俄罗斯泰纳线输油管线工程用K60钢级直缝埋弧焊管的残余应力测试分析

以巨龙钢管有限公司生产的俄罗斯泰纳线输油管线工程用K60钢级直缝埋弧焊管为测试用管，采用切块法测试了直缝埋弧焊管扩径前后的残余应力变化，并对钢管残余应力的分布特征及扩径对残余应力的改善效果进行了分析。测试分析表明：钢管扩径前存在较大的残余应力，扩径对消除钢管残余应力效果明显。     

应变时效及去应力退火对未扩径钢管力学性能的影响

通过对应变时效去及去应力退火前后未扩径钢管拉伸、冲击、硬度、导向弯曲试验的对比,分析了应变时效及去应力退火对未扩径钢管力学性能的影响。结果表明,对未扩径的钢管先经过250℃应变时效,再经过600℃去应力退火后,未扩径钢管的力学性能得到改善,表现为母材的屈服强度、抗拉强度及伸长率升高,屈强比略有减小;焊缝的抗拉强度和硬度得到提高。母材、焊缝及热影响区的冲击性能略有下降,下降幅度对其冲击性能不会造成较大影响。经应变时效及去应力退火后焊缝弯曲试样未出现裂纹。合理的应变时效及去应力退火,可提高钢管的综合力学性能,且可以充分消除焊接残余应力。     

GH4169疲劳试样加工残余应力的表征及其对低周疲劳寿命的影响

为了探究GH4169合金低周疲劳试样加工过程中表面残余应力的变化及残余应力对低周疲劳性能的影响,采用X射线衍射法对“车 磨 抛”不同加工工艺的试样表面残余应力进行表征及对成品试样进行残余应力层深度测试,通过中子衍射法对试样内部进行残余应力测试。采用电液伺服万能试验机进行了低周疲劳试验。结果表明：GH4169合金低周疲劳试样加工表面残余应力随着切削量的增加由表面残余压应力变为残余拉应力。根据残余应力层深度测试,机加工对试样表面造成残余应力层深度小于0.01 mm,内部残余拉应力减小;根据疲劳试验结果,GH4169合金疲劳寿命与表面轴向残余压应力呈正相关关系。     

GH4169疲劳试样加工残余应力的表征及其对低周疲劳寿命的影响

为了探究GH4169合金低周疲劳试样加工过程中表面残余应力的变化及残余应力对低周疲劳性能的影响，采用X射线衍射法对“车 磨 抛”不同加工工艺的试样表面残余应力进行表征及对成品试样进行残余应力层深度测试，通过中子衍射法对试样内部进行残余应力测试。采用电液伺服万能试验机进行了低周疲劳试验。结果表明：GH4169合金低周疲劳试样加工表面残余应力随着切削量的增加由表面残余压应力变为残余拉应力。根据残余应力层深度测试，机加工对试样表面造成残余应力层深度小于0.01 mm，内部残余拉应力减小；根据疲劳试验结果，GH4169合金疲劳寿命与表面轴向残余压应力呈正相关关系。     

热处理对表面纳米化工业纯锆疲劳性能影响研究

采用表面机械研磨处理(SMAT)对工业纯锆进行表面强化,使材料表面组织细化并引入残余压应力,通过热处理(HT)使表层残余压应力释放而纳米晶尺寸保持不变。利用光学显微镜(OM)和透射电子显微镜(TEM)对试样表层显微组织进行表征,利用X射线应力仪测试距试样表面不同深度处残余应力,通过四点弯曲疲劳实验对热处理前后试样疲劳性能进行测试,利用扫描电子显微镜(SEM)对疲劳断口形貌进行观察,探讨晶粒细化及残余压应力对疲劳性能的影响。结果表明：SMAT使工业纯锆表层形成150μm左右变形层且最表面晶粒细化至35 nm左右,并得到深度为334 μm最大应力为-695.5MPa的残余压应力层;热处理后SMAT处理工业纯锆表层残余压应力场深度减至115μm、最大压应力降为-148.8MPa,残余压应力场的变化对裂纹源位置及材料的疲劳极限影响明显。SMAT处理使工业纯锆疲劳极限较未处理试样提升23%;通过热处理使其表层残余压应力释放后,其疲劳极限较未SMAT处理试样疲劳极限提高13%。     

