简要叙述了关于钢强化机理的研究现状，用化学相分析+X射线小角散射、RTO方法及高分辨透射电镜对薄板坯连铸连轧钛微合金化高强耐候钢中纳米粒子的属性进行了综合分析。发现钛微合金化高强耐候钢中尺寸<36 nm的粒子，除纳米TiC以外，还存在大量的纳米Fe3C，其体积分数为同尺寸TiC体积分数的4.4倍，析出强化作用比纳米TiC粒子大，不可忽略；提出了钢的综合强化机理，指出对不同种类、不同尺寸的纳米析出粒子，应分别根据位错切割和位错绕过机理计算出析出强化贡献，然后与固溶强化和细晶强化贡献加和，求得钢的屈服强度；讨论了细晶强化与位错强化不能加和的原因以及相变对钢强度影响的表现形式， 对钛微合金化高强耐候钢屈服强度的理论计算与生产结果相符，实验钢 σ_s = 630~676 MPa，实际 σ_s=630~680 MPa。 简述了钢综合强化机理的应用情况，指出了有待进一步研究的科学问题。

This paper summarized the status of comprehensive strengthening mechanism of steel. By using chemical phase analysis, X-ray small-angle scattering, RTO and high-resolution TEM observation, the properties of nano-scale cementite precipitates in Ti micro-alloyed high strength weathering steels produced by thin slab continuous casting and rolling process were analyzed. Except nano-scale TiC, cementites precipitates less than 36 nm and high volume fraction were also found in Ti micro-alloyed high strength weathering steels.The volume fraction of cementite less than 36 nm is 4.4 times as much as that of TiC in the same size. Cementite with high volume fraction has stronger precipitation strengthening effect than that of nano-scale TiC, which can not be ignored.The precipitation strengthening contributions of nano-scale precipitates of different types and sizes should be calculated respectively according to the mechanisms of dislocation intersection and dislocation bypass, and then be added up with the contributions of solid solution strengthening and grain refinement strengthening.A formula for calculate the yield strength of low carbon steel is proposed, and the calculated yield strength considering the precipitation strengthening contributions of nano-scale precipitates and the comprehensive strengthening mechanism of steels matches the experimental results well. The calculated σ_s=630~676 MPa, while the examined σ_s=630~680 MPa. The reason for grain refinement strengthening can not directly plus dislocation strengthening and the performance form of phase transformation's influence on steel strength were debated.The applications for comprehensive strengthening theory were summarized, and several scientific questions for further study were put forward.