Q345钢连铸坯压缩状态下的高温力学性能

Q345钢应用广泛,其在拉伸状态下的高温力学性能已有部分研究,但高温压缩力学性能数据匮乏。利用Gleeble-3500热模拟机对Q345钢连铸坯试样进行了热压缩试验,研究了应变速率为0.01 s-1时试样在压缩状态下的屈服强度、抗压强度和弹性模量等随温度(973~1 673 K)的变化规律,同时探讨了试样在1 473 K时不同应变速率(0.001、0.01和0.05 s-1)下的高温力学性能。结果表明,在973~1 373 K温度内,屈服强度和抗压强度都表现出对温度的敏感性。屈服强度由90降到24 MPa,抗压强度由202降到40 MPa。在1 373~1 673 K温度内,屈服强度和抗压强度降幅都很小。弹性模量随温度的升高而减小,其值在1 473和1 573 K温度下相差最大,达1 712 MPa。屈服强度对应变速率的变化并不敏感,均在20 MPa左右,而极限抗压强度由28增加到45 MPa。最后根据试验数据绘制了Q345钢连铸坯在热压缩状态下的屈服强度等高温性能参数随温度变化的关系曲线,可为轻/重压下等技术提供参考数据。     

Kinetics of MnS precipitate coarsening in 3pct Si-Fe sheet

The growth kinetics of MnS in a 3 pct Si-Fe matrix containing excess manganese were characterized at temperatures of 925°, 975°, and 1025°C by an electron microscopy extraction replica technique. The average radius of coarsened particles at timet, •r _t, exhibited Greenwood’s predicted dependence for diffusion-controlled coarsening; namely, r3t= r3 0+kt where r_-o is the critical radius for growth andk is the rate constant. Growth rates compared favorably to those calculated from diffusion-controlled coarsening theories assuming that growth was controlled by the diffusion of sulfur. The experimentally determined activation for coarsening, ~67 kcal, was attributed to the sum of the activation for the dissolution of MnS, ~24 kcal, and for the diffusion of sulfur, ~49 kcal.     

Study on the non-uniform slab shrinkage of special steel during slab continuous casting

A full-scale finite-element stress model of a slab and its mould was developed to analyse the non-uniform slab shrinkage of special steel in a vertical caster during slab continuous casting. The stress model was based on the heat transfer model which was validated by comparing the calculated temperature with the measured ones. According to the shrinkage calculation, the single linear taper is not suitable for the continuous casting of this special steel, and the narrow face taper need to be calculated and optimised. It will provide a helpful tool for further improving the casting parameters and operations for special steel.     

Raytek非接触式在线测温系统在热轧连铸坯测温中的应用

针对宝山钢铁股份有限公司连铸坯装炉温度测量中存在的问题,设计出Raytek非接触式在线测温仪和工业控制微机相结合的温度检测与记录系统,从硬件结构和软件功能等方面论述了系统的实现。     

High temperature creep in Fe-3 pct Si

The kinetics and structure dependence of the high temperature-low stress creep of Fe-3 pct Si has been studied and compared with the predictions of current creep theories. It is shown that the steady state creep rate is diffusion controlled and exhibits a power law stress dependence in the temperature range 1393 to 1678 K and stress range 6.9×10⁴ to 1.03×10⁶ Pa. In this same range of experimental conditions the dislocation density present during steady state creep is essentially stress independent. It is shown that current creep theories are incompatible with the experimental results.     

薄板坯连铸无取向电工钢表面横裂纹分析

对无取向电工钢横裂纹进行了检测分析,调查了电工钢生产过程中的连铸工艺状况,包括扇形段压力、二冷强度、增压泵、液芯压下等,进行了不同工艺的比较分析。结果表明：无取向电工钢表面横裂纹产生的根源是由于钢中P元素的偏析造成晶界脆性,降低了钢的高温塑性,带液芯的铸坯在扇形1段受到的热应力或机械应力超出了该钢种在此高温区的临界应力所致。在提高扇形1段设备精度,减缓1段二次冷却后,表面横裂纹得到了有效控制。     

影响板坯连铸产生渣圈的因素

针对邯郸钢铁股份有限公司板坯连铸低合金钢Q345D过程中易结渣圈现象,对渣圈产生机理作了研究,通过成分分析、性能测定以及扫描电镜等分析手段确定了实验条件下导致保护渣结渣圈的各项因素。实验证实,保护渣使用过程出现分熔现象,使渣熔化不均匀,以及配碳不当是导致保护渣结渣圈的主要因素,结晶温度高以及液渣层厚也易结渣圈。     

