GTS-45-06 is a blackheart malleable cast iron under German standard DIN 1692 — "Temperguss schwarz" — and the higher-strength counterpart to GTS-35-10 within the same blackheart family. Like all GTS grades, it starts as white (chilled) cast iron with its carbon locked up as cementite, then goes through a long graphitizing anneal in a neutral or protective atmosphere. That anneal decomposes the cementite into iron plus irregular, rosette-shaped graphite nodules distributed through the matrix, rather than burning carbon out near the surface the way the whiteheart (GTW) process does. Where GTS-35-10 is annealed to leave a fully ferritic, high-elongation matrix, GTS-45-06 is processed to retain more pearlite in the matrix, trading some ductility for meaningfully higher strength and hardness.

The two numbers in its designation are guaranteed minimums: 450 N/mm² tensile strength and 6% elongation — noticeably stronger than GTS-35-10's 350 N/mm² but with less than half the elongation. That balance of higher strength with still-reasonable ductility makes GTS-45-06 a common choice for brake drums, ball joints, articulated bearing housings, clamping bodies, and agricultural machinery parts that see higher stress than a GTS-35-10 part but still benefit from malleable iron's shock resistance over as-cast gray iron.

GTS-45-06's retained pearlite makes it noticeably tougher to machine than the fully ferritic GTS-35-10, even though both share the same rosette-graphite structure and blackheart processing route. The harder pearlitic matrix increases cutting forces and abrasive wear on the tool compared with a ferritic malleable iron, while the material's inherent toughness — the same property that gives it good impact resistance in service — still resists clean chip separation the way a more brittle gray iron would shear.

That combination means tool wear becomes a bigger factor here than on GTS-35-10, while chip control remains the other half of the challenge: chips are tougher and less prone to self-breaking than in gray cast iron, so chipbreaker geometry and a properly matched grade both matter. A coated carbide grade with reasonable hot hardness handles the added abrasion from the pearlitic matrix better than an uncoated or lightly coated grade sized for the softer ferritic blackheart grades.

A sharp, moderately positive edge still outperforms a heavily honed geometry meant for harder, more brittle cast irons, since this material shears rather than crushes. Stable clamping and adequate cutting speed help keep the finish clean and prevent the smeared, dragging surface that under-speed cutting produces on ductile, malleable iron grades.