Single Treatment of Steel in Fluidized Bed

Results obtained by the author and his coworkers at the Vysokogorskii Mechanical Works in the city of Nizhny Tagil are presented. The effect of single treatment in fluidized bed on the mechanical properties of high-carbon and low-alloy steels is studied and the data are compared with the properties of these steels after toughening. A mechanized flow line for single treatment of parts from steel 40Kh in fluidized bed is described, and designs of electric furnaces/baths with fluidized bed are presented.     

Theory and Practice of Fluidized Bed Heat Treatment of Parts Fabricated from Metals and Alloys

Forty years of developments in the field of heat treatment of parts fabricated from steels, nonferrous metals, and powder (sintered) materials with the use of a universal heating medium, i.e., a fluidized bed of a fine-grained material, and special equipment for realizing the process, are analyzed. The data presented primarily concern the Ural Region, but the geography of application of the method is much wider (including foreign countries). Unfortunately, the scale of commercial realization of the method is rather modest. The peak development of fluidized bed heat treatment coincided with the period of “perestroika” in Russia, which hindered the progress of the country’s engineering and technology for many years. However, some recent developments in the industry allow us to return to this topic in the nearest future.__________Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 4 – 19, March, 2005.     

Use of a fluidized bed for the thermal and chemicothermal treatment of metals

Conclusions An investigation of the heat processes in a fluidized bed shows that this unit has a high heating rate and cooling rate, and allows direct control in the process of heat treatment; chemicothermal processing is speeded up 3–5 times.Examples of experimental-industrial and industrial use show the advantages of using the fluidized bed for rapid nonoxidative heating for thermal processing and pressure processing, and also for replacing expensive salt and metal baths. The use of the fluidized bed is promising for heating temperature-sensitive aluminum and other nonferrous alloys, and for heat processing refractory metals, and alloys [45], etc.It is desirable to use the fluidized bed as the cooling medium to achieve optimum cooling with reduced stresses in components of especially complex configuration.It would be promising to use the fluidized bed for carrying out chemicothermal processing and for creating new processes (including surface saturation with rare metals), especially with the application of electrical, and possibly strong magnetic, fields.Moscow Institute of Chemical Engineering. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 2–11, June, 1971.     

An Investigation on Low-Temperature Thermochemical Treatments of Austenitic Stainless Steel in Fluidized Bed Furnace

In this study, the feasibility of using an industrial fluidized bed furnace to perform low-temperature thermochemical treatments of austenitic stainless steels has been studied, with the aim to produce expanded austenite layers with combined wear and corrosion resistance, similar to those achievable by plasma and gaseous processes. Several low-temperature thermochemical treatments were studied, including nitriding, carburizing, combined nitriding-carburizing (hybrid treatment), and sequential carburizing and nitriding. The results demonstrate that it is feasible to produce expanded austenite layers on the investigated austenitic stainless steel by the fluidized bed heat treatment technique, thus widening the application window for the novel low-temperature processes. The results also demonstrate that the fluidized bed furnace is the most effective for performing the hybrid treatment, which involves the simultaneous incorporation of nitrogen and carbon together into the surface region of the component in nitrogen- and carbon-containing atmospheres. Such hybrid treatment produces a thicker and harder layer than the other three processes investigated.     

论新型干法氟化铝生产工艺与主要设备

从给料酸的配制及设备,氟化氢的生成及反应炉设备,氟化氢的净化及设备,氟化铝的生成及流化床设备,紧急吸收与石膏系统等方面探讨了新型干法氟化铝生产工艺与主要设备。     

9Cr1MoV类钢膜式壁现场焊接及热处理工艺

9Cr1MoV类材料已广泛应用于循环流化床锅炉、超临界机组、石化裂解炉等重工业行业中,其力学性能和热影响性不同于以往的耐热钢种。在国产循环流化床锅炉屏式再热器膜式壁管屏中使用了9Cr1MoV类材料。9Cr1MoV类钢膜式壁的现场焊接及热处理的可操作性差,通过工艺实验和工程实践,提供了适用于类似9Cr1MoV类钢膜式壁的现场焊接及热处理工艺。     

