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通过调整O含量以及优化退火温度的方法,比较研究O含量不同的两种Gr.3厚壁管经不同温度退火的显微组织与力学性能。结果发现,两种低氧Gr.3管材加工态的显微组织均为伸长的α晶粒,其中O含量为0.06%的厚壁管材组织存在大量孪晶,而O含量为0.22%的管材组织中的孪晶数量很少。另外,O含量的增加不仅可以提高钛管的强度,降低塑性,还可以提高管材的再结晶温度。O含量为0.06%的厚壁管材在600℃退火已基本完全再结晶,但O含量为0.22%的管材在650℃退火才完全再结晶。经工艺优化,当O含量为0.22%且成品退火制度为650～700℃,90min时,Gr.3厚壁管的显微组织与力学性能完全满足ASTMB338标准。鉴于其屈服强度仅略高于标准要求,建议冷轧Gr.3厚壁管材的O含量不低于0.22%。
By adjusting the O content and optimizing the annealing temperature, the microstructure and mechanical properties of two kinds of Gr.3 thick-walled tubes annealed at different temperatures were comparatively studied. The results showed that the microstructures of the two kinds of low-oxygen Gr.3 tubes were all elongated α grains. The thick-walled tubes with 0.06% O contained a large number of twins and the O content was 0.22% The number of twins in the organization is small. In addition, the increase in O content can not only improve the strength of titanium tube, reduce plasticity, but also can improve the recrystallization temperature of the pipe. Thick-walled tubes with an O content of 0.06% have been substantially completely recrystallized by annealing at 600 ° C, but tubes with an O content of 0.22% were completely recrystallized by annealing at 650 ° C. After optimization of the process, the microstructure and mechanical properties of Gr.3 thick-walled tube completely meet the ASTMB338 standard when the O content is 0.22% and the finished annealing system is 650 ~ 700 ℃, 90min. In view of its yield strength is only slightly higher than the standard requirements, recommended cold-rolled Gr.3 thick-walled pipe O content of not less than 0.22%.