What main types of fluxes do submerged arc welding flux manufacturers produce?

Submerged arc welding is a welding process in which the electric arc burns beneath a layer of flux. Its advantages—stable weld quality, high productivity, minimal arc radiation, and reduced fume and dust generation—have made it the primary welding method for fabricating critical steel structures such as pressure vessels, pipe sections, and box-girder columns. In the submerged arc welding process, the selection of flux is of paramount importance, as different types of flux are suited to different welding requirements. So, what main types of flux do manufacturers of submerged arc welding flux produce?

Broadly speaking, fluxes are mainly classified into two major categories: fusion fluxes and sintering fluxes.

Various Types of Refractory Flux

Fusion flux is produced by melting a specified proportion of various raw materials in a furnace, followed by water-quenching and granulation, drying, and screening. Depending on the formulation and application, fusion flux can be further classified into manganese-free, low-manganese, medium-manganese, and high-manganese types.

Manganese-free flux: Primarily used for welding low-carbon steels and low-alloy steels, it can meet the welding requirements of ordinary structural components where the performance requirements for the weld joint are not particularly stringent.

Low-manganese flux: Suitable for welding certain specific low-alloy steels, it provides excellent low-temperature impact toughness. For example, when welding structural components intended for service in cryogenic environments, low-manganese flux can ensure the strength and toughness of the weld joint at low temperatures.

Medium-manganese flux is widely used in the welding of critical structures such as boilers and pressure vessels. These structures typically operate under harsh conditions and demand high welding quality; medium-manganese flux delivers excellent overall weld performance, thereby meeting the requirements for long-term safe operation.

High-manganese flux: Particularly suitable for welding large-scale structures, such as rolling mill frames. Welding of such large structures is subject to substantial loads and stresses; high-manganese flux enhances the strength and wear resistance of the weld, thereby ensuring the structure’s reliability and stability.

Different Types of Sintered Flux

Sintered fluxes are produced through high-temperature sintering and other processes, and include fluorine-based, silicon-based, and manganese-based types, each with distinct characteristics and suited to different welding requirements.

Fluoride-based sintered flux: Used for critical welded structures such as boilers and pressure vessels. These structures demand high welding quality and safety; fluoride-based sintered flux can establish a stable arc atmosphere, protecting the weld metal from atmospheric contamination and thereby producing high-quality welds.

Silicon-based sintered flux: Suitable for ordinary structural steels, boiler steels, and similar grades. It provides excellent deoxidation and alloying effects in the weld, resulting in superior mechanical properties and corrosion resistance that meet the service requirements of general structural components.

Manganese-based sintered flux is used for welding metal structures in locomotives, rolling stock, mining machinery, and other applications. These structures are subjected to frequent impact and abrasion during service; manganese-based sintered flux enhances the strength and hardness of the welds, thereby extending the service life of the structures.

Various fluxes, when used in conjunction with different welding wires, can achieve excellent welds on a wide range of metallic materials. For example, when welding stainless steel, the appropriate stainless-steel welding wire and matching stainless-steel flux should be selected; for aluminum alloys, aluminum welding wire and aluminum flux are used.

In addition to the commonly used fluxes for fusion welding and sintered fluxes, there are also several specialized types of fluxes, such as bonded fluxes, which play a role in certain specific welding processes and applications.

Manufacturers of submerged-arc welding fluxes offer a wide variety of flux types, encompassing formulations with different chemical compositions and produced using diverse manufacturing processes, thereby meeting the diversified requirements for weld quality and performance across various industries and welding applications. When selecting a flux, it is essential to take into account the specific workpiece, operating environment, and relevant standards, among other factors, to ensure both weld quality and overall project safety.