--- title: "A266 — composition, equivalents and standards" description: "A266: 2 equivalent designations across 2 standards, with the recorded chemical composition shown next to the source text." canonical: https://steelequivalents.com/materials/astm/a266 language: en robots: index, follow og_type: website type: material-detail language_alternates: en: https://steelequivalents.com/materials/astm/a266.md cs: https://steelequivalents.com/cs/materiály/astm/a266.md de: https://steelequivalents.com/de/werkstoffe/astm/a266.md es: https://steelequivalents.com/es/materiales/astm/a266.md fr: https://steelequivalents.com/fr/matériaux/astm/a266.md hu: https://steelequivalents.com/hu/anyagok/astm/a266.md it: https://steelequivalents.com/it/materiali/astm/a266.md nl: https://steelequivalents.com/nl/materialen/astm/a266.md pl: https://steelequivalents.com/pl/materiały/astm/a266.md pt: https://steelequivalents.com/pt/materiais/astm/a266.md ru: https://steelequivalents.com/ru/материалы/astm/a266.md tr: https://steelequivalents.com/tr/malzemeler/astm/a266.md zh: https://steelequivalents.com/zh/材料/astm/a266.md ja: https://steelequivalents.com/ja/材料/astm/a266.md ar: https://steelequivalents.com/ar/المواد/astm/a266.md ko: https://steelequivalents.com/ko/재료/astm/a266.md pt-br: https://steelequivalents.com/pt-br/materiais/astm/a266.md hi: https://steelequivalents.com/hi/सामग्री/astm/a266.md content_hash: sha256:c2df9914e75362f186f3a2ddebe4e41933fb33b07309741cf774a4db0330bf23 generated: 2026-09-24 --- > **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/astm/a266 > Canonical URL: https://steelequivalents.com/materials/astm/a266 > 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. ASTM · United States · 2 designations # A266 25Mn is a grade designated under GB. Its recorded composition includes C 0.22–0.29%, Si 0.17–0.37%, Mn 0.7–1%, Ni ≤ 0.3% and Cu ≤ 0.25%. We list one designation recorded for this grade, in the standard ASTM. Recorded mechanical properties include Rm ≥ 490 N/mm² and A ≥ 22%. - *Designations* **2** [Search](/search "Steel grade search")[Inquiry](/inquiry?material=28b14c74-74d9-4bc0-81ed-fd433cf12ab0&designation=69a5fac3-5688-49bb-8cdc-8822568526f8 "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/astm/a266.pdf "Datasheet as PDF") ## If you came for one of these The most-used names for this grade. - [GB 25Mn This grade’s own name](/materials/gb/25mn "GB 25Mn") ## Also known as 2 designations · 2 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. ASTM United States · 1 - **A266 Indicative** GB China · 1 - [25Mn This grade’s own name](/materials/gb/25mn "GB 25Mn") Every designation on file is listed — no truncation, no “+ n more”. Each one is itself a route that leads back here. ## Chemical composition 8 elements on file · weight % What this alloy is Fe Mn Ni Si Iron — the balance, never listed by a standard — 97.8 % Mn — 0.9 % Ni — 0.3 % Si — 0.3 % Traces & impurities · 0.8 % Logarithmic scale, 0.01 % to 100 % — every value here compares directly, decade by decade. | Element | % by weight | |---|---| | C | 0.22–0.29 | | Si | 0.17–0.37 | | Mn | 0.7–1 | | P | ≤ 0.035 | | S | ≤ 0.03 | | Cr | ≤ 0.2 | | Ni | ≤ 0.3 | | Cu | ≤ 0.25 | Carbon Silicon Manganese Phosphorus Sulfur Chromium Nickel Copper 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 | 0.22-0.29 | 0.220 | 0.290 | Range | | Si | 0.17-0.37 | 0.170 | 0.370 | Range | | P | ≤0.035 | — | 0.035 | Max | | S | ≤0.03 | — | 0.030 | Max | | Cr | ≤0.2 | — | 0.200 | Max | | Mn | 0.7-1 | 0.700 | 1.000 | Range | | Ni | ≤0.3 | — | 0.300 | Max | | Cu | ≤0.25 | — | 0.250 | Max | 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 Not enough recorded composition to predict a transformation temperature for this grade — missing: Mo. ## Physical & mechanical properties Rm ≥490 N/mm² Min A ≥22% Min 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. ## Heat treatment Supply condition - Normalizing and Quenching and Tempering Test specimen diameter d=25 - Normalizing and Quenching and Tempering Test specimen size d=25 Conditions the standard permits on delivery. No temperature or medium is published for these, so no order and no alternation is implied. Source: [www.caishuku.com](https://www.caishuku.com/detail/azhlNWIxMzM2OQ__ "Source: www.caishuku.com") ## 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=28b14c74-74d9-4bc0-81ed-fd433cf12ab0&designation=69a5fac3-5688-49bb-8cdc-8822568526f8 "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/astm/a266.pdf "Datasheet as PDF")