JPH11170102A - High-speed cutting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lowering of a tool life following the increase in a cutting speed, by producing a protective coat on a CBN sintered tool. SOLUTION: Cutting is made at a CBN sintering body, contained in a CBN sintered tool, of 75% or more, and a cutting speed of 1500 m/min. or more. Also, cutting is made, by mounting plural CBN sintered tool 1, constituting a front milling cutter, matter the front milling cutter have a cutting speed of 1500 m/min. or more, and also at a feed per revolution for the blade of the tool 1, to one revolution of the front milling cutter of from 0.2 mm/rev. to 0.4 mm/rev.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting tool comprising a cubic boron nitride sintered body (hereinafter referred to as a CBN sintered tool).
The present invention relates to a high-speed cutting method using a steel sheet.

[0002]

2. Description of the Related Art There are three fundamental problems in cutting: high precision, high efficiency, and low cost. Of these three issues,
As one means for realizing high-efficiency machining, a higher cutting speed is required. CBN sintered tools have high hardness and high thermal conductivity after diamond, and have excellent cutting performance such that they do not easily cause diffusion reaction with metal materials even at high temperatures. Therefore, CBN sintered tools are suitable for cemented carbide, cermet, ceramics, etc. Suitable for high-speed cutting compared to cutting tools.

[0003]

However, as the cutting speed is increased, the cutting efficiency is improved, but the tool life is shortened and the tool cost is increased. In particular, since the CBN sintered tool is very expensive compared to other tools, it cannot solve the problem of low cost among the above three problems. Furthermore, if the tool life is shortened, the frequency of tool replacement increases, which causes a problem that productivity is deteriorated, and it is difficult to realize high-efficiency machining.

The present invention has been made to solve the above problems, and has as its object to prevent a reduction in tool life due to an increase in cutting speed by forming a protective film on a CBN sintered tool. Things.

[0005]

Generally, it is known as the Taylor's life equation that the tool life is shortened as the cutting speed is increased. C = VT ⁿ (1) where V is the cutting speed, T is the tool life, and n and C are constants determined by various conditions other than the cutting speed.

However, as a result of repeated experiments, the present inventor found that when cast iron having a pearlite structure such as FC300 or FC250 was cut at a high cutting speed using a CBN sintered tool, the above-mentioned Taylor life equation was contradicted. It was found that the tool life was prolonged as the cutting speed increased. As a result of analyzing this phenomenon, it was found that the substance contained in the cast iron having a pearlite structure adhered to the tool surface to form a protective film, and the presence of the protective film prolonged the tool life.

The present invention aims at realizing high-speed machining by utilizing the above-mentioned phenomenon, and the invention according to claim 1 provides a cutting tool containing 75% or more of a cubic boron nitride sintered body. The cast iron having a pearlite structure is formed at a cutting speed of 1500 m / min or more by the cutting tool. A second aspect of the present invention is characterized in that a milling machine is configured by using a plurality of the cutting tools according to the first aspect, and the milling cutter is used to cut a pearlite-structure cast iron at a cutting speed of 1500 m / min or more. Things.

[0008] The above phenomenon is a phenomenon that appears only when a pearlite-structured cast iron is cut at a high cutting speed, and therefore cannot be applied to other workpieces. Therefore, in order to cope with a workpiece other than cast iron having a pearlite structure, the invention according to claim 3 contains not less than 75% of a cubic boron nitride sintered body and silicon (Si), manganese (M).
n), titanium (Ti) and one or more of these oxides are combined to form a cutting tool, and the cutting tool cuts a pearlite-structured cast iron at a cutting speed of 1
The cutting is performed at 500 m / min or more.

Further, according to a fourth aspect of the present invention, a milling machine is constituted by using a plurality of the cutting tools according to the third aspect, and the milling cutter cuts a pearlite-structure cast iron at a cutting speed of 1500.
It is characterized by cutting at m / min or more. According to a fifth aspect of the present invention, the feed amount of one cutting edge of the plurality of cutting tools per rotation of the milling machine according to the second or fourth aspect is 0.2 mm / rev to 0.4 mm / rev. The invention of claim 6 is characterized in that
A true rake angle of the plurality of cutting tools constituting the milling machine according to the second or fourth or fifth aspect of the present invention is set to be -42 degrees to -58 degrees.

