US3587358A - Low-temperature fabrication of diamond-faced drilling bits - Google Patents

Abstract

DIAMOND PARTICLES ARE SECURED TO A DRILLING BIT BODY BY A METAL LAYER DEPOSITED BY ELETROCASTING. MELT SPRAYING OF THE RESULTING BIT WITH MOLTEN METAL MAY BE ADDITIONALLY CARRIED OUT. THROUGHOUT THE PROCESS, THE DIAMOND PARTICLES ARE NOT

SUBJECTED TO TEMPERATURES EXCEEDING APPROXIMATELY 150*C., WHEREBY THEIR PROPERTIES ARE NOT IMPAIRED, AND HIGH DRILLING PERFORMANCE OF THE BIT IS AFFORDED.

Description

United States Patent LOW-TEMPERATURE FABRICATION 01- DIAMOND-FACE!) DRILLING BITS 4 Claims, 14 Drawing Figs.

US. Cl 76/ 108,

51/309, 204/16 Int. Cl B2111 5/02 Field of Search 51/309;

[56] References Cited UNITED STATES PATENTS 2,147,843 2/1939 Jamar et a1. 51/309UX 2,360,798 10/1944 Seligman et al.... 5 l/309X 2,457,156 12/1948 Jones 51/309 2,978,846 4/1961 Barron 51/309X 3,046,204 7/1962 Barron 204/16 3,281,996 1 1/1966 Cuklanz 204/16X Primary Examiner-Bernard Stickney Attorney-Holman & Stern I ABSTRACT: Diamond particles are secured to a drilling bit PATENTEDJUN28I971 3.587.358

sum 1 BF 3 x xxx INVENTOR. K. Ya; H l'lr o BYMMD PATENTEDJUNZBIHYI 3,587,358

SHEET 2 OF 3 INVENTOR. S H l r a BY m, pm; v

PAT ENIEU JUN28 1971 3; S87 358 sum 3 OF 3 FIG. I3 FIG. l4

1 [i i Il'H Ill [1 l! I 1 g 1 I l I INVENTOR.

osuihro MM D HTTo/INEFS LOW-TEMPERATURE FABRICATION OF DIAMOND- FACED DRILLING BITS BACKGROUND OF THE INVENTION This invention relates to drilling machinery for drilling holes in rock and other hard material and more particularly to a new method for producing at low temperatures drilling bits faced with diamond of unimpaired properties, which bits have high drilling performance.

Heretofore, a crown .or bit faced with diamond particles (bortz or bort) for drilling holes in rock and other hard layers has generally been formed by pressing a large number of diamond particles into the inner surface of a casting mold for casting the bit and then pouring a molten metalsuch as an alloy or copper into the mold to form the bit. When a molten alloy at a temperature higher than 1,000 C. is poured in this manner, however, it is difficult to avoid heat damage or to impairment of the properties of the diamond particles, whereby the drilling performance of the bit unavoidably drops.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new and original method for fabricating diamond bits at low temperatures whereby the above-described difficulty is overcome, and whereby the production of diamond bits of high drilling performance and the sustaining of this high performance are made possible.

According to the present invention, briefly summarized, there is provided a method for producing drilling bits faced with diamond of unimpaired properties which is characterized by the steps of fabricating a bit body having a working part and securing a large number of diamond particles uniformly onto this working part by means of a metal layer deposited by electrocasting with or without a further step of melt spraying of a molten metal onto the diamond facing thus formed.

The nature, principle, details, and utility of the invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings, in which'like parts are designated by like reference numerals.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side view, in longitudinal section, of a bit body suitable for supporting a crown mounted thereon according to the invention;

FIG. 2 is a bottom plan view of a cap suitable for use in accordance with one example of the method of the invention;

FIG. 3 is an elevation, in vertical'section, showing one organization of apparatus for carrying out the method of the invention with respect to the bit body shown in FIG. 1 and with the use of the cap shown in FIG. 2;

FIG. 4 is a side view showing the external appearance of a finished diamond-faced bit fabricated in the manner indicated in FIG. 3 according to the invention;

FIG. 5 is an elevation, in vertical section, showing one example of a crown mold suitable for use in another example of practice of the invention;

FIG. 6 is a plan view of the mold shown in FIG. 5;

