动态充氢电流密度对BG110S油井管力学性能的影响

利用 MTS-810材料试验机测量了BG110S油井管在动态拉伸(边充氢边拉伸)实验中的力学性能,并利用扫描电镜观察分析了拉伸断口形貌,研究了动态充氢电流密度对油井管力学性能的作用,讨论了氢原子浓度对油井管氢脆敏感性的影响。实验结果表明：随着充氢电流密度的增加,BG110S试样的屈服强度和抗拉强度先增大后减小;试样的伸长率、断面收缩率及拉伸韧性连续降低;试样的拉伸断口形貌由韧性断裂特征向脆性断裂特征转变;试样的氢脆敏感性连续增加。当动态充氢电流密度i＜30 mA/cm2时,氢原子在 BG110S试样中呈现固溶强化作用,而当i≥30 mA/cm2后,氢原子在BG110S试样中则呈现氢致脆化作用。     

氢对中碳轴承钢C56E2微观缺陷影响

氢是造成钢铁材料失效的重要因素之一。本文通过对C56E2钢的微观缺陷观察、充氢实验和缺陷统计，结果表明，C56E2钢中氢可以导致夹杂物/基体界面出现脱粘现象，并在后续遗传至最终材料，淬火、回火热处理无法改善该微观缺陷。夹杂物平均脱粘率（AIDR）随着氢的等效扩散距离增加呈下降趋势，相关性较强，下降斜率与充氢时间无统一的规律性。AIDR与充氢时间无明显规律关系，AIDR总体随第一峰氢、第二峰氢和总氢含量的增加呈上升趋势，相关性较弱。充氢过程中氢沿着浓度下降的方向扩散，充氢实验时间（≤216 h）远远未达到氢完全形成破坏所需时间，氢含量在远端尚未达到最大值，且尚未充分转化并形成破坏。     

电流密度对TC4钛合金表面熔盐电解渗硼的影响

以TC4钛合金为基体进行熔盐电解渗硼,利用辉光放电光谱仪(GDOES)、扫描电镜(SEM)、X射线衍射仪(XRD)和显微硬度计研究电流密度对渗硼层厚度、成分、组织、相结构及硬度的影响。结果表明:电流密度在50~90 m A/cm2时,渗硼层晶粒随电流密度的增加由粗大变得细小,渗硼层厚度先增大后减小,电流密度为60 m A/cm2时渗硼层厚度最大。渗硼层不含Al,而V则易固溶于硼化物中。渗硼层主要由Ti B和Ti B2组成,在(111)晶面择优生长。渗硼层的显微硬度相对基体硬度提高了5倍。     

焊缝中氢的扩散行为及影响因素

 扩散氢会在焊缝中引起氢脆、延迟裂纹等，导致结构产生低应力断裂。为了研究氢的扩散行为，采用水银法和气相色谱法测定了逸出的扩散氢量，并采用真空抽取法测试了不同温度下残余氢的释放量。试验表明，扩散氢量不受焊道数量的影响，它的逸出时间随焊道数的增多而增长，逸出速度随合金含量的增多而降低。随着焊后冷速的降低，冷却过程中逸出的氢增多，测定出的扩散氢量减少；测氢试样在100~200℃保温时，逸出氢的总量变化不大，但逸出时间随温度的升高而明显缩短。残余氢量与扩散氢量的多少无关，它与焊缝的含氧量、组织和硬度等有关系。     

质子交换膜电解制氢氢气渗透研究进展

由于膜的吸水特性,高压质子交换膜(PEM)制氢（尤其是差压式,氢侧高压/氧侧常压）存在氢气渗透问题,影响电解堆的运行安全与效率。基于菲克定律描述的渗透通量与渗透率、分压差的关系,综述了温度/压力、膜水合程度、氢气分压差对氢气渗透的影响规律。在常规运行压力范围（3.5 MPa）内,扩散系数与溶解度主要受温度影响,温度升高则渗透率增大;氢气渗透率随膜水合程度的增加而增大;氢气分压差对渗透的影响表现出线性（渗透池环境）与非线性（电解制氢环境）两种关系,非线性可能源于膜透水性提升与水通道结构改变引起的对流渗透。考虑到电解制氢实际工况存在电流,综述了电流密度对氢渗透的影响,氢气渗透率随运行电流密度的升高而增大,氢过饱和是可能的影响机理,高电流密度下氢过饱和度升高,导致氢气通过膜的渗透增加。      

