0Cr17Ni4Cu4Nb传感器断裂原因分析

某力学传感器在出厂检验流程中发生断裂失效,为了确定失效原因,防止此类失效事件再次发生,实验对该传感器的力学性能、金相组织和断口形貌进行了分析,确定了断裂原因。结果表明,传感器的失效模式为氢致延迟开裂,材料中氢含量偏高和开裂位置机加工质量较差是导致传感器发生氢致开裂的主要原因。结合失效原因,提出了改进措施。     

冷轧厂全氢罩式退火炉内罩设备失效分析

昆钢冷轧板厂全氢罩式退火炉内罩于2004年进行增高改造，使用较短时间后。退火炉内罩增高部分发生严重腐蚀开裂泄漏，导致内罩设备提前失效，严重影响退火炉的安全生产。经过分析，确定材质是造成内罩严重腐蚀开裂的主要因素，更换材质对内罩增高部分改造,上述状况有所好转。但是要彻底解决内罩腐蚀开裂问题，需要弄清楚失效原因。     

全自动浸入式超声探伤在HIC评价中的应用

传统的氢致开裂(HIC)试样评价方法参考标准NACE TM0284,将试样进行4等分,金相检查3个截面上的裂纹,计算出CLR、CTR、CSR等3个裂纹率.在HIC评价中引入了全自动浸入式超声探伤技术,对试样进行了全面的评价,对裂纹进行了定位分析.同时,分析了全自动超声探伤的优缺点,并讨论了与传统评价方法的区别.试验材料包含了管材和板材,对氢致开裂敏感与不敏感的材料,亦比对了部分材料在不同溶液中的氢致开裂敏感程度.     

高强双相不锈钢活塞杆开裂原因分析

一种高强双相不锈钢活塞杆在加工完成后的存放过程中开裂。实验通过金相显微镜、扫描电子显微镜(SEM)、拉伸试验机、冲击试验机、硬度仪等手段，对其开裂原因进行了分析。结果表明：活塞杆横向和纵向强度均较高，纵向抗拉强度最高达1 145 MPa;布氏硬度为HBW347,高于设计要求(HBW241-285)上限21.8%;但横向韧性较低，断后伸长率最低2.0%,仅为标准要求下限值14%的14.3%,平均冲击吸收能量只有5.8 J,仅为标准规范下限值60 J的10.5%。活塞杆材料合金元素符合标准要求，活塞杆组织为回火马氏体+细条带状铁素体，但氢含量达5.4×10^-6(质量分数),高的氢含量导致在内部形成氢致延迟微裂纹是其纵向开裂的主要原因，条带状铁素体恶化了活塞杆的横向力学性能，对开裂起一定的促进作用。建议优化冶炼和热加工工艺，与此同时在活塞杆加工之前增加去氢退火，降低原材料中氢含量，以最大程度降低氢致延迟开裂倾向。     

热处理过程中氢致滚子开裂失效分析

通过体视显微镜、光学显微镜、扫描电镜及X射线能谱仪对一批送检失效滚子进行分析,滚子基体材料为20Cr钢。结果表明,滚子宏观失效形式分为三类,失效原因均为氢致脆断,沿晶断口平滑,呈冰糖块状,断面上有典型的“鸡爪形”发纹。氢脆失效主要是由滚子渗碳工艺后的直接淬火导致的,镀锌工艺也部分提供了氢的来源。     

管线钢在含氢气的煤制天然气中服役安全性评估

煤制天然气是我国煤炭清洁利用的重要发展方向.现有管道用于输送煤制天然气(最高氢分压为0.72 MPa)时需要考虑其中低压氢气的影响,因而需先进行氢致开裂安全性评估.本文利用高压釜环境下恒载荷实验和电化学充氢,模拟研究X-70管线钢和20#钢在不同氢含量下的氢损伤和氢致延迟开裂,并对其在煤制天然气中服役安全性进行评估.在总压12MPa(10 MPa N₂+2 MPa H₂)的高压釜中放置一个月,两种钢的金相试样均不出现氢损伤,U弯试样不开裂,加屈服强度σ_s的恒载荷试样不发生断裂.在含0.72 MPa的煤制天然气中长期服役时,进入两种钢的氢含量均远低于σ_s下发生氢致延迟开裂的门槛氢含量和出现氢损伤的门槛氢含量,因而X-70钢和20#钢在煤制天然气中长期服役均具有高的氢损伤和氢致开裂安全系数.      

