控制冷却对管线钢X65组织细化与性能的影响

Effect of Controlled Cooling on Microstructure Refinement and Mechanical Properties of Pipeline Steel X65

在实验室φ450热轧实验机上进行了微合金管线钢X65轧后控冷工艺的研究,以便为进一步工业化生产提供可靠的实验和理论依据.通过TEM分析可知,针状铁素体组织典型的形貌为非常微细的亚结构、高位错密度以及部分细板条铁素体,基体上弥散分布着M/A岛和渗碳体.实验表明,随卷取温度的降低和冷却速度的增加,显微组织明显细化,针状铁素体体积分数增加且力学性能得到提高.因而通过控制轧后冷却制度可以实现X65铁素体-少珠光体钢的柔性化轧制,细化组织,从而显著提高力学性能,达到甚至超过X70钢的级别.

The process of the controlled cooling after rolling was laboratorially studied on a φ450 rolling mill with the low-carbon low-alloy pipeline steel X65 as specimens to provide further an experimental and theoretical reference for actual industrial production. TEM images showed that the typical morphology of acicular ferrite is a very fine sub-structure with high dislocation density and part of ultra-fine ferrite, of which the small M/A islands and cementite are dispersing on the matrix. Experimental results showed that not only the microstructure is refined obviously but also the volume fraction of acicular ferrite increases and the mechanical properties are improved with decreasing coiling temperature or increasing cooling rate. The flexible rolling is thus available to the X65 ferrite-pearlite steel through controlled cooling after rolling, by which both its microstructure and mechanical properties can be improved so significantly even superior to the performance requirements for the Grade X70 pipeline steel.