AU2008238617A1

AU2008238617A1 - Drill string hard overlay application system

Info

Publication number: AU2008238617A1
Application number: AU2008238617A
Authority: AU
Inventors: Todd Andrew Haines
Original assignee: HAINES TODD
Current assignee: HAINES TODD
Priority date: 2007-04-16
Filing date: 2008-04-15
Publication date: 2008-10-23
Anticipated expiration: 2028-04-15
Also published as: WO2008124886A1; CL2008001080A1; PE20090009A1; AU2008238617B2

Description

WO 2008/124886 PCT/AU2008/000531 1 TITLE: DRILL STRING HARD OVERLAY APPLICATION SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention THIS INVENTION relates to a hard overlay application system 5 for drill string components. The invention is particularly suitable for, but not limited to, drill string components used in the rotary drilling industry. 2. Prior Art A need has arisen for drill string components capable of 10 withstanding the wearing effects of abrasive drill cuttings attacking the surface of the drill string on their way to the surface. Wear is caused on the drill string components, mainly by the abrasive drill cuttings striking the external surfaces of the drill string components, at various tangents, at velocities between 20-61 metres/second (4000-12000 feet/minute); and the 15 scraping or gouging wear caused by rock wedged against the components while they rotate during drilling; or a combination of both. Presently, hard overlay plate is used in high wear applications such as chutes, hoppers, crushers and other products used in minerals processing and handling. This wear plate is manufactured by a number of 20 procedures, but one of the most common is to lay alloying powders such as ferro chrome onto the plate, which is then screeded to a set thickness, and a series of welding heads oscillate along the plate, combining the plate material, welding consumable and the alloying powder during the welding process. The finished product has a high wearing surface with a mild steel WO 2008/124886 PCT/AU2008/000531 2 backing. These plates are normally manufactured in standard plate sizes. Applying hard overlay to drill string components has been occurring for many years. This overlay has included a tungsten matrix whereby tungsten grit is trickled directly into the open arc weld pool being 5 welded in a single bead or weave as the drilling component is being rotated. One of the issues when using this process is the inherently inaccurate composition of the overlay product, as not all the tungsten grit trickled onto the surface of the drilling string component is melted into the weld pool. The percentages of tungsten or other alloys used in this 10 process are difficult to manage, as the mount of alloy actually being absorbed into the weld pools varies with each setup. The height of the component, and the angle of the copper tube by which the tungsten grit is trickled onto the surface, allow different amounts of tungsten in the weld and also varying amounts of dilution of the tungsten 15 in the finished overlay. The tungsten grit is either melted into the weld pool fully or partially, and is retained in the weld pool as it cools. This is a very effective wear-resistant product, but has the disadvantage of being quite an abrasive surface for any steel that it comes 20 into contact with. As the matrix is worn away, the partially melted tungsten grit protrudes and is an effective cutting tool on the metal. Centralising bushes and pipe positioning clamps, commonly used in surface drills, are particularly vulnerable, as they are the metal components most in contact with the overlay.