X70管线钢抗氢致开裂性能研究

研究了4个批次X70管线钢抗氢致开裂(HIC)性能,结果表明,经硫化氢腐蚀试验后,试样表面均出现了氢鼓泡,仅A177批次出现氢致裂纹。试样内部夹杂物以及微观组织偏析导致了氢致裂纹的产生和生长。试样表面存在的硫化物和氧化钙夹杂物是导致氢致鼓泡产生的重要原因。     

氢致开裂机理研究

摘自北京科技大学研究生张统一的博土学位论文,导师:肖纪美教授。 本文对可逆性氢致开裂的弱键理论和氢致滞后塑性变形导致开裂的理论进行了研究。论文分四部分。(1)研究了氢对纯铁杨氏模量的影响。结果表明:纯铁中充入7～8 wppm的氢对纯铁的和原子键合力有关杨氏模量没有明显影响,充氢后表观杨氏模量的下降是由于材料内部缺陷状态的变化引起的;(2)讨论了氢在a-Fe中的应变场,并指出拉压应力下的氢渗诱数据可以求出氢在a-Fe中的应变场:(3)研究了     

氢致开裂机理研究

摘自北京科技大学研究生张统一的博土学位论文,导师:肖纪美教授。 本文对可逆性氢致开裂的弱键理论和氢致滞后塑性变形导致开裂的理论进行了研究。论文分四部分。(1)研究了氢对纯铁杨氏模量的影响。结果表明:纯铁中充入7～8 wppm的氢对纯铁的和原子键合力有关杨氏模量没有明显影响,充氢后表观杨氏模量的下降是由于材料内部缺陷状态的变化引起的;(2)讨论了氢在a-Fe中的应变场,并指出拉压应力下的氢渗诱数据可以求出氢在a-Fe中的应变场:(3)研究了     

浅析X80管线钢性能特征及技术挑战

随着国民经济的发展,各类高性能的钢材料得到了进一步的研究和应用。其中,X80管线钢是当前应用最为广泛的高强度管线钢之一,经过特定的工艺处理后,可以满足大管径、高压力环境下对管线钢的要求。因此,本文首先从冶金技术、冶金特征、焊接工艺等方面分析了X80管线钢的性能特征,进而针对腐蚀、氢致开裂、应变失效、焊缝区失效等几种服役失效类型进行了研究,以此为基础,探讨了发展X80管线钢的技术挑战,以为我国经济的可持续发展提供技术方面的保障。     

Stress Oriented Hydrogen Induced Cracking of Linepipe Steel

The stress oriented hydrogen induced cracking (SOHIC) is a typical hydrogen embrittlement phenomenon occurring in the linepipe steels exposed to sour environment containing H 2 S gas.However,even recently,the cracking mechanism of SOHIC has not been clarified because of lacking in the empirical data on the actual failure mode of SOHIC cracking.The factors affecting SOHIC are discussed in terms of metallurgy of high strength linepipe steel and hydrogen electrochemistry.The cracking mechanisms of SOHIC are examined by comparing them with the empirical failure mode of SOHIC which is developed by observation of the actual fracture sites of the hydrogen induced blister cracking (HIBC) and secondary cracks.Finally,the correlation between SOHIC and HIC is discussed.     

Effect of hydrogen on fracture and inert-environment sustained load cracking resistance of α- β titanium alloys

The fracture toughness and resistance to inert-environment sustained load crack propagation of α-β titanium alloys are usually reduced by increased hydrogen contents. The range of hydrogen contents over which either fracture toughness or threshold stress intensity for sustained load cracking was observed to decrease with hydrogen content is small (0 to 50 ppm) for Ti-6 Al-4 V, but further increases in hydrogen content can cause an increase in cracking rates. Sustained load crack propagation is characterized by a mixture of microvoid coalescence with cleavage, usually on a plane 12 to 15 deg from {0001} of the hep α phase with some {000l} cleavage. Cleavage apparently initiates ahead of the main crack front within a grains, usually near apparent α-β interfaces. Atmospheric moisture is inert with respect to sustained load cracking, that is, it does not cause stress corrosion cracking. Sustained load cracking was demonstrated in Ti-8 Al-1 Mo-1 V, Ti-6 Al-6 V-2 Sn, and several grades of Ti-6 Al-4 V.     

Fracture toughness of alloy 690 and EN52 welds in air and water

The effect of low- and high-temperature water with high hydrogen on the fracture toughness of alloy 690 and its weld, EN52, was characterized using elastic-plastic J _IC methodology. While both materials display excellent fracture resistance in air and elevated-temperature (>93 °C) water, a dramatic degradation in toughness is observed in 54 °C water. The loss of toughness is associated with a hydrogen-induced intergranular cracking mechanism, where hydrogen is picked up from the water. Comparison of the cracking behavior in low-temperature water with that for hydrogen-precharged specimens tested in air indicates that the critical local hydrogen content required to cause low-temperature embrittlement is on the order of 120 to 160 ppm. Loading-rate studies show that cracking resistance is improved at rates above ∼ 1000 MPa √m/h, because there is insufficient time to produce grain-boundary embrittlement. Electron fractographic examinations were performed to correlate cracking behavior with microstructural features and operative fracture mechanisms.     

