In-process weld inspection

Abstract

A system and method for in-process weld inspection. In some embodiments, the system includes: a weld head; and a nondestructive weld defect sensing probe, the weld head being configured to move relative to a substrate and to form a weld layer on the substrate, and the nondestructive weld defect sensing probe being configured to move relative to the substrate, at a distance of less than 50 centimeters from the weld head, and to sense defects in the formed weld layer.

Description

IN-PROCESS WELD INSPECTIONFIELD

[0001] One or more aspects of embodiments according to the present disclosure relate to welding systems, and more particularly to a system and method for in-process weld inspection.BACKGROUND

[0002] Welding is used in numerous applications, for joining pieces of metal. Under certain conditions, some welding processes may form welds that include defects.

[0003] It is with respect to this general technical environment that aspects of the present disclosure are related.SUMMARY

[0004] According to an embodiment of the present disclosure, there is provided a system, including: a weld head; and a nondestructive weld defect sensing probe, the weld head being configured to move relative to a substrate and to form a weld layer on the substrate, and the nondestructive weld defect sensing probe being configured to move relative to the substrate, at a distance of less than 50 centimeters from the weld head, and to sense defects in the formed weld layer.

[0005] In some embodiments, the substrate includes two pieces and the forming of the weld layer includes forming the weld layer on a line of contact between the pieces.

[0006] In some embodiments, the pieces form a channel along the line of contact.

[0007] In some embodiments, the weld layer is a layer of a plurality of layers formed, or to be formed, to join the two pieces.

[0008] In some embodiments, each of the two pieces is a plate.

[0009] In some embodiments, each of the two pieces is a pipe.

[0010] In some embodiments, the nondestructive weld defect sensing probe includes an eddy current probe.

[0011] In some embodiments, the eddy current probe includes two outer coils and a plurality of inner coils, an inner coil of the plurality of inner coils having a smaller diameter than an outer coil of the outer coils.

[0012] In some embodiments, the system further includes a defect sensing circuit connected to the outer coils, the defect sensing circuit being configured to drive a first coil of the outer coils with a drive signal suitable for the detection of subsurface defects.

[0013] In some embodiments, the nondestructive weld defect sensing probe is separated from the weld layer by a gap.

[0014] In some embodiments, the gap has a height of between 0.05 millimeters and 0.5 millimeters.

[0015] In some embodiments, the system further includes a cooling system for cooling the nondestructive weld defect sensing probe.

[0016] In some embodiments, the cooling system includes a cooling fluid passage in the nondestructive weld defect sensing probe.

[0017] In some embodiments: the nondestructive weld defect sensing probe is separated from the weld layer by a gap; and the cooling system includes a gas passage for causing cooling gas to flow through the gap.

[0018] In some embodiments, the cooling system is configured to cause welding shield gas to flow through the gap.

[0019] In some embodiments, a probe tip of the nondestructive weld defect sensing probe is capable of withstanding a temperature of 200 degrees Celsius.

[0020] According to an embodiment of the present disclosure, there is provided a method, including: forming a portion of a weld layer, and testing the portion of the weld layer for defects, the testing occurring within 20 seconds of the forming.

[0021] In some embodiments, the testing includes testing the portion of the weld layer with an eddy current probe.

[0022] In some embodiments, the method further includes cooling the eddy current probe.

[0023] In some embodiments, the cooling of the eddy current probe includes cooling the eddy current probe with welding shield gas.BRIEF DESCRIPTION OF THE DRAWINGS

[0024] These and other features and advantages of the present disclosure will be appreciated and understood with reference to the specification, claims, and appended drawings wherein:

[0025] FIG. 1 is a schematic cross-sectional view of two pieces being joined by a weld, and a first weld layer of the weld, according to an embodiment of the present disclosure;

[0026] FIG. 2 is a perspective view of an orbital welding system joining two pipes with a weld, according to an embodiment of the present disclosure;

[0027] FIG. 3A is a drawing of coils of an eddy current probe, according to an embodiment of the present disclosure;

[0028] FIG. 3B is a photograph of an eddy current probe, according to an embodiment of the present disclosure; and

[0029] FIG. 4 is a schematic cross-sectional view of two pieces being joined by a weld, with the probe tip of an eddy current probe in a channel at the line of contact between the pieces, according to an embodiment of the present disclosure.DETAILED DESCRIPTION

[0030] The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of a system and method for in-process weld inspection provided in accordance with the present disclosure and is not intended to represent the only forms in which the present disclosure may be constructed or utilized. The description sets forth the features of the present disclosure in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the scope of the disclosure. As denoted elsewhere herein, like element numbers are intended to indicate like elements or features.

