Examination of Plasma Nitriding Microstructure with Addition of Rare Earths

Medium-carbon alloy steel was plasma nitrided with rare earths I_a, Ce and Nd into the nitriding chamber respectively. The nitriding layer microstructures with and without rare earths were compared using optical microscope, normal SEM and high resolution SEM, as well as TEM. It was found that the extent of the influence on plasma nitriding varies with different contents of rare earth. The effect of plasma nitriding is benefit from adding of Ce or Nd. The formation of hard and brittle phase Fe2-3N can be prevented and the butterfly-like structure can be improved by adding Ce or Nd. However, pure La may prevent the diffusion of nitrogen and the formation of iron nitride, and reduce the depth of diffusion layer.     

Influence of rare earth metals on the nucleation and solidification behavior of iron and 1045 steel

Two series of experiments have been conducted to determine the influence of rare earth additions on the nucleation and crystallization behavior of pure iron and 1045 steel. In the first series, additions of rare earth suicide or cerium dioxide powder to two-Kg 1045 steel ingots indicated that rare earth suicide can refine the as-cast structure of such ingots. However, if the holding time after rare earth silicide addition is over two minutes, the grain refinement decreases. With cerium dioxide additions, a relatively large columnar zone was obtained. In the second series, the effects of cerium metal or cerium dioxide powder additions on the degree of undercooling obtainable in pure iron and 1045 steel were examined by the lévitation melting method. Surface tension measurements of the levitated droplets were carried out at the same time to investigate the possible effects of surface tension variations on the nucleation and crystallization behavior of the metals. The experimental data show that rare earth inclusions can greatly reduce the degree of undercooling of iron and steel, and that a small amount of dissolved cerium can further reduce the degree of undercooling of levitated droplets. The structure and reaction products obtained with Fe-Ce levitated droplets were examined with both optical and scanning electron microscopy as well as X-ray diffraction analysis. The experimental results clearly indicated that cerium solute redistribution during solidification is the dominant factor in refining the as-cast structure. A nucleation and solidification model for the Fe-Ce levitated droplets has been developed, which can successfully explain the experimental results. on research leave from Beijing University of Iron and Steel Technology     

Influence of rare earth metals on the nucleation and solidification behavior of iron and 1045 steel

Two series of experiments have been conducted to determine the influence of rare earth additions on the nucleation and crystallization behavior of pure iron and 1045 steel. In the first series, additions of rare earth suicide or cerium dioxide powder to two-Kg 1045 steel ingots indicated that rare earth suicide can refine the as-cast structure of such ingots. However, if the holding time after rare earth silicide addition is over two minutes, the grain refinement decreases. With cerium dioxide additions, a relatively large columnar zone was obtained. In the second series, the effects of cerium metal or cerium dioxide powder additions on the degree of undercooling obtainable in pure iron and 1045 steel were examined by the lévitation melting method. Surface tension measurements of the levitated droplets were carried out at the same time to investigate the possible effects of surface tension variations on the nucleation and crystallization behavior of the metals. The experimental data show that rare earth inclusions can greatly reduce the degree of undercooling of iron and steel, and that a small amount of dissolved cerium can further reduce the degree of undercooling of levitated droplets. The structure and reaction products obtained with Fe-Ce levitated droplets were examined with both optical and scanning electron microscopy as well as X-ray diffraction analysis. The experimental results clearly indicated that cerium solute redistribution during solidification is the dominant factor in refining the as-cast structure. A nucleation and solidification model for the Fe-Ce levitated droplets has been developed, which can successfully explain the experimental results. on research leave from Beijing University of Iron and Steel Technology     

辉光放电发射光谱技术及其在国内钢铁行业中的应用

简单介绍辉光放电发射光谱技术的基础知识及相关书籍情况,重点评述其在国内钢铁行业的应用。国内钢铁行业基体分析涉及中低合金钢、不锈钢、生铁、铸铁、高温合金等;阳极直径4 mm为主,分析元素已达24种,激发功率12～90 W,数据精密度多小于5%;而深度轮廓分析主要涉及镀锌板、镀锡板、彩涂板,氟元素测定和制备电镜样品是其应用的一大亮点。概述辉光放电发射光谱国际标准和国家标准的进展,并对辉光放电发射光谱法、X射线荧光光谱法、电感耦合等离子体原子发射光谱法、火花源原子发射光谱法在低合金钢中多元素测定的重复性和再现性进行比较,数据表明辉光放电原子发射光谱法的重复性值较低,而再现性值偏高。最后对制约辉光放电光谱技术发展的因素进行了探讨。     

