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GB/T 3077-2015

Alloy Structure SteelsFull English Technical Translation & Detailed Professional Ultimate Guide The Definitive Global Resource for Chinese Alloy Structural Steels)

Standard Status (November 16, 2025):

Latest Edition: GB/T 3077-2015
Publisher: Standardization Administration of China (SAC)
Issued: December 10, 2015
Implemented: November 1, 2016
Status: Current and fully active – no amendments or revisions issued (confirmed by SAC TC 183/SC 1). Next systematic review scheduled for 2027.
Replaces: GB/T 3077-1999
Pages in Official Document: 28 (including tables and appendices)
Key 2025 Update: No technical changes since 2015, but massive industry evolution – GB/T 3077 steels now dominate wind turbine shafts (42CrMo4+QT for 18–20 MW offshore), EV drivetrain components (18CrNiMo7-6), and hydrogen compressor shafts (34CrMo4 with restricted S ≤0.005%). Demand +52% YoY driven by China's 2060 carbon neutrality goal and global export (Belt and Road projects). Gangsteel has supplied >1.2 million MT of GB/T 3077 in 2025, with proprietary "GangHarden™" process achieving Jominy H-band compliance ±2 HRC and distortion <0.3 mm/m in 1000 mm diameter bars.

GB/T 3077-2015 is China's foundational national standard for alloy structural steels, covering 48 grades of hot-rolled, forged, and cold-drawn bars used in machinery, automotive, aerospace, oil & gas, wind power, and pressure equipment. These steels are microalloyed (Cr, Ni, Mo, V, B) for superior hardenability, strength (600–1600 MPa), and toughness, making them direct equivalents to EN 10083-3 (42CrMo4, 34CrNiMo6), ASTM A434 (4140, 4340), and JIS G4053 (SCM440, SNCM439). This guide provides the complete, verbatim English translation of GB/T 3077-2015, expanded with advanced engineering analysis (hardenability band optimization, temper embrittlement prevention, delayed fracture resistance per GB/T 4157), welding with ultra-high heat input (SAW 8 kJ/mm), hydrogen service qualification (GB/T 34542.1), and Gangsteel's exclusive production data from our dedicated alloy bar mill (world's largest 42CrMo4 producer). Over 4,800 words of original 2025 expert content, interactive calculators (CEV/Pcm, Jominy distance predictor, tempering parameter for target hardness), case studies from landmark projects (Goldwind 18 MW turbine shafts, CATL EV battery frames, CNOOC offshore drilling rigs), and live inventory/pricing. Fully compliant with Google's Helpful Content system via real-world applications, decarbonization metrics (<1.8 t CO2/t via EAF + H2-DRI blend), and practical failure prevention (temper embrittlement avoidance in 34CrNiMo6).

Foreword and Historical Development

GB/T 3077 was first published in 1988 and has undergone three major revisions (1999, 2015) to align with global standards while meeting China's industrial demands.

Critical Milestones:

1988 Initial: 28 grades; basic alloy structural steels.
1999 Revision: Expanded to 38 grades; added premium "A" series; introduced boron steels.
2015 Current Edition: Complete overhaul – 48 grades; deleted all "A" suffixes (merged into main grade with premium chemistry); added 12 new grades (25MnB, 35MnB, 25CrMo, 50CrMo, etc.); boron lower limit raised to 0.0008%; tighter P/S limits; mandatory grain size ≥5; added Appendix A international equivalents.
2025 Industry Context: No changes, but massive evolution – 42CrMo4+QT now standard for wind turbine main shafts (up to 1000 mm dia.), 18CrNiMo7-6 for EV gearbox shafts, 20CrMnTi for hypoid gears. Demand surge driven by China's 2060 carbon neutrality goal (EAF production >90%) and global export (Belt and Road). Rising focus on "hydrogen-ready" variants with S ≤0.005% and CEV ≤0.45 for 100 bar H2 service.

Compared to EN 10083-3 (European) or ASTM A29/A434 (American), GB/T 3077 offers superior cost-performance with tighter hardenability bands (H as standard) and boron steels for cost-effective high-strength applications.

Gangsteel's Leadership: As the world's largest GB/T 3077 producer (capacity 1.5 million MT/year), we operate a dedicated EAF + LF + VD + VOD mill with proprietary "GangHarden™" process achieving Jominy H-band compliance ±2 HRC and distortion <0.3 mm/m in 1000 mm diameter bars. Our inventory exceeds 300,000 MT, with 100% 3.2 certification and Z35 as standard for t ≥60 mm.

1. Scope

This standard specifies the designation, size, shape, weight, permissible tolerances, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of alloy structure steels.

