--- title: "20Cr — Case hardening steels" description: "20Cr in GB: material number 1.7027, also listed as 20Cr4. It is a material in the category Case hardening steels. Designations recorded for this grade: 25." canonical: https://steelequivalents.com/materials/gb/20cr language: en robots: index, follow og_type: website type: material-detail language_alternates: en: https://steelequivalents.com/materials/gb/20cr.md cs: https://steelequivalents.com/cs/materiály/gb/20cr.md de: https://steelequivalents.com/de/werkstoffe/gb/20cr.md es: https://steelequivalents.com/es/materiales/gb/20cr.md fr: https://steelequivalents.com/fr/matériaux/gb/20cr.md hu: https://steelequivalents.com/hu/anyagok/gb/20cr.md it: https://steelequivalents.com/it/materiali/gb/20cr.md nl: https://steelequivalents.com/nl/materialen/gb/20cr.md pl: https://steelequivalents.com/pl/materiały/gb/20cr.md pt: https://steelequivalents.com/pt/materiais/gb/20cr.md ru: https://steelequivalents.com/ru/материалы/gb/20cr.md tr: https://steelequivalents.com/tr/malzemeler/gb/20cr.md zh: https://steelequivalents.com/zh/材料/gb/20cr.md ja: https://steelequivalents.com/ja/材料/gb/20cr.md ar: https://steelequivalents.com/ar/المواد/gb/20cr.md ko: https://steelequivalents.com/ko/재료/gb/20cr.md pt-br: https://steelequivalents.com/pt-br/materiais/gb/20cr.md hi: https://steelequivalents.com/hi/सामग्री/gb/20cr.md content_hash: sha256:f6409209b29861dad9195d928ddb38616f71654d4db8706e386a4c682e3c0f13 generated: 2026-09-21 --- > **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/gb/20cr > Canonical URL: https://steelequivalents.com/materials/gb/20cr > 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. GB · China · 25 designations # 20Cr 20Cr is a designation in GB for the material held under material number 1.7027, also listed as 20Cr4. It is a material in the category Case hardening steels. We list 25 designations recorded for this grade, in the standards DIN / EN, UNS, AISI / SAE, BS, AFNOR, ISO, JIS, GB, GOST, PN, SRPS, MSZ and BDS. - [*Material no.* **1.7027**](/materials/material-no/1.7027 "Material no.: 1.7027") - [*Category* **Case hardening steels · 60 grades**](/categories/case-hardening-steels "Category: Case hardening steels · 60 grades") - *Designations* **25** [Search](/search "Steel grade search")[Inquiry](/inquiry?material=8e477857-5942-4d93-b773-15f4412c2c8b&designation=8e1dc40f-b8b5-4057-88bb-07ec9d9cc37d "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/gb/20cr.pdf "Datasheet as PDF") ## If you came for one of these The most-used names for this grade. - [DIN / EN 20Cr4 This grade’s own name](/materials/din-en/20cr4 "DIN / EN 20Cr4") - [UNS G51200 This grade’s own name · 7 grades on that route](/materials/uns/g51200 "UNS G51200") - [AISI / SAE 5120 This grade’s own name · 5 grades on that route](/materials/aisi-sae/5120 "AISI / SAE 5120") ## About Case hardening steels Case hardening steels are steels designed to develop a hard, wear-resistant surface while retaining a tough and ductile core. They are used for components such as gears, shafts and other machine parts exposed to contact wear and cyclic loading. This describes the material class as a whole. Always confirm the individual grade against the standard before ordering. ## Also known as 25 designations · 13 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 · 1 - [20Cr4 This grade’s own name](/materials/din-en/20cr4 "DIN / EN 20Cr4") UNS United States · 1 - [G51200 This grade’s own name](/materials/uns/g51200 "UNS G51200") AISI / SAE United States · 6 - [5117 Indicative](/materials/aisi-sae/5117 "AISI / SAE 5117") - [5120 This grade’s own name](/materials/aisi-sae/5120 "AISI / SAE 5120") - [5120H Indicative](/materials/aisi-sae/5120h "AISI / SAE 5120H") - [G51170 Indicative](/materials/uns/g51170 "AISI / SAE G51170") - [G51200 Indicative](/materials/uns/g51200 "AISI / SAE G51200") - [H51200 Indicative](/materials/uns/h51200 "AISI / SAE H51200") BS United Kingdom · 2 - [207 Indicative](/materials/bs/207 "BS 207") - [527A19 Indicative](/materials/bs/527a19 "BS 527A19") AFNOR France · 1 - [18C3 Indicative](/materials/afnor/18c3 "AFNOR 