浸没在金属熔池中固体颗粒熔化过程的数学模型

建立了金属熔池中固体颗粒熔化过程的数学模型。该模型包括颗粒熔点高于、等于和低于熔池中金属熔点的情况。用冰块在水中及铝颗粒在铝熔池中熔化过程的实验数据检验了模型的可靠性，并分析了颗粒尺寸、熔池温度及颗粒相对金属熔体的滑移速度等因素对熔化过程的影响。     

电弧炉中金属颗粒熔化速率的数学模型

为了描述工业电弧炉中（EAF）金属颗粒的熔化动力学,开发了将计算流体动力学模型耦合到熔似凝固颗粒的拉格朗日模型,假定液态钢水占据整个计算领域。金属颗粒为直接还原铁（DRI）,为了评价三相EAF中加入的DRI熔化速率,采用2个以前的模型,即电弧模型以及流体流动模型,评价了初始颗粒尺寸、初始DRI温度、加料位置、加料速率、电弧长度以及DRI的冶金性能影响,此外,本模型也评价了熔炼过程前期形成的凝固壳。     

圆铸锭连续铸造结晶规律性的探讨

连续铸造铸锭时靠冷却水将热量带走,使熔体金属凝固。金属从熔体转变成固体的结晶过程,直接影响到铸锭的质量。研究结晶过程中铸锭直径、水冷强度、液穴形状、铸造速度、结晶速度以及金属物理性能间的相互关系的问题,称之为结晶规律性。(一)液穴形状从熔体金属转变成固体金属的固相线形状,称之为液穴形状。正常铸造时液穴形状保持一定;当铸造速度、金属物理性能和冷却条件改变时,液穴形状就相应改变。     

TiO2含量对酸性低钛矿渣棉熔体粘度和结构的影响

以酸性低钛矿渣棉熔体为研究对象,采用旋转柱体法研究1493～1773 K温度范围内TiO2含量对熔体粘度和熔化性温度的影响,并结合粘流活化能和红外光谱分析了熔体结构的变化.结果表明,TiO2含量从0％增加至6％,熔体粘度、熔化性温度以及粘流活化能均降低;实验渣样的熔化性温度处于1498～1573 K之间,在1653 K...     

"活度"质疑

为研究二元系溶液中组元摩尔分数和气相中蒸气压的规律,考察了48个化合物在熔点固液相变的熔化熵变,发现相变时没有发生显著的化合物分解.在假设二元系溶液中存在化合物分子的情况下,组元在全浓度范围符合拉乌尔定律,不存在Lewis定义的“活度”;通过与Mg-Si、In-Sb和Fe-Mn三个二元系实测活度结果对比,证实了计算的平衡摩尔分数即为活度值,二元金属熔体不存在所谓“活度”的观点.推导了在二元系金属熔体存在一个金属间化合物条件下平衡的摩尔分数的通用公式,以及相应的A₂B或AB型金属间化合物的一般公式.将二元系溶液划分为大于纯组元熔点的温度、小于纯组元熔点温度但高于液相线和低于液相线的三个区间,提出了适应不同区间的广义拉乌尔定律的关系式.      

三菱法炼铜新技术（七）

1概况熔体的混合和流动条件以几种方式影响三菱法的连续作业，熔炼炉中固体颗粒的熔化程度主要取决于计图时间和混合条件。炉渣贪化炉中冰铜颗粒的回收也决定于炉渣的流动条件，生产控制也受溶体流动性的影响。例如，在连续吹炼炉入口处，冰铜品位变化的反应滞后时间较长。熔炼炉中新生成的冰铜与已存在的大量冰铜结合在一起，然后从熔炼中流出进入炉渣贪化炉中，在那里进行进一步的混合。炉子中熔融物的混合和流动条件可用示踪技术确定，实验数据通过混合模型表示，在此，假设炉子体积可以分成简单的，界限清楚的流型，这里：湍流的体积：…     