[0031] Referring to FIG. 1 , in a welding system two pieces of metal (e.g., metal plates or pipes) 105 may be joined by filling a groove 115 (which may have a triangular or trapezoidal (e.g., rectangular (as illustrated in FIG. 1 ) or square) cross section), at theline of contact 117 between the pieces of metal, with molten metal, in one or more passes, each pass resulting in the forming of a weld layer 120. The pieces of metal 105 (together with any partially completed weld) may together be referred to as the substrate. The filler metal may be supplied by a filler wire, and heat may be supplied by an arc. In a gas tungsten arc welding (GTAW) (or tungsten inert gas (TIG)) process, the arc may be formed between a tungsten electrode and the weld pool; in a gas metal arc welding (GMAW) (or metal inert gas (MIG)) process, the arc may be formed between the filler wire and the weld pool. In other processes, the heat may be supplied by another heat source, e.g., a laser.

[0032] Referring to FIG. 2, when performing machine (i.e., automated) pipe welding (which may also be referred to as orbital welding), two pipes 105 may be positioned end to end. The ends of the two pipes may be shaped such that a channel, or “groove” 115 is formed around the outer circumferences of the ends of the pipes. A weld head including the heat source and a filler wire feed system may be caused, by a suitable motorized drive system, to move relative to the substrate (e.g., the weld head may move (e.g., rotate about the joint), while the pieces being joined (e.g., the pipes) are held fixed, or the pieces being joined may move (e.g., rotate) while the weld head is held fixed), while the weld head deposits metal into the channel to form the weld. The channel 115 may be partially or entirely filled, using one or more weld passes, each pass forming an additional weld layer 120 in the channel.

[0033] During the welding process, heat is applied to the weld pool or to a filler wire (or to both), and the filler wire is fed, by a filler wire feed unit 210, from a filler wire spool 215, into the weld pool as the weld progresses across the substrate. The motion of the weld pool, relative to the substrate, as the weld progresses, may consist of displacement along the travel direction, and, in some circumstances, weave, which may be a back- and-forth lateral motion resulting in a weld layer 120 that is wider than the weld pool. In some welding systems, e.g., in gas metal arc welding, various welding parameters, including the filler wire feed speed, may be selected to produce desirable weld pool characteristics, the weave may be selected so that the weld has the same width as a channel in the substrate, and the layer height (i.e., the thickness of the weld layer 120deposited in the channel 115) may be selected so that the final weld will meet certain requirements (e.g., strength).

[0034] In some embodiments, a nondestructive weld defect sensing probe 220 is secured to the weld head so that it moves with the weld head relative to the substrate, e.g., relative to the two pipes 105. The defect sensing probe 220 may follow the weld head, and it may be employed to sense defects in the weld shortly after the weld layer 120 is formed. In some embodiments the distance between the defect sensing probe 220 and the weld head is selected to be as small as possible while being sufficiently large to allow the weld to cool sufficiently, by the time it reaches the defect sensing probe 220, to avoid damaging (by excessive heating) the defect sensing probe 220. In some embodiments, the delay between the forming of a portion of the weld layer 120 and the time the portion reaches the defect sensing probe 220 may be less than 10 minutes, e.g., it may be between 1 second and 100 seconds. The distance, along the weld layer 120, between the weld pool and the defect sensing probe 220 may be less than 50 centimeters (cm), e.g., it may be between 1 .0 cm and 50.0 cm.

[0035] The defect sensing probe 220 may include one or more eddy current defect sensors. Each eddy current defect sensor may include one or more drive coils and one or more sensing coils, connected to one or more defect detection circuits. In operation, a defect detection circuit may drive a drive coil of an eddy current defect sensor with a time-varying current so that it produces a time-varying magnetic field. This time-varying magnetic field may cause time-varying eddy currents to flow in the weld layer 120 being inspected, and a sensing coil may be employed to detect the time-varying eddy currents. The eddy currents produced in a weld that has a defect (e.g., a crack) may differ from the eddy currents produced in a perfect weld; as such, the sensed eddy currents may be used (by the defect detection circuit) to determine whether defects are present.

[0036] The frequency content of the time-varying current driven through the drive coil may affect the depth at which eddy currents flow in the weld layer 120. For example, most of the current in the weld layer 120 may flow within one skin depth of the surface of the weld layer 120, and the current may be increasing weak at greater depths within the weld layer 120. The skin depth may be inversely proportional to the square root of the frequency of the drive current; as such, lower frequency drive currents may besuitable for detecting defects within the bulk of the weld layer 120 (sensing in this mode may be referred to as volumetric sensing), and higher frequency drive currents may be suitable for detecting surface defects.

