图（a）（b）分别为DZ2（0.17V0Nb）钢850℃和900℃保温1h油淬至室温后在675℃回火4h的GB图，经计算，大于15°的大角度界面密度分别为1806 mm^-1和1788mm^-1；经过测量，在850℃、900℃保温淬火得到的板条块宽度分别为1.9µm和2.1µm，可见850℃淬火的试验钢的板条块宽度更小。图（c）为DZ2（0.17V0Nb）钢在850℃、900℃保温两种热处理工艺下的界面密度—取向差分布图。由图可知，DZ2（0.17V0Nb）钢在850℃保温1h后675℃回火4h的试验钢中有更高的大角度界面。

Figure (a) and (b) are GB diagrams of DZ2 (0.17V0Nb) steel held at 850℃ and 900℃ for 1h after oil quenching to room temperature and tempered at 675℃ for 4h. After calculation, the large-angle interface densities greater than 15° are 1806 mm-1 and 1788mm-1, respectively. According to the measurement, the width of the lath block obtained at 850℃ and 900℃ is 1.9µm and 2.1µm, respectively. It can be seen that the width of the lath block of the test steel quenched at 850℃ is smaller. Figure (c) shows the distribution of interface density-orientation difference of DZ2 (0.17V0Nb) steel under 850℃ and 900℃ heat treatment. It can be seen from the figure that DZ2 (0.17V0Nb) steel has higher large-angle interface in the test steel after holding at 850℃ for 1h and tempering at 675℃ for 4h.