Evolution of carbides and carbon content in matrix of an ultra-high carbon sintered steel during heat treatment process

DTA, thermal expansion, XRD, and SEM were used to evaluate the effect of quenching temperature on the mechanical properties and microstructure of a novel sintered steel Fe-6Co-1Ni-5Cr-5Mo-1C. Lattice parameters and the mass fraction of carbon dissolved in the matrix of the steel quenched were investigated. It is discovered that the hardness of the steel increases with quenching temperature in the range of 840-900℃ and remains constant in the range of 900 to 1100℃. It decreases rapidly when the temperature is higher than 1100℃. The mass fraction of carbon dissolved in the matrix of the steel quenched at 840℃ is 0.38, but when the quenching temperature is increased to 1150℃, it increases to 0.98. The carbides formed during sintering are still present at grain boundaries and in the matrix of the steel quenched at low quenching temperatures, such as 840℃. When the quenching temperature is increased to 1150℃, most of the carbides at grain boundaries are dissolved with just a small amount of spherical M23C6 existing in the matrix of the quenched steel.

Heat treatment process of new NdFeB magnet prepared by spark plasma sintering

In recent years, spark plasma sintering technique(SPS) has been a focus in the field of material preparation due to its advantages. SPS technique is first introduced for preparation of high quality NdFeB magnets. The effects of heat treatment process on the magnetic properties of SPS NdFeB magnet were investigated. Meanwhile, the effects of heat treatment process on the microstructure, tropism and dimensional precision of the SPS NdFeB magnets were also studied. The high quality NdFeB magnets with fine grains were prepared under proper heat treatment process. The results show that the magnetic properties of SPS NdFeB can be further improved through proper heat treatment process. Meanwhile, the experiment also demonstrates that it is feasible to prepare near net shape NdFeB magnets with fine grains and high magnetic property by spark plasma sintering.

Treatment of the wastewater from the sintering flue gas desulfurization process

The limestone-gypsum flue gas desulfurization （FGD） process has become the most widespread process in the world for sulfur removal. The swirl-jet-absorbing wet limestone-gypsum sintering FGD technology was developed for sintering flue gas desulfurization,and this process produces volumes of wastewater with various contaminants that requires treatment before disposal or reuse. In this study, the wastewater quality from three different sintering FGD systems at Baosteel Group was investigated and compared with wastewater from power plant FGD. A treatment process was proposed which is suitable for sintering FGD wastewater. After treatment with a neutralization, coagulation and sedimentation process, heavy metals in the sintering FGD wastewater were reduced to a level meeting the relevant emission standards ,but the pH and ammonia concentration were too high, and a further treatment process was needed. Due to certain similarities and complementarities between sintering FGD wastewater and coking wastewater, it is entirely feasible to mix the pretreated sintering FGD wastewater into a biological coking wastewater treatment system. This study indicates that it is entirely feasible to mix pretreated sintering FGD wastewater into the biological treatment systems used for coking wastewater from the iron and steel industries.

Infiltration behavior of sintering liquid on nuclei ores during low-titanium ore sintering process

Sinter strength is dependent not only on the self-intensity of the residual rude and bonding phase but also on the bonding degree between them. The infiltration behavior of sintering liquid on nuclei ores influences the bonding degree, which ultimately determines the sinter strength. Infiltration tests were conducted using micro-sinter equipment. The infiltration area index of original liquid（IAO）, infiltration volume index of secondary liquid（IVS）, and sinter body bonding strength（SBS） were proposed to study the melt infiltration behavior. The results show that the IVS first increases and then decreases with increasing TiO2 content in adhering fines, whereas the IAO exhibits the opposite behavior. Compared with the original liquid, the secondary liquid shows lower porosity, smaller pores, and more uniform distribution. The SBS increases first and then decreases with increasing IAO and TiO2 content, and reaches a maximum when the IAO and TiO2 contents are approximately 0.5 and 2.0wt%, respectively. The SBS first increases and then tends to be stable with increasing IVS. The TiO2 content is suggested to be controlled to approximately 2.0wt% in low-titanium ore sintering.

Effects of Sintering Technology on PMZN Piezoceramics Properties

Pb ( Mn1/3Sb2/3 ) x ( Zn1/3Nb2/3) y ( Zr0.535 Ti0.465 ),1-x-yO3 ( PMZN) piezoelectric ceramics were fabricated, The effects of sintering temperature and heat-treatment time on properties wen discussed, the optimum preparation technology parameters were obtained. In this case, the ceramics have the highest electromechanical coupling coefficients and mechanical quality factor and the least dielectric loss. It is revealed that the PMZN piezo-ceramics material can be utilized for high-power ultrasound transducers.

