C-,2-H-,2-F-,4-混合氣體保護(hù)下鎂及鎂合金的熔煉研究.pdf

1、西北工業(yè)大學(xué)碩士學(xué)位論文CHF混合氣體保護(hù)下鎂及鎂合金的熔煉研究姓名：王小軍申請學(xué)位級(jí)別：碩士專業(yè)：材料加工工程指導(dǎo)教師：黃衛(wèi)東20050301摘要ABSTRACTRecentlyyearsmagnesiumalloysaregettingmoreandmorewidelyusedinvariousfieldsbecauseofitsexcellentproperties.Intheprocessesofmagnesiumalloyss

2、meltingathightemperatureinairhoweverthesurfaceofmagnesiumandmagnesiumalloyswillbeoxidizedrapidlywhichcanresultincombustionofmoltenstate.Inordertopreventthehappenofoxidationandcombustionsomeignitionproofmethodsmustbetaken

3、intheprocessesofitssmelting.Thegasprotectionmethodisrelativelybeteroneinavarietyofignitionproofmethods.ThegasprotectiveresultcontainingSF6gasisthebestofthegasprotectionmethods.SF6hasasignificantimpactonthegreenhouseefect

4、.Soitsuseislimitedgradually.Itisimportantformagnesiumalloymeltingtechnologythatanewkindprotectivegaswithgoodprotectiveresultandlitledamagingefectonenvironmentisinvestigatedinfuture.Thispaperstudiesprotectiveresultsandpro

5、tectivemechanismsofanewkindofprotectivegasC2HZF4experimentally.ProtectivemeltingexperimentsofmagnesiumandmagnesiumalloyshavebeendoneunderprotectivegasesofCzHZF4mixedgasesindiferentconcentrationdifferenttemperatureanddife

6、rentexposuretime.Theexperimentalresultsshowedthattheprotectiveefectisdistinct.Therewereobviousprotectiveefectswhenthemixturecontained0.2%一0.5%C2112F4forpuremagnesium0.2%0.8%C21121`4forAZ91andAM60magnesiumalloysrespective

7、ly.TherewasabeterprotectiveresultwiththeconcentrationofC2H2F4inmixtureincreasingandthetemperaturefalling.ProtectiveresultwillheightenwhentheCzHZF4mixedgaseshave50%C02.ThecostsusingCzHZF4mixedgasesisneartothecostsusingSF6

8、mixedgases.TheC2112F4mixedgasesreactwiththemeltandformasurfaceprotectivefilmduringthecourseofprotection.TransectionandsurfacesofthefilmshavebeenobservedwithSEM.Itisfoundthatthethicknessisabout3gm.ThethickertheCzHZF4conce

9、ntrationandthelowerthetemperaturethemorecompacttheprotectivefilm.ThecomponentsofprotectivefilmshavebeenanalyzedwithenergydispersivespectrometertheresultsshowthatprotectivefilmsaremadeupofMgOandMgF2includingsimplesubstanc