Steel Grade Equivalency Guide: ASTM vs EN vs JIS Mapping for Coated Coil

Steel Grade Equivalency Page

ASTM ↔ EN ↔ JIS Mapping for Coated Coil

With Critical Engineering Disclaimers

Global roll forming businesses constantly deal with mixed specifications:

• ASTM (USA & export markets)

• EN (Europe / UK / Middle East projects)

• JIS (Japan & much of Asia)

On paper, grades may appear “equivalent.”

In reality:

• Chemical limits differ

• Mechanical tolerances differ

• Testing methods differ

• Coating mass units differ

• Surface condition requirements differ

• Certification frameworks differ

This page provides a functional engineering equivalency map — not a legal substitution chart.

⚠️ CRITICAL DISCLAIMER

This page provides approximate functional equivalency for roll forming applications only.

It does NOT:

• Authorize cross-certification

• Replace project specifications

• Guarantee regulatory compliance

• Override structural engineer approval

Always verify:

• Project specification

• Local code requirement

• Mill Test Certificate

• Governing contract language

Never substitute grades without written approval.

1️⃣ Structural Grade Mapping (Galvanized / Metallic Coated)

Yield Strength-Based Comparison

Yield (MPa)	ASTM A653	EN 10346	JIS G3302
~230 MPa	Grade 33	S220GD / DX51D	SGCC
~275 MPa	Grade 40	S280GD	—
~345 MPa	Grade 50	S350GD	SGCH (verify)
~550 MPa	Grade 80	S550GD	High Tensile variants

Important:

JIS grades do not embed yield strength as clearly as EN SxxxGD.

Mill certification required for confirmation.

2️⃣ Galvanized Coating Equivalency (Zinc Coating)

Coating mass comparison (total both sides):

ASTM	EN	JIS	Approx. g/m²
G40	Z100	Z12	~120
G60	Z180	Z18	~180
G90	Z275	Z27	~275

⚠️ Note:

Tolerance bands differ between standards.

G90 ≠ automatically identical to Z275 without reviewing tolerance tables.

3️⃣ Aluminum-Zinc (Galvalume) Mapping

ASTM A792	EN 10346	JIS Equivalent
AZ50	AZ150	Equivalent via coating mass
AZ55	AZ150	Common roofing spec
AZ60	AZ180	Higher corrosion

EN and ASTM use different naming logic:

ASTM → ounces/ft²
EN → g/m²

Always convert coating mass carefully.

4️⃣ Forming Grades (Commercial & Drawing)

Function	ASTM	EN	JIS
Commercial	CS Type B	DX51D	SGCC
Drawing	FS	DX52D	SGCD1
Deep Draw	DDS	DX53D	SGCD2
Extra Deep	EDDS	DX54D	SGCD3

⚠️ Important:

Drawing grades are not structural grades.

Do not substitute DX51D for S350GD in structural applications.

5️⃣ High Tensile Roofing Mapping

High tensile roofing steel commonly used in:

• Australia

• Middle East

• Latin America

• India

Mapping:

Yield	ASTM	EN	JIS
550 MPa	Grade 80	S550GD	Supplier-defined HT

JIS may not explicitly state 550 MPa without detailed certification.

Always verify mechanical test results.

6️⃣ Thickness Terminology Differences

Region	Common Term
USA	Nominal thickness
EU/UK	Thickness
Australia	BMT (Base Metal Thickness)
India	BMT or TCT (varies)
Latin America	Often unclear

Thickness misinterpretation causes structural risk.

Always define:

• Base metal thickness

• Coated thickness

• Tolerance standard

7️⃣ Coating Performance Differences

Even when coating mass appears equivalent:

• Zinc chemistry may differ

• Al-Zn silicon content varies

• Spangle control differs

• Surface finish differs

Corrosion performance depends on:

• Environment

• Surface preparation

• Cut-edge exposure

• Paint system

Coating mass equivalency ≠ corrosion equivalency in all climates.

8️⃣ Testing & Certification Differences

ASTM:

• US-based test methods

• oz/ft² coating units

EN:

• CE marking

• MPa-based yield designation

• g/m² coating mass

JIS:

• g/m² coating

• Strength verification via certificate

• Different bend test methods

Never assume cross-acceptance without reviewing contract language.

9️⃣ Roll Forming Engineering Implications

Even if yield strength matches:

• Elongation may differ

• Work hardening rate may differ

• Edge quality may differ

• Coating ductility may differ

This affects:

• Springback

• Pass design

• Punch performance

• Crack sensitivity

Machine setup should be validated after grade substitution.

🔟 When Substitution May Be Acceptable

Functional equivalency may be acceptable when:

• Yield strength verified

• Coating mass verified

• Thickness tolerance acceptable

• Environmental exposure similar

• Engineer approves

It is not acceptable when:

• Regulatory marking required (CE / UKCA)

• Government project specification fixed

• Warranty tied to named standard

1️⃣1️⃣ Buyer Strategy (30%)

Best Practice When Converting Standards

1. Match yield strength first

2. Match coating mass second

3. Confirm coating chemistry

4. Confirm thickness tolerance

5. Request full mill test certificate

6. Confirm surface finish

7. Get written engineer approval

Export Strategy

When exporting machines or profiles:

• Quote original specified standard

• Offer “equivalent grade” only with documentation

• Provide comparison table

• Highlight differences in writing

6 Frequently Asked Questions

1. Is S350GD the same as ASTM Grade 50?

Approximately in yield strength (345 MPa), but certification systems differ.

2. Is G90 equal to Z275?

They are close in coating mass, but tolerance and test methods differ.

3. Can SGCC replace DX51D?

Functionally similar for commercial forming, but certification differs.

4. Is Grade 80 equal to S550GD?

Yield strength is similar, but verification is required.

5. Can I substitute ASTM for EN on a CE-marked project?

Not without engineer and regulatory approval.

6. Why do equivalent grades still form differently?

Because elongation, chemistry, and processing methods vary between mills.

Final Engineering Summary

Grade equivalency across ASTM, EN, and JIS is based primarily on:

• Yield strength

• Coating mass

• Functional forming capability

However:

They are not legally interchangeable.

Differences in:

• Certification

• Testing

• Chemistry

• Tolerance

• Coating microstructure

Can affect structural compliance and corrosion performance.

For roll forming manufacturers operating globally, grade mapping should be treated as an engineering comparison tool — not a compliance shortcut.