Welding of Duplex Stainless Steel ELGA meeting 16/5 ...

Welding of Duplex Stainless Steel ELGA meeting 16/5-2013 Hans Åström

DUPLEX STEELS - Index • Chemical composition • Microstructure • Properties

- Mechanical - Corrosion

• Welding

- Welding procedures and welding methods - Shielding gases - Joint preparation - Set-up and tacking - Welding techniques - Repair welding

• Imperfections – how to avoid • Post weld cleaning • Utilizing the strength of duplex steels • Applications How to weld duplex – 2

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DUPLEX STEELS - History First duplex stainless steel was produced end 1920: Avesta 453 S

(26%Cr, 5%Ni, 1.5%Mo)

Avesta 453 E

(26%Cr, 4%Ni)

Modern duplex steels, 1960- (possible to alloy using nitrogen) Sandvik 3RE60

(18.5%Cr, 5%Ni, 2.7%Mo)

2304

(23%Cr, 4.5%Ni, 0.10%N)

2205

(22%Cr, 5.5%Ni, 3%Mo, 0.17%N)

SAF

2507®

(25%Cr, 7%Ni, 4%Mo, 0.27%N)

LDX

2101®

(21%Cr, 1,5%Ni, N, Mn)

LDX 2404

(24Cr, 3,6Ni, 1,6Mo, 3Mn, 0,27N)

How to weld duplex – 3

DUPLEX STEELS - Chemical composition Chemical composition (typical values wt-%) Grade

ASTM

EN

C (max)

N

Cr

Ni

Mo

Mn

S32101

1.4162

0.02

0.22

21.5

1.5

0.3

5

Filler LDX

-

-

0.03

0.16

23.5

7

10 mm

Surface appearance No fume and radiation

FCAW

> 2.5 mm

PAW

1-8 mm

Laser

1-8 mm

Lasertohybride How weld duplex –4-15 29 mm

High heat input Only horizontal

Productivity

Fume emission

Wide parameter box

Impact strength

Welding speed

Fit up

Surface appearance

Expensive equipment

Welding speed Surface appearance

Fit up Expensive equipment

Productivity

Expensive equipment

Weld metal properties

Parameter set up

DUPLEX STEELS – Shielding gases Method

Grades

Shielding gas

General guidelines:

MIG

LDX 2101, 2304, 2205

1. Ar+1-2%CO2 or Ar+1-3%CO2 2. Ar+1-2%CO2 or Ar+2-3%CO2

• Gas flow MIG 12-16 l/min

2507/P100

1. Ar+1-2%CO2 or Ar+1-3%CO2 2. Ar 3. Ar+30%He+1-2%N2+1-2%CO2

•Too a low or too a high flow may result in porosity.

TIG

LDX 2101, 2304, 2205, 2507/P100

1. Ar+10-30%He+2%N2 2. Ar

FCAW

LDX 2101, 2304, 2205

1. Ar+16-25%CO2 2. 100%CO2

Plasma

LDX 2101, 2304, 2205, 2507/P100

1. Ar* 2. Ar+20-30%He+1-2N2*

Laser

LDX 2101, 2304, 2205, 2507/P100

1. Ar

• Gas flow TIG 8-12 l/min

• All methods are sensitive to draughts. • Check housing, couplings etc.

* Also as plasma gas How to weld duplex – 30

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DUPLEX STEELS – Backing gases 40

15

MISONN2He

Ar + 3%N2

20

Ar

25

Ar+2%N2

30

Ar (No filler)

Temperature,°C

35

An addition of up to 3% nitrogen gives a positive effect on the resistance to pitting corrosion. Autogenous welding of special grades is not advisable.

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DUPLEX STEELS – Backing gases Unless pickling is possible an inert backing must be used when non-fluxing processes (TIG and MIG) are employed for the root run of single side welds. The backing provides protection against oxidation. If no, or inadequate, protection is provided the penetration bead and surrounding metal will be badly oxidized.


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DUPLEX STEELS – Backing gases The purging gas is often applied via: • Purge insert • Cardboard or tape The enclosed volume should flushed at least 7 times. The purging gas must be applied to at least 8 mm of weld metal. Oxygen meter is best used to measure the content.


DUPLEX STEELS – Backing gases Acceptance criteria

A straw yellow colour can normally be accepted. This requires a oxygen content of max 50-60 ppm.


