JPS5952951B2 - cemented carbide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cemented carbide for use in cutting, large side cutters, and hobs having high toughness, excellent crack damage resistance, and plastic deformation resistance.

WC-based sintered alloys are TiC-based sintered alloys (hereinafter referred to as cermets), A1□03-based sintered alloys (hereinafter referred to as ceramics), TiC, TiN, T1CN, AI□03, etc., with a hard coating layer on the WC base. Compared to surface-coated alloys applied to the surface of sintered alloys (hereinafter referred to as coated alloys), mechanical strength,
Cermet, ceramic,
It is widely used in fields where coated alloys cannot withstand use.

In particular, large side cutters and hobs are subject to large impact forces,
In the field of steel milling where thermal fluctuations cause damage to the tool cutting edge,
It shows its characteristics to a great extent.

However, recently, even in these fields, working conditions have become more efficient, and there is an increasing demand for further improvement in tool life.

The present invention relates to a WC-based sintered alloy that has significantly improved thermal fatigue properties and impact toughness in order to meet these demands and is particularly suitable for steel milling such as large side cutters, hobs, and heavy cutting cutters.

The cemented carbide according to the present invention is characterized by B containing composite carbonitrides.
In order to maximize the thermal fatigue properties, impact toughness, and wear resistance during high-speed cutting in a WC-based sintered alloy in which the hard phase consisting of an L-type solid solution and a WC phase is composed of a Fe-group bonded metal,
The aim is to optimize the combination of these configurations.

WC in the hard phase has the characteristics of high mechanical strength and high thermal conductivity, but these properties have poor stability against reactions with iron at high temperatures and oxidation resistance. It is well known that wear resistance during cutting can be improved by combining TiC with excellent properties.

On the other hand, since TiC has low mechanical strength and low thermal conductivity, it is also known that increasing the amount added tends to reduce cutting toughness.

Furthermore, it is known that a cemented carbide with high toughness and high impact toughness can be obtained by containing N in a TiN/TiC ratio of 0.1 to 0.60.

The inventors further continued research on these sintered cemented carbide alloys, and as a result, they came up with a cemented carbide that exhibits particularly excellent performance in high-speed interrupted cutting of steel.

In particular, the hardness of the steel that is the work material is 20 on the Brinell hardness H8.
When the alloy becomes hard to 0 or more, the alloy of the present invention is
This significantly exceeds the performance of the alloy shown in No. 953.

That is, in a cemented carbide composed of a hard phase consisting of WC and a Bl type solid solution and a binder phase consisting of an Fe group metal mainly composed of Co, among the components of the hard phase, Ti, w carbides, nitrides, The carbonitride part is TiC+TiN/Ti
Converting to C1TiN + WC ratio, the volume ratio is 0.4
It is in the range of 0 to 0.80, and the Bl type solid solution is TiN/T.
iC+ TiN ratio, or (TiW) N/(TiW
) C10 (TiW) Converted to N ratio, weight ratio is 0.
Cemented carbide containing N in the range of 1 to 0.60 and having a Co-based binder phase that accounts for 7 to 20% of the total volume of the final alloy has a higher cutting speed than conventional cemented carbide. It was found to have excellent wear resistance, toughness, and heat cracking resistance, making it ideal for side cutters, hobs, etc.

The reasons for this limitation will be explained below.

Among the components of the hard phase, the carbides, nitrides, and carbonitrides of Ti and W are TiC+ TiN/TiC+ TiN +
In terms of WC ratio, if the volume ratio is less than 0.40, the wear resistance is insufficient, especially when cutting high hardness steel with HB200 or more, and if it is more than 0.8, chipping is likely to occur due to lack of strength. , short tool life.

Next, the Bl type solid solution will be described.

TiN/TiC+ TiN ratio or (TiW) N
/(TiW) C+ (TiW) N When the weight ratio is 0.1 or less, the heat cracking resistance and toughness are poor.

That is, if it is less than 0.1, the size of the Bl-type solid solution crystals in the alloy will grow large, causing performance deterioration.

Conversely, by adding N, grain growth during sintering of the Bl-type solid solution is significantly suppressed, which provides high performance in this application.

If the hardness exceeds 0.6, sinterability will be inhibited and both wear resistance and toughness will be insufficient.

When the average grain size of the B1 type solid solution hard phase in the cemented carbide of the present invention is 2 μm or less, the heat cracking resistance is particularly excellent.

Note that in order to maintain the strength of the cemented carbide of the present invention, C
If the amount of the bonding metal mainly composed of O is less than 7% by volume, the toughness will be insufficient, and if it is more than 20% by volume, the wear resistance will deteriorate, which is not preferable.

Note that even if oxygen is contained in the B1 type solid solution in the cemented carbide member of the present invention, the effects of the present invention do not change.

Further, even if WC is replaced with (MoW)C, the effects of the present invention do not change.