时效温度对贝氏体型冷作强化非调质钢力学性能的影响

 研究了时效温度对一种低碳Mn-B-Ti系贝氏体型冷作强化非调质钢力学性能的影响。结果表明：试验料的强度随时效温度的升高先是增加,并在250℃时存在一个峰值,随后强度又随时效温度的升高而降低,当温度升高到400℃以上时强度明显降低;试验料的塑性和屈强比则随时效温度的升高逐渐增加,其中后者增加的幅度更显著。与未充氢试样相比,试验料拉拔并充氢后的延迟断裂性能显著降低。随着时效温度的升高,充氢试样中的氢含量降低,缺口抗拉强度RBN和延迟断裂强度比R缓慢增加,当时效温度大于200℃时,RBN和R则明显增加。因此,在满足保载永久伸长变形量及强度和塑性要求的前提下,应选择合适的时效温度,以保证材料的延迟断裂性能。     

铌中氢的行为

本文用室温电解法在多晶铌中渗氢,研究氢在铌中的行为。金相、扫描电镜和离子探针分析表明,氢含量不高时氢化物首先在晶界析出,然后向惯习面扩展。氢化物形态与氢含量有关。低的氢含量生成片状氢化物;高的氢含量形成氢化物畴结构。有人用马氏体相变的唯象晶体学理论推断氢化物可能的析出面,指出氢化物的惯习面随氢含量而变。我们用X射线劳埃背射法测出纯铌中氢化物析出惯习面为{130}c,{111}c,用X射线粉末法确定在室温电解渗氢6小时(电流密度0.2安/厘米~2)所形成氢化物的结构与NbH0.89相同。     

搪玻璃用热轧中厚钢板氢穿透时间及贮氢性能

 搪玻璃用中厚钢板是制作搪玻璃设备的关键材料,要求钢板在搪玻璃过程中具有良好的贮氢性能和抗鳞爆性能,但长期以来主要使用普通压力容器用中厚钢板Q245R,极易产生鳞爆。因此,对比常用的含0.16% C+0.013% Ti(质量分数)的热轧正火态中厚钢板Q245R,设计并工业化生产了w(C)=0.10%、w(Ti)=0.10%的搪玻璃用热轧中厚钢板B245GT,通过光学显微镜、渗氢试验和透射电镜等研究和对比分析了厚度为20 mm的2种钢板在表层、厚度1/4处和1/2处的显微组织、氢穿透时间和贮氢性能,观察并分析了B245GT中的析出相。结果表明,Q245R钢板的显微组织由带状珠光体和铁素体组成,而B245GT钢板由铁素体和极少量珠光体组成,珠光体组分远低于Q245R。对测定氢穿透时间的试样厚度归一化后,Q245R沿不同厚度处的氢穿透时间TH₂介于2.7~4.4 min/mm2,均远低于阈值6.7 min/mm2,B245GT钢板沿不同厚度处的TH₂为11.6~13.6 min/mm2,显著高于Q245R和阈值。比较不同厚度处的TH₂可以看出,Q245R钢板表层的TH₂最高、1/2厚度处即中心层的最低,而B245GT 1/2厚度处的TH₂最高、表层的最低,且从表层到1/4厚度处和1/2厚度处更加均匀。因此,w(C)≤0.10%、w(Ti)≥0.10%的B245GT中,足量的合金元素钛形成含钛的夹杂物和析出相是有益的贮氢陷阱,大量的第二相粒子显著地提高了钢板在搪玻璃过程中的贮氢性能和抗鳞爆性能,完全满足搪玻璃设备的制作要求。     

