向冶金熔池中心底吹惰性气体的两相流流场

为了适应浸入式喷嘴(风眼、多孔物)喷吹技术的发展和应用,在前人研究熔池中气体喷吹现象的基础上,采用二维两相流均流模型,对喷吹冶金熔池的两相流进行了研究。     

电弧炉吹炼金属用非水冷浸入式喷头

电弧炉生产低碳高合金钢时伴随有大量合金元素的损失。烧损一般发生在氧化期,特别是在吹炼末期,这是由于金属熔池搅拌不充分的缘故。冷态模拟试验表明,耗气量相同的条件下浸入式喷咀喷吹时的搅拌强度比不浸入的喷咀强烈。因此,研究喷吹高合金钢熔体的     

底吹CaCO3粉剂转炉复合吹炼法的研究

底吹CaCO_3粉剂转炉复合吹炼热态试验的结果证明:转炉底吹CaCO_3粉剂,作为复吹新气源,是复吹和喷射冶金工艺相结合的一种较好的复吹方法。通过保持高粉气比的连续喷粉,能使钢中氮降到0.004％以下,并能提高脱碳速度及脱磷、脱硫率。改变底喷CaCO_3粉剂量,可以有效的调整熔池搅拌强度。     

铁水包喷吹镁—碳化钙复合粉剂脱硫的数学模拟

鉴于金属镁粒和碳化钙粉这两种脱硫粉剂的物理和化学性质有着本质的区别，作重点分析研究了镁粒在脱硫过程中的热力学、反应机理和动力学。在具体分析熔池均混时间、粉剂穿透比及粉剂停留时间这３个基本参数对脱硫过程影响的基础上，建立了能体现这３个参数影响的模拟铁水喷吹镁粒和碳化钙复合粉剂脱硫处理的数学模型，并讨论了两种粉剂在脱硫过程中的耦合效果。结合水模实验、流场计算和宝山钢铁集团公司的铁水包喷粉深脱硫生产数     

复吹转炉底吹氧气和石灰粉水模拟

 为了考察复吹转炉底吹氧气和石灰粉过程中的熔池特性,建立复吹转炉底吹喷石灰粉的水模型,用水模拟铁水,用空心玻璃微珠模拟石灰粉。利用图像处理法研究了底吹氧气和石灰粉时粉剂分布情况及熔池搅拌情况。采用熔池电导率法考察了相同条件下底吹喷粉与不喷粉时的混匀时间。研究结果表明,喷粉能够促进熔池搅拌,且粉剂扩散速度随底吹载气流量增大而增大;未喷粉时,混匀时间随载气流量增大而减小;在相同底吹载气流量条件下,喷粉时熔池的混匀时间明显低于未喷粉时的混匀时间,且在试验范围内,混匀时间在底吹载气流量为2 m3/h(标准态)时出现极小值。     

铁水包喷吹镁-碳化钙复合粉剂脱硫的数学模拟

鉴于金属镁粒和碳化钙粉这两种脱硫粉剂的物理和化学性质有着本质的区别 ,作者重点分析研究了镁粒在脱硫过程中的热力学、反应机理和动力学。在具体分析熔池均混时间、粉剂穿透比及粉剂停留时间这 3个基本参数对脱硫过程影响的基础上 ,建立了能体现这 3个参数影响的模拟铁水喷吹镁粒和碳化钙复合粉剂脱硫处理的数学模型 ,并讨论了两种粉剂在脱硫过程中的耦合效果。结合水模实验、流场计算和宝山钢铁集团公司的铁水包喷粉深脱硫生产数据确定了该模型的参数 ,并对其进行了验证。模型计算结果表明 ,复合粉剂脱硫的总速率与喷粉速率、载气流量、镁蒸汽与溶解态镁的比率等有关 ;镁脱硫是以溶解态镁脱硫为主 ;在脱硫处理的不同阶段 ,镁和碳化钙的相对脱硫速率不同。并依此对喷吹工艺给出了合理的建议     

