The evolution of hot-rolled banded microstructure in low carbon microalloyed steels
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摘要: 低碳微合金钢在轧制过程中经常出现带状组织缺陷，对产品质量和使用性能都有着重要的影响。以某厂Q345热轧板坯为研究对象，通过对元素偏析，轧件热轧过程不同轧制道次、不同位置带状组织演变行为进行分析,结果表明，枝晶间溶质元素偏析是导致带状组织形成的本质原因。同时发现不同轧制道次和不同位置轧材，带状组织尺寸有着明显差异。不同轧制道次，相同位置的带状组织，压下率越大，带状组织越细小，压下率为50%时，中心带状组织宽度约为175 μm；压下率为67%时，中心带状组织宽度约为75 μm。相同轧制道次下，不同轧件位置的带状组织比较，可以发现厚度中心位置带状组织最为粗大，表面处最为细小。Abstract: Banded structure defects often appear in low carbon microalloyed steels during rolling process, which have a great impact on the product quality and service properties. In this study, Q345 hot-rolled slab in a plant was selected as the research object, and the evolution of the banded structure in different rolling passes and positions during hot rolling was analyzed. The results show that the segregation of solute elements between dendrites is the essential reason for the formation of banded structure. At the same time, it is found that there are significant differences in the banded structure size of rolled products at different rolling passes and positions. For the banded structure at the same position in different rolling passes, the larger the reduction rate is, the smaller the banded structure is. When the reduction rate is 50%, the width of the central banded structure is about 175 μm. When the reduction rate is 67%, the width of the central banded tissue is about 75 μm. Under the same rolling pass, the comparison of banded structure at different rolling positions can be made. It is found that the banded structure at half-thickness is the largest, compared to the smallest band observed at the surface.
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Key words:
- low carbon microalloyed steel /
- hot rolling /
- banded structure /
- reduction /
- evolution behavior
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图 7 第五道次工序不同位置的组织形貌
Figure 7. Structure morphology at different positions during the fifth process
图 8 第七道次不同位置的组织形貌
Figure 8. Structure morphology at different positions during the seventh pass
图 9 第九道次不同位置的组织形貌
Figure 9. Structure morphology at different positions during the ninth pass
图 10 不同位置带状组织宽度的变化
Figure 10. Changes of banded structure width at different positions
表 1 Q345主要化学成分
Table 1. Main chemical composition of Q345
% C Si Mn P S V Nb Ti N 0.14 0.20 1.40 0.014 0.006 0.028 0.025 0.02 0.007 
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表 2 轧制工艺参数
Table 2. Rolling process parameters
轧制道次 厚度/mm 道次压下率/% 总压下率/% 压缩比 0 280.0 0.0 0.0 0.00 1 247.5 11.6 11.6 1.13 2 216.0 12.7 22.8 1.29 3 186.6 13.6 33.3 1.50 4 161.0 13.7 42.5 1.74 5 140.4 12.8 50.0 2.00 6 124.7 11.2 55.5 2.25 7 111.9 10.3 60.0 2.51 8 100.0 10.6 64.3 2.80 9 92.1 7.9 67.1 3.00
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