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Dongyang magnetic materials

Dongyang magnetic material is not a simple comparison of magnetic strength. High-frequency cores focus on loss and heat, motor magnets on remanence, coercivity, demagnetisation and dimensions, and bonded magnets add resin flow and mould orientation. Powder, pressing, sintering, grinding, coating and magnetising all reshape the hysteresis loop under frequency, temperature and assembly gap.

Formation and regional foundations

Hengdian developed ferrites and electronic components early. DMEGC, Qianglian Magnetics and Kaiven provide distinct views of ferrite materials, production lines and custom parts, while the development-zone quality platform supports bonded-magnet application checks. Regional titles and output descriptions show depth but do not grant every material system or current capacity to one legal entity.

Remanence and coercivity at shipment are only a starting point. Motor gap, reverse field, rotor heat and coating damage change usable flux, while high-frequency cores heat under frequency, waveform and DC bias. Dongyang materials answer these separately rather than through one room-temperature loop.

Core geography: A Dongyang material-manufacturing area around Hengdian and the development zone for soft ferrites, permanent ferrites, bonded magnets and magnetic devices

Six Dongyang stations from powder to application

Which heat, direction and magnetising event explains flux change

Material lot and orientation span sintering, grinding, coating and magnetising; high-frequency cores and motor magnets separate into frequency or temperature duty at the final station.

  • Oxide or alloy powder lot — Chemistry, size, oxygen and blending shape later phases.
  • Press density and orientation — Cavity, field, pressure and green orientation follow the part.
  • Sintering furnace and shrinkage — Temperature, atmosphere, load and position correspond to dimensions and phases.
  • Grinding, chamfering and coating — Grinding direction, chipping, dimension and coating define part condition.
  • Magnetising and full sorting — Fixture, pulse, polarity and flux distribution bind the lot.
  • Motor or high-frequency circuit — Heat, reverse field, frequency, waveform and gap define use.

01 · A magnetic number first asks which application it serves

Soft-magnetic loss and permanent-magnet demagnetisation use different coordinates.

Dongyang covers soft ferrite, permanent ferrite, bonded magnets and magnetic devices, each using hysteresis differently. Soft cores seek low coercivity and AC loss, permanent ferrites need remanence and demagnetisation resistance, and bonded magnets add resin flow. Regional breadth does not transfer one metric across materials. Speakers, sensors and motors weight flux, drift and loss differently; a grade gains meaning only inside a magnetic circuit.

Maximum energy product alone misses hot coercivity, flux consistency, eddy loss and strength. Initial permeability alone can hide overheating under DC bias or high frequency. Sample geometry and demagnetising factor change results, so rings, bars and finished magnets are not directly comparable. “High performance” without duty coordinates has little engineering meaning.

Requirements first distinguish motor magnets, high-frequency cores, sensor magnets or moulded components, stating heat, frequency, waveform, reverse field, dimensions and gap. Permanent-magnet metrics use direction and temperature; soft loss uses frequency, peak flux and bias. Method, sample and magnetising state enter the specification, and substitution reopens thermal, magnetic and mechanical limits.

  • Magnetic performance carries frequency, heat, direction and magnetising state.

02 · Trace oxygen in powder becomes another loop after sintering

Chemistry, particle size, surface and blending set the magnetic phase.

Ferrite begins with oxide batching, calcination and milling, while bonded magnets also require control of magnetic powder, resin, additives and dispersion. Particle distribution affects pressing and sintering, and poor mixing creates local magnetic phases or uneven loading. Dongyang history shows a powder-material base, but each product still needs a link from raw lot through process analysis to its final loop. Moisture and storage changes alter forming and magnetics, so every drum keeps milling time and storage condition before blending.

Finer powder supports sintering and orientation but raises oxidation, agglomeration and safety risk. Inadequate drying or milling wear adds moisture and contaminants. Average blend chemistry may miss segregation that appears after sintering as coercivity or loss scatter. A changed recycled fraction alters particle and surface state even when major chemistry looks unchanged.

