Analysis of cracking cause of acid gas post-cooler head

doi:10.13251/j.issn.0254-6051.2023.08.043

Abstract

Abstract: Bulges and cracks appeared in the inner wall of floating head of acid gas post-cooler in a natural gas purification plant. The causes of bulges and cracks were analyzed by means of macroscopic examination, chemical composition analysis, hardness test, metallographic examination, energy spectrum analysis, fracture analysis and EBSD test. The results show that the bulge and cracking of the inner wall of the head are hydrogen bulge (HB) and hydrogen-induced cracking (HIC). Since the microstructure of the head material (20g steel) is banded ferrite+pearlite along the rolling direction, with bainite and more MnS inclusions appearing at the position of 1/2 plate thickness caused by element segregation, and the service environment of the head contains wet H₂S medium which generates hydrogen after electrochemical reaction with the steel, then the hydrogen accumulates at the defects of 1/2 plate thickness, leading to bulge and cracking of the inner wall of the head.

Key words: 20g steel, wet H₂S environment, microstructure, MnS inclusion, hydrogen-induced cracking, bulge

CLC Number:

TG115

Liu Min, Lu Meipeng, Liu Jiachen, Gu Baolan, Guo Jing, Sun Yuejun, Song Ming. Analysis of cracking cause of acid gas post-cooler head[J]. Heat Treatment of Metals, 2023, 48(8): 265-271.

References

[1]贾爱林. 中国天然气开发技术进展及展望[J]. 天然气工业, 2018, 38(4): 77-86.
Jia Ailin. Progress and prospects of natural gas development technologies in China[J]. Natural Gas Industry, 2018, 38(4): 77-86.
[2]刘云旭. 低碳合金钢中带状组织的成因、危害和消除[J]. 金属热处理, 2000, 25(12): 1-3.
Liu Yunxu. Reason of formation, harmful effect and removal of band structure in low carbon alloy steel[J]. Heat Treatment of Metals, 2000, 25(12): 1-3.
[3]Alfons H M Krom, Bakker Ad. Hydrogen trapping models in steel[J]. Metallurgical and Materials Transactions A, 2000, 31(6): 1475-1482.
[4]Huang F, Li X G, Liu J, et al. Hydrogen-induced cracking susceptibility and hydrogen trapping efficiency of different microstructure X80 pipeline steel[J]. Journal of Materials Science, 2010, 46(3): 715-722.
[5]Elboujdaini M, Revie R W. Metallurgical factors in stress corrosion cracking (SCC) and hydrogen-induced cracking (HIC)[J]. Journal of Solid State Electrochemistry, 2009, 13(7): 1091-1099.
[6]Li Jing, Gao Xiuhua, Du Linxiu, et al. Relationship between microstructure and hydrogen induced cracking behavior in a low alloy pipeline steel[J]. Journal of Materials Science and Technology, 2017, 33(12): 1504-1512.
[7]Gyu Tae Park, Sung Ung Koh, Hwan Gyo Jung, et al. Effect of microstructure on the hydrogen trapping efficiency and hydrogen induced cracking of linepipe steel[J]. Corrosion Science, 2008, 50(7): 1865-1871.
[8]杨明, 马晓勇, 龙云, 等. 碳钢在湿硫化氢环境中的应力导向氢致开裂行为[J]. 腐蚀与防护, 2014, 35(12): 1226-1229.
Yang Ming, Ma Xiaoyong, Long Yun, et al. Stress oriented hydrogen induced cracking behavior of carbon steel in wet H₂S environment[J]. Corrosion and Protection, 2014, 35(12): 1226-1229.
[9]Du X S, Cao W B, Wang C D, et al. Effect of microstructures and inclusions on hydrogen-induced cracking and blistering of A537 steel[J]. Materials Science and Engineering A, 2015, 642: 181-186.
[10]Venegas V, Caleyo F, Baudin T, et al. On the role of crystallographic texture in mitigating hydrogen-induced cracking in pipeline steels[J]. Corrosion Science, 2011, 53(12): 4204-4212.
[11]Rodrigo de Carvalho Paes Loureiro, Beres Miloslav, Masoumi Mohammad, et al. The effect of pearlite morphology and crystallographic texture on environmentally assisted cracking failure[J]. Engineering Failure Analysis, 2021, 126: 105450.
[12]Mohtadi Bonab M A, Masoumi Mohammad, Szpunar J A. Failure analysis in API X70 pipeline steel in sour environment with an emphasis on fracture surfaces and crack propagation[J]. International Journal of Pressure Vessels and Piping, 2022, 195: 104600.
[13]MohammadMasoumi, Cleiton Carvalho Silva, Miloslav Béreš, et al. Role of crystallographic texture on the improvement of hydrogen-induced crack resistance in API 5L X70 pipeline steel[J]. International Journal of Hydrogen Energy, 2016, 42(2): 1318-1326.
[14]Mohtadi-Bonab M A, Eskandari M, Karimdadashi R, et al. Effect of different microstructural parameters on hydrogen induced cracking in an API X70 pipeline steel[J]. Metals and Materials International, 2017, 23(4): 726-735.
[15]Mohtadi-Bonab M A, Eskandari M. A focus on different factors affecting hydrogen induced cracking in oil and natural gas pipeline steel[J]. Engineering Failure Analysis, 2017, 79: 351-360.
[16]Pourazizi R, Mohtadi-Bonab M A, Szpunar J A. Role of texture and inclusions on the failure of an API X70 pipeline steel at different service environments[J]. Materials Characterization, 2020, 164: 110300.