Oxidation of Silicon and Boron in Boron Containing Molten Iron

A new process of directly smelting boron steel from boron-containing pig iron has been established. The starting material boron-containing pig iron was obtained from ludwigite ore, which is very abundant in the eastern area of Liaoning Province of China. The experiment was performed in a medium frequency induction furnace, and Fe2O3 powder was used as the oxidizing agent. The effects of temperature, addition of Fe2O3, basicity, stirring, and composition of melt on the oxidation of silicon and boron were investigated respectively. The results showed that sili- con and boron were oxidized simultaneously and their oxidation ratio exceeded 90% at 1 400℃. The favorable oxidation temperature of silicon was about 1 300-- 1 350℃. High oxygen potential of slag and strong stirring enhanced the oxidation of silicon and boron.

Effect of tempering temperature on microstructure and mechanical properties of high boron white cast iron

The effect of different tempering temperatures on the microstructure and mechanical properties of airquenched high boron white cast iron was studied.The results indicate that the high boron white cast iron comprises dendritic matrix and inter-dendritic M 2 B boride;and the matrix comprises martensite and pearlite.After quenching in the air,the matrix is changed into lath martensite;but only 1-μm-size second phase exists in the matrix.After tempering,another second phase of several tens of nanometers is found in the matrix,and the size and quantity increase with an increase in tempering temperature.The two kinds of second precipitation phase with different sizes in the matrix have the same chemical formula,but their forming stages are different.The precipitation phase with larger size forms during the austenitizing process,while the precipitation phase with smaller size forms during the tempering process.When tempered at different temperatures after quenching,the hardness decreases with an increase in the tempering temperature,but it increases a little at 450 ℃ due to the precipitation strengthening effect of the second phase,and it decreases greatly due to the martensite decomposition above 450 ℃.The impact toughness increases a little when tempered below 300 ℃,but it then decreases continuously owing to the increase in size and quantity of the secondary precipitate above 300 ℃.Considered comprehensively,the optimum tempering temperature is suggested at 300 ℃ to obtain a good combination of hardness and toughness.

Effect of carbon species on the reduction and melting behavior of boron-bearing iron concentrate/carbon composite pellets

Iron nugget and boron-rich slag can be obtained in a short time through high-temperature reduction of boron- bearing iron concentrate by carbonaceous material, both of which are agglomerated together as a carbon composite pellet. This is a novel flow sheet for the comprehensive utilization of boron-bearing iron concentrate to produce a new kind of man-made boron ore. The effect of reducing agent species （i.e., carbon species） on the reduction and melting process of the composite pellet was investigated at a laboratory scale in the present work. The results show that, the reduction rate of the composite pellet increases from bituminite, anthracite, to coke at temperatures ranging from 950 to 1300~C. Reduction temperature has an important effect on the microstructure of reduced pellets. Carbon species also affects the behavior of reduced metallic iron particles. The anthracite-bearing composite pellet melts faster than the bituminite- bearing composite pellet, and the coke-bearing composite pellet cannot melt due to the high fusion point of coke ash. With anthracite as the reducing agent, the recovery rates of iron and boron are 96.5% and 95.7%, respectively. This work can help us get a further understanding of the new process mechanism.

Carbothermic reduction characteristics of ludwigite and boron–iron magnetic separation

Ludwigite is a kind of complex iron ore containing boron, iron, and magnesium, and it is the most promising boron resource in China. Selective reduction of iron oxide is the key step for the comprehensive utilization of ludwigite. In the present work, the reduction mechanism of ludwigite was investigated. The thermogravimetry and differential scanning calorimetry analysis and isothermal reduction of ludwigite/coal composite pellet were performed. Ludwigite yielded a lower reduction starting temperature and a higher final reduction degree compared with the traditional iron concentrates. Higher specific surface area and more fine cracks might be the main reasons for the better reducibility of ludwigite. Reducing temperature highly affected the reaction fraction and microstructure of the reduced pellets, which are closely related to the separation degree of boron and iron. Increasing reducing temperature benefited the boron and iron magnetic separation. Optimum magnetic separation results could be obtained when the pellet was reduced at 1300°C. The separated boron-rich non-magnetic concentrate presented poor crystalline structure, and its extraction efficiency for boron reached 64.3%. The obtained experimental results can provide reference for the determination of the comprehensive utilization flow sheet of ludwigite.

