A method of attaching a thermocouple to the inner surface of a metal tube by welding.

Abstract

To enable a thermocouple to be easily fixed by welding to an inner surface of a metal pipe such as a steel pipe.SOLUTION: A jig 1, which holds a weld electrode w and a thermocouple TC, comprises: thermocouple holding groove parts 2, 3 and 3a having enough dimensions allowing the parts to be inserted into a metal pipe T to which the thermocouple is attached and are shaped to hold the thermocouple at a position contacting an inner surface Ti of the metal pipe so that two tips Tn of the thermocouple cross each other; and a weld electrode holding communication path part 5 on which the weld electrode is held so that a tip wp of the weld electrode w contacts the inner surface of the metal pipe through a position at which the two tips of the thermocouple cross each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a jig for holding a welding electrode of a welding device, and more particularly to a jig for holding a welding electrode and a thermocouple (jig for holding welding electrode and thermocouple) A method of welding thermocouples to the inner surface of steel pipes or other metal pipes using [a specific method]. . [Background Art]

[0002] In quenching of steel pipes and various other heat treatments for metal pipes, welding for attaching a thermocouple to the surface of a metal pipe is sometimes performed for the purpose of temperature control of the metal pipe. For example, Patent Document 1 discloses that a plurality of thermocouples are attached to the outer surface of a pipe in order to measure the temperature history of the outer surface of the pipe when improving the residual stress of the pipe by moving an irradiation region in the circumferential direction while locally irradiating a laser beam onto the outer peripheral surface of a welded portion of a cylindrical pipe. [Related Art] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Laid-Open No. 2008-169444 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] During heat treatment processes for metal pipes, such as hardening steel pipes, the temperature may differ between the outer and inner surfaces of the pipe. Therefore, it is preferable to be able to measure the temperature not only on the outer surface but also on the inner surface. In this regard, when attaching a thermocouple for temperature measurement to a suitable location on the pipe surface, the thermocouple is fixed to the pipe surface by welding. However, when the inner diameter of the pipe is relatively small and the distance from the opening end of the pipe to the desired location for attaching the thermocouple is relatively long, it is not possible to bring the welding machine carrying the welding electrode into the pipe. In such cases, only the welding electrode must be extended, and its tip brought to the deepest part of the pipe where the thermocouple is to be attached. However, it is extremely difficult to stably hold the tip of the welding electrode at the desired position of the thermocouple while simultaneously holding the relatively flexible wire-like thermocouple in the desired position until welding is complete. Therefore, when welding a thermocouple to a desired location on the inner surface of a pipe, it would be convenient to have a jig that can stably hold the thermocouple and the welding electrode inside the pipe, and it is expected that the thermocouple attachment process will be greatly simplified.

[0005] Thus, the main object of the present invention is, A method for easily fixing a thermocouple to the inner surface of a metal pipe, such as a steel pipe, by welding, using a jig that holds the thermocouple and welding electrode inside the pipe. The objective is to provide. [Means for solving the problem]

[0006] According to the present invention, the above problems are solved. A method of attaching a thermocouple to the inner surface of a metal tube by welding, Welding electrodes and The aforementioned A jig for holding a thermocouple, to which the thermocouple is attached The aforementioned A jig comprising: a thermocouple holding groove portion having dimensions that allow it to be inserted into the inside of a metal tube, and shaped to hold the thermocouple in a position in contact with the inner surface of the metal tube such that the two tips of the thermocouple intersect; and a welding electrode holding passage portion that holds the welding electrode such that the tip of the welding electrode abuts against the inner surface of the metal tube through the intersection of the two tips of the thermocouple. In the above, outside the metal pipe, The steps include: holding the thermocouple in the thermocouple holding groove so that its two tips intersect, and holding the welding electrode in the welding electrode holding passage so that its tip abuts against the intersection of the two tips of the thermocouple; The steps include inserting the jig holding the welding electrode and the thermocouple into the inner surface of the metal tube such that the intersection of the two ends of the thermocouple aligns with the position where the thermocouple is to be attached, A step of welding the thermocouple to the inner surface of the metal tube. Methods including This is achieved by [method].

