Posted by: wahid nawawi | November 30, 2012

Welding Consumable Chapter 1


Welding consumables are any products that are used in the production of a weld. Welding consumables may be:

  • Covered electrodes,
  • Filler wires,
  • Electrode wires,
  • Shielding gas,
  • Purging gas,
  • Fusible inserts, etc
Each consumable is critical in respect to:
  • Classification,
  • Size,
  • Condition,
  • Treatments e.g. baking or drying,
  • Handling and storage,
  • Supplier
Characteristic SMAW welding consumable:
  1. SMAW electrode consists of core wire,
  2. The core wire material is rimmed steel,
  3. The wire is covered with a flux coating,
  4. The flux refines weld quality,
  5. The flux consists of alloying elements and refining agents, etc
The following are the functions of electrode covering:
  • To facilitate arc ignition,
  • To give arc stability,
  • To generate gas for shielding arc and protect molten metal from contamination,
  • To form protective slag blanket over the solidifying and cooling weld metal,
  • To aid position welding, etc

Three types and characteristic of electrode coverings used in SMAW are:

  1. Cellulose type with characteristic deep penetration,
  2. Rutile type  with characteristic general purpose, and
  3. Basic type  with characteristic low hydrogen type.
Below is electoda size as per ISO:
S.No             Dia.                     Lenght
1                    6.3                     350, 450
2                    5.0                     350, 450
3                    4.0                     350,450
4                    3.15                   350, 450
5                    2.5                     250, 300, 350
6                    2                        200, 250, 300, 350
========================================
Cellulose type covering characteristic:
  • Cellulose is deep penetrating electrode
  • ,Cellulose is a natural organic compound,
  • Slag former in it is titanium dioxide,
  • Main ionizers are sodium silicate / potassium silicate,
  • Not requires baking / drying,
  • Excessive heat will damage covering,
  • 4% moisture exists,
  • Hydrogen content 80-90 ml/100g of weld metal.
Adventage and Disadventage of Cellulose type:
S.No.                Advantages                               Disadvantages
1                       Deep penetration                          High in hydrogen
2                       All position electrode                     High crack tendency
3                       Fast travel speeds                         High spatter content
4                       Large volume of shielding gas        Rough cap appearance
5                       Low control                                   Low deposition rate

========================================

Rutile type covering characteristic:
  • Rutile type electrode is a general purpose electrode,
  • Slag former in it is titanium dioxide,
  • Main ionizer is sodium silicate,
  • Binding agent is clay,
  • Not requires baking,
  • Baking will damage covering,
  • Dried to lower H2 content,
  • Hydrogen content 25-30 ml/100g of weld metal.
Adventage and Disadventage of Rutile type electroda:
S.No.                Advantages                       Disadvantages
1                       Easy to use                         High in hydrogen
2                       Low cost                             High crack tendency
3                       Smoot weld profile               Low strenght
4                       Slag datacable easily            Low toughness values
5                       Low control                          Low deposition rate

========================================

Basic type covering characteristic:
  • Basic type covering is low hydrogen type,
  • It is deep penetration covering,
  • Slag former in it is fluorspar,
  • Main ionizers are sodium silicate / potassium silicate,
  • Gas former is lime stone (calcium carbonate),
  • Requires baking / drying,
  • Note: vacuum packed electrodes can be used with in four hours pack removal,
  • Can not be re-baked indefinitely,
  • Hydrogen content can have less than 5ml/100g of weld metal.
Adventage and Disadventage of Rutile type electroda:
S.No.                Advantages                        Disadvantages
1                       Deep penetration                  High in hydrogen
2                       All position electroda             High crack tendency
3                       Fast travel speeds                 High Spater content
4                       Low volume of shielding gas   Rough cap appearance
5                       Low control                           Low deposition rate
========================================
Continue to chapter 2……….

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