KR830000997B1 - Method for producing the sintered hard metal - Google Patents

Abstract

A molecular formula is expressed by (MA, MB, MC) (Cu, Nv)X, after the composite carbonizing nitride having crystal structure of B-1 type contg. w by one of the composed element, WC above 50wt % of the total weight of the cement carbide, and metal of the iron group is mixed, the cement carbide is sintered. Only M is expressed above the first element or the second element of IVa group metal, M' is above the first element of the second element of Va group metal, M" is above the first or the second element of VIIa group metal, c is carbon, N is nitrogen, x is ration composed metal element to composed nonmetal element, and A, B, C, U and V atomic ratio each other.

Description

Cemented Carbide

1 is a cross-sectional view of the four grooves used in the cutting test.

The so-called cemented carbide members, which contain WC as the main component and combine one or two or more carbides or carbonitrides of Group IV _a , V _a and VI _a group metals with one or two or more of iron group metals, are already in general use. It is put to practical use. In a thin layer that is more abrasion resistance to the surface of said cemented carbide member (薄層), for example, _{T ic, T i CN, T} i N, Al 2 O 3 , such as a thin layer covering the first layer or of two or more layers of the coated cemented carbide The member is invented, and this coated cemented carbide member is widely regarded as an excellent cutting tool having both the toughness of the base material and the wear resistance of the surface. In recent years, efforts have been made to provide materials that are superior to the coated cemented carbide members.

As one of them, a coated cemented carbide member in which the hardness of the surface layer of 10 to 200 mu in the surface of the cemented carbide base material is 2-20% lower than that of other parts by Vickers hardness is invented (Japanese Patent Laid-Open No. 52-110209).

In this invention, as a method of manufacturing the said member

(1) A slurry of a composition in which the hardness was reduced to 2-20% by the Vickers hardness with respect to the composition and properties of the base material was prepared, and then the The surface is sprayed evenly in N ₂ gas in the form of droplets so as to have a layer thickness of 10-100 μm, dried under reduced pressure, and then molded by sintering.

(2) By press working, two methods are shown in which a thin layer having a composition preferable as a surface layer of the base material is molded from a compressed gas, and sintered and molded by a normal powder metallurgy method.

However, both methods are expensive to manufacture and cannot be said to be realistic in terms of industrial performance.

The present invention is to solve the above problems and at the same time provide a better cutting tool, in particular, the composition of the cemented carbide base material and its sintering phenomenon have been examined in detail.

The inventors of the present invention previously examined the stability and sintering environment of the B-1 hard phase of a cemented carbide containing a hard phase having a B-1 crystal structure.

D일 때 불안정하나, VED

D일 때는 안정하다는 것을 발견하였다(D는 나중에 정의된다). 그리고 VEC

D일때 불안정하게 된 탄질화물(炭窒化物)결정에 W이 함유되었을 경우에는 WC이 석출한다는 것을 발견하였다.In this study, the inventors found that it is appropriate to use the outer electron number (hereinafter referred to as VEC) as an index for considering the stability of the hard phase.

Unstable at D, but VED

When D was found to be stable (D is defined later). And VEC

It was found that WC precipitates when W is contained in a carbonitride crystal that becomes unstable at D.

Also, as is well known, the molecular formula of the B-1 hard phase is (M _A , M ' _B , M " _C ) (C _U , N _V ), and (M is _a group IV _a such as T _i , Z _r , H _f ). One or two or more kinds of metals, M 'is one or two or more kinds of Group V _a metals such as V, N _b , T _a or M''is one or two of Group Wl _a metals such as Cr, M _o or W Species, at least C represents carbon, N represents nitrogen, X represents the ratio of the nonmetallic element to the metal element),

A + B + C = 1,

When U + V = 1, VEC

VEC = 4A + 5B + 6C + 4 × U + 5 × V

Becomes D is a function of nitrogen partial pressure in the sintering atmosphere, and becomes larger as the nitrogen partial pressure in the sintering atmosphere becomes smaller.

As described above, however, as a result of producing the alloy under various conditions, the alloy has a high sintering atmosphere (that is, a large D) in the alloy having a certain amount of WC equivalent in a small amount of alloy and above 50% by weight in practical use. The surface layer of the binding grade was found to be rich in type B-1 hard phase.

