I am becoming acquainted with the complexity of welding thin mild steel with a rod/arc welder; the main problem being burn through. I have read some where that putting an aluminium bar under the joint helps. Can anyone give me information on the physics/chemistry of this application? I assume the aluminium would act as a heat sink and if it works can only assume that the naturally oxide coating on the aluminium prevents the aluminium from liquefying??!!
The aluminum just supports the molten steel. If you happen to track the arc onto the aluminum surface it will create problems, vapourizing the aluminum. The Zinc in brass bar has the same problem. A much better material is copper. It has a higher melting temp and is highly conductive like aluminum acting as a heat sink to encourage the molten steel to freeze against it. The big problem is finding some copper bar. Electricians involved with high amperage systems sometimes have access to copper buss bar material. Randy
Anyone involved in metal-working should find and regularly visit their local scrap metal yards. They are a treasure trove of material and neat stuff. They will buy your small cutoffs and waste (for about .02/lb.) (and used batteries and old radiators) and sell you much larger industrial cutoffs (for about .25/lb.) Take a truck and expect to come away with far more than you deliver. Many of these yards keep a section of their yard for the better or more interesting scrap and is a great place to find small pieces of thick plate and random lengths of steel wide flange beams. They will have bins full of new cutoffs of heavy copper electrical buss material and surprisingly long pieces of heavy copper cable. Don't be surprised if you find long pieces of welding cable that only need small repairs. The quality of the scrap is dependant on the local industry and economy. If you are near a closing military base you may have a gold mine.
Wear safety boots, glasses and gloves, and a hard hat and high visibility vest is a good idea. Bring your own tape measure. Try to look like you know what you are doing. Be extra polite and STAY OUT OF THE WAY of any forklifts or heavy cranes. KEEP YOUR EYES OPEN this is a VERY dangerous environment, be very careful where you step or climb. A box of donuts for the crew will be a great investment.