Ramazan TÜTÜK, Mustafa Merih ARIKAN, Eyüp Sabri KAYALI

Effect of Reduction Ratio Below Austenite Recrystallization Stop Temperature on Mechanical Properties of an API X70M PSL2 Line Pipe Steel

Steel grades having high toughness and high strength are required for line pipes since gas and oil should be transported through them at high pressures. Thermo-mechanically controlled rolling processes are used for increasing both toughness and strength at low temperatures since the line pipes are exposed to harsh climatic conditions at full length and rather severe service conditions. Charpy, DWTT and tensile tests were conducted to determine of mechanical properties and measured toughness values were evaluated considering various criteria in this study. Fractured surfaces were examined by means of SEM to distinguish the ductile and brittle fracture areas. Thermo-mechanical rolling trials were performed at the temperature below the non-recrystallization temperature of austenite on an API X70M PSL2 grade steel, to increase the strength without sacrificing the toughness. Different reduction ratios between 60,7% and 72,8% were utilized and the effect of reduction ratios on mechanical properties and microstructures were investigated during the trials. It was observed that final grain size decreased and strength and toughness increased with increasing reduction ratios.

PDF

___

W. Yan, W. Sha, L. Zhu, Y. Shan and K.Yang, “Delamination fracture related to tempering in a high-strength low-alloy steel”, Metall. Mater. Trans. A, 41A, pp. 159-171, 2010.

S. Vervynckt, K. Verbeken, P. Thibaux, M. Liebeherr and Y. Houbaert, “Austenite recrystallization-precipitation interaction in niobium microalloyed steels”, ISIJ Int., 49, pp. 911-920, 2009.

B. Hwang, S. Lee, Y.M. Kim, N.J. Kim, J.Y. Yoo and C.S. Woo, “Analysis of abnormal fracture occurring during dropweight tear rest of high-toughness line-pipe steel”, Mater. Sci. Eng. A, 368, pp. 18-27, 2004.

J. Zhang, W. Sun and H. Sun, “Mechanical properties and microstructure of X120 grade high strength pipeline steel”, Journal of J. Iron Steel Int., 17(10) pp. 63-67, 2010.

S. Y. Shin, B. Hwang, S. Lee, N. J. Kim and S. S. Ahn, “Correlation of microstructure and Charpy impact properties in API X70 and X80 line-pipe steels”, Mater. Sci. Eng. A, 458, pp. 281-289, 2007.

B. Hwang, S. Lee, Y. M. Kim and N. J. Kim, “Correlation of rolling condition, microstructure, and low-temperature toughness of X70 pipeline steels”, Metall. Mater. Trans. A, 36A, pp. 1793-1805, 2005.

M. Kang, H. Kim, S. Lee and S. Y. Shin, “Effects of dynamic strain hardening exponent on abnormal cleavage fracture occurring during drop weight tear test of API X70 and X80 linepipe steels”, Metall. Mater. Trans. A, 45A, pp. 682-697, 2014.

H. K. Sung, S. S. Sohn, S. Y. Shin, S. Lee, N. J. Kim, S. H. Chon and J. Y. Yoo, “Effects of finish rolling temperature on inverse fracture occurring during drop weight tear test of API X80 pipeline steels”, Mater. Sci. Eng. A, 541, pp. 181-189, 2012.

S. S. Sohn, S. Y. Han, J. Bae, H. S. Kim and S. Lee, “Effects of microstructure and pipe forming strain on yield strength before and after spiral pipe forming of API X70 and X80 linepipe steel sheets”, Mater. Sci. Eng. A, 573, pp. 18-26, 2013.

V. C. Olalla, V. Bliznuk, N. Sanchez, P. Thibaux, L. A. I. Kestens and R. H. Petrov, “Analysis of strengthening mechanisms in pipeline steels”, Mater. Sci. Eng. A, 604, pp. 46-56, 2014.

A. A. Shahrani, N. Yazdipour, A. D. Manshadi and A. A. Gazder, “The effect of processing parameters on the dynamic recrystallization behavior of API-X70 pipeline steel”, Mater. Sci. Eng. A, 570, pp. 70-81, 2013.

Y. M. Kim, S. K. Kim, Y. J. Lim and N. J. Kim, “Effect of microstructure on the yield ratio and low temperature toughness of linepipe steels”, ISIJ Int., 42, pp. 1571- 1577, 2002.

C. P. Reip, S. Shanmugam and R. D. K. Misra, “High strength microalloyed CMn(V-Nb-Ti) and CMn(V-Nb) pipeline steels processed through CSP thin-slab technology: microstructure, precipitation and mechanical properties”, Mater. Sci. Eng. A, 424, pp. 307-317, 2006.

I. D. S. Bott, L. F. G. Souza, J. C. G. Teixeira and P. R. Rios, “High-strength steel development for pipelines: a Brazilian perspective”, Metall. Mater. Trans. A, 36A, pp. 443-454, 2005.

S. H. Hashemi and D. Mohammadyani, “Characterization of weldment hardness, impact energy and microstructure in API X65 steel”, Int. J. Pressure Vessels Piping, 98, pp. 8-15, 2012.

