A temperature controller is used for welding preheating and post weld heat treatment. The output number corresponds to the output cable number. The thermometer, recorder and thermocouple shall be verified to be qualified before use.
(1) heater layout. Both preheating and post weld heat treatment adopt 10kW far-infrared crawler heater with the specification of 540 mm × 415 mm; one group of crawler heater is arranged on both sides of the defect part of the valve body to reserve the area to be repaired. After the repair welding, the heating strip is used to cover the repair welding area. Three layers (about 70 mm thick) of aluminosilicate fiber cotton are used to wrap the heating plate for thermal insulation.
(2) thermocouple arrangement. Two temperature measuring points are arranged under the heater outside the defect part of the valve body. It is used to control the temperature in the heating process, and the temperature difference in the repair welding area is less than 50 ℃.
(3) post weld heat treatment. When the repair welding is completed, the valve body is cooled to (80 ~ 120) ℃ for 1 h, and then the post weld heat treatment is carried out in time. Two groups of far-infrared crawler heaters in the repair welding area were heated to (760 ± 10) ℃, and then kept constant temperature for 4 h. When the temperature is above 300 ℃, the rising and falling speed is less than or equal to 100 ℃ / h. The heat treatment process curve is shown in Figure 6.
Slag and spatter shall be removed after repair welding, and the surface of repair welding metal shall be smooth and smooth transition to base metal. Undercut, crack, lack of fusion, air hole, slag inclusion and defects lower than the surface quality requirements of adjacent base metal are not allowed in the repair welding area. After all repair welding, the surface shall be polished to keep the weld surface flat and smooth. After 24 hours of heat treatment, MT test and hardness test shall be carried out on the repair welding area and its periphery.