FIELD OF THE INVENTION

The present invention relates to a welding method and apparatus, and in particular to a forge welding method and apparatus.

BACKGROUND TO THE INVENTION

Welding of metal components together is typically achieved by application or generation of heat, for example from electrical resistance heating, electrical arcing, flame heating, friction heating or the like. In addition to heating, some welding techniques utilise pressure, such as in forge welding, in which heated components are forced together to cause material diffusion.

It is well understood in the art that the quality of a weld can be highly dependent on the quality of the components prior to welding. For example, the presence of oxides on the surface of the components can have a significant detrimental effect, and as such efforts are made to remove any oxides prior to welding.

However, even when surface oxides are removed, subsequent welding within normal atmosphere can result in a large degree of contamination by reactions with atmospheric components which create oxides and other unfavourable substances. For example, some metals, including iron based alloys such as steel, can become very reactive with oxygen at elevated temperatures - some steels may become very reactive to oxygen at temperatures in excess of 300°C. The creation and inclusion of oxides and other substances during welding can adversely affect the weld.

To address this issue it is known in the art to perform welding within an artificial environment in which reactions with adverse components are prevented, or at least substantially minimised. For example, heating and welding may be performed in a vacuum, or alternatively within a protective atmosphere. A protective atmosphere may be created to prevent or substantially minimise any reactions with the welded components, for example by use of one or more inert gases. Alternatively, a protective atmosphere may be created to assist in the removal of oxides and other contaminants from the welded components, for example by use of a reducing gas, such as nitrogen, hydrogen, carbon monoxide, methane and the like, or mixtures thereof.

Although artificial welding environments are known in the art, these are often deemed inadequate in removing more stable oxides, such as chromium oxide, which may be formed on certain grades of steel, for example. Furthermore, the requirement to establish a particular atmosphere necessitates the use of specialised equipment, which must accommodate the typical high temperatures, sealing arrangements, the size, shape and any required movement of welded components and the like, which increases complexity and costs. This requirement for specialised equipment is particularly problematic in the oil and gas industry in which proposals have been made to weld together oilfield tubulars, such as casing, to substitute more conventional threaded connections. In such oil and gas applications, the typical size of the tubulars and the restricted working area may prevent welding becoming a realistic option for an operator.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method of welding, comprising:

locating a member between opposing surfaces of first and second components;

heating the first and second components;

forcing the first and second components together to displace at least a portion of the member; and

welding the first and second components together.

Thus, in use the member will be displaced upon intimate engagement with the first and second components when said components are forced together. Accordingly, the member may provide physical isolation of one or both of the opposing surfaces of the components from the atmosphere, thus preventing the creation of, for example, oxides. This arrangement may therefore permit welding to be achieved in normal atmosphere, without any requirement for the use of a vacuum, shielding gas, reducing gas or the like. However, it should be understood that in some embodiments of the present invention artificial atmospheric arrangements may be used.

Furthermore, intimate engagement of the member and the surfaces of the components during displacement of the member may establish forces, such as viscous forces, frictional forces, shear forces and the like between the member and the components. Such forces may permit a degree of cleaning of one or both of the opposing surfaces of the components prior to welding, for example by removal of any undesirable contaminants, such as oxides.

The member may be arranged to react with one or both of the components, which may result in the removal, for example by dissolving, reduction or the like, of undesirable materials and contaminants, such as oxides. The member may comprise integrated agents, such as fluxes, which may assist in the removal of undesirable materials from one or both components. For example, the member may comprise one or more fluxes, such as borax, sodium chloride, potassium chloride, sodium fluoride, other fluorides or the like, or any suitable combination thereof.

In some embodiments the member may be arranged to be diffused into one or both of the components, which may assist in improving the quality of the weld.

The method may comprise the step of forcing the first and second components together to displace at least a portion of the member and permit engagement of the opposing surfaces of the components in advance of welding.

The method may comprise welding the components together by, for example, arc welding, gas welding, friction welding or the like.

In one embodiment the method may comprise forge welding the first and second components together. In this arrangement the first and second components may be forced together to displace the member, and then continue to be forced together to establish forge welding. The method may comprise forcing the components together to displace the member, and then increasing the force to achieve forge welding. In some embodiments the first and second components may be forced together at a varying magnitude, for example in accordance with a force profile. The force profile may be predetermined, and may be selected in accordance with welding requirements, quality requirements, temperature profiles and the like. Alternatively, a constant force may be applied.

