21CrMoV5-7 vs 15CrMoV5-9: Both Cr-Mo-V bolt steels — different strength/temperature ranges
21CrMoV5-7 vs 15CrMoV5-9
Side-by-side chemical composition and mechanical property comparison.
Overview
21CrMoV5-7
1.7709
Cr-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.
15CrMoV5-9
1.7765
Cr-Mo-V steel for elevated temperature fastener applications. Retains strength up to 540°C. Used for high-temperature bolts, studs, and nuts in power plants, steam turbines, and pressure vessel flanges. Specified in EN 10269 for creep-resistant fasteners.
| 21CrMoV5-7 | 15CrMoV5-9 | |
|---|---|---|
| Material Number | 1.7709 | 1.7765 |
| Category | Alloy Steel | Alloy Steel |
| Standard | EN 10269 | EN 10269 |
Chemical composition (wt%)
| Element | 21CrMoV5-7 | 15CrMoV5-9 | Overlap |
|---|---|---|---|
| C | 0.17–0.25% | 0.1–0.2% | Partial |
| Si | 0–0.35% | 0–0.35% | OK |
| Mn | 0.3–0.8% | 0.4–0.7% | OK |
| P | 0–0.02% | 0–0.03% | OK |
Mechanical properties
| Property | 21CrMoV5-7 | 15CrMoV5-9 | Unit |
|---|---|---|---|
| tensile_strength | 800–950 | 780–930 | MPa |
| yield_strength | ≥ 600 | ≥ 590 | MPa |
| elongation | ≥ 14 | ≥ 15 | % |
Compatibility Assessment
21CrMoV5-7 has higher C (0.17-0.25 vs 0.10-0.20) and Mo (0.55-0.80 vs 0.85-1.10) for higher room-temp strength. Both suitable to ~550°C. 15CrMoV5-9 has higher Mo for better long-term creep. Choose 21CrMoV5-7 for higher-strength bolts; 15CrMoV5-9 for maximum creep resistance.
Frequently Asked Questions
Is 21CrMoV5-7 the same as 15CrMoV5-9?
21CrMoV5-7 and 15CrMoV5-9 have a 75% composition overlap. Both Cr-Mo-V bolt steels — different strength/temperature ranges
Can I replace 21CrMoV5-7 with 15CrMoV5-9?
In many cases, yes. The compositions overlap significantly (75%). However, always verify mechanical property requirements and heat treatment compatibility for your specific application.
What is the difference between 21CrMoV5-7 and 15CrMoV5-9?
The main differences are in the following elements: C, Mo. 21CrMoV5-7 is a Alloy Steel grade, while 15CrMoV5-9 is a Alloy Steel grade.
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