基于深度置信网络的连铸坯偏析等级预测研究

连铸坯中心偏析缺陷的准确预测对于连铸坯稳定生产、提升连铸质量具有重要意义。为精准预测连铸坯中心偏析缺陷,建立连铸坯偏析等级的深度学习模型,该模型应用禁忌搜索的超参数优化法,对DBN模型的网络层和回归层进行优化,提高了偏析预测的准确率。研究表明,基于DBN-SVR模型的连铸坯中心偏析预测精度较好。     

电磁搅拌作用下铸坯宏观偏析的研究

连铸坯的宏观偏析主要包括中心偏析和带状偏析。应用电磁搅拌,可以改善连铸坯的中心偏析,但同时又伴有带状偏析的产生。在经搅拌以后的铸锭与搅拌位置对应处出现一负偏析带,即“白亮带”。本文就电磁搅拌改善连铸坯中心偏析的机理进行了试验研究。提出了应用电磁搅拌改善中心偏析的途径及具     

管线钢连铸坯中心偏析分析与探讨

对管线钢连铸坯中心偏析情况进行探讨,分析在连铸坯宽度方向和厚度方向上碳、硫、磷、锰元素偏析的变化规律,得到影响中心偏析的主要因素;将连铸坯偏析和钢板元素偏析进行对比,分析凝固组织特殊特征与元素偏析的对应关系,探讨偏析形成机理,为连铸坯中心偏析的控制提供理论依据。     

DP980双相热轧钢带状组织成因及控制

通过分析1 000 MPa级DP980铁素体马氏体双相钢带状组织、连铸坯宏观和显微组织偏析,研究了该钢种带状组织的成因及控制方法。结果表明,连铸坯中心较内部其他部位偏析严重,连铸坯的中心元素偏析与热轧带钢的中心带状偏析有对应关系;枝晶间显微偏析度与带状元素偏聚度有较好的正相关关系。随着道次增加及反向轧制,铸坯初始枝晶取向转变为与轧制方向一致。连铸过热度控制在20~25℃、拉速为1.2 m/min,同时应用铸坯轻压下技术,连铸坯宏观偏析可控制在C1.0以下,热轧带钢的带状组织可控制在1.5级以下。     

连铸坯微观及宏观偏析数学模型的研究进展

对连铸坯微观和宏观偏析模型及树枝晶间液相流动的研究进展进行了评述，采用近平衡凝固过程溶质再分配理论并结合连铸传热数学模型对连铸坯微观及宏观偏析的定量解析方法进行了分析。     

过热度对高碳钢小方坯宏观偏析影响研究

基于国内某厂高碳钢小方坯连铸生产过程,首先利用ProCAST软件进行过热度对连铸坯宏观偏析影响的模拟研究,然后对过热度分别为44、39和28℃的连铸坯横断面和纵截面进行宏观偏析和疏松缩孔的研究。模拟结果表明:连铸坯横断面中心碳偏析随着过热度的增加不断增大,过热度超过25℃时,连铸坯横断面中心碳偏析度更加严重;试验结果表明,过热度分别为44、39和28℃的连铸坯横断面中心碳最大偏析度分别为1.39、1.32和1.06。结合模拟结果能够有效指导实际生产过程中连铸参数的调整,过热度越高,连铸坯中心碳偏析、条带状疏松缩孔越严重,为了降低连铸坯宏观偏析,建议将过热度控制在25～30℃。     

82B中心网状渗碳体产生原因及改善方法

研究了网状渗碳体级别与盘条及连铸坯中心碳偏析之间的定量关系,同时分析了影响铸坯中心偏析的关键连铸参数。结果表明:盘条中偏析比超过1.20就会有网状渗碳体形成;连铸坯中碳偏析指数大于1.16,盘条中就会出现超标的网状渗碳体。降低过热度,降低拉速,增大二冷水比水量,可以有效地降低铸坯中心偏析。通过工艺调整,铸坯中心平均碳偏析指数由1.13降低为1.08,网状渗碳体判次比例由2.0%降低为0.8%。     

过热度对高碳钢小方坯宏观偏析影响研究

摘要：基于国内某厂高碳钢小方坯连铸生产过程,首先利用ProCAST软件进行过热度对连铸坯宏观偏析影响的模拟研究,然后对过热度分别为44、39和28℃的连铸坯横断面和纵截面进行宏观偏析和疏松缩孔的研究。模拟结果表明:连铸坯横断面中心碳偏析随着过热度的增加不断增大,过热度超过25℃时,连铸坯横断面中心碳偏析度更加严重;试验结果表明,过热度分别为44、39和28℃ 的连铸坯横断面中心碳最大偏析度分别为1.39、1.32和1.06。结合模拟结果能够有效指导实际生产过程中连铸参数的调整,过热度越高,连铸坯中心碳偏析、条带状疏松缩孔越严重,为了降低连铸坯宏观偏析,建议将过热度控制在25~30℃。     

