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Presentation on theme: "This Presentation is provided to you by: WPSAmerica.com Industry Standard Welding Procedures Software for AWS and ASME Codes."— Presentation transcript:

1 This Presentation is provided to you by: WPSAmerica.com Industry Standard Welding Procedures Software for AWS and ASME Codes

2 Welding Practice for the Sandvik Duplex Stainless Steels SAF 2304, SAF 2205 and SAF 2507 Presented by Frank Babish

3 Key Points Metallurgical Considerations Welding Processes Composition differences Base Metal and Filler Metal Good Mechanical and Corrosion Properties of Welds Importance of Heat Input and Interpass Temperature Role of Nitrogen Post Weld Cleaning Dissimiliar Joining Joint Design

4 Characteristics of Duplex stainless steels Excellent resistance to stress corrosion cracking Very high mechanical strength Excellent resistance to pitting and crevice corrosion High resistance to general corrosion in a variety of environments Low thermal expansion High resistance to erosion corrosion and corrosion fatigue Good weldability Lower life cycle cost

5 Duplex microstructure The austenite islands (light) are embedded in a continuous ferrite (dark) matrix. The duplex microstructure typically contains 45-65% austenite and 35-55% ferrite. Austenite Ferrite

6 Yield Strength 0,2% Austenitic vs Duplex Stainless Steel L SAF L SAF Mo+N SAF 2507

7 Coefficient of expansion (x10 -6 )°C -1 Austenitic stainless steelsapprox. 17 Duplex stainless steelsapprox. 13 Carbon steelapprox. 11,5

8 Thermal expansion, per °C (20-100°C) Duplex Carbon steel AISI 316L (x10 -6 )

9 Solidification mechanism of Duplex stainless steel As duplex stainless steels solidify the grain structure transform from a fully ferritic material to a balanced austenite and ferrite microstructure

10 Solidification mechanism of a Duplex Stainless Steel

11 HAZ of weld in SAF 2507

12 Stress strain curves Austenite, ferrite and duplex 0,00,20,40,60, austenite duplex (2205) ferrite Stress [MPa] Strain ferrite duplex austenite

13 Reasons for the high strength of duplex stainless steels Content of ferrite Fine grained structure Nitrogen

14 Embrittling of Duplex Stainless Steels

15 Welding Processes Conventional Processes GTAW GMAW SAW SMAW FCAW Avoid Autogenous Low Energy Processes Or Perform PWHT

16 Filler Metals for the Welding of Duplex Stainless Steels ParentWeldingFiller metalChemical composition, wt-% metalprocessSandvikCSiMnPSCrNiMoNFerrite Sandvikmax.max.max.All weld metal, % SAF 2304TIG, MIG, SAW23.7.L0,0200,41,50,0200, , MMA23.8.LR0,030<0,90,50,0300, , SAF 2304TIG, MIG, SAW ,51,60, ,5830, andMMA ,170,030<1,00,80,0300,02522,5930, SAF ,04<0,50,80,0300, , FCAW2209LT0.030< SAF 2507TIG, (MIG), SAW L0,0200,30,40,0200, , MMA LR0,0300,50,70,0300, , LB0,0400,40,90,0300,02525,59,540,

17 Mechanical properties of the Duplex Stainless Steels SandvikUNSYield strengthTensile strengthElong.Hardness 0,2% offset1,0% offsetA5Vickers MPaksi.MPaksi.MPaksi.% min.min.min.min.min.min.min.approx. SAF 2304S SAF 2205S SAF 2507S

18 Mechanical Properties of All Weld Metal Filler metalWeldingR po,2 R p1,0 R m A 5 ZImpact strength, J SandvikprocessMPaMPaMPa%RT-40°C 23.7.LTIG LSAW 1) LRMMA LTIG LSAW 1) LRMMA LTFCAW LTIG LSAW 1) LRMMA ) Using Sandvik 15W flux

19 Mechanical properties of welded joints. Cross-weld tensile test Parent metalFiller metalWeldingR p0.2 MPaR m MPaA5, % SandvikSandvikprocessmin.typicalmin.typicaltypical SAF LTIG LSAW 1) LRMMA SAF LTIG LSAW 1) LRMMA LTFCAW SAF LTIG LSAW 1) LRMMA ) Using Sandvik 15W flux

20 Charpy-V impact strength of welded joints Parent metalFiller metalWeldingImpact energy, J SandvikSandvikprocessRT-40°C SAF LTIG LSAW 1) LRMMA4638 SAF LTIG LSAW 1) LRMMA LTFCAW5544 SAF LTIG LSAW 1) LRMMA5839 1) Using Sandvik 15W flux

