GB2362844A

GB2362844A - Method for crushing carbide

Info

Publication number: GB2362844A
Application number: GB0113111A
Authority: GB
Inventors: Daniel Hart
Original assignee: Baker Hughes Inc
Current assignee: Baker Hughes Holdings LLC
Priority date: 2000-05-30
Filing date: 2001-05-30
Publication date: 2001-12-05
Also published as: GB0113111D0

Abstract

A method for manufacturing cutting element particles of substantially uniform shape and size for application to cutting tools, the method involves forming a billet 10 of cutting grade tungsten carbide, covering at least one surface of the billet with a uniform pattern of grooves 24 and 26, the grooves are either moulded into the billet during the moulding process or machined into the surface after moulding, crushing the billet into particles formed along orthogonal fracture planes defined by the pattern of grooves, the particles can then be brazed onto the cutting surfaces of the cutting tools.

Description

2362844 1

TITLE OF THE INVENTION

Method for Crushing Carbide CROSS REFERENCE TO RELATED APPLICATIONS Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not Applicable

BACKGROUND OF THE INVENTION

Field of the Invention - This invention is in the field of cutting tools which have cutting surfaces coated with a plurality of cutting elements consisting of crushed particles of a cutting grade material, generally tungsten carbide.

Background Art - Various cutting tools, such as those used in cutting or milling metal downhole in oil and gas wells, have cutting blades or other cutting surfaces coated with cutting elements of a very hard material. Typically, the material is tungsten carbide. The cutting elements are usually applied to the cutting surfaces of the tool by being brazed thereto. Often, the cutting elements are actually crushed particles of the cutting material, formed by mechanically crushing used carbide inserts, used draw dies, used carbide hammer heads, drill blanks, used drill bits, and other such items. After passing through the crusher, the particles are graded according to size, then bonded into brazing rods, with a matrix of brazing material. These brazing rods are then used to apply the crushed particles to the cutting surfaces of cutting tools, in substantially random patterns.

The raw material which is put into the crushing machine varies widely in shape, size, and type of material. Some of the raw material exhibits planar surfaces, such as used cutting inserts, while some exhibits a high proportion of rounded surfaces, such as drill blanks. Further, some of the material may be a good cutting grade material having a high degree of hardness, such as used metal milling inserts or drill bits, but other material may exhibit less hardness and more fracture resistance, 2 such as rock bit inserts. Therefore, the particles which come out of the crusher can vary greatly in size, shape, and material properties. Further, some of the raw material is coated, while some is not.

Crushed particles which are to be brazed onto cutting tools must be easily brazeable, they must be of a uniform size, and they must have shapes and material properties which provide good cutting properties. The crushed particles are graded according to size, with some success, thereby adding to the uniformity of the brazing process. Coated materials are not easily brazeable, making them undesirable, so they are often eliminated from the mix. However, the other variables are not as easily controlled. Some of the raw material tends to produce crushed particles having round contours. Round shapes are not conducive to good cutting properties, as they tend to slide over a metal object, rather than cutting into it. Also, some raw materials are folTnulated for high durability, rather than hardness. Materials formulated for high durability tend to exhibit lower degrees of hardness, making them less desirable as cutting elements. Finally, the crushing process itself yields a wide variety of shapes of crushed particles. Some of the particles produced are substantially rectangular, with fairly straight edges, providing relatively good cutting contours. However, many of the particles are round, thin, triangular, or irregular in shape. These shapes are not conducive to cutting. Further, even though the crushed particles can be graded for size, currently known processes often result in many of the particles being too small to be useful.

It would be useful to have a process for producing crushed particles of cutting element material that are relatively uniform in shape, size, and material properties.

BRIEF SUMMARY OF THE INVENTION

The present invention is a method of providing a billet of good cutting element material, such as a cutting grade tungsten carbide, that, when crushed in known crushing machines, will produce substantially uniform sizes and shapes of carbide particles, with the typical size and shape of the particle being optimized for brazing onto a cutting tool as a cutting element. A solid, substantially rectangular billet of cutting grade tungsten carbide is formed by a known molding and sintering 3 process. At least one surface of the billet of carbide material is provided with a uniform pattern of stress riser features, such as serrations or grooves. The serrations or grooves can be molded into the billet, or they can be machined in after the molding process. This uniform pattern of stress risers can be a plurality of intersecting linear grooves; further, the grooves can intersect at right angles, to form a pattern of rectangles over the surface of the billet. If desired, the pattern of grooves can cover only one surface of the billet, or two or more surfaces can be covered. When the billet is crushed, it tends to fragment along substantially orthogonal fracture planes defined by the serrations or grooves. Fracturing of the billet along these orthogonal fracture planes produces a high percentage of substantially rectangular particles of uniform size, with substantially flat surfaces and substantially straight edges.

