THERMAL PROCESSES IN ELECTRON BEAM WELDING ZIRCONIUM ALLOYS.

The thermal processes in electron-beam welding of sheets of zirconium alloys with 1 and 2. 5%Nb 1. 3 and 3. 5 mm in thickness without a backing sheet and with a copper or steel backing sheet and cooling straps greatly differ. The highest cooling rate of the weld zone was recorded in welding the 1 mm thick sheets on a copper backing sheet with straps, while the lowest cooling rate was obtained in welding the 3mm sheets without backing. An increase of the distance from the clamp to weld axis from 6 to 25 mm in welding pipes to plugs leads to a marked reduction of the cooling rate. With increasing distance, the effect of the clamp as an intensive heat sink becomes less marked.