JPH0251966B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method of manufacturing a high speed steel cutting tool having high cutting performance. The high-speed steel according to the present invention includes not only the high-speed steel specified by JIS and the steel type usually called powder high-speed steel, but also the steel type that contains primary carbides and undergoes secondary hardening during tempering due to precipitation of alloy carbides. This includes: [Prior Art] Various improvements have been made to high-speed steel cutting tools in recent years based on the demand for higher efficiency and higher accuracy in cutting processes, and improvements in wear resistance, toughness, and hardness of the cutting edge have been made in recent years. It's getting messy. For example, JP-A-59-
In No. 83718, a high-speed steel material is hardened and then irradiated with a laser to dissolve primary carbides contained in large amounts in the material steel, so that the surface layer structure contains almost no carbides, A method has been proposed in which the solid-dissolved carbides are finely precipitated by tempering the steel at a specific temperature to significantly accelerate secondary hardening and improve hardness, glaze properties, and wear resistance. [Problems to be Solved by the Invention] However, this method causes the following problems. First, the temperature of conventional quenching treatment for high-speed steel cutting tools is determined from the viewpoint of dissolving as much primary carbide as possible in the steel material and not causing problems such as crystal coarsening. It is hardened at a temperature just below the melting point, which is 30 to 50 degrees Celsius lower than the melting point. The hardened material treated in this manner has high hardness and rigidity, and has very low toughness and plastic deformability. On the other hand, tensile stress acts on the layer melted and rapidly solidified by laser irradiation (hereinafter referred to as the laser-treated layer) with the high-speed steel material portion (hereinafter referred to as the base material portion) adjacent to the layer. Therefore, if laser irradiation is performed after hardening treatment, cracks may occur if the tensile stress is greater than the breaking force of the laser treated layer. Furthermore, the addition of a laser processing step increases product cost. The present invention was made in view of the above circumstances, and its purpose is to provide a method for manufacturing a high-performance high-speed steel cutting tool that can prevent the occurrence of cracks when irradiated with a high-energy density beam such as a laser. This is what we are trying to provide. [Means for Solving the Problems] The method for manufacturing a high-speed steel cutting tool according to the present invention is to harden the cutting tool material at a temperature lower than the melting point of 130°C, and then irradiate the cutting edge with a high energy density beam. Alternatively, the gist lies in obtaining a high-speed steel cutting tool having a rapidly solidified layer at the cutting edge by melting and rapidly solidifying the portion where the cutting edge is to be formed, and then tempering. [Function] The present invention is constructed as described above, but in short, by adjusting the quenching temperature before irradiation with a high-energy density beam, the plastic deformability of the base material is changed, thereby increasing the quenching temperature of the high-energy density beam. This prevents cracks from occurring during irradiation. The effect will be explained below. Note that the high-speed steel cutting tool according to the present invention includes not only a tool in which the entire tool is made of high-speed steel, but also a tool in which only the cutting edge portion involved in cutting is made of high-speed steel. First, the applicant has developed a typical melt-produced high-speed steel.
SKH51, SKE55, and powder high speed steel
KHA30 was quenched at various temperatures. This was used as a test material to investigate the relationship between quenching temperature and hardness. The results were as shown in FIG. 1 and Table 1.

【table】

[Table] On the other hand, since the base material of a cutting tool is not the part that directly performs cutting, it does not need to be as hard as the cutting edge, which is directly involved in cutting. It is sufficient as long as it has sufficient strength. From this point of view, it is generally considered that a hardness of about H _R C40 is sufficient. As is clear from Figure 1,
As the quenching temperature decreases, the quenching hardness also decreases.
