Both-side single layer, high speed submerged arc welding process

In a process for both-side single layer, high speed submerged arc welding of steel plate for use in low-temperature applications such as steel pipes or other steel structures and containing up to 0.1 wt% of carbon, up to 0.35 wt% of silicon, 0.5 to 2.0 wt% of manganese, 0.01 to 0.1 wt% of aluminum and not more than 0.010 wt% of nitrogen with a welding flux and a welding wire, the improvement in which said welding flux comprises 20 to 30 wt% of SiO.sub.2, less than 25 wt% of at least one of TiO.sub.2 and ZrO.sub.2, 10 to 20 wt% of CaO, less than 10 wt% of at least one of MnO and MgO, not more than 10 wt% of Al.sub.2 O.sub.3 and 20 to 40 wt% in total of CaF.sub.2 and BaO each being not more than 20 wt%, wherein a total amount of acidic components (SiO.sub.2 %+TiO.sub.2 %+ZrO.sub. 2 %) is 30 to 45 wt%, a total amount of basic components (CaO%+MgO%+MnO%) is 20 to 30 wt% and a weight ratio of the total amount of basic components to the total amount 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=285.times.[SiO.sub.2 ]+380.times.[TiO.sub.2 ]+470.times.[ZrO.sub.2 ]+640.times.[Al.sub.2 O.sub.3 ]+653.times.[MnO]+512.times.[MgO]+602.times.[CaO]+400.times.[CaF.sub.2 ]+366.times.[BaO] (1)
• wherein a parenthesis represents a mol fraction of each component;
• said 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% of titanium and 0.01 to 0.02 wt% of boron;
• said welding flux and welding wire are used in combination with each other so that a carbon equivalent C.sub.E of the resulting weld metal is 0.35 to 0.43% as calculated from the following equation (2):
• C.sub.E (%)=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.