烧结铁矿中FeO含量对其在富氢高炉中还原行为的影响

Japan started the national project “COURSE 50” for CO₂ reduction in the 2000s. This project aimed to establish novel technologies to reduce CO₂ emissions with partially utilization of hydrogen in blast furnace-based ironmaking by 30% by around 2030 and use it for practical applications by 2050. The idea is that instead of coke, hydrogen is used as the reducing agent, leading to lower fossil fuel consumption in the process. It has been reported that the reduction behavior of hematite, magnetite, calcium ferrite, and slag in the sinter is different, and it is also considerably influenced by the sinter morphology. This study aimed to investigate the reduction behavior of sinters in hydrogen enriched blast furnace with different mineral morphologies in CO–CO₂–H₂ mixed gas. As an experimental sample, two sinter samples with significantly different hematite and magnetite ratios were prepared to compare their reduction behaviors. The reduction of wustite to iron was carried out at 1000, 900, and 800°C in a CO–CO₂–H₂ atmosphere for the mineral morphology-controlled sinter, and the following findings were obtained. The reduction rate of smaller amount of FeO led to faster increase of the reduction rate curve at the initial stage of reduction. Macro-observations of reduced samples showed that the reaction proceeded from the outer periphery of the sample toward the inside, and a reaction interface was observed where reduced iron and wustite coexisted. Micro-observations revealed three layers, namely, wustite single phase in the center zone of the sample, iron single phase in the outer periphery zone of the sample, and iron oxide-derived wustite FeO and iron, or calcium ferrite-derived wustite 'FeO' and iron in the reaction interface zone. A two-interface unreacted core model was successfully applied for the kinetic analysis of the reduction reaction, and obtained temperature dependent expressions of the chemical reaction coefficients from each mineral phases.     

Mg和La对Ca–Ti 处理钢中夹杂物演变和组织的影响

The evolution of inclusions and the formation of acicular ferrite (AF) in Ca–Ti treated steel was systematically investigated after Mg and La addition. The inclusions in the molten steel were Ca–Al–O, Ca–Al–Mg–O, and La–Mg–Ca–Al–O after Ca, Mg, and La addition, respectively. The type of oxide inclusion in the final quenched samples was the same as that in the molten steel. However, unlike those in molten steel, the inclusions were Ca–Al–Ti–O + MnS, Ca–Mg–Al–Ti–O + MnS, and La–Ca–Mg–Al–Ti–O + MnS in Mg-free, Mg-containing, and La-containing samples, respectively. The inclusions distributed dispersedly in the La-containing sample. In addition, the average size of the inclusions in the La-containing sample was the smallest, while the number density of inclusions was the highest. The size of effective inclusions (nucleus of AF formation) was mainly in the range of 1–3 μm. In addition, the content of ferrite side plates (FSP) decreased, while the percentage of AF increased by 16.2% due to the increase in the number of effective inclusions in the La-containing sample in this study.     

摩擦焊接碳钢（EN24）和镍基高温合金（IN718）的显微组织和力学性能

Continuous-drive rotary friction welding was performed to join cylindrical specimens of carbon steel (EN24) and nickel-based superalloy (IN718), and the microstructures of three distinct weld zones—the weld interface (WI)/thermo-mechanically affected zone (TMAZ), the heat-affected zone (HAZ), and the base metal—were examined. The joint was observed to be free of defects but featured uneven flash formation. Electron backscatter diffraction (EBSD) analysis showed substantial changes in high-angle grain boundaries, low-angle grain boundaries, and twin boundaries in the TMAZ and HAZ. Moreover, significant refinement in grain size (2–5 μm) was observed at the WI/TMAZ with reference to the base metal. The possible causes of these are discussed. The microhardness profile across the welded joint shows variation in hardness. The changes in hardness are ascribed to grain refinement, phase transformation, and the dissolution of strengthening precipitates. The tensile test results reveal that a joint efficiency of 100% can be achieved using this method.     

