Heavy wall steel material having superior weldability and method for producing the same

摘要

A tough high strength heavy wall steel material having superior weldability is provided, said steel material has a diameter or a side 5 mm or more in length, and comprises oxides 1 mum or less in particle diameter homogeneously dispersed at a dispersion density in a range of from 10,000 to 100,000 particles/mm² and uniform ferrite grains 2 mum or less in grain diameter formed over the entire plane making a right angle with respect to the rolling direction.