FIG. 7, 8, and 9, are elevations of the mold shown in FIG. 5 indicating three process steps in the fabrication of a crown;

FIG. 10 is a side view of a finished diamond crown fabricated by the method and mold illustrated in FIGS. 5 through 9, inclusive;

FIG. 11 is a plan view of a bit body for still another example of embodiment of the invention; 7

FIG. 12 is a relatively enlarged side view showing a single wire stud faced over approximately one-half thereof with diamond particles bonded thereto by metal plating;

FIG. 13 is a side view showing a bit body with a large number of wire studs, each as shown in FIG. 12, imbedded in the working surface thereof; and

FIG. 14 is a side view showing the external appearance of the bit illustrated in FIGS. 11, 12, and 13 in completed state.

DETAILED DESCRIPTION In one embodiment of the invention as illustrated in FIGS. 1 through 4, inclusive, a bit body having a tubular main part 1 provided with a threaded part 2 for connection to a core barrel or drill stem (not shown) and a lower rim wall 3 of reduced wall thickness with a water-passage recess 4 of the shape shown in FIG. 1 is fabricated.

Separately, a synthetic resin cap 5 of annular shape which can be fitted over the above-mentioned lower rim wall 3 with a certain space therebetween is formed, and over the entire surface of this cap, a large number of small holes 6 are formed with uniform distribution as shown in FIG. 2.

Next, the surface parts of the bit body 1 other than the lower rim wall 3 are covered by a method such as painting with a coating film 7 for masking or preventing metal plating. Thereafter, the cap 5 is fitted over the lower rim wall 3 in a manner to enclose a large number of fine diamond particlesS within the aforementioned space therebetween.

The bit body 1, diamond particles 8, and cap 5 thus assembled are then immersed in the electrolyte of an electrocasting bath 9 as indicated in FIG. 3. Electrocasting is carried out by passing electric current through the bit body and a nickel electrode plate 10 immersed in the electrolyte above the bit body as electrodes, whereupon nickel ions infiltrate through the small holes 6 of the cap 5 and adhere to the lower rim wall 3 of the bit body 1 and to the fine diamond particles 8. The bit body I is then taken out of the electrocasting bath 9, and the cap 5 is removed therefrom, whereupon a diamond bit product as shown in FIG. 4 is obtained.

Thus, by the above-described method for producing diamond bits, only a small number of process steps is necessary, and the process of filling certain parts by melt spraying of molten metal is not necessary. That is, by merely mass producing bit bodies and caps 5 respectively as illustrated in FIGS. 1 and 2, enclosing fine diamond panticles 8 within the space therebetween, carrying out electrocasting, and then removing the caps, diamond bits of unimpaired properties can be readily and conveniently produced by only a low-temperature process step.

In another embodiment of the invention, use is made of a carbon mold 11 as illustrated in FIGS. 5 and 6 which mold serves additionally as an electrode in an electrocasting process described hereinafter. The mold 111 is provided in its upper surface with an annular groove 12, at two parts of which there are provided projections 13 for forming water passages of the bit crown.

This mold is used in the following manner to fabricate a bit crown. First, a large number of diamond bortz 14 are distributed and pressed as uniformly as possible against and into theinner surface of the annular groove 12 as indicated in FIG. 7. Next, the mold 11 is immersed :in an electrocasting bath (not shown), and an electrocasting process is carried out between the mold I1 and nickel, whereupon a nickel coating layer 15 is formed within the annular groove 12 to cover the exposed surfaces of the diamond particles 14 as indicated in FIG. 8.

Then a metal for melt spray coating such as a metal commonly referred to as metallikon" is sprayed in a molten state against the surface of the nickel coating layer shown in FIG. 8 thereby to fill the interior of the groove with a melt sprayed metal layer 16 as indicated in FIG. 9. The article thus formed and hardened in the state indicated in FIG. 10 and constituting a bit facing crown is then taken out of the mold and secured by silver brazing to the lower surface of a cylindrical bit body (not shown) having a flat end surface whereupon a finished diamond bit similar to that shown in FIG. 4 is obtained. It should be observed that, in fixing the crown facing to the bit body, a low-temperature method must be used.

