DOM and HREW are both mild steel (usually 1020) and can easily be welded with MIG (or stick). The chromoly (4130) tubing is an alloy of steel, chromium and molybdenum and is quite a bit stronger and more expensive than mild steel. Most mild steel yiled strength is in the 60,000 psi range where as chromoly is in the 95,000 psi range.
Although chromoly can be welded with MIG, TIG is prefered and the welds must be heat treated after welding to relieve stress.
There is a good article on the FEB 06 4wheel and off road mag
Although chromoly can be welded with MIG, TIG is prefered and the welds must be heat treated after welding to relieve stress.
There is a good article on the FEB 06 4wheel and off road mag