JPH0669681B2 - Wood rotary cutting blade - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wood board, moulder,
The present invention relates to a blade suitable for being mounted on a machine such as an electric plane and performing plane cutting and shape processing by rotary cutting.

Conventional technology In the field of steel cutting tools, the PVD method, which has been successful in the technology of coating titanium nitride or carbide on the blade base material of cemented carbide and high-speed steel, is generally called ion plating. In addition to being non-polluting and excellent in mass productivity, the method described above is characterized in that a coating having good adhesion strength can be obtained at a processing temperature of 300 ° C to 500 ° C. This also has the advantage that this treatment can be applied to the final step of blade manufacturing using tool steels such as high-speed steel with a tempering temperature of several hundreds of degrees or more and high-chromium alloy tool steel, in addition to cemented carbide. There is.

Research to apply the PVD method having such advantages to the cutting of wood and wood-based materials has been conducted in the past,
All of them tried to use the technology used in the field of metal cutting tools as they were, and did not achieve sufficient results. The following reports can be cited as showing the difficulty of applying such conventional coating technology to the field of wood cutting.

(1) Saw tips with self-sharpening characteris tic
s, Eber Kirbach et al., The 8th Wood machining Seminar Abstract "Wood Industry"'86 .4.P40 In this report, cemented carbide tip material is used as a base material for cutting wood with a circular saw blade Al ₂ O ₃ −T on the surface
The results show that self-polishing characteristics can be obtained by iC (CVD method) coating. However, it is pointed out that this self-polishing property is still unsatisfactory in practical use, and that a base material should be used so that the wear rates of the base material and the coating layer are best synchronized.

(2) "Performance of TiN-coated tools in wood cut
ting ”MSsulonen, Surface and Coatings Technology
33C'87 P141-151 This report extends the TiN coating on cemented carbide and high speed steel. Cemented Carbide chips were coated with TiN (ion plating method) 0.7-1.0 μm to reduce rake face wear by 50% when cutting hard boards, but when cutting particle boards, paper boards and plywood The results of cutting spruce with a high-speed steel cutter with the same coating showed that rake face wear was reduced by about 20% compared to untreated blades. However, the effect is not so great.

(3) "Abrasion characteristics of TiN coated high speed steel bit" Kaoru Banshoya et al., Proc. Of the 38th Annual Meeting of the Wood Research Society of Japan (1988) A TiN (ion plating) coating of about 2 μm was performed on the melabi, spruce, semi-hard board and plywood, and as a result, no remarkable difference in wear progress was observed compared to the untreated bit. He said that he did not get good results as in the field.

Problems to be Solved by the Invention Even in the wood cutting field, unmanned operation, automatic operation, high precision,
Processing with a high operating rate is being pursued, and blades are shifting from high-speed steel to cemented carbide and from re-grinding type to throwaway replacement blade method, reducing the blade cost ratio to the production value. The task is to do so. In order to effectively use the PVD method, which is effective in steel cutting tools, steel plate shearing tools, paper slitting knives, etc., for wood cutting blades, finding a coating technology suitable for this application is a challenge. is there.

The present invention has been made to solve the above-mentioned problems of the prior art, and aims to provide a high-performance and long-life wood cutting blade for a wide range of wood cutting fields without mass production and cost increase. It is a thing.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides a cutting tool for rotary wood cutting, which uses a tool steel such as high speed steel, high chromium alloy tool steel or the like, and cemented carbide as a cutting tool base material. At least one of the flanks or the rake face is CrN, Cr ₂ N or CrN
And a chromium nitride layer composed of a mixture of Cr ₂ N and
It is coated to a thickness of 0.5 to 6.0 μm.

