| Two kinds of dual phase steels which have different components were investigated in this paper. The relationship of technics, structure and capability of the Nb-Ti hot-rolled dual phase steel was analyzed. And the precipitation of (Nb,Ti)(C,N) was studied too. The main works and corresponding results as follows:1)The microstructure of the hot-rolled dual phase steel was observed by using optics microscope and electron microscope. The relationship of the three aspects was analyzed systematically connect with the technics and capability of the studied steel.2)For A steel, trough air-cooling plus water cooling reasonable two phases structure can be gained at high finish temperature ( 830～850℃) and reasonable coiling temperature (<250℃). This kind of dual phase steel has favorable integrative capability and the size of ferrite is only 45μm.3)B steel can't gained dual phase steel which has favorable integrative capability through two segments cooling pattern.4)The apperence of carbides and nitrides of Nb,Ti in dual phase steel was observed with transmission electron microscope by using carbon extranction replica technique. And the component was analyzed by using spectrum.5)Precipitation temperature of the second phase particle was calculated by using iterative method. The equilibrium dissolution temperature of TiN is higher than the others, and then is NbC. The precipitation of NbN and TiC are very hard.6)The redissolution of (Nb,Ti)(C,N) in dual phase steel was investigated. And find that Ti can come into ( NbxTi1-x)( CyN1-y) at very high temperature. (Ti,Nb)(C,N) phase with Ti may be the solidification core of Nb,Ti complicated compounds.
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