板坯加热温度对低温技术取向电工钢抑制剂与磁性的影响

利用透射电镜研究了采用\     

高碳钢连铸板坯高温力学性能

采用Gleeble-1500热模拟试验机测量了高碳钢连铸板坯的高温力学性能,得到了第Ⅰ、第Ⅲ脆性温度区的温度范围.结果表明:第Ⅰ脆性温度区脆化的主要原因是晶界部位的低熔点物质在高温下首先熔化,从而导致试样沿晶界开裂;第Ⅲ脆性温度区脆化的主要原因是在奥氏体部位析出的网状铁素体导致试样沿晶界开裂;在奥氏体单相区,由于氮化铝的析出导致钢种的塑性恶化.     

板坯连铸工艺参数对取向硅钢铸坯中心等轴晶率的影响

通过对取向硅钢铸坯的低倍检验,研究了中间包钢水过热度、电磁搅拌电流、二冷水强度、拉速及断面尺寸对铸坯中心等轴晶率的影响。结果表明,试验条件下,中间包钢水过热度控制在14~18 ℃范围内时,因过热度不同引起的中心等轴晶率的变化较小,变化范围仅为0%~3%;电磁搅拌电流和铸坯断面尺寸对中心等轴晶率的影响较为明显,随搅拌电流的增大,中心等轴晶率呈增加的趋势,而当铸坯断面尺寸增加时其呈减小的趋势;二冷水强度和拉速对中心等轴晶率的影响相对较小,随着二冷水强度的增大,中心等轴晶率呈减小的趋势,而当拉速提高时其呈增加的趋势。     

Analysis of non-uniform thermal behaviour of special steel during slab continuous casting

A full-scale finite-element model of a slab and its mould was developed to reveal the complex thermal behaviour of special steel in a vertical caster during slab continuous casting. An inverse algorithm was applied to calculate the heat flux and combined with the temperatures measured using thermocouples that were buried in different positions of the mould. The model was validated by comparing the calculated temperature with the measured ones. The temperature distribution of the slab is not symmetric, reflecting the non-uniform nature of heat transfer and hence the necessity of formulating a full-scale model. It will provide a helpful tool for further improving the casting parameters and operations for special steel.     

Development of indices for quantification of nozzle clogging during continuous slab casting

Abstract

Deposition of alumina inclusions inside the submerge entry nozzle is a long standing problem in continuous casting of aluminium killed steel. Clogging of the casting nozzle severely affects productivity and also causes degradation of product quality. Unfortunately, very few numerical tools are available for precise quantification of the magnitude of clogging. Tools for quantifying the extent of clogging were developed during the present work and have been integrated with the control system of a running continuous slab casting shop. Reasonable match has been observed between the estimation from the developed program and the actual observations in the casting shop and subsequent products. In addition to process control, the tools were also found useful for comparing the castability of different steel grades. This feature has been utilised to study nozzle clogging during casting of steel grades that are commonly believed to have poor castability.     

Investigation of non-uniform slag films and air gap during slab continuous casting

Based on an inverse algorithm and a full-scale heat transfer model of slab/mould, the non-uniform temperature fields of mould and slab are obtained. Considering the formation mechanism and heat transfer characteristics of the slag films and air gap, a mathematical model of the heat transfer between the liquid/solid slag films and air gap is further developed. According to the model, the non-uniform distributions and evolution of liquid/solid slag films and air gap are comprehensively revealed, which proposes a theoretical foundation for exploring the complex heat transfer of mould/slab and provides a helpful tool for further improving the casting parameters and operations.     

连铸生产Mn13板坯表面纵裂控制

针对Mn13钢种在板坯连铸生产时发生表面纵裂纹缺陷的问题,结合Mn13材料凝固的特点,在工业生产中对浇铸过热度、拉速、水口对中、水口插入深度等工艺参数进行摸索,优化了保护渣化渣条件,保证了液渣在弯月面的均匀流入,改善了结晶器润滑与铸坯传热,控制了初生坯壳生长的均匀性,从而解决了Mn13板坯的表面纵裂纹缺陷,实现了Mn13的板坯多炉连铸生产,提高了铸坯合格率,由50％以下提高到96％.     

