I would like a little feedback on welding T6061 with 4043 filler wire. I am welding a seam on a small electrical components box that is .080 wide and it has to be able to withstand internal and external pressure and wide temperature ranges from around 350f. to - 30f. Anyone out there mind letting me in on some techniques for T6061 to avoid porosity? I am cleaning everything extensively.I am using pure tungsten, size 3/32. I use alcahol to swab all weld areas and wire after using scotch brite and stainless wool . How would the 5000 series wire work for this compared to the 4043? Thanks for any help--C.L.
I'll answer just a small portion of your question.
The minimum temperature your aluminum equipment must stand to is not related to the designation of the eletrode, as long as it is made of aluminum. In fact, at very low temperatures (close to absolute zero) aluminum shows a tensile strength and an impact (Charpy) toughness similar to those at room temperature. This is why cryogenic tanks (those used to store liquid oxygen, nitrogen, helium etc) which work at very low temperatures, are made of aluminum.
I hope that someone else answers the rest of your question.
Giovanni s. Crisi
Sao Paulo - Brazil
I believe that 4043 is the correct filler for your application. Use of the 5000 series as fillers can lead to a sensitization within the filler when exposed to temperatures above 150°F.
The typical ageing temperature for the 6000 series alloys is 340°F. This means that extended periods at 350°F will reduce the strength of the component. At any rate, you will get a weaker area in the HAZ due to over-ageing.
You mention porosity as a problem. You can reduce this by:
1) Ensuring that the filler and base metal is VERY clean and dry. Moisture is the big killer here.
2) Have a slow cooling rate, to allow any gas enough time to rise to the surface and escape. - Weld with higher heat inputs or higher pre-heats.
I believe that when welding the 6000 series alloys, cracking is a bigger problem. This is because the typical composition of these materials lie in the crack sensitive ranges for both Si and Mg. To overcome this problem, make sure that you melt in enough filler while welding.
Hope this helps
Regards
Niekie Jooste
Thanks for the replies. As of today, I had to weld 3 more boxes, And they all had minute leaks when presurized with 20 lbs. of helium and wetting the seam with Snoop leak detector. I have been a certified pipe welder since 1981 and certified under milspec 1595a for 3 years, And all I can say is this 6061 is a different beast from anything I have ever dealt with! I think the main culprit I am dealing with is that the boxes were nickel plated and just the edge has been masked off where the weld is. I can clean them for an hour and still have this porosity problem. I did go with zerconium tungsten this last round and it seemed to weld better. We mill the edges where the weld is too. I need to know if my wave balance and freq. settings could cause this problem, But I have tried about every combination on the dials. I get best results with the balance slightly toward the max penetration side and the frequency in the midrange area. Anyone out there that can suggest something better? Thanks again---
Are you sure that the leaks are being caused by porosity? If so, how do you know?
You mentioned minute leaks. Typically porosit in Al is a very obvious defect and would typically not be described as minute. It would have very ugly looking "holes" on the surface of the weld. Do you have such defects? - If not, I suggest that maybe you have cracking (hot - short) problems. Perform a dye penetrant test to establish if you have cracks, and if so where they are.
What does your weld prep look like? In this alloy, this can be a big factor in cracking problems.
Regards
Niekie Jooste
Thanks for taking the time to reply Neikie, I am seeing small pin holes in the weld .It is not all the way around the weld, But just in a few places. I am checking the weld visually with a 65 power optiscope before pressurizing the box with the helium. My cleanup prep is very intense and time consuming. . I am milling the surface area and also using a carbide scraper. I also wipe all the areas with alcohol and I am wearing clean white cotton gloves so I won't leave any contamination by touching the surface.I was using SS wool to clean the tigwire, But I have changed to the red scotchbrite. I also wipe the wire with alcohol before using it. I clean the wire just before welding with it everytime. My thinking is, If I have eliminated the nickel plating from the area, Maybe I have my wavebalance setting off just a little or my frequency setting. What do you think? Also, I am wondering if my speed or dwell time could cause this problem? I would love to find a procedures manual for t6061 somewhere. Anyone know where I might get one?--Thanks
Hi SEAPLANE:
I am typing a welder performance qualification for 6061 T6 tonight, and took the time to respond to your post. I have many clients who fabricate specifically with this material and the presence of randomly scattered porosity (pinholes) are quite common with this material, but the source of this discontinuity can occur from a number of different conditions. Lot's of welders fail the first round due to their technique or material preparation, usually a combination of both.