A seventh aspect of the present invention provides a dummy work made of pearlite cast iron using a cutting tool containing at least 75% of a cubic boron nitride sintered body at 1500 m / mi.
By cutting at a cutting speed of n or more, a protective film is formed on the surface of the tool by a substance contained in the dummy work, and thereafter, the workpiece is cut using the tool. Things.

The invention according to claim 8 is the invention according to claims 1 to 7, characterized in that the cutting speed is 3600 m / min or more as a preferable cutting speed.

[0012]

Next, an embodiment of the high-speed cutting method of the present invention will be described. FIG. 1 shows the CBN used in the present invention.
FIG. 2 is an enlarged view taken along the line II-II of FIG. 1, and FIG. 2 is a rake face, 3 is a chamfer portion, and 4 is a flank face. As shown in FIGS. 3 and 4, the CBN sintered tool 1 is arranged on the circumference at equal intervals to form a face mill 6.
The face milling machine 6 was used to perform face milling of FC300, which is cast iron having a pearlite structure.
The processing conditions are as follows.

Cutting speed 300 to 6000 m / min Feed amount per tooth 0.33 mm / rev Cutting depth 1.0 mm Coolant dry cutting Cutting direction Downcut FIG. 5 shows cutting speed Vm / min at 300 m / min. min, 80
0m / min, 1500m / min, 3600m / mi
It shows the relationship between the cutting distance L (m) per tooth and the flank wear width V _B (mm), which is one of the indices of tool life, when n and 6000 m / min are changed. Incidentally, the flank wear width V _B is as illustrated in FIG. 6, in which the width of the wear 4a generated in the flank 4 and chamfer portion 3.

Here, when cutting is performed at a cutting speed of 800 m / min or more, a region where tool wear hardly progresses appears. At a cutting speed of 800 m / min, a cutting distance of about 20
m to about 40 m, at a cutting speed of 1500 m / min, the tool wear hardly progresses at a cutting distance of about 20 m to about 60 m, and especially at a cutting speed of 6000 m / min, the tool wear hardly increases from a cutting distance of about 20 m. Although it did not progress, although not shown, even when the cutting distance exceeded 120 m, tool wear hardly progressed.

It can be seen that the higher the cutting speed, the longer the area where the tool wear hardly progresses, and the longer the cutting distance until the tool life is reached.
(Here, the tool life is when the flank wear width is 0.3 mm or more.) Since this result is contrary to the Taylor's life equation described above, in order to analyze this phenomenon, after cutting, SEM (Scanning Elect)
orn Microscope) observations were made. FIG. 7 shows a cutting speed of 600.
FIG. 2 is a view of the tool shape after cutting at 0 m / min, which is a view taken along the line II-II in FIG. 1. As shown in FIG.
Deposits 5 were found on the tool surface, especially on the chamfer 3 and the flank 4. The deposit 5 was observed when cutting was performed at a cutting speed of 1500 m / min or more, and was not confirmed when cutting was performed at a cutting speed lower than 1500 m / min.

As a result of analyzing the deposits, manganese (Mn), silicon (Si), titanium (Ti), or oxides thereof contained in FC300 are formed on the tool surface by heat and pressure accompanying cutting. It has been found that this deposit protects the tool and extends the tool life. FIG. 8 is a graph showing the relationship between the cutting distance L (m) and the surface roughness S (μmRz) when the cutting speed Vm / min is changed. As can be seen from FIG. 8, when the cutting speed is 3600 m / min or more, the surface roughness deteriorates.
Since this is face milling in the present embodiment, the milling rear blade comes into contact with the surface of the workpiece after cutting,
At that time, it is considered that the cause is that the deposits generated on the tool surface adversely affected the work surface. In other words, it means that the thicker the deposit is, the worse the surface roughness is. Cutting speed 1500m /
min, the surface roughness did not deteriorate despite the presence of the deposits.
15 when cutting at a cutting speed of 600 m / min or more
Since a thicker deposit is generated than when cutting at 00 m / min, it is considered that the tool life is further extended.

From the above results, the cutting speed for forming a protective film on the tool surface by cutting cast iron having a pearlite structure using a CBN sintered tool is 1500 m.
/ Min, more preferably 3600 m / min or more. Further, in a state where the protective film was formed on the surface of the CBN sintered tool, it was observed how the material of the CBN sintered tool itself affects the tool life.

