Susceptibility to Hydrogen-Induced Cracking of Weld Beads on High-Strength Structural Steel

We study the hydrogen embrittlement and rupture of specimens of high-strength low-alloy steel with weld beads subjected to hydrogenation under the conditions of cathodic polarization. The specimens fail in the heat-affected zone on the boundary between the main metal and the weld bead in the zone of application of the latter and, especially, near its end. This explained by a higher hardness of the metal in this zone caused by the specific features of the temperature field formed in the process of welding. __________ Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 2, pp. 101–104, March–April, 2005.     

Cracking of Aluminum Alloy Rivets Used in Space Application: A Metallurgical Investigation

Adaptors used in check valve inlet pressure sensors were fabricated from austenitic stainless steel. Recently, during pretest operation and during hydrogen pressurization of an engine, a leak was noticed through the adaptor. Subsequent to disassembly, the leak was attributed to a crack in the adaptor. Detailed metallurgical investigations were carried out to understand the cause of cracking. Synergistic effect of chloride ions present in marine environment, the presence of residual stresses and sensitized grains of the material led to intergranular stress corrosion cracking. This article highlights details of investigation.     

Susceptibility of Steels Exploited in Water-Steam Environments to Hydrogen-Induced Cracking

We perform the detailed investigation of 10Kh2M and 12Kh1MF ferrite-pearlite steels operating in water-steam environments in different boilers and power plants in Poland and Ukraine for up to 240,000 h with an aim of evaluation of their susceptibility to hydrogen-induced cracking (blistering). For both types of steel, we establish similar regularities of the influence of operating conditions on the properties of materials. An abrupt deterioration of the mechanical properties of materials was observed after 110,000 h of operation. It was accompanied by an increase in the concentration of residual hydrogen and pronounced changes in the parameters of the crystal lattice of iron as well as in the volume fraction and morphology of the pearlite phase. The results of hydrogen-permeation tests were used to choose the parameters characterizing the susceptibility of steels to blistering. For both types of steel, we determine the correlation between their susceptibility to blistering and changes in the microstructure in the process of operation.     

矿山支护用热轧36U型钢开裂分析

通过分析化学成分、显微组织和夹杂物对矿山支护用热轧36U型钢开裂的原因进行了分析。结果表明:非金属夹杂物是导致36U型钢开裂的主要原因,基体中带状组织严重,并存在异常贝氏体组织均能引起钢材开裂。并提出了预防措施。     

Stress Corrosion Cracking of High Strength Steel Fasteners for Space Applications

Cadmium electrodeposited Afnor 35NCD16 steel fasteners in hardened and tempered condition are used in the Indian space program. Failures were observed in size M6X17L fasteners that were under assembly load for a period of four months in an integrated test set up which involved exposure to severe humid environments. During disassembly, few of the fasteners were found to be broken at head–shank junction. Detailed metallurgical investigations carried out on failed fasteners and those, which were in assembly but did not fail, revealed their failure was caused by the synergistic effects of stress and corrosion. An attempt is made in this case history to correlate the metallurgical features collected with the failure mode of the fasteners.     

Failure Analysis: Sulfide Stress Corrosion Cracking and Hydrogen-Induced Cracking of A216-WCC Wellhead Flow Control Valve Body

The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran’s sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H₂S environment before some pits and cracks were detected in all of them during the periodical technical inspections. One failed valve body was investigated by chemical and microstructural analytical techniques to find out the failure cause and provide preventive measures. The valve body alloy was A216-WCC cast carbon steel. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results indicate that flow control valve body failed due to combination of hydrogen-induced corrosion cracking and sulfide stress corrosion cracking. According to HIC and SSC laboratory tests and also with regard to cost of engineering materials, it was evident that the best alternative for the valve body alloy is A217-WC9 cast Cr–Mo steel.     

