烧结过程二恶英污染控制的方法

<正>a.烧结前控制。分析烧结过程中二恶英的成因可以发现,氯元素的存在是烧结生产过程中二恶英形成的重要因素之一,因此,采用含氯元素低的原料是减少二恶英排放的有效途径。除尘灰和轧钢氧化铁皮的氯元素含量相对较高,通过改变除尘灰和轧钢氧化铁皮掺用比例,可改变烧结混合原料中氯元素含量;由于烧结原料中铜元素的存在对二恶英的生成有催化作用,选择含铜量低的铁矿石也可以减少二恶英的排放;烧结回用的物料(除尘灰、氧化铁皮、污泥等)杂质含量较     

赤铁精粉配比对烧结矿强度的影响

 铁精粉具有铁品位高、脉石矿物含量及有害元素少、价格较低等优点，但由于其粒度过细，会对烧结生产产生不良影响，进而导致其使用受到限制。为了明确铁矿烧结过程中赤铁精粉配比对烧结矿强度的影响规律，采用微型烧结法研究了赤铁精粉配比对烧结液相流动性及其固结强度的影响规律，并在此基础上进一步探究了优化石灰石粒度对烧结矿强度的影响规律，最终为高效使用赤铁精粉提供理论基础。研究结果表明，随着赤铁精粉配比的增大，烧结体固结强度呈现先略微降低，而后在配比为15%时大幅下降（相对于配比10%铁精粉来说固结强度降低了16%），这是由于随着赤铁精粉配比的增大，黏附粉的偏析碱度降低，进而使得黏附粉的液相流动性减小，最终导致烧结矿强度降低。然而，减小石灰石粒度，可以有效改善烧结液相流动性，进而提高烧结矿强度。     

钢屑替代品用于硅铁生产的可行性分析

针对目前铁合金冶炼生产中钢屑原料短缺的问题,介绍了利用铁硅石、氧化铁皮、球团矿、废渣代替钢屑来冶炼硅铁的工艺,对其冶炼效果和经济可行性进行了分析。结果表明:在钢屑资源短缺的地区,利用钢屑替代品冶炼硅铁是可行的。     

加拿大铁精粉对烧结体固结强度的影响及其改善方法

 加拿大铁精粉由于具有铁品位高、脉石及有害元素含量低等优点，其在烧结过程中使用具有有利条件。采用微型烧结法考察了该铁精粉配比对烧结体固结强度的影响及其机理，并研究了4种富矿粉的细粉液相流动性和粗颗粒吸液性。在此基础上，通过固结试验，探究并验证了烧结体固结强度的改善方法。研究结果表明，将该铁精粉配入混匀料中，大幅降低了黏附粉偏析碱度，减弱了液相流动性，因此恶化了烧结体的固结强度。在固定碱度的条件下，高硅铁矿粉有较高的细粉液相流动性，低气孔率铁矿粉有较弱的粗颗粒吸液性。在配加该铁精粉的条件下，选择高液相流动性铁矿粉、弱吸液性铁矿粉、强吸液性铁矿粉粗颗粒分加制粒均能有效改善烧结体的固结强度。     

不同普通铁精粉配比的含钛烧结矿矿相结构研究

针对承钢含钛烧结矿存在的强度差、低温还原粉化严重等实际问题,在实验室进行了不同普通铁精粉配比含钛烧结矿矿相结构的研究。结果表明:烧结原料中随普通铁精粉配比的增加,含钛烧结矿中金属相含量明显降低,而黏结相含量增加,其中钙钛矿含量降低,铁酸钙含量明显升高;显微结构逐渐均匀化,由粒状结构过渡到熔蚀结构,骸晶状钛赤铁矿含量降低;对应的烧结矿强度及低温还原粉化性能得到进一步改善。     

高比例铁精粉烧结生产实践

为优化原料资源配置,2016年唐钢公司在烧结生产中大幅度提高铁精粉,特别是自产精粉的使用比例。针对精粉比例由19.82%提高到30.34%的生产经营预期,中继仓位槽位由70%降至20%以下,启用机头松料器、烧结矿中的MgO含量由2.3%降至2.0%。通过优化烧结矿的成分、强化混合料制粒效果、改进布料设备等措施,确保了烧结矿的主要技术指标稳定。     