冷拔钢管的残余应力测试与结果分析

分析盲孔法测量冷拔钢管表面残余应力的测试结果,得出冷拔钢管各工序表面残余应力的分布规律,并将理论分析结果与测试结果进行对比;根据应力分布测试结果,优化冷拔加工工艺;提出消除冷拔钢管有害残余应力的方法与措施。分析认为:等径冷拔工艺生产的冷拔钢管,其表面残余应力很小,均为压应力,材料的综合性能良好;两道次冷拔中间增加一次退火,对消除成品表面残余应力没有明显效果;总变形量不变的情况下,增大第一道次冷拔变形量,减小第二道次冷拔变形量,可得到表面残余应力更小的冷拔钢管。     

复合强化对渗铝K403合金组织和力学性能的影响

针对航空发动机涡轮叶片榫头渗铝污染后产生的尺寸偏大和力学性能下降的问题,采用水吹砂+振动光饰和水吹砂+喷丸强化+振动光饰两种复合方法对渗铝后的K403合金试样进行处理,研究复合方法对K403渗铝试样微观组织和力学性能的影响。对两种方法处理后试样的微观组织、渗铝层元素分布、物相组成、残余应力和疲劳寿命进行测试。结果表明:渗铝后,试样表面存在残余拉应力,渗铝层厚度约27.3μm,主要相为β-NiAl和α-Cr;水吹砂+振动光饰处理后,试样表面产生了360 MPa的残余压应力,试样的疲劳寿命提高了1.49倍;水吹砂+喷丸强化+振动光饰方法处理后,试样表层产生了较大的残余压应力,距离表面0.04 mm处残余压应力值最大,约为686 MPa,应力影响深度约0.2 mm,试样的疲劳寿命提高了3.44倍。     

残余应力对X80 UOE钢管耐电化学腐蚀性能的影响

采用极化曲线测试和交流阻抗分析研究了不同残余应力状态下X80 UOE管线钢母材和焊缝在NS4模拟土壤溶液中的电化学腐蚀行为。结果表明,残余拉应力的存在造成局部自腐蚀电位的降低,为应力腐蚀裂纹的产生起到加速作用;X80 UOE钢管的焊缝较母材更易发生腐蚀;但残余应力对X80 UOE钢管母材应力腐蚀行为的影响更大;高残余拉应力试样的表面膜层的阻抗最小,更容易发生局部溶解腐蚀破坏。     

退火对表面机械研磨处理工业纯锆显微组织和残余应力的影响

对经表面机械研磨处理(SMAT)的工业纯锆进行不同温度的退火处理,采用偏光光学显微镜(PM)和透射电镜(TEM)对其表层显微组织进行表征,利用X射线应力仪、显微硬度计分别测试距试样表面不同深度的宏观残余应力场及硬度。利用Voigt函数拟合X射线衍射峰,分析不同退火温度下微观应变和位错密度的变化规律。结果表明：对于经退火的SMAT试样,随着退火温度的增加,试样表面残余压应力逐渐减小,且残余应力场深度、最大残余应力及其对应的深度均大幅度降低;不同退火温度下,微观应变及位错密度均随距表层深度的增加逐渐减小。     

TC4钛合金激光冲击强化与喷丸强化的残余应力模拟分析

目的 通过对激光冲击强化和喷丸强化后的试样进行残余应力测试分析,得出两种工艺在残余应力形成机理、残余应力层深以及残余应力均匀性等方面的差异.方法 一方面采用有限元方法 模拟激光冲击强化及喷丸强化的过程,将材料在两种强化冲击下的响应进行对比,研究残余应力的形成过程,并对残余应力场的分布规律进行总结分析.另一方面,分别用两种强化技术处理TC4钛合金的表面,并用剥层X射线衍射实验测试材料表层的残余应力.最后将实验结果 与测试结果 进行对比,验证有限元模拟的有效性.结果 当这两种强化效果产生-500 MPa的表面平均残余应力时,激光冲击强化后的TC4钛合金表层残余压应力层深度可达0.6 mm以上,而喷丸强化后的TC4钛合金表层残余压应力层深度只有0.15 mm左右.结论 由于诱发材料塑性变形的机制不同,激光冲击强化往往能获得比喷丸强化更好的残余压应力深度,同时激光冲击强化的材料的表面残余应力分布也比喷丸强化的材料更均匀.     

