Golds-Magnets manufactures sintered large samarium cobalt ring magnets engineered for applications requiring structural stability under elevated thermal loads and oxidative conditions. Unlike NdFeB alternatives, SmCo magnets maintain consistent magnetic flux density across thermal cycles up to 350°C and exhibit superior resistance to thermal demagnetization.
These ring geometries are processed via powder metallurgy, involving precision die pressing or isostatic pressing followed by liquid-phase sintering and precise grinding to meet tight mechanical blueprints.
Technical Specifications
|
Parameter |
Typical Specification |
|
Magnetic Material |
Sintered Samarium Cobalt (SmCo₅ / Sm₂Co₁₇) |
|
Maximum Energy Product (BH)max |
18–32 MGOe |
|
Residual Induction (Br) |
9.0–12.0 kGs |
|
Coercivity (Hcb) |
≥ 8.0 kOe |
|
Intrinsic Coercivity (Hcj) |
≥ 12.0 kOe; high-coercivity grades available |
|
Maximum Operating Temperature |
Up to 300–350°C, depending on grade and application |
|
Curie Temperature |
Typically 700–850°C |
|
Density |
8.2–8.5 g/cm³ |
|
Outer Diameter |
Up to 200 mm |
|
Inner Diameter |
From 30 mm, subject to geometry |
|
Axial Thickness |
Customized according to design and tooling |
|
Standard Dimensional Tolerance |
±0.05 mm after precision grinding |
|
Magnetization Direction |
Axial, diametrical, or customized multi-pole |
Key Features
Temperature coefficient of residual induction (α) remains approximately -0.030%/°C, yielding predictable flux output across operational ranges.
Contains minimal neodymium and higher cobalt content, eliminating the necessity for protective nickel or epoxy plating in standard dry operational environments.
High intrinsic coercivity (Hcj) prevents structural flux loss when exposed to opposing magnetic fields or high-temperature spikes.
Magnetic domains are aligned during the compaction phase along the axial or diametrical vector to concentrate flux density.
Applications
Aerospace Actuators:
Rotor and stator assemblies in flight control actuators functioning in high-heat engine compartments.
Traveling-Wave Tubes (TWTs):
Focusing electron beams within microwave communication hardware.
Magnetic Couplings:
Torque transmission units operating inside sealed chemical pumps and high-pressure autoclaves.
Downhole Petroleum Tools:
MWD (Measurement While Drilling) sensors and logging instruments exposed to subterranean thermal loads.
Customization & Commercial Terms
Large ring configurations demand strict control over magnetic orientation and structural integrity due to internal stresses inherent to rare-earth sintering.
Dimensions: Outer diameters up to 200 mm, inner diameters down to 30 mm, and variable axial thickness based on tooling availability.
Magnetic Orientation: Axial magnetization, diametrical magnetization, or multi-pole magnetizing patterns via specialized fixture coils.
Mechanical Features: Ground slots, keyways, chamfers, or segmented ring assemblies for large motor topologies.
Surface Protective Treatments: Uncoated finish (standard due to inherent oxidation resistance), passivated, or nickel-copper-nickel (Ni-Cu-Ni) electroplating to prevent particle shedding in vacuum environments.
Commercial Parameters:
• Tooling Lead Time: 15 to 25 business days for custom dimension pressing dies and fixture coils.
• Minimum Order Quantity (MOQ): Evaluated per geometry and material grade; pilot batches available for engineering validation.
Manufacturing & Quality Control
Powder Processing: Jet-milling raw alloy ingots under controlled inert gas atmospheres (argon) to prevent oxidation of reactive samarium particles.
Compaction: Isostatic pressing and magnetic field alignment presses ensure uniform density distribution across large cross-sections.
Sintering & Annealing: Vacuum sintering furnaces operating at temperatures exceeding 1100°C, followed by precise multi-stage heat treatment to precipitate the 2:17 metallurgical phase.
Machining: Diamond wire slicing, surface grinding, and CNC profile grinding utilizing wet coolants to prevent thermal micro-cracking of the brittle material.
Inspection & Testing:
• Hysteresis graph testing (Fluxmeter and Permeameter) at ambient and elevated temperatures up to 300°C to verify Br, Hcb, and (BH)max.
• CMM (Coordinate Measuring Machine) verification for dimensional and geometric tolerance compliance.
• Flaw detection via optical comparators and visual surface inspection for chipping or micro-voids.
Packaging & Documentation
Non-magnetic wooden crates lined with high-density polyurethane foam to absorb mechanical impact.
Assembly of internal steel keeper plates and flux-diverting iron sheets to reduce external stray magnetic fields below international air and ocean freight safety thresholds.
Each shipment includes a Material Test Report (MTR) detailing batch chemical composition, room-temperature magnetic properties, and dimensional inspection sheets.
FAQ
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