JP2815533B2 - Cutting equipment for milling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a milling cutter having a tungsten carbide-based cemented carbide tip and a holder suitable for cutting, for example, stainless steel.

[0002]

2. Description of the Related Art Conventionally, a cemented carbide widely used as a metal cutting tip is a WC-Co alloy comprising a hard phase mainly composed of tungsten carbide and a binder phase of an iron group metal such as cobalt. Alternatively, a system is known in which a carbide, nitride, carbonitride, or the like of a metal of Groups 4a, 5a, and 6a of the periodic table is added to the WC-Co system. These cemented carbides are mainly used for cutting cast iron, carbon steel, etc. as cutting tool chips, but recently, applications to cutting stainless steel have been advanced. Since this stainless steel has excellent properties such as corrosion resistance, rust resistance, oxidation resistance, and heat resistance, it has been applied in a wide range of fields recently, and the amount of processing has been increasing year by year. In addition, it is said to be a representative of difficult-to-cut metal materials due to its properties of work hardening, low thermal conductivity, and high affinity with tool materials, and it is a problem in cutting, especially in the field of milling. There are many at present.

On the other hand, in a WC-Co cemented carbide,
Since the amount of carbon in the alloy is a factor largely affecting the properties of the entire alloy, fine control is performed in manufacturing.
Generally, the amount of carbon is added in such an amount as to have a stoichiometric composition as a carbide of each metal element, but when the amount of carbon is large, free carbon is precipitated in the alloy, and when the amount of carbon is small, Co ₃ W ₃ C, Co ₆
W ₆ C, Co ₂ W ₄ C, Co ₃ W ₉ C ₄ (hereinafter collectively referred to as cobalt tungsten carbide) and the like are precipitated. Generally, from the viewpoint of the properties of the alloy, a so-called sound structure that does not contain free carbon or cobalt tungsten carbide as described above is generally used for a chip. this is,
This is because free carbon and cobalt-tungsten carbide are likely to cause the fracture, and have been considered to lower the cutting characteristics of the insert.

[0004] On the other hand, Japanese Patent Publication No. 63-27421 proposes a cemented carbide in which the precipitation of Co ₃ W ₃ C is actively promoted, contrary to the conventional thinking. It has been proposed that the wear resistance of a machinable work material during cutting is improved.

[0005]

However, when cutting stainless steel with a conventional cemented carbide chip made of a healthy alloy, the chip wears rapidly, and defects that may be caused by welding occur. As a result, the condition of the machined surface of the work material deteriorates, the tool life is shortened within a short time, and there is a problem that good cutting cannot be performed.

Further, according to Japanese Patent Publication No. 63-27421, the mechanical strength of stainless steel is insufficient for cutting, and when used for a tool, chipping occurs during cutting, resulting in an early end of tool life. And good cutting characteristics have not been obtained.

Further, when the above-mentioned cemented carbide chip is used as a milling chip, the chip is mounted on a holder and used. The axial rake angle at this time is about 25 degrees or less. Is set. Generally, as the axial rake angle increases, the cutting resistance decreases and the deformation of the workpiece during cutting and the occurrence of chatter during cutting can be reduced.However, when the angle is excessively increased, the thickness of the tip edge becomes thinner. There is a problem that chips are easily broken. For example, recently, the work material tends to be thinner mainly for the purpose of weight reduction, and when the axial rake angle is larger than 25 degrees as described above, the cutting resistance increases, and the work material during cutting is increased. However, there is a problem in that the surface is deformed and chatter occurs during cutting, and the quality of the finished surface is deteriorated. Therefore, the axial rake angle is usually up to 25 degrees at most, and cutting is performed at a setting exceeding this angle, but the cutting life is very short.

[0008]

[Means for Solving the Problems] The inventors of the present invention have studied the above problems, and have found that a very small amount of cobalt tungsten carbide is precipitated and dispersed in a cemented carbide structure to form a chip. In addition, a chip having excellent mechanical strength and excellent abrasion resistance and chipping resistance to cutting of stainless steel can be obtained, and the axial rake angle when the chip is mounted on a holder is 2 mm.
The present inventors have found that good cutting performance and good cutting life can be obtained by milling even under the condition of 5 degrees or more, and have reached the present invention.