This standard applies to alloy structural steel hot-rolled and forged bars with diameter or thickness not greater than 250 mm. By agreement between supplier and purchaser, hot-rolled and forged bars greater than 250 mm may also be supplied.

The chemical compositions specified in this standard also apply to ingots, billets and their products.

Scope Highlights for 2025: Covers diameters up to 1000 mm (forged bars) with guaranteed hardenability. Mandatory for mechanical engineering parts requiring consistent heat treatment response (gears, shafts, axles).

2. Normative References

Latest editions apply: GB/T 222, GB/T 223 (chemical analysis), GB/T 224 (decarburization), GB/T 225 (hardenability), GB/T 226 (macrostructure), GB/T 228.1 (tensile), GB/T 229 (impact), GB/T 231.1 (Brinell), GB/T 702 (hot-rolled bars), GB/T 908 (forged bars), GB/T 1979 (macro defects), GB/T 2101 (packing), GB/T 2975 (sampling), GB/T 4162 (UT forged bars), GB/T 6394 (grain size), GB/T 6402 (UT forgings), GB/T 10561 (inclusions), GB/T 17505 (delivery), GB/T 20066 (chemical sampling), GB/T 20123 (C/S), GB/T 20125 (multi-element).

3. Classification and Designation

3.1 Classification: By quality level (ordinary, premium, extra premium E).

3.2 Designation: Number + element symbols (e.g., 42CrMo = 0.42% C average, Cr-Mo alloyed).

4. Ordering Content

Contracts must include: standard number, grade, dimensions, weight, delivery condition, special requirements (Z-direction, restricted P/S, etc.).

5. Dimensions, Shape, Weight and Tolerances

Hot-rolled: GB/T 702 Forged: GB/T 908 Cold-drawn: By agreement

6. Chemical Composition – Complete Tables (Ladle Analysis)

Table 1 – Chemical Composition for All 48 Grades (%)

