Hiperco® 50, Hiperco® 50A & Hiperco® 50 HS

DC Magnetic Properties

DC magnetic data describes how the alloy responds to a steady applied field. Coercivity indicates how much reverse field is needed to bring the material back to zero magnetization, so lower values mean the core is easier to cycle. Maximum DC relative permeability shows how efficiently the material amplifies an applied field. The flux density columns list the induction reached at each field strength in A/m. 

AC Core Loss

Core loss is the energy dissipated as heat each time the magnetic field reverses, and it increases steeply with frequency. The table lists specific core loss in watts per pound at 60, 400, and 1000 Hz for two strip thicknesses and two heat treatments, measured at induction levels of 1.0, 1.5, and 2.0 Tesla. 

Ferromagnetically annealed material loses considerably less energy than mechanically annealed material under every condition.

Physical and Thermal Properties

Physical properties describe the bulk behavior of the alloy independent of the applied field. The Curie temperature of 938°C (1720°F) marks the point at which the material loses its magnetic ordering and sets the ceiling for any magnetic application. Electrical resistivity of 40.1 × 10⁻⁸ ohm-m limits eddy currents within each lamination. 

The thermal conductivity of 29.83 W/m°C governs how readily heat escapes a core, while the coefficient of thermal expansion is listed across four temperature ranges because it rises with temperature.

Mechanical Properties

Mechanical values shift dramatically with heat treatment. Cold-rolled, unannealed strip reaches 190 ksi ultimate tensile strength at 36 HRC but offers only 2% elongation, limiting forming. A standard magnetic anneal softens the material to 115 ksi ultimate with 5 to 15% elongation, releasing the internal stress that degrades magnetic performance. A mechanical anneal lands between the two at 135 ksi. Parts are normally stamped or machined in the harder condition and then annealed as a final operation.

Hiperco® 50A Properties

Hiperco® 50A is a low-carbon, high-permeability member of the family. The tables below separate strip data from bar data, since form has a large effect on magnetic response.

DC Magnetic Properties, Strip and Bar

In annealed 0.014″ strip, Hiperco® 50A reaches a coercivity of 30 A/m with maximum DC relative permeability of 22,000, an improvement over standard Hiperco® 50 on both counts. Bulk bar tells a different story: coercivity rises to 209 A/m and maximum permeability falls to 3,350, though saturation flux density at 16,000 A/m still reaches 2.30 Tesla. 

Engineers specifying Hiperco® 50A round bar for a solid pole piece should design around the bar figures rather than the strip figures.

AC Core Loss

Core loss for annealed Hiperco® 50A strip runs below that of comparably treated Hiperco® 50 at 60 Hz and 400 Hz, reflecting the cleaner chemistry. The three rows correspond to induction levels of 1.0, 1.5, and 2.0 Tesla.

Physical and Thermal Properties

Physical properties for Hiperco® 50A track closely with Hiperco® 50. Density, specific gravity, Curie temperature, elastic modulus, and thermal conductivity are effectively identical, and electrical resistivity differs only marginally at 240.7 ohm-cir mil/ft. 

Thermal expansion behaves the same way across the four listed ranges. Substituting Hiperco® 50A for Hiperco® 50 therefore rarely disturbs the thermal or dimensional side of a design.

Mechanical Properties

The mechanical spread between conditions is wider for Hiperco® 50A than for Hiperco® 50. Cold rolled unannealed strip reaches 195 ksi ultimate tensile strength with 1% elongation, while the standard magnetic anneal reduces that to 72.2 ksi with 6.7% elongation. The low annealed strength reflects the priority placed on magnetic performance in this grade, so parts under mechanical load generally need either a design allowance or a move to Hiperco® 50 HS.

Hiperco® 50 HS Properties

Hiperco® 50 HS is the high-strength variant, developed for rotating parts that must hold together under centrifugal load while still carrying high flux.

DC Magnetic Properties by Strength Level

This table is organized differently from the others because it shows the trade curve directly. Each row pairs a 0.2% yield strength with the flux density that material achieves at five field strengths, measured on ring laminations per ASTM A596/A596M. Raising yield strength from 73 ksi to 99 ksi costs about 1.1 kG of flux density at 800 A/m, though the penalty nearly vanishes at higher field strengths where all three conditions converge near 2.29 Tesla. 

Designers use this relationship to pick the lowest strength level that satisfies the mechanical case, preserving magnetic headroom.

Physical and Thermal Properties

Hiperco® 50 HS shares the density, Curie temperature, and thermal behavior of the other grades. The one meaningful difference is electrical resistivity, which rises to 253.0 ohm-cir mil/ft (42.1 ohm-m) because of the added columbium/niobium. Higher resistivity modestly suppresses eddy currents, a small bonus in a grade selected primarily for strength.

Mechanical Properties by Heat Treatment

This table maps ten combinations of annealing temperature and hold time to the resulting yield strength, tensile strength, and elongation in 0.006″ strip. Yield strength falls steadily as either temperature or time increases, ranging from 99 ksi after one hour at 720°C down to 64 ksi after four hours at 800°C. 

All listed treatments were run in batch furnaces under dry hydrogen with a one-hour heat-up and a controlled 180°F/hr cool. Reproducing these values depends on matching that atmosphere and cooling rate, so heat treaters should treat the footnote as part of the specification.

Hiperco® 50, 50A, 50 HS Chemistry

The chemistry table shows the nominal composition for all three grades side by side. Cobalt sits near 48.5% across the family and supplies the high saturation. Vanadium, around 1.9 to 2.0%, raises resistivity and improves hot workability. 

The real differences are in the trace elements: Hiperco® 50A cuts carbon by an order of magnitude to 0.001% and drops columbium/niobium to 0.01%, both of which reduce magnetic losses. Hiperco® 50 HS moves the other way, raising columbium/niobium to 0.30% to pin grain boundaries and build strength.

Hiperco® 50, 50A, 50 HS Specifications

All three grades meet ASTM A801 Type 1, the standard covering wrought iron-cobalt high-magnetic-saturation alloys. 

Hiperco® 50 carries the additional UNS designation R30005 Type 1 and, along with Hiperco® 50A, conforms to MIL-A-47182 for defense procurement. Specifying by standard rather than by trade name alone provides purchasing with a fallback path and supports audit requirements for regulated programs.

For additional information on specifications of the materials distributed by EFINEA, please visit the websites of the international organizations that develop and publish technical standards: ASTM International and ASM International.