AISI vs ASTM vs EN Steel Grades
AISI/SAE grade names identify familiar steel families. ASTM standards specify requirements for particular products or tests. EN uses steel names and numbers alongside product standards. A cross-reference can identify a candidate such as 4140 → 42CrMo4; it cannot establish that the supplied material meets the original order.
Start with the known grade, then compare the product form, condition, dimensions and acceptance requirements.
What do AISI, ASTM and EN actually identify?
These labels answer different questions. A grade describes the material identity; a product specification defines what must be supplied and tested. An order normally needs both.
| System | What it tells you | Example and limitation |
|---|---|---|
| AISI / SAE | Familiar carbon, alloy and stainless grade terminology; current SAE documents maintain many carbon and alloy designations. | SAE 4140 identifies an alloy grade. It does not state bar size, heat treatment or required strength. |
| ASTM | A standard designation. In steel purchasing, many specify a product; others cover tests or general requirements. | ASTM A322 covers alloy steel bars. Add the grade and order requirements. “ASTM 4140” omits the standard. |
| EN | European standards. EN 10027-1 covers steel names; EN 10027-2 covers steel numbers. | 42CrMo4 and 1.7225 identify a grade. Add the applicable product standard and delivery condition. |
| UNS | The Unified Numbering System correlates metal and alloy identities. | S30400 identifies Type 304. A UNS number does not specify form, condition or quality. |
Sources: SAE J403, ASTM steel standards, EN designation standards and ASTM E527.
SAE J403 explicitly notes that AISI no longer issues the grades listed in that document. “AISI 1045” remains familiar commercial language, but a new order should identify the governing specification. The four-digit carbon-steel naming convention does not explain stainless names such as 304 or tool-steel names such as D2.
Steel grade cross-reference charts
Use these rows to locate a comparison candidate. The ASTM column gives examples of product standards to investigate; it is not a complete order. Supplier variants, contract editions and product form still control acceptance.
On narrow screens, scroll each table sideways. A focused table can also be scrolled with the arrow keys.
Carbon, alloy and tool steels
| Known U.S. designation | EN comparison candidate | Example product route | Main point to verify |
|---|---|---|---|
| SAE 1018 | Select by chemistry and supply condition | A108 for cold-finished bar | Start with the supply condition and full chemistry limits. A chemistry label alone does not establish cold-drawn properties. |
| SAE 1020 | C22E / 1.1151 | A108 for cold-finished bar; A576 for hot-wrought special-quality carbon bar | Compare carbon and manganese limits and the ordered condition. The producer lists multiple international comparisons, not a universal identity. |
| SAE 1045 | C45 / 1.0503; C45E / 1.1191 | A108 or A576, as applicable | Specify the exact C45 variant; compare impurity limits, heat treatment, hardness and section size. |
| SAE 4130 | 25CrMo4 / 1.7218 | A322 bar; A519 mechanical tubing | A comparison candidate with differing composition limits. Define bar versus tube and any aerospace requirements. |
| SAE 4140 | 42CrMo4 / 1.7225 | A322 bar; A434/A434M quenched-and-tempered bar | Match the actual producer variant, chemistry, heat treatment and size-dependent properties. See the example below. |
| SAE 4340 | 34CrNiMo6 / 1.6582 | A322 or A434/A434M, depending on supply | A similar alloy family, with different chemistry windows. Compare nickel, chromium, carbon, cleanliness and heat-treatment response. |
| SAE 8620 | 20NiCrMo2-2 / 1.6523 | A322 bar; A519 mechanical tubing | Compare core hardenability and carburizing requirements, including case depth, grain-size controls and distortion limits. |
| SAE 52100 | 100Cr6 / 1.3505 | A295/A295M bearing steel | Bearing-quality cleanliness, carbide condition and final heat treatment matter; matching carbon/chromium is insufficient. |
| D2 tool steel | X153CrMoV12 / 1.2379 | A681 tool steel | Confirm supply hardness, carbide condition, heat-treatment route and any specified premium-quality requirements. |
| H13 tool steel | X40CrMoV5-1 / 1.2344 | A681 tool steel | Specify melt/remelt route and required toughness; the H13 label does not establish a premium die-steel quality. |
Candidate links open original producer references. ASTM route examples are drawn from the ASTM index.
