JPS62282803A - High-speed steel cutting tool - Google Patents

Abstract

PURPOSE:To obtain excellent finished surface roughness by forming a quick- coagulation layer with a secondary dendrite space of 6 mum or less on an addendum section made of high-speed steel of a cutting tool. CONSTITUTION: A quick-coagulation layer 1 is formed by being coagulated from a liquid phase at a cooling speed of about 600 deg.C/sec or more, and the secondary dendrite space becomes 6 mum or less under such high-speed cooling. Concurrently, the second layer grain of a carbide or the like becomes about 1 mum or less. For example, a beam is illuminated from the direction of a flank 3 after the rough machining of an addendum 2 to perform the finish machining of the addendum 2. The addendum 2 is tempered after beam illumination and is machined so that the quick-coagulation layer about 0.1 mm or more in width is formed from the addendum 2 to the flank 3 and a rake face 4. The flank width X and rake face width Y are made about 0.1 mm or more. Accordingly, high-precision finished surface roughness can be improved.

Description

Detailed Description of the Invention 3 Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a high-speed steel cutting tool capable of providing excellent finished surface roughness. In addition, the high-speed steel in the present invention is not only a high-speed steel specified by JIS or a steel type generally called powder high-speed steel, but also a steel type that contains primary carbides and has undergone tempering secondary hardening due to precipitation of alloy carbides. This includes the resulting t[ffi.

Hitoshiba Rai's technology] Cutting processing generally has inferior finished surface roughness compared to grinding processing, but it is widely used because it is superior in both processing efficiency and economy. However, the finished surface roughness due to cutting is
Since this often affects not only the appearance value of the product but also its performance, there is a need to improve the finished surface roughness of the cutting process. For this reason, new 5S materials such as cubic boron nitride (CBN) have been developed in recent years, and it has become possible to obtain a finished surface roughness on the order of submicrons. However, these new materials have problems such as the materials themselves are expensive, the range of application is limited, and the manufacturing process is complex. Therefore, there is a need to improve the finished surface roughness of high-speed steel tools, which are also inexpensive.

[Problems to be Solved by the Invention] High-speed steel contains many coarse primary carbides made of alloying elements such as W, Mo, Cr, and V, and cutting edge damage occurs due to their falling off and segregation. This worsens the roughness of the cutting edge and blade surface, and therefore the finished surface roughness. If powdered high-speed steel, which has finer primary carbides and improved toughness, is used as a material, the cutting edge/lunar surface roughness will be improved to some extent, and the finished surface roughness will also be improved to some extent. However, for example, in the case of broach cutting, the finished surface roughness of ordinary ingot high speed steel is Rmix = 8 t1
m, whereas in powder high-speed steel R,... = 6μ
However, on the other hand, there is also the problem of increased costs due to the complexity of the manufacturing process.

Therefore, it may be possible to improve the finished surface roughness by increasing the cutting speed. However, increasing the cutting speed leads to an increase in the temperature of the tool, and high-speed steel has the disadvantage of softening at temperatures above 600°C.
There is also a limit to improving cutting speed. To increase the cutting speed, it is necessary to improve the power and rigidity of the machine tool, and it is necessary to improve the machine tool or to optimize the tool shape and cutting conditions to suit the material to be stiffened. It is being However, these conventional techniques have reached their limits, and there is a need for the development of high-speed steel cutting tools with excellent finished surface roughness using new techniques.

The present invention was made in view of the above-mentioned problems, and it is possible to improve the cutting edge of a high-speed steel cutting tool without changing the conventional cutting conditions such as cutting speed (with a high finished surface roughness). It is an object of the present invention to provide a high-speed steel cutting tool having a structure that allows the cutting tool to be used in a variety of ways.

