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1、遼寧科技大學(xué)工程碩士論文摘要摘要近年來,汽車工業(yè)發(fā)展迅速,對汽車用鋼提出更高的要求。雙相鋼以其優(yōu)越的性能引起了人們的重視,在汽車用鋼板中具有廣闊的應(yīng)用前景。本文以熱軋雙相鋼為研究對象,對其疲勞和沖擊等行為進行了研究,主要內(nèi)容如下:1.通過對實驗鋼種進行高周和低周疲勞實驗可以發(fā)現(xiàn):疲勞裂紋起源于試樣的表面,裂紋源沿斷口周邊分布,為多源特征。材料本身的缺陷(內(nèi)部微裂紋、夾雜物和第二相粒子等)也可成為裂紋源;在疲勞擴展區(qū)可以清晰的觀察到塑性疲勞條帶,伴隨著疲勞條帶的形成,產(chǎn)生與條帶平行相間的二次裂紋,同時可以觀察到疲勞輝紋、疲勞臺階等一些疲勞斷裂的微觀特征;2.通過對實驗鋼種的
2、低溫沖擊實驗可以發(fā)現(xiàn):夾雜物以及微裂紋存在破壞了鋼基體的連續(xù)性,在外加載荷的作用下造成了該處的應(yīng)力集中導(dǎo)致斷裂,使得材料沖擊性能下降。通過不同終軋溫度、卷取溫度下實驗用鋼的沖擊實驗得知:隨著終軋溫度降低和卷取溫度的升高,晶粒細(xì)化,沖擊性能增加。3.通過熱軋雙相鋼疲勞壽命和沖擊性能的實驗可以得知,提高冶金質(zhì)量、細(xì)化晶粒和優(yōu)化工藝參數(shù)等手段可以改善材料的疲勞性能和沖擊性能。關(guān)鍵詞:熱軋雙相鋼,高周疲勞極限,低周疲勞極限,沖擊韌性Thestudyonthefatigueandimpactbehaviorforas-hotrolleddual-phasesteelAbstract
3、demandsforautomotiveplatesarebeingincreaseddramaticallywiththenationaleconomydevelopment.Recently,Peoplepaymoreandmoreattentionondual-phasesteelforitssuperiormechanicalproperties.fatigueandimpactbehaviorwerestudiedbasedontheC··Si·-Mnas·-hotrolleddual—phasesteel.Themaincontentsareasfollows
4、:1.Fromthetestofthehi曲一frequencyfatigueandlow-frequencyfatigue,itisfoundthatthefatiguecracksstartfromthesurfaceofthesample,andthesourceofthecrackisalongtheedgeoffracture.Thedefectsofsample(micro—fracture,impurities,thesecondphase)Canbethecauseofcrack.Theplasticfatiguebandcanbeobservedinth
5、efatigueextendregion,andthesecondcrackwhichisparalleltOthebandOCCurSwiththeformationoffatigueband.Themicro—features:suchasfatiguelinesandfatiguestepsearlalsobefound2.Fromtheimpactductllitytestatlowtemperature,itisfoundthattheimpuritiesandmicro-fracturesCandestroythecontinuityofsteelmatrix
6、,andthecapturecausedbystressconcen仃atlonwilldecreasetheimpactproperties.ThegrainCanberefinedandimpactpropertiesincreasedwiththedecreasingofthefinishingtemperatureandtheincreasingofthecoilingtemperaturebytheimpacttestunderthedifferentfinishingtemperatureandcoilingtemperature.3.Fromtheresul
7、tofthefatigueandimpactductilitytest,itisshowntheimprovedfatigueandimpactpropertiesCanbeobtmnedbytheincreasingthequalityofmetallurgy,refininggrainandimprovingtheparametersofhotrolling,etc.Keywords:as-hotdual—phasesteel,high-frequencyfatiguelimit,low—frequencyfatiguel