軋鋼製程及熱處理對油管用鋼氫引裂之影響

Effects of Rolling Processes and Heat Treatments for Linepipe Steels on Hydrogen Induced Cracking

氫引裂（HIC）是油管用鋼在含酸氣環境（主要為H2S）中使用常發生之破壞問題，良好的管線用鋼除需具備優良之機械性質外，如何提高其抗HIC性質也是相當重要的課題。本文主要改變不同控制軋延及正常軋延參數與後熱處理，來研究軋鋼製程及熱處理對鋼材抗HIC之影響。實驗方法包括浸泡試驗、氫滲透試驗及顯微組織分析。結果發現，所有製程中，抗HIC能力之排列順序分別為高溫淬火回火＞正常化＞正常軋延＞低溫淬火回火＞控制軋延＞正常軋延後水淬，造成彼此差異之主要原因與HIC之起始位置多寡有關。由氫擴散係數、氫滲透速率及氫捕集密度之數據，配合MnS介在物長寬比，將可預測氫脆發生之機率。

In environments containing sour gas, hydrogen induced cracking (HIC) was one of the most frequent fracture problems of a linepipe. Candidate steels for linepipes must have good corrosion resistance for HIC in addition to excellent mechanical property. The effects of different rolling processes and heat treatments for linepipe steels on HIC were investigated in this study. The experimental methods were performed including immersion test, hydrogen permeation test, and microstructure analysis. Results showed that the HIC resistant ability of steel from various manufractural processes was decreased by the following sequence: high temperature temper after quench, normalization, normal rolling, low temperature temper after quench, control rolling, and quench after normal rolling. The main reason was the variation of initiation sizes for HIC. According to the data of diffusivity, permeation rate, trapping density, and MnS inclusion aspect ratio, it is possible to predict the occurrence of hydrogen embrittlement.