冷却工艺和成分对X100管线钢组织与性能的影响

Effects of cooling process and chemical composition on microstructure and properties of X100 pipeline steel

研究了冷却工艺和化学成分对一种经济型X100钢的组织与力学性能的影响。结果表明,随着终冷温度从500~550℃降低至200~300℃,同时冷速从20℃/s提高至45℃/s,规定总延伸强度Rt0.5和抗拉强度提高,可以达到X100强度级别制管的性能要求。随着终冷温度的降低和冷速的提高,组织中板条贝氏体含量的增加是强度提高的原因。高终冷温度、低冷速时,钢中加入Mo、Cr可以增加板条贝氏体从而提高规定总延伸强度;低终冷温度、高冷速时,Mo、Cr对屈服强度的影响不明显。另外,低终冷温度、高冷速下获得的X100试验钢具有优异的冲击性能和DWTT性能,-40℃冲击吸收能量大于240 J,-30℃全壁厚试样DWTT剪切面积比大于85%。

Effects of cooling process and chemical composition on microstructure and mechanical properties of an economical X 100 pipeline steel were investigated .The results indicate that with the finish cooling temperature decreasing from 500-550 ℃ to 200-300 ℃ and the cooling rate rises from 20 ℃/s to 45 ℃/s, both the yield strength Rt0.5 and tensile strength of the experimental steels increase , which can satisfy the strength requirement for manufacturing the X 100 grade pipe .The volume fraction of lath bainite increases with decrease of finish cooling temperature and increase of cooling rate , which contributes to the improvement of strength .Under the high finish cooling temperature and low cooling rate , addition of Mo and Cr can effectively increase the volume fraction of lath bainite and thus improve the yield strength , while under the low finish cooling temperature and high cooling rate , addition of Mo and Cr plays little role in the variation of yield strength . Moreover , the X100 experimental steel produced with low finish cooling temperature and high cooling rate shows excellent impact property and DWTT property .The impact absorbing energy at -40℃is greater than 240 J and the DWTT shear area ratio of full-thickness specimen at -30 ℃surpasses 85%.