JPH0192033A - Manufacture of high speed steel cutting tool - Google Patents

Abstract

PURPOSE:To prevent the formation of crack during beam irradiation by reducing the residual stress by eliminating the brittleness generated in the tempering process by carrying out the tempering within a certain temperature range before the beam irradiation after the quenching work for a cutting tool material. CONSTITUTION:When tempering treatment is carried out at the temperature higher than 530 deg.C before the beam irradiation after quenching, formation of crack can be prevented, and in the tempering temperature range of 540-700 deg.C, formation of crack can be perfectly suppressed, in spite of the nearly equal tempering hardness to that in the quenching state. Through this method, the high energy beam 2 is irradiated to the estimated position where the cutting edge part of a high speed steel material (SKH55) 1 is formed, and after the formation of a quench coagulation layer 3, tempering treatment is carried out, and a high speed steel broach material 4 is formed. Then, groove cutting work is carried out by a grindstone 5, and the cutting edge is finishing-worked, and a high speed steel broach 6 is obtained. The formation of crack can be perfectly suppressed on the broach thus prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a high-speed steel cutting tool that can finish the cut surface of a rigid material smoothly even after long-term use.

The high-speed steel according to the present invention includes not only high-speed steel specified by JIS and steel types usually called powder high-speed steel, but also 1
Tempering 2 containing secondary carbides and due to alloy carbide precipitation
This includes steel types that undergo post-hardening.

[Prior Art] In response to demands for higher efficiency and higher accuracy in cutting, various improvements have been made to high-speed steel cutting tools in recent years, with improvements in wear resistance, toughness, and hardness of the cutting edge in particular. For example, in JP-A No. 59-83718, a high-speed steel material is quenched and then irradiated with a laser to dissolve a large amount of primary carbide contained in the steel material, thereby reducing the surface structure. A method has been shown in which the steel is made to contain almost no carbides, and then tempered at a specific temperature to cause fine precipitation of solid-dissolved carbides, significantly promoting secondary hardening and improving hardness, toughness, and wear resistance. ing.

However, the temperature of the quenching treatment in such conventional methods is such that as much primary carbide as possible is dissolved in the raw material steel,
This was determined from the viewpoint of not causing problems such as coarsening of crystal grains, and is quenched 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 way has high hardness and rigidity, and has very low toughness and plastic deformability. On the other hand, a layer melted and rapidly solidified by laser irradiation (hereinafter referred to as a rapidly solidified layer)
In this case, tensile stress acts between the layer and the adjacent high-speed steel material part (hereinafter referred to as the base material part). Therefore, when laser irradiation is performed after quenching, the tensile stress is rapidly solidified. If it is larger than the breaking force of the layer, cracking will occur;
Due to this, the roughness of the cutting edge/blade surface may be deteriorated, and as a result, the roughness of the finished surface of the rigid material may also be deteriorated.

Therefore, the present inventors came up with a technology to suppress the occurrence of cracks during high energy density beam (hereinafter simply referred to as beam) irradiation by controlling the quenching temperature, and filed a patent application. (Sho 6l-122844).

[Problems to be Solved by the Invention] Although the above applied invention has achieved the objective of suppressing the occurrence of cracks during beam irradiation, as mentioned above, the occurrence of cracks is mainly due to tension in the base material. From the perspective that this is caused by the force relationship between stress and the rupture force of the rapidly solidified layer during beam irradiation, a tempering process should be added after quenching and before beam irradiation, rather than adjusting the quenching temperature that was adopted in the previous application. At the same time, by adjusting the tempering temperature, it is possible to remove the brittleness that occurs during the tempering process and remove residual stress, and as a result, the occurrence of cracks during beam irradiation can be more effectively prevented. It was thought that it might be.

The present invention was made based on such an idea, and after hardening a high-speed steel cutting tool (hereinafter sometimes referred to as cutting tool) material, it is tempered under a certain temperature range to form a beam. It prevents the occurrence of cracks during irradiation and the accompanying deterioration of the cutting edge and blade surface roughness, and as a result, improves the performance regarding the finished surface roughness of the rigid material, and improves the wear resistance and toughness of cutting tools. It is also an object of the present invention to provide a method for manufacturing an excellent high-speed steel cutting tool.

[Means for solving the problem] The present invention further hardens a high-speed steel cutting tool material to 540%
After tempering at a temperature of ~700°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 and finished to form a rapidly solidified layer on the cutting edge. The gist is to obtain a high speed steel cutting tool.

