Synergistic Effect of Phosphate and Calcium-Containing Pigments on the Corrosion Resistance of Galvanized Steel

We studied the corrosion inhibition of galvanized steel in artificial acid rain solution by chromate-free pigments containing phosphate and calcium ions. We used the methods of electrochemical impedance spectroscopy, potentiodynamic polarization, electron microscopy, and X-ray microspectrum analysis. It was established that the combination of modified zinc phosphate and ion-exchange-type calcium-containing pigment provides a significant synergistic anticorrosion effect on galvanized steel as compared with the same inhibiting pigments used separately. The charge-transfer resistance of the metal in acid rain solution saturated with this pigment composition approaches that in the same solution with a chromate inhibitor and is significantly higher as compared with the solutions of separate pigments. Owing to the combination of nonchromate pigments, a protective film is formed on galvanized steel, which represents a complex mixture of calcium and zinc phosphates and guarantees the corrosion inhibition of galvanized steel under mixed cathodic-anodic control.     

Stress Corrosion Cracking of Pipeline Steels

This paper provides a review of the differences between high pH and near-neutral pH stress corrosion cracking of pipeline steels,influencing factors,and mechanisms.The characteristics and historical information on both forms of SCC are discussed.The prospect for research in the future is also presented.     

高强度结构钢的大气应力腐蚀试验

本文报道了两种高强度结构钢GC-4和30XICHA试样在北京和海南岛进行大气应力腐蚀试验的有关情况及长达20年的试验结果。     

Self-similarity of the Crack Front in Stress Corrosion Fracture

In this letter, a new method was proposed to visualize the crack front in stress corrosion fracture of high strength steel. The fractal characteristic of the crack front was analyzed by measuring its fractal dimension and roughness exponent at the same time. The experimental results show that the irregularity of the crack front was partly self-affine.     

Nature of Microcracks in Ferritic Steels Occurred during Fracture under Conditions of Ductile-Brittle Transition Temperature Region

It has been shown by means of EBSD techique that fracture of ferritic steel in ductile-brittle transition temperature region, along with the formation of previously discribed cleavage microcracks, results in the formation of ductile microcracks. It has also been shown that microstructure of plastic zones under brittle and ductile fracture components produced by the main crack propagation differ significantly. Better developed plastic zone under ductile fracture component protects steel from overstress. The plastic zone under brittle fracture surface, apparently, has a reduced local plasticity. Consequently, the cleavage microcracks formation precedes the fracture process. During the main crack formation such microcracks occur in steel microvolumes located both in front of its tip and in adjacent to its edges microvolumes. Further propagation of the main crack is realized in steel which already contains scattered cavities and reduces to ductile fracture of the connections between them.     

应力波和爆生气体共同作用下裂隙区范围研究

为了得到更加符合实际的裂隙区范围计算公式,从理论上分析研究了在空气不耦合装药条件下裂隙区范围的计算方法。选取2号岩石乳化炸药和4种典型的岩石参数值,对基于初始损伤和粉碎区存在的岩石裂隙区半径进行了计算,并在此基础上运用阿贝尔原理和岩石止裂条件考虑了爆生气体准静态作用下裂隙的二次扩展。研究结果表明:粉碎区范围的大小会对裂隙半径极大值产生较大影响,并且当岩石初始损伤达到0.7~0.8时,裂隙区半径受到的影响程度达到最大;得到了应力波动作用和爆生气体准静态作用下裂隙区半径计算公式。     