汽车暴露面板带有表面条状缺陷的夹杂物分布特征分析:一种定量电解方法

The specific distribution characteristics of inclusions along with the sliver defect were analyzed in detail to explain the formation mechanism of the sliver defect on the automobile exposed panel surface. A quantitative electrolysis method was used to compare and evaluate the three-dimensional morphology, size, composition, quantity, and distribution of inclusions in the defect and non-defect zone of automobile exposed panel. The Al₂O₃ inclusions were observed to be aggregated or chain-like shape along with the sliver defect of about 3–10 μm. The aggregation sections of the Al₂O₃ inclusions are distributed discretely along the rolling direction, with a spacing of 3–7 mm, a length of 6–7 mm, and a width of about 3 mm. The inclusion area part is 0.04%–0.16% with an average value of 0.08%, the inclusion number density is 40 mm?2 and the inclusion average spacing is 25.13 μm. The inclusion spacing is approximately 40–160 μm, with an average value of 68.76 μm in chain-like inclusion parts. The average area fraction and number density of inclusions in the non-defect region were reduced to about 0.002% and 1–2 mm?2, respectively, with the inclusion spacing of 400 μm and the size of Al₂O₃ being 1–3 μm.     

在酸性溶液中加压氧化三价砷离子和二价铁离子

The co-oxidation of As(III) and Fe(II) in acidic solutions by pressured oxygen was studied under an oxygen pressure between 0.5 and 2.0 MPa at a temperature of 150°C. It was confirmed that without Fe(II) ions, As(III) ions in the solutions are virtually non-oxidizable by pressured oxygen even at a temperature as high as 200°C and an oxygen pressure up to 2.0 MPa. Fe(II) ions in the solutions did have a catalysis effect on the oxidation of As(III), possibly attributable to the production of such strong oxidants as hydroxyl free radicals (OH·) and Fe(IV) in the oxidation process of Fe(II). The effects of such factors as the initial molar ratio of Fe(II)/As(III), initial pH value of the solution, oxygen pressure, and the addition of radical scavengers on the oxidation efficiencies of As(III) and Fe(II) were studied. It was found that the oxidation of As(III) was limited in the co-oxidation process due to the accumulation of the As(III) oxidation product, As(V), in the solutions.     

活化天然矿石选择性还原二氧化碳为无定形碳

Natural magnetite formed by the isomorphism substitutions of transition metals, including Fe, Ti, Co, etc., was activated by mechanical grinding followed by H₂ reduction. The temperature-programmed reduction of hydrogen (H₂-TPR) and temperature-programmed surface reaction of carbon dioxide (CO₂-TPSR) were carried out to investigate the processes of oxygen loss and CO₂ reduction. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). The results showed that the stability of spinel phases and oxygen-deficient degree significantly increased after natural magnetite was mechanically milled and reduced in H₂ atmosphere. Meanwhile, the activity and selectivity of CO₂ reduction into carbon were enhanced. The deposited carbon on the activated natural magnetite was confirmed as amorphous. The amount of carbon after CO₂ reduction at 300°C for 90 min over the activated natural magnetite was 2.87wt% higher than that over the natural magnetite.     

含钛高炉炉渣微波合成碳化钛及其介电性能测定

The preparation of functional material titanium carbide by the carbothermal reduction of Ti-bearing blast furnace slag with microwave heating is an effective method for valuable metals recovery; it can alleviate the environmental pressure caused by slag stocking. The dynamic dielectric parameters of Ti-bearing blast furnace slag/pulverized coal mixture under high-temperature heating are measured by the cylindrical resonant cavity perturbation method. Combining the transient dipole and large π bond delocalization polarization phenomena, the interaction mechanism of the microwave macroscopic non-thermal effect on the titanium carbide synthesis reaction was revealed. The material thickness range during microwave heating was optimized by the joint analysis of penetration depth and reflection loss, which is of great significance to the design of the microwave reactor for the carbothermal reduction of Ti-bearing blast furnace slag.     

