不锈钢管打底焊接工艺的进展

综述了不锈钢管打底焊接技术的进展 ,指出了各种方法的特点及应用场合。认为药芯焊丝 (棒 )TIG、细径混合气MAG以及实芯焊丝混合气TIG是我国现阶段应大力推广的打底焊工艺     

Anisotropy in Microstructures and Mechanical Properties of 2Cr13 Alloy Produced byWire Arc Additive ManufacturingEI北大核心CSCD

2Cr13 martensite stainless steel has been widely used for the manufacturing of surgical tools and turbine blades. Contrary to the conventional fabrication technologies, there are several remarkable advantages in the fabrication of 2Cr13 parts by adopting wire arc additive manufacturing (WAAM) technologies, such as excellent metallurgical bonding, high production efficiency, near-net-shape production, and limited environmental contamination. In this work, the effect of interlayer dwelling temperature (110-550 degrees C) on microstructural and mechanical properties has been revealed, providing a new approach for the active control of the performances of 2Cr13 buildups produced by wire-arc additive manufacturing. The part with a dwelling temperature of 550 degrees C was featured by elongated acicular martensite features, with a slightly enhanced fiber-like texture, along with minor fine irregular-reverse austenite structures, dispersed among martensite gaps. This special martensitic distribution was mainly caused by the grain-broken effect under the intensive thermal shock from liquid melting pool. Consequently, the enhanced tensile strength and microhardness were obtained due to grain refinement, although exhibiting an obvious anisotropy in tensile properties. The parts with dwelling temperatures of 110-180 degrees C were characterized by relatively coarsened martensite laths, with a random texture type, within block-shaped ferrite matrix. The average martensite size was gradually refined due to the increased cooling rate by lowering interlayer temperature. The isotropic mechanical properties of all three parts (110-180 degrees C) were similar because of the similar martensite laths.     

由引线引起的电力变压器过热性故障分析

通过对一例电力变压器过热性故障的分析与计算,提出了由引线与铜管内壁接触导致故障的机理,并提出了预防措施.     

大坝垂线位移监测资料分析的4种统计模型

位移监测及分析是大坝安全监测的重点内容 ,垂线是使用最普遍的位移监测手段之一 ,它具有测点多、深入坝体等特点 ,获得的监测数据包含了反映坝体安全状态的信息。为更好地分析这些信息 ,在已有的监测分析方法基础上 ,结合近期研究成果 ,阐述了目前位移监测模型的进展 ,归纳提出了可用于垂线位移分析的 4种统计模型 ,并结合实例给予说明。这些模型为全面分析垂线位移提供了可能 ,可在不同情况下选择使用。     

引张线系统在新丰江大坝的实施及运用

介绍了新丰江大坝引张线系统的全部实施过程、运用情况、现场维护及故障排查的工作经验,通过资料分析和系统综合评价,肯定了引张线在混凝土大坝变形监测工作中的可靠性和优越性.     

AAC砌块自由加载墙施工工法

AAC砌块自重轻、易切割、防火与保温性好,但其强度低、不能任意加载,开槽开洞局限较多,遇水湿胀且强度和保温性能变低。AAC砌块自由加载墙体施工工艺采用AAC砌块、页岩砖、素混凝土块混墙结构,通过BIM排块设计,在AAC砌块墙体中嵌入素混凝土块,在箱体集中处砌筑页岩砖墙体,以自由地适应加载、开槽开洞和墙体变形;利用表面网膜和界面封堵工艺,较好地解决了防渗防漏;利用砌块墙与页岩砖墙、混凝土梁柱间的厚度差,采用热桥咬合工艺,较好地解决了热桥。该工法系统地解决AAC砌块墙体的质量通病、使用局限,增强AAC砌块墙体的整体性、加载开槽开洞的便易性和防水性能,加上其工厂化生产与加工的特点,使其能更广泛地应用于室内外墙体。     

钢丝绳牵引胶带输送机动力制动系统改造

介绍了钢丝绳牵引胶带输送机制动系统改造方案前、后的对比。     

回采巷道锚网支护试验

阐述锚网支护的作用原理 ,巷道锚网支护的试验施工以及试验巷道的收敛、围岩移动和支护的试验分析。证明锚网支护无论从技术上 ,还是经济上都是一种比较理想的支护方式     

WH70高强钢采用高强度焊丝Q550常温下焊接试验

目前高强钢WH70 (σb=710MPa)在常温下 (大于 15℃ )焊接时 ,焊前需要预热、焊后需要退火。为此 ,对其焊接接头进行了试验 ,目的是为了实现在室温下焊接。试验采用CO2 气体保护焊 ,选用Q5 5 0高强度焊丝 ,同时就高强钢焊接性特点 ,制定了一整套焊接工艺。试验结果表明 ,采用Q5 5 0高强度焊丝 ,在对焊接工艺进行优化的情况下 ,可以实现高强钢WH70在常温下焊接。     

一起特高压变电站线夹开裂故障的处理

特高压变电站线夹发生断裂会造成严重的设备事故,甚至导致电网大面积停电事故。对1 000 kV某特高压变电站1号、2号主变压器中压侧套管下引线下部线夹开裂故障进行分析,确认引线设计不合理、线夹选型不当、焊接工艺差是故障发生的主要原因。对此采取了处理措施,并提出了预防措施和检修策略。