Modelling and simulation of the electric slag remelting guide vane casting (ESRC) process and its application

Modelling and experiment work is carried out for a large stainless steel casting with variable cross-section and a curved surface which is produced by the electric slag remelting casting process. The casting is part of a hydraulic runner generator at a power station of a big river.Mathematical models of the heat transfer and melted rate from an expendable metallic electrode were established. The melted rate is related to some important parameters, such as electric current and voltage, temperature and the flow rate of the cooling water in a crystallizer. Electrode melting, the moving pattern of the melted pool and the slag pool and the melt solidification in the metal pool were simulated.In order to make the enmeshment of the variable curved surface of the casting, a co-operation method of extended constructive solid geometry (CSG) from 9 to 21 uniform geometry with B-Spline surface functions is developed. By this method the guide vane casting is enmeshed. The boundary condition between the steel casting and the crystallizer cooled by water was measured.Based on the above new content the solidification simulation software ESRC3D is developed. Using it to simulate the whole process of ESRC with different parameters, instead of exploring the technological parameters of casting production by the trail-and-error method, the optimized parameters from the simulation for production of the large stainless steel castings with variable cross-section and a curved surface, such as the guide vane castings, have been used to produce them. Economic benefit and good quality of castings are obtained. Guide vane castings are widely applied to the hydraulic runner generator at numerous river power stations.     

ProCAST软件在熔模铸造工艺优化中的应用

为解决企业生产中某精铸件存在的缺陷问题,利用数值模拟软件ProCAST对其充型过程和凝固过程进行模拟,并预测缩孔和缩松的存在情况.根据数值模拟的结果对该铸件工艺方案进行相应的改进,显著降低了缩孔和缩松缺陷,并提高了产品的合格率.应用表明:铸造模拟软件能够准确地预测充型凝固过程中可能产生的缺陷,从而辅助工艺人员进行工艺优化.     

Synthesis,characterization and properties of calcium ferroaluminate belite cements produced with electric arc furnace steel slag as raw material

This study investigated the use of 10 (M1), 17 (M2) and 27 wt.% (M3) electric arc furnace steel slag (EAFS) as a raw material in the production of calcium ferroaluminate belite cement clinker, after firing at 1320 °C. The thermal behavior of the raw meals was studied by TG/DSC and XRD whereas for the analysis of the clinkers, XRD/QXRD, SEM/EDS and EPMA were employed. The resulting clinker was co-grinded with 5 and 20 wt.% Flue Gas Desulfurization (FGD) gypsum and the properties were determined by a series of tests in accordance to EN standards. The evolution of hydration was investigated by SEM and the development of compressive strength. The results revealed that the formed phases in the clinkers were C₂S, C₄AF and C₄A₃Ŝ. The main hydration products were ettringite, AFm and hydrogarnet. The leached Cr^VI was below 1 ppm in M3. Compressive strength in cements with 5 wt.% FGD gypsum was (in MPa): 18.3 for M1, 14.3 for M2 and 7.8 for M3 at 28 days, whereas for 20 wt.% FGD gypsum, the values were almost doubled.     

ZG20SiMn铸钢摇臂壳体铸造过程数值仿真及工艺优化

摇臂壳体是采煤机的重要组成部件,具有多级壁厚、变截面等异形特征。为提高采煤机摇臂壳体铸造质量,解决因铸造工艺不成熟导致的缩松、缩孔等缺陷问题。以MG325型采煤机摇臂壳体为研究对象,设计顶注式和底注式两种铸造工艺方案,采用ProCAST软件探究不同浇注工艺方案下摇臂壳体铸件充型及凝固过程,分析铸件温度场、凝固场及缩松、缩孔铸造缺陷位置。基于Niyama判据和应力场分布对底注式铸造工艺方案进行优化。结果表明:优化后摇臂壳体铸件在凝固冷却过程中保持温度梯度递增,促进铸件实现顺序凝固,铸件缺陷率明显降低且充型效果更佳,缩孔体积仅占摇臂壳体体积的0.004 9%,电机孔薄壁端面应力优化量为38.47%,输出端孔处应力优化量达到91.08%。本文研究成果为采煤机摇臂壳体的铸造工艺提供了理论基础和数据支撑。     

