Production of grinding balls resistant to abrasive wear

Low-alloy 70KhG chromium–manganese steel is investigated. The thermokinetic diagram of supercooled-austenite conversion at cooling rates 0.03–8.4°C/s is plotted. Appropriate heat treatment is developed for grinding balls of diameter 20–60 mm. The microstructure of the steel formed in heat treatment is analyzed. The temperature at which martensitic transformation begins is determined. Experimental batches of 60-mm grinding balls with bulk hardness HRC 59.5 produced by the proposed technology are tested. Their performance is excellent.     

Improving the quality of steel grinding balls

The development of steel-ball production within the Commonwealth of Independent States over the last 50 years is analyzed. Three periods are identified and characterized. The factors responsible for poor ball quality are discussed. The requirements for the production of high-quality balls with hardness up to HRC 65 are outlined, in terms of the chemical composition of the steel, the equipment required, and the production technology. Significant increase in ball quality requires the creation of specialized rolling systems. The fundamental principles to be adopted in creating such systems are reviewed.     

钢球与胶囊球磨矿对比优化试验研究

对钢球与胶囊球的磨矿效果进行了对比试验研究。其结果表明：单个球组以Ф25mm球径为最佳,胶囊球尺寸偏大;球组m（Ф40）：m（Ф30）：m（Ф25）=50：35：15及充填率达40％时,磨矿细度-0．05mm可达92．29％,再提高充填率已无必要。     

Improving the production of steel grinding balls at AO EVRAZ ZSMK

The production of steel grinding balls is improved by reducing the billet temperature before rolling, reducing the number of balls between the flanges of the quenching drum, and limiting the discharge temperature of the balls from the bunker after self-tempering. The macrostructure of the billet must be improved, and proportional increase in length and speed of the quenching drum is required.     

矿用磨球种类及性能研究现状

为了系统地了解各类磨球性能及使用情况,对磨矿行业中磨球种类进行了介绍,并对不同种类磨球的研发和使用情况做了分析.详细介绍了铬系铸铁磨球、球墨铸铁磨球以及锻(轧)磨球的化学成分要求与成形工艺;对不同种类磨球的材质、力学性能、显微组织等方面作了综合的对比与分析;简述了不同材质规格磨球的性能差异;介绍了改善磨球性能的途径和生...     

矿用耐磨钢球冲击疲劳强度偏低原因分析

通过宏观形貌观察、扫描电镜分析、能谱分析和显微组织分析等手段对落球疲劳试验时耐磨钢球冲击疲劳强度偏低的原因进行了研究。结果表明:断口平直较规则,无明显塑性变形;裂纹源处呈现冰糖块形貌,且部分晶粒尺寸超过100μm,为典型的沿晶界脆性断裂;断口附近存在少量的屈氏体组织,且沿着原奥氏体晶界分布;钢球近表面到断口处的晶粒尺寸明显不均匀,而且断口附近的晶粒较粗大。结合钢球生产工艺分析可知,钢球冲击疲劳强度偏低的主要原因是淬火组织粗大,另一重要原因是回火工序没有有效降低淬火内应力。     

高压辊磨对赤铁矿粉球团矿焙烧性能的影响

采用管式焙烧炉对一种赤铁矿粉球团的预热焙烧性能进行了研究,结果表明该赤铁矿球团预热焙烧性能较差,预热温度要达到1070℃,焙烧温度要达到1250℃时其预热焙烧球团的抗压强度才能达到生产要求.对该矿粉进行高压辊磨预加工后,其预热和焙烧性能得到改善,其预热和焙烧温度可分别降低70℃和50℃.进一步的研究结果表明,高压辊磨预加工赤铁矿粉后,小于5μm 微细颗粒含量增加,使焙烧球团的孔隙率降低,有利于Fe2 O3晶粒形成大片的晶桥连接,使得焙烧球团抗压强度得到提高.     

