35C8 vs S45C Steel: Which Grade to Choose

Q: Is S45C stronger than 35C8?

Yes. S45C carries more carbon (about 0.43-0.50% vs about 0.35% in 35C8), giving higher tensile strength (typically 620-720 MPa vs 550-640 MPa) and higher attainable hardness. The trade-off is lower ductility and reduced weldability.

The short answer

Choose S45C when the component needs higher strength, hardness, fatigue performance, or a hardened wear surface — gears, axles, crankshafts, spindles, and induction- or flame-hardened parts. Choose 35C8 when moderate strength is enough and you value easier welding, better ductility, and lower cost — general shafts, studs, levers, and fabricated parts. Both are medium-carbon plain-carbon steels; S45C simply carries roughly 0.10% more carbon than 35C8, which drives nearly every difference below.

35C8 vs S45C — side-by-side comparison

Typical values. Mechanical properties depend on section size and heat-treatment condition.
Property	35C8	S45C
Type	Medium-carbon unalloyed steel	Medium-carbon unalloyed steel (higher carbon)
Carbon (C)	0.30 – 0.40%	0.43 – 0.50%
Manganese (Mn)	0.60 – 0.90%	0.60 – 0.90%
Silicon (Si)	0.10 – 0.35%	0.15 – 0.35% (typical)
Sulphur (S)	0.045% max	0.050% max
Phosphorus (P)	0.045% max	0.040% max
Tensile Strength	550 – 640 MPa	620 – 720 MPa (≈90,000 psi+)
Yield Strength	320 – 370 MPa	340 – 460 MPa (≈50,000 psi+)
Elongation	18 – 22%	15 – 20%
Hardness (normalised)	170 – 200 HB	180 – 230 HB
Max. hardness (hardened, thin section)	≈ 48 – 55 HRC	≈ 55 – 60 HRC
Hardenability	Low (plain carbon)	Low–moderate (more carbon)
Surface hardening (induction / flame)	Limited	Well suited
Machinability	Good; best in annealed/normalised state	Good; slightly harder on tooling
Weldability	Good with normal precautions	Fair; preheat usually needed
Relative cost	Lower	Slightly higher
Equivalent grades	AISI 1035 · C35 · S35C · BS 970 080M36	AISI 1045 · C45 · EN9 · BS 970 080M46
Typical applications	Shafts, studs, levers, links, general machine parts	Gears, axles, crankshafts, spindles, hardened wear surfaces

Typical mill values. 35C8 sulphur and phosphorus are each held to 0.045% maximum. Confirm exact values against the mill test certificate for your heat.

When to choose each grade

Choose 35C8 when…

Moderate strength is sufficient for the part.
The component will be welded or cold-formed.
Better ductility and toughness matter.
Cost is a deciding factor on a high-volume part.
Typical parts: general shafts, studs, levers, links, brackets, fabricated assemblies.

Choose S45C when…

You need higher tensile strength and hardness.
The part needs an induction- or flame-hardened wear surface.
Fatigue performance and wear resistance are important.
Typical parts: gears, axles, crankshafts, spindles, sprockets, higher-stress shafts.
Read the full S45C steel page.

How to decide between 35C8 and S45C

Fix the strength target. If the design needs tensile strength above ~640 MPa or higher hardness, lean towards S45C. If moderate strength is enough, 35C8 does the job at lower cost.
Check welding and forming. If the part is welded or cold-formed, 35C8's lower carbon makes it more forgiving. S45C usually needs preheat and controlled cooling.
Decide on surface hardening. If a hard, wear-resistant surface is required (gear teeth, journals), S45C responds well to induction or flame hardening; 35C8 is limited here.
Weigh cost and availability. 35C8 is usually the cheaper of the two for the same form and size.
If neither fits, change family. EN8D (≈0.40–0.45% C) sits between the two. For much higher strength with hardenability in larger sections, move to alloy EN19 or SAE 4140; if machinability dominates, consider free-cutting EN1A.

35C8 vs S45C — frequently asked questions

Is S45C stronger than 35C8?

Yes. S45C carries more carbon (≈0.43–0.50% vs ≈0.35% in 35C8), giving higher tensile strength (typically 620–720 MPa vs 550–640 MPa) and higher attainable hardness. The trade-off is lower ductility and reduced weldability.

Can 35C8 replace S45C?

Only when the part needs moderate strength and no hardened wear surface. Where S45C is specified for strength, hardness, fatigue, or induction/flame hardening, do not substitute 35C8 without checking the load case and getting design approval.

Which is easier to weld, 35C8 or S45C?

35C8. Its lower carbon content gives a lower carbon equivalent, so it is more tolerant of welding. S45C generally needs preheating and controlled cooling, and post-weld stress relief on critical joints.

Which is cheaper?

35C8 is usually slightly cheaper than S45C for the same product form and size, because it is a lower-carbon grade. For an exact quote on either grade, contact Ambhe Ferro.

What is the carbon difference between 35C8 and S45C?

35C8 contains about 0.30–0.40% carbon (nominal 0.35%), while S45C contains about 0.43–0.50% (nominal 0.45%). That difference of roughly 0.10% carbon is what makes S45C stronger, harder, and better for surface hardening, and 35C8 more ductile and weldable.

Is S45C the same as C45 or 45C8?

They are close equivalents. S45C (JIS), C45 (EN/DIN 1.0503), AISI 1045, EN9, and 45C8 are all medium-carbon grades at roughly 0.45% carbon. Minor differences in composition and mechanical limits exist between standards, so confirm the governing specification on your drawing.

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35C8 vs S45C Steel — How to Choose