CA1165757A - Rock bit cutter construction - Google Patents
Rock bit cutter constructionInfo
- Publication number
- CA1165757A CA1165757A CA000363871A CA363871A CA1165757A CA 1165757 A CA1165757 A CA 1165757A CA 000363871 A CA000363871 A CA 000363871A CA 363871 A CA363871 A CA 363871A CA 1165757 A CA1165757 A CA 1165757A
- Authority
- CA
- Canada
- Prior art keywords
- cone
- cone blank
- blank
- bearing
- forming
- 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.)
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Abstract
ROCK BIT CUTTER CONSTRUCTION
ABSTRACT OF THE INVENTION
A conical cutter for a rolling cutter drill bit is disclosed wherein the cutter body is manufactured from a through-hardening grade of steel which has been heat treated to optimum hardness with a selectively surface hardened bearing area.
ABSTRACT OF THE INVENTION
A conical cutter for a rolling cutter drill bit is disclosed wherein the cutter body is manufactured from a through-hardening grade of steel which has been heat treated to optimum hardness with a selectively surface hardened bearing area.
Description
! 1~S7~7 _OCK BIT CUTTER CONSl'R~lCTION_ BACKGROUND OF THE INVENTIO~
This invention is related to construction methods for manufacturing the conical cutter on a rolling cutter drill bit. More particularly, the invention is directed to the metallurgical features of a cutter utilized in a tri-cone rolling cutter drill bit which utilizes hard metal inserts imbedded in the cutter. The conventional mode of manufacturing insert type cutters for drill bits is to utilize a carburizing grade of steel to form the cutter bodies. After the cutters are formed, holes are bored in the conical surfaces to receive hard metal inserts which are small cutting elements made of hard material such as tungsten carbide. The problem with these conventional type cutters is that a carburizing steel does not provide sufficient core hardness to hold the hard metal inserts in place.
The present invention overcomes this deficiency by utilizing a through-hardening grade of steel for the cutter body and then heat treating the cutter body to the optimum hardness which best results in tightly gripping the *
~ 16S7S7 inserts. The invention also utilizes a higher hardness on the bearing surfaces as a result of a selective surface hardening in the bearing race areas.
Thus, the invention contemplates a method of manu-facturing a rolling cutter drill cutter assembly which com-~~prises forming a generally conical cutter body from a medium to high carbon hardenable steel, boring a generally, centrally located bearing journal passage into the base of the body, heat-treating the body to harden the body throughout its thickness, and heating only predetermined internal bearing surface areas within the bearing journal passage in the body to surface harden these predetermined areas to a higher hardness than the remainder of the body. A pl~rality of cylindrical recesses are formed along the conical surface of the body, and, a plurality of hard metal cutting elements are tightly secured in the recesses in the conical surface.
In a further embodiment the invention includes.a process for forming a tungsten carbide insert cone for a rock bit which comprises.the steps of forming.a cone blank from a medium to high carbon hardenable steel, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity, heat treating the cone blank to.a desired core hardness, forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts, and surface hardening a generally annuIar portion of the interior surface of the bearing cavity.by applying energy substantially only to the portion to heat a layer of the cone blank at the portion, and thereafter cooling the layer.rapidly.
The invention also contemplates the cutter means ,' ~ ~657S7 themselves for a rolling cut-ter drill bit having a body, at least one downwardly projecting lug, and a bearing journal extending from the lug. The improved cutter means has a generally conical body formed of a medium to high carbon hardenable steel with the entire body being subjected to heat treatment to harden the hody through-; out its thickness, and a generally cylindrical journal bearing passage located substantially centrally in the cutter body. A plurality of insert recesses are formed in the exterior surface of the body, a plurality of hardmetal cutting elements are snuggly secured in the recesses, and, internal bearing surface areas in the passage have the steel at the surface areas which are of the same chemical composition as the remainder of the body, and are hardened to a higher hardness than the remainder of the body by heating only the surface areas.
