ELECTRON-BEAM WELDING OF BERYLLIUM.
Final technical rept. 1 May 65-31 Mar 66,
BATTELLE MEMORIAL INST COLUMBUS OH
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Electron-beam welding procedures were developed for 0.020-, 116-, 18-, and 14-inch thick beryllium sheet. For the three thicker sheets, weld undercutting and surface roughness were major obstacles in the development of satisfactory procedures. Welding procedures were developed that alleviated or entirely eliminated undercutting and surface roughness. Films observed on weld surfaces contained a large percentage of beryllium oxide. The thickness of these films increased with the oxide content of the base metal. Weld undercutting, surface roughness, and porosity increased with the beryllium oxide content of the base metal. The effects of restraint on weld cracking were evaluated by determining the preheat temperature necessary to prevent cracking when high and low restraint were imposed on butted sheets. Higher preheat temperatures were necessary when the restraint was increased. Weld distortion was measured in beryllium and compared to distortion produced in aluminum and stainless steel by electron-beam welding. Transverse shrinkage and longitudinal bowing were measured. Multiple-pass welds made with a low-power-density electron beam produced greater shrinkage that did single-pass welds made with a high-power-density electron beam. Measurements of longitudinal bowing indicated that the three metals behaved in a similar manner. Bend tests and tensile tests were performed with base-metal and welded specimens that were 116- and 18-inch thick. Bend transition temperatures from ductile to brittle behavior were about twice as large for transverse-bend specimens as for base-metal specimens. Greater bend ductility was exhibited by specimens having lower amounts of beryllium oxide.
- Fabrication Metallurgy