Furthermore, TiC and T1CN are added to the surface of the alloy of the present invention.

Needless to say, it is effective as a base material for coated carbide tools coated with a hard phase such as TiN, Al2O3, HfC, etc. in one layer or in multiple layers.

This will be explained below using examples.

[Example 1] The raw materials were blended according to the composition shown in Table 1, 1.5% by weight of paraffin was added as a press aid, and a container made of 18-8 stainless steel and a ball made of WC-Co sintered alloy were mixed. using
Ball mill mixing was performed in acetone for 120 hours.

After drying, a cutting tip was press-molded at a pressure of 1.5 t/cm□, and then kept in a vacuum at 420°C to remove paraffin, and then baked in a reduced pressure nitrogen atmosphere with a nitrogen surface partial pressure of 50 Torr. A sintered body was obtained by maintaining the sintering temperature at 1425° C. for 1 hour.

Alloy properties and cutting test results are also listed in the table.

It was found that the product of the present invention is superior to comparative alloys.

[Example 2] (TiW) (CN) powder was produced by carbonitriding reaction using TiO2 powder and WO3 powder.

For this powder and the remainder, the raw materials used in Example 1 were used, and the third
An alloy with the composition shown in the table was prepared.

Ball mill mixing time is 100 hours, sintering temperature is 1380
It is ℃.

The properties of these alloys are shown in Table 3.

These prototype alloys and commercially available t7) WC-TiC-TaC-
The results shown in Table 4 were obtained by selecting Co alloy-based alloys with materials corresponding to JIS classifications PIO, P2O, and P30.

[Example 3] Using alloy F prepared in Example 1, a test was conducted using a large side cutter.

As comparative materials, a commercially available coated material equivalent to P30 and comparative alloy B were used.

Work material: 550C (HB260) Tool used: Large side cutter - 25 inches Cutting conditions: Cutting speed 176 m/min Depth of cut 2-5 mm Feed 0.316 mm/blade The invented product has a lifespan of 6 hours, while the commercial product P30 has a lifespan of 6 hours. Comparative Alloy B had a life of 4 hours.

[Example 4] Using alloy K prepared in Example 2, a brazing hob (module 1.25, pressure angle, number of cutting grooves 14) was manufactured and tested.

Cutting conditions Workpiece material: 545C (HB280) Cutting speed: 280 m/min Feed: 5 mm/rotation Cutting oil: Water-insoluble oil The present invention can cut 120 m, whereas commercially available cemented carbide P20
Chipping occurred due to thermal cracking at 5 m and P2O at 10 m.

[Example 5] When the hob of Example 4 was coated by the publicly announced CVD and PVD methods and a cutting test was conducted, the coated product of the present invention had an improved lifespan of 150 m, but the commercially available P2
0 coated product could not be cut even 1m.

Claims (1)

[Claims] I A cemented carbide composed of a hard phase consisting of a Bl-type solid solution of carbonitrides consisting of WC, Ti, and W, and a binder phase consisting of an Fe metal mainly composed of Co, in which the components of the hard phase are is decomposed into Ti, w carbides and nitrides (TiC+
Converted to TiN) / (TiC + WC + TiN) ratio, the volume ratio is in the range of 0.40 to 0.80, and the BL type solid solution has a TiN / (TiC + TiN) ratio or (TiW) N / (TiW) C + (TiW)N
Contains N in the range of 0.1 to 0.6 in terms of weight ratio, WC is 20 to 80% by weight in the entire alloy, and CO
A cemented carbide characterized in that a binder phase mainly composed of occupies 7 to 20% by volume of the final alloy body. 2. In the cemented carbide according to claim 1, the Bl type solid solution hard phase present in the final sintered body has an average grain size of 2 μm.
Cemented carbide which is below. 3 Carbide composed of a hard phase consisting of a Bl-type solid solution of carbonitride consisting of WC and one or two selected from Ti, w, Ta, and Nb, and a binder phase consisting of Fe metal mainly composed of Co. In the alloy, the components of the hard phase are Ti,
Decomposes W as carbide and nitride (TiC+TiN)
/ (TiC + WC + TiN) The volume ratio is in the range of 0.40 to 0.80, and the Bl type solid solution is T
iN/(TiC+TiN) ratio or (TiW
) N/ (TiW) C (TiW) Contains N in the weight ratio range of O01 to 0.6 in terms of N ratio, WC is 20 to 80% by weight in the entire alloy, selected from Ta and Nb. 2 to 20% by weight of one or two of the above in the entire alloy,
CO-based binder phase accounts for 7-20% by volume of the final alloy body
Cemented carbide is characterized by having a ratio of . 4 In the cemented carbide according to claim 3, the Bl type solid solution hard phase present in the final sintered body has an average grain size of 2 μm.
Cemented carbide which is below.