In addition, the invention includes for the cutter means a tungsten carbide insert cone for a rock bit which comprises a steel cone body having a carbon content at leas~ about 0.35% including a generally conical external surface, said body having been subjected to heat treatment to harden the body throughout its thickness, a generally cylindrical internal bearing cavity, with a generally annular layer at the surface of the bearing cavity having a hardness greater than that of the steel at the core of the cone body but a carbon content the same as that of the steel at the core, and a plurality of tungsten carbide inserts in holes in the external surface of the cone body.
~ 16~7S7 BRIEF DESCRIPTION OF THE DRAWING
_ Figure 1 is a cross-sectional side view of a typical rolling cutter drill bit cutter body; Figure 2 is a partial cross-sectional view of the cutter body of Figure 1 indicating an alternate embodiment of the invention;
and, Figure 3 is a partial cross-sectional view o~ a cutter body as shown in Figure 1 indicating a third embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figure 1, a generally conical cutter body 10 is disclosed in cross-sectional configuration having raised insert lands 11 which contain cylindrical insert recesses 12 bored therein. A plurality of partially cylindrical hard metal inserts 13 are located in tight fitting relationship in the recesses.12. Inserts 13 generally have cylindrical bafie sections 13a for engagement ln recesses 12,and hemispherical or partially conical protruding ends 13b which project above the top surface of lands 11. Each cutter is substantially symmetrical about a central longitudinal.axis c-c.and an inner bore 14 is formed along axis c-c for.receiving the bearing journal of a drill bit lug. The internal bor.e passage 14 further comprises.a reaess channel 15 for,receiving a seal member bearing.race,recess 16 for receiving ball bearings, and a , pilot pin recess 17 for rece~iving the pilot pin projection on the lug journal. The.bearing,recess,area 16, located on the internal surface of cutter 10, as well as a portion of bore passage 14,,identified,at 14a, is shaded at 18 to indicate the depth of.a surface hardening treatment t l~S757 which is applied in this area to further improve the life of the roller bearing therein. The cutter body 10 is comprised of a through-hardening type metal such as one of the AISI types 4137, 4140, 4340, 4135 or 8650 steel which can be hardened through the entire thickness of the cutter body to bore 14. This through-hardened material then provides a hardened recess 12 to more tightly secure insert 13 therein. In addition to the through-hardening of cutter 10, the surface hardening 18 is applied to the 10 roller bearing race 16 to extend bearing life and reduce spalling of the bearing race during heavy loading of the rock bit.
The advantages of the present invention are clearly evident. Fore one, by utilizing a through-hardening metal, the cutter may be hardened by means known in the art through the entire thickness of body 10. This allows a very hard, tough, recess 12 around insert 13 which greatly improves the insert retention of this type of rock bit. Normally, the cutter body 10 is forged from a 20 blank forging made of the through-hardening material and then the lands and interior and exterior surfaces are machined therein and thereon. After the surfaces are machined to tolerance, the cutter body 10 is through-hardened by means known in the art such as heat treating and then the insert recesses 12 are bored in~lands 11.
After the proper amount of through-hardening has been performed on body 10, the internal surface areas are additionally surface hardened by one of several alternative methods. One advantageous method of internal surface 30 hardening has been t-o use a water cooled induction hardener with a coil segment of from 90 to 180 for induction hardening of the bearing race surface. This can be accomplished eccentrically while the cutter body ., ~ i6S7$7 is stationary or may be accomplished concentrically by rotating the cutter around the induction coil. Another miethod of surface hardening in area 16 is to utilize tungsten-inert-gas arc welding which is oscillated along axis c-c as the cutter is rotated about the arc.
A third method of surface hardening would be to utilize an oxy-acetylene water cooled ring burner inside the cutter by either rotating the cutter or oscillating the cutter. A fourth method of surface hardening would be to utilize an electron beam, laser, or plasma arc to harden the bearing surface.
After the surface hardening has been achieved by one of the four above-mentioned heating methods, the bearing surface area may be quenched by air, water, oil, synthetic quench, or other gas quench. The cutter body is then placed in the press and the individual hard metal cuttlng inserts 13 are pressed into the through-hardened cutter body utilizing an interferance fit to obtain maximum insert retention.