In high-speed steel, a hardness of about H _R C40 can be sufficiently obtained if the quenching temperature is above the austenitizing temperature. In other words, the hardness required for the base material of a cutting tool can be naturally obtained by performing a normal hardening process. Next, a high energy density beam was irradiated on the cutting edge of the high-speed steel tool that had been hardened, or the area where the cutting edge was to be formed, and the relationship between the occurrence of cracks and the hardening temperature was investigated, as shown in Figure 2. The results were obtained. The following 5-level evaluation was adopted as a criterion for determining the occurrence of cracks. 1... No cracking occurred. 2...Minute cracks occur that cannot be visually identified but are visible under 20x magnification. 3...The total length of visible cracks is less than 50 mm or the number of crack starting points is 4 or less. 4...The total length of visible cracks is 50 mm or more and less than 10 mm, or the number of crack starting points is 5 or more and 9 or less. 5...The total length of visible cracks is 100 mm or more or the number of crack starting points is 10 or more. As is clear from Figure 2, at least 130° below the melting point.
It was found that cracking could be prevented if the quenching treatment was performed at a temperature lower than ℃. When the occurrence of cracking was investigated in relation to the quenching hardness, the results shown in FIG. 3 were obtained (the criteria for determining the occurrence of cracking was the same as in FIG. 2). That is, from the viewpoint of quenching hardness, it has been found that cracks do not occur if the hardness is lowered by about H _R C5 or more from the normal quenching hardness. In other words, by performing quenching at a temperature lower than 130°C below the melting point, which was conventionally performed at 30 to 50°C below the melting point, the hardness of the cutting tool base material is reduced by more than H _R C5 than the conventional one. However, as a result, the rigidity also decreases and the plastic deformability increases. Therefore, the tensile stress between the irradiated part and the base material that occurs when a high energy density beam is irradiated on the cutting edge or the area where the cutting edge is to be formed is easily absorbed by plastic deformation, reducing cracking. It is. Note that the high energy density beam used in the present invention is not particularly limited to the type of beam, such as a laser or an electron beam, as long as it is a high energy beam capable of high-speed heating. Next, beam irradiation conditions will be explained using laser and electron beams as examples. It is theoretically possible to set the irradiation conditions when irradiating high-speed steel with a laser by determining the absorption energy density and the beam movement speed (Japanese Patent Application Laid-Open No. 1983-83718), but in general, the energy Since it is difficult to specify the absorption rate of , it is not specific to set conditions based on absorbed energy density. Therefore, in the present invention, conditions are set based on energy irradiation density. In other words, the irradiation conditions for the high energy density beam necessary to form a rapidly solidified layer with a width of Dmm or more and a depth of 0.1mm or more are the time during which one point within the irradiation surface is irradiated (interaction; T) and the time. This is approximately determined by the beam intensity (irradiation energy density; W). Experimental results showing the relationship between beam intensity (J/cm ² ) and interaction time when SKH55 (1000℃ quenched material) is irradiated with laser and electron beams are shown in the fourth section.
As shown in the figure. <Laser irradiation conditions> The preferred ranges of T and W are: 5×10 ^-4 seconds≦T≦ ^10-1 second …… 2×10 ³ J/cm ² ≦W≦2×10 ⁴ J/cm ² …… If the temperature is outside the above range, problems such as evaporation, insufficient depth of the rapidly solidified layer, defects in the rapidly solidified layer, and insufficient cooling rate may occur, as shown in Figure 4, and necessary characteristics may not be achieved. It will not be possible to do so.
Here, T and W vary depending on the laser oscillation method and irradiation method, and the following conditions are given. (1) When one or several continuous wave beams parallel to the cutting edge are scanned in parallel at the same time to form a rapidly solidified layer in which a portion of the beam where no heat-affected layer does not exist overlaps in one beam or in the overlapping area. T=S/V×0.06 (sec)...W=P/S×V×6× ¹⁰³ (J/ ^cm2 )...where S=spot diameter (mm) V=scanning speed (m/min) P = Laser output (Kw) (2) One or several parallel pulse oscillation beams are scanned in parallel at the cutting edge at the same time, and rapid solidification is performed with overlapping parts where no heat-affected zone exists in one or the overlapping parts. When forming layers. T = S × d / V × 6 × 10-4 ( ^seconds ) ... W = P × d / S × V × 6 × 10 ³ (J/cm ² ) ... As an additional condition, a continuous solidified layer is To obtain f/V(1-d/100)×16.7<S...(1-d/100)/f<0.1(sec)...[(1) is when d=100% It can be seen that it is]. Here, S, V, and P are the same as in (1). d = Duty (%) f = Frequency (Hz) (3) While vibrating in the direction crossing the cutting edge, the beam is further scanned in a direction parallel to the cutting edge to rapidly solidify. When forming layers. T=S/D×T' (seconds)... W=P/D×V×6×10 ³ (J/cm ² )... * Multiply by d for each pulse oscillation. Here, S, V, and P are the same as (1). D = amplitude (mm),
T' is the value of T obtained by or. Furthermore, if f ₀ = vibration frequency (Hz), in addition to (in pulse oscillation) the following conditions are required to obtain a continuous solidified layer. V/f ₀ ×16.7<S ... f ₀ >10 (Hz) ... <Electron beam irradiation conditions> The condition range for W changes because the absorption rate of beam energy on the metal surface is different (is the same, but change). The conditional expressions for determining W and T depending on the irradiation method are the same as in the case of laser irradiation.
