Effect of Ca, Mg on Hydrogen Absorption of Molten Al-Si Alloy

Transcription

1 ffect of a, Mg on Hydrogen bsorption of Molten l-si lloy Hiroshi Kawahara, Yoji wano JIS Mg a a e S 6 a or reducing the inferior castings of aluminum alloys caused by porosity it is necessary to clarify, the shrinkage morphology of poured melt and the factors affecting the change in shrinkage morphology. In this study, the change in the amount of porosity was investigated for JIS secondary alloy ingots from the viewpoint of hydrogen absorption by using a conical mold developed for evaluating the shrinkage morphology. The amount of porosity changes, mainly depending on the holding time and temperature of the molten metal as well as the humidity in the holding atmosphere. The change in the amount of porosity differs according to raw ingots, because the quantity of the hydrogen absorbed in the molten metal is different. The hydrogen absorption is closely related with the oxidation of the molten metal. Particularly, in the case of the ingot containing both Mg and a, remarkable hydrogen absorption occurred even during a short holding time, and the oxide formed on the melt surface was sunk. It is considered that the oxide is sunk because a improves the wettability between the oxide and the molten metal. This suggests that the oxidation of the melt is promoted, causing remarkable hydrogen absorption. It is found effective for minimizing the change in the amount of porosity to retard the melt oxidation by e addition and to remove a by S 6 gas bubbling. R& Vol. 3 No. ( )

2 l-si 5 JIS 4 9g 3K 3Pa min 7Pa ) hemical compositions of JIS alloy ingots (mass%). u Si Mg Zn e Mn r Ni Ti Sn Pb a Na l : secondary alloy ingots : virgin alloy ingot R& Vol. 3 No. ( )

3 Porosity-5m3/kg Porosity-5m3/kg.L/min 973K l-7%si 73sec. 3 ρa ρa ρt 5 m 3 /kg ρt.7 5 m 3 /kg 38Pa3K 3 4 PH O Pa 6 3K 6min Interior shrinkage xterior shrinkage ffect of humidity in atmosphere on amount of porosity in conical castings of alloy ingots ( holding temperature : 3K, holding time : 6min ). 3 Inner wall of mold 6 Holding timemin Porosity lassification of shrinkage in conical casting. ffect of holding time on amount of porosity in conical castings of alloy ingots ( holding temperature : 3K, humidity in atmosphere : 38Pa ). R& Vol. 3 No. ( )

4 Porosity-5m3/kg Porosity-5m3/kg 6min 3min min 38Pa 6min Laslaz Si u Zn e Mn lmg a Mg a ig. 3 4Mg a Mg a Holding temperature, K Hydrogen content-5m3/kg. ffect of holding temperature on amount of porosity in conical castings of alloy ingts ( holding time : 6min, humidity in atmosphere : 38Pa ). Relations between amount of porosity and hydrogen content of conical castings for alloy ingots. R& Vol. 3 No. ( )

5 a content mass% Hydrogen content -5m3/kg Mg content mass% Porosity -5m3/kg Mg a Mg a 3K 3min38Pa Mg a.3 5 m 3 /kg Mg a u l-si-mg4 a lmg a a 38Pa 3K min 6min Mga 6min (a) (b) Virgin alloy.3%mg Virgin alloy (l-6.5%si-3.5%u)... 6 s 6 s Holding recieved timemin Recieved Holding time, min. s s Holding recievedtimemin Holding Recieved time, min.8.4 Virgin alloy.3%mg Virgin alloy (l-6.5%si-3.5%u) a content, mass % hange of (a)a and (b)mg contents in conical castings of alloy ingots with holding time ( holding temperature : 3K, humidity in atmosphere : 38Pa ). ffect of a and Mg additions on amount of porosity and hydrogen content in conical castings of l-6.5% Si-3.5% u virgin alloy ingot ( holding temperature : 3K, holding time : 3min, humidity in atmosphere : 38Pa ). R& Vol. 3 No. ( )

6 ig. 3 X MgO Mgl O 4 l-mg 3min mm Optical microstructure on the cross section of the specimen made from ingot ( holding temperature : 3K, holding time : min, humidity in atmosphere : 38Pa ). MgO Mgl O 4 PM O Mg l Mg l O a a aa a MgO Mgl O 4 ig. 3 4 Optical microstructures on the cross section of the specimens made from ingot ( holding time : a) 6min and b) min, holding temperature : 3K, humidity in atmosphere : 38Pa ). Optical microstructure on the cross section of the specimen made from ingot ( holding temperature : 3K, holding time : 6min, humidity in atmosphere : 38Pa ). R& Vol. 3 No. ( )

7 Porosity-5m3/kg e 3KMg l-mge l-si e.5 38Pa e min Mg a.5 5 m 3 kg 3K min Result of PM line analysis of the oxide formed on surface of specimen made from ingot ( holding temperature : 3K, holding time : 6 min, humidity in atmosphere : 38Pa ) %e +.5%e 6 Holding timemin ffect of e addition on amount of porosity in conical castings of alloy ingots ( holding temperature : 3K, humidity in atmosphere : 38Pa ). Optical microstructure on the cross section of the specimen made from e added for ingot ( holding temperature : 3K, holding time : min, humidity in atmosphere : 38Pa ). R& Vol. 3 No. ( )

8 s recieved remelting S6 a content, mass% r-5.4%s6 r S6 r-5.4%s6 r Porosity-5m3/kg XeO eo Mg a a a S 6 a 3K.L/min S 6 5min a a.4mass%.mass% a S 6 a.mass% r- 5.4vol%S 6 a a Mg.6.mass% r S 6 a 38Pa 3min S 6 S 6 a 3min a.8 5 m 3 kg S 6 ig. 5 3min S 6 5 m 3 /kgs 6 a s received Non treatment Gas bubbling time:5min Gas flow rate :. L/min S 6 r-5.4%s 6 Gas bubbling treatment ffect of gas bubbling treatment on a content for alloy ingot. Gas flow rate :. L/min Remelting (Non treatment) Gas bubbling time:5min S 6 r-5.4%s 6 Gas bubbling treatment ffect of gas bubbling treatment on amount of porosity in conical castings of alloy ingots ( : fter degassing, : Held in humidity of 38Pa at 3K for 3min after vacuum-degassing ). R& Vol. 3 No. ( )

9 Porosity-5m3/kg l-si Mg a a ajis Mg Gas flow rate :. L/min fter degassing r r-5.4%s6 r-5.4%s 6 S Gas bubbling timemin ffect of gas bubbling time on amount of porosity in conical castings of alloy ingot held in humidity of 38Pa at 3K for 3 min after vacuum-degassing. a a a (988)6 (99)757 3 R& (99)5 4 TiwariS. N., Gupta. K. and Malhotra, S. L. The ritish oundryman(986)9 5 (966)93 6 (975)345 7 rbenz, H. Giesserei(96)5 8 GruzleskiJ.., ThomasP. M. and ntwistle, R.. The ritish oundryman(978)69 9 (98)65 rondykek. J. and Hess, P.. Trans. Met. Soc. IM (964)54 LaslazG. and Laty, P. Trans of S(99)83 (987)55 3 erezyanskayan.., rosselg., ZolotorevskiiV. S., LinzenberkO., MaiR., NovikovI. I. and Poikert, K. Sov. Non-errous Met. Res.(983)9 4 Gulyaev,.. Gasesin ast Metalsonsultant ureau New York, (965)37 5 (974)364 6 (983)3 7 (987)9 8 PillingN.. and edworth, R.. J. Inst. Metals R& Vol. 3 No. ( )

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