40Mn

Data verified

40Mn is the GB/T 699 manganese-enhanced version of grade 40 — a low-cost Q&T machinery steel common in Chinese domestic machinery where 1040-class carbon is lifted by extra manganese.

AISI1040 type (higher Mn)

GB40Mn (GB/T 699)

CategoryCarbon Steel

Chemical composition

Element	Content (%)
C	0.37–0.44
Si	0.17–0.37
Mn	0.70–1.00
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

Density	7.85 g/cm³
Note	Quench-and-temper response above plain grade 40 thanks to 0.70–1.00% Mn

Heat treatment

Quench and temper; better through-response than grade 40 in moderate sections.

Equivalent grades

Standard	Designation
aisi	1040 type (higher Mn)
gb	40Mn (GB/T 699)

Compare side by side: 40Mn 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, bolts, half-axles, crankshafts (light), connecting rods.

Processing: Machines well; weld with preheat.

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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.