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研究了基于Nb-Mo-Ti成分的大厚度高韧性X65~X80管线钢关键工艺控制因素。通过控制Nb、Ti含量和加热制度,优化轧制规程以细化粗轧板坯心部奥氏体晶粒和实现精轧后的完全动态再结晶。采用与轧制工艺和成分设计最佳配合的冷却工艺,可以得到心部细化的相变组织和弥散细小分布的析出物,改善了心部韧性。研制的基于Nb-Mo-Ti成分的X65~X80管线钢,可以满足APL 5L标准最大厚度32 mm,最低温度-20℃的落锤撕裂试验(DWTT)韧性要求。
The key process control factors of large thickness and high toughness X65 ~ X80 pipeline steel based on Nb-Mo-Ti composition were studied. By controlling the Nb, Ti content and heating regimes, the rolling schedule is optimized to refine austenite grains in the rough slab and achieve complete dynamic recrystallization after finish rolling. Adopting the cooling process which is best matched with the rolling process and composition design, the heart-thinned phase transformation structure and finely dispersed precipitates can be obtained and the heart toughness can be improved. The developed X65 ~ X80 pipeline steel based on Nb-Mo-Ti component can meet the requirement of DWTT toughness of APL 5L standard maximum thickness of 32 mm and minimum temperature of -20 ℃.