Indian Patents. 251943:CEMENTED CARBIDE BODY

Title of Invention	CEMENTED CARBIDE BODY
Abstract	The present invention relates to a cemented carbide body with the following composition: Co: 10-12 wt-%, TaC: <3 wt-%, NbC: 1- 5.5 wt-%, TiC: 3-5 wt-% and as rest WC. The cemented carbide body is particularly useful for metal cutting operations requiring high wear resistance, high edge retention and high edge toughness.

Full Text	The present invention relates to a cemented carbide twist drill particularly useful for metal cutting operations requiring high wear resistance such as drilling in cast iron etc. Drilling in metals is generally divided into two types: long hole drilling and short hole drilling. With short hole drilling is generally meant drilling to a depth of up to 3-5 times the drill diameter. Long hole drilling puts great demands on good chipformation, lubrication, cooling and chip transport. This is achieved through specially developed drill systems with specially designed drill heads attached to a drillstring. The drill head can be of solid cemented carbide but is generally of tool steel provided with a number of inserts of cemented carbide placed in such a way that they together form the cutting edge. At short hole drilling the demand is not as great and twist drills either of cemented carbide or tool steel or of tool steel provided with cemented carbide inserts are used. A twist drill of cemented carbide is manufactured from a cylindrical blank, which is machined to desired shape and dimension in particular to form cutting edges and flutes. Alternatively the chip flutes are at least preformed during the extrusion operation. As a result of the grinding sharp edges are formed. A relatively late type of drill is a drill with exchangeable • drill tip generally made of cemented carbide and removably connected to a drill shank of tool steel. A common reason to failure of a twist drill is excessive wear in the juncture between the main cutting edge and the leading edge. Another reason to failure is, when the cutting speed is increased, plastic deformation due to high temperature in the peripheral part of the cutting edge. EP-A-951576 discloses a cemented carbide drill consisting of a tough core surrounded by a more wear resistant cover. This type of drill is most suitable for toughness demanding drilling applications. It is an object of the present invention to provide a twist drill with increased tool life in applications requiring good wear resistance. Fig 1 shows a twist drill. Fig 2 shows in about 1200X magnification the microstructure of the cemented carbide according to the invention. Fig 3 shows the wear development in a performance test of a twist drill according to the present invention (■) and according to prior art ( ■ ). Fig 4 shows the wear development in a performance test of a twist drill according to the present invention(■) and according to prior art(♦) . It has now surprisingly been found that a twist drill made of a cemented carbide with the following composition gives excellent results in drilling operations requiring good wear resistance without suffering from plastic deformation and/or thermal cracking: Co: 10-12, preferably 10.5-11.5 wt-%, \| TaC: NbC: 1-5.5, preferably 2.5-5.5, most preferably 3.5-5 wt-%, TiC: 3-5, preferably 3.8-4.3 wt-% and WC: as rest, preferably 76-81 wt-%, most preferably 77-79 wt- TaC+TiC+NbC: Preferably 8-13, most preferably 9-12 wt-%. V and/or Cr: Preferably In an alternative embodiment particularly for metal sawing tips: TaC: NbC: 4-6, preferably 5 NbC+TaC: 5-7 wt-%. The average grain size of the WC is 0.4-1.5, preferably 0.8- 1.5, most preferably about 1 urn determined using linear analysis on a representative number of SEM micrographs. The hardness of the cemented carbide is 1450-1650 HV, ..preferably 1450-1550 HV. The drill is provided with a wear resistant coating as known in the art such as PVD-TiN, PVD-TiAlN or CVD coating. The drill according to the invention is made with powder metallurgical technique milling of powder forming hard constituents and binder metal, pressing or extruding the milled mixture to cylindrical blanks which are sintered and finally ground to desired shape and dimension after which the drill is provided with a wear resistant coating as known in the art. The present invention also relates to the use of a cemented carbide according to above as a rotary tool for metal machining such as solid carbide twist drill, a twist drill with exchangeable tip, end mill, hob, circular knife, hollow circular cutter for metal thread/rod shaping in particular at a peripheral speed of >150 m/min. The present invention further relates to the use of a cemented carbide according to above as a rotary tool for metal machining such as, hob, circular knife, hollow circular cutter for metal thread/rod shaping in particular a saw tip for a metal saw for metal cutting/sawing at a peripheral speed of >750 m/min or as a wear part especially for metalforming tools, e.g. canning tools Example 1 Samples were prepared by wet mixing powders of WC, Co, TiC, TaC