http://therockcolumbia.com/pen-medium/
Pen Medium
what type of loading is E6013 recommended for? Is the weld pen ration for and E 7018 deep shallow or medium?
I have never used a 6013 but here is what the designation stands for(from what i remember from college)
E-electrode
60- 60,000 psi tensile strength
1- all position welding
3- stands for composition of the flux, however i do not remeber what 3 designates and am unfortuantely too lazy to check 
7018′s are great rods, with nice arc characteristics and medium weld penetration. However 7018′s work best on atleast somewhat clean steel, and the weld puddle is very fluid making them terrible for open root welds.
If your question about loading requirements meant how much the rod was rated to hold, a 6013 is rated at 60,000 psi tensile strength, making it a fairly strong weld.
