国际上X80级别螺旋焊管的钢板厚度均未达到18.4mm。对如此极限规格和高性能要求,管线钢的合金设计、轧制及冷却工艺参数及其对组织、性能的影响等均需全面研究。

The thickness of the steel plate of the X80 grade spiral welded pipe is not up to 18.4mm. It is necessary to study the alloy design, rolling and cooling process parameters and their effects on the microstructure and properties of pipeline steel.

一般来说,热连轧过程的物理冶金过程及现象与平板轧制有所不同,X80热轧卷板管线钢的成分设计思路和工艺也有其特点。首先,为了保证低温冲击韧性即DWTT性能,C含量应在0.07%(质量分数)以下,然而在该成分范围,C含量的变化对屈服强度的影响需要认识;研究表明,低C2Mn2Nb+管线钢添加Mo,可降低中温转变温度,在较低冷却速度下得到针状铁素体和贝氏体组织,但有必要通过工业轧制试验确定Mo的最佳含量并进一步明确Mo的作用;当然,热连轧工艺对组织和性能的影响也应通过工业试验予以揭示,最终得到影响高性能管线钢组织和性能的工艺因素。

Generally speaking, the physical metallurgical process and phenomena of the hot rolling process are different from those of the plate rolling. The design ideas and processes of the X80 hot rolled coil pipe steel also have their own characteristics. First of all, in order to ensure the low temperature impact toughness of DWTT performance, the content of C in 0.07% (mass fraction), however in the composition range, the change of C content requires understanding of the impact of yield strength; research shows that low C2Mn2Nb+ pipeline steel with Mo, can reduce the temperature change in temperature, low cooling speed are acicular ferrite and bainite, but it is necessary to determine the optimum content of Mo through the industrial rolling test and further clarify the role of Mo; of course, influence of hot rolling process on Microstructure and mechanical properties should also be revealed through the industrial test, finally obtain process factors affecting the microstructure and properties of high performance pipeline.

增加C含量会影响MA岛的数量和形态,通过冷却控制可得到细小而弥散的MA岛。而在低碳范围,C含量的增加并不是影响屈服强度的主要原因。添加质量分数为0.19%～0.25%的Mo,通过调整精轧工艺,能够达到X80的强度要求;此外,添加Mo对抑制精轧时的动态再结晶有利。热卷板的精轧开轧温度应该控制在960℃以下,同时要控制压下量,防止过大的应变积累,可避免静态和动态再结晶的发生,实现平均流变应力的平稳积累,确保达到X80的强度、韧性和DWTT等性能的要求。

Increasing the content of C can affect the quantity and morphology of MA Island, and the small and dispersed MA island can be obtained by cooling control. In the low carbon range, the increase of C content is not the main cause of yield strength. Adding the mass fraction of 0.19% to, the strength of X80 can be achieved by adjusting the finishing process. In addition, the addition of Mo is beneficial to the dynamic recrystallization during the finishing process of Mo. Hot rolled plate finishing rolling temperature should be controlled at 960 DEG C, at the same time to control the amount of pressure, to prevent excessive strain accumulation, can prevent the occurrence of static and dynamic recrystallization, realize the steady accumulation of mean flow stress, ensure X80 strength, toughness and DWTT performance requirements.