and NbC to obtain a cemented carbide with a composition of 78,2 wt-% WC, 11,2 wt-% Co, 4,0 wt-% TiC, 2,1 wt-% TaC, 4,5 wt-% NbC and an average WC grain size of about 1 fim. The mixture was, after spray drying, isostatically pressed and sintered to cylindrical blanks which were ground to drills of 8 mm diameter. The microstructure is shown in Fig 2. After grinding the drills were coated with a layer of 4 urn TiAIN using PVD-technique. Example 2 Drills from Example 1 were tested in a drilling operation for drilling through holes in cast iron SS0125. As reference was used corresponding drills of Sandvik commercial grade GC 1220 commonly used for drilling in cast iron. The following data were used: Cutting speed: 100 m/min Feed: 0.25 mm/rev Through holes, 25 mm deep, were drilled with outer coolant. The result is presented in Fig 3 which shows the wear VBPmax as a function of number of holes drilled for the drill according to the invention (▲ ) and ref erence ( ■ ) . Example 3 Example 2 was repeated at an increased cutting speed of 175 m/min and internal cooling. The result is presented in Fig 4 which shows the wear VBPmax as a function of number of holes drilled for the drill according to the invention (■) and reference(♦) . Examples 2 and 3 show that the invented grade is between 35% and 50% better in wear resistance in both ordinary and increased cutting speeds. Example 4 Samples were prepared by wet mixing powders of WC, Co, TiC, CrC and NbC to obtain a cemented carbide with a composition of 78.8 wt-% WC, 11.2 wt-% Co, 4.0 wt-% TiC, 5.5 wt-% NbC, 0.5 wt-% CrC and an average WC grain size of about 1 µm. The mixture was, after spray drying, uniaxially pressed and sintered to saw tip blanks. Example 5 A circular saw blade was made of tips from Example 4. Saw tips of a commodity cemented carbide grade with the composition of 69 wt-% WC, 11 wt-% Co, 10 wt-% TiC, 8.5 wt-% TaC, 1.5 wt-% NbC and an average WC grain size of about 2.0 jam was used as reference material. All saw tip blanks were brazed onto a circular steel blade (0 285 mm x 60 tips) and ground to a width of 2.5 mm. The edge of each tip had a ground chamfer of width 0.2 mm. The tips were placed onto the saw in groups of six tips for each variant. The cutting test material was steel bar type 17Cr3, 0 52 mm. The reference cemented carbide grade is commonly used in circular metal saws for general steel, low carbon steel and stainless steel. The following data were used in the dry saw cutting test: Machine: Noritake Cutting speed: 800 rpm Feed rate: 40 mm/s Machinability additive: Supra 60S with a dropping speed of 1 drop/second The saw tip performance was measured by the flank wear after 10000 passes. Result: The saw tips of the reference grade showed a flank wear of 0.4 nun after 10000 cuts. The saw tips according to the invention had less than 0.15 mm of flank wear. Microchipping along the cutting edge with severe built-up edge (BUE) and heavy smearing could be observed at the edges of the reference grade. The saw tips according to the invention showed a nice wear pattern with good edge retention without micro chipping. Example 5 shows that the flank wear resistance is more than two times higher in the invented grade. We Claim : 1. Cemented carbide body characterized in having the following composition: Co: 10-12 preferably 10.5-11.5 wt-%, TaC : NbC : 1-5.5 , preferably 2.5 - 5.5, most preferably 3.5-5 wt-%, TiC: 3-5 , preferably 3.8-4.3 wt-% , WC: as rest, preferably 76-81 wt-%, TaC + TiC +NbC : 8-13, preferably 9-12 wt-%, and Optionally V and/or Cr: wherein an average grain size of the Wc : 0.4 - 1.5, preferably 0.8-1.5 micrometer, and hardness of said cemented carbide is 1450-1650 HV, preferably 1450-1550 HV. 2. Cemented carbide body as claimed in any of the previous claims, wherein Tac : NbC : 4-6, preferably 5 NbC+TaC : 5-7 wt-%. 3. Cemented carbide body as claimed in any of the previous claims, wherein a Wc- content of 77-79 wt-%. 4. Cemented carbide body as claimed in any of the previous claims, wherein being provided with a thin wear resistant coating as known in the art. 5. Cemented carbide body as claimed in any of the previous claims, wherein said drill is a rotator tool for metal machining. 6. Cemented carbide body as claimed in any of the previous claims wherein said rotary tool for metal machining is a solid carbide twist drill, a twist drill with exchangeable top or end mill, hob, circular knife, hollow circular cutter for metal thread/ rod shaping. 7. Cemented carbide body as claimed in any of the previous claims wherein said drill is a saw tip for a metal saw for metal cutting/sawing. 8. Cemented carbide body as claimed in any of the previous claims wherein said drill is a wear part especially for metal forming tools, e.g. canning tools. The present invention relates to a cemented carbide body with the following composition: Co: 10-12 wt-%, TaC: 5.5 wt-%, TiC: 3-5 wt-% and as rest WC. The cemented carbide body is particularly useful for metal cutting operations requiring high wear resistance, high edge retention and high edge toughness.