18C3") ISO International · 2 - [20Cr4 Indicative](/materials/din-en/20cr4 "ISO 20Cr4") - [20CrS4 Indicative](/materials/din-en/20crs4 "ISO 20CrS4") JIS Japan · 2 - [SCr420 Indicative](/materials/jis/scr420 "JIS SCr420") - [SCr420H Indicative](/materials/jis/scr420h "JIS SCr420H") GB China · 1 - **20Cr Indicative** GOST Russia / CIS · 5 - [20Ch Indicative](/materials/bds/20ch "GOST 20Ch") - [20KH Indicative](/materials/gost/20kh "GOST 20KH") - [20X Indicative](/materials/gost/20x "GOST 20X") - [20Х Indicative](/materials/gost/20kh "GOST 20Х") - [ст.20X Indicative](/materials/gost/st-20x "GOST ст.20X") PN Poland · 1 - [20H Indicative](/materials/pn/20h "PN 20H") SRPS Serbia · 1 - [Č.4120.1 Indicative](/materials/srps/c-4120-1 "SRPS Č.4120.1") MSZ Hungary · 1 - [BC2 Indicative](/materials/msz/bc2 "MSZ BC2") BDS Bulgaria · 1 - [20Ch Indicative](/materials/bds/20ch "BDS 20Ch") Every designation on file is listed — no truncation, no “+ n more”. Each one is itself a route that leads back here. ## Chemical composition 9 elements on file · weight % What this alloy is Fe Cr Mn Si Iron — the balance, never listed by a standard — 97.2 % Cr — 1.1 % Mn — 0.8 % Si — 0.4 % Traces & impurities · 0.6 % Logarithmic scale, 0.01 % to 100 % — every value here compares directly, decade by decade. | Element | % by weight | |---|---| | C | 0.17–0.23 | | Si | ≤ 0.4 | | Mn | 0.6–0.9 | | P | 0.025 | | S | 0.015 | | Cr | 0.9–1.2 | | Cu | ≤ 0.3 | | Al | ≤ 0.05 | | O | ≤ 0.002 | Carbon Silicon Manganese Phosphorus Sulfur Chromium Copper Aluminium Oxygen 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 | 0,17-0,23 | 0.170 | 0.230 | Range | | O | ≤0,0020 | — | 0.002 | Max | | Al | ≤0,05 | — | 0.050 | Max | | Si | ≤0,40 | — | 0.400 | Max | | P | 0,025 | 0.025 | 0.025 | Exact | | S | 0,015 | 0.015 | 0.015 | Exact | | Cr | 0,90-1,20 | 0.900 | 1.200 | Range | | Mn | 0,60-0,90 | 0.600 | 0.900 | Range | | Cu | ≤0,30 | — | 0.300 | 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: Ni, Mo. ## Physical & mechanical properties Density 7,85 g/cm³ Exact Transformation point Ac1 750 °C Exact Transformation point Ac3 825 °C Exact · Ac3(Acm) Transformation point Ar3 755 °C Exact · Ar3(Arcm) Transformation point Ar1 665 °C Exact Weldability readily weldable As published: without limitations. Flake sensitivity slightly susceptible As published: weakly predisposed Temper brittleness not susceptible As published: not predisposed 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 3 conditions · 47 values By delivery state**no delivery state stated** source `splav` | Delivery state | Rm N/mm² | A5% | HB | |---|---|---|---| | Pipe, GOST 8731-87 | 431 | 16 | — | | (annealing) , GOST 4543-71 | — | — | 179 | | (cold-worked) , GOST 4543-71 | — | — | 229 | | Bar GOST 10702-78 | — | — | 163 | By dimension**Quenching and drawing** source `splav` | Dimension mm | Rm N/mm² | Re N/mm² | A5% | Z% | KCU kJ/m² | |---|---|---|---|---|---| | Ø 15 | 780 | 635 | 11 | 40 | 590 | At temperature**no delivery state stated** source `splav` | Temperature °C | Density g/cm³ | Elastic modulus GPa | Thermal expansion coefficient 10^-6/K | Thermal conductivity W/(m·K) | Specific heat capacity J/(kg·K) | |---|---|---|---|---|---| | 20 | 7.83 | 216 | — | 42 | — | | 100 | 7.81 | 213 | 10.5 | 42 | 496 | | 200 | 7.78 | 198 | 11.6 | 41 | 508 | | 300 | — | 193 | 12.4 | 40 | 525 | | 400 | 7.71 | 181 | 13.1 | 38 | 537 | | 500 | — | 171 | 13.6 | 36 | 567 | | 600 | 7.64 | 165 | 14 | 33 | 588 | | 700 | — | 143 | — | 32 | 626 | | 800 | — | 133 | — | 31 | 706 | 4 further values are held for this grade under a condition the source did not name — a bound with no quantity attached. They are withheld rather than shown against a guessed condition. 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. ## Heat treatment **GJB 1220** In this order d=15 1. Quenching 880 °C 2. Quenching 780–820 °C Quenchant Water or Oil 3. Tempering 200 °C Cooling Water or Air Supply condition - Soft annealing All product forms - Spheroidize annealing - Solution annealing - Soft annealing Bar and Wire rod - Soft annealing All product forms - Soft annealing 16\