C'인 반응으로 WC이 석출되어도, 소결합금 총체로서는, 원래 WC상용량이 충분히 있기때문에, 다소 WC이 석출하여도 조직, 성능상 큰 영향은 없다.The reason for this phenomenon is assumed to be due to the following reasons. That is, since the small amount of WC equivalent is sufficiently contained in the small binder, the B-1 solid solution is (M _A , M ' _B , M _C ") (C _U , N _V )-(M _A ', M _B 'M" _C ) (C _U ', N _V ') + (C'-c)

Even if WC is precipitated by the reaction of C ', since the total amount of the WC phase capacity is large enough as the small-bonded alloy total body, even if WC is precipitated somewhat, there is no significant effect on the structure and performance.

On the other hand, during sintering, since the B-1 type hard phase of the small alloy surface layer is in equilibrium with the sintering atmosphere, denitrification occurs when the sintering atmosphere is in a high vacuum. Since there is sufficient WC equivalent in the small binder, that is, the carbon potential is in a sufficiently large state, the carburizing phenomenon of denitrified amount advances, and the amount of carbon in the B-1 type hard phase of the surface layer of the small alloy increases. When the sintering atmosphere is in the atmosphere, on the contrary, the amount of carbon in the B-1 hard phase of the surface layer decreases.

This increase or decrease in the amount of carbon has a great influence on the oiliness of the liquid phase generated during sintering. That is, there is a correlation between the amount of carbon in the B-1 hard phase and the oil value of the liquid phase generated during sintering, and the higher the carbon content, the worse the oiliness. Therefore, when the sintering atmosphere is high vacuum, the B-1 type hard phase does not get wet in the liquid phase, so it is pushed into the alloy, and the B-1 type hard phase becomes poor in the surface layer. On the contrary, when the sintering atmosphere is in an N ₂ atmosphere, since the oily property is good, the B-1 type hard phase is enriched in the surface layer.

For the reason mentioned above, when the sintering atmosphere is high vacuum, the B-1 type hard phase changes in the surface layer, and it is considered to hatch in the N ₂ atmosphere.

As described above, the inventors have invented a method for producing a cemented carbide that is extremely superior to conventional cemented carbides.

That is, the molecular formula is represented by (M _A , M ' _B , M _C ") (C _U , N _V ) x, and has a B-1 type crystal structure containing W as part of the element and the total amount of cemented carbide. A cemented carbide alloy comprising at least 50% by weight of a WC phase as a hard phase, having an iron group metal as a binding metal, and a constant surface layer having a proportion of a phase having a B-1 type crystal structure less than the other parts. .

In the present invention, the WC equivalent amount needs to be 50% by weight or more of the total amount of cemented carbide, and when the amount is less than 50% by weight, the influence of the amount of precipitated WC due to decomposition of the B-1 type hard phase is increased, and the effect of the present invention is increased. Does not appear

VEC

8.4이며 소결분위기가 온도 1300℃-1500℃, 진공도 1torr 이하의 조건으로할 필요가 있음을 알았다.In addition, as invented in Japanese Patent Application Laid-Open No. 52-110209, as a result of an experiment for improving toughness, abrasion resistance, and heat resistance in a cemented carbide having a predetermined width of a surface layer having a predetermined hardness lower than that of other parts, a difference of It was found that the cemented carbide surface layer should have less B-1 type hard phase than the other parts. And, to achieve this, VEC is 10.0

VEC

8.4 and the sintering atmosphere was found to be required to be at a temperature of 1300 ° C-1500 ° C and a vacuum of 1torr or less.

The above limitation depends on the extinction width of the B-1 type hard phase exceeding 200 mu when the VEC is 10.0 or more and less than 5 mu when the VEC is less than 8.4.

4A+5B+6C+(4U+5V)×

10.0)에 대하여 상세하게 설명한다.Again, limiting the value of VEC (8.4)

4A + 5B + 6C + (4U + 5V) ×

10.0) is demonstrated in detail.