圆坯连铸过程中坯壳生长规律

采用ANSYS软件建立了圆坯连铸过程的二维凝固传热模型,通过射钉实验以及表面温度的测定对模型进行了实验验证.结果表明模型能较准确地得到任意位置处铸坯坯壳厚度以及预测凝固终点位置.在传热模型的基础上结合铸坯低倍观察着重分析了圆坯坯壳生长规律.发现圆坯凝固过程中柱状晶区坯壳的厚度与凝固时间的平方根呈线性关系,符合平方根定律,并对平方根定律进行了修正,修正项与过热度和凝固速率有关;铸坯中心等轴区坯壳厚度与凝固时间平方根为非线性关系,凝固坯壳的生长不再符合平方根定律;间接证明了圆坯柱状晶生长是单方向传热,等轴晶生长时传热方向不唯一.     

冷却温度对AH36钢连铸坯热延展性的影响

连铸坯角部横向裂纹是连续铸钢过程中经常出现的缺陷,直接影响钢材质量和生产成本.以 AH36钢为研究对象,采用 Gleeble-3800热模拟机模拟连铸坯冷却制度对连铸坯的影响.借助金相显微镜对断口微观组织进行分析表征,研究不同冷却温度下试样的热延展性,明确冷却温度对连铸坯角部横裂纹的影响.结果表明：以10℃/s 的冷速冷却至650℃后,回温至Ac3温度以上随后再缓慢冷却至825℃时的试样断面收缩率为67.02％,并且微观组织均匀,晶粒细小.热循环冷却制度能够有效提高连铸坯表面热延展性,降低裂纹敏感性,消除角部裂纹的产生.     

连铸坯质量预测系统及应用

为满足热装热送、薄板坯连铸连轧等紧凑型生产流程技术的需要,中冶连铸技术工程股份有限公司自主研发了连铸坯质量预测系统(QES)。该系统针对容易影响铸坯质量的各个铸机参数进行实时监视,并将监视结果以缺陷发生概率的形式反映到铸流和铸坯上,实现铸流质量的在线预测以及铸坯质量预测。该系统已在山东莱芜银山钢铁厂3#板坯连铸机上成功上线应用,针对Q235B和SPHC钢种建立了判定规则,QES的铸坯判定准确率高达90.6%。     

薄板坯连铸连轧钢卷库计算机管理系统

本文简单介绍了薄板坯连铸连轧钢卷库计算机管理系统的配置、功能,以及实现产品工艺质量的自动跟踪。     

Simulation of thermal behavior during peritectic steel solidification in slab continuous casting mold

Thermal behavior of the solidifying shell in continuous casting mold is very important to final steel products.In the present work,one two-dimension transient thermal-mechanical finite element model was developed to simulate the thermal behavior of peritectic steel solidifying in slab continuous casting mold by using the sequential coupling method.In this model,the steel physical properties at high temperature was gotten from the micro-segregation model withδ/γtransformation in mushy zone,and the heat flux was obtained according to the displacement between the surface of solidifying shell and the hot face of mold as solidification contraction,the liquid-solid structure and distribution of mold flux,and the temperature distribution of slab surface and mold hot face,in addition,the rate-dependent elastic-viscoplastic constitutive equation was applied to account for the evolution of shell stress in the mold.With this model,the variation characteristics of surface temperature,heat flux, and growth of the solidifying shell corner,as well as the thickness distribution of the liquid flux,solidified flux,air gap and the corresponding thermal resistance were described.     

热芯大压下轧制连铸坯再加热时的组织遗传性

 热芯大压下轧制工艺在改善连铸坯内部缩孔、疏松缺陷的同时,可以破碎粗大的铸态组织,并通过影响再加热奥氏体化后的组织来影响最终产品的组织和性能。为了研究热芯大压下轧制后的铸坯再加热过程的组织演变,选用微合金钢和中碳钢2种具有代表性的钢种为研究对象,采用炼钢-连铸-轧制一体化试验,研究了热芯大压下轧制对连铸坯显微组织及再加热后奥氏体组织形貌的影响。研究结果表明,热芯大压下轧制可改善铸态组织,获得均匀细小的室温组织。对于中碳钢,热芯轧制获得的细小组织经再加热后无法继续保持,与无形变的坯料相比,再加热后的奥氏体晶粒反而更加粗大;而对于微合金钢,由于第二相粒子的钉扎作用,热芯大压下轧制获得的细小组织经再加热后可继续保持。