JPS6031604B2 - Throw-away tip for milling made of super hard alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a throw-away tip for milling made of a cemented carbide having extremely excellent heat cracking resistance and toughness.

Conventionally, tungsten carbide (hereinafter referred to as WC)-based superhard alloys have been used as indexable inserts for milling because of their excellent wear resistance.

However, the above-mentioned conventional WC-based cemented carbide cannot currently be used in milling cutting, which is subject to large mechanical impact forces, large thermal shock thermal amplitudes, short cycle thermal fatigue, etc., due to breakage.

From the above-mentioned viewpoints, the present inventors have discovered excellent ballability,
This ultra-hard alloy indexable insert has thermal shock resistance and thermal fatigue resistance, and can be used for heavy cutting with large mechanical shocks, large thermal amplitude, and short thermal cycles. As a result of conducting research to obtain {a
} Most of the fractures caused by mechanical impact in the conventional indexable insert for milling made of WC-based cemented carbide are due to the generation and propagation of cracks on the flank surface, and also due to thermal cracks on the tooth surface. Defects can also occur due to occurrence or transmission.

{b} When manufacturing the above-mentioned conventional WC-based superhard alloy milling indexable insert, nitrides of one or more metals from the umbrella, string, and & group metals of the periodic table are used. and one or more selected from the group consisting of carbonitrides (hereinafter referred to as metal nitrides and carbonitrides)
When a powder consisting of is mixed as a raw material powder and a green compact formed from this mixed powder is sintered in a horse mackerel charcoal atmosphere under reduced pressure, the strength and crater resistance are significantly improved, and
A throwaway chip is obtained in which a soft surface layer is formed on the surface, which is lower in hardness than the inside and is composed of a WC-Co alloy phase (a small amount of metal carbon/nitride may also be present). To be able to do it.

'c' The thickness and hardness of the surface softening layer in the indexable tip can be adjusted by adjusting the content of metal nitrides and carbonitrides and the atmosphere of the carbonitride.

'd} If a surface softening layer exists on either or both of the flank face and the scoop face of the indexable chip, the generation and propagation of cracks and thermal cracks are prevented, and there is no occurrence of defects.

As described above, I have obtained the following knowledge. This invention was made based on the above knowledge, and the weight%
It contains 0.5 to 50% of metal chlorides and carbonitrides, and if necessary, contains metals from the periodic table excluding W, for the purpose of further improving the wear resistance and heat resistance of the chip. umbrella,
One or more metals selected from the group consisting of carbides of one or more metals of the strings and the metals of the bow group (
(hereinafter referred to as metal carbide): 0.5 to 50%, Co or Co-based alloy: 2 to 20%, WC and unavoidable impurities: the remainder, and has a composition consisting of: Depending on the internal hardness, 5 to 50% of the Vickers hardness is applied to one or both of them over a thickness of 5 to 100 m from the surface.
The present invention is characterized by an indexable insert for milling made of ultra-hard metal having a surface softening layer with low hardness.

Next, the reason why the composition range and the thickness and hardness of the surface softening layer are limited as described above in the indexable tip of the present invention will be explained. 'a} Metal nitride and carbonitride Metal nitride and carbonitride components are:
In addition to the effect of improving crater resistance, as mentioned above, it has the effect of forming a strong surface softening layer mainly composed of WC-Co alloy phase on the surface in relation to the reduced pressure atmosphere of horsetail coal during dawning. However, if the content is less than 0.5% by weight, the desired effect cannot be obtained;
If the content exceeds the weight% of WC, the WC content will be relatively too low, resulting in a decrease in strength.
Its content was determined to be 0.5-5% by weight.

'b} Metal carbide Metal carbide is a component that is included as necessary when further improving wear resistance and heat resistance. However, if the content exceeds 50%, strength decreases, so the content was set at 0.5 to 50%.

[c} Co or Co-based alloy Co or Co-based alloy is a component that forms a binder phase,
If the content is less than 2% by weight, the desired high toughness cannot be achieved, while if the content exceeds 2% by weight,
If the WC content is relatively too low, the wear resistance will deteriorate, making it impossible to use it as an indexable tip for milling. Established.

(d-Thickness of the surface softening layer If the thickness is less than 5 mm, it will not be possible to prevent cracks or thermal cracks from occurring on the flank or tooth surface of the indexable insert. If the thickness exceeds 5 to 100 mm, initial wear will be significant and this is not desirable as a throw-away tip.
It was decided that Buddha m.

