KR101733661B1

KR101733661B1 - Cemented carbide for cutting tools

Info

Publication number: KR101733661B1
Application number: KR1020150179084A
Authority: KR
Inventors: 김용현; 이성구; 김영흠; 안선용
Original assignee: 한국야금 주식회사
Priority date: 2015-12-15
Filing date: 2015-12-15
Publication date: 2017-05-08

Abstract

The present invention relates to a cemented carbide for a cutting tool and a method of manufacturing the same. Wherein the cemented carbide is a cemented carbide comprising 10 to 13 wt% of Co and 2 wt% or less of tartarate and the balance of WC and inevitable impurities, wherein the settled material of the microstructure measured at a depth of 500 mu m or more from the surface, The structure is characterized by having an area ratio of 80% or more. The method is characterized in that after sintering, the steel is quenched at a cooling rate of 15 to 20 ° C / min. The cemented carbide for cutting tool according to the present invention basically has a high toughness with a high cobalt content and lowers the content of tartanide to reduce the cost and secure the chipping resistance and at the same time, It is advantageously applied to a raising tool and its life can be prolonged.

Description

{CEMENTED CARBIDE FOR CUTTING TOOLS}

The present invention relates to a cemented carbide for a cutting tool and a method of manufacturing the same. More particularly, the present invention relates to a cemented carbide having excellent toughness, excellent resistance to abrasion, chipping resistance and fracture resistance.

Conventionally, a WC-based cemented carbide obtained by bonding WC (tungsten carbide) particles with Co (cobalt) has been used as a base material of a cutting tool. Recently, in the field of cutting tools for high-tensile milling, high-hardness cemented carbide is preferred, and cost reduction is required in terms of product competitiveness.

As the Co content is increased for the high toughness, the non-uniform distribution of the Co structure and the lowering of the bending strength (endurance) and the fracture resistance at the part where the Co structure is connected, Thereby making it difficult to achieve a uniform quality.

Also, when the particle size of the WC is small in a state where the Co content is high, it is necessary to increase the particle size because the co-connecting structure is macroscopically increased and the bending strength is lowered. In order to compensate this, there is a problem in that the cost is increased by increasing the bending strength by strengthening the solid solution in the Co structure by using the expensive talc cargo, and the chipping resistance is poor due to the carburizing .

On the other hand, to improve the bending strength, the cemented carbide is manufactured by pressure sintering. However, the bending strength is improved by removing the micropores in the alloy at once.

It is an object of the present invention to provide a cemented carbide for a cutting tool having a relatively high content of cobalt and having excellent toughness and at the same time excellent cutting force, abrasion resistance, chipping resistance and breakage resistance, .

The present inventors paid attention to the liquid phase sintering process of a cemented carbide in a process of preparing various kinds of cemented carbide for a cutting tool containing a relatively high content of cobalt in the course of various examinations regarding manufacturing process conditions, In order to facilitate particle sliding and suppress precipitation of dissolution material, it was found that desired physical properties could be obtained for cemented carbide. In the process of further realizing it, presence of Co-free tartanide and WC aggregate Has been found to be important for improving the resistance to abutment, chipping resistance and fracture resistance of the light alloy according to the above-mentioned problems, leading to the present invention. The gist of the present invention based on such knowledge and recognition of the above problem is as follows.

(1) A cemented carbide comprising 10 to 13 wt% of Co and 2 wt% or less of titanate and the balance of WC and unavoidable impurities, Wherein the structure of the cemented carbide is 80% or more in area ratio.

(2) The cemented carbide according to the above (1), wherein the tartarate is at least one of Ta, Nb or Ti-based tartarate.

(3) 10 to 13 wt% Co; 2 wt% or less, and WC as a remainder, wherein the sintering is followed by quenching at a cooling rate of 15 to 20 ° C / min.

(4) The method for producing a cemented carbide according to (3), wherein the WC grain size is 2 to 6 탆.

(5) The method for producing a cemented carbide according to (3), wherein the talcum has a particle size of 0.5 to 1.5 탆.

