JP2003071573A - Manufacturing method for thermo-couple protective pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute welding, uniform and free of defect such as a notch, in welding for sealing a pipe end, in manufacturing a thermo-couple, small in diameter and thin in thickness. SOLUTION: By adopting friction welding in place of conventional arc welding, the conventional defect is eliminated and the welding work for a small diameter pipe is facilitated.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection tube for protecting a thermocouple used for temperature measurement in a thermal appliance, a kiln, etc., from damage. Steel is used. More specifically, the present invention relates to a method of manufacturing such a metal protection tube by welding. 2. Description of the Related Art Conventionally, welding for producing a metal protective tube is mainly performed by arc welding, and generally, TIG welding is used to suppress the progress of oxidation near a welded portion. In the conventional arc welding, it is difficult to ensure the welding to reach the back surface of the butt surface of the material to be welded. In the case of a large-diameter pipe, welding work can be performed from the inside of the pipe. However, the outer diameter as targeted by the present invention is 8 to
In a 30 mm small diameter pipe, welding is performed only from the outer surface of the pipe, leaving a notch that is not welded to the weld line inside the pipe.
This is a place that is vulnerable to vibration. When the welding is performed so as to reach the back side, in the thin-walled tube targeted by the present invention, there is deformation of the tube, perforation or deterioration of corrosion resistance due to a large heat input at the time of welding. In addition, it is extremely difficult and difficult to perform welding work around small diameter pipes. SUMMARY OF THE INVENTION As described in the claims of the present application, it is possible to eliminate the above-mentioned defect that leaves a notch inside the protective tube and to facilitate the welding operation. In the production of a thermocouple protection tube using a small-diameter, thin-walled steel pipe having a wall thickness of 2 to 8 mm, one end of the pipe end is butt-welded to a steel bar or a circular plate material having the same diameter. It was manufactured in the shape of a sealed thermocouple protection tube. BEST MODE FOR CARRYING OUT THE INVENTION In friction welding, a material to be welded is butt-joined, one is fixed, and one is rotated to generate frictional heat due to friction between the butted surfaces. , One of the rotations is stopped, and a force for pressing the friction surface is applied to perform welding. The device is based on the above principle and has a shape similar to that of an old lathe.
A high-speed rotation as high as 00 to 8000 rpm can be obtained, and a mechanism for pressing the welding surface so as to stop instantaneously is provided. The production of the thermocouple protection tube according to the present invention will be specifically described. The steel bar or the circular plate material to be the lid of the protection tube is fixed with the mounting tool on the fixed side,
The steel pipe to be welded thereto is fixedly attached to a fitting called a chuck of a rotating body on the rotating side to give rotation, and the welding operation is started. The number of revolutions depends on the diameter and thickness of the steel pipe to be welded.
Although the pressing force will be different for the duration of the rotation, the outer diameter of 8 to 30 mm and the wall thickness of 2 to 8 mm, which are the object of the present invention, have both the friction pressure and the pressing pressure at the final stage of 4.3 to 4.3 mm. The rotation speed was 1500 kg / mm 2 and was 1500 kg.
The preset time for stopping and pressing at ２０００2000 rpm is 2 to 5 Sec. While the rotation and pressing continue, the butted portion of the steel pipe glows red, gradually softens and stops rotating when the state where the outer diameter of the steel pipe becomes larger than the circumference of the original steel pipe is stopped, and the pressing is maintained for 2 to 5 seconds. Welded. When the steel pipe is softened at the butt surface and becomes larger than the outer diameter, that is, when the burr is increased, the amount of grinding work for removing the burr after welding increases. On the other hand, if the pressing force is too large, the steel pipe bends without enduring. When the end of a small-diameter steel pipe is sealed by friction welding, the pipe is uniformly welded over the entire surface and the entire circumference, and the notch such as arc welding is not recognized. Moreover,
Friction welding does not require much work, so the work is completed in a very short time after being installed in the welding machine, and if the necessary factors such as the number of rotations and pressing force are set, the work can be done easily without skill. I can do it.

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[Procedure amendment] [Date of submission] November 14, 2001 (2001.11.
14) [Procedure amendment 1] [Document name to be amended] Description [Item name to be amended] Brief explanation of drawings [Correction method] Addition [Content of amendment] [Brief explanation of drawings] [Fig. The place where the material to be welded is mounted on the friction welding machine is shown. The middle figure shows a bar welded to a steel pipe by friction welding. The lower figure shows the completion of the thermocouple protection tube by cutting off the steel bar. [Description of Signs] 1 ··· Friction welding machine 2 ····································································· ... Steel pipe 6 .... Completed thermocouple protection tube

Claims (1)

Claims: 1. In the manufacture of a thermocouple protection tube using a small-diameter, thin-walled steel tube having an outer diameter of 8 to 30 mm and a wall thickness of 2 to 8 mm, the ends of the steel tube have the same diameter. Characterized in that the lid is closed by butt friction welding with a steel bar or a circular plate material.