Moreover, the reason for setting the upper and lower limit values is also the same. 5×10 ⁻⁴ seconds≦T≦10 ⁻¹ seconds ……3×10 ² J/cm ² ≦W≦3×10 ³ J/cm ² …′ The processing conditions in this case are as follows. Output: 100W to 1Kw Spot diameter: 0.1 to 2mm Speed: 0.3 to 8m/min Continuous method: - If the laser is a YAG (yttrium, aluminum, garnet) laser, the conditions are the same as for electron beam irradiation due to absorption rate. It is expected that A rapidly solidified layer is formed under the above irradiation conditions, but it is not necessarily necessary to form a rapidly solidified layer on the entire cutting edge involved in the cutting tool, and depending on the type of tool, it may be formed on a part of the cutting edge. Sometimes it is only formed. Furthermore, in the case of a multi-blade tool, 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. The high-speed cutting tool according to the present invention is not only made entirely of high-speed steel, but also has a cutting edge formed by welding or shrink-fitting high-speed steel to ordinary steel, etc.
That is, it includes those in which only the cutting edge part involved in cutting is made of high-speed steel. In the investigations shown in FIGS. 2 and 3, a carbon dioxide laser was used as the beam.
The irradiation conditions were as follows. Beam spot diameter: 1.0mmφ Output: 5Kw Beam movement speed: 3m/min That is, irradiation energy density: 10 ⁴ J/cm ² interaction time: 0.02 seconds Irradiation method 40 ^□ Parallel with 8mm spacing
15 irradiations. After beam irradiation, a tempering treatment is required in consideration of surface irregularities caused by once melting, residual stress in the rapidly solidified layer, and the presence of retained austenite. Tempering is preferably performed at 500 to 600°C once or multiple times. Although the present invention prevents the occurrence of cracks during high-energy density beam irradiation by the above-mentioned effect, if the secondary dendrite interval of the rapidly solidified layer formed by beam irradiation is 6 μm or less, The effect of improving the finished surface roughness of the work material is expected, and the beam irradiation is also expected to improve the abrasion resistance and glaze properties. Incidentally, FIG. 5 shows the relationship between the beam intensity during laser beam irradiation and the maximum depth of the rapidly solidified layer. In this case, the laser processing conditions are as follows. Output: 1~5Kw Beam spot diameter: 0.3~2.5mm Machining speed: 0.3~8m/min Oscillating type Amplitude: 6mm Frequency: 100dl Pulse type Frequency: 200Hz Duty: 50% Continuous type: - The tool according to the present invention is a reamer, Includes broaches, shaving cutters, pinion cutters, rack cutters, bevel cutters, end mills, hobs, forming racks, cutting tools, phrasing cutters, milling cutters, drills, and tips and blades used in these tools. Needless to say. Examples will be described below. [Example] By the manufacturing method according to the present invention, broaches, end mills, pinion cutters, drills, milling cutters,
A hob and a bevel cutter were manufactured and a cutting test was conducted, and the results were in proportion to the conventional example. Example 1 Brooch The manufacturing method thereof is shown in FIGS. 6a to 6d. Note that e is an enlarged sectional view taken along the line E-E' in FIG. b, and f is an enlarged sectional view taken along the line FF' in FIG. A high-energy beam 2 is irradiated to the planned cutting edge formation position of the high-speed steel material (SKH55) 1 [Fig. 6a] to form a rapidly solidified layer 3, and then tempered to form a high-speed steel broach material 4. [Figure 6b].
