Steel and Metal Grade Cross Reference

AISI 4140 is roughly 42CrMo4 (1.7225) in Europe, SCM440 in Japan and EN19 in old British terms: the same family of steel under four naming systems.

This chart lines up the common carbon, alloy, tool and stainless steels and aluminium alloys across the US (AISI / SAE / ASTM / Aluminum Association), European (EN 10027 name and Werkstoff number, EN AW for aluminium), Japanese (JIS) and old British (BS 970 and EN numbers) systems, with a short note on what each grade is used for and how it machines. Type any grade into the search box, for example 1.2379, SKD61, EN24 or 6082, or pick a family from the list. Treat every row as the nearest equivalent: the chemistry overlaps but is never identical, and a dash means there is no close, widely accepted match.

Grade cross reference chart

Sources: EN 10027-1 and -2, EN 10083, EN 10084, EN 10087, EN 10088, EN ISO 4957 (tool steels), EN 573-3 (aluminium), JIS G 4051 / G 4053 / G 4303 / G 4404, BS 970, BS 4659 and the Aluminum Association designations. Equivalents are approximate and for guidance only; chemistry, strength and heat-treatment limits differ between standards. For critical parts buy to the standard on the drawing and check the mill certificate.

How the naming systems work

AISI / SAE

Four digits: the first two give the alloy family (10xx plain carbon, 11xx resulphurised, 12xx resulphurised and rephosphorised, 41xx chromium-molybdenum, 43xx nickel-chromium-molybdenum, 86xx nickel-chromium-molybdenum), the last two give carbon in hundredths of a percent. So 4140 is a chrome-moly steel with about 0.40% carbon. Tool steels use a letter for the hardening type (O oil, A air, D high-carbon high-chromium, H hot work, S shock, M molybdenum high-speed, P mould) plus a number.

EN 10027 names and Werkstoff numbers

The European name describes the steel. C45 is unalloyed with 0.45% carbon. 42CrMo4 has 0.42% carbon and about 1% chromium (the 4 is the chromium percentage times 4) plus molybdenum. A leading X means high alloy, where alloy percentages are written directly: X5CrNi18-10 is 18% Cr, 10% Ni. The Werkstoff (material) number does the same job as a code: 1.0xxx and 1.1xxx unalloyed steels, 1.2xxx tool steels, 1.3xxx special steels such as bearing and high-speed steel, 1.4xxx stainless and heat-resisting steels, 1.5xxx to 1.8xxx alloy engineering steels.

JIS

S45C is carbon steel with 0.45% carbon. SCM is chrome-moly, SNCM nickel-chrome-moly, SCr chromium, SUJ bearing steel, SUP spring steel, SUM free-cutting, SUS stainless, and SKS, SKD and SKH are alloy tool, die and high-speed steels.

BS 970 and the old EN numbers

BS 970 codes such as 080M40 read as: first three digits for the type (000 to 199 carbon and carbon-manganese, where the digits give manganese times 100; 200 to 240 free-cutting; 300 to 499 stainless; 500 to 999 alloy), a letter (A analysis, H hardenability, M mechanical properties, S stainless) and two digits for carbon times 100. The older EN numbers (EN8, EN19, EN24, EN58E) come from the 1940s version of BS 970 and are still common UK shop names. They have nothing to do with modern European "EN" standards, so "EN8" and "EN 10083" are unrelated.

Aluminium

The four-digit alloy number is the same in the US and Europe; Europe adds the prefix EN AW- (wrought) and an optional chemical name, for example EN AW-6082 [AlSi1MgMn]. The first digit gives the main alloying element: 1xxx pure, 2xxx copper, 3xxx manganese, 5xxx magnesium, 6xxx magnesium and silicon, 7xxx zinc. JIS adds an A in front (A6061).

Aluminium tempers explained

The letters after the alloy number say how the metal was processed, which matters as much as the alloy. 6061-O and 6061-T6 are the same alloy with very different strength and machinability.

Temper designations per ANSI H35.1 and EN 515.

Shop tips

• Read the whole callout. "4140" alone does not say annealed, normalised or pre-hardened. "4140 HT", "EN19T" or "42CrMo4+QT" tells you the condition and therefore the cutting speed.
• Ask for a certificate. An EN 10204 3.1 mill certificate gives the actual chemistry and properties, which is the only way to know a substitute really meets the drawing.
• Check hardness on arrival. A quick file or hardness test catches mixed-up bar. Convert readings with the Hardness Converter.
• Pick the free-machining grade when you can. 12L14 instead of 1018, 303 instead of 304 and 416 instead of 410 can double tool life, as long as the part does not need welding or the best corrosion resistance.
• Stainless work-hardens. On 304 and 316 keep a steady feed and never let a tool dwell or rub; a glazed surface is much harder to cut on the next pass.
• Machining plate? Choose T651 aluminium and stress-relieved steel for flat, stable parts.

Related calculators and charts

• Speeds & Feeds – cutting speed and feed by material
• Hardness Converter – Rockwell, Brinell, Vickers and tensile strength
• Weight & Volume Calculator – stock weight for steel, stainless and aluminium
• Raw Material Sizer – stock size to order for a finished part
• Thermal Expansion – size change with temperature for common metals
• Ductile vs Brittle Materials – chip control and built-up edge in gummy materials
• Sheet Metal Gauge Chart – gauge to thickness for steel, stainless and aluminium sheet
• Tap & Drill Size Reference – tap drill sizes for inch and metric threads

Frequently asked questions