Sintering behaviour of feldspar and influence of electric charge effects

The characterization of feldspar for electric porcelain and the behaviour of these materials after heating at 1230°C were studied. X-ray diffraction （XRD） and scanning electronic microscopy （SEM） were used to identify the present phases and the densification level. Feldspar sand was treated by flotation. The floated feldspar is constituted by microcline, quartz, and minor amounts of albite. The micro-structure of sintered feldspar at 1230°C is essentially vitreous with open microporosities. The dielectrical properties of composites were characterized by using the induced courant method （ICM）, which indicates that the charge trapping capacity depends on the mineralogical and chemical composition of feldspar.

Effect of Heat Treatment Method on Microstructure of Tailings Glass Ceramics

A Cao-Mgo-Al2O3-SiO2 quaternary system was established with the main crystal phase design based on Diopside, and the effect of once-through sintering heat treatment on microstructure of iron railings glass ceramics was studied by using DTA, SEM along with measurement of microhardness and volume density. The experimental results show that, when the total amount of FeO and Fe2O3 exceeds 10wt%, a large number of fine nuclei are produced in the annealing process, and the phenomenon of nucleus resorption happens during the process of nucleation heat treatment, which is unfavorable for preparing iron tailings glass ceramics through once-through sintering method. When the annealing temperature from 1250 ℃ to 830 ℃, setting crystallization time for 4h, without heat treatment, crystals are well grown with arrangement and interlocking in glass phase. At 830 ℃ the crystals are well developed, well distributed and of good size; with crystallization time of 4 h the crystals with radial shape have high content and regular arrangement.

Selective laser sintering of polymer-coated Al_2O_3/ZrO_2/TiC ceramic powder

A type of polymer-coated Al2O3/ZrO2/TiC ceramic powder was prepared. The laser sintering mechanism of polymer-coated Al2O3/ZrO2/TiC powder was investigated by studying the dynamic laser sintering process. It is found that the mechanism is viscous flow when the sintering temperature is between 80 ℃ and 120 ℃, and it is melting/solidification when the temperature is above 120 ℃. The process parameters of selective laser sintering were optimized by using ortho-design method. The results show that the optimal parameters include laser power of 14 W, scanning velocity of 1 400 mm/s, preheating temperature of 50 ℃ and powder depth of 0.15 mm. A two-step post-treatment process is adopted to improve the mechanical properties of laser sintered part, which includes polymer debinding and high temperature sintering. After vacuum sintering for 2 h at 1 650 ℃, the bending strength and fracture toughness of Al2O3/ZrO2/TiC ceramic part reach 358 MPa and 6.9 MPa·m1/2, respectively.

马钢2×380m^(2)烧结机节能减排实践

为进一步适应烧结生产优质、降耗、减排的发展的需求,马钢2×380m^(2)烧结机采取了一系列提质降耗技术措施。通过持续优化厚料层烧结生产经济潜力;降低固体燃耗;点火炉升级改造、带冷机改环冷机、烧结机漏风治理、大型风机变频技术等多项节能新技术的应用以及创新管理,在烧结矿质量以及节能降耗方面取得了显著改善效果,工序能耗由55 kgce/t下降至47kgce/t水平。同时对当前2×380m^(2)烧结机烧结高效、低耗生产存在的问题提出了改进方向,以进一步促进节能减排工作的持续发展。

利用SMAT和SPS在纯铁表面制备铁镍合金层

利用放电等离子烧结(SPS)技术实现了镍粉在纯铁表面铁镍合金层的制备,通过纯铁表面机械研磨(SMAT)的预处理获得表面纳米层和梯度结构有效促进了铁镍的扩散,提升了合金层厚度和结合强度。通过XRD、SEM、EDS、硬度和摩擦磨损实验等,表征铁镍合金层形貌、组成,测试了力学性能。结果表明:纯铁试样经过SMAT预处理和SPS后,在表面获得了约50μm的铁镍合金层,沿着深度方向镍元素含量梯度变化,而在未经SMAT预处理的纯铁表面仅有25μm的合金层,本方法实现了合金层厚度明显增加。SMAT预处理后的SPS试样硬度提升,表面磨损量和犁沟槽深度减少,结合力增强,耐磨性提升明显。

