共查询到19条相似文献,搜索用时 109 毫秒
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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σs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σs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. 相似文献
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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。 相似文献
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在酸性腐蚀介质环境服役的钢管,腐蚀介质与力学载荷耦合后将加速焊接接头失效.介绍了管线钢管焊接接头在酸性腐蚀介质环境下的失效模式,主要包括应力腐蚀开裂、氢致开裂以及考虑裂纹尖端H+扩散聚集的腐蚀断裂与腐蚀疲劳,并介绍了在酸性腐蚀介质环境服役管线管接头工程临界评估(ECA)的常规处理技术,以期能为今后该领域技术的发展提供参考. 相似文献
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34MnB5空心稳定杆在疲劳测试时发生开裂。试验结果表明,样品的裂纹源位于焊缝处。焊缝处的金相组织以氢脆敏感性极高的马氏体为主,且裂纹源附近区域存在晶粒粗大现象。样品裂纹源处的断口主要呈沿晶开裂形貌,且晶粒上布满细小韧窝。结合焊缝组织推测该样品的断裂行为应为氢致开裂。通过EBSD分析发现,氢促进位错面滑移,使沿晶断口、氢致裂纹周边存在明显高应变区;氢致裂纹大多沿着大角度晶界扩展,并在小角度晶界附近停止延伸。 相似文献
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牙轮大轴氢致断裂的分析 总被引:1,自引:0,他引:1
以某厂生产的石油机械零件牙轮大轴的断裂为例,用扫描电镜、电子探针等方法观察分析断口,按一般脆性断裂故障树分析思路,结合该零件的制造工艺过程进行断裂原因分析,结果表明,牙轮大轴的断裂为典型的氢致断裂,同时对机械零部件的氢脆断裂失效进行了相关讨论。 相似文献
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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。 相似文献
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采用化学分析、扫描电子显微镜、全自动洛氏硬度计、光学显微镜等手段,对断裂的高强度锁扣进行了成分、断口形貌、硬度及组织等分析。分析结果表明,锁扣断裂原因为酸洗和电镀工序渗氢,且镀锌后未及时进行去氢处理,导致车门锁扣在装配前即发生氢致延迟断裂。同时,本文对氢脆提出了预防控制措施。 相似文献
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LIU Shuo 《Baosteel Technical Research》2021,15(4):41-47
Pipeline transportation is an economical,safe,and efficient transportation method for transporting oil,natural gas,mineral slurry,and other fluids.Welding is the most critical construction process in pipeline engineering and is crucial in the safe operation and service of an entire pipeline system.Theoretically,the girth welded joint is the weakest link in a pipeline system.The unevenness of the structure and performance of the joint caused by welding frequently results in the failure of the welded joint before the failure of the base material of the pipe body,causing the pipeline to leak or even break.For steel pipes used in an acidic corrosive medium environment,the integration of the corrosive medium and mechanical load will accelerate the failure of the welded joint.This article reviews the failure modes of pipeline welded joints in acidic corrosive media,including stress corrosion cracking,hydrogen-induced cracking,and corrosion fracture,and corrosion fatigue considering the diffusion and accumulation of H+at the crack tip.It also reviews service pipelines in acidic corrosive media.The general processing technology of pipe joint engineering critical assessment(ECA)is investigated to provide a reference for the future development of technology in this field. 相似文献
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Howard G. Nelson 《Metallurgical and Materials Transactions A》1976,7(4):621-627
A study has been conducted of the terrace-like fracture morphology of gaseous hydrogen-induced crack growth in acicular alpha-beta
titanium alloys in terms of specimen configuration, magnitude of applied stress intensity, test temperature, and hydrogen
pressure. Although the overall appearance of the terrace structure remained essentially unchanged, a distinguishable variation
is found in the size of the individual terrace steps, and step size is found to be inversely dependent upon the rate of hydrogen-induced
slow crack growth. Additionally, this inverse relationship is independent of all the variables investigated. These observations
are quantitatively discussed in terms of the formation and growth of a thin hydride film along the alpha-beta boundaries and
a qualitative model for hydrogen-induced slow crack growth is presented, based on the film-rupture model of stress corrosion
cracking. 相似文献
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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. 相似文献
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Experiments on commercial and laboratory heats of a 5 pct Ni steel have delineated a wide range of hydrogen-induced cracking
behavior. Both precracked and notched specimens were tested in 0.21 MPa H2 gas at room temperature; the microstructure and hardness were held essentially constant. One extreme of behavior was exhibited
by specimens with negligible amounts of intergranular weakening due to impurity segregation; here, strain-controlled, plasticity-related
