TUNGSTEN ELECTRODES CONTAINING THREE TYPES OF RARE EARTH OXIDES

Three types of tungsten electrodes containing three rare earth oxides, namely Y₂O₃, La₂O₃, and CeO₂ and one with Y₂O₃ and CeO₂ were prepared, in which the total contents of rare earth oxides are 2.2% in mass, and the characteristics of these electrode materials were studied. By TIG welding, the welding characteristics including arc starting, arc static properties and electrode consumption of these electrodes were also analyzed. The results suggest that the electrodes added three rare earth oxides are more favorable for processing than that added two rare earth oxides. All the electrodes activated with two or more rare earth oxides are more superior to W-ThO₂ in operating, and the electrode combined with Y₂O₃ and CeO₂ shows the best properties when it is used at a heavy current for a long time. The analyses of the results of electrode consumption indicates that the rim forming during arcing is one of the important reasons for electrode's heavy erosion, and the increased Y₂O₃ content in electrodes is beneficial to retard the formation of rim, and leads to the improvement of consumption resistance of the electrodes.     

EFFECTS OF Y2O3 AND CeO2 ON PROCESSING AND CHARACTERISTICS OF TUNGSTEN ELECTRODES

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二元复合稀土钨电极材料的性能

通过粉末冶金和压力加工制备了系列二元复合稀土钨电极材料（Ｗ－Ｌａ２Ｏ３－Ｙ２Ｏ３,Ｗ－Ｌａ２Ｏ３－ＣｅＯ２,Ｗ－Ｙ２Ｏ３－ＣｅＯ２）,采用直流正接（ＤＣＳＰ）的钨极氩弧焊（ＴＩＧ）方法,系统研究了它们的焊接电弧特性,包括引弧性能、电弧静特性和电极抗烧损性能。并对它们的这些性能与单元稀土钨电极材料（Ｗ－Ｌａ２Ｏ３,Ｗ－ＣｅＯ２,Ｗ－Ｙ２Ｏ３）和钍钨电极材料进行了比较。结果表明二元复合稀土钨电极性能优     

稀土氧化物对贮氢合金电极电化学性能的影响

研究了稀土氧化物La_2O3_,CeO_2,Nd_2O_3和Y_2O_3对AB_5型贮氢电极电化学性能的影响。研究表明,除Y2_O3_外,其余的稀土氧化物可提高贮氢电极的1C放电容量和放电电压,延长贮氢电极的循环寿命,且对贮氢电极性能有利的顺序为:La2_O3_>CeO2_>Nd2_O3_;稀土氧化物添加量越多,贮氢电极的循环稳定性越好,但对贮氢电极的1C放电容量和放电电压的影响存在最佳值。造成这些结果的原因是:稀土氧化物增大贮氢合金颗粒间的接触电阻;稀土氧化物的催化作用;稀土氧化物对镍催化剂的稳定作用及抑制贮氢合金进一步氧化的作用。     

Effect of CeO2 and Y2O3 as Catalysts on Hydrogen Desorption Properties of NaAlH4

主要研究氩气气氛下通过机械球磨方法制备的掺杂两种稀土氧化物(由0~5mol%CeO2和 Y2O3)对NaAlH4放氢性能的影响。PCT测试结果显示,在相同的条件下,两种稀土氧化物引起 NaAlH4的最大放氢量和平均放氢速率的规律相似,都随着掺量的增加先增大至某一值后又开始减小。相对于 Y2O3,CeO2对NaAlH4的催化效果影响更为突出,达到相同的放氢量 4.8wt%时,1mol%CeO2-NaAlH4的放氢速率明显比1mol% Y2O3-NaAlH4要高。SEM分析结果显示,随着催化剂含量的增加,粉体颗粒更加均匀,继而团聚成絮状。同时研究发现,球磨后呈分散结构的颗粒可能比絮状结构颗粒反应接触面积大,且经过加热放氢后的试样有很多类似于蜂窝状的气孔存在。     

