HIGH-STRENGTH AIR-HARDENING MULTI-PHASE STEEL COMPRISING OUTSTANDING PROCESSING PROPERTIES AND METHOD FOR THE PRODUCTION OF A STEEL STRIP FROM SAID STEEL

본 발명은 청구항 1에서 한정된 조성으로 구성되고, 750 Mpa의 최소 인장 강도를 갖고, 우수한 가공 특성을 갖는 공강도 공기 경화 다상 강에 관한 것으로서, 상기 강으로부터 핫 스트립 또는 콜드 스트립의 연속 어닐링에서 가능한 넓은 공정 윈도우를 고려하여, 제조된 스트립 두께에 따라 Mn+Si+Cr+Mo의 총 함량은 다음과 같이 조절된다: 1.00 mm 이하에서, Mn+Si+Cr+Mo는 2.450 내지 2.800 중량%; 1.00 초과 2.00 mm 이하에서, Mn+Si+Cr+Mo는 2.600 내지 3.150 중량%; 2.00 mm를 초과하면, Mn+Si+Cr+Mo는 3.000 내지 3.450 중량%. A high-strength air-hardenable multiphase steel having minimal tensile strengths in a non air hardened state of 750 MPa and excellent processing properties includes the following elements in % by weight: C≧0.075 to ≦0.115; Si≧0.600 to ≦0.750; Mn≧1.000 to ≦1.950; Cr≧0.200 to ≦0.600; Al≧0.010 to ≦0.060; N≧0.0020 to ≦0.0120; S≦0.0030; Mo≧0.0200; Nb≧0.005 to ≦0.040; Ti≧0.005 to ≦0.030; B≧0.0005 to ≦0.0030; Ca≧0.0005 to ≦0.0060; Cu≦0.050; Ni≦0.050; remainder iron, including usual steel accompanying smelting related impurities, wherein for a widest possible process window during continuous annealing of hot strips or cold strips made from the steel a sum content of M+Si+Cr+Mo in the steel strips is a function of a thickness of the steel strips according to the following relationship: for strip thicknesses of up to 1.00 mm the sum content of M+Si+Cr+Mo is ≧2.450 and ≦2.800%, for strip thicknesses of over 1.00 to 2.00 mm the sum of Mn+Si+Cr+Mo is ≧2.600 and ≦3.150%, and for strip thicknesses of over 2.00 mm the sum of Mn+Si+Cr+Mo is ≧3.000 and ≦3.450%.