listed in Table 2. -1 type hard phase was created.

By adding WC and Co to these B-1 type hard phases, WC85
．． 5% by weight of Co, 5.5% by weight of Co, and the remaining B-1 type hard phase alloy was heated to 145% in a skin atmosphere for both competitive bonding.
It was created by sintering at 0oo for 1 hour.

(Model number: SNU432) These alloys were coated with TIC6 and further coated with AI203 by a known chemical vapor deposition method. A cutting test was conducted under the following conditions using these chips as H to L corresponding to the B-1 type hard phase used. Work material: S4, forged material ◇5 sides
30mm cutting speed 200m/m
in feed 0.4comparison/r
ev cut 1~5 fence cutting oil
Not used 2 36 inventive products, 41 in 1, 31 in J;
While the K was shaved off 38, the L added for comparison was I.
I was only able to remove Z pieces.

Claims (1)

[Claims] 1. The molecular formula is generally (M_A, M_B', M_C'') (
C_u, N_v, O_w)_x, where M is one or more group IVa transition metals M' is one or more group Va transition metals M'' is one or more group VIa transition metals C is carbon, N is nitrogen , O represents oxygen, A, B
, C, u, v, and w are their respective atomic ratios, and x is the ratio of the nonmetallic constituent elements to the metallic constituent elements. An iron group metal containing W as a constituent element and having two hard phases: a solid solution phase having a B-1 crystal structure and a WC phase, and containing 3% by weight or more and 30% by weight or less of an iron group metal. In the cemented carbide members joined at A, B, C, u, v, w,
A+B+C=1, u+v+w=1 between x 4A+5B+6C+x (4u+5v+6w)≧8.40
．． 05≦v+w≦0.5, 0.001≦w≦0.5,0
．． 6≦x≦1,1>A>0,1>B>0,0.9≧C>
0, 0.50≦u≦0.95, 0<v≦0.45, and the cemented carbide member is characterized in that the surface portion of the cemented carbide member has less B-1 type hard phase than the inside thereof. cemented carbide parts. 2 The molecular formula is generally (M_A, M_B′, M_C″) (
Cu, N_v, O_w)_x, where M is one or more group IVa transition metals M' is one or more group Va transition metals M'' is one or more group VIa transition metals C is carbon, N is nitrogen , O represents oxygen, A, B,
C, u, v, and w represent their respective atomic ratios, and x represents the ratio of non-metal group constituent elements to metal constituent elements. A solid solution phase expressed as
In a cemented carbide member bonded with iron group metal of 3% by weight or more and 30% by weight or less, A+B+C=1, u+v+w=1 4A+5B+6C+x (4u+5v+6w)≧ between A, B, C, u, v, w, x 8.40
．． 05≦v+w≦0.5, 0.001≦w≦0.5,0
．． 6≦x≦11>A>0,1>B>0,0.9≧C>0
In manufacturing a cemented carbide member, which has the following relationships: 0.50<u≦0.95, 0<v≦0.45, and the B-1 type hard phase in the surface portion is smaller than that in the inside. When sintering a green compact according to a normal powder metallurgy method, the sintering atmosphere is lower than the equilibrium value of the N and/or O chemical potential of the B-1 type solid solution phase present in the green compact. A method for manufacturing a cemented carbide member, characterized by sintering it inside. 3. A method for manufacturing a cemented carbide member according to claim 2, characterized in that the sintering atmosphere is kept at 1 Torr or less. 4 Second claim
In the method for manufacturing a cemented carbide member described in Section 1, part or all of the heating atmosphere at 600°C or higher up to the sintering temperature is heated to 1 to 60°C.
After creating a 0 TrooCO atmosphere, the sintering temperature was 0.1T.
A method for producing a cemented carbide member, characterized by sintering in a high vacuum of 1 minute or more in a high vacuum of 1 minute or more.