Low-carbon free cutting steel

A low-carbon resulfurized free cutting steel characterized by consisting of, by mass percent, C:

• 0.05-0.19%, Mn:
• 0.4-2.0%, S:
• 0.21-1.0%, Ti:
• 0.03-0.30%, Si:
• not more than 1.0%, P:
• 0.001-0.3%, Al:
• not more than 0.2%, O (oxygen):
• 0.0010-0.050% and N:
• 0.0001-0.0200%, and one or more elements selected from the group consisting of Se:
• 0.001-0.01%, Te:
• 0.001-0.01%, Bi:
• 0.005-0.3%, Sn:
• 0.005-0.3%, Ca:
• 0.0005-0.01%, Mg:
• 0.0005-0.01% and rare earth elements:
• 0.0005-0.01%, with the balance being Fe and impurities, and in which the contents of Ti and S satisfy the relation (1) given below and the atomic ratio between Mn and S satisfies the relation (2) given below and, further, which contains MnS with Ti sulfide or/and Ti carbosulfide included therein:
• Ti(% by mass)/S(% by mass)<1 (1)Mn/S≧1 (2).

A low-carbon resulfurized free cutting steel characterized by consisting of, by mass percent, C:

• 0.05-0.19%, Mn:
• 0.4-2.0%, S:
• 0.21-1.0%, Ti:
• 0.03-0.30%, Si:
• not more than 1.0%, P:
• 0.001-0.3%, Al:
• not more than 0.2%, O (oxygen):
• 0.0010-0.050% and N:
• 0.0001-0.0200%, and one or more elements selected from the group consisting of Cu:
• 0.01-1.0%, Ni:
• 0.01-2.0%, Cr:
• 0.01-2.5%, Mo:
• 0.01-1.0%, V:
• 0.005-0.5% and Nb:
• 0.005-0.1%, with the balance being Fe and impurities, and in which the contents of Ti and S satisfy the relation (1) given below and the atomic ratio between Mn and S satisfies the relation (2) given below and, further, which contains MnS with Ti sulfide or/and Ti carbosulfide included therein:
• Ti(% by mass)/S(% by mass)<1 (1)Mn/S≧1 (2).

A low-carbon resulfurized free cutting steel characterized by consisting of, by mass percent, C:

• 0.05-0.19%, Mn:
• 0.4-2.0%, S:
• 0.21-1.0%, Ti:
• 0.03-0.30%, Si:
• not more than 1.0%, P:
• 0.001-0.3%, Al:
• not more than 0.2%, O (oxygen):
• 0.0010-0.050% and N:
• 0.0001-0.0200%, one or more elements selected from the group consisting of Se:
• 0.001-0.01%, Te:
• 0.001-0.01%, Bi:
• 0.005-0.3%, Sn:
• 0.005-0.3%, Ca:
• 0.0005-0.01%, Mg:
• 0.0005-0.01% and rare earth elements:
• 0.0005-0.01%, and one or more elements selected from the group consisting of Cu:
• 0.01-1.0%, Ni:
• 0.01-2.0%, Cr:
• 0.01-2.5%, Mo:
• 0.01-1.0%, V:
• 0.005-0.5% and Nb:
• 0.005-0.1%, with the balance being Fe and impurities, and in which the contents of Ti and S satisfy the relation (1) given below and the atomic ratio between Mn and S satisfies the relation (2) given below and, further, which contains MnS with Ti sulfide or/and Ti carbosulfide included therein:
• Ti(% by mass)/S(% by mass)<1 (1)Mn/S≧1 (2).