Formation and control of the surface defect in hypo-peritectic steel during continuous casting:A review

Hypo-peritectic steels are widely used in various industrial fields because of their high strength,high toughness,high processability,high weldability,and low material cost.However,surface defects are liable to occur during continuous casting,which includes depression,longitudinal cracks,deep oscillation marks,and severe level fluctuation with slag entrapment.The high-efficiency production of hypo-peritectic steels by continuous casting is still a great challenge due to the limited understanding of the mechanism of peritectic solidification.This work reviews the definition and classification of hypo-peritectic steels and introduces the formation tendency of common surface defects related to peritectic solidification.New achievements in the mechanism of peritectic reaction and transformation have been listed.Finally,countermeasures to avoiding surface defects of hypo-peritectic steels duiring continuous casting are summarized.Enlightening certain points in the continuous casting of hypo-peritectic steels and the development of new techniques to overcome the present problems will be a great aid to researchers.

The optimization of mold fluxes used for casting the peritectic steel of heavy slabs at Baosteel

In order to solve the problem of the high surface longitudinal crack ratio of heavy peritectic steel slabs produced by the No. 3 continuous caster at Baosteel,the physical properties of the original mold flux and the optimized mold flux were compared in a comprehensive way by using analytical measures, such as a slag film heat-flow simulator, a thermowire molten flux crystallization tester and an X-ray diffractometer in the laboratory. The results reveal that one of the major reasons for the cracks is the poor heat transfer ability of the original mold flux. However, the optimized mold flux with a high basicity features a high crystallizing rate,low crystallization temperature and low heat-flow density. Therefore, the optimized mold flux is more suitable for casting peritectic steel by the heavy slab continuous caster. The test results show that the slabs produced by using the optimized mold flux had no surface longitudinal crack in four test casts, while the surface longitudinal crack ratio of the slabs produced by using the original mold flux was 5%. The optimized mold flux can effectively prevent slab surface longitudinal cracks from occurring.

Surface Detection of Continuous Casting Slabs Based on Curvelet Transform and Kernel Locality Preserving Projections

Longitudinal cracks are common defects of continuous casting slabs and may lead to serious quality accidents. Image capturing and recognition of hot slabs is an effective way for on-line detection of cracks, and recognition of cracks is essential because the surface of hot slabs is very complicated. In order to detect the surface longitudinal cracks of the slabs, a new feature extraction method based on Curvelet transform and kernel locality preserving projections （KLPP） is proposed. First, sample images are decomposed into three levels by Curvelet transform. Second, Fourier transform is applied to all sub-band images and the Fourier amplitude spectrum of each sub-band is computed to get features with translational invariance. Third, five kinds of statistical features of the Fourier amplitude spectrum are computed and combined in different forms. Then, KLPP is employed for dimensionality reduction of the obtained 62 types of high-dimensional combined features. Finally, a support vector machine （SVM） is used for sample set classification. Experiments with samples from a real production line of continuous casting slabs show that the algorithm is effective to detect longitudinal cracks, and the classification rate is 91.89%.

连铸板坯标识残留缺陷的改善

针对热轧钢卷边部的毛刺缺陷问题,分析认为是由于热轧加热工艺调整造成板坯喷印标识覆盖部位的氧化铁皮去除不净,残留在热轧钢卷边部导致。通过调整喷印丝材质,在保证现有板坯标识清晰度和附着力的前提下,较好地解决了标识覆盖部位的氧化铁皮残留问题,有效地改善了热轧钢卷边部质量。特别是采用改进后的合金喷印丝,轧后热卷边部无毛刺缺陷的比例可以达到98%以上。

铜板带水平连铸生产工艺及铸坯缺陷探究

随着国民经济的持续快速发展,国内对铜合金带材的需求量也在逐年增加。水平连铸是目前生产铜及铜合金带材的重要工艺。主要从国内外水平连铸技术的发展历史、水平连铸设备、水平连铸的生产工艺流程、结晶器的基本结构和水平连铸的优点等方面对铜板带的水平连铸进行了论述与介绍。并且重点分析了铜合金板带坯在凝固过程中产生表面凹坑、气孔、晶粒不均匀、边部裂纹、反偏析、缩松等缺陷的原因,并提出了相应的改善措施,有效预防了缺陷的产生,提高了带材的成品率,延长了结晶器的使用寿命。并对铜板带水平连铸未来的发展趋势进行了展望。