WO 2008/124886 PCT/AU2008/000531 3 Other products are available overlaying drill string components and these are normally cored welding wires that are between 1.2mm and 3.2mm in diameter, and have a combination of alloys and fluxes in the core. When the welding wire is welded onto the surface of the component, wire, 5 parent metal, alloys and fluxes all combine to produce a hard overlay. The disadvantage of this cored wire is its relatively high cost, limited abrasion resistance, and the reliance on the producer of the wire to supply a large range of suitable mixes of alloys. SUMMARY OF THE PRESENT INVENTION 10 It is an object of the present invention to place the alloying elements ahead of the weld pool so that the products are fully diluted in the weld pool. It is a preferred object to place the alloying elements ahead of the weld pool by means of at least one copper tube positioned slightly ahead 15 of the weld arc. It is a further preferred object of the present invention to enable different combinations of alloying elements to be laid ahead of the weld arc by means of using two or more tubes set at different heights from the surface of the component. 20 Other preferred objects of the present invention will become apparent from the following description. In one aspect, the present invention resides in a method of applying a hard overlay to a drill string component, including the steps of: mounting the component in a rotating support; WO 2008/124886 PCT/AU2008/000531 4 rotating the component; and applying an electric welding arc to create a molten weld pool on a portion of an external surface of the component; wherein: at least one alloying element for the hard overlay is applied to 5 the external surface of the component in advance of the molten weld pool. Preferably, the at least one alloying element is applied to the external surface by a hollow (preferably copper) tube, which has an outlet end, spaced a defined distance from the external surface. Two or more alloying elements may be applied to the external 10 surface by two or more hollow tubes, where the outlet of the first (ie., upstream) tube is spaced a smaller distance from the external surface of the component than the outlet(s) of the second or subsequent (ie., downstream) tube(s). A spatter guard and/or flux dam may be provided between the 15 hollow tube(s) and the electric welding head applying the electric welding arc generating the molten weld pool. In a second aspect, the present invention resides in: apparatus for applying a hard overlay to a drill string component, including: 20 a rotating support to releasably mount the component; means to rotate the component; and an overlay applicator operable to move along the component as the component is rotated, the overlay applicator including: an electric welding arc to create a molten weld pool on a WO 2008/124886 PCT/AU2008/000531 5 portion of an external surface of the component; and at least one hollow tube to apply at least one alloying element for the hard overlay to the external surface of the component in advance of the molten weld pool. 5 Preferably, the hollow tube has an outlet spaced a defined distance from the external surface of the component. Where two or more alloying elements are to be applied to the external surface of the component, the overlay applicator may incorporate two or more hollow tubes, where the outlet of the first (ie., upstream) hollow 10 tube is spaced a smaller distance from the external surface of the component than the outlet(s) of the second or subsequent (ie., downstream) tube(s). Preferably, the overlay applicator is mounted on a track or guide on, or associated with, the rotating support so the rate of longitudinal 15 advance of the overlay applicator is proportional to the rate of rotation of the component so that the hard overlay is applied to the external surface of the component in a continuous spiral to form a unitary hard overlay layer about the component. One preferred method of welding is the submerged arc 20 process, where the welding is effected under a covering of flux, which may be fed from a remote source. Preferably, a welding flux collection device, such as a vacuum head, is provided downstream of the electric welding arc to collect any unused flux.

