Microstructural characterization of API 5L X65 and X70 steels manufactured by TMCP process
Luan Mayk Tôrres Costa, Gudson Nicolau de Melo, Nicolau Apoena Castro, Augusto José de Almeida Buschinelli
This work shows the microstructural characterization of API-5L X65 and X70 steels manufactured by the TMCP process. Images are obtained by optical microscopy (OM), scanning electron microscopy (FEG-SEM) and atomic force microscopy (AFM). Besides, the EBSD technique pointed out that both samples are presenting a refined quasi-polygonal ferrite matrix with eutectoid aggregates in the contours and vertices of ferritic grains. Moreover, a grain size of 8.4 µm is estimated for X70 and 10.6 µm for X65 steel. In the AFM images, eutectoid aggregates displayed higher relief concerning the ferrite matrix, and these microconstituents’ higher hardness causes them. This behavior is in agreement with the results of the Vickers Hardness test. EBSD showed that the quantity of microphases in the X65 is slightly higher than in the X70. However, the X70 steel presented higher high and low angle lengths due to the greater refinement and stronger cooling rates applied during processing. The Vickers test showed that the ferrite hardness is similar for both steels. This same behavior is verified for the Vickers test in eutectoid aggregates. It indicates that the higher strength of X70 sample is mainly a consequence of the finer microstructure.
1 Agência Nacional do Petróleo, Gás Natural e Biocombustíveis. Natural gas and biofuels statistical yearbook 2019. Rio de Janeiro: ANP; 2019.
2 Green KP, Jackson T. Safety in the transportation of oil and gas: pipelines or rail? Fraser Research Bulletin. 2015;1-14.
3 Hansen ME, Dursteler E. Pipeline, rail & trucks: economic, environmental, and safety impacts of transporting oil and gas in the U.S. USA: Strata; 2017.
4 Arora KS, Pandu SR, Shajan N, Pathak P, Shome M. Microstructure and impact toughness of reheated coarse grain heat affected zones of API X65 and API X80 linepipe steels. International Journal of Pressure Vessels and Piping. 2018;163:36-44.
5 Jorge LJ, Cândido VS, Silva ACR, Garcia FC Fo, Pereira AC, Luz FS, et al. Mechanical properties and microstructure of SMAW welded and thermically treated HSLA-80 steel. Journal of Materials Research and Technology. 2018;7(4):598-605.
6 Mohammadijoo M, Valloton J, Collins L, Henein H, Ivey DG. Characterization of martensite-austenite constituents and micro-hardness in intercritical reheated and coarse-grained heat affected zones of API X70 HSLA steel. Materials Characterization. 2018;142:321-331.
7 Montes OF, Garcés RS, Reyes RFA, Robledo PCZ, López FHE, Calderón FA. Comportamiento a la corrosión del acero API X70 soldado por el proceso de doble arco sumergido inmerso en diferentes medios corrosivos. Soldagem e Inspeção. 2016;21(2):172-184.
8 Biezma MV, Andrés MA, Agudo D, Briz E. Most fatal oil & gas pipeline accidents through history: a lessons learned approach. Piepelines & Corrosion & Risk Failure Analysis. 2020;110:104446.
9 Hillenbrand H, Kalwa C. High strength line pipe for project cost reduction. World pipelines. 2002;2(1):11.
10 American Petroleum Institute. Specification for line pipe – API specification 5L. 42nd ed. Washington: API; 2000.
11 Zakharova M. Risk analysis of accidents in reservoirs and gas pipelines for conditions in the arctic. Procedia Structural Integrity. 2019;20:108-112.
12 Rosado DB, Waele WD, Vanderschueren D, Hertelé S. Latest developments in mechanical properties and metallurgical features of high strength line pipe steels. Sustainable Construction and Design. 2013;4(1):1-10.
13 Hillenbrand HG, Gras M, Kalwa C. Development and production of high strength pipeline steels. In: Proceedings of the International Symposium Niobium; 2001; Orlando, USA. Orlando, Florida: Editora Europipe.
14 Grimpe F, Meimeth S, Heckmann CJ, Leissem A. Gehrke et al. Development, production and application of heavy plates in grades up to X120. In: Proceedings of the 1st International Conference on Super-High Strength Steels; 2005; Rome. Rome: Associazione Italiana di Metalurgia/Centro Sperimentali Materiali; 2005. p. 10.
15 Turani LO. A Tecnologia CLC de produção de chapas grossas aplicada à Indústria de Petróleo e Gás. In: Anais do II Seminário de Óleo, Gás e Energias Renováveis; 2010; Ipatinga, MG. Ipatinga, MG, Brazil: Editora Usiminas SA; 2010.
16 Mandal G, Ghosh SK, Chatterjee S. Effects of TMCP and QT on microstructure and properties of ultrahigh strength steel. Materials Today: Proceedings. 2019;18:5196-5201.
17 El-Shenawy E, Reda R. Optimization of TMCP strategy for microstructure refinement and flow-productivity characteristics enhancement of low carbon steel. J Mater Res Technol. 2019;8(3):2819-2831.
18 Igi S, Sakimoto T, Endo S. Effect of internal pressure on tensile strain capacity of X80 pipeline. Procedia Engineering. 2011;10:1451-1456.
19 Hillenbrand HG, Liessem A, Biermann K, Heckmann CJ, Schwinr V. Development of grade X120 pipe material for high - pressure gas transportation lines. In: Proceedings of the 4th International Conference on Pipeline Technology; 2004; UK. Beaconsfield, UK : Scientific Surveys Ltd.; 2004. p. 823-836.
20 Sohn SS, Han SY, Shin SY, Bae JH, Lee S. Analysis and estimation of the yield strength of API X70 and X80 linepipe steels by double-cycle simulation tests. Metals and Materials International. 2013;19:377-388.
21 Wang, C; Wu, X; Liu, J; Ning X. Transmission electron microscopy of martensite/austenite islands in pipeline steel X70. Materials Science and Engineering. 2006;438-440:267-271.
22 Bott IDS, De Souza LFG, Teixeira JCG, Rios PR. High-strength steel development for pipelines: A Brazilian perspect. Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. 2005;36(2):443-454.
23 Bonnevie E, Ferrière G, Ikhlef A, Kaplan D, Orain J. Morphological aspects of martensite-austenite constituents in intercritical and coarse grain heat affected zones of structural steels. Materials Science and Engineering. 2004;385;1-2:352-335.