真空自耗熔炼工艺参数对齿轮钢凝固组织的影响

为进一步提高Cr-Co-Mo-Ni齿轮钢材料的均匀性和细晶化,建立了直径290 mm的齿轮钢钢锭真空自耗熔炼过程三维数学模型,研究了熔炼工艺参数对钢锭凝固组织分布及晶粒大小的影响规律。结果表明：在工艺参数可调范围内,冷却强度越大,晶粒尺寸越小、数目越多,二次枝晶间距越小;熔池温度越低,晶粒的细化效果越好,二次枝晶间距也越小;降低冶炼速率,形核数目增多,晶粒尺寸减小,但对二次枝晶间距的影响较小。对齿轮钢真空自耗熔炼工艺参数优化调整后,模拟结果显示,自耗锭内部等轴晶区域增大将近一倍,晶粒尺寸得到明显细化;最大二次枝晶间距减小了4.88%,合金元素分布实现均匀化。     

电渣重熔过程中传热及凝固组织的数值模拟

在凝固传热数学模型基础上,采用正态分布形核模型和二维偏心生长模型,模拟了钢锭重新凝固过程温度场及钢锭凝固组织的生长情况.数值结果表明：电渣重熔钢锭以倒“V”形的柱状晶为主,中心和底部为等轴晶,模拟结果与实验结果符合良好.随着渣温的提高,熔池变得深且宽;随着侧壁换热系数的增大,熔池深度变浅;随着重熔速度的减小,熔池深度也逐渐变浅;较低的渣池温度、较大的对流换热系数有利于等轴晶形成,而重熔速度对凝固组织的影响不大.     

气缸套铸造生产的孕育处理

铸铁的孕育处理是在铁液凝固过程中,向液态金属中添加少量其它物质,促进形核、抑制生长,达到细化晶粒的目的。从本质上说,孕育处理主要影响形核和促进晶粒游离,促进形成符合要求的显微组织,从而保证铸件的力学性能和加工性能。     

碳钢表面激光熔敷Ni基Cr3C2／（Ni＋Cr）复合涂层的研究

使用2kw连续波CO2激光器在45^#钢表面进行激光熔敷Ni合金中添加50wt%Ni Cr包敷的Cr3C2复合粉的复合少层，并对激光熔敷层的晶体生长形态、物相和硬度进行了分析。结果表明：熔敷层由下至上可分为平面前沿生长区，胸状晶区及枝晶：熔敷区的近表层由高度细小的奥氏体枝晶和C7C3、Cr3C2等物组成，熔敷层的硬度平均高达HV0.2950-1200。添加Cr3C2粒子的激光熔敷层的显微硬度比镍基合金的显微硬度平均提高了HV0.2300。     

小方坯帘线钢末搅参数的优化研究

以小方坯帘线钢的连铸生产为研究对象,采用ProCast商业软件根据实际生产的工艺参数建立铸坯的凝固传热模型,并利用射钉试验对模型进行校正以提高模型的准确性。结果表明,该凝固传热模型可以模拟帘线钢的连铸生产过程。根据射钉试验和数值模拟结果,对末搅位置进行改进,可发现铸坯中心缩孔等级下降,等轴晶率增大。     

晶粒尺寸和表面状态对S30432钢蒸汽氧化行为的影响

利用自制的蒸汽氧化装置对不同晶粒度和表面状态的S30432钢管试样在650℃下进行不同试验时间节点的蒸汽氧化试验,采用光学显微镜、扫描电镜和X射线衍射等分析方法研究了氧化层的形貌、成分和相组成.结果表明：在试验时间内,不同的S30432钢管试样的抗蒸汽氧化性能存在差异;细化晶粒及提高晶粒度均匀性有利于提高S30432钢的抗蒸汽氧化性能;喷丸处理能改变钢管试样的内壁表面状态,加快Cr从基体向内壁表面扩散,形成富Cr的致密氧化层,显著降低了氧化膜的生长速度;在蒸汽氧化过程中形成的氧化层分内外两层：内层富Cr,与基体界面处形成高铬含量愈合层,外层为铁的氧化物.     