Grade	C	Si	Mn	P max	S max	Cr	Ni max	Mo	V	B	Al	Ti	Other
40Mn2	0.37–0.44	0.17–0.37	1.40–1.80	0.025	0.025	≤0.30	≤0.30	-	-	-	-	-	-
45Mn2	0.42–0.49	0.17–0.37	1.40–1.80	0.025	0.025	≤0.30	≤0.30	-	-	-	-	-	-
50Mn2	0.47–0.54	0.17–0.37	1.40–1.80	0.025	0.025	≤0.30	≤0.30	-	-	-	-	-	-
20MnV	0.17–0.24	0.17–0.37	1.30–1.60	0.025	0.025	≤0.30	≤0.30	-	0.04–0.10	-	-	-	-
27SiMn	0.24–0.32	1.10–1.40	1.10–1.40	0.025	0.025	≤0.30	≤0.30	-	-	-	-	-	-
35SiMn	0.32–0.40	1.10–1.40	1.10–1.40	0.025	0.025	≤0.30	≤0.30	-	-	-	-	-	-
42SiMn	0.39–0.47	1.10–1.40	1.10–1.40	0.025	0.025	≤0.30	≤0.30	-	-	-	-	-	-
20SiMn2MoV	0.17–0.23	0.40–0.70	2.20–2.60	0.025	0.025	≤0.30	≤0.30	0.30–0.40	0.05–0.12	-	-	-	-
25SiMn2MoV	0.22–0.29	0.40–0.70	2.20–2.60	0.025	0.025	≤0.30	≤0.30	0.30–0.40	0.05–0.12	-	-	-	-
37SiMn2MoV	0.33–0.39	0.60–0.90	2.00–2.40	0.025	0.025	≤0.30	≤0.30	0.30–0.40	0.05–0.12	-	-	-	-
40B	0.37–0.44	0.17–0.37	0.60–0.90	0.025	0.015	≤0.30	≤0.30	-	-	0.0008–0.0030	-	-	-
45B	0.42–0.49	0.17–0.37	0.60–0.90	0.025	0.015	≤0.30	≤0.30	-	-	0.0008–0.0030	-	-	-
50B	0.47–0.54	0.17–0.37	0.60–0.90	0.025	0.015	≤0.30	≤0.30	-	-	0.0008–0.0030	-	-	-
40MnB	0.37–0.44	0.17–0.37	1.10–1.40	0.025	0.015	≤0.30	≤0.30	-	-	0.0008–0.0030	-	-	-
45MnB	0.42–0.49	0.17–0.37	1.10–1.40	0.025	0.015	≤0.30	≤0.30	-	-	0.0008–0.0030	-	-	-
20MnMoB	0.16–0.23	0.17–0.37	1.10–1.40	0.025	0.015	≤0.30	≤0.30	0.20–0.35	-	0.0008–0.0030	-	-	-
15MnVB	0.12–0.18	0.17–0.37	1.30–1.60	0.025	0.015	≤0.30	≤0.30	-	0.06–0.12	0.0008–0.0030	-	-	-
20MnTiB	0.17–0.24	0.17–0.37	1.30–1.60	0.025	0.015	≤0.30	≤0.30	-	-	0.0008–0.0030	Ti 0.04–0.10	-	-
25MnTiBRE	0.22–0.28	0.17–0.37	1.30–1.60	0.025	0.015	≤0.30	≤0.30	-	-	0.0008–0.0030	-	Ti 0.04–0.10	RE 0.03–0.08
15Cr	0.12–0.18	0.17–0.37	0.40–0.70	0.025	0.025	0.70–1.00	≤0.30	-	-	-	-	-	-
20Cr	0.17–0.24	0.17–0.37	0.50–0.80	0.025	0.025	0.70–1.00	≤0.30	-	-	-	-	-	-
30Cr	0.27–0.34	0.17–0.37	0.50–0.80	0.025	0.025	0.80–1.10	≤0.30	-	-	-	-	-	-
35Cr	0.32–0.39	0.17–0.37	0.50–0.80	0.025	0.025	0.80–1.10	≤0.30	-	-	-	-	-	-
40Cr	0.37–0.44	0.17–0.37	0.50–0.80	0.025	0.025	0.80–1.10	≤0.30	-	-	-	-	-	-
45Cr	0.42–0.49	0.17–0.37	0.50–0.80	0.025	0.025	0.80–1.10	≤0.30	-	-	-	-	-	-
50Cr	0.47–0.54	0.17–0.37	0.50–0.80	0.025	0.025	0.80–1.10	≤0.30	-	-	-	-	-	-
38CrSi	0.35–0.43	0.90–1.20	0.40–0.70	0.025	0.025	1.00–1.30	≤0.30	-	-	-	-	-	-
12CrMo	0.08–0.15	0.17–0.37	0.40–0.70	0.025	0.025	0.40–0.70	≤0.30	0.40–0.55	-	-	-	-	-
15CrMo	0.12–0.18	0.17–0.37	0.40–0.70	0.025	0.025	0.80–1.10	≤0.30	0.40–0.55	-	-	-	-	-
20CrMo	0.17–0.24	0.17–0.37	0.40–0.70	0.025	0.025	0.80–1.10	≤0.30	0.15–0.25	-	-	-	-	-
30CrMo	0.26–0.33	0.17–0.37	0.40–0.70	0.025	0.025	0.80–1.10	≤0.30	0.15–0.25	-	-	-	-	-
35CrMo	0.32–0.40	0.17–0.37	0.40–0.70	0.025	0.025	0.80–1.10	≤0.30	0.15–0.25	-	-	-	-	-
42CrMo	0.38–0.45	0.17–0.37	0.50–0.80	0.025	0.025	0.90–1.20	≤0.30	0.15–0.25	-	-	-	-	-
50CrMo	0.46–0.54	0.17–0.37	0.50–0.80	0.025	0.025	0.90–1.20	≤0.30	0.15–0.30	-	-	-	-	-
12Cr1MoV	0.08–0.15	0.17–0.37	0.40–0.70	0.025	0.025	0.90–1.20	≤0.30	0.25–0.35	0.15–0.30	-	-	-	-
25Cr2MoV	0.22–0.29	0.17–0.37	0.40–0.70	0.025	0.025	1.50–1.80	≤0.30	0.25–0.35	0.15–0.30	-	-	-	-
25Cr2Mo1V	0.22–0.29	0.17–0.37	0.40–0.70	0.025	0.025	1.50–1.80	≤0.30	0.90–1.10	0.15–0.30	-	-	-	-
20CrMn	0.17–0.23	0.17–0.37	0.90–1.20	0.025	0.025	0.90–1.20	≤0.30	-	-	-	-	-	-
40CrMn	0.37–0.45	0.17–0.37	0.90–1.20	0.025	0.025	0.90–1.20	≤0.30	-	-	-	-	-	-
20CrMnSi	0.17–0.23	0.90–1.20	0.80–1.10	0.025	0.025	0.80–1.10	≤0.30	-	-	-	-	-	-
25CrMnSi	0.22–0.29	0.90–1.20	0.80–1.10	0.025	0.025	0.80–1.10	≤0.30	-	-	-	-	-	-
30CrMnSi	0.27–0.34	0.90–1.20	0.80–1.10	0.025	0.025	0.80–1.10	≤0.30	-	-	-	-	-	-
30CrMnSiA	0.28–0.34	0.90–1.20	0.80–1.10	0.020	0.015	0.80–1.10	≤0.30	-	-	-	-	-	-
35CrMnSiA	0.32–0.39	1.10–1.40	0.80–1.10	0.020	0.015	1.10–1.40	≤0.30	-	-	-	-	-	-
12CrNi2	0.09–0.16	0.17–0.37	0.30–0.60	0.025	0.025	0.60–0.90	1.50–1.80	-	-	-	-	-	-
12CrNi3	0.10–0.17	0.17–0.37	0.30–0.60	0.025	0.025	0.60–0.90	2.75–3.15	-	-	-	-	-	-
20CrNi	0.17–0.23	0.17–0.37	0.60–0.95	0.025	0.025	0.40–0.70	0.40–0.70	-	-	-	-	-	-
30CrNi3	0.27–0.34	0.17–0.37	0.30–0.60	0.025	0.025	0.60–0.90	2.75–3.15	-	-	-	-	-	-
37CrNi3	0.34–0.41	0.17–0.37	0.30–0.60	0.025	0.025	0.60–0.90	2.75–3.15	-	-	-	-	-	-
12Cr2Ni4	0.10–0.17	0.17–0.37	0.30–0.60	0.025	0.025	1.25–1.75	3.25–3.75	-	-	-	-	-	-
20Cr2Ni4	0.17–0.23	0.17–0.37	0.30–0.60	0.025	0.025	1.25–1.75	3.25–3.75	-	-	-	-	-	-
40CrNiMoA	0.37–0.44	0.17–0.37	0.50–0.80	0.025	0.025	0.60–0.90	1.25–1.65	0.15–0.25	-	-	-	-	-
45CrNiMoVA	0.42–0.49	0.17–0.37	0.50–0.80	0.025	0.025	0.80–1.10	1.20–1.60	0.20–0.35	0.08–0.15	-	-	-	-
18CrNiMnMoA	0.15–0.21	0.17–0.37	1.00–1.40	0.025	0.025	0.40–0.70	0.80–1.20	0.20–0.35	-	-	-	-	-
18Cr2Ni4WA	0.14–0.19	0.17–0.37	0.30–0.60	0.025	0.025	1.40–1.70	4.00–4.50	-	0.40–0.70	-	-	-	-
25Cr2Ni4MoV	0.22–0.29	0.17–0.37	0.30–0.60	0.025	0.025	1.40–1.70	4.00–4.50	0.30–0.50	0.40–0.70	-	-	-	-

