Soft magnetic low-carbon steel excellent in machinability and magnetic characteristic, method of manufacturing the same and method of manufacturing soft magnetic low-carbon part

摘要

A soft magnetic low-carbon steel has a chemical composition having a C content of 0.05% by mass or below, Si content of 0.1% or below, a Mn content in the range of 0.10 to 0.50% by mass, a P content of 0.030% by mass or below, a S content in the range of 0.010 to 0.15% by mass, an Al content of 0.01% by mass or below, a N content of 0.005% by mass or below, and an 0 content of 0.02% by mass or below. In the soft magnetic low-carbon steel, Mn/S mass ratio is 3.0 or above, ferrite grain size is 100 mum or above, ferrite grains contain precipitated MnS grains of grain sizes of 0.2 mum or above in a density in the density range of 0.02 to 0.5 grains/mu²m and the precipitated MnS grains have a mean grain size in the range of 0.05 to 4 mum. The soft magnetic low-carbon steel is excellent in cold-rollability and machinability. Steel parts of the soft magnetic low-carbon steel having complicated shapes can be produced at a high yield.