Next, groove cutting is performed using the grindstone 5 [Fig. 6c].
Next, the cutting edge is finished to obtain a high-speed steel broach 6 [Fig. 6d]. In addition, 7 is the base material, 8 is the rake face, 9
is an escape. In the case of a multi-blade complete post tool such as a broach, rather than forming a rapidly solidified layer on the cutting edge and then finishing it to a specified size, it is preferable to form a rapidly solidified layer in advance at the position where the cutting edge is to be formed and then temper the blade. A method of processing and finishing is easier and more desirable. FIG. 7 shows the results of comparing the workability of blade cutting and grinding in such a process with the feed rate of a conventional example using the feed rate as a measure. A hexagonal boron nitride grinding wheel was used, and creep feed grinding was performed with a depth of cut of 3 mm. 7th
The horizontal axis of the figure is the quenching temperature, and the vertical axis is quenched at 1220℃ and 550℃.
It represents the ratio of the feed rate of this example to the feed rate of a conventional material tempered at °C. Feed amount is grinding burnt,
The feed rate was set so that grinding cracks would not occur and a finished surface equivalent to that of the conventional example could be obtained. 130℃ above melting point
Quenching at a lower temperature more than doubled the processing efficiency. The lower the temperature of quenching, the lower the hardness during grinding, resulting in better workability. When a cutting test was carried out using the broach prepared in this way, the finished surface roughness of the workpiece was improved as shown in FIG. 8, and the effect of improving wear resistance was also obtained as shown in FIG. 9. Example 2 End mill Material Comparative material 1 SKH56 2 KHA30 Laser treated material SKH56 (Quenching temperature: 1000℃) Processing conditions Comparative materials 1 and 2 Same as before Laser treated material output: 5Kw Continuous speed: 20m/min Spot diameter: 0.3mmφ Tempering : 550℃ x 3 times Cutting conditions Number of teeth: 2 Diameter: 10mm Work material: SKD11 (H _B = 380) Feed: 80mm/min Speed: 16mm/min Depth of cut: 1mm Test results Shown in Figure 10. The laser-treated material has improved wear resistance compared to conventional materials. Although not shown, good results were also obtained with laser-treated KHA30. Example 3 Pinion cutter Material Comparative material 1 SKH55 2 KHA30 Laser treated material SKH55 Processing conditions Comparative materials 1, 2 Same as before Laser treated material output: 5Kw Continuous speed: 1m/min Spot diameter: 1.5mmφ Tempering: 550℃ x 3 times Cutting conditions Work material: SCM21 Cutting stroke: (400▽ /500▽▽) str/min Radial feed: 0.12mm/min Test results are shown in Figure 11. The laser treated material obtained better results than the conventional material. Although not shown, good results were also obtained with a pinion cutter made of laser-treated KHA30. Example 4 Straight shank drill (10mmφ) Material Comparison material 1 SKH51 2 SKH51 (TiN coating treatment) Laser treated material 1 SKH51 (Laser treatment) 2 SKH51 (Laser treatment and TiN coating treatment) Processing conditions Comparison materials 1 and 2 Same as before (TiN coating treatment) Laser treated material Output: 5Kw Speed: 5m/min Spot diameter: 1.0mmφ Tempering: 550°C, 580°C, 600°C x 2 times TiN coating was PVD and thickness was 3 μm. Cutting conditions Work material: S50C (H _B 250) Hole diameter: 10mmφ Feed: 0.18mm/rev Speed: Comparative examples 1 and 2 18m/min Laser treated materials 1 and 2 25m/min Plate thickness: 20t (penetration) Test results Comparison was made based on the number of holes drilled. The results are shown in FIG. Laser-treated material 1 drilled more than twice as many holes as comparative material 1, and laser-treated material 2 1.3 times as many holes as comparative material 2. The performance of both materials was improved over the conventional material, and the reliability of the coating film was also improved. Example 