WO2012054955A1

WO2012054955A1 - Methods for providing a hardened surface, for refurbishing a cable drum, and apparatus therefor

Info

Publication number: WO2012054955A1
Application number: PCT/AU2011/000989
Authority: WO
Inventors: Maurice Gregory Smith
Original assignee: Minelink Pty Ltd
Priority date: 2010-10-29
Filing date: 2011-08-04
Publication date: 2012-05-03
Also published as: AU2011100969B4; AU2011320002B2; AU2011100969A4; AU2011320002A1

Abstract

A method for providing a hardened surface on a heavy machinery component, especially but not exclusively a dragline cable drum, comprises adding a martensitic steel to at least one area of the component by a metal deposition process, while the component is maintained at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel, machining the added steel while maintaining the temperature of the added metal at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel and then cooling the component so that at least some of the added steel obtains a greater hardness.

Description

Methods for providing a hardened surface, for refurbishing a cable drum, and apparatus therefor

Field

The present disclosure relates to a method of refurbishing a cable drum and also, more generally, to a method for providing a hardened surface on a heavy machinery component, and to apparatus therefor. The present disclosure has applicability to both manufacture and refurbishing of heavy machinery components and in a particular implementation to refurbishing a cable drum, especially but not exclusively a dragline cable drum, by adding metal thereto in order to replace metal lost by wear and tear.

Background Dragline cable drums may weigh in the region of 50 tonnes and, as of 2010, replacement cost may considerably exceed a million dollars.

During use, dragline cable drums suffer considerable wear, in particular of cable engagement regions where a dragline cable is engaged. In a known type of drum the cable engagement regions are formed with cable guiding grooves which guide the cable as it is wound on and off the drum. In a new drum cable engagement regions can be provided with a flame hardened outer region in the form of a hardened layer on the surface of the main body of the drum shell which is normally made of carbon steel, which overlies a less hard steel from which the body of the drum is formed. The hardened steel surface can have a depth of between 2 and 6 mm, depending on the hardening process used, and a hardness in excess of 40 to 55 HRC (Hardness Rockwell C scale).

It may take several months or years of use before the hardened region is worn through, but after the hardened region is worn through the rate of wear is greatly accelerated because the dragline cable then engages and wears through non hardened metal. At this time it is imperative to replace (or repair/refurbish) the drum, not least because use of a significantly worn drum greatly increases wear on the cable being used, and replacement of the cables is inconvenient and expensive.

New dragline drums are extremely expensive, and required drums might not be readily commercially available, so there can be considerable delays between ordering and obtaining such cable drums.

Recently, attempts have been made to refurbish dragline drums. In order to refurbish a dragline drum, the drum is removed from the dragline apparatus, moved to a suitable refurbishment facility for refurbishment, and refurbished in a workshop of the refurbishment facility. The dragline drum is then transported back to the dragline and reinstalled. Suitable refurbishment facilities are rare, especially in remote mining locations, not least because handling and processing of an item which weighs several tens of tonnes is difficult. Removal of a drum from a dragline, transport of a drum to a suitable facility, and refurbishment is time consuming and expensive. Downtime of the dragline is also extremely expensive.

The present disclosure relates especially, but not exclusively, to an improved method of refurbishing such drums.

Summary

According to a first aspect of the present disclosure there is provided a method of refurbishing a cable drum, the method comprising:

heating the cable drum to a preheat temperature sufficient to allow effective addition of metal thereto by a metal deposition process;

adding metal to at least one worn area of the heated cable drum by a metal deposition process;

machining at least some of the added metal to obtain a desired shape of the cable drum, while maintaining the temperature of the added metal in excess of a critical temperature at which the added metal hardens; and

cooling the item so that at least some of the added metal hardens.

In an embodiment the method is a method of refurbishing a cable drum with a mass in excess of twenty ton nes .

In an embodiment the method is a method of refurbishing a dragline cable drum. In an embodiment the metal deposition process comprises a welding process.

In an embodiment, the heating of the cable drum to a temperature sufficient to allow effective addition of metal thereto by a welding process comprises heating the cable drum to a temperature of at least 150 degrees centigrade.

In an embodiment the step of machining at least some of the added metal to obtain a desired shape of the cable drum, while maintaining the temperature of the added metal in excess of a critical temperature at which the added metal hardens, comprises maintaining the temperature of the added metal in excess of 100 degrees centigrade.

In an embodiment the step of machining at least some of the added metal to obtain a desired shape of the cable drum, while maintaining the temperature of the added metal in excess of a critical temperature at which the added metal hardens, comprises maintaining the temperature of the added metal in excess of 50 degrees centigrade.

In an embodiment, the step of adding metal to at least one worn area of the cable drum by the metal deposition process comprises adding martensitic steel.

In an embodiment, the step of adding metal to at least one worn area of the cable drum by a metal deposition process comprises adding steel with a chromium content of at least 8% by mass to at least one worn area of the cable drum by the metal deposition process.

In an embodiment, the step of adding metal to at least one worn area of the cable drum by the metal deposition process comprises adding steel with a chromium content of at least 11% by mass to at least one worn area of the cable drum by the metal deposition process.

In an embodiment, the step of adding metal to at least one worn area of the cable drum by the metal deposition process comprises adding steel with a chromium content of approximately 13 to 17% by mass to at least one worn area of the cable drum by the metal deposition process.

In an embodiment, the step of adding metal to at least one worn area of the cable drum by the metal deposition process comprises adding steel comprising 400 series martensitic steel with a chromium content of approximately 13 to 17% by mass to at least one worn area of the cable drum by the metal deposition process.

In an embodiment, the step of adding metal to at least one worn area of the cable drum comprises use of a welding process to add 400 series martensitic welding wire to the at least one worn area.

In an embodiment, the step of adding metal to at least one worn area of the cable drum by a metal deposition process comprises adding a martensitic steel which has a martensitic start temperature between 180 degrees centigrade and 500 degrees centigrade.

In an embodiment, the preheat temperature is lower than the martensitic start temperature of the metal added to at least one worn area of the cable drum.

In an embodiment, the step of adding metal to at least one worn area of the cable drum by a metal deposition process comprises adding a martensitic steel which has a martensitic finish temperature between 100 degrees centigrade and 300 degrees centigrade.

In an embodiment the step of adding metal by a metal deposition process may comprise depositing two or more layers of metal.

In an embodiment the step of adding metal by a metal deposition process may comprise a first deposition of metal on a given part of the cable drum or component, and then depositing a second deposition of metal at least partially on the first deposition.

The metal of the first deposition may be allowed to cool to below its liquidus temperature prior to depositing of the second deposition.

Depositing several layers (or several thicknesses of weld bead) may provide a desired thickness of deposited metal, and may reduce dilution effects that might result from mixing of the deposited metal with underlying metal. It will be appreciated each respectively more outer layer can be expected to be less affected by dilution from constituents of the underlying base metal (eg carbon steel), so that the more inner layers may, in use, conform less closely to the desired chemistry and characteristics of the deposited metal. In an embodiment, the critical temperature at which the added metal hardens comprises the martensitic finish temperature of the added metal. The step of cooling the cable drum so that at least some of the added metal hardens may comprise at least some of the added metal hardening to a harder state of at least two different states of hardness to which the metal may harden when the metal cools to a given temperature below the critical temperature, the two different states of hardness being achievable by different heat treatments of the added metal prior to the added metal cooling to a temperature below the critical temperature.

The harder state may be a state which is achievable by a heat treatment which results in formation of a significant amount of martensite, said heat treatment being different to a heat treatment which does not result in formation of such a significant amount of martensite.

The heat treatment which results in formation of a significant amount of martensite may be a head treatment in which metal cools rapidly from a higher temperature to a temperature below the martensitic start temperature of the metal, and said heat treatment which does not result in formation of such a significant amount of martensite may be a heat treatment in which metal cools from a lower temperature and/or less rapidly to a temperature below the martensitic start temperature. An example of heat treatment which does not result in formation of such a significant amount of martensite is a commonly used tempering treatment, for example one in which in which metal is heated to between 400 and 800 degrees centigrade and then cooled. Heat treatments which result in greater or lesser amounts of martensite formation will be understood by the skilled addressee.

The martensitic start temperature may be 300 degrees Centigrade plus or minus 150 degrees Centigrade.

The martensitic start temperature may be between 200 and 350 degrees Centigrade. The martensitic start temperature may be between 250 and 320. The martensitic finish temperature may be between 100 and 400 degrees Centigrade. The martensitic finish temperature may be between 100 and 300 degrees Centigrade. The martensitic finish temperature may be between 150 and 200 degrees Centigrade.

The martensitic finish temperature may be 150 to 250 degrees Centigrade below the martensitic start temperature.

The step of cooling the cable drum so that at least some of the added metal hardens may comprise at least some of the added metal hardening to a hardness in excess of 40 HRC.

