JPS61147841A - Hyperfine-grained sintered hard alloy - Google Patents

Abstract

PURPOSE:To improve the wear resistance and toughness of a sintered hard alloy composed of a hard phase consisting of WC and (TiW)CN having a B-1 type crystal structure and a binding phase consisting of Co-base Fe group metals by regulating the amount of N in the hard phase so that specified conditions are satisfied. CONSTITUTION:A sintered hard alloy is composed of 75-90wt% hard phase consisting of WC and (TiW)CN having a B-1 type crystal structure and 10-25wt% binding phase consisting of Co-base Fe group metals. The amount of N in the moiety of the carbides and/or nitrides of Ti and/or W in the hard phase is regulated so that 5/100-15/100 molar ratio of (TiC+TiN)/(TiC+TiN+ WC) and 10/100-50/100 molar ratio of TiN/(TiC+TiN) are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a WC-based sintered alloy suitable for tools for turning steel, particularly solid end mills.

[Conventional technology]

The WC-based sintered alloy includes TiC-based sintered alloy (hereinafter referred to as cermet), At'zO* sintered alloy (hereinafter referred to as ceramics), TiC, and TiN.

8! compared to surface-coated alloys (hereinafter referred to as coating alloys) with coating layers such as TiN C and Alzos.
Due to its excellent mechanical strength and thermal fatigue resistance, cermets, ceramics, and coated alloys are especially useful in machining fields where rotating tools are subject to repeated stress and thermal fluctuations are applied to the cutting edge of the tool. ing.

However, recently, even in these fields, working conditions have become more efficient, and demands for improved tool life are increasing.

[Problem that the invention seeks to solve]

WC in the hard phase of WC-based sintered alloy has high mechanical strength (
Although it has the characteristic of high thermal conductivity, it has poor properties such as stability against reaction with iron and oxidation resistance at high temperatures, so combining it with TiC, which has excellent properties, improves wear resistance during cutting. It is well known that it improves. However, since TiC has low mechanical strength and low thermal conductivity, there is a problem that cutting toughness decreases as the amount added increases.

The present invention provides a means for increasing strength by dispersing and strengthening WC particles by making WC particles finer, such as the micro-particle alloy (hereinafter referred to as micro-alloy) that is widely used in solid end mills, drills, etc. By applying this to composite carbonitrides, we have created a microalloy that minimizes the decrease in strength of the microalloy, has an optimized composition, has excellent thermal fatigue resistance, welding resistance, toughness, etc., and can maintain a long tool life. The purpose is to provide

[Means for solving problems]

The present invention has a WC and B-1 type crystal structure (TiW
) In the hard alloy composed of a hard phase consisting of CN and a binder phase consisting of a Fe group metal mainly composed of Co, in the carbide and/or nitride portion of Ti and/or W among the components of the hard phase. (TiC+TiN)/ (Ti
C+TiN+WC) ratio (molar ratio) is 5/100 to 15
/100, and TiN/(TiC+Ti
The hard phase accounts for 75% of the total amount of the alloy.
90% by weight, and the binder phase mainly composed of Co accounts for 10 to 25% by weight.

[For production]

When TiN is added, TiC,
A solid solution reaction occurs with WC to form B-1 type solid solution (TiW)CN.
Refine particles. Furthermore, the solid solution of W into the crystal phase progresses steadily, significantly increasing thermal fatigue resistance, toughness, etc.

In the alloy of the present invention, (T iC + T iN ) /(
TiC+TiN+WC) ratio (mole ratio) from 5/100
The reason for limiting the range to i 5/100 is that this ratio is 5/100.
If it is less than 100, no effect of addition is seen, and 15/10
This is because if it is added in excess of 0, the B-1 type solid solution becomes substantially large and the strength of the alloy is seriously reduced.

Also, the ratio (molar ratio) of TiN/(TiC+TiN) is
The reason for limiting it to the range of 10/100 to 50/100 is
If it is less than 10/100, no effect of addition can be seen;
If it is added in excess of /100, the sinterability will deteriorate and the strength of the alloy will deteriorate.

When 0.5 to 15% of NbC is substituted with one or two types, T
The practical effect of the addition of iN is further promoted, and B-1
Contributes to increasing the strength of the mold solid solution phase and suppressing particle coarsening. However, if the amount of substitution exceeds 15% by weight, the strength decreases and it cannot be put to practical use.

Note that although V, Cr, etc. are added to general microalloys in order to suppress coarsening of particles, there is no problem even if they are used in combination with the B-1 type solid solution phase.

