Steel for mechanical structures, method of hot forming of steel element and forged steel element manufactured in this way

摘要

The invention relates to a steel for mechanical construction, characterized in that its composition is, in percentages by weight: 0,35% ≦ c ≦ 1,2%; 0,10% ≦ mn ≦ 2,0%; 0,10% ≦ si ≦ 3,0%; traces ≦ cr ≦ 4,5%; traces ≦ mo ≦ 2,0%; traces ≦ ni ≦ 4,5%; traces ≦ v ≦ 0,5%; traces ≦ cu ≦ 3,5% with cu ≦ ni% + 0,6 if% if cu ≧ 0,5%; traces ≦ p ≦ 0,200, traces ≦ b ≦ 0,200%, traces ≤ sn ≤ 0,150%, traces ≤ as ≤ 0,100%, traces ≤ sb ≤ 0,150%, with 0,050% ≦ p% + bi% + sn% + as% + sb% ≦ 0,200%, traces ≦ al ≦ 0,060%; traces ≦ ca ≤ 0,050%; traces ≦ b ≦ 0,01%; traces ≦ s ≦ 0,200%; traces ≦ t e ≦ 0,020%; traces ≤ is ≦ 0,040%; traces ≦ pb ≦ 0,070%; traces ≦ nb ≦ 0,050%; traces ≦ ti ≦ 0,050%; the remainder being iron and impurities resulting from the élaboration.l' invention also relates to a method of putting in the form of a piece of steel, characterized in that: - it is provided by a steel billet of the above composition; - is heated, the billet at a temperature between the solidus and liquidus in order to obtain a liquid phase and a solid phase globular, and it performs a thixoforging of said bar in order to obtain said piece; - and the cooling of the said pièce.l' invention relates to a steel component thixoforged, characterized in that it has been manufactured by the above process.