The step of cooling the cable drum so that at least some of the added metal hardens may comprise substantially all of the added metal hardening to a hardness in excess of 40 HRC. The step of cooling the cable drum so that at least some of the added metal hardens may comprise at least some of the added metal hardening to a hardness in excess of 45 HRC.

The step of cooling the cable drum so that at least some of the added metal hardens may comprise substantially all of the added metal hardening to a hardness in excess of 45 HRC.

The step of cooling the cable drum so that at least some of the added metal hardens may comprise at least some of the added metal hardening to a hardness in excess of 52 HRC.

The step of cooling the cable drum so that at least some of the added metal hardens may comprise substantially all of the added metal hardening to a hardness in excess of 52 HRC.

In an embodiment the step of machining at least some of the added metal to obtain a desired shape of the cable drum, while maintaining the temperature of the added metal in excess of a critical temperature at which the added metal hardens comprises machining one or more grooves for guiding a cable.

In an embodiment the machining of at least some of the added metal to obtain a desired shape of the cable drum, while maintaining the temperature of the added metal in excess of a critical temperature at which the added metal hardens comprises using one or more machining heads.

In an embodiment the one or more machining heads are controlled by a computer operated control system.

In an embodiment the one or more machining heads are controlled by a CNC system.

In an embodiment the adding of metal to at least one worn area of the cable drum by a welding process comprises using one or more welding heads, such as one or more arc welding heads.

In an embodiment the one or more welding heads are controlled by a computer operated control system.

In an embodiment the one or more welding heads are controlled by a CNC system.

In an embodiment the CNC system operates the machining heads to gauge the amount of weld metal build-up required during the weld reclamation stage of the process by detecting regions of the cable drum where insufficient metal has been added by the one or more welding heads, and initiates operation of one or more of said welding heads to rectify the insufficiency.

In an embodiment the heating of the cable drum to a temperature sufficient to allow effective addition of metal thereto by a welding process is performed by using gas burners.

In an embodiment the heating of the cable drum to a temperature sufficient to allow effective addition of metal thereto by a welding process is performed by using infrared radiating heaters to heat the cable drum.

In an embodiment the method is performed with the cable drum in the vicinity of a machine in which it has previously suffered wear. In an embodiment the method is performed with the cable drum in situ, within said machine in which it has previously suffered wear. In an embodiment the method is performed using at least part of a gear train of said machine, which gear train or part thereof is used to rotate the drum during normal operation of the machine, to rotate the drum during refurbishing thereof. According to a second aspect of the present disclosure there is provided a method of refurbishing a cable drum, the method comprising:

heating the cable drum to a preheat temperature in excess of 150 degrees centigrade; adding metal to at least one worn area of the heated cable drum by a metal deposition process;

machining the added metal to obtain a desired shape of the cable drum while maintaining the temperature of the added metal in excess of 100 degrees centigrade; and

cooling the cable drum so that at least some of the added metal obtains a hardness in excess of 40 HRC.

In an embodiment the step of adding metal to at least one worn area of the cable drum by a metal deposition process comprises adding metal by a welding process.

In an embodiment the step of machining the added metal to obtain a desired shape of the cable drum while maintaining the temperature of the added metal in excess of 100 degrees centigrade, comprises machining the added metal while maintaining the temperature of at least the part of the cable drum adjacent the added metal at a temperature excess of 100 degrees centigrade. In an embodiment the step of machining the added metal to obtain a desired shape of the cable drum while maintaining the temperature of the added metal in excess of 100 degrees centigrade, comprises machining the added metal while maintaining the temperature of substantially the entire cable drum a temperature excess of 100 degrees centigrade.

In an embodiment the metal added to at least one worn area of the cable drum by a metal deposition process is a martensitic steel.

In an embodiment the metal added to at least one worn area of the cable drum by a metal deposition process is a series 400 martensitic steel.

In an embodiment the step of heating the cable drum to a temperature in excess of 150 degrees centigrade comprises heating the cable drum to a temperature which is higher than the martensitic finish temperature of the metal to be added and lower than the martensitic start temperature of the metal to be added. In an embodiment the step of machining the added metal to obtain a desired shape of the cable drum while maintaining the temperature of the added metal in excess of 100 degrees centigrade comprises machining the added metal to obtain a desired shape of the cable drum while maintaining the temperature of the added metal higher than the martensitic finish temperature of the metal to be added.

In an embodiment the step of cooling the cable drum is performed so that at least some of the added metal obtains a hardness in excess of 45 MRC.

In an embodiment the step of cooling the cable drum is performed so that at least some of the added metal obtains a hardness in excess of 52 HRC.

According to a third aspect of the present disclosure there is provided a method of refurbishing a cable drum, the method comprising:

adding a martensitic steel to at least one worn area of the cable drum by a metal deposition process, while the cable drum is maintained at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel;

machining at least some of the added martensitic steel to obtain a desired shape of the cable drum, while maintaining the temperature of the added martensitic steel at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel; and

cooling the cable drum to below the martensitic finish temperature of the martensitic steel so that at least some of the added martensitic steel increases in hardness. In an embodiment the step of cooling the cable drum so that at least some of the added metal increases in hardness comprises cooling the cable drum so that at least some of the added metal obtains a hardness in excess of 40 HRC.

In an embodiment the martensitic steel is a 400 series martensitic steel.

In an embodiment some martensitic steel may be added to at least one worn area of the cable drum and allowed to cool to below the martensitic finish temperature, for example approximately to ambient (eg room) temperature, so that the martensitic steel attains an 'as welded' hardness. This can include the drum cooling to a temperature below the martensitic finish temperature of the martensitic steel. The drum is then heated to a temperature above the martensitic finish temperature of the martensitic steel, and additional martensitic steel is then added. Machining of the additional martensitic steel to obtain a desired shape of the cable drum, while maintaining the temperature of the additional martensitic steel at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel, is then performed. Such a process should be considered to be within the scope of the present disclosure. That is, in relation to the present disclosure, the step of machining added metal to obtain a desired shape of the component, while maintaining the temperature of the added metal in excess of a specified temperature should be taken to require that added metal which is being machined is maintained above the specified temperature, and not that all added metal is maintained above that temperature.

It will be appreciated that features and/or steps set out in relation to the one of the above aspects may be applicable to one or more of the other aspects recited above. According to a fourth aspect of the present disclosure there is provided a method for providing a hardened surface on a heavy machinery component, the method comprising:

heating the component to a preheat temperature sufficient to allow effective addition of metal thereto by a metal deposition process;

adding metal to one or more surface areas of the component by a metal deposition process,

machining the added metal to obtain a desired shape of the component, while maintaining the temperature of the added metal in excess of a critical temperature at which the added metal hardens; and

cooling the component so that at least some of the added metal hardens to provide a hardened surface.

Provision of the hardened surface may be as part of a refurbishment process. In this case the method may comprise a method of refurbishing a heavy machinery component.

Provision of the hardened surface may be as part of a manufacturing process. In this case the method may comprise a method of manufacturing a heavy machinery component.

The heavy machinery component may be (but is not limited to) one of: a rope/cable drum for mining machinery; a cable/rope sheave; a crawler shoe; a track pad; a roller, which may be a load roller; a steel plate; a shaft or pin for machinery; a drive and/or idler sprocket; a ground engaging tool.

According to a fifth aspect of the present disclosure there is provided a method for providing a hardened surface on a heavy machinery component, the method comprising:

heating the component to a temperature in excess of 150 degrees centigrade;

adding metal to at least one area of the component by a metal deposition process; machining the added metal to obtain a desired shape of at least part of the component surface, while maintaining the temperature of the added metal in excess of 100 degrees centigrade; and

cooling the component so that at least some of the added metal obtains a hardness in excess of 40 HRC to provide a hardened surface. Provision of the hardened surface may be as part of a refurbishment process. In this case the method may comprise a method of refurbishing a heavy machinery component.

In an embodiment machining the added metal to obtain a desired shape of at least part of the component surface, comprises machining the added metal while maintaining the temperature of the added metal in excess of 150 degrees centigrade.

In an embodiment machining the added metal may comprise machining at least one generally concave surface portion. In an embodiment the component may be a component for heavy mining machinery, such as (but not necessarily limited to) a dragline. The heavy machinery component may be a rope/cable drum. The heavy machinery component may be a rope/cable sheave. The heavy machinery component may be an undercarriage component. The heavy machinery component may be a crawler shoe. The heavy machinery component may be a track pad.

The heavy machinery component may be a roller, which may be a load roller and /or which may be a roller for use in the undercarriage of a machine.

The heavy machinery component may be a toothed gear component, which may be a drive and/or idler sprocket.

The hardened surface may be provided on one or more teeth of the toothed gear component. The heavy machinery component may be a ground engaging tool.

In an embodiment the component may be a component for mining machinery, such as (but not necessarily limited to), a dragline. In an embodiment the component may be a component for excavating machinery.

