21CrMoV5-7 vs 21CrMoV5-11

21CrMoV5-7 (Werkstoff 1.7709) and 21CrMoV5-11 (Werkstoff 1.8070) are sister grades. 21CrMoV5-7 sits in EN 10269. 21CrMoV5-11 is the DIN 17240 transitional grade that EN 10269 superseded for the heavier-section pressure-vessel and turbine bolting service. The chemistry is closely related; the difference is in the molybdenum target. 21CrMoV5-7 carries Mo 0.55 to 0.80 percent. 21CrMoV5-11 carries higher Mo (nominally 0.90 to 1.10 percent), which extends through-thickness hardenability so heavier forged sections still fully transform to bainite during the oil quench. The mechanical-property floors at the smaller section sizes are similar; the selection driver is forged-section diameter.

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Chemistry contrast

The two grades share the Cr-Mo-V Q+T family and similar carbon, silicon, manganese, chromium and vanadium windows. The differentiating element is molybdenum:

• 21CrMoV5-7 (1.7709): Mo 0.55 to 0.80 percent, Cr 1.20 to 1.50 percent. See full chemistry.
• 21CrMoV5-11 (1.8070): Mo 0.90 to 1.10 percent (per DIN 17240 / BGH datasheet), Cr range similar to 5-7. The "5-11" naming reflects the higher Mo target (the trailing 11 maps to roughly Mo×10).

When to specify 21CrMoV5-7

• Section diameter up to about 200 mm fully-hardened (the workhorse range for stud bolts, hex bolts, and most flange bolting).
• EN 10269 procurement framework with current certification path.
• New-build projects after the EN 10269 supersession of DIN 17240.

When to specify 21CrMoV5-11

• Heavy-section forgings above 200 mm OD where 21CrMoV5-7's hardenability margin tightens.
• Legacy procurement where the original equipment specification called out 21CrMoV5-11 by Werkstoff number 1.8070 (typical on pre-1990s German plant).
• Cross-reference work on retrofits, replacement components for older steam-turbine fleets.

Related cross-references

• vs 24CrMoV5-5 — the other DIN 17240 transitional Cr-Mo-V grade
• vs Durehete 1055 (1.7729) — premium Ti+B step-up
• vs ASTM A193 B16 — closest US analogue
• EN 10269 equivalents master table

FAQs

Q. Is 21CrMoV5-11 still a current specification?
DIN 17240 was superseded by EN 10269. 21CrMoV5-11 (1.8070) is still encountered on retrofit and replacement work for legacy plant where the original procurement called it out, but new-build European projects default to 21CrMoV5-7 under EN 10269.

Q. Why pick 5-11 over 5-7?
For very heavy forged sections above about 200 mm OD where the lower Mo target of 5-7 starts to limit through-thickness hardenability. The higher Mo of 5-11 ensures full bainitic transformation in the centre of large sections during oil quench.

Q. Are the mechanical-property floors identical?
The Q+T strength floors are similar at smaller sections. The practical difference is hardenability through thick sections, not nominal mechanical floor. For thin-section bolting either grade meets the same envelope.

Q. Can TorqBolt supply both?
Yes. Both are supplied as stud bolts, hex bolts, heavy hex bolts and forged blanks with EN 10204 type 3.1 or 3.2 certification against the relevant standard (EN 10269 for 21CrMoV5-7; legacy DIN 17240 reference for 21CrMoV5-11 cross-reference work).