薄板坯液芯压下方式的探讨

结合河钢唐钢薄板坯连铸生产实践,阐述了动态和静态两种液芯压下方式在实际生产中的应用,分析了其对铸坯质量、扇形段寿命、液位波动的影响.研究表明,动态液芯压下有利于改善铸坯内部疏松和偏析,但是对设备、控制和工艺条件要求比较苛刻;静态压下在铸坯内部质量改善方面不如动态压下,但是对设备、控制和工艺条件要求比较简单,实际使用效果...     

薄板坯连铸中的液芯压下和动态软压下技术

薄板坯连铸采用液芯压下和动态软压下技术,可以提高薄板坯的内在质量,宜于采用计算机控制工艺参数,增加生产的灵活性和可靠性。     

薄板坯连铸连轧的液芯压下技术

介绍了国内外薄板坯连铸连轧流程中液芯压下技术的发展与应用情况,分析了液芯压下过程中铸坯的凝固机理以及变形的应变特点,并根据铸坯的凝固机理和坯壳凝固前沿的应变条件,提出了确定单辊压下量、压下量分配和总压下量的基本方法。     

薄板坯连铸液芯压下过程的数值仿真

基于修改的拉格朗日大变形热力耦合有限元模型,对薄板坯连铸的重要技术——液芯压下技术进行了仿真研究,并与实验结果进行了对比,两者基本吻合。研究结果显示,连铸坯经过压下辊的过程中,其应力状态发生较大的变化。研究表明,控制和优化连铸坯窄面附近区域的冷却条件是控制连铸坯窄面附近区域应力和变形的重要手段,采用提高连铸坯窄面附近区域的冷却模式,对防止连铸坯内裂纹的形成和液芯压下技术的顺利实施有重要意义     

薄板坯液芯压下技术特性的研究

介绍了薄板坯连铸过程中的液芯压下工艺,对比了液芯压下与软压下的区别。根据薄板坯连铸液芯压下工艺的技术特性,对采用液芯压下铸机的结构进行了分析,得出了薄板坯连铸的合理液芯压下工艺条件,对液芯压下技术的应用具有借鉴意义。     

薄板坯连铸连轧的液芯压下技术

介绍薄板坯连铸连轧液芯压下技术的应用和研究现状，比较了液芯压下物理模拟实验与在线热带生产中液芯压下技术的区别，并用反向堆钢理论作了解释。本文还探讨了薄板坯连铸连轧液压芯下技术今后的研究方向。     

薄板坯连铸连轧采用液芯压下技术之分析

着重说明液芯压下技术之机理，以及若干特性；涉及到速度，温度，凝固点，应力，能耗等，以及扇形段结构；分析了液芯压下之优缺点；指出应根据不同条件合理应用该技术。     

液芯压下技术在CSP生产线连铸扇形段的应用

阐述武钢CSP连铸机液芯压下扇形段的构成、控制原理、功能作用,介绍武钢CSP连铸液芯压下技术(LCR)的应用实践、常见故障及处理措施,并指出连铸液芯压下技术的进一步开发应用方向。     

薄板坯连铸连轧液芯压下工艺研究

针对薄板坯连铸工艺中的关键技术液芯压下特点,选取沿柱状晶方向的铸态钢试样分别在不同温度和应变速率下进行热压缩模拟试验,为液芯压下结构提供材料高温流变应力模型。通过建立液芯压下过程数值模型,研究和分析液芯压下工艺中铸坯变形特征和凝固坯壳的应力应变分布规律,以及液芯形态变化情况。为了找到薄板坯连铸液芯压下工艺的最佳工艺参数组合,对坯壳厚度、压下量和辊间距三个参数进行优化设计。通过建立响应面来构造液芯压下近似模型,描述各工艺参数与液芯压下结果之间的关系。在近似的模型的基础上,利用遗传算法,通过全局最优优化算法寻找出构造近似模型的最优解,从而得到板坯液芯压下最佳工艺参数组合,并进行了压下试验。     

液芯压下过程中压下量分配对铸坯变形的影响

为了优化液芯压下工艺参数,达到改善铸坯中心处偏析和疏松的目的。基于有限元法,以结晶器出口处薄板坯横截面的温度为初始条件,利用Marc软件模拟计算了薄板坯三维热-力耦合模型带液芯压下过程,分析了压下量分配对铸坯各节点应力和应变的影响。研究结果表明,总压下量相同时,均匀的压下量有利于降低铸坯表面的应力,而局部大压下更有利于改善铸坯的中心质量。     

Thin slab casting with liquid core reduction

Abstract

A liquid core reduction method has been developed for the flexible production of slabs of extensive thickness. In this method, achievement of the target slab thickness and the prevention of internal cracking are of prime importance. Using an experimental continuous caster, a series of tests of thin slab casting with liquid core reduction was conducted. The caster had three segments (1–3) for reduction at exit from the bending unit. The slabs were reduced in each segment with tapered alignment of the rollers over a 1 m length. The amount of reduction in each of the segments was changed in several patterns. The slabs were able to be reduced by 40–25 mm from 100 or 90 mm thickness without internal cracking. The variation in the amount of reduction in each segment was assessed by solidification analysis and strain analysis during liquid core reduction. In reduction along a tapered alignment, the incremental strain produced by the reduction can be comparatively low. The optimum reduction pattern to obtain the target slab thickness and to minimise tensile strain caused by the reduction has been established.     

