Weld electrode / jig for holding thermocouple for welding thermocouple to inner surface of metal pipe

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 specifically to a jig (welding electrode / thermocouple holding jig) that holds a welding electrode and a thermocouple in order to weld the thermocouple to the inner surface of a steel pipe or other metal pipe. [Background technology]

[0002] In the quenching process of steel pipes and various other heat treatment processes of metal pipes, welding may be performed to attach thermocouples to the surface of the metal pipe for the purpose of temperature control of the metal pipe. For example, Patent Document 1 discloses that when improving the residual stress of the pipe by locally irradiating the outer circumferential surface of the welded part of the cylindrical pipe with a laser beam and moving the irradiation area in the circumferential direction, a plurality of thermocouples are attached to the outer surface of the pipe to measure the temperature history of the outer surface of the pipe. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2008-169444 Summary of the Invention [Problem to be solved by the invention]

[0004] During heat treatment of metal pipes, such as quenching of steel pipes, the temperature may differ between the outer surface and the inner surface of the metal pipe, so it is preferable to be able to measure the temperature not only on the outer surface of the pipe but also on the inner surface of the pipe. In this regard, when attaching a thermocouple for temperature measurement to a suitable position on the surface of the pipe, the thermocouple is fixed to the surface of the pipe by welding. However, when the inner diameter of the pipe is relatively small and the distance to the desired position on the inner surface of the pipe from the open end of the pipe is relatively long, it is not possible to bring a welding machine carrying a welding electrode into the pipe, and only the welding electrode is extended and its tip is brought to the deep inside of the pipe to the desired position of the thermocouple. However, it is extremely difficult to stably hold the tip of the welding electrode at the welding position of the thermocouple while holding the relatively flexible wire-like thermocouple at the desired position until welding is completed. Therefore, when welding a thermocouple to a desired position on the inner surface of the pipe, it is 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 extremely simplified.

[0005] Thus, a primary object of the present invention is to provide a jig for holding a thermocouple and a welding electrode inside a metal pipe, such as a steel pipe, so that the thermocouple can be easily fixed to the inner surface of the pipe by welding. [Means for solving the problem]

[0006] According to the present invention, the above object is achieved by a jig for holding a welding electrode and a thermocouple, the jig having a dimension which enables insertion into the interior of a metal tube to which the thermocouple is attached, and having a thermocouple holding groove portion shaped to hold the thermocouple at a position in contact with the inner surface of the metal tube so that the two tips of the thermocouple intersect, and a welding electrode holding passage portion which holds the welding electrode so that the tip of the welding electrode abuts against the inner surface of the metal tube through the intersection position of the two tips of the thermocouple.

[0007] In the above, the "thermocouple" may be a wire-shaped one formed by arranging two types of coated metal wires normally used in this field in parallel, and may be capable of measuring temperatures of at least about 700 to 1000°C. The "welding electrode" may be a rod-shaped or wire-shaped metal member of a handheld welding machine used in this field, which can weld and fix a wire such as a thermocouple to a metal surface, and the tip of the electrode may be abutted against an article to be welded and an electric current is applied to achieve welding. The above-mentioned jig is formed so that its overall dimensions can be inserted into the inside of a metal tube to which a thermocouple is attached, and when the jig is inserted into the metal tube, a thermocouple holding groove portion is formed on the surface of the jig facing the inner surface of the metal tube, so that the thermocouple is held in a state in which the two tips cross at a position where the thermocouple is in contact with the inner surface of the metal tube, as described above, and further, the welding electrode holding passage portion is configured to hold the welding electrode and bring its tip into contact with the inner surface of the metal tube via the crossing position of the two tips of the thermocouple.

[0008] According to the above-mentioned jig of the present invention, the welding electrode and the thermocouple are stably positioned in the metal pipe with the tip of the welding electrode abutting the inner surface of the metal pipe via the intersection of the two tips of the thermocouple, and the thermocouple is easily fixed to the inner surface of the metal pipe by performing welding in this state. With this configuration, it is now possible to easily fix a thermocouple inside a metal pipe such as a steel pipe, which was previously extremely difficult, and to monitor the temperature inside the pipe, thereby improving the quality of the quenching process of the metal pipe.

[0009] When using the above-mentioned jig of the present invention, the position of the tip of the welding electrode relative to the welded portion of the thermocouple is determined, so that when inserting the jig into the metal pipe, the position of the thermocouple can be known by looking at the length of the welding electrode from the tip of the welding electrode. Therefore, in order to determine the position of the thermocouple in the metal pipe, a marker indicating the distance from the tip of the welding electrode may be provided on the welding electrode. Such a marker may be a colored mark on the welding electrode, or may be a separate jig indicating a distance at a position arbitrarily set at a predetermined distance from the tip of the welding electrode. Effect of the Invention

[0010] Thus, according to the above configuration, since the welding of a thermocouple can be easily achieved in a metal tube with an inner diameter that allows the insertion of a jig, a thermocouple can be easily welded to the inner surface of a metal tube with a diameter that does not allow the insertion of a welding machine. Also, since the thermocouple can be attached to the inside of the metal tube without drilling a hole in the tube, the temperature inside the tube during heat treatment can be measured more accurately. Furthermore, according to the present invention, since the temperature inside the tube during heat treatment can be observed, the condition inside the tube can be estimated without destroying the tube itself. And, since the temperature inside the tube during heat treatment can be monitored, more appropriate temperature control can be achieved, and the quality of the manufactured metal tube is expected to improve. The configuration of the present invention may be used to attach a thermocouple to the inside of various metal tubes that are subjected to heat treatment.