Measurement of the mass transfer coefficient at workpiece surfaces in heat treatment furnaces

The mass (e.g. carbon) transfer coefficient at a workpiece surface is an important kinetic factor to control the heat treatment process of the workpiece and to evaluate heat treatment equipment. The coefficient can be calculated from the carbon concentration at the surface of a sample carburized in a carburizing furnace for a given time. Two common measurement methods which use a thin plate and employ a component as samples respectively are evaluated and compared for sensitivity and uncertainty. The comparison shows that the use of a component produces higher measurement precision and also has the advantage in measuring the carbon transfer coefficients at different treated positions. This method is then extended and discussed methodologically. Also two equations are proposed to calculate the carbon transfer coefficient and its uncertainty, respectively. This method is also applied to measure the carbon transfer coefficient in a fluidized bed heat treatment furnace.     

流态床渗氮工艺的研究

本文对３Ｃｒ２Ｗ８Ｖ，Ｈ１３及３８ＣｅＭｏＡｌ钢在刚玉流态床中进行了渗氮工艺的研究。结果表明，氨气在２５％－６５％范围内变化时，对渗氮结果无明显的影响，在流态床中渗氮可减少工件表面化合物层的形成和加快渗氮的速度。采用脉冲渗氮方法可获得与非脉渗氮同样的效果，同时可降低耗气量。     

树脂旧砂的热法再生

介绍了树脂旧砂热法再生的原理及沸腾式树脂旧砂热法再生装置,研究发现,热再生砂和同种新砂相比,角形系数、发气性和受热膨胀性降低,粒形更趋圆整,砂子的集中度、型砂的抗拉强度提高,铸造工艺性能优于同种新砂。     

Development of a Cast Al-Mg2Si-Si In Situ Composite: Microstructure, Heat Treatment, and Mechanical Properties

An Al-11Mg₂Si-Si in situ composite was prepared by a modified investment casting technique that employs sub-pressure for castability improvement and immersion of ceramic shell molds in fluidized beds of silica sand and iron particles for heat extraction improvement. The microstructure of the as-cast composite is explained according to the pseudoeutectic Al-Mg₂Si phase diagram. The positive effect of a decreased number of mold investment layers and cooling assisted by immersion of the mold in a metallic bed on the tensile strength and hardness of the heat treated composite is noted. A minor presence of Fe in the master alloys constitutes an essential factor for the brittleness of the composite. Solution treatment notably improves the tensile strength of the composite; however, prolonged treatment deteriorates its ductility. The effect of time and temperature of the aging treatment on the hardness of the composite is investigated. The positive influence of cooling assisted by a metallic fluidized bed on the effectiveness of the aging treatment is noticed.     

降低热法再生设备天然气能耗的方法

通过研究热法再生设备的使用特性,分析影响热法再生设备能耗的关键因素,根据关键因素做出相应的降低天然气能耗的方案措施。提高助燃空气温度及燃烧介质的温度;降低除尘负压系统的风量;沸腾燃烧充分,燃烧反应控制在流化床内部;增加炉体保温性能及增加再生砂的保温时间;选择比热容较低的介质材料以及增加可燃烧的有机物助燃等措施均可有效的降低天然气能耗。     

Microwave plasma fluidized bed arc-PVD coating of particulate materials

A novel process for deposition of thin AlN and Al coatings on particulate carbon materials by means of an atmospheric pressure microwave plasma fluidized bed treatment is reported. The substrate powder and a fine aluminum powder are mixed and fluidized together in microwave plasma. Argon plasma yields a homogenous coating composed of pure aluminum on the substrate powder, whereas upon treatment in a reactive nitrogen plasma the deposited aluminum particles are nitrided and the resulting coating is an AlN ceramic. Coatings were characterized by means of SEM/FEM, EDX, XRD and TGA. Crystal structure of the deposited AlN was refined by Rietveld method.     

