After welding heat and heat treatment after welding |
Immediately after welding welded pieces of all (or local) heating or insulation, the corrosion process measures called cold, heat. The purpose is to reduce the heat of welding joint especially diffusion hydrogen content in the heat affected zone, it is also known to produce hydrogen treatment, prevention is important technological measures to delay the crack welding of some low alloy structural steel.
20MnNiMoNb steel welding preheating 130 DEG C, after heat temperature and time to avoid the cracks between. After the thermal effect is very significant, after welding heat 45min at 280 DEG C, can keep the welding cracks, if heated to 300~350 DEG C, can heat a shorter time.
Postweld heat treatment
After welding, heat treatment to improve the microstructure and properties of welding joints or eliminate residual stress. It is known as the heat treatment after welding.
Electroslag welding due to large heat input, heating and cooling speed is slow, high temperature and long residence time, so a very coarse grain seam, the impact toughness is very low, usually should be carried out after welding heat treatment.
Some pieces of welding, such as thick wall pressure vessel after welding to eliminate the welding residual stress of heat treatment, the commonly used method is the high temperature tempering. Low alloy steel containing vanadium at 600~620 DEG C after tempering, plasticity and toughness (brittleness), tempering temperature should be 550~560 degrees.
After the heat treatment after welding and the relationship between the two
Welding heat is not equal to the heat treatment after welding. After the heat to prevent hydrogen delayed cracking. Postweld heat treatment is to improve the microstructure and properties of welded joints, welding residual stress. In addition, the heating temperature of heat treatment after welding heat is much higher than the. , of course, if after welding parts at the same time to the two processing, such as timely post weld heat treatment, can be removed after heat treatment.