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Up Topic Welding Industry / Technical Discussions / Problems with RT
- - By Milton Gravitt (***) Date 11-11-2008 18:50
What do you guys think of  grinding and welding aluminum while you are trying to do welding on steel parts that gets 10 xrays. We are getting about 70% bad parts. Do you think we need what I call a clean room to do this type of work . The welding  process are GMAW and GTAW the first two parts that was sent to be tested check OK. Then we built 50 parts to be tested we had 3 bad parts out of the first 10 that was check and 6 out of 10 bad and then 30 out of 30 was bad but all where fixable. All your suggestions and opinions are welcome please help.

                                                          M.G.
Parent - - By jrw159 (*****) Date 11-11-2008 20:18
Milton,
  I am thinking you are having trouble with the aluminum parts, but your question reads that the steel parts get xray leading one to beleive the steel parts have the issues. So are you wondering if the steel is contaminating the aluminum or the other way around? Also, what type and grade of steel are we talking about?

I may have just confused myself even more. LOL

Anyways, I will take a quick shot at this in lue of clarification. Aluminum is not very forgiving in unclean environments where cross contamination can occur. Steel is more forgiving and I would think one would have to have a good amount of contamination to effect it much. This of course depends on the type and grade of steel as well.

We need a little more info. :-)

jrw159
Parent - - By Milton Gravitt (***) Date 11-12-2008 01:27
jrw159 I'm wondering if the aluminum grinding dust is causing the porosity in the steel and the steel is 1018 this is the cold drawn type and is fairly clean. We are welding a .375 thick pipe to a .500 thick plate and most of the porosity is at the starts and stops and we are using a turn table. I can't understand why some of the parts pass and some don't. I grind the tacks down and brush it with a SS brush .
  Where I work you maybe welding on aluminum one minute and SS the next and Cs later on while grinding is all around.
The wire for GMAW is ER70S-3 .035 the volts is 28.0 and the wire speed 437 in. a minute it is a spray transfer before I forget the gas 90% argon and 10% CO2. Maybe this will help. Thanks for your response.
                                        
         MG
Parent - - By js55 (*****) Date 11-12-2008 13:27 Edited 11-12-2008 13:29
I doubt the Al contamination from dust in the air would amount to much. Al is a common element in steel making for fine grained practices of carbon steels, and I doubt any dust would even come close to the amounts commonly used in steelmaking.
Besides, if your problem is porosity it wouldn't be caused by Al. And its certainly probable that with CO2 in the shielding gas that much of the Al will end up oxidized and in a slag coating anyhow. Al is a very aggeessive oxidizer. Thats why its used in ER70S-2 wires, and part of the reason (Zr and Ti too) why S-2 has a tendency to have a slightly heavier oxide layer on top of the solidified deposit.
You clued it in I think however with the starts and stops comment.
Still, tools and such need to be segregated. I'd actually be more concerned about Fe contamination in Al than Al contamination in steel. Though both should be controlled.
Parent - By Ke1thk (**) Date 11-12-2008 14:55
I weld in a mixed environment with aluminum, steel, stainless, and grinding.  The welding is mostly flanges, bosses, or other tubes to tubes, using turntables.  I would say your leaking issue sounds like dirt, dust, technique, or filler metal.

I recommend the parts be clean.  Don't tack a skid of parts and let them set for a week, next to a grinding station, until their welded.  I sometimes use acetone to clean the part just prior welding.
 
The start stop point is also an issue.  When I GMAW stainless tubes to flanges or tubes to bosses using my robot, I overlap the start stop points by at least .75.  I also turn up the heat at those points.  Torch angle could also be an issue.  45 degrees straight on, or pushing up to 15 degrees works well.

Another point.  I had a stainless flange to tube and boss to tube job that leaked all the time using 308 rod with my robot.  I switched to 316 rod to stop leaking. 

Good Luck!
Parent - By hogan (****) Date 11-12-2008 14:22
Milton Gravitt,
Have you considered trying ER70s-6. Maybe review the manufactures data sheets on the two and see if it fits your application more appropriately.
Parent - - By jrw159 (*****) Date 11-12-2008 15:53
Milton,
  I would say that unless you have major amounts of this aluminum dust, that your problem lies elswhere. IMHO, it would take alot of it to effect CS.

jrw159
Parent - - By Milton Gravitt (***) Date 11-13-2008 01:28
  I talk to our welding supply man today and told him about our problem. He thought it might be to hot when you get to the start and stop and the gas is cutting off to soon letting oxygen get to it before it has time to cool he suggested a GMAW machine with a post flow . When he said this a light bulb came on. I believe he hit the nail on the head. He is going to bring a demo machine to our company so we can try it out. I will get back with everybody after we get the results back from testing.  Thanks

