JPS6043457A - Sintered hard alloy for cutting - Google Patents

Abstract

PURPOSE:To obtain a sintered hard alloy fit for dry and wet cutting conditions during cutting ranging from low speed to high speed by adding Nb carbide, Hf carbide, HfN, TaN, NbN, ZrN, Mo, Mo2C and an iron group metal to WC and TiC so as to provide a specified composition and a specified ratio of Nb carbide/Hf carbide. CONSTITUTION:This sintered hard alloy consists of, by weight, 10-60% WC, 5-40% TiC, 5-30% in total of Nb carbide and Hf carbide, 3-<20% in total of one or more among HfN, TaN, NbN and ZrN, 0.5-<5% Mo or Mo2C, and 5-20% iron group metal such as Co, Ni or Fe. In the alloy, the weight ratio of Nb carbide/Hf carbide is 1/10-10/3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cutting cemented carbide used for milling, turning, etc.

Conventionally, cemented carbide used for milling and the like include tungsten carbide-based and titanium carbide-based cemented carbide.

The former tungsten carbide-based cemented carbide has the disadvantage of greater crater wear compared to titanium carbide-based cemented carbide.

On the other hand, titanium carbide-based cemented carbide has higher hardness and better heat resistance than tungsten carbide-based cemented carbide, so it is widely used for high-speed cutting, but it has lower toughness than tungsten carbide-based cemented carbide. It has the drawbacks of poor mechanical patterning and poor thermal shock resistance. In addition, this titanium carbide-based cemented carbide has poorer thermal conductivity than tungsten carbide-based cemented carbide, and when the cutting edge is locally heated during cutting, the cutting edge may crack and break if rapidly cooled. .

As described above, the range of suitable cutting conditions for tungsten carbide black cemented carbide and titanium carbide based cemented carbide is considerably limited due to their respective drawbacks.

The present invention improves the drawbacks of the conventional tungsten carbide-based and titanium carbide-based cemented carbide, and can be applied to milling, etc., from low-speed cutting to high-speed cutting, and can be applied under both dry cutting and wet cutting conditions. It is also suitable for
The object is to obtain a cemented carbide for cutting that is easier to use than conventional cemented carbide for cutting.

The present invention has a weight ratio of tungden carbide of 10 to 60%,
81 m 5-30% titanium carbide, hafnium, tantalum.

3% or more and less than 20% of one or more nitrides of aluminum, zirconium, molybdenum or molybdenum carbide, 0.5% or more and less than 5% of molybdenum or molybdenum carbide, cobalt, nickel, iron, etc. It is characterized by consisting of 5 to 20% iron group gold fFja.

This composition has superior heat resistance compared to conventional titanium carbide-based cemented carbide alloys, increases hardness without significantly reducing transverse rupture strength, and can be adapted to a wide range of cutting conditions. can.

By the way, when cutting steel or high-grade cast iron, there is nothing that can match titanium carbide as an element for reducing secondary wear and cutting face wear. Therefore, it is advantageous to increase the proportion of titanium carbide as much as possible as far as wear is concerned, but on the other hand, various problems may occur due to the extremely low thermal conductivity of titanium carbide. In order to use titanium carbide efficiently, it is possible to use tungsten carbide, tantalum carbide, niobium carbide, hafnium carbide, etc. as a solid solution. It grows into large particles. The size of these particles is a major influence factor on tool wear.

However, by adding an appropriate amount of nitride, this grain growth can be inhibited. In other words, nitride suppresses the grain growth of solid solution particles often found in titanium carbide, making the crystal grains finer, while maintaining the nucleated structure with titanium carbide as the core, which is unique to titanium carbide-based cemented carbide. I can do it by doing something. In addition, nitrides generally have higher thermal shock resistance than titanium carbide, have a smaller coefficient of friction with steel, and have smaller heat generating bodies, resulting in improved thermal shock resistance than conventional titanium carbide-based cemented carbides. be done. In this way, the addition of titanium nitride makes the grains finer, resulting in higher hardness and significantly improved wear resistance, making it suitable for not only general dry milling but also wet milling. A cemented carbide can be obtained that rarely causes chipping or dipping, and has a relatively low titanium content and exhibits high machinability.

The content ω of titanium carbide and hard nitride is preferably within the above-mentioned ranges; if it exceeds this range, the toughness will be poor, and if it is below the above-mentioned range, sufficient heat resistance and wear resistance will not be achieved i%.

