What are you going to weld?
What you are going to weld will determine the proper electrode for the job.
Electrodes come in mild steel, hi-carbon steel, special alloy steels, cast iron alloys, and non ferrous. They also come in a variety of tensile strengths as you probably know.
You should select your electrode to be as near the composition of the base metal as possible and also at least as strong.
Most of your common welding would be done with E6013, E6011, E7014 or E7018 rods which would fall in either mild steel or high carbon steel ASTM classifications. The 60 rods being 60,000 psi tensile strength and the 70 rods being 70,000 psi tensile strength. Any of these should blue alright. 6013 and 6011 are essentially the same rod, the only difference is that 6013 has a rag based coating and 6011 has a different coating which makes it penetrate deeper. 7014 and 7018 are the low hydrogen rods and work better on hi carbon steels. I have had good luck running them all, they machine well, and will blue well.