[Means for Solving the Problems] The present invention provides a cutting tool in which at least the cutting edge portion is made of high-speed steel, in which a rapidly solidified layer with secondary dendrite defects of 6 μm or less is formed at the cutting tool edge portion. Its gist lies in the fact that it is

[Operations] The present invention is constructed as described above, but in short, it is a high-speed cutting tool (hereinafter simply referred to as a tool) in which a rapidly solidified layer is formed at the cutting edge. When forming a rapidly solidified layer, it is most preferable to use a method that allows instant heat treatment at high speed, such as a method in which the tool tip is irradiated with a high energy density beam such as a laser or an electron beam. Rapid cooling is possible, and the shape of the solidified layer can be easily controlled. In addition, coarse primary carbides made of alloying elements such as W, Co, Cr, and V and carbon contained in the cutting edge are dissolved in the rapidly solidified layer, and the surface layer contains almost no primary carbides. The finished surface roughness is superior to that of ordinary high-speed steel that does not have a rapidly solidified layer or ordinary powdered high-speed steel that has finer primary carbides.

Furthermore, the rapidly solidified layer suppresses the formation of built-up edges due to improved adhesion resistance or the protective effect of the oxide film formed on the layer surface, and even if built-up edges are formed, the layer surface is stabilized. There is expected. By forming a rapidly solidified layer on the cutting edge in this way, the properties of the cutting edge are improved, and the properties of the cutting edge are easily transferred to the finished surface of the stiffened material, resulting in excellent finished surface roughness. It will be done.

The rapidly solidified layer is formed by solidifying from the liquid phase at a cooling rate of 600°C/sec or more, and by achieving such high-speed cooling, the secondary dendrite interval becomes 6 μm or less, At the same time, second phase particles such as carbides in the coagulated layer become 1 μm or less. On the other hand, when the cooling rate is less than 600° C./sec, the secondary dendrite spacing exceeds 6 μm and second phase particles such as carbides of 1 μm or more are precipitated. In the latter case, as shown in FIG. 1, only the same level of finished surface roughness as ordinary high-speed steel or powdered high-speed steel can be obtained. The reason for this is: ■ The size of the pieces falling off from the cutting edge is the same as that of ordinary high-speed steel or powdered high-speed steel, and ■ The amount of alloying elements solid-solved in the solidified layer increases with the cooling rate. : As a result, the thickness of the oxide film formed on the cutting edge becomes thinner and more uneven than when the temperature is 600°C/sec or higher, and as a result, it has the effect of improving adhesion resistance. The effect of suppressing the built-up cutting edge, or the effect of stabilizing the built-up cutting edge is lost, and as a result, the effect of improving the finished surface roughness cannot be obtained.

The laser processing conditions and cutting conditions in FIG. 1 are as follows.

Laser treatment conditions Material: 5K) 155 (1100℃ quenching) Output: 5Kw Spot diameter + 1mm Irradiation speed 20.1~4m/min Cutting conditions (bite) Work material: 548C (Hs: 250) Cutting speed = 7m
/ minute feed: 0.1 mm/rev.

Continuous cutting of cylindrical end face; cutting length 50 m Next, beam irradiation conditions as rapidly solidified layer forming conditions will be explained using a laser and an electron beam as examples.

In addition, it is theoretically possible to set the irradiation conditions when irradiating high-speed steel with a laser by determining the attraction energy density and the beam movement speed (Japanese Patent Laid-Open No. 59-83718
) However, since it is generally difficult to specify the energy absorption rate, setting conditions based on absorbed energy density is not specific. For this reason, beam irradiation in the present invention was performed as follows.

Laser irradiation conditions> The high energy density beam irradiation conditions necessary to form a rapidly solidified layer with a width of Dmm or more and a depth of 0.1 mm or more are as follows: Action:
T) and the beam intensity at that time (irradiation energy density; W)
This is almost determined by FIG. 2 shows the relationship between beam intensity (J/cm2) and interaction time (seconds) during beam irradiation. Generally preferred range of T and W is 5X
10-' seconds≦T≦10-1 seconds...■2 X
10' J/crn2≦W≦2 x 10' J/c
m” -・■ outside the above range, as shown in Figure 2, (a) evaporation occurs. (b) the depth of the rapidly solidified layer is insufficient. (A) defects occur in the rapidly solidified layer. (d) Insufficient cooling rate may cause problems such as non-solidification, making it impossible to obtain the necessary characteristics.Here, T and W vary depending on the laser excavation method and irradiation method, and the following conditions are given. .

