国内外大型扁钢锭锭型对比分析

关于国内大型扁钢锭锭型设计的论述鲜有报道,在查阅大量外文文献的基础上总结了日本大型扁钢锭的锭型参数,同时对国内大型扁钢锭锭型参数进行了汇总,计算了钢锭的宽厚比、高厚比和锥度三个关键参数。对国内外钢锭在宽厚比、高厚比和锥度参数的差异进行了对比分析,提出国内特厚板用大型扁钢锭锭型设计的几点建议。     

模铸40t钢锭凝固过程温度场研究

随着模铸钢锭锭型的不断开发以及连铸产品对模铸小规格锭型的替代与延伸,为满足产品质量提升与成本优化,大规格钢锭逐渐发展成了关键的模铸锭型。但是,在模铸生产中,随着锭型的增大,更易于产生各类质量问题,诸如:成分偏析、表面缺陷、钢锭缩孔等。使用计算机数值模拟软件可以模拟钢液凝固过程的温度场与流场变化情况,并且可预测钢锭缩孔缺陷位置。研究表明,40 t钢锭的凝固过程是从外往内、由下向上顺序凝固,不仅冒口部位易于产生缩孔缺陷,而且锭身中心也存在缩孔倾向。在锭身中心的狭长液态金属区域内,此区域锥角小、上下传热不均,易产生缩松缺陷,通过数值模拟可有效预测并推断缺陷存在的位置及原因。实践证明,40 t锭型钢锭凝固及缩孔模拟与现场实际情况吻合,验证了40 t钢锭锭型设计的有效性与科学性。     

抽锭电渣重熔718塑料模具钢板坯锭的新工艺

针对大型塑料模具毛坯电渣锭凝固过程中产生疏松和偏析等缺陷,从改变大型钢锭凝固条件角度出发,试图将大圆钢锭改为等截面面积的扁锭,同时采用双极串联供电控制渣池的温度场,以达到提高钢锭凝固质量的目的.本文介绍了采用双极串联、T型结晶器,抽锭电渣重熔工艺生产了0.32 m×2.0 m×4.0 m的718塑料模具钢板坯工业试验,重熔板坯锭的检验结果表明,板坯锭成分、低倍等凝固质量显著提高.     

水冷模铸造技术的研究现状

大型扁钢锭主要用于生产特厚钢板,随着钢锭吨位增加,钢锭上部缩孔较深,影响成材率,疏松等级高,偏析严重,大型扁钢锭的质量成为特厚板轧机能力的瓶颈。在查阅大量外文文献的基础上,结合国内水冷模铸造技术的研究现状,总结了水冷模铸造技术的相关专利,详细阐述了水冷模铸造技术对钢锭凝固速度、凝固坯壳均匀程度、凝固组织和疏松缩孔、钢锭内部偏析的影响。介绍了水冷模铸造技术生产钢锭和轧制的工业试验,同时介绍了轧制后钢板的性能情况。大型扁钢锭水冷模铸造技术具备为高品质特厚钢板提供坯料的能力。     

真空条件下锭模参数对铁镍合金缩孔分布的影响

为了减轻铸件顶部缩孔缺陷以降低冒头切除率提高铸锭成材率,基于ProCAST软件建立了铁镍合金真空下凝固数值仿真模型,通过解剖实验验证了模拟参数正确性,进而研究锭模参数对铁镍合金缩孔缩松分布的影响并得到最优锭型.研究表明:数值模拟中,关于真空条件下传热参数的设置较为合理,能较准确地模拟得到与实际生产一致的缩孔缺陷;在本研究条件下,冒口锥度对缩孔高度方向上位置的影响远大于锭身锥度和高径比对其的影响,缩孔位置随冒口锥度减小上移,中心疏松程度随锭身锥度增加而减弱,高径比对缩孔缩松影响不大;优化后的锭型能有效改善缩孔缺陷,将缩孔控制在冒口线以上提高铸锭成材率.      

