21CrMoV5-7
1.7709Cr-Mo-V high-temperature alloy steel for bolting at elevated temperatures up to ~550°C. Higher Cr and Mo than 15CrMoV5-9 for improved creep resistance. Used for turbine casing bolts, main flange bolts in steam power plants, and high-pressure/high-temperature petrochemical fasteners.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | ASTM | USA | ASTM A193 B16 (approx) | — | REF |
| 🇪🇺 | EN | Europe | 21CrMoV5-7 | 1.7709 | 100% |
Sources: ASTM A193, EN 10269:2013
Chemical composition comparison (wt%)
Side-by-side: 21CrMoV5-7 (EN) (EN 10269:2013) vs 21CrMoV5-7 (EN) (EN 10269:2013)
| Element | 21CrMoV5-7 (EN) | 21CrMoV5-7 (EN) | Overlap |
|---|---|---|---|
| C | 0.17–0.25% | 0.17–0.25% | OK |
| Si | 0–0.35% | 0–0.35% | OK |
| Mn | 0.3–0.8% | 0.3–0.8% | OK |
| P | 0–0.02% | 0–0.02% | OK |
| S | 0–0.01% | 0–0.01% | OK |
| Cr | 1.2–1.5% | 1.2–1.5% | OK |
| Mo | 0.55–0.8% | 0.55–0.8% | OK |
| V | 0.2–0.35% | 0.2–0.35% | OK |
Mechanical properties
QT
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 800–950 | MPa |
| Yield Strength | ≥ 600 | MPa |
| Elongation | ≥ 14 | % |
| Elastic Modulus | ≥ 210 | GPa |
| Density | ≥ 7.85 | g/cm3 |
Heat treatment
| Process | Temperature | Medium | Holding Time | Notes |
|---|---|---|---|---|
| quenching | 940–980 °C | oil | min 30 min | — |
| tempering | 680–740 °C | air | min 60 min | Double temper recommended for bolt applications |
Related materials
50CrV4
1.8160Chromium-vanadium spring/tool steel — identical alloy system to 51CrV4 (1.8159) but recognized as a separate grade in some standards. Dual use: heavy-duty springs (EN 10089) AND cold work tools (knives, shear blades). V improves temper resistance and grain refinement. UTS 1200-1500 QT. Used for heavy leaf springs, stabilizer bars, torsion bars, and cold work cutting tools.
51CrMoV4
1.7701CrMoV alloyed spring steel — THE European automotive suspension spring material. CrMo gives deep hardenability for large coil springs, V adds grain refinement and secondary hardening for fatigue resistance. UTS 1350-1600 MPa QT. Used for hot-formed coil springs (cars, trucks), leaf springs, torsion bars, and stabilizer bars. Excellent sag resistance to 200°C.
20MnCr5
1.7147Manganese-chromium case-hardening steel with higher core strength than 16MnCr5. Used for heavily loaded gears, shafts, camshafts, and transmission components requiring high surface hardness with tough core. Popular in automotive and heavy machinery.
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