肯尼亚天然金红石矿沸腾氯化热力学和动力学

以焦炭作还原剂,利用天然金红石和氯气制备四氯化钛。在1173到1273 K的温度范围内,对肯尼亚天然金红石颗粒在间歇式流化床中的氯化反应热力学和动力学进行研究。体系的热力学分析显示：生成CO的反应在高温下占主导地位;若生成CO反应的比率η越大,且随着体系反应受温度的影响加剧,高温下反应的吉布斯自由能越负;同时,η增大,产物中TiCl4分压对反应的吉布斯自由能的影响趋于减小。应用气-固多相反应理论和流化床两相模型建立反应的数学模型,计算了气泡相和乳相中模型的各种参数,床层高度范围内氯气的平均浓度为0.3 mol/m^3。结果表明：天然金红石氯化反应主要在乳相中进行,反应速率主要由界面反应控制。     

Progress in abrasive fluidized bed machining

The use of abrasive fluidized bed equipment in a broad range of manufacturing processes is reviewed. In particular, applications in deburring and finishing of complex-shaped metal components, in super-finishing of dies for injection molding, in cleaning and polishing of electronic devices, and in surface preparation of tungsten carbide milling tools are reviewed. Attention is focused on the effects of the most important process parameters, such as machining time, abrasive type and mesh size, and flow or jet speed. The extent of material removal and the change in surface roughness as a function of the process parameters are addressed. Selected numerical and analytical models that are useful for automation and control purposes are discussed. Finally, the industrial sustainability of the processes and equipment investigated is highlighted.     

Effect of multi-temperature aging on the characterization of aluminum based castings heat treated using fluidized bed technique

The current study investigates the influences of the fluidized bed heat treatment on the quality indices and microstructural characterization of A356.2 and B319.2 castings. Traditional heat treatment technology, employing circulating air convection furnaces (CF), was used to establish a relevant comparison with fluidized sand bed (FB) for the heat treatment of the alloys investigated, employing T6 continuous aging cycles or multi-temperature aging cycles. The results of alloys subjected to multi-temperature aging cycles reveal that the strength results obtained after the T6 continuous aging treatment of A356 alloys are not improved by means of multi-temperature aging cycles, indicating therefore that the optimum properties are obtained using a T6 aging treatment. The optimum strength properties of B319.2 alloys, however, is obtained by applying multi-temperature aging cycles such as, for example, 230 °C/2 h followed by 180 °C/8 h, rather than T6 aging treatment. In the case of multi-temperature aging cycles, the modification factor has the most significant role in improving the quality index values of 356 and 319 alloys. The FB heattreated alloys have the highest strength values for all heat treatment cycles compared to CF heat-treated alloys; however, the FB has no significant effect on the quality values of 319 alloys compared to the CF.     

蒽醌法生产过氧化氢用加氢催化剂的研究进展

从载体的改性,包括载体的预处理、制备过程中加入特定元素;以及催化剂的制备,包括活性金属负载方法、浸渍过程中添加助剂等方面,综述了蒽醌法生产过氧化氢所采用的固定床和流化床两种工艺使用的加氢催化剂的研究进展。分析认为,对于普遍使用的钯载体催化剂,助剂对载体的改性和催化剂的制备优化具有显著的效果。固定床工艺近期仍将是国内双氧水生产的主要方式,加强助剂添加和活性金属替代钯的研究具有重要的意义。引进流化床工艺取代固定床工艺,增加单套装置产能是未来国内双氧水生产发展趋势,需加强催化剂的研究开发。     

低温流态床炉的功能与用途

本文概述了低温流态床炉的多功能性,并论述了低温流态床炉在钢件、铝镁合金制件与精密弹性元件热处理方面的显著效益。     

Electric furnaces with a fluidized bed for implementing environmentally safe heat treatment processes in machine building

Current designs of electric tank furnaces with a fluidized bed that provide environmentally safe heat treatment of steels as tested under the conditions of machine-building plants are considered.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 19 – 23, September, 1996.     

Tempering of carburized steel in a fluidized bed

Conclusions The decomposition of retained austenite in carburized steel 18Kh2N4VA during tempering at 650°C in a fluidized bed is the same as that with tempering in a lead bath and occurs twice as fast as with tempering in the electric furnace. This can be explained by the greater precipitation of carbides on lattice defects due to rapid heating in the fluidized bed, and the slowed redisribution of nickel in the solid solution.Ural Polytechnical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 58–61, January, 1973.