Failure analysis of a martensitic stainless steel (CA-15M) roll manufactured by centrifugal casting. Part I: Material and fractographic characterization

The failure analysis of a martensitic stainless steel (CA-15M) roll manufactured by centrifugal casting and used in cast glass rolling was carried out by means of traditional characterization techniques (optical metallography, SEM, EDX microanalysis, tensile testing and XRD). The roll was in the as-cast condition and its microstructure featured large proportion of δ ferrite (between 20% and 27%) in a martensitic (α′) matrix, with the δ/α′ interfaces presenting an intergranular network of M₂₃C₆ carbides. The crack propagation began in the internal surface of the roll, with δ/α′ intergranular and transgranular cleavage in the “equiaxed region” of the casting, progressing to δ/α′ intergranular ductile fracture in the “columnar” and “chilled regions”. Tensile thermal stresses in the internal surface of the roll associated with microstructural embrittlement (network of interfacial carbide and microporosities) are thought to be the main causes for the premature failure of the roll. Finally, materials selection was performed to replace the CA-15M stainless steel with another class of stainless steel for centrifugal casting.     

Preparation and characterization of zeolite from waste Linz-Donawitz (LD) process slag of steel industry for removal of Fe3+ from drinking water

Cubical-shaped zeolite A was synthesized from the Linz-Donawitz (LD) process slag of the Steel Industry, utilizing conventional fusion-assisted hydrothermal treatment. Morphological and Physico-chemical characterizations were performed by various characterization techniques. A weight ratio of 1:1.2 (LD-slag: NaOH) was maintained during fusion, which provides a better binding effect with better mechanical stability to the zeolite framework. Fe³⁺ adsorption studies were performed at 273, 298, 303, and 308 K, respectively, within the range of 10–40 mg L⁻¹ Fe³⁺ ion concentration for kinetic and isotherm studies. A maximum adsorption capacity of 27.55 mg g⁻¹ was obtained at a 1.4 g L⁻¹ adsorbent dosage, with 99.99% Fe³⁺ ion removal. Moreover, the Fe³⁺ adsorption study obeyed the pseudo-second-order kinetic model, whereas multistage diffusion controlled the adsorption process. Langmuir isotherm model best fitted the equilibrium data suggesting the highly negative charge over the adsorbent surface played a vital role in the electrostatic attraction of Fe³⁺ ions. Isomorphic replacement of silicon by aluminum ion imparted a highly negative charge over the zeolite surface in the primary structure unit. For real-life sample drinking water, the Fe³⁺ ion removal efficiency increases to 97.7%.     

Modelling and simulation of the hardness profile and its effect on the stress-strain behaviour of punched electrical steel sheets

The shear cutting of electrical steel sheets has a significant influence on the magnetic and mechanical material properties. Due to plastic deformation and strain hardening in the area of the punched edge, the electrical steel sheets exhibit a characteristic hardness profile. This study deals with the modelling of the resulting hardness profile by means of finite-element simulations. Elastic-plastic material properties are obtained from spherical nanoindentation testing as a function of the local hardness. In particular, representative stress-strain values are determined by applying Tabor's concept of indentation stress-strain curves. The choice of the appropriate stress- and strain-constraint factors is discussed with respect to the nanoindentation test setup used. Following this, the representative stress-strain values are analytically described to determine true stress-strain curves for the local assignment of different material models depending on the hardness. The implementation of the modelling approach in a finite-element simulation is presented for a punched electrical steel sheet specimen under monotonic loading. The simulation results are basically in good agreement with experimental data and confirm the expected influence on the mechanical material behaviour due to the shear cutting process.     

Sustainability of process improvements: an application of the experiential learning model (ELM)

Despite the pervasiveness of process improvement (Lean or Six Sigma) programmes, there is a rising concern regarding the sustainability of these programmes. Several studies point out that initial operational efficiency gains as a result of these programmes simply disappear over time. Using process improvement implementation experiences in an aircraft manufacturing and distribution operation, we studied long-term sustainability of process improvement events. We found that process owners of successful improvement events applied experiential learning model (ELM). The ELM is a cycle of – (1) concrete experience, (2) reflective observations, and (3) abstract conceptualizations, and (4) active experimentation. This study finds that when the ELM cycle is repeated many times over an extended period to continuously improve, and documented using A3 reports, that the improvement is sustained.     

