陰極防食下におけるラインパイプ用鋼の挙動
1981 年 67 巻 2 号 p. 372-381
詳細
1981 年 67 巻 2 号 p. 372-381
Hydrogen stress cracking (HSC) susceptibility of various line pipe steels was evaluated by means of a slow strain rate technique (SSRT) as well as a conventional static load technique (SLT). Effects of strain rate, temperature, pH, applied potential, applied cathodic current density and hardness on the HSC susceptibility were made clear. The results obtained are summarized as follows:
(1) The results obtained by SSRT were quite analogous to, but more quantitative than those obtained by SLT. SSRT was proved to be quite a pertinent technique to evaluate the HSC susceptibility of line pipe steels being classified into go or no-go categories.
(2) The HSC susceptibility depended on the strain rate with highest in the strain rate region of 10-6 and 10-7 sec-1 and decrease in the higher strain rate region.
(3) The HSC susceptibility depended on the applied potential increasing with cathodic polarization.
(4) The HSC susceptibility increased markedly with increasing current density of up to 2 mA/cm2, but was almost constant and highest in the region over 2 mA/cm2.
(5) The HSC susceptibility was not affected by pH in the pH range between 4 and 12, while increased markedly with decreasing pH values of less than 4.
(6) Hardness was a vital factor ihfluencing the HSC susceptibility of line pipe steels. The critical value, below which the steel would be free from HSC, for each line pipe steel was Hv=260 for API Spec 5LX-X65CR and QT, 265 for X60CR, 220 for X42 and 240 for JIS STPY-41.
