| 摘要 |
PROBLEM TO BE SOLVED: To prevent the coarsening of ferrite grain size in the surface layer of a rolled wire rod and to obtain a wire rod excellent in softening characteristic by controlling the difference between the ferrite grain size in the surface layer and that in the inner part to a specific value or below. SOLUTION: The difference between the ferrite grain size in the surface layer and that in the inner part is controlled to 1.0 or less. It is preferable that the rolled wire rod has a chemical composition consisting of, by mass, 0.01-0.25% C, <=0.5% (not including 0%) Si, <=2.0% (not including 0%) Mn, and the balance iron with inevitable impurities and further containing at least either of <=0.05% (not including 0%) Al and <=0.01% (not including 0%) B. In this method of manufacturing the rolled wire rod, the difference between finish rolling temperature and coiling temperature is controlled to <=200 deg.C at the time of hot rolling and also the finish rolling temperature is controlled to <=900 deg.C. By this method, the rolled wire rod can be efficiently manufactured.
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