700 MPa级高强度低合金热轧铁素体钢带作为一类新型的低成本结构材料，在泵车、起重机等工程机械行业得到广泛应用。为了明确这类钢种的强化机制，选取典型热轧带钢TS700MC作为试验材料，采用拉伸试验、夏比冲击试验测定其强度和韧性，用OM、SEM、TEM表征其微观组织。结果表明，TS700MC的屈服强度和抗拉强度为715和825 MPa，伸长率为18.5%，－40℃的夏比冲击值为104 J，且韧脆转变温度不大于－40℃。微观组织接近于全铁素体，晶粒平均尺寸约为3.4μm，且含有高密度的位错。大量纳米级的(Ti，Nb，Mo)(C，N)粒子沿位错和晶内析出。高强度是固溶强化(约16%)，细晶强化(约38%)，析出强化和位错强化(约46%)等多种强化机制综合作用的结果。
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 elonga-tion 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 3.4μm. High-density dislocations existed in the microstructure. Lots of na-no-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 dislo-cation hardening (about 46%).
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