As I watched your post get hits the last couple of weeks, I was waiting to see if you would provide some specific information. I agree with Neikie's response on the filler metal selection also. Again, a good call. Did you try contacting the good people over at ALCOTEC? I travel quite extensively for work now and am slow in responding to any posts in the Forum.
Without knowing specific parameters (frequency, balance percentage, etc) I did not respond earlier. Would like to know how you ultimately figured out your problem. The guy I am issuing doumentation for now also failed the first round. I recommended specific parameter changes and a slightly different technique, as well as a recommendation to clean everything with a lint-free clean rag AFTER the alcohol wipe. He was very surprised to see what remained on the test plate and filler rod.
Have been able to resolve all but one of my clients aluminum problems. This was due to their refusal to follow specific instructions and procedures I had specified. All my other aluminum welding clientele are buzzing away happily with a minimum amount of cleanup, rework or problems.
Let me know how things work out. I won't respond to any posts to the Forum for another week due to my workload.
Thanks for the reply DGXL, Could you give me a little more detailed info on just what parameter changes were made? I would be interested in knowing what wave balance settings and frequency level settings your client is using. It would probably change depending on how thick the base metal was anyway. I am welding a seam that is two pieces of .080 tightly fitted together. My ampereage setting is at 110 with a foot pedal controling the actual amps to around 60/70. My frequency control is setting about halfway at around 60hz. My wave balance is slightly favoring the max penetration side. I will try the dry clean wipe after the alcohol and see what results I get. Thanks again for the tip-
If you are very certain that the defects are due to porosity, then the following are possible things to consider: (Just keep in mind that if you are getting leaks right through the weld due to porosity, then they can not be "minute" pores. You need a defect that goes right through your weld. This is very unlikely for isolated minute pores. You either have extensive porosity within the weld that is inter-linking, or "worm holes" or cracking as well.)
1) If you have porosity, then there are really two major causes. These being "gas evolution within the weld metal" and shrinkage.
2) Gas evolution comes mainly from contamination on weld surfaces, filler metal or shielding gas. In particular, H is a great culprit because the solubility of H in Al is much higher at elevated temperatures than lower temperatures. Any moisture or hydrocarbon contamination will result in H contamination. Another possibility is H already trapped within the metal, although this is usually a problem with castings. Another way to get moisture is with incorrect shielding gas usage. (Either too fast flow rate, too low flow rate or too acute an angle of torch to work piece.)
3) Shrinkage pores are usually associated with end craters. Just make sure your arc termination technique is good.
4) To reduce the possible effects of gas evolution within the weld, you need to give the gas as much time as possible to escape to the surface while the metal is still moulten. This means having the weld metal remain fluid for as long as possible. This is where the machine settings and technique really can make a difference. Obviously you will not have too much leeway when welding a material as thin as 0.08".
From what I can understand, you have no preperation on the edges of the plate. You are welding the two together in a "square butt" configuration. Is this correct? If it is, then I still think that you should be looking for cracking problems because you will have very little dilution of the base metal with the filler. This will result in a crack sensitive weld metal composition. Is it not possible for you to simulate the weld using some scrap material and sectioning it to see what is going on below the surface?
