strip clading

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STRIP CLADDING

By

KAMAL KISHOR

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CLADDING BY WELDING

• What is Cladding by Welding?

Corrosive Surface of CS or LAS is Cladded with Corrosion Resistant

Weld Metal ( SS, Monel, Inconel, Cupronickel, Nickel, Brass,

Bronze) by Fusion welding Process

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CLADDING BY WELDING

•Base Material: SA387 Gr11 Cl2

• Surface with SS347 weld layers

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WELDING PROCESSES FOR CLADDING

• GTAW/SMAW/FCAW/MIG/SAW/SASC/ESSC

• Manual /Automatic / Semi Automatic

• Commonly Used Processes (Automatic)

» SASC» ESSC

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SUBMERGED ARC STRIP CLADDING (SASC)

• SASC is same as SAW Process except– The Wire is replaced by Strip

• SAW Wire feeding devise & Nozzle is replaced by Strip feeding devise with guiding Shoes.

• Arc is struck between strip & base metal• Arc is covered with granular Flux• Flux is fed from both sides of strip (Arc / fusion

not visible from any side)

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• Advantages of cladding by strip over wire- Uniform Penetration for full weld width- Very low dilution level from base metal- Consistent weld chemistry within the weld bead- Flat and wide weld beads- Less number of weld over laps- Uniform thickness over full cladded area - High deposition rate / High productivity- Very low hot cracking sensitivity

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• Flux for SASC is similar to SAW Flux - Agglomerated

- Active / Alloyed

• Prime Function of SASC Flux (Same as SAW) - Stabilize the Arc- Prevent the Contamination- Even / uniform bead with out spatter

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• Power Source- DC Rectifiers- Constant Voltage Characteristic- OCV = 80 to 90V- Current Capacity up to 1500 A - 100% duty Cycle

• Strip feeding motor & feed rollers drive strip to weld pool • Strip Guiding Shoes / Nozzle

- guides the strip movement. - Ensures even distribution of current for full width of strip- Melts the strip uniformly for full width

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• Strips for SASC – Solid Metal / Alloy

• Commonly used Austenitic SS strips :-

E309, E309L, E309Mo, E309Cb, E308, E308L, E316, E316L, E347

• Commonly used Nonferrous Alloy strips:- Monel, Inconel, Cupronickel

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• SASC Strip sizeWidth 20 to 180 mm, Thickness 0.4 / 0.5 mm

• Available Standard Strip sizes 30 mm, 60 mm, 90 mm Wide × 0.5 mm Thick 120 mm &150 mm × 0.5 mm Are also available on request

• Most Commonly used Strips60 mm × 0.5 mm & 90 mm × 0.5 mm

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• Welding Parameters- Welding Current- Arc Voltage- Welding Speed- Strip Stick Out

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Typical SASC Welding Parameters

Strip Size

mm

Welding

Amp

Arc Voltage

Speed

Welding

mm/min

Bead Width

mm

Thickness Per bead

mm

Deposition Rate Kgs Per Arc Hour

30 400 22 to 24 100 to 125 32 to 36 3-5 to 4.5 7

60 750 24 to 26 100 to 125 63 to 68 3-5 to 4.5 12 -14

90 1100 26 to 28 100 to 125 94 to 98 3-5 to 4.5 17 - 20

• Strips above 90 mm width are not used for SASC• Flux fed from both sides• Continuous Arcing between strip & BM• Strip cut 45° taper while staring • Stick out = 30 mm.

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SASC

••••••••••••••••••

+ –

Strip - 60 × 0.5

Flux

Slag

WeldBase Metal

HopperPower Source 1500 AmpsFlux

+

Arc _

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ELECTROSLAG STRIP CLADDING

• ESSC Process different from SASC

• Power Source & Welding Head (Strip feeding Motor, Drive rods, Guiding shoes, Head motion) Same as SASC

• ESSC Strip Same as SAW strip (Quality marginally different from SAW)

• Quality and property of ESSC Flux totally different from SASC.