WO 2008/124886 PCT/AU2008/000531 6 Preferably, the unused flux is sieved, de-magnetised and recycled to the electric welding arc. Preferably, a quenching head, such as a water spray nozzle, applies a quenching liquid to the hot, solid hard overlay. 5 Preferably, the quenching liquid is collected and recycled to the quenching head. In third and fourth aspects, the present invention resides in drill string components having a hard overlay applied by the method of the first aspect, and by the apparatus of the second aspect, respectively. 10 BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood, preferred embodiments will now be described with reference to the accompanying drawings, in which: FIG. 1 is a schematic end elevational view of a Prior Art 15 method for applying the hard overlay to a drill string component; FIG. 2 is a schematic top plan view thereof; FIG. 3 is a schematic top plan view of a hard overlay application system of a first embodiment of the present invention; FIG. 4 is a schematic side elevational view thereof; 20 FIG. 5 is a schematic side elevational view, of a portion of the system, from the opposite side; FIG. 6 is a schematic sectional end view of the system; FIG. 7 is a schematic end elevational view of a second embodiment of the present invention; WO 2008/124886 PCT/AU2008/000531 7 FIG. 8 is a schematic top plan view thereof; FIG. 9 is a schematic end elevational view of a third embodiment of the present invention; FIG. 10 is a schematic top plan view thereof; 5 FIG. 11 is a schematic view illustrating the supply of the alloying elements to the tubes of the third embodiment; and FIG. 12 is a schematic end elevational view of a fourth embodiment. DETAILED DESCRIPTION OF THE 10 PREFERRED EMBODIMENTS FIGS. 1 and 2 illustrate a Prior Art method, where the tungsten grit is trickled directly into the open arc weld pool being welded in a single bead or a weave as the drill string component is being rotated. The drill string component C, eg., a length of drill string pipe 15 has, eg., respective male and female threads at its ends for connection to complementary other like drill string components. The drill string component C has an external surface E to which is applied a hard overlay 0 in a single bead or weave as the component C is rotated in a rotating support (not shown). 20 A molten weld pool P is created by the electric arc A generated by an electric arc welder W and tungsten grit TG is applied to the molten weld pool P via a copper tube TC which directs the tungsten grit TG into the molten weld pool P downstream (ie., behind) the electric arc welder W. As the molten weld pool P cools, the tungsten grit TG is wholly WO 2008/124886 PCT/AU2008/000531 8 or partially melted into the molten weld pool P and retained in the matrix which forms the overlay 0. As hereinbefore described with reference to the prior art, as the overlay 0 is worn away, the partially melted grit TG protrudes and becomes 5 an effective cutting tool on the metal of any drilling equipment, eg., centralising bushes or pipe positioning clamps, which engage the hard overlay 0. The first embodiment of the present invention is illustrated in FIGS. 3 to 6 where a hard overlay 120, in the form of a continuous spiral of a 10 tungsten matrix, is applied to the external surface 112 of the tubular steel body 111 of a drill string component 110. The hard overlay 120 is applied by an applicator 130, to be hereinafter described in more detail (particularly with reference to FIG. 6), where a molten weld pool 150 is created by an electric arc 136 of an electric 15 arc welder 135, and where the alloying element 140, eg., tungsten grit or ferro chrome powder, is applied to the external surface 112 of the component 110 by a hollow (copper) tube 131 which has its outlet 132 spaced a small distance from the external face 112 of the component 110, the outlet 132 of the hollow pipe 131 being upstream of the electric arc 136 20 when the drill component 110 is rotated in the direction of arrow A in FIG. 6. A rotary support 160 has an elongate bed 161 on which is mounted spaced pairs of rollers 162 to rotatably support the drill component 110. (Preferably, the pairs of rollers 162 are adjustable in both horizontal and vertical directions to enable drill components 110 with a wide range of WO 2008/124886 PCT/AU2008/000531 9 external diameters to be accommodated by the rotary support 160.) The overlay applicator 130 is mounted on a travelling head 163 which can travel along the elongate bed 161 at a preselected linear velocity via a rack and pinion drive system 164. Preferably, the linear speed is 5 adjusted so that the head 163 will travel a distance equal to the width of a spiral of the hard overlay 120 for each 3600 of rotation of the drill component 110. The drill component 110 is rotatably driven by a driving head 170 which has a large flywheel 171 axially located on the elongate bed 161 10 by locating rollers 165. A drive spigot 172 is non-rotatably engaged in the bore of the adjacent end of the drill component 110; and the flywheel 171 is driven by a drive plate 173 connected to a drive shaft 181 of a rotary power source 180 via a telescopically adjustable propeller shaft 174 and universal joints 175, 15 182. The drive shaft 181 of the rotary power source 180 is journalled in suitable bearings 183 and is driven by a chain-and-sprocket drive assembly 184 operably connected to an electric motor (or hydraulic motor) 185. 20 The propeller shaft 174 and the universal joints 175, 182 enable the rotary power source 180 to rotatably drive drill components 110 having a wide range of external diameters. The overlay applicator 130 will now be described in more detail with reference to the "schematic" sectional end view in FIG. 6.