[e- Hardness of the surface softening layer The degree of softening of the surface softening layer on the flank or scoop surface relative to the inside of the indexable tip is 5% in terms of Vickers hardness.
If it is less than 50%, the desired effect of suppressing the occurrence of cracks and thermal cracks cannot be obtained because the hardness difference is insufficient. On the other hand, if it is greater than 50%, the hardness is too soft compared to the internal hardness. Since significant initial wear occurs, the hardness of the surface softening layer is set to be 5 to 50% lower in terms of Vickers hardness than the internal hardness.

Although there is no problem even if there is a hardness gradient in the surface softening layer, the condition that the degree of softening relative to the internal hardness is 5 to 50% lower in Vickers hardness as defined above must be satisfied. .

Next, the indexable tip of the present invention will be explained using examples.

Example 1 Final component composition is WC-5% by weight TIN-5% by weight TaC
- Commercially available WC powder, TIN powder, TaC powder, and Co powder were blended so as to have a Co content of -5% by weight,
This blended powder is mixed, a green compact is formed from this mixed powder, and then this green compact is competitively bonded by holding it at a temperature of 1400 qo for 1 hour in a carburizing atmosphere containing CO gas and a pressure of 10-3 Hg. After that, the softened surface layer on the scraper surface is removed by polishing.
Chip shape with a surface softening layer only on the flank: SNMN
432 (no honing) indexable tip 1 of the present invention was manufactured.

The throw-away chip 1 of the present invention has an internal hardness (Hv
): 1450, Hardness of surface softening layer on flank surface (Hv): 1
200, and the same thickness: 30 mm. Further, for the purpose of comparison, a comparative indexable tip 1 was manufactured under the same manufacturing conditions as the indexable tip 1 of the present invention, except that the dawn atmosphere was changed to a nitrogen atmosphere.

It goes without saying that in this comparative throwaway chip 1, there is no difference in hardness between the inside and the surface of the flank. Next, regarding the above-mentioned indexable insert 1 of the present invention and comparative indexable insert 1, cutter shape: diameter 20
DN type cutter with 0 eaves, 1 little girl blade, axial rake: -50, radial rake: -5 〇 Work material: JI with dimensions of length 200 x width 100 side
S. SNCM-8 material (hardness HB: 250), cutting speed;
70/min, feed; 0.3 0.4,0. and 0.6 ribs/tooth, depth of cut: 5 side, engagement angle: oo, number of test pieces: 3 pieces for each feed rate above, cutting: not used, and a dry cutting test was conducted under the conditions of . It was measured at which feed rate a defect occurs in one pass of cutting.

As a result, in the throwaway tip 1 of the present invention,
No defects were observed under any of the feeding conditions, whereas comparative indexable tip 1 had a feeding rate of:
At 0.4 sail/blade, two out of three chips were defective,
At 0.5 and 0.6 side/blade feeds, all the pieces were chipped.

Example 2 Each sample had the final component composition shown in Table 1.
Inventive indexable chips 2 to 9 and comparison indexable chips 2 to 4 were produced under the same conditions as the manufacturing conditions for the present invention indexable chip 1 in Example 1, except for changing the blending ratio of the raw material powder. Manufactured.

The internal hardness, hardness and thickness of the softened surface layer on the flank surface of the indexable tips 2 to 9 of the present invention and the comparative indexable tips 2 to 4 obtained as a result were measured, and the measurement results were used in the first test. Shown in the table.

Note that Comparative Throwaway Chips 2 to 4 all have component compositions outside the range of the present invention. Next, for the above-mentioned throw-away tips 2 to 9 of the present invention and comparative throw-away tips 2 to 4, cutting speed: 8 blood/mi
A dry cutting test was conducted under the same cutting conditions as in Example 1, except that the feed rate was 0.5 side/blade (764 skins/min), and the presence or absence of defects was observed in Table 1. .

The observation results are also shown in Table 1. As is clear from the results shown in Table 1, the throw-away tips 2 to 2 of the present invention
Comparative indexable inserts 2 and 3 suffer from defects due to poor impact resistance, whereas Comparative indexable inserts 2 and 3 do not have any defects and exhibit excellent impact resistance. The way tip 4 was soft due to an excessively high Co content, and as a result, the wear was extremely large and it was impossible to use it as a tip. Example 3 The final component composition was WC-15% by weight TIN-5% by weight Ta
The thrower of the present invention was prepared under the same conditions as in Example 1, except that the content of C-7 wt % Co and the softened surface layer on the flank surface was removed by polishing to form a softened surface layer only on the square face. Chip 10 and comparative indexable chip 5 were each produced.

The throw-away tip 10 of the present invention has an internal hardness (Hv)
: 1350, surface softening layer hardness (Hv): 1150, and thickness: 20 fm.

