--- title: "ЭП303Б — composition, equivalents and standards" description: "ЭП303Б is a designation in GOST for the grade also listed as 55Kh20G9AN4B. We list 3 designations recorded for this grade, in the standards GOST." canonical: https://steelequivalents.com/materials/gost/ep303b language: en robots: index, follow og_type: website type: material-detail language_alternates: en: https://steelequivalents.com/materials/gost/ep303b.md cs: https://steelequivalents.com/cs/materiály/gost/ep303b.md de: https://steelequivalents.com/de/werkstoffe/gost/ep303b.md es: https://steelequivalents.com/es/materiales/gost/ep303b.md fr: https://steelequivalents.com/fr/matériaux/gost/ep303b.md hu: https://steelequivalents.com/hu/anyagok/gost/ep303b.md it: https://steelequivalents.com/it/materiali/gost/ep303b.md nl: https://steelequivalents.com/nl/materialen/gost/ep303b.md pl: https://steelequivalents.com/pl/materiały/gost/ep303b.md pt: https://steelequivalents.com/pt/materiais/gost/ep303b.md ru: https://steelequivalents.com/ru/материалы/gost/эп303б.md tr: https://steelequivalents.com/tr/malzemeler/gost/ep303b.md zh: https://steelequivalents.com/zh/材料/gost/ep303b.md ja: https://steelequivalents.com/ja/材料/gost/ep303b.md ar: https://steelequivalents.com/ar/المواد/gost/ep303b.md ko: https://steelequivalents.com/ko/재료/gost/ep303b.md pt-br: https://steelequivalents.com/pt-br/materiais/gost/ep303b.md hi: https://steelequivalents.com/hi/सामग्री/gost/ep303b.md content_hash: sha256:f6f0345f4e8db1fbbbe777e56f9149c3493fedf5fc963eef05dc1eae72ad8d11 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/gost/ep303b > Canonical URL: https://steelequivalents.com/materials/gost/ep303b > 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. GOST · Russia / CIS · 3 designations # ЭП303Б ЭП303Б is a designation in GOST for the grade also listed as 55Kh20G9AN4B. We list 3 designations recorded for this grade, in the standards GOST. - *Designations* **3** [Search](/search "Steel grade search")[Inquiry](/inquiry?material=de60da84-9597-4c11-9ef6-2c78438f57c5&designation=af39ae6d-a07f-4f2f-ba9d-71c1f8924f3e "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/gost/ep303b.pdf "Datasheet as PDF") ## If you came for one of these The most-used names for this grade. - [GOST 55Kh20G9AN4B This grade’s own name](/materials/gost/55kh20g9an4b "GOST 55Kh20G9AN4B") ## Also known as 3 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. GOST Russia / CIS · 3 - [55Kh20G9AN4B This grade’s own name](/materials/gost/55kh20g9an4b "GOST 55Kh20G9AN4B") - [55Х20Г9АН4Б Indicative](/materials/gost/55kh20g9an4b "GOST 55Х20Г9АН4Б") - **ЭП303Б Indicative** 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 Cr Mn Ni Iron — the balance, never listed by a standard — 63.5 % Cr — 21 % Mn — 9 % Ni — 4 % Traces & impurities · 2.5 % Logarithmic scale, 0.01 % to 100 % — every value here compares directly, decade by decade. | Element | % by weight | |---|---| | C | 0.5–0.6 | | Si | ≤ 0.45 | | Mn | 8–10 — Unusual | | P | ≤ 0.04 | | S | ≤ 0.03 | | Cr | 20–22 | | Ni | 3.5–4.5 | | Cu | ≤ 0.3 | | Nb | 0.4–1 | | N | 0.3–0.6 — Unusual | Carbon Silicon Manganese Phosphorus Sulfur Chromium Nickel Copper Niobium 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 | 0.5 - 0.6 | 0.500 | 0.600 | Range | | N | 0.3 - 0.6 | 0.300 | 0.600 | Range | | Si | max 0.45 | — | 0.450 | Max | | P | max 0.04 | — | 0.040 | Max | | S | max 0.03 | — | 0.030 | Max | | Cr | 20 - 22 | 20.000 | 22.000 | Range | | Mn | 8 - 10 | 8.000 | 10.000 | Range | | Ni | 3.5 - 4.5 | 3.500 | 4.500 | Range | | Cu | max 0.3 | — | 0.300 | Max | | Nb | 0.4 - 1 | 0.400 | 1.000 | 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 Not enough recorded composition to predict a transformation temperature for this grade — missing: 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=de60da84-9597-4c11-9ef6-2c78438f57c5&designation=af39ae6d-a07f-4f2f-ba9d-71c1f8924f3e "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/gost/ep303b.pdf "Datasheet as PDF")