EN 10025-3 Standard Guide

Hot Rolled Products of Structural Steels Part 3: Technical Delivery Conditions for Normalized/Normalized Rolled Weldable Fine Grain Structural Steels

1. SCOPE AND APPLICATION

1.1 Product Forms Covered

This standard covers both FLAT and LONG products of hot rolled weldable fine grain structural steels in the normalized or normalized rolled delivery condition.

Flat Products:

Hot rolled plates (3mm and above)
Sheet and strip
Wide flats

Long Products:

I and H sections (beams)
Channels
Angles
T sections
Bars (round, square, rectangular, hexagonal)
Rod

1.2 Thickness Range

Maximum thickness: 250mm for all products

1.3 Intended Use

These fine grain steels are especially intended for use in HEAVILY LOADED PARTS of welded structures for service at ambient and low temperatures, such as:

Bridges
Flood gates
Storage tanks
Water supply tanks
Pressure vessels
Heavy construction machinery

2. CLASSIFICATION AND DESIGNATION

2.1 Main Quality Classes

S275: Non-alloy quality steel (according to EN 10020)

S355: Alloy quality steel (according to EN 10020)

S420 and S460: Alloy special steels (according to EN 10020)

2.2 Steel Grades

This standard specifies FOUR steel grades: S275, S355, S420, and S460

Steel Grade	Steel Number	Description
S275N	1.0490	Normalized fine grain steel
S275NL	1.0491	Normalized fine grain, enhanced low temperature
S355N	1.0545	Normalized fine grain steel
S355NL	1.0546	Normalized fine grain, enhanced low temperature
S420N	1.8902	High strength normalized fine grain
S420NL	1.8912	High strength, enhanced low temperature
S460N	1.8901	Highest strength normalized fine grain
S460NL	1.8903	Highest strength, enhanced low temperature

2.3 Quality Designations

All grades are available in TWO quality designations based on impact test temperature:

Quality	Impact Test Temp	Minimum Energy
N	-20°C	40J average (longitudinal)
NL	-50°C	27J average (longitudinal)

2.4 Designation System

The designation consists of: S + Minimum Yield Strength (MPa) + Delivery Condition (N) + Low Temperature Designation (L if applicable)

Example: S355NL

S = Structural steel
355 = Minimum yield strength 355 MPa (for thickness ≤16mm)
N = Normalized or normalized rolled delivery condition
L = Enhanced low temperature impact properties (-50°C)

3. MANUFACTURING PROCESS

3.1 Steel Making Process

Any steel making process except open hearth (Siemens-Martin) may be used at the manufacturer’s discretion.

See Option 1, Clause 13 for details of manufacturing process.

3.2 Deoxidation and Fine Grain Structure

CRITICAL REQUIREMENTS:

Fully killed steel – complete deoxidation required
Fine grain structure – equivalent index of ferritic grain size ≥ 6 (according to EN ISO 643)
Nitrogen binding elements – sufficient to bind available nitrogen (e.g., minimum 0.020% total aluminium)

Usual guideline: minimum aluminium to nitrogen ratio of 2:1 when no other nitrogen binding elements are present. Other nitrogen binding elements and their content shall be reported in the inspection document.

3.3 Delivery Conditions

Standard delivery condition: Normalized (N) or Normalized Rolled (NR)

Normalized: Heat treatment consisting of austenitizing followed by air cooling

Normalized Rolled: Rolling process where final deformation is carried out in a specific temperature range leading to a material condition equivalent to normalized, so that specified mechanical properties are retained even after normalizing

For S420 and S460 grades: Delayed cooling or additional tempering may be carried out after normalizing/normalized rolling. This shall be noted in the inspection document if performed.

4. CHEMICAL COMPOSITION

4.1 Heat Analysis

Chemical composition determined by heat analysis shall comply with Table 1 of the standard.

For elements not defined in Table 1, limit values of Table 1 of EN 10020:2000 apply as maximum values.

Key Chemical Composition Limits (Heat Analysis):

Grade	C max %	Si max %	Mn %	P max %	S max %
S275N/NL	0.18/0.16	0.40	0.50-1.50	0.030	0.025
S355N/NL	0.20/0.18	0.50	0.90-1.65	0.030	0.025
S420N/NL	0.20	0.60	1.00-1.70	0.030	0.025
S460N/NL	0.20	0.60	1.00-1.70	0.030	0.025

Note: For long products, P and S content can be 0.005% higher.