Full Text

The present invention relates to a cemented carbide twist
drill particularly useful for metal cutting operations requiring
high wear resistance such as drilling in cast iron etc.
Drilling in metals is generally divided into two types: long
hole drilling and short hole drilling. With short hole drilling is
generally meant drilling to a depth of up to 3-5 times the drill
diameter.
Long hole drilling puts great demands on good chipformation,
lubrication, cooling and chip transport. This is achieved through
specially developed drill systems with specially designed drill
heads attached to a drillstring. The drill head can be of solid
cemented carbide but is generally of tool steel provided with a
number of inserts of cemented carbide placed in such a way that
they together form the cutting edge.
At short hole drilling the demand is not as great and twist
drills either of cemented carbide or tool steel or of tool steel
provided with cemented carbide inserts are used.
A twist drill of cemented carbide is manufactured from a
cylindrical blank, which is machined to desired shape and
dimension in particular to form cutting edges and flutes.
Alternatively the chip flutes are at least preformed during the
extrusion operation. As a result of the grinding sharp edges are
formed.
A relatively late type of drill is a drill with exchangeable •
drill tip generally made of cemented carbide and removably
connected to a drill shank of tool steel.
A common reason to failure of a twist drill is excessive wear
in the juncture between the main cutting edge and the leading
edge. Another reason to failure is, when the cutting speed is
increased, plastic deformation due to high temperature in the
peripheral part of the cutting edge.
EP-A-951576 discloses a cemented carbide drill consisting of
a tough core surrounded by a more wear resistant cover. This type
of drill is most suitable for toughness demanding drilling
applications.
It is an object of the present invention to provide a twist
drill with increased tool life in applications requiring good wear
resistance.

Fig 1 shows a twist drill.
Fig 2 shows in about 1200X magnification the microstructure
of the cemented carbide according to the invention.
Fig 3 shows the wear development in a performance test of a
twist drill according to the present invention (■) and according to
prior art ( ■ ).
Fig 4 shows the wear development in a performance test of a
twist drill according to the present invention(■) and according to
prior art(♦) .
It has now surprisingly been found that a twist drill made of
a cemented carbide with the following composition gives excellent
results in drilling operations requiring good wear resistance
without suffering from plastic deformation and/or thermal
cracking:
Co: 10-12, preferably 10.5-11.5 wt-%,
| TaC: NbC: 1-5.5, preferably 2.5-5.5, most preferably 3.5-5 wt-%,
TiC: 3-5, preferably 3.8-4.3 wt-% and
WC: as rest, preferably 76-81 wt-%, most preferably 77-79 wt-
TaC+TiC+NbC: Preferably 8-13, most preferably 9-12 wt-%.
V and/or Cr: Preferably In an alternative embodiment particularly for metal sawing
tips:
TaC: NbC: 4-6, preferably 5 NbC+TaC: 5-7 wt-%.
The average grain size of the WC is 0.4-1.5, preferably 0.8-
1.5, most preferably about 1 urn determined using linear analysis
on a representative number of SEM micrographs.
The hardness of the cemented carbide is 1450-1650 HV,
..preferably 1450-1550 HV.
The drill is provided with a wear resistant coating as known
in the art such as PVD-TiN, PVD-TiAlN or CVD coating.
The drill according to the invention is made with powder
metallurgical technique milling of powder forming hard
constituents and binder metal, pressing or extruding the milled
mixture to cylindrical blanks which are sintered and finally
ground to desired shape and dimension after which the drill is
provided with a wear resistant coating as known in the art.

