JPS60210364A - Method for controlling preheating temperature of build-up welding of inside surface of pipe - Google Patents

Abstract

PURPOSE:To maintain an adequate temp. in the weld zone of the inside surface of a pipe by detecting the temp. of the inside surface of the pipe in front of a welding torch and controlling a pipe cooler on the outside according to the detected temp. CONSTITUTION:The temp. in the part of the inside surface of the pipe 1 which is going to be welded is detected by a temp. detector in the build-up welding stage of the inside of pipe 1. The temp. signal is outputted to a comparator 16 after the voltage thereof is amplified by an amplifier 14 of a temp. controller 13. The voltage of the temp. signal is compared with the reference voltage from a reference voltage generator 15. A solenoid valve 11 is operated according to the difference thereof to supply the high-pressure air from an air source 6 or to stop the same thereby injecting water from a controlled injection nozzle 9 or stopping the injection. The pipe 1 is thereby cooled or the temp. thereof is increased by which the temp. is controlled so as to attain the prescribed preheating temp. The low-temp. crack of the base metal is prevented and the quality of the build-up weld zone is made uniform by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for preheating temperature control of an acid solution for building up the inner surface of a tube, which builds up the inner surface of the tube, for example, in order to improve the corrosion resistance of the inner surface of the tube.

[Prior art]

Conventionally, a spiral method using MIG welding or TIG welding is often used for welding the inner surface of the tube.

As shown in Figure 1, in the spiral method, the welding torch (2) is continuously moved in the direction of arrow A while swinging the welding torch (2) in the axial direction of the tube inside the tube (1) which is rotating in the circumferential direction. The bead (3) is wound around the inner surface of the tube (1) in a spiral shape.

The internal surface welding of the pipe by the above-described method is highly efficient because it can be performed continuously, but the temperature of the pipe (1) tends to rise because heat from welding is accumulated. If the temperature of the tube (1) becomes too high, the penetration of the weld will increase, resulting in a decrease in quality, and the deformation of the tube (1) will become significant.

To solve this problem, conventionally a cooling nozzle (4) linked to the welding torch (2) was provided outside the welding torch (2) of the pipe (1), and water was directed from this cooling nozzle to the outer surface of the pipe (1). A method has been used to cool the pipes by spraying water on them. However, when welding steel, there is a preheating temperature depending on the type of steel, and welding at a temperature lower than this temperature can cause harmful defects such as cracks.

Therefore, if the tube (1) was simply cooled, the tube (1) could not be maintained at an appropriate preheating temperature, which caused a problem.

(Object of the Invention) An object of the present invention is to provide a preheating temperature control method for overlay welding on the inner surface of a tube, which solves the above-mentioned problems.

[Structure of the invention]

The preheating temperature control method for welding the inner surface of a tube according to the present invention uses a temperature sensor located in front of the welding torch to weld the inner surface of the tube while cooling the already welded part behind the welding torch. This is a method of detecting the temperature, and controlling the tube cooling device installed outside the tube in front of the welding torch based on the detected temperature, so as to maintain the temperature of the welding part inside the tube at an appropriate temperature.

[Embodiments of the invention]

FIG. 2 is a schematic configuration diagram showing an apparatus used in an embodiment of the present invention, and (1) to (6) are the same as those in FIG. 1. (7) is a temperature sensor having a thermocouple attached to its surface, and is fixed to the torch holder (8) at an appropriate position, for example, about 70 degrees in front of the welding torch (2). (9
) is a control spray nozzle installed outside the pipe in front of the welding torch (2), which uses high-pressure air supplied from the air source (6) to atomize the water in the water tank 01 and spray it onto the outer surface of the pipe (1). Inject to. (b) and θ are solenoid valves that pass or block high-pressure air supplied from the air source (6). (2)
1 is a temperature control device, which is composed of an amplifier α which amplifies the temperature signal voltage output from the temperature detector (7), a reference voltage generator q5 which outputs a reference voltage, and a comparator oQ.