稀土提高40Cr钢氮化层抗冲蚀磨损性能的研究

本文研究了在气体氮化渗剂中加入微量稀土元素对40Cr钢氮化层组织、韧性及抗冲蚀磨损性能的影响。试验结果表明稀土在氮化时被渗入到钢的表层起微合金化作用,改善了渗层组织。稀土氮化层的韧性和抗冲蚀磨损性能,较普通氮化层有明显提高。扫描电子显微镜对冲蚀磨损试样表面形貌观察发现,氮化层的磨损特征为塑性变形形成的犁沟剥落,并伴随着萌生横向裂纹,有大块磨屑剥落;而稀土氮化层则为塑性变形形成的犁沟剥落。     

基于激光剥蚀-电感耦合等离子体质谱法的金属镝棒统计分布分析初探

高效、高灵敏度的原位微区分析技术开发对于固态电迁移等稀土提纯工艺具有重要意义。实验以固态电迁移提纯后金属镝棒为研究对象,将激光剥蚀-电感耦合等离子体质谱法(LA-ICP-MS)应用于高纯稀土金属的微区分布分析。研究了激光剥蚀速率对样品覆盖率和分析时间的影响,确定了剥蚀速率为50μm/s;考察了剥蚀池及ICP-MS载气流量对待测元素信号强度、氧化物产率及元素分馏效应的影响,确定了载气流量分别为0.60L/min(He)和1.0L/min(Ar)。采用线扫描方式,以基体元素~(158)Dy为内标,获得了不同电迁移区域各杂质元素的二维相对强度分布图,初步探究了各杂质元素的迁移规律。结果显示:在电迁移过程中,Al、Si、Ti、Fe、Mo、W元素从阴极向阳极迁移;Ni、Cu元素从中间区域向两极迁移。这一迁移趋势与辉光放电质谱法(GD-MS)分析结果相一致。同时,LA-ICP-MS还得到更丰富的微区统计分布信息。不同电迁移区域各杂质元素最大偏析度、相对标准偏差(RSD)值及最大偏析位置进一步揭示了各元素的迁移状态,可能与固态电迁移工艺相联系。因此,LA-ICPMS有望为稀土金属提纯工艺解析及优化提供一种新的有效分析手段。     

重量法测定电镀锌板和热镀锌板镀锌质量的比较

根据GB/T1839-2008采用的重量法分别测定了电镀锌板单面镀锌质量和热镀锌板单面镀锌质量;利用辉光放电发射光谱法测定电镀锌板和热镀锌板的镀锌质量,并表征了溶解前后电镀锌板和热镀锌板的镀层结构。结果发现:热镀锌板和电镀锌板镀层结构略有不同,但重量法能有效溶解镀锌板的镀层,使纯镀锌层、锌铁交界层及渗入钢基中的锌全都溶解下来。此外,试验还发现重量法和辉光放电发射光谱法测定电镀锌板和热镀锌板镀锌质量的分析结果有较好的一致性,这也进一步证明重量法是测定不同类型镀锌板的镀锌质量的较准确方法。另外,根据辉光放电发射光谱法测定不同镀锌板镀层结构的分析结果及电感耦合等离子体原子发射光谱法(ICP-AES)测定镀层中铁和铝含量的分析结果,讨论了重量法测定电镀锌板及热镀锌板镀锌质量误差的来源和大小。发现引起重量法测定不同镀锌板的误差主要由镀层中除锌元素以外的铁和铝元素的溶解引起的。而重量法测定电镀锌板镀锌质量的误差要远远小于重量法测定热镀锌板镀锌质量误差,这说明重量法更适合电镀锌板镀锌质量的测定。     

镀TiN和镀锌钢板的辉光放电原子发射光谱深度轮廓分析(英文)

金属或合金表面的导电或非导体镀层,对改善材料的性能,降低材料的损耗具有很大的作用。如在钢表面镀一层TiN,钢的抗磨损性能会得到提升。探讨各种元素在基体材料表面的分布和渗透行为,对新材料的研究具有十分重要的意义。本文运用直流辉光放电原子发射光谱对镀TiN和镀锌钢板进行了深度轮廓分析。放电电压、放电功率和压力对深度轮廓分析的影响进行了研究,在功率为24.5~28 W和500~1000 Pa放电压力下,可以得到每层4μm TiN的深度分辨率,并且Ti的谱线强度相对较高。结果表明在相对较低的放电功率和压力下,深度     