The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which:

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Figure I is a perspective view of a rectangular billet of cutting element material according to the present invention, with chamfered edges; Figure 2 is a perspective view of a round billet of cutting element material according to the present invention, with intersecting grooves; Figure 3 is a perspective view of a round billet of cutting element material according to the present invention, with orthogonally intersecting grooves; Figure 4 is a perspective view of a rectangular billet of cutting element material according to the present invention., with square edges; Figure 4a is a perspective view of a rectangular billet of cutting element material according to the present invention, with grooved sides; Figure 5 is a perspective view of a rectangular billet of cutting element material according to the present invention, with surface depressions between the grooves; and 4 Figure 6 is a perspective view of a rectangular billet of cutting element material according to the present invention, with surface protrusions between the grooves.

DETAILED DESCRIPTION OF THE INVENTION

As seen in Figure 1, a solid billet 10 according to the present invention can be formed in a substantially rectangular shape of cutting grade tungsten carbide material, with a top surface 12, bottom surface 14, and four side surfaces 16, 18, 20, 22. Because the top, bottom, and sides are essentially orthogonally arranged, this shape is referred to herein as being substantially rectangular, even though it has grooves on several surfaces and chamfered edges around the perimeter. Rather than tungsten carbide, the material can be some other hard material suitable for use in manufacturing cutting elements such as metal machining inserts. The top surface 12 and bottom surface 14 are criss-crossed with a uniform pattern of serrations or grooves 24, 26. The serrations or grooves 24, 26 act as stress risers. Specifically, the pattern shown is a lattice of rectangular shapes formed by the intersections of the orthogonally arranged grooves 24, 26. Other uniform patterns can also be used.

The grooves 24, 26 can be molded into the billet 10 during the molding and sintering process, or the billet 10 can first be molded without grooves, then, the grooves 24, 26 can be machined into the top surface 12 and bottom surface 14. The grooves 24, 26 must be of sufficient depth and breadth to insure that, when the billet is crushed by the application of compressive forces, the billet 10 will consistently fragment along fracture planes generated by the stress riser grooves 24, 26. The depth and breadth of the grooves 24, 26 may vary according to the type of material being used, or according to the thickness of the billet 10.

Since the grooves 24, 26 are orthogonally arranged, the resulting fracture planes will be substantially orthogonally arranged as well. Crushing of the billet 10 to cause it to fragment along these orthogonal fracture planes will result in the formation of relatively uniform carbide cutting particles, substantially rectangular in shape. Further, there will be relatively few odd sized or shaped particles, with very little wasted material. Since the particles are shaped by the grooves 24, 26, each particle will have several chamfered edges; however the shape will still be substantially rectangular. Such a shape can easily be randomly arranged on the face of a cutting tool, by brazing, to achieve a reliable cutting face on the tool. If desired, the spacing between the grooves 24, 26 can be selected to approximate the thickness of the billet 10. This will result in the formation of substantially cubical particles of tungsten carbide. It can be seen, then, that a billet 10 can be formedwhich has a thickness which approximates the desired size of the crushed particle. Selection of the appropriate groove spacing will then result in the formation of particles of the desired size and shape. The uniform pattern of rectangular shapes fonlied by intersecting grooves can cover just one of the major sides of the billet 10, or it can cover two opposing major sides, as seen in Figure 1. Arranging the stress risers on two opposing sides of the billet 10 further promotes fragmentation along the desired fracture planes.

Figure 2 shows a second embodiment of a billet 30 according to the present invention. This embodiment can be formed in a substantially round shape of cutting grade tungsten carbide material, with a top surface 32, bottom surface 34, and a right cylindrical side surface 36. The top surface 32, bottom surface 34, and side surface 36 are essentially orthogonally arranged. The top surface 32 and bottom surface 34 are criss- crossed with a uniform pattern of serrations or grooves 38. Theserrationsor grooves 38 act as stress risers. Specifically, the uniform pattern selected has the grooves 38 cut on intersecting diameters of the billet 30. Other uniform pattems can also be used.

The grooves 38 must be of sufficient depth and breadth to insure that, when the billet 30 is crushed by the application of compressive forces, the billet 30 will consistently fragment along fracture planes generated by the stress riser grooves 38. The depth and breadth of the grooves 38 may vary according to the type of material being used, or according to the thickness of the billet 30.

Since the grooves 38 are arranged in an intersecting pattern, the resulting fracture planes will intersect as well. Crushing of the billet 30 to cause it to fragment along these fracture planes will result in the formation of relatively uniform carbide cutting particles, substantially triangular in shape, with uniform thickness. Further, 6 there will be relatively few odd sized or shaped particles, with very little wasted material. Since the particles are shaped by the grooves 38, each particle will have several chamfered edges; however the shape will still be substantially triangular.