Challenges in Procurement of HIC Resistant Steel Pipes

Welded pipes ordered for wet sour service are required to be manufactured from hydrogen-induced cracking (HIC) resistant steel plates. Pipe manufacturers procure steel plates with HIC testing, and other additional requirements with respect to chemistry, mechanical testing, and non-destructive testing (NDT) to meet client requirements. There have been several worldwide instances when the pipes ordered for wet sour service have failed HIC test at the pipe mill resulting in significant project delays. The causes of HIC test failures range from deliberate mistakes to improper testing practices. Also, subtle changes in steel making and rolling practices contributed to the HIC test failure following the pipe fabrication. Saudi Aramco has established several lines of defense to prevent recurrence of similar failures. Saudi Aramco reservation on mandatory HIC test requirement on seamless pipes as per the latest API 5L 44th edition, is discussed.     

冷轧超低碳烘烤硬化钢再结晶温度测定及应用实践

在实验室模拟不同退火温度下冷轧BH铜的力学性能及金相组织变化。利用强度示差分析法确定BH铜再结晶温度,并经大生产实践验证确认;在此基础上,进一步确定了BH铜最优退火温度。     

舰艇用低磁钢的开发及应用

本文从舰艇对低磁钢的需求背景出发,简要介绍了舰艇用低磁钢的概况,并较详细地阐述了国内外舰艇用低磁钢研制的历史沿革和技术发展的现况,还给出其在舰艇中的应用实例,最后就我国舰艇用低磁钢发展思路进行了探讨。     

航空工业钛合金紧固件失效分析研究进展

分析了航空工业钛合金紧固件的受力条件,综述了国内外学者关于钛合金紧固件失效形式及影响因素的相关研究,详细介绍了氢含量、加工过程、热处理、金属头部流线、装配过程等影响因素,总结出在生产制造过程与装配过程中,进一步提高钛合金紧固件使用性能的工艺手段与措施.     

用止裂法研究X56G管线钢焊缝金属的应力腐蚀破裂

采用ＣＴ试样在恒位移ＳＣＣ试验机上，测试了Ｘ５６Ｇ管线钢焊缝在混合硝盐溶液中的应力腐蚀抗力和应力腐蚀裂纹扩展速率。试验结果表明：用止裂法代替传统的启裂法可以大大简化ＳＣＣ试验。通过力衰减曲线不仅可以研究材料应力腐蚀裂纹扩展速率ｄａ／ｄｔ，而且可获得ＳＣＣ的临界值，且ＪＭＳＣＣ是与施加的载荷无关的材料常数。     

FN-2合金及其在催化裂化装置波纹管中的应用

概述了耐高温、耐腐蚀的FN 2合金的基本性能及实际应用情况 ,认为FN 2合金是替代 18 8型奥氏体不锈钢用来制造波纹管的理想材料 ,可有效地防止波纹管的腐蚀破坏。     

淬硬轴承钢平面磨削变质层的特性

采用扫描电子显微镜(scanning electron microscopy,SEM)、维氏硬度仪和X射线衍射仪(X-ray diffraction,XRD)分别观测了不同磨削条件下淬硬轴承钢GCr15磨削表层的微观组织、显微硬度和残余应力,对淬硬轴承钢磨削变质层进行了系统的实验研究.研究发现,磨削表层由表及里依次是白层、暗层和基体组织,暗层与白层的厚度之比在1.6～3.2之间变动.白层由致密的细晶马氏体、碳化物和残余奥氏体组成,而暗层由不同的回火组织构成,白层主要是磨削热和材料的强烈塑性变形共同作用的结果.白层硬度最大值达到983 HV,比基体组织高,而暗层硬度值仅为512 HV,较基体组织低.白层表面存在大小为612.24 MPa的残余拉应力,且随着白层的增厚而增大,而暗层则呈现出残余压应力.当白层较厚时,白层内会出现微裂纹,其中以贯穿白层的中位裂纹以及白层外侧和白层/暗层过渡区的横向裂纹居多.     

