JP2001198710A - Cemented carbide extruded material, manufacturing method and cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cemented carbide extruded material improvable in mechanical characteristic by an orientation, even if normally used WC grain of an aspect ratio 2 or below is used without specially generating planar WC grain and orienting the WC grain, an useful method for manufacturing the cemented carbide extruded material and a cutting tool capable of increasing traverse rupture strength by using the cemented carbide extruded material as a material. SOLUTION: This cemented carbide extruded material is made by including 70 mass % or more of WC and including one kind or more of iron family elements selected from a group of Co, Ni and Fe in the remainder. The average grain diameter of the WC is 1 μm or below. When X-ray diffraction peak strength of a (001) surface on a surface perpendicular in an extruding direction when Cu is measured as a target material and X-ray diffraction peak strength of a (100) surface on a surface perpendicular in the extruding direction are shown as h(001) and h(100), respectively, the ratio [h(001)/h(100)] is 0.35 or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cemented carbide extruded material useful as a material for wear-resistant parts such as cutting tools, cold working tools and hot working tools, and to such a cemented carbide extruded material. The present invention relates to a useful method for manufacturing, and a cutting tool and the like which can increase the bending strength by using such a cemented carbide material as a raw material.

[0002]

2. Description of the Related Art A WC cemented carbide material containing WC as a hard phase and an iron group element such as Co, Ni, Fe or the like as a binder phase is disclosed in US Pat.
Conventionally, a hard coating such as TiN or (AlTi) N is formed on the surface thereof, and it is widely used as a material for cutting tools such as drills and end mills, or as a material for hot working tools or cold working tools.

[0003] Such cemented carbide materials are prepared by mixing raw material powders →
Drying / granulation → molding → degreasing / semi-sintering → processing → sintering → HIP
Manufactured in the process of processing (hot isostatic pressing)
The mechanical properties of those produced in this way are usually isotropic.

A technique has been proposed in which the mechanical properties of the cemented carbide materials as described above are made anisotropic to improve the properties (toughness and strength). Until now, all of these techniques use a special method to grow WC grains into a plate shape and then orient the WC grains by hot working. The following describes a prior art which aims to improve characteristics by containing a plate-like WC crystal.

JP-B-47-23049 and JP-B-47-23
No. 050 uses a porous agglomerate colloidal WC powder composed of particles in the range of 0.01 to 0.1 μm to sinter, so that the maximum size is 0.1 to 50 μm and the maximum size is 3 μm. It describes a plate-like WC-containing cemented carbide that is at least twice as large. However, in such a method, it is very difficult to control the size, content, dispersion state, and the like of the plate-like WC crystal, and there is a problem that mechanical properties are rather deteriorated. In addition, a complicated process is required, which leads to an increase in cost.

JP-A-57-34008 discloses that WC powder is strongly pulverized to cause a carbonization reaction in the presence of an iron group metal.
A method for obtaining a plate-like twin WC in which WC is joined at a (001) crystal plane is described. In this method, there are problems of the content and separation of the obtained plate-like twin WC.

Japanese Patent Application Laid-Open No. 2-47239 describes a method for a cemented carbide which uses a composite carbide in which W is dissolved in supersaturation as a raw material and crystallizes plate-like WC crystals during sintering. However, in this method, a step of obtaining a supersaturated solid solution of W is necessary, and there is a problem that the production rate of the plate-like WC crystal and the applicable composition are limited.

In Japanese Patent Application Laid-Open No. Hei 5-33939, WC powder having an average particle size of 0.5 μm or less and a cubic compound are used.
A method for producing a cemented carbide having plate-like WC crystals sintered at a temperature of 1450 ° C. or higher is described. in this way,
Long-term pulverization is required, and there is a problem of contamination such as an oxygen amount, or a problem that the generation rate of plate-like WC crystals is small and size control cannot be performed.

Japanese Patent Application Laid-Open No. Hei 7-278179 discloses a composite carbide containing Co and / or Ni, W and carbon of 1 μm.
m, a cemented carbide containing 20 vol% or more of a plate-like WC crystal having an average particle diameter of 1 μm or less and an aspect ratio of 2 to 20 using the mixed powder of the composite carbide and carbon as a starting material. Is described. Also, JP-A-7-29
No. 2426 discloses a first process in which a composite carbide containing Co and / or Ni powder, carbon powder, W powder, or W and C is produced, and a reaction between the composite carbide and residual carbon to form a plate-like WC. Plate-like W including a second process in which grains are generated
A method for producing a C-crystal-containing cemented carbide is described. However, in these methods, a composite carbide used as a starting material needs to be manufactured in advance, and the process is complicated and leads to an increase in cost.