Figure 2 illustrates an alternate embodiment of the invention wherein a different surface area 116 has been surface hardened inside the internal bore recess 114 of a cutter body 110. Surface area 116 comprises the journal or sleeve bearing surface 116a and the radial thrust half 116b of the ball bearing race su~rface. In Figure 3 a third embodiment is illustrated in which a cutter body 210 having an internal bore passage 214 is surface hardened only and in area 216 which comprises the radial thrust portion of an inner ball bearlng race surface in the cutter body.
Thus, the present invention discloses a method of manufacturing a cutter body and the resulting cutter body manufactured thereby wherein an improved metallurgical - ~ 16~7S7 configuration is utilized to provide greater insert retention. A through-hardening material is utilized in the cutter construction and the internal bearing surfaces which receive the greatest amount of wear and stress are surface hardened to provide additional hardening in the bearing area.
Although certain preferred èmbodiments of the invention have been herein described in order to provide an understanding of the general principles of the invention, it will be appreciated that various changes and innovations can be effected in the described rolling cutter drill bit without departing from these principles. Therefore, the invention is declared to cover all changes and modifications of the specific invention herein disclosed for purposes of illustration which do not constitute departures from the spirit and scope of the invention.
..
. ~ : . i, .
This invention is related to construction methods for manufacturing the conical cutter on a rolling cutter drill bit. More particularly, the invention is directed to the metallurgical features of a cutter utilized in a tri-cone rolling cutter drill bit which utilizes hard metal inserts imbedded in the cutter. The conventional mode of manufacturing insert type cutters for drill bits is to utilize a carburizing grade of steel to form the cutter bodies. After the cutters are formed, holes are bored in the conical surfaces to receive hard metal inserts which are small cutting elements made of hard material such as tungsten carbide. The problem with these conventional type cutters is that a carburizing steel does not provide sufficient core hardness to hold the hard metal inserts in place.
The present invention overcomes this deficiency by utilizing a through-hardening grade of steel for the cutter body and then heat treating the cutter body to the optimum hardness which best results in tightly gripping the *
~ 16S7S7 inserts. The invention also utilizes a higher hardness on the bearing surfaces as a result of a selective surface hardening in the bearing race areas.
Thus, the invention contemplates a method of manu-facturing a rolling cutter drill cutter assembly which com-~~prises forming a generally conical cutter body from a medium to high carbon hardenable steel, boring a generally, centrally located bearing journal passage into the base of the body, heat-treating the body to harden the body throughout its thickness, and heating only predetermined internal bearing surface areas within the bearing journal passage in the body to surface harden these predetermined areas to a higher hardness than the remainder of the body. A pl~rality of cylindrical recesses are formed along the conical surface of the body, and, a plurality of hard metal cutting elements are tightly secured in the recesses in the conical surface.
In a further embodiment the invention includes.a process for forming a tungsten carbide insert cone for a rock bit which comprises.the steps of forming.a cone blank from a medium to high carbon hardenable steel, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity, heat treating the cone blank to.a desired core hardness, forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts, and surface hardening a generally annuIar portion of the interior surface of the bearing cavity.by applying energy substantially only to the portion to heat a layer of the cone blank at the portion, and thereafter cooling the layer.rapidly.
The invention also contemplates the cutter means ,' ~ ~657S7 themselves for a rolling cut-ter drill bit having a body, at least one downwardly projecting lug, and a bearing journal extending from the lug. The improved cutter means has a generally conical body formed of a medium to high carbon hardenable steel with the entire body being subjected to heat treatment to harden the hody through-; out its thickness, and a generally cylindrical journal bearing passage located substantially centrally in the cutter body. A plurality of insert recesses are formed in the exterior surface of the body, a plurality of hardmetal cutting elements are snuggly secured in the recesses, and, internal bearing surface areas in the passage have the steel at the surface areas which are of the same chemical composition as the remainder of the body, and are hardened to a higher hardness than the remainder of the body by heating only the surface areas.
In addition, the invention includes for the cutter means a tungsten carbide insert cone for a rock bit which comprises a steel cone body having a carbon content at leas~ about 0.35% including a generally conical external surface, said body having been subjected to heat treatment to harden the body throughout its thickness, a generally cylindrical internal bearing cavity, with a generally annular layer at the surface of the bearing cavity having a hardness greater than that of the steel at the core of the cone body but a carbon content the same as that of the steel at the core, and a plurality of tungsten carbide inserts in holes in the external surface of the cone body.
