加氢反应器氢致开裂的有限元分析

本文以高温高压气相充氢试验为基础,采用有限元方法来模拟计算钢中的氢扩散及氢浓度变化规律,分析不同的冷却过程对材料氢致开裂的影响,结果表明,冷却速度越大,残留的氢浓度越高,加氢反应器越易发生氢致开裂。     

压力容器用钢氢致开裂的声发射试验研究

氢致开裂是在役压力容器一种常见的失效形式。声发射技术是监测动态破坏过程的有效手段。为了研究压力容器用钢氢致开裂过程的声发射特征,对电解充氢过程中的20R钢进行了监测。试验结果表明,碳钢表面电解充氢并腐蚀的过程和内部氢致裂纹的产生均会对材料的声发射活动产生影响。氢致裂纹的发展过程可分为孕育期和扩展期两个阶段,随着裂纹的生长,高幅声发射信号的数量明显增多。试验结果为压力容器现场检验提供了参考。     

波形膨胀节爆炸事故的失效分析

分析了波形膨胀节爆炸失效的原因，发现304不锈钢冷加工成形时（液压）发生马氏体相变，在湿硫化氢环境下含形变马氏体的304奥氏体不锈钢发生了湿硫化氢引起的氢致开裂（HIC）或应力导向氢致开裂（SOCHIC），当裂纹扩展到某一临界尺寸时便发生了低应力脆断型的爆炸事故。     

天然气管道开裂失效分析

摘要：对发生开裂的天然气管道进行了系统的分析与测试,如宏观分析、成分分析、金相组织分析、硬度测试、氢含量测试、扫描电镜观察等。结果表明,管道开裂的机理为氢致开裂,管道局部的划伤是管道发生开裂的主要原因。     

X90管线钢焊接接头氢致开裂敏感性研究

X90管线钢在石油天然气管道中具有广泛应用前景,其焊接接头在服役过程中存在氢致开裂(Hydrogen induced cracking,HIC)倾向。采用电化学氢渗透试验和预充氢慢应变速率拉伸试验(Slow strain rate tensile test,SSRT),对X90管线钢焊接接头的氢捕获效率和氢致开裂敏感性进行了研究。利用场发射扫描电子显微镜(Field emission scanning electronic microscope,FE-SEM)对试样断口形貌及裂纹处夹杂物进行观察和分析,采用氢微印技术(Hydrogen microprint technique,HMT)对显微组织中氢的局部分布和聚集进行分析。结果表明,不同充氢电流密度下,X90管线钢焊接接头SSRT试样的断裂位置均为焊缝,其氢致开裂敏感性明显高于母材。与X90管线钢母材相比,焊缝中氢扩散系数较小,氢浓度、可逆和不可逆氢陷阱密度均较高。焊缝中的针状铁素体、贝氏体组织晶界及其亚晶界和夹杂均是有效的氢捕获陷阱,具有较高的氢捕获效率;焊缝中尺寸大于2μm夹杂物的数量多于母材,氢致裂纹易在富Al、富S、富Si夹杂...     

电化学充氢条件下夹杂物对管线钢氢致开裂敏感性的影响

对X52、20、X70管线钢在0.5mol·L-1H2SO4溶液中进行电化学充氢试验,研究了钢中夹杂物形态、大小、数量、分布对管线钢氢致开裂(HIC)的影响。结果表明:X52钢的HIC敏感性远小于20钢和X70钢的;20钢中的MnS夹杂物并不是氢致裂纹的必然形核位置,而Al2O3、复合氧化物/铁的碳化物、硅夹杂物则是更为有害的氢致裂纹源;X70钢中以Al2O3、铁的碳化物造成的氢致开裂危害最大;相邻夹杂物形成的裂纹源不断扩展并合成了更大的裂纹。     

2205双相不锈钢氢致开裂行为的试验分析与模型预测

开展了2205双相不锈钢(Duplex stainless steel,DSS)氢致开裂(Hydrogen assisted cracking,HAC)行为的研究,考察了组织形态对2205双相不锈钢中氢致裂纹萌生和扩展的影响.结果表明,横向组织中的氢致裂纹扩展的长度比纵向组织中的裂纹更明显,裂纹优先萌生的位置在铁素体相...     