A temperature and/or pressure profile may be achieved subsequent to welding, which may permit suitable heat and/or other material treatments to be achieved.

The method may comprise heating one or both of the components to a target temperature. The target temperature may be suitable for forge welding. In one embodiment the target temperature may be in excess of 600°C, for example in excess of 1000°C. In some embodiments the target temperature may be in the region of 1200°C, which may be suitable for steel components. However, lower or higher temperatures may be selected in accordance with specific requirements, materials, conditions and the like.

One or both components may be heated by induction heating, electrical resistance heating, flame heating or the like.

One or both of the components may be heated and subsequently brought into contact with the member. One or both of the components may be heated to a target temperature and then brought into contact with the member. One or both of the components may be brought into contact with the member while being heated. In one embodiment the method may comprise bringing one or both of the components into contact with the member and then initiating heating of the components. In this arrangement the member may provide surface protection during heating of one or both of the components. This may provide isolation from the atmosphere during the heating stage when the components may be considered to be most reactive.

The method may comprise forcing the components together while said components are being heated. The method may comprise forcing the components together to displace the member while said components are being heated.

The member may comprise a solid member. The member may be deformable to permit displacement by forcing the components together. The member may be malleable. The member may comprise a substantially rigid member. The member may be softer than one or both of the components.

The member may be adapted to be softened. The method may comprise softening the member to permit displacement by forcing the components together. In one embodiment the member may be adapted to be softened by heating. The method may comprise softening the member by heating.

The member may comprise a material selected to have a softening temperature, or heat distortion temperature, which is lower than that of one or both of the components. The member may comprise a softening or heat distortion temperature which is lower than a target temperature of one or both of the components.

The member may be adapted to be melted. The method may comprise melting the member. The member may comprise a material selected to have a melting temperature which is lower than that of one or both of the components. The member may comprise a melting temperature which is lower than a target temperature of one or both of the components. Melting the member may be advantageous in assisting in the removal of undesirable materials from one or both of the components. For example, liquids are much denser than gases, and as such the member once melted may be particularly effective at removing stable compounds from one or both components which may otherwise be difficult to remove by gases. Such stable compounds may include chromium oxide.

The member may be configured to be evaporated. This may eliminate any remains of the member following welding.

The member may be heated independently of one or both components. For example, the member may be heated by induction heating, electrical resistance heating, flame heating or the like. Alternatively, or additionally, the member may be heated by proximity to or engagement with one or both of the components. Accordingly, heat may be transferred to the member during heating of one or both components. This may permit a single or simplified heating arrangement to be utilised.

The member may be configured to be trimmed to match the shape, dimensions or the like of one or both components. The member may be trimmed at any suitable stage in the method of the present invention, for example prior to being displaced by the components.

The member may be electrically conductive.

The member may be electrically insulating. This arrangement may permit one or both components to be electrically heated, for example by resistance heating, without causing electrical shorting across the member.

The member may comprise a metal or metal alloy. The member may comprise one or more of, or alloy of, lead, copper, nickel, silver or the like.

The member may comprise a glass material.

The member may comprise a composite material.

The member may comprise a polymer material

The member may comprise a unitary portion.

The member may comprise multiple portions. Different portions may comprise a common material. Different portions may comprise different materials. For example, a first portion may comprise metal, and a second portion may comprise glass.

In one embodiment a first member portion may be associated with the first component, and a second member portion may be associated with the second component.

The member may be secured to one or both of the components, for example by screwing, interference fitting or the like. In this arrangement the member may function as a protective sheath, cover or the like to the surface of one or both of the first and second components. Such a protective cover may be advantageous during transportation, storage, manipulation and the like on the components.

The member may be configured to accommodate the surface shape of one or both components. For example, the member may comprise a profiled portion configured to interengage with a profiled surface of one or both components. For example, a surface of at least one component may comprise a male bevef profile, and the member may comprise a corresponding female bevel shape. The components may be forced together by movement of at least one of the components. In one arrangement both components may be moveable. Alternatively, one component may be stationary and the other component may be moveable.

In one embodiment the method may be suitable for use with a component having a generally circular cross-section, such as a pipe. In this arrangement the member may comprise a circular member, such as a ring member. The member may be plate-shaped.

