| 摘要 |
PURPOSE:To improve low-temp. toughness in welding of a low-alloy heat- resisting steel by incorporating a specific ratio each of CaO, CaF2, MgO, etc., into a flux for submerged arc welding and specifying the basicity thereof to a specific value or above. CONSTITUTION:The flux for welding is composed of 15-30% CaO (weight % for all %), 8-20% CaF2, 5-20% MgO, 15-35% SiO2, 5-25% K2O, and 0.02-1.0% B compd. in terms of B2O3. The value of the basicity expressed by (CaO+CaF2+MgO)/SiO2 is specified to >=1.0. The basicity is increased and the low-temp. toughness of a weld metal is improved by using such flux in the sage of providing a groove to base metals 1 (low-alloy heat-resisting steel), welding said metals by using the flux for submerged arc welding and subjecting the joint part to an embrittlement accelerating treatment by annealing and tempering.
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