4.2 Product Analysis

Product analysis shall be carried out when specified at the time of order (Option 2). The limits for product analysis are given in Table 2 of the standard with appropriate deviations from heat analysis limits.

4.3 Carbon Equivalent Value (CEV)

The maximum CEV values based on heat analysis are given in Table 3 and calculated using the IIW (International Institute of Welding) formula:

CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

Maximum CEV Values (Heat Analysis):

Grade	≤63mm	>63-100mm	>100-250mm
S275N/NL	0.40	0.40	0.42
S355N/NL	0.43	0.45	0.45
S420N/NL	0.48	0.50	0.52
S460N/NL	0.53	0.54	0.55

4.4 Hot-Dip Zinc Coating Considerations

When products are supplied with controlled Si content for hot-dip zinc coating (Option 5), the maximum CEV values shall be increased:

For Si ≤ 0.04%, increase CEV by 0.02
For Si ≤ 0.25%, increase CEV by 0.01

5. MECHANICAL PROPERTIES

5.1 General Requirements

Under the inspection and testing conditions specified, and in the delivery condition, mechanical properties shall comply with Tables 4 to 6 of the standard.

IMPORTANT: Properties shall comply both in the delivery condition AND after normalizing heat treatment after delivery (including delayed cooling or tempering if needed for S420 and S460).

Heat Treatment Warning:

Stress relief at more than 580°C or for over 1 hour can lead to deterioration of mechanical properties. For flat products, maximum stress relief temperature should be 560°C.

If stress relief at higher temperatures or longer times is intended, minimum mechanical property values after such treatment should be agreed upon at time of order.

5.2 Yield Strength and Tensile Strength

Minimum yield strength (ReH) and tensile strength range (Rm) values are specified for different thickness ranges (see Table 4).

Mechanical Properties Summary (Thickness ≤16mm):

Grade	ReH min MPa	Rm MPa	A min %	Impact J
S275N	275	370-510	24	40 @ -20°C
S275NL	275	370-510	24	27 @ -50°C
S355N	355	470-630	22	40 @ -20°C
S355NL	355	470-630	22	27 @ -50°C
S420N	420	520-680	19	40 @ -20°C
S420NL	420	520-680	19	27 @ -50°C
S460N	460	540-720	17	40 @ -20°C
S460NL	460	540-720	17	27 @ -50°C

Note: Yield strength decreases with increasing thickness. Full thickness-dependent values are specified in Table 4 of the standard.

5.3 Impact Properties

Impact testing is mandatory for all grades and qualities (except for products <6mm thick or <16mm diameter).

Standard test direction: Longitudinal V-notch test pieces

Acceptance criteria:

Average of 3 tests ≥ specified minimum value
One individual value may be below minimum but not less than 70% of minimum
If criteria not met, 3 additional tests required with average of 6 tests ≥ minimum

Optional:

Impact test at other temperatures (Option 24)
Transverse test pieces instead of longitudinal (Option 30) – minimum values: 20J at -20°C (N) or 16J at -50°C (NL)
Impact test on each plate or coil (Options 13 and 14)

5.4 Through-Thickness Properties

If agreed upon at time of order, flat and long products shall comply with improved deformation properties perpendicular to the surface according to EN 10164 (Option 4):

Z15: 15% minimum reduction of area
Z25: 25% minimum reduction of area
Z35: 35% minimum reduction of area

6. TECHNOLOGICAL PROPERTIES

6.1 Weldability

All steels specified in this standard shall be suitable for welding. General requirements for arc welding are given in EN 1011-2.

Cold Cracking Warning:

With increasing product thickness and strength level, cold cracking can occur. Cold cracking is caused by the combination of:

Diffusible hydrogen in weld metal
Brittle structure in heat affected zone
Significant tensile stress concentrations

6.2 Formability

6.2.1 Hot Forming

Products shall comply with the requirements of Tables 4-6 if hot forming is carried out after delivery. Hot forming must be followed by normalizing heat treatment to restore specified properties.

IMPORTANT: CEN/TR 10347 provides guidance for forming of structural steels.