高铁低硅烧结矿配矿技术的试验研究

通过配加不同铁精粉、澳洲粗粉、巴西粗粉等一系列烧结试验,优化出济钢目前原料条件下合理的烧结原料结构。     

提高铁精粉入烧配比的实践

为适应资源环境的变化,唐钢在2015年开始使用PMC公司生产的南非铁精粉替代巴卡粗粉,司营精粉和研山精粉替代澳矿粉,测算烧结工序铁精粉配比将提高10个百分点左右。针对铁精粉配比提高给烧结生产带来的影响,通过研究铁矿粉的基础特性,制定合理烧结矿成分控制基准,优化配混料以及布料设备参数等措施,实现了烧结铁精粉配比由24.48%提高到36.15%的预期目标,取得良好的生产效果。     

齐大山铁矿烧结试验研究

为考察不同SiO2含量对烧结过程以及烧结矿性能的影响规律,对鞍山集团矿业公司齐大山铁矿生产的铁精粉,进行了烧结试验研究。得出随SiO2含量降低,烧结混合料的适宜水分有所升高,烧结料层的垂直烧结速度有减慢的趋势,烧结矿的转鼓强度、成品率有降低趋势,烧结矿的低温还原粉化性能变差,烧结矿的还原度略有降低,烧结矿的软化开始温度升高,软化区间变窄,软化性能改善。综合烧结过程和烧结矿的各项性能指标来看,SiO2含量过低,不利于烧结矿性能的改善。在烧结矿SiO2含量〉5.5%以上时,提铁降硅对烧结生产影响不大,但当SiO2〈5.5%,尤其是SiO2〈5.0%时,随着SiO2含量逐步降低,烧结矿质量明显下降。结合选矿的生产实践,齐大山铁矿合理经济品位的赤铁矿铁精粉中SiO2含量以5.0%-5.5%为宜。     

赤铁精粉烧结技术的研究

从物理、化学和表面特性上分析了赤铁精粉的烧结特点,提出了赤铁精粉烧结适宜的粘结相是多元铁酸钙,相适应的烧结条件是低温、高碱度和氧化性气氛,结合对铁矿石烧结过程的研究,给出与赤铁精粉的烧结相适宜的烧结技术：优化混合料粒度分布,强化造粒,改善料层透气性;优化燃料在烧结料层内分布,提高完全燃烧比例,充分利用有效热量;选择适宜的粘结相量;利用烧结添加剂获得合理矿相结构;采用厚料层操作,充分利用燃烧热量,降低烧结固体燃耗等。     

Recyclability assessment of Al 7075 chips produced by cold comminution and consolidation using spark plasma sintering

A solid-state recycling route for processing aluminium alloy 7075 chips is proposed. This process involves pulverizing the chips using an industrial scale comminution line to produce a broad particle size distribution of granulated products and powders. Upon sieving, the ?140 mesh fraction of the pulverised material was consolidated by spark plasma sintering into fully dense compacts, i.e. >99%. The properties of the pulverised powders and compacts were compared to commercially available aluminium alloy 7075 powder used in industrial press-sinter applications. The comminution line produced powder particles which possessed a 7·9?±?0·6-nm thick native oxide layer with adhering exogenous contaminants, and aluminium oxide particles dispersed throughout the powder. The presence of the oxide layer and exogenous contaminants was found to be deleterious to the powder consolidation and mechanical properties. A flexural strength and strain and hardness of 94·7?±?7·2?MPa, 2·1?±?0·3% and 69·3?±?5·2 HV were obtained, respectively.     

粉末冶金工艺对纯铁软磁材料性能的影响

利用粉末冶金技术制备纯铁软磁材料,在不同温度和压力下将不同粒径铁粉压制成生坯,并在保护气氛下进行烧结。结果表明:不同粒径铁粉混合有助于压坯密度的增加,适宜的压制温度可以有效地促进粉末流动,避免大尺寸孔洞的形成,优化组织。140℃、800 MPa温压条件下雾化铁粉压坯密度最高可达7.35 g·cm-3。对比常温压制,温压压坯烧结后孔洞分布均匀。烧结体密度随温度的升高而上升,雾化铁粉压坯在1250℃烧结后密度最高可达7.47 g·cm-3。在一定范围内,软磁材料磁性能与密度成正比,混粉压制试样的密度接近理论值,但在混合铁粉中,较细的铁粉夹杂于粗粉中,阻碍磁畴壁移动,造成饱和磁化强度（M_s）偏小、矫顽力（H_c）偏大的现象,M_s为205.51 emu·g-1,Hc为7.9780 Oe。     