0.9, 0.01

B

0.5, 0.1

C

0.9,

0.01

∨

0.5, 0.60

×

1.0인 것이 바람직하다.The constituents of the B-1 hard phase are free within the above ranges, but the B-1 hard phase represented by the molecular formula (M _A , M ' _B , M _C ") (C _U , N _V ) × About 0.1

0.9, 0.01

B

0.5, 0.1

C

0.9,

0.01

∨

0.5, 0.60

×

It is preferable that it is 1.0.

C

0.9인 것이 바람직하다. 0.1 미만에서는 효과가 빈약하고, 0.9 이상이면, 그 경질상의 소멸폭이 200μ를 넘어 바람직하지 못하다. 또한 Vl_a족 원소가운데서도, 특히 W는 그 경질상의 소결성 향상에 현저한 효과가 있어 바람직하나 W의 량은 원자비로 0.1-0.5인 것이 바람직하다. 이것은 0.1 미만에서는 강도가 저하하고 0.5를 넘으면 효과가 포화하기 때문이다.VEC is Group IV _a metal 4, Group V _a metal 5, Group VI _a metal 9, carbon 4 and nitrogen 5. First, with respect to this hard-phase nonmetallic element, nitrogen has a larger VEC than carbon, and thus, it is effective to stably store VEC above a certain value, and the present invention also denitrates the B-1 type hard phase and the sintering atmosphere. Nitrogen is indispensable because it uses nitriding phenomena, and V should be 0.01 or more to enhance the effect of denitrification and nitriding. On the other hand, when V exceeds 0.5, since the sinterability of an alloy deteriorates, it is preferable that it is 0.5 or less. In addition, when X is less than 0.6, the composition of the A-1 type hard phase is so large that the difference in stoichiometric composition is so large that the strength is lowered, which is not preferable. If the value of X is too small, the value of VEC becomes small, which is also not suitable. Subsequently, the Vla group metal has a VEC of 6 with respect to the hard metal component, and the Group IV _a element is preferable because it increases the strength of the hard phase.

C

It is preferable that it is 0.9. If it is less than 0.1, the effect is poor, and if it is 0.9 or more, the hard phase extinction width exceeds 200 micrometers, and it is unpreferable. Also in the group Vl _a element, W is particularly effective in improving the sinterability of the hard phase, but the amount of W is preferably 0.1-0.5 in atomic ratio. This is because the strength decreases below 0.1 and the effect saturates above 0.5.

B

0.5인 것이 바람직하다. 0.01미만이면 효과가 빈약하고, 0.5이상에서는 효과가 포화하기 때문이다. 또 V_a족 금속은 본 발명에서 꼭 필요한 것은 아니지만 효과를 보다 높이는 역할을 수행하고 있음은 말할것도 없다. IV_a족 금속은 특히 T_i에 관하여는 VEC가 4로 작지만, 그 경질상의 경도를 높이는데 필요하고, 0.1

A

0.9인 것이 바람직하다. 0.1미만에서는 그 경질상을 포함하는 초경합급의 내마모성이 양호하지 못하고 0.9 이상이면 그 경질상의 소멸폭이 5μ미만이 되어버려 바람직하지 못하다.Next, with respect to _a V-group metal, increase the heat resistance on the light by preferred, and 0.01

B

It is preferable that it is 0.5. This is because the effect is poor at less than 0.01, and the effect is saturated at 0.5 or more. In addition, group V _a metal is not necessary in the present invention, it goes without saying that it plays a role of enhancing the effect. Group IV _a metals have _a small VEC of 4, especially with respect to T _i , but are required to increase their hardness in 0.1,

A

It is preferable that it is 0.9. If it is less than 0.1, the wear resistance of the cemented carbide containing the hard phase is not good, and if it is 0.9 or more, the extinction width of the hard phase is less than 5 µ, which is not preferable.

The cemented carbide according to the present invention has general general properties required for toughness and wear resistant cutting tools, but also has the following properties.

In other words, the rigidity is strong and has a strong property against thermal cracking. In the cemented carbide, the larger the B-1 type hard phase, the smaller the thermal conductivity and elastic modulus.

In the cemented carbide according to the present invention, the ratio of the B-1 type hard phase in the surface layer decreases, so that the thermal conductivity and elastic modulus of the surface layer increase simultaneously.