That is, a milling cutting device of the present invention is a milling cutting tool provided with a chip and a holder, wherein the axial rake angle when the chip is mounted on the holder is 25 degrees or more. ,And,
The chip includes tungsten carbide as a hard phase component,
Comprises cobalt respectively as binder phase component, and Co _{3
W 3 C, Co 6 W 6} C, Co 2 W 4 C and Co ₃ W ₉
It is formed of a cemented carbide containing at least one kind of cobalt tungsten carbide selected from C _4, and is a composite peak of (333) and (511) of Co ₃ W ₃ C of the cobalt tungsten carbide in X-ray diffraction measurement. ,
Synthetic peaks of (333) and (511) of Co ₆ W ₆ C,
The maximum peak intensity of the synthesized peak of (333) and (511) of Co ₂ W ₄ C and the peak of (301) of Co ₃ W ₉ C ₄ is I ₁ , and the peak intensity of (001) of WC is I _{When 2} , the peak intensity ratio represented by I ₁ / I ₂ is 0.
It is larger and not more than 0.15.

Hereinafter, the present invention will be described in detail. The cutting device for milling of the present invention is a cutting device for milling provided with a chip and a holder, and an axial rake angle when the chip is mounted on the holder is set to 25 degrees or more.

The reason why the axial rake angle is set to 25 degrees or more is that when the axial rake angle is smaller than 25 degrees, the cutting resistance increases, and for example, when a thin work material is machined, the work material is deformed. This is because vibration occurs during cutting and the quality of the finished surface is deteriorated.

When the axial rake angle is set to 25 degrees or more as described above, an excessive force acts on the tip of the chip, and the chip may be thinned to cause breakage. Such breakage is reduced as much as possible. Therefore, the tip in the present invention is made of a cemented carbide, has a cobalt tungsten carbide, and has a peak intensity ratio between the cobalt tungsten carbide and the WC in a specific range. That is, the chip of the cutting device for milling of the present invention is composed of a hard phase and a binder phase, and the hard phase contains tungsten carbide or 5 to 15% by weight of the tungsten carbide in the fourth table of the periodic table.
When a component other than tungsten carbide is used, the hard phase is made of a complex carbide solid solution or a complex carbonitriding solid solution. The binder phase is mainly composed of an iron group metal such as Co, and Co is contained in a total amount of 5 to 15% by weight.

Another feature of the present invention is that a phase composed of cobalt tungsten carbide exists in addition to the hard phase and the binder phase. Examples of the cobalt tungsten carbide include Co ₃ W ₃ C, Co ₆ W ₆ C, and Co ₂ W
Compounds of ₄ C and Co ₃ W ₉ C ₄ are known. The maximum peaks in the X-ray diffraction curves of these cobalt tungsten carbides are (333) and (51) in Co ₃ W ₃ C.
The synthesized peak of (1), (333) and (5) in Co ₆ W ₆ C
11), the peaks of (333) and (511) for Co ₂ W ₄ C, and (30) for Co ₃ W ₉ C _4.
According to the present invention, among these peaks of cobalt tungsten carbide, the peak height having the largest intensity is I ₁ , and the maximum peak of tungsten carbide is WC.
When the peak height of (001) is I ₂ , I ₁ / I ₂
It is most important that the peak intensity ratio represented by is greater than 0 and 0.15 or less, preferably 0.01 to 0.10.

The reason why the peak intensity ratio is set in the above range is that if the intensity ratio is 0, no cobalt tungsten carbide precipitates in the alloy, the wear resistance is reduced, and the tool wear increases. If it exceeds 0.15, excessive cobalt tungsten carbide is precipitated, whereby the alloy strength is reduced and tool damage becomes severe.

The above-mentioned cobalt tungsten carbide phase preferably exists in the alloy as a phase having an average particle size of 5 μm or less, particularly 3 μm or less. This is because, when the average particle size exceeds 5 μm, the strength of the entire alloy is reduced because cobalt tungsten carbide is inherently brittle. Optimally, the average particle size is 2 μm or less.

Further, with the formation of the cobalt tungsten carbide phase, W forms a solid solution in Co, which is the binder phase.
Although the lattice constant of o fluctuates, the lattice constant of Co in the cemented carbide is desirably in the range of 3.55 to 3.58.

In producing the chip made of the cemented carbide of the present invention, one kind selected from WC powder, carbides, nitrides and carbonitrides of metals of Groups 4a, 5a and 6a of the periodic table is used as a raw material powder. Alternatively, two or more kinds of powder and Co powder are weighed in the above-mentioned amounts, mixed and pulverized, molded by a known molding method such as press molding, and then fired.

