应用扫描电子显微镜及其动态拉伸台对高、中、低碳钢的拉伸形变过程，进行了全程跟踪观察，从微观的角度对碳钢的性能进行了探讨。结果表明，高碳钢的强、硬度主要取决于珠光体的片间距以及渗碳体的大小和分布。珠光体片层间距减小，铁素体、渗碳体变薄，相界面增多，高碳钢的强、硬度提高；中碳钢的强、硬度主要取决于珠光体团的直径、铁素体的大小和分布。较小、较弥散分布的珠光体、铁素体会使中碳钢的强度、硬度提高；低碳钢的力学性能主要取决于铁素体的晶粒大小，珠光体团的大小和分布对材料的力学性能也有一定的影响。铁素体的晶粒越小，珠光体团越小、分布越弥散，钢的强度、塑性越好。

The mechanical properties of low carbon steel, middle carbon steel and high carbon steel have been studied on internal microstructure by the scanning electron microscopy in-situ tensile test. The microstructure mechanism of their mechanical properties has been analyzed. The results are: the mechanical properties of the high carbon steel dependent on the size of pearlite lump and the distance between ferrite lamella and cemetite lamella and the cemetite size and distribution. The finer the pearlite lamella, the thinner the ferrite and the cemetite, the more the boundary between the ferrite and the cemetite, the higher the mechanical properties of the higher carbon steel. The mechanical properties of the middle carbon steel dependent on the size of ferrite grain and pearlite lump. The smaller the size of ferrite grain and pearlite lump and the more dispersed distribution of the paertite made the mechanical properties of the middle carbon steel increased. The mechanical properties of the low carbon steel dependent on the grain size of ferrite and was also affected by the peartite size and distribution. The smaller the size of ferrite grain and pearlite lump and the more dispersed distribution of the paertite, the higher the mechanical properties of the middle carbon steel.