TEMPALOYAA-1超超临界锅炉用18Cr-10Ni-3Cu—Ti—Nb不锈钢的开发

目前，火力电站锅炉的设计温度和压力较过去的高，尤其是在全世界范围内超超临界锅炉技术取得了巨大的成果。这类锅炉的用钢必须较传统的18—8型奥氏体不锈钢具有更高的高温强度。在分析了各种合金元素对18—8型奥氏体不锈钢的蠕变断裂强度的作用后，开发出新型的耐热钢（0．1C-18Cr-10Ni-3Cu—Ti—Nb）。该钢在600～700℃下的蠕变断裂强度比ASMESA-213TP347H要高出30％。由于加入约3％重量的cu，使该钢在服役时产生微细弥散、沉淀于奥氏体内的富铜相，并与其互相密合，从而显著地改善蠕变断裂强度。其中添加的微量Ti和Nb也进一步改善了蠕变断裂强度。Ti和Nb的含量限制在一定范围内，这样部分C可以和他们形成碳化物，其余的C与Cr形成碳化铬（M23C6）。这些弥散的MmgCr和（Ti，Nb）C改善了新开发钢的蠕变断裂强度。该钢的成本优势也可以预期的，由于该钢的高强度，在锅炉上使用可以减薄钢管壁厚，从而降低成本。可以预期的是，这种新开发出的钢将是超超临界锅炉的备选材之一。     

稀土Dy掺杂CdO薄膜的结构与光学特性

采用真空热蒸发法,在玻璃衬底上制备稀土Dy掺杂CdO薄膜并进行热处理。对薄膜进行结构和光学特性测试分析。实验给出:掺Dy后CdO薄膜沿(111)晶向的衍射峰增强,随掺Dy含量的增大峰强度逐渐减弱。掺Dy含量为5%时可促进薄膜晶粒的生长改善薄膜的晶相结构特性。制备的薄膜表面颗粒均匀,存在颗粒聚集现象。随掺Dy含量增加薄膜的透光率增大,掺Dy含量为9at%时,在波长大于900nm的区域透光率可达90%,略高于纯CdO薄膜。     

XRF元素录井技术在四川地区的地质应用研究

XRF元素录井技术是建立在x射线荧光光谱分析理论基础上，并结合岩石地球化学理论的一种创新技术。XRF元素录井岩性解释方法通过对元素含量、元素比值、定量岩性含量曲线随井深的变化特征与变化趋势进行分析，从而得到最终的解释结果：陆相地层的岩性识别主要根据Si、Fe的变化来判断砂岩、泥岩，海相地层主要根据Ca、Mg、S的变化来判断灰岩、白云岩、石膏岩，Ba、Ti的变化可以判断岩屑中的泥浆材料含量。该方法对样品要求低，能够很好地识别各种细碎岩性，建立地层剖面，划分地层界线。此外，XRF元素录井还可以用于判断沉积环境：Sr含量相对高、低分别指示海、陆沉积环境：在储层评价方面：陆相储层Si含量变大，说明储层质量变好，而Al、Fe、Ti等3种元素含量变大，预示着储层质量变差；海相储层S含量与溶孔发育程度具有正相关性。以上研究成果在川西4口井、川东北6口井现场应用后．岩屑剖面符合率达到90％。     

过冷/闪沸/超临界燃料喷雾特性的试验研究

利用高速Mie散射成像技术和紫外吸收/可见光散射技术对过冷/闪沸/超临界喷雾的宏观特性（气相和液相的贯穿距离、投影面积）及浓度场进行了试验测量，探讨了超临界喷雾的雾化过程及伪沸线对雾化所起的作用。结果表明：超临界喷雾的雾化过程可由伪沸线划分为类液相喷射和类气相喷射；超临界喷雾液相贯穿距离和投影面积远小于过冷喷雾和闪沸喷雾；气相贯穿距离发展速度远快于过冷喷雾和闪沸喷雾，同一喷油压力下，气相投影面积随时间呈对数函数关系，并且与喷油温度几乎无关；喷射压力在5 MPa～20 MPa范围内，采用超临界喷射策略比提高喷油压力更有利于加快蒸发和提高雾化效果；超临界喷雾浓度分布更均匀。     

EAF-RH-LF-CC生产Q345B的洁净度研究

在炼钢过程各工位取样,分析研究了EAF-RH-LF-CC工艺下Q345B无缝管钢的洁净度.试验结果表明：（1）铸坯中的总氧含量可以稳定在0.002%左右;（2）非金属夹杂物以近似球形的氧化物和硫化物居多,其数量依炼钢流程工序不断降低,且精炼过程中降幅最大.（3）LF过程有明显的增氮现象,需控制LF过程的二次氧化;（4）与RH过程相比,在LF结束时钢中10～20μm的夹杂数量较多,应适当延长LF脱氧后的软吹时间;（5）RH精炼初渣中w（FeO＋MnO）过高,RH钢包渣需进行改质处理.     

