--- title: "F26 — Heat-resistant structural steels" description: "F26 in ISO: material number 1.5415, also listed as 15Mo3. Category: Heat-resistant structural steels. Designations recorded for this grade: 38." canonical: https://steelequivalents.com/materials/iso/f26 language: en robots: index, follow og_type: website type: material-detail language_alternates: en: https://steelequivalents.com/materials/iso/f26.md cs: https://steelequivalents.com/cs/materiály/iso/f26.md de: https://steelequivalents.com/de/werkstoffe/iso/f26.md es: https://steelequivalents.com/es/materiales/iso/f26.md fr: https://steelequivalents.com/fr/matériaux/iso/f26.md hu: https://steelequivalents.com/hu/anyagok/iso/f26.md it: https://steelequivalents.com/it/materiali/iso/f26.md nl: https://steelequivalents.com/nl/materialen/iso/f26.md pl: https://steelequivalents.com/pl/materiały/iso/f26.md pt: https://steelequivalents.com/pt/materiais/iso/f26.md ru: https://steelequivalents.com/ru/материалы/iso/f26.md tr: https://steelequivalents.com/tr/malzemeler/iso/f26.md zh: https://steelequivalents.com/zh/材料/iso/f26.md ja: https://steelequivalents.com/ja/材料/iso/f26.md ar: https://steelequivalents.com/ar/المواد/iso/f26.md ko: https://steelequivalents.com/ko/재료/iso/f26.md pt-br: https://steelequivalents.com/pt-br/materiais/iso/f26.md hi: https://steelequivalents.com/hi/सामग्री/iso/f26.md content_hash: sha256:9c408325fc0729567c44e777517c26a293e3686c1a931fce64a62436753c9e0c generated: 2026-09-22 --- > **Machine-readable Markdown rendering.** This is a Markdown representation of a web page, > served for AI agents and crawlers as a token-efficient alternative to the full HTML. > Full interactive HTML version: https://steelequivalents.com/materials/iso/f26 > Canonical URL: https://steelequivalents.com/materials/iso/f26 > Available languages: en, cs, de, es, fr, hu, it, nl, pl, pt, ru, tr, zh, ja, ar, ko, pt-br, hi > Change detection: `content_hash` is the SHA-256 of this document's Markdown body — everything > below this block, whitespace-trimmed, excluding the front-matter. Compare it to detect a real > content change; `generated` moves on every render and is not a change signal. ISO · International · 38 designations # F26 F26 is a designation in ISO for the material held under material number 1.5415, also listed as 15Mo3. It is a material in the category Heat-resistant structural steels. We list 38 designations recorded for this grade, in the standards DIN / EN, UNS, AISI / SAE, ASTM, BS, AFNOR, UNE, ISO, JIS, UNI, SS, ČSN, STN, PN, SRPS and ÖNORM. - [*Material no.* **1.5415**](/materials/material-no/1.5415 "Material no.: 1.5415") - [*Category* **Heat-resistant structural steels · 62 grades**](/categories/heat-resistant-structural-steels "Category: Heat-resistant structural steels · 62 grades") - *Designations* **38** [Search](/search "Steel grade search")[Inquiry](/inquiry?material=d5e99ae8-10a9-4218-a336-a7ceaa81837b&designation=91142b14-ca30-4bf7-927d-40d5fd28dfd6 "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/iso/f26.pdf "Datasheet as PDF") ## If you came for one of these The most-used names for this grade. - [DIN / EN 16Mo3 This grade’s own name](/materials/din-en/16mo3 "DIN / EN 16Mo3") - [UNS K11820 This grade’s own name · 2 grades on that route](/materials/uns/k11820 "UNS K11820") ## 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 38 designations · 16 standards · nothing hidden This grade’s own name recorded in our sources as this grade’s own designation under that standard. Indicative taken from a published cross-reference table; a close match, not a guarantee of interchangeability. Verify against the mill certificate before ordering. Withdrawn designation no longer current — a separate column from the two above, so a name can be same grade and withdrawn at once. DIN / EN Europe · 4 - [1.5415 Indicative](/materials/material-no/1.5415 "DIN / EN 1.5415") - [15Mo3 This grade’s own name Withdrawn](/materials/din-en/15mo3 "DIN / EN 15Mo3") - [16Mo3 This grade’s own name](/materials/din-en/16mo3 "DIN / EN 16Mo3") - [A204Gr.B Indicative](/materials/din-en/a204gr-b "DIN / EN A204Gr.B") UNS United States · 4 - [K11820 This grade’s own name](/materials/uns/k11820 "UNS K11820") - [K12020 This grade’s own name](/materials/uns/k12020 "UNS K12020") - [K12320 This grade’s own name](/materials/uns/k12320 "UNS K12320") - [K12822 This grade’s own name](/materials/uns/k12822 "UNS K12822") AISI / SAE United States · 4 - [A204 (A) Indicative](/materials/aisi-sae/a204-a "AISI / SAE A204 (A)") - [A204Gr.A Indicative](/materials/aisi-sae/a204gr-a "AISI / SAE A204Gr.A") - [A204Gr.B Indicative](/materials/din-en/a204gr-b "AISI / SAE A204Gr.B") - [ASTM A204Gr.A Indicative](/materials/aisi-sae/astm-a204gr-a "AISI / SAE ASTM A204Gr.A") ASTM United States · 4 - [A 182 Grade F1 Indicative](/materials/astm/a-182-grade-f1 "ASTM A 182 Grade F1") - [A 234 Grade WP1 Indicative](/materials/astm/a-234-grade-wp1 "ASTM A 234 Grade WP1") - [A 335 Grade P1 Indicative](/materials/astm/a-335-grade-p1 "ASTM A 335 Grade P1") - [A204 Indicative](/materials/astm/a204 "ASTM A204") BS United Kingdom · 4 - [1501-240 Indicative](/materials/bs/1501-240 "BS 1501-240") - [1503-243B Indicative](/materials/bs/1503-243b "BS 1503-243B") - [240 Indicative](/materials/bs/240 "BS 240") - [243 Indicative](/materials/bs/243 "BS 243") AFNOR France · 2 - [15D3 Indicative](/materials/afnor/15d3 "AFNOR 15D3") - [15M03 Indicative](/materials/afnor/15m03 "AFNOR 15M03") UNE Spain · 3 - [16Mo3 Indicative](/materials/din-en/16mo3 "UNE 16Mo3") - [F.2601 Indicative](/materials/une/f-2601 "UNE F.2601") - [F.2601 -16 Mo 3 Indicative](/materials/une/f-2601-16-mo-3 "UNE F.2601 -16 Mo 3") ISO International · 3 - **F26 Indicative** - [P26 Indicative](/materials/iso/p26 "ISO P26") - [TS26 Indicative](/materials/iso/ts26 "ISO TS26") JIS Japan · 1 - [STBA12 Indicative](/materials/jis/stba12 "JIS STBA12") UNI Italy · 3 - [15Mo3 Indicative](/materials/din-en/15mo3 "UNI 15Mo3") - [16Mo3 Indicative](/materials/din-en/16mo3 "UNI 16Mo3") - [16Mo3KW Indicative](/materials/uni/16mo3kw "UNI 16Mo3KW") SS Sweden · 1 - [2912 Indicative](/materials/ss/2912 "SS 2912") ČSN Czechia · 1 - [15020 Indicative](/materials/csn/15020 "ČSN 15020") STN Slovakia · 1 - [15 020 