鞍钢搪瓷用热轧带钢的开发与应用

制取了9种不同Ti含量的试样,通过实验室正火处理等方法调整析出相的析出状态,通过测试氢渗透时间、搪瓷试验等研究了Ti含量和析出状态对抗鳞爆性能的影响。结果表明,氢渗透时间随Ti含量及Ti／C比值的升高而延长。当Ti以析出粒子存在时,钢板具有更好的抗鳞爆效果。介绍了基于研究结果开发的双面搪瓷用热轧钢板的技术特点、实际性能水平和应用情况。     

氢致绝缘铁氧体材料电学改性研究

研究了在电化学原子氢作用下绝缘NiZnCu铁氧体陶瓷的电阻和介电性能变化,并研究了电化学原子氢处理所用阴极电流密度(30~120 A.m-2)和温度(20~60℃)对氢致半导化的影响。研究结果表明,在原子氢处理初期,绝缘N iZnCu铁氧体陶瓷电阻率急剧下降,出现半导化,然后随处理时间延长而下降减缓,并逐渐趋稳;介电常数随原子氢处理时间延长而逐渐增加,达到一个极大值后,又出现下降。电流密度与温度对铁氧体半导化的速率和程度的影响没有简单的单向关系。在120 A.m-2,40℃下进行原子氢处理时,铁氧体电阻率降低最快,在2 m in内从8.29×108Ω.m下降到1.32Ω.m,下降了近9个数量级,且电阻率下降趋稳后的取值最小。从氢致N iZnCu铁氧体陶瓷半导化的过程,即吸附-侵入-扩散理论解释了温度以及电流密度对半导化的影响。并从电化学原子氢对铁氧体的掺杂和化学反应作用,对NiZnCu铁氧体绝缘陶瓷电阻和介电性能的变化进行了探讨。     

Predicting the kinetics of hydrogen generation at the tips of corrosion fatigue cracks

A model has been developed to predict the rate of generation of hydrogen atoms at the tips of fatigue cracks for steel cathodically protected in marine environments. The model incorporates crack-tip chemistry, scraping electrode measurements, and crack-tip deformation. The current density for generation of hydrogen atoms by reduction of water at the crack tip has been calculated for a range of electrochemical and mechanical variables (electrode potential, cyclic frequency, waveform, ΔK, and R value). The crack-tip current density is always greater than on adjacent crack walls and tends to increase with decreasing (more negative) potential. However, at potentials more negative than about-900 mV (SCE), at a cyclic frequency of 0.1 Hz, cathodic reduction of water on the external surface of the steel is predicted to be the dominant source of hydrogen atoms. Decreasing the frequency reduces the crack-tip current density and further emphasizes the dominance of bulk charging. There is little difference in hydrogen charging current densities at the crack tip for sinusoidal, triangular, or positive sawtooth waveforms, but square-wave loading provides a greater charging current. Increasing ΔK and R value have only a small effect on crack-tip current density but increase the area of the active surface and thus lead to more significant charging. Hydrogen-atom concentration profiles in fracture mechanics specimens and in tubular sections have been calculated for conditions in which bulk charging of the steel with hydrogen is dominant. To ensure that crack growth rates are “steady-state” values, test times have to be long enough to establish steady conditions of hydrogen charging. Crack growth data from fracture mechanics specimens may not be directly relevant to cracking in tubular sections because of hydrogen concentration gradients in the latter.     

Phase transformation of austenitic stainless steels as a result of cathodic hydrogen charging

The effects of cathodic hydrogen charging and aging on surface phase transformations were studied in solution treated and cold worked specimens of two austenitic stainless steels. Quantitative phase evaluation using an X-ray technique has shown that cathodic hydrogen charging and aging can result in a considerable amount of surface transformation toε andα ′ martensites. The extent of this surface transformation differs significantly from deformation-induced transformation at the same temperature, and abnormally high volume fractions ofε martensite are produced by the charging process. A minimum charging current density is necessary to induce transformation. In cold-worked samples, further surface transformation due to hydrogen charging and aging is inhibited by high volume fractions of pre-existing martensite. A. P. BENTLEY, formerly with the Department of Metallurgy and Materials Science, University of Cambridge     

