连铸过程铸坯皮下裂纹的产生及控制

摘要：通过数值模拟的方法研究了典型大方坯（325mm×280mm）连铸过程中温度场和应力场分布,分析了铸坯皮下裂纹产生的原因和主要影响因素,制定了控制铸坯皮下裂纹的具体措施。结果表明：在连铸过程中铸坯的最大回温为121℃,二冷一区最高回热速率达到217.48℃/m,二冷二区最高回热速率达到131.95℃/m,其他各区回热速率都较低。温度回升后铸坯横断面距铸坯表面15~30mm处的最大应力应变值已经超过了钢的极限应力应变值,因此,二冷一区和二区温度回升是铸坯产生皮下裂纹的主要原因。增加二冷一区水量,将此水量在二冷三区和四区相应地减小,可以降低二冷一区回热速率,降低最大回热温度到88℃,控制铸坯皮下裂纹的产生。     

齿轮钢矩形坯皮下裂纹的成因

 利用光学显微镜、扫描电镜和能谱仪分析了齿轮钢矩形坯皮下裂纹的特征及成因。结果表明：皮下裂纹产生于矩形坯铸坯侧面,距离表面1~5mm,具有明显位置性;结晶器中钢液凝固前沿聚集的Al2O3夹杂物是皮下裂纹形成的主要原因;改变浸入式水口类型和控制钢水过热度可以改善结晶器中夹杂物分布和促进夹杂物上浮,避免皮下裂纹的产生,同时防止了棒材表面线纹的发生。     

45钢连铸坯裂纹原因分析

本文在联样分析的基础上，结合现场生产情况探讨了二钢厂供热连轧厂45钢连铸坯裂纹形成的原因及防止措施。     

电炉钢连铸坯表面裂纹攻关

天津钢管公司电炉炼钢厂主要设备 :1座1 50ｔ超高功率偏心炉底出钢电炉 ,1座 1 50ｔＬＦ及ＶＤ装置 ,1套 4机 4流的弧形圆坯连铸机。连铸机的主要参数为 :型式 :弧形、多点矫直、圆坯 ,弧形半径为 1 0 .5、1 3.5、1 8.0、30 .5,冶金长度约2 1ｍ ,拉速范围 0 .77～ 1 .7ｍ ｍｉｎ。ＭＤ材质 :无氧铜 ,内壁镀硬铬。铸坯浇铸尺寸 :Φ2 1 0ｍｍ、Φ2 70ｍｍ、Φ31 0ｍｍ ,主要生产品种为石油套管、高压锅炉管等 ,铸坯主要供轧管厂 ,少量作为商品坯销售。生产工艺路线为 :1 993年纵裂废品 1 41 6 .358ｔ,占总废品的4 2 % ,纵裂率为 3.98‰ ,越来…     

石钢连铸大方坯内裂纹产生原因及控制途径

对石钢连铸大方坯内裂纹的产生原因、影响因素进行了分析,提出了降低内裂纹的相应技术措施。     

20钢水平连铸圆坯中间裂纹形成研究

通过对衡阳钢管厂２０钢水平连铸坯的（Ｐ），（Ｓ），Ｍｎ／Ｓ及其对应的中间裂纹统计，得出：（Ｐ），（Ｓ），Ｍｎ／Ｓ对中间裂纹有较大影响，随（Ｐ）的增加，中间裂纹的敏感性增大，随（Ｓ）的增加，敏感性增大；随Ｍｎ／Ｓ增加，敏感性变小。     

大方坯连铸漏钢原因分析及控制研究

针对Q235KZ钢230 mm×230 mm大方坯连铸二冷区频繁漏钢事故,采用扫描电镜、低倍腐蚀、成分分析、黏度测定、模拟计算等方法开展研究。研究发现连铸坯表面存在较长的纵裂纹,且漏钢坯壳附近存在夹渣。此外,发现结晶器内的初始凝固坯壳生长不均匀,在结晶器出口处最薄坯壳厚度为7.9 mm,最厚为20.2 mm。通过调整保护渣碱度、降低渣膜导热速率、优化二冷区水量分配,大方坯漏钢次数显著降低。     

小方坯连铸HRB335钢裂纹浅析

主要对HRB335钢产生横裂纹的原因进行全面的分析，以及采取相应的措施取得的效果。     

莱钢转炉优钢连铸坯中间裂纹成因分析与控制

针对中间裂纹特征，分析了形成原因，并提出了设备、工艺、检验改进措施，有效控制了转炉优钢连铸坯中间裂纹的产生。     

铸坯皮下裂纹的演变规律研究

热轧卷板上出现的不同于常规发纹的短直形边部直裂纹缺陷对产品的影响较大。轧钢环节的中间坯显示铸坯清角部位出现规则性斜向裂纹,通过使用电镜、金相、酸洗等检测方法对卷板、中间坯、连铸坯进行检测分析其形成机理,研究连铸皮下裂纹演变规律,对解决卷板成品边部缺陷提出指导。     

