Fluxes:

For submerged arc welding, fluxes are granulated to controlled size and might be of the fused, agglomerated or sintered type. At first a fused, crushed and graded flux was utilized. The advantages claimed for such a flux being that it was completely free of moisture and not hygroscopic. Both of the chemical composition and the state of division of the flux have an vital bearing on the way it behaves in welding.

Agglomerated fluxes are built by mixing the finely ground constituents with an aqueous solution of a binder such like sodium silicate. The aim is to generated particles a few mm in diameter made up of a mass of finer particles of the constituent minerals. After agglomeration the flux is dried at the temperatures up to 800 °C. Sintered fluxes are built up by heating pelletised powdered constituents to temperatures just below the melting point of some constituents. The temperatures attained during manufacture place limitations on the composition of fluxes. To fuse a flux, temperatures ought to be so high that carbonates and various other minerals are decomposed. As a consequence, basic fluxes incorporating carbonates might be made by one of the other processes such as agglomeration.

Throughout welding some of the granulated flux is melted to cover both the weld pool and the metal particles being transferred from the electrode to the pool. In both of these stages reactions take place between the metal and the flux involving particularly silicon and manganese, the elements that play a vital role in controlling the strength and soundness of the deposit.