Fusion depth

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I have seen this mentioned in textbooks but have not seen anyone talk about it. It would appear that if you were to run a series of mig beads and started turning down the voltage and wire speed, the bead would get to the point of barely fusing to the metal. Anyone have any info on this?
Reply:probably just the process of not "mixing" the two metals together with enough heat.?StangnetShop Full Of Stuff. Joey
Reply:Fusion depth or penetration can be varied by a variety of factors.  welding gas, wire, voltage, and amperage are some primary factors.  these are set before you start your weld.  Travel speed , stickout, and gun angle will also have an effect.  These are secondary factors that you can adust on the fly.
Reply:I see penetration as taking two pieces of metal and joining them so they are completely welded where they touch each other. If you had two 1/4 thick strips and butt welded them but only joined one half of the thickness, that would not be full peneration. Would not that be defined as incomplete penetration?
Reply:There are many joints that are spec'd as partial penetration so don't get hung up on trying to get full penetration assuming you will achieve maximum strength.A better way to look at peneteration is that it is unwise to believe that your weld heat is sinking into the parent metal enough to joint any part of those 1/4 inch plate pieces.   If you want 1/8th penetration you should be preparing the edges of the butt joint. with a bevel 1/8th deep.   Comments like " I turned the heat up, that should do it"  don't cut it when welding to a code.An interesting point is that in structural code a weld symbol of a butt joint with no indication of penetration depth required must have 100 percent penetration.   Making the rule work this way covers everyone's butt but often creates cost overruns doing unecessarry operations.The important thing in all this is: Are you getting good fusion to the edges of your preparation??!!!
Reply:Originally posted by lotechman There are many joints that are spec'd as partial penetration so don't get hung up on trying to get full penetration assuming you will achieve maximum strength.A better way to look at peneteration is that it is unwise to believe that your weld heat is sinking into the parent metal enough to joint any part of those 1/4 inch plate pieces.   If you want 1/8th penetration you should be preparing the edges of the butt joint. with a bevel 1/8th deep.   Comments like " I turned the heat up, that should do it"  don't cut it when welding to a code.An interesting point is that in structural code a weld symbol of a butt joint with no indication of penetration depth required must have 100 percent penetration.   Making the rule work this way covers everyone's butt but often creates cost overruns doing unecessarry operations.The important thing in all this is: Are you getting good fusion to the edges of your preparation??!!!