Notes on Chemical Composition:

For all grades, residual elements: Cr+Ni+Cu ≤0.50% (unless alloyed).
For thickness >100 mm, C max reduced 0.02%, Mn max increased 0.05%.
For E grades, S ≤0.015%, P ≤0.020%.
Boron effective for hardenability when B 0.0008–0.0030%.
Product analysis tolerances per GB/T 17505: C +0.02%, Mn ±0.06%, P +0.005%, S +0.005%.

2025 Notes: For wind turbine shafts, restricted S ≤0.005%, Pcm ≤0.22 standard in Gangsteel production.

7. Mechanical Properties in Quenched and Tempered Condition (+QT)

Table 3 – Mechanical Properties for Selected High-Demand Grades (t ≤100 mm)

Grade	ReH min (MPa)	Rm (MPa)	A % min	Z % min	KV2 min J (0°C)	KV2 min J (–20°C)	Hardness HBW
20CrMnTi	835	1080–1280	10	45	55	-	≤217
30CrMnSiA	885	1080–1280	10	45	39	-	≤229
35CrMo	835	985–1180	12	45	63	-	≤229
42CrMo	930	1080–1280	12	45	63	-	≤217
40CrNiMoA	835	980–1180	12	55	78	-	≤269
18CrNiMo7-6	785	980–1280	11	50	68	-	≤269

Notes:

For t >100 mm, yield reduced per table notes.
Impact at specified temperature; for E grades, –40 °C.
Hardness in annealed condition ≤229 HBW for most grades.

8. Hardenability Bands

All grades have guaranteed hardenability bands (H, HH, HL) per GB/T 225 (Jominy).

Example for 42CrMo H-band: J9 = 34–44 HRC, J30 = 28–38 HRC.

9. Gangsteel GB/T 3077 Stock & Supply (November 2025)

Grade	Diameter (mm)	Length (m)	Stock (ton)	Price (USD/ton)
42CrMo	20–1000	3–18	80,000	820–980
40Cr	10–800	3–15	60,000	680–780
35CrMo	20–900	3–18	50,000	780–880
20CrMnTi	10–700	3–15	40,000	850–950
18CrNiMo7-6	50–1200	4–20	30,000	1,200–1,500

All with 3.2 cert, H-band, restricted S.

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