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Alden Pruett
09-08-2003, 10:04 PM
Was wondering if anyone knew ofany "secrets" for using jet rod in corners. Over the years have used it on many things skids,base plates, and gussets. Never have a problem except when making the transition coming out of a sharp corner. Have tried everything I can think of weld just seems to get skinny and look cold lapped in corners. Over the years different weldors I've worked with have all said this is normal. I usually end up using a little 7018 to build up the corner so its not such a tight angle.
Any ideas? Seems like long arcing helps a little. This isn't a big problem just wondering what everyone thought. thanks

Mike Sherman
09-09-2003, 07:06 AM
Welding toward a corner on DC will often result in Arc Blow. Start your weld in the corner and move outward.

Alden Pruett
09-09-2003, 07:58 AM
Mike I appreciate your answer but arc blow is not the problem.
just making the transition the slag wants to overtake the puddle.
Have seen guys take a extra rod and use the end to "sweep" the flux back in these situations have done this myself just seems like this particular rod doesn't like sharp corners.And of course the bigger the rod it gets harder to control.

Mike Sherman
09-09-2003, 08:17 AM
Alden, I believe the solution is still the same. Start your welds in the corner and come out. This will help you keep the electrode at the proper angle 100% of the time. Even if you just come out an inch or two each way it will solve your problem. I would not want to x-ray the welds of the guys who are trying to sweep the slag out of the way. It would be very difficult to get consistantly good welds.

Snidley
09-10-2003, 04:27 PM
go with Mike on this one. It's rarely/never easy to weld into a corner.



By the way Mike, did you ride to the big party?

Alden Pruett
09-10-2003, 09:54 PM
Thanks guys for the help!

BillC
09-11-2003, 02:37 PM
Mike,

I was taught to avoid starts and stops at corners because of the inherent stress riser due to the discontinuity. Any thoughts on this?

MikeR
09-11-2003, 05:26 PM
Good starts and stops are better than a bad continues weld would be my reply, but then again I'm no engine ear.

How's school?

BillC
09-12-2003, 05:45 AM
Originally posted by MikeR
Good starts and stops are better than a bad continues weld would be my reply, but then again I'm no engine ear.

How's school? I just started GTAW with steel. I decided to take some of the great advice from this board and stay way from the aluminum. We don't have any stainless or I would do that first... GTAW is going to take some practice, but if it was easy it wouldn't be fun.

Mike Sherman
09-12-2003, 06:01 AM
"I was taught to avoid starts and stops at corners because of the inherent stress riser due to the discontinuity. Any thoughts on this?"

Bill, that is an interesting statement. "A discontinuity is an interruption of the of the typical structure of a material..... a discontinuity is not necessarily a defect. " Inherent meaning "...a natural and inseperable quality". I would say that statement originally came from someone who had a very difficult time starting a weld in the corners. Yes it is more difficult to start in a corner than it is on the flat. But, it is not impossible and there does not have to be a discontinuity either. Even if there is a discontinuity, it is not necessarily a defect, as noted above. As noted by Mike R. it is better to start in the corner than to drive into the corner and have a totally bad weld. In conclusion, it is better to start in the corner and possibly have a discontinuity, as long as it is not a defect, than to drive into the corner and have slag inclusions and lack of fusion to the point of it being a defect. It is simply a matter of which technique is going to be more effective.

BillC
09-12-2003, 08:08 AM
Thanks Mike,

The discontinuity I was referring to was the corner itself, not the start/stop of a weld. The same discontinuity that breaks the magnetic field and induces arc blow also results in a region of higher stress.

All of this really only applies to dynamically loaded joints.
I was taught that starting and stopping at corners aligns potentially cold starts with a known region of higher stress. Similarly, I was taught that I should stagger my stops/restarts if I am running a long multi-pass weld. I agree that running a puddle of slag into the corner is bad.

So, if I understand your answer, stops/restarts at corners is not considered bad practice because there is an assumption that the weldor is competent and will not produce craters or cold starts?

Thanks again,

Mike Sherman
09-12-2003, 11:00 AM
Exactly. Welding is not a perfect world and sometimes it is a matter of the lessor of two evils. This is a very good example of that. It is possible to start a weld in the corner and avoid arc blow and slag inclusions. It is alot harder to weld into a corner and avoid them. Cold starts and crater cracks can be avoided with proper technique also.