--- title: "Cl.A — Nitriding steels" description: "Cl.A in AISI / SAE: material number 1.8509, also listed as 41CrAlMo7-10. Category: Nitriding steels. Designations recorded for this grade: 44." canonical: https://steelequivalents.com/materials/aisi-sae/cl-a language: en robots: index, follow og_type: website type: material-detail language_alternates: en: https://steelequivalents.com/materials/aisi-sae/cl-a.md cs: https://steelequivalents.com/cs/materiály/aisi-sae/cl-a.md de: https://steelequivalents.com/de/werkstoffe/aisi-sae/cl-a.md es: https://steelequivalents.com/es/materiales/aisi-sae/cl-a.md fr: https://steelequivalents.com/fr/matériaux/aisi-sae/cl-a.md hu: https://steelequivalents.com/hu/anyagok/aisi-sae/cl-a.md it: https://steelequivalents.com/it/materiali/aisi-sae/cl-a.md nl: https://steelequivalents.com/nl/materialen/aisi-sae/cl-a.md pl: https://steelequivalents.com/pl/materiały/aisi-sae/cl-a.md pt: https://steelequivalents.com/pt/materiais/aisi-sae/cl-a.md ru: https://steelequivalents.com/ru/материалы/aisi-sae/cl-a.md tr: https://steelequivalents.com/tr/malzemeler/aisi-sae/cl-a.md zh: https://steelequivalents.com/zh/材料/aisi-sae/cl-a.md ja: https://steelequivalents.com/ja/材料/aisi-sae/cl-a.md ar: https://steelequivalents.com/ar/المواد/aisi-sae/cl-a.md ko: https://steelequivalents.com/ko/재료/aisi-sae/cl-a.md pt-br: https://steelequivalents.com/pt-br/materiais/aisi-sae/cl-a.md hi: https://steelequivalents.com/hi/सामग्री/aisi-sae/cl-a.md content_hash: sha256:21af702403203b513c1b8b0bf883368b3f7d270bd7d5947478e7f39e5540727b 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/aisi-sae/cl-a > Canonical URL: https://steelequivalents.com/materials/aisi-sae/cl-a > 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. AISI / SAE · United States · 44 designations # Cl.A Cl.A is a designation in AISI / SAE for the material held under material number 1.8509, also listed as 41CrAlMo7-10. It is a material in the category Nitriding steels. We list 44 designations recorded for this grade, in the standards DIN / EN, UNS, AISI / SAE, BS, AFNOR, UNE, SAE AMS, JIS, GB, GOST, UNI, SS, ČSN, STN, PN, SRPS and KS. - [*Material no.* **1.8509**](/materials/material-no/1.8509 "Material no.: 1.8509") - [*Category* **Nitriding steels · 11 grades**](/categories/nitriding-steels "Category: Nitriding steels · 11 grades") - *Designations* **44** [Search](/search "Steel grade search")[Inquiry](/inquiry?material=3347e740-98e5-4e96-8b22-555c184cab53&designation=26320931-08a4-48af-be0a-a415038b67a0 "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/aisi-sae/cl-a.pdf "Datasheet as PDF") ## If you came for one of these The most-used names for this grade. - [DIN / EN 41CrAlMo7-10 This grade’s own name](/materials/din-en/41cralmo7-10 "DIN / EN 41CrAlMo7-10") - [UNS K24728 This grade’s own name](/materials/uns/k24728 "UNS K24728") - [BS 905M39 This grade’s own name · 2 grades on that route](/materials/bs/905m39 "BS 905M39") - [AFNOR 40CAD612 This grade’s own name · 2 grades on that route](/materials/afnor/40cad612 "AFNOR 40CAD612") - [SAE AMS 6470H This grade’s own name](/materials/ams/6470h "SAE AMS 6470H") ## About Nitriding steels Nitriding steels are alloy steels designed for nitriding, a surface-hardening treatment that produces a hard, wear-resistant surface while retaining a tough supporting core. They are used for gears, shafts, dies and other components requiring resistance to wear, repeated loading and dimensional change in service. This describes the material class as a whole. Always confirm the individual