Carbon Equivalent and Sour Service
Высокопрочные ветроустойчивые башни электропередачи – Исследования и разработки
январь 31, 2026Carbon Equivalent and Sour Service
3. Chemical Integrity: Carbon Equivalent and Sour Service
For subsea pipelines, weldability is paramount. To ensure the heat-affected zone (Азартный) does not become brittle, the Углеродный эквивалент (ЕС) is strictly limited.
We typically use the IIW Formula:
$$CE_{IIW} = C + \frac{Mn}{6} + \frac{Cr + Mo + V}{5} + \frac{Ni + Cu}{15}$$
For X65QO, $CE_{IIW}$ is usually kept below 0.39, ensuring that offshore welding can be performed with minimal preheating, speeding up the pipe-lay process.
Кроме того, because many offshore reservoirs contain $H_2S$, these pipes are often tested for HIC (Hydrogen Induced Cracking) а также SSCC (Sulfide Stress Corrosion Cracking). This requires extremely low sulfur levels ($\leq 0.002\%$) and calcium treatment for inclusion shape control (converting elongated sulfides into spherical shapes).