Such a shape can easily be randomly arranged on the face of a cutting tool, by brazing, to achieve a reliable cutting face on the tool. It can be seen, then, that a billet 3 0 can be formed which has a thickness which approximates the desired thickness of the crushed particle. Selection of the appropriate groove pattern and spacing will then result in the formation of particles of the desired size and shape. The uniform pattern of triangular shapes formed by intersecting grooves can cover just one of the major sides of the billet 30, or it can cover two opposing major sides, as seen in Figure 2.

Arranging the stress risers on two opposing sides of the billet 30 further promotes fragmentation along the desired fracture planes.

As seen in Figure 3, a solid billet 40 according to a third embodiment of the present invention can be formed in a substantially round shape of cutting grade tungsten carbide material, with a top surface 42, bottom surface 44, and right cylindrical side surface 46. The top, bottom, and sides are essentially orthogonally arranged. The top surface 42 and bottom surface 44 are criss-crossed with a uniform pattern of serrations or grooves 48, 49. The serrations or grooves 48, 49 act as stress risers. Specifically, the pattern shown is a lattice of rectangular shapes formed by the intersections of the orthogonally arranged grooves 48, 49. Other uniforni patterns can also be used.

The grooves 48, 49 must be of sufficient depth and breadth to insure that,

when the billet 40 is crushed by the application of compressive forces, the billet 40 will consistently fragment along fracture planes generated by the stress riser grooves 48, 49. The depth and breadth of the grooves 48, 49 may vary according to the type of material being used, or according to the thickness of the billet 40.

Since the grooves 48, 49 are orthogonally arranged, the resulting fracture planes will be substantially orthogonally arranged as well. Crushing of the billet 40 to cause it to fragment along these orthogonal fracture planes will result in the formation of relatively uniform carbide cutting particles, most of which will be substantially rectangular in shape. Further, there will be relatively few odd sized or 7 shaped particles, with very little wasted material. Since the particles are shaped by the grooves 48, 49, each particle will have several chamfered edges. Such a shape can easily be randomly arranged on the face of a cutting tool, by brazing, to achieve a reliable cutting face on the tool. If desired, the spacing between the grooves 48, 49 can be selected to approximate the thickness of the billet 10. This will result in the formation of mostly cubical particles of tungsten carbide. It can be seen-, then, that a billet 40 can be formed which has a thickness which approximates the desired size of the crushed particle. Selection of the appropriate groove spacing will then result in the formation of particles of the desired size and shape. The uniform pattern of rectangular shapes formed by intersecting grooves 48, 49 can cover just one of the major sides of the billet 40, or it can cover two opposing major sides, as seen in Figure 3. Arranging the stress risers on two opposing sides of the billet 40 further promotes fragmentation along the desired fracture planes.

Figure 4 shows a rectangular billet 50 much like the billet 10 shown in Figure 1, except that the edges of the billet 50 are not chamfered. The top surface 52 and bottom surface 54 are criss-crossed with a uniform pattern of serrations or grooves 56, 58, to act as stress risers.

Figure 4A shows a rectangular billet 60 much like the billet 50 shown in Figure 4, with a top surface 62, a bottom surface 64, and four side surfaces 66. The top surface 62 and bottom surface 64 are criss-crossed with a uniform pattern of serrations or grooves 67, 68. Further, in this embodiment, the four side surfaces 66 are scored with vertical serrations or grooves 69. The inclusion of the vertical grooves 69 further promotes the fragmentation of the billet 60 along orthogonal fracture planes generated by the grooves 67, 68, 69.

Figure 5 shows a rectangular billet 70 much like the billet 60 shown in Figure 4A, with the top, bottom, and side surfaces criss-crossed with uniform patterns of serrations or grooves 72, 74, 76. Further, in this embodiment, a surface deformation in the form of a depression 78 is formed in each of the rectangular spaces formed by the uniform pattern of grooves 72, 74. The depressions 78 can enhance the machining characteristics of the resulting carbide particles. The depressions 78 shown in Figure 5 are four-faceted depressions sunk into the top surface of the billet 8 70. Other types of depressions can also be used, and depressions can also be formed in the rectangular spaces formed by the uniform pattern of grooves on the bottom and side surfaces of the billet 70.

Figure 6 shows a rectangular billet 80 much like the billet 70 shown in Figure 5, with the top, bottom, and side surfaces criss-crossed with uniform patterns of serrations or grooves 82, 84, 86. However, in this embodiment, a surface deformation in the form of a protrusion 88, rather than a depression, is formed in each of the rectangular spaces formed by the uniforni pattern of grooves 82, 84. The protrusions 88 can enhance the machining characteristics of the resulting carbide particles. The protrusions 88 shown in Figure 6 are four-faceted protrusions sunk into the top surface of the billet 80. Other types of protrusions can also be used, and protrusions can also be formed in the rectangular spaces formed by the uniform pattern of grooves on the bottom and side surfaces of the billet 80.