(1) When one or several parallel continuous wave beams are scanned along the cutting edge to form a rapidly solidified layer in which a part of the heat-affected layer where no heat-affected layer does not exist overlaps in one beam or in an overlapping area.

T=-Xo, 0B (seconds)...■■ Here, S=Nispot ([Ilm) ■=Scanning speed (m/I [1in)] P=Laser output (in W) (2) Single or parallel When several pulse oscillation beams are scanned along the cutting edge to form a rapidly solidified layer in which a part of the heat-affected layer where no heat-affected layer exists overlaps in one beam or in an overlapping area.

Furthermore, as an additional condition, it is necessary to obtain a continuous solidified layer [it can be seen that (1) is the case when d=100%].

Here, s, v, and p are the same as in (1) d = Duty (%) f = Frequency (Hz) (3) While vibrating in the direction intersecting the cutting edge, scan the beam roughly parallel to the cutting edge and rapidly cool it. When forming a coagulated layer.

T=-XT (seconds)...■W=-x
6 x 103 (J/cm') ・(@XV *For pulse oscillation, multiply by d.

Here, s, v, and p are the same as in (1). D=amplitude (mm),
T=value of T obtained by ■ or ■. Furthermore, if f0 = vibration frequency (Hz), in order to obtain a continuous solidified layer, ■
, @(■ in pulse oscillation.

In addition to (■), the following conditions are also required.

■ −x l 6 , 7 < S
...■f.

folio (Hz), @electron beam irradiation conditions>, <yttrium, aluminum,
Garnet laser irradiation conditions> Since the absorption rate of beam energy on the metal surface is different, the condition range regarding W changes (■ is the same, ■ is changed). The conditional expressions for determining W and T depending on the irradiation method are the same. Further, the reason for setting the upper limit and lower limit is the same as in the case of laser irradiation.

5X10-' seconds≦T≦10-1 seconds...■
3 x 10” 47cm2≦W≦3 x 103J
/am'・=■' A rapidly solidified layer is formed under the above irradiation conditions, but it is not always necessary to form a rapidly solidified layer over the entire cutting edge involved in the cutting tool, and it may depend on the type of tool. may be formed only on a part of the cutting edge.

In addition, in the case of multi-blade tools, the rapidly solidified layer is not necessarily formed on all the blades, but may be formed only on the cutting edge of some blades, or even only on a part of the cutting edge. .

In addition, the high-speed cutting tool according to the present invention is not only a tool whose entirety is made of high-speed steel, but also a tool whose cutting edge is processed by welding or shrink-fitting high-speed steel to ordinary steel, that is, a tool that participates in cutting. This also includes those in which only the cutting edge is made of high-speed steel.

Once the rapidly solidified layer is formed, the cutting edge is finished.The size of the rapidly solidified layer at the finishing stage is 0.1 mm or more from the cutting edge to the flank, and 0.1 m+n or more from the cutting edge to the rake face. shall have the following. The reason for setting such a width is as follows. That is, in many cases, the life of a finishing cutting tool is controlled by a flank wear width of 0.1 + nm, and it is thought that the flank roughness within this range is transferred to the finished surface. On the other hand, it is thought that the area within about 0.1 a++n from the cutting edge is where chips adhere to the rake face and the core of the built-up cutting edge is formed. Therefore, it is necessary to form a rapidly solidified layer in a range of at least 0.1 mm from the cutting edge to the flank and rake sides.

The processing state of the tool material before the formation of the rapidly solidified layer may be quenched at any temperature, quenched, tempered, or simply annealed. Ultimately, this should be determined by the physical properties required for the tool for parts other than the rapidly solidified layer forming part, but it is possible to improve toughness and workability by quenching at a temperature below the normal quenching temperature. It is desirable that the material has a certain degree of rigidity. After forming the rapidly solidified layer, finishing processing is always required because surface irregularities are unavoidable due to once melting. Since residual stress and retained austenite are present in the rapidly solidified layer, finishing is preferably performed after one or more tempering treatments at 500 to 600°C.

