Manganese Steel ASTM A128 Grade A

Designations: Hadfield steel · UNS J91109 · X120Mn12ASTM A128 Grade A is austenitic manganese steel — Hadfield steel — and it behaves unlike any other casting alloy. It is soft when delivered, around 200 HB, and work-hardens to over 500 HB at the wearing surface under impact while the core stays tough. That combination is why it has not been displaced in a century. It is specified for crusher jaws and cones, hammers, dredge parts and rail crossings. Kormax casts A128 Grade A to order.

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Chemical Composition

Manganese Steel ASTM A128 Grade A — chemical composition, % by weight
Element	Symbol	Range / limit %
Carbon	C	1.05–1.35
Manganese	Mn	11.0 min
Silicon	Si	1.00 max
Phosphorus	P	0.07 max
Iron	Fe	Balance

Mechanical Properties

Manganese Steel ASTM A128 Grade A — mechanical properties
Property	Metric	Imperial
Tensile Strength	780 MPa	113 ksi
Yield Strength	400 MPa	58 ksi
Elongation	30%	30%
Hardness, as delivered	200 HB	200 HB
Hardness, work-hardened in service	500–550 HB	500–550 HB

ASTM A128 specifies chemical composition and heat treatment. It specifies no mechanical properties, so these are typical values, not requirements. The two hardness rows are the point of the alloy: it is delivered soft and machinable, and hardens where it is struck.

Got the numbers you needed? Kormax pours A128 Grade A in chemically bonded sand casting.

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Comparable and Related Specifications

The standards and grades below may have similar composition, properties or applications, but they should not be treated as direct equivalents without review. Chemistry, heat treatment, toughness requirements and testing provisions can differ between standards.

ASTM / SAE: A128 Grade A / A12875
UNS: J91109
DIN: GX120Mn12
Afnor: Z120M12
EN (EU/US): 1.3401 X120Mn12
GB (Chinese Standard): GB/T 5680 ZG120Mn13
ISO (International): ISO 13521 Gr GX120Mn13
BS (British Standard): BW10