WO 2008/124886 PCT/AU2008/000531 10 The alloying element, eg., ferro chrome powder or tungsten grit 140, is supplied to a hopper or funnel 133, at the upper end of the hollow pipe 131, by a metering unit 190 which receives ferro chrome powder or tungsten grit 140 from a "bulk" supply not shown. 5 The electric welding head 135, which supplies the electric welding arc 136 to create the molten weld pool 150, operates on the submerged arc process, where the welding takes place under a covering of welding flux 138. The welding flux 138 is gravity fed from a hopper 137. The hopper 137 receives the welding flux 138 from a pump mechanism 139 10 connected to a bulk source 191 of the welding flux 138 and also to a recycling mechanism 192 which incorporates a vacuum head 193, downstream of the electric arc welder 135, connected to a source of vacuum 194 and to a sieving and de-magnetising apparatus 195 which supplies the recycled flux to the pumping mechanism 139. 15 The arc welding wire (not shown) is supplied to the electric arc welder 135 via a suitable conduit 196, the welding wire being drawn from a roll (not shown) mounted on the head 163. A quenching head 197 has a water spray nozzle 198 connected to a pump 199 where the quenching water, to cool the hard overlay 120 is 20 collected via a collection tray 199A (provided below the drill component 110) and connected to the pump 199 via a filter apparatus 199B. By this arrangement, the amount of water, or other quenching liquid, can be reduced; and the filtering apparatus 199B ensures that only high quality quenching water or other liquid is applied to the molten weld pool 150 to cool WO 2008/124886 PCT/AU2008/000531 11 the molten metal therein into the hard overlay 120 having a uniform composition. When the drill component 110 has been located on the rotary support 160 and connected to the rotary drive means 180, the ferro chrome 5 powder or tungsten grit 140 is applied to the external surface 112 of the steel body 111 of the drill component 110 in a narrow strip upstream of the electric arc 136 applied by the electric arc welder 135. Any unused flux 138, which is not in the molten weld pool 150, is collected via the vacuum head 193 and recycled to the hopper 137, the lost volume of welding flux 138 being made 10 up from supplies drawn from the welding flux source 191. The water nozzle 198 of the quenching head 197 applies quenching water to the hot, solid weld to ensure rapid quenching thereof and the formation of the hard overlay 120. The quenching water is collected in the tray 199A and returned via the filter means 199B to the pump 199 for 15 recycling. By placing the ferro chrome powder/tungsten grit/alloying elements upstream of the electric arc 136, the weight of welding flux 138 over the ferro chrome powder/tungsten grit/alloying elements 140 will prevent the latter from being blown away by the jet blast of the electric arc 136. 20 Also, by placing the tungsten grit/other alloying elements 140 ahead of the welding arc 136, the tungsten grit/other alloying elements 140 are fully diluted in the molten weld pool 150 before they reach the quenching head 198, and so there will be no partially melted ferro chrome powder or tungsten grit 140 in the resultant hard overlay 120 which can damage other WO 2008/124886 PCT/AU2008/000531 12 steel components as the hard overlay 120 wears. By placing the outlet 132 of the hollow tube 131 close to the external surface 112 of the drilling string component 110, this allows the energy of the ferro chrome powder/tungsten grit/alloying elements 142 5 "bounce" off the external surface 112, of the drill string component 110, but to be then contained by the inside of the hollow tube 131, ensuring that the ferro chrome powder/tungsten grit/alloying elements 140 are applied to the drill string component 110 within a set strip width that is within the width of the molten weld pool 150. 10 As the ferro chrome powder/tungsten grit/alloying elements 140 enter the molten weld pool 150 at its point of maximum temperature, complete melting/dilution of the ferro chrome powder/tungsten grit/alloying elements 140 in the molten weld pool 150 can be assured. Referring now to the second embodiment of the present 15 invention illustrated in FIGS. 7 and 8, the drill string component 210 has a tubular steel body 211, with an external surface 212, releasably mounted in the rotatable support (not shown) to enable the drill string component 210 to be rotated about its longitudinal axis 213. Rotary drive means may be connected to some of the rollers, 20 or to the drill string component 210, to enable the drill string component 210 being "cradled" to be rotated about its longitudinal axis 213 at a pre-selected rotational speed. As shown in FIG. 8, the hard overlay 220 is applied to the external face 212 of the drill string component 210 in a continuously spirally WO 2008/124886 PCT/AU2008/000531 13 wound bead using the overlay applicator 230, to be hereinafter described in more detail, which is mounted on a movable head (not shown) to advance the applicator 230 a longitudinal distance substantially equal to the width of the bead for each 3600 rotation of the drill string component 210. 