Abstract：As a novel kind of low-cost structural materials， 700 MPa grade high strength low alloy hot rolled ferritic steel strip has been widely used in the construction machinery industry， such as pumps， cranes in recent years. In the current study， to understand the strengthening mechanism， a typical strip steel TS700MC was selected as experimental material. Tensile test and charpy impact test were used to evaluate the strength and the toughness， the microstructure was characterized by OM， SEM and TEM. The results showed that the yield strength， the tensile strength， the elongation and the charpy impact value at －40 ℃ of TS700MC were 715， 825 MPa， 18.5%， 104 J， respectively. The charpy fracture appearance transition temperature was lower than －40 ℃. Virtually fully ferritic microstructure was obtained， and the average grain size was approximately 3.4 μm. High-density dislocations existed in the microstructure. Lots of nano-sized (Ti，Mo，Nb)(C，N) particles precipitated along the dislocation and in the matrix. The high strength results from a combination of solid solution hardening (about 16%)， grain refinement hardening (about 38%)， precipitation and dislocation hardening (about 46%).
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2016, Vol. 51 
