What is the difference between EN8 and EN9?

EN9 has more carbon (about 0.55% against 0.40%), so it is harder and wears better, but it is less tough and harder to weld. EN8 is the more general-purpose grade.

Can EN9 be induction hardened?

Yes. Induction or flame hardening gives a hard surface of around 55–58 HRC over a softer core, which suits gears, cams and rollers.

Is EN9 the same as C55?

They are close equivalents: EN9 (070M55) and C55 both have about 0.55% carbon. Small differences in the limits exist between the standards.

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EN9 steel

Also called: 070M55, 55C8, C55, AISI 1055, S55C, EN9 material

EN9 is a plain carbon steel with about 0.55% carbon, known today as 070M55. It is harder and more wear-resistant than EN8 but less tough, and is used for parts that need a hard-wearing surface, such as gears, sprockets, cams and rollers.

Quick facts

Type: Medium-high carbon (unalloyed) steel
Carbon: About 0.50–0.60%
Typical hardness: About 200–250 HB as supplied; much harder when surface hardened
Surface hardening: Induction or flame hardening to about 55–58 HRC
Machinability: Fair; harder to machine than EN8
Weldability: Poor: needs preheating and slow cooling

Equivalent grades

Standard	Closest grade
BS 970 (old / current)	EN9 / 070M55
IS 1570 (India)	55C8
DIN / EN 10083	C55 (1.0535)
AISI / SAE	1055
JIS	S55C

Equivalents are close, not identical. Name the standard on your drawing if the exact grade matters.

Typical chemical composition (070M55)

Element	%
Carbon (C)	0.50–0.60
Silicon (Si)	0.10–0.40
Manganese (Mn)	0.50–0.90
Sulphur (S)	0.050 max
Phosphorus (P)	0.050 max

Heat treatment

Normalising: about 810–840 °C, cool in air
Hardening: about 810–840 °C, quench in oil or water, then temper
Induction or flame hardening gives a hard surface, around 55–58 HRC, over a tougher core
Like EN8, it hardens fully only in small sections

Typical uses

Gears, sprockets and pinions for moderate loads
Cams, rollers and wear pads
Shafts that need a hard-wearing surface
Agricultural and machine parts that see abrasion

EN8 or EN9?

	EN8	EN9
Carbon	About 0.40%	About 0.55%
Strength and wear	Good	Higher
Toughness	Better	Lower
Welding	Fair with preheat	Poor
Typical use	General shafts, pins, studs	Gears, cams, wear parts

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Questions

What is the difference between EN8 and EN9?: EN9 has more carbon (about 0.55% against 0.40%), so it is harder and wears better, but it is less tough and harder to weld. EN8 is the more general-purpose grade.
Can EN9 be induction hardened?: Yes. Induction or flame hardening gives a hard surface of around 55–58 HRC over a softer core, which suits gears, cams and rollers.
Is EN9 the same as C55?: They are close equivalents: EN9 (070M55) and C55 both have about 0.55% carbon. Small differences in the limits exist between the standards.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 8 October 2026.