6.2.2 Cold Formability

General Warning: Cold forming leads to reduction in ductility. Risk of brittle fracture in connection with hot-dip zinc coating.

Flangeability (Option 11):

For plate, sheet, strip, and wide flats with nominal thickness ≤16mm, suitable for flanging without cracking with minimum bend radii:

S275 and S355: 2× thickness (transverse), 2.5× thickness (longitudinal)
S420 and S460: 4× thickness (transverse), 5× thickness (longitudinal)

Roll Forming (Option 12):

Plate, sheet, and strip with nominal thickness ≤8mm shall be suitable for cold rolling production of sections with same minimum bend radii as flangeability.

6.3 Hot-Dip Zinc Coating (Option 5)

EN ISO 14713-2 provides guidance on hot-dip galvanizing. Option 5 allows ordering steels with controlled chemical composition for hot-dip zinc coating:

Category A: Si ≤ 0.03% AND Si + 2.5P ≤ 0.09%
Category B: 0.14% ≤ Si ≤ 0.25%
Category D: 0.25% < Si ≤ 0.35%

Warning: Steels above S460 may be sensitive to cracking during galvanizing.

6.4 Machinability

Standard grades have normal machinability for structural steels. For improved machinability, higher sulfur content may be agreed upon at time of order (Option 27).

7. TESTING AND INSPECTION

7.1 Types of Inspection

Products are delivered with SPECIFIC INSPECTION which includes:

Heat analysis (mandatory)
Tensile test (mandatory)
Impact test (mandatory, except for products <6mm thick or <16mm diameter)

7.2 Inspection Documents (EN 10204)

The type of inspection document must be specified at time of order:

Type	Name	Description
2.2	Test report	Issued by manufacturer
3.1	Inspection certificate	Validated by manufacturer’s inspector
3.2	Inspection certificate	Validated by manufacturer AND independent body

7.3 Frequency of Testing

7.3.1 Chemical Analysis

Heat analysis: Once per cast

Product analysis: As specified at time of order (Option 2)

7.3.2 Mechanical Tests

Test Unit Definition:

60 tonnes or part thereof (standard)
80 tonnes or part thereof for heavy sections (>200 kg/m) OR casts >200 tonnes

One tensile test and one set of six impact test pieces shall be taken from one sample product of each test unit.

7.4 Test Methods

7.4.1 Chemical Analysis

Test methods: EN 10315, EN ISO 15350, or CR 10320

7.4.2 Tensile Test

According to EN ISO 6892-1. Manufacturer may choose method A or B.

Upper yield strength (ReH) shall be determined. If no yield phenomenon, determine 0.2% proof strength (Rp0.2).

7.4.3 Impact Test

According to EN ISO 148-1 using V-notch specimens with 2mm striker.

7.4.4 Ultrasonic Testing (Optional)

If specified at time of order (Options 6, 7, 8):

Flat products (≥6mm): EN 10160
H and IPE beams: EN 10306
Bars: EN 10308

8. MARKING, LABELING, AND PACKAGING

8.1 Required Marking

Products shall be legibly marked using methods such as painting, stamping, laser marking, barcoding, durable adhesive labels, or attached tags.

8.2 Marking Content

Mandatory information:

Grade and quality (e.g., S355NL)
Identification number (cast and sample identification)
Manufacturer’s name or trademark

The type of marking may be specified at time of order (Option 10).

Note: For hot-dip galvanizing, marking methods and materials should be agreed to avoid interference with preparation.

8.3 Marking Location

Marking shall be at a position close to one end of each product or on the end cut face, at manufacturer’s discretion.

For products supplied in securely tied bundles, marking may be on a label attached to the bundle or on the top product.

If specified at time of order, either no die stamping or only die stamping at positions indicated by purchaser (Option 31).

9. SURFACE PROPERTIES

9.1 Plates and Wide Flats

EN 10163-1 and EN 10163-2 apply for permissible surface discontinuities and repair of surface defects by grinding and/or welding.

Default: Class A, subclass 1 of EN 10163-2

Class B regarding grinding or subclasses 2 or 3 regarding repair by welding can be agreed upon (Option 15).

9.2 Sections

EN 10163-1 and EN 10163-3 apply for permissible surface discontinuities and repair of surface defects by grinding and/or welding.