(6) The method for producing a cemented carbide according to (3), wherein the tartaric material is at least one of Ta, Nb or Ti-based tartaric material.

The cemented carbide for cutting tool according to the present invention basically has a high toughness with a high cobalt content and lowers the content of tartanide to reduce the cost and secure the chipping resistance and at the same time, It is advantageously applied to a cutting tool and its service life can be prolonged.

1 is a microstructure photograph of a conventional cemented carbide.
2 is a microstructure photograph of a cemented carbide according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The cemented carbide according to the present invention is a WC-based cemented carbide composed of a hard phase composed mainly of WC particles and a subcomponent composed of tartan and a binder phase composed mainly of an iron family metal such as Co. Wherein the cemented carbide comprises 10 to 13 wt% of Co and 2 wt% or less of tartarate, the balance of WC and unavoidable impurities, and the settled material of the microstructure measured at a depth of 500 mu m or more from the surface, And the structure is 80% or more in area ratio.

The WC constitutes the main component of the hard phase and constitutes the remainder of the alloy component excluding Co and tartanide, and preferably has a content of 85 to 88 wt% with respect to the total weight of the sintered body.

In this case, the average grain size of the WC for forming the sintering mixed powder is preferably controlled to 2 to 6 mu m. If the average particle size of WC is less than 2 탆, it is excellent in abrasion resistance but it is difficult to form aggregate group structure with tartanide, and bending strength, toughness and breakage resistance are also lowered. On the contrary, when the thickness is more than 6 m, the particle decayability during cutting is high, and when a hard coating is added to the surface of the alloy, the coating easily peels off and is not preferable from the standpoints of chipping resistance and breakage resistance.

The tartarate constitutes a hard phase together with WC, and at least one of Ta, Nb or Ti-based tartaric materials may be selected, and the tartaric material includes Ta, Nb or Ti-based carbonitrides. The present invention is characterized in that tartanide is strengthened by forming an aggregate structure together with a WC hard phase through cooling treatment after sintering unlike the case where solid solution strengthening is performed with Co as a conventional state in the conventional case.

In this case, since the tartan powder is expensive, it is preferable that the content thereof is controlled to 2 wt% or less so as to improve the bending strength at minimum cost and not to deteriorate the chipping resistance.

In addition, the average particle size of the tartan powder for forming the sintering mixed powder is preferably controlled to 0.5 to 1.5 mu m. If the average particle size of the tartan powder is greater than 1.5 占 퐉, the particle decayability during cutting is high, and addition of a soft coating on the surface of the alloy may cause peeling of the coating, which is not preferable.

The Co constitutes a bonded phase, and a part thereof may be substituted with another iron group element such as Ni, but Co may be sufficient. The Co content is maintained at a relatively high content in order to ensure high toughness, and 10 to 13 wt% is preferable. When the Co content is less than 10 wt%, the toughness is deteriorated, and when it is more than 13 wt%, the strength and abrasion resistance are deteriorated.

The average particle size of the Co powder for forming the sintering mixed powder is preferably controlled to 1.2 to 1.6 탆. When the average particle size of the Co raw material powder is less than 1.2 탆, a structure in which WC, titanate and Co are easily formed is not preferable in terms of fatigue shock, and the tool life is shortened during the intermittent machining, and the average particle size of the Co raw powder is fine There is also a problem that the manufacturing cost increases as the number of devices increases. On the contrary, when the average particle size is more than 1.6 탆, it is difficult to secure toughness due to the presence of local Co, and it is undesirable because it lowers the bending strength and causes unexpected breakage in processing, nourishing the tool life.

On the other hand, the average particle size of the WC described above can be influenced by the raw material powder blending process for producing the alloy. If the blending time for the raw material powder becomes too long, WC can be smaller than the intended average particle size and it is difficult to form the aggregate group structure associated with the tartanization, and accordingly, it can be appropriately adjusted according to the particle size and the compounding method of the raw material Need to be.

