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为了提高亚包晶钢连铸坯表面质量,运用低倍显微观察以及模拟等手段对亚包晶钢连铸坯角部横裂纹的形成机理进行了研究,研究结果表明:不同钢种角部横裂纹附近组织不一,碳质量分数为0.15%的钢种裂纹附近组织为均匀的铁素体+珠光体,而碳质量分数为0.093%的钢种的裂纹主要发生在厚度约50μm的沿晶先共析铁素体薄膜上,后者裂纹的发生率约为前者的3倍;碳含量对钢种塑性有根本性影响,从而影响角部横裂纹的发生,工业试验结果表明在碳质量分数低于0.1%范围内,将碳质量分数降低至0.07%,角部横裂纹的发生率可由原来的44%降低至约4%。二冷数值模拟优化结果表明,优化采用的弯曲段前弱冷模式及弯曲段之后内弧强冷模式的冷却方案可保证连铸坯内外弧角部温度均避开第Ⅲ脆性区,优化后裂纹数量及长度大幅度降低,角部横裂纹的发生可得到良好控制。
In order to improve the surface quality of sub-peritectic steel billets, the formation mechanism of the transverse transverse cracks in the sub-peritectic steel billets was studied by means of low magnification microscopic observation and simulation. The results show that: In the vicinity of the transverse cracks, the microstructure of the steel is uniform and the microstructure of the steel with the carbon mass fraction of 0.15% is uniform ferrite + pearlite. The cracks of the steel with the carbon mass fraction of 0.093% mainly occur along the grains with the thickness of about 50 μm The first eutectoid ferrite film, the latter the incidence of cracks about 3 times the former; carbon content of the plasticity of the steel have a fundamental impact, thereby affecting the corner of the transverse cracks, industrial test results show that the carbon mass fraction Below 0.1%, the carbon mass fraction was reduced to 0.07%, and the incidence of corner transverse cracks was reduced from 44% to about 4%. The results of numerical simulation of the secondary cooling show that the optimized cooling mode before the cold bending mode and the cooling mode with the inner arc cooling mode after the curved section can ensure that the temperature inside and outside the arc corner of the slab avoids the third brittle zone and the crack after optimization Significantly reduce the number and length, corner of the occurrence of lateral cracks can be well controlled.