False welding is a common welding defect of welded pipes. It seems that the front and rear steel strips are welded together during welding, but in fact they are not integrated, and the strength of the joint surface is low. The welding seam has to go through a complicated process, especially in the high-temperature furnace area and the high-tension tension-leveling area. The weld seam that is weakly welded is likely to cause a broken belt accident, which will affect the normal operation of the production line.
False welding means that the temperature of the joint surface of the weld is too low during welding, the size of the nugget is small, and it has not reached the degree of melting. After rolling, it is barely bonded together. It seems to be welded well, but in fact it is not completely fused.
The reasons and steps for analyzing the false welding can be carried out in the following order:
1. Check the surface of the welded joint for rust, oil and other impurities, or unevenness and poor contact, which will increase the contact resistance, reduce the current, and make the surface temperature of the welded joint insufficient.
2. Check whether the weld overlap is normal. With the reduction of the overlap, the bonded area of the front and rear steel strips is too small, and the total stress area is reduced, which cannot withstand large tensile forces. Especially the crack phenomenon on the drive side will cause stress concentration, making the crack bigger and bigger, leading to fracture.
3. Check whether the current setting symbol does not meet the process regulations, and whether the current setting increases when the product thickness changes, resulting in insufficient current during welding and poor welding.
4. Check whether the pressure of the welding wheel is reasonable, if the pressure is not enough, the actual current will decrease due to excessive resistance. If the resistance exceeds a certain range, it will exceed the limit of current compensation, and the current cannot be increased and cannot reach the set value. In this case, an alarm will be issued when the system is working normally.
In actual operation, if the cause of false welding cannot be found, both ends of the steel pipe to be welded can be cleaned, and the amount of welding overlap, welding current and welding wheel pressure can be increased. Pay attention to the state of weld seam formation during welding. If there is a problem with the control system, or the fluctuation of the grid voltage causes the weld seam to fail to weld, other measures need to be taken.
False welding means that the temperature of the joint surface of the weld is too low during welding, the size of the nugget is small, and it has not reached the degree of melting. After rolling, it is barely bonded together. It seems to be welded well, but in fact it is not completely fused.
The reasons and steps for analyzing the false welding can be carried out in the following order:
1. Check the surface of the welded joint for rust, oil and other impurities, or unevenness and poor contact, which will increase the contact resistance, reduce the current, and make the surface temperature of the welded joint insufficient.
2. Check whether the weld overlap is normal. With the reduction of the overlap, the bonded area of the front and rear steel strips is too small, and the total stress area is reduced, which cannot withstand large tensile forces. Especially the crack phenomenon on the drive side will cause stress concentration, making the crack bigger and bigger, leading to fracture.
3. Check whether the current setting symbol does not meet the process regulations, and whether the current setting increases when the product thickness changes, resulting in insufficient current during welding and poor welding.
4. Check whether the pressure of the welding wheel is reasonable, if the pressure is not enough, the actual current will decrease due to excessive resistance. If the resistance exceeds a certain range, it will exceed the limit of current compensation, and the current cannot be increased and cannot reach the set value. In this case, an alarm will be issued when the system is working normally.
In actual operation, if the cause of false welding cannot be found, both ends of the steel pipe to be welded can be cleaned, and the amount of welding overlap, welding current and welding wheel pressure can be increased. Pay attention to the state of weld seam formation during welding. If there is a problem with the control system, or the fluctuation of the grid voltage causes the weld seam to fail to weld, other measures need to be taken.
