JPH0941102A - Sintered head alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a sintered head alloy excellent in strength and toughness, used as material for jigs tools, such as cutting tool. SOLUTION: This sintered hard alloy is produced by mixing 1-10wt.%, based on the total weight, of the grains of one or >=2 kinds selected from carbides, nitrides, and carbonitrides with a matrix powder having a composition consisting of, by weight, 1.0-4.5% C, <=2.0% Si, <=2.0% Mn, 3-10% Cr, <=30% W and/or <=20% Mo in the range satisfying W+2Mo<=45%, 2-10% of V and/or Nb, <=20% Co, and the balance Fe with inevitable impurities and binding the resultant mixture by sintering. Further, in this sintered hard alloy, the carbides, carbides, nitrides, and carbonitrides are constituted from plural metallic elements among the group IVa, Va, and VIa elements and are preferably W-containing double carbides, double nitrides, and double carbonitrides.

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, and a tap, a mold for metal plastic working, a tool and a jig, a mold and a tool for resin molding, various blades, The present invention also relates to 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 Nos. 55-6096 and 57
-2142, JP-A-57-181367, JP-A-5-5
No. 8-181848 discloses a high-hardness sintered alloy capable of obtaining a hardness of HRC71 or higher. These alloys contain a large amount of alloying elements such as W and Mo that form M ₆ C carbides, and V that form MC carbides, or further contain a large amount of hard substances such as TiN. Higher costs, lower toughness, and lower grindability are major problems. Therefore, Japanese Patent Publication No. 5-75821 and Japanese Patent Publication No. 5-75822 are known to solve these problems.

These are all Ceq = 0.06Cr
When + 0.033W + 0.063Mo + 0.2V, by setting higher carbon than 0 ≦ C−Ceq ≦ 0.6 and Ceq, and by dispersing a relatively small amount (2 to 12%) of hard particles. The hardness after heat treatment is HRC 72 or more, which is extremely high hardness. The alloy disclosed in Japanese Patent Laid-Open No. 2-125848 by the present inventors is Ti
It is a hard alloy having a fine structure in which N particles and carbides have an average particle size of 5 μm or less and an average particle gap of 5 μm or less, and are particularly alloys excellent in mechanical properties and grindability. Furthermore, in Japanese Examined Patent Publication No. 5-55587, more than 10% to 2
Dispersion strengthened sintered alloy hot working tool with 5% dispersed phase consisting of composite metal carbonitride of two or more metals selected from Ti, Zr, Hf, Ta, Nb, V and W A member is disclosed.

[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 sintered hard alloy, 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 is It is said that it will spread greatly. 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 is lowered, so the sintering temperature is raised (specifically 1250 ° C or higher). It is necessary. Therefore, there is a cost disadvantage.

The present inventor has solved the above-mentioned conventional drawbacks,
Various examinations were carried out to increase the strength and toughness by applying ordinary sintering temperature. Then, as the hard particles as dispersed particles, carbides, nitrides, and carbonitrides are not composed of a single metal element as in the conventional case, 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 carbonitrides, and have accomplished the present invention. 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,
C 1.0-4.5%, Si 2.0% or less, Mn 2.0% or less, Cr3
~ 10%, W and Mo are W30% or less, Mo 20% or less 1 or 2 types with W + 2Mo 45% or less, V and Nb 1 or 2 types 2-10%, Co 20% or less. Base powder having a composition containing the balance Fe and unavoidable impurities is mixed with 1 to 10% of the total weight of one or more particles selected from carbides, nitrides and carbonitrides, and baked. In a cemented sintered cemented carbide, a carbide, a nitride, and a carbonitride are a double carbide, a double nitride, and a double carbonitride in which a carbide, a nitride, and a carbonitride are composed of a plurality of metal elements of the IVa group, the Va group, and the VIa group. It is a sintered cemented carbide with excellent strength and toughness.

In the present invention, the carbides, nitrides and carbonitrides to be mixed with the matrix powder are not composed of a conventional compound of a single metal element and carbon or nitrogen, but a plurality of metals. It is characterized in that it is a double carbide, a double nitride, and a double carbonitride composed of elements, and the advantages thereof are as described below. (1) It is possible to eliminate the defects while making the best use of the characteristics of each carbide, nitride, and carbonitride. For example, W is added to Ti carbonitride called Ti (C, N) (T
i, W) (C, N) takes into account the high toughness characteristic of W, and it becomes possible to improve the toughness and strength of the hard alloy added as dispersed particles.