Optimization of the process variables of roller compaction,on the basis of granules characteristics (flow,mechanical strength,and disintegration behavior): an application of SeDeM-ODT expert system

The objective of the study was application of SeDeM-ODT expert system for optimization of process variables for roller compaction and for the preparation of granules with better flow, compressibility, and disintegration behavior. In the present study, granules were prepared at pre-determined (on the basis of factorial design) process variables and characterized using SeDeM-ODT expert system. Compatibility of ribavirin with excipients (microcrystalline cellulose, tablettose-80, cross carmellose sodium, and magnesium stearate) was evaluated by binary mixture approach, using FTIR. According to the SeDeM-ODT expert system, granules were characterized for various parameters related to flow, compressibility and disintegration behavior and Index of Good Compressibility and Buccodispersibility (IGCB) was calculated. The process variables resulting in highest IGCB value were considered as optimum. Ribavirin was found compatible with all the excipients used in the study and characteristics peaks were present in FTIR spectra after subjecting to stress conditions (75% relative humidity at 45?±?5?°C) for 30?days. Both Ribavirin powder and Ribavirin containing powder blend had poor flow and compressibility while disintegration behavior was good due to higher water solubility. Screw speed of 35?rpm and roller speed at 12?rpm resulted in granules with acceptable characteristics. The IGCB value (5.63) of the granules was highest of all, indicating its better characteristics. SeDeM-ODT expert system presents a more practical picture of the granules and also predicts the mechanical strength and disintegration behavior of the tablets prepared from the granules. By proper optimization of screw and roller speed, efficiency of the process can be improved.     

锑掺杂二氧化锡纳米粉体的改性及在涂料中的应用

利用硅烷偶联剂、醇、油酸钠及自制高分子表面活性剂对锑掺杂二氧化锡纳米粉体(ATO)进行表面处理,研究了不同改性剂对粉体分散性的影响.以改性纳米ATO分散浆料和水性聚氨酯为原料,采用共混法制备了纳米复合涂料,并对其隔热性及基本性能进行测试.TEM及离心实验表明,ATO粉体经自制高分子表面活性剂或硅烷偶联剂改性后,分散性明显提高.性能测试表明:ATO粉体的加入能显著提高涂膜硬度及隔热性.     

Finite element analysis on shape deformation of the macro-structure region during hot-rolling process for gear steel FAS3420H and its modification

The rectangular macro-segregation region in the core of hot-rolled steel bar has a great influence on the heat treatment distortion of an automotive gear steel FAS3420H. In order to understand the distortion process of the segregation region during hot-rolling process, a finite element (FE) analysis of the whole hot-rolling process was carried out by software DEFORM-3D, and a constructed constitutive model was embedded into DEFORM-3D to describe the deformation process. The results show there is an inhomogeneous strain distribution at the cross-section of hot-rolled round bar, which results in uneven distortion of the segregation region in different directions. A square segregation region, which can reduce inhomogeneous distortion of gear in the subsequent heat treatment, is obtained after being rolled by simulation calculation verified through experiment.     

我国新一代极轨气象卫星（风云三号） 工程地面应用系统

风云三号气象卫星是实现全球、全天候、多光谱、三维、定量遥感的我国第二代极轨气象卫星系列,已成为世界气象组织在亚洲的重要业务卫星,为提高我国气象卫星在世界气象组织卫星观测系统中的地位奠定了重要的基础,世界气象组织已将风云三号气象卫星纳入世界气象卫星全球观测业务序列。依靠我国自主力量设计与建设的新一代极轨气象卫星风云三号地面应用系统首次利用海内外接收站网实现了上、下午星全球资料的高时效获取,首次利用国产卫星实现了大气三维探测,实现了臭氧和辐射收支等探测的高精度处理,突破了卫星资料定量反演、数值预报同化应用以及气候应用等核心技术。     

