介绍了管线钢的微生物腐蚀及其危害，分析了近年来管线钢微生物腐蚀的失效案例，总结了管线钢微生物腐蚀的研究现状及管线的微生物腐蚀防治措施。从材料自身角度阐述了耐微生物腐蚀管线钢的研究进展，在此基础上提出了耐微生物腐蚀管线钢的发展方向。

Microbiologically influenced corrosion (MIC) has been an important reason leading to the damage and failure of pipeline steels, bringing a great economic loss. Development of MIC resistant pipeline steel is a new strategy to mitigate MIC from the aspect of material itself, having important scientific significance and application value. By proper Cu alloying design to the traditional pipeline steels, aiming at continuous release of Cu ions to kill the bacteria and inhibit the formation of bacterial biofilm, a creative strategy for improving the MIC resistance of pipeline steels has been proposed. This article briefly introduces the MIC of pipeline steel and its research status, and then the research progress on alloy design, microstructure, mechanical properties, hydrogen induced cracking resistance and MIC resistance of novel Cu-bearing pipeline steels are reviewed, and the research results on MIC resistance of the novel Cu-bearing pipeline steels under the laboratory conditions are stressed, and finally the future tendency on research and development of this type of novel steels is suggested.

With increase of the pipeline failure cases caused by microbiologically influenced corrosion (MIC), it is of great engineering significance to develop new measures for MIC mitigation. The Cubearing pipeline steel is a novel strategy for MIC mitigation from the material design aspect, which has shown good MIC resistance. Based on the previous reports, this review mainly summarizes the research progresses on phase transformation kinetics, thermoplasticity, and precipitation control of nanosized Curich phase, etc., in order to help better understanding of this novel type of Cubearing MIC resistant pipeline steels, guide the future production practice, and promote the application and development of Cubearing pipeline steels.

面对与日俱增的管线微生物腐蚀失效问题，发展微生物腐蚀防治新措施具有重要的工程应用意义。含铜管线钢是从材料自身设计角度发展的一种防治管线微生物腐蚀措施的新方案，已显示出良好的耐微生物腐蚀效果。在前期综述报道的基础上，主要总结了含铜管线钢的相变动力学、热塑性、纳米富Cu相的调控析出等方面的研究进展，以增进对新型耐微生物腐蚀含铜管线钢的认识和了解，并对含铜管线钢的未来实际生产具有重要指导意义，从而推进其应用与发展。

Microbiologically influenced corrosion (MIC) is becoming a serious problem for buried pipelines. Developing environmentally friendly strategies for MIC control is increasingly urgent in oil/gas pipeline industry. Copper (Cu) in steels can not only provide aging precipitation strengthening, but also kill bacterium, offering a special biofunction to steels. Based on the chemical composition of traditional X80 pipeline steel, two Cu-bearing pipeline steels (1% Cu and 2% Cu) were fabricated in this study. The microstructure, mechanical properties and antibacterial property against sulphate-reducing bacteria (SRB) and Pseudomonas aeruginosa (P. aeruginosa) were studied. It was found that the novel pipeline steel alloyed by 1%Cu exhibited acicular ferrite microstructure with nano-sized Cu-rich precipitates distribution in the matrix, resulting in better mechanical properties than the traditional X80 steel, and showed good MIC resistance as well. The pitting corrosion resistance of 1% Cu steel in as-aged condition was significantly better than that of X80 steel. A possible antibacterial mechanism of the Cu-bearing pipeline steel was proposed.

Microbiologically induced corrosion (MIC), particularly those caused by sulfate-reducing bacteria (SRB), is considered as a destructive mechanism in buried pipeline steels, which has received considerable attention since its discovery a century ago. Research has shown that sessile cells that are attached to a metal surface embedded in biofilms with extracellular polymeric substances (EPS) are responsible for the occurrence of MIC. However, the commonly used MIC control strategy, i.e., biocides, cannot perform sterilization of sessile cells because of the protection of the biofilm. Cu-bearing pipeline steel is a newly developed steel that can be used for MIC control in buried pipes. The continuous release of cytotoxic Cu ions from the steel matrix leads to MIC resistance. However, the influence of Cu content on MIC resistance remains unclear. A lower Cu content in steel is not beneficial to its MIC resistance, whereas a higher Cu content can increase the cost and may cause “hot shortness” during thermal processing. Therefore, clarifying the influence of Cu content on the properties of Cu-bearing pipeline steel is important for the practical application of the steel. In the present study, the influence of Cu content (0, 0.7%, and 1.34%; mass fraction) on the corrosion behavior of X65 grade Cu-bearing pipeline steel was investigated through electrochemical measurements and surface analysis during 14 d immersion in sterile and SRB-inoculated NS4 solutions, respectively. Experimental results demonstrated that the antibacterial properties and corrosion resistance of the steel improved with the increase of Cu content. When Cu content was increased to 1.34%, the pitting corrosion of the steel in the SRB-inoculated medium was almost suppressed. The protective corrosion products formed in the sterile medium and antibacterial Cu ions continuously released from the steel in the SRB-inoculated medium resulted in the remarkable corrosion resistance of Cu-bearing pipeline steels.

