Flux cored arc welding (FCAW) uses a tubular electrode filled with flux, which shields the arc and delivers additional alloying elements into the weld pool. Which elements, and in what proportion, depends on what the application asks of the joint. These are the ones that come up most often.
- Carbon (C) — affects the strength and hardness of the weld metal. Higher carbon increases strength but also makes the weld more prone to cracking.
- Manganese (Mn) — deoxidises the weld metal and improves strength and toughness. It also helps control the formation of undesirable compounds.
- Silicon (Si) — improves the fluidity of the weld metal and deoxidises the pool. It can also enhance strength and ductility.
- Nickel (Ni) — increases strength, toughness and corrosion resistance, and helps control the formation of austenite in the deposit.
- Chromium (Cr) — improves corrosion resistance and high-temperature strength, and helps prevent grain growth during welding.
- Molybdenum (Mo) — enhances strength and creep resistance, particularly at elevated temperatures.
- Vanadium (V) — improves strength, toughness and hardenability, and refines the grain structure.
- Titanium (Ti) — acts as a deoxidiser and grain refiner, and can improve strength and corrosion resistance.
- Copper (Cu) — improves electrical conductivity and corrosion resistance, and enhances strength and toughness.
- Aluminium (Al) — deoxidises the weld metal and improves its fluidity. It can also enhance strength and corrosion resistance.
- Zirconium (Zr) — refines the grain structure, improving strength and toughness.
- Boron (B) — added in small amounts to improve hardenability and control grain size.
These elements are combined in different proportions to meet specific requirements — strength, ductility, corrosion resistance, mechanical properties. The choice of flux cored electrode and its alloying elements depends on the base metal, the welding process parameters and the properties wanted in the finished weld.
One point that is easy to overlook: the alloy only helps if it arrives in the arc as intended. Particle size and flow behaviour decide whether the powder fills the tube evenly and transfers predictably, which is why the specification of the powder matters as much as its chemistry.
AIM Alloys LLP manufactures ferro alloy and metal powders for welding consumables, with particle sizes made to customer requirement. For enquiries, email info@aimalloys.in.