Reduction–melting behaviors of boron-bearing iron concentrate/carbon composite pellets with addition of CaO

Although the total amount of boron resources in China is high, the grades of these resources are low. The authors have already proposed a new comprehensive utilization process of boron-bearing iron concentrate based on the iron nugget process. The present work describes a further optimization of the conditions used in the previous study. The effects of CaO on the reduction-melting behavior and properties of the boron-rich slag are presented. CaO improved the reduction of boron-bearing iron concentrate/carbon composite pellets when its content was less than lwt%. Melting separation of the composite pellets became difficult with the CaO content increased. The sulfur content of the iron nugget gradually decreased from 0.16wt% to 0.046wt% as the CaO content of the pellets increased from 1wt% to 5wt%. CaO negatively affected the iron yield and boron extraction efficiency of the boron-rich slag. The mineral phase evolution of the boron-rich slag during the reduction-melting separation of the composite pellets with added CaO was also deduced.

真空扩散对奥氏体灰铸铁渗硼层组织与性能影响的研究

为了改善奥氏体灰铸铁渗硼层厚度不足和脆性过大的问题,研究了渗硼处理和渗硼/真空扩散复合处理对奥氏体灰铸铁表面改性层摩擦磨损性能的影响和影响机理。利用光学显微镜、能谱仪、X射线衍射仪、电子探针等设备对单一处理和复合处理试样的渗层进行了金相组织、元素分布、物相组成、表面硬度、截面硬度以及磨痕分析。结果表明:真空扩散对渗硼层有着增厚的作用,能够有效的将脆性较大的FeB相转化为脆性相对较小Fe2B相,改善渗硼层的耐磨性,但会使得渗层的表面硬度略微降低,渗层中石墨的粗化现象更为加重。

硼对铁焦微观结构的影响

为探究硼原子对铁物种在焦炭分子骨架中的分布和价态组成的影响及对铁焦微观结构和强度的促进机理,以添加不同质量分数的硼酸制备的复合铁焦为研究对象,通过光学显微镜、X射线光电子能谱仪、X射线衍射仪等仪器,对比分析了硼添加前后铁焦微晶结构、光学组织、气孔结构和显微强度的变化。结果表明:在硼添加量为0.2%时,所制备的铁焦的Mf+Mm+Mc+Fi结构的含量达到最大,为68.25%,各向同性结构的含量降低,光学组织指数(OTI)和显微强度(MSI)均达到最大,分别为138和49.3,气孔率下降到59%,孔壁厚度增大到20μm;而随着硼添加量的进一步增大,铁焦的OTI和MSI均呈现下降趋势,气孔率上升,孔壁厚度减小。添加适量的硼后,硼原子以层间插入物进入铁焦石墨晶格,从而导致铁焦的稠环增大,中等尺寸各相异性结构含量增加,可促进热解成焦过程中类似粗粒镶嵌等强度较高的显微组织的形成,增大铁焦的壁厚。并且,硼原子对铁焦骨架的掺杂所形成的BC3结构使得铁焦微晶的石墨化程度增强,从而有助于改善铁焦的显微结构强度,有利于增强其稳定性。

预浸对烧结钕铁硼HEDP电镀铜的影响

[目的]烧结钕铁硼(Nd Fe B)的电镀前处理技术还不够成熟,开发适宜的前处理工艺极其重要。[方法]在电镀铜前,先采用以羟基乙叉二膦酸(HEDP)为主配位剂的溶液对NdFeB进行预浸。预浸液组成和工艺条件为:HEDP 20~30 g/L,氢氧化钾20~25 g/L,碳酸钾10~15 g/L,葡萄糖酸钾1~2 g/L,乙酸0.5~1.0 g/L,室温,时间60 s。通过电化学测试对比了Nd Fe B基体有无预浸处理时,铜在其表面的电沉积行为,并通过金相显微镜、扫描电镜、能谱仪和荧光光谱测厚仪,对比了有无预浸处理的Nd FeB基体表面Cu镀层的宏观和微观表面形貌、截面形貌、元素分布及厚度分布均匀性。[结果]Nd Fe B基体预浸后表面被活化,静态电位降低。预浸液能够填满基体表面的孔隙并形成一层水薄膜,在后续电镀铜时保护基体不被腐蚀。预浸处理的Nd Fe B基体表面所得Cu镀层均匀、致密,不易氧化发黑,结合力和耐蚀性较好。[结论]对烧结钕铁硼进行预浸处理,能够保证其在后续电镀铜过程不被腐蚀,提高Cu镀层的综合性能。