〔Example〕

Next, the microalloy of the present invention will be explained using examples.

(Example 1) Commercially available WC powder (average particle size 0.7 μm), T1CN powder (TiN/(TiC+TiN) ratio 1/10° 2/10.
3/10.4/10.5/10.6/10) (average particle size 1.O#a+) and Co powder (average particle size 1°3μm) were mixed with the composition shown in Table 1 and then molded. , sintering was performed at 1350° C. for 1 hour.

The hardness, transverse rupture strength, and fracture toughness value (K + c) of the obtained alloy were measured.

In addition, an 8φ, 2-flute solid end mill was manufactured and a cutting test was conducted under the following conditions. The results are shown in Table 2.

Work material SCM440 (Hs 40)
Cutting speed 45m/win Feed 0.02a+m/blade
.

Depth of cut 8emm During cutting 41 Cutting Oil Oil-based cutting method One-sided cutting Cutting length 5 wheels As a result of cutting under the above conditions, the one that does not contain B-1 total solid solution (NO, 1) reached the end of its life due to boundary wear. On the other hand, those containing the entire B-1 solid solution (NO, 2 to 6) had less boundary wear and a good finished surface. Furthermore, when the B-1 total solid solution was increased, chipping increased in both the stationary region and the boundary region due to insufficient strength.

(Example 2) Using the same powder as in Example 1, the composition shown in Table 3 was mixed and then molded, followed by sintering at 1350° C. for 1 hour.

The hardness, transverse rupture strength, and fracture toughness value (K+c) of the obtained alloy were measured.

In addition, an 8φ, two-flute solid end mill was manufactured, and a cutting test was conducted under the same conditions as in Example 1. The results are shown in Table 4.

As described above, the addition of TiN increases the effect of suppressing particle coarsening, and improves the welding resistance of the alloy.
Chipping is also reduced.

However, as the TiN ratio increases, the wear resistance of the B-1 type solid solution itself deteriorates, and the wear resistance of the alloy itself also deteriorates.

(Example 3) The same powder as in Example 1 and further Ta(Nb)C powder (average particle size 1 μl) were mixed with the composition shown in Table 5, then molded, and sintered at 1350°C for 1 hour. I did it.

When measuring the physical properties of the obtained alloy,
A solid end mill with single blades was manufactured and a cutting test was conducted under the same conditions as in Example 1. The results are shown in Table 6.

As described above, the addition of Ta(Nb)C improves the wear resistance, impact resistance, and chipping resistance of the alloy.
The synergistic effect with TiN becomes even more pronounced.

(Example 4) Invention alloy NO, 14, 16 shown in Table 5 of Example 3 and commercially available microalloy A (BalWc-2,0
%TaC-14%Co)Original B (BalWC-6,0
%TiC-6%TaC-14%Co), and cutting tests were conducted under the following conditions using an 8φ two-flute solid end mill made of these alloys.

The results are shown in Table 7.

As seen in Table 7, it can be seen that the products using the alloy of the present invention are superior to commercially available products in both wear resistance and toughness.

Work material 80M440 (Hs 40)
Cutting conditions (using cutting oil) ■=30IIl/IIin Ad=8um Rd=0.5aim fz=0.02ma+/blade [Effects of the invention] As described above, the alloy of the present invention has excellent wear resistance, toughness, etc. It has excellent properties, and tools such as solid end mills manufactured using this method have a long lifespan, so it has great industrial effects.

Claims (3)

[Claims] (1) (TiW)C with WC and B-1 type crystal structure
In a cemented carbide composed of a hard phase consisting of N and a binder phase consisting of an Fe group metal mainly composed of Co, in the carbide and/or nitride portion of Ti and/or W among the components of the hard phase, ( TiC+TiN)/(TiC+T
iN+WC) ratio (molar ratio) is 5/100 to 15/10
0 and the ratio (molar ratio) of TiN/(TiC+TiN) is in the range of 10/100 to 50/100, and these hard phases account for 75 to 90% by weight of the total amount of the alloy. , the Co-based binder phase is 1
An ultrafine particle cemented carbide characterized by comprising 0 to 25% by weight. (2) In claim 1, a part of the hard phase is 0.5 to 15% by weight of one or both of TaC and NbC.
An ultrafine particle cemented carbide characterized by substitution. (3) In claim 1, both the WC phase and the B-1 type solid solution hard phase present in the final sintered body have an average particle size of 1.
An ultrafine cemented carbide characterized by a particle size of μm or less.