發(fā)布時(shí)間：2018-03-30 21:37

  本文選題：CO_2腐蝕　切入點(diǎn)：焊接性能　出處：《北京科技大學(xué)》2016年博士論文

【摘要】：為了應(yīng)對日益加劇的C02腐蝕問題帶來的嚴(yán)峻挑戰(zhàn),一類新型高性價(jià)比含Cr低合金鋼在近年得以開發(fā),并受到越來越多的關(guān)注和研究。含Cr低合金鋼作為目前經(jīng)濟(jì)性與安全性結(jié)合最為理想的抗CO2腐蝕管線鋼,有望替代傳統(tǒng)碳鋼成為新一代主流集輸管線材料。然而,其焊接性能的不完善和抗C02腐蝕機(jī)理的不明確,大大限制了其在油氣工業(yè)領(lǐng)域的推廣和發(fā)展。因此,本文針對焊接接頭力學(xué)性能、焊接接頭電偶腐蝕、高溫高壓C02腐蝕以及抗C02腐蝕機(jī)理對低Cr鋼進(jìn)行了研究,主要包括以下幾個(gè)方面：首先,通過大量焊接實(shí)驗(yàn)及焊接接頭力學(xué)性能測試和對比研究,開發(fā)出目前與3Cr管線鋼匹配最為理想的焊接材料,并制定了合理的現(xiàn)場焊接工藝。對比商用TGS-2CML和H08Cr3MoMnA焊絲,采用自制AR01自動(dòng)焊焊絲結(jié)合半自動(dòng)焊焊接工藝得到的焊接接頭焊縫區(qū)晶粒最為均勻細(xì)密,且焊縫區(qū)與熱影響區(qū)過渡更為自然,各項(xiàng)力學(xué)性能也均能較好滿足挪威船級社制管工藝DNV-OS-F101標(biāo)準(zhǔn)。焊接接頭各區(qū)域間形成理想的“大陽極(BM)+小陰極(WZ、HAZ)"電偶組合,對管線的服役安全和使用壽命十分有利。其次,利用高溫高壓C02腐蝕模擬實(shí)驗(yàn)和電化學(xué)測試,研究了3Cr鋼表面腐蝕產(chǎn)物膜生長過程的演變,并建立了其腐蝕產(chǎn)物膜生長模型。該模型指出3Cr鋼表面腐蝕產(chǎn)物膜的生長可以分為三個(gè)階段,即FeOH/CrOH動(dòng)態(tài)吸附階段、不完整產(chǎn)物膜覆蓋階段、完整產(chǎn)物膜穩(wěn)定生長階段。最后,通過高溫高壓原位電化學(xué)及pH監(jiān)測手段,明確了低Cr鋼區(qū)別于傳統(tǒng)碳鋼的陰極反應(yīng)機(jī)制,給出了低Cr鋼耐蝕性能評價(jià)的一個(gè)關(guān)鍵指標(biāo)——自發(fā)半鈍化,并進(jìn)一步提出了低Cr鋼完整的自發(fā)半鈍化機(jī)制。低Cr鋼中Cr的加入通過對陰極過程和陽極過程的共同影響來誘發(fā)基體的自發(fā)半鈍化,從而大大提高其耐蝕性能。對于陽極過程,基體中Cr的加入使陽極過程附加Cr的系列反應(yīng),導(dǎo)致基體表面在腐蝕初期被完整致密的Cr(OH)3膜覆蓋,陽極電流密度降低。對于陰極過程,基體中Cr的加入可以通過快速降低基體表面溶液pH來驅(qū)動(dòng)陰極過程由HC03-的還原向H+的還原轉(zhuǎn)變,從而導(dǎo)致混合電位的正移,進(jìn)入鈍化電位區(qū)間,發(fā)生自發(fā)半鈍化。另外,本文發(fā)現(xiàn)并提出了3Cr鋼表面Cr(OH)3膜的形成與苯甲酰胺緩蝕劑吸附行為的競爭機(jī)制,認(rèn)為在苯甲酰胺濃度低于200 mM時(shí),緩蝕劑的存在對3Cr鋼表面Cr(OH)3膜的生成基本沒有影響,此時(shí)Cr(OH)3膜的生成占據(jù)主導(dǎo)過程。而當(dāng)苯甲酰胺濃度達(dá)到或超過600 mM時(shí),緩蝕劑則可以快速富集并吸附于基體表面,從而對Cr(OH)3膜的生成起到完全抑制作用,影響基體的鈍化行為。在介于200 mM與600 mM之間,緩蝕劑吸附與Cr(OH)3膜的生成共同發(fā)生。該競爭機(jī)制的提出對工業(yè)應(yīng)用中低Cr鋼緩蝕劑的匹配及濃度選擇具有重要的指導(dǎo)和借鑒意義。
[Abstract]:In order to meet the severe challenge brought by the increasing corrosion problem of CO2, a new type of low alloy steel containing Cr with high performance and price ratio has been developed in recent years. Cr-containing low alloy steel, as the most ideal CO2 corrosion resistant pipeline steel combining economy and safety, is expected to replace traditional carbon steel as a new generation of mainstream pipeline materials. The imperfection of its welding properties and the unclear mechanism of corrosion resistance to CO2 greatly limit its popularization and development in the field of oil and gas industry. Therefore, the mechanical properties of welded joints and the galvanic corrosion of welded joints are studied in this paper. The corrosion mechanism of high temperature and high pressure CO2 and the mechanism of corrosion resistance to CO2 are studied. The main contents are as follows: firstly, through a large number of welding experiments, the mechanical properties of welded joints are tested and compared. The most ideal welding material matching with 3Cr pipeline steel is developed, and a reasonable welding process is made. Compared with commercial TGS-2CML and H08Cr3MoMnA welding wire, The grain size of weld zone obtained by self-made AR01 automatic welding wire combined with semi-automatic welding process is the most