Magnetic field effect on the quality of nickel base alloy slabs produced by arc-vacuum melting

It is shown that magnetic displacement CH = 60-120 Oe of a melt of VDP nickel alloy ingots in a bath leads not only to reduction in the size of the grains but also to the formation on the macrostructure of spherical light spots, spot segregation, to the development of general chemical inhomogeneity vertically and along the cross-section and to a reduction in the stability of the metal condensate on the crystallizer walls. The influence of chemical composition on the susceptibility of the alloy to spot segregation is considered. The studies were performed with nickel alloys Ehl692 and EhI 437 BU (containing 2.7-2.9% Ti) and chromium-nickel alloys Kh20N80, KhN70TYuR, KhN73MBTYu and VKh4. In the general case, the susceptibility of an alloy to spot segregation is determined by its solidification range - the greater this range, the bigger the segregation spots and the more pronounced the tendency of the alloy to form them. For example, spot segregation does not occur in ingots of the alloy Kh20N80 with the solidification range of 20degC but it does in the alloys Eh143BU and EhIl698 (solidification range 60-70degC), while the largest segregation spots appear in the chromium-base alloy VKh4 (solidification range 150degC). (author)