Ce对FH40船板钢轧态组织及拉伸性能的影响

Effect of Ce on Rolling Microstructure and Tensile Properties of FH40 Shipbuilding Steel Plate

利用真空感应炉制备不同Ce含量的FH40实验钢,采用OM、SEM、TEM和EDS手段观察钢的轧态组织,并对其拉伸性能和断口形貌进行测试与分析,研究了Ce对FH40钢轧态组织以及拉伸性能的影响机制。结果表明,随着Ce含量从0增加到0.058%(质量分数,下同),钢的轧态组织得到细化,由多边形铁素体变为细小的等轴状铁素体,同时出现粒状贝氏体;含0.0273%Ce和0.058%Ce钢中分别产生了Ce-O-S+TiN和Ce-O-S复合夹杂物,并且分别诱发了4条和5条晶内针状铁表体(IAF)。含0.058%Ce实验钢的屈服强度、抗拉强度较基体钢分别提高了31、33 MPa。当Ce含量为0.0273%时实验钢的延伸率达到了22.8%。实验钢均表现为位错强化和第二相强化,基体钢中析出相主要是Nb-Ti的复合相,含0.058%Ce实验钢中主要是Nb-Ti-Ce的复合相,且更加弥散细小,位错密度更高;同时断口形貌更加均匀,韧窝由小而浅转变为大而深,使其在切应力的作用下更不易断裂,因而提高了钢材的抗拉强度。

FH40 experimental steel with different Ce contents was prepared by vacuum induction furnace.The rolling microstructure of the steel was observed by OM,SEM,TEM and EDS,and its tensile properties and fracture morphology were tested and analyzed.The influence mechanism of Ce on the rolling microstructure and tensile properties of FH40 steel was studied.The results show that with the increase of Ce content from 0 to 0.058 wt%,the rolling microstructure of the steel is refined.The rolling microstructure changes from polygonal ferrite to fine equiaxed ferrite,with the formation of granular bainite.The composite inclusions of Ce-O-S+Ti N and Ce-O-S are produced in the steel containing 0.0273 wt%Ce and 0.058 wt%Ce,with four and five pieces of intragranular acicular ferrite(IAF)induced,respectively.The yield strength and tensile strength of the experimental steel containing 0.058 wt%Ce are 31 MPa and 33 MPa higher than those of the experimental steel without Ce,respectively.The experimental steels show dislocation strengthening and second phase strengthening.The precipitates in the experimental steel without Ce are mainly the composite phase of Nb-Ti.Nb-Ti-Ce is the main composite phase in the experimental steel containing 0.058 wt%Ce,and it is more dispersive and finer with higher dislocation density.The fracture morphology is more uniform.The dimple becomes larger and deeper,which makes it more difficult to fracture under the action of shear stress,thus improving the tensile strength of steel.