影响辉光放电发射光谱分析准确性的因素探讨

基于辉光放电发射光谱分析定量原理讨论了影响其分析结果准确性的几个因素:深度剖析中,浓度的定量取决于经溅射率校正的校准曲线是否能够覆盖所有元素的浓度值,必要时需要拓展校准曲线;深度的定量准确性则依赖于加权平均法密度与实际密度间的一致性,相差较大时,可以通过软件或硬件进行修正;样品中存在有机物质时,辉光放电等离子体中的分子谱带对其他元素谱线强度形成干扰,导致分析结果中出现“伪峰”或定量分析结果出现较大偏差,需要根据样品的工艺实际对分析结果进行甄别;比较深度剖析与其他分析技术的定量结果,应考虑镀层均匀性和取样量差异的影响;成分分析的重复性和再现性能够满足金属固体样品快速分析的要求,最新国家标准中的精密度结果令人满意;元素痕量分析时,需要关注谱线发射强度是否大幅降低,长时间溅射低熔点金属或有机物样品少量物质沉积于透镜处是原因之一。     

Surface morphology and compound layer pores of plasma nitrocarburized low carbon steel

This article deals with various aspects of nitrocarburizing of AISI 1010 steel by DC plasma at 600 °C. The initial stages of nitride formation and the effects of surface bombardment by hydrogen plasma species, as well as the effect of treatment current density on the surface morphology, were investigated in detail. The results show that in the pearlitic region carbides are removed during treatment in hydrogen plasma and that the current density influences the surface morphology significantly. A porous surface formed in a 1-minute treatment under high current density (8 mA/cm²), whereas a lower current density (2.4 mA/cm²) resulted in a highly stressed surface attributed to uneven thermal gradients. Iron nitrides were identified on the surface in either set of conditions. A pure epsilon compound layer was obtained by plasma nitrocarburizing for 6 hours and quenching. The pores in this layer are discussed in view of the 1-minute treatment results and are also compared to those observed in a nitriding treatment. The lack of carbon species in the nitriding plasma results in different mechanisms for pore formation and growth during the treatment. These results are discussed in view of current models for plasma nitriding and gas nitrocarburizing.     

射频辉光放电发射光谱法测定不锈钢成分的研究

研究了射频辉光放电发射光谱法(rf-GD-OES)测定不锈钢成分C,Si,Mn,P,S,Cr,Ni,Cu,Co,Al。考察了射频功率、载气气压、预溅射时间等仪器参数对不锈钢元素谱线发射强度及相对强度稳定性的影响和直流自偏压与射频功率和载气气压的关系。以此为基础,优化后的最佳分析条件为:射频功率90 W、载气气压300 Pa、预溅射时间100 s、积分时间20 s。方法用于测定不锈钢标准样品,测定值与认定值相符,精密度良好。     

An Intercomparison Study of Analytical Methods for the Determination of Magnesium in Low Alloy Steel

In an intercomparison study three low alloy steel materials were analyzed on their content of the trace element Mg, and five different analytical techniques were used, namely spark‐OES, inductively coupled plasma optical emission spectrometry (ICP‐OES), inductively coupled plasma time of flight mass spectrometry (ICP‐TOFMS), inductively coupled plasma quadrupole mass spectrometry (ICP‐QMS), and glow discharge mass spectrometry (GD‐MS). Solid steel discs were used for analysis with spark‐OES and GD‐MS. For the analyses with ICP‐OES, ICP‐TOFMS, and ICP‐QMS steel chips were wet‐digested in aqua regia, and the wet‐digestion was performed either in polypropylene tubes placed in a heating block or in Teflon pressure vessels using a microwave assisted system. The Mg concentrations obtained for the three steel materials were: 2.0, 2.8, and 10.3 µg g^?1, respectively, and the spread in results was acceptable, giving RSD values in the range of 20–30%.     

直流辉光放电光谱法测定不锈钢中11种元素

通过对直流辉光放电光谱法(GD-OES)分析不锈钢样品光谱行为的研究,考察了工作参数如放电电压、电流、预溅射时间和积分时间对光谱强度和稳定性的影响。在此基础上对工作参数进行优化,确定预溅射时间40 s、积分时间6 s、放电电压1 100 V、放电电流40 mA为最佳分析条件,据此建立了直流辉光放电光谱法测定不锈钢中C,Si,Mn,P,S,Cr,Ni,Cu,Ti,Co,Al的方法,考察了该方法分析不锈钢的精密度和准确度,各元素的测定结果与认定值或化学方法测定值吻合较好。     

过时效段露点对双相钢表面色差的影响

 冷轧双相钢具有较高的抗拉强度和较低的屈强比,成形性能优异,被汽车工业广泛用于生产形状比较复杂的结构件。由于冷轧双相钢中含有较多的易氧化的合金元素如锰、硅等,因此在退火时容易出现表面色差缺陷。采用镀锌模拟器研究了退火的过时效段工艺对该缺陷的影响,分别采用扫描电镜和辉光放电光谱分析了冷轧双相钢试样的表面形貌以及元素分布。结果表明,过时效段的露点温度对表面合金元素的富集和氧化有显著影响,较高的过时效露点温度会导致出现明显的色差缺陷。     