[0037] FIG. 3A (which is drawn to scale, for one embodiment) shows a coil configuration, in some embodiments. Two large coils 305 may be used for relatively low frequency (volumetric) measurements (which may use one or more frequencies in the range from 500 Hz to 500 kHz) which may be used to detect subsurface defects, with one of the two large coils 305 being operated as the drive coil and the other of the two large coils 305 being operated as the sensing coil. A plurality of additional coils (e.g., smaller coils) 310a, 310b (collectively referred to as smaller coils 310) may be operated in a G4 (Axial) mode or in a G3 (Transverse) mode to detect defects in or near the surface of the weld layer 120. In such a measurement, for example, a first pair of smaller coils 310a may be operated as the drive coil and the other three smaller coils 310b may be operated as sensing coils. In some embodiments, other coil driving and sensing arrangements are employed, e.g., one coil of the first pair of smaller coils 310a may be may be operated as a drive coil and the other one of the first pair of smaller coils calls 310a may be operated as a sensing coil.

[0038] FIG. 3B is a photograph of an eddy current probe, in some embodiments. The eddy current probe includes a probe tip 325 and a probe body 330. The probe tip 325 includes the coils 305, 310 and may be sufficiently narrow to fit in the channel 115. The probe body may include provisions for cooling the probe (as discussed in further detail below).

[0039] FIG. 4 is a cross-sectional view of a weld in progress, in which one weld layer 120 has been formed. The tip 325 of the eddy current probe extends into the channel 115, and is employed to test the weld layer 120 for defects. This mode of operation may be superior to alternate approaches in which the entire weld (which may include a plurality of weld layers 120) is tested, after it is completed, using eddy current inspection, in that (i) the present method may make it possible to detect defects in lower weld layers 120, which may be too far below the surface of the completed weld to be detected using eddy current inspection and (ii) welding conditions resulting in a low-quality weld layer (e.g., incorrect arc parameters, incorrect filler wire feed rate, or insufficient shield gas)may be detected quickly (e.g., within less than 20 seconds, e.g., within a time interval between 0.1 seconds and 30.0 seconds) of the occurrence of such conditions.

[0040] Various methods and design features may be employed to prevent damage to the eddy current probe. For example, the probe tip 325 may be supported in a metal (e.g., stainless steel) holder. Such a holder may have an opening between the lower surface of the probe tip 325 and the weld, so as to avoid shielding the weld from the magnetic field produced by the drive coils and so as to avoid shielding the sensing coils from the magnetic fields produced by eddy currents in the weld layer 120. This holder may be pressed (e.g., by a spring) against the top surface of the weld layer 120 and it may support the probe tip 325 so that a small gap 410 exists between lower surface of the probe tip 325 and the upper surface of the weld layer 120. The gap 410 may prevent any roughness of the upper surface of the weld layer 120 from abrading or otherwise damaging the lower surface of the probe tip 325, and it may act as an insulating layer reducing the rate of conductive heat transfer from the weld layer 120 to the probe tip 325. In some embodiments, air, or another gas (e.g., welding shield gas, which may be supplied to the weld head to shield the weld, and a portion of which may be diverted to instead cool the probe tip 325) may be caused to flow through the gap 410 to further reduce the rate of conductive heat transfer and to cool the probe tip 325. The height of the gap 410 (i.e. , the separation between the lower surface of the probe tip 325 and the upper surface of the weld layer 120) may be between 0.1 mm and 10.0 mm.

[0041] Liquid cooling of the eddy current probe may also be employed; cooling passages may be present for this purpose in the probe body 330 or in the probe tip 325 (or in both) to remove heat from the probe tip and from the probe body 330. In some embodiments, heat-resistant materials may be used to construct the probe tip 325 or the entire eddy current probe, to further improve its ability to be operated near a recently- formed weld layer 120. In some embodiments, the probe tip 325, or the entire eddy current probe, is capable of withstanding a temperature of 200 Celsius.

[0042] As used herein, “a portion of” something means “at least some of” the thing, and as such may mean less than all of, or all of, the thing. As such, “a portion of” a thing includes the entire thing as a special case, i.e., the entire thing is an example of a portion of the thing. As used herein, the word “or” is inclusive, so that, for example, “A or B”means any one of (i) A, (ii) B, and (iii) A and B. As used herein, when a method (e.g., an adjustment) or a first quantity (e.g., a first variable) is referred to as being “based on” a second quantity (e.g., a second variable) it means that the second quantity is an input to the method or influences the first quantity, e.g., the second quantity may be an input (e.g., the only input, or one of several inputs) to a function that calculates the first quantity, or the first quantity may be equal to the second quantity, or the first quantity may be the same as (e.g., stored at the same location or locations in memory as) the second quantity. As used herein, a rectangle is a special case of a trapezoid (e.g., a rectangle is an example of a trapezoid) and a square is a special case of a rectangle (e.g., a square is an example of a rectangle).