In JP-A-11-269573, as starting materials, a zinc-containing substance made of metal zinc and / or a zinc compound, a metal source powder made of metal tungsten powder, carbon and / or graphite, Co and / or Ni Using powder, the oxides on the W and Co surfaces are reduced by zinc vapor during sintering and become active, producing a large number of fine and uniform composite carbides at low temperature, and a fine and Large ratio (3 or more) plate-shaped W
It is described that a large amount of C crystal is formed. However, in this method, the zinc compound evaporates during the sintering process.
It is necessary to remove by scattering, and there is a problem of deterioration of mechanical properties due to residual zinc and a problem of bore and crack due to its vapor pressure.

As described above, several methods of forming a plate-like WC having an aspect ratio of 2 to 3 or more have been reported.
Each requires a special process, and the plate-like W
Problems such as the generation rate of C grains, size control, and cost, and other adverse effects due to taking special steps are caused.

As a method for orienting the formed plate-like WC crystal, Japanese Patent Publication Nos. 47-23049 and 47-2
No. 3050 or "Powder and Powder Metallurgy" (Vol. 36, No. 4) describes a hot press method. However, the hot press method has problems such as (a) a large processing rate cannot be obtained, (b) only a plate-shaped product can be obtained, and (c) a high manufacturing cost. In addition,
JP-A-23049 and JP-A-47-23050 also describe a part of the method by extrusion, but hardly give any concrete description on the extrusion conditions.

[0013]

DISCLOSURE OF THE INVENTION The present invention has been made under such a circumstance, and the object of the present invention is not to generate plate-like WC grains and to align them,
In order to produce a cemented carbide extruded material capable of further improving mechanical properties by orientation even if WC grains having an aspect ratio of 2 or less are used, and to produce such a cemented carbide extruded material. It is an object of the present invention to provide a useful method, and a cutting tool capable of increasing the bending strength by using the above-mentioned extruded cemented carbide material as a material.

[0014]

The extruded cemented carbide material of the present invention, which has achieved the above objects, contains 70% by mass or more of WC and the balance is selected from the group consisting of Co, Ni and Fe. A hard metal extruded material containing at least one iron group element, wherein the average particle diameter of the WC is 1 μm or less, and a plane perpendicular to the extrusion direction when measured using Cu as a target material. The X-ray diffraction peak intensity of the (001) plane of h (001) is (10) on the plane perpendicular to the extrusion direction.
The gist is that the ratio [h (001) / h (100)] is 0.35 or less when the X-ray diffraction peak intensity of the 0) plane is expressed as h (100).

In this extruded cemented carbide material, it is also useful to replace part of WC with at least one of transition metal carbides, nitrides, and carbonitrides so that the total amount thereof is 35% by mass or less. Thus, oxidation resistance, wear resistance, welding resistance, and the like can be improved. Further, by forming a hard coating on the surface of the cemented carbide material as described above, a cutting tool with further improved wear resistance can be obtained.

On the other hand, in producing the above-mentioned extruded cemented carbide material, at least 70% by mass of WC is contained, and at least one of iron group elements selected from the group consisting of Co, Ni and Fe is used. An extruded material having an average particle size of WC of 1 μm or less and a relative density of 90% or more is obtained, the extruded material is extruded at a liquid phase appearance temperature or higher, the extruding ratio is 4 or more, and the extruding speed is adjusted. Hot extrusion may be performed so that (stem speed × extrusion ratio) becomes 40 to 4000 mm / sec.

Further, in this method, (1) Extrusion in which a part of WC is replaced by at least one of transition metal carbides, nitrides and carbonitrides so as to be 35% by mass or less of the total amount. Preferred embodiments include using a raw material, and (2) loading the extruded raw material into a metal capsule with a hardly sinterable material disposed around the extruded raw material, and extruding the capsule.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors, instead of producing plate-like WC crystals and orienting them, orienting commonly used WC grains having an aspect ratio of 2 or less. From the viewpoint of further improving the performance of cemented carbide materials, studies have been made from various angles. As a result, it has been found that if hot extrusion treatment is applied using WC particles having an average particle size of 1 μm or less, the WC particles can be arranged to improve the mechanical properties of the cemented carbide material. Was completed. In the extruded cemented carbide material obtained in this way, a long member having excellent strength and wear resistance can be obtained at low cost, and such a long member is useful as a material for an end mill or a drill.

