Is preheating necessary for welding when the ambient temperature is below zero?
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Atmospheric pressure vessel, with an ambient temperature of minus 10 degrees. Q235B steel plate, thickness less than 14. Is preheating of the sheet material required for welding? If preheating is required, to what temperature should it be preheated, and by what method? Newbie seeking advice
As clearly specified in NB/T47015-2011, 3.6.3.2: When the temperature of the welded piece is between -20°C and 0°C, it should be preheated to above 15°C within a range of 100 mm from the starting point of welding. Before welding, use a torch to heat the area to be welded, and use a temperature meter to check the temperature on the back side of the weldment
Hello, master! For example, if I need to weld a length of 1.8 meters, and I use heat to do it, does that mean someone has to keep heating it back and forth? Otherwise, the ambient temperature is too low; before welding even begins, the temperature drops again.
My understanding is that preheating is required within the 100mm area where welding begins; simultaneously, the unwelded parts are also heated during the welding process.
The correct answer is that during welding, it is essential to ensure that the temperature within 100 mm of the starting point of welding remains above 15°C; there’s no need to worry about areas further away, as their temperatures will certainly be higher than 15°C. If something goes wrong during welding and the process has to be stopped, preheating is still necessary before resuming welding, to ensure that the temperature within 100 mm of the starting point stays above 15°C
Heat it with a gas welder; the appropriate temperature can be felt by touch.