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DUPLEX STEELS – Key to success Five keys for a successful result 1. Use the right filler metal to achieve right structure = right properties 2. Choose “optimal” welding method for each application 3. Right joint preparation, proper fit-up and clean weld zone 4. Let the welders train how to weld duplex and follow the welding procedure 5. Chose right and make the post weld cleaning carefully


DUPLEX STEELS - Joint preparation •

Avoid small joint angels

•

Root gap is essential for full penetration

•

Edge preparation: 1. Milling 2. Plasma cutting followed by smooth grinding 3. Grinding the joint shall be avoided

•

Cleaning of the joint after preparation: • Edge burs • Degreasing Keep the joint and plate clean before welding


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DUPLEX STEELS - Joint preparation FCW, MIG, MMA, TIG I-joint, t = 2-4 mm D = 2-2,5 mm V-joint, t = 4-16 mm  = 60-70° C = 1,5-2 mm D = 2-3,5 mm

FCW welding can be performed using ceramic backing (round type) D = 4-6 mm How to weld duplex – 37

DUPLEX STEELS - Joint preparation FCW, MMA, SAW X-joint, t = 14-30 mm  = 60-70° (SAW 80-90°) D = 2-2,5 mm (SAW 0 mm) C = 2-2,5 mm (SAW 3-8 mm)



B C

By choosing X-joint instead of V-joint the consumption of consumables can decrease be app. 10% and the distortion will be minimised


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DUPLEX STEELS - Joint preparation

Root face 8 mm

16 mm plate Bevel angel 45

Example SAW 2205, t=16 mm How to weld duplex – 39

DUPLEX STEELS – Fit-up • Greater distortion then mild steel but less than for austenitic steel • Careful fit-up - keep the root gap! • Tack welds should be “removed” before welding • Avoid misalignment 150-200 mm


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DUPLEX STEELS – Fit-up • Bridges, bullets or horses can be used when fitting-up the joint. Keep the root gap!! • Tacking of the bridge must be performed using suitable duplex filler metal. • All tacks outside the joint must be removed by removed properly. • Disalignment should be avoided Good tacking is essential for a proper result Good relation between ”tackers” and welders How to weld duplex – 41



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DUPLEX STEELS - Temperatures • Pre-heating not necessary. Welding outside in humid and cold weather condition requires a slight pre-heating (max 40°C) to avid moist in the joint • Interpass temperature max 150°C • Heat input 2205, 2304 LDX 2101, 2507

0.5 – 3.0 kJ/mm 0.3 – 1.5 kJ/mm

• No post weld heat treatment should be carried out • Hot forming using flame should be avoided due to risk of carbon pick-up


DUPLEX STEELS - Welding techniques • Two side welding is easier than one side unless FCW against ceramic backing is used • Visual inspection between each run • Grinding should be performed between runs to “open” up the joint (be careful with the plate surface) • Grinding of start and stops • Stringer beads (horizontal) • Weaving (vertical-up) • Avoid to thin runs (porosity) • Protect the weld area from wind and draught How to weld duplex – 44

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DUPLEX STEELS - Welding sequence Root run • Sound weld metal • Full penetration • Single side runs using MMA or TIG • TIG requires root protection Filler runs • High deposition rate without imperfections • MMA, FCW, MIG, SAW Cap runs • Surface appearance • Minimum of post weld cleaning How to weld duplex – 45

DUPLEX STEELS - Welding procedures Welding Procedure Specification

ELGA AB Issued by:

Hans Åström Charge:

Basematerial:

A: B:

Welding position:

10 mm 10 mm

PA (1G)

Preheat:

B C A C 1 2-3 4-5

Run 1 2-3 4-5

80° 1,5-2,5 mm

Gro up:

B

0,5-1,5 mm

PWHT

N.A.

Backing:

No

Joint prep.

Milled

Filler material ELGA 2205 ELGA 2205 2205

Dia. 1,6 2,4 3,25

Batch No.

Polarity

Current

Speed

Energy kJ/mm 0,6-0,8 0,5-0,6 1,4-2,1

Voltage

Ampere

Volt

mm/s

10-12 10-12 20-25

0,8-1,5 1,5-2,5 6-9

1(1)

Date:

2006-05-11

Establish a proper welding procedure and follow it!

P ipe Ø:

No

°C

Max.150°

°C

°C

h

Notes: Welding from one side. Purging gas: Ar (10-15 l/min). Purging applied for all runs.

Process GTAW GTAW SMAW

60-80 80-110 100-120

Side:

ø400-1000 mm ø400-1000 mm

Interpass temp.

A

Run

Thickness:

2205 (EN 1.4462) 2205 (EN 1.4462)

WPS No: HÅ155

Gas/Flux Ar +2% N2 (5-8 l/min)

Pulsed arc Wire feed Note: m/min


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DUPLEX STEELS – Overlay welding Duplex filler metals can be used for all types of overlay welding of carbon steel. The duplex overlay is resistant to both corrosion and wear resistance. The dilution with the carbon steel should be minimised and MMA and TIG gives generally the lowest dilution. SAW gives generally a very high dilution and should be avoided. The dilution can be heavily affected with the welding technique and parameter set-up. 309L or 309MoL is an cost efficient alternative as first layer.




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DUPLEX STEELS – Dissimilar welds

?