grade against the standard before ordering. ## Also known as 44 designations · 17 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 · 3 - [1.8509 Indicative](/materials/material-no/1.8509 "DIN / EN 1.8509") - [41CrAlMo7 This grade’s own name Withdrawn](/materials/din-en/41cralmo7 "DIN / EN 41CrAlMo7") - [41CrAlMo7-10 This grade’s own name](/materials/din-en/41cralmo7-10 "DIN / EN 41CrAlMo7-10") UNS United States · 3 - [E71400 Indicative](/materials/aisi-sae/e71400 "UNS E71400") - [K24065 Indicative](/materials/uns/k24065 "UNS K24065") - [K24728 This grade’s own name](/materials/uns/k24728 "UNS K24728") AISI / SAE United States · 7 - [A290C1M Indicative](/materials/aisi-sae/a290c1m "AISI / SAE A290C1M") - [A355CI.A Indicative](/materials/aisi-sae/a355ci-a "AISI / SAE A355CI.A") - **Cl.A Indicative** - [E71400 Indicative](/materials/aisi-sae/e71400 "AISI / SAE E71400") - [J24056 Indicative](/materials/uns/j24056 "AISI / SAE J24056") - [K24065 Indicative](/materials/uns/k24065 "AISI / SAE K24065") - [K24728 Indicative](/materials/uns/k24728 "AISI / SAE K24728") BS United Kingdom · 3 - [41B Indicative](/materials/bs/41b "BS 41B") - [905M39 This grade’s own name](/materials/bs/905m39 "BS 905M39") - [EN 41 B This grade’s own name](/materials/bs/en41b "BS EN 41 B") AFNOR France · 3 - [40CAD2 Indicative](/materials/afnor/40cad2 "AFNOR 40CAD2") - [40CAD6 Indicative](/materials/afnor/40cad6 "AFNOR 40CAD6") - [40CAD612 This grade’s own name](/materials/afnor/40cad612 "AFNOR 40CAD612") UNE Spain · 5 - [41CrAlMo7 Indicative](/materials/din-en/41cralmo7 "UNE 41CrAlMo7") - [CrAIMo7 Indicative](/materials/une/craimo7 "UNE CrAIMo7") - [F.174 Indicative](/materials/une/f-174 "UNE F.174") - [F.1740 Indicative](/materials/une/f-1740 "UNE F.1740") - [F.1740-41 Indicative](/materials/une/f-1740-41 "UNE F.1740-41") SAE AMS United States / Aerospace · 2 - [6431 Indicative](/materials/ams/6431 "SAE AMS 6431") - [6470H This grade’s own name](/materials/ams/6470h "SAE AMS 6470H") JIS Japan · 1 - [SACM645 Indicative](/materials/jis/sacm645 "JIS SACM645") GB China · 1 - [38CrMoAl Indicative](/materials/gb/38crmoal "GB 38CrMoAl") GOST Russia / CIS · 7 - [38Ch2MJuA Indicative](/materials/gost/38ch2mjua "GOST 38Ch2MJuA") - [38G2MF Indicative](/materials/gost/38g2mf "GOST 38G2MF") - [38GST Indicative](/materials/gost/38gst "GOST 38GST") - [38Kh2MYuА Indicative](/materials/gost/38kh2myua "GOST 38Kh2MYuА") - [38KhNM Indicative](/materials/gost/38khnm "GOST 38KhNM") - [38Х2МЮА Indicative](/materials/gost/38kh2myua "GOST 38Х2МЮА") - [38ХМЮА Indicative](/materials/gost/38khmyua "GOST 38ХМЮА") UNI Italy · 2 - [41CrAiMo7 Indicative](/materials/uni/41craimo7 "UNI 41CrAiMo7") - [41CrAlMo7 Indicative](/materials/din-en/41cralmo7 "UNI 41CrAlMo7") SS Sweden · 2 - [2940 Indicative](/materials/ss/2940 "SS 2940") - [SIS 14 2940 This grade’s own name](/materials/ss/sis-14-2940 "SS SIS 14 2940") ČSN Czechia · 1 - [15340 Indicative](/materials/csn/15340 "ČSN 15340") STN Slovakia · 1 - [15 340 Indicative](/materials/csn/15340 "STN 15 340") PN Poland · 1 - [38HMJ Indicative](/materials/pn/38hmj "PN 38HMJ") SRPS Serbia · 1 - [Č.4784 Indicative](/materials/srps/c-4784 "SRPS Č.4784") KS South Korea · 1 - [SACM645 Indicative](/materials/jis/sacm645 "KS SACM645") 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 Cr Al Mn Iron — the balance, never listed by a standard — 95.7 % Cr — 1.7 % Al — 1 % Mn — 0.6 % Traces & impurities · 1.1 % Logarithmic scale, 0.01 % to 100 % — every value here compares directly, decade by decade. | Element | % by