EP2205382A1 - Method of making a cemented carbide powder with low sintering shrinkage and the powder obtained - Google Patents

Method of making a cemented carbide powder with low sintering shrinkage and the powder obtained

Info

Publication number
EP2205382A1
EP2205382A1 EP08833090A EP08833090A EP2205382A1 EP 2205382 A1 EP2205382 A1 EP 2205382A1 EP 08833090 A EP08833090 A EP 08833090A EP 08833090 A EP08833090 A EP 08833090A EP 2205382 A1 EP2205382 A1 EP 2205382A1
Authority
EP
European Patent Office
Prior art keywords
bodies
powder
milling
cemented carbide
sintering shrinkage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08833090A
Other languages
German (de)
French (fr)
Inventor
Jan Qvick
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Seco Tools AB
Original Assignee
Seco Tools AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Seco Tools AB filed Critical Seco Tools AB
Publication of EP2205382A1 publication Critical patent/EP2205382A1/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/14—Treatment of metallic powder
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
    • B22F2009/043—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by ball milling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the present invention relates to a method of making cemented carbide powder with low sintering shrinkage, particularly useful for cutting tool inserts for turning, milling and drilling of metals and the powder obtained.
  • Cemented carbide bodies is made by wet milling of powders forming hard constituents and binder phase to a slurry, drying the slurry generally by spray drying, pressing the dried powder in pressing tools to bodies of desired shape and finally sintering .
  • the milling operation is an intensive milling performed in mills with milling bodies.
  • mills There are essentially two types of mills: rotating ball mills and attritor mills.
  • rotating ball mill the milling time is conventionally within 15 to 60 hours and such processing is believed to be necessary in order to obtain a uniform distribution of the constituents.
  • the bodies shrink about 16-20 % linearly.
  • the shrinkage depends on pressing pressure, WC grain size, grain size distribution and Co-content. Pressing tools are expensive to make and are therefore made for a standard shrinkage such as 17.5 %.
  • the shrinkage is determined at a standard pressing pressure. If the shrinkage at the standard pressure is high, the pressing pressure at the predetermined shrinkage will be high. If the shrinkage at the standard pressure is low, the pressing pressure at the predetermined shrinkage will be low.
  • a high pressing pressure is not desirable because of the risk of pressing cracks in the pressed bodies and abnormal wear and even risk of pressing tool failure including injuries to humans.
  • a low pressing pressure may lead to bodies that are not fully dense after sintering. Moreover, dimensional control of the sintered bodies is facilitated if the pressing pressure is kept within a certain interval. Inserts produced with a high pressing pressure often show edges with pressing cracks.
  • the milling bodies can be in various forms as balls or short cylindrical rods.
  • US 3,531,280 discloses the size to be about 1/8 to 1/4 inch and the material of the milling bodies to be cobalt bonded tungsten carbide containing about 6% cobalt.
  • US 3,525,610 discloses the size of the milling bodies to be within 0.1 to 0.3 inch and the material to be WC cemented with 5 to 10 wt-% Co. This size interval is chosen in order to obtain milling bodies with sufficient weight and size to obtain a high milling efficiency.
  • EP 1043413 discloses a method of making a cemented carbide with submicron WC grain size with a low compacting pressure.
  • EP 1749601 discloses a method of making a ready to press cemented carbide powder with low compaction pressure suitable for the production of submicron cemented carbide.
  • the method comprises using 1-3 wt-% pressing agent of the following composition, ⁇ 90 wt-% PEG and 10-75 wt-% of blends of high molecular weight (C12- ⁇ C20) saturated or unsaturated fatty acids, or salts thereof containing at least one element of Al, Ba, Ca, Co, Cr, Mg, N, Na, V or Zn.
