1. Specifications & Capability
FUSHUN METAL forges marine shafting in 42CrMo4 (1.7225), 34CrNiMo6 (1.6582) and AISI 4340, 500-1200 mm in diameter and up to 12 m long, as single-piece or semi-built shafts. The plant holds factory approval from seven classification societies – CCS, BV, DNV, GL, LR, KR and ABS – so every shaft is witnessed and certified at the stage the vessel’s class requires.
Crankshafts are supplied integral or semi-built, with crank throws, main journals and crank pins forged separately for red-shrink or hydraulic assembly; tail shafts receive taper ends and keyways machined to shipyard drawings.
| Grade / Section (mm) | Rm (MPa) | Rp0.2 (MPa) | A (%) | KV (J) |
|---|---|---|---|---|
| 42CrMo4, up to 250 | 750-950 | 520 min | 14 | 27 min |
| 34CrNiMo6, up to 250 | 900-1100 | 700 min | 12 | 40 min |
| 250-500 | 800-950 | 600 min | 13 | 35 min |
| 500-1200 | – | – | – | Per class rules |
Values follow EN 10250-3; final acceptance follows the applicable classification society rules, with test coupons and witness points agreed with the shipyard and surveyor.
2. Components & Service Conditions
FUSHUN METAL forges the complete marine shafting set: crankshafts (crank throws, main journals and crank pins), propeller (tail) shafts, intermediate shafts and thrust shafts. The propeller shaft is among the most heavily surveyed items on a vessel, carrying full propulsion torque through the shaft alley, while the thrust shaft transfers propeller thrust to the hull.
Service conditions combine torsion, bending and seawater exposure, with the tail shaft additionally subject to corrosion fatigue at the taper and keyway. Forging aligns the grain flow with the load path and closes internal defects, giving a fatigue life substantially higher than a casting or a welded fabrication, which is why classification societies require forged shafts for propulsion lines. Each shaft is quenched and tempered, machined to shipyard drawings, and witness-tested under class survey.
3. Grade Equivalents – 42CrMo4 / 34CrNiMo6 / AISI 4340
| Designation | Standard | Notes |
|---|---|---|
| 42CrMo4 / 1.7225 | EN 10250-3 | Standard marine shaft steel |
| 34CrNiMo6 / 1.6582 | EN 10250-3 | High-toughness shaft steel |
| AISI 4340 | SAE J404 | US equivalent of 34CrNiMo6 |
| AISI 4140 | SAE J404 | US equivalent of 42CrMo4 |
| SNCM439 | JIS G4053 | Japanese equivalent |
| 40CrNiMoA | GB/T 3077 | Reference only, not used in certification |
| Grade | C | Si | Mn | Cr | Ni | Mo |
|---|---|---|---|---|---|---|
| 42CrMo4 (1.7225) | 0.38-0.45 | 0.40 max | 0.60-0.90 | 0.90-1.20 | – | 0.15-0.30 |
| 34CrNiMo6 (1.6582) | 0.30-0.38 | 0.40 max | 0.50-0.80 | 1.30-1.70 | 1.30-1.70 | 0.15-0.30 |
| AISI 4340 | 0.38-0.43 | 0.15-0.35 | 0.60-0.80 | 0.70-0.90 | 1.65-2.00 | 0.20-0.30 |
The higher nickel content of 34CrNiMo6 / AISI 4340 improves hardenability and toughness for the deepest sections, while 42CrMo4 covers standard shafting requirements economically.
4. Manufacturing Process
Steelmaking. FUSHUN METAL melts in an electric arc furnace with ladle refining and vacuum degassing, controlling sulfur and residual elements for the toughness classification societies require.
Forging. Shafts are forged with a minimum 4:1 reduction ratio on a 20/80 MN fast forging press; crankshaft throws are upset and drawn to orient grain flow around the pin and journal.
Heat treatment & machining. Quenching and tempering is followed by machining of taper ends, keyways and coupling flanges to shipyard drawings, with red-shrink or hydraulic assembly for semi-built crankshafts.
Testing. Full-section UT, MT on machined surfaces, and mechanical tests, with class surveyor witness at the required stages.
5. Standards & Certification
Marine shafting is supplied to classification society rules – ABS, DNV, LR, CCS, BV, KR, RINA and NK – with class certificates and witness points at the required stages. FUSHUN METAL holds factory approval from CCS, BV, DNV, GL, LR, KR and ABS, plus ISO 9001 and AS9120B quality system certification.
Related forging: rudder stocks and pintles.
6. Typical Applications
Slow-speed diesels
Crankshafts for large low-speed marine diesel engines.
Propeller shafts
Tail shafts with taper ends and keyways for propellers.
Shaft alley lines
Intermediate and thrust shafts for propulsion shaft lines.
Merchant & offshore
Shafting for merchant vessels and offshore service craft.
7. Inquiry Essentials
To quote your marine shafting, please provide the shafting arrangement drawing, the classification society, the required grade, and the sampling and witness requirements agreed with the shipyard.
