t6061 welding procedure

Date 09-13-2011 17:00

Not enough information. Does the production work receive heat treatment? If so, you need to heat treat your coupon prior to testing. 6061 anneals during welding, and remember it is time at temperature sensitive. That is to say, the more heat input you subject the aluminum to, the greater the chance you're going to have sub-standard tensiles. HOWEVER; you can make it easier on yourself with the correct gas and filler.

In order for us to help you, we need to know a lot more about what you're doing. Gas, filler type and size, joint configuration would be a good start.

By firstpass (**)

Date 09-14-2011 05:40

filler is 4043
coupons sch 80 2 inch open butt/ and backing.

i thought of going to a thicker schedule. position being an essential variable table 3.3.

position welded is 6G to cover.

could move faster with a 2G/ 5g combination

any assistance would be appreciated

By bozaktwo1 (***)

Date 09-14-2011 16:54 Edited 09-14-2011 17:18

I would say go thicker AND larger diameter. Get all your tests out of one coupon if you can.

Gas: You didn't say what you're using. I would try a 50/50 Ar/He mixture. This will give you positive control of your arc, and allow you to weld hotter with less current. Use the biggest cup and gas lens you can find. Poor gas coverage can cause all sorts of problems which can contribute to poor strength properties.

How is doing two coupons in two positions faster than doing one?

CLEAN, CLEAN, CLEAN. When you think it's clean, clean again. Every instance of porosity, however small and "allowed by code," detracts from your tensile strength.

I hope some of this helps. Good luck, and let us know how it goes!

EDIT: I completely forgot to ask what type of tungsten you're using.

By 99205

Date 09-13-2011 17:11

This might help.

http://www.alcotec.com/us/en/education/knowledge/qa/Tensile-Strength-Too-Low.cfm

This may also add some insight, even though it's a different process.

http://www.esabna.com/us/en/education/knowledge/qa/i-have-problems-passing-the-tensile-test-requirements-with-6061-t6.cfm

By ssbn727 (*****)

Date 09-13-2011 18:29 Edited 09-13-2011 18:36

This quote from both of Tony Anderson's answers in Alcotec & ESAB's queries are the keys to success...

"The code provides minimum dimensions for groove weld test plate size. You must comply with this requirement; in fact, if practical, use a larger test sample than specified.
This will provide for superior heat sink and lower the possibility of excessive overheating and prolonged time at temperature within the heat-affected zone.

Secondly, comply with the preheating and interpass temperature requirements of the code, which for this type of material specifies 250 deg F as the maximum preheat
and interpass temperature. Also, observe the holding time at temperature requirement, which is not to exceed 15 minutes.

If possible, conduct the certification testing without preheating, or at lower preheating temperatures, and allow the base material to cool to well below the maximum interpass temperature before welding resumes.

A major contributor to the overall heat input of a weld is the travel speed during the welding process. For this reason, it is preferable to select a welding sequence and technique which makes use of faster stringer type weld beads as opposed to slower weaving techniques."

Focus on these points and you should achieve your goals provided you do not miss a step... Best of luck to you. :wink:

P.S. My colleague Curt A.K.A bozaktwo1's advice is also golden and must be followed... So include this step also prior to testing

Respectfully,
Henry

By Lawrence (*****)

Date 09-13-2011 19:07

Good research Henry!

Those notes are the best. I like Tony.

Anything to increase travel speed is also a plus (for manual welding this usually means practice or a rotating fixture)

By bozaktwo1 (***)

Date 09-14-2011 16:44

When is Ross going to add that "thumbs-up" button to these threads?

Thanks, Hank, as usual you nailed it.

By 803056

Date 09-15-2011 02:44 Edited 09-15-2011 02:50

6061 is a heat treatable aluminum alloy.