Hydrogen Softening in the Thin Plate of Microcrystalline 316L Stainless Steel

The thin‐plate specimen of 316L austenite stainless steel was charged with hydrogen using a cathodic charging technique. Despite the short diffusion distance of hydrogen predicted by the diffusion‐controlled model for a semi‐infinite sheet, the Vickers hardness measurements revealed the full effect of hydrogen in the center of the cross‐sections of thin‐plate specimens as well as in the vicinity of the outer surfaces, which appears to be due to the short‐circuit diffusion mechanism along the grain boundaries. The room‐temperature tensile properties of both undeformed and deformed (20, 40%) samples were examined and compared. Hydrogen softening was apparent in both types of samples. For example, the 40% deformed sample showed an approximately 17 and 7% lower yield and tensile strength, respectively, after H charging at a strain rate of 2 × 10^?4 s^?1 with a concomitant decrease in ductility compared to that without H.     

超高强度热冲压用钢中H的扩散与氢致滞后开裂行为

采用阴极充H、恒载荷拉伸和电化学H渗透等试验方法,研究了超高强度钢22MnB5Nb的H扩散行为及氢致滞后开裂性能,并与常用热冲压钢22MnB5进行了对比。结果表明,H在22MnB5Nb钢中的扩散系数为3.02×10-7 cm2/s,显著低于22MnB5钢;与22MnB5钢相比,22MnB5Nb钢具有较好的耐氢致滞后开裂性能;这是由于22MnB5Nb钢晶粒较细小,增加了晶界的有效面积,使H陷阱分布更均匀,进而抑制H向裂纹尖端扩展,避免了局部H的富集。     

Study on hydrogen induced delayed fracture of 1500 and 2000MPa hot stamping steels

The application of hot-stamping steel (HS) in the automobile is an inevitable trend, but the hydrogen embrittlement sensitivity of HS steel still needs to be studied and improved. The hydrogen diffusion behavior and hydrogen embrittlement sensitivity of 1500 and 2000MPa hot stamping steels were studied by means of hydrogen penetration, slow strain rate tensile (SSRT), and fracture analysis. The results show that the apparent diffusion coefficient Dap (1.71×10-7cm2/s) of 1500HS is significantly less than the Dap (3.45×10-7cm2/s) of 2000HS; delayed fracture resistance of 1500HS is superior to 2000HS. From the fracture analysis, under the same hydrogen charging conditions, the fracture morphology of 1500HS changed from typical dimple ductile fracture to quasi cleavage brittle fracture, while 2000HS changed from dimple morphology to intergranular brittle fracture with the increase of hydrogen charging current density. While the deformation degree of 2000HS was very small, the local hydrogen content and stress value had reached the critical deal. The hydrogen reduced the bonding force between grains, resulting in the nucleation and propagation of microcracks. Therefore, with the improvement of the strength of HS steel, Ti and V micro alloyed elements should be properly added to form nano precipitates, as irreversible hydrogen traps to capture hydrogen atoms, hinder their diffusion and segregation, and effectively refine the structure and pinning dislocations, to improve the resistance to hydrogen induced delayed fracture of HS steel.     

Embrittlement of amorphous Fe40Ni38Mo4B18 alloy by electrolytic hydrogen

The effects of hydrogen on the tensile properties and fracture processes at room temperature were investigated. Specimens were tested at various strain rates in air or under different cathodic charging-current densities. The slopes of the stress-strain curves were essentially identical for all the specimens, except that the fracture points varied under different test conditions. Macroscopically, hydrogen only affected the elastic deformation behavior, but microscopically, the embrittlement was caused by the heterogeneous nucleation of localized plastic deformation. The degree of hydrogen embrittlement increased as the charging current increased or as the strain rate decreased. With the same charging current and time, longer dynamic charging resulted in more severe embrittlement. Before fracture took place, the strength of the alloy could be completely restored if hydrogen had been removed. Hydrogen diffusivity and solubility were used to draw the time-dependent hydrogen concentration profiles for the specimens under different charging conditions. The difference in the mechanical properties was correlated with the hydrogen concentration within the specimen. Formerly Graduate Student, Department of Materials Science and Engineering, National Tsing Hua University.     