大宽厚比扁钢锭的锭型设计和61tQ345B钢扁锭的生产实践

对国内外扁钢锭的宽厚比进行了分析,并得出宽厚比对扁锭质量的影响。研发了60 t大宽厚比扁钢锭模和大型水冷模铸装备。对EAF-LF-VD冶炼Q345B钢(/%:0.19C,0.36Si,1.39Mn,0.010P,0.003S)浇铸成61 t扁锭(宽3 070 mm,厚1 022 mm,宽-厚比3.0,浇铸温度1 580℃),并轧成220 mm特厚板。探伤和取样试验结果表明,钢锭质量优良,钢板屈服强度348~373 MPa,抗拉强度562~588 MPa,-40℃冲击功40.76~88.80 J,延伸率17.00%~28.50%,Z向断面收缩率33.79%~60.88%,晶粒度8~9级,达到标准要求;钢板探伤性能达到JB/T4730-2005Ⅰ级探伤要求。工业试验表明,大宽厚板扁钢锭水冷模铸技术具备为高品质特厚板提供坯料的能力。     

钢锭成材钢板常见缺陷定性及改进措施钢锭成材钢板常见缺陷定性及改进措施

以舞钢公司扁锭生产低合金系列特厚钢板探伤不合的缺陷为研究对象,根据钢锭的凝固理论、钢板缺陷各项检测分析以及大钢锭锭型数据模拟优化,从钢水质量、控制手段、锭型设计各方面着手,分析常见缺陷的性质及产生原因,提出了解决扁锭内部缺陷的措施。     

高碳镇静钢钢锭的宏观偏析

本文建立了一个模拟包钢矩形高碳钢B114钢锭凝固过程的二维数学模型。并通过实测B114钢锭凝固过程中钢锭模外表面的温度变化,验证了本模型的基本合理性。利用本数模的计算结果和B114钢锭的解剖资料,描述了B114钢锭的A型偏析,计算了沉积锥的大小,讨论了中心偏析的特点。通过与包钢B98钢锭对比,为B114钢锭模设计参数的选取提供了一定的依据。     

扁锭凝固和冷却过程的计算

与方型断面钢锭一样,扁锭的传搁时间表也可以用计算方法制定,但基本方程要用二维导热方程,故计算量较一维显著增多。文中介绍了计算用基本方程和置换为显式差分格式的各差分方程,举例说明计算步骤及所得数据的实用价值。计算结果可以用来制定钢锭传搁时间表,确定钢锭凝固率,凝固层厚度以及钢锭含有的凝固潜热量,确定装炉热锭载热情况,并在此基础上制定扁锭的合理加热制度和加热时间等。计算还可用于均热炉计算机控制扁锉冷却数字模型的离线解析计算。方锭是扁锭的一个特例,因此,扁锭计算完全适用于方锭。     

大型扁钢锭锭型设计和评价

目前国内多条特厚板轧机相继投产,特厚板坯料成为制约特厚板生产的关键技术,大型扁钢锭是特厚板轧机的重要原材料,国内关于大型扁钢锭锭型设计的论述鲜有报道。研究的目的是通过对大量外文文献的分析,论述大型扁钢锭锭型参数对钢锭质量的影响。同时对国内外大单重扁钢锭的现状进行了介绍,并对大型扁钢锭锭型进行了评价,对用于生产特厚板的大型扁钢锭锭型设计提出了几点建议。     

过热度对GCr15SiMn轴承钢钢锭宏观偏析的影响

针对GCr15SiMn钢锭易出现宏观偏析凝固缺陷的问题,研究了过热度对GCr15SiMn钢锭宏观偏析的影响规律,使用真空感应炉冶炼1 kg的GCr15SiMn钢锭,通过酸侵试验与OPA技术分别测定了钢锭的凝固组织与宏观偏析,并结合ProCAST软件分析了钢液流动的规律。结果表明,高过热度(70 ℃)时,中心下部出现一定程度的负偏析,中心上部形成了较严重的正偏析同时伴随疏松;中过热度(50 ℃)时,疏松范围较小,碳元素分布较均匀;低过热度(20 ℃)与极低过热度(-20 ℃)时,疏松范围扩大,凝固初期是严重负偏析,凝固末期是严重正偏析。过热度影响偏析的机理为,高过热度时,凝固过程热对流较强,溶质上浮,钢锭上部的正偏析严重;当过热度过低时,初期凝固大量形核并保留在钢锭底部,在底部形成严重的负偏析。     

