基于CTOD工艺的焊接质量控制技术

荔湾3-1导管架是中国首个自主建造的深水导管架项目,项目建造过程中采用大量的厚板设计。为降低建造成本,提高建造效率,广泛应用免除焊后热处理的CTOD工艺,该工艺对焊接热输入、预热与层间温度以及层道布置非常敏感,给现场的焊接质量控制工作带来了较大的困难。基于海洋石油工程(青岛)有限公司的项目实践,总结了CTOD工艺的焊接质量控制技术,对其他的类似项目具有一定的借鉴作用。     

INFLUENCE OF LOCAL BRITTLE ZONE ON THE FRACTURE TOUGHNESS OF HIGH-STRENGTH LOW-ALLOYED MULTIPASS WELD METALS

1.IntroductionManyillvestigatiolls[1--5]havefOllndthattilelocalbrittlezone(LBZ)playsanimportantroleinfyacturetoughnessofheat--affectedzoneinthebasemetalfornormalizedandthermomechanicallycontrolledprocessingsteels,aswellasdirectquellchedandtemperedsteels.Therearefewreportsaboutthisphellomellainhigh-strengtllmllltipassweldmetals.Inmultipasswelds,thereareprimaryweldmetalandweldmetalreheatedtovarioustemperaturesbythesubsequentbeads[6'71.Thereheatedregionfinderabeadcanbedividedintoacoarsegrainedz…     

金属焊缝CTOD试样疲劳裂纹前沿平直度研究

在金属厚板焊缝CTOD试样中预测前沿平直的疲劳裂纹，是CTOD试验的一个关键难题。通过实验，研究了疲劳裂纹前沿平直度St与疲劳载荷比f之间的关系，发现两者高度正相关，为预制具有平直裂纹前沿的疲劳裂纹提供了有效的途径和方法。     

全焊接管线球形阀体焊缝免焊后热处理安全评估

为了科学有效地评估全焊接管线球阀的安全性,同时为免除焊接接头焊后热处理提供依据,介绍了一种评价全焊接管线球阀焊接接头安全性的方法：裂纹尖端张开位移（CTOD）断裂韧性试验方法。根据试验得到的CTOD值及球阀的相关参数,并采用API Std 1104-2008标准附录A和BS7910所介绍的＂焊接结构中缺陷的可接受性评定方法＂,对焊接接头的安全性进行评估,得出评估曲线及评估点,直观展示评估结果。评估结果对焊接接头免除焊后热处理的可能性提供依据。     

THE CRACK INITIATION TOUGHNESS FOR BRITTLE FRACTURE OF SUPER DUPLEX STAINLESS STEEL

Abstract— The occurrence of brittle stable crack growth before unstable fracture was demonstrated with the aid of heat-tinting, for a ferritic matrix super duplex stainless steel which had been age-hardened at 475°C. The critical crack tip opening displacement for stable crack growth, i.e. the crack initiation toughness, was measured using the direct-current-potential drop crack monitoring technique. A quantitative model for the effect of temperature and age-hardening on the brittle crack initiation toughness is described.     

Strip Yield Model Numerical Application to Different Geometries and Loading Conditions

A new numerical method based on the strip yield analysis approach was developed for calculating the Crack Tip Opening Displacement (CTOD). This approach can be applied to any crack geometry, of either infinite or finite extent, with arbitrary applied loading conditions. The technique is an adaptation of the dislocation-density based boundary element method to obtain crack-face opening displacements at any point on a crack, and succeeds in obtaining the requisite values as a series of definite integrals, the functional parts of each of which are evaluated exactly in closed form. The power of the technique is demonstrated by obtaining solutions to several crack configurations of practical interest.     

The effect of specimen thickness on the experimental and finite element characterization of CTOD in extra deep drawn steel sheets

Recent experimental results by us have indicated that the load-drop technique can serve as a valid fracture criterion for predicting elastic-plastic fracture in extra deep drawn (EDD) steel sheets or in predominantly plane stress conditions. The purpose of this investigation is to examine the validity of aJ-integral as a fracture parameter and theJ-CTOD relation for the determination of critical CTOD in predominantly plane stress fracture (CTOD-crack tip opening displacement). Fracture tests were performed and experimental results were generated on fracture behaviour of EDD (0·06%C) steel sheets with CT specimens and using ‘load-drop’ as a fracture criterion. Critical CTOD was determined by using theJ-CTOD relation in addition to several existing techniques. A full 3-D finite element model was formulated to verify the critical load, critical CTOD and plastic-zone size. The critical CTOD was shown to increase with increasing specimen thickness and appeared to be approaching a higher limiting value. The characteristic features of predominantly plane stress fracture or general yielding fracture mechanics are summarized in conclusion     

X80钢管焊接接头断裂韧性试验分析

通过对进口钻井隔水管X80钢管进行理化性能分析,了解了国外钻井隔水管材料的性能水平,为隔水管国产化工作的开展提供了一些参考数据;通过对X80管线钢焊接接头的CTOD试验研究,发现焊接接头的断裂韧性在热影响区相对较弱;通过对比分析焊接接头的夏比冲击功和CTOD试验结果,表明CTOD试验对材料的断裂韧性评价是可靠的.     

一种评价导管架焊接接头韧性的方法

按照英国BS7448标准，介绍了裂纹尖端张开位移(简称CTOD)试验方法，并用这种试验方法，评价了番禺项目导管架厚板焊接接头的韧性。结果表明：CTOD试验评价焊接接头韧性，效果良好；CTOD试验可作为焊接工艺认可试验；被评价的两项焊接工艺用于导管架建造，焊后允许不进行热处理，缩短了建造工期，降低了成本。     

Ti,N和C对X70管线钢管焊缝热影响区韧性的影响

介绍了7种Ti,N,C含量不同的X70管线钢的理化特性,并通过CTOD试验、夏比冲击试验和Gleeble热模拟试验,分析了不同Ti,N,C含量对X70管线钢管环焊缝热影响区韧性的影响。最后指出,当Ti含量和Ti/N比都降低时,TiN粗大晶粒的数量将随之减少,焊缝热影响区韧性提高。