AISI vs ASTM vs EN Steel Grades
A practical cross-reference for buyers who need to compare American and European steel designations without turning a close candidate into an unapproved substitute.
Do not expect one AISI number, one ASTM designation and one EN number to be interchangeable labels.
"ASTM 4140" and "ASTM 304" are incomplete because ASTM designations identify documents, not a universal alloy list.
Use a chart to find candidates, then compare chemistry, form, size, condition, properties and test evidence.
Record the accepted standard, edition, grade, condition, certificate and substitution rule on the purchase order.
A steel designation is only one layer of the purchase specification
AISI, SAE, ASTM and EN are often placed in the same chart, but they are not four parallel grade systems. A legacy AISI or current SAE number such as 4140 points mainly to a chemistry family. An ASTM reference such as A322 Grade 4140 defines a route for a particular product, in this case hot-wrought alloy steel bar. An EN route may require the steel name or material number, the relevant product standard and a delivery condition such as +QT.
That distinction matters because two materials can have broadly comparable chemistry but arrive with different heat treatment, section-size property requirements, toughness evidence, tolerances, surface condition or inspection documentation. Those differences can change machining, forming, welding, fatigue life and regulatory acceptance.
Use a cross-reference to answer "what should I investigate next?" Never use it alone to answer "is this substitute approved?"
Material identity
SAE grade, EN steel name, material number or UNS identifier.
Product specification
Bar, sheet, plate, tube, pipe, forging or structural section route.
Delivery condition
As rolled, annealed, normalized, cold drawn, quenched and tempered or solution annealed.
Acceptance evidence
Dimensions, properties, tests, marking, traceability and inspection certificate.
Composition family
Useful for familiar carbon and alloy identities such as 1020, 1045, 4140 and 4340.
Does not finish the purchase specification.Product requirements
A document may define product form, chemistry, mechanical properties, heat treatment, tests and marking.
The designation is the document route.Name or material number
EN 10027 provides naming and numbering rules, while product standards complete delivery requirements.
Suffixes such as +N or +QT matter.Index and correlation
UNS is valuable for cross-referencing alloy identities, but it does not establish product form, condition or quality.
An identifier is not a specification.Steel Grade Cross-Reference Finder
Choose a familiar designation to see a common comparison candidate, a typical ASTM product route and the checks that still control approval.
Start with the known designation
Select the material written on the drawing, supplier quote or legacy bill of materials.
42CrMo4 / 1.7225
A common close European candidate for SAE 4140, but not an automatic one-for-one substitute.
Match A - common close comparison- Compare chemistry limits line by line, including residual limits where relevant.
- Match heat treatment and mechanical properties at the actual ruling section.
- Confirm hardenability, impact testing, certificate and customer approval requirements.
This tool organizes the first review. It does not certify equivalence, establish a welding procedure or replace the governing drawing, code or purchase specification.
Three labels, three different purchasing functions
AISI and SAE
Buyers still say "AISI 4140," but the current SAE system maintains many familiar carbon and alloy grade designations. Final digits in common four-digit grades broadly indicate nominal carbon in hundredths of a percent.
- Example: SAE 1045
- Example: SAE 4140H
- Do not drop an H hardenability suffix
ASTM
An ASTM designation identifies a standard. The same alloy identity can appear in different ASTM routes depending on whether the order is bar, plate, sheet, pipe or forging.
- A322: hot-wrought alloy steel bars
- A240: stainless plate, sheet and strip
- A182: forged or rolled alloy/stainless piping parts
EN
European steel names can be based on application and properties or on chemical composition. A material number gives a stable numerical identity, but the product standard and delivery condition still complete the order.
- S355J2+N
- 42CrMo4 / 1.7225
- X5CrNi18-10 / 1.4301
The alloy name alone does not tell a mill what to deliver
Sheet, plate, bar, tube and forging standards can apply different dimensional tolerances, heat treatments, testing frequencies, surface requirements and mechanical property rules. A useful cross-reference therefore starts with the physical product, not only the chemistry.
That is why "AISI 304 sheet" and "ASTM 304 sheet" should be rewritten into a complete form such as an applicable ASTM or EN product specification, type or material number, dimensions, finish, condition and inspection document.
Read the letters, numbers and suffixes before comparing the grade
An EN designation often carries information that a simple four-digit SAE grade does not. Preserve every suffix when requesting a quote or approving a substitution.
S355J2+N
S structural steel. 355 is the specified minimum yield strength for the relevant smallest thickness range. J2 identifies an impact-energy category at a stated low temperature. +N identifies a normalized or normalized-rolled delivery condition where applicable.