There are no particular restrictions on the tools to which the present invention is applied, but for example, in the case of a broach that can process not only planar shapes but also complex shapes with high precision from rough machining to finishing machining, (a) It is a multi-edged general tool, (+1)
Since it is characterized in that it is re-ground with a clearance angle of about 3 degrees, at least an effect on the finished surface can be obtained by forming a rapidly solidified layer on the finished blade. Also, if the flank is irradiated with a beam, the rapidly solidified layer on the flank will spread, making re-grinding easier. Here, the finished blade means at least 1
Based on the blade whose cutting depth per month is 0, the previous 2
This refers to a total of 4 blades, 1 blade and 1 rear blade. When the blade with the depth of cut of 0 changes due to re-grinding, a new standard is set, and at least the four blades that satisfy the above relationship become the finishing blades.

The high-speed steel reamer used for finishing holes is also a multi-blade tool, but unlike a broach, the multi-blade has a finishing cutting part. From the biting edge to the peripheral edge involved in this finishing cutting, it is necessary that there is a rotating rapidly solidified layer corresponding to at least the feed amount per blade. Therefore, in order to retract the biting blade so as to reduce the worn portion of the peripheral cutting edge, re-grinding is performed parallel to the flank of the biting blade. Therefore, a shaving cutter in which a rapidly solidified layer is used for finishing the gear blade surface up to the end of the outer peripheral edge is a multi-edge tool in which all blades participate in finishing cutting. Therefore, it is necessary to form a rapidly solidified layer on the cutting edge of every blade.

Incidentally, the tool in the present invention is the above-mentioned broach.

Not only reamers and shaving cutters, but also pinion cutters, bevel cutters, end mills, hobs, forming racks, cutting tools, phrasing cutters,
This includes cutting tools such as milling cutters and drills, as well as chips and blades used in these tools. Examples will be described below.

[Example] Example 1 Fig. 3 shows the depth obtained when a rapidly solidified layer was formed by laser irradiation on a normally heat-treated material of high-speed wISKH51 under various conditions.

Output: 1~5Kw Beam spot diameter: OJ ~2.5 m+n Processing speed = 0.3~8m/min Oscillation method: 100Hz, amplitude 6mm pulse method +
200Hz, duty 50% continuous method: - By irradiating in the above condition range, at least 0.1
It has a depth of more than mm, and the secondary dendrite spacing is 6 μm.
A rapidly solidified layer having a second phase particle size of 1 μm or less was obtained.

Figure 4 is a micrograph (substituting for a drawing) showing the structure of the rapidly solidified layer.
Magnification: 400 times), and the lower part of the photograph is the base material side.

Moreover, FIG. 5 is a micrograph (magnification: 400 times) used as a drawing of the structure of a high-speed steel base material treated by a conventional method.

Example 2 A cutting test was conducted using a cutting tool in which a normally heat-treated material of high-speed steel 5KH59 was irradiated with an electron beam to form a rapidly solidified layer on the cutting edge. Figure 6 shows the results. It can be seen that the finished surface roughness of the tool L on which the rapidly solidified layer was formed is excellent. Irradiation conditions and test conditions are as follows.

(Irradiation conditions) Out crab 400W Spot diameter: 0.5 mm Scanning speed: 5m/min Irradiation direction: Perpendicular to the flank (Cutting test conditions) Work material: S CM 440 (Ha: 300) Cutting speed = 7 to 17m /min Feed: O, OF+~0.1 mm/r
ev.

Lubrication: Water-soluble cutting oil Relief angle = 2° Rake angle: 10° Figure 7 shows the finishing method. After rough machining of the cutting edge, beams were irradiated from three directions on the flank surface to finish the cutting edge. After beam irradiation, the material was tempered so that the rapidly solidified layer had a width of 0.1 mm or more from the cutting edge to the flank face 3 and rake face 4. (al) is before finishing, (al) is after finishing. 5 is a high speed steel material. Another example is a method of finishing the cutting edge by irradiating a beam from four directions on the rake surface after cutting the cutting edge [(bl)=(b2)];
Irradiate the beam from the direction where the scoop 4 is to be formed,
How to cut the blade and finish the blade edge [(cl) -=
(c-) ], a method of irradiating the beam from the direction in which the flank 3 is to be formed and finishing the cutting edge of one blade [(
dt) −' (al) ]. In both cases, the rapidly solidified layer (flank surface) width X and the rapidly solidified layer (rake surface) width Y are 0.1 mm or more.