AZ91合金消失模铸造充型过程研究

利用电触点法研究TT艺参数对消失模铸造AZ91合金的流动形态和流动速度的影响．结果表明,AZ91合金熔液以凸弧形平稳地向前逐层置换泡沫,这是由于裂解产物在流动前沿尤其模样边缘处的大量堆积造成的．充型时间随浇注温度、真空度的提高而变短．充型过程中充型速度呈现交替变化．以熔融金属作为振子,熔体和泡沫模之间的气层作为弹簧建立弹簧一振子模型,可以诠释充型速度的交替变化．     

气雾化球形金属粉末形成机理的研究进展

气雾化法是最早用来生产球形金属粉末的技术之一,有力地支持着3D打印技术的发展。由于粉末形成过程复杂,难以直接观察研究,为此研究人员采用仿真模拟的方法再现气雾化过程,揭示粉末形成机理。综述了气雾化过程中气流速度分布特征、金属熔体到粉末过程中破碎、球化、飞行、凝固的理论模型的研究成果,总结了影响粉末颗粒的形成过程相关的物理性能参数与工艺参数。最后指出气雾化制粉理论研究的发展趋势。     

铸咀型腔铝熔体流态分析

以两种铸咀型腔熔体流动为研究对象，分析了在常规铸轧和超薄快速铸轧时，铸咀型腔的熔体速度，型腔结构，熔体流动雷诺数的变化对铝熔体流态的影响规律，并得出结论：无论是常规铸轧还是超薄快速铸轧，铸咀型腔体流动都存在不同强度的紊流区域，但是在铸咀出口处为准层流。     

液态锌对固态金属腐蚀相变的研究

液态Zn对低碳钢及Fe2Al5腐蚀相变过程的研究表明,该腐蚀是由原子扩散引起的、由相平衡推动的相变过程所引起的固态金属的定向熔化过程。在液态Zn与固态金属不形成中间相的腐蚀条件下,液态Zn对纯金属及其固溶体的腐蚀为"溶解型腐蚀",固态金属被液态Zn直接熔化;在液态Zn与固态金属形成中间相(或固体本身就是中间相)的腐蚀条件下,合金的腐蚀为"瓦解型腐蚀"。腐蚀相变规律遵循:腐蚀区域成分的变化对应于腐蚀温度下合金相平衡。     

Mathematical modelling of alloy melting in steel melts

This paper deals with a mathematical model for melting of ferro-manganese particles in liquid iron in a ladle. With the assumption that the resistance of heat transport in the iron shell that initially freezes at the particle surface is zero, the particle melting time can be calculated analytically. To describe the total melting rate of alloy particles added into the ladle, a melting distribution function is introduced. It includes the melting time of the individual particles, the particle size distribution, and the addition function of the particles. The factors influencing the melting behaviour of the addition are investigated. The melting behaviour is greatly affected by the particle size distribution, the temperature of the melt, and the particle-melt slip velocity. The addition time and the addition function have only a small influence on the melting behaviour.     

Laboratory experiments and process modelling of the melting and dissolution of low‐density ferro‐molybdenum in steel melts

A low‐density sintered ferro‐molybdenum is presented as a new alloying agent. The paper describes laboratory studies about the dissolution in liquid iron of briquettes of this alloy and of classical high density ferro‐molybdenum pieces. It presents further a mathematical model of the melting and dissolution process. During dissolution, an approximately 1mm thick layer infiltrated by melt forms on the particle surface. The infiltrated melt solidifies in the plane where the temperature has reached the eutectic temperature in the system iron‐molybdenum. Internal dissolution of alloy material in the layer is weak, which means that the dissolution proceeds almost exclusively from the outer surface of the briquette. Dissolution rate increases with sinking briquette density. The lower molybdenum content per volume in the briquettes which is proportional to the density has the effect that the liquidus concentration and the liquidus temperature at the solid‐liquid interface decrease in comparison with compact material. This reduces the mass transfer rate and increases the heat transfer rate. The effect is a faster movement of the interface. Below a critical density of approximately 5200 kg/m³ for the alloy considered, the molybdenum concentration on both sides of the interface becomes equal. From this moment, the alloy is liquefied solely by melting of the moving interface. Mass transfer from the interface gets negligible and distribution of the molten alloy into the bulk melt takes place only by the outer mixing process. From the described behaviour it follows, that below the critical density the melting rate is solely determined by heat transfer. Since heat transfer is faster than mass transfer, melting of alloys with reduced density is correspondingly accelerated. The extremely slow dissolution rates of high melting alloys can thus, be overcome by giving the alloy a certain porosity. The mathematical process model describes the phenomena quantitatively.     