冶炼钢铁过程中多种固体废物的鉴别

在钢铁的冶炼过程中,主要产生炉渣、除尘灰和氧化皮等固体废物,其中氧化皮是国家规定可以进口的固体废物,炉渣和除尘灰属于不能进口的固体废物。实验针对冶炼钢铁过程中产生的固体粉末进行鉴别,首先利用肉眼和扫描电镜(SEM)对样品进行初步判断,例如炉渣的外观不是正常天然矿物的块状或粉状,而除尘灰颗粒较细、较轻,氧化皮呈鳞片状、有金属光泽。再利用X射线荧光光谱(XRF)对制得粉末中的元素进行分析,炉渣的主要元素为钙、硅、镁和铝,铁的含量极低;而除尘灰中铁的含量很高,同时含有锌和钙;氧化皮的主要元素也是铁。最后利用X射线衍射(XRD)技术对粉末中存在的物相进行分析,从而推断出固体粉末的属性,炉渣中的主要物质是CaO-MgO-Al₂O₃-SiO₂形式存在的配合物;除尘灰中的主要物质是铁的氧化物以及一些氧化锌;氧化皮的主要物质也是铁的氧化物,其中氧化亚铁的含量高。通过实验建立了这3种固体废物的鉴别方法,对进口固体废物的监管提供指导。     

Microstructure and strength of CuFe in situ composites obtained from prealloyed CuFe powders

Copper-iron in situ composites have been produced from prealloyed, extruded powders. The extruded rods were subsequently cold drawn to various stains when the iron particles are drawn into fine fibres. The dependence of the tensile stress and the ductility on cold work has been analysed and the different microstructures have been examined to quantify their evolution with cold work. The fine scale of the initial microstructure makes it possible to obtain a high tensile stress after a relatively small reduction in area during working. The strength of such composites has previously been explained by models based on the rule of mixtures and these models are modified here to take into account the nanometre scale of the iron ribbons. Analysing the mechanical properties, it appears that the very fine scale of the ribbon-shaped iron particles makes them very strong such that they deform elastically up to very high stresses, even when the composite begins to deform in a non-elastic manner. The strength of the fine ribbons after very large drawing strain is considered to reach the theoretical limit, as the ribbons are reduced to thicknesses of about 3 nm, and beyond such strains the composite strength will probably increase at a slower rate or may saturate.     

Processing and performance of Cr2O3–Fe2O3 reference electrode powders prepared by oxide coprecipitation

Abstract

Cr₂O₃–Fe₂O₃ based oxide mixtures for reference electrode powders of oxygen sensors were processed using oxide coprecipitation route. A special method for preparing reference electrode powders has been developed by mixing coarse Cr particles with the oxide mixture in the form of Cr–Fe hydroxide. Morphology and size of the mixed oxide powders were characterised by means of scanning electron microscopy and laser diffraction method. With the coprecipitation process, chemically homogeneous and very fine powders with a mean particle size of 1.53 μm were prepared. This powder mixture adhered and loosely coated to Cr particles. The processed reference electrode powders were tested in low level oxygen concentration measurements of steelmaking process under industrial scale. The reference electrode powders showed excellent results in terms of electromotive force reproducibility, response time and accuracy in soluble aluminium predictions at the oxygen concentration measurements. Most of the particles of the reference electrode powder remained separated after dipping to molten steel.     

Manufacture of magnetic cores from various iron powders

Conclusions Coercive force measurements were made on grades PZh4M3, PZhCh3SV, PZhCh3MV, NC 100.24, PZhR(0) and PZhÉ iron powders and magnetic cores heat treated in the temperature range 750–1200°C. Iron powders of large specific surface are characterized by greater coercive forces compared with powders of small specific surface. Grades PZhCh3SV, PZhCh3MV, NC 100.24, and PZhR(0) iron powders are suitable for the manufacture of magnetic cores after they have been alloyed with elements decreasing internal stresses in alloys. Sintered magnetic cores from PZhÉ electrolytic iron powder meet all the requirements of TU 16-538.225-74 without alloying. The properties of grades EMP300M, PM282N, KiP 270.MS, and SC 100.26 iron powders were assessed. KiP 270.MS and SC 100.26 powders possess the same properties as PZhCh3SV, PZhCh3MV, and NC 100.24 powders, but in grade SC 100.26 powder high oxygen contents are not permissible. Consequently, magnetic cores made from this powder will exhibit high coercivity. Grades EMP300M and PZhR(0) iron powders are similar in all their properties, and the magnetic characteristics of cores made from them will therefore also be comparable. Grade PM282N iron powder is produced by the electrolysis of solutions and characterized by a dendritic particle shape. Owing to the large specific surface of the particles of this powder, its coercive force will be 25–30 A/m greater than that of PZhÉ. In the manufacture of magnetic cores from this powder recourse must therefore be had to alloying with silicon in order to decrease their coercivity.Translated from Poroshkovaya Metallurgiya, No. 6(234), pp. 73–78, June, 1982.     