Here, the hard nitrides include HfN and TaN.

It is particularly essential that the material be selected from NbN and ZrN. The reason is as follows.

The main acid components of the alloy of the present invention are TiC and WC, but nitrides generally do not dissolve in WC, and nitrides mainly form a solid solution with TiC. In this case, 1-1F, 1 which is different from Ti metal
-Nitrides such as a, Nb, Zr etc. (7) Hard rf
If the formation of a J-body is avoided, the hardness will be sharply improved compared to a solid solution of TiC and TiN, resulting in poor cutting performance.

As mentioned above, hafnium carbide and niobium carbide are used to efficiently contain titanium carbide, but by using N11C and 1-1fc together, the wear resistance and high temperature properties of the alloy can be improved. The inventors have found that the deformation resistance is significantly improved at IC0, where the NbC/l-1fc weight ratio is 1/10 to 10/
A range of '3 is desirable; outside this range, the wear resistance is poor.

No significant improvement in deformation resistance can be expected.

Particularly in the present invention, what is noteworthy is the amount of molybdenum or molybdenum carbide added.

In other words, the inventors have discovered that molybdenum or molybdenum carbide has remarkable effects on two points: sinterability and deformation resistance at high temperatures.

It is already well known that the sinterability of TiC-Ni alloys is significantly improved by adding about half the amount of MO to the amount of Ni, but in systems where WC is added, only a very small amount of MO is added. However, as a result of various studies, the inventors discovered that the effect of improving sinterability is significant.

Furthermore, since hard nitrides are added to water-based alloys, the hard particles become very thin.As a result, although they have excellent toughness at room temperature, they have high deformation resistance and creep resistance when MO is not added. ) is confirmed to be inferior to

The inventors have discovered that MO dramatically improves the deformation resistance at high temperatures and, in turn, improves the wear resistance during cutting.

Here, the optimal amount of molybdenum or molybdenum carbide is 0
．． If it is 5% or more and less than 5%, if it is less than 0.5%, it will have little effect on improving sinterability, and if it exceeds 5%, the wear resistance against rubbing will decrease. The important point is to select the optimum amount of molybdenum or molybdenum carbide to be added within this range, and in this respect it should be clearly distinguished from Japanese Patent Publication No. 58-9137.

(above) By selecting the desired composition, it is possible to obtain the effect of lowering the resistance by 1Ω in both continuous cutting and interrupted cutting.

Example WC-10%TiC-5%ZrN-3,5%NbC
-3.5% fC - 3% MO2C - 12% Ni, mixed in a ball mill for 72 hours, then pressure molded and sintered at 1400°C. (Sample A) In addition, as a comparison material, Sample B to which no MO2C was added was also produced at the same time, and the two were compared. The transverse rupture strength value of sample A is 240 kg 71 m
2. Is it 180 for sample B? l/mm2, and MO
Sinterability was significantly improved by adding 2C.

In addition, when the strain rate under a stress of 72 kg/mm2 at 1000°C was measured, the strain rate of sample A was 0.0012
-4° x 107 minutes, sample B becomes 4,5x +o, l' minutes,
It was confirmed that the addition of MO2C significantly improved deformation resistance.

Next, 7 steps of cutting were performed using a lathe.

The cutting specifications are a cutting speed of 180 m/min and a depth of cut of 2 mm.

The feed was 0.3 mm, 7' rotation, and the workpiece was US CM 440.

After 25 minutes of cutting, the flank wear width on the specimen is O, OG n
The flank wear width of Sample B was 0.33 mn1.

As explained above, according to the present invention, a cemented carbide for cutting has improved bending strength at room temperature and improved deformation resistance at high temperatures. It is possible to obtain −C.

Claims (1)

[Claims] Tungsden carbide 10-60%, titanium carbide 5% by weight
・~40%, total of niobium carbide and hafnium carbide f55
~30%, total amount of one or more of HfN, TaN, NbN, ZrN, 3% or more 20%
Less than 0.5% of molybdenum or molybdenum carbide 5
Less than %, iron 71χ metals such as cobalt, nickel, iron, etc.5
- A cemented carbide for cutting, comprising ~20% of the component and having a weight ratio of niobium carbide/'hafnium carbide in the range of 1/'10 to 10/3.