Alloying design as well as strength and toughness of high Mn steels for LNG tank building
CHEN Jun1, LIU Ning2, LIU Zhenyu1, WANG Guodong1
1. The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, Liaoning, China; 2. Technology Center, Hunan Valin Lianyuan Iron and Steel Co., Ltd., Loudi 417009, Hunan, China
Abstract：Recently,there is a sharp increase in the number of Liquefied Natural Gas (LNG) dual-fuel green ships. It is attracted more and more attentions that high Mn steels for LNG tank building act as one of key cryogenic materials. Effects of alloying elements and their increments on strength and cryogenic impact toughness were systematically investigated in order to enhance strength and cryogenic impact toughness of high Mn steels for LNG tank building by alloying design. Effects of low-temperature hot-rolling and cooling modes on microstructure and mechanical properties were also analyzed. The results show that the substitutional solid solution elements of Ni,Mo and Al have positive effect on yield strength,Cr has negligible effect on yield strength,and Mn has negative effect on yield strength. Except for Mo,the tensile strength is lowered by the other substitutional solid solution elements. However,the cryogenic impact toughness can be improved by the substitutional solid solution elements. The yield strength and tensile strength can be simultaneously enhanced by interstitial solid solution element of C,whereas it deteriorates cryogenic impact toughness. The strength can be also enhanced by microalloying elements of Nb and V,which can retard recrystallization. Moreover,the partially recrystallized structures are harmful to cryogenic impact toughness. In addition, the obviously strengthening effect can be realized for the addition of 0.3%Nb or 0.5%V (mass fraction). But they deteriorate cryogenic impact toughness. The strengthening of high Mn steels is always accompanied by the deterioration of cryogenic impact toughness,leading to a difficulty in developing high Mn steels with high strength and toughness. However,it is found that the strength can be effectively enhanced and excellent cryogenic toughness can be also obtained at the same time by solid solution strengthening,grain boundary strengthening and deformation mechanism controlling on the basis of Al addition. The excellent cryogenic impact toughness can be obtained for the stacking fault energy ranging from 40 to 44 mJ/m2 at room temperature. The solid solution strengthening coefficients of Ni,Mo,Cr,Mn,Al and C are estimated to be 7.0,32.0,0.5,-3.0,22.0 and 290.0 MPa/%,respectively. The present work provides the experimental support for the design of high Mn steels with high strength and toughness.
陈俊, 刘宁, 刘振宇, 王国栋. LNG储罐用高锰钢合金化设计及强韧性[J]. 中国冶金, 2023, 33(6): 73-80.
CHEN Jun, LIU Ning, LIU Zhenyu, WANG Guodong. Alloying design as well as strength and toughness of high Mn steels for LNG tank building[J]. China Metallurgy, 2023, 33(6): 73-80.
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2023, Vol. 33 