Default: Class C, subclass 1 of EN 10163-3

Class D regarding grinding or subclasses 2 or 3 regarding repair by welding can be agreed upon (Option 16).

9.3 Bars and Rods

EN ISO 9443 applies for permissible surface discontinuities and repair of surface defects by grinding and/or welding.

Default: Class A of EN ISO 9443

Other classes can be agreed upon (Option 17).

9.4 Strip

The surface condition should not impair application appropriate to the steel grade if adequate processing of the strip is applied.

10. DIMENSIONS AND TOLERANCES

10.1 Applicable Standards

Dimensions, tolerances on dimensions and shape shall be in accordance with requirements given in the order by reference to the following standards:

Product Type	Standard
Hot rolled plates	EN 10029 (Class A default, Option 18 for other)
Plates cut from strip	EN 10051 (Option 34 for EN 10029)
Strip	EN 10051
I/H sections	EN 10034, EN 10365
Channels	EN 10279, EN 10365
Angles	EN 10056-1, EN 10056-2
Flat bars, wide flats	EN 10058
Square bars	EN 10059
Round bars	EN 10060
Hexagon bars	EN 10061
Rod	EN 10017

10.2 Nominal Mass

The nominal mass shall be determined from nominal dimensions using a volumetric mass of 7850 kg/m³.

11. AVAILABLE OPTIONS (CLAUSE 13)

A total of 19 options are available for this standard. Key options include:

Manufacturing and Chemical Composition:

Option 1: Details of steel making process
Option 2: Product analysis
Option 5: Chemical composition for hot-dip zinc coating
Option 32: Maximum S content 0.010% for special applications (e.g., railways)

Mechanical Properties:

Option 4: Through-thickness properties (Z15/Z25/Z35)
Option 13: Impact test on each plate or coil
Option 14: Impact and tensile test on each plate or coil
Option 24: Agreement on other impact test temperature
Option 30: Impact properties verified on transverse test pieces

Formability:

Option 11: Flangeability without cracking (≤16mm)
Option 12: Roll forming of flat products (≤8mm)

Testing:

Option 6: Ultrasonic testing for flat products
Option 7: Ultrasonic testing for H beams and IPE beams
Option 8: Ultrasonic testing for bars

Surface and Dimensional:

Option 15: Other surface class for plates and wide flats
Option 16: Other surface class for sections
Option 17: Other surface class for bars and rods
Option 18: Other thickness tolerance for plates than Class A
Option 34: For plates cut from strip, thickness tolerances according to EN 10029

Marking and Documentation:

Option 10: Special type of marking
Option 31: Die stamping not allowed or at special position
Option 33: No CE marking (for products not covered by CPR)

12. QUICK REFERENCE SUMMARY

12.1 Most Popular Grades

Grade	Typical Applications
S275NL	General-purpose fine grain steel for heavily loaded structures at low temperatures. Bridges, storage tanks, pressure vessels.
S355N	Most widely used fine grain structural steel. Bridges, offshore structures, cranes, heavy machinery.
S355NL	Enhanced low temperature toughness for extreme conditions. Arctic applications, LNG tanks, cryogenic vessels.
S460NL	High strength for weight-critical heavily loaded structures. Long-span bridges, offshore platforms, mobile cranes.

12.2 Key Points to Remember

All grades are normalized or normalized rolled – this delivery condition is essential for achieving fine grain structure
Fine grain structure required – grain size index ≥ 6 according to EN ISO 643
Fully killed steel with nitrogen binding elements – minimum 0.020% total aluminium or equivalent
NL quality provides -50°C impact resistance – critical for Arctic or cryogenic applications
Hot forming requires normalizing after forming – to restore specified properties
Cold forming reduces ductility – consider brittle fracture risk with hot-dip galvanizing
Stress relief temperature limits – maximum 580°C for >1 hour (560°C for flat products)
CE marking typically required – unless Option 33 is specified
Impact testing mandatory – except for products <6mm thick or <16mm diameter
Can be normalized after delivery – properties shall comply both before and after normalizing
Weldability excellent – but beware cold cracking with increasing thickness and strength
Part 3 is stand-alone – includes complete technical delivery conditions without Part 1 (for non-CE applications)