A Fracture Probability Competition Mechanism of Stress Corrosion Cracking

The stress corrosion cracking (SCC) of austenitic stainless steel was studied via polarization, slow strain rate and scanning electron microscope (SEM) techniques. Many SCC mechanisms have been proposed in which hydrogen embrittlement and passive film rupture-repassivation theories are generally accepted, but they can hardly explain the SCC mechanism of austenitic stainless steel in acidic chloride solution adequately, because the steel is in active dissolution state and cathodic polarization can prevent it from occurring. Our experiment shows that the anodic current increases the creep rate and decreases the plastic strength of the material on single smooth specimen as well as at the SCC crack tip. The fractured surface was characterized as brittle cleavage, while the surface crack of smooth specimen was almost vertical to the tensile strength, which can confirm that the cracks were caused by tensile stresses. A fracture probability competition mechanism of SCC was proposed on the basis of the experimental results combined with the viewpoint of ductile-brittle fracture competition. When the anodic dissolution current is increased to a certain degree, the probability of fracture by tensile stress will exceed that by shear stress, and the brittle fracture will occur. The proposed SCC mechanism can riot only explain the-propagation of SCC cracks but can explain the crack initiation as well. The strain on the surface distributes unevenly when a smooth specimen is deformed, so does the anodic current distribution. The crack will initiate at a point where the anodic current density is large enough to cause the material at a specific point to fracture in brittle manner.     

辛基酚聚氧乙烯醚磷酸酯在钢表面的吸附与缓蚀作用

采用辛基酚聚氧乙烯醚为原料,合成了辛基酚聚氧乙烯醚磷酸酯(OPP)缓蚀剂,用挂片失重法、极化曲线法研究了OPP在饱和CO2的盐水中对Q235钢的缓蚀效果,通过吸附理论和热力学方法分析了OPP在钢表面的吸附行为.结果表明:OPP吸附在钢的表面,主要抑制了阳极反应,其吸附符合Fmmkin吸附模型,OPP用量仅需10 mg/L,其缓蚀效率即可达到95%以上.     

Role of Crack Tip Blunting in Stress Corrosion Cracking of High-strength Steels

This paper analyzes the role of crack tip blunting in stress corrosion cracking by localized anodic dissolution of high-strength eutectoid steel. The results of the tests show an apparent improvement of fracture resistance in aggressive environment — measured in terms of critical stress intensity factor - in relation to its reference value in an inert (air) environment. The explanation can be sought in the effects of crack tip blunting, i.e., of the increase of crack tip radius as a consequence of the dissolution process. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fracture of Polymethylmethacrylate under Pulse Loading Conditions

Crack propagation in polymethylmethacrylate has been investigated experimentally under shock loading conditions generated by a pulse magnetic field. Using microstructural investigations, dynamic fracture surfaces of polymethylmethacrylate were analyzed and compared depending on the distance from the notch tip. A diagram of various fracture types depending on the pulse loading duration has been constructed.     

Stress Corrosion Cracking and Blue Brittleness of Rotor Steels in High Temperature Aqueous Solutions

The tensile behaviors of two bolt steels 20Cr12NiMoWV and 25Cr2MoV, and rotor steel 30Cr2Ni4MoV used in a nuclear power plant were studied at different temperatures up to 280 degreesC in air and aqueous solution. The results showed that blue brittleness occurred near 230 degreesC and 180 degreesC for steels 30Cr2Ni4MoV and 25Cr2MoV, respectively. No blue brittleness was found for the steel containing higher Cr content. Susceptibility to stress corrosion cracking.(SCC) for the steels in aqueous solution at the test temperatures was very low except at the blue brittleness temperature. At the blue brittleness temperatures, however, the susceptibility to SCC was very high.     

管线钢的应力腐蚀研究现状及损伤机理

回顾了管线钢的应力腐蚀研究现状,并比较了发生在管道外的“经典型”的高pH应力腐蚀开裂与近十多年来发现和研究的近中性pH应力腐蚀开裂的特征,讨论了它们的影响因素以及开裂机理,最后展望了埋地管道的未来研究方向。     

Stress Corrosion Cracking and Blue Brittleness of Rotor Steels in High Temperature Aqueous Solution

1. IntroductionThe phenomenon of increase in yield strength anddecrease in elongation when soft steels are strained at150"C to 300"C, which makes them brittle, is calledblue brittleness[1]. When the diffusion velocity of thecloud of impurities like C and N, which surround thedislocations, matches the velocity of dislocation motion, the yield and aging will happen alternately orsimultaneouslys termed dynamic strain aging, resulting in blue brittleness[1]. For low alloy steels withmedium carbo…     

Influence of Temperature and Carbon-Dioxide Pressure on the Corrosion and Stress-Corrosion Fracture of Pipe Steels in Model Stratal Water

Materials Science - We study the influence of temperature (20–120°C) on the corrosion and stress-corrosion fracture of JFE-13CR-80 (I), JFE-13CR-95 (II), JFE-HP1-13CR-110 (III), and...     

