Abstract:
An earth boring drill bit comprising a milled cutter having rows of hardfacing guides on the cutter. Hardfacing is applied between adjacent hardfacing guides to form a hardfacing web that serves as a cutting element. The hardfacing web defines an interface between the hardfacing web and the hardfacing guide. The hardfacing web may extend past the crest of the hardfacing guides or end along the hardfacing guides flanks. Projecting hardfacing is provided on the interface to form trimmers.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation in part of and claims priority to and the benefit of co-pending U.S. application Ser. No. 12/239,025, filed Sep. 26, 2008, the full disclosure of which is hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The disclosure herein relates in general to rolling cone earth boring bits and in particular to improving the performance of a steel tooth bit. 
         [0004]    2. Description of Prior Art 
         [0005]    Drilling systems having earth boring drill bits are used in the oil and gas industry for creating wells drilled into hydrocarbon bearing substrata. Drilling systems typically comprise a drilling rig (not shown) used in conjunction with a rotating drill string wherein the drill bit is disposed on the terminal end of the drill string and used for boring through the subterranean formation. 
         [0006]    Drill bits typically are chosen from one of two types, either drag bits or roller cone bits. Rotating the bit body with the cutting elements on the outer surface of the roller cone body crushes the rock and the cuttings may be washed away with drilling fluid. One example of a roller cone bit  11  is provided in a side partial perspective view in  FIG. 1 , the bit  11  having a body  13  with a threaded attachment  15  on the bit  11  upper end for connection to a drill string (not shown). The bit  11  further includes legs  18  extending downward from the bit body  13 . Each bit leg  18  is shown having a lubricant compensator  17 . 
         [0007]    The bit body  13  is further illustrating having a nozzle  19  for directing pressurized drilling fluid from within the drill string to cool and clean bit  11  during drilling operation. A plurality of cutters  21  are rotatably secured to respective bit legs  18 . Typically, each bit  11  has three cutters  21 , and one of the three cutters is obscured from view in  FIG. 1 . 
         [0008]    Each cutter  21  has a shell surface including a gage surface  25  and a heel region indicated generally at  27 . Teeth  29  are formed in heel region  27  and form a heel row  28  of teeth. The heel teeth  29  depicted are of generally conventional design, each having leading and trailing flanks  31  which converge to a crest  33 . Each tooth  29  has an inner end (not shown) and an outer end  35  that joins to crest  33 . 
         [0009]    Typically steel tooth bits are for penetration into relatively soft geological formations of the earth. The strength and fracture toughness of the steel teeth permits the use of relatively long teeth, which enables the aggressive gouging and scraping actions that are advantageous for rapid penetration of soft formations with low compressive strengths. However, geological formations often comprise streaks of hard, abrasive materials that a steel-tooth bit should penetrate economically without damage to the bit. Although steel teeth possess good strength, abrasion resistance is inadequate to permit continued rapid penetration of hard or abrasive streaks. Consequently, it has been common in the arts since at least the 1930s to provide a layer of wear-resistance metallurgical material called “hardfacing” over those portions of the teeth exposed to the severest wear. The hardfacing typically consists of extremely hard particles, such as sintered, cast, or macrocrystalline tungsten carbide, dispersed in a steel matrix. 
         [0010]    Typical hardfacing deposits are welded over a steel tooth that has been machined similar to the desired final shape. Generally, the hardfacing materials do not have a tendency to heat crack during service which helps counteract the occurrence of frictional heat cracks associated with carbide inserts. The hardfacing resists wear better than the steel tooth material, therefore the hardfacing on the surface of steel teeth makes the teeth more resistant to wear. 
         [0011]    A front view of a cutter  21  is illustrated in  FIG. 2 . Shown formed on the cutter  21  is an inner row  36  having inner row teeth  37  extending radially inward from the heel  27  (see  FIG. 1 ). The inner row teeth  37  have flanks  31  and crests  33  similar to those of the heel teeth  29 . An apex  38  is shown proximate to the cutter  21  center, the apex  38  having grooves  39  radially extending from the apex  38  midpoint to its outer periphery. A layer of hardfacing  35  is shown having been applied to surfaces of the heel teeth  29  and the inner row teeth  37 . 