Example First, the process of problem solving is described. By coating the flank of the blade with hard chrome plating or vanadium carbide by the molten salt method, the rake face is selectively worn and the sharp cutting edge regenerates self-polishing characteristics, resulting in a long cutting surface. Succeeded in obtaining a longevity (Abstracts of the 5th Annual Meeting of the Japan Wood Processing Technology Association). However, since the molten salt method is processed at a high temperature of 800 ° C to 1000 ° C, there are difficulties in mass production, such as the need for subsequent quenching and tempering and the tendency to generate distortion. Further, hard chrome plating is inferior in uniform electrodeposition, so in order to obtain a uniform film thickness over the entire length of the blade, it is necessary to make the current density distribution uniform according to the shape of the blade, which is not always good in productivity. There is a problem that there is no. Hard chromium plating is coated with high-speed steel with high wear resistance or high-chromium alloy tool steel with high wear resistance and corrosion resistance as a base material in planing at cutting speeds of tens of meters per minute or less. Although the wear of the surface that does not wear precedes the coating layer, the self-polishing property appears and the wear suppression effect appears, but the wear suppression effect is insufficient in rotary cutting at a cutting speed of 1000 to 3000 m per minute. There was a limit.

Furthermore, as a result of research, we tried to cut spruce, which is a representative practical tree species, with a blade coated with TiN or TiC on the flanks to a thickness of 2 to 3 μm by various PVD methods using high speed steel as a base material. Is there no wear suppression effect?
Alternatively, it has been found that there is only a slight effect, and in any case, performance improvement commensurate with the surface treatment cost cannot be obtained.

From this standpoint, various studies were conducted using high speed steel, high chromium alloy tool steel and cemented carbide as base materials. First of all, vanadium nitride is a possible coating material for the PVD method.
VN and zirconium nitride ZrN were coated on the flank of the test blade, and the coated surface was examined by X-ray diffraction. As shown in FIGS. 2a and 2b, ZrN shows a particularly clear diffraction peak and VN also shows a clear diffraction peak. Therefore, it was confirmed that the desired substances were coated. As a result of cutting, these two materials are TiN and TiC.
Similar to the above, almost no effect of suppressing wear was observed. In addition, the inventors flanked the chromium in the crucible by resistance heating in a vacuum chamber, ionized it in a thermal filament, introduced N ₂ as a reaction gas, and applied a negative voltage to it. Chromium nitride was coated on and the coated surface was examined by X-ray diffraction. Incidentally, this coating method is a kind of thermionic activated ion plating method. As shown in Fig. 2-c and Fig. 2-d, clear diffraction peaks of CrN and Cr ₂ N appear, so confirm that the desired substances are coated and rotate the spruce. As a result, the cutting edge was worn in the shape shown in FIG. 1-a, and a good wear suppressing effect of chromium nitride was confirmed.

Studies have revealed that chromium nitrides, which have rather low hardness, are effective in cutting wood with respect to high hardness Ti nitrides or carbides, vanadium nitrides and zirconium nitrides. The reason why the effect is apparently different in this way is that the mechanical wear effect is small in the cutting of wood, whereas the deterioration of the cutting edge surface layer due to chemical reactions such as corrosion and oxidation greatly affects the progress of wear. Therefore, not only hardness, but also corrosion resistance and oxidation resistance, etc.
Chemical stability is necessary to control wear. Further, it has been found that chromium is an additive element for steel and cemented carbide, and the characteristics of the element, which has a large effect of imparting corrosion resistance and oxidation resistance, act advantageously.

Based on such knowledge, various studies were further conducted on the usage of chromium nitride, and the following results were obtained. Table 1 shows the values generally known as the micro hardness of various nitrides.
("Trend of surface modification technology", heat treatment, vol27-5)
See for reference.

(1) Coating method and morphology of chromium nitride In addition to the thermionic activation ion plating method described above, evaporation and ionization of chromium are performed with a enamel cathode gun.
As a result of cutting test with a blade coated with chromium nitride by three methods of HCD method and arc discharge ion plating method of evaporating and ionizing chromium by arc discharge, the adhesion strength of the coating layer is sufficient for all blades. Those which did not peel off and which showed the diffraction patterns of FIGS. 2C to 2I when the coating surface was examined by X-ray diffraction showed a good wear suppressing effect.

The arc discharge ion plating method is the cathode arc plasma deposition process (VADTEC SYSTEM, IN
C company) and the ionic bond coating process (Japan Multi-Arc Company). In the present specification, these are collectively referred to as ion plating.