weight | |---|---| | C | 0.38–0.45 | | Si | ≤ 0.4 | | Mn | 0.4–0.7 | | P | 0.025 | | S | 0.035 | | Cr | 1.5–1.8 | | Mo | 0.2–0.35 | | Al | 0.8–1.2 | Carbon Silicon Manganese Phosphorus Sulfur Chromium Molybdenum Aluminium 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 | 0,38-0,45 | 0.380 | 0.450 | Range | | Al | 0,80-1,20 | 0.800 | 1.200 | Range | | Si | ≤0,40 | — | 0.400 | Max | | P | 0,025 | 0.025 | 0.025 | Exact | | S | 0,035 | 0.035 | 0.035 | Exact | | Cr | 1,50-1,80 | 1.500 | 1.800 | Range | | Mn | 0,40-0,70 | 0.400 | 0.700 | Range | | Mo | 0,20-0,35 | 0.200 | 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 Not enough recorded composition to predict a transformation temperature for this grade — missing: Ni. ## Physical & mechanical properties Density 7,57 g/cm³ Exact Transformation point Ac1 800 °C Exact Transformation point Ac3 940 °C Exact · Ac3(Acm) Transformation point Ar1 730 °C Exact Weldability not suitable for welding As published: is not used. Flake sensitivity susceptible As published: 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 5 conditions · 52 values By thickness**Quenched and tempered** source `steelnumber` | Thickness mm | Rm N/mm² | A% | |---|---|---| | 16 – 40 | 950 – 1150 | 11 | | 40 – 100 | 900 – 1100 | 13 | | 100 – 160 | 850 – 1050 | 14 | | 160 – 250 | 800 – 1000 | 15 | By delivery state**no delivery state stated** source `splav` | Delivery state | Rm N/mm² | A5% | HB | |---|---|---|---| | Pipe, GOST 21729-76 | 392 | 20 | — | | 38Kh2MYuА ( 38Х2МЮА ) (annealing) , GOST 4543-71 | — | — | 229 | | 38Kh2MYuА ( 38Х2МЮА ) (cold-worked) , GOST 4543-71 | — | — | 255 | By delivery state**Soft annealed** source `steelnumber` | Delivery state | HB | |---|---| | Soft annealed | 248 | By dimension**Quenching and drawing** source `splav` | Dimension mm | Rm N/mm² | Re N/mm² | A5% | Z% | KCU kJ/m² | |---|---|---|---|---|---| | Ø 30 | 980 | 835 | 14 | 50 | 880 | 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 | 7.71 | 209 | — | 33 | — | | 100 | — | 202 | 11.5 | 33 | 496 | | 200 | — | 194 | 11.8 | 32 | 517 | | 300 | — | 190 | 12.7 | 31 | 533 | | 400 | — | 181 | 13.4 | 20 | 546 | | 500 | — | 174 | 13.9 | 20 | 575 | | 600 | — | 162 | 14.7 | 28 | 609 | | 700 | — | 147 | 14.9 | 27 | 638 | | 800 | — | 137 | — | 27 | 676 | 1 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 Supply condition - Nitriding - Soft annealing Bar, Rod, Flat product, Forging and Semi-finished product - Quenching and Tempering Bar, Flat product and Forging 16≤d≤40 - Quenching and Tempering d=30 - Annealing and Tempering and Normalizing Supply condition - Quenching and Tempering 16≤d≤40 8≤t≤20 - Quenching and tempering Test specimen 30 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/azhlNWIxMTcwNTA_ "Source: www.caishuku.com") ## Similar grades — and why Selection rule, stated so you can disagree with it: same number class 1.8, a shared category, and a published range for Cr / Al 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. [34CrAlNi7-10 1.8550 Cr 1,50-1,80 · Al 0,80-1,20 - ΔCr 0.00 - ΔAl 0.00 - 5 designations](/materials/din-en/34cralni7-10 "34CrAlNi7-10")[34CrAl6 1.8504 Cr 1,20-1,50 · Al 0,80-1,10 - ΔCr 0.30 - ΔAl 0.05 - 2 designations](/materials/din-en/34cral6 "34CrAl6") ## 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=3347e740-98e5-4e96-8b22-555c184cab53&designation=26320931-08a4-48af-be0a-a415038b67a0 "Inquiry")[**Datasheet as PDF** Print-ready A4 document **Generating …** **Download started** **Try again**](/materials/aisi-sae/cl-a.pdf "Datasheet as PDF")