Example 3 A flat broach was manufactured by irradiating a normally heat-treated material of high-speed steel 5KH55 with a 002 laser beam to form a rapidly solidified layer on the finished cutting edge.

This was used to cut the connecting rod mating surface. The results are shown in FIG. The vertical axis shows the number of processes until the finished surface roughness (Ra) reaches 3 μm. Regardless of whether or not regrinding was performed, a significant increase in the number of laser irradiated materials processed was observed. The irradiation conditions and processing conditions were as follows.

(Irradiation conditions) Output: 5Kw Spot diameter + 1.0 mm Scanning speed: 3m/min Irradiation direction: Perpendicular to the flank surface (Cutting conditions) Work material: S48C (Ha: 250) Connecting rod mating surface cutting Speed: 10 III/min Cut depth: 4.8 mm/5 stroke Lubrication:
Oil-based cutting oil machining length: 22 mm Laser irradiation is applied to the flank 3 of the cutting edge obtained by rough machining of the cutting edge after predetermined quenching and tempering, as illustrated in Fig. 9.
I did it for Finishing was performed after further tempering. (a) is a cross-sectional view of a broach in which a rapidly solidified layer 1 is formed after rough machining of the cutting edge 2, and (b) is a cross-sectional view of the broach in which the cutting edge has been subjected to finishing machining. 5 is a high-speed steel material, and 6 is a cross section of the blade before cutting edge finishing processing.

As shown in Figure 10, the cutting edge is not rough-processed before irradiation, and after forming a rapidly solidified layer 1 on the surface where the flank surface is to be formed, creep field grinding is performed with a large depth of cut and a small feed rate. It is also possible to perform blade cutting and blade edge finishing at the position of the rapidly solidified layer 1 at the same time by applying
This method is desirable because it requires fewer steps. (a) is a diagram showing a state in which a rapidly solidified layer is formed on the surface of the high-speed steel cable material 5 where the cutting edge flank 3 is to be formed, and (b) is a diagram showing the state in which a rapidly solidified layer is formed on the surface of the high-speed steel cable material 5 where the cutting edge flank surface 3 is to be formed.
AA' sectional view, (c) is an enlarged view of the rapidly solidified portion of (b), and is an explanation showing the processing form of the cutting edge. Note that 7 is the surface on which the flank surface is to be formed, and 8 is the contour of the blade after the cutting edge has been finished.

Here, when the average roughness (Ra) of the finished surface became 3 μm or more, re-grinding was performed from the rake face 4 side by the maximum wear width of the flank face.

Example 4 A normally heat-treated material of high-speed steel 5KH55 was irradiated with a laser beam to form a rapidly solidified layer on the cutting edge to produce a reamer and a shaving cutter. The results of machining using this are shown in FIGS. 11 and 12. In both cases, it was noted that the finished surface roughness improved due to the formation of the rapidly solidified layer. In FIG. 12, (a) shows the results of machining with a laser-treated shaving cutter, and (b) shows the results of machining with a comparative material using the conventional treatment method. In addition, in Figure 13 (a
) is a diagram showing an example of the cross-sectional shape of the reamer peripheral blade, (b)
is a region where a rapidly solidified layer is formed, 9 is a biting edge, and 10 is a peripheral edge. Further, FIG. 14 shows a longitudinal cross-sectional view of the serration portion of the round shaving cutter. These beams
This figure shows the general shape of a shaver and a shaving cutter, and the area where the rapidly solidified layer is formed. The irradiation conditions and processing conditions are as follows. .