Note that the sample symbols shown in FIGS.
The measured values of the interplanar spacing d of each peak are shown in Table 2 as -1 to Cr-N-7. The base material of each sample is SK for Cr-N-1 to 6
H51, Cr-N-7 is a high chromium alloy tool steel (8.5% Cr steel containing W, Mo, V). Table 2 shows only the base metal (SKH51) and
The peak values in the diffractograms of the above-mentioned samples of VN and ZrN are also shown. Since chromium is an element that is relatively easy to transmit X-rays, in the X-ray diffraction of each substance having a film thickness of 1.5 to 2.5 μm, the base material, tempered martensite (α-Fe), and
In some cases, primary carbon carbide and other diffraction peaks appear. The present X-ray diffraction is based on Cu-α1 radiation, and integrated diffraction is performed 1 to 5 times, and graphic processing such as background removal and smoothing is performed. The number of repeats of integrated diffraction is shown in each figure of FIG.

To have either wear inhibiting effect of the mixture of Figure 2 and any one of CrN or Cr ₂ N in CrN system from the state of the X-ray diffraction in Table 2, or CrN and Cr ₂ N, it was confirmed .
For CrN, the (200) or (220) plane is used, and for Cr ₂ N, (11
Since the diffraction peaks of the 1) plane are the most prominent, the diffraction peaks of Cr-N
It was possible to confirm the constituent element ratios and crystal states of the substances regarded as effective coating substances in the system.

As the blade base material, in addition to the high speed steel and the high chromium alloy tool steel listed here, an alloy tool steel and a carbon tool steel can be used. In other words, these tool steels are inferior in wear resistance and corrosion resistance to high-speed steels and high-chromium alloy tool steels, so it is obvious that the effect of suppressing wear of chromium nitride in wood cutting is relatively strong. A tempering temperature of 200 ° C to 300 ° C is suitable for these inexpensive tool steels, but according to the PVD method, it is possible to coat chromium nitride without greatly exceeding this temperature and thus without causing a significant decrease in hardness. .

(2) (a) If chromium nitride is coated only on the flank of the blade, the rake face will be worn before cutting the wood as shown in Fig. 1-a, and the self-polishing property that the sharp cutting edge is regenerated will be obtained. To be The self-polishing property does not appear in the uncoated blade shown in FIG. 1-b, and the wear suppressing effect is not observed in the blade coated with ZrN on the flank shown in FIG. 1-c.

Note that Fig. 1-a, b, c are: ・ Blade: SKH51 Rake angle 30 ° Blade angle 50 ° Clearance angle 10 ° ・ Flute number: 1 ・ Material to be cut: Spruce ・ Cutting speed: 1963m / min (cutting edge diameter φ125, rotation speed 5000
rpm) ・ Feeding speed: 5.0m / min ・ Cutting depth: 0.8mm is the result of rotary plane cutting. Fig. 1-b shows no coating, Fig. 1-a shows CrN (film thickness 2.0μm) 1) and FIG. 1-c are coatings of ZrN (film thickness 2.5 μm) on the flanks. The cutting material lengths are shown in the figure.

As can be seen by comparing FIGS. 1 b, c and a, it is clear that the coating of chromium nitride reduces the amount of retreat of the cutting edge, keeps the roundness of the cutting edge to a minimum, and the rake face has a considerable range from the cutting edge. Maintained almost parallel to the original rake face.

Shape cutting tools are jointing and joining cutters for joining, etc. [Finger cutters (Fig. 4) Horizontal strip cutters, mortise cutters, etc.] Chamfering cutters and round bar cutters (5th) for forming furniture Although there is a figure), etc., these are generally used in the form of re-polishing the rake face with a blade whose shape is formed in the outer peripheral direction according to the shape to be processed. A common problem with these is the side clearance angle δ as shown in Fig. 4C.
If the value is increased, δ cannot be increased because the shape changes greatly when the rake face is re-polished. Therefore, flank wear occurs in the conventional cutting upright portion, resulting in the wear shape shown in FIG. That is, since the side clearance angle is negative, the friction with the cutting surface is increased, and the cutting material is burnt and burnt. By applying a chrome nitride coating to the flank, the wear morphology as shown in FIG. 6B is exhibited. That is, the relief angle is maintained without the bulge of the side surface.
As a result, burns and burns are less likely to occur on the cutting material.

