JP2003326413A - Cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tool which has a long breakage life and indicates excellent corrosion resistance and can be manufactured at a low cost. <P>SOLUTION: In a cutting tool where a plurality of inserts are removably mounted on the tip of a tool body, the thickness of the insert mounting part is two or less times as much as the thickness of an insert. The tool body has a composition consisting of 0.2-0.6 wt.% C, 1.2 or less wt.% Si, 0.5-1.5 wt.% V, and 2-6.5 wt.% (Cr+1/2Mo), and the rest substantially consisting of Fe. The surface of at least the tool body is formed of an alloy steel having HRC40 or more. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting tool used for milling or the like, in which a plurality of inserts are removably attached to the tip of a tool body made of alloy steel.

[0002]

2. Description of the Related Art In milling, a cutting tool (for example, a cutting edge type radius end mill) having a plurality of inserts containing cemented carbide chips removably attached to the tip of a tool body is used as the main spindle of a processing machine. Predetermined processing is performed on the work material by mounting and rotating the main shaft. The tool body constituting the above cutting tool is usually formed of alloy steel for machine structure such as SCM material or SNCM material, which is usually defined by JIS, mainly for cost reduction. These alloy steels are made by quenching the material to improve the mechanical properties and further imparting toughness, for example,
It is used after being tempered at a high temperature of 400 to 500 ° C.

However, when the SCM material or the SNCM material is heated to 200 ° C. or higher during cutting, the hardness thereof decreases in proportion to the temperature (for example, when heated to 500 ° C., the HR is decreased).
C35 or less. ), The fatigue strength also decreases, and there is a problem that it cannot withstand long-term use. More specifically, when the tool body is made of SCM material or SNCM material, the tip of the tool body is forcibly cooled by the coolant in wet cutting, so that the hardness of the tool body is not significantly reduced, In order to improve the cutting efficiency in consideration of the
When heavy-duty cutting is performed by dry method, the tip of the tool body is not sufficiently cooled, so that the hardness of the tip of the tool body decreases and the fatigue strength also decreases. As a result, the tip of the tool body may be broken at a cutting length of several tens of meters, and if the amount of protrusion of the tool is long, there is a problem that the tool is more likely to break. As a countermeasure, for example, Japanese Patent Laid-Open No.
No. 01-277009 discloses a tool body made of Ni, C.
A cutting tool set in the range of HRC43 to 48 is proposed by forming the special steel to which r, Mo, V, and Cu are added and tempering at a temperature of 435 to 630 ° C.

[0004]

According to the above cutting tool, since the tool body is formed of special heat-resistant special steel, even if it is dry cutting, it is possible to suppress the decrease in hardness due to the temperature rise of the tool body. It is possible to prevent cracks and the like, and the tool life can be made longer than that of SCM or SNCM materials. However, since alloying elements such as Ni and Cu are added to the tool body in order to improve heat resistance, the material itself is expensive, and the cost is higher than that of the conventional SCM material or SNCM material. Is disadvantageous, and the corrosion resistance is SCM material or SN.
It is almost the same as the CM material, and its improvement is required. Therefore, an object of the present invention is to provide a cutting tool that has a long breakage life, exhibits good corrosion resistance, and can be manufactured at low cost.

[0005]

In order to achieve the above object, the cutting tool of the present invention is a cutting tool in which a plurality of inserts are removably mounted on the tip of the tool body, and the thickness of the insert mounting portion is large. Is less than twice the insert thickness, and the tool body has a weight ratio of C: 0.2 to 0.6.
%, Si: 1.2% or less, V: 0.5 to 1.5%, Cr
Or containing Cr and Mo, (Cr + 1 / 2Mo): 2
6.5%, the balance: substantially Fe,
At least the surface of the tool body is formed of an alloy steel having an HRC of 40 or more.

