Lead-free steel for the fabrication of machine structures with a specific composition in which the useful calcium content is governed by a relationship between the calcium and oxygen contents

摘要

Steel for the fabrication of machine structures contains: (a) C : 0.1 - 0.6 %; (b) Si : 0.01 - 2.0 %; (c) Mn : 0.2 - 2.0 %; (d) S : 0.005 - 0.20 %; (e) P : 0.1 % or less; (f) Ca : 0.0001 - 0.01 %; (g) N : 0.001 - 0.02 %; (h) Al : 0.1 % or less; (i) Fe and impurities. The useful calcium concentration is defined by a relationship between the calcium and oxygen contents: (Ca)e = t.(Ca) - (t.(O)/(O)ox) asterisk (Ca)ox where (i) (Ca)e is the concentration of useful Ca in ppm; (ii) T.(Ca) is Ca content in ppm; (iii) T.(O) is the oxygen content in ppm; (iv) (O)ox is the oxygen content in the oxide inclusions; (v) (Ca)ox is the Ca content in the oxide inclusions; (vi) is equal or less than 5 ppm. An Independent claim is also included for a method for the preparation of this steel.