GG35 is one of the highest-strength grades commonly specified in the DIN 1691 gray iron series, guaranteeing a minimum tensile strength of 350 N/mm². Reaching that level demands a fine, tightly distributed graphite flake structure in a fully pearlitic matrix, sometimes with minor alloying to stabilize the pearlite and suppress the coarser graphite forms that develop at slower cooling rates. The result trades away some of gray iron's legendary free-machining character in exchange for real strength and wear resistance.

GG35 is typically reserved for heavily loaded, highly stressed gray iron applications: large diesel engine blocks and cylinder liners, high-pressure hydraulic valve bodies, heavy machine tool structures where stiffness and wear resistance both matter, and components that see sustained thermal cycling. Its fine structure gives excellent surface finish potential and good pressure tightness, which matters for parts that seal against liquid or gas pressure. Like every grade in the DIN 1691 family, GG35 has essentially no ductility, so it's chosen for compressive strength, stiffness, and wear resistance rather than tensile or impact service.

GG35 is where the DIN 1691 gray iron series starts machining noticeably more like a hard casting than a free-cutting one. The fine graphite structure still gives chip fracture and short, discontinuous chips, so evacuation and chip control remain non-issues. But there's simply less free graphite by volume relative to a fully pearlitic matrix loaded with hard iron carbide lamellae, so cutting forces, edge temperatures, and abrasive flank wear are all substantially higher than on the softer grades.

Because the matrix carries less soft ferrite to absorb deformation, tool engagement on GG35 generates more localized heat at the cutting edge, and that heat accelerates diffusion and abrasive wear mechanisms on uncoated or lightly coated tooling. Coated carbide with strong hot hardness and abrasion resistance isn't optional at this grade the way it might be for GG10 or GG15 — it's the difference between predictable tool life and rapid, uneven wear.

Surface finish quality is generally good on GG35 thanks to the fine grain structure, provided the edge stays sharp and wear-consistent through the cut. Rigid setups and conservative depths of cut on interrupted or scaled surfaces help avoid the edge chipping that a harder, more brittle matrix is more prone to than the softer ferritic grades.