The heavy machinery component may be (but is not limited to) one of: a roller, which may be a load roller; and a steel plate.

According to a sixth aspect of the present disclosure there is provided a method for providing a hardened surface on a heavy machinery component, the method comprising:

adding a martensitic steel to at least one area of the component by a metal deposition process, while the component is maintained at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel,

machining the added metal to obtain a desired shape of the hardened surface, while maintaining the temperature of the added metal at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel; and

cooling the item to below the martensitic finish temperature of the martensitic steel so that at least some of the added metal increases in hardness to provide a hardened surface.

In an embodiment the step of cooling the cable drum so that at least some of the added metal increases in hardness comprises cooling the cable drum so that at least some of the added metal obtains a hardness in excess of 40 HRC.

In an embodiment the step of cooling the cable drum so that at least some of the added metal increases in hardness comprises cooling the cable drum so that at least some of the added metal obtains a hardness in excess of 48 HRC. Provision of the hardened surface may be as part of a refurbishment process. In this case the method may comprise a method of refurbishing a heavy machinery component.

In an embodiment the heavy machinery component has a mass in excess of 100kg. In an embodiment the heavy machinery component has a mass in excess of one tonne.

In an embodiment the heavy machinery component has a mass in excess of ten tonnes.

It will be appreciated that, without limiting the scope of any of the aspects set out herein, characteristics, features and/or steps set out in relation to any one or more of the fourth, fifth, or sixth aspects may be applicable to any other of the fourth, fifth, or sixth aspects.

In embodiments of methods according to various aspects the methods comprise providing a thicker layer of hardened metal at one or more regions where it is anticipated that there will be greater wear, and a less thick layer of hardened metal at one or more regions where it is anticipated that there will be lesser wear.

This may be achieved by providing an underlying surface shape, upon which added metal is deposited, which requires a greater thickness of hardened metal thereon at one or more regions where it is anticipated that there will be greater wear, and a lesser thickness of hardened metal thereon at one or more regions where it is anticipated that there will be less wear, in order to provide a desired final surface shape. According to a seventh aspect of the present disclosure there is provided a method for providing a hardened surface on a metal item, the method comprising:

adding metal to at least one area of the item by a metal deposition process;

machining at least some of the added metal to obtain a desired shape of surface, while maintaining the temperature of the added metal at a temperature in excess of a critical temperature at which the added metal hardens; and

cooling the item to a temperature below the critical temperature so that at least some of the added metal increases in hardness to provide a hardened surface.

In an embodiment the adding of metal to at least one area of the item by a metal deposition process is performed while the object is maintained at a preheat temperature, the preheat temperature being sufficient to allow effective addition of metal thereto by the metal deposition process.

In an embodiment the adding of metal to at least one area of the item by a metal deposition process comprises adding a martensitic steel.

In an embodiment the preheat temperature is above a martensitic finish temperature of the martensitic steel. In an embodiment the preheat temperature is in excess of 150 degrees centigrade.

In an embodiment the preheat temperature is below a martensitic start temperature of the martensitic steel. In an embodiment the critical temperature at which the metal hardens is a martensitic finish temperature of the martensitic steel. In an embodiment maintaining the temperature of the added metal at a temperature in excess of a critical temperature at which the added metal hardens comprises maintaining the temperature of the added metal at a temperature in excess of a martensitic finish temperature of the martensitic steel and below a martensitic start temperature of the martensitic steel.

In an embodiment cooling the item to a temperature below the critical temperature so that at least some of the added metal increases in hardness to provide a hardened surface comprises cooling the item to a temperature below the martensitic finish temperature of the martensitic steel so that the metal increases in hardness by virtue of martensitic transitions therein.

In an embodiment maintaining the temperature of the added metal at a temperature in excess of a critical temperature at which the added metal hardens comprises maintaining the temperature of the added metal at a temperature in excess of 150 degrees centigrade.

In an embodiment the method comprises providing a hardened surface on a metal item which has previously been worn by use in order to refurbish the metal item.

In an embodiment adding metal to at least one area of the item by a metal deposition process comprises adding metal to at least one worn area of the item.

In an embodiment the metal item is a heavy machinery component.

In an embodiment the metal item is a cable drum.

In an embodiment adding metal to at least one area of the item by a metal deposition process comprises adding metal to at least one worn area of the cable drum by a metal deposition process.

In an embodiment adding metal to at least one area of the item by a metal deposition process comprises adding martensitic steel to at least one worn area of the cable drum by a metal deposition process.

It will be appreciated that, without limiting the scope of any of the aspects set out herein, characteristics, features and/or steps set out in relation to the first, second and/or third aspects may be applicable to any one or more of the fourth to seventh aspects recited above. In this case, recitation of characteristics, features and/or steps relating to a cable drum in statements made in relation to the first to third aspects should, or may, be considered as being more generally applicable to the heavy machinery component when considered in relation to the fourth, fifth, or sixth aspects or to the metal item as set out in the seventh aspect, as logic or context dictate.

Similarly, it will be appreciated that, without limiting the scope of any of the aspects set out herein, characteristics, features and/or steps set out in relation to the fourth, fifth, or sixth aspects may be applicable to the seventh aspect recited above. In this case, recitation of characteristics, features and/or steps relating to a heavy machinery component in statements made in relation to the fourth, fifth, or sixth aspects should, or may, be considered as being more generally applicable to the metal item when considered in relation to the seventh aspect, as logic or context dictate. As stated above, deposited (eg weld) metal may be deposited in a number of thicknesses. It will be appreciated each respectively more outer layer can be expected to be less affected by dilution from constituents of the underlying base metal (eg carbon steel), so that the more inner layers may, in use, conform less closely to the desired chemistry and characteristics of the deposited metal. References to the martensitic start and/or martensitic finish temperature of the deposited metal should be taken as referring to the martensitic start and/or martensitic finish temperature of the metal ignoring dilution effects, and/or to the metal of machined surface.

According to an eighth aspect of the present disclosure there is provided apparatus for providing a hardened surface on a metal item comprising:

a computerised controller;

at least one welding head;

at least one machining head, controllable by the computerised controller;

the at least one welding head and the at least one machining head being arranged to be able to simultaneously operate on said metal item.

In an embodiment the computerised controller comprises a CNC controller. In an embodiment the apparatus is for refurbishing a metal item.

In an embodiment the metal item is a heavy machinery component. In an embodiment the apparatus is for refurbishing a heavy machinery component.

In an embodiment the at least one welding head is controllable by the CNC controller. In an embodiment the at least one welding head is controllable by a power source of the at least one welding head.

In an embodiment the apparatus further comprises at least one heating apparatus arranged to maintain said metal item at a temperature in excess of 150 degrees while the at least one welding head and the at least one machining head simultaneously operate on said metal item.

In an embodiment the CNC controller is adapted to control at least one machining head to gauge regions of the metal item where insufficient metal has been added by the at least one head, and to control one or more of said welding heads to rectify the insufficiency.

In an embodiment the apparatus further comprises a motorised mechanism for rotating the metal item during refurbishing of the metal item.

In an embodiment the apparatus is adapted to operate on a cable drum.

In an embodiment the apparatus is adapted to operate on a cable drum while the cable drum is in situ in a machine in which the cable drum has suffered wear.

In an embodiment the apparatus is adapted to operate on a cable drum while the cable is rotated using at least part of a gear train of said machine, which gear train or part thereof is used to rotate the drum during normal operation of the machine. According to a further aspect there is provided a metal item manufactured or refurbished by a method in accordance with any one or more of the first to seventh aspects.

According to a further aspect there is provided heavy machinery component manufactured or refurbished by a method in accordance with any one or more of the first to seventh aspects. Brief Description of the Drawings

Embodiments will now be described, by way of example only, with reference to the accompany drawings, in which:

Fig. 1 is a schematic block diagram illustrating a known method of refurbishing a dragline cable drum;

Fig. 2 is a schematic block diagram illustrating a method of refurbishing a dragline cable drum in accordance with the present disclosure;

Fig. 3 is a schematic perspective view of apparatus in accordance with an aspect of the present disclosure; Fig. 4 is a schematic plan view of the apparatus of FIG. 3;

Fig. 5 is a cross section on A-A of Fig. 4;

Fig. 6 is an enlarged view of part of Fig. 5;

Fig.s 7(a) to 7(d) are schematic cross sectional views illustrating sequential stages in the manufacture of an article;

Fig. 8 is a schematic perspective view illustrating a stage in the manufacture of the article of Fig. 7;

Fig. 9 is a schematic perspective view illustrating a stage in the manufacture of a different article; and Fig. 10 illustrates schematically, a vertical axial cross sectional view of part of a cable drum which is manufactured by a method in accordance with the present disclosure.

