高铌X80管线钢的组织和性能

基于低C-Si-Mn加0.10%Nb而不加Mo的合金化设计,用高温轧制工艺(HTP,hightemperature processing)在实验室制得API X80级别管线钢.本次试验确定的主要技术参数为:精轧终轧温度830~850℃,终冷温度500~550℃,冷速25~28℃/s,精轧总压下率不小于75%.得到的组织以针状铁素体为主,加少量块状铁素体和粒状贝氏体,并在晶界分布有岛状组织.对冲击断口的金相、SEM(scanning electronmicroscopy)和EDS(energy dispersion scanner)观察发现脆性第二相粒子和原始奥氏体晶界是该管线钢的主要裂纹源.因...

Microstructure and Mechanical Properties of High Niobium X80 Pipeline Steel

The low carbon-silicon-manganese alloyed billets with 0.10% niobium instead of molybdenum were rolled to be the X80 pipeline steel via HTP (high temperature processing) in lab, of which all the mechanical properties came up to the standard API Spec 5 L. The main parameters in rolling schedule were as follows: finishing temperature 830~850°C; end cooling temperature 500~550°C, cooling rate 25~28°C/sec; total percent reduction in finish rolling not less than 75%. It was found that the microstructure of the steel plate thus rolled is mainly composed of acicular ferrite with small parts of massive ferrite and granular bainite, and the island structure is found on grain boundary. Such a structure can provide high tensile strength and impact toughness. Metalloscopy, SEM and EDS were applied to observing the impact fracture and it was found that the brittle 2nd-phase particles and prior austenite grain boundaries are the main cracking sources. So, controlling the brittle 2nd-phase particles and avoiding the prior austenite grain boundaries will improve the toughness of the pipeline steel efficiently.