金属镁粉在铁水预处理脱硫生产中的应用

阐述了在铁水预处理中采用钝化金属镁－钙质粉剂进行复合喷吹和混合喷吹两种工艺及特点，并分析了在铁水预处理中影响金属镁脱硫率的主要因素，从而提出一个合理工艺制度。     

复合旋转喷吹铁水脱硫预处理工艺研究与应用

鞍钢股份有限公司炼钢总厂结合复合喷吹脱硫和KR搅拌脱硫两种工艺的优势,研制了复合旋转喷吹铁水脱硫预处理工艺,并且增加了脱硫喷枪的喷吹孔数量,调整了喷枪旋转转速,优化了喷吹孔位置分布以及喷吹孔径尺寸等参数。实践表明,采用复合旋转喷吹铁水脱硫预处理工艺可以降低脱硫粉剂消耗约30%,脱硫率提高了4.25%。     

铁水喷粉脱硫的数学模型

铁水喷粉脱硫 ,特别是用镁粒脱硫 ,已为越来越多的钢铁厂所采用。预测喷吹操作和粉剂特性对脱硫效率影响的动力学模型将有助于改善喷吹操作 ,并使喷吹操作达到最佳化。对于铁水喷粉脱硫 ,热力学和化学动力学条件 (脱硫剂和温度 )通常是固定的。脱硫效率主要由传质动力学 (喷吹参数和在罐内的混合程度 )决定。因经 ,有必要对传质动力学进行详细的系统的模拟研究 ,以提高粉剂的利用率和铁水的脱硫率。通过动力学分析 ,能得到一些重要的可决定脱硫率和粉剂利用率的参数。这些重要参数是粉剂进入铁水的穿透比 (ＰＲ) ,粉剂在熔池内的停留时间分…     

煤粉与熔剂混合喷吹管道偏析行为的数值模拟

为了探究高炉煤粉与熔剂混合喷吹时的偏析行为，对高炉喷吹煤粉和熔剂取样并进行测试，得到喷吹煤粉的工业分析结果和元素分析结果，以及煤粉和熔剂的成分检测结果。在此基础上使用Fluent软件对喷吹煤粉与熔剂混合喷吹输送过程中的不同颗粒沉降规律进行数值模拟分析，解析熔剂添加量、载气速度以及管道长度对偏析的影响。试验结果表明，熔剂添加量对偏析的影响较小；随着载气速度的增大，偏析程度逐渐降低；管道越长，受偏析影响的粉煤量也越多。因此，提高载气速度有助于抑制偏析；管道过长不仅会增加颗粒的沉降度，还会加大偏析的影响。研究结果可为煤粉和熔剂混合喷吹技术的应用提供指导。     

Predicting segregation of metal powders

Abstract

Close tolerances in powder quality are necessary for efficient production and control of these tolerances can be achieved only by detailed analysis of materials and processes. The quantification and identification of segregation effects has been a challenge, especially with the powders typically used in PM. An attempt to quantify segregation as a first step towards the predicting segregation behaviour of general powders is reported. Experiments have been undertaken using a lubricated iron alloy powder to analyse rolling segregation, and using am unlubricated powder to determine the effect of height of discharge on segregation. Bulk particulates characterised by small particle sizes, narrow size distributions, free flow, high particle densities and high inter-particle forces require careful experimental procedures to obtain repeatable results.     

