EN is less penetrating than EP. If I had to run a root with 6013 I would likely run it EP, requirements of the WPS and the manufacturer's recommendation notwithstanding. What 357 says is true: if you test it, you gain firsthand experience and that may help you decide what type of application the electrode is best suited to. This is also why we have a WPS, to give us these variables in advance. All WPS are not created equal: therefore, you might want to have a basic understanding of what all those little zoomies are doing inside that arc and how the electricity interacts with your base metal and filler metal to make the "perfect" weld. This is also why current and polarity are listed as essential variables on a WPS. Now, if you're just in your back yard fooling around, then you can pretty much do whatever you want. However, as one starts adding stress to a welded joint, it becomes a little more important to ensure that the weld is sound. Now I can grab a stinger and sling just about any stick you give me and make a "good" looking bead. However, a good looking bead isn't enough. You have to make sure that it actually joins the two parts of your weldment, that it will hold...this is now called a sound weld. There are two elements to making a sound weld: a procedure and a technique. The procedure is easy. The technique can take years or tens of years to perfect. The most important and most difficult variable in the welding process is the welder.
I'm glad you want to learn, dude. What is that flange in the photo for? It looks really thin on the pipe side.
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