~ 16~7S7 BRIEF DESCRIPTION OF THE DRAWING
_ Figure 1 is a cross-sectional side view of a typical rolling cutter drill bit cutter body; Figure 2 is a partial cross-sectional view of the cutter body of Figure 1 indicating an alternate embodiment of the invention;
and, Figure 3 is a partial cross-sectional view o~ a cutter body as shown in Figure 1 indicating a third embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to Figure 1, a generally conical cutter body 10 is disclosed in cross-sectional configuration having raised insert lands 11 which contain cylindrical insert recesses 12 bored therein. A plurality of partially cylindrical hard metal inserts 13 are located in tight fitting relationship in the recesses.12. Inserts 13 generally have cylindrical bafie sections 13a for engagement ln recesses 12,and hemispherical or partially conical protruding ends 13b which project above the top surface of lands 11. Each cutter is substantially symmetrical about a central longitudinal.axis c-c.and an inner bore 14 is formed along axis c-c for.receiving the bearing journal of a drill bit lug. The internal bor.e passage 14 further comprises.a reaess channel 15 for,receiving a seal member bearing.race,recess 16 for receiving ball bearings, and a , pilot pin recess 17 for rece~iving the pilot pin projection on the lug journal. The.bearing,recess,area 16, located on the internal surface of cutter 10, as well as a portion of bore passage 14,,identified,at 14a, is shaded at 18 to indicate the depth of.a surface hardening treatment t l~S757 which is applied in this area to further improve the life of the roller bearing therein. The cutter body 10 is comprised of a through-hardening type metal such as one of the AISI types 4137, 4140, 4340, 4135 or 8650 steel which can be hardened through the entire thickness of the cutter body to bore 14. This through-hardened material then provides a hardened recess 12 to more tightly secure insert 13 therein. In addition to the through-hardening of cutter 10, the surface hardening 18 is applied to the 10 roller bearing race 16 to extend bearing life and reduce spalling of the bearing race during heavy loading of the rock bit.
The advantages of the present invention are clearly evident. Fore one, by utilizing a through-hardening metal, the cutter may be hardened by means known in the art through the entire thickness of body 10. This allows a very hard, tough, recess 12 around insert 13 which greatly improves the insert retention of this type of rock bit. Normally, the cutter body 10 is forged from a 20 blank forging made of the through-hardening material and then the lands and interior and exterior surfaces are machined therein and thereon. After the surfaces are machined to tolerance, the cutter body 10 is through-hardened by means known in the art such as heat treating and then the insert recesses 12 are bored in~lands 11.
After the proper amount of through-hardening has been performed on body 10, the internal surface areas are additionally surface hardened by one of several alternative methods. One advantageous method of internal surface 30 hardening has been t-o use a water cooled induction hardener with a coil segment of from 90 to 180 for induction hardening of the bearing race surface. This can be accomplished eccentrically while the cutter body ., ~ i6S7$7 is stationary or may be accomplished concentrically by rotating the cutter around the induction coil. Another miethod of surface hardening in area 16 is to utilize tungsten-inert-gas arc welding which is oscillated along axis c-c as the cutter is rotated about the arc.
A third method of surface hardening would be to utilize an oxy-acetylene water cooled ring burner inside the cutter by either rotating the cutter or oscillating the cutter. A fourth method of surface hardening would be to utilize an electron beam, laser, or plasma arc to harden the bearing surface.
After the surface hardening has been achieved by one of the four above-mentioned heating methods, the bearing surface area may be quenched by air, water, oil, synthetic quench, or other gas quench. The cutter body is then placed in the press and the individual hard metal cuttlng inserts 13 are pressed into the through-hardened cutter body utilizing an interferance fit to obtain maximum insert retention.