The "average particle size" is a value measured by the Fullman method. The average particle size is d, and the particles per unit length hit by an arbitrary straight line on the microscope surface. When the number is N1 and the number of particles contained in an arbitrary unit plane is N2, the number is represented by the following equation (1). d = (4 / π) × (N1 / N2) (1)

The present inventors have considered that as a specific means for improving the mechanical properties by the orientation of the WC particles, a hot extrusion method capable of obtaining a large working ratio is optimal. As for this hot extrusion method, no concrete application report has been made so far on a cemented carbide material containing a very large amount of WC particles as ceramics. However, the present inventors have repeatedly studied the applicability of this method,
It has been found that extrusion can be sufficiently performed even with a cemented carbide material containing a large amount of WC particles if various measures are taken.

The present inventors have clarified in the course of examining the applicability of extrusion processing that the average particle size of WC largely controls the flowability during extrusion. That is, WC
If the average particle size of the particles is larger than 1 μm, the flowability of the cemented carbide material (extruded material) during extrusion is rapidly deteriorated, and as a result, the surface condition of the extruded material is deteriorated (unevenness is increased). ), And a defect occurs inside. The surface irregularities cause an increase in the amount of processing at the time of manufacturing the product, and the internal defects cause a decrease in strength. From such a viewpoint, the average particle size of the WC particles in the cemented carbide material of the present invention needs to be 1 μm or less.

It is preferable that the WC particles have a particle size of 0.5 μm or less. However, since the effect of the orientation decreases as the particle size decreases, the particle size is preferably set to 0.1 μm or more. Further, the maximum length of the WC particles is preferably 10 μm or less, more preferably 5 μm or less. This is because even if the average particle diameter of the WC particles is 1 μm or less, if large particles are contained, there is a possibility that a defect may be formed in the vicinity thereof.

The average particle size defined by the method of the present invention is as follows:
Means just before extrusion, but before extrusion
The WC particle size after the extrusion may be regarded as having almost no difference, and it is not necessary to distinguish the average particle size before and after the extrusion. It means that the average particle size of the latter (ie, the extruded material of cemented carbide) is also 1 μm or less.

Incidentally, the relative density of the raw material (extruded raw material) immediately before extrusion needs to be 90% or more. In this extrusion process, the purpose is to achieve densification at the same time as the arrangement, but if the relative density immediately before extrusion is less than 90%, the pores cannot be filled, and the residual pores thus generated will be the starting point of fracture. It causes a decrease in strength.
The residual pores can be removed by a post-treatment such as hot isostatic pressing (HIP). However, such treatment not only lowers the degree of orientation of the oriented WC grains but also increases the cost. Will lead to

In carrying out the above-described extrusion, it is preferable that the extrusion material is filled in a capsule. This capsule is used for the purpose of keeping the temperature of the extruded material heated to the liquidus temperature or higher and generating hydrostatic pressure during the extrusion. That is, if the capsule is not used, the temperature of the surface of the material is reduced and the pressure is biased during extrusion, which causes inconveniences such as cracks in the extruded material. As the material of the capsule, various materials such as a metal material, glass, or a solidified powder can be used, but there must be no large flow difference from the extruded material, and the capsule is easy to handle. It is preferable to use steel for the following reasons.

Since the capsule and the extruded material come into contact with each other at a very high temperature, it is necessary to suppress the reaction between them at this time. For this reason, it is necessary to interpose a material for preventing the reaction between the capsule and the super-extruded material. The present inventors also examined such materials and found that it is preferable to use a powder that is difficult to sinter. In other words, as a material to be interposed between the capsule and the extruded material, in addition to the purpose of preventing the reaction between the two, the extruded flowability must not be significantly different from that of the capsule or the cemented carbide material. Considering the necessity of the property that it can be easily removed, etc., the above-mentioned material is hardly sinterable Al
It is preferably N powder or BN powder. Even if these powders are heated to about 1300 ° C., they do not easily sinter, and can prevent reaction and maintain fluidity during extrusion. In addition, it can be easily removed even after extrusion.