Detailed Description With reference to Fig.s 1 to 6, a method of refurbishing a dragline cable drum, in accordance with the present disclosure, will be described. In order to properly describe the method in accordance with the present disclosure, it is considered useful to describe a previous method which has been used, by way of comparison. It is known that dragline cable drums suffer considerable wear due to use of robust metal cables, and high loads. Recently attempts have been made to refurbish such drums. One previously used refurbishment method is illustrated by Fig. 1. However, prior to detailed description of Fig. 1, an overview of the previously used refurbishment method will be provided.

In order to refurbish the surface of the drum onto which a cable can be wound, this surface is 'built up' by addition of a suitable metal. Cable drums normally wear more severely in their axially central regions, and less at the end regions of their, normally generally cylindrical, cable engaging parts. A drum which requires refurbishment may have suffered wear of approximately 5mm to 20mm depth at its axially central region (so that the diameter in that region is reduced by approximately 1 to 40mm) but only 1mm to 5mm depth at the end regions of its cable engaging part. Since toughness of the surface after refurbishment is important, the metal must be added and treated in a manner that adequately integrates the added metal with the rest of the dragline cable drum. When a typical dragline cable drum is newly manufactured, at least the hard outer surface, which forms a cable engaging surface onto which a cable can be wound, is formed from carbon steel, which in some a typical dragline cable drum may have a carbon content approximately 0.5 percent carbon. Such a carbon content can provide a steel composition which, when formed by known forging and metalworking processes, can be hardened to an adequate degree (by suitable treatment, such as flame hardening) and which has adequate toughness (ie it is not impracticably brittle).

In contrast, metal deposited onto the drum as part of the drum refurbishment method is added to the drum by an arc welding process. The deposited weld metal must be adequately hard and adequately robust (ie not unduly brittle) after refurbishment of the drum. Carbon steel of the type used for initial manufacture of the drum, eg with a carbon content of around 0.5 per cent, is rendered brittle if deposited by arc welding. That is, such welded carbon steel is considered to be too brittle for use in forming, the cable engaging part of a cable drum. An alternative metal is therefore used.

Steel with a high chromium content (eg with approximately 0.15 to 0.35 percent carbon and approximately 10 to 18 per cent chromium) has been found to have both suitable hardness and suitable toughness if processed appropriately during and after welding.

Welding wires formed from AISI series 400 steels conform to this overall composition, and have been found suitable for deposition by arc welding to provide an outer surface of a dragline cable drum.

The added metal is typically induction hardened in order to provide the required hardness. The induction hardening comprises hardening the weld metal by heating using an induction heating process, and then quenching, so that the cooled added metal has the required hardness.

In the known cable drum refurbishment method, such induction hardening of the cable engagement regions is performed after cable engaging grooves are machined in the added weld metal. It will be appreciated that in a dragline cable drum the cable engagement regions provide helical cable guiding grooves and (due, to the

considerable hardness required of the cable engagement regions, and the large size of the drums and the region to be machined) it is not practicable to form the grooves in hardened metal. It is also well understood by those skilled in the art that after deposition by arc welding the added weld metal is stress relieved, for example by heating to a suitable temperature, for a suitable period of time. Air cooled, recently deposited weld metal (for example 400 series steel) may have high hardness, making machining

impracticable. Thus, in the known cable drum refurbishment method the heating process used to stress relieve the deposited weld metal is also used to reduce the hardness of the weld metal so that it can be machined to form the cable guiding grooves. Thus the added weld metal is heat treated to relieve stresses and so that it can be machined, is machined so that the cylindrical grooved cable engagement regions are formed, and subsequently induction hardened to provide an induction hardened outer layer approximately 4mm to 6mm thick.

With reference to Fig. 1 , in the known cable drum refurbishment method, the dragline cable drum is removed from the dragline, block 5. The dragline cable drum is then transported to a specialised refurbishment facility, block 10.

At the refurbishment facility the drum is heated in a large oven, block 15, to a temperature in excess of 600 degrees Centigrade in order to remove residual hardness from the cable engagement regions to allow machining of these regions prior to applying the weld build up layer. Such machining is necessary because a finish machined layer of added weld metal at least 5mm to 6mm thick is to be added, and regions which have not worn by as much as 5mm to 6mm must be machined to allow for addition of the weld metal. It is necessary to add a layer of weld metal at least 5mm to 6mm thick because an induction hardened layer of that depth is required in the refurbished drum, and the metal characteristics are adversely affected if the induction hardening is applied to, and affects, both the added high chromium steel and the carbon steel of the drum as originally manufactured. Thus in order to allow induction hardening to a depth of 5mm to 6mm, without simultaneously trying to induction harden both high chromium steel and the original carbon steel in the same region, a layer of high chromium steel at least 5mm to 6mm thick must be provided and accommodated.

The drum is allowed to cool, block 20, and the cable engagement region(s) are then machined as required, block 25, to allow addition of the high chromium weld metal.

The drum is then taken to a welding station where it is heated, block 30, to a temperature in excess of 150 degrees centigrade, and normally about 250 degrees centigrade, in order to allow weld metal to be laid down on the worn cable engagement region(s) by a welding process. If the drum is not heated the weld metal cannot be effectively laid down on the drum. Such preheating to facilitate weld deposition of metal is known per se and will be understood by the skilled addressee. Heating may be achieved by use of gas burners which heat the interior of the drum and, thereby, the entire drum. The gas burners are then used to maintain the drum at the desired temperature for as long as is required.

Laying of the weld metal onto the drum, block 35, may be performed by using one or more CNC controlled welding heads which may lay down in the region of 7kg of weld metal per hour while the drum is rotated in order to allow the weld metal to be laid down about the circumference of the generally cylindrical cable engagement region.

The weld metal is deposited by arc welding. The added weld metal may be a series 400 martensitic steel, which provides a hardness in excess of 40 to 55 HRC when it cools to room temperature (provided the conditions for adequate martensite formation are met). As mentioned above, high chromium steel has been found to be a suitable metal. It may take many hours or days to add the required amount of weld metal, as at least several hundred kilograms of added weld metal may be required. After sufficient weld metal is added, the drum is to be machined so that cable guiding grooves can be reformed onto the cable engagement region(s). The weld reclaimed drum is therefore allowed to cool, block 40, so that it can be removed from the welding station.

Upon cooling the added weld metal may have a hardness in excess of 45 HRC. In order to allow the weld metal to be machined its hardness must be reduced. This is achieved by heating the drum, block 45, typically in the large oven mentioned above, to a temperature in excess of 600 degrees Centigrade. As mentioned above this also effects stress relieving of the recently added weld metal. The drum is then allowed to cool, block 50. The cable engaging regions of the cooled drum are then suitable for machining, since the heating (and cooling) reduces the hardness of the weld metal.

Since it takes hours or days to heat the drum to a temperature suitable for adding weld metal (or for stress relieving and hardness reduction), or to allow the drum to cool to close to ambient temperature, in order to avoid unnecessarily prolonging the refurbishment process it is important to avoid unnecessary repetition of this heating and/or cooling. It is thus important to ensure that sufficient weld metal is added before the drum is allowed to cool, and it is therefore preferable to add an excess of weld metal rather than risk adding an insufficient amount of weld metal.

After the heating of the drum, block 45, for stress relieving and hardness reduction, and subsequent cooling, block 50, the drum is then moved to a machining station and machined, block 55, to provide the desired cable guide grooves. This can practicably be achieved using CNC controlled machining tools to provide one or more helical grooves, as desired, on the cable engagement region(s).

When the drum is formed as desired, the surface of the cable engagement region is hardened, block 60, by heating and quenching successive small regions of the cable engagement region to a temperature in excess of 900 degrees Centigrade. It has been found that an effective way to achieve this is to use suitable induction heating apparatus, as foreshadowed above. This can typically provide a hardened layer of 4 to 6mm. The drum is then allowed to cool. The dragline cable drum is then transported back to the dragline, block 65, and reinstalled, block 70. An example of the time taken for the refurbishment process illustrated in Fig. 1 , excluding removal from the dragline, transportation and re-installation in the dragline, is set out in the followin table Table 1 .

This previously used method thus requires around four to five weeks to perform the specified steps in refurbishment of the cable engaging regions of the drum.

It will be appreciated that the above times are provided by way of comparison with an embodiment of a method in accordance with the present disclosure, as will be described hereafter. Thus the times stated in Table 1 may be approximate, and Table 1 may omit some of the steps and processes typically required for drum refurbishment, for example: transport and loading times, time required to disassemble a two-part drum, time required to clean and inspect the drum and effect any required structural repairs (eg of cracks), time required to refurbish parts of the drum other than the cable engaging parts (eg the drum spigots), time required to reassemble a two-part drum and time taken to finish (eg sand blast and paint) the drum.