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

[0012] [Figure 1] Fig. 1(A) is a schematic perspective view of a jig for holding a welding electrode and a thermocouple according to this embodiment, and Fig. 1(B) is a schematic perspective view of the jig according to this embodiment inserted into a metal pipe. Figs. 1(C) and (D) are schematic side and bottom views of the jig according to this embodiment, and Figs. 1(E) and (F) are schematic side and bottom sectional views of the jig according to this embodiment with a welding electrode and a thermocouple attached. Fig. 1(G) is a schematic side sectional view of the jig according to this embodiment inserted into a metal pipe. [Diagram 2] Fig. 2(A) is a schematic diagram of a thermocouple attached to the jig according to this embodiment, and Fig. 2(B) is a schematic perspective view of a state in which a thermocouple is welded to a surface of an article. Fig. 2(C) is a schematic diagram of a state in which a thermocouple is attached to the outside and inside of a metal tube. Fig. 2(D) and (E) are a schematic perspective view and a side cross-sectional view of a state in which a thermocouple is to be welded into a metal tube without the jig according to this embodiment (conventional technology). [Diagram 3]FIG. 3 is a schematic cross-sectional view of an example of a tube to which a thermocouple can be attached using the jig according to this embodiment. [Explanation of symbols]

[0013] 1...Welding electrode / thermocouple holding jig, 2...thermocouple bundle wire holding groove, 3, 3a...thermocouple 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 point, M...welding machine BEST MODE FOR CARRYING OUT THEINVENTION

[0014] The present invention will now be described in detail with reference to some preferred embodiments thereof with reference to the accompanying drawings, in which like reference numerals indicate like parts.

[0015] Thermocouple and Welding Machine Configuration In the quenching process in which a metal pipe such as a steel pipe is heated to about 700 to 1000°C, it is preferable to be able to measure the temperature inside and outside the pipe in order to check whether the temperature inside and outside the pipe is properly controlled. Therefore, a thermocouple capable of measuring the temperature in the above temperature range is attached to the surface of the pipe by welding using a welding machine. The thermocouple used here has a wire-like structure TC (e.g., about 1.4 mm in diameter) in which two thin wires TA (e.g., about 0.5 mm in diameter) each made of a bare wire Tn (e.g., about 0.2 mm in diameter) of a different metal are bundled together, as shown in FIG. 2(A). When welding the thermocouple TC onto the object K, as shown in FIG. 2(B), the bare metal wire Tn is placed at the welding position P on the object K with the tip of the wire crossed, the cathode G of the welding machine is placed on the object K, and the tip wp (e.g., about 5 mm in diameter) of the welding electrode (anode) w held by the hand-held box-shaped welding machine body M is abutted against the welding position P via the intersection of the bare metal wire Tn, and the switch sw is pressed to pass current between the electrodes, melting the object K and the bare metal wire Tn, thereby fixing the tip of the thermocouple TC to the welding position P.

[0016] Therefore, as shown in FIG. 2(C), when attaching a thermocouple TC not only to the outer surface but also to the inner surface of a 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 T 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 shown in Figs. 2(D) and (E) as a schematic diagram, the welding machine main body M cannot be brought into the pipe. Also, if the length of the welding electrode cantilevered from the welding machine main body M is too long, it is difficult to stably position it. Since the thermocouple TC is a relatively flexible wire-like material, even if the bare wire parts of the thermocouple are placed in a crossed state at the position Pt where the thermocouple is to be attached and the welding electrode tip wp is then brought into contact with the position Pt, the welding electrode tip wp may not reach the position Pt, or even if it does reach the position Pt, it is very difficult to stably hold the thermocouple and the welding electrode in that position until welding is completed.

[0017] Configuration of the jig according to this embodiment and its use In view of the difficulty of attaching a thermocouple to the inside of a metal pipe as described above, in this embodiment, as shown in Figs. 1(A) to (G), a jig 1 is provided which is formed to a size that allows it to be inserted into a metal pipe T, and which holds a welding electrode w and a thermocouple TC in a state in which two bare wires Tn at the tips of the thermocouple TC are abutted against the inner surface of the metal pipe in a crossed state, and a tip wp of a welding electrode w is abutted on the bare wires Tn.

