Optimization of PGNAA device and algorithm for testing basicity index of sinter mixture

Sinter is the main raw material in the blast furnace iron-making process,and basicity(CaO/SiO2)is an important quality index of sinter.Prompt gamma neutron activation analysis is a multi-elemental online detection technology that has been successfully applied in cement,coal,etc.Compared with cement as a raw material,sinter exhibits poor moderation ability and a large neutron absorption cross section.Therefore,cement detection devices are not suitable for sinter mixture detection.In this study,a prompt gamma neutron activation analysis equipment used for testing cement was re-optimized to render it suitable for measuring a sinter mixture.Using Monte Carlo simulation,the comprehensive detection efficiency of the detection device improved by 71.52%.Because of the gamma-ray self-shielding effect of the sinter mixture,the detection errors of CaO and SiO2 are significant.By applying the gamma-ray self-shielding correction algorithm,the detection accuracies improved,and their linear correlation coefficients R2 exceeded 0.99.Furthermore,by applying an improved analyzer to a sintering plant,the first-grade product rate of the factory increased by 4.64%.

Effect and function mechanism of sinter basicity on softening-melting behaviors of mixed burden made from chromium-bearing vanadium-titanium magnetite

The effect of sinter basicity on softening-melting behaviors of mixed burden made from chromium-bearing vanadium-titanium magnetite(Cr-V-Ti magnetite) was investigated and the function mechanism was simultaneously analyzed.The results show that with increasing sinter basicity from 1.71 to 2.36,the softening interval tends to increase from 149.3 ℃ to 181.7 ℃while the melting interval tends to decrease from 178.0 ℃ to 136.7 ℃.The location of cohesive zone moves downwards firstly and then ascends slightly,but the cohesive zone becomes thinner.The softening-melting characteristic value becomes small,which indicates that the permeability of burden column is improved.The dripping ratio of mixed burden tends to increase firstly and then decrease,which comes to the highest value of 74.50%when the sinter basicity is 2.13.The content and the recovery of V and Cr in dripping iron are all increased.The generation amount of components with high melting point in slag becomes little with the increase of sinter basicity,which could improve the permeability of mixed burden.Taking softening-melting behaviors of mixed burden and recovery of valuable elements into account,the proper sinter basicity is no less than 2.13 for smelting mixed burden made from Cr-V-Ti magnetite in blast furnace.

Basic characteristics of Australian iron ore concentrate and its effects on sinter properties during the high-limonite sintering process

The basic characteristics of Australian iron ore concentrate (Ore-A) and its effects on sinter properties during a high-limonite sintering process were studied using micro-sinter and sinter pot methods. The results show that the Ore-A exhibits good granulation properties, strong liquid flow capability, high bonding phase strength and crystal strength, but poor assimilability. With increasing Ore-A ratio, the tumbler index and the reduction index (RI) of the sinter first increase and then decrease, whereas the softening interval (Delta T) and the softening start temperature (T (10%)) of the sinter exhibit the opposite behavior; the reduction degradation index (RDI+3.15) of the sinter increases linearly, but the sinter yield exhibits no obvious effects. With increasing Ore-A ratio, the distribution and crystallization of the minerals are improved, the main bonding phase first changes from silico-ferrite of calcium and aluminum (SFCA) to kirschsteinite, silicate, and SFCA and then transforms to 2CaO center dot SiO2 and SFCA. Given the utilization of Ore-A and the improvement of the sinter properties, the Ore-A ratio in the high-limonite sintering process is suggested to be controlled at approximately 6wt%.

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.