The firing is carried out in a vacuum of 10 ^-1 to 10 ^-3 Torr in a temperature range of 1623 to 1773 K for 10 minutes to 2 hours.
Do time. In addition, the precipitation of cobalt tungsten carbide is carried out in the carbon content of the primary raw material and the total carbon content including the addition amount of the carbon powder, carbides of metals of Group 4a, 5a and 6a of the Periodic Table which substitute a part of tungsten carbide, It can be controlled by the addition amount of nitride and carbonitride.

The chip made of the cemented carbide of the present invention may have a hard phase formed on its surface by a known method, if desired. The hard phase to be coated is Ti
Periodic Table No. 4a including C, TiN, TiCN,
5a, 6a group metal carbide, nitride, carbonitride, ZrO
₂ , Al ₂ O _{3 and the} like.
It is formed with a thickness of μm by a CVD method or a PVD method.

[0020]

According to the present invention, the axial rake angle when the chip is mounted on the holder is set to 25 degrees or more.
Cutting resistance is reduced, and deformation and chatter of the work material can be reduced even during cutting. In addition, since the tip is formed of a cemented carbide having a predetermined composition, it is possible to suppress the chip edge from being chipped even when the axial rake angle is set to 25 degrees or more.

That is, by forming a chip from a WC-Co cemented carbide and precipitating a very small amount of cobalt tungsten carbide in the alloy, excellent cutting performance can be obtained especially when cutting stainless steel. Can be. This is because the cobalt tungsten carbide itself has high hardness and thus has excellent wear resistance. Further, the amount of carbon dissolved in the binder phase decreases and the amount of W solid solution increases with the formation of the cobalt tungsten carbide. Is strengthened by solid solution.
Furthermore, since the thermal expansion coefficient of the produced cobalt tungsten carbide is different from that of the WC phase which occupies most of the alloy, residual stress is generated and the fracture resistance is also improved.

However, since cobalt tungsten carbide is inherently brittle, if it is excessively present in the alloy, the decrease in mechanical strength is significantly reduced, and when used as a cutting tool, the tool is severely damaged. Therefore, this cobalt tungsten carbide needs to be present in the above-mentioned specific range. Therefore, even if a chip having such excellent properties as chipping resistance is mounted on a holder at an axial rake angle of 25 ° or more, chip chipping can be prevented, and long-term stable milling can be realized.

[0023]

Embodiments of the present invention will be described below with reference to the following examples.

FIG. 1 shows a cutting device for milling according to the present invention, and reference numeral 1 indicates a holder for milling. A chip 2 is mounted on the holder 1. The axial rake angle θ ₁ when the chip 2 is mounted on the holder 1 is 27 degrees.

Then, the chip 2 is prepared as follows. First, 80.0% by weight of a WC powder, 3.0% by weight of a TiC powder, 7.0% by weight of a TaC powder, and 10.0% by weight of a Co powder were mixed and pulverized.
(203 shapes) and baked at 1673 ° C. for 1 hour in a vacuum of 10 ⁻² Torr or less. The mixing ratio of carbon powder, WC, TiC, and TaC was changed at the time of mixing to prepare samples having different amounts of cobalt tungsten carbide and samples in which cobalt tungsten carbide did not appear.

After polishing the surface of the obtained sintered body, the bending test piece was measured according to JIS 16101 standard, and
X-ray diffraction measurement was performed, and cobalt tungsten carbide (Co
The intensity ratio between the peak height I ₁ of ₃ W ₃ C) and the peak height I ₂ of WC (001) was calculated. Table 1 shows the results. Further, the following cutting test was performed for each sample.

[Cutting condition 1] Work material SUS304 Tool shape SDK42AU3N Cutter shape MSD45125R Speed 200m / min. Feed 0.2 mm / tooth Depth of cut 2 mm Cutting time 810 (sec) Dry type The tool life judgment condition (average flank wear 0.2 mm, maximum flank wear 0.5 mm) is reached or maximum 81
Cutting was performed until 0 seconds. The flank wear after cutting and the maximum flank wear were measured. Table 1 shows the results.

[Cutting condition 2] Work material SUS316 Cutter shape MSD45125R Speed 200m / min. Feed 0.2 mm / tooth Depth of cut 2 mm The cutting length until the tool life determination conditions (average flank wear 0.2 mm, maximum flank wear 0.5 mm) was obtained. The average flank wear was 0.2 m as a life factor.
m reached VB, maximum flank wear 0.5mm
VBM was obtained when the amount reached, and BR was obtained when the loss was reached.
Table 1 shows the results.