This four to five week process provides a hardened metal layer on the cable engagement region(s) about 4-6mm thick, which might provide several months or years use before further refurbishment or replacement of the dragline drum is required. This has been found to represent a substantial cost saving over merely replacing the worn cable drum with a new drum, and has helped to mitigate problems and delays in sourcing new dragline drums. However, as will be described below, the present disclosure provides a method which has advantages over the method described above. Although the method described with reference to Fig. 1 is described as known, nothing in this specification should be taken as a statement that such a method is common general knowledge, in Australia or in any other country.

With reference to Figure 2 an example of a method in accordance with the present disclosure will be described. The method has some similarities with the method illustrated in Fig. 1 , and the description below thus focuses on the differences.

The dragline cable drum is removed from the dragline, block 110, and transported to the refurbishment facility, block 120.

The dragline cable drum is then taken to a welding station where it is heated, block 130, to a temperature in excess of 150 degrees centigrade, and normally about 200 to 300 degrees centigrade, in order to allow weld metal to be laid down on the worn cable engagement region(s) by a welding process. Heating may be achieved by any suitable means. For example heating may be achieved by use of gas burners or gas or electric infrared radiation heaters placed inside, and/or around the outside of, the drum. The gas burners or gas or electric infrared radiation heaters are then used to maintain the drum at the desired temperature for as long as is required.

The above steps, represented by blocks 110, 120 and 130 may be similar or identical to the steps 5, 10 and 30 in the previous, known method. However, it will be noted that the steps of initially heating the drum in order to remove residual hardness, block 15, cooling the drum, block 20, and machining to allow addition of weld metal, block 25, are not used in this embodiment, for reasons which will be explained in due course.

A further notable difference to the method of Fig. 1 is that the following steps are performed so that the drum is kept above 150 degrees Centigrade, and preferably between approximately 180 and 250 degrees Centigrade (in this example, although this temperature may vary), from the beginning of laying down the weld metal, through to the end of the machining process which occurs prior to hardening of the drum outer surface. This has been found to be a practicable way of machining the drum, and to prevent the weld metal attaining a high degree of hardness prior to machining. This process therefore eliminates the need to subsequently heat the laid down weld metal (in a step corresponding to block 45) in order to soften it for machining. Laying of the weld metal onto the drum, block 135, is performed using one or more CNC controlled welding heads while the drum is rotated. However, unlike the previously known method, the step of machining the grooves is provided without allowing the drum to cool after the welding process. (It will be appreciated that although embodiments are described with reference to adding or laying metal by use of a welding process, other forms of metal deposition may be practicable, without falling outside the scope of the present disclosure, and if such other methods are used the 'weld metal' referred to herein for convenience, could be substituted, as appropriate, by metal added by any such alternative practicable method.)

In one embodiment the weld metal may be laid down on the drum and after it has been determined that sufficient weld metal has been added, machining is performed, but without allowing the weld metal to cool to a temperature at which it attains high hardness. That is, in such an embodiment, the weld is laid down while the drum is maintained at approximately 180 to 250 degrees Centigrade, and then the welding ceases, and machining is performed with the temperature of the drum maintained at approximately 180 to 250 degrees Centigrade.

However, rather than performing the method as set out in the above paragraph, it is currently preferred that machining process, block 140, begins while weld metal is still being laid down. The machining heads are placed sufficiently far from the welding heads that the temperature of the metal being machined is substantially the same as the mean temperature of the cable engaging region of the drum (ie substantially cooler than the temperature of the weld metal as it is being laid down). The machining of the cable engagement region(s), to provide the desired cable guide grooves, is preferably performed using, an automatically controlled, preferably CNC (computed numerical control) controlled machining tools to provide helical grooves, as desired, on the cable engagement region(s). The CNC system is programmed to provide the desired groove shape and configuration. Furthermore, the CNC controlled machining head(s) can gauge the amount of weld metal required in worn areas of the cable guiding grooves as well as identifying any positions where there is less weld metal than is desired. Since the CNC system also controls the welding head(s), and the drum temperature allows continued and/or additional laying down of weld metal during the machining stage, this allows any insufficiency in the amount of weld metal at any particular position to be rectified without difficulty during the combined welding/machining process. This allows enhanced control of the amount of weld metal applied, and reduces the need to apply an excess amount of weld metal as a precaution against applying insufficient weld metal. This in turn reduces the amount of machining required. The gauging between the machining head(s) and the welding head(s), via the CNC system is illustrated schematically in Fig. 2 by block 145. After sufficient weld metal has been added to the drum and machined to provide a cable engaging region, and cable guiding grooves, of the desired shape, the welding and machining cease. The drum is then allowed to cool, block 150, which results in hardening of the weld metal. The drum can then be transported back to the dragline, block 55 and reinstalled, block 160.

It is important to appreciate that keeping the weld metal at about 200 to 250 degrees Centigrade (a temperature which will of course vary depending upon the metal/alloy used as the weld metal, and which in the broad context of broad aspects of the present disclosure is a temperature above a critical temperature at which the metal hardens) allows effective machining at that temperature, and also effectively halts the hardening process of the weld metal, but does not prevent the hardening process resuming to an extent that allows adequate hardness to be achieved when the temperature of the weld metal is allowed to fall to room-temperature levels. (In an embodiment the weld metal is a martensitic steel, and is maintained above the martensitic finish temperature during machining, as will be explained in more detail in due course.) This fact is utilised to considerable advantage in the above described method. Further, it has been discerned that because the hardening of the (machined) high chromium steel weld metal occurs upon normal or controlled cooling, the characteristics of the drum surface are not unduly adversely affected by having only a thin layer (eg 2mm) of the high chromium steel overlying the original carbon steel, at the end, or less worn, regions of the drum. Thus if an end (or other) region of the cable engaging region of the drum has suffered only little (eg 1mm or 2mm) wear, that region can be refurbished by applying a thinner layer of high chromium steel weld metal over the original carbon steel, rather than requiring machining back of the original carbon steel and application of much more weld metal to allow induction hardening without adversely affecting the characteristics of the drum or the hardening process.

Further, it will be appreciated that when the drum has cooled, substantially all of the weld metal applied during the refurbishment that remains on the drum will have attained a hardened form. This can result in a layer of hardened metal, in the parts of the cable engaging regions which had been most severely worn, of approximately 5mm to 20mm thick. This can greatly exceed the thickness of the hardened layer which would have been obtained by induction hardening, which in turn can potentially extend the working life of the drum, before replacement or further refurbishment becomes necessary, by a corresponding factor. Furthermore, it will be appreciated that the areas which have suffered most wear in use (normally the cable grooves or cable groove parts towards the centre of the drum) require more metal to be added in order to bring the surface back to its original shape. This means that in the finished refurbished drum the parts of the drum which have suffered most wear, and which are likely to suffer most wear in the future when the drum is put back into service, will be provided with a thicker layer of hardened metal than parts of the drum which have suffered less wear, and which are likely suffer less wear in the future. Thus a substantially increased working life (before replacement or further refurbishment becomes necessary) can be provided without the expense of providing an

unnecessarily thick hardened layer in areas where such a thick layer is not useful. Typically the grooves towards the axial centre of the drum will suffer more wear than the grooves towards the axial ends of the drum.

An example of the time taken for the refurbishment process illustrated in Fig. 2, excluding transportation and installation times, is set out in the following table (Table 2).

The steps and times set out in Table 2 are presented by way of approximate comparison with the steps and times set out in Table 1. As in Table 1 , the steps and times set out in Table 2 are intended to be illustrative and indicative, not all steps that might be required are presented. For example, setting up the drum at the workstation may take approximately two days. Further, some pre-machining may be required to remove roping or other wear related defects prior to weld reclamation. However, such pre-machining will usually be required in areas of deeper wear where no residual harness exists, so the step of initial heating to remove residual hardness will typically not be required. Thus in contrast to the method illustrated in Fig. 1 the method illustrated in Fig. 2 requires some two to three weeks less time to effect refurbishment. Further, the method illustrated in Fig. 2 provides a hardened metal layer on the cable engagement region(s) of up to about 5 to 20 mm thickness.

It will be appreciated that if the drum is refurbished in situ (which is facilitated by the method disclosed herein, as will be described in due course) a considerably great time saving can be achieved. In an embodiment, the metal added to build up the worn areas is a martensitic steel. In a particular embodiment the weld metal used is a 400 series martensitic steel. A steel with a composition of approximately 0.15 to 0.35 per cent carbon, approximately 12 to 17 per cent chromium, and approximately 1 per cent molybdenum has been successfully trialled. A welding consumable known as chromecore 420 has been found suitable for use (although this does not preclude the use of other steels).

Broadly speaking, suitable martensitic steels, including the series 400 martensitic steels, rely on formation of martensite during cooling to attain high hardness. A martensitic steel has a martensitic start temperature, Tms, below which martensite formation begins, and a martensitic finish temperature Tmf, at which martensite formation due to cooling ceases. The Tmf of suitable steels is normally between about 150 and about 250 degrees Centigrade below the Tms.