脆性材料在双向应力下的断裂和失效研究

采用热力学方法对脆性薄片试样成功地进行了双向和单向平面拉伸试验,通过观察和记录试片中心的直通裂纹的扩展和断裂过程,测试出玻璃和陶瓷薄片的断裂韧性在双向和单向拉伸载荷时的差别．结果表明双向拉伸使裂纹阻力增强,平行于裂纹的应力对裂纹扩展有影响．该研究表明,对线弹性材料在双向载荷作用下,传统的应力强度因子准则不适用．裂纹张开的应变依赖性被证实在双向应力的断裂评价中．     

Cl-浓度对超级13Cr油管钢应力腐蚀开裂行为的影响

采用慢应变速率拉伸(SSRT)应力腐蚀开裂(SCC)的实验方法,通过应力应变(σ-ε)曲线、扫描电镜( SEM)、能谱分析(EDS)和X射线衍射分析(XRD)等手段分析了超级13Cr油管钢在NaCl溶液中的抗拉强度、延伸率、断裂时间、应力腐蚀开裂敏感性指数(kscc)和断口形貌,研究了Cl-浓度对其应力腐蚀开裂行为的影响.结果显示:当NaCl溶液浓度低于15％时,超级13Cr油管钢应力腐蚀的程度较轻,抗应力腐蚀开裂性能较好;而当NaCl溶液浓度大于25％时,其应力腐蚀的程度严重,抗应力腐蚀开裂性能较差;随溶液Cl-浓度的增大,超级13Cr油管钢的力学性能降低、抗SCC性能降低、应力腐蚀开裂的倾     

生物膜作用下管线钢应力腐蚀开裂行为研究进展

生物膜是一种依附于载体表面的特殊微生物聚集体,它的存在会创造异样的表面环境从而影响管线钢的应力腐蚀。近年来,管线钢在生物膜作用下应力腐蚀开裂行为已经成为学界的一个研究重点。本文综述了生物膜的形成和应力腐蚀开裂行为的机理及其影响因素,总结了关于生物膜和应力协同作用下管线钢应力腐蚀开裂行为的研究现状,分析了当前研究中存在的不足并作了展望。     

Corrosion Fracture of Structural Metallic Materials: Effect of Electrochemical Conditions in Crack

Abstract: The work is a compressed review based on the summarised results and the original approach for study of corrosion crack growth, taking into account local electrochemical conditions in the crack tip, which was developed at the Karpenko Physico‐Mechanical Institute of NASU. The model scheme of the pre‐fracture zone in the corrosion crack tip, which can be defined by the local values of pH of solution, electrode potential of metal E and stress intensity factor K_I is proposed. For its realisation, the special method and testing equipment for corrosion crack growth study and local electrochemical measurements in the crack were developed. The variation of the electrochemical conditions in corrosion cracks was studied, and it has been found that some stabilised levels of the pH and E values can be achieved in the tip of a non‐propagating and a propagating crack under static and cyclic loading during of exposure time. On this ground, the method for forecasting of the threshold stress intensity factor K_ISCC under stress corrosion cracking was proposed using these characteristic values of pH and E. This method was also adopted for the determination of the threshold stress intensity factor K_th under corrosion fatigue. The special method for determining corrosion fatigue crack growth rate diagrams based on consideration of extreme electrochemical conditions in the crack tip was developed. It has been proven that such diagrams reflect the extreme influence of the environmental factor on corrosion fracture of material, and they may be recommended as the base for the remaining lifetime calculation of the structural elements exploited under environmental conditions.