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Published byEllen Weaver Modified over 9 years ago
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Welding Processes
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HH elps spot problems LL eads to better inspection GG ains respect of welders GG ains cooperation Welding Process Knowledge - A Benefit to Inspectors
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Source of energy Source of shielding Filler metal (optional) { autogenous or hetrogeneous} Common Features of Welding Processes
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SMAW
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To provide a gas to shield the arc To produce a slag blanket to protect the hot weld metal from the air To improve the smoothness and stability of the arc Deoxidisers to cleanse the weld Adding alloying elements Functions of the Electrode Coating
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1- Cellulose - Organic compound cellulose - Limited amount of slag - used for all positions - E 6010, E 6011 Types of coating
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2- Basic - Calcium carbonates - Low hydrogen content - E 7015, E 7018 3- Rutile - Titanium dioxides - Heavy slag - E 6013, E 6024 Types of coating
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E X X X X-X E ELECTRODE XX Deposite weld metal tensile strength Ksi X the position SMAW Electrode Identification System
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Welding Positions
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1 - used in all positions 2 - used in flat or horizontal fillets only 3 - not used at present time 4 - used for ‘downhill’ progression Position Description
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E X X X X-X X Coating/Operating Characteristics X Alloying elements percent SMAW Electrode Identification System
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Electrode Suffixes - 1 of 2
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Electrode Suffixes - 2 of 2
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E 7010 E 6013 Example of electrode classification
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F1 - EXX20, EXX24, EXX27 F2 - EXXX2, EXXX3, EXXX4 F3 - EXX10, EXXX1 F4 - EXXX5, EXXX6, EXXX8 Electrode Coating Classification F #s
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Types end in a ‘5’, ‘6’, or ‘8’ Purchase in sealed, metal containers Store after opening in heated, vented oven Limit atmospheric exposure Low Hydrogen Electrodes
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E308, E308L - Weld 304 and 304L E316, E316L - Weld 316 and 316L E309 - Weld Stainless to Carbon Steel Stainless Steel Electrodes
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Simple equipment Inexpensive Very portable Welds most alloys Less sensitive to wind & draft air Not required shielding gas SMAW Advantages
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SMAW Limitations Relatively slow Slag removal Electrode storage considerations Arc blow It can not weld refractory materials ( tantalum, Mo, Cr, W ) or reactive materials ( Titanium,..
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Porosity Slag inclusions Spatter Incomplete joint penetration Incomplete fusion SMAW Discontinuities
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Gas Tungsten Arc Welding Equipment
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GTAW Nomenclature
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AWS Tungsten Electrode Classifications
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Carbon Steels ER70S-2, ER70S-3, etc. Stainless Steels ER308, ER308L, ER316, etc. GTAW Filler Metals
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Effect of DCEN Current on GTAW
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Effect of DCEP Current on GTAW
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Effect of AC Current on GTAW
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ARGON - High density ( suitable in flat position ) - Weld all metal except reactive & refractory materials - High spatter - Recommended flow rate 7 : 16 L /min SHIELDING GASES
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Helium - Low density ( suitable in overhead position position ) - Good penetration - Recommended flow rate 14 : 24 L /min SHIELDING GASES
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Good for thin materials High quality welds Good appearance Very clean No slag Autogeneous ( without filler metal )&heterogeneous GTAW Advantages
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Relatively slow Low tolerance for contamination Shielding gas expensive Purging gas expensive GTAW Limitations
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Porosity Incomplete fusion Incomplete joint penetration Tungsten inclusions GTAW Discontinuities
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Contact between: Tungsten and base metal Tungsten and filler metal Excess current Excess tungsten extension Improper tungsten tip grinding Causes of Tungsten Inclusions
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Submerged Arc Welding (SAW)
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SAW
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F X X X - E X X X F Flux X Tensile strength X Heat Treatment X Impact Test Temperature SAW Filler Metal Identification System Flux
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F X X X - E X X X E Electrode X (Low, Medium, High - Mn%) XX (8 through 16 for chemistry) SAW Filler Metal Identification System Flux
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F7A6-EM12K SAW Filler Metal Example
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SAW Equipment
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High deposition rate Deep penetration Mechanized process Not required black lenses Good for overlay of large areas Less smoke than SMAW SAW Advantages
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Flat or horizontal fillets only Extensive setup time Needs positioning equipment Arc not visible to operator Slag removal SAW Limitations
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Groove alignment Slag inclusions Porosity Incomplete fusion Cracking (W/D ratio) SAW Discontinuities
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GMAW
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GMAW Equipment
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GMAW Nomenclature
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E R X X S – X E Electrode R Rod S Solid XX Stregngth of deposite weld metal X Chemical Composition GMAW Electrode Identification System
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Semiautomatic process High productivity No slag to remove Clean process Continuous filler metal feed Welds most alloys GMAW Advantages
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Unsuitable for windy conditions Little tolerance for contamination Usually limited to shop welding Equipment is more complex GMAW Limitations
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Porosity Incomplete fusion Incomplete joint penetration GMAW Discontinuities
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