The melting of something prior to a subsequent process.
Under proper melting conditions there was no influence of the number of premelts on the homogeneity of the ingots2013, R. I. Jaffee, N. E. Promisel, The Science, Technology and Application of Titanium, page 35:
premelt
verb
Etymology From pre- + melt.
1
To melt before a subsequent process.
In pulsed-current MIG welding, a low background current maintains the arc and premelts the electrode tip.1973, R. J. C. Dawson, Fusion Welding and Brazing of Copper and Copper Alloys, page 11: