Low-hydrogen coated electric arc welding bar

Abstract

The invention provides a coated electrode which can obtain a weld metal with excellent cracking resistance and low-temperature toughness in welding of a high-tensile steel with a yield strength of 690 MPa class or more, and which ensures good weldability in all position welding. A coating ratio of a coating flux is 25 to 45 % by mass. A steel core wire contains 0.06 % by mass or less of C relative to the total mass of the steel core wire. The coating flux contains, relative to the total mass of the coating flux, 14.7 to 22.4 % by mass of metal carbonate (in terms of CO2 ), 13.1 to 24.8 % by mass of CaF2, 0 to 8 % by mass of TiO2, 0 to 8 % by mass of ZrO2, 1.1 to 3.0 % by mass of SiO2, 0 to 0.8 % by mass of Al2O3, 0.01 to 0.05 % by mass of C, 2.5 to 6.0 % by mass of Si, 2.2 to 8.0 % by mass of Mn, 1.8 to 7.0 % by mass of Ni, and 0.2 to 3.7 % by mass of Cr + Mo, and the balance including Fe, alkali metal fluoride, alkali metal oxide, alkali-earth metal fluoride (except for CaF2), alkali-earth metal oxide, B, Al, and Mg, and inevitable impurities (P, S, V, Nb, Sn). The following formula is satisfied: D=8.42-0.18CO2+0.05CaF2+0.50TiO 2-1.36SiO2-4.36Al2O3+0.71ZrO2<=3.8.

Description

technical field [0001] The present invention relates to a low-hydrogen type covered arc electrode effective for welding high-tensile steel with a yield strength of 690 MPa or higher, and particularly relates to a welding operation in all-posture welding capable of obtaining a welded portion excellent in crack resistance and low-temperature toughness Low-hydrogen covered arc electrode for high-tensile steel with good performance. Background technique [0002] With the increase in size of steel structures in recent years, in order to achieve weight reduction of steel structures, the application of high-tensile steel to steel structures is advancing. In particular, in the fields of marine structures and pressure vessels, good low-temperature toughness is required, and the demand for welding materials satisfying this is increasing. So far, welding consumables with relatively good low-temperature toughness and crack resistance have been used in covered arc welding and submerged ...

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Problems solved by technology

In addition, in this patent document, there is no awareness of the toughness in the low-temperature region of about -60°C, and, like JP-A-9-327793, no study has been made on the improvement of welding workability in consideration of all posture welding.

[0008] In addition, in JP-A-3-294088, although the toughness of weld metals with a tensile strength of 70 to 90 kg in the low temperature range of about -40°C was evaluated, for example, in recent years, the low temperature range of about -60°C It is still not sufficient for the strict high toughness requirements represented b

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