Stainless steels
| Known U.S. designation | EN comparison candidate | Example product route | Main point to verify |
|---|---|---|---|
| 304 / S30400 | X5CrNi18-10 / 1.4301 | A240/A240M flat products; A276/A276M bar; A312/A312M pipe | Compare the actual product limits, finish, condition and corrosion requirements. |
| 304L / S30403 | X2CrNi18-9 / 1.4307 | A240/A240M, A276/A276M or A312/A312M | 1.4306 is another low-carbon 304-family comparison with different chemistry. Confirm the exact grade and dual-certification evidence. |
| 316 / S31600 | X5CrNiMo17-12-2 / 1.4401 | A240/A240M, A276/A276M or A312/A312M | Check molybdenum and nickel limits, product condition and the service environment. |
| 316L / S31603 | X2CrNiMo17-12-2 / 1.4404 | A240/A240M, A276/A276M or A312/A312M | Match low-carbon chemistry, solution treatment and any corrosion or welding requirements. |
| 321 / S32100 | X6CrNiTi18-10 / 1.4541 | A240/A240M, A276/A276M or A312/A312M | Check titanium stabilization, thermal exposure and ordered corrosion testing. |
| 410 / S41000 | X12Cr13 / 1.4006 | A240/A240M or A276/A276M, as applicable | A martensitic steel: identify annealed or hardened-and-tempered condition before comparing properties. |
| 420 family | 1.4021, 1.4028, 1.4031 or 1.4034 may appear in comparisons | Exact type/chemistry within the applicable flat-product or bar standard | One-to-many comparison. Specify carbon range and heat-treated properties rather than ordering an undefined “420 equivalent.” |
| 430 / S43000 | X6Cr17 / 1.4016 | A240/A240M or A276/A276M | Compare finish, formability and corrosion requirements for the intended product. |
| 630 / 17-4 PH / S17400 | X5CrNiCuNb16-4 / 1.4542 | A564/A564M bar; A693 flat products; A705/A705M forgings | Specify the solution/aging condition and properties at the actual section. Different H-conditions are not interchangeable. |
Names and numbers: BSSA and Outokumpu references. The separate 304 / 1.4301 guide covers the detailed stainless comparison.
Structural products
| ASTM product specification | EN comparison to investigate | EN product route | Main point to verify |
|---|---|---|---|
| ASTM A36/A36M | S235 or S275 families may enter a comparison | EN 10025-2 product route and exact subgrade | No automatic match. S235JR does not by its grade designation establish the A36 yield requirement; see the worked example. |
| ASTM A572/A572M Grade 50 | S355 family | Appropriate EN structural product standard | Compare thickness-dependent strength, chemistry and toughness. JR, J0 and J2 carry different impact-test temperatures. |
| ASTM A992/A992M shapes | S355 section grades | Relevant EN section grade and dimensional standards | Review shape-specific yield/tensile controls, section properties, weldability and design-code acceptance. |
| ASTM A588/A588M | An EN weathering grade such as S355J2W | EN 10025-5, exact grade and product | State the A588 grade; compare alloy chemistry, thickness, toughness and weathering exposure. “Weathering steel” alone is incomplete. |
| ASTM A500/A500M Grade C HSS | An S355 hollow-section grade | EN 10219 cold-formed or EN 10210 hot-finished route | HSS means hollow structural sections. Match manufacturing route, geometry, tolerances, corner behavior and governing design values. |
These are product-family comparisons, not grade identities. Review the structural producer reference and the applicable product standards. An ASTM requirement cannot be replaced merely by choosing a similar EN strength number.