For example, a WC powder having a particle size of about 2 to 6 μm and 85 to 88 wt% based on the total weight of the sintered body, a powder of tartan powder having a particle size of about 0.5 to 1.5 μm and 2 wt% or less based on the total weight of the sintered body, When the mixed powder is composed of 10 to 13 wt% of Co powder based on the total weight of the sintered body, if the mixed powder is prepared by wet-mixing with a ball milling mixer and then spray-dried, the mixing time is 1 to 3 Hour, 3 to 5 hours, and 7 to 10 hours.

The cemented carbide of the present invention is characterized in that the aggregate structure in which the titanate is combined with WC among the microstructures measured at a depth of 500 mu m or more from the surface thereof is 80% or more in area ratio.

The formation, the process and the meaning of such a group group organization will be described in more detail. Generally, cemented carbide is produced by liquid phase sintering process and solid phase particles grow as sintering progresses. The driving force of particle growth during liquid phase sintering is to minimize the interface energy by reducing the interface between the solid / liquid. At the early stage of liquid phase sintering, WC and tartanization coalesced with similar crystal structure and orientation, and finally, particle swing by liquid phase formation actively rearranges. In the late stage of liquid phase sintering, when solids have different solubility at high solubility, the solubility of small particles is larger than that of large particles, so the solubility difference causes the mass transfer from small particles to large particles. As a result, the small particles continue to melt and become smaller, and larger particles grow and become larger, resulting in an increase in the average particle and the desired properties can not be obtained. Accordingly, since the WC and the titanate coalesced or the particle sliding are facilitated and the precipitation of the dissolution material is suppressed in the initial stage of the liquid phase sintering, the WC and the group of the group of the group of the titanate are sufficiently distributed in the microstructure at a sufficient area ratio, .

Fig. 1 is a microstructure photograph of a conventional cemented carbide, and Fig. 2 is a microstructure photograph of the cemented carbide according to the present invention. In the drawing, the brightest color is WC, the light gray is tartanite, and the black is Co.

Referring to FIG. 1, a conventional cemented carbide aggregate structure is a structure in which WC, titanate and Co are combined as shown by a dotted line. For high toughness cemented carbide must be excellent in bending strength (wherein jeolryeok) with which can withstand a substantial impact toughness one, WC and tartan cargo, in the case of a set of the group organization of Co is engaged wherein jeolryeok is 200kgf / mm ² to a low performance less than There is a problem of fatigue shock at the time of evaluation, initial breakage at the time of steel intermittent processing, and early life ending.

2, the aggregate structure of the cemented carbide according to the present invention is a structure in which WC and tartanide are combined with each other as shown by a dotted line. Most of the WC grains are in contact with the boundaries of the tartanite grains, Are not adjacent. The aggregate structure combined only with WC and tartan cargo has a high resistance of 250kgf / mm ² or more, which is basically required in the tough cemented carbide, The cemented carbide cutting tool having a group structure in which WC, tonalite and Co are combined at the time of machining is 2 to 5 ea. However, the cemented carbide cutting tool having a group structure in which only WC + 22 ea. It is superior in terms of processing yield, and has excellent fracture resistance at 300 psi steel interrupted processing.

As described above, in the present invention, it is preferable that the aggregate group structure in which WC and tartanide are combined is at least 80% or more in area ratio so as to realize desired physical properties such as resistance force and to prevent degradation of lifetime in performance evaluation. In this case, the measurement of the area ratio of the aggregate structure is preferably performed at a depth of 500 mu m or more of the alloy from the surface because the Co load layer, that is, the CFL layer, may exist on the surface of the cemented carbide.

As one of the important factors relating to the formation of the aggregate group structure of WC and tartanite, it is important to select the starting composition and the particle size of the above-mentioned alloy, and in this case, It is important that the mixing time is made small and that the particle size of the tartan powder is in the range of 05 to 1.5 mu m.

