Welding Processes

HH elps spot problems LL eads to better inspection GG ains respect of welders GG ains cooperation Welding Process Knowledge - A Benefit to Inspectors

 Source of energy  Source of shielding  Filler metal (optional) { autogenous or hetrogeneous} Common Features of Welding Processes

SMAW

 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

1- Cellulose - Organic compound cellulose - Limited amount of slag - used for all positions - E 6010, E 6011 Types of coating

2- Basic - Calcium carbonates - Low hydrogen content - E 7015, E Rutile - Titanium dioxides - Heavy slag - E 6013, E 6024 Types of coating

E X X X X-X E ELECTRODE XX Deposite weld metal tensile strength Ksi X the position SMAW Electrode Identification System

Welding Positions

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

E X X X X-X X Coating/Operating Characteristics X Alloying elements percent SMAW Electrode Identification System

Electrode Suffixes - 1 of 2

Electrode Suffixes - 2 of 2

E 7010 E 6013 Example of electrode classification

 F1 - EXX20, EXX24, EXX27  F2 - EXXX2, EXXX3, EXXX4  F3 - EXX10, EXXX1  F4 - EXXX5, EXXX6, EXXX8 Electrode Coating Classification F #s

 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

 E308, E308L - Weld 304 and 304L  E316, E316L - Weld 316 and 316L  E309 - Weld Stainless to Carbon Steel Stainless Steel Electrodes

 Simple equipment  Inexpensive  Very portable  Welds most alloys  Less sensitive to wind & draft air  Not required shielding gas SMAW Advantages

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,..

 Porosity  Slag inclusions  Spatter  Incomplete joint penetration  Incomplete fusion SMAW Discontinuities

Gas Tungsten Arc Welding Equipment

GTAW Nomenclature

AWS Tungsten Electrode Classifications

Carbon Steels  ER70S-2, ER70S-3, etc. Stainless Steels  ER308, ER308L, ER316, etc. GTAW Filler Metals

Effect of DCEN Current on GTAW

Effect of DCEP Current on GTAW

Effect of AC Current on GTAW

 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

 Helium - Low density ( suitable in overhead position position ) - Good penetration - Recommended flow rate 14 : 24 L /min SHIELDING GASES

 Good for thin materials  High quality welds  Good appearance  Very clean  No slag  Autogeneous ( without filler metal )&heterogeneous GTAW Advantages

 Relatively slow  Low tolerance for contamination  Shielding gas expensive  Purging gas expensive GTAW Limitations

 Porosity  Incomplete fusion  Incomplete joint penetration  Tungsten inclusions GTAW Discontinuities

 Contact between:  Tungsten and base metal  Tungsten and filler metal  Excess current  Excess tungsten extension  Improper tungsten tip grinding Causes of Tungsten Inclusions

Submerged Arc Welding (SAW)

SAW

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

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

F7A6-EM12K SAW Filler Metal Example

SAW Equipment

 High deposition rate  Deep penetration  Mechanized process  Not required black lenses  Good for overlay of large areas  Less smoke than SMAW SAW Advantages

 Flat or horizontal fillets only  Extensive setup time  Needs positioning equipment  Arc not visible to operator  Slag removal SAW Limitations

 Groove alignment  Slag inclusions  Porosity  Incomplete fusion  Cracking (W/D ratio) SAW Discontinuities

GMAW

GMAW Equipment

GMAW Nomenclature

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

 Semiautomatic process  High productivity  No slag to remove  Clean process  Continuous filler metal feed  Welds most alloys GMAW Advantages

 Unsuitable for windy conditions  Little tolerance for contamination  Usually limited to shop welding  Equipment is more complex GMAW Limitations

 Porosity  Incomplete fusion  Incomplete joint penetration GMAW Discontinuities