本文選題：薄壁高強(qiáng)度樁管鋼　切入點(diǎn)：腐蝕性能　出處：《南京航空航天大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著沿海地區(qū)經(jīng)濟(jì)開發(fā)和灘涂以橋代路工程的迅速發(fā)展,高強(qiáng)度樁管鋼的研究和應(yīng)用受到了高度的重視。鋼管樁應(yīng)用過程中損壞失效的最大威脅來自腐蝕,高強(qiáng)度樁管鋼的耐蝕性能成為決定高層建筑和橋墩等建筑工程使用壽命的關(guān)鍵,因此低成本耐蝕薄壁高強(qiáng)度樁管鋼的研究開發(fā)具有重要的理論和應(yīng)用價(jià)值。本文利用光學(xué)顯微鏡(OM)、X射線衍射儀(XRD)、掃描電鏡(SEM)及其附帶能譜儀(EDS)、拉伸試驗(yàn)、極化曲線測試及電化學(xué)阻抗譜測試等多種分析和測試方法,系統(tǒng)研究了Cr、Cu等合金化元素和熱處理工藝對低合金高強(qiáng)度樁管鋼的組織、性能和在高鹽度服役環(huán)境下的腐蝕行為的影響規(guī)律,為低成本薄壁高強(qiáng)度鋼的研究開發(fā)和應(yīng)用發(fā)展提供理論指導(dǎo)。結(jié)果表明:低碳低合金樁管鋼在飽和Na Cl鹽水環(huán)境下主要發(fā)生電化學(xué)腐蝕,其中液-氣界面區(qū)腐蝕最為嚴(yán)重。在普通碳鋼基礎(chǔ)上添加0.2%Cu(質(zhì)量分?jǐn)?shù),下同)和0.2%Cu+0.2%Cr后,其熱軋空冷態(tài)樣品液-氣界面區(qū)的點(diǎn)蝕坑逐漸細(xì)小密集,最大點(diǎn)蝕深度從普通低碳鋼的0.44 mm降低到0.2Cu-0.2Cr鋼的0.11 mm,腐蝕類型從點(diǎn)蝕向均勻腐蝕轉(zhuǎn)變。與普通低碳鋼相比,0.2Cu鋼腐蝕速率為0.0388mm/y,降低了71%,0.2Cu-0.2Cr鋼腐蝕速率為0.0346 mm/y,降低了74%。對比普通碳鋼,加入0.2%Cu、0.2%Cu+0.2%Cr后測試試樣的極化阻抗Rp從482.6??cm2分別提高到854.5??cm2、1136??cm2。銹層中Cu、Cr元素的增加抑制了電化學(xué)腐蝕反應(yīng)的陽極過程。Cu、Cr元素富集于銹層與基體的界面處,在基體腐蝕慢的區(qū)域銹層中往往伴隨著更多的Cu和Cr元素,而腐蝕快的區(qū)域則其含量較少。普通低碳鋼中添加0.5-2.0%Cr,其控軋控冷態(tài)組織由多邊形鐵素體加少量珠光體轉(zhuǎn)變?yōu)樨愂象w、鐵素體和M-A島,屈服強(qiáng)度由304MPa提升到503MPa。隨著Cr含量的增加,基體電極電位從-0.646V不斷升高到-0.544V,但裸鋼的極化阻抗值Rp卻從1586?·cm2降低到了795.5?·cm2。鋼中Cr含量的增加在5個(gè)月的半浸泡腐蝕中并未提高其耐腐蝕性,腐蝕速率反而由0.0292mm/y略微增加到0.0304mm/y,其原因在于高的Cr含量導(dǎo)致鋼中生成了易腐蝕相貝氏體和M-A島。在腐蝕產(chǎn)物中發(fā)現(xiàn)Cr元素富集于銹層與基體的界面處,隨著基體中Cr含量的增高,富集現(xiàn)象越明顯,尤其在2.0Cr鋼中內(nèi)銹層Cr含量明顯高于基體中的含量,銹層也更加致密。普通低碳鋼中添加0.5-2.0%Cr,調(diào)質(zhì)處理后的各試樣組織皆為回火索氏體:其中0.5Cr鋼中的鐵素體充分再結(jié)晶轉(zhuǎn)化為多邊形鐵素體,而1.1Cr和2.0Cr鋼中的很多鐵素體由于Cr對其回火過程中再結(jié)晶的推遲作用使其仍然保持著板條狀;屈服強(qiáng)度從0.5Cr鋼的391MPa提高到了2.0Cr鋼的510MPa。調(diào)質(zhì)態(tài)樁管鋼試樣在3.5%鹽溶液中一直處于活化狀態(tài),且隨著Cr含量增加,試樣自腐蝕電位變化不大,皆在-0.57V左右,但腐蝕電流密度icorr從1.657×10-5 A·cm-2降低到了1.391×10-5 A·cm-2,極化阻抗值Rp從1014?·cm2增大到了1611?·cm2。隨著Cr含量的增加,鋼在液-氣界面處腐蝕情況改善明顯,與熱軋空冷態(tài)、控軋控冷態(tài)試樣相比,其腐蝕程度顯著減輕。當(dāng)Cr含量為2%時(shí),試樣耐蝕性最好,年腐蝕速率為0.0234mm/y,比Cr含量為0.5%的試樣降低了8.6%。Cr元素在銹層中發(fā)現(xiàn)富集現(xiàn)象,在浸泡區(qū)主要富集于與基體接觸的內(nèi)銹層區(qū),而在液-氣界面區(qū)則富集于遠(yuǎn)離基體的外銹層區(qū)。少量合金元素對樁管鋼試樣腐蝕銹層的物相組成沒有明顯的影響,銹層均主要由α-Fe OOH、β-Fe OOH、γ-Fe OOH、Fe3O4和Fe2O3等組成。與液-氣半浸泡實(shí)驗(yàn)相比,液-固腐蝕實(shí)驗(yàn)中試樣的腐蝕速率普遍極小,皆在0.004 mm/y以下,因此合金元素、熱處理方式對鋼的腐蝕性影響均不明顯,鋼的腐蝕速度完全由環(huán)境因素,主要是氧含量控制。樁管鋼埋在泥土中的部分生成的銹層比浸泡在水溶液中的更加均勻致密。電化學(xué)測試表明,樁管鋼在飽和水土壤中隨時(shí)間的推移,極化阻抗Rp不斷增大,即表面銹層不斷增厚,對基體保護(hù)性增強(qiáng)。
[Abstract]:With the rapid development of economic development in coastal areas and beaches to bridge and road engineering, research and application of high strength steel pipe pile is highly emphasized. The biggest threat to the failure damage process of steel pipe pile in the application of high strength pile from corrosion, corrosion resistance of the steel tube decided to become a key service life of high-rise buildings and bridge pier construction therefore, the research and development of low cost and high strength thin-walled steel tube pile corrosion has important theoretical and practical value. In this paper, by using optical microscope (OM), X ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS), tensile test, polarization curves and electrochemical impedance spectroscopy a variety of analysis and testing method, system of Cr, alloying elements and heat treatment process of Cu alloy of high strength