引水用压力钢管弧坑缺陷的安全评定

对含弧坑缺陷的引水压力铜管,根据有限元计算分析结果,运用在用合缺陷压力容器安全评定标准进行了安全评定,评定结论为该压力钢管壁上的弧坑缺陷是在允许范围内的.     

压力钢管弧坑缺陷有限元分析

结合因弧坑缺陷引发压力铜管焊缝开裂的工程实例,采用有限元分析软件Ansys对钢管焊缝弧坑缺陷处的应力分布进行计算,分析了在单个弧坑情况下应力强度值的分布规律,以及在多个弧坑情况下弧坑处应力强度值和应力集中系数之间的相互影响,从而为该压力铜管的安全评定提供了力学依据。     

压力钢管表面凹坑缺陷的安全评定

基于有限元分析结果,采用国家标准GB/T19624<在用含缺陷压力容器安全评定>,对含表面凹坑缺陷的压力钢管进行了安全评定.根据凹坑缺陷不同的分布状况,分别采用了不同的方法进行评定.当相邻两凹坑缺陷边缘间的最小距离在20 mm范围内时,应采用常规评定的方法.结果表明,其对应的评定点落在评定曲线定义的安全范围内.这表明所评定的缺陷是可以接受的.当相邻两凹坑缺陷边缘间的最小距离大于20 mm时,可采用凹坑评定的方法.两种方法评定结果均表明,压力钢管壁上的表面凹坑缺陷是可以接受的.     

含缺陷压力管道的应力腐蚀断裂及其安全评定

在严重的腐蚀介质中，压力管道等含缺陷构件常常易于发生应力腐蚀脆性断裂.本文分析了应力腐蚀环境下临界应力强度因子KISCC的含义，给出了含缺陷构件的应力腐蚀失效判据为KI≤KISCC.在实际工程中，由于临界应力强度因子门槛值KISCC均通过实验方法来获取，给评定过程带来了一定困难且不便于推广应用.为此，本文推荐了一种简要的KISCC工程计算方法。结果表明：工程计算方法所得计算结果与实验测定结果有较好的吻合，可用于压力管道等含缺陷构件的安全评定.      

压力管道缺陷评定中焊接残余应力的处理分析

分析了压力管道对接焊缝焊接残余应力的产生机理和分布规律,提出了在压力管道缺陷评定中如何处理焊接残余应力的方法。     

在用压力容器局部坑状腐蚀的安全状况等级评定

通过对在用压力容器局部坑状腐蚀所产生的凹坑应力进行分析，得出了不同坑深的在用压力容器安全状况等级的评定。     

压力钢管的焊接工艺规程WPS

黄河小浪底压力钢管属超大型压力钢管，采用美国ASME标准的高强调质钢，A517和高强正火钢A537钢板。此工程由外商总承包，并严格按美国ASME标准检查和验收。为确保焊接质量，编制了焊接工艺规程WPS，并按此规程针对不同板厚、不同接头形式、不同焊接方法分别作了工艺评定试验，其结果均符合小浪底压力钢管技术规范要求，符合美国ASTM标准和外商的评定要求。     

防止5Ni钢弧坑裂纹的工艺措施

本文分析了５Ｎｉ钢焊接过程中生产弧坑裂纹的原因，提出了防止弧坑裂纹的工艺措施。     

含焊接缺陷构件的疲劳可靠性评定

在试验的基础上,应用模糊集理论,综合评定了焊接缺陷对于构件疲劳强度的影响,综合考虑了缺陷种类、大小、位置、缺陷间的相互干涉四个因素,得出了一个评定焊接缺陷对构件疲劳强度危害程度的特征参量μ(X)。将特征参量μ(X)与质量带理论结合,做出了含缺陷构件的μ-S-N-P图。运用μ-S-N-P图,初步解决了构件中已知缺陷形态如何进行构件的可靠性评定等工程上关心的问题。特征参量μ(X)与作者提出的主疲劳源模型相符合。     

Mathematical modelling of the process of formation of a shrinkage crater in surfacing

The mathematical model of the formation of a crater in arc deposition of metal as a result of volume shrinkage is proposed. The model can be used to calculate the shape of the crater surface on the basis of the evolution of the temperature field with time.     