The present invention also relates to the use of a cemented
carbide according to above as a rotary tool for metal machining
such as solid carbide twist drill, a twist drill with exchangeable
tip, end mill, hob, circular knife, hollow circular cutter for
metal thread/rod shaping in particular at a peripheral speed of
>150 m/min.
The present invention further relates to the use of a
cemented carbide according to above as a rotary tool for metal
machining such as, hob, circular knife, hollow circular cutter for
metal thread/rod shaping in particular a saw tip for a metal saw
for metal cutting/sawing at a peripheral speed of >750 m/min or as
a wear part especially for metalforming tools, e.g. canning tools
Example 1
Samples were prepared by wet mixing powders of WC, Co, TiC,
TaC and NbC to obtain a cemented carbide with a composition of
78,2 wt-% WC, 11,2 wt-% Co, 4,0 wt-% TiC, 2,1 wt-% TaC, 4,5 wt-%
NbC and an average WC grain size of about 1 fim. The mixture was,
after spray drying, isostatically pressed and sintered to
cylindrical blanks which were ground to drills of 8 mm diameter.
The microstructure is shown in Fig 2. After grinding the drills
were coated with a layer of 4 urn TiAIN using PVD-technique.
Example 2
Drills from Example 1 were tested in a drilling operation for
drilling through holes in cast iron SS0125. As reference was used
corresponding drills of Sandvik commercial grade GC 1220 commonly
used for drilling in cast iron.
The following data were used:
Cutting speed: 100 m/min
Feed: 0.25 mm/rev
Through holes, 25 mm deep, were drilled with outer coolant.
The result is presented in Fig 3 which shows the wear VBPmax
as a function of number of holes drilled for the drill according
to the invention (▲ ) and ref erence ( ■ ) .
Example 3
Example 2 was repeated at an increased cutting speed of 175
m/min and internal cooling.

The result is presented in Fig 4 which shows the wear VBPmax
as a function of number of holes drilled for the drill according
to the invention (■) and reference(♦) .
Examples 2 and 3 show that the invented grade is between 35%
and 50% better in wear resistance in both ordinary and increased
cutting speeds.
Example 4
Samples were prepared by wet mixing powders of WC, Co, TiC,
CrC and NbC to obtain a cemented carbide with a composition of
78.8 wt-% WC, 11.2 wt-% Co, 4.0 wt-% TiC, 5.5 wt-% NbC, 0.5 wt-%
CrC and an average WC grain size of about 1 µm. The mixture was,
after spray drying, uniaxially pressed and sintered to saw tip
blanks.
Example 5
A circular saw blade was made of tips from Example 4. Saw
tips of a commodity cemented carbide grade with the composition of
69 wt-% WC, 11 wt-% Co, 10 wt-% TiC, 8.5 wt-% TaC, 1.5 wt-% NbC
and an average WC grain size of about 2.0 jam was used as reference
material. All saw tip blanks were brazed onto a circular steel
blade (0 285 mm x 60 tips) and ground to a width of 2.5 mm. The
edge of each tip had a ground chamfer of width 0.2 mm. The tips
were placed onto the saw in groups of six tips for each variant.
The cutting test material was steel bar type 17Cr3, 0 52 mm.
The reference cemented carbide grade is commonly used in circular
metal saws for general steel, low carbon steel and stainless
steel.
The following data were used in the dry saw cutting test:
Machine: Noritake
Cutting speed: 800 rpm
Feed rate: 40 mm/s
Machinability additive: Supra 60S with a dropping speed of 1
drop/second
The saw tip performance was measured by the flank wear after
10000 passes.
Result:

The saw tips of the reference grade showed a flank wear of
0.4 nun after 10000 cuts.
The saw tips according to the invention had less than 0.15 mm
of flank wear.
Microchipping along the cutting edge with severe built-up
edge (BUE) and heavy smearing could be observed at the edges of
the reference grade.
The saw tips according to the invention showed a nice wear
pattern with good edge retention without micro chipping.
Example 5 shows that the flank wear resistance is more than
two times higher in the invented grade.

