Submerged arc welding (including submerged arc surfacing and electroslag surfacing) is a welding method in which the arc is burned under the flux layer. Its inherent advantages of stable welding quality, high welding productivity, no arc light and little smoke make it the main welding method in the production of important steel structures such as pressure vessels, pipe section manufacturing, box beam and column. In recent years, although there have been many new welding methods with high efficiency and high quality, the application field of submerged arc welding has not been affected. From the perspective of the share of the weight of the deposited metal in various fusion welding methods, submerged arc welding accounts for about 10%, and has changed little over the years.

When the welding wire is determined (usually depending on the type of steel welded), the matching flux becomes the key material, which directly affects the mechanical properties of the weld metal (especially plasticity and low temperature toughness), crack resistance, welding defect incidence and welding productivity. The weight ratio of welding wire and flux is welding wire: flux =1.1 ~ 1.6, depending on the type of welding joint, the type of flux used, and welding specification parameters. Compared with melting flux, the amount of sintered flux is less, about 20% less.

The amount of flux used in China fluctuates around 50,000 tons, of which about 70% is melting flux and the rest is non-melting flux. Industrial developed countries in Europe and the United States are mainly non-melting-type flux, about 80%, 90% or more, but there are still melting-type flux production and sales, melting flux this durable productivity is related to some of its inherent characteristics.

In recent years, a new welding method for steel bars has been developed in our country, that is, vertical electric arc - electroslag pressure welding. Compared with the previous steel bar lap manual arc welding method, steel can be saved by more than 15%, the productivity is greatly improved, the consumption cost of welding materials is also reduced, and the development trend of replacing the latter is indeed widely used. This method mainly uses melting flux, which plays the role of arc maintenance, electroslag heating, metal solidification mold and so on. At present, about one-fifth of the melting flux in China is used for the welding of vertical steel bars.

The manganese ore resources in China are relatively short, especially the manganese ore suitable for producing melting flux with high grade, low phosphorus content and low iron content is even less. The country only in Guangxi, Yunnan, Hunan and other provinces have manganese ore veins, after years of mining, in line with the production of flux of manganese ore commodities increasingly tense. In order to replace high manganese slag flux, it has become an urgent task to develop and popularize medium manganese and low manganese flux. With the expansion of production and supply of welding wire containing appropriate amount of manganese, medium manganese and low manganese slag flux should have a broad market.

As for the technical performance description of commercial flux, the current common practice in the industry is that the melting flux gives its chemical composition and the mechanical properties of the deposited metal with a welding wire, and the sintering flux only gives its slag system composition and the mechanical properties of the deposited metal with a welding wire. This does not seem practical enough. Few users carry out batch by batch chemical composition analysis of the chemical composition of the flux, because in addition to the difficulty of the analysis method and equipment, the result is still far from the user's use requirements.