铁液中Al_2O_3纳米颗粒溶解和熔化的热力学研究

与块体材料相比,纳米材料尺寸小、界面能大,导致其溶解和熔化过程的热力学不同于块体材料.从理论上推导了Al2O3纳米颗粒在铁液中的元素平衡溶度积以及熔化温度与颗粒尺寸之间的关系,结果表明,随颗粒尺寸减小,平衡溶度积逐渐增加,熔化温度逐渐下降,而且粒径越小,平衡溶度积和熔化温度的变化率越大.经计算,1873K铁液中Al2O3的质量分数为0.01%时,半径为0.1nm的Al2O3颗粒比块体Al2O3的平衡溶度积增加了11.71%;半径为1nm的Al2O3颗粒在空气和铁液中的熔化温度分别为1849K和1267K,比块体Al2O3的熔化温度分别下降了454K和1036K.     

电解铝液直接生产超薄箔坯料的熔体质量控制

针对电解铝液直接铸轧坯生产超薄铝箔坯料过程中所存在的质量缺陷,结合铸轧法生产铝箔坯料所采用电解铝液的特点,全面分析了生产过程中铝合金熔体处理工艺对熔体质量的影响因素,并研究制定了相应的铝熔体处理措施。有效改善了熔体质量,消除/减少了电解铝液生产超薄铝箔坯料的质量问题,实现了低成本、高效率、高品质、稳定生产超薄箔坯料的目标。     

Melt-solid interactions in laser cladding and laser casting

Experimental data in conjunction with mathematical models are used to explain various aspects of laser casting and laser cladding by the preplaced powder method. For increasing speed, the data can be distinguished between substrate melting, dilution-free clad bonding, bond-free casting, and poor contact breaking the melt track into spheres. Results include a thermodynamic explanation of the wide range of process parameters over which dilution-free clad deposits can be produced, as the process switches from heating of the insulating powder to additional cooling when the melt front reaches the substrate. Also, the interaction of the melt pool with the powder bed is analyzed to identify why laser castings have microscopically uneven surfaces and do not bind with the substrate. The advancement of the melt front through the powder layer is governed by heating, melting, and incorporation of each individual grain. Although most powder grains are in the small size range for the case studied, the few particles up to a factor 3 larger delay and therefore govern the front advancement due to much slower melting and surface tension driven incorporation, depending on the particle size in a non-linear manner.     

Marco- and microseparation in Ga-Pb melts

A procedure for the separation of the contributions of two liquid phases making up a binary metallic melt with a miscibility gap to its diffraction pattern is proposed. The simulation of the structures of two such liquids in the Ga-Pb system indicates that they are qualitatively different: the liquid phase based on the component with a lower melting point is microinhomogeneous, and the liquid based on the component with a higher melting point exhibits a virtually statistical atomic distribution.     

反向凝固法生产复合奥氏体不锈钢薄带的研究

采用１．２ｍｍ厚的１５Ｆ热轧板为母带,以奥氏体不锈钢１Ｃｒ１８Ｎｉ９作为覆层材料,在实验室条件下研究了反向凝固法生产复合奥氏体不锈钢薄带的可行性。实验表明,随着母带在钢液中浸渍时间的增加,新相层的生长经历“快速生长”、“平衡相持”和“迅速回熔”阶段,新相层厚度着钢液过热度的增加而近似线笥地减少。此外,线带表面状态、母带在钢液中的浸渍时间及过热度对铸带质量有显著影响,控制合适的工艺参数可以获得质量优     

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%。     

SiCP增强泡沫铝基复合材料制备工艺及润湿性研究

对采用熔体发泡法直接制备碳化硅颗粒增强泡沫铝基复合材料进行了探索，讨论了制备过程中SiCp与铝液间的润湿性、发泡工艺参数与温度控制等对制备工艺的影喻。表明该工艺简单，易于操作，不需任何增粘措施，处理后的SiCp浸润性好且分布均匀，孔洞分布均匀。