We Claim :
1. Cemented carbide body characterized in having the following composition:
Co: 10-12 preferably 10.5-11.5 wt-%,
TaC : NbC : 1-5.5 , preferably 2.5 - 5.5, most preferably 3.5-5 wt-%,
TiC: 3-5 , preferably 3.8-4.3 wt-% ,
WC: as rest, preferably 76-81 wt-%,
TaC + TiC +NbC : 8-13, preferably 9-12 wt-%, and
Optionally V and/or Cr: wherein an average grain size of the Wc : 0.4 - 1.5, preferably 0.8-1.5
micrometer, and hardness of said cemented carbide is 1450-1650 HV, preferably
1450-1550 HV.
2. Cemented carbide body as claimed in any of the previous claims, wherein
Tac : NbC : 4-6, preferably 5 NbC+TaC : 5-7 wt-%.
3. Cemented carbide body as claimed in any of the previous claims, wherein a Wc-
content of 77-79 wt-%.
4. Cemented carbide body as claimed in any of the previous claims, wherein being
provided with a thin wear resistant coating as known in the art.
5. Cemented carbide body as claimed in any of the previous claims, wherein said
drill is a rotator tool for metal machining.

6. Cemented carbide body as claimed in any of the previous claims wherein said
rotary tool for metal machining is a solid carbide twist drill, a twist drill with
exchangeable top or end mill, hob, circular knife, hollow circular cutter for metal
thread/ rod shaping.
7. Cemented carbide body as claimed in any of the previous claims wherein said drill
is a saw tip for a metal saw for metal cutting/sawing.
8. Cemented carbide body as claimed in any of the previous claims wherein said
drill is a wear part especially for metal forming tools, e.g. canning tools.

The present invention relates to a cemented carbide body with
the following composition: Co: 10-12 wt-%, TaC: 5.5 wt-%, TiC: 3-5 wt-% and as rest WC. The cemented carbide body
is particularly useful for metal cutting operations requiring high
wear resistance, high edge retention and high edge toughness.

Documents:

38-KOL-2005-ABSTRACT-1.1.pdf

38-kol-2005-abstract.pdf

38-KOL-2005-AMANDED CLAIMS.pdf

38-KOL-2005-AMANDED PAGES OF SPECIFICATION.pdf

38-kol-2005-assignment.pdf

38-KOL-2005-CANCELLED PAGES.pdf

38-kol-2005-claims.pdf

38-KOL-2005-CORRESPONDENCE 1.2.pdf

38-kol-2005-correspondence 1.4.pdf

38-KOL-2005-CORRESPONDENCE-1.1.pdf

38-KOL-2005-CORRESPONDENCE-1.3.pdf

38-kol-2005-correspondence.pdf

38-kol-2005-description (complete).pdf

38-KOL-2005-DRAWINGS-1.1.pdf

38-kol-2005-drawings.pdf

38-kol-2005-form 1.pdf

38-KOL-2005-FORM 18.1.pdf

38-kol-2005-form 18.pdf

38-KOL-2005-FORM 2-1.1.pdf

38-kol-2005-form 2.pdf

38-KOL-2005-FORM 3-1.2.pdf

38-KOL-2005-FORM 3.pdf

38-KOL-2005-FORM 5-1.1.pdf

38-KOL-2005-FORM 5.pdf

38-kol-2005-form 6.pdf

38-kol-2005-gpa.pdf

38-KOL-2005-GPA1.1.pdf

38-KOL-2005-GRANTED-ABSTRACT.pdf

38-KOL-2005-GRANTED-CLAIMS.pdf

38-KOL-2005-GRANTED-DESCRIPTION (COMPLETE).pdf

38-KOL-2005-GRANTED-DRAWINGS.pdf

38-KOL-2005-GRANTED-FORM 1.pdf

38-KOL-2005-GRANTED-FORM 2.pdf

38-KOL-2005-GRANTED-SPECIFICATION.pdf

38-KOL-2005-OTHERS.pdf

38-KOL-2005-OTHERS1.1.pdf

38-KOL-2005-PA.pdf

38-KOL-2005-PETITION UNDER RULE 137.pdf

38-KOL-2005-REPLY TO EXAMINATION REPORT.pdf

38-KOL-2005-REPLY TO EXAMINATION REPORT1.1.pdf

38-kol-2005-specification.pdf

38-kol-2005-translated copy of priority document.pdf

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Patent Number

251943

Indian Patent Application Number

38/KOL/2005

PG Journal Number

16/2012

Publication Date

20-Apr-2012

Grant Date

18-Apr-2012

Date of Filing

25-Jan-2005

Name of Patentee

SANDVIK INTELLECTUAL PROPERTY AB

Applicant Address

S-811 81 SANDVIKEN

Inventors:

#	Inventor's Name	Inventor's Address
1	OUCHTERLONY HÉLÈNE	HANSTAVIK, S-134 61 INGARÖ

PCT International Classification Number

B22F7/06; C22C29/08

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0400141-8	2004-01-26	Sweden