?450mm圆坯碳偏析影响因素及改进措施

研究了?450mm连铸圆坯横断面上沿直径方向碳元素分布情况,结合连铸圆坯的工艺特点和设备条件分析讨论了生产过程中连铸工艺参数对碳元素偏析的影响。结果表明:过热度、二冷比水量及电磁搅拌强度等是影响铸坯横断面碳偏析的主要因素。过热度越高越促进于偏析的形成。比水量较低不利于偏析控制,而较高的比水量对偏析影响不明显。电磁搅拌的位置和强度均对偏析有影响。采用合适的过热度、二冷比水量及电磁搅拌方式是控制铸坯碳偏析的有效措施。     

小方坯齿轮钢连铸过程中的宏观偏析模拟

基于国内某厂齿轮钢小方坯连铸生产过程,利用ProCAST软件建立移动切片模型,能够高效模拟连铸过程中的宏观偏析,模型分别模拟研究了不同过热度、二冷水量和拉坯速度等对宏观偏析的影响。模拟结果与碳偏析检测结果吻合良好,验证了移动切片模型模拟连铸坯宏观偏析的准确性。由于溶质浮力的影响,内弧侧的宏观偏析强于外弧侧。随着过热度的增加,铸坯中心碳偏析度从1.06增加至1.15。过热度控制在25 ℃范围内,可以保证铸坯的宏观碳偏析度控制在1.10范围内。随着连铸二冷水量的增加,铸坯中心偏析改善程度较小,铸坯中心碳偏析度从1.16降低至1.13。随着拉坯速度的增加,铸坯中心偏析呈现加重的趋势,铸坯中心碳偏析度由1.14增加至1.21,拉坯速度控制在1.4 m·min–1范围内,可保证铸坯中心碳偏析度低于1.15。      

减轻铸坯中心偏析的动态二冷技术优化

介绍某厂在直弧型板坯连铸机生产中碳钢过程中,通过对动态二冷技术和参数进行研究优化,完善动态连铸控制工艺,使中碳钢连铸坯中心偏析得到明显改善,B级偏析率平均由15．91％下降到12．28％。     

J55热轧钢卷分层原因分析

用光学金相显微镜等分析手段对J55热轧钢卷在焊管生产时一剖二的过程中发现的分层缺陷进行分析。结果表明其产生的原因是由于钢板内部存在严重的MnS和含有Nb、Ti的CN化合物夹杂以及C、P元素的偏析,偏析来自于连铸坯。     

Influence of Grain Boundary Complexion on Deformation Mechanism of High Temperature Bending Creep Process of Cu Bicrystal

Despite of substantial advancement, the effect of grain boundary (GB) complexions on high temperature creep deformation process has not been fully understood. In this paper, we have studied the high temperature bending creep deformation of copper bicrystal with various GB complexions under different loads using molecular dynamics simulation. It has been found that specimen with normal kite GB complexion have better creep resistance properties when subjected to comparatively lower applied load. In case of monolayer Zr segregation, a drastic decrease in creep strength as well as creep plasticity is observed due to inhibition of GB migration. On the other hand, deviation between creep properties for specimen with split-kite GB complexion and split-kite bilayer Zr segregation GB complexion is minimal. Enhanced creep plasticity is observed in case of split-kite bilayer Zr segregation GB complexion, which is due to formation of interpenetrating icosahedral clusters in the necking region. Fracture in specimen with monolayer Zr segregation GB complexion has occurred by means of slip phenomenon at lower deformation load whereas amorphization and necking is observed at higher deformation load. In case of specimen with bilayer Zr segregation GB complexion, it is found that fracture has occurred through amorphization and necking at all deformation loads due to higher GB thickness.     

GCr15轴承钢连铸方坯与电渣重熔铸锭的 原位统计分布分析

GCr15轴承钢作为高碳钢,其元素偏析尤其是碳元素的偏析对于钢的组织和性能有很大影响。实验应用原位统计分布分析技术对GCr15轴承钢连铸方坯整个横截面以及GCr15电渣锭的中心区域进行了对比分析,并重点研究了C和Cr元素的偏析情况以及试样表面的疏松情况。通过C和Cr元素含量二维等高图以及统计偏析度的对比分析可知,连铸方坯横截面的C和Cr元素都存在严重的中心偏析现象,同时在中心偏析区域外围观察到由于树枝晶搭桥而造成的环状、不连续的C元素负偏析带;GCr15电渣锭中心区域的C和Cr元素分布则较为均匀,即偏析现象得到明显改善。此外,电渣重熔前后试样表面的统计致密度和统计疏松度表明,电渣锭的致密程度要明显优于连铸方坯。     

Inverse segregation

Inverse, segregation at the chill face and the region adjacent to the chill face has been calculated for the AlCu,AlZn, and SbBi alloys using a finite difference analysis. In the calculations the effect of changes in composition and temperature, as well as the volume change on freezing, were considered during the solidification process. The calculations agree in general with the reported values of chill face segregation in the AlCu and SbBi alloys. They differ appreciably in the 40 pet composition region of the AlZn alloy, where a depression in the chill face segregation/composition curve is obtained instead of a peak. In the region adjacent to the chill face, the inverse segregation is found to drop rapidly with distance from the face, the rate decreasing with increasing solute concentration. The presence of an air gap between the solidifying metal and the chill can markedly influence the chill face and adjacent segregation. The air gap size in turn is dependent on the pouring temperature of the melt and the chill material. In one case the calculated air gap size was 3 Μm.     