42CrMo4
The leading number relates to nominal carbon content; Cr and Mo identify significant alloying elements; the final factor reflects approximate alloy content under EN naming rules. Use the full product standard and condition, such as +QT, when properties matter.
X5CrNi18-10
1.4301
X indicates a high-alloy steel. 5 relates to nominal carbon. CrNi18-10 describes approximate principal alloy content. 1.4301 is the numerical steel number commonly cross-referenced to Type 304.
Common AISI, SAE, ASTM and EN comparison candidates
These rows are screening references. Match A means a widely used close comparison, not guaranteed interchangeability. Match B needs a closer clause-by-clause review. Match C is one-to-many or strongly product-dependent.
| Known designation | Common EN candidate | Typical ASTM product route | Match | Buyer checks before approval |
|---|---|---|---|---|
| SAE 1018 | No universal one-to-one match; C17E2C / 1.1147 may appear in limited cold-heading comparisons | A108 for cold-finished bar; route varies by product | B/C | Product form, cold work, surface quality, core properties and chemistry windows. |
| SAE 1020 | C22E / 1.1151 | A29/A29M or A108 depending on bar route | A/B | Carbon and manganese range, condition, size-dependent properties and weldability. |
| SAE 1045 | C45 / 1.0503 or C45E / 1.1191 | A29/A29M, A108 or another product-specific route | A | Cleanliness variant, heat treatment, hardness, decarburization and ruling section. |
| SAE 4130 | 25CrMo4 / 1.7218 | A322, A519 or an aerospace/product-specific route | B | Carbon range, normalized/QT condition, tubing versus bar requirements and toughness. |
| SAE 4140 | 42CrMo4 / 1.7225 | A322 Grade 4140 for hot-wrought bar; A434/A434M for QT bar routes | A | Chemistry limits, hardenability, QT condition, section-size properties and impact evidence. |
| SAE 4340 | 34CrNiMo6 / 1.6582 | A322 or A434/A434M depending on product and condition | B | Nickel/chromium/molybdenum limits, cleanliness, strength level and fracture-toughness needs. |
| SAE 8620 | 20NiCrMo2-2 / 1.6523 | A322, A29/A29M or case-hardening product route | A/B | Core hardenability, carburizing response, grain size and case-depth process validation. |
| SAE 52100 | 100Cr6 / 1.3505 | A295 for high-carbon anti-friction bearing steel | A | Cleanliness, carbide distribution, spheroidized condition and bearing-quality test route. |
| AISI D2 | X153CrMoV12 / 1.2379 | A681 tool steel route | A | Annealed condition, carbide structure, dimensional change and final heat-treatment recipe. |
| AISI H13 | X40CrMoV5-1 / 1.2344 | A681 tool steel route | A | Premium quality, electroslag remelting, toughness, heat checking and hardness range. |
| AISI/ASTM type and UNS | Common EN steel name / number | Typical ASTM routes | Match | Buyer checks before approval |
|---|---|---|---|---|
| 304 / S30400 | X5CrNi18-10 / 1.4301 | A240 plate/sheet, A276 bar, A312 pipe | A | Product standard, finish, condition, dimensional tolerances, corrosion service and test certificate. |
| 304L / S30403 | X2CrNi18-9 / 1.4307; 1.4306 is another 304L-family material | A240, A276, A312 | A/B | Low-carbon limit, nitrogen/nickel window, dual certification and weld/corrosion qualification. |
| 316 / S31600 | X5CrNiMo17-12-2 / 1.4401 | A240, A276, A312, A182 | A | Molybdenum range, product route, pitting environment and solution-annealed condition. |
| 316L / S31603 | X2CrNiMo17-12-2 / 1.4404 | A240, A276, A312, A182 | A | Carbon, molybdenum, ferrite/welding requirements, finish, PMI and corrosion test needs. |
| 321 / S32100 | X6CrNiTi18-10 / 1.4541 | A240, A276, A312 | A | Titanium stabilization, heat treatment, high-temperature service and intergranular corrosion tests. |
| 410 / S41000 | X12Cr13 / 1.4006 | A240, A276, A479 depending on product | A | Condition, hardness, tempering, toughness and welding procedure. |
| 420 family | May map to 1.4021, 1.4028, 1.4031 or 1.4034 depending on carbon and properties | A240/A276 type designation plus product route | C | Exact carbon range, hardness target, corrosion behavior and heat treatment. Never select by "420" alone. |
| 430 / S43000 | X6Cr17 / 1.4016 | A240 plate/sheet or A276 bar | A | Formability, surface finish, grain condition, weldability and corrosion appearance. |
| 630 / 17-4 PH / S17400 | X5CrNiCuNb16-4 / 1.4542 | A564/A564M bar, A693 plate/sheet, A705 forging | A | Solution treatment, H900-H1150 condition, section size, toughness and supplementary tests. |
| ASTM structural product | Common EN comparison candidate | Why buyers compare them | Match | Why approval is still required |
|---|---|---|---|---|
