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Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FLUX CORED ARC WELDING TWI Training & Examination Services EWF/IIW Diploma Course.

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Presentation on theme: "Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FLUX CORED ARC WELDING TWI Training & Examination Services EWF/IIW Diploma Course."— Presentation transcript:

1 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FLUX CORED ARC WELDING TWI Training & Examination Services EWF/IIW Diploma Course

2 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Flux cored arc welding FCAW methods With gas shielding - Outershield Without gas shielding - Innershield (114) With metal powder - Metal core With active gas shielding (136) With inert gas shielding (137)

3 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Outershield process

4 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Innershield process

5 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Structure of the cored wires provide form stability to the wire serves as current transfer during welding Functions of metallic sheath: Function of the filling powder: stabilise the arc add alloy elements produce gaseous shield produce slag add iron powder

6 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Core elements and their function Aluminium - deoxidize & denitrifyAluminium - deoxidize & denitrify Calcium - provide shielding & form slagCalcium - provide shielding & form slag Carbon - increase hardness & strengthCarbon - increase hardness & strength Manganese - deoxidize & increase strengthManganese - deoxidize & increase strength Molybdenum - increase hardness & strengthMolybdenum - increase hardness & strength Nickel - improve hardness, strength, toughness & corrosion resistanceNickel - improve hardness, strength, toughness & corrosion resistance Potassium - stabilize the arc & form slagPotassium - stabilize the arc & form slag Silicon - deoxidize & form slagSilicon - deoxidize & form slag Sodium - stabilize arc & form slagSodium - stabilize arc & form slag Titanium - deoxidize, denitrify & form slagTitanium - deoxidize, denitrify & form slag

7 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Types of cored wire not sensitive to moisture pick-upnot sensitive to moisture pick-up can be copper coated better current transfercan be copper coated better current transfer thick sheath good form stability 2 roll drive feeding possiblethick sheath good form stability 2 roll drive feeding possible difficult to manufacturedifficult to manufacture good resistance to moisture pick-upgood resistance to moisture pick-up can be copper coatedcan be copper coated thick sheaththick sheath difficult to seal the sheathdifficult to seal the sheath Seamless cored wire Butt joint cored wire Overlapping cored wire sensitive to moisture pick-upsensitive to moisture pick-up cannot be copper coatedcannot be copper coated thin sheaththin sheath easy to manufactureeasy to manufacture

8 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Cored wire manufacturing process Strip reel Thin sheet metal Flux input Draw die Closing rollers Forming rollers

9 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FCAW wire designation Wire designation acc. BS EN 758: Standard number Tubular cored electrode Tensile properties Impact properties Light alloy additions Type of electrode core Shielding gas Welding position (optional) Diffusible hydrogen content (optional) EN T Ni B M 4 H5 EN 758T4631NiMB 4H5

10 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FCAW wire designation Wire designation acc. AWS A-5.20: Welding position (0 - F/H only; 1- all positions) Electrode usability (polarity, shielding and KV); can range from 1 to 14 E 71 T-6 M J H8 Designates an electrode Minimum UTS of weld metal (ksi x 10) Flux cored electrode E 7 1 T-6 Shielding gas for classification M 27J at -40°C requirement (optional) Diffusible hydrogen content (optional); can be 4, 8 or 16 JH8

11 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FCAW - differences from MIG/MAG usually operates in DCEP but some Innershield wires operates in DCENusually operates in DCEP but some Innershield wires operates in DCEN power sources need to be more powerful due to the higher currentspower sources need to be more powerful due to the higher currents doesn't work in deep transfer modedoesn't work in deep transfer mode require knurled feed rollsrequire knurled feed rolls Innershield wires use a different type of welding gunInnershield wires use a different type of welding gun

12 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FCAW - differences from MIG/MAG 350 Amps self shielded welding gun Courtesy of Lincoln Electric Contact tip Thread protector Conductor tube Trigger Handle Hand shield 24V insulated switch lead Welding gun cable Close wound stainless steel spring wire liner (inside welding gun cable)

13 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FCAW - differences from MIG/MAG Self shielded electrode nozzle

14 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Travel Angle 75° 90°

15 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Backhand (drag) technique Advantages preferred method for flat or horizontal positionpreferred method for flat or horizontal position slower progression of the weldslower progression of the weld deeper penetrationdeeper penetration weld stays hot longer easy to remove dissolved gassesweld stays hot longer easy to remove dissolved gasses Disadvantages produce a higher weld profileproduce a higher weld profile difficult to follow the weld jointdifficult to follow the weld joint can lead to burn-through on thin sheet platescan lead to burn-through on thin sheet plates

16 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology Forehand (push) technique Advantages preferred method for vertical up or overhead positionpreferred method for vertical up or overhead position arc is directed towards the unwelded joint preheat effectarc is directed towards the unwelded joint preheat effect easy to follow the weld joint and control the penetrationeasy to follow the weld joint and control the penetration Disadvantages produce a low weld profile, with coarser ripplesproduce a low weld profile, with coarser ripples fast weld progression shallower depth of penetrationfast weld progression shallower depth of penetration the amount of spatter can increasethe amount of spatter can increase

17 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FCAW advantages less sensitive to lack of fusionless sensitive to lack of fusion requires smaller included angle compared to MMArequires smaller included angle compared to MMA high productivityhigh productivity all positionalall positional smooth bead surface, less danger of undercutsmooth bead surface, less danger of undercut basic types produce excellent toughness propertiesbasic types produce excellent toughness properties good control of the weld pool in positional welding especially with rutile wiresgood control of the weld pool in positional welding especially with rutile wires seamless wires have no torsional strain twist freeseamless wires have no torsional strain twist free ease of varying the alloying constituentsease of varying the alloying constituents no need for shielding gasno need for shielding gas

18 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FCAW advantages Deposition rate for carbon steel welding

19 Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FCAW disadvantages limited to steels and Ni-base alloyslimited to steels and Ni-base alloys slag covering must be removedslag covering must be removed FCAW wire is more expensive on a weight basis than solid wires (exception: some high alloy steels)FCAW wire is more expensive on a weight basis than solid wires (exception: some high alloy steels) for gas shielded process, the gaseous shield may be affected by winds and draftsfor gas shielded process, the gaseous shield may be affected by winds and drafts more smoke and fumes are generated compared with MIG/MAGmore smoke and fumes are generated compared with MIG/MAG in case of Innershield wires, it might be necessary to break the wire for restart (due to the high amount of insulating slag formed at the tip of the wire)in case of Innershield wires, it might be necessary to break the wire for restart (due to the high amount of insulating slag formed at the tip of the wire)


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