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Up Topic Welding Industry / General Welding Discussion / Metal Cored wire
- - By Topher Date 09-02-2016 22:42
Hello all! I am new to the AWS forum site and am a brand new CWI of about a month. I am sure I will be here frequently to ask questions.
My question today pertains to metal cored wire. I have always noticed a line that forms longitudinal down the center of the weld. I have asked what it is to people and done re-search it but I come up with various answers. Can anyone tell me what this truly is? Thank you.
Parent - - By welderbrent (*****) Date 09-03-2016 00:44
Topher,

WELCOME TO THE ORIGINAL AWS WELDING FORUM!!

Been a while since I ran any metal core, but, I think I know what you are referring too.

I believe if you slightly increase the wire feed speed per the volts used it may diminish.  If I remember correctly, you will see it on spray arc and metal core depending upon joint configuration and welding parameters. 

You may also be trying to get too wide of a pass so through the center it is affected by depth to width ratios as well as cooling rates from such a high arc heat to a quicker cooling compared to many processes. 

You could try narrowing the weld bead as well as adding a bit of wire feed speed.  And, if your materials are not very thick you may want to lower the volts and amps. 

He Is In Control, Have a Great Day,  Brent
Parent - By Topher Date 09-03-2016 14:49 Edited 09-03-2016 17:44
I am welding 3/4 inch plate to an I-beam that has a flange about 5/16". Print asks for a 1/4" weld and I am running .052 metal cored with settings about 26.5volts and a wire feed of about 310.
Now, I have heard what you are saying, among other things. Some people have said that this line means good fusion, but I was inclined to believe that. I have also heard that the line is from the wire dragging, but in spray arc, the wire really never drags in the puddle, correct? It sort of "chops off" between the electrode and work piece.
Also, to the rest of my question, does this line create the chance of a longitudinal crack? I was told that it could be a weak point.
Parent - By pipewelder_1999 (****) Date 09-04-2016 02:57
The center-line crease you see is probably the result of shrinkage and becomes more prominent with higher energy/travel speed welds. The last part to cool is usually along the center especially with a concave or flat profile.

A high depth to width ratio as in a deep penetrating fillet weld can cause shrinkage along the sides of the weld to be pretty rapid and the centerline of the weld has to absorb all of the shrinkage stress.

In extreme cases and certain conditions, it could be a crack however I have performed MT and PT on some of these indications and found nothing, in other cases I have.

A rapid travel speed, teardrop shaped puddle, and high voltages can work together to create this discontinuity. I would suggest cutting some samples and seeing if it is anything to be concerned with. Maybe it is, maybe it isnt.
Parent - By pipewelder_1999 (****) Date 09-04-2016 03:36 Edited 09-04-2016 03:39
Up Topic Welding Industry / General Welding Discussion / Metal Cored wire

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