[Function] The present invention is constructed as described above, and by hardening the cutting tool material as described above and then tempering it in a certain temperature range before beam irradiation, the brittleness caused by the tempering process is removed and the residual stress is reduced. This reduces the amount of cracking caused by beam irradiation and prevents cracks from occurring during beam 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 present applicant et al.
5KH55 and KHA30, which is a powdered high speed steel, were quenched at various temperatures and then tempered. This was used as a test material to investigate the relationship between heat treatment conditions and hardness. The results were as shown in Figure 1.

As is clear from Figure 1, when the tempering temperature exceeds 560°C, the quenched hardness also decreases, but in high-speed steel, if the tempering temperature is below 700°C, a hardness of about 1 (1c) 40 is sufficient. By the way, since the base material of a cutting tool is not a part that directly undergoes cutting, it does not need to be as hard as the cutting edge, which is directly involved in cutting, and it is not necessary to have the same hardness as the cutting edge that is directly involved in cutting. It is sufficient that the material has sufficient strength, but if it is too hard, it will cause various problems.From this point of view, it is generally said that a hardness of about HRC 40 is sufficient.That is, the tempering temperature is 530 to 700°C. If so, the hardness required for the base material of the cutting tool is naturally maintained.

Next, we irradiated the cutting edge of the high-speed steel tool that had undergone quenching and tempering treatment with a beam, and investigated the relationship between the occurrence of cracks and the quenching temperature, as shown in Figure 2. I got the result. The following 5-level evaluation was adopted as a criterion for determining the occurrence of cracks.

1... No cracking occurred.

2...Minute cracks 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 origins is 4 or less.

4... Total length of visible cracks 50mm or more1
Less than 00ma+ or the number of crack starting points is 5 or more and 9 or less.

5...The total length of visual cracks is toomm or more or the number of crack starting points is 10 or more.

As is clear from Figure 2, after quenching and before beam irradiation, the
It was found that cracking could be prevented if the tempering treatment was performed at a temperature higher than ℃. In addition, the tempering temperature is 530 to 560℃
In this range, cracking is completely suppressed even though the tempered hardness is almost the same as that in the quenched state. This means that if the temperature range of the tempering process is within the above range, the brittleness generated in the quenching process will be sufficiently removed, the residual stress will also be sufficiently suppressed, and the tensile stress between the base material and the rapidly solidified layer will be reduced by the beam irradiation. This shows that the breaking force of the rapidly solidified layer is controlled to be smaller than that of the rapidly solidified layer.

By the way, the beam used in the present invention may be any type of laser, electron beam, or other beam as long as it is a high-energy beam capable of high-speed heating, and the type of beam is not particularly limited. Next, beam irradiation conditions will be explained using laser and electron beams as examples.

Setting the irradiation conditions when irradiating high-speed steel with a laser is as follows:
A method of determining the absorption energy density and beam movement speed is also theoretically possible (Japanese Patent Laid-Open No. 59-83718).
However, since it is generally difficult to specify the energy absorption rate, it is not specific to set conditions based on absorbed energy density.Therefore, in the present invention, conditions were 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 Da- or more and a depth of 0.1 am or more are the time during which one point in the irradiation surface is irradiated (interaction; T ) and the beam intensity at that time (irradiation energy density;
W). Beam intensity (J/cm) when 5KH55 is irradiated with laser and electron beam
”) and the interaction time.
As shown in the figure.

Laser irradiation conditions> The preferred range of T and W is 5X10-' seconds≦T≦10-1 seconds...■2X
10'J/cm"≦W≦2 x 10' J/c
m2-■ outside the above range, evaporation occurs as shown in FIG. Rapid solidification layer depth is insufficient. Defects occur in the rapidly solidified layer. Problems such as insufficient cooling rate occur, and necessary characteristics cannot be obtained.

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 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 is present overlaps in one beam or in an overlapping area.

T--Xo, 0B (seconds) ...■■ W-12-x 6 x 10' (J/ca+2)
-■xv Here S-spot diameter (+am) ■! Scanning speed (m/m1n) P depth - output (Kw) (2) One or several parallel pulse oscillation beams are scanned in parallel at the cutting edge at the same time to form a heat-affected layer in one or overlapping areas. In the case where a rapidly solidified layer is formed where a portion of the layer that does not exist overlaps.

Furthermore, as an additional condition, <0.1 (extract)...■ is required to obtain a continuous solidified layer [it can be seen that (1) is for the case of d-100%].

Here, s, v, and p are the same as in 1) (%) f-frequency (Hz) Electron beam irradiation conditions> The condition range regarding W changes because the absorption rate of beam energy on the metal surface is different. (■ is the same, ■ is different), and 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.

5xlO-' seconds≦T≦10-1 seconds...
■3 X 102J/cm'≦W≦3 X 10'
J/cm”-■.

The processing conditions in this case are as follows.

