Comparison: atmospheric or vacuum cladding

Although atmospheric cladding is an effective process there appear to be advantages if the explosive bonding process is carried out under vacuum. Apart from the fact that the vacuum process is much quieter, its greatest advantage is that it is not necessary to remove any air from the advancing, explosive-bonding jet.

For this reason less violent explosives can be used for bonding and this, in turn, produces a smoother wave bond between the aluminium and steel which is often barely visible. A turbulent wave motion can trap oxides resulting in 'holes' being visible in the bond zone. These are in fact, undesirable agglomerations of oxides as shown in the illustration on the right. If this product is subjected to the hammer bend test it can be seen that the fractures initiate at these points. Vacuum clad products do not have this problem. The table below shows the comparative properties of atmospheric and vacuum clad products.




Coarse oxide agglomerations with porosity at the steel-aluminium interface. Oxide agglomerations & porosity initiate fracture.
atmosph
Oxide agglomerations & porosity can eventually cause corrosion, in spite of protective coatings. Bending of aluminium-steel strips can be difficult due to the coarser bond structure. Production control is limited by variable weather conditions. Aluminum - steel joint is hard making sawing and forming difficult.






100% dense, homogenous joint. Very good formability due to ductile aluminium-steel joint.
vac
Optimal process control due to constantly reproducible vacuum conditions.
Easy sawing and forming thanks to ductile aluminium-steel joint.