On the other hand, comparative indexable tip 5 has hardness (Hv): 1
It had 350. Next, regarding the present invention indexable tip 10 and the comparative indexable tip 5, cutter shape: the same as in Example 1, workpiece material: JIS dimensions of 25 mm length x 80 mm width.
・SNCM-8 material (hardness HB: 220), cutting speed: 1
5 melon h/min, feed: 0.3 skin/blade (86 h/min
Dry cutting test was conducted under the following conditions: depth of cut: 3 ribs, engagement angle: oo, number of pieces tested: 3 pieces, cutting oil: not used, cutting time: 10, 20, and 3 ribs. The average wear width on each flank surface was measured.

The measurement results are shown in Table 3. Further, the present invention indexable tip 10 and the comparative indexable tip 5
Cutter shape: Same as Example 1, Work material: JIS with length 45 x width 90 side dimensions.
．． SNCM-8 village (hardness HB: 300), cutting speed: 1
35m/mjn, feed: 0.5 legs/blade (129 teeth/m
In), depth of cut: 5 side, engagement angle: oo, number of test pieces: 3 pieces, cutting oil: used, We conducted a wet cutting test under the following conditions, and at what pass out of the 1st pass did the defect appear? I observed that.

Table 3 As a result, the present invention indexable tip 10
In comparison indexable tip 5, one out of three chips showed no defects even after 10 passes and continuous cutting was possible. Another one was lost after two passes, and the remaining one was lost after three passes. When the comparative indexable chip 5 was observed, which was damaged, it was confirmed that the cause of the damage was a thermal crack that had occurred on the scoop surface. As is clear from the above results,
The throw-away tip 10 of the present invention has almost the same excellent wear resistance as the comparative throw-away tip 5 which does not have a surface softening layer, and also has excellent wear resistance.
It has significantly superior impact resistance compared to other materials.

Example 4 Raw material powders were blended to have the final component composition shown in Table 4, and this blended powder was milled in a wet ball mill for 70 minutes.
The mixed powder was mixed for an infancy, a green compact was formed from the mixed powder, and the green compact was then sintered by holding it at a temperature of 1420°C for 1 hour in a carburizing atmosphere containing CO gas at a pressure of 10-4 Hg. After that, the soft surface layer on the flank surface is removed by polishing, and the chip shape has a soft surface layer only on the scoop surface: SNMN432 (
Throwaway tip of the present invention (without honing) 11~
No. 17 and comparative indexable tips 6 to 9 were manufactured, respectively.

Throwaway chips 11-1 of the present invention obtained as a result
7 and the internal hardness of comparative indexable tips 6 to 9,
Measure the hardness and thickness of the surface softening layer on the scraper surface, and
Shown in the table.

Next, a wet cutting test was conducted on the indexable tips 11 to 17 of the present invention and comparative indexable tips 6 to 9 under the same conditions as the wet cutting test in Example 3.

The results showed test results similar to those of the wet cutting test in Example 3, and the indexable tips 11 to 17 of the present invention
It is clear that these tips exhibit superior impact resistance and superior cutting characteristics compared to Comparative Indexable Tips 6 to 9 whose component compositions are outside the range of the present invention. As is clear from the results shown in Table 4, the indexable insert for milling made of cemented carbide of the present invention has excellent toughness, thermal shock resistance, and thermal fatigue resistance, as well as excellent wear resistance. Because of its excellent cutting properties, it can be used for heavy cutting with large mechanical shocks and heavy cutting with large thermal amplitudes and short thermal cycles, and it also maintains extremely excellent cutting characteristics under these harsh operating conditions. It shows itself.

Claims (1)

[Scope of Claims] 1. One or more metals selected from the group consisting of nitrides and carbonitrides of one or more metals from groups 4a, 5a, and 6a of the periodic table. :0.5~50
%, Co or Co-based alloy: 2 to 20%, tungsten carbide and unavoidable impurities: the remainder (more than % by weight). A surface softening layer having a hardness 5 to 50% lower in terms of Vickers hardness than the internal hardness over a thickness of 5 to 100 μm from the surface on either or both of the face and flank face. Throwaway tip for milling made of super hard alloy. 2. One or more metals selected from the group consisting of nitrides and carbonitrides of one or more metals from groups 4a, 5a, and 6a of the periodic table: 0.5 to 50
%, one or more metals selected from the group consisting of carbides of one or more metals from Groups 4a, 5a, and 6a of the periodic table excluding tungsten: 0.5
~50%, Co or Co-based alloy: 2~20%, tungsten carbide and unavoidable impurities: the remainder (at least % by weight). A soft surface layer having a hardness 5 to 50% lower in terms of Vickers hardness than the internal hardness extends from the surface to a thickness of 5 to 100 μm on either or both of the rake face and flank face. A throw-away tip for milling made of ultra-hard alloy.