Kinetics and catastrophic swelling during reduction of iron ore in carbon bearing pellets

Abstract

The rate of reaction between iron oxides and charcoal, agglomerated together as pellets, has been correlated with the swelling of the pellets and with the morphology of the iron formed. The experimental techniques employed were thermogravimetric analysis, X-ray diffraction analysis, and microscopic examination of partially reduced pellets. The experiments were performed in the temperature range 1223–1423 K. The conditions that favour the growing of iron in the form of whiskers, and hence lead to catastrophic swelling, have been determined.     

核反应堆堆芯用HEA304电渣锭的试制

HEA304为低碳奥氏体不锈钢,具有优良的高温性能、抗腐蚀性及抗辐射性,主要用于核反应堆堆芯材料,该钢种电渣重熔后易出现碳、氮、晶粒度超标,经过对电渣重熔渣系及电渣工艺的摸索试验,确定电渣重熔渣系及工艺要点,并经锻造、热处理工艺处理,可以生产出优质的核材用HEA304锻件,满足标准要求。     

CaF2-SiO2-Al2O3-CaO-MgO五元渣系黏度的试验研究

为了研究含氟渣系成分变化对黏度的影响,根据五因素二次正交旋转回归法设计渣系配方,使用RTW-10熔渣物性测定仪,采用旋转柱体法,在1 600～1 300℃降温过程中对CaF2-SiO2-Al2O3-CaO-MgO渣系的黏度进行连续测定;建立了1 600℃下五元含氟渣系黏度的回归模型,研究了各组元对熔渣黏度的影响.结果表明:当CaF2的含量(质量分数,下同)在10％～70％时,随CaF2含量增加,黏度减小,随SiO2、Al2O3和MgO含量增加,黏度增大,CaO易受其他组元的作用而对黏度产生不同影响;在w(SiO2)=10％、w(MgO) =10％和w(CaF2)=50％时,随w(CaO)增加,黏度先增大后减小,w(CaO)=10％时黏度最大.在w(Al2 O3) =20％、w(MgO)=10％和w(CaF2)=50％时,随着w(CaO)增加,当w(SiO2)＜20％时,黏度先增大后减小;当w(SiO2)＞20％时,黏度持续减小.     

120t电渣重熔炉电极升降液压控制系统研究

对传统电渣炉电极升降系统进行改进设计;采用液压缸取代传统的滚珠丝杠系统,并采用电液比例调速阀进行液压缸速度控制,实现对电渣炉电极升降的传动和调速控制;建立了系统的数学模型,进行了控制系统仿真分析,获得了较好的控制效果。     

TiO2含量对于CaF2—Al2O3—CaO—MgO—TiO2五元电渣重熔渣系物性参数的影响

在电渣重熔含钛高温合金时, 加入Ti O₂可以抑制合金中钛的烧损.而渣系的物理性质关系着冶炼的平稳进行和产品的优良品质.本研究以Ca F₂-Al₂O₃-Ca O-MgO为基, 加入不同含量的Ti O₂, 设计了电渣重熔高温合金用五元渣系, 并研究了Ti O₂含量对渣系熔点、黏度、密度、光学碱度和电导率等物性参数的影响规律.结果表明, 熔点变化范围为1264¹296℃, 且随着Ti O₂含量增加, 渣相中低熔点相逐渐生成, 渣系的熔点逐渐降低;渣系中加入Ti O₂可以降低黏度, 且渣系黏度在高温段 (1350¹550℃) 受温度变化影响不大, 利于改善电渣重熔钢锭的表面成形质量;Ti O₂质量分数0⁹%范围内, 渣系电导率、光学碱度和密度随Ti O₂含量增多呈降低趋势, 且密度和光学碱度变化范围不大, 五组渣系都符合电渣重熔对密度和光学碱度的要求.     

含钛渣冷却过程中的物理化学性质

研究了含钛渣的粘度、电导率与温度、渣成分、时间的关系,获得了渣中初始结晶相CaTiO3结晶过程的动力学参数,建立了CaTiO3相的结晶温度与渣碱度之间的关系式。     

电渣重熔过程中的危害因素及防范措施

电渣重熔技术具有产品性能的优越性、生产的灵活性、工艺的稳定性及经济的合理性等优势,近年来得到快速发展。但电渣重熔生产中存在的氟化物、爆炸、高温、窒息、触电、火灾及非电离辐射等危害因素,严重威胁着作业人员的身体健康,甚至是生命安全。在电渣重熔危害因素产生的原因分析的基础上,提出的针对性的防范措施,对减少安全事故的发生、保护作业人员的健康具有一定指导意义。     

25t单相复合式电渣重熔炉的设计与应用

25t单相复合式电渣重熔炉是赛瑞公司设计开发的一种双臂式冶炼高合金钢的二次熔炼设备。介绍25t单相复合式电渣重熔炉主要参数、多功能设计、结构技术特点及控制系统等。     

电渣重熔炉电极熔化速度对重熔过程的影响

建立了重熔钢锭的数学模型,确定了材料的物理边界条件,采用有限差分法对电渣重熔钢锭凝固过程的非稳态模型进行了求解,研究了电极熔化速度与准稳态熔池深度的关系.     