The extrusion ratio at the time of extrusion needs to be 4 or more. That is, in order to maintain good extrudability (surface properties and presence or absence of internal defects), the average particle size of the WC particles needs to be 1 μm or less. Examination of the conditions necessary for improving the mechanical properties by arranging the WC particles has revealed that when the extrusion ratio is 4 or more, sufficient improvement of the properties by arranging can be achieved.
The upper limit of the extrusion ratio is not limited, but if it is too high, internal defects occur.

Also, the extrusion speed (stem speed × extrusion ratio) at the time of hot extrusion needs to be appropriately adjusted, and is set to 40 to 4000 mm / sec in the present invention. That is, when the extrusion speed is less than 40 mm / sec, sufficient orientation cannot be obtained, and when the extrusion speed exceeds 4000 mm / sec, internal defects occur.

The cemented carbide extruded material produced as described above has a state in which the WC particles are oriented, and as a quantitative index indicating this orientation, the present inventors consider that the WC particles are oriented in the extrusion direction. (001) plane and (10)
It has been found that it is useful to use the X-ray diffraction peak intensity ratio when the measurement is performed with Cu as the target on the 0) plane.

That is, when extruded, (00
1) The surface tends to be parallel to the extrusion direction, and (10)
The 0) plane tends to be perpendicular to the extrusion direction. And
As values indicating these degrees, (00) in a plane perpendicular to the extrusion direction when measuring with Cu as a target.
When the X-ray diffraction peak intensities of the 1) plane and the (100) plane are expressed as h (001) and h (100), respectively, the intensity ratio [h (001) / h (100)] is used. It was found that when the value of this ratio was 0.35 or less, the mechanical properties were significantly improved.

As described above, the extrusion ratio is set to 4 or more and the extrusion speed is set to 40 to 4000 mm / min. Without using particles obtained by growing WC particles in a large plate shape.
sec, the WC produced in the normal process
Even if particles are used, the desired arrangement can be obtained, and the mechanical properties can be improved. The intensity ratio [h (00
1) / h (100)] is preferably 0.35 or less in any section of the cemented carbide material.
This is not always necessary, and the object of the present invention can be achieved if 90% or more of the measured intensity ratios in any cross section satisfy the above range.

In the cemented carbide extruded material according to the present invention, the iron group element (Co,
Ni, Fe, etc.) must also be properly adjusted. When the WC content is less than 70% by mass, the amount of the binder phase (binder amount) increases, so that the extrusion can be easily performed by utilizing the plastic deformation of the binder phase, but the hardness is lowered and the resistance is reduced. Abrasion becomes worse. As described above, examples of the type of the binder phase include iron group elements such as Co, Ni, and Fe. These may be used alone or in combination.

In the cemented carbide material of the present invention, its W
Part of C is Ti, Ta, Mo, Ti, Cr, V, N
It is also useful to replace with any one or more of carbides, nitrides or carbonitrides of transition metals such as b, Zr, Hf and the like. , Abrasion resistance, welding resistance and the like can be further improved. However, if the replacement amount exceeds 35% by mass with respect to the total amount of the extruded material of the cemented carbide, the effect of the arrangement of the WC particles is hardly exerted.
Should be: In order to exhibit the above-mentioned effects, it is preferable that the added carbide, nitride or carbonitride is as fine as possible.

The cemented carbide extruded material according to the present invention exhibits high strength and toughness and is hard to break even when formed into a long member.
It is useful as a material for cold working tools or hot working tools. When a cemented carbide material according to the present invention is used as a cutting tool product, TiN or (AlT
i) It is preferable to form a hard coating such as N.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are not intended to limit the present invention, and any change in design based on the above and following points is not limited to the present invention. It is included in the technical range of.

[0036]

EXAMPLES As raw materials, WC powder, binder (Co, Ni, Fe) powders of various particle sizes, and carbides, nitrides or carbonitrides of transition metal elements are prepared and used to obtain various composition ratios. After mixing and drying with a wet attritor as described above, CIP molding (cold isostatic pressing) is performed,
Thereafter, it was calcined to obtain an extruded material.

The relative density of the extruded material immediately before extrusion was measured (two pieces of the extruded material were prepared in various types, one of which was used for extrusion, and the other was used for measuring the relative density). Hot extrusion was performed under various extrusion conditions (extrusion temperature, extrusion ratio, extrusion speed) to obtain various cemented carbide extruded materials. At this time, mild steel was used as a capsule material, and the stem speed during extrusion was 10 to 85 mm.
/ Sec, and hot extrusion was performed in a state where various reaction inhibitors (hard sintering materials) were interposed between the capsule and the extruded material. At this time, the mixing ratio of the raw materials, the extrusion conditions (extrusion temperature, extrusion ratio, stem speed, extrusion speed) and the type of the reaction inhibitor are collectively shown in Table 1 below. In the column of "Extrusion temperature" in Table 1 below, the case where the extrusion temperature is equal to or higher than the liquid phase appearance temperature is marked with a circle, and the case where the extrusion temperature is not higher is marked with a cross.

