Impact Strength for Hot Rolled Steels

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Hot-rolled steel plates, sheets and coilsProcessing of materialImpact strength and through-thickness properties

We have compiled in this data sheet general information on the impact strength of our hot-rolled steel products and their through-thickness properties (properties perpendicular to the plate surface, Z properties) to provide help in selecting materials.

HR 5.3.01 02.2007�

Selection of material. Impact strength and through-thickness properties

• DefinitionsImpact strength refers to the ability of a material to sustain impact loads. A fracture caused by an impact may be either brittle or ductile. The impact strength of steels is measured with an impact test standardised in EN 10045-1:1990. A typical impact test procedure is Charpy V.

A material’s ductility, i.e. its deformation properties perpendicular to the plate surface, is measured in the through-thickness tensile test. The through-thickness tensile test gives the percentage reduction of area in the through-thickness direction, or the Z property. Conduct-ing a through-thickness tensile test is standardised in EN 10164:2004. If required, hot-rolled steel plates can be delivered with improved through-thickness deforma-tion properties, which are referred to as Z plates.

• Symbols of impact strengthThe impact test temperature, as stated by the steel manufacturer, does not represent the lowest permis-sible service temperature for the steel. It rather serves for experimental checking of quality and for comparison between steel grades. In some standards, the impact strength designation means the same as the quality designation.

For flat products, the test specimens for impact strength are taken either in the transverse or longitudinal direc-tion to rolling. The direction is specified on the steel standard, or it has been stated in the data sheet of the steel grade. The impact energy obtained with transverse specimens is usually lower than that with longitudinal specimens. In some standards, the direction of impact testing is made subject to agreement.

Table 1 provides a list of impact strength designations used in new and old standards and related explanations. The designations used for steel grades conforming to EN standards are given in EN 10027-1:2005.

• Selection of impact strength classParticular attention is to be paid to the selection of impact strength class already in the design stage for applications, where the service temperature remains constantly below -40°C and the structure is either welded or subject to impact loads.

The impact strength class of a steel grade makes only a little difference to its price per unit weight. From the user’s point of view, a great variety of steel grades with different impact properties tends to increase costs, while a limited variety of steel grades means lower costs in the storage and handling of materials. The impact

strength class affects, for example, the selection of welding consumables. By using steel grades with a lim-ited number of impact strength classes, the fabricator becomes familiar with those particular steels and can have suitable working methods developed for them.

The selection of steel grade for a structure, when done on the basis of impact strength, depends on several fac-tors:- Temperature during transports and installation: < +20°C- Service temperature: < +20°C- Heavy plate: thickness > 20 mm- Steel grade: Fe, alloyed- Load, stress rate- Welded structure, welding process, weld locations- Thermal cutting- Structural solutions, shape and form.

Selection of the impact strength class can also be affected by the availability of steel products.

Standards and calculation instructions applied in certain fields specify impact strength requirements for steels:- The Finnish Ministry of the Environment Building Code B7, Guidelines for Steel Structures.- ENV 1993-1-1:1993, Design of steel structures – General rules, Appendix C (Eurocode 3).- ENV 1993-2:1997, Design of steel structures – Bridges, Appendix C (Eurocode 3).- Standard EN 13001-1:2004, Cranes – General design General principles and requirements.- Standard EN 14015:2004, specification for the design and manufacture of metal tanks for the storage of liquids.- Pressure Equipment Directive, PED 97/23/EY; standard EN 13445-2, pressure vessels.- Proposal for a European standard ENV 1993-4-2:1999 (Eurocode 3), large unpressurised steel silos and tanks.- National regulations on the impact strength requirements in various steel structures in different fields.

Building Code B7:�996The proper impact strength class of steel in accordance with the Finnish Ministry of the Environment Building Code B7 concerning steel structures can be derived from Table 2.

The Building Code B7 divides steel structures into three main classes:- Structural class 1 includes buildings frequently occupied by a large number of people and special structures, such as masts and towers.

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The values of various factors to be used in calculations are determined as shown in Table 3.

Table 4 shows the lowest permissible service tempera-ture for some of the most common structural steels cal-culated according to the method described above, using the service condition class S2, rate of loading class R1 and consequences of fracture class C2. In terms of stat-ics, the case represents the frame of a simple building.

