JP2005068514A - Hard metal containing fine particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard metal containing fine particles for a small diameter tool, which has a grain-controlling effect enough to inhibit the grain growth of a hard WC-dispersed phase, and as a result, has high hardness, high toughness, superior fracture resistance and superior chipping resistance. <P>SOLUTION: The hard metal containing fine particles has a metal composition comprising, by mass%, 2-13% Co and/or Ni, 0.1-1.8% Cr, 0.01-0.6% Ta and the balance W with unavoidable impurities; contains the particles of a hard dispersion phase mainly formed of WC with an average diameter of 0.8 μm or smaller; and has Cr oxides with sizes of 100 nm or smaller existing in the hard dispersion phase. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a so-called fine cemented carbide alloy having particles mainly composed of tungsten carbide having an average particle diameter of 0.8 μm or less, which is used for a small diameter tool having a blade diameter of 0.6 mm or less, particularly a small diameter drill.

A fine cemented carbide containing a WC hard dispersed phase having an average particle diameter of 1 μm or less is widely used in small diameter end mills, small diameter drills, various shearing blades and the like because of its high hardness and toughness. In recent years, as the number of finely processed products has increased, the diameter of end mills and drills has been rapidly reduced, and the average particle size of fine-grained alloys has become smaller and higher in hardness and toughness. Therefore, in order to suppress grain growth of the WC hard dispersed phase during sintering, metals such as V, Cr, Ta or their compounds (carbides, nitrides, carbonitrides, etc.) are used as grain growth inhibitors for WC. It has been proposed. As specific examples of these, Patent Documents 1 to 6 are disclosed.
In Patent Document 1, by adding V and Cr in combination, a large amount of V or Cr is not added so that a third phase that causes a reduction in the toughness of the alloy is generated, and in a 100 MPa Ar atmosphere after vacuum sintering. By performing the HIP treatment, a cemented carbide having V and Cr dissolved in the binder phase and essentially consisting of two phases, ie, a WC phase and a binder phase, and having an average WC grain size of 0.7 μm or less is obtained. It is disclosed.
In Patent Document 2, two types of V and Cr are added, pressure sintering is performed at 5.9 MPa after vacuum atmosphere sintering, and quenching is performed, whereby WC is a thin layer of precipitated composite carbide of V, W, and Cr. A cemented carbide with higher strength is disclosed by coating and eliminating the precipitation of (V, W, Cr) C in the binder phase.
In Patent Document 3, pressure sintering is performed at 4.9 to 14.7 MPa after vacuum atmosphere sintering, and quenching is performed at 50 to 100 degrees / minute, so that V, W, and Cr are contained in a binder phase mainly composed of Co. A cemented carbide with higher strength is disclosed by finely dispersing and dispersing a hard dispersed phase composed of the precipitated composite carbide of WC and coating WC with a thin layer of the precipitated composite carbide of V, W and Cr. .
In Patent Document 4, three types of V, Cr, and TaC or (Ta, Nb) C are added, and after vacuum sintering, HIP treatment is performed at 100 MPa in an Ar atmosphere to obtain (Ta, W) C or a certain amount or less. A cemented carbide having an average particle diameter of WC of 0.6 μm or less and improved welding resistance is disclosed by precipitating a solid solution (Ta, Nb, W) C in the alloy.
Patent Document 5 describes the addition of V, Cr, Ta, pressure sintering at 5.9 MPa after vacuum atmosphere sintering, and a WC hard dispersion phase having an average particle size of 0.6 μm or less is dispersed. Disclosed is a cemented carbide that disperses solid solution particles of carbides or carbonitrides such as V, Cr, Ta, etc. in the base of the hard alloy, and prevents the decrease in the toughness of the alloy by making the maximum particle size 3 μm or less. ing.
In Patent Document 6, a Co-phase alloy is formed of a Co-based alloy containing a W and C component, and further a V component, and the remaining dispersed phase is dispersed and distributed in a substrate with Co-based alloy ultrafine particles having a particle size of 100 nm. A cemented carbide having a structure is disclosed.
However, in the prior arts disclosed in Patent Documents 1 to 3 and 6, V and Cr are added, but Ta is not added, the bond between WC grains is weak, the toughness is inferior, and the high temperature characteristics are inferior. There are drawbacks. That is, for example, as the circuit density of printed circuit boards and the like increases, drilling work with small-diameter drills becomes faster and more efficient, and the drill itself due to frictional heat between the drill and the work material. In spite of the tendency for the temperature to increase, the hardness and toughness decrease at high temperatures, and there is a drawback that the life is reached at an earlier stage due to wear and breakage. On the other hand, in Patent Documents 4 and 5, although all of V, Cr, and Ta are added, there is a defect that the toughness is inferior to that of a Ta-free product. For this reason, for example, when it is used for a small-diameter drill for drilling a printed circuit board, there is a drawback that the life is reached at an earlier stage due to minute chipping or breakage.

