How to weld > Magnetic arc blow
Welding sequences
Tack welds and root runs diminish and/or redistribute the magnetic fields in the joint.
This effect is brought on by:
- Heating of the joint due to welding.
- A redistribution of the magnetic field. This is facilitated if weld metal is present in the joint. It can then acts as a bridge for the magnetic flux flow.
The following two steps can be utilized to plan the welding sequences appropriately so that the level of magnetism is below 40 Gauss in sections of the joint: First, mark the locations in the joint where the local magnetism is below 40 Gauss. Then place tack welds at suitable locations along the marked areas. Long individual lengths of tack welds are preferred. Their individual lengths should generally be set to a minimum of 50 mm each. Welding of joints with a plate thickness up to 8 mm may be done with shorter tack lengths than 50 mm. Repeat this procedure until the magnetism is below 40 Gauss in the complete joint. Then the rest of the welding procedures can be performed.
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