本文選題：奧氏體不銹鋼 + 應力腐蝕��； 參考：《青島理工大學》2017年碩士論文

【摘要】：奧氏體不銹鋼具有抗腐蝕性強、焊接性好、韌性大等優(yōu)良的特點。奧氏體不銹鋼因其價格低、抗蝕性好、在很寬的溫度范圍內(nèi)具有較好的機械性能、能用在淡水環(huán)境、海水環(huán)境及酸性環(huán)境,本文以離心機轉(zhuǎn)鼓用奧氏體不銹鋼發(fā)生生產(chǎn)事故進行分析、研究。本論文從力學性能的測試、金相組織結(jié)構(gòu)的觀察、分析奧氏體不銹鋼表面殘余應力產(chǎn)生的原因、通過熱處理消除殘余應力及對循環(huán)物中控制氯離子對不銹鋼腐蝕機理的探討,從這幾方面著手,分析并確定轉(zhuǎn)鼓筒體碎裂、鼓底產(chǎn)生周向裂紋的原因,并提出合理化的建議,避免類似的事故再次發(fā)生。本論文主要的研究內(nèi)容和結(jié)果如下:1.通過對試樣的機械力學性能試驗,和分析試驗成果,可以得出:筒體材料的化學成分中Cr、Ni含量均未達到標準值,但是很接近,從對其進行機械性能測試結(jié)果分析,材料的綜合機械性能是良好的,是典型的塑性材料。此種材料仍屬于奧氏體不銹鋼,確切的說接近于301不銹鋼,而不是要求使用的304不銹鋼。2.金相分析確定了:從碎片化驗結(jié)果來看,Ni含量表面有明顯降低,Ni含量對抗應力腐蝕作用甚大,同樣應力腐蝕也會首先降低Ni的濃度,這完全符合應力腐蝕的特征。進一步觀察,局部還可以看到二次裂紋和表面腐蝕坑。由某公司提供的“301”不銹鋼材在某些腐蝕介質(zhì)中,它的耐腐蝕能力是不夠的。建議在考慮經(jīng)濟成本的前提下,選用含鉬奧氏體鋼(例0Cr18Ni12Mo2)或更加優(yōu)良的雙相不銹鋼如00Cr22Ni5Mo3N。3.304不銹鋼殘余應力的研究。采取X射線衍射的方法測量不銹鋼輪廓的殘存應力。在冷加工成型過程,不銹鋼轉(zhuǎn)鼓的外輪廓面出現(xiàn)較大的殘存拉應力,這是導致轉(zhuǎn)鼓在現(xiàn)實應用中發(fā)生應力腐蝕裂紋的主要原因。4.去應力熱處理的研究。先對304不銹鋼有差別溫度的去應力熱處理,在把處理前后的外輪廓殘存應力做比較,說明了熱處理之后,不銹鋼表面殘余拉應力轉(zhuǎn)變成壓應力,且應力的數(shù)值有所降低。這對提高不銹鋼的抗應力腐蝕性能是非常有用的。5.通過探討循環(huán)物中Cl~-控制和對不銹鋼腐蝕的機理,分析出離心機的物料中含有氧元素和硫酸根離子。引起設備應力腐蝕的介質(zhì)是此物料引起的,應盡量避免。
[Abstract]:Austenitic stainless steel is characterized by strong corrosion resistance, good weldability and high toughness.Austenitic stainless steel has good mechanical properties in a wide range of temperature because of its low price and good corrosion resistance. It can be used in fresh water, seawater and acid environment.In this paper, the production accident of austenitic stainless steel used in centrifuge drum is analyzed and studied.In this paper, the causes of residual stress on austenitic stainless steel surface are analyzed by testing mechanical properties and observing metallographic structure. The residual stress is eliminated by heat treatment and the corrosion mechanism of stainless steel caused by controlling chlorine ion in circulating material is discussed.From these aspects, this paper analyzes and determines the causes of the breakage of the drum body and the circumferential crack in the bottom of the drum, and puts forward some reasonable suggestions to avoid the recurrence of similar accidents.The main contents and results of this thesis are as follows: 1.Through the mechanical and mechanical property test of the sample and the analysis of the test results, it can be concluded that the content of Cr-Ni in the chemical composition of the cylinder material is not up to the standard value, but it is very close.The comprehensive mechanical properties of the materials are good and typical plastic materials.The material is still austenitic stainless steel, close to 301 stainless steel, rather than 304 stainless steel. 2.Metallographic analysis shows that the surface of Ni content can obviously reduce the content of Ni to resist the stress corrosion, and the same stress corrosion will decrease the concentration of Ni at first, which fully accords with the characteristic of stress corrosion.Further observation shows that secondary cracks and surface corrosion pits can also be seen locally.The "301" stainless steel supplied by a company in some corrosive media has insufficient corrosion resistance.It is suggested that the residual stress of molybdenum bearing austenitic steel (0Cr18Ni12Mo2) or better duplex stainless steel such as 00Cr22Ni5Mo3N.3.304 stainless steel should be studied on the premise of economic cost.The residual stress of stainless steel profile was measured by X-ray diffraction.In the process of cold working, there is a large residual tensile stress on the outer contour of the stainless steel drum, which is the main reason for the stress corrosion cracking in the practical application of the drum.Study on stress free heat treatment.The residual stress of the surface of 304 stainless steel before and after treatment is compared. The residual tensile stress on the surface of 304 stainless steel is transformed into compressive stress and the value of stress is reduced.This is very useful for improving the stress corrosion resistance of stainless steel.By discussing the mechanism of Cl-control and corrosion of stainless steel in the circulating material, the oxygen element and sulfate ion in the material of centrifuge were analyzed.The medium that causes the equipment stress corrosion is caused by this material and should be avoided as far as possible.
【學位授予單位】：青島理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG142.71;TG161

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