To be honest, I have no idea what E6 steel is so I guess that it is best to treat it like mystery metal. If you have a section of that bar left, it doesn't have to be more than a couple of inches long, heat it to non-magnetic, soak it in the fire for about a minute, then quench in water. After that strike it with a hammer. If it shatters then it probably has enough carbon in it to make a good knife. If it just bends I would suggest that you chalk one up to experience and get some known steel from some place like, Admiral Steel, Kelly Cupples, or Arlo-The New Jersey Steel Baron and start over.
If the bar does shatter then I would heat the blade to non-magnetic and let it cool at least to a black heat three time. That's normalization. After normalization I would again heat the steel to non-magnetic and then let it soak for about one minute and quench in warm oil. Take the blade directly from the quenchant and place it in an oven that has been pre-heated to about 375 degrees, pausing only long enough to scrub the oil off with hot soapy water, and temper the blade for three, two hour cycles.
Do a finish grind on the blade taking it down to a course edge. Get a piece of plain steel wire, something about bailing wire weight, and try to cut through the wire by striking the spine of the blade with a mallet. Hopefully, it will do it without any damage to the edge. If the edge chips out, then retemper at 25 degrees higher after you grind the chip out. If the edge rolls over then you are going to have to requench the blade and retemper at 25 degrees lower. Retest after repeating the heat treating and readjust the temperatur for tempering by 25 degree higer. Contunue in 25 degree incriments as needed until you have the hardness in the edge that you want. It is easier to sneak up on the proper temper from the low side because that will allow you to adjust the tempering heat without having to reharden (quench). That process really puts the steel through some changes and you always run the risk of cracking to some degree.
By the way, where did you find the weld steel E6? If it was down at the local hardware store there's a real good chance that it's structural steel that's too low in carbon to make blades with. Reguardless, I hope that things work out for you.
Doug Lester