  • a cemented carbide powder with a low sintering shrinkage at a constant pressing pressure can be made from powder mixtures that are produced in ball mills with milling bodies larger than conventional.
  • the present invention relates to a method of making a cemented carbide powder with low sintering shrinkage and excellent compacting properties for cemented carbide bodies preferably cutting tool inserts for metal machining comprising WC and 4-15 wt-% Co, preferably 5-12 wt-% Co and up to 20 wt-% cubic carbide forming elements from the Groups 4b and 5b of the Periodic Table of the Elements preferably Ti, Zr, Ta and Nb by means of the powder metallurgical techniques wet milling, pressing and sin- tering.
  • the wet milling is performed in a rotating ball mill with a ratio between the weight of milling bodies and powder of 2-5.
  • the milling bodies are shaped either as spheres or cylinders with semi-spherical end surfaces.
  • the spherical bodies have a diameter of 10 to 15 mm, preferably 11 to 14 mm.
  • the cylindrical bodies have a diameter and height of 10 to 15 mm, preferably 11 to 14 mm.
  • the composition of the milling bodies is WC with 6 to 10 wt-% Co, preferably 7 to 9 wt-% Co with a sintered WC grain size of 1 to 5 ⁇ m. In order to reach the desired grain size of the milled powder it may be necessary to prolong the milling time compared to milling according to prior art.
  • a cemented carbide powder with desired low sintering shrinkage and excellent compacting properties for cemented carbide bodies preferably cutting tool inserts for metal machining comprising WC and 4-15 wt-% Co, preferably 5-12 wt-% Co and up to 20 wt-% cubic carbide forming elements from the Groups 4b and 5b of the Periodic Table of the Elements preferably Ti, Zr, Ta and Nb.
  • the WC-grains have an FSSS average grain size in the range 3- 9 ⁇ m, preferably 4-7 ⁇ m.
  • the powder has a sintering shrinkage of 16.5 to 17.5 %, preferably within 16.7 to 17.3 % at a compacting pressure of 123 MPa.
  • a cemented carbide powder with the composition WC-9 wt-% Co, 0.5 wt-% (Ta, Nb)C (90/10) and 2.0 wt-% PEG 3400 was prepared according to the invention.
  • the Fisher Sub Sieve Sizer (FSSS) value of the WC was 5.4 ⁇ m.
  • the total batch weight was 450 kg and the weight of the milling bodies was 1340 kg.
  • the milling was carried out in a mixture of 93.2 litres ethanol and 20 wt-% water.
  • the milling bodies were cylindrical with diameter and height of 12 mm and a composition of WC with 8.5 wt-% Co and grain size 2.5 ⁇ m.
  • the milling time was 32 hours.
  • the powder batch was spray dried and compacted to bodies with the approximate size 15x15x7 mm at the standard pressure 123 MPa.
  • the bodies were sintered at 1430 0 C at standard sintering conditions. The exact dimensions of the bodies were determined before and after sintering.
  • the linear shrinkage of the bodies was 17.0 % and the coer- civity was 9.3 kA/m indicating an average grain size of 2.4 ⁇ m.
  • Example 1 was repeated with exception of the milling time, which was 16 hours.
  • Example 1 was repeated with exception of the size of the milling bodies that was 8 mm.
  • the linear shrinkage of the bodies was 18.1 % and the coer- civity was 9.9 kA/m indicating an average grain size of 2.2 ⁇ m.
  • Example 2 was repeated with exception of the size of the milling bodies that was 8 mm.
  • the linear shrinkage of the bodies was 17.8 % and the coer- civity was 9.1 kA/m indicating an average grain size of 2.5 ⁇ m.
  • the Examples 1-4 show that milling with large milling bodies leads to a powder with a low sintering shrinkage implying that the compacting pressure will be low at a given shrinkage.
  • the Examples show that a longer milling time is needed in order to obtain the same coercivity/grain size of the sintered body.
  • compacting at a low pressure is pre- ferred to milling for a long time.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)