(B) The results shown in FIGS. 3a, 3b and 3d were obtained by coating chromium nitride on the rake face of the blade.

The cutting conditions are the same as in Fig. 1. Fig. 3-a Base material: SKH51CrN (film thickness 2.0 µm), Fig. 3-b
Base material: 8.5% Cr alloy tool steel CrN (film thickness 2.0 μm), Fig. 3-
d Base metal: cemented carbide (JIS K30) CrN (film thickness 2.0 μm) CrN was coated on each rake face. Fig. 3 -c Cemented Carbide (JIS K30) No coating. The cutting material lengths are shown in the figure.

As is clear from contrasting Fig. 3-a with Fig. 1-b and Fig. 3-d with Fig. 3-c, coating the rake face with chromium nitride reduces the amount of retreat of the cutting edge. As a result, the flank surface is sufficiently worn by repeated friction with the cutting surface, and the wear surface formed on the flank surface side is maintained substantially parallel to the tangent line of the cutting edge arc.

By the way, generally, in rotary plane cutting, since a plurality of blades (2-4 pieces) are transferred to the plane, this method of aligning the heights of the blades is achieved by rotating the planes on the plane and wrapping the blades on the blades. A whetstone is applied lightly. This method of aligning the cutting edges is called honing, whereby the flanks of the cutting edges are formed in the same plane as the circular arc of the cutting edge over a considerable range from the cutting edge. This range is 50μm-100μm
It is well known that there is no problem in practical use in the following cases. From this fact, the flank does not bulge out of the cutting edge arc and is almost parallel to the tangent of the cutting edge arc as shown in FIGS. 3a, 3b and 3d. Good wear can be maintained if the shape is worn. In this way, the flank is worn, and the rake face is maintained almost as the original rake face by the coating layer.

As described above, it is important to coat chromium nitride on only one of the flanks or the rake face.If there are coating layers on both sides, the phenomenon that one side preferentially wears does not occur, so it is sharp. The cutting edge is not maintained. Therefore, it is necessary that one surface has a coating layer having a predetermined thickness up to the tip of the cutting edge and the other surface has no coating layer extending from the cutting edge to the inside. In order to make the coating layer like this, either one surface may be polished with a blade after coating, or if it is necessary to coat after polishing with a blade due to the convenience of the blade manufacturing process, the When mounting the blade on the jig, place the surface you do not want to coat (non-coating surface) so that it is shaded against the chromium evaporation source.
Also, by reducing the gap between the jig surface and the non-coated surface, good one-sided coating can be obtained. Even if some wraparound occurs on the non-coating surface, there is no practical problem if the film thickness is a fraction of the coating surface side or less. With PVD coating, there is almost no shadow like wet chrome plating or the CVD method, and there is no wraparound in narrow gaps, so no special masking is required on the non-coated surface, and especially the throwaway replacement blade is mass produced. Is easy to apply.

(3) Thickness of coating film When the film thickness of chromium nitride is 0.5 μm or less, no good wear suppressing effect was observed. On the other hand, when the film thickness is 6 μm or more, not only the coating required time becomes long, but also cracks are apt to occur due to internal stress in the coating layer, resulting in loss of the layer, resulting in impaired sharpness and rather poor wear control effect. Become. For this reason, the coating thickness of chromium nitride on wood cutting tools is 0.5-6.
It is necessary to set to μm. The wear control effect and sharpness are well balanced, and the best film thickness range is 1.0 to 3.5 μm.
Is.

