Water modeling of molten steel flow in a multi-strand tundish with gas blowing

Fluid flow characteristics in a four-strand tundish with gas blowing were studied by water modeling experiments.It is found that gas blowing can greatly improve the flow characteristics in the tundish with a turbulence inhibitor.It dramatically increases the peak concentration time,and greatly decreases the dead volume,and reduces the minimum residence time.The gas blowing location,gas flow rate,and porous plug area greatly influence the flow characteristics in the tundish;the gas blowing location near t...     

Precipitation and stability of reversed austenite in 9Ni steel

A new method was used to analyze the factors affecting the precipitation of reversed austenite during tempering. The samples were kept at various tempering temperatures for 10 min and their length changes were recorded. Then, the precipitation of reversed austenite which led to the length reduction was shown by thermal expansion curves. The results show that the effects of process parameters on the precipitation of reversed austenite can be determined more accurately by this method than by X-ray diffraction...     

Electrical conductivity changes of bulk tin and Sn-3.0Ag-0.5Cu in bulk and in joints during isothermal aging

The changes of electrical conductivity(resistance) between Sn-3.0Ag-0.5Cu solder joints and printed circuit board(PCB) assembly during aging at 125℃were investigated by the four-point probe technique.The microstructural characterizations of interfacial layers between the solder matrix and the substrate were examined by optical microscopy and scanning electronic microscopy.Different types of specimens were designed to consider several factors.The experimental results indicate that electrical conductivitie...     

Solid state interfacial reactions in electrodeposited Ni/Sn couples

Ni/Sn couples,prepared by sequentially electroplating Ni layers and Sn layers on metallized Si wafers,were employed to study the mierostructures and growth kinetics of Ni-Sn intermediate phases,when the Ni/Sn couples were aged at room temperature or annealed at temperatures from 150 to 225℃for various times.The results show that the NiSn phase and Ni_3Sn_4 phase are formed,respectively,in the aged couples and annealed couples.The Ni_3Sn_4 layer is continuously distributed between the Ni and Sn sides in t...     

Effect of cooling rate on the phase transformation and stability of the mushy zone during the solidification of Waspaloy

Scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDAX) were used to study the microstructure,microsegregation, and fluid flow tendency of the superalloy Waspaloy in the mushy zone,which had been solidified at different cooling rates. The investigation was accompanied with the calculation of Rayleigh numbers.It is found that Ti is the main segregating element and the content of Ti is the highest in the final liquid at the cooling rates of 3-6℃/min.The eta phase(η) precipitate present...     

Sodium-modification of Ca-based bentonite via semidry process

In order to improve the quality of Hunyuan inferior Ca-based bentonite (Ca-Bent), semidry process was used to modify Ca-Bent into superior Na-based bentonite (Na-Bent). The factors affecting sodium-modification were investigated. The optimized experimental parameters are obtained as follows: Na₂CO₃ dosage 4.0%, ageing time 25 d, briquetting pressure 25 MPa and briquetting moisture 20%. Under the optimization conditions, the modified Na-Bent has a colloid value of 73.6 mL/(3g), dilation of 38 mL/g and water absorption in 2 h (2HWA) of 465%, respectively. The balling results indicate that the modified Na-Bent pellets have higher drop strength and compression strength than the Ca-Bent pellets.     

水泥在料配料控制系统设计

本文研究水泥生料配料控制系统的工艺流程,分析了系统的参数特点,在系统上位机进行主副随动的基础上,设计了物料配料控制器。分析和设计基于PID控制算法的水泥生料配料系统控制算法。实际工程应用表明,该系统具有很好的控制效果。     

基于双闭环控制的供水系统

双闭环控制供水系统采用自整定模糊PID控制算法,以水泵电动机的转速和管网水压为设定参数,实现恒压供水。该系统实时控制性能良好,节能效果显著。     

中国银行利率风险实证分析

随着中国融入世界的步伐加快,加入WTO中要求中国放开金融市场的开放程度,利率管制的放松也将逐步的实行,利率风险日益成为中国商业银行面临的重要风险之一。本文从理论和实践角度对中国商业银行的利率风险进行了分析和研究,剖析中国商业银行存在的诸多障碍,指出了商业银行风险管理中存在的问题,并提出中国商业银行利率风险管理建议。     

半导体封装生产线工艺流程分析

本文介绍了半导体生产线后道封装流程,并对相关设备的自动化程度进行分析。