Japanese Patent No. 1539991 JP-A-11-350061 Japanese Patent No. 3291562 Japanese Patent No. 1487479 JP-A-6-81072 Japanese Patent No. 3214385

  The problem to be solved by the present invention is that it has a sufficient grain suppression effect and can sufficiently suppress grain growth of the WC hard dispersed phase, so that it has high hardness, high toughness, chip resistance and chipping resistance. It is to provide a fine cemented carbide material for a small diameter tool having excellent properties.

  The present invention comprises, in mass%, 2 to 13% of Co and / or Ni, 0.1 to 1.8% of Cr, 0.01 to 0.6% of Ta, and the balance of W and inevitable impurities. The hard dispersed phase mainly composed of WC having a metal component has an average particle size of 0.8 μm or less, and Cr oxide having a size of 100 nm or less exists in the hard dispersed phase. It is a fine cemented carbide. By adopting this configuration, since the elements contained in the alloy have a sufficient grain suppression effect, the grain growth of the WC hard dispersed phase is sufficiently suppressed, the hardness is high, and the toughness is high. It is possible to provide a fine cemented carbide material for small diameter tools having excellent chipping and chipping resistance.

  By adding Cr and Ta in combination, the grain growth of the WC hard dispersed phase can be sufficiently suppressed, and a high-hardness cemented carbide material with an average particle diameter of 0.8 μm or less can be realized, and WC is mainly used. By precipitating a Cr oxide having a size of 100 nm or less in the hard phase, the strength of the grain boundary is increased and high toughness can be realized. This is because the finer oxide of Cr precipitates in the WC hard dispersion phase, and the oxygen concentration at the interface between the WC hard dispersion phase and the binder phase or between the WC hard dispersion phase is controlled appropriately, thereby reducing the interface strength. This is due to an increase in toughness as a result. Also, by adding Cr and Ta in combination, the heat resistance of the cemented carbide material is increased, and a small diameter tool having excellent wear resistance and fracture resistance even when the cutting edge temperature of a small diameter drill or the like is increased. A fine cemented carbide material can be provided. For example, when a small-diameter drill for drilling a printed circuit board is produced using the fine cemented carbide material of the present invention, a small-diameter drill capable of drilling with high speed, high efficiency and high accuracy can be realized.

  In the present invention, a predetermined amount of Cr and Ta is added to produce a fine cemented carbide material, the average particle size is made 0.8 μm or less, the sintering conditions are devised, and a vacuum of 1.3 to 13.2 Pa. After holding at a predetermined temperature in the range of 1330 to 1480 degrees for 0.5 to 2 hours in the atmosphere, the atmosphere is changed to a pressurized atmosphere of pressure: 4.9 to 14.7 MPa, and the pressurized atmosphere is changed to 15 to 60 minutes. After holding the so-called Sinter HIP process, Cr oxide with a size of 100 nm or less can be precipitated in the hard phase by rapidly cooling up to 1200 degrees at a cooling rate of 50 to 100 degrees / minute. By adding Cr and Ta, it is possible to realize a fine cemented carbide material having high toughness and fracture resistance and excellent chipping resistance while sufficiently suppressing grain growth of the WC hard dispersed phase. By precipitating a Cr oxide having a size of 100 nm or less in the hard dispersed phase, the strength of the interface between the WC hard dispersed phase and the binder phase or the interface of the WC hard dispersed phase is increased, and the toughness is high. In addition, it is possible to realize a fine cemented carbide material for small diameter tools having excellent hardness and toughness. This is because fine Cr oxide precipitates in the WC hard dispersion phase, so that the oxygen concentration at the interface between the WC hard dispersion phase and the binder phase or between the WC hard dispersion phase is moderately controlled. This increases the strength of the interface, and as a result, the toughness and heat resistance are considered to increase. By adding Cr and Ta in combination, it is possible to realize a fine cemented carbide material having an average particle size of 0.8 μm or less and a high hardness, and a Cr oxide having a size of 100 nm or less and a hard material mainly composed of WC. High toughness can be achieved by precipitation in the phase. Also, by adding Cr and Ta in combination, the heat resistance of the cemented carbide material is increased, and a small diameter tool having excellent wear resistance and fracture resistance even when the cutting edge temperature of a small diameter drill or the like is increased. A fine cemented carbide material can be provided. For example, when a small-diameter drill for drilling a printed circuit board is produced using the fine cemented carbide material of the present invention, a small-diameter drill capable of drilling with high speed, high efficiency and high accuracy can be realized. In order to allow Cr oxide having a size of 100 nm or less to exist in the hard dispersed phase, it is effective to use WC powder to which Cr is added in the raw material powder production stage as a raw material and to rapidly cool after sintering HIP. Regardless of the fact, the presence of a Cr oxide having a size of 100 nm or less in the hard dispersed phase increases the strength of the interface between the WC hard dispersed phase and the binder phase or the interface of the WC hard dispersed phase. Is important. The presence of Cr oxide having a size of 100 nm or less in the WC hard dispersed phase means that a fine cemented carbide alloy is observed at 125 k times with a transmission electron microscope (hereinafter referred to as TEM), and a TEM apparatus is used. This can be confirmed by analyzing the composition with an attached energy dispersive X-ray analyzer (hereinafter referred to as EDX). When the microstructure of the fine cemented carbide of the present invention is observed at a magnification of 125 k by TEM, the proportion of Cr oxide having a size of 100 nm or less in the hard dispersed phase is 1 to 5 in 50 views. Therefore, further excellent toughness can be obtained.