[0007] In the above, the "thermocouple" is a wire-like device consisting of two types of coated metal wires, commonly used in this field, arranged in parallel, and may be capable of measuring temperatures of at least 700 to 1000°C. The "welding electrode" is a rod-shaped or wire-shaped metal component of a handheld welding machine used in this field, capable of welding and fixing wires such as thermocouples to a metal surface, and welding may be achieved when the tip of the electrode comes into contact with the object to be welded and an electric current is applied. The above-mentioned jig is formed such that its overall dimensions allow it to be inserted into the metal tube to which the thermocouple is attached, and when the jig is inserted into the metal tube, a thermocouple holding groove is formed on the surface of the jig facing the inner surface of the metal tube, as described above, to hold the thermocouple with its two tips intersecting at a position in contact with the inner surface of the metal tube, and further, a welding electrode holding passage is configured to hold the welding electrode and bring its tip into contact with the inner surface of the metal tube via the intersection of the two tips of the thermocouple.

[0008] According to the jig of the present invention described above, the welding electrode and thermocouple are stably positioned inside the metal pipe with the tip of the welding electrode in contact with the inner surface of the metal pipe via the intersection of the two tips of the thermocouple. By performing welding in this state, the thermocouple is easily fixed to the inner surface of the metal pipe. With this configuration, thermocouples can be easily fixed inside metal pipes such as steel pipes, which was previously extremely difficult, and the temperature inside the pipe can be monitored, thereby improving the quality of processes such as hardening of metal pipes.

[0009] When using the jig of the present invention described above, the position of the tip of the welding electrode relative to the welding site of the thermocouple is determined. Therefore, when inserting the jig into the metal tube, the position of the thermocouple can be determined by observing the length of the welding electrode from the tip of the welding electrode. Accordingly, a marker indicating the distance from the tip may be provided on the welding electrode to determine the position of the thermocouple inside the metal tube. Such a marker may be a colored mark on the welding electrode, or it may be a separate jig indicating the distance at a predetermined distance arbitrarily set from the tip of the welding electrode. [Effects of the Invention]

[0010] Thus, with the above configuration, thermocouple welding can be easily achieved in metal tubes with an inner diameter that allows the jig to be inserted, making it possible to easily weld thermocouples to the inner surface of metal tubes with diameters that cannot be accommodated by a welding machine. Furthermore, since thermocouples can be attached to the inside of a metal tube without drilling holes in the tube, it becomes possible to measure the temperature inside the tube during heat treatment more accurately. Moreover, according to the present invention, since the temperature inside the tube can be observed during heat treatment, the conditions inside the tube can be estimated without damaging the tube itself. And by monitoring the temperature inside the tube during heat treatment, more appropriate temperature control can be achieved, and an improvement in the quality of the manufactured metal tubes can be expected. The configuration of the present invention may be used to attach thermocouples to the inside of various metal tubes that undergo heat treatment.

[0011] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention. [Brief explanation of the drawing]

[0012] [Figure 1]Figure 1(A) is a schematic perspective view of the jig for holding welding electrodes and thermocouples according to this embodiment, and Figure 1(B) is a schematic perspective view of the jig according to this embodiment inserted into a metal tube. Figures 1(C) and (D) are schematic side and bottom views of the jig according to this embodiment, and Figures 1(E) and (F) are schematic side cross-sectional views and bottom views of the jig according to this embodiment with welding electrodes and thermocouples attached. Figure 1(G) is a schematic side cross-sectional view of the jig according to this embodiment inserted into a metal tube. [Figure 2] Figure 2(A) is a schematic diagram of a thermocouple attached to the jig according to this embodiment, and Figure 2(B) is a schematic perspective view of the process of welding a thermocouple to the surface of an object. Figure 2(C) is a schematic diagram of a state in which thermocouples are attached to the outside and inside of a metal tube. Figures 2(D) and (E) are schematic perspective and side cross-sectional views of the state when attempting to weld a thermocouple inside a metal tube without the jig of this embodiment (prior art). [Figure 3] Figure 3 is a schematic cross-sectional view of one example of a tube on which a thermocouple can be attached using the jig according to this embodiment. [Explanation of Symbols]

[0013] 1...Jig for holding welding electrodes and thermocouples, 2...Motorcouple bundle holding groove, 3, 3a...Motorcouple thin wire holding groove, 4...Welding hole, 5...Welding electrode holding passage, 6...Welding electrode fixing cover, 7...Fixing screw, 10...Positioning jig, w...Welding electrode, TC...Thermocouple (bundle), TA...Thermocouple (thin wire), Tn...Thermocouple (bare wire), T...Metal pipe, P...Welding location, M...Welding machine [Best Mode for Carrying Out the Invention]

[0014] The present invention will be described in detail below with reference to the attached figures, with reference to several preferred embodiments. In the figures, the same reference numerals indicate the same parts.