Determination of major and minor ash-forming elements in solid biofuels

The development of reliable and appropriate methods for the accurate determination of major (Al, Ca, Fe, K, Mg, Na, P, Si, Ti) and minor (As, Ba, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Tl, V, Zn) ash-forming elements in solid biofuels was the major goal of Task III.2 of the EU project BioNorm. For this purpose, wood+bark, straw and olive residues were analysed using several digestion and determination methods. The digestion methods included wet decomposition in closed vessels with different acid mixtures as well as dry-ashing techniques. The determination systems included FAAS, GFAAS, CVAAS, ICP-OES, ICP-MS, XRF as well as direct Hg-determination. Tests were carried out to optimise the methods applied. To summarise the outcomes of these tests, different digestion procedures were developed for major and minor elements. Digestion with H₂O₂/HNO₃/HF followed by neutralisation with H₃BO₃ was validated for major element analyses, while digestion with H₂O₂/HNO₃/HF was validated for minor element analyses. The validation results show that the applied digestion methods can be recommended for solid biofuel analyses. For the determination of the elements investigated in solid biofuels, the following detection systems can be recommended: FAAS for Ca, Fe, K, Mg, Na, Si, Mn, Zn; ICP-OES for Al, Ca, Fe, K, Mg, Na, P, Si, Ti, Mn, Zn, Ba, Cr, Cu, Mn, Ni, V, Zn; GFAAS for Cd, Cr, Cu, Ni, Pb; ICP-MS: P, Ti, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, V, Zn and direct determination as well as CVAAS for Hg.     

Crystal evaluation of spherical silicon produced by dropping method and their solar cell performance

The characterization of silicon spheres 1 mm in diameter, which were produced by a dropping method and solar cell performance using spheres are reported. Scanning electron microscopy observations of the Si spheres after Dash etching and X-ray pole figures indicate that the spherical Si has many defects and crystal grains. Systematic study of the crystal growth temperature and the atmosphere in the dropping area yields improvements in the crystallinity as well as a decrease in the concentrations of oxygen and carbon. Moreover, the spherical Si solar cell performance improved because these impurities are the prime factor for recombination centers.     

Microstructural study of super Ni laminated composite/1Cr18Ni9Ti steel dissimilar welded joint

Abstract

Super Ni laminated composite and 1Cr18Ni9Ti stainless steel were welded by the tungsten inert gas process with the Cr25–Ni13 filler alloy. The microstructure, element distribution and phase formation near the fusion zone were evaluated by standard technique. Results indicated the formation of four main regions: the fusion transition region on the 1Cr18Ni9Ti steel side, the fusion transition region on the super Ni laminated composite side, a columnar crystal weld region and the weld centre region. The microstructure on either side of the weld was characterized by strong directionality and changed from columnar austenite to equiaxed austenite in the weld centre. A Ni, Fe and Cr element transition region, about 30 μm wide, was formed at the fusion zone on the super Ni side. The phase formed into welded zone was composed mainly of austenite, δ-Fe, γ-Ni(Cr, Fe) and FeNi intermetallic compounds.     

Oxidation behavior of ferritic stainless steel containing Nb,Nb–Si and Nb–Ti for SOFC interconnect

The effect of Nb on the oxidation kinetics, electrical conductivity and Cr evaporation behavior of FSS has been discussed depending on the Nb content and oxygen active element such as Ti and Si. Nb in ferritic stainless steel is saturated during heat treatment as NbO₂ at the outermost oxide scale and as both Nb₂O₅ and Laves phase near the oxide scale/alloy interface. Excess Nb (>4.7 wt%) suppresses precipitation of Nb₂O₅, because of rapid Laves phase growth. Nb enhances selective Ti oxidation, whereas Ti retards Nb₂O₅ precipitation near the scale/alloy interface. On the other hand, Si suppresses Nb enrichment near the scale/alloy interface and it reduces the precipitation of both Nb₂O₅ and Laves phase. Nb also suppresses Si enrichment and the formation of continuous Si oxide at the scale/alloy interface. Co-addition of Nb and Ti is effective to decrease the electrical resistance and Cr evaporation rate of oxide scale.     

