Lead-containing free-machining steel

Abstract

Provided is a lead-containing free-machining steel having excellent machinability. This lead-containing free-machining steel contains, in terms of mass%, 0.005-0.2% C, 0.3-2.0% Mn, 0.005-0.2% P, 0.01-0.7% S, 0.03-0.5% Pb, 0.004-0.02% N, and 0.003-0.03% O, with the remainder comprising Fe and impurities. The steel contains Pb inclusions (40) having a diameter of 0.01-0.5 μm in terms of equivalent-circle diameter, the number of the inclusions being 10,000 per mm2 or larger.

Description

technical field [0001] The present invention relates to free-cutting steel, and more specifically, to lead-containing free-cutting steel containing lead. Background technique [0002] General mechanical products such as automobiles and electrical products consist of many parts. These components are mostly produced by machining. Therefore, "easy machinability", that is, excellent machinability is required for steel which is a raw material of parts. [0003] Free-cutting steel has excellent machinability. Typical free-cutting steels are, for example, SUM23 and SUM24L specified by JIS standards. Since Pb improves the machinability of steel, free-cutting steels often contain Pb. Hereinafter, free-cutting steel containing Pb is referred to as lead-containing free-cutting steel. [0004] In recent years, due to environmental considerations, free-cutting steels with suppressed Pb content and Pb-free free-cutting steels that do not contain Pb have been proposed. However, lead-...

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Problems solved by technology

[0011] However, in the case of lead-containing free-cutting steel, sufficient machi

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