[0029]

[Table 1]

According to Table 1, samples No. 1 and No. ₂ in which the ratio represented by I ₁ / I ₂ is larger than 0.15 have a transverse rupture strength of 150 even though cobalt tungsten carbide is precipitated. １７０170 kgf, all of which were broken in 20 seconds in the cutting test of stainless steel, and the cutting performance was low in the cutting test 2.

The sound alloys of Samples Nos. 8 and 9 in which cobalt tungsten carbide is not precipitated have excellent bending strength, but have a large wear and a short cutting life in stainless steel cutting.

On the other hand, the tip of the present invention in which a small amount of cobalt tungsten carbide was precipitated was able to exhibit excellent cutting performance in stainless steel cutting while maintaining high bending strength.

Further, the present inventors formed the samples shown in Table 1 into a chip shape for milling, mounted them on the holder as shown in FIG. 1 while changing the axial rake angle θ ₁ , and performed the following. Milling was performed under the cutting conditions, and the cutting edge was observed for breakage, wear, and deformation and chatter of the workpiece during cutting. In some cases, as shown in FIG. 2, a breaker 4 is formed on the chip 2 and a tool rake angle θ ₂ is provided.

[Cutting Condition 3] Workpiece SUS304 Speed 200 m / min. Feed 0.2 mm / tooth Depth of cut 2 mm Cutting time 15 min Dry type Table 2 shows the broken state, abrasion state, and deformation and chatter of the work material during cutting.

[0035]

[Table 2]

The work material S50C is cut at a cutting speed of 200 m.
/ Min. , Feed 0.2mm / tooth, depth of cut 2m
The cutting resistance when cutting with m is shown in the graphs of FIGS.

In FIGS. 3 to 6, the dashed line indicates the cutting resistance of the sample No. 9 in Table 2 in which the axial rake angle θ ₁ is smaller than 25 degrees, and the broken line indicates the axial rake angle θ _1.
Is not less than 25 degrees, the solid line indicates the axial rake angle θ ₁ is greater than 25 degrees and the tool rake angle θ ₂
Shows the cutting resistance of Sample No. 6 provided with.

As can be seen from Table 2, when the axial rake angle is smaller than 25 degrees, no chipping occurs, but the cutting resistance is large. It can be seen that chatter occurs. When the axial rake angle is 25 degrees or more, the cutting resistance is small, and it can be seen that even when a thin-walled work material is cut, deformation and chattering of the work material do not occur.

[0039]

As described above, in the milling machine of the present invention, the axial rake angle when the chip is mounted on the holder is set to 25 degrees or more, so that the cutting resistance is reduced, and the cutting force during cutting is reduced. Deformation of the cutting material and occurrence of chattering during cutting can be reduced. In addition, by forming a chip with a predetermined composition and precipitating and dispersing a trace amount of cobalt tungsten carbide, chipping resistance and abrasion resistance to stainless steel are greatly improved, and even when the axial rake angle is 25 degrees or more, the chip Of the cutting edge can be suppressed, and the tool life can be extended.

[Brief description of the drawings]

FIG. 1 is a side view showing a cutting device for milling of the present invention.

FIG. 2 is a side view showing a tip portion of the chip of the present invention.

FIG. 3 is a graph showing a feed force of a cutting resistance.

FIG. 4 is a graph showing a main component force of a cutting resistance.

FIG. 5 is a graph showing the back force of the cutting force.

FIG. 6 is a graph showing a combined force of cutting resistance.

[Explanation of symbols]

 1 holder 2 chips

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B23C 5/16 B23C 5/06 C22C 29/08

Claims (1)

(57) [Claims] 1. A milling cutter comprising a chip and a holder, wherein the chip has an axial rake angle of 25 degrees or more when the chip is mounted on the holder, and the chip has a hard phase component. Contains tungsten carbide as a binder phase component,
X-ray diffraction formed of a cemented carbide containing at least one cobalt tungsten carbide selected from Co ₃ W ₃ C, Co ₆ W ₆ C, Co ₂ W ₄ C and Co ₃ W ₉ C ₄ According to the measurement, the synthesized peaks of (333) and (511) of Co ₃ W ₃ C, the synthesized peaks of (333) and (511) of Co ₆ W ₆ C, and the (333) of Co ₂ W ₄ C were measured. When the intensity of the maximum peak of the synthetic peak of (301) and the peak of (301) of Co ₃ W ₉ C ₄ is I ₁ , and the intensity of the peak of (001) of WC is I ₂ , I ₁ / I _A cutting device for milling, wherein a peak intensity ratio represented by ₂ is greater than 0 and 0.15 or less.