| 摘要 |
A process for both-side single layer, high speed submerged arc welding of steel plate for use in low-temperature applications having a particular chemical composition with a welding flux and welding wire is disclosed. The welding flux comprises 20 to 30 wt % of SiO2, less than 25 wt % of at least one of TiO2 and ZrO2, 10 to 20 wt % of CaO, less than 10 wt % of at least one of MnO and MgO, not more than 10 wt % of Al2O3 and 20 to 40 wt % in total of CaF2 and BaO each being not more than 20 wt %, wherein a total content of acidic components (SiO2 %+TiO2 %+ZrO2 %) is 30 to 45 wt %, a total content of basic components (CaO %+MgO %+MnO %) is 20 to 30 wt % and a weight ratio of the total content of basic components to the total content of acidic components is within a range of 0.5 to 0.8; said these components being compounded so that a surface tension F of slag is not more than 450 dyne/cm as calculated from the following equation (1): F=285x[SiO2]+380x[TiO2]+470x[ZrO29 +640x[Al2O3]+653x[MnO]+512x[MgO]+ 602x[CaO]+400x[CaF2]+366x[BaO](1) wherein a parenthesis represents a mol fraction of each component. The welding wire is composed of a steel wire containing up to 0.10 wt % of carbon, up to 0.4 wt % of silicon, 1.0 to 2.5 wt % of manganese, 0.015 to 0.05 wt % of aluminum, not more than 0.008 wt % of nitrogen, 0.10 to 0.18 wt % to titanium and 0.01 to 0.02 wt % of boron. The welding flux and welding wire are used in combination with each other so that a carbon equivalent CE of the resulting weld metal is 0.35 to 0.43% as calculated from the following equation (2): CE(%)=C(%)+1/24Si(%)+1/6Mn(%)+1/4Mo(%) +1/5Cr(%)+1/40Ni(%)+1/14V(%) (2) to thereby obtain a weld metal containing not more than 0.008 wt % of nitrogen, 0.025 to 0.035 wt % of oxygen, 0.0015 to 0.0030 wt % of boron, 0.015 to 0.030 wt % of titanium and 0.010 to 0.030 wt % of aluminum and having a high low-temperature toughness without weld defects.
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