采用超声组装与滚压工艺制备铝–碳纳米管复合材料

This study introduced a novel fabrication of aluminum–carbon nanotube (CNT) composites by employing bulk acoustic waves and accumulative roll bonding (ARB). In this method, CNT particles were aligned using ultrasonic standing wave in an aqueous media, and the arrayed particles were precipitated on the aluminum plate substrate. Then, the plates rolled on each other through the ARB process with four passes. Optical and scanning electron micrographs demonstrated the effective aligning of CNTs on the aluminum substrate with a negligible deviation of arrayed CNTs through the ARB process. The X-ray diffraction pattern of the developed composites showed no peaks for carbon and aluminum carbide. In addition, tensile tests showed that the longitudinal strength of the specimens processed with aligned CNTs was significantly greater than that of the specimens with common randomly dispersed particles. The proposed technique is beneficial for the fabrication of Al–CNT composites with directional mechanical strength.     

深基坑桩锚支护位移及内力数值模拟分析

利用FLAC3D数值模拟软件,按照实际施工工序模拟基坑开挖支护全过程,得到了桩锚支护结构以及基坑外土体沉降和基坑侧壁水平位移随基坑开挖的变形规律:随基坑开挖深度的增加,基坑外土体沉降逐渐增大,变化曲线呈"勺状"分布;基坑顶和基坑侧壁水平位移随开挖深度增加均逐渐增大且都在开挖至基坑底时位移最大;桩身弯矩最大值处基本出现在基坑开挖深度1.5 m以上的位置,最大负弯矩值为76.7;锚索轴力最大位置出现在锚索的端头处,且从端头位置向端尾位置逐渐减小,而第1排至第3排锚索最大值逐渐增大,说明支护结构中第2、3排锚索起主要作用,验证了深基坑桩锚支护的可行性。     

基坑开挖扰动变形特征及控制效果模拟分析

坑中坑的开挖对于基坑的稳定性有诸多方面的影响,内坑的开挖会造成土体回弹,引起基坑土体抗力的损失,降低基坑的整体稳定性。运用FLAC^3D对合肥恒大中心C地块坑中坑式基坑进行了开挖与支护模拟,计算采用摩尔-库伦本构模型,通过模拟计算得出了基坑应力、桩基应力、桩锚应力,验证了基坑中外坑和内坑最易失稳破坏区域,并对利用负泊松比(negative Poisson’s ratio, NPR)锚索对该类基坑进行加密支护的控制效果进行了评价。通过施加位移监测得到了不同开挖阶段基坑地表位移、坑中坑底部位移、以及坑中坑周围土体位移,确定了基坑极易发生破坏的区域以及滑动面位置,建立了坑中坑物理模型,并验证了数值模拟的正确性,研究结论可为类似工程条件基坑的开挖及加固提供理论支撑和实践基础。     

土钉墙与预应力锚杆在深基坑中的联合应用

土钉墙与锚杆在京东地区深基坑中的联合应用,此种方法能在很大程度上降低工程造价,节省成本,在本工程中运用此种方法完成了14m深的基坑支护工程。     

偏压条件下排桩加内支撑支护深基坑受力与变形分析

基坑开挖受周围环境制约较大,需根据具体条件采取不同的支护方式。尤其对于狭长基坑两侧存在偏压的情况,基坑变形以及支护结构受力会存在较大差异。本文以西安科技八路综合管廊深基坑支护工程为研究对象,采用数值模拟与现场监测相结合的方法,对偏压条件下基坑的变形以及支护结构受力变化规律进行了深入的研究分析。研究结果表明：随着基坑开挖,水平位移和竖向位移均呈逐渐增大趋势,锚杆和内支撑对水平位移控制效果明显。桩身内力在锚杆与内支撑位置突变明显,避免了桩身受力过大。由于受右侧已开挖基坑的影响,导致基坑两侧变形有所差异,但位移值相差不大。说明该深基坑支护方案设计合理,支护效果良好,满足偏压条件下对基坑变形控制的要求。研究结果可为类似基坑工程的支护与开挖提供一定的指导。     