烧结烟气的循环流化床焚烧处理方法

烧结烟气是钢铁生产的烧结工序产生的废气,含NO_(x)、SO_(2)、二噁英、挥发性有机物等污染物成分。用烧结烟气替代燃煤循环流化床锅炉空气以焚烧处理,既能有效资源化利用废气中CO和余氧,又能借助循环流化床中脱硫脱硝设备与高温环境,将烧结烟气中SO_(x)和NO_(x)等污染物与燃煤产生的污染物一并去除,有望成为高效的烧结烟气一体化污染物处理技术。然而,目前燃煤循环流化床燃烧背景下烧结烟气中二噁英、挥发性有机物等污染物脱除的研究尚不足。针对该问题,先通过化学反应动力学模拟,研究烧结烟气作为助燃剂燃烧过程,发现燃烧过程中产生的氢等自由基在二噁英分解过程中发挥重要作用,燃烧反应温度提高能显著促进二噁英及挥发性有机物的脱除,而燃尽烟气的余氧量降低对二噁英的脱除也有较显著促进作用。通过计算颗粒流体动力学的方法,模拟以烧结烟气为助燃剂的燃煤循环流化床锅炉运行情况,发现燃烧过程流态化情况好,烧结烟气中低浓度CO基本燃尽,旋风分离器出口CO质量浓度约100 mg/m^(3),燃烧温度达到去除污染物的要求,验证了将烧结烟气作为燃煤循环流化床锅炉中助燃剂的可行性。在唐山某钢铁企业开展了烧结烟气的循环流化床焚烧方法工程验证,测试发现低低温省煤器出口处烟气二噁英脱除率超过99.5%,低至0.0057 ng TEQ/m^(3),CO质量浓度低至108 mg/m^(3),此外烟气中NOx和SO2质量浓度低至38、24 mg/m^(3),满足超低排放要求。工程验证证实循环流化床烧结烟气一体化焚烧处理技术有效。

热处理温度对冷烧结SnSe热电性能的影响研究

SnSe热电材料具有低热导率、低成本、环境友好等优势,成为目前热电领域的研究热点材料之一。本文利用水热法和冷烧结工艺制备了多晶SnSe块体,然后进行热处理,研究热处理温度对合成多晶SnSe热电性能的影响规律。XRD结果显示,各样品的主衍射峰与SnSe卡片相匹配。SEM结果表明,颗粒由块状变为片状结构且材料内部空隙随退火温度升高而降低。正电子湮灭测量结果表明,冷烧结的SnSe样品中可能存在各种空位型缺陷,如V_(Se)、V_(Sn)、V_(SnSe)和大空位团簇,这些空位型缺陷是有效的声子散射中心,导致晶格热导率降低,随着退火温度的升高,空隙减小与空位型缺陷逐渐恢复导致晶界势垒降低使电导率逐渐增大。电导率、功率因子和无量纲热电优值(ZT)的变化趋势几乎相同,都是随着退火温度的升高而增加。在测试温度为773 K时,500℃退火样品的电导率σ高达4.1×10^(3) S/m,功率因子为3.71μW/(cm·K^(2));而热导率随着退火温度的提升减小了声子散射中心而略有升高。最后,计算500℃退火样品的ZT值为0.70,比未退火样品的ZT值高出35.7%。因此,表明了冷烧结工艺和热处理在SnSe材料研究中有巨大潜力,为制备出高性能热电材料奠定了理论依据。

石英玻璃纤维织物基底柔性电极制备与性能研究

目的研制用于石英玻璃纤维织物基底的银/苯氧树脂基丝网印刷导电银浆,印制具有良好导电性能和力学性能的柔性电极,并探索烧结方式对电极性能的影响。方法以苯氧树脂为有机载体,不同粒径银粉为导电填料,二元酸酯混合物(DBE)为溶剂制备导电银浆。在石英玻璃纤维织物表面丝网印刷柔性电极,对比不同电极体积电阻率优化银浆组分配比。通过弯折实验表征电极力学性能,通过加热实验研究电极温度稳定性,对比高温烧结与电磁感应烧结对电极的影响。结果银浆含质量分数50%的片状银粉和质量分数10%的超细银粉时,印刷后电极体积电阻率最低且为1.75×10^(-5)Ω·cm,触变性满足丝网印刷要求。电极与基底附着力达到5B级别,弯折后电阻变化率<3%。电极在220℃高温烧结后导电性提升了51.54%,但烧结时间长达1h;经电磁感应烧结在14s内导电性提升了46.7%。结论使用大、小粒径银粉组合可提高石英玻璃纤维织物表面印刷电极中银颗粒的堆积密度,有利于实现电极的良好导电性和稳定性,电磁感应烧结方法可进一步快速提升电极导电性。本文提出的柔性电极制备方法有望对航空航天材料的多功能化、智能化发展提供重要技术支撑。

