Detecting residual magnetism in ferromagnetic materials

Various manufacturing processes use increasingly complex and sensitive methods, which are dependent of a high quality of the intermediate product stages. Processes such as coating, welding, shaping or stamping depend on a minimum possible residual magnetism on materials, parts, tools, and machinery. To meet the high demanding requirements these processes often rely on the absence of residual magnetism.

Residual magnetism of such components is measured using hand-held magnetic field strength meters. Other common terms for these are Gaussmeters or Teslameters.

Due to its nature, residual magnetism can only be measured on the surface of a part. The detected value depends on the construction and design of the probe, its location referring to the surface, and the configuration of the magnetic field.

Typical production parts made of ferromagnetic steel show a highly inhomogeneous pattern of residual magnetism. Beside adequate instrumentation, this calls for an adequate search method for finding the maximum residual magnetism on the surface. The strength of the residual magnetic field on the surface of the material has a crucial impact on the quality of industrial processes like; cleaning, galvanic coating and welding processes.

Another important impact is given by ambient magnetism, such as the magnetic field of earth. These fields create an induced magnetism in ferromagnetic materials, which adds up vectorially to the residual magnetism inherent in the material. Induced magnetism depends on the location and the position of the part within its ambient surrounding.

If you wish to know more, or if you are looking for assistance in detecting residual magnetism, feel free to contact us.