Figure 2 illustrates an alternate embodiment of the invention wherein a different surface area 116 has been surface hardened inside the internal bore recess 114 of a cutter body 110. Surface area 116 comprises the journal or sleeve bearing surface 116a and the radial thrust half 116b of the ball bearing race su~rface. In Figure 3 a third embodiment is illustrated in which a cutter body 210 having an internal bore passage 214 is surface hardened only and in area 216 which comprises the radial thrust portion of an inner ball bearlng race surface in the cutter body.
Thus, the present invention discloses a method of manufacturing a cutter body and the resulting cutter body manufactured thereby wherein an improved metallurgical - ~ 16~7S7 configuration is utilized to provide greater insert retention. A through-hardening material is utilized in the cutter construction and the internal bearing surfaces which receive the greatest amount of wear and stress are surface hardened to provide additional hardening in the bearing area.
Although certain preferred èmbodiments of the invention have been herein described in order to provide an understanding of the general principles of the invention, it will be appreciated that various changes and innovations can be effected in the described rolling cutter drill bit without departing from these principles. Therefore, the invention is declared to cover all changes and modifications of the specific invention herein disclosed for purposes of illustration which do not constitute departures from the spirit and scope of the invention.
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. ~ : . i, .
Claims (26)
1. In a rolling cutter drill bit having a body, at least one downwardly projecting lug, and a bearing journal extending from said lug, the improvement comprising:
cutter means having a generally conical body formed of a medium to high carbon hardenable steel, the entire body being subjected to heat treatment to harden the body throughout its thickness;
a generally cylindrical journal bearing passage located substantially centrally in said cutter body;
a plurality of insert recesses formed in the exterior surface of said body;
a plurality of hard metal cutting elements snuggly secured in said recesses; and, internal bearing surface areas in said passage, the steel at said surface areas being of the same chemical composition as the remainder of the body, and being hardened to a higher hardness than the remainder of the body by heating only said surface areas.
cutter means having a generally conical body formed of a medium to high carbon hardenable steel, the entire body being subjected to heat treatment to harden the body throughout its thickness;
a generally cylindrical journal bearing passage located substantially centrally in said cutter body;
a plurality of insert recesses formed in the exterior surface of said body;
a plurality of hard metal cutting elements snuggly secured in said recesses; and, internal bearing surface areas in said passage, the steel at said surface areas being of the same chemical composition as the remainder of the body, and being hardened to a higher hardness than the remainder of the body by heating only said surface areas.
2. The drill bit of Claim 1 wherein said cutter body is formed from an alloy steel selected from the group of AISI4135, AISI4137, AISI4140, AISI4340, and AISI8650.
3. The drill bit of Claim 1 or Claim 2 wherein said surface hardened surface areas comprise a generally cylindrical friction bearing surface and a generally hemispherical ball bearing race.
4. The drill bit of Claim 1 or Claim 2 wherein said surface hardened bearing surface comprises an annular layer at the surface of the bearing recesses.
5. A tungsten carbide insert cone for a rock bit comprising:
a steel cone body having a carbon content at least about 0.35% including a generally conical external surface, said body having been subjected to heat treatment to harden the body throughout its thickness;
a generally cylindrical internal bearing cavity and a generally annular layer at the surface of the bearing cavity having a hardness greater than that of the steel at the core of the cone body but a carbon content the same as that of the steel at the core; and a plurality of tungsten carbide inserts in holes in the external surface of the cone body.
a steel cone body having a carbon content at least about 0.35% including a generally conical external surface, said body having been subjected to heat treatment to harden the body throughout its thickness;
a generally cylindrical internal bearing cavity and a generally annular layer at the surface of the bearing cavity having a hardness greater than that of the steel at the core of the cone body but a carbon content the same as that of the steel at the core; and a plurality of tungsten carbide inserts in holes in the external surface of the cone body.