[0015] Thermocouple and welding machine configuration In quenching treatment for heating metal pipes such as steel pipes to about 700 to 1000°C, it is preferable that the temperature inside and outside the pipe can be measured in order to confirm whether the temperature inside and outside the pipe is properly controlled. Therefore, a thermocouple capable of measuring temperature within the above temperature range is attached to the surface of the pipe by welding using a welding machine. As schematically shown in Fig. 2(A), the thermocouple used herein has a wire-shaped (e.g., about 1.4 mm in diameter) structure TC formed by bundling two thin wires TA (e.g., about 0.5 mm in diameter) each covering a bare wire Tn (e.g., about 0.2 mm in diameter) made of different types of metal. When welding the thermocouple TC onto an article K, as shown in Fig. 2(B), the bare metal wires Tn are arranged at the welding position P on the article K in a state where the vicinity of their ends cross each other, a cathode G of the welding machine is arranged on the article K, and the tip wp (e.g., about 5 mm in diameter) of a welding electrode (anode) w held by a hand-held box-shaped welding machine main body M is brought into contact with the welding position P via the intersection of the bare metal wires Tn. Then, the switch sw is pressed to pass current between the electrodes, so that the article K and the bare metal wires Tn melt, thereby fixing the tip of the thermocouple TC to the welding position P.

[0016] Therefore, as schematically shown in Fig. 2(C), when it is intended to attach the thermocouple TC not only to the outer surface but also to the inner surface of the metal pipe T, it is necessary to bring the tip wp of the welding electrode w and the tip of the thermocouple TC to the position inside the metal pipe where the thermocouple is to be attached and hold them stably. However, when the inner diameter of the metal pipe T is relatively small and the distance from the open end of the metal pipe T to the position where the thermocouple is to be attached is relatively long, as schematically shown in Figs. 2(D) and 2(E), the welding machine main body M cannot be brought into the pipe, and if the length of the cantilevered welding electrode from the welding machine main body M is too long, stable positioning is difficult. Moreover, since the thermocouple TC is a relatively flexible wire-shaped rod, eventually, even if one attempts to arrange the bare wire portion of the thermocouple in a crossed state at the position Pt where the thermocouple is to be attached and further bring the welding electrode tip wp into contact therewith, the welding electrode tip wp cannot reach the position Pt, or even if it can reach, it is extremely difficult to stably hold the thermocouple and the welding electrode at that position until welding is completed.

[0017] Configuration and use of the jig according to this embodiment In view of the difficulty of attaching a thermocouple to the inner side of a metal pipe as described above, the present embodiment provides a jig 1 formed to have dimensions allowable for insertion into a metal pipe T, as schematically illustrated in FIGS. 1(A) to 1(G), wherein the jig 1 holds a welding electrode w and a thermocouple TC in a state where two bare wires Tn at the tip of the thermocouple TC intersect and are abutted against the inner surface of the metal pipe, and the tip wp of the welding electrode w is abutted thereover.

[0018] Specifically, in the jig 1, as shown in FIGS. 1(C) and 1(D), when the jig 1 is brought into the inner side of the metal pipe T, a groove portion 2 for accommodating a bundled portion TC of the thermocouple TC, a groove portion 3 for accommodating two coated thin wire portions TA of the thermocouple TC, and a groove portion 3a for accommodating two bare wire portions Tn of the thermocouple TC in an intersecting state are formed on a bottom surface 1a facing the inner surface Ti of the metal pipe T. The groove width may be adjusted such that the coatings of the bundled portion TC and the thin wires TA are slightly compressed when accommodated in the respective grooves, so that the bundled portion TC of the thermocouple and the coated thin wires TA do not easily fall out of the grooves 2 and 3. Further, a welding hole 4 penetrating upward is formed at the intersecting portion of the bare wire portions Tn. On the other hand, a passage portion 5 for holding the stem portion of the welding electrode w is formed on the upper side of the jig 1, and a lid 6 is configured to be fixed above the passage portion 5 by a fixing screw 7. When the thermocouple TC and the welding electrode w are attached to the jig 1 having such a configuration, as shown in FIGS. 1(E) and 1(F), the bundled portion TC, the thin wire portions TA, and the bare wire portions Tn of the thermocouple TC are arranged to be accommodated in the groove portions 2, 3, and 3a respectively. The bent tip wp of the welding electrode w is passed through the welding hole 4, the stem portion of the welding electrode w is fitted into the passage portion 5 such that the tip wp abuts against the intersecting portion of the bare wire portions Tn of the thermocouple TC, the lid 6 is closed from above and fixed by the fixing screw 7, whereby the welding electrode w is fixed.