直流辉光放电发射光谱法同时测定硅钢中11种元素

通过直流辉光放电光谱分析硅钢样品的光谱行为,考察放电电压、放电电流、预溅射时间和积分时间对光谱强度和稳定性的影响。以铁为内标元素,优化分析条件为放电电压1 100V,放电电流50 mA,预溅射时间45 s,积分时间10 s,建立直流辉光放电光谱法测定硅钢中11种元素的定量分析方法。考察方法的精密度和准确度,其中Si、Mn、Cr、Ni、Cu、Al、B、Ti的相对标准偏差(RSD)小于2%,C、S、P的相对标准偏差(RSD)小于4%,各元素的测定结果与认定值吻合。     

Applications of X-ray fluorescence analysis of rare earths in China

A review was presented on the applications of X-ray fluorescence(XRF) analysis in Chinese rare earth industry during the last 20 years.The application consisted of the analysis of rare earth elements in ores and soil,concentrates,compounds,metals,alloys,functional materials,fast and online analysis in separation process,and so on.The analytical method was described on pressed powders,fused beads,liquid thin films and solid pieces.The detections of rare earth elements and compounds were concerned in iron and steel,nonferrous metals,petrochemical,geology,biology,electronic materials and other fields.     

Applications of X-ray fluorescence analysis of rare earths in China

A review was presented on the applications of X-ray fluorescence (XRF) analysis in Chinese rare earth industry during the last 20 years. The application consisted of the analysis of rare earth elements in ores and soil, concentrates, compounds, metals, alloys, functional materials, fast and online analysis in separation process, and so on. The analytical method was described on pressed powders, fused beads, liquid thin films and solid pieces. The detections of rare earth elements and compounds were concerned in iron and steel, nonferrous metals, petrochemical, geology, biology, electronic materials and other fields.     

直流辉光放电质谱法测定海绵钛中杂质元素

将海绵钛样品压制成片,在缺乏合适标样情况下可以用多种金属得出的典型RSFX值对测定结果进行校正,建立了直流辉光放电质谱法(GD-MS)测定海绵钛中Be、B、C、N、O、Na、Mg、Al、Si、P、S、Cl、K、Ca、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、As、Y、Zr、Nb、Mo、Sn、Sb、Pb、Bi等32个痕量杂质元素的分析方法。考察了放电参数对分析信号灵敏度和稳定性的影响,优化后的放电参数如下:辉光放电电流为38 mA,放电电压为650 V,放电气体流量为450 mL/min,预溅射时间为30 min。通过选择合适的同位素,在高分辨(HR,分辨率R=10 000)质谱模式下测定K,在中分辨(MR,R=4 000)模式下测定其他元素可消除质谱干扰。将实验方法应用于海绵钛实际样品中32个杂质元素的测定,结果的相对标准偏差(RSD,n= 10)为3.3%～30%,主要金属杂质元素含量的测定结果与采用电感耦合等离子体质谱法(ICP-MS)的分析结果基本一致。采用实验方法分析商用0级海绵钛样品(样品1)和1级海绵钛样品(样品2),所得结果与国家标准(GB/T 2524—2010)中对两种等级海绵钛的含量要求一致。其中Fe、Si、Cl、C、N、O、Mn、Mg的测定结果与采用国家标准GB/T 4698—2011的分析结果相吻合。     

Electronic Theoretical Study of the Interaction between Rare Earth Elements and Impurities at Grain Boundaries in Steel

Rareearths(RE)aresurfaceactiveelements ,theirapplicationsinmetalmaterialscanbesum marizedaspurification ,modificationandall oying[1～ 3 ] .Itisaveryattractivesubjectthattheinter actionofREelementswithlowmeltingpointimpuri tiesintheregionofGBs ,suchasP ,S ,As ,Sbandsoon .ResultsofexperimentsshowthatsegregationinGBsofasmallamountofREinsteelrestrainsharmfulimpuritiessuchasP ,S ,As ,Pb ,Sb ,tosegregateto wardsGBs ,soREelementscancleanseandenhanceGBs ,therebyimprovethehightemperatureducti…     

辉光放电光谱法分析超薄钢板中各元素的含量

介绍了采用辉光放电光谱法测定超薄钢板中各元素含量的试验方法。对辉光光谱仪的光源参数和分析参数的设定进行了研究,建立了辉光放电光谱分析法同时测定超薄板材中C、Si、Mn、P、S、Ni、Cr、Mo、Cu、A1元素含量的分析方法,该方法具有良好的准确度和精密度,可应用于企业中大量的检化验工作中。