Flux for submerged arc welding

Abstract

To provide a flux for submerged arc welding that has good welding workability and can reduce the moisture-absorption amount of the flux and the diffusion hydrogen content in a weld metal, even in the use of either an alternating current or a direct current welding power source. The flux for submerged arc welding is set at the composition including: Al 2 O 3 : 15 to 35% by mass; SiO 2 : 10 to 30% by mass; MgO: 10 to 25% by mass; F in terms of CaF 2 : 10 to 25% by mass; Mn in terms of MnO: 3 to 20% by mass; a total of at least one or more of Na in terms of Na 2 O, K in terms of K 2 O and Li in terms of Li 2 O: 0.5 to 6.5% by mass; Fe in terms of FeO: 0.5 to 8% by mass; CaO: 6% by mass or less (including 0% by mass); TiO 2 : 8% by mass or less (including 0% by mass); water-soluble SiO 2 : 1.0% by mass or less (including 0% by mass); water-soluble Na 2 O: 1.0% by mass or less (including 0% by mass) ; and water-soluble K 2 O: 0.8% by mass or less (including 0% by mass), wherein a C content is 0.2% by mass or less (including 0% by mass), and the flux satisfies the following numerical expression (I), where [Al 2 O 3 ] is the Al 2 O 3 content, [MgO] is the MgO content, and [MnO] is a content as the Mn in terms of MnO. 0.20 ‰¦ MgO A l 2 O 3 + MnO ‰¦ 0.80

Description

technical field [0001] The present invention relates to a flux for submerged arc welding. Background technique [0002] Flux used for submerged arc welding can be broadly classified into melting type flux and firing type according to its form. Melting flux is produced by melting various raw materials in an electric furnace and crushing them. On the other hand, firing-type flux is produced by combining various raw materials with a binder such as alkali silicate, granulating them, and firing them. [0003] In addition, sintered flux is classified according to the firing temperature. Generally, those fired at 400°C or higher and lower than 600°C are called low-temperature sintered fluxes, and those fired at 600-1200°C are called high-temperature sintered fluxes. Furthermore, in low-temperature firing-type fluxes, various studies have been made in order to reduce the diffusion of hydrogen into the weld metal (see Patent Documents 1 to 3). For example, Patent Documents 1 to 3 ...

AI Technical Summary

Problems solved by technology

In addition, in the technology described in Patent Document 4, the specific surface area is attempted to be reduced, but the specific surface area of ​​the flux has a significant influence on the protective properties of the slag during welding.

Specifically, if the specific surface area of ​​the flux is reduced, the protective properties of the slag will be impaired, the nitrogen content in the weld metal will increase, and the toughness of the weld metal will deteriorate.

[0014] On the other hand, the technology described in Patent Document 5 regarding high-temperature sintered flux, in which the flux components are designed for the main purpose of dealing with AC welding power sources, is most likely to occur when using DC welding power sources. Sexual deterioration not considered

That is, with the flux described in Patent Document 5, if the welding power source is a direct-current type, the same effect as when an alternating-current type is used cannot be obtained.

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