Structural steel materials with excellent fatigue crack propagation characteristics and coating durability and their manufacturing methods

摘要

PROBLEM TO BE SOLVED: To provide a structural steel material having excellent fatigue crack propagation characteristics and coating durability. SOLUTION: A steel material has a microstructure having a predetermined composition, a composite structure composed of a hard phase and a soft phase, a volume fraction of the hard phase of 0.25 to 0.80, and a soft phase. The average particle size of ferrite in the above is 5 to 50 μm. [Selection diagram] None