Numerical simulation of stress and deformation of in-service welding onto gas pipeline

SYSWELD was used to simulate in-service welding process of gas pipeline of X70 pipeline steel. Welding thermal cycle, stress and deformation of in-service welded joint were studied. The results show that peak temperature of coarse grain heat-affected zone （CGHAZ） of in-service welding onto gas pipeline is the same with routine welding, but ts/5, ts/3 and ts/1 decrease at certain degree. For the zone near welded seam, axial stress and hoop stress in the inner pipe wall are compressive stress when welding source passes through the cross-section that is studied, but residual axial stress and residual hoop stress after welded are all tensile stress. Transient deformation and residual deformation are all convex deformation compared with the original pipe diameter size. Deformation achieves maximum when welding thermal source passes through the cross-section that is studied and then decreases during the cooling process after welding.     

基于正交试验设计的高温管道焊接工艺优化

P91耐热钢焊接接头广泛用于电厂管道,厚壁管道焊接残余应力分布比较复杂,而焊接接头残余应力的大小对其高温环境下运行的蠕变又有着较大的影响.文中运用正交试验设计方法,以焊接残余应力为评价指标,对P91耐热钢管道焊接的工艺参数进行优化没计,然后采用大型有限元分析软件ABAQUS对最优焊接工艺的焊接残余应力进行数值模拟,获得了P91厚壁管道焊接接头的残余应力分布状况.结果表明,焊接速度对焊接残余应力的影响最为显著,其次电弧电压、焊接电流和坡口间隙等.研究结果为优化高温管道焊接工艺,有效控制焊接残余应力提供了可能.     

磁应力检测技术在双金属复合管检测上的实践

在高腐蚀性油气输送管道中,已经使用双金属复合管,其中内层是较薄的耐蚀合金内衬层,起到防腐蚀的作用,外层是较厚的普通钢质输送管用作结构支撑增加管材强度。内衬耐蚀合金层与钢质管材结合处的缺陷,以及管线焊接施工中造成的焊缝处的缺陷,通常会造成外层钢管内壁腐蚀的加速,引发管道腐蚀穿孔而发生泄漏,影响油气输送管道的安全运行。针对常规内、外检测方法难于适用在役双金属复合管线的检测与评价,采取非接触磁应力检测与评价技术,在国内某油田集输管道进行了现场的检测实践,取得了较好的效果。     

Cr-Mo钢管子局部焊后热处理加热宽度准则的确定

采用粘弹塑性有限元方法从应力释放角度讨论了Cr-Mo钢局部热处理下各种优化加热条件.研究表明,局部热处理过程产生的瞬态和残余应力受蠕变性能和温度关系弹性模量等因素的影响.当加热宽度足够大时,局部热处理后的应力与炉中热处理的应力接近.通过与现有标准的比较,从应力释放角度位于焊缝中心5√Rt的加热宽度较为合理.提出了考虑焊接冷却过程Cr-Mo低温膨胀现象的相变模型.给出了焊接残余应力与局部焊后热处理应力的试验结果与模拟结果的对比.     

Measurement of residual stress in steel using the magnetic Barkhausen noise technique

Surface residual stresses on a structural beam steel sample were evaluated using a non-destructive technique based on the measurement of surface magnetic Barkhausen noise (MBN). MBN measurements were performed using a high resolution probe consisting of a small magnetic read head mounted between the poles of a ferrite U-core magnet. Applied stress magnitudes were correlated to MBN energy levels for calibration purposes. MBN energy measurements were done at various locations on the steel sample. The magnitude of the residual stress component along the sample beam axis was evaluated across the width of the beam using these calibration curves. The range of sensitivity of the MBN signal to stress as defined by the calibration curves was limited by the direction of easy magnetization. The effect of stress on the MBN signal was interpreted in terms of the active 180° domain wall population. The validity of the residual stress results was confirmed experimentally using conventional methods: cutting and sectioning and hole drilling. Possible sources of residual stresses and their distribution on the structural steel specimen are discussed.     

