Usually stick welding is known as SMAW welding process wherein a flux-coated stick electrode is used to fill the joint. In this process, the electrode is used as a filler metal (consumable electrode), also carries the electric current to obtain desired heat. Stick welding is used for the welding of most common metals and alloys effectively.
Power source and current calculation in stick welding
Both AC and DC currents are used in stick welding processes. Direct current (DC) is
Preferred for the sound welding operation.
the thumb rule to calculate Current required for Welding is:
Current (Amp) = [Diameter of Electrode (mm) X 40] ± 20
Flux covered electrodes
The first coated welding electrode was invented by Oscar Kjellberg in 1904. Flux covered electrodes are used in stick welding to protect the weld pool from atmospheric contamination.
Materials content in Flux
There are various types of materials are used in welding flux such as calcium carbonate, sodium silicate, potassium, magnesium, aluminum, iron oxide, china clay, mica, etc.
The function of flux
The main function of flux is as follows:
- As a gas shielding ingredients
- Arc stabilizing consistents
- Arc stability
- Improving Arc behavior and bead appearance
Additionally, Flux has many other functions such as suitable coating that will improve metal deposition rates. and proper coating ingredients produce weld metals resistant to hot and cold cracking.
Application of flux on a core wire
Following methods are applying for flux coating on the core wire:
- By dipping a bare wire into the molten flux.
- By extrusion method.
Choosing a right kind of electrode for stick welding, is an important factor for achieving the desired properties in welding joints such as:
- Chemical composition: The chemical composition of the electrode should be more or less similar to that of the base metal to be welded.
- The diameter of the electrode: The electrode diameter should be less than the thickness of the base metal to be welded.
- Nature of flux coating on the rod:( cellulose, rutile, low hydrogen, etc)
Electrodes can be divided according to their flux coating as basic electrodes, rutile electrodes, cellulose electrodes etc.
Basic electrodes provide an arc with moderate penetration and excellent mechanical properties. There is less hydrogen in the coating, calcium fluoride (CaF), titanium dioxide (TiO) are mixed in addition to iron powder. The deposition occurs rapidly in basic electrodes. It is suitable for flat, horizontal, vertical-up and overhead welding.
Cellulosic electrodes produces a thin, easily removable, fast-freezing slag. It is suitable for all-position and provides a digging/driving arc with deep penetration. It contains.
Rutile electrodes provide a softer arc with lighter penetration than cellulosic electrodes. The slag is easily controlled and commonly used in general construction applications.
Factors to consider in stick welding
Some basic factors that should be tackcare in stickwelding
- Electrode positioning as per the joint type
- Work angle
- Arc travel
- Arc spacing
- Pushing or pulling
- Type of power source(AC or DC)
- Type of polarity (DCSP, DCRP)
- Weld bead geometry
- Amount of weld metal to be deposited