Solid wire and method of manufacturing welded joint

A solid wire comprising, as a chemical composition, by mass % with respect to a total mass of the solid wire:

• C:
• 0.003% to 0.080%;
• Si:
• 0.0010% to 0.50%;
• Mn:
• 0.050% to 1.80%;
• Al:
• 0.030% to 0.500%;
• Ni:
• 8.0% to 16.0%;
• P:
• 0.0200% or less;
• S:
• 0.0100% or less;
• O:
• 0.050% or less;
• Ta:
• 0% to 0.1000%;
• Cu:
• 0% to 0.5%;
• Cr:
• 0% to 0.5%;
• Mo:
• 0% to 0.5%;
• V:
• 0% to 0.20%;
• Ti:
• 0% to 0.10%;
• Nb:
• 0% to 0.10%;
• B:
• 0% to 0.010%;
• Mg:
• 0% to 0.80%;
• REM:
• 0% to 0.050%;
• and
• a remainder:
• Fe and impurities,
• wherein α defined by Formula a described below is 1.35% to 5.50%, and
• Ceq defined by Formula b described below is 0.250% to 0.520%,
• α=2×[Mn]+[Al]+1.5×[Ti]+[Mg]+10×[Ta] (Formula a)
• Ceq=[C]+[Si]/24+[Mn]/6+[Ni]/40+[Cr]/5+[Mo]/4+[V]/14 (Formula b)
• in Formulae a and b, each element with [ ] indicates an amount of the element by mass % with respect to the total mass of the solid wire.