It can be seen from experience that this experience of looking at temperature is slowly accumulated by working at ordinary times. In addition, flame correction can't be solved by temperature alone, especially the steel structure is an integral component. After welding, the connection of each point will produce stress, and the work progress and welding quality of each welder are very different, so the stress will be different. These correction experiences need to be accumulated slowly.

If accurate temperature is needed, one is to have a temperature chromatogram as a reference, and the other is to measure it with a thermometer. (The temperature inside and outside the heating point is different)

It is incorrect to say that the place that needs to be corrected is red and the stress is released according to the distortion of deformation. This has nothing to do with the impermeability of red, and the node of pressure release and correction is also very important. In addition, some deformations can be corrected only by relaxing and tightening the stress without flame heating.