Abstract

6 Abstract The present invention relates to a method of making cemented carbide powder with low sintering shrinkage comprising WC and 4- 15 wt-% Co and up to 20 wt-% cubic carbide forming elements from the Groups 4b and 5b of the Periodic Table of the Elements by 5 means of the powder metallurgical techniques wet milling, press- ing and sintering. According to the method wet milling is per- formed in a rotating ball mill with a ratio between theweight of milling bodies and powder of 2-5. The milling bodies are shaped either as spheres or cylinders with semi-spherical end 10 surfaces. The spherical bodies have a diameter of 10 to 15 mm and the cylindrical bodies have a diameter and height of 10 to 15 mm. The composition of the milling bodies is WC with 6 to 10 wt-% Co. The present invention also relates to a powder made according 15 to the method.

Description

Method of making a cemented carbide powder with low sintering shrinkage and the powder obtained
The present invention relates to a method of making cemented carbide powder with low sintering shrinkage, particularly useful for cutting tool inserts for turning, milling and drilling of metals and the powder obtained.
Cemented carbide bodies is made by wet milling of powders forming hard constituents and binder phase to a slurry, drying the slurry generally by spray drying, pressing the dried powder in pressing tools to bodies of desired shape and finally sintering .
The milling operation is an intensive milling performed in mills with milling bodies. There are essentially two types of mills: rotating ball mills and attritor mills. In a rotating ball mill, the milling time is conventionally within 15 to 60 hours and such processing is believed to be necessary in order to obtain a uniform distribution of the constituents.
During sintering, the bodies shrink about 16-20 % linearly. The shrinkage depends on pressing pressure, WC grain size, grain size distribution and Co-content. Pressing tools are expensive to make and are therefore made for a standard shrinkage such as 17.5 %. The shrinkage is determined at a standard pressing pressure. If the shrinkage at the standard pressure is high, the pressing pressure at the predetermined shrinkage will be high. If the shrinkage at the standard pressure is low, the pressing pressure at the predetermined shrinkage will be low. A high pressing pressure is not desirable because of the risk of pressing cracks in the pressed bodies and abnormal wear and even risk of pressing tool failure including injuries to humans. A low pressing pressure may lead to bodies that are not fully dense after sintering. Moreover, dimensional control of the sintered bodies is facilitated if the pressing pressure is kept within a certain interval. Inserts produced with a high pressing pressure often show edges with pressing cracks.
The milling bodies can be in various forms as balls or short cylindrical rods. US 3,531,280 discloses the size to be about 1/8 to 1/4 inch and the material of the milling bodies to be cobalt bonded tungsten carbide containing about 6% cobalt. US 3,525,610 discloses the size of the milling bodies to be within 0.1 to 0.3 inch and the material to be WC cemented with 5 to 10 wt-% Co. This size interval is chosen in order to obtain milling bodies with sufficient weight and size to obtain a high milling efficiency. EP 1043413 discloses a method of making a cemented carbide with submicron WC grain size with a low compacting pressure. The method consists in premixing all components except WC for about three hours, adding the WC powder and then finally milling for about ten hours . EP 1749601 discloses a method of making a ready to press cemented carbide powder with low compaction pressure suitable for the production of submicron cemented carbide. The method comprises using 1-3 wt-% pressing agent of the following composition, <90 wt-% PEG and 10-75 wt-% of blends of high molecular weight (C12-<C20) saturated or unsaturated fatty acids, or salts thereof containing at least one element of Al, Ba, Ca, Co, Cr, Mg, N, Na, V or Zn.
It has now surprisingly been found that a cemented carbide powder with a low sintering shrinkage at a constant pressing pressure can be made from powder mixtures that are produced in ball mills with milling bodies larger than conventional.
