JPH09111422A - Sintered superhard alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the strength and toughness of a superhard alloy by sintering powder contg. specified amounts of C, Si, Mn, Cr, W, Mo, V, Nb, Co, Fe and the (double) carbides, (double) nitrides and (double) carbon nitrides of group IVa, Va, and VIa elements. SOLUTION: Matrix powder having a compsn. contg., by weight, 1 to 4.5% C, <=2% Si, <=2% Mn, 3 to 10% Cr, one or more kinds of <=30% W and <=20% Mo so as to satisfy <=45% W+2Mo, one or more kinds of V and Nb by 2 to 10% and <=20% Co, and the balance substantial Fe and powder contg. the double carbides, double nitrides and double carbon nitrides composed of plural metallic elements among group IVs, Va and VIa elements by 1 to 10% to the total weight of the matrix powder are mixed, sintered to form into the objective sinthered superhard alloy.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a material for a cutting tool such as a drill, an end mill, a drill tip, a tap, a mold for metal plastic working, a tool material and a jig, a mold and a tool for resin molding, and various blades. , And a sintered cemented carbide used as an industrial wear resistant part and the like.

[0002]

2. Description of the Related Art As a method of improving the service life of a high speed tool steel as a cutting tool, the first consideration is to improve the hardness. Actually Japanese Patent Publication No. 55-6096, Japanese Patent Publication No. 57-
2142, JP-A-57-181367, JP-A-58-
No. 181848 discloses a high hardness sintered alloy capable of obtaining a hardness of HRC71 or higher. These alloys are M
It contains a large amount of alloying elements such as W and Mo which form 6C carbides or V which forms MC carbides, or T
Since it contains a large amount of a hard substance such as iN, it poses a serious problem in practical use such as an increase in price, a decrease in toughness, and a decrease in grindability. Therefore, as a means for solving these problems, Japanese Patent Publication No. 5-75821 and Japanese Patent Publication No. 5-758.
No. 22 is known. In all of these, the balance value for the alloying element of carbon content is Ceq = 0.06Cr +
When 0.033W + 0.063Mo + 0.2V,
The hardness after heat treatment is HRC72 by setting 0 ≤ C-Ceq0.6 to be higher carbon than Ceq and dispersing a relatively small amount (2 to 12%) of hard particles.
The hardness is extremely high as described above.

Further, Japanese Patent Application Laid-Open No. 2-1258 by the present inventors
The alloy disclosed in No. 48 is a hard alloy having a fine structure in which the average particle size of TiN particles and carbides is 5 μm or less and the average particle gap is 5 μm or less, and it has excellent mechanical properties and grindability. It is an excellent alloy. Further fairness 5
-55587 discloses that the dispersed phase of more than 10% to 25% is T.
Disclosed is a hot work tool member made of a dispersion strengthened sintered alloy, which is made of a composite metal carbonitride of two kinds or three kinds or more of i, Zr, Hf, Ta, Nb, V and W.

[0004]

These sintered cemented carbides described above have intermediate properties between high speed tool steels and cemented carbides, and are superior in wear resistance to high speed tool steels. It is characterized by higher toughness than alloys, and is applicable to fields where cemented carbide cannot be used due to chipping, and high-speed tool steels have a short life due to wear. However, in the above-mentioned conventional hard alloys, the strength is not sufficient in some cases, and like the cemented carbide, it may reach the end of its life, so if the strength and toughness can be further increased, its field of use will greatly expand. It is said that the current situation is. Further, in the above-mentioned sintered alloy disclosed in Japanese Patent Publication No. 55857/1993, a large amount of dispersed phase is added and the sinterability decreases, so the sintering temperature is raised (specifically, 1
It should be 250 ° C or higher). Therefore, there is a cost disadvantage.

The present inventor has conducted various studies to solve the above-mentioned conventional drawbacks and apply a normal sintering temperature to significantly enhance strength and toughness. Then, carbide, nitride, and carbonitride particles that are hard particles as dispersed particles are not composed of conventional single metal elements, but are composed of a plurality of metal elements such as a double carbide, a double nitride, and a double nitride. The inventors of the present invention have found that the properties of strength and toughness can be significantly improved by using carbonitride and a carbide, nitride or carbonitride composed of a single metal element in combination. An object of the present invention is to provide a sintered cemented carbide which can be used in a wide range of fields by significantly increasing strength and toughness.

