Sub arc flux application in different fields

Since 1950s, sub arc flux is put into use in China and widely used in boiler, pressure vessel, ship building, petrochemical, heavy machinery, bridge building, pipeline construction, steel structural buildings, etc.

(1) boilers and pressure vessel.

Longitudinal and horizontal welding of cylinder body, butt welding of circumferential seam, joint welding of cylinder and cover, water-cooled membrane wall welding is mostly finished by submerged arc welding process. Power station boiler and pressure vessel is developing towards large scale in nowadays. Although low alloy high strength steel is used, vessel cylinder is thicker than 200mm. To improve welding efficiency, narrow gap welding is adopted for these thick plates joint, and sub arc flux with excellent welding performance is a must. Some thick plate welding is finished by electroslag welding. Matched flux is used during the process. Some low pressure vessel, for example, LPG cylinder for civil use, is welded by submerged arc welding process, which consumes lots of welding flux.

(2) ship building

In recent years, ship building industry in China is developing fast. In 1992, we broke the 1 million tonnage records. It grows 200-300 thousand tons every year since then. To shorten the construction time and improve production capacity, high efficiency welding technology is promoted. Except gas shield welding, submerged arc welding is used for medium & thick plate welding and fillet welding.

(3) heavy machinery

Some thick plates and H beams are welded by SAW process.

(4) building & construction

In China, we used electrog slag welding for reinforcing bars joint at construction sites. The sub arc flux type for this purpose is HJ431. It consumes about 20000 tons per year. In recent years, some moderate Mn content fused flux and agglomerated flux is used.

(5) Metallurgy

For rolls and conticaster rollers rebuilding purpose, surfacing and strip cladding is used.

(6) pipes

For domestic market, LSAW and SSAW pipes are manufactured by submerged arc welding process. Pipes welding consumes large amount of sub arc flux every year.

(7) bridge building

In recent years, joint process in bridge building is changing from SMAW to SAW. Compared with SMAW, submerged arc welding process has the advantages of uniform weld pass, high quality and high efficiency. Sub arc flux for bridge building must has low impurities and high impact toughness.

In recent years, market demand for agglomerated flux is increasing gradually. In the project of Pudong bridge, Wuhu bridge, pipeline for oil & gas, lots of agglomerated flux is used.