ENV �993-�:�997, Appendix C (Eurocode 3)Steel bridgesMaterials used in bridges are required to have suffi-cient resistance to brittle fracture at the lowest service temperature that is to be expected during the life time of the structure. The lowest service temperature is to be defined in the initial data for design. If the specifica-tions shown in Table 5 are met, a separate assessment of the brittle fracture can be omitted. The table has been compiled using the calculation method proposed in the standard ENV 1993-2:1997.

- Structural class 2 covers buildings that do not belong to any of the structural classes 1 and 3. Structural class 3 includes buildings only occasionally occupied by people.

ENV �993-�-�:�993, Appendix C (Eurocode 3)The calculation method to prevent brittle fracture pre-sented in Eurocode 3, part 1-1, Appendix C, takes into consideration factors such as the service conditions, rate of loading, consequences of fracture, strength of the steel, material thickness, service temperature, toughness of the material and type of structural com-ponent. The calculation method must not be applied for temperatures below -40°C.

Service conditions:S1:- Unwelded structure.- Welded structure with no local tensile stresses higher than 0.2 times the yield stress.- Welded structure that has been annealed and has no local tensile stresses higher than 0.67 times the yield stress.

S2:- Welded structure with no local tensile stresses higher than 0.67 times the yield stress.- Structures that have been annealed after welding and no local (calculated) stress concentrations occur at rates higher than 2 times the yield stress.

S3:- Welded structure with no (calculated) local tensile stresses higher than 2 times the yield stress.- Structures that have been annealed after welding and have no local (calculated) tensile stresses 3 times higher than the yield stress.

Classes S2 and S3 represent ordinary welded steel structures so that class S2 refers to a statically defined structure of simple geometry. Plastic hinges occur in structures of class S3 in failure limit state.

Rate of loading:R1: Normal static load; floor load, traffic load, wind or surge load, elevator load.R2: Impact load; sudden yield, explosion, collision.

Consequences of fracture:C1: Non-critical members in which fractures cause local damage.C2: Critical members in which local damage will result in total collapse of the structure and thereby risk human life or great material values.

Lowest permissible service temperature for the structure

Tmin

= 1,4 · Tcv

+ 25 + β + (83 – 0,08fyl) · k

d

0,17

β = 100 · (InKIC

– 8,06)

Tcv

= Charpy-V test temperature at whichthe impact energy reaches the value of 27 J

KIC

= (γcα)0,55 ·

fyl · t0,5

1,226

α = 1

ka + k

bIn t + k

c

t 0,5

t1) t

1)

Calculated yield point fyl

fyl = f

y0 – 0,25 ·

t · f y0

t1 235

fy0

= basic value of the yield stresst = thickness (mm)t1 = 1 mm

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• Through-thickness properties of steelMaterial selection can also be affected by through-thick-ness properties. The percentage reduction of area in the through-thickness direction is connected with the sus-ceptibility of the material to lamellar tearing, which can be caused by shrinking stresses in welded joints on the surface of the steel plate or by external loading on the joint, for example.

Through-thickness material properties for steel are determined according to the standard EN 10164:2005,

which specifies the improved through-thickness proper-ties presented as Z quality classes, i.e. minimum values for reduction of area in through-thickness tensile test.These Z quality classes are Z15, Z25 and Z35.

To verify the occurrence of lamellar tearing, steel struc-tures may also be inspected after manufacturing. The risk of lamellar tearing can be reduced by using steel plates provided with guaranteed Z properties, and in particular by using proper structural solutions applied when designing the structure.

• Symbols of impact strength in the designations of steel grades Table 1according to some new and old standards

Impact strength Symbols in the designation

Longitudinal Transverse

t °C KV J t °C KV J

EN 10025-2:2004

SnnnJR 20 27 – – S = structural steelnnn = minimum R

eH (MPa) for thickness range ≤ 16 mm

J = 27 J, K = 40 J, L = 60 JR = 20 °C, 0 = 0 °C, 2 = -20 °C, 3 = -30 °C, 4 = -40 °C, 5 = -50 °C and 6 = -60 °CE = engineering steelC = grade suitable for cold forming

The designations of steel grades are presented in standard EN 10027-1:2005.

