High Strength Steel for Steel Constructions

Transcription

1 High Strength Steel for Steel Constructions Ronny Willms AG der Dillinger Hüttenwerke Dillinger Colloquium Constructional Steelwork 1

2 CONTENT Introduction Delivery Conditions -AR -N / NE -Q + T - Advantages of -Processing - Economics Examples Dillinger Colloquium Constructional Steelwork 2

3 Introduction High strength steel What s that? End of 1920: Introduction of the steel grade St52 (S355) for bridge-building (Prof. Klöppel) St52 was called a high strength steel for a long period Now: S355 is a standard material for bridge-building Definition of high strength depends on the technical developement Today s Definition: high strength steel Steel with R eh > 355 MPa Dillinger Colloquium Constructional Steelwork 3

4 Introduction High strength steel Weight reduction Economical processing Dillinger Colloquium Constructional Steelwork 4

5 Introduction Coking plant Blast furnaces Ingot casting Sintering plant Steel mill Desulphurisation Converter Vacuum treatment Continuous casting Rolling mill Dillinger Colloquium Constructional Steelwork 5

6 Introduction Coking plant Blast furnaces Ingot casting Sintering plant Steel mill Desulphurisation Converter Vacuum treatment Continuous casting Rolling mill Dillinger Colloquium Constructional Steelwork 6

7 Delivery Conditions DELIVERY CONDITIONS AR Q+T N Dillinger Colloquium Constructional Steelwork 7

8 Delivery Conditions Dillinger Colloquium Constructional Steelwork 8

9 Delivery Conditions AR hot rolling Dillinger Colloquium Constructional Steelwork 9

10 Delivery Conditions AR As Rolled T Classical rolling Normalising Transition area: α-fe - γ-fe Cooling on calm air Dillinger Colloquium Constructional Steelwork 10 t

11 Delivery Conditions N hot-rolling + Normalising Dillinger Colloquium Constructional Steelwork 11

12 Delivery Conditions N Normalising T Classical rolling Normalising Transition area: α-fe - γ-fe Cooling on calm air Cooling on calm air Dillinger Colloquium Constructional Steelwork 12 t

13 Delivery Conditions N Normalising rolling T Phase 1 Phase 2 (T > 900 C) Waiting time Transition area: α-fe - γ-fe Definition: After an additional normalising in the furnace, the properties of a normalised rolled plate must fulfil the mechanical requirements of the standard. Cooling on calm air t Dillinger Colloquium Constructional Steelwork 13

14 Delivery Conditions Q+T hot-rolling Quenching + Tempering Dillinger Colloquium Constructional Steelwork 14

15 Delivery Conditions Q+T Quenching + Tempering T Classical rolling Quenching Tempering core surface Dillinger Colloquium Constructional Steelwork 15 t

16 Q+T [ C] 1390 Effect of quenching Carbon solved in the lattice Austenite Delivery Conditions 910 Ferrite + Cementite (Carbon can leave the lattice) Martensite (Carbon stays in the lattice, distorted structure) slow cooling: Ferrite + Perlite fast cooling: Martensite Dillinger Colloquium Constructional Steelwork 16

17 Delivery Conditions Q+T Effect of tempering Charpy-V [J] A4 A3 A2 A1 quenched Temperature [ C] Dillinger Colloquium Constructional Steelwork 17

18 Delivery Conditions Q+T Effect of tempering Yield point Ultimate stength Strength [MPa] quenched A1 A2 A3 A4 Temper-Parameter Dillinger Colloquium Constructional Steelwork 18

19 Delivery Conditions Q+T Typical applications Dillinger Colloquium Constructional Steelwork 19

20 Delivery Conditions ThermoMechanical rolling Dillinger Colloquium Constructional Steelwork 20

21 Delivery Conditions Thermomechanical rolling T Phase 1 Phase 2 (T > 900 C) Phase 3 (T > 700 C) Waiting time Waiting time Accelerated cooling with water (ACC) Cooling on calm air Dillinger Colloquium Constructional Steelwork 21 t

22 Delivery Conditions Thermomechanical rolling γ (coarse) γ (fine) recrystallised γ (fine) formed α Heating Grain refinement TEMPERATURE Final rolling Cooling on air Accelerated cooling Tempering TIME Dillinger Colloquium Constructional Steelwork 22

23 Advantages of -steel - Processing PROPERTIES OF -steel: Fine grain High toughness Low carbon content Low preheating temperatures Excellent WELDABILITY Dillinger Colloquium Constructional Steelwork 23

24 Advantages of -steel - Processing Fine grain Normalised (air) (ACC) Hall-Petch: Grain size Strength Toughness + Excellent weldability Dillinger Colloquium Constructional Steelwork 24

25 Advantages of -steel - Processing High toughness / High safety S355J2+N S460ML S690QL Charpy-V [J] Temperature [ C] Dillinger Colloquium Constructional Steelwork 25

26 Advantages of -steel - Processing High toughness / High safety Charpy-V [J] S355J2+N S460ML S690QL Temperature [ C] Welding leads to toughness reduction High toughness in the base material reduces the risk of brittle fracture and gives saftey! Dillinger Colloquium Constructional Steelwork 26

27 Advantages of -steel - Processing High toughness / High safety Example: Ilverich Rhine Bridge (Germany) DI-MC 460 with a thickness up to 100 mm Charpy tested at - 80 C Dillinger Colloquium Constructional Steelwork 27