Mechanism of effect of rare earth oxides on high temperature corrosion resistance of weld metal

Through the addition of rare earth oxides into the coming of electrodes, the high temperature oxidation and sulphidation resistance of weld metal were studied. The transfer mechanism of rare earth oxides from coating to the welding pool and the physicochemical reaction during the process were analyzed. With the application of scanning electron microscope and energy spectrometer, the mechanism of weld metal corrosion in air and sulphur environment were studied. The result shows that the addition of rare earth oxides can improve the high temperature resistance of weld metal, especially in sulphidation environment. The electrodes in which La2O3 is added have better performance than the electrodes in which CeO2 is added. The existence form and distribution characteristic of rare earth are defined. It is believed that the marked effect of rare earth oxides in sulphur environment is related to the corrosion mechanism.     

复合稀土氧化物在钨电极中的分布规律和作用机理

本文研究了稀土氧化物在钨极氩弧焊（ＴＩＧ焊接）用复合稀土钨电极 材料中的作用及行为。采用ＳＥＭ方法观察燃弧后电极尖部的表面形貌,并通过ＥＤＡＸ能谱分析对稀土元素在电极尖部表面上的颁进行探测,用光学显微分析（ＯＭ）方法观察燃弧后电极尖部轴向剖面的金相组织,采用ＡＥＳ深度剖析方法考察燃弧前后稀土元素在电极尖部表层的分布特征。结果表明,不同稀土氧化物在电极工作时的行为不同,复合稀土钨电极中稀土氧化物的协     

Y_2O_3对锌熔再生硬质合金组织及性能的影响

以锌熔回收的WC为原料制备YG8硬质合金以及添加稀土氧化物的YG8-RE合金,通过金相、SEM分析了稀土氧化物的作用机理。研究发现,添加稀土氧化物能改善合金的晶粒均匀性和孔隙度,提高合金的性能。添加稀土氧化物能够使得合金粘结相中α-Co的稳定性增强,并使断裂方式发生改变,提高了合金强度。     

Y2O3对Fe-Al-Si-B等离子熔覆层组织与性能的影响

采用等离子弧熔覆技术,在Q235基体钢板表面熔覆了一层Fe-Al-Si-B原位复合涂层,并通过在熔覆粉末中添加稀土氧化物Y2O3改善熔覆层的组织与性能。利用光学显微镜(OM) 、扫描电镜( SEM) 、X射线衍射仪( XRD)、显微硬度仪、摩擦磨损试验机对熔覆层的组织、相组成、显微硬度及磨损性能进行了分析。结果表明：Y2O3的加入净化了晶界,使得晶界处夹杂物均匀化,明显改善了晶界处夹杂物的形态,形成了致密均匀、无缺陷且显著细化的熔覆层组织。当稀土氧化物Y2O3含量为0.9%时,熔覆层的硬度达到510HV,耐磨性能达到最佳。     

Partitioning properties of rare earth ores in China

1 IntroductionChinese rare earth resources are dominant in theworld with a total amount up to 80% of the wholeworld resources. Rare earth resources in China notonly have high grade and various types, but also dis-tribute reasonably. There are many rare ea…     

MnO2碳热还原动力学及添加剂的影响

在测定ＭｎＯ２碳热还原表观活化能的基础上,确认ＭｎＯ２碳热还原可以分为三个阶段：１）在ｆ〈０．３时,其控制环节为气相扩散,２）当０．３〈ｆ〈０．６时,其控制环节为碳气化反应,３）当ｆ〉０．６时,其控制环节为固相扩散。稀土氧化物（Ｌａ２Ｏ３,ＣｅＯ２和Ｃｅ２Ｏ３）对ＭｎＯ２碳热还原有催化作用,并以Ｌａ２Ｏ３效果最佳。催化的机理在于对碳气化反应的催化。     

