連鑄結(jié)晶器內(nèi)異相遷移行為的數(shù)學(xué)物理模擬.pdf

1、連鑄結(jié)晶器內(nèi)異相遷移行為的數(shù)學(xué)物理模擬摘要始速連鑄技術(shù)己成“新連鑄技術(shù)研究開發(fā)的重點(diǎn)隨著拉坯速度的提高，來自水口出口的鋼水主流股的流速增大，結(jié)品器液面波動(dòng)加劇，下降流股的沖擊深度增加，造成較多的夾雜物和氣泡滯留在鋼中，成為鑄坯缺陷，甚至引起鋼渣卷混的發(fā)生。的結(jié)晶器技術(shù)如電磁制動(dòng)、水口優(yōu)化等成為開發(fā)高速連鑄技術(shù)中的核心技術(shù)。本論文共分為三部分。第一部分以某鋼廠結(jié)晶器為研究對象。建立結(jié)晶器水模型，對保護(hù)渣覆蓋下結(jié)晶器內(nèi)鋼液流動(dòng)和液面渣鋼卷混

2、進(jìn)行模擬研究，分析了結(jié)晶器內(nèi)鋼渣卷混的機(jī)理和影響因素，并提出了相應(yīng)的控制措施第二部分從力平衡原理出發(fā)，建立了描述夾雜物和氣泡在凝固前沿運(yùn)動(dòng)的數(shù)學(xué)模型，分析了夾雜物和氣泡的運(yùn)動(dòng)行為第三部分利用數(shù)值模擬手段研究各種操作條件下電磁制動(dòng)對鋼液流動(dòng)、夾雜物和氣泡運(yùn)動(dòng)行為的影響，從而確定電磁制動(dòng)的最佳位置。1.結(jié)晶器內(nèi)鋼渣卷混沙“結(jié)果概括”下’(1)結(jié)晶器內(nèi)鋼渣卷混現(xiàn)象有四種基本形式:第一種是在結(jié)晶器窄面附近發(fā)生的由鋼液表面回流引起的鋼渣卷混，這是

3、高速連鑄生產(chǎn)中發(fā)生鋼渣卷混的基本方式第二種卷渣現(xiàn)象與液面非對稱流引起的漩渦有關(guān):第三種卷渣現(xiàn)象是由水口吹氫造成的第四種發(fā)生在連鑄即將結(jié)束時(shí)，來自水口的鋼水流股直接沖擊保護(hù)渣層而造成的卷渣。(2)基于功能原理和速度邊界層理論，建立了描述渣鋼卷混機(jī)理的數(shù)學(xué)模型，并推導(dǎo)出鋼液臨界流速和渣滴臨界直徑計(jì)算公式。r._(P)“(=)U31r36(P，一PS)BamsIu“=t寧Lol—II—III—ILPmll`ml]LPsJdj=9ams(P，一

4、P)8結(jié)果表明:鋼液臨界流速與渣金密度、粘度和界面張力有關(guān)，其中粘度是一個(gè)重要因素。在實(shí)際生產(chǎn)中，當(dāng)保護(hù)渣粘度為22.3X10“3Pas時(shí)，鋼液表面臨界流速為。.556ms當(dāng)保護(hù)渣的粘度為177.9X10Pas時(shí)，臨界流速為。.852ms。(3)通過增大渣粘度、水口向下張角和浸入深度，以及減慢拉坯速度，減小吹氫量，可以降低卷渣發(fā)生的可能性。(4)在實(shí)際生產(chǎn)過程中，控制吹氫量是防止鋼渣卷混發(fā)生的有效手段之一。當(dāng)渣粘度ABSTRACTNUM

5、ERICALSIMULATIONPHYSICALMODELLINGOFTRANSPTPHENOMENAOFDIFFERENTPHASESINTHECONTINUOUSCASTINGMOULDABSTRACT:Atpresentthehighspeedcastingtechnologyhasreceivedaconsiderableatentioninthedevelopmentofnewcontinuouscastingtechnolo

6、gies.Withtheincreaseofthecastingspeedthevelocityofmoltensteelfromthesubmergedentrynozzleincreasesaswellasthefreesurfaceinthemouldbecomesmoreturbulentandthepenetrationdistanceofthestreamdirecteddownwardsincreases.Conseque

7、ntlymoreinclusionsandbubblescausingslabdefectsremainintheslabandevenslagentrapmentoccurs.ThereforethetechnologiesdevelopinginthemouldsuchaselectromagneticbrakeargoninjectionintheSENhavebeenoftheimportanceforthehighspeedc

8、asting.Thethesisconsistsofthreeparts.Inthefirstpartaccordingtotheoperationconditionoftheslabcontinuouscastingmould恤asteelmakingfactoryawatermodelwasbuilttostudythefluidflowandslagentrapmentinthemould.Theformationmechanis

9、msofslagentrapmentandthemainfactorswereanalyzedandthecorrespondingmeasurestoeliminateslagentrapmentwerealsoproposed.Inthesecondpartbasedontheforcebalancetheoryamathematicalmodeltodescribemovementofinclusionandbubbleneart

10、hesolidifyingshellwasestablishedandthetrajectoriesofinclusionsandbubbleswerenumericallystudied.Inthelastpartbythemeansofthenumericalsimulationtheeffectofelectromagneticbrakeonthemoltensteelflowandthemovementofinclusionsa

11、ndbubblesinthemouldunderdifferentoperationconditionswerestudiedandtheoptimizedpositionoftheelectromagneticbrakewasobtained.Theresultswereasfollows:I.Slagentrapmentinthemould(1)Therewerefourtypesofslagentrapmentintheconti

12、nuouscastingmould.Thefirsttypewhichwascausedbythesurfacestreamoccurrednearthenarrowfaceinthemould.Itwasthemaintypeofslagentrapmentinthehighspeedcasting.Thesecondtypewasrelatedtothevorticescausedbytheunsymmetricalsurfaces

13、tream.Thethirdwascausedbythesubmergedentrynozzlewithargoninjection.Thefourthoccurredattheendofthecontinuouscastingduetothestrikingofthemoltensteelfromthenozzletotheslaglayer.(2)Basedonthetransferrelationshipbetweenenergy