  Next, the reason for the numerical limitation will be described. When Co and / or Ni is less than 2%, sufficient fracture resistance cannot be obtained when the diameter is reduced, and when it exceeds 13%, wear resistance is reduced and the drill diameter is significantly worn. . Therefore, the content of Co and / or Ni is set to 2 to 13%. When the Cr content of the entire alloy is less than 0.1%, the growth of the WC hard dispersion phase proceeds during sintering, and the average particle size exceeds 0.8 μm, resulting in the disadvantage that wear resistance and toughness are reduced. On the other hand, if it exceeds 1.8%, the Cr content in the binder phase is excessively increased, resulting in a drawback that the toughness is lowered. Therefore, the Cr content is 0.1 to 1.8%. Further, when the content of Ta is less than 0.01%, the growth of the WC hard dispersion phase progresses during sintering, and the wear resistance and toughness are lowered and the heat resistance is lowered. On the other hand, if it exceeds V, precipitation of Ta compound increases and the toughness decreases. Therefore, the content of Ta is set to 0.01 to 0.6%. In addition, when the average particle size of the hard dispersed phase mainly composed of WC exceeds 0.8 μm, the hardness and toughness of the fine-grain cemented carbide are greatly reduced, and the wear resistance and fracture resistance are insufficient. Therefore, the average particle size of the hard dispersed phase made of WC is set to 0.8 μm or less. The same effect can be obtained by replacing 1 part of Cr and Ta with a small amount of V or Zr. However, if it exceeds 0.5%, the toughness is lowered, and the fracture resistance and chipping resistance are remarkably increased. Deteriorating defects appear.

