Causes and consequences of residual magnetism in metal machining
The main causes
Ferromagnetic materials are usually magnetized during various machining phases. The causes of the magnetism may be different depending on the machining:
- Parts held with magnetic chucks
- Magnetoscopic checks and crack analysis
- Welding
- Bending
- Punching
- Turning
- Straightening
- Hardening induction
- Cold forging
- Drilling
- Erosion
- Cutting
- Hardness checks
- Some types of laser marker
- Some type of induction
- Magnetic and electromagnetic lifters used for the movement of raw materials or finished parts.
- Induced magnetism, caused by machining, abrasion, friction between the parts and tools.
The main consequences
- friction
- limited fluency
- rumourosity
- early wear and reduced life
- It interferes, limits and impedes various production processes causing unjustified costs:
- it limits washing quality: particles and micro-particles adhere to the magnetized parts
- Difficulties and/or impossibility of welding
- Machine downtimes and slowing due to the magnetized parts that cannot be transferred correctly
- impediment in the depositing of materials for magnetized parts: particles and micro particles cannot be uniformly distributed over the surface to be treated.
- Surface irregularities in chroming processes.
- Difficulty and impediment in machining with wire cutting
- It causes errors of measurement and disturbs the precision of instruments. The magnetic field sensors may be activated incorrectly.