In addition, since the thermal conductivity of the surface layer is large, thermal gradients are alleviated even when generated on a very intense thermal stress layer tool surface such as milling, and the thermal stress generated is small, and defects due to thermal stress are significantly reduced. In addition, since the elastic modulus is large, the rigidity of the whole cemented carbide is improved. In particular, in recent years when W is expensive, a cutting tool which is inexpensive and has good rigidity is suitable for industrial use as in the present invention. In view of the fact that the specific gravity of the WC phase is large at 15.6, the cemented carbide according to the present invention is sufficiently large in terms of rigidity, and since the WC phase is small as a whole, the specific gravity is small, which is preferable in mechanical design.

The cemented carbide according to the present invention again has excellent toughness of the surface layer, so that the so-called chipping phenomenon is reduced.

The cemented carbide according to the present invention may be used as a cutting tool as it is, but when used as a base material of the so-called coated cemented carbide, a further cutting tool can be obtained by synergy with the coating layer.

That is, one or two or more selected from the group consisting of carbides, nitrides and oxides of metals of the Periodic Tables lV _a , V _a and Vl _a of the Periodic Table of the Carbide are coated with one or more layers. The lower surface is used as a better cutting tool.

By the extremely easy method according to the present invention, it is possible to provide a cemented carbide, which is extremely excellent and inexpensive compared to the conventional cemented carbide, with respect to toughness, abrasion resistance, heat resistance, and other properties required as cutting tools.

Hereinafter, embodiments of the present invention will be described.

Example 1

9.6 weight% of T _i N, 14.1 weight% of T _i C, and 76.3 weight% of WC were mixed and hot-pressed at 1,800 ° C. for 1 hour, and then pulverized to form a composite carbonitride.

The results showed that the composite carbonitrides had a composition of (Ti 0.75 W 0.25) (C 0.68 N 0.32), and the X-ray diffraction showed a B-1 type crystal structure.

4.0 wt% of the composite carbonitride, 85.5 wt% of WC, 5.0 wt% of Ta 0.75 Nb 0.25 C, and 5.5 wt% of Co were added thereto, and acetone was added thereto, followed by wet mixing with a stainless zebble mill using a cemented carbide mill. 3 weight% of camphor was added to the di-mixed powder, and pressed at 2 ton / cm 2. (Model No. SNV 432) was sintered at 10 ^-3 torr as 1,450 deg.

The obtained alloy was examined under a microscope. As a result, the B-1 hard phase completely disappeared from the surface to 10 mu.

A chakbeop of known chemistry for this alloy is referred to as the A coated with T _i C 6μ. For comparison, the above-mentioned press work was sintered in an atmosphere of N ₂ partial pressure 10torr, and then 6B coated with T _i C as described above is referred to as B.

The alloy of the present invention and the composition ratio of W, T _i , T _a , Nb, Co are the same, but the content of nitrogen in the B-1 type hard phase used as starting materials is mixed and pressed in the same process with an atomic ratio of 0.01 or less, Sintered thing is called C.

(A, B, and C are all SNU 432 types) and the cutting test was performed under the following conditions.

As a result of 100-blade cutting test for each chip, A showed 0% breakage, 83% for B, and 45% for C, indicating that the present invention had increased toughness without compromising wear resistance.

Example 2

In the same manner as in Example 1 (Ti 0.75 W 0.25) (C 0.68 N 0.32) was made. This complex carbonitride was 6.3% by weight, WC 75.7% by weight, T _a 0.75 N _b 0.25 C 7.5% by weight, Co10.5% by weight, and a press-formed product was prepared in the same manner as in Example 1 to prepare a press-worked product at 1,380 ° C and 10- ^. Sintered under ³ torr. On the chip (model number sup422), 6 µC of T _i C was coated in the same manner as in Example 1.

When the 100 blade test was carried out under the condition (2) of Example 1 as this chip, the breakage rate was 3%, whereas the coating chip coated with 6 T _i C on a commercial P-40 alloy had a breakage rate of 86%.

