US2003152476A1PendingUtilityA1

Low-carbon free cutting steel

Assignee: SUMITOMO METAL INDPriority: Feb 4, 2002Filed: Feb 4, 2003Published: Aug 14, 2003

Est. expiryFeb 4, 2022(expired)· nominal 20-yr term from priority

Inventors:Naoki Matsui Yasutaka Okada Koji Watari

C22C 38/14C21D 7/13C22C 38/04C22C 38/60C22C 38/00

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Abstract

The invention provides a low-carbon resulfurized free cutting steel containing no lead and at least comparable in machinability to the conventional leaded free cutting steels. The steel consists 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%, with the balance being Fe and impurities, the contents of Ti and S satisfying the relation (1) given below and the atomic ratio between Mn and S satisfying the relation (2) given below, and the steel containing MnS with Ti sulfide and/or Ti carbosulfide included therein: Ti(% by mass)/S(% by mass)<1 (1) Mn/S≧1 (2). The steel may further contain, in addition to the above components, one or more elements selected from the group consisting of Se, Te, Bi, Sn, Zr, Ca, Mg and rare earth elements and/or from the group consisting of Cu, Ni, Cr, Mo, V and Nb.

Claims

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What is claimed is:  
     
         1 . 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%, 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 and/or Ti carbosulfide included therein: 
       Ti(% by mass)/S(% by mass)&lt;1  (1)Mn/S≧1  (2). 
     
     
         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 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)&lt;1  (1)Mn/S≧1  (2). 
     
     
         3 . 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)&lt;1  (1)Mn/S≧1  (2). 
     
     
         4 . 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)&lt;1  (1)Mn/S≧1  (2). 
     
     
         5 . A low-carbon resulfurized free cutting steel according to any of  claims 1  to  4 , wherein the Si content is less than 0.1% by mass.

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