硼强化铁离子活化过硫酸盐高效降解荧蒽的研究

采用硼(B)强化铁离子活化过硫酸盐(PS)降解荧蒽(FLT),阐明了B的强化机理,从FLT的降解效果和PS利用率角度研究了B强化三价铁(Fe^(3+))活化PS的优越性,探究了水质条件对FLT降解的影响,验证了PS/Fe^(3+)/B体系在实际地下水中降解FLT和其他多环芳烃的可行性。结果表明:PS/Fe^(3+)/B体系中FLT降解的拟一级反应动力学常数k_(obs)为0.043 9 min^(-1),PS/Fe^(2+)/B体系中k_(obs)在30 min后从0.044 7 min^(-1)降低至0.009 6 min^(-1),证明PS/Fe^(3+)/B体系可实现FLT的持续高效降解。当Fe^(3+)浓度在0.02~0.08 mmol/L之间时,PS/Fe^(3+)/B体系均可高效降解FLT,表现出更强的可操作性。结合X射线光电子能谱仪的分析结果、Fe^(2+)和PS的浓度变化,证明Fe^(3+)的持续释放和B的持续还原性可以保障体系中活性氧物种(ROS)的高效利用。水质条件影响试验结果表明,酸性条件有利于FLT的高效降解,碳酸根离子和高浓度的腐殖酸不利于FLT的降解。实际地下水的复杂环境对FLT的降解有一定的抑制作用,但是通过预调酸pH=4.0后FLT去除率达到99.9%,同时PS/Fe^(3+)/B体系对萘和菲也具有良好的去除效果。

Fe/BN催化剂的制备及其费托合成性能

为开发基于高热传导性载体的催化剂,提高费托合成反应性能,以高比表面积的球磨氮化硼(BN)为载体,通过溶剂热法(溶剂热温度分别为120℃、160℃和200℃)制备了系列Fe/BN催化剂(Fe/BN-120、Fe/BN-160和Fe/BN-200),并研究了催化剂对费托合成的催化性能(温度为280℃、压力为2.0 MPa、合成气V(H2):V(CO):V(Ar)=16:8:1且空速为3000 mL/(g·h),以48h时的反应结果计)。采用N_(2)吸/脱附、电感耦合等离子体-原子发射光谱(ICP-AES)、X-射线衍射(XRD)、透射电子显微镜(TEM)、X-射线电子能谱(XPS)和H_(2)/CO程序升温还原(H_(2)/CO-TPR)等对催化剂进行了表征。结果表明,与Fe/BN-120相比,Fe/BN-160、Fe/BN-200中γ-Fe_(2)O_(3)的平均粒径分别由7.2 nm增加至13.6 nm、14.7 nm,同时Fe 2p结合能逐渐向低结合能方向偏移。与Fe/BN-120和Fe/BN-160相比,在电子效应和尺寸效应的作用下,Fe/BN-200的还原、碳化得到明显促进。在费托合成的CO_(2)和H_(2)O气氛中,还原得到的α-Fe、Fe_(3)O_(4)和球磨氮化硼表面的BOx在高温条件下发生反应生成硼酸铁。随着溶剂热温度的升高,催化剂的碳化程度逐渐升高,与Fe/BN-120相比(CO转化率为39.1%、CH_(4)选择性为24.3%和C_(5+)选择性为37.8%),Fe/BN-200的CO转化率提高至68.9%,CH_(4)选择性降至12.9%,C_(5+)选择性增加至51.1%。在Fe/BN催化剂上,通过改变溶剂热温度可以调控催化活性和产物分布,这为提高氮化硼负载的Fe基催化剂的费托合成反应性能提供了思路。

