KCWONG. Shielded Metal Arc Welding (SMAW) Gas Metal Arc Welding (GMAW/MIG) Flux-cored Arc Welding (FCAW) Gas Tungsten Arc Welding (GTAW/TIG) KCWONG

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1 1 Shielded Metal Arc Welding (SMAW) Gas Metal Arc Welding (GMAW/MIG) Flux-cored Arc Welding (FCAW) Gas Tungsten Arc Welding (GTAW/TIG) 2

2 Working Principle Equipment Filler metals Advantages Limitation 3 4

3 Can also be called Manual Metal Arc Welding (MMAW) or (MMA) 5 Arc is established between electrode and base metal Heat is generated by the arc to melt with electrode and base metal Molten metal is protected by both solidified slag and fumes 6

4 P Power source, AC or DC El t d holder h ld Electrode Protective helmet Can be AC or DC Other accessories 7 8

5 AC or DC Power Source And Controls Electrode Electrode Holder Arc Workpiece Lead Electrode Lead Work 9 Operation Shielded Metal Arc Welding Electrode Size (mm) Arc Current (A) Min. Protective Shade Suggested Shade No. Less than 2.5 Less than More than

6 Grinder Electrode Holder Wire Brush Chipping Hammer Wldi Welding Tong 11 National Standards (BS EN ISO) BS EN 499 (Covered electrodes for manual metal arc welding of non-alloyed and fire grain steels) EN ISO 2560:2005 (Classification of Welding Consumables for Covered Electrodes for Manual Metal Arc (111) Welding of Non-Alloy and Fine Grain Steels) Welding and Cutting Processes CASTCO 12

7 Supersede BS EN 499 Applies a dual approach to classification of electrode using g methods A and B Welding and Cutting Processes CASTCO 13 Welding and Cutting Processes CASTCO 14

8 Welding and Cutting Processes CASTCO 15 National Standards N i ls d d (AWS) AWS A5 A5.11 (Specification for carbon steel electrodes for shielded metal arc welding) ldi ) AWS A5.5 A5 5 (Specification for low lowalloy steel electrodes for shielded metal arc welding) Welding and Cutting Processes CASTCO 16

9 E XXXX E Electrode XX - Tensile strength x 1000 (psi) X - Welding position 1 - all position 2 - flat or horizontal fillet position 4 - down hill position 17 X - coating characteristics Chemical composition of the coating, current type, and operating characteristic of the electrode. Numbercanbefrom0to8 For example, 5, 6, 8 are low hydrogen electrode that required keeping in sealed container or preheat prior welding to eliminate i moisture it levell 18

10 Simple and easy set up Portable Low cost equipment 19 Productivity relatively slow Slag removal 20

11 Electrode (low hydrogen type) must be appropriately p storage 21 Porosity Arc blow Spatter Slag inclusion Incomplete fusion 22

12 Magnetic field produced d Around electrode Forward Blow Welding Electrode Back Blow Welding Direction 23 24

13 Can also l be called ll d Metal Inert Gas Welding g (MIG) 25 26

14 Heat is generated by arc (between filler wire and work-piece) to melt and fuse work-piece together th Molten metal is protected by either inert or active gas (MAG) Solid filler wire is continuously fed to welding ggun through wire feeding unit Commonly employed as a semi-automatic process 27 Power source (DC prefer) Electrode wire feed unit Control console Shielding gas supply system Welding gun Water cooling system if necessary 28

15 29 Wire Feeding Unit 30

16 Cable Assembly 31 Welding Gun 32

17 Some typical standards for specification of steel wire are BS EN (Welding consumables wire electrodes, wires, rods and deposits for gas shielded metal arc welding of high strength steels Classification) AWS A5.18 (Specification for carbon steel filler metals for Gas Shielded Arc Welding) A01T09-pp1-dt_ndt_II.ppt 33 ER XXS-XX ER - Electrode Rod XX - Tensile strength x 1000 (psi) S - Solid Wire X - Chemical Composition (2-7, G) 34

18 Spray Transfer Globular Transfer Short Circuiting Transfer Pulse Transfer 35 Higher-current density and is considered d to be the hottest t one Very fine droplets Best for heavier section material Good for full penetration ti weld joint 36

19 Less stable, increase spatter Less heat than spray transfer mode Droplets of filler wire is significantly larger than spray transfer mode Only on down hand position 37 The least amount of heating Excellent for welding of sheet metal and having excessive gap Incomplete fusion (insufficient heat) Allows for all position welding 38

20 Protect molten pool against atmosphere Argon, Helium and their mixtures CO 2 or argon mixture are commonly used for welding of carbon steel 39 Capable of welding most alloys No slag to be removed Higher productivity Lower labour cost 40

21 Less smoke generated, improve workshop environment easily observe the action of molten puddle to improve arc control no flux contamination, lowest hydrogen problems 41 Not suitable for field work Complexity and high cost of equipment Unstable wire feed due to worn liner and contact tube Easy to contaminate with working environment 42

22 Porosity due to Lack of shielding contamination Incomplete fusion 43 44

23 Very similar to GMAW Tubular electrode (granular flux contains) M l Molten metall is i covered db by a layer l of f flux fl as was the case for SMAW 45 46

24 May not need shielding gas depend on the type of filler wire Some filler wire capable of providing sufficient protection to the molten puddle and so called self-shielding 47 E XXT-X (AWS A5.20) E X X - Electrode - Tensile strength x (psi) -Welding gposition 0 (flat or horizontal fillet position) 1 (all position) T - Tubular Wire 48

25 X - Chemical Composition and operating characteristics, such as Type of current Polarity 49 Similar to GMAW High current capacity power source as compared to GMAW Lack of shielding gas supply system if self-shielding is used 50

26 Suitable for field welding Good performance on contaminated surface Higher deposition rate, increase productivity 51 Advantages Well penetration Less skill required for operator compared with SMAW 52

27 Require slag removal Fumes and gases hazards Complexity in equipment set up as GMAW and increase initial iti cost 53 Slag inclusion Porosity Incomplete fusion 54

28 55 Can also l be called ll d Tungsten g Inert Gas Welding (TIG) 56

29 Non-consumable electrode Electrode is made of pure or alloyed tungsten Arc is created between tungsten electrode and work piece 57 Filler metal must be added manually or by mechanical feed if necessary Arc and molten metal is shielded by using of inert gas no slag is required to remove 58

30 Welding direction Filler Rod Gas Nozzle Tungsten Electrode Weld meta Protective Gas Arc 59 Power source (AC and/or DC) Control console Shielding gas supply system Welding torch Water cooling system if necessary Electrode wire feed unit if necessary 60

31 High frequency generator aids to initiate welding g arc especially p y for welding reactive material, such as aluminum and magnesium Remote control (foot pedal or some devices mounted on the torch) 61 62

32 AWS Code Type Tip Colour EWP Pure Tungsten Green EWCe % Ceria Orange EWLa-1 1 % Lanthanum Oxide Black EWTh % Thoria Yellow EWTh % Thoria Red EWZr % Zirconia Brown 63 Excellence for welding thin section material Usually used for welding root pass Capable of welding most materials Perform high quality and excellence visual appearance 64

33 No slag to be removed Process is a clean and controllable no filler metal is added if the joint design is permitted 65 Tolerance for contamination is quite low, High level required by the operator Not suitable for windy situation Low productivity as the process is too slow 66

34 Porosity Incomplete fusion Tungsten inclusion 67 68