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试验钢采用低碳Nb、Ti、Ni、Cu、Mo等合金化设计理念进行X100管线钢化学成分设计,用真空感应电炉冶炼,并经试验轧机TMCP工艺控制轧制,轧后弛豫并在机后快速冷却线中进行快速冷却。冷却后采用显微分析方法和力学性能测试等手段研究终冷温度对试验钢微观组织和性能的影响。结果表明:随着终冷温度的降低试验钢显微组织的变化规律是由多边形铁素体向准多边形铁素体、粒状贝氏体、贝氏体铁素体、马氏体型转变。在418℃时出现板条状贝氏体组织且随着终冷温度降低,组织中板条状贝氏体的含量增加,贝氏体板条束的直径变小板条间距变窄,提高了试验钢的强度和韧性指标。301℃时出现马氏体组织,试验钢的强韧性有所降低。未发现终冷温度对原始奥氏体晶粒尺寸有影响,因为影响试验钢原始奥氏体晶粒度的主要因素为控轧工艺。
The test steel adopts the alloying design concept of low carbon Nb, Ti, Ni, Cu, Mo, etc. to design chemical composition of X100 pipeline steel, smelting with vacuum induction electric furnace and controlled by TMCP process of rolling mill. After rolling and relaxation, After rapid cooling line for rapid cooling. After cooling, microscopic analysis and mechanical properties test were used to study the effect of final cooling temperature on microstructure and properties of test steel. The results show that the microstructure of the test steel changes from polygonal ferrite to quasi-polygonal ferrite, granular bainite, bainitic ferrite and martensite with the decrease of the final cooling temperature. At 418 ℃, lath-like bainite appeared and with the decreasing of the final cooling temperature, the content of lath-shaped bainite in the tissue increased and the diameter of the bainite lath became smaller and the spacing of laths increased, Test steel strength and toughness indicators. The martensite appeared at 301 ℃, the toughness of the test steel decreased. No final cooling temperature was found to have an effect on the original austenite grain size because the primary factor that affects the original austenite grain size of the test steel is the controlled rolling process.