SnnnJ0 0 27 – –

SnnnJ2 -20 27 – –

SnnnK2 -20 40 – –

S185 – – – –

E295 – – – –

EN 10025:1990. Old standard

Fe nnn B FN 20 27 – – nnn = minimum Rm (MPa) for thickness range < 3 mm

B, C = impact strength and delivery conditionFN = rimming steel not permittedD2, D2, DD1, DD2 = impact strength and delivery condition

Fe nnn C 0 27 – –

Fe nnn D1, Fe nnn D2 -20 27 – –

Fe nnn DD1, Fe nnn DD2 -20 40 – –

SFS 200:1986. Old standard

Fe nn B 20 27 – – nn = designation for the tensile strength for thickness range < 3 mm

Fe nn C 0 27 – –

Fe nn D -20 27 – –

Multisteel. Ruukki’s product name

Multisteel -20 40 – – Multisteel = structural steelN = normalised structural steelW = structural steel with a lower CEV

Multisteel N -20 40 – –

Multisteel W -20 40 – –

Laser. Ruukki’s product name

Laser nnn C 20 27 – – nnn = minimum ReH

(MPa) C = grade suitable for cold formingMC = high-strength, formable

Laser nnn MC -20 40 – –

Optim. Ruukki’s product name

Optim nnn MC -20 40 – – nnn = minimum ReH

(MPa)C = grade suitable for cold formingM = delivery condition: thermo-mechanically rolledQ = delivery condition: quenchedL = low test temperature for impact strength

Optim 900 QC -40 60 1) -40 50

Optim 960 QC -40 50 1) -40 50

Optim nnn ML -50 27 – –

COR-TEN®. Weathering structural steels. Ruukki’s product name

COR-TEN® A – – – – ReL

≤345 MPa

COR-TEN® B – – – –

COR-TEN® B-D -20 27 – –

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EN 10025-5:2004. Structural steels with improved atmospheric corrosion resistance. Old standard: EN 10155:1993

SnnnJ0W 0 27 – – S = structural steelnnn = minimum R


J = 27 J and K = 40 J 0 = 0 °C and 2 = -20 °CW = weathering steelP = higher content of phosphorusG1 = delivery condition: normalised or normalised rolledG2 = delivery condition may be selected by the manufacturer1) Impact strength to be verified only per separate agreement.

SnnnJ2W -20 27 – –

SnnnJ0WP 1) 0 27 – –

SnnnJ2WP 1) -20 27 – –

SnnnK2G1W, SnnnK2G2W -20 40 – –

EN 10025-3:2004. Normalised fine-grained structural steels. Old standard: EN 10113-2:1993

SnnnN 1) -20 40 -20 20 S = structural steelnnn = minimum R


N = delivery condition: normalised or normalised rolledL = low test temperature for impact strength1) Longitudinal test pieces are used unless otherwise agreed.

SnnnNL 1) -50 27 -50 16

EN 10025-4:2004. Normalised fine-grained structural steels. Old standard: EN 10113-3:1993

SnnnM 1) -20 40 -20 20 S = structural steelnnn = minimum R


M = delivery condition: thermo-mechanically rolledL = low test temperature for impact strength1) Longitudinal test pieces are used unless otherwise agreed.

SnnnML 1) -50 27 -50 16

EN 10028-2:2003. Non-alloy steels with specified elevated temperature properties

PnnnGH – – 0 27 P = steel for pressure purposesnnn = minimum R


G = non-alloy steelH = high temperature service

16Mo3 – – 20 31

DIN 17155:1983. Old standard

H I – – 0 31

1) For a material thickness of > 60 ≤ 150 mm, KV is 27 J.

H II – – 0 31

17 Mn 4 – – 0 31

19 Mn 6 – – 0 31

15 Mo 3 – – 20 31 1)

EN 10028-3:2003. Normalised fine-grain steels for pressure purposes

PnnnN, PnnnNH 1) -20 45 -20 30 P = steel for pressure purposesnnn = minimum R


N = normalised or normalised rolledH = high service temperatureL = low service temperature1) Transverse test pieces are used unless otherwise agreed.

PnnnNL1 1) -50 30 -40 27

PnnnNL2 1) -50 42 -50 27

SFS 1100:1970. Ordinary pressure vessel steels. Old standard

Fe nn B P 0 27 – – nn = designation for the tensile strengthB, D = impact strengthFe nn D P -20 27 – –

SFS 1150, 1977. Fine-grained pressure vessel steels. Old standard

Fe nnn CP 0 27 – – nnn = minimum ReL

(MPa)C, D, E = impact strengthFe nnn DP -20 27 – –

Fe nnn EP -40 27 – –

DIN 17102:1983. Old standard

StE nnn 1) -20 39 -20 21 S, WS, TS, ES = impact strength

1) Transverse test pieces are used unless otherwise agreed.