X80管线钢氢致断裂断口分析

用光学显微镜和扫描电镜观察了不同充氢电流下恒载荷拉伸试样、慢应变速率拉伸试样的显微组织和断口形貌。结果表明：随氢浓度增加、应力减小或应变速率降低，试样断口逐渐从韧性断口向脆性断口过渡；氢致开裂微裂纹通常在杂质处形成并呈不连续扩展，形成穿晶断裂。     

30CrMnSiNi2A钢轮轴表面镀硬铬区域开裂的原因及控制措施

未服役30CrMnSiNi2A钢轮轴在存放一段时间后,其表面镀硬铬区域出现裂纹,通过形貌观察、化学成分分析、显微组织观察、力学性能分析、氢含量及残余应力测试等方法研究了轮轴表面开裂原因,并提出了控制开裂的措施。结果表明:在电镀硬铬过程中渗入轮轴表面的氢和在磨削加工硬铬层时引入的拉应力的协同作用,导致轮轴发生氢致延迟开裂(氢脆);通过采取改进电镀工艺、镀后及时除氢、改善镀层磨削加工工艺和增加去应力退火工序等措施,该类轮轴未再出现开裂现象。     

残极破碎机静刀刀具断裂的原因

残极破碎机静刀刀具在使用不到4个月后发生断裂,采用宏观形貌观察、化学成分分析、金相检验、断口分析及能谱分析等方法对刀具的断裂原因进行了分析。结果表明:其断裂性质为氢致开裂型的应力腐蚀开裂;刀具在运输和使用过程中在环境介质和应力作用下,发生应力腐蚀,腐蚀过程中析出氢原子,氢原子扩散并聚集在晶界和夹杂物上,导致发生氢致开裂型的应力腐蚀开裂。     

液化石油气贮罐氢致分层的超声检测

简要地探讨液化石油气贮罐母材中氢致分层类缺陷的超声波检测，对检测的几种超声波反射波形进行了分析，并给出了确定缺陷边界和深度范围的方法。     

管线钢应力腐蚀破裂的机理与寿命预测

阐述了管线钢在高pH和近中性pH环境中的应力腐蚀破裂（SCC）机理，高pH SCC为阳极溶解，而近中性pH环境较复杂，主要观点是阳极溶解和（或）氢致开裂。分析了SCC裂纹萌生和扩展过程。介绍了相关的SCC寿命预测方法，重点讨论了Weibull分布和Monte Carlo模拟。     

Review on Stress Corrosion and Corrosion Fatigue Failure of Centrifugal Compressor Impeller

Corrosion failure,especially stress corrosion cracking and corrosion fatigue,is the main cause of centrifugal compressor impeller failure.And it is concealed and destructive.This paper summarizes the main theories of stress corrosion cracking and corrosion fatigue and its latest developments,and it also points out that existing stress corrosion cracking theories can be reduced to the anodic dissolution(AD),the hydrogen-induced cracking(HIC),and the combined AD and HIC mechanisms.The corrosion behavior and the mechanism of corrosion fatigue in the crack propagation stage are similar to stress corrosion cracking.The effects of stress ratio,loading frequency,and corrosive medium on the corrosion fatigue crack propagation rate are analyzed and summarized.The corrosion behavior and the mechanism of stress corrosion cracking and corrosion fatigue in corrosive environments,which contain sulfide,chlorides,and carbonate,are analyzed.The working environments of the centrifugal compressor impeller show the behavior and the mechanism of stress corrosion cracking and corrosion fatigue in different corrosive environments.The current research methods for centrifugal compressor impeller corrosion failure are analyzed.Physical analysis,numerical simulation,and the fluid-structure interaction method play an increasingly important role in the research on impeller deformation and stress distribution caused by the joint action of aerodynamic load and centrifugal load.     

X70管线钢的断口分离现象分析研究

在系列夏比冲击试验的基础上,使用OM、SEM、TFM等方法分析了国产X70管线钢断口分离现象产生的机理及其对性能的影响;研究表明：脆性带状组织及夹杂物是造成X70管线钢断口分离现象的主要原因;断口分离可使韧脆转变温度降低;X70管线铜中带状组织的氢致开裂（HIC）敏感性较高,为HIC的成核及扩展提供了便利场所。     

论高强度螺栓的材料及其强度问题

本文从高强度螺栓的服役条件出发论述了高强度螺栓选材的考虑因素。用低碳马氏体钢和中碳调质钢进行了静拉伸、偏斜拉伸、冲击韧性、疲劳强度和延迟断裂强度等试验。试验结果表明,与中碳调质钢相比,低碳马氏体钢的强度提高1/3以上,同时保持较高的塑性和韧性,螺栓的承载能力提高45～70%,而缺口偏斜敏感性并不显著升高;螺栓的疲劳强度与中碳钢调质态螺栓大体相同：低碳马氏体钢的延迟断裂敏感性比相同强度水平的40Cr钢小,并且在盐水和水中对延迟断裂是不敏感的。因此,选用低碳马氏体钢作高强度螺栓材料,不仅在综合机械性能方向有许多优点,而且其优良的工艺性能更是中碳钢不能比拟的。本文还进行了热处理前和后滚制螺纹对螺栓疲劳强度的影响试验,结果表明,热处后滚制螺纹可有效地提高螺栓的疲劳强度。根据本文的试验结果,作者对低碳马氏体螺栓钢的成分设计作了某些探讨。     