low alloy steel pipe pile, performance and corrosion behavior under the environment of service in high salinity influence, To provide theoretical guidance for the development and application of research and development of low cost thin wall and high strength steel. The results showed that the low carbon low alloy Na Cl pile in saturated saline environment mainly electrochemical corrosion of steel tube, the liquid gas interface corrosion is most serious. Add in the ordinary carbon steel on the basis of 0.2%Cu (mass fraction, the same below) and after 0.2%Cu+0.2%Cr, the hot rolling cold pit sample liquid gas interface area gradually dense, maximum pit depth decreases from 0.44 mm to the ordinary low carbon steel 0.2Cu-0.2Cr steel 0.11 mm, change the type of corrosion pitting corrosion from to uniform. Compared with the ordinary low carbon steel, the corrosion rate of 0.2Cu steel is 0.0388mm/y, reduced 71%, the corrosion rate of 0.2Cu-0.2Cr steel is 0.0346 mm/y, reduced 74%. compared with ordinary carbon steel, adding 0.2%Cu, 0.2%Cu+0.2%Cr test Rp samples from the polarization impedance 482.6?? cm2 were increased to 854.5?? cm21136? Cm2.? Cu in the rust layer, Cr elements can inhibit the anodic process of.Cu electrochemical corrosion reaction, Cr elements in the rust layer at the interface of the matrix and the matrix corrosion rust layer in the area of slow often accompanied by more Cu and Cr elements, and the area of the corrosion speed is less content. Addition of 0.5-2.0%Cr low carbon steel, and its control the cold rolling microstructure is composed of polygonal ferrite and pearlite transformation of bainite, ferrite and M-A islands, the yield strength increased from 304MPa to 503MPa. with the increase of Cr content, the matrix electrode potential rising from -0.646V to -0.544V, but the polarization resistance of bare steel anti Rp value from 1586 cm2? Reduced to 795.5? Cr content in cm2. steel increased in semi immersion for 5 months did not improve its corrosion resistance, but the corrosion rate increased slightly by 0.0292mm/y to 0.0304mm/y, the reason is that the high content of Cr in steel is generated in the bainite phase corrosion And the island of M-A. In the corrosion products found in the Cr elements in the rust layer at the interface with the substrate, with the increase of Cr content in the matrix, the enrichment phenomenon is more obvious, especially in 2.0Cr steel inner rust layer Cr content is significantly higher than the content in the matrix, the rust layer became more compact. Adding 0.5-2.0%Cr in low carbon steel after quenching and tempering, their microstructure is tempered sorbite: 0.5Cr steel in ferrite recrystallization fully into polygonal ferrite, and a lot of 1.1Cr and 2.0Cr steel in ferrite due to delayed effect of Cr on recrystallization in the tempering process makes it still keeps the strip; the yield strength of 0.5Cr steel from 391MPa to 2.0Cr steel 510MPa. quenched and tempered steel pipe pile sample in 3.5% salt solution has been in the active state, and with the increase of Cr content, the specimen corrosion potential changed little, all in about -0.57V, but the corrosion current density from icorr 1.657脳10-5 A路cm-2闄嶄綆鍒頒簡1.391脳10-5 A路cm-2,鏋佸寲闃繪姉鍊糝p浠，

本文編號：1651072