含Cu耐微生物腐蚀管线钢的开发和应用是解决管道微生物腐蚀难题的有效措施。本工作利用电化学测试及SEM、激光共聚焦显微镜(CLSM)等分析技术，研究了不同Cu含量(0、0.7%、1.34%，质量分数)的X65级管线钢在无菌和接种硫酸盐还原菌(SRB)的近中性模拟土壤浸出液(NS4)中的腐蚀行为，为耐微生物腐蚀管线钢的优化设计提供依据。结果表明，随着Cu含量的升高，含Cu管线钢的抗菌性能和耐蚀性能均有所提高；当Cu含量从0增加到0.70%时，试样表面的点蚀坑密度从714 cm^-2下降到244 cm^-2；当Cu含量达到1.34%时，点蚀坑密度进一步下降到67 cm^-2；含Cu钢在腐蚀过程中持续释放的铜离子在接菌环境中的杀菌作用和其对腐蚀产物层的改善作用，以及其在无菌环境中所形成的Cu₂O等保护性腐蚀产物是含Cu管线钢具有优异耐蚀性能的关键原因。

P92 steel has been used for a long time in the hightemperature components of power station, and the different welding process has an important effect on the microstructure and properties of the joint. The influence of automatic and manual welding processes on the microstructure and properties of P92 welded joints was studied, and the microstructure and mechanical properties of P92 steel welded joints under different welding processes were tested by means of scanning electron microscopy, transmission electron microscopy and mechanical property testing. The results show that the weld microstructure under different welding processes is tempered martensite microstructure, and the weld metal microstructure under automatic welding process is finer. Due to the small heat input of automatic welding, the width of the heat affected zone of P92 steel is only 10-15mm, while the massive ferrite structure can be seen in the heat affected zone of manual welding joints, and the width of the heat affected zone is 3-4mm. Compared with the manual welding process, the tensile strength of the joint welded by automatic welding is also higher, especially the impact toughness. Compared with the manual welding, the impact toughness of the weld metal of P92 automatic welding is increased by 100%, and the impact toughness of the heat affected zone is increased by 58%. Therefore, the automatic welding method can significantly improve the performance of P92 steel welded joints, and help to improve the high temperature creep resistance of joints.

P92钢长期被用于电站机组中的高温部件，不同的焊接工艺对其接头的组织和性能有着重要的影响。研究了自动焊和手工焊焊接工艺对P92焊接接头组织和性能的影响，并采用扫描电镜，透射电镜和力学性能测试等方法对不同焊接工艺下的P92钢焊接接头的显微组织和力学性能进行检测，结果表明：不同焊接工艺下焊缝组织均为回火马氏体组织，自动焊焊接工艺下焊缝金属组织较为细小；且由于自动焊焊接热输入较小，P92钢的热影响区的宽度仅为1.0～1.5mm，而在手工焊焊接接头热影响区可见块状铁素体组织，热影响区宽度在3～4mm。与手工焊焊接工艺相比，自动焊焊接接头抗拉强度也较高，尤其是冲击韧性，P92自动焊焊接接头的焊缝金属的冲击韧性相比手工焊提高了100%，热影响区冲击韧性提高了58%。因此采用自动焊焊接方法可显著提高P92钢焊接接头性能，并有助于提高接头的高温抗蠕变性能。

The corrosion behavior of X65 steel was investigated in the seawater inoculated with sulfate reducing bacteria (SRB) under the aerobic environment by electrochemical impedance techniques and immersion tests. The corroded morphologies and the composition of the corrosion products were investigated. The variation of the solution parameters including the bacterium number, the pH value and the soluble iron concentration were also investigated. The results indicated that in the SRB-containing system, the impedance responses presented a depressed semi-circle in the initial period, which then turned into the blocked electrode characteristic during the later immersion. The biofilm, mainly composed of extracellular polymeric substances, Fe(OH), γ-FeOOH and α-FeO, formed and degraded with the SRB growth. The soluble iron concentration initially increased, then rapidly decreased and later slowly increased. In the SRB-containing seawater under the aerobic environment, the X65 steel was corroded in the initial immersion. The corrosion became inhibited with the forming of the biofilm during the subsequent immersion. The inhibition efficiency rapidly increased in the logarithmic phase, remained stable in the stationary phase and then decreased in the declination phase. In the corrosion process, the biofilm metabolized by SRB played a key role in the corrosion inhibition of X65 steel.Copyright © 2018 Elsevier B.V. All rights reserved.

Sulfate reducing bacteria (SRB) are often the culprits of microbiologically influenced corrosion (MIC) in anoxic environments because sulfate is a ubiquitous oxidant. MIC of carbon steel caused by SRB is the most intensively investigated topic in MIC because of its practical importance. It is also because biogenic sulfides complicate mechanistic SRB MIC studies, making SRB MIC of carbon steel is a long-lasting topic that has generated considerable confusions. It is expedient to think that biogenic H2S secreted by SRB acidifies the broth because it is an acid gas. However, this is not true because endogenous H2S gets its H+ from organic carbon oxidation and the fluid itself in the first place rather than an external source. Many people believe that biogenic H2S is responsible for SRB MIC of carbon steel. However, in recent years, well designed mechanistic studies provided evidence that contradicts this misconception. Experimental data have shown that cathodic electron harvest by an SRB biofilm from elemental iron via extracellular electron transfer (EET) for energy production by SRB is the primary cause. It has been demonstrated that when a mature SRB biofilm is subjected to carbon source starvation, it switches to elemental iron as an electron source and becomes more corrosive. It is anticipated that manipulations of EET related genes will provide genetic-level evidence to support the biocathode theory in the future. This kind of new advances will likely lead to new gene probes or transcriptomics tools for detecting corrosive SRB strains that possess high EET capabilities.