Dual certification means the material satisfies both stated specifications and their relevant requirements. Two names printed on a quotation, or a row in this chart, do not demonstrate that result.
How to read an EN steel name
Some EN names describe use and mechanical properties; others describe composition. Keep the full name and delivery suffix when comparing a drawing with a supplier’s offer.
S355J2+N
S identifies structural steel. 355 refers to a minimum yield-strength level in MPa for the relevant thinner product range; thicker material may have a lower specified minimum.
J2 identifies a Charpy impact category of 27 J at −20°C, subject to the standard’s specimen and acceptance rules. +N denotes normalized or normalizing-rolled delivery where the product standard permits it.
42CrMo4+QT
42 represents approximately 0.42% nominal carbon in this naming convention. CrMo identifies chromium and molybdenum; the final number follows the alloy-content factors in EN naming rules.
+QT means quenched and tempered. It describes a delivery condition, not a single hardness or strength valid at every diameter.
X5CrNi18-10
X identifies a high-alloy steel. 5 relates to approximately 0.05% nominal carbon; 18-10 describes approximate chromium and nickel contents.
The paired steel number is 1.4301. The numbers in the name help identify the grade; use the actual specified chemistry limits for acceptance.
Naming framework: EN 10027. Product examples: SSAB S355J2+N, Ovako 42CrMo4 and BSSA stainless designations.
Why does a close cross-reference sometimes fail?
Overlapping chemistry does not mean identical specification limits. Properties also depend on heat treatment, cold work, size and the way the product was made. Two examples show why the extra information matters.
4140 and 42CrMo4: the producer’s variant and diameter matter
Ovako distinguishes variants within its 42CrMo4 family; specific variants carry explicit SAE 4140 compliance statements. Its 6082 quenched-and-tempered round-bar data also show how properties change with diameter:
| Bar diameter band shown by Ovako | Minimum yield strength | Tensile-strength range |
|---|---|---|
| 25 to 40 mm | 750 MPa | 1,000–1,200 MPa |
| 40 to 100 mm | 650 MPa | 900–1,100 MPa |
| 100 to 160 mm | 550 MPa | 800–950 MPa |
Source: Ovako 42CrMo4, variant 6082, +QT round bar. Producer-specific values; confirm exact diameter boundaries. These are not universal 4140 guarantees.
A 50 mm bar and a 120 mm bar fall in different property bands. See the 4140 properties and heat-treatment guide.
A36 and S235JR: similar use does not establish the same minimum
For a 10 mm thickness, SSAB’s published A36 plate range has a minimum yield strength of 36 ksi—about 248 MPa by unit conversion. Salzgitter’s S235JR data give 235 MPa for nominal thickness up to 16 mm. An S235JR grade claim therefore does not by itself establish the A36 yield requirement.
These are producer data for their stated product ranges, not a complete standards comparison. Product form, tensile strength, chemistry, dimensions, impact requirements and the design basis still need review. A higher-strength S275 candidate also needs that review; the larger number does not approve the substitution. SSAB A36 data; Salzgitter structural-steel data.
Choose the product standard before comparing properties
The same stainless identity can appear in plate, bar and pipe specifications. Those products can have different dimensional rules, test sampling and delivery conditions. Likewise, a chemistry-grade label such as 1018 does not establish the strength created by a particular cold-drawing process.
For 304 or 316L flat products, ASTM A240/A240M and applicable A480/A480M general requirements are a different route from an EN flat-product order. For general-purpose stainless flat products, EN 10088-2 is one relevant route; pressure applications may require another.
For bar or pipe, investigate the relevant product standard—for example A276/A276M for stainless bars and shapes or A312/A312M for austenitic stainless pipe. Do not carry a sheet standard onto a pipe order.
See the A240 versus A480 guide for flat-product details.
ASTM A29/A29M provides general requirements for hot-wrought carbon and alloy bars. It is not a shortcut for omitting the applicable product requirements, condition or properties. For a quenched-and-tempered alloy bar, an A434/A434M route adds requirements that a bare “4140” label does not communicate. ASTM product-standard index.
