Welding with Backing Tape
Tapes today are manufactured with superior adhesive properties and efficiently adhere with light pressure. Using tape can save you time and lead to more uniform welds. The two primary types are Alu-Fiber backing tape and ceramic backing tape.
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Alu-Fiber Backing Tape
The non-metallic backing system is recommended where purging is required, but not easy. The product is designed to eliminate the need to back purge, save cleaning costs, and eliminate weld defects. It is designed for stainless steel and alloyed metals and is suitable for sheet, plate, pipes and vessels. The tape should be adhered to the side opposite of the weld on thin-wall stainless or vessels. The tape will support the weld pool and keep argon from the torch. The under-bead profile will be more consistent. Check manufacturer’s specifications, but cloth should support up to 130 amps with a 2” strip.
Ceramic Backing Tape
Ceramic backing tape is common in the ship building and automotive industry. The tape is composed of ceramic tiles attached to an aluminum tape. Heat resistant adhesives are used. The tape can be used for general welding. Ceramic backing tape can be used with most types of electric arc welding equipment including MIG, TIG, and submerged arc. It will produce a smooth homogenous weld by supporting the puddle and forming consistent back beads during plane welding. Welds should be free from porosity and inclusions. Ceramic tape eliminates back gouging and root passes.
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You’ll find both channeled and flat tape. Channel tape has a “U” shaped bottom. Flat tape has an aluminum wrapper. Press the foil tape into the side of the ceramic tape. Put the ceramic and foil tape over the root. Press the foil tape onto the back of the plate to weld. Center the tape onto the root of a clean plate.
Weld joints are done from one side; the tape is opposite. The ceramic backing tape acts like a mold for the electrode to fill. Weld quality improves and tape requires less skill. You’ll save time with ceramic backing tape when you use it to convert two-sided projects into a single-side weld. When finished, peel off tape and discard. The tape will not cause chemical or metallurgical changes.
Welding with ceramic backing tape is very similar to doing an open root weld, except easier. Here is the trick – it’s all about the angle. The angle of the reverse grip FCAW being pulled or moved is crucial. The electrode must press a deep puddle in the film. If you are doing vertical up welding, the angle of the electrode should be pointing down.
Fill in the ceramic mold. Move slowly from side to side. You should have a puddle to start the edge of the track and allow the metal to fill the joint. After both sides have been merged with the slope, the electrode never has to leave the pool. If you get out of the puddle the wire has a tendency to push the tape off the plate.
Practice on some smaller pieces or scrap and soon you’ll be using ceramic backed tape to save you time – all of the time.