GCr15SiMn轴承钢中碳元素偏析与疏松的相关性

针对GCr15SiMn钢锭在凝固过程中容易出现宏观偏析与疏松等凝固缺陷的问题,为了制定更合理的模铸浇注工艺,通过真空感应炉冶炼1 kg的GCr15SiMn钢锭,从模铸工艺和钢锭宏观组织的角度研究了实验室与工业生产的相似性,采用OPA、SEM等检验方法研究了碳偏析与疏松的相关性。研究表明,碳元素的偏析最为严重,碳元素偏析与疏松相关。得出了碳偏析与疏松的相关性公式SC=0.92P－0.89,该公式所体现出的基本规律适用于工业生产的铸锭。根据SEM和OPA的统计结果,建立了疏松的当量直径与其定量表征值(表观致密度P)的对应关系。结果表明,随着疏松的当量直径增大,碳的偏析度逐渐增大。利用Scheil微观偏析模型从原理上进行了分析与讨论,得出碳的偏析度和钢液收缩量呈正相关关系。     

Three‐dimensional Simulation of Thermosolutal Convection and Macrosegregation in Steel Ingots

Thermosolutal convection and macrosegregation formation during the solidification of steel ingots are numerically simulated in three dimensions. The simulation is based on a fully coupled model for mass, momentum, energy, and species conservation equations. The interdendritic flow in the mushy zone is governed by Darcy's law, and the permeability term is discretized using an interpolated liquid fraction method. The numerical results for a benchmark test of macrosegregation in a Pb‐Sn alloy are compared with experimental data taken from the literature. The present model is applied to simulate the solidification of industrial steel ingots. Preliminary predictions are obtained, including the positive segregation in the hot top, and the conically shaped negative segregation zone at the bottom of the ingot. The predicted variation of the segregation ratio in carbon along the vertical centreline of an ingot is compared with measurements, and generally good agreement is observed. Future attention should be paid to the precision of prediction by considering complex solidification issues, such as the sedimentation of free equiaxed grains and the formation of shrinkage cavity.     

GCr15SiMn轴承钢铸锭的原位统计分布分析

对真空感应炉熔炼后浇注的GCr15SiMn轴承钢铸锭进行原位统计分布分析,研究过热度对铸锭C、Si、Mn、Cr元素偏析以及疏松的影响。研究表明:过热度较低时(25 ℃),受溶质元素在凝固前端大量形核以及钢液热对流差等影响,铸锭的凝固末端出现明显的偏析和缩孔,C元素的统计偏析度达7.83%,统计疏松度为1.76%;随着过热度的进一步提高(55 ℃),钢液的热对流有所加强,各元素的偏析情况得到一定的改善,C元素的统计偏析度和疏松度均达到最低,分别为4.06%和1.34%;当过热度较高时(75 ℃和105 ℃),钢液的热对流较为强烈,溶质元素上浮,使得铸锭凝固末端的偏析以及疏松情况又有所恶化。因此,通过铸锭偏析和疏松的定量分析可知,过热度55 ℃为最佳浇注工艺参数。     

模铸轴承钢线材中心黑点产生机理及对策

中心偏析是钢锭凝固过程中常见的主要缺陷,对材料最终性能有显著影响。钢锭尺寸越大,凝固时间越长,偏析程度越严重。模铸生产的轴承钢GCr15线材产品易出现中心黑点缺陷,经过试验检测、现场测温和数值模拟等手段分析,确认黑点缺陷是由于模铸帽口中心碳、铬等元素偏聚引起的。在采取降低浇铸过热度、加强帽口保温和钢锭带模热送等工艺措施后,基本解决了黑点缺陷问题。     

Improvement in Quality and Yield of the Low Alloy Steel Ingot Casting Through Modified Mould Design

The internal quality and yield in 4 ton steel ingot of 40cmd8 grade was studied by comparing its solidification in a square cross-section mould with a slender rectangular cross-section mould, using FEM simulation. The model predicted various solidification aspects like fluid flow, thermal and solidification profiles, mushy zone, local solidification time, porosity and piping for both the molds. The convective flow of the molten metal during solidification showed higher velocity in square ingot than rectangular ingot under similar conditions due to lower surface area to volume ratio that affected the heat transfer in the rectangular ingot. Higher amount of air gap between the ingot and the mould was formed in rectangular ingots. Lower microsegregation as measured in terms of local solidification time was observed in rectangular ingot. Based on microstructure parameters such as thermal gradient and rate of solidification, it was found that the square ingot had more equiaxed zone than rectangular ingot. The rectangular ingot solidified at a faster rate and showed more propensity for core porosity than the square ingot. The ingot yield was improved by 3.6% through mould shape modification from square to rectangular. Model was validated to limited extent by carrying out a typical experiment with square mould.     