As described above, if the starting particle size of the WC is less than 2 탆, the abrasion resistance may be improved due to the increase of the hardness of the base material. However, it is difficult to form the aggregation group of only WC and the cargo material and the bending strength is lowered. The fatigue shock and the breakage resistance are remarkably lowered. In this case, if the mixing time is too long, the particle size of the WC becomes too small, and the above-mentioned problem arises.

In addition, with respect to the particle size of tartan powder, when the starting particle size is less than 0.5 탆, the unit cost of tartanite rises first and is easily dissolved in Co during the sintering process, which makes it difficult to form aggregates of WC and tartanite and irregularly re- It is not preferable because it causes deterioration of physical properties. If the starting particle size is larger than 1.5 탆, uniform powder mixing is difficult, and it is difficult to form aggregates of WC and tartanite in the microstructure of the cemented carbide. In addition, when the cemented carbide is used for cutting, the particle deterioration is increased, which is undesirable because it affects the tool life.

The cemented carbide according to the present invention is produced by compounding and sintering the WC, titanate and Co particles having a predetermined content and particle size, followed by quenching to room temperature. In this case, it is important to quench to room temperature after sintering with respect to the formation of the aggregate group combined with only WC and tartanite, and the cooling rate should be at least 15 to 20 ° C / min Is preferably controlled. After the sintering, in the case of slow cooling or furnace cooling at a rate of less than 15 ° C / min, dissolution material precipitation time is given, and it is difficult to obtain a desired aggregate group structure of WC and tartanite alone.

Hereinafter, the present invention will be described more specifically based on preferred embodiments of the present invention. However, it should be understood that the technical spirit of the present invention is not limited thereto, and various modifications may be made by those skilled in the art.

( Example One)

Manufacture of cemented carbide

To evaluate the physical properties of the cemented carbide according to the present invention and to compare the properties thereof, WC-Co cemented carbide was prepared by varying the starting material composition, WC particle size, mixing time and cooling rate after sintering as shown in Table 1 below. In this case, tartan cargo was prepared with TaNbC. The starting materials prepared as shown in Table 1 were mixed at a mixing time of 1 to 3, 3 to 5, and 7 to 10 hours using a ball milling mixer. The mixture was sieved using a spray dryer , And sintered spherical compacts. In both of the comparative examples and the examples, the sintering process was performed by dewaxing at a low temperature region of 250 ° C, pre-sintering at 1200 ° C for 1 hour, and then sintering at 1400 ° C. The cemented carbide bodies were cooled by different cooling conditions as shown in Table 1.

Psalter Composition (wt%) Tartan cargo
Particle Size (㎛) WC
Particle Size (㎛) Full
Mixing time (hr) Cooling conditions after sintering Remarks WC Co Tartan cargo Cooling conditions Cooling rate One 91 8 One 0.3 to 0.5 2 to 6 1-3 Lowon 5 ° C / min Comparative Example 2 90 9 One 2.0 to 4.0 2 to 6 4 to 6 Quenching 20 ° C / min Comparative Example 3 89 10 One 2.0 to 4.0 2 to 6 1-3 Lowon 5 ° C / min Comparative Example 4 89 10 One 2.0 to 4.0 2 to 6 4 to 6 Quenching 20 ° C / min Comparative Example 5 89 10 One 2.0 to 4.0 0.5 to 2 1-3 Quenching 20 ° C / min Comparative Example 6 88 10 2 2.0 to 4.0 2 to 6 7 to 10 Quenching 20 ° C / min Comparative Example 7 88 10 2 0.3 to 0.5 2 to 6 1-3 Lowon 5 ° C / min Comparative Example 8 89 11 0 0.5 to 1.5 0.5 to 2 4 to 6 Slow cooling 10 ° C / min Comparative Example 9 88 11 One 2.0 to 4.0 2 to 6 7 to 10 Quenching 20 ° C / min Comparative Example 10 87 13 0 0.5 to 1.5 0.5 to 2 4 to 6 Slow cooling 10 ° C / min Comparative Example 11 86 13 One 2.0 to 4.0 2 to 6 7 to 10 Quenching 20 ° C / min Comparative Example 12 85 13 2 0.5 to 1.5 2 to 6 4 to 6 Quenching 20 ° C / min Comparative Example 13 85 14 One 0.5 to 1.5 2 to 6 1-3 Quenching 20 ° C / min Comparative Example 14 90 9 One 0.5 to 1.5 2 to 6 1-3 Quenching 20 ° C / min Example 15 89 10 One 0.5 to 1.5 2 to 6 1-3 Quenching 20 ° C / min Example 16 89 10 One 0.5 to 1.5 2 to 6 1-3 Quenching 20 ° C / min Example 17 87 11 2 2.0 to 4.0 2 to 6 4 to 6 Quenching 20 ° C / min Example 18 85 13 2 0.5 to 1.5 2 to 6 1-3 Quenching 20 ° C / min Example

