本发明公开了一种适用低温的X80大口径厚壁直缝埋弧焊管及其制造方法，焊管母材化学组成按照质量百分比为C：0 .04～0 .08％、Si：0 .15～0 .30％、Mn：1 .60～1 .85％、S：≤0 .004％、P：≤0 .010％、Ni：0 .15～0 .30％、Cr：0～0 .30％、Cu：0 .1～0 .3％、N b ：0 .0 5～0 .1 0％、V ：0 .0 0 5～0 .04％、Ti：0 .015～0 .03％、Mo：0 .10～0 .35％、Al：0 .02～0 .05％、N：≤0 .008％、B：0 .0003～0 .0005％，制造方法包括：按照所上述化学组成的质量百分比制备热轧钢板，钢板超声波检验、铣边、预弯边、JCO成型、预焊、内焊、外焊、焊缝X射线检测、钢管扩径、静水压试验、焊缝超声波检测、管端X射线检测、倒棱、管端磁粉检测、外观质量检查。本发明的焊管焊接接头具有良好的低温韧性，可以在制管后不对焊管进行热处理的前提下，直接在-45℃及更低温度下使用。

The invention discloses an X80 large-caliber thick wall longitudinal submerged arc welded pipe suitable for low temperature and a manufacturing method thereof. The chemical composition of the base material of the welded pipe is C: 0.04-0.08%, Si: 0.15-0.30%, Mn: 1.60-1.85%, S: ≤ 0.004%, P: ≤0 010%, Ni: 015 ~ 0 30%, Cr: 0 ~ 0 30%, Cu: 01 ~ 0 3%, N B: 0 05 ~ 0 0%, V: 0 05 ~ 0 04%, Ti: 015 ~ 0 03%, Mo: 0.10 ~ 0. 35%, Al: 0.02 ~ 0. 05%, N：≤0 .008％、B：0 .0003～0 .0005％，Manufacturing method includes: according to the quality of the chemical composition of the percentage of preparation of hot rolled steel plate, steel plate ultrasonic inspection, milling, bending side, JCO forming, welding, welding, welding, welding seam X-ray detection, steel tube expander, hydrostatic test, weld ultrasonic testing and X-ray detection tube, chamfering, tube end magnetic particle testing, the appearance quality inspection. The welded joint of the welded pipe of the invention has good low-temperature toughness and can be directly used at -45℃ or lower temperature without heat treatment of the welded pipe after making the pipe.