5 The overlay applicator 230 includes a hollow (copper) tube 231 which has its outlet 232 spaced a predetermined distance from the external surface 212 of the drill string component 210. Tungsten grit and/or other alloying elements pass through the tube 231 and are directed onto the external surface 212 of the drill string component 210 upstream of the molten 10 weld pool 250 created by the electric arc 236 of the electric arc welder 235 spaced a small distance downstream of the hollow tube 231. A spatter guard 239 is provided intermediate the hollow tube 231 and the electric arc welder 235, to minimise likelihood of blockage of the outlet 232 of the hollow tube 231 due to spatter generated by the open arc 15 welding process. Once again, by placing the ferro chrome powder/tungsten grit/other alloying elements ahead of the welding arc 236, they are fully diluted in the molten weld pool 250 and so there will be no partially melted tungsten grit 240 in the resultant hard overlay 220 which can damage other 20 steel components as the hard overlay 220 wears. Also, by placing the outlet 232 of the hollow tube 231 close to the external surface 212 of the drilling string component 210, this allows the energy of the tungsten grit/alloying elements 240 to bounce off the external surface 212, but to then be contained by the inside of the hollow tube 231, WO 2008/124886 PCT/AU2008/000531 14 ensuring the tungsten grit/alloying elements 240 are applied to the drill string component 210 within a set width that is within the width of the molten weld pool 250. The molten weld pool 250 may be widened by oscillating the 5 electric arc welder 235 or by welding with twin arcs, which is a process where two welding wires are fed into the same weld pool 250. The welding wires would be, eg., 5-10 mm apart from each other. Referring to the third embodiment of the present invention illustrated in FIGS. 9 to 11, different combinations of alloy elements 340A, 10 340B can be laid ahead of the weld arc 336 by means of using two hollow tubes 331A, 331B set at different heights from the external surface 312 of the drill string component 310. It will be noted that the outlet of the first, or upstream, hollow tube 331A is spaced a smaller distance from the external surface 312 of the 15 drill string component 310 than the outlet of the second, or downstream, hollow tube 331 B. Once again, the ferro chrome powder/tungsten grit/alloying elements 340A, 340B are laid on the external surface 312 of the drill string component upstream of the molten weld pool 350 so that the elements 20 340A, 340B are fully melted before the molten weld pool 350 cools to form the bead of hard overlay 320. The two hollow tubes 331A, 331B will allow many alloys to be used by means of double hoppers 333A, 333B on each tube 331A, 331B. By adjusting flow rates of the alloying elements, many different combinations WO 2008/124886 PCT/AU2008/000531 15 of hard overlay 320 can be manufactured. With this embodiment of the present invention, the manufacturer can readily "tune" the type of hard overlay 320 applied to the drill string component 310 to suit, eg., the material of the drill string 5 component 310 and/or the intended use of the drill string component, eg., for drilling coal, rock or other materials. The second and third embodiments illustrated in FIGS. 7 and 8 and 9 to 11, respectively, illustrate electric arc welders 235, 335, where the welding arcs 236, 336 are generated using solid wire in the gas shielded 10 open arc process. It will be readily apparent to the skilled addressee that cored wire could also be used. A further welding option able to be used in this process would include self shielding (inner shield) cored wire. 15 In the fourth embodiment of the present invention illustrated in FIG. 12, the electric arc welder 435 has a submerged arc 436 where the welding arc 436 is covered by a flux powder 437. In this embodiment, a flux dam 439 is provided intermediate the hollow tube 431 which applies the tungsten grit/alloying elements 440 to the 20 external surface 412 of the drill string component 410 and the electric arc welder 435 to prevent the arc flux granules 437 blocking the outlet of the hollow tube 431. It will be readily apparent to the skilled addressee that the present invention provides methods of, and apparatus for, the efficient WO 2008/124886 PCT/AU2008/000531 16 application of a hard overlay to drill string components, where all the alloying elements are totally melted into the molten weld pool before it cools to form the matrix that provides the hard overlay on the external surfaces of the drill string components. 5 The selection of the alloying elements, and the selective spacing of the outlets of the hollow tubes from the external surfaces of the drill string components, can be varied to suit the particular intended application/materials employed. Various changes and modifications may be made to the 10 embodiments described and illustrated without departing from the present invention.

