Abstract
During the process of electroslag remelting (ESR) of steel containing titanium and aluminum, the activity ratio between titania and alumina in CaF2-CaO-MgO-Al2O3-TiO2 slag must be fixed in order to guarantee the titanium and aluminum contents in the ESR ingots. Under the condition of fixed activity ratio between titania and alumina in the slag, the melting temperature of slag should be investigated to improve the surface quality of ESR ingots. Therefore, this paper focuses on finding a kind of slag with low melting temperature that can be used for producing steel containing titanium. In the current study, the thermodynamic equilibrium of 3[Ti] + 2(Al2O3) = 4[Al] + 3(TiO2) between SUS321 steel and the two slag systems (CaF2:MgO:CaO:Al2O3:TiO2 = 46:4:25:(25 − x):x and CaF2:MgO:CaO:Al2O3:TiO2 = 46:4:(25 − 0.5 x):(25 − 0.5 x):x) are studied in an electrical resistance furnace based on Factsage software. After obtaining the equilibrium slag with fixed activity ratio between titania and alumina, the melting temperatures of the two slag systems are studied using slag melting experimental measurements and phase diagrams. The results show that the slag systems CaF2:MgO:CaO:Al2O3:TiO2 = 46:4:25:(25 − x):x, which consists of pre-melted slag S0 (CaF2:MgO:CaO:Al2O3 = 46:4:25:25) and pre-melted slag F1 (CaF2:MgO:CaO:TiO2 = 46:4:25:25), can not only control the aluminum and titanium contents in steel, but also have the desired low melting temperature property.
Highlights
Electroslag remelting (ESR) [1,2] is one of the processes used to produce high quality special steels
For superalloy or stainless steel with a melting temperature lower than 1370 ◦C (1643 K), the melting point of the slag used for ESR of superalloy and stainless steel should be lower than 1270 ◦C (1543 K)
It is clear that: (i) with a CaO/(Al2O3 + TiO2) ratio = 1, the melting temperature of the slag S0-F1 is lower than slag S0-F2 7wofi1th0 a CaO/Al2O3 ratio = 1 under the condition of increasing TiO2 content in slag; (ii) when the TiO2 content reaches more than 9%, the melting temperatures of slag S0F1-3 and S0F1-4 are much lower than that of slag S0F2-4 and S0F2-5; (iii) the melting temperatures of slag S0F1-T4hiesnmthuecmh ellotiwngertetmhapnertahtautreosfosflathgerSm0Fo2d-y4nianmTicabeqleul7iburinudmersltahgescyostnedmitsioinnToafblfeix7ing satreeeml ewaistuhreldg iwn sla/gwmelti5n.g03e;xp(ievr)imthenetsm, aenltdintghetreemsupletsraatruerleistoefd tihneTasblaleg3.S0-F2 system
Summary
Electroslag remelting (ESR) [1,2] is one of the processes used to produce high quality special steels. It is essential to investigate the melting temperature of CaF2-CaO-MgO-Al2O3-TiO2 slag under the condition of fixing activity ratio of titania and alumina in the slag during the ESR process. Jiang [8,9,10,11,12,13,14,15,16] investigated the thermodynamic equilibrium of 3[Ti] + 2(Al2O3) = 4[Al] + 3(TiO2) and the effect of slag components on activities of Al2O2 and TiO2 in CaF2-CaO-MgO-Al2O3-TiO2 slag system, and TiO2 in slag was calculated to control the titanium and aluminum contents in ESR ingot. After obtaining the equilibrium slag with fixed activity ratio between titania and alumina, the melting temperature of CaF2-CaO-Al2O3-MgO-TiO2 slag was studied by slag melting experimental measurements and phase diagram.
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