X

Z


DUPLEX STEELS – Dissimilar welds SAF 2507

2205

2507

2304

2304

2304

2205

2507

2205

2205 2101

2205

2205

2507

SAF 2507

2507

2507

2507

2507

2101 309MoL 309L 2304 309MoL 309L 2205 309MoL 309L 2507 309MoL 309L

2101 309MoL

625

2304 309MoL

625

2205 309MoL

625

2507 309MoL

625

Carbon Steel

2205

2304

254 SMO

2304

2101

316

LDX 2101

LDX 2101

304

Grade

2101 309MoL 309L 2304 309MoL 309L 2205 309MoL 309L 2507 309MoL 309L


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Weld defects in DSSDSS •

Solidification cracking

•

Porosity

•

Slag inclusions

•

Spatter

•

Weld oxides

•

Precipitates • •

Sigma phase Nitrides

Field experience next …..

How to weld duplex – 51 5


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DUPLEX STEELS - Be aware of… The penetration into base material is less for duplex steels than f ex 1.4301 (304) and 1.4401 (316). Risk for incomplete penetration. 

Full penetration essential for structural integrity and good properties



2 - 2,5 mm root gap + 30° bevel angle


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DUPLEX STEELS - Be aware of… The high nitrogen content in base material and consumable increase the sensitivity for porosity formation compare to 1.4301 (304) and 1.4401 (316).  To thin or thick beads increase the risk


DUPLEX STEELS - Be aware of… Striking scars, grinding scars, surface oxides, crevice all decreases the corrosion resistance  repair welding must be performed using filler


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DUPLEX STEELS - Be aware of… Too low energy gives high cooling rate  a high ferrite content and nitrides  decreased corrosion resistance and toughness

Too high energy gives low cooling rate  risk for precipitation's of inter metallic phases  decreased corrosion resistance and toughness

DUPLEX 2304, 2205 max 3 kJ/mm DUPLEX LDX 2101, 2507 max 1,5 kJ/mm


DUPLEX STEELS - Repair Imperfections must be removed and repair • Grinding or plasma gauging to sound metal (use stainless tools) • Protect the surrounding area from spatter (cardboard or choke paint) • Consider the width and depth • Penetrant testing • Welding with suitable method • Inspection • Repair can be performed several times without harming the base metal Establish repair procedure!!


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DUPLEX STEELS - Repair


Post weld cleaning - Applications


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DUPLEX STEELS - Storage & handling • Covered electrodes and FCW are sensitive to moist • •

Porosity Bad weld bead apperance

• Product should be stored in original packaging in a moist and heat controlled room (80%/20°C) • After use back to package and storage room. No electrodes/FCW/Flux ”over night” • Re-drying at 250-280º for 3 hours (SMAW and Flux)


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DUPLEX STEELS - Applications

2205

Civil Engineering Bridges, crash barriers, rebars, lamp-posts, aerial masts, flood-gates, beams 2205

LDX 2101

2205

LDX 2101

2304


DUPLEX STEELS - Applications Pressure vessels Process vessels, heat exchangers, domestic heaters

Process vessel

Domestic Heat exchanger heater How to weld duplex – 68

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DUPLEX STEELS - Applications Transportation Bus frames, car bodies, mobile vessels Barge tank

Trailer chassis

Chassi


DUPLEX STEELS - Applications Heavy Industry Pipe systems

Continuous digester

Petro chemical

Sulphuric acid production

Batch digesters

Flue gas cleaning

Papper machine


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DUPLEX STEELS - Applications Cargo tanks


DUPLEX STEELS - Applications Storage tanks Caustic liquor, petroleum products, wine, water, etc. Marble slurry tanks, Norway

Palm oil tanks, Netherlands

White liquor tank, Finland


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DUPLEX STEELS - Utilizing strength Mechanical and physical properties, RT, minimum values Grade

Rp0.2 [MPa]

Rm [MPa]

E [GPa]

 [x103 kg/m3]

 [x10-6/°C]

304L

210

520

200

7.9

16.0

460

640

200

7.8

13.0

450

650

200

7.7

13.0

2205

(S32205)

LDX 2101

(S32101)

Factors influencing how the strength can be utilized:

• Function – e.g. cylinder with internal pressure • Constraints: Shape (diameter, height etc.) Loading condition (wind loads – instability etc.) Material standards and design codes (design stresses etc.)


DUPLEX STEELS - Cost advantage tank 1.4301

LDX LDX2101 2101

64.9 tons

36.6 tons m 14 12

Required gauge 1.4301 Required gauge LDX 2101 Min gauge (stability) = 6 mm

10 8 6 4 2

[mm]

Ø 17 m

16

12

8

4

0


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DUPLEX STEELS - Conclusions • Chose the right filler for the duplex type • Chose right welding method • Importance of right joint preparation • Full penetration • Slag control • Control of the melt pool • Be careful with fit-up and tacking • Controlled heat input • Protect the weld area from wind and draught • Clean weld area • No pre-heating • Handling and storage (stainless is sensitive) • Repair procedures • Post weld cleaning

Use right filler and follow the welding procedure How to weld duplex – 75

Welding Duplex Stainless Steels is not difficult just different


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