WStE nnn 1) -20 39 -20 21

TStE nnn 1) -40 31 -50 16

EStE nnn 1) -40 40 -50 27

Shipbuilding steels approved by classification societies

A 1) 1) Normal-strength shipbuilding steels A = 20 ºC, KV = 27 J High-strength shipbuilding steels A = 0 ºC, KV = 27 J TM-rolled shipbuilding steels A = 0 ºC, KV = 27 J Offshore steels approved by classification societies A = 0 ºC, KV = 27 J

B 0 27 – –

D -20 27 – –

E -40 27 – –

F -60 27 – –

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• Selection of the impact strength class Table 2

Calculation of the weighting factor Z: Z = Za + Z

b + Z

c + Z

d

Influencing factor

Structural class

Weighting

factor Za

Influencing factor

Service temperature

T

°C

Weighting

factor Zb

Influencing factor

(selected on the basis of

the thickest component

to be joined) mm

Weighting

factor Zc

Influencing factor

Tensile stress s in

failure limit state

MPa

Weighting

factor Zd

123

741

+100 >T ≥ 0 0 >T ≥ -20 -20 >T ≥ -30 -30 >T ≥ -40

0 5 810

t < 1515 ≤ t < 2525 ≤ t < 3535 ≤ t < 4545 ≤ t < 100

02468

s < 235235 ≤ s < 275275 ≤ s < 355355 ≤ s

0123

The lowest impact strength class of steelSum of weighting factors

Z = Za + Z

b + Z

c + Z

d

Structural member with welds or

flame-cut components

Structural member with no welds or

flame-cut components

Z ≤ 1212 < Z ≤ 1818 < Z ≤ 2222 < Z ≤ 24

JRJ0J2J4

JRJRJRJ0

• Values of the constants in classes S, R and C Table 3

Constant Value of the constant

Service condition classk

a

kb

kc

S10.180.400.03

S20.180.150.03

S30.100.070.04

Rate of loadingk

d

R110-3

R21.0 –

Consequences of fractureγ

c

C11.0

C21.5 –

• Lowest permissible service temperatures for some structural steels Table 4

Material thickness mm Lowest permissible service temperature °C 1)

S235JR S355J2 S420ML

5 10 15 20 25 30 35 40 45 50 60 80100120150

-66-44-31-21-13-7-2 3 7 11 17 28 36 42 50

-83-62-49-39-31-25-19-15-10-7 0 10 18 25 33

-110-88-75-65-58-52-46-41-37-33-27

1) Service conditions class = S2.

Rate of loading class = R1. Consequences of fracture class = C2.

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• Maximum material thicknesses for steels according to Table 5EN �00��:�00� at various service temperatures

Standard Maximum material thickness mm

Service temperature °C

EN 10025-2:2004 EN 10025-3:2004, 1)

EN 10025-4:2004

EN10025-5.2004 0 -10 -20 -30 -40 -50

S235J0S235J2

S235J0WS235J2W

100140

85120

75100

6085

5575

4560

S275J0S275J2

S275N/MS275NL/ML

90130150200

80110130170

6590110150

558090130

506580110

40556590

S355J0S355J2S355K2

S355N/MS355NL/ML

S355J0WS355J2WS355K2W

80110130130175

6590110110150

55809090130

45658080110

4055656590

3045555580

S420N/MS420NL/ML

115155

95135

80115

7095

5580

4570

S460N/MS460NL/ML

105150

90125

75105

6090

5075

4060

1) The thicknesses are valid for N/NL steels in accordance with EN 10025-3. The maximum thickness for M/ML steels is 120 mm.

This data sheet is accurate to the best of our knowledge and understanding. Although every effort has been made to ensure accuracy, the company cannot accept responsibility for any loss, damage or other consequence resulting from the use of this publication.

We reserve the right to make changes.

Copyright © 2007 Rautaruukki Corporation. All rights reserved. Ruukki, More With Metals, Rautaruukki, Laser, Raex and Multisteel are trademarks of Rautaruukki Corporation. Optim is a registered trademark of Rautaruukki Corporation.

COR-TEN® is a registered trademark of United States Steel Corporation.

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Impact Strength for Hot Rolled Steels