铁矿粉种类和成分对其烧结基础特性的影响

铁矿粉的同化性能、黏结相强度与液相流动性等基础特性是烧结优化配矿的重要基础。对BX、YLJ和NFJ等多种铁矿粉进行基础特性检测,并将2种及2种以上铁矿粉混合进行拓展研究。分析铁矿粉基础性能的主要影响因素和三大矿种的基础性能特征,提出基于同化性能、液相流动性的互补配矿思路,为增加性价比高的缺陷矿用量、提高生产质量、降低配矿成本提供理论指导。

烧结时间对高碱度烧结矿冶金性能的影响研究

高碱度烧结矿因具有良好的粉化还原率以及软熔性能而被用于高炉冶炼,但其含有的铁酸钙含量和不同形态会对烧结矿的质量和性能产生较大影响。文章研究了烧结时间对烧结矿中铁酸钙含量和形态的影响,以及铁酸钙含量及形态对烧结矿低温粉化性能以及还原性的影响。随着烧结时间的增加,烧结矿中抗压强度较高的针状铁酸钙含量逐渐降低,从而导致烧结矿力学性能逐渐下降。烧结过程中赤铁矿逐渐转变为磁铁矿,内应力有所升高,导致烧结矿更容易粉化和破碎。

Some basic properties of granules from ore blends consisting of ultrafine magnetite and hematite ores

Some basic properties of granules,including the granule size distribution,packed-bed permeability,and chemical composition of the adhering layer,were investigated in this study for four iron ore blends consisting of 5wt%,25wt%,and 45wt%ultrafine magnetite and 25wt%ultrafine hematite concentrates.The effects of varying the sinter basicity(CaO/SiO2 mass ratio=1.4 to 2.2)and adding ultrafine concentrates on the variation of the adhering-layer composition and granule microstructure were studied.Moreover,the effect of adhering-layer compositional changes on sintering reactions was discussed in combination with pot sintering results of ore blends.Increasing sinter basicity led to an increase in the basicities of both the adhering layer and the fine part of the sinter mix,which were higher than the overall sinter basicity.When the sinter chemistry was fixed and fine Si-bearing materials(e.g.,quartz sand)were used,increasing the amount of ultrafine ores in the ore blends tended to reduce the adhering-layer basicity and increase the SiO2 content in both the adhering layer and the fine part of the sinter mix,which will induce the formation of low-strength bonding phases and the deterioration of sinter strength.The adhering-layer composition in granules can be estimated in advance from the compositions of the-1 mm fractions of the raw materials.

Texture analysis of ultra-high coercivity Sm_(2)Co_(7) hot deformation magnets

Bulk anisotropic Sm_(2)Co_(7) nanocrystalline magnets were successfully prepared by hot deformation process using spark plasma sintering technology.The coercivity of the isotropic Sm_(2)Co_(7) nanocrystalline magnet is 34.76 kOe,further,the ultra-high coercivity of 50.68 kOe is obtained in the anisotropic hot deformed Sm_(2)Co_(7) magnet when the height reduction is70%,which is much higher than those of the ordinarily produced hot deformed Sm_(2)Co_(7) magnet.X-ray diffraction(XRD)analysis shows that all the samples are Sm_(2)Co_(7) single phase.The investigation by electron backscatter diffraction indicates that increasing the amount of deformation is beneficial to the improvement of the(001) texture of Sm_(2)Co_(7) magnets.The Sm_(2)Co_(7) nanocrystalline magnet generates a strong c-axis crystallographic texture during large deformation process.

碱性氧化物对仿古砖低温高质的烧结性能研究

由于目前陶瓷烧结温度高,难以通过传统方式降低陶瓷的烧结温度。通过以仿古砖配方原料为基础,引入碱性氧化物K_(2)O、CaO,基于球磨法、常压烧结法制成低温烧结的复合陶瓷,利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)对复合陶瓷的形貌和物相组成进行分析,研究K_(2)O、CaO的引入量、烧结温度对复合陶瓷性能的影响。结果表明:碱性氧化物的引入,不仅可以降低复合陶瓷的烧结温度,还可以提高其性能。其中引入质量分数为1%的K_(2)O和CaO,使复合陶瓷的烧结温度从1120℃降低到1080℃。并且K_(2)O的引入拓宽了陶瓷的烧结范围,CaO的引入使其抗折强度从38.87 MPa提高到52.15 MPa,同时吸水率、体积密度也能满足行业标准要求。基于微观形貌分析发现:K_(2)O和CaO的引入,促使陶瓷的共融熔液相在低温下出现,填充陶瓷内部孔隙,有利于陶瓷致密化。

Grain-refining fabrication of nanocrystalline(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)high-entropy ceramics by ultra-high pressure sintering

