STEEL FOR HIGH-CLEANLINESS SPRINGS EXCELLENT IN FATIGUE CHARACTERISTICS AND HIGH-CLEANLINESS SPRINGS

摘要

An object of this invention is to provide a steel for high-cleanliness spring which is useful for the production of a spring excellent in fatigue characteristics in high Si steels. The steel for high-cleanliness spring with excellent fatigue characteristics according to the invention contains: in terms of mass %, C: 1.2% or less (excluding 0%); Si: 1.8% to 4%; Mn: 0.1% to 2.0%; and total Al: 0.01% or less (excluding 0%), with the remainder being iron and inevitable impurities, in which the Si amount and a solute (SIMS) Ca amount in the steel satisfy a relationship of the following expression (1): Si × 10 - 7 ‰¤ solute SIMS Ca ‰¤ Si × 5 × 10 - 7 (in which each of the solute (SIMS) Ca and Si represents the amount thereof (mass%) in the steel).