Precipitates and Hydrogen Permeation Behavior in Vanadium-Bearing Microalloyed Low Carbon Steel

The precipitates and hydrogen permeation behavior were studied in the low carbon steel for enameling.During the preparation of samples,Ti containing and Ti free in vanadium-bearing microalloyed low carbon steel heating at 750℃ for 3 h,were adopted after cold-rolling.It was found that the a large number of fine VC,TiC,TiN and Ti 4 C 2 S 2 precipitates were in samples of Vanadium-bearing microalloyed low carbon steel with Ti element.And fine VC,Fe 3 C and MnS precipitates were in steels without Ti element.So the numbers of precipitates in the former is more bigger than the later.The activation energies for hydrogen diffusion in both samples are 26.5 and 23.7 kJ/mol,respectively.But at 25℃,the effective diffusion coefficients in the samples for Ti containing and Ti free in Vanadium-bearing microalloyed low carbon steel were measured as 2.71×10-6 and 4.22×10-6 cm 2 /s,respectively.No fishscaling defect occurred in the former and heavy fishscaling defect in the later.     

碳含量对Mn-B钢氢致延迟断裂行为的影响

采用电化学阴极充氢、氢热分析(TDS)和慢应变速率拉伸等试验方法,研究了4种不同碳含量Mn-B钢经不同热处理制度处理后的氢致延迟断裂行为。结果表明,在低于400℃回火时,随着碳含量的增加,试验钢的氢脆敏感性升高,当碳的质量分数高于0.3%后,试验钢的氢脆敏感性几乎不再增加;碳含量一定时,试验钢的氢脆敏感性随回火温度的升高而降低,且以20MnB试验钢的降低趋势最为明显;当回火温度达到600℃时,各试验钢对氢几乎不再敏感;TDS分析表明,试验钢充氢后的氢含量明显增加,其中以可扩散性氢量的增加为主;随碳含量的增加,试验钢充入的氢量增加;当碳含量一定时,随回火温度的升高,试验钢充入的氢量减少;SEM断口观察表明,试验钢充氢后的脆性断裂倾向性增加;随着碳含量的升高,试验钢的断裂方式由韧性断裂向脆性断裂转变;碳含量一定时,随回火温度的升高,试验钢由淬火态的脆性断裂向高温回火态的韧性断裂转变。     

Hydrogen pressure dependence of the fracture mode transition in nickel

A relationship between fracture mode, grain boundary composition, and hydrogen pressure has been determined for nickel straining electrode samples tested at cathodic potentials. This relationship can be expressed asCs/* αCH2/− nwhereCs/* is the critical grain boundary sulfur concentration corresponding to 50 pct transgranular and 50 pct intergranular fracture andP _{H 2} is the hydrogen pressure. The value ofn was found to be between 0.34 and 0.9. This expression was derived by relatingCs/* to the hydrogen overpotential with the Nernst equation. At a cathodic test potential of −0.3 V (SCE),Cs/* was equal to 0.20 monolayers of sulfur and at higher cathodic potentials or higher hydrogen pressures,Cs/* decreased such that at −0.72 V (SCE)Cs/* was equal to 0.045 monolayers of sulfur. The inverse hydrogen pressure dependence observed with cathodic hydrogen is similar to that for the hydrogen permeation rate or a critical hydrogen concentration derived by Gerberichet al.6 for gaseous hydrogen. This similarity between gaseous and cathodic hydrogen suggests that grain boundary impurities contribute to the hydrogen embrittlement process without altering the embrittlement process although this result does not indicate whether decohesion or plasticity dependent processes are responsible for the combined sulfur-hydrogen effect on the intergranular fracture of nickel.