The processing conditions at this time were such that a pearlite structure cast iron was cut with a face mill at a cutting speed of 6000 m / min so that a protective film was surely formed, and other processing conditions were as follows.・ CBN sintered tool content of CBN sintered tool 41% ~ 89% ・ Feed amount per blade 0.33mm / rev ・ Cut 1.0mm ・ Coolant dry cutting ・ Cutting direction Downcut Fig.9 It is one of the indices of the cutting distance L (m) per tooth and the tool life when the content of the CBN sintered body contained in the CBN sintered tool is changed to 41%, 77% and 89%. It shows the relationship with the flank wear width V _B (mm).

Here, when the CBN sintered tool content of the CBN sintered tool is 77%, the cutting distance is between about 30 m and about 120 m, and when the CBN sintered tool content of the CBN sintered tool is 89%, the cutting is performed. Tool wear hardly progresses from a distance of about 30 m, and tool wear hardly progresses even if the cutting distance exceeds 200 m. As described above, as the content of the CBN sintered body contained in the CBN sintered tool increases, the region where the tool wear hardly progresses becomes longer, and the cutting distance until the tool life is reached is increased. Recognize.

From the above, it can be seen that the CBN sintered tool CBN
As the content of the sintered body increases, the cutting distance to reach the tool life becomes longer, and from the above results, the tool wear does not progress from the content of the CBN sintered body of around 77%. C containing 75% or more of CBN sintered body
It is considered preferable to use a BN sintered tool. Furthermore, the feed amount of one blade of the CBN sintered tool per one rotation of the face mill was changed using a face mill equipped with a CBN sintered tool having a content of the above CBN sintered body of 89%. The relationship between the feed amount and the tool life was as shown in FIG.

FIG. 10 shows that the feed amount per blade is equal to 0.1.
The tool life increases from 2 mm / rev to about 0.3 mm / rev.
It was found that the peak reached near rev, and then the tool life decreased. For this reason, the feed amount per blade is preferably from 0.2 mm / rev to 0.4 mm / rev, and the optimum value is around 0.3 mm / rev.

Next, an observation was made on the tool life depending on how the CBN sintered tool was attached to the face mill. This CB
The observation of how the N-sintered tool is attached to the face mill observes the tool life when changing the true rake angle T, which is considered to have a deep relationship with the cutting force and the tool life of the CBN sintered tool. did. Here, the true rake angle T is represented by the following equation.

Tan T = tan R · cos C + tan A · sin C (2) where R is a radial rake angle, A is an axial rake angle, and C is an approach angle, as shown in FIGS. 3 and 4, respectively.
As shown in the figure, the angle is when the CBN sintered tool is attached to the face mill. FIG. 11 shows the results obtained by observing the tool life when the true rake angle obtained from the above equation (2) is changed between -62 degrees and -42 degrees.

The processing conditions at this time are as follows.・ Cutting speed 6000m / min ・ CBN sintered body content of CBN sintered tool 89% ・ Feed amount per tooth 0.33mm / rev ・ Cut 1.0mm ・ Coolant dry cutting ・ Cutting direction Down cut This As shown in FIG. 11, the relationship between the true rake angle and the tool life is such that the tool life tends to increase when the true rake angle is between -60 degrees and -48 degrees, and falls from about -48 degrees. .

For this reason, the true rake angle is practically preferably from -42 to -58 degrees, and the optimum value is around -48 degrees. From the above results, the cutting speed at which a protective film can be formed on the blade surface of the CBN sintered tool is 1500 m / m.
When the content of the CBN sintered body of the CBN sintered tool is 75% or more, the tool life can be extended.

These cutting speeds and CBN of the CBN sintered tool
The feed rate per blade is 0.2
The tool life can be further extended by setting the mm / rev to 0.4 mm / rev or setting the true rake angle from -58 degrees to -42 degrees. On the other hand, if the workpiece is FC
In the case of cast iron having a pearlite structure such as 300, cutting is performed while generating the tool protective film as described above, so that high-speed cutting is possible. However, a protective film is not generated by cutting a workpiece made of a material other than cast iron having a pearlite structure. Therefore, an embodiment of a cutting method for a workpiece of an arbitrary material will be described.

