Weld Integrity – EB Welding is essentially a machine-controlled process in which precise parameters can be determined at the development stage and logged for future use in the production of the component.
The EB weld process is a vacuum remelt of parent materials, providing parts are thoroughly clean and correctly fitted, results are highly respectable and of excellent quality.
Hence, providing that the weld development is designed to accurately simulate the physical geometry and material specification of the actual component the results achieved on the test pieces will be repeatable within very close tolerances on the production components.
Non-destructive testing of EB welds is a subject in its own right but a brief summary of the principal NDT methods used should be included:-
- Visual Inspection – All welds are visually inspected using x 10 or greater magnification as necessary. Surface defects e.g. cracks, mis-alignment, under penetration or undercutting can usually be detected by this method.
- Penetrant Crack Detection – Normally the water washable fluorescent dye technique is used to identify possible surface defects that may not be readily seen by visual examination.
- Radiography – Where the component joint geometry permits, an X-ray examination technique can identify sub-surface defects that would be hidden from the Visual and Penetrant Inspection methods. In particular, internal porosity and crack defects can be identified and recorded on film. Radiography is, however, a relatively expensive NDT technique and for this reason is sometimes used on a sample basis, typically 10% of the batch of components welded.
- Ultrasonic Testing – Subject to component geometry, Ultrasonic testing can provide a cost effective and reliable method for detecting internal weld defects. Results can be assessed against a go/no go setting and printed to provide a permanent record.
- Pressure or Vacuum Leak Testing – These provide, again subject to component configuration a performance test of individual components.
- Batch Control Test Pieces – Test pieces directly simulating the component weld and material condition can be used for quality control and can be run either before, after or during the production batch. They provide the opportunity for NDT and macro and micro section examination.
- Process Control Specification – ENISO now offer process control and acceptance criteria specification. EBP has its own specification for weld acceptance criteria, EBP/QAS/01 latest issue. which is available on request.