Weld cleaner

Date 04-29-2008 02:16

I don't have any experience with the combination you mentioned, but I have to ask, did the cleaner evaporate completely before welding? Did the cleaner leave any residue after evaporation? Were the parts lapped such there is a chance the cleaner wicked between the two members and failed to evaporate before welding?

You didn't mention what base metal you are welding in your post. It does make a difference.

Best regards - Al

By GRoberts (***)

Date 04-29-2008 04:12

The cleaner claims to completely evaporate- although the welder also used a rag to wipe as a cleaner that isn't wiped off just leaves behind the contaminants it just dissolved. The joint is an open root single V- so no chance of overlap there.

The steel in question is a European designation I can't remember off the top of my head right now, but we ran some mock-ups with 1/2" thick x 8" wide A36 flat bar and the porosity was repeatable.

We're also trying to elimnate all other possible causes as we can, but I hadn't run across these being used as pre-weld cleaners before.

By aevald

Date 04-29-2008 06:39

Hello Greg, are you sure that the cleaner is the culprit? In other words have you ruled out all other factors that could be causing the porosity? Forgive me if I am asking everything that you have already considered. Is this only one operator that is having this issue or is it plant wide? Have there been any changes made to the equipment that is being used? Is this possibly a new machine set-up?

Things to check:
---- too high of a flow-rate on shielding gas causing excessive turbulence
---- bad O-rings on the welding gun where it connects to the feeder
---- wrong type of gas-line from the regulator/flowmeter, some contain oils that can cause contamination
---- deterioration of insulating materials on the inside of the shielding nozzle or an obstructed diffuser
---- internal obstructions or leaks of the gas system inside the feeder assembly or gun adapter,
there are sometimes in-line screens in the inlet fitting on the feeder, there are other lines and fittings
inside the feeder that could possibly have developed leaks or been pinched somehow or the solenoid
could be malfunctioning and not opening fully or the valve could be obstructed with debris
---- damage to gun whip from having something drop on it and cut or crush it, not always readily visible
---- contaminated wire roll from having something spilled on it or possibly not being rotated with new stock
---- use of a wiper assembly on the wire with wrong wire lube or something else on it
---- possible sub-standard shielding gas, contaminated cylinder or something along that line
---- possible contaminated liner from previous use for something else(pretty slim)

A very remote possibility exist that if you are using an over-sized liner, say .065, and running .035 solid wire in it and the liner has been bent or stretched internally somewhere close to the connection to the feeder you could see gas leaking through the conduit and escaping back through the wire path into the area of the drive rolls. Sometimes when the trigger is depressed you will see puffs of dust coming back through the guide area immediately in front of the drive rolls, if this condition seems excessive it might be worth changing out the gun assembly. Are you able to verify gas flow-rates at the nozzle and compare them to the set rates at the regulator/flow-meter? I realize these may not be exactly the same, but they shouldn't be excessively different either. If you are running fairly long distances with your gas supply hoses you may want to consider installing a flow-meter in closer proximity to the feeder to avoid "puffing", having an excessive pressure build-up in the gas line and then once the trigger is activated there is a fairly high-pressure rush of shielding gas creating turbulence each time a weld is initiated.
Finally are there any operator initiated practices that could possibly affect this? excessive use of anti-spatter compounds or nozzle dips? excessive wire stick-out? anything else? As I mentioned before, please forgive me if you have already considered and ruled out any of what I have mentioned. Hope you get it figured out and please post-up what you found if you would. Best regards, Allan

By GRoberts (***)

Date 04-29-2008 15:56

The prolem is in one small area of the plant, as we normally don't use much GMAW (usually FCAW and SAW). Only one welder has had his work x-rayed though. Some mock-ups with break tests were also conducted as we tried to eliminate sources for porosity. We started with the obvious ones first, and are now getting down to the less likely ones.

The welder is one of our better welders and is keeping a consistant and short stickout. He is fastidious about keeping the nozzle clean as well. I have seen the problems with the nozzle insulation fraying causing problems before too, but didn't think of that one this time yet. I'll check it out, but I'm betting it is probably ok.

