盐水泥浆中碳钢的腐蚀疲劳断裂

钻井液中钻具因受到各种作用应力，加上井下高温高压的腐蚀环境，使其易发生腐蚀疲劳断裂。为探讨钻具的断裂过程以期能找到有效的防护措施，实验室内建立了模拟试验装置。针对盐水泥浆中４５钢的腐蚀疲劳断裂行为，通过自制的旋转弯曲腐蚀疲劳试验机，模拟钻具的运转受力情况，研究了不同泥浆介质、应力、载荷频率和温度对４５钢腐蚀疲劳断裂行为的影响，并结合动态腐蚀试验和断口分析，讨论了各影响因素的作用。结果表明，盐水泥浆的ｐＨ值、Ｃｌ－含量等对４５钢的疲劳寿命有直接影响，腐蚀疲劳寿命与与局部腐蚀的程度大小有密切关系；随着加载频率的增大，４５钢的腐蚀疲劳寿命有较大提高；在１５～８０℃温度范围内，４５℃左右时４５钢的腐蚀疲劳寿命最短。

Corrosion Fatigue of Carbon Steel in Salts Drilling Fluids

Under load stresses and corrosion environment with high temperature and pressure, drill pipes occur corrosion fatigue crack easily in drilling mud. A simulated testing apparatus was used to study the crack process of drill pipes so as to find an efficient protection method in laboratory. Corrosion fatigue behaviors of steel 45 are studied using self-made rotary type bending corrosion fatigue testing apparatus in salt drilling fluids, as well the effect of some mechanics factors and medium factors, such as cyclic stress, load frequency, temperature, on the corrosion fatigue crack of steel 45 . Results showed that corrosion fatigue crack of steel45 was depended on the corrosion rate of steel 45,especially the extent of pitting corrosion. The corrosion fatigue life of steel 45 increased with the increase of load frequency. While temperature reached 45 C or so, the corrosion fatigue crack of steel 45 was the most quickly.