Precipitation behavior of composite precipitates in Nb-Ti micro-alloy EH36 offshore steel
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摘要: 基于EH36海工钢屈服强度影响因素的主成分回归分析,结合复合析出相固溶析出计算和经典析出动力学理论,系统研究了影响EH36海工钢屈服强度的主要因素和复合析出相的析出行为,并探讨了轧制过程奥氏体形变储能对复合析出相析出动力学的影响。结果表明,影响EH36海工钢屈服强度的主要因素为Ti、Nb和N。MN和M(C,N)分别在1728.5 K和1430.0 K开始析出,主要为(Ti,Nb)N和(Nb,Ti)C。在奥氏体相区,MN和M(C,N)的最大析出量分别为0.0165%和0.0277%,最大析出体积分数分别为0.000228%和0.000389%,发生晶界形核的最快沉淀析出温度分别为1580.3 K和1228.3 K。随着奥氏体形变储能的增加,MN和M(C,N)相对形核率呈增加趋势,析出孕育期明显缩短且沉淀强化作用增强。Abstract: Based on the principal component regression analysis of the factors affecting the yield strength of EH36 offshore steel, combined with the solid solution precipitation calculation of composite precipitation phase and the classical precipitation kinetics theory, the main factors affecting the yield strength of EH36 offshore steel and the precipitation behavior of composite precipitation phase in γ were systematically studied, and the influence of austenite deformation and energy storage during rolling on the precipitation kinetics of composite precipitation phase was discussed. The results show that the main factors affecting the yield strength of EH36 offshore steel are Ti, Nb and N. MN and M(C,N) began to precipitate at 1728.5 K and 1430.0 K, respectively, and were mainly (Ti,Nb)N and (Nb,Ti)C. In the austenite phase region, the maximum precipitation amounts of MN and M(C,N) are 0.0165% and 0.0277% respectively, and the maximum precipitation volume fractions are 0.000228% and 0.000389% respectively. The fastest precipitation temperatures for grain boundary nucleation are 1580.3 K and 1228.3 K respectively. With the increase of deformation energy storage, the relative nucleation rate of MN and M(C,N) increases, the incubation period of precipitation is obviously shortened and the precipitation strengthening effect is enhanced.
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表 1 EH36海工钢主要化学成分
Table 1. Main chemical composition of EH36 steel
% C Si Mn S P Al Ti Nb N Ni, Mo, Cu, V 0.12~0.16 0.20~0.40 1.20~1.50 0.0010~0.0040 0.015~0.020 0.020~0.050 0.012~0.016 0.020~0.030 0.0030~0.0050 残余 表 2 相关参数统计及变量定义
Table 2. Statistics of related parameters and definition of variables
统计项 屈服强度/MPa 厚度/mm w/% C Si Mn P S Al Nb N Ti (因变量) (x1) (x2) (x3) (x4) (x5) (x6) (x7) (x8) (x9) (x10) 极小值 357 42 0.07 0.13 1.28 0.01 0.001 0.02 0.02 0.0018 0.007 极大值 472 80 0.17 0.41 1.58 0.028 0.008 0.05 0.033 0.0068 0.016 均值 421.17 50.69 0.12 0.24 1.35 0.018 0.0038 0.033 0.025 0.0041 0.012 标准差 24.56 7.79 0.0092 0.048 0.05 0.0034 0.0018 0.0049 0.0029 0.0006 0.0019 注:统计量为230个。 表 3 各成分的特征根和方差贡献率
Table 3. Characteristic root and variance contribution rate of each component