Raw-material control records supplier lot, chemistry, size, moisture or oxygen, calcination and milling by material system, with multi-location blend sampling. Storage and transfer limit air, water and mixing, and use time stays with the lot. Magnetic drift is stratified by powder and furnace position before averaging, while recycled-content change receives a separate pilot.

  • Powder lot connects to final magnetics and furnace position.

03 · Pressing direction breaks open the word isotropic

Density gradient, orientation field and die friction enter the green body.

Magnetic powder in a die experiences pressure, friction and orientation field, so green density and grain direction affect shrinkage and magnetics. Axial pressing, radial orientation and multipole moulding use different tools. Dongyang bonded-magnet projects broaden forming, but a part still states resin, loading, gate and orientation rather than merely “complex shape.” Orientation uniformity, fill density and die-wall friction shape the compact; correct geometry may still hide a magnetic gradient.

Uniaxial pressing creates density gradients and ejection friction can produce latent cracks that emerge after sintering. Weak orientation or obstructed flow misaligns local magnetisation, while mould flow may align fibres or plate-like powder. Average density misses local differences, and an intact surface does not establish an uncracked interior.

Forming records loose fill, filling, pressure curve, dwell, orientation field, die temperature and ejection force, preserving direction on the green body. First and cavity samples check density, dimensions, cracks and orientation, with die wear trended. Bonded magnets use sections and flux maps to verify gate and flow, repeating shrinkage and magnetics after resin or loading changes.

  • Part orientation remains from pressing through magnetising and assembly.

04 · Furnace position gives one lot different histories

Temperature uniformity, atmosphere and loading define phase and size.

Sintering densifies green bodies and forms magnetic phases; heating, hold, cooling, atmosphere and load density shape grains and shrinkage. Parts of different thickness or furnace position can have distinct histories. Development-zone plans show ongoing capacity building but do not replace current furnace uniformity and lot records. The furnace trace also maps load tier and boat position; average temperature cannot explain edge-to-centre shrinkage differences.

Denser loading changes atmosphere and thermal response, leaving edge and centre parts with different dimensions or coercivity. A furnace thermocouple at setpoint does not establish product core or every level. Excess sintering grows grains, while insufficient sintering lowers density and strength; later grinding fixes size but not phases or internal pores.

The furnace record links recipe, pressed lot, loading map, level, thermal cycle, atmosphere and alarms, periodically confirming the qualified zone. Density, dimensions, microstructure and magnetics are sampled by position before pooling edge and centre. Changed loading, setters or thickness revalidates uniformity, and an uncontrolled run remains isolated until stratified results exist. Load position remains in the record.

  • Magnetic anomalies return to run, level and thermal curve.

05 · One grinding chip turns a magnetic gap into a local hotspot

Dimension, finish and microcracks enter the assembled magnetic circuit.

Sintered magnets are hard and brittle and require grinding for thickness, parallelism, arc and gap. Direction, wheel, coolant and holding influence chips, microcracks and stress. A missing motor-magnet corner changes local gap and flux, while an uneven core joint adds reluctance; average dimension does not cover critical edges. Excess grinding feed or weak cooling creates microcracks and stress that can fail during assembly or thermal cycling despite correct size.

Faster feed raises output but increases heat damage and chipping; excessive chamfer removes useful magnetic volume. A part can deform in measurement and spring back, then shift again with adhesive and slot. Final sampling alone misses wheel-wear trends, while remaining debris can damage coating or bonding.

The drawing separates thickness, parallelism, profile, chamfer, allowed chipping and magnetising direction, with gauges using actual support. First pieces check size and cracks by furnace lot and machine, while wheel life and key dimensions trend the process. Clean parts receive enlarged and suitable NDT inspection, followed by assembly checks of gap, bond thickness and rotor balance.

  • Critical edges and magnetising direction share the part drawing.

06 · A coating pinhole lets corrosion begin at one point

Substrate, pretreatment, thickness and edge coverage define corrosion resistance.