[Cutting surface of JIS K30 cemented carbide as a base material and a rake face coated with CrN] Fig. 7-a is Fig. 3-d, Fig. 7-b is Fig. 3-c, These are the cut surface roughness when the spruce board surface of the same wood removal is cut in reverse stitch. Since the roughness measurement is performed so as to scan across the annual rings, it can be seen from FIG. 7-b that the roughness is large as a whole and the reverse blurring of the spring wood part is large. On the other hand, FIG. 7-a shows a good cutting surface because the cutting surface roughness is still small. From this, it was confirmed that the CrN coating has a good wear suppressing effect even when the practical cemented carbide is used as the base material. When the cutting surface roughness in Fig. 7-b is set as the life limit, the life ratio of the coated blade is 2.
Was 5.

"Practical test of knives with SKH51 as the base material or CrN coating on the flank" SKH51 as the base material, rake face or flank face of the throwaway replacement blade to be attached to the planer barrel of No. 61-122804 To Cr
Table 3 shows the practical cutting test conditions and the results of coating N with a film thickness of 2 to 2.5 μm by the ion plating method. The test symbols A, B, and C are those of the throwaway replacement blade coated with the flank. The replacement blade was coated with a blade and then coated. For test symbols D and E, the coating was performed mainly on the rake face, and then the flank face was polished with a blade. In the table, the life ratio is the life ratio of the conventional SKH51 non-coated conventional throwaway blade. The blade wear shape in Table 3 is
It is a typical state of the cutting edge at the end of the life of each test. In all of the life judgments, the roughness of the cutting surface is used as a guide, and in addition to the progress of wear as shown in the figure, the edge spillage increases or expands, and the reverse spillage becomes large, and the life is reached. In any case, the life ratio is 3 to 4 times. Generally, in wood cutting applications, the life ratio of high speed steel and cemented carbide is in the range of 1: 2.5 to 5 times. It was confirmed by coating that a high speed steel can be used as a base material and a life comparable to that of cemented carbide can be obtained.

It should be noted that in FIGS. 1, 3 and Table 3 showing the shape of the cutting edge, the upper surface side is shown as a rake face.

"As a method to further improve the wear suppression effect of chromium nitride in wood cutting and to make it practical" (1) To relax the adhesion stress between the base material and the chromium nitride layer, the thermal expansion coefficient of both Apply a thin material having a coefficient of thermal expansion in the middle of the above as a coating base, for example SKH51 as the base material and CrN
When coating, TiN and Cr are suitable as the base material.

Material Thermal expansion coefficient Steel 11.5 to 12 × 10 ^-6 CrN 2.3 × 10 ^-6 Cr 8.4 × 10 ^-6 TiN 9.4 × 10 ^-6 (2) Suppressing grain growth of CrN or Cr ₂ N to increase the strength of the coating layer. To raise the thickness, thin alternate layers of CrN or Cr ₂ N are used to obtain the required thickness. Also CrN and CrCN (chromium carbonitride)
And may be laminated. Such laminated coating can be easily performed by adjusting the flow rate of N ₂ gas during coating by the ion plating method or by alternately flowing N ₂ gas and CH ₄ gas. Since CrCN has the same hardness as CrN and has the corrosion resistance and oxidation resistance inherent to Cr element, even if laminated with CrN or Cr ₂ N, the wear suppressing effect of the wood cutting blade is not impaired. As you can see from this, CrN or Cr ₂ N
In the range where N is larger than C, the wear suppressing effect does not change even if it is partially replaced with C. The notation of the substance in this case is conventionally Cr (C, N) or Cr ₂ (C, N), but the crystal form is CrN or Cr ₂ N, and the X-ray diffraction pattern is shown in FIG. 2c.
Are almost the same as those shown in ~ i. Therefore, CrN and Cr ₂ N as used herein include those in which N is partially replaced by C.

(3) To make it clear that it is a coated blade, for example, when the regrinding face of a re-grinding type plane blade is coated with chrome nitride (gray) and the user re-grinds the flank face. In order to avoid carelessly performing rake lapping as is often done in the past, the outermost surface of the coating layer is coated with a colored coating such as TiN (golden) or ZrN (yellow). In addition, if either the rake face or the flank face can be polished with a cemented carbide peeling blade, for example, a cemented carbide peeling re-polishing blade is a CVD
Although it is possible to coat chromium nitride by the CVD method, in the CVD method, the metal components such as titanium and chromium are also supplied in the form of gas, so by changing the introduced gas, the nitride of such dissimilar metals can be easily formed. It has the advantage of being stackable.

