METHOD FOR CONTROLLING PREHEATING TEMPERATURE OF BUILD-UP WELDING OF INSIDE SURFACE OF PIPE

摘要

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.