Alloy Grade UNS: HH – Higher in Chromium

  • Overview

    Alloy HH (25-12) is higher in chromium than MTEK 20-10 and will resist scaling to 2000° F with applications in the 1600 to 1900° F range. For maximum strength above 1500° F, the composition must be balanced to insure a stable austenitic structure. For applications requiring higher ductility at service temperatures, the composition can be balanced to give some ferrite in the structure. This increase in ductility is accompanied by a considerable loss in creep strength. Specification ASTM A447 designates two classes of the alloy: Type I, with some ferrite in the structure, for maximum ductility, and Type II, completely austenitic for maximum strength.

  • Typical Uses

    Convection furnace components, grate bars, rabble arms, radiant tubes, and refractory support hardware.

  • MetalTek Grade

    MTEK 25-12

Similar Specifications

Cast UNS: J93503

Wrought UNS: S30900

Wrought Grade: 309

Cast Grade: HH

Cast ASTM: A297, A608

Typical Chemical Composition (% by wt.)

Aluminum: n/a

Carbon: 0.20-0.50

Chromium: 24-28

Manganese: 2

Iron: n/a

Copper: n/a

Nickel: 11.0-14.0

Lead: n/a

Tin: n/a

Silicon: 2

Zinc: n/a

Minimum Mechanical Properties

Tensile, ksi

0

Tensile, MPa

0

Yield, ksi

0

Yield, MPa

0

Elongation

0%

Heat Treatment: Not Heat Treated