IMPROVEMENT OF THE WELD SEAM BY STRIP EDGING
If the slit edge is used as a functional edge, the edge quality of the slit strip is not adequate to produce a high quality product. Less than 35 % of the edge area is cut cleanly. The rest is broken and exposes the ruggedness of the slit, unevenness concerning straightness, angle and structure. Coatings (e.g. with tin, aluminum ...) and oxidation disturb the welding process. The V-shaped opening between the edges widens with increasing strip thickness and decreasing tube diameter. The cross-section of the two edges which have to be welded diminishes and the area which has to be liquefied grows.
This means that the areas which must be compressed as well as the compressing force after welding have to increase. The weld setup grows and the weld seam has to be shaped at the inside and the outside of the tube. Modern welding processes – such as laser welding – demand machining of the slit edge as a pre-condition for efficient processing.
The optimization of the strip edge is a basic condition to benefit entirely of the advantages of modern welding methods.
Optimization of the weld seam by strip edge trimming by metal-cutting
The JULIUS strip edge trimming machines treat the edges by metal-cutting. The edges are steadily cleaned and straight. They meet requested dimensions and expose the inner structure at the surface.
The edges are treated at an adjustable angle so that any coating is removed and the V-angle is shaped to any angle.
The area where the edges touch each other is optimized so that less material has to be liquefied. The result is:
- less energy input and/or higher welding speed
- less compression and less bulge
- less shaping at the inner and outer welded seam
- fewer rejections
- gain of material, because less compression force means less strip width addition
- homogeneous welding structure
- better shape due to less compression