管线钢板亚表面隐蔽式裂纹缺陷成因分析

采用喷砂、着色探伤、冷弯、阶梯式刨削及高、低倍金相检验分析方法,研究了两种规格管线钢板受力后表面所产生的板条状翘皮裂纹缺陷（卷板）和开口呈撕裂状纵向裂纹缺陷（平板）的形成原因。结果表明,两种规格钢板受力后不同的表面缺陷同属于一种缺陷的不同表现形式,受力后表面缺陷形成的主要原因是铸坯皮下气孔遗传所致。     

Study on Intermediate Crack in Continuous Casting Slab of Medium Carbon Steel

According to the analysis of the macro and micro characteristics of the center of continuous casting blooms by acid wash, SEM, metallographic and scanning-type electron microscope, there was a serious segregation and some shrinkage cavities in the slab; Cracks occurred at the end of the columnar crystal and spread along the boundary of the primary dendrite. At the crack enriched a large number of impurity elements, carbon, phosphorus, sulfur, whose crystal boundary segregation is the internal factor of the intermediate cracks. Determining the originated location of intermediate cracks and calculating the total strain in this area during solidification process of slab, it is found that the load is the ex- ternal factor of cracks’ generation and expansion.     

高碳钢小方坯裂纹形成机理及控制措施

简述了高碳钢小方坯裂纹的形成机理,并分别对高碳钢小方坯表面裂纹和内部裂纹产生的机理进行了分析,提出了改进小方坯质量的一些方法。由于连铸坯各种裂纹形成机理的不同,以及出于对高碳钢中心偏析的考虑,某些方法在两个方面有时会起着相悖的作用,需要根据生产实际找到平衡点,以得到最优化的工艺参数。     

钢中皮下夹杂产生原因分析

皮下夹杂是造成表面裂纹的原因之一。为了查清皮下夹杂的来源 ,分别向钢中添加保护渣、耐火材料、炉渣和模内残留物铸试验锭。将试验锭与空白锭对比 ,通过对钢中夹杂物进行低倍检验、金相检验和能谱分析 ,研究了四种加入物在钢中形成夹杂物的特征 ,对钢中夹杂物的来源提供了判断依据。     

唐钢连铸坯表面纵裂的研究

对生产中的出现的表面纵裂进行了分析研究，提出了改进措施。     

Technology Development for Controlling Slab Transverse Corner Crack of Typical Micro-alloyed Steels

A mathematical model for simulating the fluid flow,heat transfer and solidification in the conventional mold and the chamfer mold,together with a finite element stress-strain model in the straightening process of both molds,were established for the typical niobium,vanadium,and titanium micro-alloyed steels.On the basis of both numerical analysis,the mold copper plate with an optimum chamfered shape was designed and applied in industrial tests.The predicted results from numerical simulation of fluid flow,heat transfer and solidification in the conventional mold and the chamfer mold show that the increased chamfered angle leads to an approximately linear increase of the slab surface temperature,but it also causes strong flow near the slab corner.Very small chamfered length can lead to a significant increase of the temperature near the slab corner.However,with further increasing the chamfered length,the temperature of the slab corner increased slightly.The calculated results from the finite element analysis of stress-strain during the straightening process show that at the same slope width,the tangential strain on the slab edges and corners is minimum when the chamfered angle is 30°and 45°,which is only 40% to 46% of rectangular slabs with the same cross-section area.At the same chamfered angle of 30°,when the chamfered length is controlled between 65-85 mm,the tangential strain on the part of the slab edges and corners is relatively smaller.Industrial test results show that the slab corner temperature at straightening segment increases about 100 ℃ by using chamfer mold compared to the conventional molds.The slab transverse corner cracks have been reduced more than 95% in comparison with those in the conventional mold.     

Control of Sulfur Content in the Production of Clean Steel in Panzhihua Steel

This article mainly introduced the process of clean steel with different ways in Panzhihua Steel based on high sulfur content hot metal. With the development and application of sulfur control technologies in hot metal pretreatment, converter steel-making and refining processes, Panzhihua Steel had achieved the production of clean steel such as 350km/h steel for high speed railway, electric steel, etc.     

转炉生产轴承钢顶锻裂纹原因分析

分析了造成转炉生产轴承钢顶锻不合格的主要原因,指出了钢中氢高且生成气体而导致表面针孔。为此,通过采取加强对原材物料的检查控制及延长精炼时间等措施,解决了顶锻裂纹的问题。