车轮钢中的白点(一)

研究了车轮钢中白点形成的机理以及白点对断口形貌的影响.结果表明,氢和空位聚集导致鼓泡形核和长大,随着鼓泡内氢气压力的升高,裂纹从鼓泡核壁形核、扩展导致白点形成.白点的断口为准解理,和氢致滞后开裂断口相同,含白点试样的断口形貌依赖于断裂方式和试样厚度.钢中的白点除了产生二次裂纹和局部准解理断面外,对各种断口形貌均没有明显的影响.     

Grain boundary composition and associated hydrogen cracking of modified 4130 steels

Earlier work on AISI 4130 steels showed that phosphorus segregation to prior austenite grain boundaries was the primary cause for intergranular fracture of these steels when exposed to hydrogen. Reduction of P segregation to grain boundaries by removing the strong segregation couples of Mn-P and Si-P was expected to increase the hydrogen stress cracking resistance of 4130 type steels. Elimination of Mn and/or Si did reduce the concentration of P at prior austenite grain boundaries, but allowed segregation of S and N which acted in the same manner as P, promoting intergranular hydrogen stress cracking.     

Hydrogen effects on low-cycle fatigue of the single-crystal nickel-base superalloy CMSX-2

The effects of hydrogen on the low-cycle fatigue behavior of CMSX-2 [001]-oriented single crystals were examined. Fatigue tests were conducted under constant plastic strain amplitude control. Cyclic stress-strain curves and fatigue life data at different plastic strain amplitudes were determined for hydrogen-free and hydrogen-charged specimens. Two charging procedures, leading to different hydrogen concentrations, were applied. Hydrogen was found to decrease significantly the number of cycles to failure under the various experimental conditions. The increasing hydrogen concentration and ratio of the hydrogen to nonhydrogen-containing volume were found to shorten fatigue life in hydrogen-charged specimens. Based on the analysis of cyclic stress-strain curves and optical and transmission electron microscopy (TEM), it was established that hydrogen enhanced strain localization and promoted crystallographic, stage I cracking, leading to embrittlement. The overall fracture mechanism is discussed in conjunction with Duquette and Gell’s stage I fracture model.[16]     

裂解炉减温器及超高压蒸汽管线损坏分析及对策

介绍了大庆石化公司化工一厂的裂解炉减温器及出入口超高压蒸汽管线泄漏问题,通过失效分析认为,蒸汽管线开裂的失效性质可以确定为脆性延迟断裂类型中的热疲劳,造成管体开裂的原因为管内温度波动产生的交变热应力,锅炉给水调节阀不能按预期特性曲线工作,其波动是导致交变热应力产生的直接原因,管体内壁的原始加工沟痕是裂纹萌生的内在因素,加速了泄漏的发生。采取更换装置管线及恢复原设计方案可解决此问题。     

The structure of tempered martensite and its susceptibility to hydrogen stress cracking

A series of 4130 steels modified with 0.50 pct Mo and 0.75 pct Mo were tempered at temperatures between 300 and 700 °C for one hour. The changes in the carbide dispersion and matrix substructure produced by tempering were measured by transmission electron microscopy. These measurements were correlated with resistance to hydrogen stress cracking produced by cathodic charging of specimens in three-point bending. Scanning electron microscopy showed that specimens tempered between 300 and 500 °C failed by intergranular cracking while those tempered at higher temperatures failed by a transgranular fracture mode. Auger electron spectroscopy showed that the intergranular fracture was associated with hydrogen interaction with P segregation and carbide formation at prior austenite grain boundaries. Transgranular cracking was initiated at inclusion particles from which cracks propagated to produce flat fracture zones extending over several prior austenite grains. The 4130 steels modified with higher Mo content resisted tempering and showed better hydrogen stress cracking resistance than did the unmodified 4130 steel. The transition in fracture mode is attributed to a decohesion mechanism in the low temperature tempered samples and a pressure mechanism in the highly tempered samples.     

高压锅炉用水冷壁管失效开裂分析

应用扫描电镜、光学显微镜及X射线能谱仪等实验分析方法，对高压锅炉用水冷壁管失效开裂原因进行分析研究，结果表明．高压锅炉用水冷壁管开裂为应力腐蚀开裂，同时还有氢脆的作用。