T91钢焊接接头弧坑裂纹分析

T91钢淬硬倾向和裂纹敏感性较大,常出现弧坑裂纹,分析出现弧坑裂纹的原因主要有:T91钢合金元素含量高,容易淬硬且焊接性较差;收弧时速度较快且未将弧坑填满;焊接过程中未采取合理的防风措施等。针对这些因素采取相应的措施:严格按照规程执行焊接工艺及热处理制度;选用S、P等易偏析元素含量低和高w(Mn)/w(S)的焊条;采用合理的接头形式,控制对口间隙;加强对焊接收弧时的工艺控制;注意打磨接头收弧处弧坑;严格控制焊接作业环境。     

供热蒸汽管线安全评估

采用化学成分分析、宏观检验、能谱分析、金相检验和力学性能测试等方法对某热电厂蒸汽管进行了检测和分析。结果表明:涉及管线安全运行的关键部位焊缝存在弧坑、咬边、未焊透、夹渣和裂纹等严重的焊接缺陷,加上长期腐蚀,使该蒸汽管线卷板管存在重大安全隐患,继续使用可能造成局部泄漏。建议在探伤的基础上更换有严重焊缝缺陷的卷板管或停止使用该蒸汽管线卷板管。     

Metallurgical assessment of critical defects in continuous hot dip galvanized steel sheets

Development of hot dip zinc coated sheets in new applications increased demand for production of high quality galvanized coatings, but the presence of surface defects reduces the quality of these products. In order to alleviate the problem, one needs to know the extent to which the properties of a galvanized sheet are influenced by the presence of a given defect. In this paper, specimens including any of the four major defects of continuously galvanized steel sheets produced in an industrial continuous process have been studied. The defects, including scratches, bare spots, pimples and wrinkle bands, were microstructurally characterized and their influence on corrosion behavior of the coated sheet was evaluated. The defects, originating from insufficient cleaning procedure, improper quality of steel substrate or adhered metallic particles to the substrate surface, exert their main effects on corrosion resistance and surface quality. Corrosion behavior was examined via standard salt spray test and polarization test. Based on the experimental results, it was concluded that the corrosion resistance was influenced by severity of defects; bare spots reduced the overall corrosion resistance of galvanized sheet by 39% ± 1% and pimples by 10% ± 1% as compared to defect free specimens.     

铝合金型材对搭接搅拌摩擦焊接头中Hook缺陷的安全评定

基于断裂力学理论对铝合金型材对搭接搅拌摩擦焊接头中Hook缺陷进行安全评定,并通过疲劳试验进行验证.金相显示Hook缺陷的本质是搭接面在搅拌头剧烈搅拌作用下向上迁移的结果,显现为裂纹的形式.将Hook缺陷归一化为延伸到焊缝内部的单边裂纹,裂纹扩展速率线性拟合得出应力强度因子幅度门槛值ΔKth为2.509 MPa·m1/...     

含表面缺陷的双相不锈钢管道非匹配焊接接头的安全评定

采用欧洲经济共同体提出的结构完整性评定方法SINTAP(Structural integrity assessment procedure),对焊趾处含有表面裂纹(裂纹长度和深度分别为2．5mm和1．1mm)的SAF2205双相不锈钢管道非匹配焊接接头进行了安全评定。根据拉伸试验结果,建立了双相不锈钢管道焊接接头焊缝和母材的一级、二级评定曲线,测定了SAF2205钢焊接接头的低温(-18℃)断裂韧度,为安全评定提供了试验依据。评定结果表明,不论是采用一级或是二级评定,各评定点均在评定曲线定义的范围内,说明该结构是安全的。根据计算得到的极限裂纹尺寸进行了疲劳裂纹扩展寿命估算,最终疲劳寿命为0．133年。     

阶段变断面型材的挤压工艺及挤压缺陷的处理

试验分析了阶段变断面铝合金型材挤压过程中各种挤压缺陷的形成原因,提出了相关的解决办法,为后续的精整工序打好了基础,大大提高了生产效率,提高了成品率。     

Compensation for machining defects due to spindle dilatation

Defects are a common occurrence in industry when it comes to prolonged machining tasks (machining moulds, series of work-pieces, etc.). The relatively long machining time is generally what gives significant value added to the work-piece. We therefore need to avoid having to produce test work-pieces as much as possible [NC Machines, Hermès Paris (1997)]. This article considers dispersions introduced by dilatation of the spindle during machining on NC machine tools. Such dispersions are obviously prejudicial to obtaining accurate dimensions along the Z-axis of the machine. Firstly, we introduce the context of the study and the problem we had to confront. Secondly, the experimental study enabled us to highlight those parameters having an influence and quantify defects. By expressing dilatation and relaxation in the form of an equation, we were then able to calculate defects at a given instant. This enabled us to generate an algorithm for processing of the N.C. program so we could correct errors by compensating for defects during machining. We completed the study by machining a series of work-pieces using the programme integrating compensation for dilatation so as to validate the approach.