21 Typical CPT Values from G-48A Tests for Parent Metals and Welded Joints SandvikFillerWeldingShieldingRootCPT °C metalprocessgasgas SAF 2304~15 All weld metal23.7.LTIGAr-<15 Joint23.7.LTIGArAr<15 Joint23.7.LSAW 1) --<15 Joint23.8.LRMMA--<15 SAF All weld metal LTIGAr Joint LTIGArAr20-23 Joint LTIGAr - 2% N 2 90 N H (or pure N 2 ) All weld metal LSAW 1) Joint LSAW 1) All weld metal LRMMA Joint LRMMA SAF Autogenous TIG welding40 All weld metal LTIGAr Joint LTIGArAr40-45 Joint LTIGAr90 N H (or pure N 2 ) Joint LTIGAr + 2% N 2 90 N H (or pure N 2 ) All weld metal LSAW 1) Joint LSAW 1) All weld metal LRMMA Joint LRMMA ) Using Sandvik 15W flux

22 Quench annealing of Duplex Steel welds SandvikHolding temperatureQuenching °C media SAF Water SAF Water SAF Water

23 Chromium nitrides Intermetallics High quenching temp Rapid cooling Low quenching temp. Slow cooling

24 Intermetallic phase

25 Chromium nitrides Intermetallics Recommended heat input SteelHeat inputInterpass temperature SAF 23040,5 - 2,5 kJ/mm<250°C SAF 22050,5 - 2,5 kJ/mm<250°C SAF 25070,2 - 1,5 kJ/mm<150°C

26 Welding recommendations SandvikHeat inputInterpass temperature kJ/mm°C SAF 23040,5 - 2,5<250 SAF 22050,5 - 2,5<250 SFA 25070,2 - 1,5<150

27 The roll of Nitrogen Nitrogen is a very important alloying element in DSS Improves corrosion resistance Improves austenite reformation At TIG welding, the loss of nitrogen is compensated for by using Ar %N2 as a shielding gas

28 Ferritic area in SAF 2507 weld owing to the loss of nitrogen in fusion line Shielding gas Ar 99,99%

29 Nitrogen addition to the shielding gas Ar 99,99% Ar + 5% N 2

30 Ferrite content in TIG-welds, SAF 2507 Filler Shielding Root Ferrite content, vol-% metal gas gas + error with 95% Sandvik confidence interval L Ar Ar , L Ar 90% N % H , L Ar + 5% N 2 90% N % H ,0

31 Nitrogen Content in TIG welds of SAF N=0,25% in the filler metal Filler metal ShieldingRootWeight-% N Sandvik gasgasin deposit L Ar90% N % H 2 0, L Ar + 3% N 2 90% N % H 2 0, L Ar + 6% N 2 90% N % H 2 0,33

32 GMAW SHIELDING GASES General recommendations: Short arc welding gives very convex beads. Ar+30 He+1 O2 Spray arc welding Ar+30 He+1 O2 (22Cr duplex) Ar+2 CO2(Super duplex) Pulsed arc welding Ar+30 He+1 O2 (22Cr duplex) Ar(99,996%) for super duplex

33 Nitrogen Analysis from the Top of a TIG weld % Nitrogen in position (oclock)Analysis at Welder No. 10,170,180,150,160,190,19Top side Welder No. 20,18-0,190,19-Top side 0,20-0,210,20-Root side Welder No. 30,22-0,210,20-Top side 0,21-0,210,20-Root side In all cases the filler metal had a nitrogen content of 0,25%

34 Stress relieving temperatures °C for 10 hours

35 Post Weld Cleaning Pitting potential Pickling bath or pickling paste HNO 3 -HF Wire brush Blasting

36 Dissimilar Joints SAF Carbon steelAISI 200AISI 904L, and 300-Sanicro 28, series254 SMO, etc L L L LR LR LR LT LT LT L L L LR LR LR LT LT LT L LSanicro LR LRSanicro 60

37 Joint preparation One sided butt welding

38 Joint preparation Butt welding from both sides

39 Tube to tube sheet welding. Joint preparation >WT >1.5 x WT 45° >3 mm (0.12) or >1.5 x WT r >1.5 x WT a b c d

40 Hydrogen pick-up from covered electrodes Sandvik LR MMA H 2, ml/100 g

41 Hydrogen pick-up from SAW flux H 2, ml/100 g SAW

42 Hydrogen pick up from shielding gas at TIG welding Shielding gas Ar + 5% H 2 Shielding gas Ar + 10% H 2 TIG - no root gas H 2, ml/100 g

43 Hydrogen pick up from shielding gas and root gas at TIG welding TIG - with root gas H 2, ml/100 g Shielding gas Ar Root gas Ar Shielding gas Ar Root gas 90% N % H 2

44 Conclusions Key Areas Good Weldability Uses Conventional Welding Processes Joint Design Role of Nitrogen Heat Input Important Interpass Temperature


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