40CrNiMoA
Data verified40CrNiMoA is the GB/T 3077 Ni-Cr-Mo steel corresponding to AISI 4340 — China’s high-hardenability grade for large, highly loaded Q&T parts, with the “A” suffix marking the high-quality (low P/S) melt.
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 | 0.60–0.90 |
| Ni | 1.25–1.75 |
| Mo | 0.15–0.25 |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Tensile strength | ≥980 MPa (GB/T 3077 reference Q&T) |
| Yield strength | ≥835 MPa (reference) |
| Density | 7.85 g/cm³ |
| Hardenability | Very high (large sections) |
Heat treatment
Quench 850 °C oil; temper 550–600 °C class; avoid the tempered-martensite embrittlement range.
Equivalent grades
| Standard | Designation |
|---|---|
| din | 1.6511 (36CrNiMo4, near) |
| aisi | 4340 |
| jis | SNCM439 (near) |
| gb | 40CrNiMoA (GB/T 3077) |
Compare side by side: 40CrNiMoA vs 4340
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Large shafts, gears, turbine and compressor parts, high-strength fasteners.
Processing: As 4340; machine annealed, weld only with strict preheat/post-weld practice.
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Ask for a quotationVisit NasteelSource: GB/T 3077 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.