連鑄結晶器內異相遷移行為的數學物理模擬.pdf

1、連鑄結晶器內異相遷移行為的數學物理模擬摘要始速連鑄技術己成“新連鑄技術研究開發(fā)的重點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，結品器液面波動加劇，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。的結晶器技術如電磁制動、水口優(yōu)化等成為開發(fā)高速連鑄技術中的核心技術。本論文共分為三部分。第一部分以某鋼廠結晶器為研究對象。建立結晶器水模型，對保護渣覆蓋下結晶器內鋼液流動和液面渣鋼卷混

2、進行模擬研究，分析了結晶器內鋼渣卷混的機理和影響因素，并提出了相應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動的數學模型，分析了夾雜物和氣泡的運動行為第三部分利用數值模擬手段研究各種操作條件下電磁制動對鋼液流動、夾雜物和氣泡運動行為的影響，從而確定電磁制動的最佳位置。1.結晶器內鋼渣卷混沙“結果概括”下’(1)結晶器內鋼渣卷混現象有四種基本形式:第一種是在結晶器窄面附近發(fā)生的由鋼液表面回流引起的鋼渣卷混，這是

3、高速連鑄生產中發(fā)生鋼渣卷混的基本方式第二種卷渣現象與液面非對稱流引起的漩渦有關:第三種卷渣現象是由水口吹氫造成的第四種發(fā)生在連鑄即將結束時，來自水口的鋼水流股直接沖擊保護渣層而造成的卷渣。(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理的數學模型，并推導出鋼液臨界流速和渣滴臨界直徑計算公式。r._(P)“(=)U31r36(P，一PS)BamsIu“=t寧Lol—II—III—ILPmll`ml]LPsJdj=9ams(P，一

4、P)8結果表明:鋼液臨界流速與渣金密度、粘度和界面張力有關，其中粘度是一個重要因素。在實際生產中，當保護渣粘度為22.3X10“3Pas時，鋼液表面臨界流速為。.556ms當保護渣的粘度為177.9X10Pas時，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)在實際生產過程中，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