In the present invention, the tool body is made of Cr or C.
r and Mo, and (Cr + 1 / 2Mo) is 2-6.
Since it is made of an alloy steel having a hardness of 5% and a surface hardness of HRC 40 or more, the softening resistance and the fatigue strength are increased, and the protrusion amount is lengthened even if heavy cutting is performed by dry type. In addition, the breakage life can be extended, and since a large amount of Cr is contained, good corrosion resistance is exhibited, and since expensive Ni is not contained, it is possible to reduce the manufacturing cost. Next, the tool body is HRC44-
It is preferably made of chromium-molybdenum steel which is 46. Furthermore, even if the tool body is mounted on a processing machine such that the protruding amount thereof is twice or more the blade diameter and heavy-duty cutting is performed, it can withstand long-term use.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be specifically described below with reference to the accompanying drawings. 1 is a front view showing the cutting tool of the present invention, and FIG. 2 is a left side view of the cutting tool of the present invention shown in FIG. The number of blades in FIG. 1 is partially omitted with respect to the number of blades in FIG. A cutting edge exchangeable radius end mill (hereinafter, simply referred to as an end mill) indicated by reference numeral 1 in FIG. 1 is a tool main body 2 to be mounted on an arbor (not shown), and a plurality of insert mounting portions formed on a tip portion 3 thereof at equal intervals. 4 and
It has an insert 5 mounted on each insert mounting portion 4. In this type of end mill, when the number of blades is increased, for example, the thickness t2 of the insert mounting portion 4 may be twice the thickness t1 of the insert 5 or less as shown in FIG. When the mounted arbor is attached to the main shaft of the processing machine, and the amount of protrusion is made twice as long as the cutting diameter D or more and heavy cutting is performed by the above-mentioned dry type, the tip portion 3 of the tool body 2
Are easily broken. In order to prevent such breakage,
In the present invention, the tool body is made of alloy steel having the following specific composition.

The tool body 2 has a weight ratio of C: 0.2 to.
0.6%, Si: 1.2% or less, V: 0.5 to 1.5
%, Cr or Cr and Cr are included, (Cr + 1 / 2M
o): 2 to 6.5% and the balance: substantially Fe. This composition may include impurities that are unavoidable in manufacturing, but it is preferable to reduce the content of elements such as P, S, and Sn that promote temper embrittlement. The reasons for limiting the above components are as follows. If C is less than 0.2%, the mechanical strength decreases,
If it exceeds 0.6%, it becomes brittle, so the content is made 0.2 to 0.6%. Si is added as a deoxidizer, but 1.
If it exceeds 2%, the non-machinability decreases and it becomes difficult to process it into a predetermined shape, so it is made 1.2% or less. However, if the Si content is 0.8% or more, it is effective in improving the fatigue strength. V precipitates fine carbides in the matrix to improve wear resistance, but if too much V reduces toughness, 0.5
The range is up to 1.5%. Cr can improve the hardness after quenching and can maintain the hardness and also improve the corrosion resistance, but if it is contained in a large amount, the cost becomes high. M
o is half the amount of Cr added, and has the same effect as Cr that the hardness after quenching can be improved and the hardness can be maintained, and also has the effect of delaying temper embrittlement. Therefore, in the present invention, Cr may be added alone or Cr and Mo may be added in combination, and the addition amount is
It may be selected such that the above (Cr + 1 / 2Mo) is in the range of 2 to 6.5%.

The tool body of the present invention is produced by preparing a steel material having the above composition, quenching and tempering it, and then machining it into a predetermined shape. For tempering of alloy steel, for example, in consideration of ductility, low temperature toughness, fracture toughness and delayed fracture property, tempering is performed at a high temperature exceeding the tempering embrittlement temperature range, and the tempering temperature is set so as to rapidly cool the tempering embrittlement temperature range. The present invention can be applied to the present invention.
Particularly, in the present invention, in order to impart a predetermined softening resistance to the tool body and to process the insert mounting portion, the tempering temperature is at least HR at least on the surface of the tool body.
It may be set to a range of C40 or more, preferably HRC44 to 46, and specifically a temperature range of 600 to 620 ° C. is desirable.

The results of comparing the softening resistance and fatigue strength of the alloy steel of the present invention with the conventional SCM440 material are shown in FIGS. 3 and 4. In the example of the present invention, C: 0.2 to 0.6% by weight,
Si: 1.2% or less, V: 0.5 to 1.5%, containing Cr or Cr and Mo, (Cr + 1 / 2Mo): 2 to 6.5
%, The balance: substantially Fe. From FIG. 3, the conventional material exhibits a maximum hardness value HRC49.5 near 180 ° C., and the hardness decreases as the temperature rises.
It can be seen that the hardness of 5 is maintained and the softening resistance is excellent. Further, it can be seen from FIG. 4 that the material of the present invention can withstand a repeated stress of about 1.5 times that of the conventional material and has much higher fatigue strength than the conventional material. In the cutting tools shown in FIGS. 1 and 2, the inserts are arranged in the same manner, but the present invention is not limited to this, and it is needless to say that the present invention can be applied to those in which the inserts are arranged in an uneven manner. Of the plurality of insert mounting parts, the thinnest insert mounting part is applied to a cutting tool in which the thickness of the insert is twice or less.