热轧板带材表面翘皮缺陷成因与控制研究现状

热轧板带表面翘皮一直是困扰高品质钢带材生产的常见缺陷。钢材表面翘皮缺陷的产生原因可能贯穿于钢铁生产冶炼、连铸、热轧和冷轧全过程,翘皮缺陷种类多、影响因素复杂。依据其形貌和组织特征,可将常见翘皮缺陷的诱因分为5类,分别是皮下夹杂、表面裂纹、皮下气泡、氧化皮压入以及中间坯折边。加强生产设备与工序界面管理,尤其是从源头上提高连铸工艺水平,改善铸坯表面质量,可以大大降低产品翘皮缺陷的发生几率。

Correlation between longitudinal crack occurrence and mold heat transfer in continuous casting based on process data mining

The correlation between the longitudinal crack occurrence and integrated heat transfer of the mold with data mining methods was investigated.Firstly,three kinds of support vector machine models based on principal component analysis with different input features were established to explore the effect of integrated heat transfer on the accuracy of the prediction model for the longitudinal crack.The results show that the accuracy was improved while features including mean and standard deviation of integrated heat transfer were added.Then,the difference in integrated heat transfer between defect and normal samples under the same process parameters was quantitatively compared.Compared with normal samples,the temperature difference of cooling water for defect samples decreased by 0.65%,and the temperature difference fluctuation increased by 31.1%.Finally,the literature data were used to provide support for the quantitative correlation according to defect formation mechanism.A new criterion for the prediction of longitudinal crack and a discovering method for correlation between product quality and process parameters in the manufacturing industry have been provided.

基于改进YOLOv7算法的连铸坯表面缺陷检测

针对连铸坯表面缺陷检测存在的参数量大、小目标检测效果较差、人工标注数据集质量的不稳定性等问题,提出了一种基于改进YOLOv7算法的连铸坯表面缺陷检测模型。首先,引入MobileNetv3 block模块轻量化主干网络,降低计算量,减少参数与复杂度;其次,融合双层路由注意力机制,实现更灵活的计算分配和内容感知;最后,使用WIoU损失函数替换原损失函数,使模型获得更好的泛化能力。改进后的模型检测精度达到了89.3%,角部横裂的检测精度提升了6.6%;权重文件大小减少为原来的56.5%,检测速度达到了98 fp/s。结果表明,所提出的算法参数量小、检测速度快、精度高,能够满足连铸坯表面缺陷在线检测工作需求。

Q355B宽带钢表面开裂原因

某Q355B钢边部表面发生开裂现象。采用宏观观察、化学成分分析、金相检验、扫描电镜及能谱分析等方法分析了裂纹产生的原因。结果表明:钢板表面裂纹产生于连铸工艺环节,裂纹附近存在砷、铜等有害元素富集现象;砷、铜等有害元素形成了低熔点的富集相,使钢板的塑性变差,破坏了钢基体连续性,在拉应力的作用下,钢板表面发生开裂现象。

连铸坯窄面凹陷缺陷产生原因分析及预防

本文针对连铸坯窄面纵向凹陷缺陷,借助连铸坯缺陷宏观形貌分析、连铸坯低倍酸洗分析、金相组织分析和化学成分检测等手段,结合连铸坯生产工艺,分析了连铸坯窄面纵向凹陷缺陷产生原因。确定了连铸结晶器窄面冷却水量不合理造成的铸坯初生坯壳冷却不均,结晶器锥度过大对结晶器坯壳产生挤压是缺陷产生的主要原因。通过采取结晶器冷却水量优化、结晶器窄面锥度调整控制及保护渣性能优化等措施,有效提高了连铸板坯表面质量,杜绝了连铸坯窄面纵向凹陷缺陷发生。

连铸薄板坯的质量缺陷及其改善措施研究

分析了连铸薄板坯在冶炼及连铸过程中产生的表面夹渣、内部非金属夹杂,铸坯凝固过程中产生的表面裂纹、中心偏析及中心疏松等质量缺陷。讨论了如何从炼钢到连铸过程中通过采用先进的生产技术和设备来达到工艺的优化,从而改善铸坯质量,发挥出薄板坯连铸连轧的产量和产品质量优势。