(2) A compound which is unstable and cannot be applied by itself as a compound on the structure becomes stable and applicable by compounding with another metal element. For example, WN, M
In the case of a nitride such as oN, the standard free energy of formation is positive and normally cannot exist stably. However, it can be applied as a stable compound by forming a complex solid solution with Ti, Ta and the like. .

(3) Those which cannot be left in the alloy as dispersed particles because they are easy to react or form a solid solution by themselves and can be prevented from reacting or forming a solid solution by forming a composite carbide of a solid solution and exist as dispersed particles. It is possible to let For example, when WC is added, it reacts with a matrix or the like to change the WC into M ₆ C type carbide and does not remain as a single particle, but it is stabilized and dispersed by using (W, Ti) C. It can be a particle.

(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 depending on the types and proportions of the composite metal in combination with the amounts of C and N, and the combination of characteristics is greatly expanded, and the characteristics can be freely selected according to the purpose.

As described above, the metal forming the carbide, the nitride and the carbonitride is not composed of a single metal element as in the prior art, but a double carbide or a composite nitride composed of a plurality of metal elements. A hard alloy having various properties can be obtained by using the compound and the double carbonitride. However, in the case where the dispersed particles which are the above-mentioned hard substance include W, the double carbide (for example, (( T
The high toughness and elastic modulus of WC which occupies a part of (i, W) (CN)) can be utilized, and a hard alloy having particularly excellent properties can be obtained. In addition to these, addition of a conventionally used single element carbide, nitride, or carbonitride together should not be restricted. This is because these compounds also have the potential of forming a compound compound. Carbonitride,
As a method of forming a nitride, a double nitride, and a double carbonitride, for example, by contacting pressurized nitrogen gas with molten steel before atomizing the base powder, a part or all of nitrogen is preliminarily contained in the base powder. Means for forming a solid solution and reacting it with a carbide, a carbonitride, or a double carbide added during sintering is also effective. In this case, the chemical composition of the base powder is 0.02 to 0.5% by weight of nitrogen (N) within the range of each element described above.
It will be included to some extent. The preferred range is 0.
It is 1 to 0.25%.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Dispersion of double carbide, double nitride and double carbonitride particles is one of the most important constituent requirements in the present invention. This is because, in the present invention, by adding these, it is possible to obtain a material having a high hardness of HRC71 or higher and having both high strength and high toughness. Here, if the addition amount of the double carbide, the double nitride and the double carbonitride is less than 1%, this effect is not sufficient, and if it exceeds 10%, the sinterability is deteriorated.
It is necessary to make the total of 1 type or 2 or more types 1 to 10%.
In the above-mentioned sintered body of Japanese Patent Publication No. 5-55587, the addition amount of hard particles exceeds 10%, so the sintering temperature is 1250 to 1
Sinterability is not guaranteed unless the temperature is high at 280 ℃. Also,
If the added amount is large, the strength will decrease, so the limit is 10%.

The action of each element in the present invention other than N described above and the reasons for limiting numerical values will be described below.
C combines with W, Mo, V, etc. added at the same time to form 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. In the composition range of the present invention, when C is less than 1.0%, the hardness of the matrix is not sufficiently obtained, and the amount of carbide formed is small. vice versa
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. However, if it exceeds 2.0%, the toughness decreases, so S
i must be 2.0% or less. Mn also has a deoxidizing effect and further has an effect of enhancing hardenability, so 2.0%
It is contained below. Especially when the above Si content is high, Si that stabilizes ferrite and raises the A ₁ transformation point
Since the adverse effect of Mn can be mitigated by Mn, it is preferable to contain Mn in an amount of 2.0% or less, preferably 0.25 to 2.0%.