While the particular invention as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages hereinbefore stated, it is to be understood that this disclosure is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended other than as described in the appended claims.

9

Claims

CLAIMS 1 claim:

1 1. A method of forming crushed particles for use in coating cutting tools,

2 said method comprising:

3 forming a billet of cutting element material, said billet having a plurality of stress risers formed in a uniform pattern covering at least one surface of said billet; and crushing said billet to fragment said billet into a plurality of particles, said particles being at least partially defined by a plurality of fracture planes generated along said plurality of stress risers.

4 5 6 7 8 9 12 13 14 comprises:

is 16 17 18 19 4.

21 comprises:

22 23 24 25 2. The method recited in claim 1, wherein said cutting element mateidal 11 comprises tungsten carbide.

3. The method recited in claim 1, wherein said forming of said billet constructing a mold having a cavity with a uniform pattern of surface protrusions therein; and molding said billet in said mold to produce said pattern of stress risers on said billet, with said pattern of mold cavity surface protrusions.

The method recited in claim 1, wherein said forming of said billet molding said billet without said stress risers; and machining said stress risers into said at least one surface of said molded billet.

5. The method recited in claim 1, further comprising forming said 26 plurality of stress risers as a plurality of grooves in said at least one surface of said 27 billet.

28 29 31 32 33 34 36 37 38 39 41 42 43 44 squares.

46 47 48 49 51

6. The method recited in claim 1, further comprising: forming said uniform pattern as a plurality of intersecting stress risers; and fragmenting said billet into a plurality of particles, said particles being at least partially defined by a plurality of intersecting fracture planes generated along said plurality of intersecting stress risers.

7. The method recited in claim 6, further comprising: forming said uniform pattern of intersecting stress risers arranged in a plurality of substantially rectangular shapes on said at least one surface of said billet; and fi-agmenting said billet into a plurality of substantially rectangular particles defined by a plurality of substantially orthogonal fracture planes generated along said plurality of intersecting stress risers.

8. The method recited in claim 7, wherein said rectangular shapes are

9. The method recited in claim 1, farther comprising: forming a plurality of surface deformations between said plurality of stress risers; and fragmenting said billet into a plurality of fragments having said surface deformations thereon.

52

10. The method recited in claim 9, further comprising forming said 53 plurality of surface deformations as depressions.

54 11. The method recited in claim 9, further comprising forming said plurality of surface deformations as protrusions.

11 58

12. The method recited in claim 1, further comprising forming said 59 plurality of stress risers in at least two uniform patterns covering at least two opposing surfaces of said billet.

61 62

13. The method recited in claim 1, flu-ther comprising forming said 63 plurality of stress risers in a plurality of uniform patterns substantially-covering all 64 surfaces of said billet.

66 67 68 69 71 72 73 74 75

14. A method of coating cutting tools, said method comprising: forming a billet of cutting element material, said billet having a plurality of stress risers formed in a uniform pattern substantially covering at least one surface of said billet. crushing said billet to fragment said billet into a plurality of particles, said particles being at least partially defined by a plurality of fracture planes generated along said plurality of stress risers; and brazing said plurality of particles to a cutting tool.

15. The method recited in claim 14, further comprising forming said 76 plurality of stress:risers as a plurality of grooves in said at least one surface of said 77 billet.

78 79 so 81 82 83 84 86 87 88

16. The method recited in claim 14, further comprising: forming said uniform pattern as a plurality of intersecting stress risers, and fragmenting said billet into a plurality of particles, said particles being at least partially defined by a plurality of intersecting fracture planes generated along said plurality of intersecting stress risers.

The method recited in claim 16, further comprising: forming said uniform pattern of intersecting stress risers arranged in a plurality of substantially rectangular shapes on said at least one surface of said billet; and 12 89 fragmenting said billet into a plurality of substantially rectangular particles defined by a plurality of substantially orthogonal fracture planes generated along said plurality of intersecting stress risers.

91 92 93 18. The method recited in claim 14, further comprising forming said 94 plurality of stress risers in at least two uniform patterns substantially covering at least two opposing surfaces of said billet.

96 97 19. The method recited in claim 14, further comprising forming said 98 plurality of stress risers in a plurality of uniform patterns substantially covering all 99 surfaces of said billet. 100 101 102 103 104 105 106 107 108 20. A billet for use in forming cutting elements, comprising:

solid body of hard cutting element material; and plurality of stress multiplying grooves formed in a uniform pattern covering at least one surface of said body-, wherein said plurality of grooves are of sufficient depth and breadth to generate a plurality of fracture planes through said body upon application of compressive stress to said body.