Pitfals in welding repair - fixing parts in house

[twistedneck]

Need help with lessons learned and potential gotcha's with in plant weld repair methods. Point is to repair and ship as good parts with proper repairs.

Is there a repair standard out there?

1. MIG process
2. 1010 steel
3. 2.5" sheet steel, fillet welded.

In addition, what is key to minimizing weld variation specifically tip changes and tip to work distances. tips are changed frequently.

 

[MikeHalloran]

My friend Lenney used to weld pipes in nuke plants, where the quality standard, and incentive, was pretty simple; third failed radiograph, no time limit, and you're out of a job. I think he failed two in 20 years.

My point is, the welder is necessarily paying attention, and _knows_ when there's a flaw in the weld. If he has a stronger incentive to keep going than he has to stop and fix the weld, he keeps going.

You're laying down, what 1/8" wire at 500A? And paying your welders by the spool consumed?

Think about the incentives you provide, and what behaviors they encourage.



Mike Halloran
Pembroke Pines, FL, USA

 

[twistedneck]

Mike, I guess that is the one aspect I have little control over. I would like to know if there is a way to deal w/ setup - changeovers - repairs as a single thing, w/ a focus on what repairs can be made properly and what is not good practice in repair.

There is a std. It covers some repairs - but not all. I've seen weld defect standards for ISO. None of these directly address what we find.

 

[MikeHalloran]

Did I understand you correctly?

Two and a half inch thick steel?

And you're getting a significant number of defects?



Mike Halloran
Pembroke Pines, FL, USA

 

[twistedneck]

2.5mm - maybe i'm the root cause of defects..LOL.

 

[weldtek]

Back in 1970 I worked for ~ 3 months at an auto frame plant. We head quite a few repairs to make and did these mosttly with E6011.
What kind of defects are you finding?

 

[twistedneck]

Mostly welds that wander off line, slot welds where the slot isn't filled, fillet welds that are 'wavy', reverse crater at end of plug weld (can't find this in ISO 5817, weld imperfection charts).

Don't see a lot of porocity, crater crack, undercut, etc.

 

[stanweld]

What type of weld defects defects are you experiencing? Assuming that you are using the short circuiting mode of transfer, what shielding gas mix are you using and at what flow rate; and what filler metal are you using? Frequent contact tip repairs are often caused by inconsistent wire feeding resulting from improperly maintained wire drive rolls, wire guide tubes and long distances from wire spools to torch. The wire cast may also wear the contact tube causing insufficient/inconsistant electrical contact. These prblems can all cause voltage/current excusions and result in lack of fusion and porosity.

 

[unclesyd]

Take a look at this website. There is a lot of very good information and guidance along with a lot of extraneous matter. You might want to purchase Ed's book, a lot more information.

http://www.weldreality.com/default2.htm

 

[weldtek]

If I understand correctly, you're asking if there's a standard repair procedure? Considering the application and defects you describe, it seems that you just need to re weld areas that are underfilled, or weld areas that have been missed. That may require consideration of cosmetics, and you may want to repair with an alternate process, such as GTAW to avoid overwelding, and rough looking welds.
In certain applications there certainly is a proper way to make repairs, and fabricators are often required to submit repair procedures for customer approval, prior to making any repairs.

 

[twistedneck]

guys, we are building a repair procedure exactly like weldtek described. they are cosmetic in nature, we GTAW over the old welds if they need it.

Customer agrees on our internal criteria, that is good. the other side of this gets to what unclesyd, stanweld, and MikeHalloran talk about.

I need to take action now based the inital posts, i'll let you know if anything turns up.

the toughest part gets to what Mike mentioned, the culture, behaivior and incentives - but this is a fully automated multistation setup, therefore its the setup and tip changeover people were talking about. thoughts? these are experienced guys who know welding, yet we keep having issues, production halts, returned parts, etc.

 

[MikeHalloran]

I'm suspicious that the experienced guys are resentful of being "reduced" to machine maintenance technicians, and are sabotaging the machines. They are smart enough to not be obvious about it.

Fire the lot of them.

Yeah, I know, you can't.

So hire a not too bright high school graduate with a good work ethic, teach him the job, and let him show them up, just by doing exactly what he's been told. You must specifically instruct him to not accept input from the other guys, and you must instruct them to not give it. Physically isolate him if necessary.



Mike Halloran
Pembroke Pines, FL, USA

 

[stanweld]

Agree with Mike; welders can certainly sabotage work. Incentives can mitigate problems and speed production, especially when tied to piece work production of acceptable welds. Korean manufacturers/contractors and others have been using these types of incentives for years. "Win-win" situations can be created.

You must also develop a planned maintenance program and daily system checks of GMAW welding equipment; e.g., clean out or replace wire guide tubes, check drive roll tension, replace when worn, replace worn contact tips, purchase "flat wound" wire spools, etc.

Finally, assure that welders are properly trained for the work. There used to be great apprentice training programs through unions but now the employers must take that responsibility and all too often they do not.