大型电渣重熔设备横臂液压系统DSHplus仿真研究

大型电渣炉的横臂升降控制采用液压系统实现。横臂下降过程是电渣冶金的给料过程,其控制过程直接决定了电渣冶金的产品质量。针对120 t大型电渣炉横臂升降液压系统,采用DSHp lus系统仿真软件,对液压系统的关键参数及运动性能进行了仿真研究,验证了系统设计的合理性。     

CaF2-SiO2-Al2O3-CaO-MgO五元渣系的电导率

为了系统研究五元含氟渣系各组元对熔渣电导率的影响,根据5因素2次正交旋转回归法设计渣系,使用RTW-10熔渣物性测定仪,采用交流4探针法,测定了1 600℃下各渣系的电导率;研究了各组元对含氟渣系电导率的影响。结果表明：当CaF2的含量（质量分数,下同）在10%～75%时,随着Al2O3和SiO2含量的增加电导率逐渐减小,而随着CaF2、MgO和CaO含量的增加电导率逐渐增大;在w（Al2O3）=20%、w（MgO）=10%和w（CaF2）=50%时,当w（CaO）小于7%,随着w（SiO2）的递增电导率逐渐减小,而当w（CaO）大于7%时,随着w（SiO2）的递增电导率逐渐增大;在w（SiO2）=10%、w（MgO）=10%和w（CaF2）=50%时,当w（Al2O3）小于11%时,随着w（CaO）的递增电导率逐渐减小,当w（Al2O3）大于11%,随着w（CaO）的递增电导率逐渐增大。     

钒钛磁铁矿预还原球团及熔分渣的理化性能

给出了预还原球团、熔分渣的电导率及粘度的某些测试结果，并作了相应的数据处理及机理浅析，同时对它们的物相结构作了概述。     

非均相高钛渣的电导率和粘度

采用交流阻抗谱技术测量了含有固态TiC的非均相高钛渣的电导率,研究了TiC的浓度、粒度对炉渣电导率的影响,并测量了含有CaF2和部分氧化物添加剂的高钛渣的粘度.研究结果表明,TiC降低炉渣的电导率;渣中的负离子在TiC表面形成双电层分布,增加TiC的体积,它是炉渣粘度较大的原因之一.CaF2、CaO、MgO、MnO显著降低炉渣粘度,TiO2对炉渣粘度没有明显的影响.     

Numerical investigation on the fluid flow and heat transfer in electroslag remelting furnace with triple-electrode

Electroslag remelting (ESR) furnace with triple-electrode is always used to produce large ingots and the process complexity makes the application not widely spread. Thus, a transient three-dimensional coupled model in industrial scale has been developed to investigate the coupled magneto-hydrodynamics two-phase flow and heat transfer in system. Different from the previous studies with multi-electrode, the current work reveals the triple-electrode ESR with the formation of metal droplets and the solidification of liquid metal. Compared with single-electrode system with the same fill ratio, the heat source in the slag pool with triple-electrode is much more dispersive, and the U-shape metal pool in the ESR furnace with triple-electrode is much shallower and flatter than the V-shaped one in the single-electrode system. A shorter distance from each electrode to the center of system brings a higher heat efficiency, as well as a deeper and narrower metal pool.     

电渣重熔工艺对30CrMnSiA钢质量的影响

在工业生产条件下 ,研究了电渣重熔工艺对 3 0CrMnSiA钢质量的影响。结果表明 ,金属熔池深度达到重熔钢锭直径 1 /3～ 1 /4时钢锭组织和质量良好。提高输入功率和调整渣成分可提高重熔速度 ,从而提高生产率。     

镍渣在高硅锰硅合金生产中的应用

介绍了在高硅锰硅合金生产中,通过配入适量镍渣,调整渣型,减少了高CaO渣型对生产的不利影响,改善了电炉运行环境,对提高生产指标、降低成本起到了积极作用。     

Mathematical modelling of electroslag remelting P91 hollow ingots process with multi-electrodes

Abstract

Electroslag remelting (ESR) hollow ingot process with T-shape current supplying mould is a new metallurgical technology. A mathematical model was developed to describe the interaction of multiple physical fields of this process for studying the process technology. Maxwell, Navier-Stokes and heat transfer equations have been adopted in the model to analyse the electromagnetic field, magnetic driven fluid flow, buoyancy driven flow and heat transfer using finite element software ANSYS. Moreover, the model has been verified through the metal pool depth measurements, which were obtained during remelting of 10 electrodes into Φ900/500 mm hollow ingots of P91 steel, with a slag composition of 50–60 wt-% CaF₂, 10–20 wt-% CaO, 20–30 wt-% Al₂O₃, ≤8 wt-% SiO₂. There was a good agreement between the calculated results and the measured results. The calculated results show that the distribution of current density, magnetic induction intensity, electromagnetic force, Joule heating, fluid flow and temperature are symmetric but not uniform due to the multi-electrode arrangement in two symmetric groups. Simulation of the ESR hollow ingot process will help to understand the new technology process and optimise operating parameters.