Preparation of Reduced Iron Powders from Mill Scale with Microwave Heating: Optimization Using Response Surface Methodology

Preparation of the reduced iron powder has been attempted with mill scale as the iron-bearing material and with wood charcoal as the reducing agent through microwave heating. The response surface methodology (RSM) is used to optimize the process conditions, with wood charcoal, process temperature, and holding time being the three process parameters. The regressed model equation eliminating the insignificant parameters through an analysis of variance (ANOVA) was used to optimize the process conditions. The optimum process parameters for the preparation of reduced iron powders have been identified to be the wood charcoal of 13.8 pct, a process temperature of 1391 K (1118 °C), and a holding time of 43 minutes. The optimum conditions resulted in reduced iron powders with a total iron content of 98.60 pct and a metallization ratio of 98.71 pct. X-ray fluorescence (XRF) was used to estimate the elemental contents of the reduced iron powder, which meets the specification of the HY100.23 first-class iron powder standard. Additionally X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) analysis were performed and the results are compiled.     

Preparation and Properties of Iron Powder Plated with Nickel and Cobalt

The magnetic properties (magnetic induction and coercive force) of iron powder coated with nickel and cobalt as a result of chemical deposition from hypophosphite electrolytes are studied. Thermogravimetry, differential thermal and x-ray phase analyses are used to study in detail the kinetics and mechanism of high-temperature oxidation in air (up to 1200°C) for the original and coated powders. The phase composition of oxide films on specimens annealed at all temperatures of the DTA-curve peaks is determined. The possibility of increasing the high-temperature oxidation resistance of iron powder coated with nickel or cobalt is demonstrated.     

汽车大梁钢粉状氧化铁皮剥落定量评价分析

大梁钢板热轧生产后直接用于汽车零件的冲压成型，其表面氧化铁皮的控制直接关系到冲压过程的稳定性及车间环境，因此开展汽车大梁钢粉状氧化铁皮剥落定量评价分析具有重要的理论与实践意义。针对大梁钢氧化铁粉剥落严重的问题，通过工业试验，开展了不同热轧终轧温度及卷取温度下氧化铁粉剥落量检测与成分分析，采用扫描电镜分析了氧化铁皮的层状结构与致密度，并定量研究了610L大梁钢热轧卷氧化铁皮中Fe₃O₄、FeO含量与氧化铁皮剥落的关系，得到氧化铁皮中Fe₃O₄质量分数为80%且FeO质量分数为3%左右时，610L钢的氧化铁皮最不容易脱落，形成不掉粉、高塑性的“黑皮钢”特性。针对后续冷加工过程中氧化铁皮剥落问题，通过三点弯曲试验进行了FeO含量与氧化铁粉剥落特性关系研究，发现FeO含量高的氧化铁粉在塑性弯曲的小变形阶段，其剥落多于FeO含量少的样品，但在大变形情况下，氧化铁粉剥落少于FeO含量较少的样品，其剥落质量差呈现出“先负后正”的特点。随着弯曲位移的增大，氧化铁皮剥落逐渐增多，且受压面氧化铁皮剥落多于受拉面。受拉面...     

氧化物共还原制取W-Cu和Mo-Cu复合材料的研究

近些年来,国内外研究了一些制备高分散度W/Cu和Mo/Cu复合粉末的方法,高分散度的粉末具有高的烧结致密度,用氧化物共还原粉末可在较低温度下进行烧结得到接近和达到100%的理论密度。这样的复合材料有细而均匀的组织和较好的性能。本文报道近来的研究状况,并就共还原法所用的前驱体原料种类、工艺条件、粉末特性和复合材料的性能进行评述。