Magnetic Remanence Testing
Magnetic remanence testing checks how strongly a material stays magnetized after removing a magnetic field. This gives information about the structure and hardness of the material.
Physicochemical mechanism of action
Magnetic remanence testing measures the magnetic attraction of a material after removing an external magnetic field. This residual magnetism (remanence) depends on the microscopic structure and hardness distributions in the material.
Metallurgical relevance & risks in welding
Remanence can be an indicator of microstructural changes, such as the formation of martensite or austenite. Too high remanence can also indicate incomplete cooling or a high susceptibility to hot cracking. This can be crucial in material selection and the welding process to avoid cracks or hardness variations.
Workshop practice & action instructions
Use a magnetometer to measure remanence. The recommended measurement is done after welding and cooling of the material. A high remanence value (e.g., above 10 Gauss) may indicate incomplete cooling or excessive hardness. Ensure that the material is sufficiently cooled and that the weld is not too hard.