GGG-NiMn23.4 takes a different path to the austenitic Ni-Resist structure than the chromium-bearing grades: instead of chromium, it uses roughly 4% manganese alongside 22–24% nickel to stabilize the fully austenitic matrix. The result is a chromium-free austenitic ductile iron with the highest elongation in the family — commonly around 25% — giving it exceptional ductility and low-temperature impact toughness. That combination is exactly why it's recognized under ASTM A571, the specification covering austenitic ductile iron castings intended specifically for pressure-containing parts in low-temperature and cryogenic service.

Being chromium-free, GGG-NiMn23.4 leans on its nickel content for corrosion resistance in much the same way GGG-Ni22 does, without the added oxidation resistance chromium provides. What sets it apart is toughness: the manganese addition and resulting matrix give it outstanding resistance to brittle fracture even at very low temperatures, making it a natural fit for valve bodies, pump housings, and pressure-boundary components in LNG, cryogenic, and other low-temperature systems where impact toughness at sub-zero conditions is the primary design driver.

GGG-NiMn23.4 has no chromium and therefore no hard chromium-carbide constituents to accelerate flank wear, which in isolation would make it one of the friendlier Ni-Resist grades to cut. But its manganese addition and the resulting high elongation — the highest in the austenitic ductile iron family — mean this grade is also the toughest and gummiest of the group, with a genuine tendency toward the kind of work hardening associated with manganese-alloyed austenitic irons and steels, even though the manganese content here is far below that of true high-manganese (Hadfield-type) alloys.

In practice, that means treating it with the same discipline used on tough austenitic stainless steel: constant, adequate feed to avoid rubbing or dwelling, sharp positive cutting edges to shear cleanly rather than deform the material, and rigid, vibration-free setups. Because there's no carbide abrasion working against you, tool life on a properly matched grade can actually hold up reasonably well — the challenge here is managing toughness and heat, not abrasive wear.

Reduced cutting speeds relative to standard ferritic ductile iron, a tough coated carbide grade, and generous coolant to manage heat buildup at the edge all help keep this alloy's gummy tendencies in check.