The present invention relates to a method of making a cemented carbide powder with low sintering shrinkage and excellent compacting properties for cemented carbide bodies preferably cutting tool inserts for metal machining comprising WC and 4-15 wt-% Co, preferably 5-12 wt-% Co and up to 20 wt-% cubic carbide forming elements from the Groups 4b and 5b of the Periodic Table of the Elements preferably Ti, Zr, Ta and Nb by means of the powder metallurgical techniques wet milling, pressing and sin- tering.
The wet milling is performed in a rotating ball mill with a ratio between the weight of milling bodies and powder of 2-5. The milling bodies are shaped either as spheres or cylinders with semi-spherical end surfaces. The spherical bodies have a diameter of 10 to 15 mm, preferably 11 to 14 mm. The cylindrical bodies have a diameter and height of 10 to 15 mm, preferably 11 to 14 mm. The composition of the milling bodies is WC with 6 to 10 wt-% Co, preferably 7 to 9 wt-% Co with a sintered WC grain size of 1 to 5 μm. In order to reach the desired grain size of the milled powder it may be necessary to prolong the milling time compared to milling according to prior art.
According to the invention there is also provided a cemented carbide powder with desired low sintering shrinkage and excellent compacting properties for cemented carbide bodies preferably cutting tool inserts for metal machining comprising WC and 4-15 wt-% Co, preferably 5-12 wt-% Co and up to 20 wt-% cubic carbide forming elements from the Groups 4b and 5b of the Periodic Table of the Elements preferably Ti, Zr, Ta and Nb. The WC-grains have an FSSS average grain size in the range 3- 9 μm, preferably 4-7 μm. The powder has a sintering shrinkage of 16.5 to 17.5 %, preferably within 16.7 to 17.3 % at a compacting pressure of 123 MPa.
Example 1
A cemented carbide powder with the composition WC-9 wt-% Co, 0.5 wt-% (Ta, Nb)C (90/10) and 2.0 wt-% PEG 3400 was prepared according to the invention. The Fisher Sub Sieve Sizer (FSSS) value of the WC was 5.4 μm. The total batch weight was 450 kg and the weight of the milling bodies was 1340 kg. The milling was carried out in a mixture of 93.2 litres ethanol and 20 wt-% water. The milling bodies were cylindrical with diameter and height of 12 mm and a composition of WC with 8.5 wt-% Co and grain size 2.5 μm. The milling time was 32 hours. The powder batch was spray dried and compacted to bodies with the approximate size 15x15x7 mm at the standard pressure 123 MPa. The bodies were sintered at 14300C at standard sintering conditions. The exact dimensions of the bodies were determined before and after sintering.
The linear shrinkage of the bodies was 17.0 % and the coer- civity was 9.3 kA/m indicating an average grain size of 2.4 μm. Metallographic investigation indicated a porosity of AOOBOOCOO.
Example 2
Example 1 was repeated with exception of the milling time, which was 16 hours.
The linear shrinkage of the bodies was 16.9 % and the coer- civity was 8.4 kA/m indicating an average grain size of 2.8 μm. Metallographic investigation indicated a porosity of AOOBOOCOO. Example 3-Prior Art
Example 1 was repeated with exception of the size of the milling bodies that was 8 mm.
The linear shrinkage of the bodies was 18.1 % and the coer- civity was 9.9 kA/m indicating an average grain size of 2.2 μm.
Metallographic investigation indicated a porosity of AOOBOOCOO.
Example 4 - Prior Art
Example 2 was repeated with exception of the size of the milling bodies that was 8 mm.
The linear shrinkage of the bodies was 17.8 % and the coer- civity was 9.1 kA/m indicating an average grain size of 2.5 μm. Metallographic investigation indicated a porosity of AOOBOOCOO. Thus, the Examples 1-4 show that milling with large milling bodies leads to a powder with a low sintering shrinkage implying that the compacting pressure will be low at a given shrinkage. Furthermore, the Examples show that a longer milling time is needed in order to obtain the same coercivity/grain size of the sintered body. However, compacting at a low pressure is pre- ferred to milling for a long time.

