TC4钛合金钻杆在腐蚀条件下的力学性能研究

为研究适用于腐蚀环境下的钛合金钻杆材料，参照NACE和GB规范中的腐蚀要求和试验标准，首先对TC4钛合金试件进行腐蚀处理（设置未经腐蚀处理的对照组），然后进行拉伸、冲击和硬度试验，研究其在腐蚀条件下的综合力学性能. 结果表明:在NaCl、H₂S、CO₂、205 ℃条件下，TC4钛合金的拉伸性能下降不超过10%，冲击性能变化仅为0.33%，硬度下降3.21%，说明TC4钛合金具有出色的耐腐蚀性，在腐蚀条件下能够保持良好的综合力学性能. 以API规范中对钢钻杆材料的力学性能要求为指标，腐蚀处理后TC4钛合金的力学性能表现为屈服强度、拉伸强度及伸长率均不低于X级钢；冲击吸收功高于API对钢钻杆要求的62%（20 ℃）；硬度超过G级钢约37%，接近S级钢；故可将TC4钛合金应用于腐蚀性油气井钻杆中以避免或减轻钻杆腐蚀失效. 

Evaluation of Mechanical Properties of TC4 Titanium Alloy Drill Pipe in Corrosive Environment

In order to study the adaptability of titanium alloy drill pipe materials to corrosive environments, according to corrosion requirements and test standards in NACE and GB, several processes were carried out. Firstly, some TC4 titanium alloy specimens were corroded and a comparison group without corrosion treatment was set. And then a series of tensile, impact and hardness tests were carried out to study its comprehensive mechanical properties under corrosive conditions. The results show that under the corrosion conditions of NaCl, H₂S, CO₂ and 205 ℃, the tensile properties of TC4 titanium alloy decrease by no more than 10%, the impact performance changes by only 0.33%，and the hardness decreases by 3.21%, indicating that TC4 titanium alloy possesses high corrosive resistance, can maintain better comprehensive mechanical properties under corrosive conditions. Taking the requirements of steel drill pipe materials in the API as an index, the mechanical properties of TC4 after corrosion treatment are shown as follows, yield strength, tensile strength and elongation are not lower than that of X grade steel, impact absorption energy is 62% higher than that of API requirement (20 ℃), the hardness exceeds that of G grade steel by about 37%, close to that of S grade steel. Therefore, TC4 titanium alloy can be used in corrosive well drill pipes to avoid or reduce the corrosion failure of the drill pipes.