5 Groove slicing Material Comparative material 1 SKH55 2 KHA30 Laser treated material SKE55 Processing conditions Comparative materials 1, 2 Conventional Laser treated material output: 3Kw Speed: 5m/min Spot diameter: 1.0mmφ Tempering: 550℃ x 3 times Cutting conditions Work material: S40C (H _B 150) Cutting speed: 17.6 m/min Feed rate: 90 mm/min Groove depth: 1.14 mm Test results Comparison was made based on the number of grooves cut. The results are shown in FIG. The number of processes was 2.5 times that of Comparative Material 1 and twice that of Comparative Material 2, and the final performance was improved. The material ratio is also cheap. Example 6 Regular blade hob Hob specifications Material SKH55, module 2.5, pressure angle
20°, number of threads: 3, number of grooves: 12 Work gear specifications Spur gear, number of teeth: 31, helix angle: 0°,
SCM415H (H _B 150) 82.5〓×50 ^w Cutting conditions Cutting speed: 98m/min Feed: 4.0mm/rev Kleis cut No shift Laser treatment Output: 5Kw Spot diameter: 1.5mmφ Speed: 3m/min Tempering: 580℃×3 The test results are shown in Figure 14. Craters and flank wear were reduced, and both life and finished surface roughness were improved. Example 7 Bevel cutter Material SKH51 Work gear specifications Pitch circle diameter: 154.08mm Teeth: 36 Helix angle: 35゜ Face width: 23.0mm Tooth height: 10.5mm Material: SCM415 (H _B 150) Cutting conditions Cutting speed: 43m /min Feed: 0.12mm/blade Laser processing output: Speed: Spot diameter: 5Kw 3m/min 1mmφ bottom blade output: Speed: Spot diameter: 5Kw 5m/min 2.5mmφ outer blade, inner blade Tempering: 580℃ x 3 tests The results are shown in Figures 15 and 16. Compared to the conventional example, there were fewer craters and flank wear was also reduced. Effects: Improved service life (long life due to breakage due to bottom cutter crater) Improved tooth surface roughness (outer cutter, inner cutter) [Effects of the invention] Since the present invention is configured as described above, formation of a rapidly solidified layer is prevented. It is possible to prevent the occurrence of cracks during processing, and to improve the performance of the tool, such as the finished surface roughness, wear resistance, and toughness.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between quenching temperature and quenching hardness.
Figure 2 is a diagram showing the relationship between quenching temperature and crack occurrence status, Figure 3 is a diagram showing the relationship between quenching hardness and crack occurrence status, Figure 4 is a diagram showing the relationship between beam intensity and interaction time, Figure 5 is a diagram showing the relationship between beam intensity and the maximum depth of the rapidly solidified layer, Figure 6 is a diagram showing the broach manufacturing method, and Figure 7 is a diagram showing the relationship between grinding feed rate ratio and quenching temperature. Figure 8 shows the performance of the broach in terms of finished surface roughness, Figure 9 shows the performance of the flank wear resistance of the broach, Figure 10 shows the performance of the end mill, and Figure 11 shows the performance of the pinion cutter. Figure 12 shows the performance of the drill, Figure 13 shows the performance of the milling cutter, Figure 14 shows the performance of the hob, Figure 15 and Figure 1.
Figure 6 shows the performance of the bevel cutter. 1...High speed steel material, 2...High energy beam, 3...Rapid solidification layer, 4...Broach material, 8
...Broach cutting edge rake surface, 9...Broach cutting edge flank surface.

Claims (1)

[Claims] 1. After hardening the cutting tool material at a temperature below the melting point of 130°C, the cutting edge or the area where the cutting edge will be formed is melted and rapidly solidified by irradiation with a high energy density beam, and then tempered to rapidly cool the cutting tool material. A method for manufacturing a high-speed steel cutting tool, characterized in that a high-speed steel cutting tool having a solidified layer is obtained.