Claims

Claims
1. Method of making cemented carbide powder with low sintering shrinkage comprising WC and 4-15 wt-% Co and up to 20 wt-% cubic carbide forming elements from the Groups 4b and 5b of the Periodic Table of the Elements by means of the powder metallurgical techniques wet milling, pressing and sintering c h a r a c t e r i s e d in wet milling in a rotating ball mill with a ratio between the weight of milling bodies and powder of 2-5, the milling bodies being shaped either as spheres or cylin- ders with semi-spherical end surfaces whereby the spherical bodies have a diameter of 10 to 15 mm and the cylindrical bodies have a diameter and height of 10 to 15 mm and with a composition of the milling bodies of WC with 6 to 10 wt-% Co.
2. Cemented carbide powder with low sintering shrinkage compris- ing WC and 4-15 wt-% Co and up to 20 wt-% cubic carbide forming elements from the Groups 4b and 5b of the Periodic Table of the Elements with WC-grains with an average grain size in the range 3-9 μm c h a r a c t e r i s e d in that the powder has a sintering shrinkage of 16.5 to 17.5 %, preferably of 16.7 to 17.3 % at a compacting pressure of 123 MPa.
EP08833090A 2007-09-28 2008-09-24 Method of making a cemented carbide powder with low sintering shrinkage and the powder obtained Withdrawn EP2205382A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0702172A SE0702172L (en) 2007-09-28 2007-09-28 Ways to make a cemented carbide powder with low sintering shrinkage
PCT/SE2008/051069 WO2009041901A1 (en) 2007-09-28 2008-09-24 Method of making a cemented carbide powder with low sintering shrinkage and the powder obtained

Publications (1)

Publication Number Publication Date
EP2205382A1 true EP2205382A1 (en) 2010-07-14

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EP08833090A Withdrawn EP2205382A1 (en) 2007-09-28 2008-09-24 Method of making a cemented carbide powder with low sintering shrinkage and the powder obtained

Country Status (4)

Country Link
US (1) US20100260641A1 (en)
EP (1) EP2205382A1 (en)
SE (1) SE0702172L (en)
WO (1) WO2009041901A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2246113A1 (en) * 2009-04-29 2010-11-03 Sandvik Intellectual Property AB Process for milling cermet or cemented carbide powder mixtures
CN102389969B (en) * 2011-12-05 2013-10-09 北京工商大学 Powder metallurgical material for cold stamping mold and mold forming method using same

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL6516429A (en) * 1964-12-16 1966-06-17
US3531280A (en) * 1969-06-23 1970-09-29 Du Pont Heterogeneity by mixing diverse powders prior to consolidation
US4070184A (en) * 1976-09-24 1978-01-24 Gte Sylvania Incorporated Process for producing refractory carbide grade powder
US5045277A (en) * 1990-09-10 1991-09-03 Gte Products Corporation Method of producing metal carbide grade powders and controlling the shrinkage of articles made therefrom
SE518810C2 (en) * 1996-07-19 2002-11-26 Sandvik Ab Cemented carbide body with improved high temperature and thermomechanical properties
SE509616C2 (en) * 1996-07-19 1999-02-15 Sandvik Ab Cemented carbide inserts with narrow grain size distribution of WC
US6245288B1 (en) * 1999-03-26 2001-06-12 Omg Americas, Inc. Method of preparing pressable powders of a transition metal carbide, iron group metal of mixtures thereof
SE519603C2 (en) * 1999-05-04 2003-03-18 Sandvik Ab Ways to make cemented carbide of powder WC and Co alloy with grain growth inhibitors

Non-Patent Citations (1)

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Title
See references of WO2009041901A1 *

Also Published As

Publication number Publication date
SE531330C2 (en) 2009-02-24
WO2009041901A1 (en) 2009-04-02
US20100260641A1 (en) 2010-10-14
SE0702172L (en) 2009-02-24

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