HAZ hydrogen cracking of 9Cr-0.5 Mo-1.7W steels

Advanced creep-resistant steels have been developed to meet the demanding requirements of fossil power plants that strive to improve the generation efficiency by enhancing the steam temperature and pressure. These are ferritic steels with nominal chromium content ranging from 2% to 12% with significant addition of tungsten besides Nb, V, and N in small level. One of the candidate materials is 9Cr-0.5Mo-1.7W steel, developed for steam circuit components of tubes, and pipes of power plants for an operating temperature of 600°C. Hydrogen cracking is a major issue in welding of this steel, due to solid-state metallurgical transformations that lead to untempered martensite in the HAZ of weld joint. The hydrogen cracking does not occur below a threshold stress level called critical cracking stress. The critical stress for cracking in this steel was determined by carrying out implant weldability tests using shielded metal arc welding process for various levels of diffusible hydrogen in the weld metal and an empirical model relating levels of diffusible hydrogen and time taken for cooling from 800°C to 500°C to the critical stress has been developed. Results of current study also showed that residual diffusible hydrogen plays a major role in deciding hydrogen cracking than the initial diffusible hydrogen in the weld metal.     

Effect of microstructure and chemical composition on cold crack susceptibility of high-strength weld metal

The effects of the microstructural constituents, chemical composition, and retained austenite on high-strength weld metal were studied using preheat-free steels and GMAW solid wires with a low hydrogen content. The cold cracking susceptibility of these GMAW wires was evaluated using the y-groove Tekken test. The results showed that acicular ferrite produced the greatest resistance to cold cracking and that the microstructure of the deposit was more important than the hardness and diffusible hydrogen content in low-hydrogen weld metal. Crack blunting and branching occurred when a crack propagated through fine acicular ferrite because of the fine interlocking nature of the microstructure. Alloying elements for nucleating acicular ferrite, such as Ti, Al, and V, are required for proper austenite grain size, and sequence of inclusion formation was identified in the present paper. Furthermore, the retained austenite was not found to play the role of a hydrogen trapping site and so had no effect on the cold cracking susceptibility at a low preheating temperature (≤100°C) and low heat input (≤1.5 KJ/mm) to the weld metal.     

2.25Cr-1Mo钢焊后产生焊接裂纹的原因及返修措施

本文针对 2 2 5Cr- 1Mo钢焊接后产生裂纹的原因进行了分析 ,结果表明产生裂纹的主要原因是氢浓度过高而引起的氢致延迟裂纹 ,并根据实际的产品特点提出了合适的返修措施。     

Microstructure and mechanical properties of laser-MIG hybrid welding of 1420 Al-Li alloy

This paper investigates the microstructure and mechanical properties of 1420 aluminum–lithium (Al-Li) alloy joints before and after heat treatment by CO₂ laser-metal inter gas (MIG) hybrid welding. The 5-mm-thick 1420 Al-Li alloy plates were welded by CO₂ laser-MIG hybrid welding. Full penetration joints without any defects were produced. Optic and scanning electron microscopy were used to study the microstructure and fractograph characteristics. The results show that the microstructures of the heat-affected zone (HAZ) and fusion zone exist as a predominantly discontinuous equiaxed dendritic structure and as a fine cellular dendritic structure, respectively. After heat treatment, the microstructures change from dendritic structure to a spheroidal crystal; the grain size of fusion zone is obviously larger than that of the base metal and the HAZ. Furthermore, the hardness recovers substantially to a level similar to that of the parent material. The tensile strengths of the joints in the as-welded condition and after heat treatment are 223 and 267 MPa, reaching up to 57 and 68 % of the parent materials’ strength, respectively. The fractographs show that the joint as-welded condition exhibits the characteristics of dominated dimples and a small amount tear ridges, which are associated with the mixed ductile and brittle facture mechanisms. The fracture mode transforms from a transgranular to an intergranular after heat treatment; cleavage cracking coupled with an intergranular microvoid coalescence fracture mechanism occurs.