Composition and method for the production of multiphase steels

摘要

The composition comprises, by weight C: 0.04-0.13 %; Mn: 1.0-2.1 %; Si: a maximum of 0.3 %; S: a maximum of 0.025 %; P: a maximum of 0.025 %; Al: 0.01-0.1 %; N: a maximum of 0.009 %; Nb: a maximum of 0.08 %; Ti: a maximum of 0.08 %; Mo: a maximum of 0.8 %; B: 0.0005-0.005 %; the remainder essentially consisting of iron and unavoidable impurities. The composition is suitable for manufacturing multiphase steels of various qualities such as high strength, weldable and high ductile steels, both coated or uncoated. The various end qualities can be produced from the same composition by only changing the thermomechanical treatment of the coil throughout the production process thereof. The thermomechanical treatment may be the following: (i) hot rolled band; (ii) cold rolled band and bell annealing; (iii) cold rolled band, bell annealing and hot dip galvanization, or (iv) cold rolled band and hot dip galvanization.