JPH0210217B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high-hardness sintered body for cutting, and particularly to a high-hardness sintered body that maintains the bonding strength of diamond crystal grains.
The grindability and machinability are improved. Conventionally, this type of diamond sintered body is known to be far superior to cemented carbide cutting tools when applied to cutting non-ferrous metals such as aluminum alloys, ceramics, and plastics. . Furthermore, compared to a diamond cutting tool machined from a single natural diamond stone, a sintered diamond tool has excellent toughness and cutting performance. However, when processing it as a sintered diamond tool, its hardness requires excellent grinding techniques by experts, and re-grinding becomes a problem, and improvements in grindability are desired. The present invention has been made in view of the above points, and improves the bonding means of diamond crystal grains, and by selecting the composition of the bonding material, maintains wear resistance, toughness, and hardness. The object of the present invention is to provide a high-hardness sintered body for cutting, which is obtained by applying ultra-high pressure and high temperature and has improved properties. Hereinafter, one embodiment of the high-hardness sintered body for cutting of the present invention will be described with reference to the drawings. In Figure 1, 1 indicates that diamond grains are
This is a high hardness sintered body for cutting, consisting of a diamond sintered body with a volume of 50% and the remainder being a binder. This sintered body 1 was manufactured by being exposed to ultra-high pressure and high temperature conditions using a suitable ultra-high pressure and high temperature apparatus. And diamond crystal grains are usually 1 to 20μ
The surface of the raw material diamond is coated in advance with a coating layer made of Al or an Al alloy. in this case,
The Al alloy is selected from WAl and TiAl, and the coating layer is usually obtained by CVD or PVD. The amount of the coating layer is preferably in the range of 0.5 to 5% by volume based on the volume of the diamond. The reason why the coating layer of Al or Al alloy is provided is to suppress grain growth of diamond crystal grains and maintain uniformity of grain size. If the amount is less than 0.5% by volume, grain growth cannot be suppressed and uniformity of grain size cannot be obtained. Moreover, if it exceeds 5%, the hardness will be insufficient and a problem will occur. Furthermore, the binder is at least one selected from three groups: first group to third group.
That is, the first group includes W, Mo, Nb, Ta and
The second group is selected from carbides of metals or alloys of the first group, and the third group is selected from one or two of Co and Ni. Regarding the binding material constructed in this way,
The components of the first group have the function of imparting toughness to the components of the second and third groups and increasing high-temperature strength. Furthermore, the second group of components has the function of increasing the high-temperature strength of the binder phase by dispersing high-hardness particles. Furthermore, the components of the third group play a role as a bonding agent, especially with respect to the components of the second group, and as a result, strong bonding strength is obtained. This is because the components of the third group tend to alloy or form intermetallic compounds and increase the hardness of the binder. Regarding the component ratios in the first group to the third group, the component ratios between the first group and the second group are 1:12 to 3:1. in this case,
If the content of the first group component is less than 1/12, the bonding strength with diamond crystal grains will be weakened, and if it exceeds 3 times, the toughness of the binder phase will be reduced, so the above range is appropriate. Also, between the first group and the third group, 1:3 ~
It has a component ratio of 2:1. In this case, if the content of the third group component is less than 1/2, the bonding strength of the binder is reduced, which is a problem, and if it exceeds 3 times, the high-temperature strength of the binder is reduced, which is a problem. Furthermore, from the above-mentioned relationships of the first group: the second group and the first group: the third group, the relationship of the first group: the second group: the third group is calculated to be 1:12:3 to 6:2. : There will be a relationship of 3. As mentioned above, the components of the third group play the role of a bonding agent with respect to the components of the second group, and if the amount is less than 1/4, the function as a bonding agent decreases, weakening the bonding strength. Moreover, if it exceeds 1.5 times, the high-temperature strength function of the second group component will be reduced, resulting in a problem. Therefore, the sintered body 1 of the present invention suppresses the grain growth and skeletonization of diamond grains, and bonds the grains to each other by using a binder made of three group components through a strong Al or Al alloy coating layer. It is an integrated system. Therefore, although the sintered body 1 of the present invention has approximately the same wear degree, toughness, and hardness as compared to a diamond sintered body that emphasizes the degree of skeleton between diamonds, it is difficult to grind with a diamond grindstone. It can be easily processed. That is, in relatively coarse grinding using a diamond grinding wheel, the grain boundary bonding metal is first worn down, causing the diamond grains to fall off one by one, and in finishing grinding using a fine-grained diamond grinding wheel, the metal in the sintered body 1 is removed. There are no diamonds falling off,