基坑开挖对周边环境的影响分析

为探究基坑降水开挖过程中基坑及周边环境的响应,以西北某实际基坑工程为背景,通过Plaxis 3D软件建立模型,分析了基坑开挖过程中基坑及周边环境产生的变形和围护结构锚杆上力的变化.结果表明:基坑开挖产生的土体变形是一个三维问题,剖面土体的变形受基坑阴、阳角的影响,这种影响的强弱与剖面距基坑阴、阳角的距离有关;在基坑围护结构中,锚杆锚固效果比土钉好30%左右,桩锚支护效果比复合土钉墙好20%左右;下排锚杆比上排锚杆承担更多的主动土压力,其自由段轴力比上排锚杆大;位于复合土钉墙支护段附近的道路受基坑开挖影响,其倾斜方向由最开始的朝坑外倾斜转变为朝坑内倾斜;位于桩锚支护段附近的既有建筑变形均在相关规范允许范围内,周边既有建筑处于安全状态.     

土岩组合深基坑围护结构受力与变形特性分析——以青岛海天中心深基坑为例

为了研究土岩组合二元地层超基坑受力、变形和邻近建筑沉降随基坑开挖的演化规律,依托于青岛海天中心城市综合体桩锚支护结构体系超深基坑工程,对预应力锚索轴力、基坑水平和竖向位移以及周边建筑物沉降进行了实时监测。结果表明,基坑开挖期间内,预应力锚索轴力随时间的变化规律主要分快速下降、稳定变化和基本稳定3个阶段,锚索轴力平均损失率约为15.08%;基坑最大水平位移为12.30 mm,最大竖向位移为11.01 mm,基坑临近建筑物最大沉降量为1.2 mm,远小于设计和现行《建筑基坑工程监测技术标准》的容许变形值,说明桩锚支护结构体系可以有效控制基坑变形,确保毗邻建筑物安全;同时表明该基坑的支护设计方案有较大的优化空间,从而节约工程成本。研究成果对相似地质条件的超深基坑围护结构设计具有重要参考价值。     

非预应力喷锚网在深基坑支护工程中的设计与应用

根据某大厦深基坑非预应力喷锚网联合支护结构的设计计算方法、施工技术措施及监测结果,探讨了非预应力喷锚网联合支护技术在深基坑支护中经济合理的设计方案、安全高效的施工方法以及科学有效的监测管理手段,可为非预应力喷锚网联合支护技术的推广和应用提供工程参考.     

条桩综合护坡体系在基坑支护施工中的应用

我对北京嘉利来世贸中心工程的基坑支护，采用综合支护体系为条桩及锚索结合旋喷的基坑支护方案，并根据现场条件，将多种施工工艺结合起来，成功运用于基坑支护工程。     

主动区溶洞对桩锚支护基坑稳定性的影响

为了研究存在最危险滑移面时主动区溶洞对桩锚支护基坑稳定性的影响,首先运用FLAC3D软件模拟出没有溶洞时基坑最危险滑移面的位置,然后再分别模拟出主动区不同位置、不同大小的溶洞对桩体最大水平位移和弯矩、锚索最大轴力以及地表最大沉降位移的影响规律,最后提出主动区溶洞的处理方法.结果表明:最危险滑移面的剪出口出现在强风化石灰岩与中风化石灰岩的分界线处,最危险滑移面为与基坑内壁夹角约45.方向的弧形面;在同一溶洞中心埋深下,越靠近最危险滑移面的溶洞对基坑稳定性影响越大,当溶洞中心埋深不同但都在最危险滑移面上时,越靠近剪出口的溶洞对基坑稳定性影响越大;溶洞边长越大,对基坑稳定性影响越大,当边长大于等于2 m时,需要对溶洞进行处理,且利用增大锚索预应力的处理方法对主动区溶洞的处理效果比较明显.可见,考虑最危险滑移面的不利影响对研究主动区溶洞对桩锚支护基坑稳定性的影响是必要的.     

预应力锚杆复合土钉支护模拟研究

通过工程实例,采用数值分析的方法,模拟研究基坑开挖过程中预应力锚杆与土钉墙复合支护结构的受力性状、工作性能和作用机理,并在数值分析中利用强度折减法分析基坑开挖后的稳定性。