How to weld > Magnetic arc blow
Residual magnetism in steels
Ferromagnetic steels, including the Hardox® and Strenx® grades, can contain varying levels of residual magnetism.
The magnetic flux density gradually lowers as the distance from the electrode increases. When it is high enough, this magnetism can interfere with the magnetic field from the welding torch and cause magnetic arc blow. Common sources that enhance the magnetism of the steel include:
- Magnets used in jacking equipment
- Storage in a place with high levels of magnetic flux densities.
Low levels of magnetism in the joint will not influence the stability of the arc. Arc blow disturbances can occur when the magnetic flux density is approximately 40 Gauss or above.
The Hardox® and the Strenx® grades are high strength steels with favorable resistance to residual magnetism. However, there are instances when they can obtain magnetic flux densities of 40 Gauss or more. The sensitivity towards magnetic arc blow, caused by residual magnetism in the steel, is generally more emphasized with:
- Hardox® grades of higher hardness
- Higher strength Strenx® grades.
The objective in the following context is to further describe the nature of magnetic arc blow. Suitable remedies are then provided on how to counteract this effect.
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