用白钨矿冶炼合金钢的动力学分析

运用动力学理论对白钨矿粉的化还原过程和渣中ＷＯ３的还原过程进行了计算和分析。结果表明：白钨矿粉在钢液中的熔化还原是白钨矿粉还原过程的关键环节。在高温电弧作用下,白钨矿粉的熔化还原速率很快。为了加速白钨矿粉的熔化还原。５白钨矿粉应放在炉底并远离炉壁。渣中ＷＯ３的扩散是其还原过程的限制性环节。它与渣 中ＷＯ３的传质系数及反应界面有关,改善渣 的流动性及扩大反应界面能加快ＷＯ３的还原过程。     

Fe-1.0Cu-2.0Ni-0.55Mo扩散型合金钢粉的研制

本文针对莱粉公司生产的Fe-1.0Cu-2.0Ni-0.55Mo扩散型合金钢粉的生产工艺、粉末性能及其烧结件性能进行了研究。结果表明,采用本工艺生产的扩散型合金钢粉基本保持了基体粉末压缩性高、流动性好的特点,可获得高的压坯密度和烧结体密度;合金粉末损失少且分布均匀,制件尺寸精度高、机械性能稳定;扩散合金化效果好,制件具有较高的硬度和抗拉强度。同时,该生产工艺减少了合金粉末(细粉)的损失和飞扬,生产环境得以很大改善。     

电热全自动16管推舟炉生产不同粒度钼粉的生产实践

工业生产过程中为了生产的稳定,通常将焙解与一次还原工艺参数设定不变,利用二次还原工艺参数的调整生产出不同粒度的钼粉。本文使用一种电热全自动16管推舟炉生产钼粉,探讨生产实践过程中二次还原的工艺控制方法对钼粉粒度的影响;对比分析实际生产过程中不同物理特性钼酸铵原料对钼粉粒度的影响。最终得到钼粉费氏粒度3.0~4.0μm、4.0~5.0μm、5.0~6.0μm范围的钼粉。     

不同结晶态的钼酸铵SEM形貌探讨及应用

介绍了结晶态钼酸铵不同的ＳＥＭ形貌及其在动态焙解还原制取钼粉中的应用情况。试验表明：适用于动态焙解还原的钼酸铵结晶态ＳＥＭ形貌呈棱柱、树枝状，焙解时分散性、流动性好，钼粉一次成品率高。ＳＥＭ形貌呈团絮、雪球状晶形的钼酸铵不适用于动态焙解还原制取钼粉，其分散性、流动性较差，制取的钼粉假颗粒团较多，成品率低。     

一种精密异型件自动冲压成型用钼粉造粒工艺研究

钼粉经喷雾造粒可以增加粒度,提高松装密度,改善流动性。通过对撒料盘转速、料浆固液比、粘结剂含量的调整及球磨处理等可以改善造粒效果。     

基于天钢铁矿粉高温性能的烧结优化配矿

在对天钢生产中常用七种铁矿粉同化性、液相流动性测试分析的基础上,根据矿粉高温特性互补的配矿原则提出了五组优化配矿方案,并进行烧结杯实验。结果显示:与基准配矿(当前生产)方案相比,优化配矿方案的烧结综合指标有所增加,烧结矿的转鼓强度、冶金性能也得到改善,表现为还原性提高,低温还原粉化性能变好,开始软化温度升高,软化及滴落区间变窄。基于铁矿粉高温性能的优化配矿为现场生产变料及合理采购原料提供了有力的技术支持。     

几种低品质进口粉烧结性能的研究

在宣钢目前原料条件下,通过液相流动性和烧结杯试验研究了菲律宾粉、马来西亚粉、毛里塔尼亚粉、印度粉等四种低品质进口粉的烧结性能,为今后宣钢烧结生产中使用低品质进口粉维持或改善烧结矿质量,保证高炉稳定顺行,降低生产成本,提高企业竞争力提供技术储备.     

生产钽粉的钠还原工艺的改进

通常,钽粉是用液体钠还原氟钽酸钾工艺进行工业规模生产的。如果用作固体钽电容器,钽粉末要压成小片,再烧结成稳定的多孔体,随后进行阳极化处理使多孔体表面生成一电介质氧化物层。除纯度、流动性和生坯强度外,表面积是钽粉最重要的性能:表面积大,粉末粒度就小。     

基于细粒级铁矿粉基础性能的烧结研究

在烧结用混匀矿中配加5%~20%的A、B、C细粒级铁矿粉,检测各自的制粒效果,分析了各粒级生成烧结液相的比例和粘接强度等基础烧结性能,并据此进行了烧结杯试验。结果表明:细粒级矿粉中2mm以下粒级的基础性能可有效用于评价该矿粉烧结效果;A矿粉流动性合适,粘结强度高,能有效改善烧结矿质量,可与B粉或C粉搭配使用;B粉流动性很好,C粉2mm以下粒级同化温高、粘结强度差。建议在烧结生产中不要同时使用B粉和C粉。     