       SUMMARY OF INVENTION 
       [0012]    Disclosed herein is an earth boring drill bit comprising, a milled cutter having rows of hardfacing guides on the cutter. Hardfacing is applied between adjacent hardfacing guides to form a cutting element. The hardfacing may extend past the crest of the hardfacing guides or end along the hardfacing guides flanks. In one embodiment, an earth boring bit includes a body, a leg depending from the body, a bearing shaft extending radially inward from the leg, a cutter mounted on the bearing shaft, the cutter having a row of cutting hardfacing guides, the hardfacing guides having a base and flanks extending from the base and joining to form a crest, and hardfacing extending from a first flank onto an oppositely facing second flank, wherein the first flank and second flank are disposed on adjacently disposed hardfacing guides. An interface is formed between the hardfacing and the hardfacing guide on which additional hardfacing is provided. The additional hardfacing on the interface can project upwards from the hardfacing guide surface to form a trimmer. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]    Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
           [0014]      FIG. 1  is a side perspective view of a prior art roller cone bit. 
           [0015]      FIG. 2  depicts a front view of a prior art milled steel tooth cutter. 
           [0016]      FIGS. 3A-3C  illustrate front and sectional views of a prior art cutter with hardfacing. 
           [0017]      FIG. 4  illustrates a rear view of a prior art cutter having hardfacing. 
           [0018]      FIGS. 5 and 6  depict examples of hardfacing on interfaces between a cone and hardfacing in accordance with the present disclosure. 
           [0019]      FIG. 7  is a sectional view of hardfacing applied to an interface between a cutter and hardfacing. 
           [0020]      FIG. 8  is a perspective view of a cutter having hardfacing applied to a cone and hardfacing interface in accordance with the present disclosure. 
       
    
    
       [0021]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0022]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0023]    With reference now to  FIG. 3A  a prior art example of a roller cone with cutter  44  having hardfacing is illustrated in a front view. The cutter  44  comprises heel teeth that serve as hardfacing guides  48  arranged on its outer periphery forming a heel row  46 . The heel hardfacing guides  48  are defined by flanks  50  on opposing sides of the hardfacing guides  48 . The flanks  50 , which comprise leading  53  and trailing  55  flanks of the teeth, are inwardly angled upward from a base  49  and join to form a crest  52 . Flanks  53 ,  55  are integrally formed from the steel body of the cutter  44 . In  FIG. 3B , a prior art example of a portion of the heel row,  46  is depicted in perspective view illustrating an inner side  57 . 
         [0024]    Referring now to  FIG. 4 , hardfacing  54  has been added to the gap between oppositely facing flanks  50  of adjacently disposed hardfacing guides  48 . The hardfacing  54  is affixed to the flanks  50  and comprises a cutting structure for use in earth boring operations when implementing the cutter  44  with an earth boring bit. In one example of use, the hardfacing guides  48  comprise steel, which is softer than hardfacing, thus wearing quicker during boring operations. As the steel hardfacing guides  48  wear down, the hardfacing  54  remains affixed between adjacently disposed hardfacing guides  48  to continue providing a cutting surface. As the hardfacing  54  wears, the circumferential cutting contact length decreases to improve drilling. The hardfacing  54  upper surface can optionally form a generally sharp crest  67  which can have roughly the same thickness as crests  52  of the hardfacing guides  48 . Also, the hardfacing crest has a generally curved contour from one tooth hardfacing guide  48  to an adjacent tooth hardfacing guide  48 . The curved contour preferably bulges out leaving a valley  66  between the crests. The hardfacing  54  can be flush with one or both of the inner side  57  or outer side  59 . Similarly, hardfacing  54  can be flush or bulge outward on the inner row  56  sides. 