Effect of alloying elements on hydrogen environment embrittlement of AISI type 304 austenitic stainless steel

The chemical composition of an AISI type 304 austenitic stainless was systematically modified in order to evaluate the influence of the elements Mo, Ni, Si, S, Cr and Mn on the material’s susceptibility to hydrogen environment embrittlement (HEE). Mechanical properties were evaluated by tensile testing at room temperature in air at ambient pressure and in a 40 MPa hydrogen gas atmosphere. For every chemical composition, the corresponding austenite stability was evaluated by magnetic response measurements and thermodynamic calculations based on the Calphad method. Tensile test results show that yield and tensile strength are negligibly affected by the presence of hydrogen, whereas measurements of elongation to rupture and reduction of area indicate an increasing ductility loss with decreasing austenite stability. Concerning modifications of alloy composition, an increase in Si, Mn and Cr content showed a significant improvement of material’s ductility compared to other alloying elements.     

A FIXED GRID FRONT-TRACKING MODEL OF THE GROWTH OF A COLUMNAR FRONT AND AN EQUIAXED GRAIN DURING SOLIDIFICATION OF AN ALLOY

In a new model of alloy solidification in a square mold, the interface being followed by a front-tracking technique is representative of a curve joining the tips of growing solid dendrites. The coupled heat equation is solved via an Eulerian control-volume formulation. In the absence of convection, the nucleation and nonequilibrium growth of both a front of columnar grains and a single equiaxed grain have been modeled and animated. This is a major step toward the computationally efficient complete direct numerical simulation of the developing grain structure in a casting process.     

Oxide modification by chi phase formed on oxide/metal interface of Fe-22Cr-0.5Mn ferritic stainless steel for SOFC interconnect

The effect of tungsten addition to Fe-22Cr-0.5Mn ferritic stainless steel on the oxidation, electric property and Cr evaporation is investigated for application to the solid oxide fuel cell interconnects. The mass gain, area specific resistance and Cr evaporation rate are evaluated to examine the feasibility of these alloys for an interconnect material. Addition of 4-6 wt.% W reduces the oxidation rate, evaporation rate of Cr vapor species and area specific resistance of Fe-22Cr-0.5Mn steel. When more than 4 wt.% W is added, chi (χ) phase particles are formed, especially beneath the interface between the oxide layer and substrate steel. These second phase particles are responsible for suppressing the fast diffusion of Cr, so that the surface Cr content is reduced while Mn content is increased. This reduction in Cr content at the surface is responsible for the lower Cr evaporation rate and area specific resistance.     

Promising alloys for intermediate-temperature solid oxide fuel cell interconnect application

The formation of a low Cr-volatility and electrically conductive oxide outer layer atop an inner chromia layer via thermal oxidation is highly desirable for preventing chromium evaporation from solid oxide fuel cell (SOFC) metallic interconnects at the SOFC operation temperatures. In this paper, a number of ferritic Fe–22Cr alloys with different levels of Mn and Ti as well as a Ni-based alloy Haynes 242 were cyclically oxidized in air at 800 °C for twenty 100-h cycles. No oxide scale spallation was observed during thermal cycling for any of these alloys. A mixed Mn₂O₃/TiO₂ surface layer and/or a (Mn, Cr)₃O₄ spinel outer layer atop a Cr₂O₃ inner layer was formed for the Fe–22Cr series alloys, while an NiO outer layer with a Cr₂O₃ inner layer was developed for Haynes 242 after cyclic oxidation. For the Fe–22Cr series alloys, the effects of Mn and Ti contents as well as alloy purity on the oxidation resistance and scale area specific resistance were evaluated. The performance of the ferritic alloys was compared with that of Haynes 242. The mismatch in thermal expansion coefficient between the different layers in the oxide scale was identified as a potential concern for these otherwise promising alloys.