Service Reliability Assessment of Weld Repaired CrMoV Steel Rotors

This research deals with the service evaluation of a retired CrMoV steel rotor that has been repaired using deep groove multi‐pass submerged arc welding (SAW) and gas tungsten arc welding (GTAW). Accelerated creep tests were conducted at several elevated temperatures and extrapolated to the service temperatures. The coalescence of carbides and cavity growth during creep were evaluated. For the CrMoV‐GTAW samples, it was found that the creep life depended on the location of the crossweld in the welded specimen. The service lives of the weldments were extrapolated.     

A3钢焊缝区在酸性介质中氢致腐蚀裂开行为的研究

本文应用慢应变速率拉伸试验法、金相和扫描电镜技术研究了带焊缝的A3钢试样在会缓蚀剂的盐酸溶液中的氢致腐蚀裂开行为。结果表明,在酸液中带焊缝试样的断裂均发生在热影响区;带焊缝A3钢试样的脆断敏感程度显著高于其母材;缓蚀剂的添加可以较大程度地改变带焊缝材料的脆断敏感性。     

07MnCrMoVR钢焊件疲劳裂纹扩展速率

为鉴定０７ＭｎＣｒＭｏＶＲ钢焊件的疲劳性能，通过试验得到了焊接接头以及焊接热影响区的疲劳裂纹扩展速率，同时给出了它们存活率为９７．７３％时的各自疲劳裂纹扩展速率，并对焊接接头与焊接热影响区疲劳裂纹扩展速率进行比较。最后还把结果与“在役含缺陷压力容器安全评定规程”［１］和ＢＳＩＰＤ６４９３［２］推荐结果进行了对比，认为该钢种疲劳裂纹扩展速率在其容许范围内慢于１６ＭｎＲ钢的疲劳裂纹扩展速率     

304不锈钢焊缝在室温酸性氯化物溶液中的应力腐蚀行为

本文用慢应变速率实验(SSRT)方法研究了奥氏体304不锈钢焊接接头在室温HCl+NaCl溶液中应力腐蚀开裂(SCC)敏感性H+浓度和Cl-浓度是影响该体系发生SCC的两个重要因素,H+浓度的改变可使材料的腐蚀形态发生变化,对SCC敏感的酸度范围为:5.0x10-4～30MH+,并给出体系“304不锈钢焊缝/HCl+NaCl”的应力腐蚀状态图([Cl-]-[H+]-SCC图)焊缝区是焊接接头的SCC敏感区,应力腐蚀裂纹是沿着被选择性溶解的奥氏体枝晶间的δ-铁素体扩展的,断口具有奥氏体枝晶骨架的形貌.该体系     

用于弧焊焊缝跟踪的空气超声传感系统

本文利用声电匹配和聚焦声透镜技术，研制出１，１５ＭＨｚ高灵敏度、高分辨率空气超声传感器。设计了单片机信号采集、处理、控制软硬件系统和纠偏执行机构。首次实现扫描式、固定式超声传感二维自动跟踪，跟踪精度横纵向均达到０．５ｍｍ。     

中国实验快堆栅板联箱焊接件与钠的相容性

在模拟中国实验快堆运行工况条件下，对用不同来源304不锈钢制造的栅板联箱焊接件进行试验研究，分析和测试在450℃钠中浸泡3000h后焊接件的晶间腐蚀状况及其力学性能变化。试验结果表明：在本试验条件下，焊接件试样的平均腐蚀速率均小于0.9mg/（m_²•h）；焊接件的焊接区及热影响区表面均未出现晶间腐蚀；试验前后，试样的屈服强度、抗拉强度及延伸率均无明显变化。     

Failure assessment on offshore girth welded pipelines due to corrosion defects

Corrosion is an electrochemical process in offshore pipelines where the material strength begins to decrease as corrosion advances. Numerous studies have been performed to determine the remaining strengths (failure pressure) of corroded pipelines. Currently the axial corrosions of the girth welded pipelines still leave much to be understood. This study attempted to simulate girth welded pipeline with various corroded depths and lengths in order to compare with offshore pipeline design manuals. Based on the numerical results, the influence of corrosion defects parameters on remaining strengths were investigated for girth welded pipelines. The investigation on the effect of strength mismatch revealed that in the cases of under‐matched, higher failure pressures are obtained. Comparisons of current results with B31G‐2012 and DNV‐RP‐F101 demonstrated that both codes may produce somewhat conservative predictions on the failure pressure. Furthermore, an equation was proposed to evaluate the corrosion progress across girth welded pipelines.     

TC21钛合金电子束焊接接头超高周疲劳行为研究

采用超声疲劳试验方法(20 k Hz),研究TC21钛合金电子束焊接接头的超高周疲劳性能与断裂机理。结果表明,TC21钛合金电子束焊接接头的疲劳性能要远低于母材的疲劳性能。在短寿命阶段,电子束焊接接头和母材的疲劳裂纹均在表面萌生;当寿命增大时,两者疲劳裂纹的萌生位置均由表面转向内部,母材的疲劳裂纹主要萌生于内部显微组织,而电子束焊接接头疲劳裂纹主要萌生于内部焊接气孔缺陷。当寿命较长时,疲劳源区会出现"鱼眼"形貌特征,源区附近有白色颗粒状细晶区,即细晶区(Fine granular area,FGA),其应力强度因子在2.90~3.33 MPa·m1/2,与疲劳寿命没有直接关系,可以认为是疲劳裂纹扩展门槛值。此外,基于AKINIWA小裂纹扩展理论,定量分析气孔尺寸与TC21焊接接头疲劳极限、疲劳应力的关系。     

Correlation between microstructure and creep performance of martensitic/austenitic transition weldment in dependence of its post-weld heat treatment

This paper deals with the influence of post-weld heat treatment (PWHT) of T92/TP316H martensitic/austenitic transition weldment on the resulting microstructure and creep characteristics. Experimental weldments were fabricated by gas tungsten arc welding using a nickel-based weld metal (Ni WM). After the welding, two individual series of produced weldments were heat-treated according to two different PWHT procedures. The first “conventional PWHT” was carried out via subcritical tempering (i.e. bellow Ac₁ temperature of T92 steel), whereas the other one, the so-called “full PWHT” consisted of a complete reaustenitization of the weldments followed by water-quenching and final tempering. The use of “conventional PWHT” preserved microstructural gradient of T92 steel heat-affected zone (HAZ), consisting of its typical coarse-grained and fine-grained subregions with tempered martensitic and recrystallized ferritic–carbidic microstructures respectively. In contrast, the “full PWHT” led to the complete elimination of the original HAZ via transformation processes involved, i.e. the reaustenitization and back on-cooling martensite formation. The observed microstructural changes depending on the initial PWHT conditions were further manifested by corresponding differences in the weldments’ creep performance and their failure mode. The weldments in “conventional PWHT” state ruptured after long-term creep tests by premature “type IV failure” within their recrystallized intercritical HAZs. On the contrary, the long-term creep behavior of the weldments processed by “full PWHT” was characterized by their remarkable creep life extension but also by the occurrence of unfavorable “decohesion failure” along T92/Ni WM interface.