In the process of manufacturing a CBN sintered tool, CB
In addition to N powder and commonly used binders such as TiC and Al ₂ O ₃ , SiO ₂ and MnO ₂ are mixed in advance and press-formed in this state in the same manner as in the conventional production method, and sintered under high temperature and pressure. I do. Since the CBN sintered tool thus obtained contains SiO ₂ and MnO ₂ in advance, the CBN sintered tool contains the CBN sintered body in the same manner as when cutting the pearlite-structured cast iron. If the cutting rate is set to 75% or more and the cutting speed is set to 1500 m / min or more, the tool protection film is generated by SiO ₂ and MnO ₂ in the tool by the pressure and heat accompanying the cutting, regardless of the material of the workpiece. Tool life is extended. Further, similar to the above when cutting the pearlite structure cast iron,
Feed amount per blade from 0.2mm / rev to 0.4m
m / rev and the true rake angle from -58 degrees to -4
If it is set twice, the tool life can be further extended.

As described above, SiO ₂ and M
Rather than mixing nO ₂ with CBN powder and TiC, Al ₂ O _3, etc. to form a CBN sintered tool, SiO ₂ and MnO ₂ are added only to the blade surface of the CBN tool, and the protective film is cut in advance. It may be a method of forming it on a surface. FIG. 11 illustrates another embodiment of a high-speed cutting method for a workpiece of an arbitrary material. Reference numeral 6 denotes a face mill, which is a CBN containing at least 75% of a not-shown CBN sintered body at its tip. A sintering tool is installed. 7 is an object to be processed, 8 is FC300 which is a cast iron having a pearlite structure.
, And both are fixed to a table (not shown).

In the above configuration, the milling tool 6 is driven to rotate by a motor (not shown), and the front milling tool 6 and the table are moved relative to each other to 1500 m / m.
The dummy work 8 is cut at a cutting speed of at least in. Then, since a protective film is generated on the tool surface as described above, an arbitrary workpiece 7 is cut in a state where the protective film is generated. Here, since the protective film is formed on the tool surface, the cutting of the workpiece 7 does not shorten the tool life even if the cutting speed is increased.

When the cutting distance to the object 7 is long, the protective film on the tool surface is worn during the cutting. In this case, the dummy work 8 may be cut again to form the protective film. By repeatedly cutting the dummy work 8 and the workpiece 7, it is possible to cope with a workpiece having a long cutting distance. In addition, the timing of this repetition should just select the optimal timing according to the material of a workpiece, a cutting speed, etc.

FIG. 12 shows another embodiment, in which a dummy work 8 is integrally fixed to a table so as to sandwich the object 7 to be processed. In this state, cutting is performed with a CBN sintered tool at a cutting speed of 1500 m / min or more.
Then, the CBN sintered tool cuts the workpiece 7 in this state after the protective film is formed when the dummy work 8 is cut, so that the tool life is increased in spite of high-speed cutting. It does not decline.

Here, in the above-described embodiment, the dummy work 8 is arranged so as to sandwich the object 7 to be processed. However, the present invention is not limited to this. 7 only needs to be arranged so that it can be cut. Although the above embodiment is directed to face milling, the present invention is not limited to this, and can be used for other cutting operations.

According to the cutting method of the present invention, in the case of milling, the cutting speed is 3600 m / min or more, and as described above, due to the presence of the protective film, when the rear edge of the milling cutter comes into contact with the workpiece, the surface roughness is reduced. However, by adopting inclined cutting, in which the spindle axis is inclined with respect to the object to be machined, it is possible to prevent the trailing edge of the milling cutter from coming into contact with the object to be machined. Deterioration can be prevented, and the three problems of high accuracy, high efficiency, and low cost can be satisfied together.

[0034]

According to the high-speed cutting method of the present invention, CBN
Using a CBN sintered tool containing 75% or more of a sintered body, a pearlite structure cast iron is cut at a cutting speed of 1500 m / min or more to form a protective film on the tool surface. It is possible to obtain a long-life tool that does not decrease the tool life with an increase in the cutting speed without performing any processing.

When a milling cutter is used in the high-speed cutting method of the present invention for cutting a pearlitic cast iron at a cutting speed of 1500 m / min or more using a CBN sintered tool containing 75% or more of the above-mentioned CBN sintered body. To set the feed amount of one blade per milling revolution from 0.2 mm / rev to 0.4 mm / rev, or to set the true rake angle from -58 degrees to -42 degrees, or
By setting both the feed amount per tooth and the true rake angle to the above values, the tool life can be further extended.

Further, when cutting a work piece of any material other than pearlite cast iron, the CBN sintered tool should contain not less than 75% of a CBN sintered body, as well as SiO ₂ and MnO _2. And cutting speed 1500m
By cutting at a rate of / min or more, a protective film is formed on the tool surface in the same manner as in the case of cast iron having a pearlite structure, and a long-life tool without reducing the tool life can be obtained.