The method may be configured for use in welding together pipe components. Such pipe components may be welded together in end-to-end relation. The method may be configured for use in welding together oilfield tubulars, such as casing tubulars, liner tubulars, screen tubulars, coiled tubing, production tubulars and the like. The method of the present invention may be considered to be advantageous in such an oilfield environment as the requirement to provide a specialised welding environment may be eliminated. Furthermore, the method according to the present invention may permit convention threaded pipe connections to be eliminated, along with their associated problems which are well known in the art.

According to a second aspect of the present invention there is provided a welding apparatus, comprising:

a heating arrangement configured to heat first and second components to be welded together;

a member configured to be interposed between first and second components, wherein said member is adapted to be displaced by forcing the first and second components together; and

a manipulation arrangement configured to manipulate at least one of the first and second components to force said components together.

The apparatus according to the second aspect may comprise features associated with, and be used in accordance with, the method according to the first aspect.

According to a third aspect of the present invention there is provided a method of welding tubulars together, comprising:

locating a member between opposing surfaces of first and second tubulars; heating the first and second tubulars;

forcing the first and second tubulars together to displace at least a portion of the member; and

welding the first and second tubulars together.

The tubulars may comprise oilfield tubulars, such as casings, liner, screened tubulars, slotted tubulars, production tubing, coiled tubing or the like. According to a fourth aspect of the present invention there is provided a method of forming a tubing string, comprising:

arranging one end face of a first tubular to oppose an end face of a second tubular;

interposing a member between the opposing faces of the first and second tubulars;

heating the first and second tubulars;

forcing the first and second tubulars together to displace at least a portion of the member; and

welding the first and second tubulars together.

The method may comprise welding a third tubular to the second tubular. The third tubular may be welded to the second tubular in the same manner as the first and second tubulars are welded together. This process may be repeated until a tubing string of the desired length is achieved.

Other aspects of the present invention relate to the member, as defined as part of the preceding aspects.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figures 1A and 1 B are diagrammatic representations of steps in a known tubular forge welding method;

Figured 2A, 2B and 2C are diagrammatic representations of steps in a welding method in accordance with an embodiment of the present invention;

Figure 3 is a diagrammatic representation of a welding process step in accordance with an alternative embodiment of the present invention; and

Figure 4 is a diagrammatic representation of a member arrangement interposed between two pipes to be welded, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Figures 1A and 1B diagrammatically represent a known forge welding technique for welding together first and second pipes 10, 12. In this prior art example the pipes 10, 12 are arranged such that opposing end regions 14, 16 are aligned with each other, in non-contact relationship. The end regions 14, 16 are electrically heated using electrode pairs 18, 20 to raise the temperature of the pipe material to a target temperature required for forge welding. A sealed chamber 22, shown in broken outline, is arranged around the end regions 14, 16, wherein this chamber 22 permits an artificial environment to be achieved. The artificial environment may be defined by a vacuum, inert gases, reducing gases or the like, and is established in order to prevent the pipe material from reacting with normal atmospheric elements and producing compounds, such as oxides, that are adverse to weld quality.

Once the target temperature is reached, the electrode pairs 18, 20 are disengaged and the pipes 10, 12 are forced together to forge weld the end regions 14, 16.

The present invention provides a novel method and apparatus which may permit disadvantages associated with the sealed chamber and artificial environment to be alleviated. However, it should be understood that the present invention may be used in combination with an artificial environment.

Reference is now made to Figures 2A, 2B and 2C which represent sequential stages in a method of welding first and second steel pipes 30, 32 together, in accordance with an embodiment of the present invention. In this particular embodiment the method does not require the presence of an artificial environment, although such may be provided.

In this embodiment each pipe 30, 32 comprises bevel-profiled end regions 34, 36 which are aligned to oppose each other, as shown in Figure 2A. The bevelled end regions are provided to assist in establishing a desired weld quality, for example by permitting a desirable stress and strain distribution, material diffusion and the like to be achieved during welding.

A member 38, which in this embodiment is a solid metal ring, for example comprising copper, is interposed between and intimately engaged with the end regions 34, 36 of the pipes 30, 32. The end regions 34, 36 are electrically heated with respective electrode pairs 40, 42, with the intention of reaching a target forge welding temperature, which may be in excess of 1000°C, for example around 1200°C. During heating the pipes are forced together, as represented by arrows 44, 46.