邯钢非主流矿的基础特性与互补配矿的试验研究

对邯钢烧结用非主流矿的物化性能及高温特性进行了系统研究,并针对南非精粉同化性及流动性差的问题开展了互补配矿的优化研究。结果表明,杨迪粉与南非精粉混合比例为3:1时,混合矿粉的同化性能和液相流动性明显改善,可以达到烧结生产提质增效的要求。     

利用转炉烟尘铁粒制造粉末冶金用铁粉

转炉在吹炼过程中形成的铁粒，经过表面除杂和表面粗糙化处理后，其化学成分和粉末工艺性能符合粉末冶金用铁粉的要求。研究发现，铁粉松装密度由原始的3.82g/cm^3可降低到2.72g/cm^3。当铁粉松装密度为2.72g/cm^3时，粉末流速为29.3s/50g。该粉末在压力为420MPa的条件下压制，压坯密度达6.68g/cm^3，压坯强度高达12.68MPa，比具有相近松装密度的还原铁粉在相同压制条件制的压坯强度提高40％。铁粉的应用试验结果表明，该铁粉的压制和烧结性能良好。改性后的转炉烟尘铁粉可作为粉末冶金用铁粉新的制造原料。     

白云鄂博铁精矿氢气流化还原试验

通过可视流化床研究不同温度和氢气流速下对还原白云鄂博铁精矿的影响。试验表明,同一温度下,氢气流速的增加有利于提高流化还原反应的还原效率,但这种作用在低温下更为明显。随温度的升高,流化还原效率提高,但高温下流化效率增长幅度小于低温。应用热重分析研究了不同温度下氢气还原白云鄂博铁精矿的还原动力学,结果表明:其反应的限制性环节为内扩散,活化能随还原时间呈现先下降后上升的现象,而表观活化能的降低更有利于反应的加速进行。在试验条件下,5~10 min时的还原反应速度较快。     

添加铁矿粉对焦炭质量影响的研究

高反应性焦炭能够降低高炉焦比,减少CO2的排放量,改善高炉内铁矿石还原反应的反应效率。研究了在配合煤中添加碱性铁矿粉和酸性铁矿粉炼焦,铁矿粉的配入量对焦炭热性能的影响规律。试验结果表明,随着铁矿粉配入量的提高,焦炭的反应性增大,随后增幅放缓,且添加碱性矿粉的焦炭反应性高于添加酸性矿粉的焦炭,反应后强度与机械强度均有明显劣化;焦炭的灰分增大、硫含量逐步下降;焦炭的各向异性指数不断下降。     

用铁精粉进行铁水脱钛预处理的工艺开发

铁水脱钛预处理的目的是为了预先降低铁水中的Ti含量,减轻炼钢过程中脱Ti的任务,使成品钢中Ti含量进一步降低,以此来满足如轴承钢、弹簧钢等低钛钢种的质量要求。研究了采用铁精粉作为脱钛剂进行铁水脱钛的技术开发和实际应用问题。首先利用500kg感应炉进行了实验室热模拟实验。结果表明,脱钛率平均为68.70%,最高脱钛率为83.60%。在此基础上,开发了用铁精粉进行机械搅拌脱钛新工艺,并成功应用到工业生产中,取得了脱钛率为86.64%的良好效果。还对脱钛过程中伴随的Si、Mn、C等元素的氧化行为进行分析研究,证明了铁精粉脱钛新工艺的可行性和先进性。     

表征铁矿粉烧结液相流动性能的新方法

为了弥补传统评价铁矿粉烧结液相流动性能指标不考虑液相流动速度、温度及升温速率或不考虑温度对液相流动速度影响的不足和采用多个指标分开来表征液相流动速度与温度所带来的使用上的不便.利用可视卧式高温炉观测铁矿粉试样的熔化流动过程,结合试验中试样收缩与流动规律定义了烧结液相流动始末点,并提取重要参数指标:流动温度、流动时间、面积增长率和升温速率;给出了定量表征温度对烧结液相流动速度影响的函数关系式v(T);在此基础上建立了以实际烧结生产温度为基准,包含流动过程各种关键信息及其内涵的流动性特征数(LD).对比2种方法得到的结果,发现采用流动性特征数可以进一步区分出不同铁矿粉的流动性差异,提高了表征精度,从而为评价铁矿粉流动性能提供了可靠的参考依据.     

