Characterization of microstructure,mechanical properties and corrosion resistance of dissimilar welded joint between 2205 duplex stainless steel and 16MnR

The joint of dissimilar metals between 2205 duplex stainless steel and 16MnR low alloy high strength steel are welded by tungsten inert gas arc welding (GTAW) and shielded metal arc welding (SMAW) respectively. The microstructures of welded joints are investigated using scanning electron microscope, optical microscope and transmission electron microscopy respectively. The relationship between mechanical properties, corrosion resistance and microstructure of welded joints is evaluated. Results indicate that there are a decarburized layer and an unmixed zone close to the fusion line. It is also indicated that, austenite and acicular ferrite structures distribute uniformly in the weld metal, which is advantageous for better toughness and ductility of joints. Mechanical properties of joints welded by the two kinds of welding technology are satisfied. However, the corrosion resistance of the weldment produced by GTAW is superior to that by SMAW in chloride solution. Based on the present work, it is concluded that GTAW is the suitable welding procedure for joining dissimilar metals between 2205 duplex stainless steel and 16MnR.     

深圳市排水支管管网设计与改造经验探讨

目前我国各地城市污水管网建设有着必要性和紧迫性.结合工程实践提出了排水系统支管管网设计的主要思路和应注意的问题.介绍了在前期准备工作中确定改造片区的方法、管线普查的范围、管道勘察钻孔间距的确定等经验.提出了排水体制确定、具体改造方法、管材选择、施工方式选择等方案.探讨了设计和管理方面需特别注意的一些问题.