MELT TYPE HIGH BASICITY FLUX FOR SUBMERGED ARC WELDING USE
High basicity melt flux for submerged arc welding use which is used when preparing high strength weld metal and gives sound, high toughness weld metal free of top slag-in is provided. The melt flux for submerged arc welding use which is used when welding the seams of UO pipe for pipeline use having a tensile strength of a base material of 800 MPa to 1200 MPa is melt flux for submerged arc welding use characterized by containing, by mass%, CaO: 5.0% to 25.0%, MgO: 1.0% to 5.0%, Al 2 O 3 : over 15.0% to 30.0%, CaF 2 : 30.0% to 50.0%, SiO 2 : 10.0% to 20.0%, and MnO: 0.5% to 15.0% and having a basicity B of 1.2 to 3.2.
1 . Melt type high basicity flux for submerged arc welding use which is used when welding the seams of UO pipe for pipeline use having a tensile strength of a base material of 800 MPa to 1200 MPa, said melt type high basicity flux for submerged arc welding use characterized by containing, by mass %,
CaO: 5.0% to 25.0%,
MgO: 1.0% to 5.0%,
Al 2 O 3 : over 15.0% to 30.0%,
CaF 2 : 30.0% to 50.0%,
SiO 2 : 10.0% to 20.0%, and
MnO: 0.5% to 15.0%,
having a balance of unavoidable impurities, and having a basicity B obtained by formula (1) of 1.2 to 3.2:
B=6.05N[CaO]+4.0N[MgO]+5.1N[CaF 2 ]+4.8N[MnO]−0.2N[Al 2 O 3 ]−6.31N[SiO 2 ] (1)
wherein, N[k] indicates the molar percentage of the ingredient “k”
2 . Melt type high basicity flux for submerged arc welding use as set forth in claim 1 characterized by further containing, by mass %, one or both of Li 2 O and K 2 O in a total of 0.2% to 5.0%.