40

Data verified

40 is the GB/T 699 counterpart of AISI 1040 / JIS S40C — a step below 45 (1045) in carbon, chosen where weldability and toughness matter slightly more than peak strength.

DIN1.0511 (C40)

AISI1040

JISS40C

CategoryCarbon Steel

Chemical composition

Element	Content (%)
C	0.37–0.44
Si	0.17–0.37
Mn	0.50–0.80
P	≤0.035
S	≤0.035
Cr	≤0.25

Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.

Properties

Tensile strength	≥570 MPa (GB/T 699 reference, normalized blank)
Yield strength	≥335 MPa (reference)
Density	7.85 g/cm³

Heat treatment

Normalize or quench-and-temper; induction/flame hardening common for wear parts.

Equivalent grades

Standard	Designation
din	1.0511 (C40)
aisi	1040
jis	S40C
gb	40 (GB/T 699)

Compare side by side: 40 vs 1040

Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.

Applications & Processing

Applications: Shafts, gears (light duty), tie rods, bolts, crank parts.

Processing: Machines well normalized; weld with preheat (150–250 °C).

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Source: GB/T 699-2015 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.