440C stainless steel equivalents

440C stainless steel is nearest to EN 1.4125 (X105CrMo17), JIS SUS440C and China GB 108Cr17. These are nearest equivalents, not identical grades: the governing standard or mill certificate decides.

Designations follow EN 10027 and EN 10088-1. Updated 6 October 2026.

EN steel number for 440C

1.4125

X105CrMo17 · SUS440C · 108Cr17

440C = EN 1.4125 X105CrMo17 = JIS SUS440C = GB 108Cr17

AISI / ASTM / SAE US: 440C
EN steel number EN 10027-2: 1.4125
EN steel name EN 10027-1: X105CrMo17
JIS Japan: SUS440C
GB China: 108Cr17
Family: Martensitic stainless, high carbon

Nearest-equivalent designationsCheck the mill certificate

About 440C

Martensitic stainless, high carbon. General characteristics; check the standard and the supplier for anything critical.

What it is

A high-carbon martensitic stainless steel. It reaches the highest hardness and wear resistance of the standard stainless grades, with moderate corrosion resistance.

Typical uses

Stainless ball bearings and races, valve seats, nozzles, knife blades and wear parts in mildly corrosive service.

Machining notes

Machine in the annealed condition and leave grinding stock: after hardening it is finished by grinding.

Related grades

Grades people often compare with this one.

420 stainless steelLower-carbon martensitic grade, easier to machine1.4021 · SUS420J1 · 20Cr13 52100 steelStandard non-stainless bearing steel1.3505 · SUJ2 · GCr15

Fasteners and tapping

Stainless fasteners

Stainless bolts are graded to ISO 3506 (for example A2 and A4 austenitic), not to the ISO 898-1 classes in the bolt torque chart. Do not use those torque values for stainless fasteners; stainless threads also gall easily, so use an anti-seize and the fastener maker's figures.

Bolt torque chart

Tapping stainless

Stainless work-hardens and grips the tap. Aim for about 60–70 % thread: one size larger than the usual tap drill is common. The tap drill chart shows the percentage each drill leaves.

Tap drill chart

All stainless steel grades

Nearest equivalents across the five designation systems.

Stainless steel grade equivalents
AISI / ASTM	EN name	EN number	JIS	China GB
304	X5CrNi18-10	1.4301	SUS304	06Cr19Ni10
304L	X2CrNi18-9	1.4307	SUS304L	022Cr19Ni10
316	X5CrNiMo17-12-2	1.4401	SUS316	06Cr17Ni12Mo2
316L	X2CrNiMo17-12-2	1.4404	SUS316L	022Cr17Ni12Mo2
321	X6CrNiTi18-10	1.4541	SUS321	06Cr18Ni11Ti
303	X8CrNiS18-9	1.4305	SUS303	Y12Cr18Ni9
310S	X8CrNi25-21	1.4845	SUS310S	06Cr25Ni20
201	X12CrMnNiN17-7-5	1.4372	SUS201	12Cr17Mn6Ni5N
430	X6Cr17	1.4016	SUS430	10Cr17
410	X12Cr13	1.4006	SUS410	12Cr13
420	X20Cr13	1.4021	SUS420J1	20Cr13
440C	X105CrMo17	1.4125	SUS440C	108Cr17
17-4PH (630)	X5CrNiCuNb16-4	1.4542	SUS630	05Cr17Ni4Cu4Nb
2205 duplex	X2CrNiMoN22-5-3	1.4462	SUS329J3L	022Cr23Ni5Mo3N

Equivalents are nearest matches, not identical grades. Composition limits, mechanical properties and test requirements differ in detail between standards and product forms. For anything that matters, the governing standard, the drawing and the mill certificate decide.

Common questions

What is the European equivalent of 440C stainless steel?

The nearest EN grade is 1.4125, steel name X105CrMo17.

What is the JIS equivalent of 440C stainless steel?

The nearest Japanese grade is SUS440C.

What is the Chinese GB equivalent of 440C stainless steel?

The nearest Chinese GB grade is 108Cr17.

Is 1.4125 the same as 440C?

1.4125 (X105CrMo17) is the nearest European equivalent of 440C, not an identical grade. Composition limits and required properties differ in detail, so check the governing standard or the mill certificate when it matters.

What is 440C used for?

Stainless ball bearings and races, valve seats, nozzles, knife blades and wear parts in mildly corrosive service.