Active Flux in Submerged Arc Welding (SAW)
Active fluxes are types of fluxes that contain small amounts of manganese, silicon, or both. These elements act as deoxidizers and are added to the flux to enhance its ability to resist porosity and weld cracking caused by contaminants present on or within the base metal.
The main purpose of using active fluxes is to create single-pass welds, particularly on oxidized base metals. It is important to consider the following points when working with active fluxes:
- Active fluxes contain deoxidizers such as manganese and silicon, which can affect the composition of the weld metal based on changes in arc voltage. Increasing the levels of manganese or silicon can enhance the strength and hardness of the weld metal in multipass welds, but it may have a negative impact on its impact properties. Therefore, tighter control of the voltage may be necessary when using active fluxes for multipass welding compared to neutral fluxes.
- Not all fluxes have the same level of activity. Some fluxes are more active than others, meaning they offer better resistance to porosity caused by surface oxides on the base metal in single-pass welds. However, these highly active fluxes may present more challenges in multipass welding scenarios.
In summary, active fluxes with manganese and silicon deoxidizers are effective in preventing porosity and weld cracking in single-pass welds on oxidized base metals.
However, careful control of arc voltage is required for multipass welding to balance the desired strength and hardness of the weld metal with its impact properties.
The level of flux activity should also be considered, as highly active fluxes provide better resistance to porosity but may pose difficulties in multipass welding.