| ASTM A36/A36M | S235JR or S275JR are common candidates, depending on product and design basis | General structural carbon steel with overlapping strength/use cases | C | No single exact EN equivalent; chemistry, thickness, yield, Charpy category, shape/plate route and code differ. |
| ASTM A572/A572M Grade 50 | S355JR, S355J0 or S355J2 family | Similar nominal high-strength structural category | B/C | Impact-temperature suffix, thickness-dependent yield, chemistry/CEV and product standard must match. |
| ASTM A992/A992M Grade 50 shapes | S355 structural section grades | Building column and beam strength comparison | B/C | A992 includes shape-specific controls; compare section standard, yield range, Y/T ratio, weldability and design code. |
| ASTM A588/A588M Grade 50 or A709 Grade 50W | S355J2W under EN 10025-5 may be a candidate | Atmospheric-corrosion-resistant structural steel | B | Weathering chemistry, patina environment, notch toughness, thickness and bridge/code requirements differ. |
| ASTM A500/A500M Grade C HSS | S355...H hollow sections under EN 10219 or EN 10210 | Structural hollow-section strength class | B/C | Cold-formed versus hot-finished route, corner properties, tolerances, toughness and design values differ. |
How to use the charts: first identify a candidate, then obtain the current standards and supplier documents. Tables cannot capture every edition, optional clause, dimension range, customer requirement or national adoption.
Close chemistry does not guarantee equal performance
A responsible supplier treats equivalence as a documented engineering conclusion, not a sales synonym.
Limits overlap without matching
Carbon, manganese, chromium, nickel, molybdenum, nitrogen, residuals and grain-refining elements can have different minimums, maximums or reporting rules.
Properties belong to a state
Tensile strength, yield, hardness and toughness depend on heat treatment, cold work, product thickness and ruling section.
Complete the Charpy requirement
Impact energy without test temperature, specimen orientation, thickness and acceptance frequency is incomplete.
Plate is not bar is not forging
Reduction ratio, grain flow, surface quality, straightness, tolerances and inspection routes change with the product.
Welding and heat treatment can diverge
Carbon equivalent, hardenability, temper response, hot cracking and sensitization risk may change even when a chart says "equivalent."
The code or customer may control
A design code, approved vendor list, drawing note or customer specification can prohibit substitutions that appear technically reasonable.
The same alloy identity can require a different standard for each form
Before comparing properties, define what the mill or distributor must physically supply.
Bar
Hot-rolled, forged, turned, peeled, ground and cold-finished bar routes can have different tolerances, decarburization, straightness and mechanical property requirements.
Write diameter, length, finish and condition.Sheet and plate
Specify thickness, width, length, finish, edge, flatness, surface condition and whether a plate, sheet or strip standard applies.
Do not treat a type number as the product standard.Tube and pipe
Seamless versus welded route, OD, wall, schedule, heat treatment, hydrostatic/NDT and end preparation can control suitability.
Separate pressure pipe from mechanical tubing.Forging
Forging specification, heat treatment, mechanical test location, grain flow, ultrasonic examination and machining allowance can be critical.
Grade identity does not define forging quality.Structural section
Shape, plate and hollow-section standards set distinct yield, toughness, dimensional and design-code conditions.
Confirm the applicable structural design system.Part drawing
The drawing can add hardness zones, case depth, weld procedure, coating, dimensional inspection, NDT and customer approval beyond the raw material standard.
The drawing remains part of acceptance.How to approve an international steel substitute
Use the same sequence for a new RFQ, legacy drawing conversion, supplier deviation or dual-source qualification.
Capture the exact designation
Record every grade, type, class, suffix, UNS number and standard edition shown by the source document.
Define product form
State bar, plate, sheet, tube, pipe, forging, casting or structural section and the manufacturing route.
Identify the governing standard
Obtain the complete applicable product specification rather than relying on a reseller chart.
Find candidate identities
Use SAE, EN names/material numbers and UNS correlation to build a shortlist, not an approval.