6. A method of manufacturing a rolling cutter drill cutter assembly, said method comprising:
forming a generally conical cutter body from a medium to high carbon hardenable steel;
boring a generally, centrally located bearing journal passage into the base of said body;
heat-treating said body to harden the body through-out its thickness;
heating only predetermined internal bearing surface areas within said bearing journal passage in said body to surface harden these predetermined areas to a higher hardness than the remainder of the body;
forming a plurality of cylindrical recesses along the conical surface of said body; and, tightly securing a plurality of hard metal cutting elements in said recesses in said conical surface.
forming a generally conical cutter body from a medium to high carbon hardenable steel;
boring a generally, centrally located bearing journal passage into the base of said body;
heat-treating said body to harden the body through-out its thickness;
heating only predetermined internal bearing surface areas within said bearing journal passage in said body to surface harden these predetermined areas to a higher hardness than the remainder of the body;
forming a plurality of cylindrical recesses along the conical surface of said body; and, tightly securing a plurality of hard metal cutting elements in said recesses in said conical surface.
7. The method of Claim 6 wherein said predetermined internal bearing surface areas are surface hardened by means of induction hardening.
8. The method of Claim 6 or Claim 7 wherein said body is formed of a steel alloy selected from the group of AISI4135, AISI4137, AISI4140, AISI4340, and AISI8650, and said heating to surface harden is accomplished by induction heating.
9. The method of Claim 6 wherein said cutting elements are tungsten carbide inserts pressed into an interference fit in said recesses in said conical surface, and said journal bearing passage is formed having cylindrical friction bearing surfaces and hemispherical ball bearing race surfaces, the annular layer of these surfaces being heated to surface harden them.
10. The method of Claim 9 wherein said heating to surface harden is accomplished by the use of an electron beam.
11. The method of Claim 9 wherein said heating to surface harden comprises the steps of applying an oxygen-acetyline flame to said journal bearing passage.
12. The method of Claim 6 or Claim 9 wherein said heating to surface harden is accomplished by a laser.
13. A process for forming a tungsten carbide insert cone for a rock bit comprising the steps of:
forming a cone blank from a medium to high carbon hardenable steel, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity;
heat treating the cone blank to a desired core hardness;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts; and surface hardening a generally annular portion of the interior surface of the bearing cavity by applying energy substantially only to said portion to heat a layer of the cone blank at said portion, and thereafter cooling the layer rapidly.
forming a cone blank from a medium to high carbon hardenable steel, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity;
heat treating the cone blank to a desired core hardness;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts; and surface hardening a generally annular portion of the interior surface of the bearing cavity by applying energy substantially only to said portion to heat a layer of the cone blank at said portion, and thereafter cooling the layer rapidly.
14. A process as recited in Claim 13 wherein energy is applied by placing an induction coil adjacent said portion and rotating the cone blank about the induction coil for exposing the circumference of said portion to energy from the in-duction coil for heating it; and thereafter said portion is quenched by directing coolant against it.
15. A process as recited in Claim 13 wherein the step of applying energy comprises directing an electron beam against said portion and rotating the cone blank about its axis for exposing the circumference of said portion to the electron beam for heating it.
16. A process as recited in Claim 13 wherein the step of applying energy comprises directing a high energy beam against said portion and rotating the cone blank about its axis for exposing the circumference of said portion to the high energy beam for heating it.
17. A process as recited in Claim 13 wherein the step of applying energy comprises induction heating said portion.
18. A process for forming a tungsten carbide insert cone for a rock bit comprising the steps of:
forming a cone blank from a steel containing at least about 0035% carbon, the cone blank including a generally conical external surface, and a generally cylindrical in-ternal bearing cavity;
heat treating the cone blank for producing a relatively high core hardness in the cone blank;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts;
surface hardening a generally annular portion of the interior face of the bearing cavity by placing an induction coil adjacent said portion, rotating the cone blank about the induction coil for exposing the circumference of said portion to energy from the induction coil for heating substantially only said portion, and thereafter cooling said portion sufficiently rapidly for selectively hardening it to a hardness greater than the core hardness of the cone blank.
forming a cone blank from a steel containing at least about 0035% carbon, the cone blank including a generally conical external surface, and a generally cylindrical in-ternal bearing cavity;
heat treating the cone blank for producing a relatively high core hardness in the cone blank;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts;
surface hardening a generally annular portion of the interior face of the bearing cavity by placing an induction coil adjacent said portion, rotating the cone blank about the induction coil for exposing the circumference of said portion to energy from the induction coil for heating substantially only said portion, and thereafter cooling said portion sufficiently rapidly for selectively hardening it to a hardness greater than the core hardness of the cone blank.