离子液体电沉积铝及其合金在NdFeB永磁体表面的应用

[目的]近年来,在材料表面电沉积轻质、耐腐蚀和低成本的铝及铝合金备受关注。离子液体以其高导电性、宽电化学窗口和低毒性,被视为环保电解液的首选。采用离子液体电沉积铝及铝合金能有效提升材料的耐蚀性和力学性能,这为低耐蚀性NdFeB永磁体材料的应用提供了新思路。[方法]综述了以AlCl3为主盐的离子液体在铝及铝合金电沉积工艺、机理及应用的最新进展,重点介绍了该技术在NdFeB永磁体中的研究和应用现状,指出了目前存在的问题。[结果]离子液体电沉积铝及铝合金在NdFeB永磁体表面的应用以Al及Al-Mn合金为主。[结论]尽管将离子液体电沉积铝及铝合金作为NdFeB永磁体表面防护已受到业界的广泛关注,并取得了一定的进展,但成本高、镀液黏度大、沉积难等问题仍亟待解决。

Study on Electrochemical Formation of Neodymium-Iron Alloy

The cyclic voltammetry was used to investigate the electrode processes of Nd(III) reduced on iron electrode and Nd(III),Fe(II) reduced on molybdenum electrode in molten chlorides. The Nd-Fe and Nd-rich RE-Fe alloys contained rare earth up to 90wt% were prepared by consumable cathode and electrolytic codeposition. The mechanism of electrochemical formation of Nd-Fe alloy had been discussed.

赣州市钕铁硼永磁材料产业现状及发展建议

赣州市,拥有丰富的稀土资源,也是一个重要的稀土材料产业基地,对于该产业的发展具有重要的影响。然而,随着环保要求的提高、市场竞争的加剧,该产业也面临着诸多问题和挑战。因此,本文试图通过实地调查,深入了解该产业的现状,发现其存在的问题和瓶颈。同时,本文从产业政策、市场前景、技术创新等多个角度进行分析和讨论,旨在提出有针对性的发展建议,为赣州市钕铁硼永磁材料产业的可持续发展提供参考和借鉴。

烧结钕铁硼速凝薄片片厚差异现象改善研究

针对烧结钕铁硼速凝薄片出现片厚差异的现象,通过对坩埚浇注倾倒时序程序优化改善,设计增加浇注系统的结构组成,控制冷却铜辊的装配同轴度和中间包角度,使速凝薄片的片厚差异现象得到了改善。结果表明,出现片厚差异的速凝薄片的比例由原来的36.1%降低至6.7%,降低了29.4%。速凝薄片的片厚差值富集区域由原先的0.1 mm~0.15 mm降低至0.03 mm~0.06 mm,片厚差值平均值由原来的0.129 mm减小至现在的0.046 mm,减小了0.083 mm,改善效果显著。

高硼铁基耐磨合金的研究进展

高硼铁基耐磨合金具有硬度高、价格低的特点,熔覆于部件表面,可以有效地减少磨损。以硼化物代替传统耐磨材料中的碳化物作为耐磨硬质相,虽具有良好的耐磨性能,但由于硼化物的脆性问题,导致合金存在韧性不足的缺点。本文综述了高硼铁基耐磨合金的分类和研究进展,重点分析亚共晶和过共晶高硼铁基合金的耐磨性,以及不同工艺对于合金韧性的改善,并对高硼铁基耐磨合金的研究进行了展望。

硼镁铁精粉的烧结性能试验及工业应用

为了拓展可用铁矿资源的来源途径,本文对一种含硼、镁的铁矿资源(丹东硼镁铁精粉)的烧结性能进行试验研究,并开展相关工业应用试验。结果表明:硼镁铁精粉的同化性能与杨迪粉接近,液相流动性能与PB粉接近;在现有烧结原料和工艺条件下,硼镁铁精粉等比例替代地方磁精粉,有利于提高烧结矿的成品率,降低固体燃料消耗,改善烧结矿的低温还原粉化性能。该铁精粉配比低于10%对提高烧结机利用系数和烧结矿转鼓强度有利,高于10%对上述两个指标有负面影响。工业应用试验结果表明,配加3%的硼镁铁精粉后,烧结矿的全铁品位略有降低,烧结矿中B_(2)O_(3)质量分数增加,达到0.56%;烧结矿的粒度组成得到优化,(5,10)mm和≤5 mm的粒级占比分别降低0.79%和1.29%,>40 mm的粒级占比增加3.01%;烧结机利用系数由1.60 t/(m^(2)·h)提高到1.62 t/(m^(2)·h),烧结矿转鼓强度提高2.22个百分点,低温还原粉化指数(>3.15 mm)由58.80%上升至60.29%,烧结矿产、质量指标均有明显改善。