[0018] Specifically, as shown in Fig. 1(C) and (D), when the jig 1 is brought inside the metal tube T, a groove portion 2 for accommodating the bundle portion TC of the thermocouple TC, a groove portion 3 for accommodating the two coated thin wire portions TA of the thermocouple TC, and a groove portion 3a for accommodating the two bare wire portions Tn of the thermocouple TC in a crossed state are formed on the bottom surface 1a of the jig 1 facing the inner surface Ti of the metal tube T. In addition, the groove width may be adjusted so that the bundle portion TC and the coating of the thin wire TA are slightly compressed and accommodated in each groove so that the bundle portion TC and the coated thin wire TA of the thermocouple do not easily fall out of the grooves 2 and 3. In addition, a welding hole 4 is formed that penetrates to the top at the intersection of the bare wire portions Tn. Meanwhile, a passage portion 5 for holding the trunk portion of the welding electrode w is formed on the upper side of the jig 1, and a cover 6 is fixed from 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 bundle portion TC, the thin wire portion TA, and the bare wire portion Tn of the thermocouple TC are arranged to be accommodated in the groove portions 2, 3, and 3a, respectively, and the bent tip wp of the welding electrode w is inserted through the welding hole 4 and the trunk portion of the welding electrode w is fitted into the passage portion 5 so that it abuts against the intersection portion of the bare wire portions Tn of the thermocouple TC. Then, the lid 6 is closed from above and fixed with the fixing screw 7, thereby fixing the welding electrode w.

[0019] Then, as shown in FIG. 1(G), the jig 1 is inserted into the inside of the metal pipe T while holding the thermocouple and the welding electrode, and is moved so that the welding hole 4 where the bare wires of the thermocouple cross is aligned with the position Pt where the thermocouple is to be attached, and the switch sw of the welding machine is pressed to perform the welding process (the inner diameter of the metal pipe may be about 1 to several cm). At that time, the crossing part of the bare wires Tn of the thermocouple and the tip wp of the welding electrode are stably positioned at the position Pt, so that the welding process is extremely easy. After the welding is completed, the jig 1 is taken out of the pipe together with the welding electrode, but since the thermocouple is welded to the inner surface of the pipe, it comes off from the jig 1 with a slight force and remains inside the pipe. (After the temperature control is completed, the thermocouple can be peeled off from the inner surface of the pipe together with the welded part by pulling it with a somewhat strong force.)

[0020] However, when the thermocouple and the welding electrode are carried into the metal pipe using the jig 1 as described above, if the diameter of the pipe is small, it is difficult for the worker to visually check the positions of the jig 1, the thermocouple, and the welding electrode in the pipe. In this regard, the positions of the intersection of the bare wires Tn of the thermocouple and the tip wp of the welding electrode are aligned by the jig, and the welding electrode w has a relatively high rigidity, so that it is possible to know the position of the intersection of the bare wires Tn of the thermocouple in the pipe by the length from the tip of the welding electrode to an arbitrary position on the welding electrode. Therefore, a marker indicating the distance from the tip of the welding electrode may be provided at an arbitrary position on the welding electrode. As the marker, for example, a colored mark may be given at a position equal in length from the tip of the welding electrode to the distance between the desired position of the thermocouple and the open end of the pipe, or a jig 10 indicating the position as exemplified in Figs. 1(A), (B), and (G) may be attached. As a result, by aligning the marker with the open end of the pipe, the welding hole 4 of the jig 1 is aligned with the position Pt where the thermocouple is to be attached, making it possible to easily attach the thermocouple at the desired position even if the position of the jig 1 cannot be visually observed.

[0021] According to the above-mentioned jig of the present embodiment, it is possible to weld and attach a thermocouple to the inner surface of a metal pipe at a position far from the open end where it was difficult to weld the thermocouple in the past. The jig of the present embodiment may be used to attach a thermocouple to the inside of metal pipes of various inner diameters. For example, as illustrated in FIG. 3, in the case of a pipe whose inner diameter φa to φc (for example, between 18 to 24 mm) changes, temperature variation may occur during quenching treatment, so it is preferable to be able to measure and monitor the temperature at each of the positions with different diameters. However, by using the jig of the present embodiment, it becomes extremely easy to attach a thermocouple to each of the positions Pt1 to Pt3 with different diameters.

[0022] The above description has been given in relation to the embodiment of the present invention, but it will be apparent to those skilled in the art that many modifications and changes can be easily made thereto, and that the present invention is not limited to the embodiment exemplified above, but can be applied to various devices without departing from the concept of the present invention.

Claims

[Claim 1] A jig for holding a welding electrode and a thermocouple, the jig having a dimension that allows insertion into the interior of a metal pipe to which the thermocouple is attached, the jig having a thermocouple holding groove portion shaped to hold the thermocouple at a position in contact with the inner surface of the metal pipe so that the two tips of the thermocouple intersect, and a welding electrode holding passage portion for holding the welding electrode so that the tip of the welding electrode abuts against the inner surface of the metal pipe through the intersection position of the two tips of the thermocouple.

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