19. A process as recited in Claim 18 wherein the cooling step comprises directing coolant against said portion for quenching it.
20. A process for forming a tungsten carbide insert cone for a rock bit comprising the steps of:
forming a cone blank from a steel containing at least about 0.35% carbon, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity;
heat treating the cone blank for producing a relatively high core hardness in the cone blank;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts;
surface hardening a generally annular portion of the interior surface of the bearing cavity by directing an electron beam against said portion and rotating the cone blank for exposing the circumference of said portion to the electron beam for heating it, and cooling said portion sufficiently rapidly for selectively hardening it to a hardness greater than the core hardness of the cone blank.
forming a cone blank from a steel containing at least about 0.35% carbon, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity;
heat treating the cone blank for producing a relatively high core hardness in the cone blank;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts;
surface hardening a generally annular portion of the interior surface of the bearing cavity by directing an electron beam against said portion and rotating the cone blank for exposing the circumference of said portion to the electron beam for heating it, and cooling said portion sufficiently rapidly for selectively hardening it to a hardness greater than the core hardness of the cone blank.
21. A process for forming a tungsten carbide insert cone for a rock bit comprising the steps of:
forming a cone blank from a steel containing at least about 0.35% carbon, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity;
heat treating the cone blank for producing a re-latively high core hardness in the cone blank;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts;
surface hardening a generally annular portion of the interior surface of the bearing cavity by directing a high energy beam against said portion and rotating the cone blank for exposing the circumference of said portion to the high energy beam for heating a thin layer at said portion, and cooling the layer sufficiently rapidly for selectively hardening it to a hardness greater than the core hardness of the cone blank.
forming a cone blank from a steel containing at least about 0.35% carbon, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity;
heat treating the cone blank for producing a re-latively high core hardness in the cone blank;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts;
surface hardening a generally annular portion of the interior surface of the bearing cavity by directing a high energy beam against said portion and rotating the cone blank for exposing the circumference of said portion to the high energy beam for heating a thin layer at said portion, and cooling the layer sufficiently rapidly for selectively hardening it to a hardness greater than the core hardness of the cone blank.
22. A process for forming a tungsten carbide insert cone for a rock bit comprising the steps of:
forming a cone blank from medium to high carbon hardenable steel, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity;
heat treating the cone blank for producing a relatively high core hardness;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts; and selectively heating and cooling substantially only a generally annular portion of the interior surface of the bearing cavity for forming a surface layer thereon having a hardness greater than the core hardness of the cone blank.
forming a cone blank from medium to high carbon hardenable steel, the cone blank including a generally conical external surface, and a generally cylindrical internal bearing cavity;
heat treating the cone blank for producing a relatively high core hardness;
forming insert holes in the external surface of the cone blank for insertion of tungsten carbide inserts; and selectively heating and cooling substantially only a generally annular portion of the interior surface of the bearing cavity for forming a surface layer thereon having a hardness greater than the core hardness of the cone blank.
23. A process as recited in Claim 22 wherein the surface layer is heated by placing an induction coil adjacent said portion and rotating the cone about the induction coil for exposing the circumference of said portion to energy from the induction coil.
24. A process as recited in Claim 22 wherein the surface layer is cooled by directing coolant against said portion for quenching it.
25. A process as recited in Claim 22 wherein the surface layer is heated by directing an electron beam against said portion and rotating the cone blank for exposing the circumference of said portion to the electron beam.
26. A process as recited in Claim 22 wherein the surface layer is heated by directing a high energy beam against said portion and rotating the cone blank for exposing the cir-cumference of said portion to the high energy beam.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US9131679A | 1979-11-05 | 1979-11-05 | |
| US091,316 | 1979-11-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1165757A true CA1165757A (en) | 1984-04-17 |
Family
ID=22227156
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000363871A Expired CA1165757A (en) | 1979-11-05 | 1980-11-03 | Rock bit cutter construction |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1165757A (en) |
-
1980
- 1980-11-03 CA CA000363871A patent/CA1165757A/en not_active Expired
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