(4) For masking one side, for example
When coating chrome nitride on the rake face of the throwaway spare blade used for the 61-122804 planer barrel, if the spare blade is attached to a cylindrical jig or a flat surface jig as it is, the flank and the jig surface will be formed. Since a gap corresponding to the thickness of the spare blade (1 to 2 mm) is formed between the two, a coating layer is also formed on the flank. It is possible to reduce this gap and prevent coating on the flank surface, but it is possible to shape the jig, but as an alternative method, a masking substance is mainly attached to the flank surface before coating and then the rake face. Is polished with a blade and a predetermined coating is performed. As a masking substance, if the base material is tool steel such as high-speed steel or high-chromium alloy tool steel, an iron oxide film is formed by an alkali oxidation method (black dye), and if the base material is a cemented carbide, a CVD method is used. Al ₂ O _{3 and the} like.

Effects With the above-described configuration, the present invention has the following effects.

Since it contains a chromium nitride layer, the characteristics of the additive element that imparts corrosion resistance and oxidation resistance to steel and cemented carbide have an advantageous effect, and the cutting edge surface layer due to chemical reactions such as corrosion and oxidation by components contained in wood Reduce the deterioration of.

Since chromium nitride has such corrosion resistance, oxidation resistance and appropriate hardness, it exhibits a good wear suppressing effect when wood is rotationally cut, and the coating has a film thickness of 0.5 μm-
Since the thickness is 6 μm and is applied to only one surface, the non-coated surface precedes the coated surface, and the coated surface side is suppressed from being worn so that the roundness of the cutting edge is kept to a minimum. Therefore, for example, when the high-speed steel or the like is used as the base material and coated on either the flank or rake face, the cutting surface can be finished beautifully without fluffing, denting, or misalignment. It has a long service life comparable to that of hard alloys and, at the cost of coating, includes about half the cost of cemented carbides and saves valuable resources. Further, cutting power and cutting noise can be reduced. Further, even if a practical cemented carbide is used as a base material, the wear-suppressing effect of chromium nitride is great, so that a longer life can be achieved.

[Brief Description of Drawings] Fig. 1-a shows SKH51 as a base material with chrome nitride coated on the flank, b shows no coating, and c shows SKH5.
Cross-sectional view of ZrN coated on the flank with 1 as the base material after cutting, Fig. 2 -c, d, e, f, g, h, i for chromium nitride a ZrN, b for VN, j The figure showing the X-ray diffraction intensity of the coating surface of the blade base material (SHK51), Fig. 3-a shows the SKH51 base material coated with chrome nitride on the rake surface,
The same b is a high chrome alloy tool steel as the base material and chrome nitride is coated on the rake face, the same c is a cemented carbide base material and is not coated, and the same d is a chrome nitride base metal made of cemented carbide. Sectional view after cutting of the rake face coated object, Fig. 4 a is a side view of the finger cutter, b is a view from the rake face side, c is a sectional view taken along the line A-A of c, and Fig. 5 a is a circle Side view of the bar shaving cutter, B is a view from the side of the rake face, C is a sectional view taken along the line BB of B, Fig. 6A is a wear explanatory diagram without coating on the flank of Fig. 4C, B is FIG. 7-a is a diagram showing wear of a chrome nitride coated on the flank, FIG. 7-a is a diagram showing surface roughness cut by a blade in a state of FIG. 3-c Is.

Claims (1)

[Claims] 1. A blade for rotary wood cutting, which uses any of tool steel such as high speed steel and high chromium alloy tool steel and cemented carbide as a blade base material, and at least one of a flank and a rake surface is CrN. or Cr ₂ N or CrN and Cr ₂ N wood rotational cutting tool that the layer comprises chromium nitride layer consisting of a mixture is characterized in that it is coated on 0.5~6.0μm thick.