(Irradiation conditions) Output: 5Kw Spot diameter: 1. Ommφ Scanning speed: 5 m/min Irradiation direction: Perpendicular to the flank surface (reamer cutting conditions) Work material: S 40 C (Ha: 210) Cutting speed:
10.8m/a+in Feed: 0.1~0.4 mm/rev
.

Machining depth: 25+[1m Machining hole diameter: 101 (shaving cutter cutting conditions) Work material: S CM 415 ()II! l:140)
(Module: 3. Number of teeth, 27. Pressure angle: 20°, helix angle: 0°) Shaving allowance: 0.05 mm Cutter rotation speed: 150 rpm Plunge feed speed: 0.7 mm/min Example 5 High speed! An end mill was manufactured by irradiating 5KH56 with a laser beam to form a rapidly solidified layer on the cutting edge. Fig. 15 shows the processing results using this.

Comparison material 1 (S KH) for both finished surface roughness and flank wear amount
56 treated by the conventional method) and comparative material 2 (KH
It showed a two to three times improvement in performance compared to A50 (processed using conventional methods).

(Irradiation conditions) Out crab 5Kw Scanning speed: 5 m/m1n (Tempering conditions) Tempering: 540℃ x 3 times (Cutting conditions) Work material: S K D 11 (Ha: 380) Cutting speed: 80m/min Depth of cut: 0.1 mm Fig. 16 shows the finished surface roughness with the conventional broach (SKH55) and the finished surface roughness with the laser irradiation broach (SKI55). The processing conditions in this case are as follows.

Laser processing output: 5Kw Spot diameter: 1mmφ Processing speed = 3m/min Work material: S 50 C()la 245), 25
wx 50'' Cutting speed: 6 m/min Depth of cut: 0.04 to Omm/As seen in the blade diagram, the tool using the present invention maintained good finished surface roughness even when the machining length was increased.

[Effects of the Invention] By forming a rapidly solidified layer on the cutting edge of a high-speed steel cutting tool as described above, the present invention can obtain an effect of improving the finished surface roughness with high precision that has not been previously available. In addition, by limiting the formation of the rapidly solidified layer to the areas where it is necessary, it is possible to suppress the rise in material and manufacturing costs, and furthermore, when using cutting tools, conventional cutting conditions and conventional machine tools can be used as they are. Can be done.

[Brief explanation of the drawing]

Figure 1 shows the relationship between secondary dendrite spacing and finished surface roughness, Figure 2 shows the conditions for forming a rapidly solidified layer, Figure 3 shows the laser irradiation conditions and the width of the rapidly solidified layer, and Figure 4 is a photomicrograph showing the structure of the rapidly solidified layer, Fig. 5 is a photomicrograph showing the structure of the high-speed steel base material processed by the conventional method, Fig. 6 is a photo showing the finished surface roughness in a cutting tool cutting test, Fig. 7 8 is a diagram showing the processing result of a flat broach, FIG. 9 is a cross-sectional view showing the method for manufacturing the broach cutting edge, and FIG. 10 is a diagram showing the method for manufacturing the broach. Figure 11 is a diagram showing the hole machining results of the beam machine, Figure 12 is a diagram showing the tooth surface machining results of the shaving cutter,
Fig. 13 shows the region where the rapidly solidified layer is formed in the external frequency of the beam, Fig. 14 is a cross-sectional view of the cereshimin in the round shaving cutter, Fig. 15 shows the machining results of the end mill, and Fig. 16 shows the actual process. FIG. 3 is a diagram showing the finished surface roughness of broaches in Examples and Comparative Examples. X... Width of the rapidly solidified layer (flank surface) Y... Width of the rapidly solidified layer (rake surface) 1... Rapidly solidified layer 2... Cutting edge 3... Flank surface of the cutting edge 4... Rake surface of the cutting edge 5...High speed steel material

Claims (1)

[Claims] A cutting tool in which at least a cutting edge portion is made of high-speed steel, the cutting tool having a secondary dendrite interval of 6 μm at the cutting edge portion.
A high-speed steel cutting tool characterized by having the following rapidly solidified layer formed thereon.