Investigations into the tendency to stress corrosion of joints welded in austenitic and duplex steels

Austenitic stainless steel is welded as a cladding on the inner surface of a reactor pressure vessel (RPV) made of low alloy steel. In order to assess the structural integrity of the RPV precisely, the residual stress distribution caused by weld-overlay cladding and post-weld heat treatment (PWHT) is evaluated. Since the cladding layer is very thin compared to the vessel wall, it is necessary to evaluate the residual stress distribution around the weld fusion line, which can be very steep. In this study, cladded specimens were fabricated using different welding methods. Residual stress measurements using both sectioning and deep hole drilling (DHD) methods were then performed to evaluate the residual stress distributions through the weld fusion line. Three-dimensional thermal-elastic-plastic-creep analyses based on the finite element method were also conducted to evaluate the residual stress caused by weld-overlay cladding and PWHT. It was shown that analytical results provided reasonable agreements on weld residual stress with experimental results. It was also clarified that the main cause of residual stress due to welding and PWHT was the difference of thermal expansion between weld and base metals.     

激光冲击处理后X80焊接接头表面质量对腐蚀性能的影响

利用激光冲击波对X80管线钢焊接接头进行强化处理,用金相显微镜、光学轮廓仪分析激光冲击处理前后金相组织与表面粗糙度,并用应力测试仪测试了激光冲击处理前后残余应力和残余奥氏体的变化,分析了激光冲击波改善焊接接头表面质量的机理.结果表明,激光冲击处理后焊接接头表面晶粒细化,表面粗糙度有所提高;激光冲击处理形成了残余压应力,残余奥氏体向马氏体转化;激光冲击处理后表面粗糙度和残余奥氏体对慢拉伸性能的影响起主要作用,内积功下降3.8%;激光冲击处理后应力腐蚀敏感指数I_SCC由50.94%下降至45.10%,残余压应力和晶粒细化是提高其抗应力腐蚀的主要机制.     

焊后热处理对P92钢管道焊接残余应力场的影响

采用红外热成像仪测量了P92钢管道在焊接过程中的温度场分布,由此获得P92钢焊接过程的温度循环曲线;采用有限元方法模拟了P92钢管道多层多道焊的整个焊接过程,获得焊接温度场分布,与P92钢焊接温度场实测结果吻合良好,验证了模拟计算的准确性;采用间接法,利用温度场结果计算了P92钢管道环焊缝焊接形成的残余应力场,并重点分析了焊后热处理前后的焊接残余应力变化情况.结果表明,焊后热处理对P92钢管道焊接残余应力具有明显的消除作用,但不能完全消除,焊缝中依然存在较大的拉伸残余应力.     

Case Study: Pitting and Stress Corrosion Cracking in Heat-Affected Zone of Welded Underground 304 Stainless Steel Pipe

A jacketed underground pipeline made of 304 stainless steel tubing to transport utility water in a petrochemical plant at ambient temperature was perforated after few months of operation. Perforation started preferentially at the outer bottom surface of the pipe in the weld heat-affected zones where the insulating coating was damaged. Detailed microstructural characterization was carried out to determine the cause of failure using optical metallography, x-ray diffraction, scanning electron microscopy combined with energy dispersive spectroscopy, and transmission electron microscopy. Experimental results indicated that the failure occurred by interaction between the outer bottom surface of the pipe and surrounding environment leading to pitting and stress corrosion cracking in the presence of chloride ions. This could have been aided by residual welding stresses and the characteristic low stacking fault energy of the material.     

核电SA508-3钢大型筒体环焊残余应力分析

为了准确地预测核电SA508-3钢的大型筒体环焊温度和残余应力变化规律,基于ANSYS有限元软件,引入子结构法优化焊接模拟过程,并比较模拟结果与试验数据.结果表明,文中采用的计算方法成功地模拟了更加接近真实的筒体环焊过程,且模拟结果与实测值基本吻合;焊缝上所有节点的热循环曲线相似,热影响区的模拟宽度为4 mm左右;筒体外表面焊缝中心线上任意节点的残余应力大小相近,仅在靠近筒体外表面焊缝中心线附近存在一定的轴向压应力,其它区域大部分为拉应力,环向保持较高的拉应力;筒体焊后产生内凹残余变形;结果可为分析大型筒体环焊残余应力提供参考数据.