Flow rate has been 30-35 CFH with a 5/8" nozzle- definately not too high for that size nozzle.
It is a new welding gun, but we are trying a different one this morning just in case.
We are using the same type of gas line we use everywhere else in the plant. I'm not exactly sure what the materail is, but is is designed for shielding gas.
We measured the flow rate at the nozzle and it matches the flowmeter at the bottle rather well- better than most other setups I have checked- almost exactly the same.
We also put on a new roll of ER70S-6 in case the roll we had been using had been contaminated.
No lube on the wiper- it seems to just collect more dust that way- so I'm not a fan of apply it. And the wiper is also brand new.
The liner for the gun is also new as it is a new gun, and is a .045" liner, and we are running .045" wire.
We were getting some surge, so installed a flow regulator at the wire feeder, and it smoothed right out.
The gas manufacturer will be picking up a bottle for testing today, but it will take a while to get results back.

So, as you can see, we have been trying the obvious, so since I hadn't run into those cleaners before, I was something to check out anyway.

By hogan

Date 04-29-2008 17:43

We also put on a new roll of ER70S-6 in case the roll we had been using had been contaminated.

was it a different lot #?

By GRoberts (***)

Date 04-29-2008 19:11

Nope, we only have one lot of wire that we can use for this job as our customer is making us use EN440 G42 4 M G3Si1 (which I order dual certified to ER70S-6 so that we don't have to re-qualify our procedures). So our wire came from Germany (Bohler-Thyssen), and is all one lot. Every time porosity issues come up, welders always question the wire, and it seldom if ever is the wire (at least for solid GMAW wire). Has anyone ever had GMAW porosity where the porosity was attributed to the wire (not contaminants that got onto the wire)- such as insufficient deoxidizers?

By aevald

Date 04-29-2008 21:04

Hello Greg, here's kind of a shot in the dark, but you could possibly take a bit of this wire and lay down some welds with it using a GTAW torch and see what kind of deposits you end up with. If it's truly a wire issue I would think this might help to determine it. Just a thought. Best regards, Allan

By GRoberts (***)

Date 04-30-2008 00:19

We just got another one back from X-ray. We tried a different lot of gas, changed the welding gun (even though the old was was pretty much new), and used acetone only. No improvement though.

In the context of the wire lots, we had been doing all the welding so far with 1.2mm (.045") wire, but if I switch to .9mm (.035") wire- although not the prefererd size in this application- I do have another lot approved for production that I can try. So tomorrow, I will try that on another welding machine (in case it is some crazy electrical thing).

By GRoberts (***)

Date 05-02-2008 18:42

Well, since my last post, we tried two different lots of wire. One from a different manufacturer. The first time we ran both other lots of wire, the same manufacturer's wire was good enought to pass RT, but still had some porosity, and the other manufacturer's was crystal clear, except 3 minor pinholes 1/4" from the start/stop area. So we tried again with the same manufacturer's wire on the same machine, same welder, and got enough to fail RT. Then we tried the other manufacturer's wire on a different machine and on that it had a lot of porosity. I still haven't gotten the gas suppliers tests back yet, but we also did an RT of a weld with the same wire from a month ago on a old test plate, and full of porosity. Different buidling, different machine. We sill have yet to see a single gas hole break the surface of the weld, every single bit of it has been internal. I think I'll be going crazy soon if this doesn't get figured out. Not to mention we aren't getting any product built, so no one around this project is happy.

By Bonniweldor (**)

Date 05-07-2008 02:45

Suggest look at liner cleanliness, spool protection from condensate, leak or contamination of gas stream in manifold length. Could joint configuration and nozzle geometry combine to cause turbulence of the shielding gas stream? I'm confident you don't use those felt lubrication thingys on the wire or fish oil anti-spatter.

Let some of the cleaner evaporate off a clean glass a number of cycle and see if a residue builds up, warm glass works faster.

