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| KINETICS OF Mg EVAPORATION DURING VAR OF A Ni-BASE SUPERALLOY |
| FU Jie; WANG Hui; WANG Di (Beijing University of Iron and Steel Technology); CHEN Enpu (Changcheng Steel Works; №3 Branch in Jiangyou; Sichuan) |
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Cite this article:
FU Jie; WANG Hui; WANG Di (Beijing University of Iron and Steel Technology); CHEN Enpu (Changcheng Steel Works; №3 Branch in Jiangyou; Sichuan). KINETICS OF Mg EVAPORATION DURING VAR OF A Ni-BASE SUPERALLOY. Acta Metall Sin, 1983, 19(2): 126-133.
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Abstract The remelting of consumable electrode and the Mg distribution in various zones at electrode tip during VAR process of a Ni-base superalloy Ni-10Cr-15Co-6W-6Mo-4Al-2Ti were studied. It was found that a remelted metal ring sticks to the electrode surface near tip. The Mg distributes in the metal ring rather homogeneously, but in remelted metal layer or in the liquid-solid binary phase zone heterogenously. The thickness of the remelted metal layer is varied with its position from electrode tip and averaged 1—1.5mm. The Mg content increased gradually with the increase of distance from the metal film/atmosphere interface via liquid/ solid binary phase zone to the unmelted electrode. The Mg concentra-tion either in the remelted metal ring, [Mg]_r, or in the outer layer of remelted liquid metal was less than that in the remelted ingot, [Mg]_i. Under present experimental conditions, [Mg]_(0.15)=0.18[Mg]_e=[Mg]_r; [Mg]_(0.40)=0.30[Mg]_e =[Mg]_i, where [Mg]_(0.15) and [Mg]_(0.40)=Mg concentration in the outer layer of remelted liquid metal at 0.15 and 0.40mm respectively; [Mg]_e and [Mg]_i=Mg concentration in electrode and in ingot respectively. It seems that the Mg is mainly evaporized in the droplet forming period during VAR process. The liquid metal flows round the surface of electrode tip and is unable to expose fully under vacuum. The process of Mg evaporation may be controlled by the transfer rate of Mg atoms from unmelted electrode into the liquid metal film/atmosphere interface. The coefficient of mass transfer K_(12)=0.107 cm·s~(-1). The Mg content in remelted ingot, [Mg]_i=[Mg]_e exp(-K_(12)Aγw~(-1). Thus, the optimum [Mg]_i can be realized by controlling [Mg]_e and the remelting rate w.
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Received: 18 February 1983
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10 Johnson. E. W., J. Met., 12 (1960) . 850．
11 曲英,炼钢学原理,冶金工业出版社,1980,p.74． |
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