自变量成分 初始特征值 方差贡献率/% 累积贡献率/% Z1 3.347 33.474 33.474 Z2 2.015 20.155 53.628 Z3 1.8 17.995 71.623 Z4 1.018 10.175 81.798 Z5 0.584 5.836 87.634 Z6 0.399 3.994 91.628 Z7 0.322 3.223 94.851 Z8 0.241 2.413 97.264 Z9 0.196 1.96 99.224 Z10 0.078 0.776 100 表 4 主成分的成分矩阵
Table 4. Component Matrix of Principal Components
主成分向量 标准化后的自变量 x1* x2* x3* x4* x5* x6* x7* x8* x9* x10* l1 0.622 0.767 0.815 0.597 −0.158 −0.516 −0.093 0.118 −0.105 0.076 l2 0.383 −0.133 −0.306 0.483 0.157 0.337 −0.675 0.944 0.658 −0.092 l3 −0.221 0.266 0.08 −0.18 0.583 −0.181 −0.219 −0.109 0.397 0.707 l4 0.144 0.217 −0.079 0.1 0.572 0.445 0.417 0.181 −0.441 0.083 表 5 回归系数显著性检验结果
Table 5. Test results of significance of regression coefficient
自变量 标准化系数 差异性显著的检验值sig Z1 −0.070 −0.024 Z2 0.061 0.028 Z3 0.149 0.043 Z4 −0.152 0.055 表 6 各成分对屈服强度影响的多元线性回归方程
Table 6. Multiple linear regression equation of the influence of each component on yield strength
屈服强度/MPa 回归方程系数 厚度 C Si Mn P S Als Nb N Ti Y*=f(xi*) −0.101 −0.008 −0.023 −0.102 0.075 −0.013 0.029 −0.083 0.03 0.094 Y=f(xi) −0.013 −0.838 −0.477 −2.033 22.153 −7.453 5.928 −28.684 24.96 49.572 表 7 不同成分的EH36海工钢
Table 7. EH36 marine steel with different compositions
% 编号 C Si Mn P S Al Nb N Ti 1# 0.10 0.20 1.20 0.010 0.0010 0.020 0.020 0.0030 0.010 2# 0.12 0.24 1.35 0.018 0.0038 0.033 0.025 0.0041 0.012 3# 0.17 0.41 1.58 0.028 0.0050 0.050 0.033 0.0068 0.016 相 固溶度积公式 控制元素扩散系数D/(cm2·s−1) 界面能 σ/(J·m−2) 摩尔体积×105/(m3·mol−1) 晶格常数/nm NbC 3.70-9100/T 530 exp(-344000/RT) 1.3435-0.6054×10−3T 1.345 0.4470 TiC 2.75-7000/T 0.15 exp(-251000/RT) 1.2360-0.5570×10×3T 1.212 0.4318 NbN 2.80-8500/T 530 exp(-344000/RT) 1.2999-0.5858×10−3T 1.277 0.4394 TiN 0.32-8000/T 0.15 exp(-251000/RT) 1.1803-0.5318×10−3T 1.147 0.4282 表 9 晶界形核和位错形核条件下不同形变储能下复合析出相MN和M(C,N)形核参量的计算结果
Table 9. Nucleation parameters of MN and M(C,N) at different deformation energies and with grain boundary nucleation
T/K MN,lg(I/K) M(C,N),lg(I/K) 晶界形核 位错形核 晶界形核 位错形核 0 J/mol 2000 J/mol 4000 J/mol 0 J/mol 2000 J/mol 4000 J/mol 0 J/mol 2000 J/mol 4000 J/mol 0 J/mol 2000 J/mol 4000 J/mol 1353 −27.95 −27.56 −27.18 −33.16 −32.64 −32.13 −36.31 −35.93 −35.54 −84.44 −83.92 −83.41 1303 −28.32 −27.92 −27.52 −33.13 −32.59 −32.06 −34.44 −34.04 −33.63 −59.79 −59.26 −58.72 1253 −28.7 −28.29 −27.87 −33.28 −32.73 −32.17 −33.95 −33.54 −33.12 −50.9 −50.34 −49.78 1203 −29.1 −28.67 −28.23 −33.55 −32.97 −32.39 −33.95 −33.52 −33.08 −46.87 −46.29 −45.71 1153 −29.39 −28.94 −28.49 −33.57 −32.97 −32.36 −34.18 −33.73 −33.27 −44.89 −44.28 −43.68 1103 −29.65 −29.17 −28.7 −33.37 −32.73 −32.1 −34.48 −34 −33.53 −43.36 −42.73 −42.09 1053 −29.93 −29.43 −28.94 −33.59 −32.93 −32.27 −34.37 −33.88 −33.38 −41.2 −40.54 −39.88 -
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