Post weld heat treatment
The post-weld heat treatment process shall be specified in the welding or heat treatment process documents and shall be subject to the welding process assessment and inspection. Unless otherwise stipulated in the design document, the heat treatment of the pipeline shall be carried out according to (annex table 1).
The lower limit of high alloy content should be selected for the heat treatment temperature of the welded joint between romo molybdenum steel with different alloy composition.
The heat treatment after welding can adopt the method of integral heat treatment or local heat treatment. Heat treatment shall control the process of heating, constant temperature and cooling according to the determined heat treatment process parameters. When the design is not specified, the pipeline heat treatment shall meet the following requirements;
A. After heating up to 300℃, the heating rate shall be calculated according to 5125 (℃/h) and no greater than 220℃/h;
B. The temperature at each temperature measurement point during the constant temperature period shall be within the range specified by the heat treatment temperature, and the deviation shall not exceed 50℃;
C. The cooling rate after constant temperature shall be calculated according to 6500/ (℃/h) and shall not be greater than 260℃/h. After cooling to 300℃, it can be cooled naturally.
SH/T3554 is required for the heating method, heating width, insulation width and arrangement of temperature measuring points of the pipeline heat treatment.
On 2018-08-08 11:45:46