100W to IKW Spot diameter: 0.1 to 2 Speed = 0.1 to 8 m/min In addition, the laser is YAG (yttrium, aluminum,
In the case of a garnet) laser, it is expected that the conditions will be the same as those for electron beam irradiation due to the absorption rate.

Although a rapidly solidified layer is formed under the above irradiation conditions, it is not always necessary to form a rapidly solidified layer on the cutting edge assembly involved in the cutting tool, and depending on the type of tool, it may be formed only on a part of the cutting edge. may be formed. *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 the negative part of the blade, or even on a further part of the cutting edge. .

In such a case, even if the cutting edge part is not irradiated with laser or the like, it is necessary to provide at least the same performance in terms of hardness and the like as that of one that has undergone normal hardening and tempering.

Therefore, even if the cutting edge part has not been subjected to treatments such as laser irradiation, it will be 530 to 56
It is desirable to temper at 0°C.

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, that is, the cutting edge involved in cutting. This also includes those whose only part is made of high-speed steel. In the investigation shown in FIG. 2, a carbon dioxide laser was used as the beam. The irradiation conditions were as follows.

Beam spot diameter: 1.00111φ output
: 5Kw Beam movement speed: 3m/min, i.e., irradiation energy density: 10'J/c+a" Interaction time: 0.02 seconds Irradiation method: 40 ports x 150 fL 15 beams were placed parallel to the surface of the hardened material at intervals of 8 am under the above conditions. Main irradiation.

After beam irradiation, a tempering treatment is required in consideration of surface irregularities caused by first 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 rigid material is expected, and the beam irradiation is also expected to improve the wear resistance and toughness.

Incidentally, FIG. 4 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.

Crab output 1~5Kw Beam spot diameter: 0.3~2.5am Processing speed: 0
．． 1 to 8 m/min pulse method % formula %: 50 The tools according to the present invention are reamers, broaches, shaving cutters, pinion cutters, rack cutters, bevel cutters, end mills, and hobs.

Needless to say, the products include forming racks, cutting tools, phrasing cutters, milling cutters, drills, and chips and blades used in these tools.

Examples will be described below.

[Example] A broach was manufactured by the method of the present invention, and a cutting test was conducted to compare it with a conventional example.

The manufacturing method is shown in FIGS. 5(a) to 5(d). Shang (e
) is an enlarged sectional view taken along line E-E' in figure (b), and (f) is an enlarged cross-sectional view of figure (C).
FIG.

A high-energy beam 2 is irradiated to the planned cutting edge formation position of the high-speed steel material (SKH55) 1 [Fig. 5(a)],
After forming the rapidly solidified layer 3, a tempering treatment is performed to obtain a high-speed steel broach material 4 [FIG. 5(b)], and then grooving is performed with a grindstone 5 [FIG. 5(c)]. Next, finish machining the cutting edge to obtain a high-speed steel broach 6 [Figure 5 (
d)], 7 is the base material, 8 is the rake face, and 9 is the flank face.

The broach produced in this way had no cracks at all, and cutting tests showed that the finished surface roughness of the stiffened material was improved as shown in Figure 6, and the wear resistance was improved as shown in Figure 7. It also had the effect of improving sex.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to prevent the occurrence of cracks during the formation of a rapidly solidified layer, improve the finished surface roughness of the rigid material, and improve the wear resistance of the cutting tool. and performance such as toughness can be improved.

[Brief explanation of the drawing]

Figure 1 shows the relationship between tempering temperature and tempering hardness of high-speed steel specimens, Figure 2 shows the relationship between tempering temperature and cracking frequency, and Figure 3 shows the relationship between beam strength and tempering hardness. Figure 4 shows the relationship between the working time, Figure 4 shows the relationship between the beam intensity and the maximum depth of the rapidly solidified layer, Figure 5 shows the broach manufacturing method, and Figure 6 shows the finished surface roughness of the broach. Diagram showing performance, No. 7
The figure shows the flank abrasion performance of the broach. 1... High speed steel material 2... High energy beam 3... Rapidly solidified layer 4... Broach material 8
... Broach cutting edge rake surface 9... Broach cutting edge flank surface 1 豐cQ - Takus:, Takashi Yasutsuku Omitted Figure 3 Electron beam intensity (J/CM2) Laser beam intensity (J/CM2) Figure 5 Sea bream'h@Wk Beak (field)

Claims (1)

[Claims] Harden high-speed steel cutting tool material to further increase 540 to 700
After tempering at a temperature of °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 further tempered and finished to form a high-speed solidified layer on the cutting edge. A method for producing a high speed steel cutting tool, characterized in that a steel cutting tool is obtained.