Electron beam welding applied to a thick aluminium blank for an aeronautic part

Nose fuselage shapes of new generation of aircraft, as Airbus A350XWB, are in double curvature. Large parts as windows frames are machined from the billet and inducing a significant buy to fly, which can reach 20. Several... [ view full abstract ]

Nose fuselage shapes of new generation of aircraft, as Airbus A350XWB, are in double curvature. Large parts as windows frames are machined from the billet and inducing a significant buy to fly, which can reach 20.
Several options exist to reduce the quantity of raw material, as it can lead to drastic cost savings. One option consists in rebuilding a sketch with a near-net shape closed to the final dimensions, by welding parts of raw material. One issue is the fact that materials commonly used are precipitation-hardening aluminium alloys, with a low capability for welding. Electron beam then offers the opportunity to bring enough energy, guarantying a local application for high thicknesses.

A particular attention has been brought to the main issues of the technology. The first consists in the minimization of residual stresses during heat treatment phases. Numerical simulations and tests have been performed to evaluate the best compromise between residual stresses and mechanical properties. The second one concerns the control of dimensions during the whole process, offering to the machining experts a detailed view of the state of the sketch, in order to avoid huge deformations in the milling phase.

In order to prove feasibility and reduce uncertainties, a technology demonstrator, based on A350XWB lateral windows framing, has been achieved. The whole manufacturing process has been investigated and can be described through the following steps:
- Welding key process parameters for 7175 thick plates have been determined
- An initial sketch has been welded, assembling 7175 plates with a thickness value equal to 100mm with approximately 1200mm height and 1000mm width
- A specific heat treatment cycle has been done in order to regenerate sufficient mechanical properties in the heat affected zones
- The part has been machined to the final dimensions, balancing the effects of residual stresses