What hardness can EN31 reach?

About 60–64 HRC after hardening in oil and tempering at low temperature (around 150–200 °C).

Is EN31 the same as 100Cr6 and 52100?

Yes, they are equivalent bearing steels with about 1% carbon and 1.5% chromium, with small differences in the limits.

Can EN31 be used for dies?

For short runs and small punches, yes. For long-run blanking and forming dies, a tool steel such as D2 lasts much longer.

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EN31 bearing steel

Also called: 100Cr6, AISI 52100, SUJ2, 103Cr1, 535A99, EN31 material

EN31 is a high-carbon chromium steel, the classic bearing steel, equivalent to 100Cr6 and AISI 52100. Hardened, it reaches about 60–64 HRC, giving very high wear resistance for bearing races, rollers, punches and gauges.

Quick facts

Type: High-carbon chromium (bearing) steel
Carbon / chromium: About 1% carbon, 1–1.6% chromium
Hardened hardness: About 60–64 HRC
As supplied: Annealed, soft enough to machine (about 200–230 HB)
Wear resistance: Very high when hardened
Weldability: Not suitable for welding

Equivalent grades

Standard	Closest grade
BS 970 (old / current)	EN31 / 535A99
IS 4398 (India)	103Cr1
DIN / EN ISO 683-17	100Cr6 (1.3505)
AISI / SAE	52100
JIS	SUJ2

Typical chemical composition

Element	%
Carbon (C)	0.90–1.20
Silicon (Si)	0.10–0.35
Manganese (Mn)	0.30–0.75
Chromium (Cr)	1.00–1.60

Ranges vary slightly between standards; 100Cr6 is tighter (C 0.93–1.05, Cr 1.35–1.60).

Heat treatment

Supplied spheroidise-annealed so it can be machined
Hardening: about 810–850 °C, quench in oil
Tempering: about 150–200 °C for maximum hardness (about 60–64 HRC)
Rough machine, harden, then grind to final size
Thin or uneven sections can distort or crack in quenching; design generous radii

Typical uses

Bearing races, balls and rollers
Rollers and wear pins
Press tool punches and small dies for short runs
Gauges and measuring tools
Spindles and cams that need a very hard surface

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Materials

Questions

What hardness can EN31 reach?: About 60–64 HRC after hardening in oil and tempering at low temperature (around 150–200 °C).
Is EN31 the same as 100Cr6 and 52100?: Yes, they are equivalent bearing steels with about 1% carbon and 1.5% chromium, with small differences in the limits.
Can EN31 be used for dies?: For short runs and small punches, yes. For long-run blanking and forming dies, a tool steel such as D2 lasts much longer.

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.