--- title: "5S21 — composition, equivalents and standards" description: "5S21: 2 equivalent designations across 1 standards, with the recorded chemical composition shown next to the source text." canonical: https://steelequivalents.com/materials/bs/5s21 language: en robots: index, follow og_type: website type: material-detail language_alternates: en: https://steelequivalents.com/materials/bs/5s21.md cs: https://steelequivalents.com/cs/materiály/bs/5s21.md de: https://steelequivalents.com/de/werkstoffe/bs/5s21.md es: https://steelequivalents.com/es/materiales/bs/5s21.md fr: https://steelequivalents.com/fr/matériaux/bs/5s21.md hu: https://steelequivalents.com/hu/anyagok/bs/5s21.md it: https://steelequivalents.com/it/materiali/bs/5s21.md nl: https://steelequivalents.com/nl/materialen/bs/5s21.md pl: https://steelequivalents.com/pl/materiały/bs/5s21.md pt: https://steelequivalents.com/pt/materiais/bs/5s21.md ru: https://steelequivalents.com/ru/материалы/bs/5s21.md tr: https://steelequivalents.com/tr/malzemeler/bs/5s21.md zh: https://steelequivalents.com/zh/材料/bs/5s21.md ja: https://steelequivalents.com/ja/材料/bs/5s21.md ar: https://steelequivalents.com/ar/المواد/bs/5s21.md ko: https://steelequivalents.com/ko/재료/bs/5s21.md pt-br: https://steelequivalents.com/pt-br/materiais/bs/5s21.md hi: https://steelequivalents.com/hi/सामग्री/bs/5s21.md content_hash: sha256:7d4f20f7427cf3184ffcebe4c0be1ed844c2631eb1848a7f3f52a41fe427929e 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/bs/5s21 > Canonical URL: https://steelequivalents.com/materials/bs/5s21 > 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. BS · United Kingdom · 2 designations # 5S21 5S21 is a grade designated under BS. We list one designation recorded for this grade, in the standard BS. No chemical composition is recorded for this material. - *Designations* **2** [Search](/search "Steel grade search")[Inquiry](/inquiry?material=dc04b82c-b2d7-482a-bc6b-c0c1e7573f45&designation=55894ead-7a30-45e6-82fd-fb33ae21a324 "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/bs/5s21.pdf "Datasheet as PDF") ## Also known as 2 designations · 1 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. BS United Kingdom · 2 - **5S21 This grade’s own name** - [S21 Indicative](/materials/bs/s21 "BS S21") Every designation on file is listed — no truncation, no “+ n more”. Each one is itself a route that leads back here. ## Predicted transformation temperatures Not enough recorded composition to predict a transformation temperature for this grade — missing: C, Mn, Si, Ni, Cr, Mo. ## 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. ## 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=dc04b82c-b2d7-482a-bc6b-c0c1e7573f45&designation=55894ead-7a30-45e6-82fd-fb33ae21a324 "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/bs/5s21.pdf "Datasheet as PDF")