Aggregate organization and property evaluation

For each sintered body manufactured through this process, a surface grinder was used to polish the surface of the alloy from the surface by at least 500 μm, and the microstructure of the polished surface was observed using a scanning electron microscope (SEM) , And the area ratio of the aggregate group of WC and tartan cargo was measured using an image analyzer. The physical properties of each sintered body were measured and evaluated as follows.

(1) Bending strength (uniaxial force): 3-point bending of a rod-shaped specimen with a rectangular cross section using a universal testing machine (UTM) to measure the load until fracture.

(2) Abrasion resistance: Forged SCr420 workpiece (Φ100 * length 200mm) The outer diameter is vc200, fn 0.25, ap 1.5mm, wetted to compare the processing quantity by sample.

(3) Inner chipping property: Prepare four workpieces on the outer diameter of forged SCr420 workpiece (Φ100 * length 200mm) to prepare cutting material for intermittent impact. vc200, fn 0.2, ap 1.5mm, and wet conditions.

(4) Fracture resistance: Forged SCr420 workpiece (Φ300 * length 500mm) The outer diameter is vc100, fn 0.25, ap 1.5mm, wetted to compare the machining distance to sample breakage.

The measurement and evaluation results are summarized in Table 2 below.

Psalter WC
Tartan cargo
Collective army organization
(%) Anti-radiation
(kgf / mm ² ) Abrasion resistance Chipping resistance Breakage resistance 100 pi outer diameter processing quantity 4 grooved grooves 100 pie end cutting quantity 4 grooves 300 pie Outside diameter machining distance (m) One 20 200 20 2 0.2 2 60 225 18 13 1.2 3 65 180 17 7 0.8 4 60 170 17 7 1.1 5 20 150 17 8 0.7 6 10 130 19 3 1.8 7 50 175 15 9 1.1 8 60 170 15 18 1.8 9 50 145 14 11 2 10 50 150 13 7 0.2 11 40 160 12 8 0.5 12 35 135 10 9 0.9 13 75 187 10 17 0.9 14 80 290 18 20 6.1 15 85 300 16 21 7.5 16 90 320 16 21 7.2 17 90 315 14 21 7.5 18 90 330 13 22 7.8

As shown in Table 1, when the starting particle size and the mixing time of the starting materials and the cooling conditions after the sintering were set as shown in Table 1, in the specimens 1 to 13 according to the comparative examples, WC And 80% of the assemblage group, which is combined with the cargo cargo.

As a result of evaluating the physical properties of the specimen according to the comparative example in which the aggregate group structure of the WC and the tartan cargo was less than 80%, the specimens 1 and 6 according to the comparative examples showed that the particle sizes of the WC and the tar cargo were within the ranges specified in the present invention As the cooling rate was slower and the mixing time increased, the wear resistance and the chipping resistance were more than a certain level but the fracture resistance required for the hardness grade was low. In addition, the specimens 2 and 8 according to the comparative examples were evaluated to have a low abrasion resistance and a fatigue impact because the abrasion resistance was 15 to 18EA, but the area of the aggregate structure was 60% or less. In addition, the specimens 3, 4, 5, 7, 10, 11, and 12 according to the comparative examples were prepared in such a manner that quenching conditions were slower than those in the Examples, , It was evaluated that even when the particle size falls within the range, the abrasion resistance, abrasion resistance, and chipping resistance are remarkably lowered as the mixing time becomes longer. In addition, the specimen 9 according to the comparative example showed an improvement in the chipping resistance, but the formation of the aggregate group was less, and the resistance of the specimen 13 was lower. Similar to No. 9, the chipping resistance was excellent, and the toughness was evaluated to be low.