[0006]

[Means for Solving the Problems] That is, specifically, the present invention is such that, by weight%, C 1.0 to 4.5%, Si 2.0% or less, and Mn 2.0%.
Hereinafter, one or two of Cr 3 to 10%, W 30% or less and Mo 20% or less is 45% or less at W + 2Mo, and 1 or 2 of V and Nb.
A base powder containing 2 to 10% of seed and 20% or less of Co, and having a composition of balance Fe and inevitable impurities, is added to 1 to 10% of the group IVa, Va, and VIa based on the total weight of the base powder. One or more kinds of double carbides, double nitrides, and double carbonitrides composed of a plurality of metal elements of the group elements, and 1 to 10% of group IVa, group Va, and group VIa based on the total weight. It is a sintered cemented carbide that is characterized by mixing carbides, nitrides, and carbonitrides of group elements with one kind or two or more kinds and combining them by sintering. Further, it is desirable that the double carbide, the double nitride and the double carbonitride contain W.

In the present invention, the carbides, nitrides and carbonitrides to be mixed with the matrix powder are not limited to the conventional compounds composed of a single metal element and carbon or nitrogen, but a plurality of compounds. It is characterized in that both a double carbide, a double nitride and a double carbonitride composed of a metal element and a single metal element and a compound composed of carbon and nitrogen are used together. The advantages of using double carbides, double nitrides, and double carbonitrides composed of elements are as described below.

(1) It is possible to eliminate the defects while making the most of the characteristics of each carbide, nitride, and carbonitride. For example, adding W to Ti (C, N) carbonitride (T
i, W) (C, N), the feature of high toughness of W is added, and the toughness and strength of the hard alloy added as dispersed particles can be improved. (2) A substance that cannot be applied as a compound on the texture by itself because it is thermodynamically unstable is thermodynamically stable and applicable even if it is compounded with other metal elements. For example,
In the case of nitrides such as WN and MoN, the standard free energy of formation is positive and usually cannot exist stably.
By forming a complex solid solution with a or the like, it becomes a stable compound and can be applied.

(3) Even if it is difficult to remain in the alloy as dispersed particles because it is easy to react or form a solid solution by itself, it is possible to prevent the reaction or the solid solution by forming a solid solution composite carbide or the like to obtain dispersed particles. It becomes possible to exist. For example, when WC is added, it reacts with a matrix or the like to change WC into M ₆ C carbide and does not remain as a single particle, but it is stabilized by (W, Ti) C to disperse particles. Can be (4) Organization control becomes possible. By utilizing the fact that the reactivity with the matrix differs depending on the type of metal element, the shape of dispersed particles can be controlled by changing the type and ratio of the metal element. (5) An extremely large number of combinations are possible by changing the type and ratio of the metal to be combined with the amounts of C and N in the compound, and the combination of characteristics is greatly expanded, and the characteristics can be freely selected according to the purpose. It becomes possible to do.

As described above, the carbides, nitrides and carbonitrides are not composed of conventional single metal elements, but are composed of a plurality of metal elements such as double carbides, double nitrides and double carbonitrides. By doing so, hard alloys having various characteristics can be obtained. However, when the dispersed particles which are the above-mentioned hard substance contain W, a double carbide (for example, (Ti, W) (CN It is possible to make use of the high toughness and elastic modulus of WC which occupies a part of ()), and it is possible to obtain a hard alloy having particularly excellent properties. In the present invention, double carbides, double nitrides and double carbonitrides composed of the above-mentioned plurality of metal elements, and further carbides, nitrides and carbonitrides which are compounds of a single metal element and carbon or nitrogen. Both are used together. The use of carbides, nitrides and carbonitrides composed of a single metal element in addition to the double carbides, double nitrides and double carbonitrides further brings about the following advantages.

(1) The degree of freedom in the combination of dispersed particles dispersed in the structure is increased, and a composite structure can be obtained in which the respective characteristics are utilized. That is, it is possible to use the unique and excellent properties of carbides, nitrides and carbonitrides together. (2) When properties equivalent to those of the double carbide, the double nitride and the double carbonitride can be obtained, the cost can be reduced by using the carbide, the nitride and the carbonitride. In general, the manufacturing process of double carbide, double nitride and double carbonitride is more complicated than the manufacturing process of carbide, nitride and carbonitride, and the reaction temperature for forming the compound is high,
As a result, the prices of double carbide, double nitride and double carbonitride powders are higher than the prices of carbide, nitride and carbonitride powders.