Investigation on grinding wear behaviour of austempered ductile iron as media material during comminution of iron ore in ball mills

An attempt has been made to assess the grinding wear behaviour of austempered ductile iron (ADI) as media material in comminution of Kudremukh haematite iron ore in a ball mill. Spheroidal graphite (S.G) iron balls were austenitised at 900°C for one hour and austempered at 280°C and 380°C for different time durations. These materials were characterized by measuring hardness, carrying out X-ray diffraction analysis, studying microstructures using scanning electron microscope (SEM). Grinding wear behaviour of ADI was assessed during wet grinding at different pH of the mineral slurry. The wear resistance of ADI was compared with that of forged En 31 steel balls under similar grinding conditions. It was found that ADI balls austempered at 280°C for 30 minutes which contains lower bainite registered superior wear resistance. It was also noted that the wear resistance of ADI was more at higher pH range of the slurry.     

赤铁粉矿在H2气氛中的闪速还原行为

通过高温下的动力学实验对铁粉矿在H_2气氛中的闪速还原行为进行了研究.采用XRD、SEM和金相显微镜对反应后铁粉矿的物相组成和单个粉矿颗粒表面及内部微观形貌的演变规律进行了分析,采用化学分析法获得了反应后赤铁粉矿的还原度.结果表明:铁粉矿高温下发生的闪速还原仍然遵循Fe_2O_3→Fe_3O_4→FeO→Fe的逐级还原规律.粉矿颗粒的剖面由未反应核和产物层构成,符合未反应核模型的描述.采用模型函数配合法得出铁粉矿与H_2在高温下发生闪速还原反应的限制性环节是界面化学反应,进一步基于动力学模型计算得到,闪速还原的表观活化能为311 kJ/mol.     

钢球用圆钢的开发与质量改进

介绍50mm的钢球用圆钢B2的开发过程,并对开发过程中出现的质量问题进行分析改进。永钢开发B2钢球用钢过程中出现了低倍中心裂纹的质量问题。采取延长加热时间、提高收集温度等措施后质量均能满足客户要求。     

低铬白口铸铁磨球的新工艺设计

低铬铸铁磨球显微组织应该由尽可能多的硬组织体,在实现断网的基础上形态发生显著变化的碳化物和马氏体组成,同时应设法减少和控制零件中的内应力、显微裂纹及不连续性组织是新工艺的设计理念和目标.从控制冷速、成分设计、铸造冶金处理、热处理等方面较为一致地体现了新工艺设计的原则.     

Evaluation of carbothermal reduction for processing of banded hematite quartzite iron ore

ABSTRACT

This study evaluates iron recovery from low grade banded hematite quartzite iron ore. The ore was found susceptible to microwaves and hence carbothermal reduction was pursued. The susceptibility of iron phases to microwave exposure and their selective absorption assists in the liberation of iron values. It was observed that ferrite balls were formed when a small fraction of ore-charcoal mixture was microwave irradiated. The adequate presence of bonded silica content leads to an easy formation of the fayalite phase which leads to fall in the iron grade. Microwave carbothermal reduction at the varying charcoal dosage (6–11%) yielded Fe_G 45–48% at Fe_R 40–70%. However, at higher charcoal dosage (11%), ferrite ball formation was observed. Taguchi L₉ statistical design revealed the formation of ferrite ball at the higher charcoal dosage (9–12%) and higher power (720–900 W) which accounts for 8–10% of total iron values contained.     