Alloying constituents are added to aluminum that "clump" within the atomic lattice of the grains. The clumping action strains the lattice thereby increasing the strength of the alloy. Let's step back a little and go through the mechanism in better detail. The aluminum alloy is heated to a high temperature to allow the alloying elements to go into solid solution. The alloy is then quenched to prevent the alloying constituents from precipitating out of the solid solution. The alloy is then "aged" at a lower temperature to permit the alloying elements to "clump" within the atomic lattice of the individual grains. The clumping action stresses the surrounding lattice which increases the strength of the base metal.

When the heat treatable aluminum alloy is welded (or held at an elevated temperature) there is a tendency for the alloying constituents to precipitate (diffuse) along the grain boundaries. Precipitation of the alloying elements along the grain boundaries weakens the base metal. In that condition, the alloy is overaged. Some heat treatable aluminum alloys age at ambient temperatures, that is, once the super saturated solid solution is quenched to room temperatures, the clumping action takes place slowly (it may take months) at ambient temperatures.

It can be said that many of the heat treatable aluminum alloys are "time at temperature" sensitive. They will overage if they are subjected to "elevated" temperatures for a period of time. To overcome the problem of overaging the alloy, the time spent at elevated temperature must be minimized. The time at temperature is additive, meaning that each weld pass increases the temperature for a period of time. If multiple passes are required to complete a joint, each weld pass increases the time at temperature and overaging will result.

I have found that it is beneficial to use no preheat when welding heat treatable aluminum alloys. Force cool the part between each weld bead. I use blowers or fans to cool the weld as quickly as possible between each weld bead. DO NO USE COMPRESSED AIR! You get compressed air from compressors. Most compressors use oil as a lubricant. The lubricant mixes with the compressed air and contaminates the aluminum if it is directed onto the surface of the aluminum. Porosity in the weld is often associated with hydrocarbon contamination, i.e., oils from compressed air, waxes used to keep sanding disks from loading up, finger prints, etc.

Minimize the heat input, i.e., use high current and high travel speeds to minimize the heat input per pass, but minimize the number of weld passes required to reduce time at temperature. Use GMAW (spray mode transfer) whenever possible to reduce the number of weld passes needed to produce the required weld.

There is no reason to preheat aluminum before welding. Aluminum does not respond to rapid cooling the same as carbon steel does. Rapid cooling is not going to cause the aluminum to harden, but it will help mitigate the chance of precipitation that will weaken the heat treatable aluminum alloy.

Best regards – Al

By 99205

Date 09-15-2011 06:59

Minimize the heat input, i.e., use high current and high travel speeds to minimize the heat input per pass, but minimize the number of weld passes required to reduce time at temperature. Use GMAW (spray mode transfer) whenever possible to reduce the number of weld passes needed to produce the required weld.

A lot of welders will have a problem with that statement, because they don't have a complete understanding on how heat input affects aluminum.

By Milton Gravitt (***)

Date 09-15-2011 12:22

Have you tried to GTAW DCEN using helium this would let you move faster than AC BTW what welding machine are you using.

M.G.

By 803056

Date 09-16-2011 02:07

I figured that would separate the welders from the boys. :eek:

Since 6061 heat treatable aluminum alloy was mentioned in the post, I will confine my comments to that alloy. A welding process such as GMAW spray mode transfer deposits more metal in a short period of time and utilizes higher travel speed than GTAW. As a result, GMAW spray transfer has lower heat input than GTAW when the total heat input for the completed weld is considered. Assuming the welder cools the weldment between passes, less time at temperature, better mechanical properties are obtained.

Q=ExIx60/V ///// (heat input = voltage x amperage x 60 / travel speed)

Best regards - Al

By ssbn727 (*****)

Date 09-16-2011 03:46

Just to add on to Al's excellent response is the fact that pulsed spray transfer on Aluminum is the method of transfer to use with thinner members of 6061-t6...

This method of transfer alternative will come very close to GTA quality weld deposits and as a bonus, enable one to weld this material out of position which could not be as flexible with standard spray transfer. :lol:

The only downside is whether or not certain codes will force you to qualify the procedure(s) before using pulsed spray transfer and under certain circumstances, for very good reasons. :eek:

Oh oh! I think I inadvertently opened up a new discussion, or should I say: "A can of worms!" :lol:

Respectfully,
Henry

By Lawrence (*****)

Date 09-16-2011 11:13

No can of worms on this thread Henry.