Wear occurs due to abrasion from the surface side of the diamond grains. On the other hand, with conventional diamond sintered bodies that have a rigid diamond skeleton, grinding with a relatively coarse diamond grinding wheel (140 to 170 mesh, outlet 100) destroys the diamond grains one by one and does not wear out. Cracks occur from places where the degree of bonding of the skeleton is weak or from places where the grain strength is weak, causing the particles to fall off in bunches, resulting in chipping. Furthermore, in light grinding that does not cause chipping, due to diamond grain growth and non-uniform hardness, only the diamond grinding wheel is subject to severe wear, resulting in large chips. FIG. 2 shows a diamond sintered body 11 consolidated on a support member 10 made of sintered carbide such as WC-Co. For example, as shown in FIG. 12 are constructed. In this case, the diamond sintered body 11 and the support member 10 are solidified by applying ultra-high pressure and high temperature conditions using an appropriate ultra-high pressure and high temperature apparatus. Also, in the case of the diamond sintered body 11 consolidated on the support member 10, the bonding strength of the diamond crystal grains was sufficiently maintained, and its toughness and wear resistance were also sufficient, and there was no problem in terms of cutting performance. . Example 1 Diamond crystal grains have an average grain size of 4 μm,
This was coated with 3% by volume of Al using the CVD method and used as a sintering raw material. In terms of composition, 89% by volume of diamond crystal grains coated with Al
(hereinafter simply referred to as %), and for the remaining binding material,
3% W of 1 μm from the first group and 0.5 μm of W from the second group.
3% WC and 5% Co of 3 μm from the third group were selected. This experiment was conducted with the aim of increasing the component proportion of the third group and confirming its connectivity with the first group. These mixed powders were mixed with acetone in a ball mill for 4 hours, then vacuum dried.
It was sintered in a Zr container while being placed on a support member 10 made of WC-Co-based sintered carbide. The sintering conditions in the high-pressure vessel at this time were 60,000 atmospheres and 1,400 atmospheres.
The obtained sintered body 1 was sintered at ℃ for 20 minutes.
1 and the support member 10 were cut by electrical discharge machining, brazed, and ground to produce a throw-away tip 12 as shown in FIG. Next, using this throw-away chip 12, a 10% SiAl alloy casting having a width of 50 mm and a length of 400 mm was milled in the longitudinal direction. The cutting conditions at this time were: cutting speed V = 500 m/min, depth of cut d = 0.5 mm,
Table feed F = 200 mm/rev and water-soluble cutting oil was used. As a result, the product of the present invention was capable of cutting over 800 passes, whereas the comparative product, in which the diamond crystal grains were not coated with Al or Al alloy,
It became impossible to cut after 800 passes. Regarding the components of the third group, the upper limit for the first group is valid up to 1:3 in the ratio of components of the first group: the third group, similar to No. 5 and No. 6 of Example 3, which will be described later. It was confirmed. Example 2 Diamond crystal grains have an average grain size of 6 μm,
While vibrating this in a sputtering device,
Covered with 2% Al. In terms of composition, 88% was diamond crystal grains coated with Al, and the remaining binder was 1 μm thick from the first group.
2% W, 3% Nb of 3 μm, 1 μm from the second group
WC of 2% and Co of 3 μm from the third group were selected as 5%. This experiment was conducted specifically to confirm the function of the second group of components. Therefore, consideration was given to determining the lower limit of the components of the second group with respect to the components of the first group and the third group. These mixed powders were held in the pressure chamber of an ultra-high pressure and high temperature generator through the same process as in Example 1, and then sintered at 60,000 atm, 1400° C., and 20 minutes. The obtained sintered body 1 was as shown in FIG. 1, and was assembled into a clamp holder, and a workpiece made of brass was turned. The cutting conditions at this time are
Cutting speed V = 300m/min, feed f = 0.12mm/rev,
Depth of cut d = 0.2mm, flank wear width 0.2mm
Cut for 70 minutes until reaching . In contrast, the conventional product for comparison (diamond 90% +
A high-hardness sintered body made of 10% Co) chipped after 40 minutes of cutting. From the results of Example 2 and other experimental results, it was confirmed that the components of the second group can be applied up to a component ratio of 3:1 with respect to the lower limit of the first group:second group. Regarding re-grinding after wear of the sintered bodies 1 and 11 used in Examples 1 and 2, after using a diamond grinding wheel of 140 to 170 mesh for rough grinding and 800 mesh for finish grinding, the rake face of
Finished with a 5μm diamond wrap. On the other hand, with the conventional product used for comparison, chipping occurred on the cutting edge during rough grinding, so it was necessary to reduce the grinding allowance and grind for a long time at 400 meshes. Furthermore, for raw materials having a coating layer made of Al or Al alloy on the surface of diamond grains,
The first group components W, Mo, Nb, Ta are on the surface.