By js55

Date 05-07-2008 13:31

Greg,
I didn't see anywhere in your posts where you described what the porosity looks like.
This is one place to start.

By GRoberts (***)

Date 05-08-2008 16:48

We have used new liners, brand new rolls of wire, and have obviously checked for gas leaks- (single bottle/regulator set ups in this case, no manifold). We have had consistant porosity with all of them. Also tried acetone only, and it didn't improve.

The other day, we were considering the possibility of the joint designs causing us problems because they are narrower due to the European design than what we are used to. For instance, a single V with 2mm root opening, 2mm face and only 50 degree included angle, or a single bevel tee joint with 2mm root opening, 2mm root face, and only a 40 degree included angle. So with the narrow angles, I was thinking it might cause turbulance as the gas has to "accelerate" of of the narrow joint. Possibly a verturi type thing. So we opened the joint up a little and also slowed the flow rate down to 25 CFH. We tried 2 tests that way and both of them still had a little porosity, but it was definatly reduced.

I was also working with QC to get the right interpretation of the film once I found out they were using a more stringent criteria than necessary. The Eurpean code we were able to dig out actually seems quite lenient with the amount of porosity allowed, although is isn't as easy to understand not having worked with it before. Once that was accomplished, we only had a couple of rejects instead of all of them. I still want to find out what is giving us the problem, but for right now, at least we are back in production.

As far as the porosity description, it is very uniformly distributed on the RT. In the break tests, we have found it in the root, fill and cap passes. Most of it is 1/32" or less in diameter, with about 10-20% being larger (but all but one or two being less than 3/32" in diameter).

By js55

Date 05-08-2008 17:53

Greg,
Thinkin outside the box:
Are you sure you're dealing with gaseous porosity?
You seem to have pretty much eliminated the possibility.
You mentioned nothing is breaking the surface.
While this is certianly not necessary for gaseous porosity it is most common if its that pervasive.
Maybe you're dealing with inclusions that are coalescing and are being pushed along the solidification front until they just won't be pushed anymore.
I've seen inclusions look like porosity and its typical that they don't break the surface. You generally have to grind down into the pass to even know they're there.
Though the sizes you describe are quite large for inclusions.
Are you using a highly oxidizing gas?
What's the base metal? Could it be that Ti, Zr, Al, or other microalloys are present that can create inclusions (Al especially since it is used for grain refinement)that can cause pores and not float to the top.
I know your'e using S-6 or compatible but if the microalloys are there in large enough volume percents and you have an oxidizing gas it may not be enough.Just some thoughts.

By GRoberts (***)

Date 05-08-2008 19:11

When you do a break test, the holes are nice and shiny. I havn't see any holes that contain inclusions to this point. I also haven't seen any RT with that many inclusions- all rounded. I've seen film with that much inclustions (i.e. slag), but when it is that much, it always comes out linear. It's a good thought, but I don't think it is our problem.

We are using 90% Ar, 10% CO2. We aren't getting excessive silicon islands either. The top of the weld is usually nice and clean. We have also used a Eurpean steel similar to S355, A36, and A516 Gr. 70, and had porosity with all of them.

By js55

Date 05-08-2008 20:49

Greg,
If you slow down the travel speed (and/or increase amps/volts) and thereby slow down solidification and cooling, and the porosity reduces it most likely indicates a gaseous problem. The gas has had more time to evolve. If it doesn't it may lean more towards a chemistry problem. Just a thought.

By GRoberts (***)

Date 05-08-2008 23:13

I know what you mean. The place I'm working now is the exact opposite as the last one. The last one, you couldn't get the welders to speed up, the place I'm at now, you can't get them to slow down. I've tried to get them to slow down some, but not as much as I would like. From what I've seen, our customer that specified the process and electrode can produce some weld beads quite a bit larger than ours. (i.e. one pass per layer from root to cap in 1/2"-3/4" material.) I have trouble getting the welders here to do one pass per layer if the groove gets more than 3/8"-1/2" wide.