Due to the intimate engagement of the metal ring 38 with the pipe end regions

34, 36, the metal ring 38 will also become heated. In the present embodiment the material of the metal ring 38 is selected to have a softening temperature which is lower than that of the pipes 30, 32, such that the force applied to move the pipes 30, 32 together in the direction of arrows 44, 46 will result in deformation and displacement of the ring 38, as represented in Figure 2B, from between the pipes, permitting the pipes to eventually be brought into engagement ready for welding. Accordingly, the ring 38 will provide physical isolation of the end regions 34, 36 from the atmosphere, thus preventing the creation of, for example, oxides. Furthermore, intimate engagement of the ring 38 and the end regions 34, 36 during deformation and displacement of the ring 38 will establish forces, such as viscous forces, frictional forces, shear forces and the like between the ring 38 and the pipe end regions 34, 36. Such forces may permit a degree of cleaning of the pipe end regions 34, 36 prior to welding, for example by removal of any undesirable contaminants, such as oxides. This arrangement may therefore permit any oxides and the like which may have formed on the pipe end regions 34, 36 following forming of the bevel profiles to be conveniently removed, without requiring the use of reducing gases within an artificial atmosphere, and then subsequently protect the pipe end regions 34, 36 from reacting with the atmosphere to produce further oxides while at the significant elevated temperature.

The ring 38 may comprise integrated agents, such as fluxes, which may assist in the removal of undesirable materials from the pipes 30, 32. For example, the ring 38 may comprise one or more fluxes, such as borax, sodium chloride, potassium chloride, sodium fluoride, other fluorides or the like, or any suitable combination thereof. In some embodiments the ring 38 may be arranged to be diffused into one or both of the components, which may assist in improving the quality of the weld.

Following displacement of the ring 38, and achieving the desired target temperature, the force between the pipes 30, 32 may be increased, as represented by larger arrows 48, 50 in Figure 2C, to cause the pipe end regions 34, 36 to be forged welded together. The method may comprise steps for maintaining a particular temperature or pressure within the pipes 30, 32, for example to achieve particular material/weld properties.

Figure 3 shows a similar embodiment to that in Figure 2, However, in this case a ring 138 is interposed between two pipes 130, 132 and is then trimmed to more closely match the dimensions of the end regions 134, 136 of the pipes. This may permit easier deformation and displacement of the ring 138 from between the pipes 130, 132. Furthermore, the reduced volume of material within the ring will minimise the heat transfer from the pipes 130, 132, thus permitting more efficient heating by electrode pairs 140, 142.

Although the ring 138 in Figure 3 is trimmed to match the dimensions of the pipe end regions 134, 136, the ring may be manufactured to more closely match the pipe dimensions, such that trimming is not required. In the embodiment described in Figure 2 above, the ring 38 comprises a metal. However, in other embodiments alternative materials may be utilised. For example, in some alternative embodiments a ring may be provided that comprises glass. Such an arrangement may advantageously permit electrical isolation of the pipes, which may have benefits during electrical heating of the pipes.

Reference is now made to Figure 4 in which a further alternative embodiment of the present invention is shown. In this embodiment a member, again a ring shaped member 238, is interposed between two pipes 230, 232. The member 238 is formed of multiple portions, specifically a pair of metal portions 238a with a glass portion 238b interposed therebetween. This arrangement may permit appropriate material interaction/diffusion to be achieved between the pipes 230, 232 and the ring member 238, while maintaining the pipes 230, 232 electrically isolated from each other.

Embodiments of the present invention may relate to welding together oilfield tubulars, for example to produce a tubing string, such as a casing string, to be deployed into a subterranean wellbore. The method of the present invention may be configured for use on an oilfield platform, such as onshore and offshore platforms.

Embodiments of the present invention may relate to creating pipelines, for example pipelines for transporting water, oil, gas or the like.

It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention. For example, the present invention is not limited to use with forge welding - other types of welding, such as arc, gas, friction welding may be utilised following displacement of the interposed member.

Further, the method may be utilised to weld together components of any shape, and is not limited to tubular components such as the exemplary pipes disclosed.

Additionally, the interposed member may be formed of any suitable material, and is not limited to the exemplary metal of glass disclosed in the specific embodiments described above. For example, a composite material, polymeric material or the like may be utilised.