Regards
Niekie Jooste
Thanks for taking the time to reply again Neikie, The box I am welding is hobbed out of a solid billett of aluminum. The lid is possibly cast, I really don't know. These pieces were very expensive to produce, So I have had to simulate the weld joint with flat plate for the preliminary weld schedule. I had no problems with the flat plate having porosity.We did do weld sections and destructive testing on the simulated weld joints. Once we are in full production of this box, We will be using a stamped out box , But for now , We are having to mill out the solid billett. Your point about cast aluminum might be something I need to address. If the Lid is cast, Can it be the reason for the small pin holes and porosity? Can the cast aluminum be welded to the Billett successfully?The pin holes are usually right on the edge of the weld. This weld joint is like a raised lip around the edge of the box. The lid fits inside the box and is welded on top of the raised lip edge. The box has to be nickel plated so some threaded fittings can be soldered to it. The nickel plating is masked off around the edge of the box and lid for the weld area, But I am wondering just how much nickel might seep into the weld area. We certainly did enough cleaning and scraping on it. The first few boxes we welded , Turned out fine. Now we are welding some that a different vendor sent to us.I also taper the arc off slowly and use a post flow setting of about 5 seconds. If there is anything you might be able to add to your above post, Please do. Thanks for all the tips so far. I will post any improvements as I progress.
You say that the pores tend to be to the edge of the weld. Do they lie towards any particular side of the weld? (e.g. the lid) If so, it would be an indication that the problem originates from that particular parent metal.
You also say that the box is hobbed out of a solid billet. If this billet is of a rather large size, then it would indicate that it did not see much reduction in size during its preparation. This could also mean that some gas trapped during casting could still be within the material.
Regards
Niekie Jooste
I am not an aluminum guy so take this as no more than the guess that it is.
Is it possible that in machining the box some contaminant might have been driven into the surface of the metal either from the mill itself or the coolant?
Since the spec says the device has to survive 350 deg perhaps heating to that could volitilize whatever contaminant might exist.
Perhaps the plating could be done after the welding.
Bill
Here are a few practical hands on Ideas to supplement the excellent technical illustrations posted above.
To speak to your balance control question, Here it is important to understand the underlying principals of AC welding, because faceplates of different machines may become confusing for somebody who is looking for solid reliable parameters (this can happen even within a brand), For instance a Miller Synchrowave 250 or 351 will have a balance control knob that has a 1-10 graduation that actually represents 45-80 percent dwell time on the Negative side of the half cycle. Where as the Miller Aerowave and Dynasty have digital readouts that provide real percentages of dwell time between 30 and 90 percent dwell time on the Negative side of the half cycle. So, when you say that your machine is set slightly toward max penetration it can mean a lot of things. With this in mind, tell us a bit more about your powersources and bead appearances and profiles.
Looking at your welds surface appearance can give some clues as to how well your balance control is set. First the etch, look for a good consistent etch extending beyond a shiny wet toe of the weld, the point of diminishing returns is often noted when the etch disappears and a *grainey* appearance on the top of the weld buildup is noted. This grainey appearance is not limited in cause to balance control but if adjustment toward the cleaning side (EP) make it disappear, than you know you're on the right track. With the plating and masking a little more cleaning action may not be a bad thing. Additional balance toward max cleaning will make your bead profile a bit wider but trials have proven that you will loose little or no penetration. The melt is wider but usually the effect on depth is negligible and sometimes even deeper. This goes against conventional shop wisdom and I did not believe it myself until I saw the proof presented at an AWS Expo seminar about 4 years ago.
Speaking to frequency. 6061 aluminum 0.080 requires no special frequency adjustments. The benefits of high frequency adjustability in AC manual TIG occur in situations of extremes, both thick and thin. Adjusting the frequency higher (up to 200 Hz) will help arc stability and directional control on very thin aluminum fillets. Lower frequency (below 60 hertz) is beneficial welding heavy sections. So to sum it up in your case. Your ok anywhere between 60 and 100 Hz. Anything more is just gonna make your shop noisey.
Speaking to technique, I agree with the above posts that thru porosity is very unusual and that close inspection may prove that cracks are the culpret. Also as previously stated elevated molten temps facilitate higher levels of Hydrogen in the pool which may not be able to escape and leave you with porosity. One technique that can have an immediate effect here is to go to the next larger size filler wire, for example 0.063 to 0.090 wire. This can help control the heat in the puddle and also makes for better stops. Many discontinuities are found at the beginning and ends of weld passes due to filler starvation. 6061 is notorious for this.