As a method of forming the double nitride, the double carbonitride, the nitride, and the carbonitride, for example, by using a means of bringing pressurized nitrogen gas into contact with molten steel before atomizing the base powder, nitrogen It is also effective to form a part or all of the solid solution in the matrix powder in advance and to react it with the double carbide, double carbonitride, carbide, carbonitride, etc. added during sintering. In this case, the chemical composition of the base powder is 0.02 to 0. 0% by weight of nitrogen (N) within the range of each element described above.
The content is about 5%. A desirable range is 0.1 to 0.25%.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Dispersion of double carbide, double nitride, double carbonitride particles and carbide, nitride, carbonitride particles is the most important constituent requirement in the present invention. This is because, in the present invention, by adding these, it is possible to obtain a material having high hardness of HRC71 or higher and having high strength and high toughness at the same time. Here, if the addition amount of double carbide, double nitride and double carbonitride is less than 1%, this effect is not sufficient, and conversely, if it exceeds 10%, the sinterability deteriorates. It is necessary to make 1 to 10% in total of one kind or two or more kinds of compound and double carbonitride. For carbides, nitrides, and carbonitrides added at the same time, if the addition amount is less than 1%, this effect is not sufficient.
On the other hand, if it exceeds 10%, the sinterability decreases, so carbides,
1 to 10 in total of 1 or 2 or more of nitrides and carbonitrides
%.

The action of each element in the present invention other than the above-mentioned nitrogen, double carbides and the like and carbides and the reasons for limiting the numerical values will be described below. C is added at the same time W, M
Combined with o, V, etc., it forms a hard carbide, and has the effect of enhancing wear resistance. In addition, some of them have a solid solution in the matrix to increase the hardness of the matrix and also have the effect of improving wear resistance. Therefore, there is an optimum C content in consideration of the addition amounts of carbide forming elements such as W, Mo, and V. Within the scope of the present invention, C is
If it is less than 1.0%, the hardness of the matrix is not sufficiently obtained, and the amount of carbide formed is small. On the other hand, if it exceeds 4.5%, the toughness deteriorates, so C must be 1.0 to 4.5%. Si has the effect of improving the steel quality as a deoxidizing element. Further, there is also an effect of increasing the hardness of the base by forming a solid solution in the base. But 2.0%
If it exceeds 1.0, the toughness decreases, so Si must be 2.0% or less.

Mn also has a deoxidizing effect and further has an effect of enhancing hardenability, so that it is contained in an amount of 2.0% or less. Especially when the above Si content is high, ferrite is stabilized,
Since the adverse effect of Si that raises the A ₁ transformation point can be mitigated by Mn, Mn is 2.0% or less, preferably in the range of 0.25 to 2.0%.
It is good to contain. Cr has the effect of forming carbides and increasing wear resistance, and further forms a solid solution with the substrate to impart hardenability and also improves the corrosion resistance of the matrix. If Cr is less than 3%, the above effect is small, and if it exceeds 10%, the hardness is difficult to obtain by heat treatment.
Must be%. W and Mo combine with C to form M ₆ C-type carbides, which are important for improving wear resistance and seizure resistance, and some of W and Mo are dissolved in the matrix. Later, it is also precipitation hardened by tempering, which also has the effect of increasing the hardness of the matrix. W 30% or less, Mo 20% or less 1
One or two types have a W + 2 Mo content of more than 45%, the toughness is remarkably reduced, so the W + 2 Mo content needs to be 45% or less. The amount of W + 2Mo is preferably 18 to 40%, more preferably 25 to 40%.

Co has the effect of forming a solid solution in the matrix to increase the hardness of the matrix. However, if Co exceeds 20%, the toughness decreases, so the Co was made 20% or less. V and Nb combine with C to form MC type carbides. If this carbide is finely and uniformly dispersed, the wear resistance and seizure resistance can be greatly improved. As a result of various studies on the amounts of V and Nb added, the amount was set to 2 to 10%, and the amount of double carbide, double nitride, and double carbonitride as dispersed particles was set to 1 to 1 as described later.
It was found that good characteristics were obtained when the amount of carbides, nitrides, and carbonitrides added at the same time was 0 to 10%. If the content of V or Nb in the matrix is less than 2%, the effect is not sufficient, and if it exceeds 10%, the toughness decreases, so the content must be 2 to 10%.

[0017]

EXAMPLES The present invention will now be described in more detail with reference to examples. (Example 1) C 3.03%, Si 0.41%, Mn 0.29%, Cr 4.22%, W
10.18%, Mo 7.90%, V 8.53%, Co 7.79% Water atomized powder consisting of steel composition with the balance Fe was prepared and
It was crushed in. To this matrix powder, various double carbides, double nitrides, double carbonitrides and carbides, nitrides and carbonitrides shown in Table 1 were added, mixed and granulated, and then a pressure of ² tf / mm ² was applied. And press-molded to obtain a molded body. After degreasing this molded body, vacuum sintering was performed at 1200 to 1250 ° C to produce a sintered body. After annealing the sintered body, quench it at 1240 ℃, 560
Tempering was carried out 3 times at ℃ × 1 hour. Then, after that, hardness (HRC), transverse rupture strength, and absorbed energy were measured. Here, the absorbed energy is the energy added to the test piece at the time of measuring the transverse rupture strength, and is a value representing the toughness. Table 1 shows the measurement results.