高温连铸坯表面缺陷的机器视觉无损检测

针对高温连铸坯表面缺陷无法在线检测问题,采用机器视觉技术和相应的试验装置,建立了高温背景下CCD快门控制时间成像模型,同时设计分类器算法对缺陷种类进行归类。系统所选CCD成像装备采用水冷风冷双层冷却方式,在高温状态下能长时间连续工作。系统可检测最大铸坯宽度为3000 mm,能有效抑制铸坯表面振痕产生的图像噪声影响,实现热态铸坯表面缺陷在线检测与分类。

亚包晶钢连铸板坯表面纵裂纹的研究

针对 重钢七厂 板坯连铸 的实际 生产条件 ，通过现 场试 验，研 究了 钢水 质量、结晶 器液 面状况、结晶 器保护 渣和设备 检修等 对板 坯 表面 质量 的 影响 。分 析了 板坯 表 面缺 陷的 类 型、数 量 和分布，并 提出了控 制板坯表 面质量 的措施。

板坯表面纵裂的成因分析及控制措施

为了提高连铸板坯质量,结合临汾钢铁公司实际生产数据,对连铸板坯表面纵裂纹的形成原因和影响因素进行了分析。结果表明:中间包、结晶器液面的波动是板坯产生纵裂的根源,而含硫量和浇注温度的偏高、拉速的不稳定以及结晶器锥度的不合理等因素加速了裂纹的扩展。提出了控制连铸板坯表面纵裂纹的措施。

连铸板坯表面星状裂纹的形成与控制

研究了连铸成品板坯表面的微裂纹缺陷——板坯表面星状裂纹的特征、形成机理、影响因素及解决措施。

基于脉冲涡流技术的连铸坯表面缺陷检测

为了实现高温连铸坯表面及近表面缺陷在线检测和缺陷坯及时分拣,提出了连铸坯表面缺陷脉冲涡流检测方法并进行了实验研究。对连铸坯表面缺陷的脉冲涡流检测信号进行差分分析和时域分析,提取了连铸坯表面缺陷信号的电压峰值、峰值时间及过零时间等特征量,并分析得到点缺陷、线缺陷、星状裂纹等缺陷对脉冲涡流检测信号特征值的影响规律。研究表明,采用脉冲涡流技术实现高温连铸坯表面及近表面缺陷的无损在线检测技术是可行的,电压峰值、过零时间和峰值时间与缺陷种类及缺陷的形态密切相关,为进一步研究高温铸坯表面缺陷检测和重构奠定了基础。

基于多尺度数学形态学的连铸坯缺陷边缘检测方法

连铸坯的缺陷会对轧制工艺产生影响,通过对连铸坯表面图像特征进行分析,提出了一种基于多尺度数学形态学的连铸坯表面缺陷检测方法。该缺陷检测方法能够有效去除噪声,并对水痕、氧化铁皮、渣痕等伪特征具有较好的抑制作用。实验结果表明,与Sobel方法、Prewitt方法、Canny方法、Laplacian方法等边缘检测方法相比较,该方法对缺陷边缘提取完整、平滑、定位准确,识别准确率达96.37%。

CSP工艺生产的薄板坯连铸表面纵裂纹缺陷研究

针对珠江钢厂 CSP薄板连铸坯出现的表面纵裂纹的特征和形成过程进行了深入的研究分析 ,探讨了不同的工况条件对形成纵裂纹缺陷的影响 。

连铸板坯表面纵向裂纹的形成原因

对连铸板坯表面纵向裂纹的形成原因进行了分析研究,发现浸入式水口在浇注过程中损坏和结晶器保护渣性能不佳是主要因素。采取了相应的改进措施后,钢板表面线状缺陷的发生率大幅度降低。

连铸结晶器过程综合冶金行为的数值模拟

结合连铸机设备工艺条件和所采用浸入式水口结构进行了结晶器内钢水流动、自由液面以及传热凝固等冶金现象的综合描述和数值分析。结果表明:浸入式水口通过控制钢水射流形态和强度可以显著影响结晶器熔池液面的起伏波动;上旋涡流股由液面返回时的抽引作用是波动起伏的主要原因,波谷处的液面流速最大;除钢水射流及其邻近钢水外,结晶器熔池中绝大部分钢水都因强烈对流和湍流扩散而保持其温度在液相线上恒定,研究条件下的熔池液面钢水最大过热度可达2 K以上,但此时的液面最大波高差和最大流速分别为9 mm和0.36m/s。