Meaning
Resistance to demagnetization defines the magnetic field strength required to reduce the magnetization of a saturated ferromagnetic material to zero. Measured in kiloamperes per meter, coercivity correlates inversely with grain size in tungsten carbide cobalt hard metals. Coercivity acts as a non-destructive measure of grain size and binder distribution within sintered hard metals.
The measurement governs quality classification for carbide tooling inserts and slitting blades, where magnetic domain wall movement reflects microstructural refinement. The boundary of coercivity testing applies strictly to ferromagnetic binder systems, losing diagnostic utility in non-magnetic or fully austenitic matrix alloys.
Microstructural Correlation
Grain boundaries in sintered tungsten carbide pin magnetic domain walls within the cobalt binder phase. Fine grain structures create higher boundary density, which impedes domain wall rotation and increases the field strength necessary for demagnetization. Measurements of coercivity allow precise determination of mean carbide grain size down to sub-micron dimensions without destructive metallographic preparation.
Coarse grain microstructures allow domain walls to move freely, resulting in lower magnetic resistance values.
Saturation Magnetization
Magnetic saturation measurements complement grain size evaluations by isolating binder composition from structural refinement. Dissolved tungsten in the cobalt matrix lowers magnetic saturation without altering structural boundary spacing.
Process Control
Industrial quality control protocols for battery electrode shearing tools specify coercivity ranges to verify grain size stability across production batches. Deviations in measured values signal grain growth during liquid phase sintering or carbon content variations within the furnace atmosphere. Carbon deficiency forms brittle double-carbide phases that alter magnetic response, whereas excess carbon causes free graphite precipitation.
Tool manufacturers set acceptance thresholds between twenty and thirty kiloamperes per meter depending on the target grain size grade. Hard metal blades that fall outside specified coercivity bands experience inconsistent wear profiles during continuous foil cutting. Quality audits track coercivity data to validate batch-to-batch microstructural consistency before final diamond grinding operations.