It is thought that martensite formation only occurs when the steel cools rapidly from a high temperature (such as the arc welding deposition temperature, or the liquidus temperature, of the steel), to below the martensitic start temperature. In particular, rapid cooling from deposition (liquidus) temperature to the preheat temperature (below Tms) allows martensitic transformation in a manner that tempering (eg to 450-600 or so deg C) and then allowing to cool would not. Thus the preheat temperature (ie the temperature to which the drum is heated to facilitate addition of the weld metal (and at which the cable engaging regions of the drum are machined) should be below the martensitic start temperature Tms, so as not to inhibit martensite formation.

It is believed that the weld metal can be machined at the temperatures used because the weld metal is kept above the martensitic finish temperature Tmf, so that continued martensite formation, and consequent hardening of the weld metal to a hardness which makes machining impracticable, is postponed. When machining is complete, and the drum is allowed to cool down to and below the martensitic finish temperature Tmf, martensite formation resumes and is effectively completed. This results in hardening of the weld metal. The martensitic start temperature Tms, and martensitic finish temperature Tmf, vary according to the composition of the metal concerned, and various theoretical and empirical determinations could be used in order to assist in implementing the methods disclosed herein. Tms is considered to be reduced by increased levels of carbon, chromium, nickel, molybdenum, etc.

One study has suggested that for some types of martensitic steel Tms can be determined by the formula

Tms (deg C) = 540 - (497 x %C + 6.3 x %Mn + 36.3 x %Ni + 10.8 x %Cr + 46.6 x % o)

This formula is presented by way of example only, and it is likely that this formula is not applicable to at least some 400 series martensitic steels. A different study has calculated that for a specific formulation of 420 steel Tms is 284 degrees Centigrade (although it will be appreciated that 420 steel can have various compositions, and correspondingly different Tms).

It will be appreciated that the temperatures which can practicably be used will vary according to the characteristics of the metal added, and in particular the Tms and Tmf.

Although a preheat temperature of 200 to 300 degrees Centigrade, and a maintained (machining) temperature of not less than 150 or 180 degrees Centigrade has been found appropriate, preheat and/or machining temperatures as low as 90 degrees centigrade could be feasible for some suitable steels, and should be considered within the scope of the present disclosure.

Further, it should be noted that the present disclosure, and in particular the potential to eliminate cooling of the weld metal and subsequent reheating for stress relieving (with consequent reduction in hardness, and requirement for an additional hardening process), takes advantage of the inventor discerning that stress relieving of the deposited metal may not be required when a relatively thin layer of weld metal is applied to a robust substrate, such as a component of heavy machinery. Fig s 3 to 6 illustrate an embodiment of apparatus, in accordance with an aspect of the present disclosure, for refurbishing a dragline cable drum, and which can be utilized in performing the refurbishment method described above.

The apparatus, generally designated 200, comprises a welding head 210 controllable by a CNC system 220. The welding head is adapted to lay down weld metal on a drum 240 to be refurbished. The CNC system 220 also controls a machining tool 230 which is adapted to machine a cable engaging region 245 of the drum 240 at a temperature of approximately 250° centigrade. The welding head 210 and machining tool 230 are provided on a support frame 211 , which can be moved relative to the drum 240 on axial rails 212, the movement on the axial rails 212, in the axial direction of the drum, being controlled by the CNC system 220. The machining tool 230 is supported relative to the support frame 211 by axial machining tool rails 213 (to allow movement of the machining tool relative to the support frame 211 in the axial direction of the drum) and by transverse machining tool rails 214 (to allow movement of the machining tool relative to the support frame 211 in the transverse direction of the drum).

In an embodiment the weld metal deposited by the welding head 210 is a steel alloy with a carbon percentage in the region of 0.15 - 0.35 % and a chromium percentage in the region of 10 - 18%. In an embodiment the weld metal is a martensitic steel. In an embodiment the weld metal is a series 400 martensitic steel. In an embodiment the weld metal is a series 420 martensitic steel. A steel having a carbon percentage of approximately 0.28% and a chromium percentage of approximately 13.1% has been found to provide good results. Further, a steel comprising approximately 0.28% C, approximately 13.1% Cr approximately 0.787% Si, approximately 0.551% Mn, approximately 0.032% P, approximately 0.006% S, approximately 0.582% Ni, with the balance being Fe, has been used effectively and has provided a final outer surface hardness of between 52 and 55 HRC in methods according to the present disclosure.

In an embodiment, in which the weld metal is a martensitic steel, the temperature at which machining occurs is lower than the martensitic start temperature and higher than the martensitic finish temperature. The temperature of the drum 240 may be controlled in any suitable manner (for example, by provision of burners within a central cavity) but in the illustrated embodiment is controlled by one or more radiating heaters 248 (Fig. 5) which can be provided on a generally opposite side of the drum to the welding head 210 and machining tool 230. The ends of the drum may be closed off and insulated to minimize heat loss. The apparatus for performing the refurbishment methods described above further comprises a mechanism for rotating the drum during welding and machining. Such a mechanism may comprise first and second and disks (not shown) adapted to fit within the ends of the drum and to thereby support the drum 240 and allow it to be rotated by a suitable driving arrangement, for example a suitably powerful electric motor (not shown). The mechanism for rotating the drum is also controlled by the CNC system, or least provides input to the CNC system, in order to allow welding and machining of the drum to be coordinated with the rotation of the drum. Electrically powered

mechanisms for rotating dragline drums are known per se, and will not be described herein in detail.

Although the method of refurbishing a dragline cable drum is described above with reference to refurbishment taking place in a dedicated facility, the method disclosed herein can also be utilized in order to refurbish a cable drum in situ. That is, not least because the method may be performed without heating the drum to temperatures greater than approximately 250 degrees centigrade, the entire operation may take place in the dragline. In an embodiment in which the drum 240 is being refurbished in situ in a dragline, the motor may be in the form of a pony drive (not shown), controlled by the CNC system, which may drive the drum via a gear train which is part of the dragline, and which is used to rotate the drum during operation of the dragline.

In order to perform such refurbishment in situ, the cable rope and any related accessories are removed from the vicinity of the dragline cable drum and of course any materials which might be damaged by the temperatures which are to be used should be removed and/or protected. The refurbishment apparatus, comprising one or more welding heads, one or more machining heads and a CNC system, is positioned suitably for operation adjacent the drum. In one desirable implementation, the drum can be brought up to a temperature of approximately 200° to 250° Centigrade and the weld metal can be added without substantial prior machining, and the machining of the weld metal can be performed prior to cooling of the weld metal to a temperature below approximately 200" centigrade.

It will be appreciated that this can allow an extremely high quality refurbishment, as described above, to be performed expeditiously, in situ. As described above, in order to heat the drum to a temperature of 200° to 250° Centigrade when the refurbishment is being performed in a suitable refurbishment facility, gas burners may be provided inside the drum. Provision of gas burners inside the drum is typically not practicable in the dragline due to the manner in which the drum is integrated into the dragline. It has been found that a cable drum can be heated to, and maintained at, a suitable temperature (such as, for example, approximately 250° centigrade) using gas or electric infrared radiation heaters. Thus when refurbishment is taking place inside the dragline, suitably positioned gas or electrically powered infrared heaters can be used in order to heat the drum and maintain it at a desired temperature. Suitable infrared heaters are known per se and commercially available. The power requirement for a heater or bank of such heaters will vary depending on the mass of metal to be heated, ambient temperature, and other factors which contribute to heat loss from, or heat retention in, the drum.

Electrical power sources of suitable output are typically readily available in a dragline environment. During the refurbishment process the drum can be rotated by connecting a ponydrive unit to a gear train (or other mechanism) which normally rotates the drum during dragline operation, with appropriate communication and/or feedback into the CNC system.

It will be appreciated that while the above description is provided with reference to refurbishing a dragline cable drum, the teachings of the present disclosure can be applied to refurbishment of other items, such as components of heavy machinery. For example, rope sheaves such as those used in draglines could be refurbished by a corresponding method, as could other items which have high surface hardness as a desirable characteristic. Further examples of items which could beneficially be refurbished by the disclosed method include: rollers, which may, for example be load rollers or steel industry rolling mill rollers; tread pads; track pads; crawler shoes;

undercarriage components, for example those for mining and/or excavating machinetry; steel plates; shafts or pins for machinery; sprockets such as drive and/or idler sprockets; ground engaging tools; and numerous other items.

Further, the principles disclosed herein can be used for manufacture (rather than refurbishment) of items, including components for heavy machinery. It will be appreciated that manufacturing processes and methods will have similarities to refurbishment processes and methods, and may for example be applicable to at least the same items.

By way of example, Fig.s 7(a) to 7(d) illustrate schematically manufacture of a roller which is required to have a smooth hardened steel cylindrical outer surface, in accordance with the present disclosure.