高强度低合金调质钢两相区超塑性机理研究

研究了10CrNi3MoV钢超塑性温度拉伸应力应变特征,分析了不同程度变形钢的微观组织和断裂行为,用塑性应变分布场数值模拟研究了高强度低合金调质钢两相区超塑性机理。研究结果表明,低屈服应力的奥氏体相围绕高屈服应力的铁素体相呈网状联通分布,通过自身的塑性变形起到"润滑油"作用;经过一定程度的变形后,强烈的应变硬化使奥氏体相的应力超过铁素体相的屈服应力,促进铁素体相的塑性变形;高应变区的铁素体相转变生成奥氏体相,为后续变形补充"润滑油";持续的"塑变-相变"行为维持大变形中的整体连续性,材料表现为超塑性。     

HN2154非调质钢中Ti、Nb的控制

文章研究了加Ti、Nb对HN2154非调质钢的组织、力学性能和晶粒大小的影响。研究结果表明,随着Ti、Nb的加入,HN2154钢的强度和硬度出现较明显下降,塑性略有提高,加Ti和加Nb对HN2154钢热轧状态下钢材的晶粒大小没有明显影响;但加Ti、Nb能细化HN2154钢经常规加热正火后的晶粒。加Ti和Nb对感应加热锻造后锻件的晶粒大小影响很小。根据研究结果,确定了HN2154钢中Ti、Nb的控制。     

Thermoelastic Characterization of Changing Phase Distribution in Hardened Steel by Laser Ultrasonics

The increase of hardness of steel during a heat treatment intended to give components more performance is a result of a drastic change in grain size and microstructure, which in turn can be analyzed via changes in acoustic wave scattering. The degree of scattering is related to the grain size, alloy phases, elastic anisotropy, and phonon spectra, which are connected with the structural heterogeneity. In this study, an axially oriented hardening profile in a steel rod was induced by a Jominy test. All-optical photoacoustic excitation and detection schemes were used to establish the relation between the hardness, the elastic modulus, the elastic scattering, and the thermal diffusivity on a series of eight samples cut out from the gradient part of the rod. For each sample, the scattering of the photoacoustically excited traveling surface acoustic waves detected in a heterodyne diffraction and beam deflection setup was extracted from their damping behavior at different wavelengths and frequencies. Also, the thermal diffusivity was determined by fitting the slow time evolution of the laser-induced photo-thermoelastic displacement signal, and was found to be decreasing with decreasing grain size and increasing hardness.     

地铁用U型头的开裂原因分析

地铁用U型头服役多年后在其表面发现多条裂纹,通过宏观分析、化学成分分析、非金属夹杂物评定、扫描电镜形貌分析和能谱分析以及金相检验对U型头开裂的原因进行了分析.结果 表明:U型头为302奥氏体不锈钢,在晶界析出碳化物,导致晶界周围贫铬,产生晶间腐蚀,随着零件运行时间的延长,被腐蚀的晶界作为裂纹源,在Cl-和外力的作用下,...     

非调质贝氏体钢转向节的弯曲疲劳试验

在MTS810,500kN试验系统上对五十铃非调质贝氏体钢转向节进行了弯曲疲劳试验.用SAFL方法进行数据处理,并用统计分析方法对实验结果进行了分析,对非调质贝氏体钢转向节的使用可靠性进行了预测.结果表明:在名义工作应力下,非调质钢转向节的疲劳寿命安全程度很大,SAFL方法评价零件的疲劳寿命是可行的.     

非调质钢曲轴感应淬火裂纹失效分析

目的分析非调质钢曲轴感应淬火时出现裂纹的原因。方法首先统计了裂纹的分布规律,并确定了裂纹源位置,之后通过金相检验、低倍检验,从锻打工艺、材料偏析等角度对裂纹进行了原因分析。结果产生在分模面位置的裂纹,是因产品结构造成该区域材料在锻打过程中发生流速不均,当材料的框型偏析位置在锻造挤压下流动到此处时,偏析的材料产生了微细空洞,该微细空洞在后续感应淬火时成为裂纹源而引起开裂。结论该裂纹的产生与材料框型偏析有直接关系。研究对控制非调质钢曲轴生产中的裂纹缺陷,提高曲轴生产质量,具有重要应用价值。