Hydrogen Generation on NaBH4 Catalyzed by Co-B/Rare Earth Oxides

研究了催化物体系Co2B/稀土氧化物对NaBH4放氢性能的影响。结果显示,掺杂Co-B/CeO2和Co2B/Sm2O3明显增加了NaBH4的放氢量,在所有的掺杂试样中,掺杂Co2B:CeO2比例为1:1混合催化剂的试样具有最大放氢量274 mL。然而,掺杂混合催化剂试样放氢速率的研究显示,掺杂系统混合催化剂使得NaBH4的放氢速率明显下降。此外,掺杂试样的微观结构研究显示,与掺杂Co2B的试样相比,掺杂混合催化剂试样的微观结构更加松散。Co2B/CeO2催化剂的研究发现,多孔状的微观结构对提高NaBH4放氢量是有益的,但是,对Co2B/La2O3和Co2B/Sm2O3等催化剂的研究结果显示,微观结构中的多孔结构与NaBH4放氢量没有直接关系。     

Yb2O3或Y2O3掺杂Cu-(NiFe2O4-10NiO)惰性阳极的导电性和耐蚀性

在氧分压约为100 Pa的氮气氛下烧结制备了掺杂Y2O3、Yb2O3的10Cu-(NiFe2O4-10NiO)金属陶瓷,并对其进行导电性能测试和10h(Na3A1F6-Al2O3体系中)铝电解实验.采用XRD、SEM和EDS分析稀土氧化物以及其与陶瓷基体反应产物的分布,考查电解实验后材料表层显微结构变化尤其是金属相的流失情况,评价稀土氧化物的添加对金属陶瓷电解初期腐蚀行为的影响.结果表明:掺杂稀土氧化物均使NiO相呈连通迹象,掺杂Yb2O3金属陶瓷晶粒较未掺杂的粗大,其与陶瓷相反应生成物成点线状分布于NiFe2O4相晶界,Y2O3与陶瓷相反应生成物则分布于NiO与NiFe2O4相间;所制备材料具有半导体特征,随着稀土氧化物的掺杂,材料导电性呈下降趋势;掺杂稀土氧化物尤其是Yb2O3有利于提高材料的耐蚀性能.     

La2O3-Gd2O3-Mo secondary emission material

A new kind of materials La2O3-Gd2O3-Mo has been produced by powder metallurgy method.The composition and microstructure of the material were studied by XRD and SEM.It shows that no chemical reaction takes place among La2O3,Gd2O3,Mo and the rare earth oxides exist along molybdenum grain boundaries and in the pores.The emission property measurement results of this material show that adding rare earth oxide into molybdenum can improve the secondary emission coefficient of the emitter,and the emission property depends on the activation temperature.After La2O3-Gd2O3-Mo was activated at 1360℃,the maximum secondary emission coefficient can be high to 2.62,which has exceeded that for practical uses(2.0).     

烧结制备泡沫陶瓷过滤器工艺的优化

采用Al2 O3 和耐火粘土代替贵重的ZrO2 作为基体 ,制备泡沫陶瓷过滤器。并通过添加稀土氧化物Y2 O3 及CeO显著缩短高温烧结时间 ,提高生产效率。烧结的过滤器在液态球墨铸铁中浸泡 ,抗损坏时间延长。所制备的过滤器完全可以满足过滤液态球墨铸铁的要求。     

稀土Y在90W-7Ni-3Fe合金中的存在形态和分布特征

以喷雾干燥法制备的不同稀土Y含量的90W-7Ni-3Fe复合粉末为原料,在不同的烧结温度下制备出不同稀土含量的钨合金,采用XRD、SEM和EDX研究了稀土Y在90W-7Ni-3Fe合金中的存在形态和分布规律。结果表明:稀土Y以Y2O3的形式存在于合金中,且钨颗粒内部未发现稀土Y的存在。Y的添加量为0.4%时,以富Y颗粒的形式分布在钨颗粒与粘结相之间;当添加量为5%时,在粘结相中形成了富Y区域。添加稀土Y可以有效地细化钨颗粒。     

Effects of Y_2O_3 on the microstructure and wear resistance of cobalt-based alloy coatings deposited by plasma transferred arc process