While moving the cooling spray nozzle (4) and control spray nozzle (9) shown in the figure in the direction of arrow A in conjunction with the welding torch (2), the inside of the pipe (1) is rotated. During overlay welding, the control VH nozzle (9) controls the temperature rise due to heat transmitted from the already joined part of the pipe (1) from the crack to the part to be overlay welded. That is, the temperature of the part of the tube (1) to be welded is detected by the temperature detector (7), and this temperature signal voltage is input to the amplifier CI4 of the temperature control device (2), amplified, and then sent to the comparator 9. Output.

On the other hand, a reference voltage corresponding to a preset temperature is output from the reference voltage generator U→ of the temperature control device 01 to the comparator O-pass, and the reference voltage and the temperature signal voltage are compared in the comparator QQ. When the temperature signal voltage reaches the reference voltage or higher, the comparator αQ outputs a temperature control signal voltage to open the solenoid valve q), supplying high pressure air from the air source (6) to the control injection nozzle (9), The water in the water tank (G) is turned into a mist through the pipe (
1) Inject outward and cool the tube (1) with the heat of vaporization of water to lower the temperature of the tube (1). Next, when the temperature signal voltage detected by the temperature detector (7) reaches below the reference voltage due to the temperature drop of the tube (1), the temperature control signal voltage output from the comparator lJQ becomes zero, and the solenoid valve (b) is closed, the supply of high pressure air to the control injection nozzle (9) is cut off, and the pipe (
1) The cooling of tube (1) is stopped to increase the accuracy of tube (1). This operation is repeated as shown in the first whipyard of FIG. In Fig. 6, Vη is the temperature signal voltage, 9 o'clock is the reference voltage, (
6) indicates the temperature control signal voltage. In this way, the tube (
As shown in FIG. 4, the temperature of these parts to be welded in step 1) can be maintained within a substantially constant range Δ'r relative to the target temperature TI).

In addition, the cooling spray nozzle (4) can be operated with a solenoid valve (
6) is activated to spray mist water onto the outer surface of the tube (1) for supplementary cooling.

〔Effect of the invention〕

As explained above, this invention detects the temperature of the inner surface of the pipe to be welded and controls the temperature to a predetermined preheating temperature, which prevents cold cracking of the base metal. Since the thickness can be kept constant, the overlay weld can be made homogeneous. Furthermore, continuous welding is possible with a large-capacity welding torch, which improves welding efficiency and reduces man-hours.

[Brief explanation of drawings]

Fig. 1 is a partial cross-sectional view showing the configuration of a conventional pipe inner surface welding method, Fig. 2 is a schematic configuration diagram showing the configuration of an apparatus used in an embodiment of the present invention, and Fig. 3 is a partial cross-sectional view showing the configuration of a conventional pipe inner surface welding method. FIG. 4 is a time chart of an embodiment of the present invention, and FIG. 4 is a preheating temperature characteristic diagram in an embodiment of the present invention. (1)...Pipe, (2)...Welding torch, (3)...
・Bead, (4)... Cooling injection nozzle, (5), α
Groan...water tank, (6)...air source, (7)...
Temperature detector, (8)...Torch holder, (9)...
Control injection nozzle, alpha, (2)... solenoid valve, (b).
...Temperature control device, α◆...Amplifier, (c)...Reference voltage generator, R time...Comparator, αη...Temperature signal voltage, 0 o'clock...Reference voltage, α ... Temperature control signal voltage, (TP) ... Preheating target temperature. Agent Patent Attorney Sanro Kimura Figure 1 Figure 4 Special Area

Claims (1)

[Claims] When overlay welding is performed continuously on the inner surface of the tube while cooling the already welded part behind the welding torch using a cooling device installed outside the tube, the temperature sensor located in front of the welding torch detects the A preheating temperature control method for overlay welding on the inner surface of a tube, characterized by detecting the temperature of the inner surface of the tube to be welded, and controlling a cooling device installed outside the tube in front of the welding torch based on the detected temperature.