uniform and compact, and the transition between weld zone and heat affected zone is more natural. All mechanical properties can also meet the DNV-OS-F101 standard of pipe making process of Norwegian Classification Society. An ideal combination of "large anode BMM small cathode WZZHAZ)" is formed between the regions of welded joints, which is very beneficial to the service safety and service life of the pipeline. Secondly, The growth process of corrosion product film on 3Cr steel was studied by means of high temperature and high pressure corrosion simulation experiment and electrochemical test. The growth model of corrosion product film on 3Cr steel was established. The model indicates that the growth of corrosion product film on 3Cr steel can be divided into three stages: dynamic adsorption stage of FeOH/CrOH, covering stage of incomplete product film, stable growth stage of intact product film. By means of high temperature and high pressure in situ electrochemistry and pH monitoring, the cathodic reaction mechanism of low Cr steel and traditional carbon steel is clarified. A key index for evaluation of corrosion resistance of low Cr steel, spontaneous semi-passivation, is given. Furthermore, the mechanism of complete spontaneous semi-passivation of low Cr steel is put forward. The addition of Cr in low Cr steel induces spontaneous semi-passivation of matrix through the influence of cathodic process and anode process, which greatly improves the corrosion resistance of low Cr steel. The addition of Cr in the substrate results in the addition of a series of reactions of Cr to the anode process, which results in the substrate surface being covered by a complete and compact Cr(OH)3 film at the beginning of corrosion, and the anode current density decreases. The addition of Cr in the matrix can drive the cathodic process from reduction of HC03- to reduction of H by rapidly reducing the pH of the solution on the substrate surface, which leads to the positive shift of the mixed potential into the range of passivation potential and spontaneous semi-passivation. In this paper, the competitive mechanism between the formation of Cr(OH)3 film on 3Cr steel surface and the adsorption behavior of benzoamide inhibitor is proposed. It is considered that when the concentration of benzoamide is less than 200mm, the existence of inhibitor has little effect on the formation of Cr(OH)3 film on 3Cr steel surface. However, when the concentration of benzoamide reached or exceeded 600mm, the inhibitor could be rapidly enriched and adsorbed on the substrate surface, which completely inhibited the formation of Cr(OH)3 film. Affects the passivation behavior of the substrate. Between 200 mm and 600 mm, Adsorption of corrosion inhibitor and formation of Cr(OH)3 membrane occur together. This competitive mechanism has important guidance and reference significance for industrial application of medium and low Cr steel corrosion inhibitor matching and concentration selection.
【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG406;TG178
，

本文編號：1687738