6 mm低温压力容器钢的开发及组织性能研究

DEVELOPMENT AND MICROSTRUCTURE OF 6 mm LOW-TEMPERATURE PRESSURE VESSEL STEEL

采用低C和Nb-Ti微合金化的成分设计,平轧+卷轧的轧制方式生产了6 mm低温压力容器钢,并使用光学电子显微镜、拉伸力学和低温冲击实验等手段,研究了不同工艺条件下钢的显微组织、拉伸力学性能和-40℃低温冲击韧性随生产工艺的变化情况。结果显示:控轧工艺生产的钢板为多边形铁素体+少量珠光体组织,控冷工艺的钢板为多边形铁素体+粒状贝氏体+少量珠光体的复合组织,均没有带状组织亦没有出现纵向轧制带来的各向异性的变形带组织。与空冷工艺相比,轧后采用控冷工艺的钢板因出现了强化相的贝氏体组织,强度提高了40~60 MPa;采用控轧工艺的钢板晶粒尺寸明显小于不控轧工艺的钢板,-40℃低温冲击韧性明显优于未控轧工艺,提高到了60 J以上。采用粗轧+精轧+卷轧+水冷的3阶段控轧控冷生产模式,终轧温度870℃,终冷温度630℃生产的6 mm低温压力容器钢为多边形铁素体+粒状贝氏体+少量珠光体的复合组织,钢板综合力学性能最好。

6 mm low-temperature pressure vessel steel was manufactured through flat rolling combined with roll milling employing a low-C content along with Nb-Ti microalloying design.Optical electron microscopy,tensile testing methods as well as experiments on low temperature impact toughness were utilized to investigate its microstructure variations under diverse processing conditions.Results indicate that under controlled rolled processing conditions,resulting in a polygonal ferrite plus limited pearlite composition for one type,while another type achieved via controlled cooling exhibited a combination comprising polygonal ferrite alongside granular bainite plus some pearlite-without any evidence of band or anisotropic deformation structures induced from longitudinal milling processes.In comparison to air-cooled procedures,post-milling strength for plates subjected to controlled cooling experienced an increase ranging between 40~60 MPa owing to reinforced phase bainitic structures.Furthermore,grain sizes for plates processed via control rolled techniques were notably smaller compared to those lacking such controls;additionally,impact toughness at-40℃significantly surpassed non-controlled counterparts-exceeding values greater than 60 J.Employing rough-rolling followed by fine milling then roll milling coupled with three-stage water-cooled control during production resulted in final temperatures reaching 870℃during roller operations and 630℃during subsequent cooling stages.The resultant product-a composite structured material consisting primarily of polygonal ferrites complemented by granular bainites alongside minor amounts of pearlite-exhibited superior overall mechanical properties.