As the section size of manganese steel increases, tensile strength and ductility decrease substantially in specimens cut from heat-treated castings. This occurs because, except under specially controlled conditions, heavy sections do not solidify in the mold fast enough to prevent coarse grain size, a condition that is not altered by heat treatment.

Fine grain specimens may exhibit tensile strength and elongation as much as 30% greater than those of coarse-grain specimens. Grain size is also the main reason for the differences between cast and wrought manganese steels -- the latter are usually on fine grain size.

Mechanical properties vary with section size. Tensile strength, tensile elongation, reduction in area and impact strength are substantially lower in 102 mm (4 inches) thick sections than in 25 mm (1 inch) thick sections. Because section thicknesses of production castings are often from 102 to 152 mm (4 to 6 inches), this factor is an important consideration for proper grade specification.

Austenitic manganese steel remains tough at subzero temperatures above the Ms temperature. The steel is apparently immune to hydrogen embrittlement. There is gradual decrease in impact strength with decreasing temperature. The transition temperature is not well defined because there is no sharp inflection in the impact strength-temperature curve down to temperatures as low as -85oC. At a given temperature and section size, nickel and manganese additions are usually beneficial for enhancing impact strength, while higher carbon and chromium levels are not.

Resistance to crack propagation is high and is associated with very sluggish progressive failures. Because of this, any fatigue cracks that develop might be detected, and the affected part or parts removed from service before complete failure occurs.

Yield strength and hardness vary only slightly with section size. The hardness of most grades is about 200 HB after solution annealing and quenching, but this value has little significance for estimating machinability or wear resistance.