Ferrites and bonded magnets may require surface protection and bonding preparation in humid, saline or adhesive environments. A coating name and average thickness do not describe pinholes, edge coverage or adhesion; corrosion fitness still depends on substrate, pretreatment, layer system and later handling. Beyond salt-spray hours, blistering, pinholes and edge corrosion are separated because each points to a different pretreatment cause.

Grinding residue, oil or sharp edges thin a coating, and transport damage may expose substrate that corrodes only after assembly. Equal salt-spray hours are not comparable with different cut edges, scratches or criteria. Adhesive, coolant or cleaner interaction means a single laboratory environment may not represent motor thermal-humidity cycling.

The coating specification states substrate condition, pretreatment, layers, critical thickness, pinholes, adhesion and repair, using production-equivalent edges. Exposure covers humidity, salt or actual medium and measures flux and bonding afterward. Packaging limits impact and condensation; scratches retain location and exposed area rather than receiving an undocumented touch-up.

  • Corrosion results are interpreted with machining damage and assembly media.

07 · The magnetising fixture decides where flux lands

Pulse, polarity, direction and fixture gap form the final field.

A sintered magnet may remain unmagnetised until fixture, pulse energy, direction, temperature and position create the final field. Multipole rings and bonded magnets rely on pole pitch and phase, so one flux point does not describe spatial distribution. Dongyang bonded-magnet capability still uses fixture revision and field maps for each assembly. Multipole width, phase and leakage remain tied to fixture identity; a passing peak flux cannot replace spatial distribution.

Insufficient pulse leaves incomplete magnetisation, while excess heats coil and part; fixture wear or gap shifts pole boundaries. A reversed part may retain average flux while motor back-EMF or sensor phase is wrong. First-piece scanning alone misses gradual coil heating, energy decay and fixture drift through a long lot.

Magnetising locks fixture revision, part direction, pulse voltage and current, coil heat and cooling interval, with a full field map on first pieces. Production uses risk-based full flux, polarity or waveform checks and challenges thresholds with boundary parts. Maintenance or fixture change repeats phase and uniformity, while anomalies stratify by time and position instead of blind remagnetising.

  • Flux sorting retains fixture, pulse and part orientation.

08 · Hot motors and high frequency split a room-temperature pass

Demagnetisation, AC loss and assembly circuit close under duty.

Motor magnets approach demagnetisation under rotor heat, reverse stator field and overload current; high-frequency cores incur loss under AC flux, DC bias and winding heat. Parts from one Dongyang area do not share one pass sheet. Regional capability can supply materials and devices, while machine outcome depends on gap, cooling, winding and control. Motor speed magnifies eddy loss and retention load together, so thermal balance includes sleeve, adhesive and cooling path.

Magnets with equal room-temperature flux can differ in hot coercivity, and assembly gap or eddy current adds local heat. A core passing sinusoidal loss may heat under PWM or DC-biased waveforms. Whole-machine efficiency cannot locate degradation, while post-test removal loses operating stress, so traceable signals are planned into validation.

Motor validation links magnet lot, rotor position, gap, heat and control current to back-EMF, torque and demagnetisation under overload and cooling faults. Core validation uses actual frequency, waveform, peak flux, bias and winding temperature with loss and hotspots. Failure returns through powder, furnace, machining, coating and magnetising, and only reproducible causes change the process. Changes after thermal cycling are recorded as well.

  • Final validation uses motor duty cycles and core waveforms separately.

Sources and reading notes

Magnetic performance appears with sample geometry, magnetising state, measurement temperature and method. Powder and sintering explain material; grinding, coating and assembly explain parts. Regional output and planned projects provide context without replacing a product lot or test.

  • Dongyang includes several magnetic materials and devices; soft, permanent and bonded magnets use different chemistry, processes and acceptance.
  • Regional history and the Magnet City title establish concentration, not one company’s output, customers or share.
  • Post-completion project capability remains planned or under construction; company capability uses current entities, sites and operating products.
  • Motor magnets and high-frequency cores from one area still face demagnetisation and AC-loss verification separately.

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Sources

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