Electron beam welding is a process used in the aerospace industry for its ability to make precise, low distortion welds under clean vacuum conditions which promote the formation of high quality welds in many materials.
As conventionally applied, the technique can make welds with very low heat inputs, at relatively high weld speeds. It also has the potential for other materials processing tasks, as well as advanced welding techniques.
The EB heat source can be 'split' during welding so that a portion of the beam's energy can make the weld in the normal way, and the remainder can be 'shared' between locations elsewhere on the workpiece. The beam is cycled between the different locations many hundreds of times a second, so the weldpool does not 'know' the beam has gone. Elsewhere, the beam can heat the workpiece up, or make a second perhaps cosmetic weld pass at the same time as the main weld pass is made.
Manipulating the electron beam so that it effectively becomes multiple heat sources can allow a radical change in the application of the welding process to materials that would be likely to suffer cracking or other welding difficulties when welded in a more conventional fashion.
The application of multiple heat sources to the welding process allows the solidification rate of the weld metal to be controlled, as well as some of the stresses around the solidifying and cooling weld metal. Welds made in this way are frequently made at lower weld speeds than would normally be the case for EB welds, and are made with a higher heat input per unit length. Despite this, levels of distortion in such welds are frequently relatively low.
This special welding procedure can consist of a simple 'travelling preheat' zone ahead of the weldpool. At its most complex, a large change in the stresses around the weld can also be achieved and welds with microstructures not normally found in welds of low distortion are made.
The practical application of this family of welding strategies requires the fitment of additional equipment to an otherwise standard EB machine, and careful development and control of the welding procedures themselves for optimum results.
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