Heavy Metal. Part 7 - Things To Look For In Welding Material Selection, Mill Scale
The MIG welding and Stick welding processes typically handle mill scale better than TIG as the deoxidizers in the wires and the more molten puddle that is created leave time for impurities to float to the surface and bond with the deoxidizers from the filler metal and in the flux before becoming entrapped in the weld. But there are other alternatives to having to combat mill scale before welding. One of the best solutions is to buy the metal already descaled and ready for welding. You can do this by purchasing cold rolled material or Pickled and Oiled hot rolled steel. Both of these already have the mill scale removed. Not everything is available in cold rolled or hot rolled P&O steel, and cold rolled isn’t always ideal for the job since it has some different properties than regular mild hot rolled steel. These options do cost more but save on labor spent in prep and clean up. Pickled and oiled metal and Cold rolled still have a thin layer of oil to protect against rust, but both are essentially ready to weld with a quick wipe down of the metal with a rag with acetone or other approved degreaser. At this point, if the oils are removed, the metal is usually ready to TIG weld without any further prep work. P&O steel is not always available at every metal supplier, but because of its appearance, is sometimes mistakenly referred to as cold rolled steel when it is not. The pickling process involves removing the scale with acid followed with a light oil that keeps it free of rust. The appearance of sheet metal that has been pickled and oiled is somewhat similar to the bluing found on gun or rifle. Note: do not use chlorinated solvents or other similar cleaners such as brake cleaner or it will generate poisonous gas when welded and can and will lead to serious injury or death.
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