自动化控制系统在矿山碎矿磨矿中的应用

介绍了山东金仓矿业股份有限公司自动化控制系统的测控原理、硬件配置,以及通过监控管理实现的功能;该系统有助于提高碎矿磨矿能力,降低生产成本,减轻工人劳动强度,增强企业竞争力。     

鲕状赤铁矿深度还原物相及结构的演化规律

为了研究深度还原过程中鲕状赤铁矿石物相及结构的演化规律，采用X射线衍射（XRD）和扫描电子显微镜（SEM）考察了不同还原阶段还原样品的物相转化和微观结构变化，并建立了相应的深度还原机理和微观结构演化模型。结果表明，鲕状赤铁矿石深度还原过程中铁矿物按照Fe2O3→Fe3O4→FeO（Fe2SiO4，FeAl2O4）→Fe的顺序还原为金属铁，杂质组分则主要依据Fe- Al- Si- O→Fe- Ca- Al- Si- O→Ca- Al- Si- O的历程形成渣相；矿石鲕状结构按照由鲕粒边缘至鲕粒内部的空间顺序逐渐发生破坏，矿石微观结构演变过程阶段；金属相及渣相的形成与聚集生长是矿石微观结构破坏的直接动力。     

淬火温度对含碳化物等温淬火球墨铸铁耐腐蚀磨损性能的影响

通过等温淬火获得含碳化物等温淬火球墨铸铁(carbidic austempered ductile iron,简称CADI),并分别在中性、酸性和碱性腐蚀介质中进行腐蚀磨损实验,研究淬火温度对CADI在不同腐蚀介质中耐腐蚀磨损特性的影响,并与低铬铸铁进行对比。结果表明:在酸性和碱性介质中,CADI的质量磨损随等温淬火温度升高先增加,然后再减少;在中性介质中,CADI的质量磨损随等温淬火温度升高而逐渐增加;CADI在酸性介质中的耐腐蚀磨损性能相对较差;CADI在不同p H值溶液中的耐磨损性能均优于低铬铸铁,是一种优良的耐腐蚀磨损材料。     

湿式半自磨工艺在黄金选矿生产中的应用实践

广西凤山天承黄金矿业有限责任公司选矿厂原设计采用湿式半自磨、球磨闭路式磨矿流程.由于矿石中黏土矿物含量较高,试生产中出现矿物过磨及两段磨矿负荷不平衡等问题.根据矿石性质及3个月的试生产实践,将原半自磨、球磨闭路磨矿流程改为半自磨机与分级机闭路流程,不但保证了磨矿产品的质量,提高了回收率,简化了工艺流程,提高了磨矿效率,而且降低了生产成本,取得了良好的经济效益.     

铁矿石烧结箅条糊堵现象成因机制

箅条糊堵现象是铁矿石烧结生产面临的重要共性问题,给烧结经济技术指标及设备都带来不利影响.为弄清并解决这一问题,首先对箅条糊堵物进行了分类和物相特征分析,随后从原燃料条件、工艺条件和箅条自身性能3个方面综合分析了烧结台车箅条糊堵的形成机制及影响因素,最后基于箅条糊堵物的物相特征及形成机制总结了预防及解决箅条糊堵问题的技术...     

Influence of corrosive environments on near-threshold fatigue crack growth in 403 stainless steel

The near-threshold fatigue crack growth behavior of 403 stainless steel has been investigated in low O₂ steam (<1 ppm), high O₂ steam (40 ppm), and boiling water with various concentrations of NaCl and Na₂SO₄ at a test frequency of 160 Hz. High O₂ steam tends to increase the crack propagation rates in the threshold region, relative to low O₂ steam. Values of threshold stress intensity range, ΔK_th, slightly increase with an increase in the concentration of NaCl in the solution. During threshold crack growth, the percentage of intergranularity decreases with a decrease inAK. Varying pH from 5.0 to 10.0 in a 0.1 gm NaCl plus 1.0 gm Na₂SO₄ per 100 ml H₂O solution does not affect the rates of near-threshold crack propagation. However, increasing the hydrazine level from 30 to 10⁷ ppb in the same salt solution enhances the resistance to crack growth while reducing the percentage of intergranular fracture to nearly zero.     

富氧在磨矿浸出中的应用

在氰化边磨边浸工艺中,采用富氧磨矿,改善了磨矿过程中金氰化浸出效果,提高了金氰化浸出率,取得了显著的经济效益。