SP2215/T92异种钢焊接接头微观组织与力学性能研究

采用手工钨极氩弧焊和ERNiCr-3焊丝制备了SP2215/T92异种钢钢管焊接接头,研究了热处理前后接头的微观组织,力学性能及拉伸断裂机理。结果表明:焊缝金属以完全奥氏体组织凝固成柱状枝晶,Nb元素在枝晶间偏析并形成富Nb第二相粒子,焊后热处理对焊缝组织无显著影响;T92与焊缝金属界面以及SP2215与焊缝金属界面均形成岛状或半岛状宏观偏析,跨T92与焊缝金属界面存在一定程度的碳迁移,而跨SP2215与焊缝金属界面碳迁移现象不明显,焊后热处理对宏观偏析和碳迁移无显著影响;T92侧粗晶热影响区硬度最高,细晶热影响区硬度次之,临界热影响区硬度最低,焊后热处理显著降低了粗晶热影响区和细晶热影响区的硬度,改善了T92 热影响区的微观组织和力学性能;T92侧熔合线附近形成了δ铁素体,是整个接头硬度最低区域,焊后热处理对δ铁素体的硬度无明显影响;焊态和热处理态接头室温拉伸均在焊缝处以韧性方式断裂,而650℃高温拉伸时均在T92侧以韧性方式断裂。     

The Awesome and Capricious Language of Past,Present and Future Digital Moods

Can cultural progress be held back by linguistic limitations? Architect and educator Marjan Colletti , cofounder of London practice MAM-arch, examines the nouns, adjectives and adjectival compounds used by the architectural profession during the first and second digital turns. He reflects on how restricted vocabularies can cause initially forward-looking concepts to descend into the realm of doctrine and ‘-isms’, and argues that true advancement requires constant evolution of the language employed to describe it.     

应用VB实现AGA8-92DC气体压缩因子计算方法

天然气压缩因子在天然气工程计算中具有重要的地位,其计算方法有多种,其中就包括由美国燃气协会提出的基于气体组成来计算压缩因子的AGA8-92DC方程。根据GB/T 17747.2-2011标准所给出的AGA8-92DC方法计算过程,用Visual Basic6.0 program编写了计算程序。为了验证程序的正确性,分别将程序计算值与GB/T 17747.2标准提供的计算值和含碳贫气气样实测值进行了对比,且获得了较小的计算误差。由计算值与实测值的对比结果可知,通过Visual Basic6.0 program所编写的AGA8-92DC方法计算程序而得到的计算结果能够满足工程上的要求;对于中高压含碳贫气,AGA8-92DC方法具有较高的计算准确度;当气体温度升高时,AGA8-92DC方法的计算误差将有所减小。     

高Cr铁素体耐热钢中的Z相

高Cr铁素体耐热钢是广泛应用于电厂恶劣环境下的新型钢种,在长期服役后的高Cr铁素体耐热钢中发现了Z相。综述了Z相的基本特性和T91、T92、T122钢3种典型的高Cr铁素体耐热钢中Z相的研究进展,概述了Z相对材料性能影响的微观机理,并对未来研究的重点进行了展望。     

超超临界机组T92钢高温受热面管爆管原因分析

某电厂的后屏过热器T92钢管段发生爆管。通过宏观检验、化学成分分析、硬度检验、拉伸性能测试、金相检验以及相关计算分析了爆管的原因。结果表明：管段发生短时过热后,其显微组织为Acl-Ac3相变产物,失去了原典型的回火板条马氏体组织特征,材料强度大幅度降低,从而使得强度不足以抵抗管子的使用应力而发生爆管。另外,通过检验获得了不同状态下的组织与性能的对应关系,有利于长期运行中的金属监督检验。     

化学成分及热加工工艺对P92钢管坯组织性能的影响

P92钢近年来在国内越来越多地用于超(超)临界锅炉的高温主蒸汽管道,是制造电站锅炉四大管道关键材料,其长期性能和其组织有密切关系。探讨了δ铁素体组织与化学成分、冶炼及热加工工艺的关系。通过对成分、冶炼及热处理工艺的优化,抑制了δ铁素体的生成,生产出合格的P92钢管坯。     

Phase evolution in P92 and E911 weld metals during ageing

Phase evolution in the weld metals of P92 and E911 steels weld joints were studied during ageing at 625 °C for up to 9000 h. The phases: ferrite + M₂₃C₆ + MX + Laves found by means of analytical TEM in the annealed states agree with the results of the thermodynamic calculation of equilibrium phases. The cross-weld hardness values, HV10, after 1000, 3000, and 9000 h ageing overlap each other and are approximately 15 units below that of the post-weld heat-treated (PWHT) state. Charpy impact energy with the notch at the centerline of the weld metal was measured. Its values decrease after ageing from approximately 60–80 to 12 J compared to the PWHT state. In 9–12%Cr steel with W this phenomenon can be explained by a priori heterogeneity in the weld metal, its large former austenite grain size, the precipitation and growth of M₂₃C₆ and Laves phase particles on grain and packet boundaries.     

摩擦压力对Super304H/T92摩擦焊焊接接头性能的影响

利用连续驱动摩擦焊技术焊接Super304H和T92钢管,焊接接头具有良好的显微组织和力学性能。考察摩擦压力对焊接接头显微组织和力学性能的影响,研究表明:随着摩擦压力增加,焊合区和热影响区晶粒尺寸没有明显变化,热影响区碳化物析出相的数量略微增加,显微硬度逐渐增大,冲击韧性逐渐降低,拉伸断裂位置和拉伸强度没有变化。     

Research on elastic-plastic creep damage of notched P92 steel specimens

Creep tests were performed on P92 steel specimens with notches of three different sizes at 650 °C. The results showed that the specimens switched from exhibiting ductility to showing brittleness at their center and at the notch root under multiaxial stress, but to varying degrees. This transformation was accompanied by a decrease in the reduction in area as well as in the number of dimples in the sample cross-section. The multiaxiality had a marked impact on the precipitation of the secondary phase, with its value determining the extent of precipitation of the secondary phase at the center and the root of the notch during creep. Using finite element analysis, an elastic-plastic creep damage model is embedded into the interface program and the creep behavior of the notched specimens was simulated. The results showed that plastic deformation at the notch root can accelerate specimen damage.     

Three results on frequency assignment in linear cellular networks

In the frequency assignment problem we are given a graph representing a wireless network and a sequence of requests, where each request is associated with a vertex. Each request has two more attributes: its arrival and departure times, and it is considered active from the time of arrival to the time of departure. We want to assign frequencies to all requests so that at each time step any two active requests associated with the same or adjacent vertices use different frequencies. The objective is to minimize the number of frequencies used.We focus exclusively on the special case of the problem when the underlying graph is a linear network (path). For this case, we consider both the offline and online versions of the problem, and we present three results. First, in the incremental online case, where the requests arrive over time, but never depart, we give an algorithm with an optimal (asymptotic) competitive ratio . Second, in the general online case, where the requests arrive and depart over time, we improve the current lower bound on the (asymptotic) competitive ratio to . Third, we prove that the offline version of this problem is NP-complete.