Also, a protective film is formed on the tool surface by cutting a dummy work made of cast iron having a pearlite structure, and the tool on which the protective film is formed is used to cut an object to be processed. Even if the cutting speed is increased when cutting an object, the tool life is not shortened and the high-speed cutting can be realized at low cost.

Further, by repeatedly cutting a dummy work made of cast iron having a pearlite structure and a processing object, it is possible to cope with a processing object having a long cutting distance. By simultaneously cutting the object, the cycle time can be reduced as compared with the case of repeatedly cutting as described above.

In particular, if the high-speed cutting method of the present invention is used,
With conventional tools, chipping occurs immediately after cutting starts and machining becomes impossible, or chipping does not occur immediately after cutting starts, but cutting at a high cutting speed that shortens the tool life extremely becomes possible. Efficient processing can be realized.

[Brief description of the drawings]

FIG. 1 is a top view of a CBN sintered tool.

FIG. 2 is an enlarged view taken along the line II-II of FIG.

FIG. 3 is a front view of the front milling machine.

FIG. 4 is a side view of the front milling machine.

FIG. 5 is a graph showing a relationship between a cutting distance and a tool flank wear width.

FIG. 6 is a tool flank wear width V generated on a CBN sintered tool.
FIG.

FIG. 7 is an enlarged view taken along the line II-II of FIG. 1, showing a state of a tool surface when cutting is performed at a cutting speed of 6000 m / min.

FIG. 8 is a graph showing a relationship between a cutting distance and a surface roughness.

FIG. 9 is a graph showing the relationship between the cutting distance per blade and the flank wear width V _B (mm) when the content of the CBN sintered body is changed.

FIG. 10 is a graph showing a relationship between a feed amount per tooth and a tool life.

FIG. 11 is a graph showing a relationship between a true rake angle and a tool life of a CBN sintered tool attached to a face mill.

FIG. 12 is a perspective view showing a high-speed cutting method of the present invention.

FIG. 13 is a perspective view showing another embodiment of the high-speed cutting method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CBN sintered tool 2 Rake surface 3 Chamfer part 4 Flank 5 Adhesion (tool protection film) 6 Face milling 7 Workpiece 8 Dummy work

Claims (8)

[Claims] 1. A high-speed cutting method comprising forming a cutting tool containing 75% or more of a cubic boron nitride sintered body, and cutting a pearlite-structure cast iron at a cutting speed of 1500 m / min or more by the cutting tool. Method. 2. A high-speed cutting method for milling a work made of cast iron having a pearlite structure by milling,
Forming a plurality of cutting tools constituting the milling mill containing at least 75% of a cubic boron nitride sintered body, and cutting the pearlite structure cast iron at a cutting speed of 1500 m / min or higher while rotating the milling mill; High-speed cutting method characterized by the following. 3. A cubic boron nitride sintered body containing not less than 75% and silicon (Si), manganese (M
n), titanium (Ti) and one or more of these oxides are combined to form a cutting tool, and the cutting tool cuts a pearlite-structured cast iron at a cutting speed of 1
A high-speed cutting method characterized by cutting at 500 m / min or more. 4. A high-speed cutting method for milling a workpiece by milling, wherein a plurality of cutting tools constituting the face mill contain 75% or more of a cubic boron nitride sintered body and silicon (Si). ), Manganese (M
n), titanium (Ti) and one or more of these oxides are formed in combination, and cutting is performed by the milling cutter at a cutting speed of 1500 m / min or more. 5. The high-speed cutting method according to claim 2, wherein one feed of the plurality of cutting tools per one rotation of the face mill is 0.2 mm / rev to 0.4 mm / rev. A high-speed cutting method, characterized in that: 6. The high-speed cutting method according to claim 2, wherein the true rake angle of the cutting tool is from -42 degrees to -58 degrees. . 7. A cutting tool is formed by containing at least 75% of a cubic boron nitride sintered body, and a dummy work made of cast iron having a pearlite structure is formed using said cutting tool at 1500 m / m.
by cutting at a cutting speed of at least in, a protective film is formed on the surface of the tool by a substance contained in the dummy work, and then the workpiece is cut using the tool. High speed cutting method. 8. The high-speed cutting method according to claim 1, wherein said cutting speed is 3600 m / min or more.