When applied to a double coating of one or more types of Ti and Ti, good results were obtained with good wettability with the binder. Example 3 In Example 3, the volume % of diamond crystal grains was changed and the binder composition was changed. The compositions, cutting tests, etc. of these are shown in Table 1. That is, regarding No. 1 and No. 3, the relationship between the component ratios of the first group and the second group was set in order to determine the upper limit of the second group relative to the first group. In addition,
Regarding the upper limit of the first group to the second group, a 3:1 relationship is obtained in Example 2. In addition, regarding No. 2, in the relationship of the component ratio of the first group: the third group, the upper limit of the first group relative to the third group is determined, and regarding No. 4 to No. 6, the first group was set to determine the upper limit of the third group for

【table】

[Table] Added high hardness sintered body.
The cutting test was conducted using the conventional product (diamond 90% capacity + Co10
As shown in Table 1, the products of the present invention were superior in all cases. This is mainly due to the binder composition. Regarding grindability, compared to the product of the present invention coated with Al or Al alloy, the comparison product had the same composition of diamond crystal grains and binder, and added Al or Al alloy in the same amount as the coating amount. It is added in powder form. As a result, the product of the present invention was clearly superior to the comparative product in terms of grinding ratio. In this case, the grinding ratio is the value obtained by dividing the amount of wear on the sintered body by the amount of wear on the grinding wheel, and the grinding conditions are a #400 diamond cup wheel (φ150 mm).
50 for the inventive product and comparative product using
The settings were made when pressing with a pressure of Kg/cm ² and grinding the end face for 5 hours. The above cutting tests, grindability tests, and Examples 1 to
From Example 2, the relationships between the first group to the third group were obtained as follows. 1st group: 2nd group = 1:12-3:1 1st group: 3rd group = 1:3-2:1 1st group: 2nd group: 3rd group = 1:12:3-6:
2:3 That is, regarding the component ratio of the first group: the second group, 1:12 is based on No. 3 of Example 3, and 3:
1 is based on Example 2. In addition, regarding the component ratio of the first group: the third group, 1:3 is Example 3
No. 4 to No. 6, 2:1 are based on No. 2 of Example 3. Furthermore, the relationships between the first group to the third group are determined by calculating the component ratios described above. It has been confirmed that the components of the first to third groups are effective in terms of machinability and grindability within the above-mentioned ranges and according to the functions and roles described above. As explained above, the present invention suppresses the grain growth of diamond crystal grains by selecting a diamond crystal grain holding means and a binding material for a high hardness sintered body for cutting obtained by applying ultra-high pressure and high temperature. Since it has good grindability and machinability while maintaining bonding strength with the binder, toughness, and wear resistance, it has the advantage of expanding its range of application.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the high-hardness sintered body for cutting according to the present invention, FIG. 2 is a perspective view showing a modified example, and FIG. be. 1, 11... Diamond sintered body, 10... Support member.

Claims (1)

[Scope of Claims] 1. A high-hardness sintered body for cutting in which diamond crystal grains account for 50 to 95% by volume and the remainder is a binder, wherein the diamond crystal grains are covered with Al or WAl coated in advance on the surface thereof. , has a coating layer made of TiAl, and this coating layer covers diamond crystal grains within a range of 0.5 to 5% by volume, and remains after sintering to directly connect adjacent diamond crystal grains. The binding material is a first group consisting of one or more of W, Mo, Nb, Ta, and Ti, and a second group consisting of carbides of metals or alloys of the first group. At least one member from the third group consisting of one or two of Co and Ni is included, and the relationship between the first group: second group: third group is 1:12:3. A high hardness sintered body for cutting, characterized by a component ratio of ~6:2:3.