1.7709
1.7709 is the material number of the grade also listed as 21CrMoV5-7. It is a material in the category Heat-resistant structural steels. We list 14 designations recorded for this grade, in the standards DIN / EN, AFNOR, GOST, ČSN, STN, PN and MSZ.
- Material no. 1.7709
- Category Heat-resistant structural steels · 62 grades
- Designations 14
If you came for one of these
The most-used names for this grade.About Heat-resistant structural steels
Heat-resistant structural steels are structural steels designed to retain useful strength and dimensional stability at elevated temperatures. They are used for load-bearing components in hot-service equipment where mechanical performance must be maintained during heating.
This describes the material class as a whole. Always confirm the individual grade against the standard before ordering.
Also known as
14 designations · 7 standards · nothing hiddenEvery designation on file is listed — no truncation, no “+ n more”. Each one is itself a route that leads back here.
Chemical composition
10 elements on file · weight %What this alloy is
Logarithmic scale, 0.01 % to 100 % — every value here compares directly, decade by decade.
| Element | % by weight |
|---|---|
0.17–0.25 | |
≤ 0.4 | |
0.4–0.8 | |
0.025 | |
0.03 | |
1.2–1.5 | |
0.55–0.8 | |
0.6 | |
0.2–0.35 | |
≤ 0.03 |
The scale is logarithmic, not the element’s raw share of the alloy — the only honest way to fit 0.01 % and 100 % in one picture, and it means every value here can be compared with every other.
| Element | As publishedsource text, verbatim | Min% by weight | Max% by weight | Bound |
|---|---|---|---|---|
| C | 0,17-0,25 | 0.170 | 0.250 | Range |
| Al | ≤0,030 | — | 0.030 | Max |
| Si | ≤0,40 | — | 0.400 | Max |
| P | 0,025 | 0.025 | 0.025 | Exact |
| S | 0,03 | 0.030 | 0.030 | Exact |
| V | 0,20-0,35 | 0.200 | 0.350 | Range |
| Cr | 1,20-1,50 | 1.200 | 1.500 | Range |
| Mn | 0,40-0,80 | 0.400 | 0.800 | Range |
| Ni | 0,6 | 0.600 | 0.600 | Exact |
| Mo | 0,55-0,80 | 0.550 | 0.800 | Range |
The published column is the source string byte-for-byte, decimal comma and all; Min and Max are the parsed bounds. Elements not listed have no value on file — they are omitted, never inferred.
Predicted transformation temperatures
computed from composition · °CThese four temperatures are a CALCULATION from this grade's own composition, using the published Li, Niebuhr, Meekisho & Atteridge (1998) model — never a measurement, and computed from the UPPER BOUND of each element's specified range, not a mid-range figure. Where this grade also has a measured transformation point (Ac1, Ac3, Ar1, Ar3) on file, it is shown separately, in Physical & mechanical properties, and is never replaced by the predicted figures here — Ae (predicted, equilibrium) and Ac/Ar (measured, on heating or cooling) are different physical quantities and can differ by tens of degrees; a mismatch between the two is not an error in either.
Physical & mechanical properties
An absent property means we hold no value for it — it is left out rather than estimated, interpolated from a neighbouring grade, or filled from a handbook. It does not mean the property is undefined for the material.
Properties by condition
6 conditions · 43 valuessplav| Delivery state | HB |
|---|---|
| 25Kh1MF ( 25Х1МФ ) (quenching, tempering) | 241 – 321 |
| 25Kh1MF ( 25Х1МФ ) (hot-rolled, annealing) , GOST 20072-74 | 229 |
steelnumber| Delivery state | HB |
|---|---|
| Annealed to achieve spheroidization of the carbides | 229 |
steelnumber| Delivery state | HB |
|---|---|
| Treated to improve shearability | 255 |
splav| Dimensionmm | RmN/mm² | ReN/mm² | A5% | Z% | KCUkJ/m² |
|---|---|---|---|---|---|
| max thickness 25 | 880 | 735 | 14 | 50 | 590 |
splav| Heat-treated condition | RmN/mm² | ReN/mm² | A5% | Z% | KCUkJ/m² |
|---|---|---|---|---|---|
| Bar, band, GOST 20072-74 | 780 | 665 | 16 | 50 | 590 |
splav| Temperature°C | Densityg/cm³ | Elastic modulusGPa | Thermal expansion coefficient10^-6/K | Thermal conductivityW/(m·K) | Specific heat capacityJ/(kg·K) | Electrical resistivitynΩ·m |
|---|---|---|---|---|---|---|
| 20 | 7.84 | 217 | — | — | — | — |
| 100 | — | 211 | 11.3 | 39.8 | 462 | 312 |
| 200 | 7.79 | 206 | 11.7 | 37.9 | — | 396 |
| 300 | — | 198 | 12.8 | 36.9 | — | 475 |
| 400 | 7.72 | 191 | 13.9 | 35.9 | — | 574 |
| 500 | — | 180 | 14.2 | 34.8 | — | 680 |
| 600 | 7.65 | 167 | 14.4 | — | — | 826 |
Every figure holds only for the condition on its own row. Values are never merged across conditions or across sources, never averaged, and never interpolated between two rows. An em dash means no value on file — never zero. Figures are converted to the unit in the column header; the source’s own wording is kept and shown where the two differ.
Similar grades — and why
Selection rule, stated so you can disagree with it: same number class 1.7, a shared category, and a published range for Cr / Mo that overlaps this grade’s. These are neighbours in composition space — they are not equivalents, and none is claimed to be interchangeable with this grade.
Looking for this grade under another name?
Search the catalogue by designation, material number or composition — every name on this page is itself a way in.