I am not sure what your setup looks like but when i weld up my frame this is what i did. I did a butt weld but i grinded one side of each piece to an angle that way when you put the two pieces together it forms a "V". That is so when you weld it up you weld both sides of the steel. Also when you grind down your weld you have some weld left in the joint. Then i would recommend putting a gusset over the welded area. I know some don't but i feel more confortable knowing there is extra strength in the welded areas. Here is a pic of my gusset and underneath it is welded just like i explained. Good luck and feel free to ask any more questions if you have any.