[0043] It will be understood that, although the terms “first”, “second”, “third”, etc., may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed herein could be termed a second element, component, region, layer or section, without departing from the spirit and scope of the inventive concept.

[0044] Spatially relative terms, such as “beneath”, “below”, “lower”, “under”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature’s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that such spatially relative terms are intended to encompass different orientations of the device in use or in operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” or “under” other elements or features would then be oriented “above” the other elements or features. Thus, the example terms “below” and “under” can encompass both an orientation of above and below. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can bethe only layer between the two layers, or one or more intervening layers may also be present.

[0045] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concept. As used herein, the terms “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art.

[0046] As used herein, the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. Further, the use of “may” when describing embodiments of the inventive concept refers to “one or more embodiments of the present disclosure”. Also, the term “exemplary” is intended to refer to an example or illustration. As used herein, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively.

[0047] It will be understood that when an element or layer is referred to as being “on”, “connected to”, “coupled to”, or “adjacent to” another element or layer, it may be directly on, connected to, coupled to, or adjacent to the other element or layer, or one or more intervening elements or layers may be present. In contrast, when an element or layer is referred to as being “directly on”, “directly connected to”, “directly coupled to”, or “immediately adjacent to” another element or layer, there are no intervening elements or layers present.

[0048] Any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of"1.0 to 10.0" or “between 1.0 and 10.0” is intended to include all subranges between (and including) the recited minimum value of 1 .0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1 .0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Similarly, a range described as “within 35% of 10” is intended to include all subranges between (and including) the recited minimum value of 6.5 (i.e. , (1 - 35 / 100) times 10) and the recited maximum value of 13.5 (i.e., (1 + 35 / 100) times 10), that is, having a minimum value equal to or greater than 6.5 and a maximum value equal to or less than 13.5, such as, for example, 7.4 to 10.6. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein.

[0049] Although exemplary embodiments of a system and method for in-process weld inspection have been specifically described and illustrated herein, many modifications and variations will be apparent to those skilled in the art. Accordingly, it is to be understood that a system and method for in-process weld inspection constructed according to principles of this disclosure may be embodied other than as specifically described herein. The invention is also defined in the following claims, and equivalents thereof.

Claims

WHAT IS CLAIMED IS:

1. A system, comprising: a weld head; and a nondestructive weld defect sensing probe, the weld head being configured to move relative to a substrate and to form a weld layer on the substrate, and the nondestructive weld defect sensing probe being configured to move relative to the substrate, at a distance of less than 50 centimeters from the weld head, and to sense defects in the formed weld layer.

2. The system of claim 1 , wherein the substrate comprises two pieces and the forming of the weld layer comprises forming the weld layer on a line of contact between the pieces.

3. The system of claim 2, wherein the pieces form a channel along the line of contact.

4. The system of claim 3, wherein the weld layer is a layer of a plurality of layers formed, or to be formed, to join the two pieces.

5. The system of claim 2, wherein each of the two pieces is a plate.

6. The system of claim 2, wherein each of the two pieces is a pipe.

7. The system of claim 1 , wherein the nondestructive weld defect sensing probe comprises an eddy current probe.

8. The system of claim 7, wherein the eddy current probe includes two outer coils and a plurality of inner coils, an inner coil of the plurality of inner coils having a smaller diameter than an outer coil of the outer coils.

9. The system of claim 8, further comprising a defect sensing circuit connected to the outer coils, the defect sensing circuit being configured to drive a first coil of the outer coils with a drive signal suitable for the detection of subsurface defects.

10. The system of claim 1 , wherein the nondestructive weld defect sensing probe is separated from the weld layer by a gap.11 . The system of claim 10, wherein the gap has a height of between 0.05 millimeters and 0.5 millimeters.

12. The system of claim 1 , further comprising a cooling system for cooling the nondestructive weld defect sensing probe.

13. The system of claim 12, wherein the cooling system comprises a cooling fluid passage in the nondestructive weld defect sensing probe.

14. The system of claim 12, wherein: the nondestructive weld defect sensing probe is separated from the weld layer by a gap; and the cooling system comprises a gas passage for causing cooling gas to flow through the gap.

15. The system of claim 14, wherein the cooling system is configured to cause welding shield gas to flow through the gap.

16. The system of claim 1 , wherein a probe tip of the nondestructive weld defect sensing probe is capable of withstanding a temperature of 200 degrees Celsius.

17. A method, comprising: forming a portion of a weld layer, andtesting the portion of the weld layer for defects, the testing occurring within 20 seconds of the forming.

18. The method of claim 17, wherein the testing comprises testing the portion of the weld layer with an eddy current probe.

19. The method of claim 18, further comprising cooling the eddy current probe.

20. The method of claim 19, wherein the cooling of the eddy current probe comprises cooling the eddy current probe with welding shield gas.

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