How to review a proposed steel substitute
Compare the original requirement with the proposed supply in a written matrix. Separate a requirement that is met from a deviation that still needs approval.
- Capture the complete requirement.Record the standard and edition, grade, suffixes, product form, dimensions, manufacturing route and delivery condition. Keep the drawing and supplementary purchase clauses with the review.
- Compare acceptance limits and test conditions.Check chemistry minima and maxima, heat versus product analysis rules, strength, hardness and toughness at the relevant size. Match specimen direction, test temperature and sampling frequency where specified.
- Review what happens during fabrication.Consider heat-treatment response, forming, machining, welding and surface processing. Matching a grade table does not demonstrate that an existing qualified process remains applicable.
- Resolve evidence and deviations.Obtain the supplier’s proposed specification and inspection plan. Identify missing results, changed limits or unverified conditions. The responsible design or customer authority must accept any departure before material is released for use.
- Order and receive the agreed material.Put the approved route and substitution rule on the order. On receipt, link markings to the certificate and verify the results required by that order.
An H hardenability designation, an L stainless grade, a J2 impact category, a +QT delivery condition and a 17-4 PH aging condition carry different information. They cannot be treated as optional formatting.
Turn an incomplete label into a useful inquiry
“AISI 4140 round bar” leaves the product standard and delivery condition open. The following is an illustrative inquiry after identifying 42CrMo4 as a candidate; it is not evidence that the alternate is approved.
Quote 20 round bars, 50 mm diameter × 3,000 mm, proposed as 42CrMo4 / 1.7225 in +QT condition. Identify the applicable product standard and edition, dimensional tolerances, surface condition, and mechanical requirements for the supplied diameter. Provide the proposed EN 10204 Type 3.1 inspection document and a comparison against the attached original specification. No substitution is accepted without written approval.
Before this becomes an order, resolve the proposed edition, tolerances, properties and any additional tests.
What should the material certificate prove?
The inspection document should connect the delivered material to its heat or lot and to the agreed requirements. Check the stated grade and product standard, reported chemistry, delivery condition, required mechanical results, test details and traceability markings.
EN 10204 Type 3.1 includes a statement of compliance with the order and results of specific inspection, validated by the manufacturer’s authorized inspection representative independent of production. Type 3.2 adds validation by the purchaser’s authorized representative or an inspector designated by official regulations. The contract and applicable rules determine which document is needed. Inspection-document references.
The certificate type is not the steel grade, and a 3.1 or 3.2 document does not itself approve an alternate material. Verify the actual document against the order and the material received. Any required independent inspection should be arranged before manufacture or shipment.
For a welding, cleaning or marking trial with Oceanplayer Laser, send the exact grade, product standard, delivery condition, thickness, surface state and required result. Include the material certificate and proposed joint or treatment area so the sample reflects the intended workpiece.
Discuss a material and laser-process trialSources and further reading
Producer references are linked beside their grade rows and examples. Use the contractually required editions of the full standards when setting acceptance criteria.
- SAE J403_202402: Chemical Compositions of SAE Carbon Steels. SAE grade terminology and heat/product analysis context.
- ASTM International: Steel Standards. Product and general-requirement standard titles used in the charts.
- ASTM E527-23: Unified Numbering System. Explains why a UNS identifier is not a product specification.
- BSI: EN 10027-1, steel names and EN 10027-2, numerical system.
- Euro Inox: Stainless Steel Tables of Technical Properties, hosted by BSSA. EN names, numbers and U.S. grade comparisons; use current product requirements for acceptance. Producer context: Outokumpu Core, Supra and Dura ranges.
- Structural products: ArcelorMittal’s structural grades and weathering-steel brochure; Mannesmann EN 10210-1 hollow sections; BSI EN 10219-1 cold-formed hollow sections.
- Inspection documents: BS EN 10204; BSSA’s certificate-type explanation; SSAB Hardox Guarantees, inspection-document section.