[0019] Then, as shown in Figure 1(G), the jig 1, holding the thermocouple and welding electrode, is inserted into the inside of the metal tube T. The jig is then moved so that the welding hole 4 where the bare wires of the thermocouple intersect aligns with the desired attachment position Pt. At this point, the welding machine switch sw is pressed, and the welding process is performed (the inner diameter of the metal tube can be 1 to several centimeters). At this time, since the intersection of the bare wires Tn of the thermocouple and the tip wp of the welding electrode are stably positioned at position Pt, the welding process becomes extremely easy. After welding is complete, the jig 1 is removed from the tube along with the welding electrode. Since the thermocouple is welded to the inner surface of the tube, it can be easily detached from the jig 1 with minimal force and remains inside the tube. (After temperature control is complete, the thermocouple can be detached from the inner surface of the tube along with the welded portion by pulling it with a moderate amount of force.)

[0020] Incidentally, when carrying a thermocouple and a welding electrode into a metal pipe using the jig 1 as described above, if the pipe diameter is small, it becomes difficult for the worker to visually confirm the positions of the jig 1, thermocouple, and welding electrode inside the pipe. In this regard, the positions of the intersection of the bare wire Tn of the thermocouple and the tip wp of the welding electrode are aligned by the jig, and since the welding electrode w has relatively high rigidity, it is possible to determine the position of the intersection of the bare wire Tn of the thermocouple inside the pipe by the length from the tip of the welding electrode to any position on the welding electrode. Therefore, a marker indicating the distance from the tip of the welding electrode may be provided at any position on the welding electrode. As a marker, for example, a colored mark may be placed at a position equal to the distance from the tip of the welding electrode to the position where the thermocouple is to be attached and the opening end of the pipe, or a jig 10 that displays a position as exemplified in Figures 1(A), (B), and (G) may be attached. As a result, the marker aligns with the open end of the pipe, causing the welding hole 4 of the jig 1 to align with the position Pt where the thermocouple is to be attached. This makes it possible to easily attach the thermocouple to the desired position even if the position of the jig 1 cannot be visually confirmed.

[0021] With the jig according to this embodiment, it becomes possible to weld thermocouples to the inner surface of a metal tube even at positions far from the opening end where welding would have been difficult in the past. Furthermore, the jig according to this embodiment can be used when attaching thermocouples to the inside of metal tubes of various inner diameters. For example, as illustrated in Figure 3, in the case of a tube with an inner diameter of φa to φc (for example, between 18 and 24 mm), temperature variations may occur during the quenching process. Therefore, it is desirable to be able to measure and monitor the temperature at each of the different diameter positions. Using the jig according to this embodiment, it becomes extremely easy to attach thermocouples to each of the different diameter positions Pt1 to Pt3.

[0022] While the above description is made in relation to embodiments of the present invention, many modifications and changes are readily possible for those skilled in the art, and it will be clear that the present invention is not limited to the embodiments illustrated above, but can be applied to various devices without departing from the concept of the present invention.

Claims

[Claim 1] A method for attaching a thermocouple to the inner surface of a metal tube by welding, A jig for holding a welding electrode and a thermocouple, comprising: a thermocouple holding groove portion having dimensions that allow it to be inserted into the metal tube to which the thermocouple is attached, and shaped to hold the thermocouple in a position in contact with the inner surface of the metal tube such that the two ends of the thermocouple intersect; and a welding electrode holding passage portion for holding the welding electrode such that the tip of the welding electrode abuts against the inner surface of the metal tube through the intersection of the two ends of the thermocouple, wherein, outside the metal tube, the thermocouple is held in the thermocouple holding groove portion such that its two ends intersect, and the welding electrode is held in the welding electrode holding passage portion such that its tip abuts against the intersection of the two ends of the thermocouple, The steps include inserting the jig holding the welding electrode and the thermocouple into the inner surface of the metal tube such that the intersection of the two ends of the thermocouple aligns with the position where the thermocouple is to be attached, A step of welding the thermocouple to the inner surface of the metal tube. A method that includes this.

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