In the above-described process steps, the electrocasting of course, is a low-temperature process. Furthermore, even when the molten metal in the melt spraying process is at a high temperature, the molten metal particles blown by the spraying action against the coating layer surface of the diamond particles are at temperatures which do not exceed approximately 150 C. Therefore, there is no possibility of the diamond particles within the metal coating layer being subjected to damage or a change in properties.

Thus, since the diamond bit fabricated as described above in accordance with the invention is subject to no heat damage or impairment of properties of its diamond particles as in some instances in known bits, its rock-drilling performance is high, and this high performance, moreover, can be positively and reliably sustained.

' In still another embodiment of the invention as illustrated in FIGS. ll through 14, inclusive, a bit body 17 has an annular bottom surface 18 in which a large number of holes 19 are drilled in a uniformly distributed pattern to receive and hold the root ends of corresponding wire studs 20. Each of the wire studs 20 made of steel (or an alloy containing tungsten, nickel, molybdenum, and/or cobalt) has a metal-plated layer 21 covering the outer surface of approximately one-half thereof, the layer 21 serving to secure a large number of diamond bortz 22 to the wire stud 20 the bortz 22 being of still smaller particle size than those used in the aforedescribed examples. These wire studs 20 can be mass produced in the following manner.

The wire studs 20 are cut to equal lengths from a steel wire stock of a diameter suitable for fitting into the above-mentioned holes 19. A large number of the studs 20 thus cut are suspended vertically at the same height so that their lower halves are immersed in an electrocasting bath (not shown) containing a large number of diamond particles. Then, as the wire studs are thus suspended, metal plating (e.g., nickel plating) thereof is carried out, whereupon a large number of diamond faced wire studs 20, each as illustrated in FIG. 12, can be mass produced simultaneously.

The diamond-faced wire studs 20 thus produced are next fitted into and secured in respective holes 19 in the bottom surface 18 of the bit body 17, whereupon the bit assumes the state shown in FIG. 13.

Finally, a molten metal 23 such as metallikon" is sprayed onto the group of wire studs, whereupon a completed bit as shown in FIG. 14 is obtained.

The step of securing the diamond particles to the wire studs 20 in the above-described process according to the invention is a low-temperature process. Furthermore, in the melt spraying of metal to obtain the bit in the state shown in FIG. 14, the temperature imparted by the particles of molten metal to' the sprayed surface is of the order of C. as in the aforedescribed examples of the invention. Therefore, there is no possibility of heat damage to the diamond particles or of change in properties thereof.

An advantageous feature of the above-described organization of the diamond-faced bit is that, since the diamond particles are held in the axial direction of the large number of wire studs, wear and reduction of the leading particles during drilling are immediately compensated for by the successive participation in the drilling action of the following particles. Furthermore, labor such as that for brazing a molded bit crown onto a bit body is unnecessary.

lclaim: v

1. A method for producing drilling bit crowns faced with diamond of unimpaired properties, which comprises:

preparing a mold provided in its one surface with an annular groove, at least one portion of which is provided with a projection to form water passage of the bit crown to be produced;

uniformly placing a large number of diamond particles against the inner surface of the annular groove; immersing the entire mold into an electrocasting bath to conduct electrocasting between the mold and a nickel electrode in the bath, the mold servirtg also as an opposite electrode to the nickel electrode in the electrocasting process, to secure the diamond particles to each other by means of a metal coating layer formed within the annular groove by the electrocasting;

filling the interior of the annular groove structure with a metal to form a crown; and

extracting the crown from the mold.

2. The method as defined in claim 1, in which the mold is made of a material selected from the group consisting of carbon and a synthetic resin which is made electroconductive.

3. The method as defined in claim 1, in which the metal to fill in the interior of the annular groove is a low melting point metal.

4. The method as defined in claim 1, in which the crown thus formed is melt sprayed with a molten metal.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,5 7,3 Dat June 28. 197;

Invent0 Kunihiro Yoshino It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Cover Page,left-hand column, between lines 5 and 6, the following should be inserted --[73] Assignee Kabushiki Kaisha Tone Boring, Tokyo, Japan-- Signed and sealed this 11th day of January 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOT'I'SCHALK Attesting Officer Acting Commissioner of Patents 5 FORM PO-105O (10-697 USCOMM-DQ eoare. U 5 GOVERNMENT PRINTING OFFICE \9'9 0-365-334

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