Effect of post-processing annealing treatments on microstructure development and hydrogen embrittlement in API 5L X70 pipeline steel
| Autor: | Enyinnaya Ohaeri, Joseph Omale, K. M. Mostafijur Rahman, Jerzy A. Szpunar |
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| Rok vydání: | 2020 |
| Předmět: |
010302 applied physics
Materials science Annealing (metallurgy) Hydrogen damage Mechanical Engineering Metallurgy 02 engineering and technology 021001 nanoscience & nanotechnology Condensed Matter Physics Microstructure 01 natural sciences Mechanics of Materials 0103 physical sciences Ultimate tensile strength Thermomechanical processing General Materials Science Tempering 0210 nano-technology Embrittlement Hydrogen embrittlement |
| Zdroj: | Materials Characterization. 161:110124 |
| ISSN: | 1044-5803 |
| Popis: | The mechanical properties of steels are strongly influenced by microstructure and texture developed during thermomechanical processing. Here, different annealing treatments have been performed on pipeline steel at inter-critical temperatures. The aim of this study is to relate hydrogen embrittlement behavior to the microstructural characteristics obtained through one-step, and two-step annealing treatments. Similar grain orientation distributions were observed after the initial hot rolling and the two-step annealing procedures. However, in the later process a dual-phase (i.e. ferrite-martensite) structure was formed; unlike in the starting material where only segregated patches of martensite were observed within a ferritic microstructure. The one-step treated steel was comprised of relatively large and primarily ferrite grains. As a result, the preliminary processing revealed the highest strength, with reduced ductility. The one-step treatment lowered strength and ductility. Although the two-step treated steel showed the lowest strength, it was the most ductile with improved resistance to hydrogen embrittlement. The tempering operation introduced in the two-step process created minimal strain and tempered martensite inside the steel. This reduced the tendency for hydrogen damage. A direct relationship was established between high tensile strength and increased embrittlement risks. Lowering the strength and hardness through double heat treatment cycles delayed the onset of cracking after pre-hydrogen charging. |
| Databáze: | OpenAIRE |
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