G. J. Baczynski, J. J. Jonas and L. E. Collins, “The influence of rolling practice on notch toughness and texture development in high-strength linepipe”, Metall. Mater. Trans. A, 30A, pp. 3045- 3054, 1999.

Specification for line pipe, API specification 5L, forty-fifth edition, December, American Petroleum Institute, 2012.

D. Clover, B. Kinsella, B. Pejcic and R. D. Marco, “The influence of microstructure on the corrosion rate of various carbon steels”, J. App. Electrochem., 35, pp. 139-149, 2005.

P. Korczak, “Influence of controlled rolling condition on microstructure and mechanical properties of low carbon micro-alloyed steels”, J. Mater. Process. Technol., 157- 158, pp. 553-556, 2004.

R. Barbosa, F. Boratto, S. Yue and J. J. Jonas, “The influence of chemical composition on the recrystallization behavior of microalloyed steels”, Process. Microstruct. Prop. HSLA Steels, pp. 51-61, 1988.

D. Q. Bai, S. Yue, W. P. Sun and J. J. Jonas, “Effect of deformation parameters on the no-crystallization temperature in Nbbearing steels”, Metall. Mater. Trans. A, 24, pp. 2151-2159, 1993.

D. Q. Bai, R. L. Bodnar, J. Ward, J. Dorricott and S. Sanders, “Development of discrete X80 line pipe plate at SSAB Americas”, International Symposium on the Recent Developments in Plate Steels, pp. 13-22, 2011.

F. Fletcher, “Meta-analysis of Tnr measurements: determining new empirical models based on composition and strain”, Austenite Processing Symposium, pp. 1- 14, 2008.

S. Y. Nastich, S. V. Soya, A. A. Efimov, M. A. Molstov and I. S. Vasil’ev, “Accelerated strip cooling to form ferritic-bainitic microstructure in low-alloy X70 steel strip”, Steel in Translation, 42, pp. 357-364, 2012.

Y. D. Morozov, E. A. Goli-Oglu, S. Y. Nastich, S. V. Denisov and P. A. Stekanov, “Thermomechanical treatment of microalloyed low-carbon steel at a 5000 mill for the production of cold-resistant thick strip”, Steel in Translation, 42, pp. 171-176, 2012.

S. Y. Nastich, N. V. Filatov, Y. D. Morozov, I. V. Lyasotskii and E. V. Shul’ga, “Structuring and deposition of nanoparticles in X70 steel during coiling and subsequent cooling”, Steel in Translation, 39, pp. 814-819, 2009.

P. Korczak, “Modeling of steel microstructure evolution during thermomechanical rolling of plate for conveying pipes”, J. Mater. Process. Technol., 153- 154, pp. 432-435, 2004.

Y. Kim, S. Y. Shin, Y. G. Kim and N. J. Kim, “Effects of strain rate and test temperature on torsional deformation behavior of API X70 and X80 linepipe steel”, Metall. Mater. Trans. A, 41A, pp. 1961-1972, 2010.

F. Rivalin, A. Pineau, M. D. Fant and J. Besson, “Ductile tearing of pipeline-steel wide plates I. Dynamic and quasi-static experiments”, Eng. Fract. Mech., 68, pp. 329-345, 2001.

F. Rivalin, J. Besson, A. Pineau and M. D. Fant, “Ductile tearing of pipeline-steel wide plates II. Modeling of in-plane crack propagation”, Eng. Fract. Mech., 68, pp. 347-364, 2001.

B. Hwang, Y. G. Kim, S. Lee and N. J. Kim, “Effects of microstructure on inverse fracture occurring during drop-weight tear testing of high-toughness X70 pipeline steels”, Metall. Mater. Trans. A, 36A, pp. 371-387, 2005.

J. Fang, J. Zhang and L. Wang, “Evaluation of cracking behavior or critical CTOA values of pipeline steel from DWTT specimens”, Eng. Fract. Mech., 124-125, pp. 18-29, 2014.

S. Y. Shin, B. Hwang, S. Kim and S. Lee, “Fracture toughness analysis in transition temperature region of API X70 pipeline steels”, Mater. Sci. Eng. A, 429, pp. 196- 204, 2006.

Q. Sha and D. Li, “Microstructure, mechanical properties and hydrogen induced cracking susceptibility of X80 pipeline steel with reduced Mn content”, Mater. Sci. Eng. A, 585, pp. 214-221, 2013.

B. Strnadel, P. Ferfecki and P. Zidlik, “Statistical characteristics of fracture surfaces in high-strength steel drop weight tear test specimens”, Eng. Fract. Mech., 112-113, pp. 1-13, 2013.

W. Wang, Y. Shan and K. Yang, “Study of high strength pipeline steels with different microstructures”, Mater. Sci. Eng. A, 502, pp. 38-44, 2009.

API recommended practice 5L3, third edition, February, American Petroleum Institute, 1996.

ASTM A370-17a, Standard test methods and definitions for mechanical testing of steel products, 2017.

ASTM E436-03(2014), Standard test method for drop-weight tear tests of ferritic steels, 2014.