Example 3

In the same manner as in Example 1 WC 85.5 weight% (T _i 0.75 W 0.25) (C 0.68 N 0.32) 4.0 weight% (T _a 0.75 N _b 0.25) C weight 5 weight%, Co 5.5 weight%, and The amount of carbon contained was appropriately adjusted, and the press-formed body (the mold method SNU 432) was sintered at 1,450 ° C and 10 ^-3 torr in the same process as in Example 1. After sintering, carbon analysis of the alloy was carried out, D, 0.03 wt% precipitated E, 0.15 wt% precipitated F, 0.30 wt% precipitated G, 0.45 wt% precipitated, and the free carbon was not precipitated H, What precipitated 0.60 weight% is set to I. By chemical vapor deposition in their home to T _i C was coated 6μ, the Al ₂ O ₃ 1μ. These chips were examined for cutting lifespan of workpiece SCM ₃ (H _B = 280) cutting speed of 170 m / min, feed 0.36 mm / rev, cutting depth of 1 mm, and abrasion wear of 0.25 mm. D cut for 37 minutes, E for 36 minutes, F for 29 minutes, G for 21 minutes, H for 16 minutes, and I could cut for only 2 minutes. For comparison, a commercially available Al ₂ O ₃ / T _i C double coated cemented carbide member (hereinafter referred to as J) was capable of cutting for 22 minutes.

These chips were tested as 100 blades of each chip under the condition (2) of Example 1, and D was 24%, E was 12%, F was 6%, G was 0%, H was 0%, and I was 0. J showed 49% failure rate compared with% failure rate.

Example 4

Various alloys were made in the same manner as described in Example 1. The alloy composition and the sintering atmosphere at that time are shown in Table 1 below. (The composition of the B-1 hard phase is the composition of the raw materials, and the model number is SNU 432). (Sintering temperature is 1,380 ℃, 1 hour, Co content is 10% by weight.)

TABLE 1

The VEC-type hard phase VEC of various alloys shown in Table 1 is 8.70, i is 9.02, n is 8.30, and p is 10.0 in i-m.

After the sintering, the chip was cut and irradiated, i showed 20μ slightly B-1 type hard phase than the surface, whereas in j the type B-1 hard phase was slightly reduced than the inside, and in K, 20μ completely lower than the surface. Type B-1 hard phase disappeared.

In I, type B-1 hard phase completely disappeared from the surface to 10μ, whereas in m, only B-1 type hard phase and Co were identified up to 5μ on the surface, and WC was completely extinguished.

n was completely uniform from the surface to the inside, and in O, the B-1 hard phase disappeared from the surface to 100 µ, whereas in P, the B-1 hard phase disappeared from the surface to 200 µ.

Among them, K, O, and P are coated with 6μ T _i N by a known method, and the cutting test is performed with workpiece SCM ₃ (H _B = 280), cutting speed 170 mm / min, feed 0.36 mm / rev, depth of cut 2 mm, the frankfurter wear bars by the 0.2mm as life, and 36 minutes at K, 31 minutes at O, it was possible 21 minutes at P is cut (as N T _i-coated cemented carbide of a commercially available cutting is 37 minutes, and only the base material 16 minutes Cutable).

Subsequently, a tube material of workpiece SCM ₃ (H _B = 280) 200 × 100 was milled at a cutting speed of 108 m / min, a supply of 0.18 mm / blade and a depth of cut of 2 mm as O, m and k (the cutting machine is NFL 06 R), respectively. The number of thermal cracks seen on the blade after five passes was not cut at the time of two passes due to thermal cracks in the case of k in one case and six in O.

Claims (1)

_A composite carbonitride having a molecular formula represented by (M _A , M ' _B , M _C ") (C _U , N _V ) _x and having a B-1 crystal structure containing W as one of its components, and the total amount of cemented carbide A method of producing a cemented carbide, characterized in that after sintering at least 50% by weight of WC and an iron group metal, and sintering in an atmosphere having a temperature of 1,300 ° C.-1,500 ° C. and a vacuum degree of 1 Torr or less. Provided that M is one or two or more of Group IV _a metals, M 'is one or two or more of Group V _a metals, and M''is one or two or more of Group VI _a metals, and C is Carbon represents N, nitrogen represents A, B, C, U, and V represents the respective atomic ratios, X represents the ratio of nonmetallic elements to metal components, and 0.1 ≦ A ≦ 0.9, 0.01 ≦ B ≦ 0.5, 0.1≤C≤0.9, 0.6

1.0, so A + B + C = 1, 8.4 if U + V = 1

4A + 5B + 6C 4Ux + 5Vx

10.0.

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