28 Advantages of -steel - Processing Low carbon content S 460 NL S 460 ML acc. Auxiliary acc. Auxiliary EN Data EN Data C < 0,20 0,17 < 0,16 0,09 Si < 0,60 0,45 < 0,60 0,30 Mn 1,00-1,70 1,65 < 1,70 1,50 P < 0,030 0,015 < 0,030 0,011 S < 0,025 0,010 < 0,025 0,005 Nb < 0,05 - < 0,05 < 0,04 V < 0,20 0,17 < 0,12 < 0,05 Mo < 0,10 - < 0,20 - Ni < 0,80 0,29 < 0,45 0,25 CE 0,50 0,39 Pcm 0,29 0,20 CET 0,34 0,28 Carbon equivalents: Plate thickness 50 mm CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni+Cu)/15 Pcm = C +Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/ Dillinger Colloquium Constructional Steelwork 28

29 Advantages of -steel - Processing Low preheating temperatures EN Recommendations for arc welding of ferritic steels T p = 697 CET tanh d HD ( 53 CET 32) Q 328 T p - Preheating temperature [ C] CET - Carbon equivalent [%]: CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40 d - Plate thickness [mm] HD - Hydrogen content [cm³/100 g] Q - Heat input [kj/mm] Preheating is necessary to avoid: Preheating is necessary to avoid: excessive hardening cold cracking Dillinger Colloquium Constructional Steelwork 29

30 Advantages of -steel - Processing Low preheating temperatures Hydrogen content of welding consumable [cm 3 /100g] S355M 25 C 50 C 75 C typisc her Bereich für H2 Gehalte S460M 25 C 50 C 75 C 100 C typischer Bereich für H2 Gehalte Hydrogen content of welding consumable [cm 3 /100g] Plate thickness [mm] Plate thickness [mm] Calculated with Q = 2.5 kj/mm (submerged arc welding) and for typical CET s Dillinger Colloquium Constructional Steelwork 30

31 Advantages of -steel - Economics Cost efficiency Low preheating 1. Reducing preheating temperatures Gas consumption Heating time 2. Avoiding preheating No installations No setting up time No gas Dillinger Colloquium Constructional Steelwork 31

32 Advantages of -steel - Economics Cost efficiency Low preheating Often underestimated, but worth to think about 1. Reducing preheating temperatures Gas consumption Heating time 2. Avoiding preheating No installations No setting up time No gas Dillinger Colloquium Constructional Steelwork 32

33 Advantages of -steel - Economics Cost efficiency Low preheating Often underestimated, but worth to think about 1. Reducing preheating temperatures Gas consumption Heating time 2. Avoiding preheating No installations No setting up time No gas Biggest potential for saving costs Dillinger Colloquium Constructional Steelwork 33

34 Advantages of -steel - Economics Cost efficiency Low preheating t 1 t 1 = t 2 S355NL changing delivery condition Possibility to avoid preheating! no gas consumption no set-up times higher capacity in the work shop t 2 S355ML EN : T pcet = 750 x CET % CET ca. 7.5 C T p CET [ C] ,2 0,3 0,4 0,5 Carbon equivalent CET [%] Dillinger Colloquium Constructional Steelwork 34

35 Advantages of -steel - Economics Cost efficiency Low preheating Sauertal Bridge (Germany) Box-girder-bridge Length: 1195 m Width: 27 m 11 Spans: m Tonnage: 13,000 t Grade: S355J2+N 3000 t > 25 mm thickness Dillinger Colloquium Constructional Steelwork 35

36 Advantages of -steel - Economics Cost efficiency Low preheating Alternative: S355J2+N > S355M No preheating Conditions: 30,000 h welding time 15 % for preheating 50 /h labour costs A) Saving preheating times B) Additional costs S355M (25 /t) BENEFIT A = 30,000 h x 15 % x 50 /h B = 3,000 x 25 /t C = A - B 225,000 75, , Dillinger Colloquium Constructional Steelwork 36

37 Advantages of -steel - Economics Cost efficiency Low preheating Low preheating temperatures are not only a matter of costs! Also in terms of job safety, low preheating temperatures are beneficial! NO HOT SURFACES / NO HANDLING WITH GAS / BETTER WORKING CONDITIONS Dillinger Colloquium Constructional Steelwork 37

38 Advantages of -steel - Economics Cost efficiency High strength t 1 t 2 < t 1 t 2 S355NL fy = 315 Mpa increasing yield strength S460NL Weight reduction Bigger assembling units possible Less holding times in the workshop Less welding consumables Reduction of welding time Reduction of testing time t t A A,B ~ t 2 Welding costs ~ t² Plate thickness Dillinger Colloquium Constructional Steelwork 38

39 Advantages of -steel - Economics Cost efficiency High strength 100 mm 73 mm 73 mm S355NL fy = 315 Mpa increasing yield strength S460NL changing delivery condition S460ML Weight reduction (ca. 30%) Bigger assembling units possible Less holding times in the workshop Less welding consumables Reduction of welding time Reduction of testing time Avoiding/Reducing preheating Better weldability High toughness reserves => High safety Dillinger Colloquium Constructional Steelwork 39

40 Choosing the right steel Strength Delivery Toughness condition Dillinger Colloquium Constructional Steelwork 40

41 Choosing the right steel Strength Delivery Toughness condition Dillinger Colloquium Constructional Steelwork 41

42 Reference Projects Airbus-Hangar (Frankfurt / M.) - -Steel S460ML - constant yield strength up to 120 mm Dillinger Colloquium Constructional Steelwork 42

43 Reference Projects World Financial Center (Shanghai) - -Steel S460M - thickness up to 100 mm - constant yield strength Dillinger Colloquium Constructional Steelwork 43

44 Reference Projects Øresund Bridge (Denmark-Sweden) - -Steel - S460M/ML up to 80 mm Dillinger Colloquium Constructional Steelwork 44

45 Thank you for your attention! Dillinger Colloquium Constructional Steelwork 45