710MPa级热轧高强钢的组织性能

用1750mm热连轧机组,通过控轧控冷工艺轧制了8mm厚的高强汽车板,利用光学显微镜、扫描电镜(SEM)、透射电子显微镜(TEM)等对其组织与性能进行了研究.结果表明,试验钢的组织主要为细晶铁素体和分布在铁素体晶界处的碳化物;试验钢的屈服强度为650MPa左右,抗拉强度达到740MPa左右,应变硬化指数和塑性应变比分别为0.12和0.80,达到了很好的强韧性匹配;细化的铁素体晶粒及尺寸细小的TiC析出物有效提高了试验钢的强度.

Microstructure and Mechanical Properties of 710 MPa Hot-Rolled High-Strength Steel

The high-strength 8 mm-thick autobody sheets were prepared via TMCP on a 1750 mm hot tandem mill. Then, the microstructure and mechanical properties of specimens of the sheet were tested and investigated by means of optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the microstructure of specimen is mainly composed of fine-grained ferrite and carbides distributed along the ferrite grain boundaries. The yield and tensile strengths of specimens are about 650 and 740 MPa, respectively, and the values of strain hardening exponent (n) and plastic strain ratio (r) are 0.12 and 0.80, respectively, thus providing well-matched strength with toughness. In short, the fine-grained ferrite and TiC nano-precipitates play an effective role in strengthening the steel.