覆膜砂选区激光烧结后处理试验研究

通过在激光烧结成型的覆膜砂试块上粘贴热电偶测温的方式,测量玻璃珠中试块的实际温度随时间的变化曲线,并测试分析相应的试块强度差异,对进一步优化激光烧结砂芯的性能具有实际参考意义。

烧结温度对Ti_(2) AlNb合金显微组织及高温拉伸性能的影响

采用放电等离子烧结(SPS)技术制备了Ti_(2)AlNb合金,研究烧结温度对Ti_(2)AlNb合金微观组织及力学性能的影响,并使用电子万能试验机及维氏硬度仪对其拉伸性能及硬度进行测试。结果表明:烧结温度为1000℃时,Ti_(2)AlNb合金因为析出O相最多,所以其高温拉伸性能最佳、硬度最高。随着烧结温度的升高,析出O相变少,高温拉伸性能及硬度均降低。对1200℃烧结制备的Ti_(2)AlNb合金进行不同工艺的热处理。热处理后,Ti_(2)AlNb合金的组织由等轴组织转变为魏氏组织,且采用炉冷方式冷却的Ti_(2)AlNb合金组织细化最明显,析出O相最多,硬度最高。

生活垃圾焚烧飞灰烧结处理技术研究

飞灰处理是生活垃圾焚烧处理工艺中必不可少的环节,现行技术在实际应用中飞灰重金属浸出率较低,处理速率较慢,无法达到预期的处理效果,为此提出生活垃圾焚烧飞灰烧结处理技术。通过对飞灰酸消解,去除飞灰中可溶性盐污染物,应用小型圆盘式造球机将飞灰制造成直径10 mm的球团,利用烧结炉对飞灰球团烧结,完成生活垃圾焚烧飞灰烧结处理。试验证明:设计技术飞灰重金属浸出率不低于90%,处理速率可为2 t/h以上,在生活垃圾焚烧飞灰处理方面具有良好的应用前景。

无氧铜表面玻璃绝缘层烧制工艺研究

为解决天线内置型射频等离子体中无氧铜线圈的匝间绝缘问题,本文研究了一种能够在无氧铜表面烧制玻璃绝缘层的工艺,并详细研究该工艺中不同表面处理方式、粘结剂、烧制温度等因素对玻璃绝缘层性能的影响。结果表明:对无氧铜表面进行酸洗预处理相对于碱洗能够显著提高低温釉料在铜表面的润湿性,减少绝缘层表面“孔隙”的产生;同时添加适量的Na_(2)SiO_(3)·5H_(2)O粘结剂能够改善玻璃绝缘层与铜表面的界面结合效果,并提高玻璃绝缘层表面的硬度;此外,绝缘层表面硬度随着烧制温度的升高逐步提高,且绝缘层表面的“孔隙”数量逐步减少;最终根据该工艺制备了表面烧制玻璃绝缘层的无氧铜线圈天线,实现了长时间的放电维持,有效解决了放电过程中匝间的绝缘问题。

兴澄特钢烧结全流程减排生产实践

烧结作为长流程钢铁行业生产中的重要组成部分,生产过程会排放出大量的含有SO_(2)、NO_(x)、粉尘等污染物的烟气,是钢铁行业环境治理的重要对象。兴澄特钢烧结分厂秉承源头削减、过程控制和末端治理的理念,在烧结全流程中通过控制高硫精粉比例,配加全焦粉和氧化铁皮,从源头上减少SO_(2),NO_(x)的生成;通过减少设备漏风、防止内循环系统的串风振动、改进脱硫脱硝烟温换热器,控制烟气中的氧含量;将碱度控制在1.9以上,保持高碱度烧结,控制焦粉中小于0.5 mm的粒度比例,并积极利用烟气内循环系统,减少烧结过程中污染物排放;采用电除尘和活性焦一体化脱除系统,从末端完成污染物的控制,烧结烟气中SO_(2)、NO_(x)和粉尘排放指标分别为4 mg/m^(3)、41 mg/m^(3)和2 mg/m^(3),全部达到了国家钢铁行业大气污染物超低排放的标准。

转炉OG泥消化及烧结应用试验

ＯＧ泥与白灰粉混合，反应产物为松散状消化料。白灰配比、混合时间等因素影响消化料的粒度组成和水含量。消化料可用于烧结生产。

高密度合金烧结后的热处理

综述了高密度合金烧结后的多种热处理工艺及参数 ,分析了热处理工艺参数对高密度合金力学性能的影响 ,为优化高密度合金烧结后的热处理工艺提供参考。