Influence of Lubricants on Dimensional Changes and Mechanical Properties of Sintered Ferrous Compacts

Abstract

The influence of admixed zinc stéarate on the shrinkage of uniaxially pressed iron powder compacts has been studied. For pressing conditions which caused inhibition of compaction the removal of the stéarate during sintering produced an increase in shrinkage parallel to the pressing axis and in direct proportion to lubricant content. Additions of stearic acid (varying particle size), zinc stearate, lithium stearate, stearamide, and Cosmic 64 wax were used to investigate the influence of lubricant on mechanical properties of green and sintered iron powder compacts. Green strength was reduced relative to unlubricated material only by lubricants whose physical and chemical properties enabled them to produce and maintain extensive interparticle films during pressing. Vapour from the rapid initial decomposition of lubricants which reduced green strength could have a deleterious physical influence on the tensile strength of dewaxed or sintered Fe compacts. Decomposing lubricants also produced undesirable chemical effects. These arose from reactions between lubricant decomposition products and the matrix or by these products interfering with reactions between matrix and sintering atmosphere.     

超纯铁精矿粉直接还原制备超细铁粉

将超纯铁精矿粉气流粉碎到微米级,用氢气直接还原制备超细铁粉,利用正交实验法研究还原温度、时间、氢气流量等工艺参数对还原率的影响。结果表明:对超纯铁精矿粉还原率的影响程度从大到小依次为温度、时间、氢气流量,综合考虑生产成本,确定最佳的还原工艺参数为温度780℃、时间60 min、氢气流量0.3 L/min。在此工艺条件下得到的超细铁粉,全铁含量为98.58%,氢损0.45%,酸不溶物含量为0.19%,其化学成分符合粉末冶金用铁粉标准,一次粒度小于5μm。     

About the foamability of iron - carbon alloys

The foamability of iron-carbon alloys using the powder metallurgical process route was investigated. Pure iron and carbon powder with an addition of foaming agent were mixed and compacted. The foaming process started during heating the sample as soon as a temperature above the solidus temperature of the iron-carbon alloy was reached. Result of the process is an iron foam with a porosity of up to 60%. It was investigated, how the foaming behaviour is influenced by the parameters of alloy composition and compaction process. Different foaming agents (alkaline earth metal carbonates and metal nitrides) as well as different carbon additions and compacting processes were tested. It can be seen that sort and amount of foaming agent have an unexpected low influence on the expansion process whereas an increasing carbon content supports the expansion significantly. The use of different compacting processes has only little influence on the expansion itself, but highly effects both the pore distribution and homogeneity. The poor effect of the foaming agent cannot be satisfactorily explained. Investigations of a possibly premature gas emission or of a not gas-tight inclusion of the foaming agent do not show clear results. The support of the expansion by carbon additions can be attributed to the formation of CO-gas by the Vacher-Hamilton law during simultaneous formation of the liquid Fe-FeC-eutectic phase. The more inhomogeneous pore structure of iron foams caused by the use of hot-or hot isostatically pressed semi-finished products can be traced back to a higher internal gas pressure in the sample which results in a burst of the microstructure of the semi-finished product.     

稀土铁基自熔基合金抗硫化氢腐蚀性能的实验研究

近年来关于稀土在热喷涂（焊）材料中的应用研究正日益受到人们的重视。铁基自熔合金末作为一种广泛使用的热喷涂（焊）材料具有价格低廉，喷涂（焊）层的耐磨性较好等优点，但其耐蚀性较差。为此，本研究引入稀土对其改性。通过熔炼－雾化工艺制备了稀土铁基自熔合金粉末，并考察了稀土对铁基自熔合金喷焊层在硫化氢介质中气蚀和在含硫化氢的中性氯化钠溶液中浸蚀的影响。结果表明，铁基自熔合金（含稀土和不含稀土）喷焊层试样表现出较强的抗硫化氢能力。铁基合金喷焊层试样在含硫化氢的4Wt%NaCl溶液中的腐蚀速率随稀土的添加量增加量增加而逐渐降低，且稀土添加量有最佳值0.2Wt%。     

New insights into influencing variables of water atomisation of iron

Abstract

Trace amounts of surfactants have an acute influence on measured surface tension of melts and may influence viscosity. A water atomisation experiment was performed to investigate if variations of these elements could affect quality. Effects of water pressure, melt superheat, and sulphur content, iron scrap oxygen content, and aluminium content were studied. Responses studied were particle size distribution, apparent density, flow, powder chemistry, morphology, green density, and dimensional change. A large sulphur addition reduced the particle size, as a result of a reduction of surface tension, but the largest effect came from changing water pressure. Higher water pressures also resulted in powders with lower apparent density, lower flowrate, and reduced swelling during sintering. An empirical water atomisation model is proposed. Aluminium additions reduced the powder size standard deviation and increased the carbon content of the powder. A reduced powder size standard deviation was seen also for melts with raised superheating.