GGG-NiSiCr30-5-2 is an austenitic ductile (spheroidal-graphite) cast iron under German standard DIN 1694, a mid-range member of the NiSiCr "Ni-resist" family alongside the 20-5-2, 35-5-2, and 30-5-5 grades. The designation numbers are nominal weight-percent alloy targets — roughly 30% nickel, 5% silicon, and 2% chromium. That nickel content is well above what's needed to fully stabilize the iron matrix as austenite, giving the casting a non-magnetic structure that doesn't undergo the phase transformations responsible for thermal-fatigue cracking and permanent growth in ordinary pearlitic or ferritic ductile iron. The silicon addition promotes a stable, adherent oxide layer that protects the surface from scaling under repeated heating and cooling, while the more modest 2% chromium (versus 5% in the 30-5-5 grade) trades some oxidation resistance for a somewhat more machinable, lower-cost alloy.

This balance of alloy content makes GGG-NiSiCr30-5-2 a common choice for pump and compressor components, valve bodies, and general process equipment exposed to elevated temperature or mildly corrosive media, where the full 5% chromium of the 30-5-5 grade isn't required. Like the rest of the family, its spheroidal graphite structure also delivers meaningfully better ductility and impact toughness than an equivalent flake-graphite gray iron.

GGG-NiSiCr30-5-2's 30% nickel content puts it well into fully-austenitic territory, so it machines much more like an austenitic stainless steel than like a conventional pearlitic or ferritic ductile iron. The matrix work-hardens under the mechanical and thermal stress of cutting rather than shearing cleanly, so a dull edge or an under-speed pass will burnish the surface and complicate the next cut — the same behavior seen across the whole Ni-resist family, and one of the main reasons cutting parameters for these alloys can't simply be read off a standard cast-iron hardness chart.

Lower thermal conductivity than plain ductile iron keeps more of the cutting heat concentrated at the tool-chip interface instead of carrying it away in the chip, which limits practical cutting speed more than the material's moderate bulk hardness would suggest. A sharp, positively-oriented edge that shears rather than crushes the material reduces both work hardening and heat buildup at the edge, and steady, adequate chip load helps the tool keep cutting instead of rubbing.

As with the other NiSiCr grades, the spheroidal graphite nodules provide some internal lubrication and chip-breaking, so overall chip control stays reasonable, but tool life and achievable cutting speed will trail what the same hardness number would deliver on a standard nodular cast iron.