钢中带状组织及其研究现状

带状组织是铸坯热轧过程中形成的常见组织缺陷，严重影响钢材后续加工性能和使用性能。对常见亚共析钢带状组织的形成机制、危害、控制措施和评级方法等研究现状与认识进行系统评述。分析认为，合金元素微观偏析是形成带状组织的根本原因，合理地控制合金成分、枝晶形态和热加工工艺也是抑制带状组织的重要途径。由微观偏析导致的枝晶内和枝晶间Ar3转变温度差异越大，带状组织越易形成。奥氏体分解过程中的冷却速率和奥氏体晶粒尺寸是形成带状组织的主要影响因素。较高的冷却速率、较大的奥氏体晶粒尺寸均会抑制带状组织发生。还分别阐述一次、二次碳化物对过共析钢带状组织形成的主要作用。同时,提出促进合金元素均匀扩散、减少连铸坯凝固组织微观偏析是减轻或消除带状组织的主要途径。带状组织中可能存在长条状夹杂物，然而，钢中夹杂物的大小、形貌和分布对带状组织的影响程度至今还不清晰。精细地表征与定量评价带状组织及其危害程度是亟待开展的重要工作。此外，铸坯加热制度对消除带状组织和控制组织晶粒度的综合影响也有待深入认识。

Research status of banding phenomena in steels

Banding phenomena is a common interior structural defect in steels which is harmful to the processability and usability of steel. The research status and understandings of the formation mechanism of banded structure in hypoeutectoid steels, the harm to mechanical properties of steels, the way to eliminate banded structure and the method of rating banded structure were systematically formulated. The analysis showed that the residual interdendritic microsegregation was the fundamental reason of banding, and reasonable controls of the alloy composition, dendrite morphology and hot working process were also the important ways to eliminate banded structure. The bigger the difference of the Ar3 transformation temperature between the interdendritic regions and the dendritic regions caused by microsegregation is, the easier banded structure formed. The cooling rate in an austenitic transformation and the austenitic grain size were the main factors to form the banded structure. Both the higher cooling rate and the bigger austenitic grain size can eliminate banded structure. The main effects of primary carbide and secondary carbide on the formation of banded structure in hypereutectoid steel were also formulated. To make the alloy elements distribute equality and reduce the amounts of micrcosegregation were the main ways to alleviate or eliminate the banded structure. There may be a long strip of inclusions in banded structures, however, the effects of the size, morphology, and distribution of inclusions in steel on the formation of banded structure were not clear. How to carry on the quantitative analysis of banded structurein steel was a key problem to be solved. In addition, the influences of heating system of slabs on the banded structure and grain size were needed to study further.