Research On TMCP Processes Of600MPa Grade Hot Rolled Dual Phase Wheel Steel

The objective of new generation light weight vehicle body is to reduce20%-30%of vehicle total mass, in order to attain the aim of saved resoures, reduced cost and protected environment. Dual phase steel becomes new type vehicle punched steel due to the merit of high tensile strength, low yieled ratio, high rate of work hardening and excellent elongation. At present, there are several enterprises who have the ability to produce600MPa hot rolled dual phase steel, generally, various alloying elements such as Cr, Mo, Nb and so on have been added to coil at the medium temperature. The article aims at the developing demand of one domestic steel company for dual phase steel, it improves the new alloying constituent and explores hot rolling process combined with domestic and overseas productive technology to produce the steel, which meet the requirement performance of production and reduce cost. The main work and conclusions are as follows:1) The alloy design project of C-Si-Mn-Mo has been adopted, the specific composition of the steel is0.08%～0.13%C,0.07%～0.09%Si,1.30%～1.80%Mn and0.06%～0.12%Mo.2) The stress-strain curve at different deformed temperatures and strain rates has been determined by single pass compression tests. The influence of three deformed parameters for curve has been analyzed. A mathermatical model has been chosen correctly to regress the flow stress.3) The deformed and undeformed austenite continuous cooling transformation curves have been drawn via MMS-300thermal modeling tests. The effect of different cooling rate on the evolution of microstructure has been investigated. The law of impact of deformation on the mechanism of phase transformation has been studied. The various phase transformation started temperature and critical cooling rate have been obtained at two kinds of conditions. The theory of TMCP has been established.4) Hot rolled test with Φ450hot mill in lab has been done. Two stage cooling(one is low temperature coiled,the other is middle temperature coiled) and continuous cooling pattern have been used. The mechanics property and microstructure of products have been analyse. The factors of hot rolled procees for property and microstructure have been discussed, It provides the optimum hot rolled procees in two ways5) The forming of cold bend, hole expansion and impact toughness test have been done, the factor of influencing the forming and impact toughness have been discussed.6) Two ways of optimum controlled rolling and cooling have been attained:two stage cooling(coiled in low temperature) and continuous cooling methods. The tensile strength exceeds600MPa, elongation surpasses25%, hole expansion rate reaches75%for trail steel. It has fine cold formation and impact toughness.The hot procees have provide a theoretical basis for industrial trail produce.