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When welding to plates together using SMAW, how do you find the root opening? We thought it was the size of the uncoated rod but that seems to big? So is it the found by the size of the rod or by the size of the plate?
Do you mean; what dictates the root opening on a particular weld joint setup? What is your setup?
Root opening is not last choice. Root face has a great influence in weld penetration. I think size of uncoated electrode is a good idea and your problem has been for thin root face (I understood your weld has had excessive penetration).
However, mass of work piece and preheating influence welding penetration, too.
The more mass of work piece, the more heat sink. When heat sink increase; welding penetration decrease.
Also, Preheating decrease heat sink and increase penetration.
You can find some ranges for root opening and root face in D1.1 figure 3.4.
What`s the joint desing? square butt joint, single v-groove or double v-groove?
We are using a single v-groove. As for what my question was is that we were using 1/4 mild steel plate and 1/8 E6011. It seems right that the root opening should be 1/16" which would be half the diameter of the rod. Does this hold true if using larger rod?
on these two pieces that are beveled...are they at a knife edge? ..or is the edge ground down a little?...once you have the bevels complete...take a grinder to them both...and flatten the edge...this is called (in my class) a "land" its purpose is to hold the metal with out blowing through it...it should be only about 1/16...and your root opening.. the 1/8 is the max you should have try a 3/32.... thats what i use..and i can keep the electrode in the keyhole better with out blowing through. and also..check your amps....when i use a 1/8 6011 rod for a root pass this type of set up...i use about 68-72amps (depending on the machine) in my mind....you shouldnt have to go over 80amps.
a general rule is....the root opening should be the same as your diameter of your rod...but...some people prefer to go smaller on the root like me...dont go over the diameter of the rod..stay under.
I know that there is a sliding scale for rod selection for a specific metal thickness. I.E. : 1/4 " Mild steel plate, uses 1/8" E6011 rod with a root opening of 1/16". But what are the "increments" ? Question being : what is the electrode size and root opening for 1/2 mild steel plate, 1" plate? etc, etc....HELP!
The best way to get your root opening is...
Determine the size and type of rod you want for your root pass. EX....E6010,6011,7018, 3/32, 1/8, 5/32, 3/16..etc.
Also read the prints because the engineer may have a specific root opening that he wants. If you're going to have a full pen. weld, you can go a little heavy on the land to make sure you can use a bigger electrode for a larger deposit. That way you can possibly just backgrind the other side, and not have to gouge.
As far as increments for 1/2", 3/4", 1".....Use a root opening that you're comfortable with...
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