As an important A_(2)B_(2)O_(7)-type ceramic,(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)high-entropy pyrochlore pos-sesses promising properties such as high melting point,high chemical durability,and low thermal conductivity.However,the low sintering ability limits its application in thermal barrier coating and radioactive waste immobilization.It usually needs long-term high-temperature soaking to achieve full density,but with inevitable grain growth.In this work,dense and grain-refined nanocrystalline(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)ceramics were prepared with ultra-high pressure sintering(UHPS)method under 10 GPa at a low temperature of 800℃.The densification behavior,microstructure evo-lution,and properties of the UHPS-ed samples were then investigated.The grain size of as-prepared(La_(0.2)Nd_(0.2)Sm_(0.2)Gd_(0.2)Eu_(0.2))_(2)Zr_(2)O_(7)ceramic was only 151 nm,which is 40%smaller than that of raw pow-der.In addition,it exhibited advantageous properties including both high hardness and aqueous durabil-ity.Plastic deformation under ultra-high pressure was believed as the dominant densification mechanism responsible for grain refinement and property improvement.

长钢烧结配加国内精粉生产实践

为优化原料资源配置,长钢在烧结生产中使用了大比例的国内铁精粉。通过对国内精粉的同化性、液相流动性、黏结性等基础特性进行研究,探讨其对铁矿粉烧结基础特性的影响机理,以改善烧结矿质量,指导烧结优化配矿。烧结生产在增加铁精粉配比的同时,采取了大量措施强化制粒效果、优化烧结过程的透气性,为开发优质、高产、廉价的烧结矿生产技术提供科学依据。

Anisotropic thermal expansion in high-entropy multicomponent AlB_(2)-type diboride solid solutions

High-entropy(HE)ultra-high temperature ceramics have the chance to pave the way for future applications propelling technology advantages in the fields of energy conversion and extreme environmental shielding.Among others,HE diborides stand out owing to their intrinsic anisotropic layered structure and ability to withstand ultra-high temperatures.Herein,we employed in-situ high-resolution synchrotron diffraction over a plethora of multicomponent compositions,with four to seven transition metals,with the intent of understanding the thermal lattice expansion following different composition or synthesis process.As a result,we were able to control the average thermal expansion(TE)from 1.3×10^(−6)to 6.9×10^(−6)K^(−1)depending on the combination of metals,with a variation of in-plane to out-of-plane TE ratio ranging from 1.5 to 2.8.

改善烧结矿低温还原粉化性能的措施

某钢铁企业结合烧结生产实际,通过分析影响烧结矿低温还原粉化率的因素,采取提高烧结矿碱度优化配矿、改善烧结工艺条件、调整烧结矿中脉石成分、规范取制样等措施,改善了烧结矿低温还原粉化性能,烧结矿低温还原粉化指标RDI+3.15mm由65.71%提高到71.12%,取得良好效果。

Forced boiling of nonazeotropic immiscible mixture in a supercapillary microchannel array for ultra-high heat flux removal with chip junction temperature below 85℃

In this study,a structure-optimized two-phase microchannel heat sink with sintered submicron nucleation sites was developed and tested.The copper-based microchannels had a rectangular cross-section with an equivalent hydraulic diameter of 222μm.The subcooled flow boiling characteristics were comprehensively compared between pure HFE-7100 and a non-azeotropic,immiscible binary mixture of HFE-7100 and water,considering heating areas of 1 and 5 cm^(2).The total heating power input to the test section were 100–1500 and 250–3000 W for a 1 and 5 cm^(2)heat source,respectively,with a flow rate ranging from 50 to150 L/h.Compared to pure HFE-7100,the non-azeotropic immiscible binary mixture of HFE-7100/water in the sintered porous microchannels exhibited a much higher overall heat transfer coefficient and lower power consumption.To maintain the junction temperature of a high power electronic chip below 85℃,the proposed supercapillary microchannel heat sink could effectively dissipate the heat flux of 1275 W/cm^(2)over 1 cm^(2)heat source and 500 W/cm^(2)over 5 cm^(2)heat source.In addition,the volume ratio of the binary mixture strongly influence the two-phase flow heat transfer characteristics.An optimal volume ratio exist in terms of the thermal resistance–pumping power minimization(HFE-7100:water=2:8 is recommended in this study).The findings of this investigation on the flow boiling properties of non-azeotropic immiscible mixtures help fill a gap in the related field.