[0011]

Embodiments of the present invention will be described with reference to FIGS. After quenching the above-mentioned material of the present invention, it is tempered at 600 ° C. to be tempered to HRC45, and then, the insert portion 4 (thickness t2 = 5 mm) at five locations is worked into the tip portion 3 of the tool body 2 in equal divisions. , Insert 5 in each insert mounting part 4
By fixing (thickness t1 = 4.76 mm, circular piece having a diameter of 10 mm) with a clamp screw, the wall thickness t2 of the insert mounting portion is 1.06 times the insert thickness t1, and the blade diameter D
An end mill 1 having a diameter of 52 mm was produced. For comparison, an end mill similar to the above was manufactured except that the tool body was formed of SCM440 material and the thickness t2 of the insert mounting portion was 6 mm (1.3 times the insert thickness t1). Milling was performed under the same conditions as above, and the cutting area was obtained.

A straight arbor equipped with the above end mill is attached to the main shaft of a milling machine, and the protrusion amount L (distance from the end face of the collet to the cutting edge) is 150 mm (L / D =
2.9) and 180 mm (L / D = 3.5), and S50C (hardness: HS34) was used as the work material for milling. The cutting conditions are cutting speed 146
m / min, spindle speed 894 rpm, feed per blade 0.3 to 1 mm / blade, table feed 1341
The cutting depth was changed at 4,000 mm / min, the radial cutting width was 22 mm, the axial cutting depth was changed, and the vibration noise was measured for each predetermined feed amount to obtain the cutting region in which good cutting can be performed. The results are shown in FIGS.

From FIGS. 5 and 6, the solid line in the figure indicates the protrusion amount L.
Is a cutting area of 150 mm, and the protrusion amount L is 18 in the broken line.
A cutting area of 0 mm is shown. In the example of the present invention, although the insert mounting portion is thinner than in the comparative example, the vibration noise is low, and in particular, when the protrusion amount L is 180 mm, it can be seen that a wider cutting area than the conventional case can be obtained.

[0014]

As described above, by applying the present invention, the softening resistance and the fatigue strength of the tool body are increased, so that even if the insert mounting portion is thin and the protrusion amount is large, Even if cutting is performed under severe conditions such as dry type and heavy cutting, it is difficult to break and the tool life can be extended. In addition, it is possible to obtain a wider cutting area than before. Furthermore, since the cutting tool of the present invention contains a large amount of Cr, the corrosion resistance is improved. Moreover, since the alloy steel forming the tool body does not contain expensive Ni, it can be manufactured at the same price as conventional materials.

[Brief description of drawings]

FIG. 1 is a front view of a cutting tool of the present invention.

FIG. 2 is a left side view of the cutting tool of the present invention shown in FIG.

FIG. 3 is a diagram showing softening curves of a material of the present invention and a conventional material.

FIG. 4 is a diagram showing fatigue strength characteristics of the material of the present invention and the conventional material.

FIG. 5 is a diagram showing a cutting region of the cutting tool of the present invention.

FIG. 6 is a view showing a cutting area of a conventional cutting tool.

[Explanation of symbols]

1: Exchangeable blade radius end mill 2: Tool body 3: Tip 4: Insert mounting part 5: Insert

Claims (3)

[Claims] 1. A cutting tool in which a plurality of inserts are removably mounted at the tip of a tool body, wherein the thickness of the insert mounting portion is not more than twice the insert thickness, and the tool body has a weight ratio. , C: 0.2 to 0.6%, Si:
1.2% or less, V: 0.5 to 1.5%, Cr or Cr and Mo are included, (Cr + 1 / 2Mo): 2 to 6.5%, and the balance is substantially Fe. However, at least the surface of the tool body is formed of an alloy steel having an HRC of 40 or more. 2. The cutting tool according to claim 1, wherein the tool body is made of chromium molybdenum steel having an HRC of 44 to 46. 3. The cutting tool according to claim 1, wherein the amount of protrusion of the tool body is at least twice the blade diameter.