It will be appreciated that the example of manufacture of a roller having a smooth cylindrical surface is provided by way of example only and that the described method of manufacturing an item is applicable to many other items, including but not limited to components for draglines and other mining and/or excavating machines. For example, cable drums, rope/cable sheaves and other items mentioned above as being potentially refurbished by methods disclosed herein. It will be appreciated that whether in relation to refurbishment or manufacture, the present disclosure provides methods well-suited to finished items that have shaped surfaces, such as concave surface portions, since machining (including relatively delicate machining) is facilitated compared to machining of hardened metal. In cable drums and rope sheaves, for example, sufaces having concave surface portions are used to accommodate ropes/cables. In some other items, for example track pads with apertures for receipt of fixing pins, circular cross section, concave surfaces, such as the surface defining the interior of a generally cylindrical aperture, may be provided. Further, in toothed gears or sprockets gaps between adjacent teeth may be regard as concave portions.

Returning to the illustrative example of a roller having a cylindrical surface, as illustrated in Fig. 7(a) roller body 300 is made from steel having a suitable chemical composition, such as (for example) mild steel with a carbon content of 0.2% and little or no chromium content. It will be appreciated that steel of this type will typically be inexpensive compared to the steel used to provide the hardened surface.

As illustrated in Fig. 7(b), the roller body 300 has been heated to, and is maintained at, a suitable preheat temperature (in an embodiment, between about 200 and 300 degrees Centigrade) and a metal deposition arrangement, in this embodiment a welding head 350, deposits a suitable hardenable metal, in this embodiment a martensitic steel, onto the roller body 300 to provide an outer layer 310 of the hardenable metal. The preheat temperature is lower than the martensitic start temperature and higher than the martensitic finish temperature. Several layers (or several thicknesses of weld bead) may need to be built up on the roller body, to provide the desired thickness of metal layer, and to allow for any dilution effect that might result from mixing of the weld metal with the metal of the roller body, which might lead to adverse changes in the characteristics of the weld metal. It will be appreciated each respectively more outer layer can be expected to be less affected by dilution from constituents of the underlying base metal (eg carbon steel), so that the more inner layers may, in use, conform less closely to the desired steel (weld metal) chemistry and characteristics.

As illustrated in Fig. 7(b) the external surface of the outer layer 310 has the less than smooth character of newly laid weld, which is not the surface characteristic desired of the finished item.

As illustrated in Fig. 7(c), a machining head 360 operates on the external surface of the outer layer 310, while the temperature at which machining occurs is maintained lower than the martensitic start temperature and higher than the martensitic finish

temperature. Weld metal deposition may continue after machining has started. As illustrated in Fig. 7(c), part of the external surface of the outer layer 310 is machined to the smooth cylindrical condition 311 which is the desired surface characteristic. Weld deposition will typically finish before machining is completed (except, perhaps, if there are parts of the surface on which an 'as welded' finish is acceptable), and machining continues (at a temperature lower than the martensitic start temperature and higher than the martensitic finish temperature) until machining is completed.

The metal deposition and machining may be performed by apparatus similar in principle to the apparatus of Fig.s 3 to 6: the welding head and machining (milling) tool may be supported by a support structure and their operation and movement controlled by a CNC system. The roller body may conveniently be rotated, about its longitudinal axis, to facilitate weld deposition and machining.

When machining is completed, as illustrated in Fig. 7(d), the finished roller 370 comprises the roller body 300 and outer layer 310, with the outer layer having a smooth cylindrical outer surface 312 (although, of course, other surface characteristics could be machined if desired). The roller 370 is then cooled, or allowed to cool, to below the martensitic finish temperature, resulting in hardening of the weld metal, so that the finished article, roller 370, has the desired characteristics.

Fig. 8 is a schematic perspective illustration of a stage in the process of manufacturing the roller 370. It will be appreciated that the present disclosure is applicable to refurbishment and manufacture of many types of item, including components for heavy machinery and, of course, not only to items which are generally cylindrical. Fig. 9 illustrates a generally planar component (or part of a component) 400 during refurbishment or manufacture, in which a layer 410 of hardenable martensitic steel is being deposited by a welding head 450, the component being maintained at a temperature lower than the martensitic start temperature and higher than the martensitic finish temperature while machining is performed by a machining head 460. A smooth machined area 411 of weld deposited metal is created. When the machining is completed, the component 400 is cooled, or allowed to cool, to below the martensitic finish temperature, resulting in hardening of the weld metal, and thus rapid and efficient production (or refurbishment) of a component with a machined, hard surface.

As described above, in relation to refurbishment of a cable drum, it may be desirable to provide a thicker layer of hardened metal in regions of an article which are anticipated to be subject to greater wear, and a less thick layer of hardened metal in regions of an article which are anticipated to be subject to less wear. This approach can also be beneficially applied to manufacture of items. Fig. 10 illustrates schematically, and by way of example, a vertical axial cross sectional view of part of a cable drum which is manufactured by a method in accordance with that described above. A drum body portion 500 is formed from mild steel, which is relatively inexpensive and easily machineable. The drum body portion 500 is provided with a number of grooves which form a base shape upon which the hardenable, in this embodiment martensitic, metal 510 is then deposited and machined prior to obtaining its hardened state to provide a hard surface layer, to provide a surface 520 of the drum of the desired (grooved but generally cylindrical) shape. The configuration of the grooves provided in the mild steel drum body portion 500 is arranged so that in order to provide a surface of the drum of the desired shape, a thicker layer of hardenable metal is provided on areas anticipated to be subject to greater wear, and a less thick layer of hardenable metal is provided in regions of an article which are anticipated to be subject to less wear. More specifically, in this embodiment, axially more central grooves 521a, 521b, 521c, 521d, (which are anticipated to be subject to greater wear) are provided by deposition of a greater thickness 531 of hardened metal upon more recessed grooves 541a, 541b, 541c, 541 d, formed in the mild steel drum body portion 500. Grooves 522a, 522b, 522c, 522d, at the axial ends of the drum (which are anticipated to be subject to least wear) are provided by deposition of a lesser thickness 532 of hardened metal upon less recessed grooves 542a, 542b, 542c, 542d, formed in the mild steel drum body portion 500. Axially intermediate grooves 523a, 523b, 523c, 523d (between the axial endmost grooves and the axially central grooves of the drum) are anticipated to be subject to an intermediate amount of wear, and are provided by deposition of a medium thickness 533 of hardened metal upon grooves 543a, 543b, 543c, 543d formed in the mild steel drum body portion 500, which are less recessed than the grooves 541a, 541 b, 541c, 541 d, but more recessed than the grooves 542a, 542b, 542c, 542d. The layer of greater thickness 531 of hardened metal may be about 10 to 20mm, and the layer of lesser thickness 532 of hardened metal may be about 2 to 4 mm. It will be appreciated that Fig. 10 is not intended to be to scale, but rather to present a representation in which the described characteristics are emphasized. Thus in this embodiment there is provided a cable drum with increased thickness of high hardness metal in the areas which are anticipated to be subject to greatest wear, without incurring the manufacturing or material cost of providing an unnecessarily thick layer of high hardness metal in the areas which are anticipated to be subject to less wear.

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

It will be understood to persons skilled in the art of the invention that many

modifications may be made without departing from the spirit and scope of the invention.

Claims

1. A method of refurbishing a cable drum, the method comprising:

cooling the item so that at least some of the added metal hardens.

2. A method according to claim 1 wherein the method is a method of refurbishing a dragline cable drum.

3. A method according to either preceding claim wherein the metal deposition process comprises a welding process.

4. A method according to any preceding claim wherein the heating of the cable drum to a temperature sufficient to allow effective addition of metal thereto by a welding process comprises heating the cable drum to a temperature of at least 150 degrees centigrade.

5. A method according to any preceding claim wherein the step of machining at least some of the added metal to obtain a desired shape of the cable drum, while maintaining the temperature of the added metal in excess of a critical temperature at which the added metal hardens, comprises maintaining the temperature of the added metal in excess of 100 degrees centigrade.

6. A method according to any preceding claim wherein the step of adding metal to at least one worn area of the cable drum by the metal deposition process comprises adding martensitic steel.

7. A method according to claim 6 wherein step of adding metal to at least one worn area of the cable drum by the metal deposition process comprises adding steel comprising 400 series martensitic steel.

8. A method according to either of claims 6 or 7 wherein the preheat temperature is lower than the martensitic start temperature of the metal added to at least one worn area of the cable drum and wherein the critical temperature at which the added metal hardens comprises the martensitic finish temperature of the added metal.

9. A method according to any of claims 6 to 8 wherein the step of adding metal to at least one worn area of the cable drum by a metal deposition process comprises adding a martensitic steel which has a martensitic finish temperature between 100 degrees centigrade and 300 degrees centigrade.

10. A method according to any of claims 6 to 9 wherein the martensitic finish temperature of the added metal is between 100 and 400 degrees Centigrade.