激光诱导击穿光谱原位分析仪和电子探针在CrMo耐磨铸钢元素偏析分析中的联合应用

CrMo耐磨铸钢是重要的耐磨钢铁材料,凝固过程中的溶质元素偏析是影响CrMo耐磨铸钢组织和性能的重要因素,了解凝固过程中的溶质元素偏析对于CrMo耐磨铸钢的工业化生产具有重要的借鉴意义。宏观偏析和微观偏析是衡量材料偏析程度的两个指标,准确的测量其偏析状况是研究溶质元素偏析的基础。实验以CrMo耐磨铸钢为研究对象,采用激光诱导击穿光谱原位分析仪(LIBSOPA)和电子探针(EPMA)分析钢锭不同部位的宏观偏析和凝固组织中的微观偏析,结果发现,Cr、V和Mn元素在CrMo耐磨铸钢铸锭中宏观偏析程度较小,偏析比接近1,而Mo元素宏观偏析程度较大,其最大宏观偏析比超过1.20;Cr、Mo、V和Mn元素在CrMo钢凝固组织中均存微观偏析,且随着冷却速度的增加,Cr、Mo、V和Mn微观偏析程度也随之增加,其最大微观偏析比分别为1.39、2.63、3.47和1.83。LIBSOPA与EPMA在CrMo耐磨铸钢元素偏析分析中的联合应用,对全面了解CrMo钢铸锭元素偏析,优化铸造以及后续的热加工工艺具有重要借鉴意义。     

7 t锭型本体高度对凝固过程和冶金质量影响的数学模拟

锭型对钢锭凝固过程中的疏松、缩孔等缺陷有一定影响。对本体高度1 885 mm矮粗型（A）和2075mm细长型（B）两种7 t钢锭,通过铸造模拟分析温度场、凝固分数、凝固时间以及中心疏松缩孔情况进行分析对比, 7t（B）细长型钢锭本体中心长970 mm的封闭高温液相区,并且本体中心疏松率超过20%的疏松区域大约为180 cm³, 7t（A）矮粗型钢锭只有保温帽处有少量轻微疏松,本体基本没有。综合各项考虑,建议7 t钢锭采用7 t（A）矮粗型的钢锭设计。     

Influence of Mould and Insulation Design on Soundness of Tool Steel Ingot by Numerical Simulation

 The solidification of 4. 4 t cold work tool steel ingot type X210Cr12 was simulated by Magma software. By the reduction of ingot height, solidification modeling and pouring of a new 3 t ingot were performed and decreasing the porosity formation potential in 3 t ingot in comparison with 4. 4 t ingot on the basis of Niyama criterion was observed which was in good accordance with experimental data. In order to produce sound ingot, a new 2. 8 t ingot mould was designed which includes some parameteric changes in mould such as mould slope, slenderness ratio, mould concavity radius, fillet radius of mould internal corners and feeding diameter to ingot upper diameter ratio. Furthermore, the effects of insulating between kokil and feeding ring and also insulating the outer surface of feeding ring as well as insulating the outer surface of one third of kokil upper part on centerline porosity formation were investigated in both 2. 8 and 4. 4 t ingots. The results show that the ingot which was produced in new designed 2. 8 t mould has a better Niyama pattern and the centerline porosities were eliminated.     

Modeling of Species Transport and Macrosegregation in Heavy Steel Ingots

In the current study, two significant phenomena involved in heavy steel ingot casting, i.e., species transport and macrosegregation, were numerically simulated. First, a ladle–tundish–mold species transport model describing the entire multiple pouring process of heavy steel ingots was proposed. Carbon distribution and variation in both the tundish and the mold of a 292-ton steel ingot were predicted. Results indicate high carbon concentration in the bottom of the mold while low concentration carbon at the top of mold after the pouring process. Such concentration distribution helps in reducing both negative segregation in the bottom of the solidified ingot and positive segregation at the top. Second, a two-phase multiscale macrosegregation model was used to simulate the solidification process of industrial steel ingots. This model takes into account heat transfer, fluid flow, solute transport, and equiaxed grain motion on a system scale, as well as grain nucleation and growth on a microscopic scale. The model was first used to analyze a three-dimensional industry-scale steel ingot as a benchmark. Then, it was applied to study macrosegregation formation in a 53-ton steel ingot. Macrosegregation predicted by the numerical model was presented and compared with experimental measurements. Typical macrosegregation patterns in heavy steel ingots are found to be well reproduced with the two-phase model.