Calcium-containing graphite steel having excellent machinability, and manufacturing method therefor
AssigneePosco
InventorsSangwoo CHOI, Namsuk LIM
Life of this patent
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Abstract
The present invention relates to a graphite steel having excellent machinability, and a manufacturing method therefor, and more specifically, to a calcium-containing graphite steel having machinability superior to that of normal free-cutting steel and a manufacturing method therefor.
Claims7
A graphite steel comprising, in percent by weight (wt %), 0.60 to 0.90% of carbon (C), 2.0 to 2.5% of silicon (Si), 0.7 to 1.3% of manganese (Mn), 0.2 to 0.5% of sulfur (S), 0.01 to 0.05% of aluminum (Al), 0.005 to 0.020% of titanium (Ti), 0.003 to 0.015% of nitrogen (N), 0.0001 to 0.050% of calcium (Ca), and the balance of iron (Fe) and inevitable impurities,
- wherein the graphite steel includes a microstructure in which graphite grains are distributed in a ferrite matrix, has a graphitization rate of 95% or more, and includes a total of 5 wt % of MnS inclusions and pearlite.
A method for manufacturing a graphite steel, the method comprising:
- preparing a billet including, in percent by weight (wt %), 0.60 to 0.90% of carbon (C), 2.0 to 2.5% of silicon (Si), 0.7 to 1.3% of manganese (Mn), 0.2 to 0.5% of sulfur (S), 0.01 to 0.05% of aluminum (Al), 0.005 to 0.020% of titanium (Ti), 0.003 to 0.015% of nitrogen (N), 0.0001 to 0.05% of calcium (Ca), and the balance of iron (Fe) and inevitable impurities;
- hot rolling the billet to prepare a wire rod;
- and
- performing graphitizing heat treatment on the prepared wire rod.
Dependencies are inferred from the claim text.