Solute segregation behavior in spray-atomized Pd-Rh-V(Co) powders

In the present study, two palladium-based ternary alloys, with nominal compositions of Pd-4.9 wt pct Rh-0.72 wt pct V and Pd-5 wt pct Rh-1 wt pct Co, were spray atomized into micron-sized powders using a high-energy gas atomization technique. Solute segregation in the spray-atomized powders was systematically investigated. It was found that, as the powder size decreases, the solute segregation level decreases, either in terms of standard deviation of solute content from the average value, or in terms of the percentage of segregation-free regions in the powder, or in terms of the maximum (Rh)/minimum (Co, V) solute content in the powder. Moreover, theoretical analyses were carried out to evaluate the percentage of segregation-free regions, as well as the maximum/minimum solute content, in each powder. The theoretical analysis indicated that, among the different mechanisms governing the solute segregation behavior, undercooling levels experienced by the droplets, both prior to and after nucleation, played the most important role in decreasing the solute segregation level as the powder size decreased.     

水雾化铁粉与钢粉新产品的开发

介绍了鞍钢冶金粉材厂近几年来研制开发的水雾化铁粉和钢粉新产品的特性及其应用。新产品包括低合金钢粉、无偏析混合钢粉、易切削钢粉、烧结贝氏体钢粉和阀座粉等 5个系列。     

粘结剂种类及用量对预混合钢粉粉末性能影响的研究

将钢铁粉末中的合金元素进行粘结处理制备成预合金钢粉末是一种减少粉末在操作过程中扬尘和成分偏析的新技术.研究了不同粘结剂种类和用量对预混合钢粉粉末流动性、松装密度、合金元素粘结率的影响.发现粘结处理大幅改善了预混合钢粉的性能,而不同粘结剂对预混合钢粉性能的影响各不相同.当使用0.1%(质量分数)的粘结剂时预混合粉对C的粘结率达到76%～90%,对Cu的粘结率达到38%～72%;粉末的流动性为21.7～24.6s/50g,且不随放置时间增加而发生明显的改变.粘结剂加入量增加时预混合钢粉中合金元素粘结率和粉末流动性继续提高,粘结剂加入量为0.2%(质量分数)时对C和Cu的最高粘结率分别达到94%和80%,粉末流动性达到约21s/50g,粉末的松装密度可以通过改变石蜡加入量进行调节.     

钇含量对CoNiCrAlY合金微观组织的影响

分别采用真空感应熔炼及真空惰气雾化的方法制备了CoNiCrAlY铸锭及粉末,并对其铸态组织进行了研究。结果表明:随着钇含量的增加,钇偏聚程度也逐渐增大,在铸锭铸态组织中存在明显的枝晶组织,钇含量较低时其形貌呈现细长条状。而当钇含量达到1.40%时,铸锭中枝晶开始呈现鱼骨状。另外,研究表明粉末中的显微组织与铸锭中相似,但当钇含量为0.61%时,钇的偏聚不明显。     

The role of particle size on the laser sintering of iron powder

The effects of powder particle size on the densification and microstructure of iron powder in the direct laser sintering process were investigated. Iron powders with particle sizes ranging from 10 to 200 μm were used. It was found that the sintered density increases as the laser energy input is increased. There is, however, a saturation level at which higher density cannot be obtained even at very intensive energy input. This saturation density increases as the size of the iron particles decreases. Meanwhile fine powders with narrow particle size distributions have a tendency toward agglomeration, and coarse powders with broad particle size distributions have a tendency toward segregation, both of them resulting in lower attainable density. In order to investigate the role of particle size, a “densification coefficient (K)” was defined and used. This coefficient depends on the particle size and the oxygen content of iron powder. The results of this investigation demonstrate that the presence of oxygen significantly influences the densification and pore morphology of laser-sintered iron. At higher oxygen concentrations, the iron melt pool is solidified to agglomerates, and formation of pores with orientation toward the building direction is more likely to occur. When the oxygen concentration is kept constant, the densification coefficient decreases with decreasing the particle size, meaning the densification kinetics enhances. This article presents the role of powder characteristics and the processing parameters in the laser sintering of iron powder as a model material. The mechanism of particle bonding and microstructural features of laser-sintered parts are addressed.     