Compare chemistry
Build a limit-by-limit matrix, including residual, microalloying and hardenability controls where relevant.
Compare properties
Use the actual thickness or ruling section and the required delivery condition, not a typical brochure value.
Review processing
Check heat treatment, welding, forming, machining, coating and corrosion implications.
Align tests and documents
Map tensile, impact, hardness, PMI, NDT, corrosion and inspection-certificate requirements.
Confirm governance
Verify design code, customer specification, regulatory rules and approved-vendor restrictions.
Approve in writing
Record the exact accepted route on the PO, drawing deviation or engineering change before shipment.
What a cross-reference looks like in a real RFQ
The examples show why the candidate grade is only the start of the conversation.
"AISI 4140 round bar"
The request identifies a familiar alloy family but leaves the supplier to guess the product route, size-dependent properties and condition.
- Add diameter, length and surface finish.
- Select the applicable ASTM or EN product standard.
- State annealed, normalized, prehardened or +QT condition.
- Add hardness/strength, NDT and inspection-certificate requirements.
Supplier offers 42CrMo4+QT
This is a technically plausible candidate for many 4140 applications, but the offer must identify the EN product standard and prove properties at the supplied section.
- Confirm 42CrMo4 / 1.7225 and the governing EN standard.
- Compare chemistry and hardenability controls.
- Check +QT mechanical properties at the ruling section.
- Obtain the required EN 10204 certificate and written approval.
ASTM A36 plate offered as S235JR
S235JR may be a comparison candidate for some general structural uses, but A36 has no universal one-to-one EN equivalent.
- Compare thickness-dependent yield and tensile ranges.
- Check product standard and dimensional tolerances.
- Resolve impact category: JR, J0 or J2 if service requires it.
- Confirm welding, design-code and customer acceptance.
Type 316L sheet offered as 1.4404
This is a strong common identity cross-reference, yet the flat-product route, finish and corrosion service remain part of approval.
- Specify the ASTM or EN sheet/plate standard.
- Compare carbon, molybdenum and any nitrogen limits.
- State finish, dimensions, flatness and solution-annealed condition.
- Add PMI, corrosion testing and certificate requirements where needed.
Build a clearer RFQ or purchase-order line
The generated sentence is a drafting aid. Replace example values with the approved specification and add project-specific clauses.
Describe the required material
Complete the material route
Also add tolerances, surface, straightness, marking, packaging, code clauses, supplementary tests and approved deviations where the application requires them.
A grade claim needs heat-specific evidence
Request the inspection document during inquiry and ordering, not after delivery. The material certificate should connect the delivered item to a heat or lot and report the results required by the governing specification and purchase order.
EN 10204 Type 3.1 is commonly requested for industrial steel purchases. Type 3.2 or additional third-party/customer verification may be required for critical or controlled work. A generic distributor certificate or catalogue page is not a replacement for heat-specific conformance evidence.
Ten questions before accepting an "equivalent" steel
Is the original identity complete?
Capture standard, grade/type, UNS/material number, suffixes and edition instead of a shortened commercial label.
Is the product route the same?
Confirm sheet, plate, bar, tube, pipe, forging, casting or structural section and its manufacturing process.
Do dimensions and tolerances align?
Review size range, thickness tolerance, straightness, flatness, edge, finish and machining allowance.
Does chemistry pass limit by limit?
Use official specification minima and maxima, not typical values copied from a supplier webpage.
Is the delivery condition equivalent?
Match annealed, normalized, cold worked, solution annealed, +QT or other required condition.
Do properties apply to this size?
Check tensile, yield, elongation, hardness and toughness for the actual section and test orientation.
Will processing remain qualified?
Review welding, forming, machining, heat treatment, coating and corrosion consequences.
Are tests and frequencies equivalent?
Align specimen location, lot definition, test frequency, NDT method and supplementary requirements.
Is the documentation acceptable?
State the required inspection certificate, marking, heat traceability and independent verification.
Who has authority to approve?
Obtain written engineering, code, customer or regulatory acceptance before procurement and processing.
Short labels that create expensive ambiguity
ASTM is not a universal alloy prefix. Write the applicable ASTM product specification and Type 304.
Select the product route, such as an applicable bar specification, plus grade, condition and properties.
A36 has no single universal EN equivalent. Product, thickness, properties and impact category control the comparison.
It is a common close candidate. Compare current chemistry, condition and ruling-section properties before approval.
These are frequently compared, but chemistry, cleanliness, strength and toughness requirements can differ.