                     MG
Parent - - By aevald (*****) Date 11-13-2008 02:04
Hello Milton, generally you will not need a pre/post flow shielding requirement on steel parts. A lot of the time if you are seeing porosity on something like you have described it is due to contamination issues from sawing fluids or preservatives that are present on the materials prior to and after fit-up. Do any of these parts have ends that have material identification paint on them from the supplier? This paint, if it is left on a part and welding is attempted over it without removal, will cause porosity a lot of the time. Are these parts a captured part, meaning while these welds are being done is this the final weld on a contained/enclosed part? Is there any possibility of internal pressures being released through this seam due to heat and expansion? On another thread a long time ago there were issues of metal preservatives being "melted" and their residue was flowing down the internal bore of the part and leaching out from under the part and being drawn into and contaminating the weld puddle. Is there any possibility of this occurring? Are you using nozzle dip? If so, is the operator possibly getting carried away with it's use, there might be some porosity issues showing up if that is the case. How about shielding gas flow rates? Are these set on the upper end of the flow requirement? If so, you could be experiencing turbulence or a venturi effect and having weld pool contamination as a result of this. These are a few other considerations for you to think about. Best regards, Allan  
Parent - - By Milton Gravitt (***) Date 11-13-2008 02:52
Allan it not building up internal pressures the pipe is open at the upper end and as for any kind of paint I haven't notice any. We clean the parts real good and wipe them off with alcohol. I try to grind the tacks down so they will be consumed in the welding process.I'm hoping this post flow will help.This pipe is .375 thick and about 2.5" or 3.5" across the diameter so it don't take long to get around it @28 volts and the wire speed is 437 ipm. I believe the weld is so hot at the starts & stop when you let off the trigger the gas shut off so quick that it maybe oxidizing. You know like tig welding you have to let off the foot pedal real slow and let the inert gas stay on until the weld is completely cool.
                                                        Thanks Allan
                                                          MG
Parent - - By aevald (*****) Date 11-13-2008 03:41
Hello again Milton, on the parts that you had that failed, where were the failures, what types of failures, were they only at the start and stop points? Did you have root, throat, face indications/porosity? I have a few more thoughts here: Is your current welding set-up one that has been used for other jobs/purposes without any problems? Is there any possibility that the gun whip or any other parts of the welding package could have been compromised by being damaged in any way? Could you possibly bring over another welding machine and use it to see if it has the same issues? That would be the quick way to make a possible equipment failure determination and rule that issue out. Here is another one that might be out in left field a bit, yet still a possibility. Is your gas supply source located remotely from the feeder and does it use a fairly long length of hose to reach the feeder? If that is the case and the hose doesn't have rigid sidewalls it could be pressurizing while the welding isn't taking place and then when welding is initiated you could have a big "rush" of shielding gas(possibly causing turbulence and a questionable weld bead start) and then the flow sometimes subsides almost to the point that it isn't sufficient to maintain proper shielding. Just a few more possibilities, you'll certainly have to let us know what you have determined when you get this worked out. Best regards, Allan
Parent - - By Milton Gravitt (***) Date 11-15-2008 04:32
Allan we talk to the people that did the RT yesterday and he said it was porosity and lack of penetration. What had happen I did a part that simulated a real part. They sent it out to be check and it past. I also sent the paperwork with all the welding sittings hoping it would be the WPQ. When it came back and it pasted they wanted to do all 50 parts we tried to get them to do 10 parts and wait but that didn't happen, but the next run that's what were going to do.
The parts was tack-up and they had to set for a while around grinding dust but I did clean the parts with alcohol and SS wire brush.
We have a miller 350-pulse welding machine that I'm going to try next week. I think we're going to saw one up and have it etched and check on the depth of penetration before we send any to RT. Allan do you know anything on this machine any help would be appreciated.
                                              MG
Parent - By aevald (*****) Date 11-15-2008 04:56
Hello Milton, are you referring to the Millermatic 350P? If so, I believe Lawrence has quite a bit of experience with this particular machine and could possibly give you some pointers on how to get it dialed in for your purpose. We do not have one of these in our shop and my experience with the machine has been limited to welding with it on some aluminum work that I have done at one of the local fab shops. I believe you could also contact Miller directly through their Tech department and they may have some suggestions and ideas for approaching your particular challenge. I have one more thought here, you mentioned cleaning them with alcohol, how soon before the welding occured did you do this? If this was possibly done right before doing the welding you may have had some of the alcohol wicking between the two parts underneath where they are in contact and once the welding started this was volitalized and may have contributed to the porosity issue. Kind of a shot in the dark but still a possibility. As to the lack of penetration, this could possibly be contributed to the weld progression and the gun angle being off. You should probably be using a trailing type progression as opposed to pushing the weld if that is your current set-up. Gotta run for now, if I think of anything else I'll try to include it later. Best regards, Allan
Up Topic Welding Industry / Technical Discussions / Problems with RT

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