Cr has the effect of forming carbides to enhance wear resistance, and further forms a solid solution with the substrate to impart hardenability,
It also improves the corrosion resistance of the base. If Cr is less than 3%, the above effect is small, and if it exceeds 10%, it is difficult to obtain hardness by heat treatment. Therefore, it is necessary that Cr is 3 to 10%. W and Mo are combined with C to form M ₆ C
It is important for forming carbides in the mold and improving wear resistance and seizure resistance. Further, some of W and Mo are solid-solved in the matrix during quenching, and then are precipitation hardened by tempering, which also has the effect of increasing the hardness of the matrix. One or two of W 30% or less and Mo 20% or less has a W + 2Mo content, and if it exceeds 45%, the toughness is remarkably reduced, so the W + 2Mo 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 Co was set to 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 addition amounts of V and Nb, when 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 10% as described later. It has been found that excellent characteristics can be obtained. If the content of V and 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 2-10%. In the present invention, V, N
In addition to the method of preliminarily containing one or two kinds of b in the matrix powder, carbides such as VC and NbC may be used as dispersed particles at the same time as one or more kinds of carbides, nitrides and carbonitrides. It is also possible to adopt an addition method in which both are added and the total amount becomes 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
A water atomized powder having a steel composition of%, balance Fe was prepared and pulverized with an attritor. For this base powder,
Various types of double carbides, double nitrides, double carbonitrides and carbides, nitrides, carbonitrides shown in Table 1 were added, mixed and granulated, and then press-molded at a pressure of 2 tf / mm2 to obtain a molded body. Obtained. After degreasing this molded body, vacuum sintering was performed at 1200 to 1250 ° C to produce a sintered body. After the sintered body was annealed, it was quenched at 1240 ° C. and tempered three times at 560 ° C. for 1 hour.
Then, after that, hardness (HRC), transverse rupture strength, and absorbed energy were measured. 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 without addition of carbides (No. 1) or with too little addition (No. 10), and when carbides are single elements (No. 8, No. 9). ,
No. 19) or when the addition amount of double carbide is too large (No. 1)
5, No. 16) has extremely low transverse rupture strength and absorbed energy. On the other hand, applicable to the present invention, when using an appropriate amount of one or two or more of double carbide, double nitride and double carbonitride, hardness HRC71 or more, transverse rupture strength 200 kgf / mm ² or more, absorption It can be seen that it is possible to obtain a sintered product having excellent properties with an energy of 200 kgfmm or more.

(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 diameter of 1 to 3 µm shown in Table 3 were prepared at the ratios shown in the same table. After mixing, drying, press molding under 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, quench at 1240 ℃,
It was tempered 3 times at 560 ° C for 1 hour. The hardness (HRC), transverse rupture strength, and absorbed energy of this sintered product were measured, and the results are shown in Table 3. Table 3 shows that among the water atomized powders shown in Table 2, A, A ′, B and B'are displayed as a representative.

[0021]

[Table 2]

[0022]

[Table 3]

From Table 3, in No. 1 and No. 10 in which the double carbide is not added and No. 13 in which the addition amount is small, the hardness of HRC70 is not obtained, and the addition amount is too large. In No. 17, the transverse rupture strength and the absorbed energy are remarkably low, while the hardness HRC7 when the appropriate amount of the double carbonitride corresponding to the present invention is used.
1 or more, transverse strength 200 kgf / mm ² or more, absorbed energy 200 kgf
It can be seen that it is possible to obtain a sintered product having excellent characteristics of mm or more.

[0024]

As described above, according to the present invention,
In a sintered cemented carbide containing hard particles, carbides, nitrides and carbonitrides that are hard particles added as dispersed particles are composed of a plurality of metal elements of IVa group, Va group and VIa group elements. By using a carbide, a double nitride, or a double carbonitride, strength and toughness can be significantly improved as compared with the case of using a conventional single element carbide, nitride or carbonitride. As a result, the sintered cemented carbide of the present invention can greatly improve the fracture resistance as a cutting tool, etc., and is extremely useful for expanding the applications of the sintered cemented carbide as various molds and jigs. It is valid.

Claims (2)

[Claims] 1. C 1.0-4.5% by weight%, Si 2.0% or less,
Mn 2.0% or less, Cr 3 to 10%, W 30% or less, 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 comprising the balance Fe and unavoidable impurities, including the following, and one or more kinds selected from 1 to 10% of carbide, nitride and carbonitride based on the total weight of the base powder. In the cemented carbide, which is obtained by mixing the above particles with each other and combining them by sintering, the carbide, nitride and carbonitride are IVa group, Va group, VI group.
A sintered cemented carbide, which is a double carbide, double nitride, or double carbonitride composed of a plurality of metal elements of the group a elements. 2. The sintered cemented carbide according to claim 1, wherein the compound of any of double carbide, double nitride and double carbonitride contains W.