永洋特钢集团炼铁厂低镁铝比冶炼实践

研究了烧结矿在不同的MgO含量条件下对烧结性能的影响,并对高炉炉渣镁铝比的降低进行了实践。实现了中大型高炉炉渣镁铝比在0.37~0.46理论最低条件下的高炉长期稳定顺行及指标优化,高炉炉渣镁铝比控制水平在行业内同级别高炉处于领先水平。

铁矿石的烧结基础特性之新概念

长期以来，人们对烧结用铁矿石的评价主要集中在化学成分、粒度组成、矿物特征等常温性能方面，而对铁矿石在烧结过程中的高温行为和作用知之甚少．根据对这一问题的深入思考和实验室的基础研究，提出了“铁矿石的烧结基础特性”的概念．该概念包括同化性能、液相流动性，粘结相强度性能和铁酸钙生成性能等．研究烧结过程中这些高温物理特性，有利于完善烧结理论、改善烧结矿质量和优化烧结工艺过程．

包钢常用铁矿粉烧结基础特性

采用微型烧结法研究了包钢常用六种铁矿粉的烧结基础特性.结果表明,不同铁矿粉的烧结基础特性差别较大.铁矿粉的CaF_2,FeO,MgO,SiO_2和结晶水含量是影响其烧结基础特性的主要因素.包钢含氟磁铁矿的烧结基础特性为同化温度低于1250℃,液相流动性指数大于8.0,粘结相自身强度低于450N/个,铁酸钙生成量小于10%,连晶固结强度高于560N/个.

碱度对钒钛烧结矿显微结构的影响

采用光学显微镜研究了碱度对钒钛烧结矿显微结构的影响。研究表明:碱度由2.1提高到2.5,烧结矿中钛磁铁矿、铁酸钙与硅酸二钙含量增加,钛赤铁矿与玻璃质含量降低;骸晶状赤铁矿与包边结构减少,显微结构由斑状向交织熔蚀结构过渡;相应的烧结矿强度增加。碱度为2.5时,铁酸钙主要以柱状、针状形态存在,钛磁铁矿主要以他形粒状形态存在,钙钛矿主要呈十字形和他形晶形态存在。

MgO对烧结矿软熔性能的影响

为进一步提高烧结矿的质量,考察了不同MgO质量分数烧结矿的高温冶金性能,并研究了MgO对烧结矿软熔性能的影响机理.试验结果表明,随着MgO质量分数的增加,烧结矿的软化区间不大,但由于初渣中含MgO的高熔点物质增多,烧结矿熔化带和软熔带区间显著增加,尤其对低碱度烧结矿的影响更加明显.试验条件下,MgO质量分数由1.3%增加至3.0%时,低碱度烧结矿(R=1.36)的软熔带温度区间从217.2℃增加到325.5℃;碱度R为1.76时,烧结矿软熔带温度区间从310.5℃增加到389.3℃.因此,降低烧结矿中MgO质量分数,有利于改善烧结矿的高温冶金性能.

高碱度烧结矿的矿物组成与矿相结构特征

采用X射线衍射、光学显微镜和扫描电镜对莱钢、宝钢、鞍钢和酒钢烧结矿进行了研究，提出了高碱度烧结矿（w（CaO）／w（SiO2）=1．84～2．11）的矿物组成与矿相结构共性特征和差异。研究发现，其矿物组成主要有赤铁矿、磁铁矿、铁酸钙和硅酸钙，其中赤铁矿主要以自形晶和少量的他形晶存在，与铁酸钙之间具有明显的界面，而磁铁矿主要以粒状他形晶存在，与铁酸钙呈熔蚀结构。铁酸钙多以柱状和针状形态存在，中间交织着柱状或粒状的β-硅酸二钙。另外，烧结矿粘结液相内适当地增加Al2O3含量，有助于针状铁酸钙生成。