| 摘要 |
Provided is a free machining steel with lead having excellent machinability. A free machining steel with lead (1) according to an embodiment of the present invention contains, in mass%, 0.005 to 0.2% carbon (C), 0.3 to 2.0% manganese (Mn), 0.005 to 0.2% phosphorus (P), 0.01 to 0.7% sulfur (S), 0.03 to 0.5% lead (Pb), 0.004 to 0.02% nitrogen (N), and 0.003 to 0.03% oxygen (O), with the remainder comprising iron and impurities. Among free machining inclusions (8) in the steel, the ratio of the number of Pb-MnS inclusions having an equivalent circular diameter of at least 5 μm with respect to the total number of free machining inclusions (8) having an equivalent circular diameter of at least 5 μm is at least 5%. The free machining inclusions (8) are not more 200 μm long. The average of length of the free machining inclusions (8) in the steel having an equivalent circular diameter of at least 5 μm is not more than 50 μm. Among the free machining inclusions (8), there are at least 500/mm2 having an equivalent circular diameter of at least 2 μm and having an aspect ratio of not more than 10. |
