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首页> 外文会议>European Conference of Fracture >EVALUATION OF NOVEL POST WELD HEAT TREATMENT IN FERRITICSTEEL REPAIR WELDS BASED ON NEUTRON DIFFRACTION
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EVALUATION OF NOVEL POST WELD HEAT TREATMENT IN FERRITICSTEEL REPAIR WELDS BASED ON NEUTRON DIFFRACTION

机译：基于中子衍射的新型铁素体修复焊后焊后热处理评价

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The occurrence of cracks in – normally welded – components with safety relevance in, e.g.nuclear installations or in the(petro-)chemical industry, is not an unusual event.In most cases such cracking is detected in periodic inspections prior tocomplete failure of the component.Sometimes a detected defect necessitates repair of the damaged component to facilitateits further operation.Repairing of a crack would normally be performed by excavating of the material surrounding the crack and subsequent fillingof the excavation by welding.However, such a repair welding process leaves the component in a sensitive state in that itgenerates a complicated residual stress pattern and that the heat affected zone of the weld might become very susceptible tothe formation of new cracking.Post weld heat treatment of a repaired component can be an option to mitigate the damaging impact of the welding process.Through heat treatments residual stresses can be severely reduced or redistributed to obtain stress fields around the welddeemed less detrimental.At the same time a heat treatment process could positively influence the HAZ sensitivity for furthercracking.In any case, a thorough assessment of the welding process is necessary to ensure a safe continued operation of therepaired component.In this context letterbox repair welds applied to thin ferritic steel plates to simulate repair of postulated shallow cracks havebeen manufactured.The excavations of postulated cracks for these experiments were filled with 20 to 30 welding passes.Components have been made available in the as welded state and after the application of PWHT.Two different heat treatmentprocesses are compared: a.a full scale treatment, where the entire test piece has been subjected to an elevated temperaturefor several hours in order to significantly reduce the residual stresses, and b.an alternative treatment whereby the heat isapplied locally for a short period of time in order to redistribute the stresses in a controlled manner.In this paper the experimental determination of these residual stresses in the as welded and in the heat-treated states ispresented.Such measurements have been performed by neutron diffraction at the High Flux Reactor (HFR) of the JointResearch Centre of the European Commission in Petten, the Netherlands.The principle of residual stress measurements by neutron diffraction is introduced and the particular considerations forperforming such measurements in multi-pass butt welds are briefly outlined .The experimental approach is presented andexplained and an outline is given on the data analyses.Results are depicted in the form of comparison between the asreceived and the heat treated stress states.The derived data facilitate conclusions on the effects and effectiveness of theapplied heat treatments and they also demonstrate that neutron diffraction is a very suitable tool for non-destructive analysis ofinternal residual stress fields in such welded components of considerable thickness.In addition, the method is well suited forthe validation of predictive numerical models.
机译：在安全的相关部件中（例如，核设施或在（石油）化学工业中）发生的裂纹（通常是焊接）并非罕见事件。在大多数情况下，在部件完全失效之前的定期检查中会发现这种裂纹。有时，检测到的缺陷需要修复受损的零件以利于进一步操作。裂缝的修复通常是通过挖掘裂缝周围的材料并随后通过焊接填充基坑来进行的。在敏感状态下，它会生成复杂的残余应力模式，并且焊缝的热影响区可能非常容易形成新的裂纹。对修复后的零件进行焊后热处理可以减轻焊缝的破坏性影响。通过热处理，残余应力可以大大降低或重新分布以获得应力焊缝周围的ss磁场被认为有害程度较小。同时热处理可能会对热影响区的敏感性产生积极影响，进一步裂化。在任何情况下，都必须对焊接过程进行彻底评估，以确保已修复组件的安全连续运行。在薄铁素体钢板上模拟了假定的浅层裂纹的修复情况，制造了上下文信箱修复焊缝。这些实验的假定裂纹的开挖填充了20到30个焊接道次。比较了两种不同的热处理工艺：a全面处理，其中整个试件都经受了高温几个小时以显着降低残余应力，b。另一种处理方式是局部加热短时间以重新分配压力本文介绍了在焊接状态和热处理状态下这些残余应力的实验确定方法。这些测量是在欧洲委员会联合研究中心的高通量反应堆（HFR）上通过中子衍射进行的介绍了通过中子衍射法测量残余应力的原理，并简要概述了在多道次对接焊缝中进行此类测量的特殊注意事项。提出并解释了实验方法，并对数据分析给出了概述。结果以接受应力状态和热处理应力状态之间的比较形式表示。得出的数据有助于得出有关所应用热处理的效果和有效性的结论，它们还表明中子衍射是非常适合内部无损分析的工具。这种焊接部件的残余应力场相当大另外，该方法非常适合于预测数值模型的验证。

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