[0018]

[Table 1]

Here, the ratios of metal elements and C, N in the table
All ratios are weight ratios. From Table 1, hardness HRC70 cannot be obtained when no carbides are added (No. 1) or when it is added too little (Nos. 10 and 17), and when carbides are a single element (Nos. 8, 9 and 10). 26), or when the added amount of double carbides or carbides is too large (No. 15, 16, 2)
2, 23), the transverse rupture strength and the absorbed energy are extremely low. On the other hand, one or more double carbides, double nitrides, and double carbonitrides composed of a plurality of metal elements of group IVa, group Va, and group VIa corresponding to the present invention and group IVa,
Carbides, nitrides and carbonitrides of Va group and VIa group elements 1
When an appropriate amount of one kind or two or more kinds is added in combination, hardness HRC71 or more, bending strength 200kgf / mm ² or more, absorbed energy
It can be seen that a sintered body having excellent characteristics of 200 kgfmm or more can be obtained.

(Example 2) Water atomized powders A to I consisting of 11 kinds of steel compositions shown in Table 2 were prepared, and double carbides having an average particle size of 1 to 3 μm and carbides shown in Table 3 were prepared. After mixing at a ratio shown in Table 1 and drying, press molding was performed at a pressure of 1.5 tf / mm ² , degreasing, and vacuum sintering at 1200 to 1250 ° C. to produce a sintered body. After annealing the sintered body, 1240 ℃
And tempered at 560 ° C. for 1 hour, and then tempered 3 times. Hardness (HRC), transverse rupture strength, absorbed energy
Was measured and the results are shown in Table 3. Among the water atomized powders shown in Table 2, Table 3 shows representatively A, A ', B and B'.

[0021]

[Table 2]

From Table 3, no carbides are added (No. 1, 1
In the case of 0) or under-addition (No. 14), HRC70
If the hardness is not obtained and the addition amount of the double carbides and the carbides is too large (No. 17), the transverse rupture strength and the absorbed energy are remarkably low, whereas the IVa group corresponding to the present invention,
One or more of double carbides, double nitrides, and double carbonitrides composed of a plurality of metal elements of Va group and VIa group elements, and carbides and nitrides of IVa group, Va group, VIa group element When one or two or more carbonitrides are added in an appropriate amount, a sintered body having excellent properties having a hardness of HRC71 or more, a bending strength of 200 kgf / mm ² or more, and an absorbed energy of 200 kgfmm or more is obtained. You can see that

[0023]

[Table 3]

[0024]

As described above, according to the present invention,
In sintered cemented carbide containing hard particles, IVa group, Va group
Compound carbides, compound nitrides and compound carbonitrides composed of a plurality of metal elements of Group VIa group VIa elements, and IVa
By adding the carbides, nitrides, and carbonitrides of Group III, Va, and VIa elements in combination, the strength and toughness can be improved as compared with the conventional case where only the single element carbides, nitrides, and carbonitrides are used. Can be greatly improved. As a result, the sintered cemented carbide of the present invention can significantly improve the fracture resistance as a cutting tool, and is extremely useful for expanding the applications of the sintered cemented carbide as various other molds and jigs. It is valid.

Claims (2)

[Claims] 1. C 1.0 to 4.5% by weight, Si 2.0% or less,
Mn 2.0% or less, Cr 3 to 10%, W 30% or less and Mo 20% or less, 1 type or 2 types with W + 2Mo, 45% or less, 1 or 2 types of V and Nb, 2 to 10%, Co 20% A base powder having a composition consisting of the balance Fe and unavoidable impurities, including the following: 1 to 10% of group IVa, Va, VI with respect to the total weight of the base powder.
One or more kinds of double carbides, double nitrides, and double carbonitrides composed of a plurality of metal elements of the group a elements, and 1 to 10% of group IVa with respect to the total weight of the base powder. , V
Carbides, nitrides and carbonitrides of group a and VIa elements 1
A sintered cemented carbide, characterized in that it is a mixture of two or more kinds and they are combined by sintering. 2. The sintered cemented carbide according to claim 1, wherein the double carbide, the double nitride and the double carbonitride contain W.