This is a great thread. Lots of valuable inputs here, Thanks posters
I have seen this problem also and use most of the answers that you have recieved here. I have a couple more that you can try. I switched to a Miller Dynasty Tig with a pointed tunsten which kept me heat effect zone as small as possable. I also changed to a 75% Helum 25% Argon mix that seemed to help more than anything. I also changed to a 4047 filler metal and that also helped. Can't think of anything else right now but I hope these ideas may help. Also a back up gas of argon in the box won't hurt.
Regards
Bob
O.K., I have made some adjustments on technique and also on the cleaning process with some positive results. I Think two of the things that helped was to file a very slight bevel on the two edges and I also slowed down my travel speed a little. The last box I welded didn't have to have any repairs on the weld. The Box did have a small hole in the side that had to be repaired when it went to the solder sequence. The parent material must be really trashy. I would love to try some of the 4047 filler wire, But it looks like we will be locked in on the 4043. Another thing I did was to adjust the wave balance twords the cleaning side a little. Thanks for all the help everyone. It's great to have this forum when a problem like this pops up, Best Regards--C.L.
Here is something that I just found out about the problem I was having. We sent 6 test sections to a local university for analizing. To make a long story short, There was still a trace of nickel plating in the aluminum. Even after milling about .010 off the surface . I don't know what the next step is, But we are going to have to figure out a way to keep this nickel out of the weld area. The Vender that does the plating is required to mask off the area around the edge to be welded.I am wondering just how deep the nickel absorbs into the aluminum. It looks like they are going to have to find a better way to mask the edges.
I trust the electrodeposition mask. This technology is well developed and presently is effective to the microscopic level. Of course there is a reasonable presumption here that the plater knows how to do his job.
I believe Lawrence or Bill suggested the trouble might have been contaminants dragged in from machining. It is much more likely this is the source of the contamination. Only you know all the details of the manufacturing process, though. Perhaps machining before plating would be a viable option?
You are probably aware that small deposits of contaminants on the mill bit itself can be dragged into the aluminum from work completed days prior to your job.
I believe there are cleaning processes (chemical dips) that can be specified prior to plating ,if necessary, to insure cleanliness which selectively addresses the Ni... but then again simply a new mill would solve the problem also, if that is indeed the source. I am a little confused about details of the manufacture process and curious as to why it is being plated before welding.
Regards,
d
Dee, That is a good point about the Mill contaminating the aluminum.I will have to do a double check on that situation.We can only machine the lid of the box for final fitting before welding. The box is plated with nickel to allow some threaded nipple electrical connectors to be soldered to the box after the lid is welded in place. The box has been manufactured for quite some time, But the lid was previously soldered . Now we are going with the welded lid . I have had some decent results on the last couple of boxes that have been welded. Thanks for the information, C.L.
Seaplane,
I've been going a little crazy looking for a recent reference I know I have which specifies the cleaning bath chemistry I mentioned. I gave up for now, but I am glad your luck has taken a turn for the better. I am sure a chemist from anywhere, particularly your plating jobber, could help if you find your back to the wall, and if my reference turns up I will drop you a line.
At least knowing Ni contamination is the cause of the problem is half the battle.
Regards,
d
When you say that you found traces of Ni, how much exactly? Many Al alloys (especially cast alloys) have Ni added in "trace amounts" to improve the corrosion resistance, strength and heat treatability.
Some of the casting alloys have as much as 0.55% Ni. More commonly however are additions of around 0.05 - 0.15% Ni.
Send some of the unplated material for analysis and see if it also contains the Ni.
If your Al contains amounts of Ni less than 0.15%, then I do not believe this can be your problem. Even if you have higher percentages of Ni, I do not believe that this will result in porosity. It would rather lead to cracking.
Regards
Niekie Jooste
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