On the other hand, in the specimens 14 to 18 according to the embodiment of the present invention, the aggregate group structure in which WC and tartanide were combined in the microstructure measured at a depth of 500 μm or more from the surface was found to be 80% or more, and the abrasion resistance, It was found that both the chipping resistance and the breakage resistance were evaluated to be superior to each other, and it was confirmed that the present invention can be advantageously applied to machining requiring high toughness.

( Example 2)

In order to evaluate the influence of the mixing time of the cemented carbide on the texture and physical properties of the cemented carbide in the cemented carbide manufacturing process according to the present invention, the WC starting grain size was set to 2 to 6 탆 and the tartanate starting grain size was set to 0.5 to 1.5 탆, And the sintered spheroidized powder was sintered using a spray dryer in the same manner as in Table 3, except that the sintering time was varied from 0.5 to 1, 2 to 4, 5 to 7, and 8 to 10 hours. Tartan cargo was prepared with TaNbC. The sintering process was carried out in the same manner as in Example 1 by dewaxing at a low temperature region of 250 ° C, pre-sintering at 1200 ° C for 1 hour, and then sintering at 1400 ° C. RTI ID = 0.0 > C / min. &Lt; / RTI > For each of the sintered bodies manufactured through this process, test pieces were fabricated in the same manner as in Example 1, and measurement and physical properties of the group structure of WC and tartanite were evaluated, and the results are summarized in Table 3 below.

Psalter Composition (wt%) Full
combination
time
(hr) WC
Tartan cargo
Collective army organization
(%) Anti-radiation
(kgf / mm ² ) Wear out
Maternity Chipping resistance Breakage resistance
(m) Remarks WC Co Tartan cargo One 89 10 One 0.5 10 120 5 2 0.1 Comparative Example 2 89 10 One One 60 200 10 7 1.0 Comparative Example 3 89 10 One 2 85 350 16 21 7.5 Example 4 89 10 One 3 90 370 16 21 7.2 Example 5 89 10 One 4 85 357 18 22 6.8 Example 6 89 10 One 6 60 170 25 7 1.1 Comparative Example 7 89 10 One 9 35 135 29 9 0.9 Comparative Example

Referring to Table 3, when the full-blend time is relatively long as in the case of the test pieces 6 and 7 according to the comparative examples, as the particle size is reduced due to the crushing effect of the WC and the titanate, It is confirmed that the wear resistance of the cemented carbide is excellent, but the chipping resistance and the breakage-proof life are terminated prematurely. Also, it was confirmed that, when the full-blending time was relatively short as in the case of the test pieces 1 and 2 according to the comparative examples, the WC, the tartan powder and the Co raw material powder were not uniformly mixed and were unevenly mixed by agglomeration, .

On the other hand, in the specimens 3 to 5 according to the embodiment of the present invention, excellent wear resistance and excellent toughness were obtained over a suitable full-time period, which showed a non-biased cutting life. Particularly, , And fracture resistance.

(Example 3)

In order to evaluate the influence of the cooling conditions on the texture and the texture of the cemented carbide aggregates in the cemented carbide manufacturing process according to the present invention, the WC starting grain size was set to 2 to 6 탆 and the starting grain size of the titanate was set to 0.5 to 1.5 ㎛ for 2 ~ 4 hours by ball milling, and sintered spheroidized powder was sprayed using a spray dryer. Tartan cargo was prepared with TaNbC. The sintering process was performed in the same manner as in Example 1 by performing a dewaxing process at a low temperature region of 250 ° C, preliminarily sintering at 1200 ° C for 1 hour, and then sintering at 1400 ° C. In this case, the cooling rate after the sintering was differently performed in the range of 5 to 25 ° C / min as shown in Table 4 below. For each of the sintered bodies manufactured through the above process, test pieces were prepared in the same manner as in Example 1, and the measurement and physical properties of the group structure of WC and tartanite were evaluated.