Principles in cast rolling with liquid core of thin slab continuous casting

Dynamic rolling deformation behavior of continuously cast slabs with liquid core is studied with the aid of the thermomechanically coupled finite element method (FEM) of elastic-plasticity. The effects of shell thickness and related height reduction on the longitudinal tensile strain of strand are analyzed from a simplified three-dimensional (3-D) model. The results show that the longitudinal tensile deformation can be omitted for strands with thin shell, but it cannot be neglected for those with thick shell. A new concept of inward pushing or pushing into the liquid core is put forward based on the analysis, which leads to a reasonable explanation and better understanding of the liquid core cast-rolling processes in the present Inline Strip Production (ISP) thin slab casting.     

Influence of charcoal replacing coke on microstructure and reduction properties of iron ore sinter

This study was carried out to determine the influence of using charcoal as a supplementary fuel on the microstructure and reduction properties of sinter. The primary fuel was coke breeze with 0, 20, 30 and 40% replacement of weight input with charcoal to produce sinter. Experimental results indicate that when the replacement percentage of charcoal to coke breeze increased from 0 to 40%, the porosity and FeO content of sinter also rose. These changes result in an enhancement from 79.8 to 84.3% for the reducibility index due to the increased reducing surface area. In addition, the reduction degradation of sinter also improves since degradation during crystalline transformation is restricted. Therefore, replacing coke breeze with charcoal is able to improve the reducing properties of sinter, which is beneficial to small and large blast furnace operation.     

平整压下率对TS290组织性能的影响

 为了研究平整压下率对TS290组织性能的影响,为品种开发制定合理的工艺参数提供参考,采用激光共聚焦显微镜检测了样品显微组织,采用TEM观察了样品位错形态及其分布,采用拉伸试验机检测了样品力学性能。结果表明,随着平整压下率从0增大到3.0%,TS290屈服强度先减小后增大,抗拉强度先缓慢增加后趋于平稳。加大平整压下率对组织细化作用有限,但可以显著增大基体位错密度,进而提高材料屈服强度。平整压下率控制在2.0%左右时,试验钢屈服强度为290 MPa,抗拉强度为400 MPa,洛氏硬度为59.0,性能达到TS290质量设计要求。     

钢带喂入比对铸坯组织的影响

通过试验设计,研究了不同钢带喂入比对铸坯组织的影响。结果表明:钢带在恒温钢液中的熔化过程分为两个阶段,开始时钢带残余厚度随喂入时间的增加而快速增加,最多增加100%;钢带厚度达到最大值后开始缓慢减小,直到钢带在钢液中全部熔化,此时钢带残余厚度变为零。钢带喂入比影响铸坯等轴晶率和等轴晶晶粒大小,钢带喂入比从0增加到3%,铸坯等轴晶率从49.3%增加到75.3%,提高52.7%,平均等轴晶晶粒尺寸减小55.4%。过大的喂入比导致铸坯芯部疏松,合适的钢带喂入比为1%。     

Surface microstructure control of microalloyed steel during slab casting

Lots of work has been done to investigate slab surface microstructure evolution during continuous casting in order to improve hot ductility and avoid transverse cracks.The slab surface microstructure after continuous casting was characterized by optical microscopy, and the precipitation behavior was investigated by transmission electron microscopy.At the same time, the mechanical properties of the slabs were measured using a Gleeble 1500D thermal simulator and the transformation temperatures were examined by means of a thermal dilatometer.The experimental results show that homogeneous microstructure without film-like ferrites and chain-like precipitates at grain boundary can be obtained through surface intensive cooling and transverse cracks do not occur on the slab surface.For the ex-perimental steel, fine ferrite can form at slab surface when the water flow rate is larger than 1560 L/min at vertical section.As the distance to surface increases, microstructure turned to ferrite and pearlite. Moreover, nano-size carbonitrides precipitated in the ferrite grain and the size was larger at the junc-tion of the dislocations.The mechanical experiment results show that the hot ductility of the sample deformed at 650℃ was better than that of the sample deformed at 750℃.The reason is that film-like ferrite formed at the grain boundary in the sample deformed at 750℃.Thus, the slab must be cooled quickly below A r3 to prevent the occurrence of film-like ferrite and transverse cracks on the slab surface during casting.     

高温加热制度对380CL连铸板坯枝晶偏析及轧材带状组织的影响

通过设计6种热处理工艺和4种热轧工艺分别完成气氛保护热处理试验和热轧试验,借助电子探针面分析和定量分析手段检测板坯热处理前后Mn元素枝晶偏析程度的变化,并比较不同加热制度下板材显微组织的差异,从而分析了高温加热制度对380CL板坯枝晶偏析以及轧材带状组织的影响程度。结果发现:加热温度从1 140 ℃逐步升高到1 300 ℃,热处理前后偏析比变化量从1.65%逐渐增大到3.52%,1 200 ℃时保温时间从0.5 h、1.0 h延长到2.0 h,偏析比变化量从1.79%、2.12%增大到3.59%,即加热温度每升高50 ℃左右,或保温时间延长0.5~1.0 h,枝晶偏析减轻0.1%~1.5%;热轧工艺时加热温度从1 140 ℃升高到1 200 ℃,板材带状组织可减轻1级,带状偏析程度可改善20%左右。     

Surgical reduction of "big eyes"

We report a case of central retinal vein occlusion (CRVO) in a young woman with polycystic ovarian syndrome (PCOS). CRVO in young patients is a rare condition, frequently associated with a severe underlying systemic disorder. This is the first report of CRVO associated with documented PCOS. We discuss the therapeutic dilemma.