用粘结剂处理的预合金Mo钢基预混粉取代扩散粘结粉

现已采用成本较低的粘结剂处理预混粉FLOMET 44A和44B取代扩散粘结粉。为避免镍与铜的偏析和改善预混粉的流动性。将以0．85％Mo预合金ATOMET 4401作基体粉，并添加镍、铜与石墨制取的预混粉进行粘结剂处理。其性能类似于扩散粘结粉。FLOMET 44A和44B已用于制造汽车、电动工具与农机零件。研究了它们的压缩性、重量稳定性、力学性能与显微组织，并分别与含1．75％Ni和4．0％Ni的扩散粘结粉做对比。低成本的粘结剂处理预混粉其尺寸变化、稳定性和力学性能与扩散粘结混合粉相同。     

<Emphasis Type="Italic">In-situ</Emphasis> reactive processing of nickel aluminides by laser-engineered net shaping

Nickel aluminide intermetallics (e.g., Ni₃Al and NiAl) are considered to be attractive materials for high-temperature structural applications. Laser-engineered net shaping (LENS) is a rapid prototyping process, which involves laser processing fine metal powders into three-dimensional shapes directly from a computer-aided design (CAD) model. In this work, an attempt has been made to fabricate aluminide intermetallic compounds via reactive in-situ alloying from elemental powders using the LENS process. In-situ reactive alloying was achieved by delivering elemental Ni and Al powders from two different powder feeders, eliminating segregation observed in the samples deposited by using the premixed elemental powders. Nickel aluminides of various compositions were obtained easily by regulating the ratio of their feed rates. The aluminide deposits exhibited a high solidification and subsolidus cracking susceptibility and porosity formation. The observed porosity resulted from a water-atomized Ni powder and can be minimized or eliminated by the use of a N₂-gas-atomized Ni powder of improved quality. Cracking was due to the combined effect of the high thermal stresses generated from the LENS processing and the brittleness of the intermetallics. Crack-free deposits were fabricated by preheating the substrate to a temperature of 450 °C to 500 °C during LENS processing. Compositionally graded Ni-Al deposits with a gradient microstructure were also produced by the in-situ reactive processing.     

合金粉末预氧化法制备Ag-SnO2-Y2O3电接触材料的研究

Ag-SnO2是各国电接触材料研究人员近年来新开发的一种无镉新型触头材料,它具有较好的导电导热性,优良的耐热性、抗电弧烧蚀性和抗熔焊性,是目前代替Ag-CdO的最理想材料。本文通过合金粉末预氧化法、复合粉体改性处理技术来制备Ag-SnO2-Y2O3电接触材料,添加稀土后合金粉末容易氧化,氧化粉体经改性处理后可有效改善氧化物颗粒与银基体间的润湿性、改善材料的后续加工性能,并且所制备的Ag-SnO2-Y2O3材料密度高、组织均匀、不存在宏观偏析,SnO2和Y2O3颗粒在材料中弥散均匀分布。     

化学镀制备镍包铜复合粉末的工艺与表征

本文分别选用次亚磷酸钠、联氨做还原剂，通过化学镀制取了镍包铜复合粉末，实验发现：次亚磷酸钠作还原剂时，用盐酸活化、酸化后的铜粉，可直接在其表面进行化学镀，镀覆效果良好，可取代昂贵的氯化钯活化处理；而用联胺作还原剂，可以直接在铜粉表面实现镀覆。采用SEM（包括EDS），XRD对制取的复合粉进行了分析测试，结果表明：复合粉末表面较原始粉末粗糙，包覆层均匀；用次亚磷酸钠作还原剂，所得到的复合粉末包覆层为镍磷合金，而用联胺作还原剂，制取的复合粉末仅由镍铜两相组成，未引入其他元素。对Ni／Cu复合粉的化学成分进行测试，结果表明：Ni／Cu复合粉末符合粉末冶金材料的要求，通过氢还原可以降低含碳量、氢损，提高复合粉的粉末冶金性能指标。