11. A method according to any preceding claim wherein the step of adding metal by a metal deposition process comprises depositing two or more layers of metal, by adding a first deposition of metal on a given part of the cable drum or component, and then depositing a second deposition of metal at least partially on the first deposition.

12. A method according to any preceding claim wherein the machining of at least some of the added metal to obtain a desired shape of the cable drum, while maintaining the temperature of the added metal in excess of a critical temperature at which the added metal hardens, comprises using one or more machining heads.

13. A method according to claim 12 wherein the one or more machining heads are controlled by a computer operated control system.

14. A method according to claim 13 wherein the adding of metal to at least one worn area of the cable drum by a welding process comprises using one or more welding heads.

15. A method according to claim 14 wherein the one or more welding heads are controlled by a computer operated control system.

16. A method according to either of claims 14 or 15 wherein the computer operated control system operates the machining heads to gauge the amount of weld metal build-up required during the weld reclamation stage of the process by detecting regions of the cable drum where insufficient metal has been added by the one or more welding heads, and controls operation of one or more of said welding heads to rectify the insufficiency.

17. A method according to any preceding claim wherein the heating of the cable drum to a temperature sufficient to allow effective addition of metal thereto by a welding process is performed by using infrared radiating heaters to heat the cable drum.

18. A method according to any preceding claim wherein the method is performed with the cable drum in situ, within a machine in which it has previously suffered wear.

19. A method according to claim 18 wherein the method is performed using at least part of a gear train of said machine, which gear train or part thereof is used to rotate the drum during normal operation of the machine, to rotate the drum during refurbishing thereof.

20. A method of refurbishing a cable drum, the method comprising:

21. A method according to claim 20 wherein the step of machining the added metal to obtain a desired shape of the cable drum while maintaining the temperature of the added metal in excess of 100 degrees centigrade, comprises machining the added metal while the temperature of substantially the entire cable drum is at a temperature excess of 100 degrees centigrade.

22. A method according to either of claims 20 or 21 wherein the metal added to at least one worn area of the cable drum by a metal deposition process is a martensitic steel.

23. A method according to claim 22 wherein the metal added to at least one worn area of the cable drum by a metal deposition process is a series 400 martensitic steel.

24. A method according to either of claims 22 or 23 wherein the step of heating the cable drum to a temperature in excess of 150 degrees centigrade comprises heating the cable drum to a temperature which is higher than the martensitic finish temperature of the metal to be added and lower than the martensitic start temperature of the metal to be added.

25. A method according to any of claims 22 to 24 wherein the step of machining the added metal to obtain a desired shape of the cable drum while maintaining the temperature of the added metal in excess of 100 degrees centigrade comprises machining the added metal to obtain a desired shape of the cable drum while maintaining the temperature of the added metal higher than the martensitic finish temperature of the metal to be added.

26. A method of refurbishing a cable drum, the method comprising: adding a martensitic steel to at least one worn area of the cable drum by a metal deposition process, while the cable drum is maintained at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel;

cooling the cable drum to below the martensitic finish temperature of the martensitic steel so that at least some of the added martensitic steel increases in hardness.

27. A method according to claim 26 wherein the step of cooling the cable drum so that at least some of the added metal increases in hardness comprises cooling the cable drum so that at least some of the added metal obtains a hardness in excess of 40 HRC.

28. A method according to either of claims 26 or 27 wherein the martensitic steel is a 400 series martensitic steel.

29. A method for providing a hardened surface on a heavy machinery component, the method comprising:

adding metal to one or more surface areas of the component by a metal deposition process;

30. A method according to claim 29 wherein provision of the hardened surface is part of a refurbishment process.

31. A method according to claim 29 wherein provision of the hardened surface is part of a manufacturing process.

32. A method according to any of claims 29 to 31 wherein the added metal is a martensitic steel and wherein the critical temperature is the martensitic finish temperature of the martensitic steel.

33. A method according to any of claims 29 to 32 wherein he heavy machinery component is one of: a rope/cable drum for mining machinery; a cable/rope sheave; a crawler shoe; a track pad; a roller, which may be a load roller; a steel plate; a shaft or pin for machinery; a drive and/or idler sprocket; a ground engaging tool.

34. A method for providing a hardened surface on a heavy machinery component, the method comprising:

heating the component to a temperature in excess of 150 degrees centigrade;

cooling the component so that at least some of the added metal obtains a hardness in 5 excess of 40 HRC to provide a hardened surface.

35. A method according to claim 34 wherein provision of the hardened surface is part of a refurbishment process.

36. A method according to claim 34 wherein provision of the hardened surface is part of a manufacturing process.

0 37. A method according to any of claims 34 to 36 wherein machining the added metal comprises machining at least one generally concave surface portion.

38. A method according to any of claims 34 to 37 wherein the added metal is a martensitic steel and wherein cooling the component comprises cooling the component to a temperature below the martensitic finish temperature of the martensitic5 steel.

39. A method for providing a hardened surface on a heavy machinery component, the method comprising:

adding a martensitic steel to at least one area of the component by a metal deposition process, while the component is maintained at a temperature below the martensitic 0 start temperature of the martensitic steel and above the martensitic finish temperature of the martensitic steel,

machining the added metal to obtain a desired shape of the hardened surface, while maintaining the temperature of the added metal at a temperature below the martensitic start temperature of the martensitic steel and above the martensitic finish temperature5 of the martensitic steel; and

40. A method according to claim 39 wherein provision of the hardened o surface is part of a refurbishment process.

41. A method according to claim 39 wherein provision of the hardened surface is part of a manufacturing process.

42. A method according to any of claims 39 to 41 wherein the step of cooling the cable drum so that at least some of the added metal increases in hardness 5 comprises cooling the cable drum so that at least some of the added metal obtains a hardness in excess of 48 HRC.

43. A method according to any of claims 39 to 42 wherein the heavy machinery component has a mass in excess of 100kg.

44. A method according to any of claims 39 to 43 wherein the component is a component for mining machinery.

45. A method according to claim 44 wherein the component is a component for a dragline.

46. A method according to any of claims 39 to 45 wherein he heavy machinery component is one of: a rope/cable drum; a cable/rope sheave; a crawler shoe; a track pad; a roller, which may be a load roller; a steel plate; a shaft or pin for machinery; a toothed gear component, which may be a drive and/or idler sprocket; a ground engaging tool.

47. A method as claimed in any preceding claim comprising providing a thicker layer of hardened metal at one or more regions where it is anticipated that there will be greater wear, and a less thick layer of hardened metal at one or more regions where it is anticipated that there will be lesser wear.

48. A method as claimed in any claim 47 wherein the method comprises providing an underlying surface shape, upon which added metal is deposited, which requires a greater thickness of hardened metal thereon at one or more regions where it is anticipated that there will be greater wear, and a lesser thickness of hardened metal thereon at one or more regions where it is anticipated that there will be less wear, in order to provide a desired final surface shape.

49. Apparatus for providing a hardened surface on a metal item comprising:

a computerised controller;

at least one welding head;

at least one machining head, controllable by the computerised controller;

50. Apparatus according to claims 49 wherein the at least one welding head is controllable by the computerised controller.

51. Apparatus according to either of claims 49 or 50 wherein the apparatus is for refurbishing a metal item.

52. Apparatus according to any of claims 49 to 51 wherein the apparatus is for refurbishing a heavy machinery component.

53. Apparatus according to any of claims 49 to 52 wherein the computerised controller comprises a CNC controller.

64. Apparatus according to any of claims 49 to 53 wherein the apparatus further comprises at least one heating apparatus arranged to maintain said metal item at a temperature in excess of 150 degrees while the at least one welding head and the at least one machining head simultaneously operate on said metal item.

55. Apparatus according to any of claims 49 to 54 wherein the computerised controller is adapted to control at least one machining head to gauge regions of the metal item where insufficient metal has been added by the at least one head, and to control one or more of said welding heads to rectify the insufficiency.

56. Apparatus according to any of claims 49 to 55 wherein the apparatus further comprises a motorised mechanism for rotating the metal item during provision of said hardened suface.

57. Apparatus according to any of claims 49 to 56 wherein the apparatus is adapted to operate on a metal item which is a cable drum.

58. Apparatus according to claim 57 wherein the apparatus is adapted to operate on said cable drum while the cable drum is in situ in a machine in which the cable drum has suffered wear.

59. Apparatus according to claim 58 wherein the apparatus is adapted to operate on a cable drum while the cable drum is rotated using at least part of a gear train of said machine, which gear train or part thereof is used to rotate the drum during normal operation of the machine.

60. A metal item manufactured or refurbished by a method in accordance with any of claims 1 to 48.

61. A metal item as claimed in claim 60 wherein the metal item is a heavy machinery component.

62. A metal item as claimed in claim 61 wherein the heavy machinery component is a cable drum or a sheave for a dragline.