Psalter Composition (wt%) Cooling conditions
(° C / min) Group
group
(%) Anti-radiation
(kgf / mm ² ) Wear out
Maternity Chipping resistance Breakage resistance
(m) Remarks WC Co Tartan cargo One 89 10 One 20 90 315 13 22 7.8 Example 2 89 10 One 15 90 320 16 21 7.2 Example 3 89 10 One 25 20 150 17 8 0.7 Comparative Example 4 89 10 One 2 60 170 One 18 1.8 Comparative Example 5 89 10 One 5 50 150 3 17 0.2 Comparative Example 6 89 10 One 10 20 200 7 22 0.2 Comparative Example

As shown in Table 4, when the cooling rate is excessively high as in the case of the specimen 3 according to the comparative example, the sintering process is not complete and defects such as pores and cracks are generated. As a result, Respectively. In the case of the specimens 4 to 6 according to the comparative examples, if the cooling rate is too slow, it is difficult to form a group structure of WC and tartanite due to grain growth of the WC, uneven grain growth of the tartanite, and precipitation of the dissolving material, It was confirmed that abrasion resistance was poor but abrupt breakage occurred and the cutting life was terminated prematurely.

On the other hand, the specimens 1 and 2 according to the embodiment of the present invention were found to have excellent abrasion resistance, chipping resistance, and breakage resistance by forming a group structure of sufficient WC and tartanite through an appropriate cooling rate.

( Example 4)

In order to evaluate the influence of the raw material powders, particularly the WC grain size, on the texture and the texture of the cemented carbide aggregates in the cemented carbide manufacturing process according to the present invention, the WC starting grain size was 0.08 to 2 μm, 6 to 12 ㎛, and the particle size starting from tartan powder was selected to be 1 탆, followed by ball milling for 2 to 4 hours, followed by sintering the spheroidized powder using a spray dryer. The sintering step was carried out in the same manner as in Example 1 by performing a dewaxing process at a low temperature region of 250 ° C, presintering at 1200 ° C for 1 hour, and then sintering at 1400 ° C. And cooled at a cooling rate of 20 DEG C / min. For each of the sintered bodies manufactured through this process, test pieces were prepared in the same manner as in Example 1, and the measurement and physical properties of the group structure of WC and tartanite were evaluated and summarized in Table 5 below.

Psalter WC
content
(wt%) WC
Granularity
(탆) Co
content
(wt%) Get
Carbide content
(wt%) Granularity
(탆) Group
group
(%) Anti-radiation
(kgf / mm ² ) Wear out
Maternity Internal tooth
Ping Sung Implosion
Sonicity (m) Remarks One 89 0.08 10 One 0.08 20 100 25 9 0.1 Comparative Example 2 89 0.5 10 One 0.08 65 180 23 7 2.5 Comparative Example 3 89 2 10 One 1.0 87 350 17 18 7.8 Example 4 89 4 10 One 1.0 90 392 19 18 8.0 Example 5 89 5 10 One 1.0 85 384 21 23 8.7 Example 6 89 7 10 One 3.0 60 221 11 7.8 10 Comparative Example 7 89 10 10 One 3.0 15 280 0.3 1.7 15 Comparative Example

Referring to Table 5, when the WC starting particle size is small as in the case of the test pieces 1 and 2 according to the comparative example, the simple abrasion resistance is good, but the amount of formation of the aggregate group of WC and tartan is insufficient, . On the other hand, even when the starting particle size of WC is relatively large as in the specimen pieces 6 and 7 according to the comparative examples, the amount of formation of aggregate grouping of WC and tartan is not sufficient as in the case of specimens 1 and 2 due to nonuniform grinding of WC during the mixing process In addition, it was found that the simple fracture resistance was good but both the resistance to abrasion, wear resistance and fatigue were poor.

