Usually stick welding is known as the shielded metal arc welding, wherein a flux-coated stick electrode is used to fill the joint. Stick welding is a widely used welding process due to its portability and simplicity.
Stick welding is a manual welding process, in which all positions and almost all metals can be easily welded.
Stick welding electrodes
In this process, the electrode is used as a filler metal (consumable electrode), which also conducts an electric current to obtain the desired heat.
The electrodes used in this method are flux coated, these fluxes burn with the rod to form a gaseous atmosphere (vacuum) around the weld pool. Which protects the weld pool from contamination of the atmosphere. 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.
Selection of stick electrode
The selection of electrodes prior to welding operation is an important subject, the materials are identified and cataloged globally, and the steels/alloys are manufactured and produced according to certain standards, which makes it easier to join metals, repair, or manufacture a product.
Stick electrode chart
To avoid possible welding defects, stick welding electrodes are designed and used according to the mechanical properties of the base metal.
Power source and current calculation in stick welding
Stick welding machines
As we know, electricity is used to generate arc in stick welding, for which different types of power sources (machines) are used, such as AC transformer, dc generator, inverter, etc.
Stick welding ac or dc
Both AC and DC currents are used in stick welding processes. Direct current (DC) is preferred for the sound welding operation. Stick welding is effectively used for welding most common metals and alloys.
Calculation of current for stick welding
the thumb rule to calculate the Current required for Welding is:
Current (Amp) = [Diameter of Electrode (mm) X 40] ± 20
Principle of operation
In this method, the electric current reaches the base metal through the electrode, the electrode is scratched on the base metal to generate a welding arc.
After the welding arc is generated, it is maintained at a distance of about 1.5 ml from the base metal so that the arc stability is maintained and the generated heat remains constant.
Thereafter, the electrode is moved forward and or backward by rotating it in a specified wave pattern and the molten electrode is installed as a weld bead.
Use of Flux in stick welding
In stick welding, flux is used to shield the weld pool from atmospheric gases.
As the electrodes begin to melt, the flux also burns up, forming a gaseous atmosphere of shielded gas around the weld pole and escaping the atmospheric gases from around the weld pool, meanwhile the burnt flux forms slag, envelops the weld pool, which separates after solidification.
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 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
The following methods are applied for flux coating on the core wire:
- By dipping a bare wire into the molten flux.
- By extrusion method.
- 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 stick electrodes
Basic electrodes provide an arc with moderate penetration and excellent mechanical properties. There is less hydrogen in the coating, and calcium fluoride (CaF), and 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 produce 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 tack care of in stick welding
- 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
The largest and smallest appliances can be built and repaired by this method.