Claims

1. A method of applying a hard overlay to a drill string component, including the steps of: mounting the component in a rotating support; 5 rotating the component; and applying an electric welding arc to create a molten weld pool on a portion of an external surface of the component; wherein: at least one alloying element for the hard overlay is applied to the external surface of the component in advance of the molten weld pool. 10

2. The method of Claim 1, wherein: the at least one alloying element is applied to the external surface by a hollow tube, which has an outlet end, spaced a defined distance from the external surface of the component.

3. A method as claimed in Claim 1, wherein: 15 two or more alloying elements are applied to the external surface by two or more tubes, where an outlet of a first, or upstream, tube is spaced a smaller distance from the external surface of the component than the outlet(s) of the second, or subsequent, downstream, tube(s).

4. A method as claimed in Claim 2 or Claim 3, wherein: 20 a spatter guard and/or flux dam are provided between the hollow tube(s) and an electric welding head applying the electric welding arc generating the molten weld pool.

5. A method as claimed in Claim 2 or Claim 3, wherein: the electric welding arc is operated under a submerged arc WO 2008/124886 PCT/AU2008/000531 18 process where the electric welding arc is covered by flux; and unused flux from an electric welding head, applying the electric welding arc, is collected downstream of the electric welding arc by a welding flux collection device, such as a vacuum head. 5

6. A method as claimed in Claim 5, wherein: the unused flux is sieved, de-magnetised and recycled to the electric welding arc.

7. A method as claimed in any one of Claims 1 to 6, wherein: a quenching liquid is applied to hot, solid weld deposition, 10 forming the hard overlay by a quenching head, such as a water spray nozzle.

8. A method as claimed in Claim 7, when dependent on either Claim 5 or Claim 6, wherein: the quenching liquid is applied downstream of the collection of the unused flux. 15

9. A method as claimed in Claim 7 or Claim 8, wherein: the quenching liquid is collected and recycled to the quenching head.

10. An apparatus for applying a hard overlay to a drill string component, including: 20 a rotating support to releasably mount the components; means to rotate the components; and an overlay applicator operable to move along the component as the component is rotated, the overlay applicator including: an electric welding arc to create a molten weld pool on a WO 2008/124886 PCT/AU2008/000531 19 portion of an external surface of the component; and at least one hollow tube to apply at least one alloying element for the hard overlay to the external surface of the component in advance of the molten weld pool. 5

11. An apparatus as claimed in Claim 10, wherein: the hollow tube has an outlet spaced a defined distance from the external surface of the component.

12. An apparatus as claimed in Claim 11, wherein: when two or more alloying elements are to be applied to the 10 external surface of the component, the overlay applicator incorporates two or more hollow tubes, where an outlet of a first, upstream, hollow tube is spaced a smaller distance from the external surface of the component than the outlet(s) of the second, or subsequent, downstream, tube(s).

13. An apparatus as claimed in any one of Claims 10 to 12, 15 wherein: the overlay applicator is mounted on a track or guide on, or associated with, the rotating support, so that the rate of longitudinal advance of the overlay applicator is proportional to the rate of rotational of the drill of the component, so arranged that the hard overlay is applied to the external 20 surface of the component in a continuous spiral to form a unitary hard overlay layer about the component.

14. An apparatus as claimed in any one of Claims 10 to 13, wherein: a welding flux collection device, such as a vacuum head, is WO 2008/124886 PCT/AU2008/000531 20 provided downstream of the electric welding arc to collect any unused flux from an electric welding head applying the electric welding arc under a submerged arc process.

15. An apparatus as claimed in Claim 14, and further including: 5 apparatus to sieve, de-magnetise and recycle the unused flux to the electric welding arc.

16. An apparatus as claimed in any one of Claims 10 to 15, and further including: a quenching head, such as a water spray nozzle, to apply a 10 quenching liquid to hot solid, weld deposition forming the hard overlay.

17. An apparatus as claimed in Claim 16, and further including: apparatus to collect and recycle the quenching liquid to the quenching head.

18. A drill string component having a hard overlay applied to at 15 least a portion of an external surface of the component by the method as claimed in any one of Claims 1 to 9.

19. The component as claimed in Claim 18, wherein: the hard overlay includes a tungsten matrix where at least one alloying element is a tungsten grit; or ferro chrome matrix.

20 20. A drill string component having a hard overlay applied to at least a portion of an external surface applied to the component by the apparatus of any one of Claims 10 to 17.

21. The component as claimed in Claim 20, wherein: when the hard overlay is a tungsten matrix, the at least one WO 2008/124886 PCT/AU2008/000531 21 hollow tube applies tungsten grit as the at least one alloying element to the external surface of the component.

22. A hard overlay applied to an external surface of a drill string component by the method of any one of Claims 1 to 9. 5

23. A hard overlay applied to an external surface of a drill string component by the apparatus of any one of Claims 10 to 17.