本文選題：高鉻鐵素體不銹鋼 + 腐蝕　； 參考：《蘭州理工大學(xué)》2017年碩士論文

【摘要】：本文研究開發(fā)的高鉻鐵素體不銹鋼主要應(yīng)用在化工領(lǐng)域中的低溫?zé)峄厥障到y(tǒng),該合金要求在硫酸、磷酸及氯離子環(huán)境下具有優(yōu)良的耐腐蝕性能。合金元素銅、鈦鈮、稀土和熱處理工藝都影響材料的耐腐性能,本文主要考察合金元素和熱處理工藝對高鉻鐵素體不銹鋼腐蝕性能的影響,希望通過這些研究來拓展其應(yīng)用。本文以高鉻鐵素體不銹鋼為研究對象,采用真空中頻感應(yīng)冶煉工藝,熔煉了不同設(shè)計成分的高鉻鐵素體不銹鋼,考察合金元素Cu、Ti+Nb、稀土和固溶處理對合金在H_2SO4、H_3PO_4、NaCl及FeCl_3溶液中耐蝕性能的影響。用浸泡實驗測定合金的全面腐蝕速率;用電化學(xué)實驗測定合金的極化曲線和阻抗譜,觀察合金自腐蝕電流、自腐蝕電位、維鈍電流和阻抗的變化;利用掃描電鏡與萊卡光學(xué)顯微鏡分析了實驗鋼的組織、析出相變化及在晶界處的分布等特點;使用掃描電子顯微鏡觀察浸泡腐蝕后合金表面腐蝕形貌,能譜儀分析腐蝕后的合金表面保護膜和組織析出相,觀察合金元素的添加對鈍化膜形貌和析出相及成分的影響。結(jié)果表明:在90%H_2SO_4溶液、40%H_3PO_4溶液和3.5%NaCl溶液中,隨著銅含量的增大,試樣的腐蝕速度先變小后變大,在合金銅含量為1%時,高鉻鐵素體不銹鋼的耐全面腐蝕性能最優(yōu)。當合金中銅含量小于1%時,隨著銅含量的增加不銹鋼表面胞狀的鈍化膜逐漸變厚變大、蝕坑數(shù)減少和面積變小。當合金中銅含量大于1.0%時,合金鈍化膜出現(xiàn)缺陷,蝕坑數(shù)量變多,面積增大。在FeCl_3溶液中,隨著氯離子含量增大不同成分的高鉻鐵素體不銹鋼的平均腐蝕速度均增大,在相同濃度FeCl_3中,隨著合金中銅的增加合金耐腐蝕性先增大后減小,在銅含量為1.5%時合金腐蝕速率最小。過量銅的添加使鋼中過飽和的銅以富銅相ε-Cu相析出,他們多分布在晶界處又會降低合金的耐腐蝕性。在銅含量為1.0%的基礎(chǔ)上,相繼添加鈦鈮和稀土,在三種溶液中,合金鋼耐腐蝕性均逐漸增強,對銅含量為1.0%含鈦鈮和稀土的高鉻鐵素體不銹鋼在950℃、1000℃、1050℃和1100℃固溶處理。結(jié)果表明在三種溶液中,固溶溫度在1050℃時,合金的耐腐蝕性能最強。實驗研究發(fā)現(xiàn)向鐵素體不銹鋼中添加銅,析出物在晶界處的數(shù)量明顯減少,并且析出相變小,銅的添加會使(Fe,Cr)_(23)C_6等析出相在晶間上的析出受到抑制。當引入鈦鈮和稀土后,鈦鈮可以生成很穩(wěn)定的鈦碳化物與鈮碳化物從而抑制富鉻析出相的生成,稀土的添加可以凈化鐵素體晶界,提高組織的均勻性,從而使其耐蝕性能顯著增強。本文的研究結(jié)果對高鉻鐵素體不銹鋼的理論研究和實際應(yīng)用的發(fā)展具有很好的促進作用,為設(shè)計開發(fā)出耐蝕性能優(yōu)異的高鉻鐵素體不銹鋼提供了理論參考,為進一步挖掘高鉻鐵素體不銹鋼在化工生產(chǎn)中應(yīng)用也具有十分重要的現(xiàn)實意義。
[Abstract]:The high chromium ferrite stainless steel developed in this paper is mainly used in the low temperature heat recovery system in the chemical field. The alloy requires excellent corrosion resistance in sulfuric acid phosphoric acid and chloride ion environment. Alloy elements copper, titanium niobium, rare earth and heat treatment process all affect the corrosion resistance of the material. This paper mainly studies the effect of alloy elements and heat treatment process on the corrosion resistance of high chromium ferrite stainless steel, hoping to expand its application through these studies. In this paper, high chromium ferrite stainless steel with different design components was melted by vacuum medium frequency induction smelting process. The effects of the alloying elements Cu-Ti NB, rare earth and solid solution treatment on the corrosion resistance of the alloy in H _ S _ 2SO _ 4 / H _ 3PO _ 4 / FeCl_3 solution were investigated. The total corrosion rate of the alloy was measured by immersion test, the polarization curve and impedance spectrum of the alloy were measured by electrochemical experiment, the changes of corrosion current, corrosion potential, blunt current and impedance of the alloy were observed. The microstructure, precipitation phase change and distribution at grain boundary of the experimental steel were analyzed by scanning electron microscope and Leica optical microscope, and the corrosion morphology of the alloy after immersion corrosion was observed by scanning electron microscope. The surface protective film and precipitated phase of the alloy after corrosion were analyzed by EDS, and the effect of the addition of alloy elements on the morphology, precipitation phase and composition of the passivated film was observed. The results show that the corrosion rate of the sample decreases first and then increases with the increase of copper content in the 90%H_2SO_4 solution 40 H3PO4 and 3.5%NaCl solution. When the copper content of the alloy is 1%, the overall corrosion resistance of the high chromium ferrite stainless steel is the best. When the copper content in the alloy is less than 1, with the increase of copper content, the cellular passivation film on the stainless steel surface becomes thicker and larger, the number of pits decreases and the area becomes smaller. When the copper content in the alloy is greater than 1.0, defects appear in the passivation film, and the number of etch pits increases and the area increases. In FeCl_3 solution, the average corrosion rate of high chromium ferrite stainless steel with different composition increases with the increase of chloride ion content. In the same concentration of FeCl_3, the corrosion resistance of the alloy increases first and then decreases with the increase of copper content in the alloy. The corrosion rate of the alloy is the lowest when the copper content is 1.5. With the addition of excessive copper, the supersaturated copper in the steel precipitates in copper-rich 蔚 -Cu phase, and most of them distribute at grain boundaries and decrease the corrosion resistance of the alloy. On the basis of 1.0% copper content, titanium niobium and rare earth elements were added in succession. The corrosion resistance of alloy steel increased gradually in the three solutions. The high chromium ferrite stainless steel containing 1.0% copper, containing titanium, niobium and rare earth, was treated at 950 鈩，

本文編號：1926989