Effects of B_4C Addition on Properties of Al_2O_3-SiC-Si_3N_4 Castables for Iron Trough

Effects of B4C additions （0,0.2%,0.4%,and 0.6%） on cold physical properties and hot modulus of rupture of Al2O3-SiC-Si3N4 castables for iron trough were investigated. The phase composition and microstructure were analyzed by XRD and SEM. The results show that bulk density,cold strength,and hot modulus of rupture of the castables first increase and then decrease while apparent porosity first drops and then increases with B4C addition increasing. The optimum addition of B4C is 0.4%. B4C mainly contributes to sintering and antioxidation. Compared with the specimens without B4C,the specimens with B4C have more fibrous O＇-SiAlON with larger length-diameter ratio. The growth mechanism of O＇-SiAlON crystals is deduced to gas-solid mechanism.

高性能钕铁硼永磁晶界扩散技术最新进展与未来展望

钕铁硼永磁在新能源等战略新兴领域有着广阔的发展前景。应用端的发展对钕铁硼磁体的高温性能和矫顽力提出了更高的要求。晶界扩散技术是烧结钕铁硼磁体的一项重大进展。它主要将重稀土元素或稀土合金以晶界扩散的方式渗透入磁体内部,通过强化硬磁相晶粒表面的薄弱区域,在有效提高磁体矫顽力的同时,大大减少了重稀土的用量,减小了重稀土对剩磁和磁能积的不利影响,显著降低了材料成本。自本世纪初发展至今,晶界扩散技术已迅速实现了工业化。最近几年,晶界扩散在理论和技术层面都有了较大的发展和创新。目前通过晶界扩散技术,烧结磁体的最大磁能积(MGOe)+内禀矫顽力(kOe)已达75以上。基于近期国内外的产业现状和研究前沿,总结了近年来扩散剂、扩散剂包覆技术、扩散方法、选区扩散和扩散基材的最新进展,并对晶界扩散的未来发展进行展望,为高性能钕铁硼永磁体的研发提供参考。

CeO_(2)添加量对铁基粉末冶金材料表面渗硼层组织与摩擦磨损性能的影响

在渗硼剂中添加CeO_(2),采用固体粉末渗硼法对Fe-2%Cu-0.4%C铁基粉末冶金材料进行950℃×5 h渗硼处理,研究了CeO_(2)添加量(0,2%,4%,质量分数)对渗硼层显微组织和摩擦磨损性能的影响。结果表明:不同CeO_(2)添加量下的渗硼层均形成单一Fe_(2)B相;随着CeO_(2)添加量的增加,渗硼层的表面粗糙度增大,厚度、硬度及耐磨性能呈先增大后减小趋势;当CeO_(2)添加质量分数为2%时,渗硼层的厚度和硬度均最大,分别约为144μm和58.0 HRC,此时渗硼层的表面完整性相对较好,磨损量最小,约为0.008 g,耐磨性能最佳。

碳化硼对铁矿石混凝土亚高温后性能的影响研究

以5%的碳化硼等质量取代褐铁矿砂,制备了强度等级C50和密度等级RS2的铁矿石防辐射混凝土,研究了其在不同亚高温温度下的热工性能以及145℃处理5 d前后力学及耐久性能,分析了碳化硼在亚高温前后对铁矿石混凝土性能的影响规律和机理。结果表明:碳化硼的掺入提高了铁矿石混凝土的比热容、导热系数、热扩散系数、抗折强度,但降低了铁矿石混凝土的表观密度、抗压强度;亚高温后,碳化硼的填充效果明显,优化了气泡参数,提高了铁矿石混凝土微观结构的稳定性,有利于减缓铁矿石混凝土耐久性能劣化过快的情况,维持铁矿石混凝土亚高温后的防辐射稳定性。