• Welding Parameters – Current, Voltage, Speed - different from SASC

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ESSC FLUX• ESSC Strip & Flux Available from

- Soudokay – Belgium (Soudotape … + Record …)

- Sanvik - Sweden

• Flux requires baking – 300 to 350°C for 2 to 3 Hrs.• Holding Temp – Appx. 100°C

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• ESSC Process – Strip Electrode moves into a layer of electro conductive

molten slag– Electro conductive molten slag is formed by fusing the

electro slag flux – Very high electric current is passed through the molten

slag with very high electric resistance– Exothermic reaction when flux fuses to slag – The process generates continuous heat– Strip and base metal surface in contact with the flux, get

melted continuously – Molten strip gets deposited in molten base metal

surface– On cooling the surface gets solidified with strip metal

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Equipment & accessories same as SASC• Power Source

- DC Rectifiers- Constant Voltage Characteristic- OCV = 80 to 90V- Current Capacity up to 2500 A - 100% duty Cycle

• Strip feeding motor & feed rollers drive strip to weld pool• Strip Guiding Shoes / Nozzle

- guides the strip movement. - Ensures even distribution of current for full width of strip- Melts the strip uniformly for full width

• Magnetic Steering Devise- Generates external magnetic field/force opposite to the magnetic field of

molten weld pool- Minimize the turbulence in weld pool- Obtain smooth and uniform weld beads

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•••

+ –

Strip - 90 × 0.5

Flux

SlagWeld

Base Metal

HopperPower Source 2500 AmpsFlux

+

_•••

Magnetic steering

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Base Material: SA387 Gr11 Cl2Consumable: SS309L + SS347

Strip Size: 120 x 0.5mm

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Welding with wider strips – 90, 120, 150 mm wide

• Weld Pool Electro conductive – With very high Current• Subjected to very high magnetic field / force• Weld metal try to flow towards centre due to magnetic force

– Results in

- uneven weld bead- Poor wetting along the toes- Narrow weld bead

- Undercuts- Poor slag detachability

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Magnetic Steering Devise

• Generates External Magnetic Field

• Equivalent and in opposite direction of magnetic field of welding

• Field generated by two solenoids placed on both sides of stripe

• Location of solenoids 15 mm away from strip and base metal surface

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Welding with Magnetic Steering – 90, 120, 150 mm wide• Magnetic Steering System (MSS) essential for strips of 90 mm and above in width• MSS desirable for 60 mm wide• MSS not required for strips below 60 mm wide• 3 to 5 amps current is supplied to two solenoids / MSS• MSS generates magnetic force in opposite direction

- Results in- Symmetric solidification line- Smooth and uniform weld bead - Uniform weld thickness

- Free from undercuts- Good slag detachability

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Difference between SASC & ESSC

SASC ESSC

Flux - Agglomerated Flux – Electro slag

Continuous Arc between strip & BM No Arc except in the starting

Flux fed on both side of strip Flux fed only from front side

Comparatively low Amp High Amp

Comparatively low deposition rate High deposition rate

High consumption of flux Low consumption of flux

Comparatively high penetration & dilution Low Penetration & low dilution

Minimum two layers required Single layer can also meet requirement

Arc fully covered with flux Back side fusion visible

Low hot cracking sensitivity Very low hot cracking sensitivity

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Strip Size in mm

Welding current

Welding Voltage

Bead width mm

Deposition rate Kgs/ Arc Hr

30 550 - 650 22 - 24 32 – 36 10

60 1200 - 1300 23 – 25 63 – 66 22

90 1800 - 1850 24 – 25 93 – 97 33

120 2000 - 2400 24 - 25 124 - 128 42

• Welding Speed = 140 to 180 mm/min

• Stick out = 28 to 32 mm

• No arcing except in staring

• Flux is fed only in front

• Strip is cut 45° taper while staring

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Continuous Step Over Technique

in circumferential weld overlay

Average Deposition: 700 Kg/ Day

Base Material: SA387 Gr11 Cl2Consumable: SS309L + SS347

Strip Size: 120 x 0.5mm

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Thank You

strip clading

Documents

width of strip

sascessc strip

pool strip

strip movement

strip saw wire

saw strip quality

sides of strip arc fusion

strip base metalarc