Fusible pattern casts housing profile to expect the chemical stability of active to melt alloy element studies

23 　 [document label is piled up] A 　 [article number] 1001-4381(1999)06-0020-02Study Of Chemical Stability Of Investment Casting ShellMaterial To Active Elements In Molten AlloyZHANG Yong, XIA Ming-ren(Institute Of Aeronautical Materials, BSeijin100095, china)Abstract: The Chemical Reaction Between Three Different Shell Materials And Nd, a More Active Metal, was Studied.

The Results Show That The Mineralization In Shell Material Easily React To Active Metal, and The Shell Made Of Y2O3 Has Excellent Chemical Stability.

Key Words: 　 of Investment Casting;shell-mould;chemical Stability casts a process in fusible pattern in, housing serve as " container " was full of melt metal, be in especially directional with single crystal craft in, the time that alloy carries liquid state is as long as 60min, housing material each groups the portion produces chemical reaction very easily with alloy fluid, reflect housing material and the condition that alloy happening reacts for better land, this experiment is chosen contain some alloy with more Nd of element of strong active metal to regard research as the object, the reaction situation that studied gold of confluence of all sorts of carapace material and this kind of frit, provide a basis to choose suitable case material. 1 experiment method experiments to be with the bases of alloy: 28 ％ of Nd 24% ～ , b 0.

7% ～ 1.

2 ％ , al ＜ 0.

05% , si ＜ 0.

1% , fe surplus. The case that the experiment uses 3 kinds to make crucible record, housing profile expects and in group the circumstance sees a table 1. Coating of makings of oar of carapace of The Shell Mould Adopted In The Test of 　 of the carapace that expresses 1 experiment to use Table 1 category hangs kaolin of ＋ of pink of corundum of ＋ of collosol of arenaceous A silicon (mineralizer) yttria of frit of report of ＋ of collosol of silicon of C of arenaceous 　 of corundum of pink of corundum of ＋ of collosol of silicon of corundum arenaceous B powdery yttria is arenaceous 10kg alloy, in ZG-0.

025 model warm up inside vacuum induction furnace to 20min of 1550 ℃ heat preservation, 20Pa of force of furnace internal pressure, nature is cooling, use after sampling can the Al in alloy of chart appearance analysis, the content of each element such as Si and Y. 2 tests result and discuss the analysis that uses element of part of alloy of 3 kinds of carapace fusion to see a table as a result 2. The analytic result after expressing 2 alloy and 3 kinds of housing reaction (Wt ％ ) carapace of The Analytical Result Of Reaction Between Three Shell Materials And Alloy of Table 2 　 AlSiYA0.

35 ＜ 0.

10-B0.

15 ＜ 0.

10-C- ＜ 0.

100.

0084 　 from the watch 2 can see, become split phase to compare with former alloy, the alloy composition after using 3 kinds of carapace fusion changes somewhat, the specification issues 3 kinds of carapace as shirt-sleeve as frit golden hair to had given birth to proper chemical response in high temperature, among them the reaction of housing A is most severe, content of the Al in causing alloy raised about 7 times. The most important characteristic in the constituent of housing A is to contain the kaolin that passes calcination to serve as mineralizer. The bases of kaolin is SiO2 and Al2O3, look from micromechanism, have layer shape structure, oxygen of a silicon is tetrahedral overlap each other with octahedron of an aluminous oxygen, with oxygen key joins between the layer and the space is larger, when be being contacted with alloy fluid below high temperature, the Nd of active metal element in alloy enters the structure between the layer in great quantities, with its medium Al2O3 produces displacement reaction, the Al that displacement gives enters alloy in, reaction form is as follows: 　 of 2Al of ＋ of 2Nd ＋ Al2O3Nd2O3 looks as a result from the analysis, housing B also has the reaction of certain level, this carapace as different as housing A point is not to contain mineralizer, contain electric frit corundum only, the bases of electric frit corundum is Al2O3, the Al2O3 of the recrystallization after fusing forms crystal with the spread out of plumbic oxygen octahedron, key structure is stable, want to destroy this kind of structure to need very high energy, when electric frit corundum and alloy are contacted, nd atom comes out Al displacement in the crystal lattice of not easy and thorough Al2O3, but the Al that still the part is in crystal brim attended reaction, just measure very few, comparative result A and B, a few mineralizer (make an appointment with 4wt ％ ) the Al that is come out by displacement and electric frit corundum (make an appointment with 95wt ％ ) in the Al that is given by displacement is almost equal. This explains, when producing chemical reaction with alloy when housing material, the active of mineralizer is bigger than the active of electric frit corundum much. From the analysis the result looks, the yttric content in the fusion alloy that employs housing C fusion is only 0.

0084 ％ , the quantity of this specification and the Y2O3 that alloy reacts is very few, its react type is: Y2 of ＋ of Nd2O3 of → of 2Nd ＋ Y2O3. Because Y2O3 is the electrovalent bond compound of structural adamancy, key structure is very stable, look from atomic structure, the atomic radius of Nd and Y and photograph of tervalent and ionic radius are about the same, because of this chemistry very close, nd is not so easy displacement Y. Y2O3 of only little part attended chemical reaction, this also shows yttria case model have very good chemical stability. To the SiO2 in mineralizer and binder SiO2, be like next reaction: SiO2 ＋ Nd2O3Nd2O3. SiO2, nd2O3 is taken by raw material or arise in fusion process, nd2O3. SiO2 frit enters alloy fluid in, because produce conditional control, it is finite that the belt of Nd2O3 enters an amount, the Si content change that sees 3 kinds of cases from reaction result is not big. 3 conclusion fall in this experiment condition, 3 kinds of carapace in, the active metal element in the carapace that contains kaolin as shirt-sleeve as frit gold produces serious chemistry to react, and yttria carapace chemical stability is best. CNC Milling CNC Machining