[0038]

[Table 1]

With respect to the obtained cemented carbide material, its WC
The average particle diameter of the particles, the X-ray intensity ratio, the transverse rupture force were measured, and the surface condition was observed. At this time, the average particle diameter of WC was measured by the above-mentioned Fulman method, the surface state was observed using a stereoscopic microscope, and the state of the unevenness was evaluated according to the following criteria. ◎: very good; irregularities of 0.0 to 0.2 mm by microscopic observation ○: good; irregularities of 0.2 to 0.4 mm by microscopic observation △: normal; 0.4 to 0.6 mm of microscopic observation Unevenness ×: poor; unevenness larger than 0.6 by microscopic observation.

The X-ray intensity ratio was determined using an X-ray diffractometer.
(001) plane and (100) with Cu as target
X-ray diffraction peak intensities [h (001) and h
(100)] and their ratio [h (001) / h
(100)] was calculated. In measuring the X-ray diffraction peak intensity ratio, the cemented carbide material was measured from two orthogonal directions (a direction parallel to and perpendicular to the extrusion direction), and the lowest value was adopted. In addition, the transverse rupture force is determined by a JIS transverse bending test [JI
SB 1404 (7.2)]. These results are collectively shown in Table 2 below. At this time, as a material exhibiting isotropic characteristics (comparative example), after mixing with a wet attritor, drying, molding, and sintering, HIP treatment (1
The results of the transverse rupture test of a sample (300 ° C., 100 MPa) (this sample is referred to as “HIP material”) are also shown.

[0041]

[Table 2]

As is evident from these results, it can be seen that the examples satisfying the requirements specified in the present invention have good surface properties and excellent strength. On the other hand, in the case of the comparative example lacking any of the requirements specified in the present invention, one of the properties was inferior (defective extrusion, internal defect, small arrangement).

[0043]

The present invention is constituted as described above. Instead of generating plate-like WC grains and orienting them, a commonly used W-C having an aspect ratio of 2 or less is used.
Even if C grains are used, a cemented carbide extruded material capable of further improving mechanical properties can be realized by orientation, and such a cemented carbide extruded material can be used for cutting tools and the like that require high bending strength. Useful as a material.

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Claims (6)

[Claims] (1) WC is contained in an amount of 70% by mass or more, and the balance is C
An extruded cemented carbide material comprising at least one iron group element selected from the group consisting of o, Ni and Fe,
When the average particle size of the WC is 1 μm or less and the Cu is used as a target material, the X-ray diffraction peak intensity of the (001) plane in the plane perpendicular to the extrusion direction is h (00).
1) When the X-ray diffraction peak intensity of the (100) plane in the plane perpendicular to the extrusion direction is expressed as h (100), the ratio [h (001) / h (100)] is 0.35. An extruded cemented carbide material characterized by the following: 2. The WC so as to be 35% by mass or less of the total amount.
The cemented carbide extruded material according to claim 1, wherein a part of the material is replaced with at least one of a transition metal carbide, nitride, and carbonitride. 3. A cutting tool comprising a hard film formed on the surface of the cemented carbide according to claim 1 or 2. 4. In producing the cemented carbide material according to claim 1, WC contains 70% by mass or more and the balance is C.
o, Ni and Fe are mixed so as to contain at least one iron group element selected from the group consisting of
m and an extruded material having a relative density of 90% or more, an extruded material having an extruding ratio of 4 or more at a liquid phase appearance temperature or more and an extruding speed (stem speed × extrusion ratio) of 4
A method for producing a cemented carbide extruded material, characterized in that the material is hot extruded so as to have a pressure of 0 to 4000 mm / sec. 5. A WC such that it is 35% by mass or less of the total amount.
5. The method according to claim 4, wherein an extruded material in which a part of the material is replaced with at least one of a transition metal carbide, nitride and carbonitride is used. 6. The method according to claim 4, wherein the extruded material is loaded into a metal capsule with a hardly sinterable material disposed around the extruded material, and the capsule is extruded.