GGG-35.3 is a fully ferritic ductile (nodular, spheroidal-graphite) cast iron standardized under the older German DIN 1693 system, carried forward today as EN-GJS-350-22. The "GGG" prefix marks it as Gusseisen mit Kugelgraphit — cast iron with spherical graphite — and the "35" in the designation points directly to its guaranteed minimum tensile strength of roughly 350 N/mm². Unlike gray cast iron, where graphite forms as sharp interconnected flakes that act as stress risers, GGG-35.3 is treated during casting (typically with a magnesium addition) so the graphite precipitates as round nodules. Those nodules interrupt the iron matrix far less severely than flakes, which is why ductile iron families as a whole deliver dramatically better tensile strength, ductility, and impact toughness than gray iron at a comparable base composition.

Within the ductile iron family, GGG-35.3 sits at the softer, more ductile end: it's produced with a fully ferritic matrix and is prized for its high elongation (commonly specified at a 22% minimum) rather than for outright strength or hardness. That combination of moderate strength with genuinely good ductility and toughness — including reasonable low-temperature impact behavior — makes it a practical choice for housings, brackets, pipe fittings, and structural castings that see shock loading or need to absorb impact without cracking, rather than parts that are pushed hard on raw strength or wear resistance.

GGG-35.3's fully ferritic, high-elongation matrix makes it one of the more forgiving ductile irons to machine. The spheroidal graphite nodules act as small internal chip-breakers and provide a degree of self-lubrication at the tool-chip interface, which keeps cutting forces and heat generation lower than in an equivalent-strength steel. Because the matrix is soft and ferritic rather than pearlitic, abrasive wear from hard carbide constituents is minimal — tool life is generally good with a properly matched grade.

The trade-off is ductility itself: this grade's high elongation and softness mean it can be prone to built-up edge and a slightly torn or smeared finish if cutting speeds are too low or the edge isn't sharp enough, since the material wants to deform and tear rather than shear cleanly. Chip control also needs attention — softer ferritic ductile iron can throw longer, more continuous chips than a harder pearlitic ductile iron, so chipbreaker geometry matters more here than on harder cast iron grades.

A CVD or PVD coated carbide grade with a sharp, positive-leaning edge preparation generally outperforms a heavily honed, negative-rake geometry on this material — the goal is clean shearing rather than the crushing action that suits harder, more brittle irons. Stable clamping and adequate cutting speed keep the finish clean and prevent the smeared, dragging surface that under-speed cutting tends to produce on soft ductile iron.