Improvement of microstructure and properties of air-cooled 46MnVS5 forging steel rod for fracture splitting connecting by thermomechanical control process (TMCP) and by niobium micro alloying

Microstructure control and properties of air-cooled high-strength 46MnVS5 forging steel rod for fracture splitting connecting were systematically investigated by quantitative metallographic analysis, thermomechanical simulation and industrial trials etc. The results indicate that the critical cooling rate for bainite transformation in the steel is about 1.5 °C/s–2 °C/s during continuous cooling. Cooling parameters are optimized in two sections. That is, the specimen is firstly cooled to 750 °C at a rate of 4 °C/s, then continuously cooled to 570 °C at 1 °C/s, 1.5 °C/s. Addition of 0.024 wt.% niobium improves the fracture splitting performance by 10 %–20 % reduction of decarburization sensitivity. Finally, the optimized parameters for the niobium micro alloyed steel in the laboratory were successfully applied to produce the connecting rod with excellent fracture splitting performance on the traditional production line.     

Fast patterning of poly(methyl methacrylate) by a novel soft molding approach and its application to the fabrication of silver structures

A novel single-step approach for the fabrication of poly(methyl methacrylate) structures by soft molding of a 5 wt% solution in acetone is reported. The use of a low weight solution and of a solvent with high volatility ensures a very fast patterning, down to 10 s. In addition, the process is extremely simple and cost-effective, since just one elastomeric mold is needed, and areas as large as 1 cm² were patterned uniformly and defect-free. The process was applied to the fabrication of silver structures by silver deposition via electroless plating or evaporation followed by poly(methyl methacrylate) removal. Structures of various shapes and sizes, with dimensions in the micrometer and submicrometer range were successfully fabricated, showing the versatility of the process. This silver patterning process is particularly well suited for applications in microelectronics and optoelectronics, such as the fabrication of transparent electrodes for solar cells and displays, manufacturing of metal etching masks and wiring of printed circuits.     

Electrochemical characterization of deoxyribonucleic acid on aluminum(III)/poly(l-glutamic acid) film and its application for the detection of phosphinothricin acetyltransferase gene-specific sequence

A simple strategy of transgenic sequence-specific detection without a special amplification procedure was developed on the basis of aluminum(III)/poly(l-glutamic acid) (PLGA) film. An aluminum ion (Al(III)) thin film was assembled on the surface of PLGA via the electrostatic binding of Al(III) with carboxyl, namely Al(III)/PLGA. The immobilization of deoxyribonucleic acid (DNA) was carried out on this Al(III)/PLGA film by Al(III)-single strand DNA (ssDNA) interaction. Surface hybridization between the immobilized ssDNA and its complementary ssDNA was monitored by electrochemical impedance spectroscopy (EIS) using [Fe(CN)₆]^3−/4− as a redox probe. Under the optimal conditions, this DNA electrochemical sensor was applied to determine the specific gene sequence related to phosphinothricin acetyltransferase transgene (PAT) in the transgenic plants by label-free EIS.     

Multivariate analysis of anionic, cationic and nonionic textile surfactant degradation with the H(2)O(2)/UV-C process by using the capabilities of response surface methodology

Anionic, cationic and nonionic surfactants being frequently employed in the textile preparation process were subjected to H(2)O(2)/UV-C treatment. As a consequence of the considerable number of parameters affecting the H(2)O(2)/UV-C process, an experimental design methodology was used to mathematically describe and optimize the single and combined influences of the critical process variables treatment time, initial H(2)O(2)concentration and chemical oxygen demand (COD) on parent pollutant (surfactant) as well as organic carbon (COD and total organic carbon (TOC)) removal efficiencies. Multivariate analysis was based on two different photochemical treatment targets; (i) full oxidation/complete treatment of the surfactants or, alternatively, (ii) partial oxidation/pretreatment of the surfactants to comply with the legislative discharge requirements. According to the established polynomial regression models, the process independent variables "treatment time" (exerting a positive effect) and "initial COD content" (exerting a negative effect) played more significant roles in surfactant photodegradation than the process variable "initial H(2)O(2) concentration" under the studied experimental conditions.