Type 420 covers a family. Several EN grades may be candidates depending on carbon, hardness and intended use.
H, L, J2, +N, +QT, H900 and other suffixes can change hardenability, toughness or delivery condition.
Typical values are not acceptance limits. Compare the official minimum and maximum requirements.
A thin test coupon or catalogue value may not represent a large-diameter bar or thick forging.
Do not mix inch-pound and SI requirements unless the standard explicitly permits the selected designation route.
A dual-stamped certificate must independently demonstrate compliance with every claimed specification.
Inspection documents and supplementary tests must be ordered before production or shipment.
Record the exact approved material, route and deviations in controlled purchasing or engineering documents.
A substitution can affect weld qualification, heat treatment, machining, coating and service performance.
Related steel and fabrication guides
AISI, ASTM and EN steel grade questions
Short answers for sourcing teams reviewing international quotes.
Is ASTM the same as AISI?
No. AISI historically maintained many familiar steel grade designations, while ASTM publishes product specifications, test methods and related standards. A material identity such as 4140 may appear within an ASTM product specification, but "ASTM 4140" alone does not identify the complete purchase route.
Does AISI still issue carbon and alloy steel grade designations?
SAE J403 states that AISI is no longer involved in issuing the listed grade designations and that they are SAE grades. Industry language still commonly uses "AISI 4140," so buyers should recognize the term while writing current, complete procurement requirements.
Is 42CrMo4 exactly equivalent to SAE 4140?
No. 42CrMo4 / 1.7225 is a common close European comparison for SAE 4140, but current chemistry limits, product standards, heat treatment, hardenability, section-size properties, toughness and documentation must be compared before substitution.
What is the EN equivalent of ASTM A36?
There is no single exact EN equivalent. S235JR and S275JR are common comparison candidates depending on product, thickness, strength and design basis. The EN product standard, impact category, chemistry, tolerances and applicable design code must be reviewed.
Is ASTM A572 Grade 50 equivalent to S355?
They occupy a similar structural strength category and are often compared, but they are not automatically interchangeable. Check thickness-dependent yield, tensile range, chemistry or carbon-equivalent rules, impact-temperature suffix, product standard, dimensional requirements and design-code approval.
Is Type 304 the same as EN 1.4301?
Type 304 / UNS S30400 and X5CrNi18-10 / 1.4301 form a strong, common cross-reference. The order still needs an applicable product standard, dimensions, finish, condition, testing and certificate requirements.
Is Type 316L the same as EN 1.4404?
Type 316L / UNS S31603 and X2CrNiMo17-12-2 / 1.4404 are commonly paired. Approval still depends on the exact chemistry limits, product route, finish, solution-annealed condition, corrosion service, welding requirements and inspection evidence.
Is matching chemical composition enough to approve a substitute?
No. Mechanical properties, toughness, product form, manufacturing route, condition, dimensions, tests, certification, processing behavior and governing code or customer requirements also control suitability.
Is a UNS number a complete material specification?
No. ASTM E527 explains that a UNS number supports identification and cross-referencing but does not itself establish form, condition, quality or other product requirements. Pair the UNS identity with the governing product specification.
What should a steel purchase order include?
At minimum: product and manufacturing route, dimensions and quantity, standard and edition, grade/type/material number, delivery condition, required properties, tolerances and surface, tests/NDT, inspection certificate, marking/traceability and a written substitution rule.
Authoritative references and further reading
- SAE J403_202402, Chemical Compositions of SAE Carbon Steels - current SAE grade context and reporting requirements.
- ASTM A1040, Standard Guide for Specifying Harmonized Standard Grade Compositions for Wrought Carbon, Low-Alloy, and Alloy Steels - history and harmonized grade context.
- ASTM E527-23, Unified Numbering System (UNS) - explains correlation and why a UNS number is not itself a specification.
- BS EN 10027-1:2016, Designation systems for steels - Steel names - rules for property- and chemistry-based steel names.
- BS EN 10204, Metallic products - Types of inspection documents - inspection certificate framework.
- Ovako 42CrMo4 / 1.7225 steel grade data - producer reference for one commonly compared European alloy route.
- SAE/ASTM Metals and Alloys in the Unified Numbering System - cross-reference resource for registered alloy identities.
Standards are revised. Use the editions required by the contract and obtain the full official documents before writing acceptance criteria.
Send the drawing. Get a clause-by-clause material review.
Share the current designation, product form, dimensions, delivery condition, target properties, service environment and required certificate. Oceanplayer can help connect the approved material route to cleaning, welding, marking or automation trials.