Indicative](/materials/csn/15020 "STN 15 020") PN Poland · 1 - [16M Indicative](/materials/pn/16m "PN 16M") SRPS Serbia · 1 - [Č.7100 Indicative](/materials/srps/c-7100 "SRPS Č.7100") ÖNORM Austria · 1 - [15Mo3KW Indicative](/materials/onorm/15mo3kw "ÖNORM 15Mo3KW") Every 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 Fe Mn Si Cr Iron — the balance, never listed by a standard — 97.6 % Mn — 0.7 % Si — 0.4 % Cr — 0.3 % Traces & impurities · 1.1 % Logarithmic scale, 0.01 % to 100 % — every value here compares directly, decade by decade. | Element | % by weight | |---|---| | C | 0.12–0.2 | | Si | ≤ 0.35 | | Mn | 0.4–0.9 | | P | 0.025 | | S | 0.01 | | Cr | ≤ 0.3 | | Mo | 0.25–0.35 | | Ni | 0.3 | | Cu | ≤ 0.3 | | N | 0.012 | Carbon Silicon Manganese Phosphorus Sulfur Chromium Molybdenum Nickel Copper Nitrogen 0.01 % 0.1 % 1 % 10 % 100 % 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 published source text, verbatim | Min% by weight | Max% by weight | Bound | |---|---|---|---|---| | C | 0,12-0,20 | 0.120 | 0.200 | Range | | N | 0,012 | 0.012 | 0.012 | Exact | | Si | ≤0,35 | — | 0.350 | Max | | P | 0,025 | 0.025 | 0.025 | Exact | | S | 0,01 | 0.010 | 0.010 | Exact | | Cr | ≤0,30 | — | 0.300 | Max | | Mn | 0,40-0,90 | 0.400 | 0.900 | Range | | Ni | 0,3 | 0.300 | 0.300 | Exact | | Cu | ≤0,30 | — | 0.300 | Max | | Mo | 0,25-0,35 | 0.250 | 0.350 | 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 · °C Predicted Ae3 816 °C Predicted Ae1 721 °C Predicted Acm 432 °C Predicted Bs 565 °C These 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 Density 7,85 g/cm³ Exact 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 2 conditions · 18 values By thickness**Normalized** source `steelnumber` | Thickness mm | ReH N/mm² | Rm N/mm² | A% | |---|---|---|---| | ≤ 16 | 275 | — | — | | 16 – 40 | 270 | — | — | | 40 – 60 | 260 | — | 23 | | ≤ 40 | — | — | 24 | | ≤ 60 | — | 440 – 590 | — | | 60 – 100 | 240 | 430 – 580 | 22 | | 100 – 150 | 220 | 420 – 570 | 19 | | 150 – 250 | 210 | 410 – 570 | — | By thickness**Quenched and tempered** source `steelnumber` | Thickness mm | ReH N/mm² | Rm N/mm² | |---|---|---| | ≤ 250 | 265 | 440 – 570 | | 250 – 500 | 250 | 420 – 550 | 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 1.5, a shared category, and a published range for Mn / Ni 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. [21MoV5-3 1.5404 Mn 0,50-0,80 · Ni 0,3 - ΔMn 0.00 - ΔNi 0.00 - 1 designations](/materials/din-en/21mov5-3 "21MoV5-3")[17MoV8-4 1.5406 Mn 0,50-0,80 · Ni 0,3 - ΔMn 0.00 - ΔNi 0.00 - 1 designations](/materials/din-en/17mov8-4 "17MoV8-4")[15MnMoV4-5 1.5402 Mn 0,90-1,40 · Ni 0,3 - ΔMn 0.50 - ΔNi 0.00 - 1 designations](/materials/din-en/15mnmov4-5 "15MnMoV4-5")[18MnMo4-5 1.5414 Mn 0,90-1,50 · Ni 0,3 - ΔMn 0.55 - ΔNi 0.00 - 4 designations](/materials/din-en/18mnmo4-5 "18MnMo4-5") ## 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. [Search](/search "Steel grade search")[Inquiry](/inquiry?material=d5e99ae8-10a9-4218-a336-a7ceaa81837b&designation=91142b14-ca30-4bf7-927d-40d5fd28dfd6 "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/iso/f26.pdf "Datasheet as PDF")