Cobalt-based alloys with different Y2O3 contents were deposited on Q235A-carbon steel using plasma transferred arc (PTA) welding machine. The effect of Y2O3 on the microstructure and wear resistance properties of the cobalt-based alloys were investigated using an optical microscope, a scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that a cobalt-based solid solution with a face-centered cubic crystal structure was presented accompanied by the secondary phase M7C3 with a hexagonal crystal structure in the Y2O3-free cobalt-based alloy coating. Several stacking faults exist in the cobalt-based solid solution. The addition of Y2O3 leads to the existence of the Y2O3 phase in the Y2O3-modified coatings. Though stacking fault exists in the Y2O3-modified coatings, its density increases. The addition of Y2O3 can refine the microstructure and can increase the wear resistance properties when its contents are less than or equal to 0.8 wt.%. However, further increase of its contents will lead to the agglomeration of undissolved Y2O3 particles at the γ-Co grain boundary, and will lead to a coarse microstructure and lower wear resistance properties.     

Forecasting of mechanical properties of covered electrode containing La/CeO_2 based on fuzzy neutral network

In order to improve the mechanical properties of deposited metal of ilmenite type welding electrode,CeO_2/La rare earth elements were added into electrodes based on E4301 electrode, then electrodes were produced,test plates were welded, and mechanical properties were tested based on National Standards of China. For the sake of solving the problems of large amount of mechanical properties tests, long test cycle and high test cost during the conventional production process of electrode, a prediction model of the mechanical properties of deposited metal based on Takagi-Sugeno(T-S) fuzzy neural network was established. Mn, Si and C contents of medium manganese in electrode, CeO_2, and La contents of electrode and welding speed were selected as input variables of the prediction model, and the tensile strength, lower yield strength, elongation, impact energy and hardness of deposited metal were selected as output variables. Finally,predicting experiment was done under test samples, and results show that average relative prediction error of the tensile strength, lower yield strength, elongation and hardness are 0.91 %, 2.57 %, 4.94 % and 1.94 %, respectively, which reach the need of actual production. The results of prediction show that the mechanical properties of deposited metal of electrode containing rare earth can be forecasted accurately through material composition of electrode and welding parameters based on T-S fuzzy neural network model.     

混合稀土氧化物对镁质耐火材料结构与性能的影响

研究了添加Y2O2的混合稀土氧化物对镁质耐火材料的烧结性、力学性能和显微结构的影响。结果表明：添加含Y2O3的混合稀土氧化物可以促进镁质耐火材料的烧结，提高材料的力学性能，同时改善材料的组织结构。含Y2O3的混合稀土氧化物的添加，使镁质耐火材料的结合方式由硅酸盐相结合转化为高熔点的稀土硅酸盐相结合，从而导致镁质耐火材料的高温强度得到显著地提高。     

GCr15销轴固体渗Cr层的生长机制及孔隙成因探索

低扩渗效率和渗层孔隙是困扰着渗铬生产的两个重要难题。本文采用固体包埋法在GCr15表面制备渗Cr涂层，重点探讨了渗层的生长机制、孔隙成因及不同稀土氧化物的催渗作用。结果表明，加入稀土氧化物后渗层厚度明显提高，三种稀土氧化物的催渗效率依次为Y2O3>CeO2>La2O3。渗Cr层明显的分为双层结构，外层是以（Cr，Fe）23C6相为主的多孔层，内层为（Cr，Fe）7C3相为主的致密层。扩渗初期在基材表面首先生成的（Cr，Fe）23C6相层阻碍了表面活性Cr原子向内扩散，其自身作为Cr源向内扩散促进了致密层的生长，Cr原子扩散速度的差异及渗层中的应力是产生孔隙的主要原因。发现降低基体碳含量抑制（Cr，Fe）23C6相层的生成或细化该相层晶粒增加Cr原子扩散通道可有效降低孔隙率，这为改进渗铬层质量提供了一个重要思路。