         [0025]    The cutter  44  of  FIG. 3A  also includes an inner row of hardfacing guides  58  forming an inner row  56  concentric within the heel row  46 . The inner row of hardfacing guides  58  also include flanks  60  angled inward to form a crest  62  at the outward end of the hardfacing guides  58 . Hardfacing  54  may optionally be included within the gaps existing between the oppositely facing flanks  60  on adjacently disposed hardfacing guides  58 . The cutter  44  also optionally includes an apex  64  provided on its upper surface, the apex  64  can have hardfacing guides  65  thereon forming a grooved or profiled upper surface and include hardfacing  54  thereon. 
         [0026]    Embodiments exist where hardfacing  54  is applied only between hardfacing guides  48  of the heel row  46  or optionally only between hardfacing guides  58  of the inner row  56  or rows not shown. The amount of hardfacing  54  can also vary. The hardfacing  54  can extend outward from the gap past the crests  52  of adjacently disposed hardfacing guides  48 ,  58 . Optionally, hardfacing  54   a  can be added having a terminal upper surface remaining within the gap. 
         [0027]      FIG. 3C  is a cross sectional view of a portion of an embodiment of the cutter  44  of  FIG. 3A . Hardfacing  54  is shown extending away from the trough of a heel row  46  with a generally planar inner surface  63  and an outer surface  68  contoured toward the front surface  63  so at the hardfacing crest  67  width is smaller than the heel row  46  width. 
         [0028]      FIG. 4  depicts a rearward view of an embodiment of a cutter  44   a  having webs of hardfacing  54  spanning between adjacent heel hardfacing guides  48  formed on the roller cone with cutter  44   a . In this view the hardfacing  54  extends downward below the crest  52  of the heel hardfacing guides  48  and terminates at a cutter hub  51 . Spaces  71  are shown between adjacent webs  54 , however the hardfacing can comprise a single member over the hardfacing guides. Although hardfacing  54  is not shown on the gage surface in this embodiment, hardfacing  54  can be applied to the gauge surface. 
         [0029]    Additional hardfacing can be included between the cutter  44   a  and the hardfacing  54 . Shown in a front view in  FIG. 5  is an example of hardfacing  80  added along the interface  81  of the cutter  44   a  and applied hardfacing  54 . As illustrated in  FIG. 5 , the hardfacing  80  spans across the interface  81  and is joined to the hardfacing guides  48 ,  58  on the cutter  44   a  and also to the hardfacing  54 . Being adhered to both the cone shell and the hardfacing  54  reinforces the bond between the hardfacing  54  and the hardfacing guides  48 ,  58 . In the example of  FIG. 5 , the hardfacing  80  projects upward from the interface  81 . Thus when in use, the hardfacing  80  can provide a trimmer function. Beads or ridges of hardfacing  80  can also be added to the interfaces  81  on the rearward sides of the rows. An example of hardfacing  80  along a cutter  44   a  and hardfacing  54  interface  81  is depicted in  FIG. 6 . Here the hardfacing  80  is optionally added along the web&#39;s entire periphery, shown on both lateral sides of the web and adjacent the hub  51 . 
         [0030]      FIG. 7  presents a sectional view of hardfacing  80  on the hardfacing guide  48  and hardfacing  54  interface  81 . In this view the hardfacing  80  is semi-elliptical, but can take on any other shape, including semi-circular, rectangular, or triangular. Moreover, although shown as substantially symmetric about its mid-section, the hardfacing  80  can be asymmetrically shaped. In an example, the hardfacing  80  leading side (side in first contact boring operations) may be thicker, both upwards and laterally. Other embodiments exist having smaller sections of hardfacing  80  that do not span the interface&#39;s  81  entire length. 
         [0031]      FIG. 8  provides in perspective view an example of a cutter  44   b  having hardfacing  54  spanning between adjacent hardfacing guides  48  on a cutter row. In this embodiment hardfacing  80  along the interface  81  forms a “V: shaped member that upwardly projects from the hardfacing guide  48  surface. The raised V shaped members shown form bar trimmers. In the embodiment of  FIG. 8 , the hardfacing  54  is provided on alternating adjacent hardfacing guides  48 . 
         [0032]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, the scope of this disclosure includes roller cones having more than two rows of cutting elements on a roller cone land. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.