Steel

Low-medium carbon unalloyed steel. Good balance of strength, weldability, and formability. Used for lightly loaded shafts, bolts, levers, and general machine parts. Can be case-hardened for wear applications. Between C10 and C35 in properties.

Low-carbon unalloyed steel for case hardening and general engineering — 0.17-0.24% C. After carburizing: surface HRC 55-60, soft tough core. Much cheaper than alloy case-hardening steels (16MnCr5, 20MnCr5). Modern designation for Ck22. Used for pins, bolts, levers, lightly loaded gears, and any carburized part where alloy additions are not justified. Also used as cold-heading wire.

Mid-carbon unalloyed Q&T steel — 0.27-0.34% C. Between C22E and C35E — good weldability with moderate strength after Q&T. Modern designation for Ck30. Used for lightly loaded shafts, levers, bolts, and machine parts.

Medium-carbon unalloyed steel with moderate strength. Good machinability and weldability. Used for lightly stressed components like levers, axles, bolts, and general machine parts.

Mid-carbon unalloyed Q&T steel — 0.32-0.39% C. Good balance between strength and toughness/weldability. Modern designation for Ck35. Used for moderately loaded shafts, axles, bolts, connecting rods, and machine parts where C45 would be too hard and C22E too soft. Also suitable for surface hardening (flame/induction) to HRC 50-55.

Medium-carbon unalloyed steel between C35 and C45 in properties. Good balance of strength and machinability. Used for moderately stressed machine parts, shafts, studs, axles, and crankshafts.

Mid-carbon unalloyed Q&T steel — 0.37-0.44% C. Slightly below C45E in carbon content but very similar properties. Modern designation for Ck40. Used for crankshafts, connecting rods, axles, bolts, and machine parts. Suitable for flame/induction hardening to HRC 52-56.

Medium carbon unalloyed quality steel. Good machinability and moderate strength after heat treatment. Widely used for shafts, spindles, pins, studs, and general machine parts.

Medium-high carbon unalloyed steel between C45 and C55. Good strength and wear resistance after QT. Used for springs, axles, shafts, coupling parts, and machine components where moderate hardness is sufficient without alloy steel cost.

High-carbon unalloyed Q&T steel — 0.47-0.55% C. Higher strength than C45E at the expense of reduced weldability and toughness. Modern designation for Ck50. Suitable for induction hardening to HRC 55-60. Used for heavy-duty shafts, rail wheels, clutch plates, and springs where maximum unalloyed strength is needed. Also used for agricultural equipment and wear parts.

Medium-high carbon unalloyed steel. Higher strength than C45 with reduced weldability. Used for rail wheels, agricultural equipment, springs, hand tools, and wear-resistant parts. Often used for induction-hardened components.

High-carbon unalloyed Q&T steel — 0.52-0.60% C. Modern designation for Ck55. Good strength after Q&T (UTS 800-950 MPa) and excellent surface hardness after induction hardening (HRC 56-60). Used for rail wheels, crankshafts, heavy-duty shafts, and wear parts.

High-carbon unalloyed quenching and tempering steel. High hardness and strength after heat treatment but difficult to weld. Used for springs, hand tools (screwdrivers, pliers), agricultural blades, wear parts, and railway components.

Medium-high carbon spring steel — C 0.65-0.72%. The E suffix denotes controlled S+P (<=0.025% each). Used for cold-rolled spring strip (EN 10132-4), spring wire (EN 10270-1), and flat springs. Lower C than C75S/C85S = better toughness and formability. Also used for circular saw blades, scrapers, and clips. Hardened & tempered to HRC 55-60.

Unalloyed cold-rolled spring strip steel — THE standard flat spring material. 0.65% C gives high hardness after hardening (HRC 60+). Very good fatigue properties when properly heat-treated. Much cheaper than alloyed spring steels (51CrV4, 55Cr3). Used for flat springs, circlips/snap rings, saw blades, scrapers, reed valves, and leaf springs in small dimensions.

High-carbon unalloyed spring steel. Near-eutectoid composition (0.70-0.80% C). Excellent elastic properties after hardening and tempering. Limited hardenability — effective oil quench diameter ≤12mm. Cost-effective for small/medium springs. Used for spring wire, clock springs, saw blades, retaining rings, and precision strip springs. ≈ AISI 1075.

High-carbon spring strip steel — C 0.70-0.80%. Between C67S (0.65-0.72%) and C85S (0.83-0.90%). Good fatigue strength and edge retention. Used for flat springs, leaf springs, saw blades, snap rings, and reed valves. Available as cold-rolled precision strip in hardened & tempered condition (HRC 58-62).

Highest-carbon standard unalloyed spring steel. 0.75-0.85% C gives maximum hardness (60+ HRC) among unalloyed grades but with increased brittleness. Limited hardenability — effective quench diameter ≤10mm. Used for high-hardness springs, saw blades, scrapers, and precision strip where maximum elastic limit is needed. ≈ AISI 1080.

Highest-carbon unalloyed spring strip steel — C 0.83-0.90%. Maximum achievable hardness (HRC 62-65) and fatigue strength in the cold-rolled spring strip series. Used for the most demanding flat spring applications where maximum hardness is critical: saw blades, scraper blades, precision springs, and high-frequency reed valves. Higher C than C67S (0.65-0.72%) and C75S (0.70-0.80%).

Soft martensitic (supermartensitic) stainless steel with good corrosion resistance and high toughness. Low carbon prevents embrittlement. The standard material for hydraulic turbine runners, pump impellers, compressor components, and offshore valves.

Plain carbon quenched & tempered steel — 0.57-0.65% C. Highest practical C for Q&T without excessive brittleness. Good surface hardness (HRC 55-60) with adequate core toughness. Modern designation C60E (EN 10083-2), traditional Ck60 still widely used. Used for crankshafts, connecting rods, rail wheels, axles, and machine tool spindles where alloy cost is not justified.

Crucible Particle Metallurgy stainless cold work steel — virtually identical to Böhler M390 and Carpenter CTS-204P. 1.9% C, 20% Cr, 4% V, 1% Mo. The highest corrosion resistance of any PM tool steel while maintaining 58–62 HRC hardness and outstanding edge retention. Considered the current benchmark for premium stainless knife steel. Also used for plastic injection mold cavities (mirror polish + corrosion resistance) and food processing cutting tools.

Crucible Particle Metallurgy high-speed steel with exceptionally high vanadium (4%) and carbon (1.42%) content. Combines the red hardness of M2 HSS with wear resistance approaching carbide. PM process ensures uniform fine carbide distribution impossible in conventional melting. Hardened to 62–66 HRC. Used for end mills, broaches, hobs, form tools, cold heading dies, slitter knives and applications where conventional HSS wears too fast but carbide is too brittle. Popular in knife community for extreme edge retention.

Crucible Particle Metallurgy martensitic stainless tool steel with extreme vanadium content. C 2.3%, Cr 14.0%, V 9.0%, Mo 1.0%. Highest wear resistance among PM stainless steels. Hardness 56–60 HRC. Corrosion resistant. Applications: premium knife blades, plastic injection screws/barrels with glass-filled or mineral-filled compounds, industrial cutting tools, food processing blades.