  As the raw material powder, a WC powder containing Cr3C2 and having an average particle diameter of 0.8 μm prepared by dissolving and / or diffusing Cr in the powder production stage was used. The amount of Cr3C2 contained in the WC powder is six types of 0.1, 0.3, 0.5, 0.7, 0.9, and 1.1%. In addition, Cr3C2 powder having an average particle size of 1.5 μm, TaC powder of 1.2 μm, and Co powder are prepared. These raw material powders are blended into a predetermined composition, mixed for 12 hours with an attritor, and dried under reduced pressure. Further, after adding a wax and a solvent and mixing for 1 hour, long shaped bodies having a diameter of 2.5 mm were prepared by an extrusion molding machine, and after dewaxing these long shaped bodies, 1.3 to After holding at a predetermined temperature within a range of 1330 to 1480 degrees for 0.5 to 2 hours in a vacuum atmosphere of 13.2 Pa, the atmosphere is changed to a pressurized atmosphere of pressure: 4.9 to 14.7 MPa, and this pressurized atmosphere After being held for 15 to 60 minutes, a long sintered material having a diameter of 2 mm made of a fine cemented carbide was manufactured by rapidly cooling up to 1200 degrees at a cooling rate of 50 to 100 degrees / minute. The Cr3C2 powder having an average particle size of 1.5 μm was used when the Cr3C2 content was insufficient with only the WC powder containing Cr. The composition of the long sintered material was quantitatively analyzed with a fluorescent X-ray apparatus, and the contents of W, Co, Cr and Ta were measured. The average crystal grain size was determined by mirror-polishing the cross section of the sintered material, then clarifying the grain boundaries by etching with Murakami's reagent for 0.5 minutes and aqua regia for 0.5 minutes, and then using a scanning electron microscope (Hereinafter referred to as SEM), an image taken at a magnification of 10 k was enlarged and copied, and this was calculated by analyzing it with an image analyzer. Further, whether or not the fine cemented carbide material is mainly composed of a binder phase composed of Co and a hard dispersed phase, and Cr oxide having a size of 100 nm or less exists in the hard dispersed phase, is determined by TEM. It was evaluated by observing 50 visual fields at a magnification and measuring the composition of each region by EDX. Table 1 summarizes the composition of the present invention material and the average particle diameter of the hard phase mainly composed of WC and the number of fields of view in which Cr oxide having a size of 100 nm or less was observed in the hard dispersed phase. It was. As an observation example of Cr oxide, FIG. 1 shows a TEM image of Cr oxide observed in Example 10 of the present invention. The results of EDX analysis of the fine particles were, by mass, Cr: 72.4%, O: 4.7%, W: 19.8%, Co: 3.1%. Also, for the purpose of comparison, the furnace is cooled in a furnace at a cooling rate of about 10 degrees / minute after holding the sintering conditions at a predetermined temperature in the range of 1350 to 1480 degrees in a vacuum atmosphere of 6.6 Pa for 1.5 hours. Thus, a comparative example was prepared. As the raw material powder, WC powder having an average particle diameter of 0.8 μm, Cr3C2 powder having an average particle diameter of 1.5 μm, TaC powder of 1.2 μm, and Co powder were used. Table 1 shows the characteristics of the comparative example evaluated under the same conditions as the examples of the present invention. When the TEM was observed at a magnification of 125 k, all of the comparative examples were mainly composed of a binder phase composed of Co and a hard dispersed phase, but fine particles having a Co component of about 50% were found, but Cr oxidation of 100 nm or less was observed. Nothing was found.

  Three long blades each having a shank diameter of 2.0 mm and a cutting edge diameter of 0.1 mm were produced using the long sintered material produced from the inventive examples and comparative examples. Using this, two glass epoxy plates with high-Tg (Tg is the glass transition temperature) 0.2mm-thick double-sided Cu are stacked on top of each other under the conditions of a rotational speed of 240000 / min and a feed of 0.01mm / rev. A drilling test was conducted. This condition is a cutting condition where the cutting edge temperature tends to be higher at a higher speed. The smaller of the number of holes drilled until 5% wear occurred on the outer diameter of the outer peripheral blade or the number of holes drilled until breakage was measured, and the average of the three holes was defined as the average drilling life. Table 1 also shows the results of measuring the average drilling life of each small-diameter drill produced from the inventive examples and the comparative examples.

  From the results shown in Table 1, each of Inventive Examples 1 to 18 had at least one visual field in 50 visual fields and a Cr oxide having a size of 100 nm or smaller in the hard dispersed phase, whereas In Comparative Examples 19 to 36, no visual field was observed. Comparing the drilling life of the small diameter drills produced using the inventive examples 1 to 18 and the comparative examples 19 to 36, the present invention was found to have almost the same composition and the particle size of the WC hard dispersed phase. The small diameter drill produced using the example is 1.5 times or more superior to the comparative example. For example, the drilling life of Comparative Example 33 is 1290 holes, while Inventive Example 15 is 1940 holes, 1.5 times better than the Comparative Example. Also, in the present invention example, a Cr oxide having a size of 100 nm or less was observed in 6 fields out of 50 fields in the hard dispersion phase, despite the same Co amount and the particle size of the WC hard dispersion phase. The drilling life of Invention Example 13 is 1850 holes, whereas the drilling life of Invention Example 12 observed in 5 fields out of 50 is 2910 holes, which is 1.5 times or more better. I understood.

FIG. 1 shows a photograph obtained by TEM observation of the alloy structure of the example of the present invention at a magnification of 500 k.

Explanation of symbols

  1: Cr oxide

Claims (1)

It has a metal component consisting of 2 to 13% of Co and / or Ni, 0.1 to 1.8% of Cr, 0.01 to 0.6% of Ta, and the balance of W and inevitable impurities. The hard dispersed phase mainly composed of WC has an average particle size of 0.8 μm or less, and a Cr oxide having a size of 100 nm or less is present in the hard dispersed phase. alloy.