JPH0128674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a preheating temperature control method for overlay welding on the inner surface of a tube, in which overlay welding is performed on the inner surface of the tube, for example, in order to improve the corrosion resistance of the inner surface of the tube.

[Prior art]

Pipe inner surface welding is conventional
A spiral method using MIG or TIG welding is often used.

As shown in Fig. 1, the spiral method involves continuously moving the welding torch 2 in the direction of arrow A while swinging the welding torch 2 in the axial direction of the tube inside the tube 1 rotating in the circumferential direction. This is a method in which beads 3 are wound spirally around the inner surface of 1.

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 temperature of the tube 1 will increase.
deformation becomes significant. To solve this problem, conventionally a cooling spray nozzle 4 linked to the welding torch 2 is provided outside the welding torch 2 of the pipe 1, and water is sprayed onto the outer surface of the pipe 1 from this cooling spray nozzle to cool the pipe. methods have been taken. However, when welding steel, there is a preheating temperature depending on the type of steel, and welding at a temperature lower than this temperature will result in toxic defects such as cracks. Therefore, simply cooling tube 1 will
There was a problem that the tube 1 could not be maintained at an appropriate preheating temperature.

[Purpose of the invention]

The 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 two sets of cooling devices to weld the inner surface of the tube while cooling the already welded part behind the welding torch, and one of the cooling devices always keeps the tube constant. At the same time, for the other cooling device, a temperature sensor located in front of the welding torch detects the temperature of the inner surface of the tube to be welded, and the detected temperature controls the spraying of cooling water to cool the inside of the tube. This is a method to keep the welding part temperature at an appropriate temperature.

[Embodiment of the Invention] FIG. 2 is a schematic configuration diagram showing an apparatus used in an embodiment of the invention, and numerals 1 to 6 are the same as those in FIG. 1. Reference numeral 7 denotes a temperature detector having a thermocouple on its surface, and is fixed to the torch holder 8 at an appropriate position, for example, about 70 mm in front of the welding torch 2. 9 is a control spray nozzle installed to control the temperature of the part to be overlaid in contrast to the cooling spray nozzle 4, and is located approximately 10 mm behind the welding torch 2. If the temperature inside the pipe rises too much, high-pressure air supplied from the air source 6 will cool the water tank 1.
The water in the tube 1 is atomized and sprayed onto the outer surface of the tube 1.
On the other hand, the cooling spray nozzle 4 is for cooling the part where the overlay bead 3 has already been placed (already welded part) from the outside of the pipe, and is placed at a position approximately 50 mm behind the welding torch 2. , Spray water is constantly sprayed during overlay welding. Reference numerals 11 and 12 are electromagnetic valves that pass or block high-pressure air supplied from the air source 6. 13 is a temperature control device, and a temperature detector 7
Amplifier 1 that amplifies the temperature signal voltage output from
4. It is composed of a reference voltage generator 15 that outputs a reference voltage and a comparator 16.

While moving the cooling spray nozzle 4 and the control spray nozzle 9 shown in the figure in the direction of arrow A in conjunction with the welding torch 2, the cooling spray nozzle is used to perform overlay welding inside the pipe 1 while rotating the pipe 1. If cooling by 4 is insufficient, a controlled spray nozzle 9 is used,
The temperature rise due to heat transmitted from the already welded part to the part of the pipe 1 to be overlay-welded is controlled. 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 sent to the temperature control device 1.
After inputting the signal to the amplifier 14 of 3 and amplifying it, the comparator 1
Output to 6. On the other hand, the reference voltage generator 15 of the temperature control device 13 adjusts the temperature to a preset temperature (for example, in the case of carbon steel pipes, the set temperature is set to 150°C).
shall be. ) is output to the comparator 16, and the comparator 16 compares the reference voltage and the temperature signal voltage. For example, if the temperature of the part of the pipe 1 that is about to be welded rises by 15 degrees Celsius from the above set temperature of 150 degrees Celsius,
When the temperature signal voltage at that time reaches the reference voltage or higher, the comparator 16 outputs a temperature control signal voltage, opens the solenoid valve 11, supplies high pressure air from the air source 6 to the control spray nozzle 9, and supplies the water tank with high pressure air. The water of No. 10 is sprayed in the form of a mist onto the outer surface of the tube 1, and the tube 1 is cooled by the heat of vaporization of the water, thereby lowering the temperature of the tube 1. Next, when the temperature of the tube 1 drops, for example, by 15°C from the set temperature of 150°C, when the temperature signal voltage detected by the temperature detector 7 reaches the reference voltage or less, the temperature control signal voltage output by the comparator 16 becomes zero. Then, the solenoid valve 11 closes, cutting off the supply of high-pressure air to the control injection nozzle 9, stopping the cooling of the pipe 1, and increasing the temperature of the pipe 1. This operation is repeated as shown in the time chart of FIG. In FIG. 3, 17 indicates a temperature signal voltage, 18 indicates a reference voltage, and 19 indicates a temperature control signal voltage. In this way, the temperature of these parts of the pipe 1 to be welded is adjusted to the target temperature as shown in FIG.
It can be maintained within a substantially constant width ΔT with respect to Tp.

〔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, thereby preventing cold cracking of the base metal, while also increasing the penetration depth of the welded part. Since it can also be made 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 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 spray nozzle, 5, 10... Water tank, 6... Air source, 7... Temperature detector, 8... Torch holder, 9... Control spray nozzle, 11, 12
... Solenoid valve, 13 ... Temperature control device, 14 ... Amplifier, 15 ... Reference voltage generator, 16 ... Comparator, 17 ... Temperature signal voltage, 18 ... Reference voltage,
19... Temperature control signal voltage, Tp... Preheating target temperature.

Claims (1)

[Claims] 1. When performing overlay welding on the inner surface of a tube continuously while cooling the already welded part behind the welding torch using a cooling device installed outside the tube, two sets of the cooling devices are used, and one cooling device is used to perform overlay welding. The other cooling device uses a temperature sensor located in front of the welding torch to detect the temperature of the inner surface of the tube to be welded, and controls the cooling water spray based on the detected temperature. A preheating temperature control method for overlay welding on the inner surface of a tube.