Resistance welding for galvanized steelgreenspun.com : LUSENET : Resistance Welding : One Thread
We are a fabricating firm who manufactures air-con cabinets for an appliance company. For the air-con cabinets, we use gauge 22 galvanized steel. After forming we need to weld a gauge 23 galvanized bracket on the cabinet. We use a berrylium copper electrode for the machine and the electrode is dressed like a cone however life of the electrode are short before wearing out. I would like to seek some advise on how to get a good weld on welding this type of material as well as information on the type of electrode ( material, dressing, maintenance)
-- Ben Chan (firstname.lastname@example.org), June 18, 2001
Working in the automotive industry, i am used to setting up welding systems for hot dip galvanised components, after experimenting with the welding pocess, we found the most suitable weld quality and tip life to be through using to weld cycles, i.e. weld1 short weld time high current to burn coating away localised area - weld2 average weld time average current (pogram you curently use).
Additionally, you may want to try experimenting with different electrode material - berrylium is a very had material, also gives off harmfull fumes when welding (depending on berylium content), one type of weld tip you could try using is Ni-trode welding caps, they are speciffically designed for welding coated mateials.
You will always have a problem with tip life as compared to standard welding, where the coating is burned into the tip, copper + zinc = Brass, so frequent tip dressing is essential to remove this brass coating forming on the tip. If this is a manual process, tip dressing should include cleaning the tip face along with keeping the tip diameter at the necessary size. If you give further information, maybe i can help more.
Regards and good luck,
-- Gareth Bonnell (email@example.com), June 23, 2001.
There is always different ways to solve a problem. Although I have used the method described by Mr. Bonnel. With some success, I usually reserve this method for a secondary solution rather than a first choice. As a first choice solution, I subscribe to the preheat/ upslope weld set-up for welding galvanized material. This method brings the lower melting temperature galvanized/ aluminized material to a molten stage with the electrode force squeezing the coating to the circumference of the weld zone. A second welding time and current is applied similar to that of bare steel. The hold time is set short so that the outer molten coating material can flow back over the weld zone as the electrode is removed.
The fumes given off by the coated material is hazardous. Normally spot welding in a well ventilated area can be done without requiring smoke removal devices. However, this should be evaluated for each individual application. I believe that the electrode material - beryllium only gives off harmful fumes when the material is machined, and the dust particles are inhaled.
I agree you will never achieve the electrode tip life of bare welded materials. However, the electrode manufacturers are constantly updating the materials used for welding coated materials, in an attempt to improve electrode tip life. It should be noted that the cost of these different materials need to be evaluated for cost effect. Presently “Z-Trode”, “Nitrode”, “Glid-Cop” alloys as well as Cryogenic materials are just a few of the different materials used.
-- Bob Balla (firstname.lastname@example.org), June 25, 2001.
I agree with the advice given by the previous correspondents and would add that the tip life and weld quality can be improved by ensuring that the weld set up is good for the weld as described.
However heatstepping increases heat and therefore your cooling at the electrode tip should be good and a flow of 5 ltrs per minute will improve tip life.
Then frequent tip dressing just to remove contamination from the face will retain condition of the electrode instead of reclaiming it and wearing it away.
Too frequently tip dressers machine too much material from the electrode when not needed.
You can contact me for more info if needed.
Regards, Martin Smith
-- Martin D Smith (email@example.com), August 20, 2001.