GGG-70 is a high-strength, predominantly pearlitic ductile (nodular/spheroidal graphite) cast iron defined under the German DIN 1693 standard, corresponding to EN-GJS-700-2 under EN 1563. The "70" guarantees a minimum tensile strength of 700 N/mm², with minimum elongation dropping to around 2% — reflecting a matrix that is now almost entirely pearlite rather than the mixed ferritic-pearlitic structure seen in GGG-50.

At this strength level, ductile iron starts to compete directly with cast and even some wrought steels on a strength-to-cost basis, while retaining cast iron's advantages in castability, vibration damping, and near-net-shape production of complex geometries. The trade-off is ductility: with elongation guaranteed at only around 2%, GGG-70 is noticeably less forgiving of shock loading or stress concentrations than GGG-50 or GGG-60, so section design and fillet radii matter more at this strength tier.

Typical uses include heavy-duty gears, high-load crankshafts, camshafts, and press or machine tool components where the combination of high static strength and good wear resistance from the pearlitic matrix outweighs the reduced impact tolerance — applications where a forged or heat-treated steel part would otherwise be specified but a casting is preferred for geometry or cost reasons.

GGG-70's mostly pearlitic matrix pushes machinability further in the same direction as GGG-60, but more sharply. With little remaining ferrite to soften the cut, cutting forces and flank wear rates climb noticeably, and heat generation at the tool-chip interface becomes a bigger factor in tool life. The graphite nodules still fragment chips effectively, so chip control itself isn't the concern — edge wear and heat management are.

At this hardness range, coating quality and substrate toughness both matter more than at GGG-50/60. A grade that's slightly under-specified for hardness will show accelerated flank wear quickly, while one with adequate hot hardness and a wear-resistant CVD or PVD coating will hold up through a normal production run. Reduced cutting speeds relative to the lower-numbered grades help keep edge temperature in the coating's effective working range.

Edge preparation should stay on the strong side — generous honing and a solid negative land width protect against chipping in the denser pearlitic structure, and rigid setups matter more here since higher cutting forces make chatter and edge damage more likely on marginal fixturing.