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试验研究了在贝氏体基体中形成针状铁素体,来改善高强度管线钢的综合机械性能,特别是低温韧性。为了研究轧制工艺参数对组织的影响,以及获得合适的轧钢条件,以保证强度和韧性的最佳结合,达到X80和X120的性能要求,首先运用Gleeble进行了热模拟,然后,根据热模拟的试验结果,进行了试验轧制。根据组织观察和性能分析,阐述了微观结构和力学性能的关系。结果表明:随着冷却速度的提高,上贝氏体的体积比增加,并且,通过控制冷却速度和终止冷却温度,可以控制各构成相的体积比,从而获得不同的强度级别;由于针状铁素体的有效晶粒尺寸小,贝氏体基体中针状铁素体的含量越多,上架能量(USE)越大,并且针状铁素体能降低韧脆转变温度(DBTT);初轧阶段采用大的压下率对组织细化有很大影响。
Experimental study of the formation of acicular ferrite in bainitic matrix to improve the overall mechanical properties of high strength steel, especially low temperature toughness. In order to study the influence of rolling process parameters on microstructure and obtain the proper rolling conditions to ensure the best combination of strength and toughness, the performance requirements of X80 and X120 are met. First, the thermal simulation is carried out by using Gleeble. Then, As a result of the test, test rolling was carried out. According to the microstructure observation and performance analysis, the relationship between microstructure and mechanical properties was expounded. The results show that the volume fraction of upper bainite increases with the increase of the cooling rate, and the volume ratio of each constituent phase can be controlled by controlling the cooling rate and cooling temperature. As the acicular iron The effective grain size of the ferrite is small. The more the acicular ferrite is in the bainite matrix, the larger the rack energy (USE) is, and the acicular ferrite can reduce the ductile-brittle transition temperature (DBTT) Using a large reduction rate on the organization has a great impact on thinning.