On the other hand, the test pieces 3 to 5 according to the embodiment of the present invention have a sufficient group of WC and aggregate group of tailgate by selecting the appropriate WC starting grain size, and thus have excellent abrasion resistance, abrasion resistance, Respectively.

( Example 5)

In order to evaluate the influence of the raw material powder, particularly the tartanization particle size, on the texture and physical properties of the aggregate group of the cemented carbide in the manufacturing process of the cemented carbide according to the present invention, the WC starting grain size was set to 2 to 6 탆 as shown in Table 6 below, The particle size was selected to be less than 0.5 탆, 0.5 to 1.5 탆, and 2.0 to 4.0 탆, followed by ball milling for 2 to 4 hours, followed by sintering the spheroidized powder using a spray dryer. The sintering step was carried out in the same manner as in Example 1 by performing a dewaxing process at a low temperature region of 250 ° C, presintering at 1200 ° C for 1 hour, and then sintering at 1400 ° C. And cooled at a cooling rate of 20 DEG C / min. For each of the sintered bodies manufactured through this process, the specimens were prepared in the same manner as in Example 1, and the measurement and physical properties of the aggregate structure of the WC and the titanate were evaluated and are summarized in Table 6 below.

Psalter WC
content
(wt%) Co
content
(wt%) Get
Carbide content
(wt%) Tartan cargo
Granularity
(탆) Group
group(%) Anti-radiation
(kgf / mm ² ) Wear out
Maternity Internal tooth
Ping Sung Implosion
Sonicity (m) Remarks One 89 10 One 0.3 10 100 12 7 3.0 Comparative Example 3 89 10 One 0.5 85 358 17 18 9.2 Example 4 89 10 One 1.0 92 425 19 18 8.8 Example 5 89 10 One 1.5 90 384 21 23 8.5 Example 6 89 10 One 3.0 65 176 9 8 3.5 Comparative Example 7 89 10 One 5.0 15 190 11 0.7 2.8 Comparative Example

Referring to Table 6, when the starting particle size of the tartanic starting material is small as in the case of the test piece 1 according to the comparative example, since the tartanic material is easily dissolved in the Co, the aggregate formation amount of the WC and the tar group is insufficient, Was found to be low. On the contrary, even when the starting grain size of WC is relatively large as in the specimen pieces 6 and 7 according to the comparative example, the amount of formation of aggregate grouping of WC and tartanite is not sufficient as in the case of specimen 1 due to nonuniform grinding of tartan Simple fracture resistance was found to be satisfactory, but resistance, abrasion resistance and internal chipping were found to be poor.

On the contrary, the test pieces 3 to 5 according to the embodiment of the present invention select the starting particle size of the appropriate tartarate to form the aggregate group structure of the WC and the untreated tartanite, that is, the aggregate group structure of the sufficient WC and the tartanite, Resistance to abrasion, resistance to chipping and resistance to breakage.

Claims

A cemented carbide containing 10 to 13 wt% of Co and 2 wt% or less of titanate and the balance of WC and unavoidable impurities, wherein the aggregate structure in which the titanate is combined with WC among the microstructures measured at a depth of 500 mu m or more from the surface is an area By weight based on the total weight of the cemented carbide.

The cemented carbide as set forth in claim 1, wherein the tartanite is at least one of Ta, Nb or Ti-based tartarite.

10 to 13 wt% Co; 2 wt% or less of talc, and WC as a remainder, the method comprising the steps of:
The grain size of the tartanite is 0.5 to 1.5 탆,
Wherein the steel is quenched at a cooling rate of 15 to 20 占 폚 / min after the sintering.

The method of manufacturing a cemented carbide according to claim 3, wherein the WC grain size is 2 to 6 mu m.

delete

The cemented carbide manufacturing method according to claim 3, wherein the tartanite is at least one of Ta, Nb or Ti-based tartarate.