薄壁大口径Gr12钛合金超长无缝管生产工艺的研究

从Gr12钛合金铸锭的杂质含量的变化对管材加工性能的影响、不同温区斜轧穿孔加热速度对管材表面氧化程度的影响、三辊冷轧最佳轧制速度的选择及成品管材最佳矫直方式的确定等4个方面，研究了薄壁大口径Gr12钛合金超长无缝管的生产工艺。结果表明，严格控制Gr12钛合金铸锭的化学成分，使其N≤0．01％，C≤0．03％，H≤0．005％，Fe≤0．08％，O≤0．08％，可保证该合金的冷加工性能，轧出薄壁大口径超长无缝管；斜轧穿孔加热时不同的温区应选择不同的加热速度，低于650℃，氧化层较致密，氧化速度较慢，氧和氮不容易被吸入，升温速度要慢，在5～5．5℃／min，在650-820℃，氧化层开始疏松，氧化速度加快，氧、氮较容易被吸入，升温速度要稍快些，在6．8—7．2℃／min；在820℃以上，氧化层更为疏松，氧化速度更快，氧和氮吸入更容易，表面将更氧化严重，升温速度进一步提高，在7．6～8．5℃／min，避免管材严重氧化；三辊冷轧的合适的轧制速度应为60～70r／min；成品管最佳矫直方式是先进行预平整，使其不直度∠2mm／m，再在矫直机上进行精矫，这样不会矫凹或成椭圆形。

Preparation of Extra-long Seamless Gr12 Titanium Alloy Tube with Large Diameter and Thin Wall

The process of production for extra-long seamless Gr12 tuhe with large diameter and thin wall was investigated through analyses in four respects which is the effect of impurity content on the processing performance of the tube, the effect of the heating rate in different area during pyramidal rolling perforation on the surface oxidation of the tube, selection of optimum rolling speed for cold rolling with three roller, and defining optimum straightening way for finished tube. The results show that when the chemical composition of the Gr12 titanium alloy ingot is controlled into N≤0.01%, C≤0.03%, H≤0.005%, Fe≤0.08%, O≤0.08%, the tube with excellent properties can be obtained. During pyramidal rolling perforation, at the temperature lower than 650℃ and heating rate of 5- 5.5 ℃/min the compact oxide layer can be attained, which will protect the titanium tube from oxidation and nitridation; at the temperature range of 650-820 ℃ the oxide layer becomes to loose, which accelerates oxidation of Gr12 tube; at the ,temperature higher than 820 ℃ and heating rate of 6.8-7.2 ℃/min the oxide layer is more loose, which leads to serious oxidation of the tube surface; continuously increasing the heating rate to 7.6-8.5 ℃/min can avoid serious oxidation of the tube. In order to obtain high quality tube, the suitable rolling speed for cold rolling should be 60-70 r/min; the optimum straightening way is as follows： smoothing the tube with incline ∠ 2 mm/m first, then straightening on the straightener exactly.