An analytical electron microscope study of the kinetics

The detection and quantification of the segregation of Bi to grain boundaries in Cu using Analytical Electron Microscopy is demonstrated and the effects of time and temperature are observed. The experimental data are compared with the theoretical prediction of McLean’s segregation isotherm. Special grain boundaries are also considered. The analysis shows that the detection of the variation of segregation with time and temperature as well as grain boundary characteristics is possible using analytical electron microscopy and that the quantification techniques used here agree well with theoretical calculations of the segregant levels.     

提高Q550NQR1耐候钢-40℃冲击功的工艺实践

研究分析了8.0 mm厚Q550NQR1高强耐候钢-40℃低温冲击功偏低的原因,于其心部组织观察到多条珠光体偏析带,该偏析带虽宽度窄,且较分散、不连续,但是数量多,占比约5.8%;经检测,该心部偏析对试验钢力学性能影响不大,认为主要是铌钒微合金化的细晶强化和析出强化效果,保证了试验钢的高强度;然而,铁素体/珠光体的界面相对薄弱,利于裂纹的产生和扩展,并且珠光体偏析带可能使材料的韧脆转变温度升高,从而使得试验钢的低温冲击韧性变差。通过提高加热温度并保证足够的加热时间、提高层流冷却段冷却速度、控制Nb和V含量的改进工艺进行轧制,所得产品组织细化、珠光体偏析带消失、常规力学性能符合要求,且富余量合适、-40℃低温冲击值均值上升84.3 J。     

Atomistic vs phenomenological approaches to grain boundary segregation: Computer modeling of CuAg alloys

Experimental investigations of grain boundary segregation, for example the Auger electron spectroscopy (AES), as well as the associated thermodynamic analyses, are principally macroscopic. On the other hand, computer modeling of grain boundary segregation provides a very detailed picture of the atomic structures of segregated boundaries. In order to investigate the relationship between macroscopic and microscopic approaches we have performed molecular statics and Monte Carlo simulations of grain boundaries in CuAg alloys in which Ag segregates strongly to grain boundaries. On the atomic level segregation is inhomogeneous, the segregated region extends several lattice spacings away from the boundary and the segregation process cannot be described in the framework of simple thermodynamic analyses. Energetics as well as entropic interactions between solutes play important role and structural transformations may be induced by segregation. However, on the macroscopic level the picture is much simpler. The average concentration of the segregant in the boundary region follows the McLean's isotherm but no obvious relationship between the “effective” segregation enthalpy and atomistically determined segregation enthalpies can be established. Furthermore, the Auger analysis assuming a homogeneous distribution of the segregant gives correct average concentrations but for the case when the segregant is confined to a single atomic layer. Hence, macroscopic analyses of the segregation are insensitive to complex atomic level processes and although they give correct average concentrations of the segregant, no conjectures regarding the atomic level processes associated with segregation can be made on the basis of such studies.     

影响退火钢板表层Mn析聚的因素及提高2030钢板抗锈蚀能力的对策

从2030与1420两冷轧单元工况上的差异出发,考察了2030CAPL和2030BAF中影响Mn等易氧化元素在钢板表面富集的因素.结果表明,退火温度、退火时间、退火前清洗介质中含Si与否、钢卷冷轧时的变形量等对Mn等的析聚有较大的影响;宝钢2030冷轧板表面Mn等元素的过度析聚也归因于退火温度(过高)、退火时间(过长)、CAPL退火前清洗介质中含有Si、钢卷冷轧时的变形量与退火温度时间的不完全匹配等的共同作用.考虑到2030冷轧单元对这些关键因素进行严格地控制和匹配较为困难,提出了"退火后轻微酸洗处理"的提高2030冷轧板抗锈蚀能力的措施.     

Interfacial two-dimensional phase transitions and impurity segregation

Impurity segregation to surfaces and grain boundaries are investigated within a phenomenological theory. Next neighbour interactions between segregating species are taken into account in a regular solution model. Resulting phase transitions because of interfacial miscibility gaps are discussed for equilibrium segregation as well as for the kinetics of segregation in ternary systems with repulsive interaction between both segregants. The rate determining step for segregation kinetics remains volume diffusion in these cases. In contrast structural interfacial transitions may delay the kinetics of segregation significantly because nucleation of the second phase requires at least locally an oversaturation up to a critical value compared with the pure thermodynamically determined coverage of the first structure. Computer simulations based on a model which characterizes both structures by different saturation values and segregation energies were carried out. A comparison with surface segregation measurements of Pb in Ag and Sn in Fe shows a good agreement.