50钢板表面龟裂纹的形成原因与控制

炼钢 ›› 2023, Vol. 39 ›› Issue (2): 62-67.

50钢板表面龟裂纹的形成原因与控制

王冠¹，郑万²，许博³

1.广东韶关钢铁有限公司炼钢厂，广东韶关 512123；
2.武汉科技大学钢铁冶金与资源利用教育部重点实验室，湖北武汉 430081；
3.华南理工大学国家金属材料近净成形工程技术研究中心，广东广州 510640

出版日期:2023-04-05 发布日期:2023-04-06

Formation reason and control of craze cracks on the surface of 50 steel plate

Online:2023-04-05 Published:2023-04-06

摘要/Abstract

摘要： 针对50钢200 mm厚连铸坯轧制钢板的严重表面龟裂（发生率7.92 %）问题，采用扫描电镜、光谱分析等方法，研究了表面龟裂的形貌、分布、成分等特征。结果表明，表面龟裂随机出现在钢板上，宽度方向上表面龟裂没有固定位置，裂纹深度较浅，两边呈现高亮度组织和氧化原点特征，光谱分析显示裂纹处碳含量比基体高，增碳质量分数0.2 %～0.3 %。分析认为，连铸过程中铸坯局部增碳，在加热、粗轧过程中热塑性不均匀而导致裂纹及明显的高温氧化特征。根据连铸保护渣增碳机理，优化了结晶器渣线调整模式、铸坯拉速、水口形状、结晶器保护渣成分等连铸工艺参数，有效降低了连铸坯表面局部增碳及钢板龟裂的发生率。

关键词: 50钢, 表面缺陷, 局部增碳, 结晶器液面波动, 保护渣

Abstract: Aiming at the problem of serious surface craze cracks (incidence rate 7.92 %) of 50 steel plate rolled by 200 mm thick continuous casting slab, the morphology, distribution and composition of surface cracks were studied by means of scanning electron microscopy and spectral analysis. The results showed that surface cracks randomly appeared on the steel plate without fixed position in the width direction of the steel plate, and the crack depth was shallow, and the two sides of them showed the characteristics of high-brightness structure and oxidation dots. Spectral analysis showed that the carbon mass fraction at the crack was 0.2 %-0.3 % higher than that of the matrix, which showed that the slab of 50 steel was partially carbonized during the continuous casting process by mold flux with some carbon content. Subsequently, cracks and obvious high temperature oxidation characteristics were caused by uneven thermoplasticity of the slab during heating and rough rolling. According to the carburizing mechanism of continuous casting mold flux, the continuous casting process parameters such as mold slag line adjustment mode, casting speed, nozzle shape, mold flux composition, etc. were optimized, which effectively reduced the occurrence of local carburization on the surface of the continuous casting slab and cracking of the 50 steel plate.

Key words: 50 steel, surface defects, local carburization, mold liquid level fluctuation, mold slag

王冠, 郑万, 许博. 50钢板表面龟裂纹的形成原因与控制[J]. 炼钢, 2023, 39(2): 62-67.

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