cracking occurred along surfaces of maximum shear stress within the prior austenitic grains. As impurity segregation increased
(due to 480 °C aging of samples with Mn and Si) increasing amounts of stress-controlled cracking occurred along prior austenite
grain boundaries. The latter produced a steady decrease in the stress intensity for crack extension and the local stress for
fracture of the notched bars. The mechanisms involved and the practical implications of these phenomena are discussed. 相似文献
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Howard G. Nelson 《Metallurgical and Materials Transactions A》1976,7(5):621-627
A study has been conducted of the terrace-like fracture morphology of gaseous hydrogen-induced crack growth in acicular alpha-beta titanium alloys in terms of specimen configuration, magnitude of applied stress intensity, test temperature, and hydrogen pressure. Although the overall appearance of the terrace structure remained essentially unchanged, a distinguishable variation is found in the size of the individual terrace steps, and step size is found to be inversely dependent upon the rate of hydrogen-induced slow crack growth. Additionally, this inverse relationship is independent of all the variables investigated. These observations are quantitatively discussed in terms of the formation and growth of a thin hydride film along the alpha-beta boundaries and a qualitative model for hydrogen-induced slow crack growth is presented, based on the film-rupture model of stress corrosion cracking. 相似文献
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Gaseous hydrogen-induced cracking of Ti-5Al-2.5Sn 总被引:2,自引:0,他引:2
The kinetics of hydrogen-induced cracking have been studied in the Ti-5Al-2.5Sn titanium alloy having a structure of acicular
α platelets in a β matrix. It was observed that the relationship between hydrogen-induced crack growth rate and applied stress
intensity can be described by three separable regions of behavior. The crack-growth rate at low stress-intensity levels was
found to be exponentially dependent on stress intensity but essentially independent of temperature. The crack-growth rate
at intermediate stress-intensity levels was found to be independent of stress intensity but dependent on temperature in such
a way that crack-growth rate was controlled by a thermally activated mechanism having an activation energy of 5500 cal per
mole and varied as the square root of the hydrogen pressure. The crack-growth rate at stress-intensity levels very near the
fracture toughness is presumed to be independent of environment. The results are interpreted to suggest that crack growth
at high stress intensities is controlled by normal, bulk failure mechanisms such as void coalescence and the like. At intermediate
stress-intensity levels the transport of hydrogen to some interaction site along the α-β boundary is the rate-controlling
mechanism. The crack-growth behavior at low stress intensities suggests that the hydrogen interacts at this site to produce
a strain-induced hydride which, in turn, induces crack growth by restricting plastic flow at the crack tip. 相似文献
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The effect of hydrogen on the mechanical properties of a series of nineteen experimental heats of 21-6-9 stainless steel was
investigated. The nineteen material groups covered a variety of forging processes, strength levels, grain sizes, and microstructures.
The data show that absorbed hydrogen acts as an interstitial strengthener which increases the flow stress of 21-6-9 similar
to the effects of carbon, nitrogen, and other interstitial atoms. The true stress for tensile instability was observed to
be ∼1130 MPa for both uncharged and hydrogen charged specimens and appeared to be independent of process variables. Thermal
charging and/or tensile testing in high pressure hydrogen indicates this austenitic stainless steel is susceptible to hydrogen-induced
cracking at grain boundaries, slip bands, and other interfaces. A lack of hydrogen-induced effects at true stresses below
1100 MPa indicates a lower limit for the hydrogen-induced reduction in interfacial strength. Above a true stress of 1100 MPa
the extent of hydrogen induced reductions in interfacial strength is dependent on hydrogen concentration and increases as
the hydrogen concentration increases. These observations are discussed in terms of several proposed hydrogen embrittlement
theories. 相似文献