There are *no* prequalified procedures for aluminum in any code to the best of my knowledge. :)

By 803056

Date 09-17-2011 02:55

I'll bite Henry.

What do you consider to be a thin aluminum member? :cool:

By Lawrence (*****)

Date 09-17-2011 03:13

"Thin" is a bit of a relative term eh Al?

I think of thin as anything below 1/8"

Of course that begs the question of the scope of D1.2 when you start getting that thin or thinner

What do you consinder "thin" aluminum Al?

By 803056

Date 09-17-2011 20:53

That's why I said, "I'll bite."

I've used spray mode transfer on 1/8 inch 6061 in the vertical position, square groove, 0-inch root opening and I was able to get CJP consistently. We were welding to MIL-W-8604 and MIL-STD-2219 at the time. I had 32 welders in one company pass the test in the flat, horizontal, and vertical positions. We had no need to test in the overhead, so we didn't try it, but I see no reason that it would be a problem.

I'm not a major advocate of pulse transfer. Too many variables for most welders to adjust, too many variations from one manufacturer to another, too many variations from one model to another, and too much faith placed in the hands of the manufacturer that is only interested in selling equipment.

I suppose it has its place in a one man shop where code work isn't involved, but in a larger shop that has several different machines from several manufacturers, it only invites serious problems.

As for the new ASME Section IX requirements for recording the instantaneous power for pulsing on the PQR, it is another case of BS overcoming the power of common sense. The only way you can know what is happening is to use an oscilloscope to record the nature of the pulse parameters and the slope of the pulses. Then you might have a snowflake’s chance in hell to set several different machines to the same parameters and obtain consistency from one machine to the next.

Back to your question; pulse GMAW on materials on the order of 1/16-inch or so may be reasonable. GTAW would be my choice for anything less than 1/8-inch. Aluminum needs heat to overcome the thermal conductivity of the aluminum. Limiting the heat input by using pulsing usually works against you on material thicker than 1/8-inch. When you have to meet code imposed mechanical properties and fluid tight joints are required the use of low heat input, i.e., pulsing, usually translates into fusion type defects. As for D1.2, I don't recollect a minimum thickness limitation. I could be wrong, but I don't have my copy to check.

That’s my opinion on the subject. But my opinion is just one of thousands out there floating around. Just ask someone and I’m sure they will have a different take on the subject.

If you need someone to support the position that pulsing is the best thing since sliced bread it would be best to enlist the opinion of a salesman that sells pulse GMAW power sources.

I have several clients using pulsed power supplies, but for the life of me, I don’t know why. They are welding in the flat and horizontal positions, relatively thick materials, i.e., 1/8 –inch and thicker, on stainless, carbon steel, and high strength low alloy steels. For the most part, spray mode transfer would serve them better, but now that they have paid the big dollars for the machines, they have to use them or answer to management why they spent the big dollars.

Best regards - Al

By ssbn727 (*****)

Date 09-18-2011 04:23 Edited 09-18-2011 04:27

"If you need someone to support the position that pulsing is the best thing since sliced bread it would be best to enlist the opinion of a salesman that sells pulse GMAW power sources."

Nobody said or even implied this Al... Not all joints are CJP Al... There's company or two in southwest PA that use Pulsed spray with pythons "push-pull" 50' guns on 6061t6 both thin & thick members, and they're experiencing practically no rejects compared to what they were having results with standard spray transfer, and these folks both work to Mil specs including the 2 you mentioned...

My point is that it does work great for out of position welding when it comes to both quality & cosmetics for these folks where before they had a hard time achieving the quality they consistently do now with the bonus of cosmetically superior welds to boot..

The customer is very satisfied with the improvements which is why their orders have increased to the fabricator due also to the increased efficiencies & production achieved by adapting to pulse spray to their welding process choices.

This is no sales pitch Al... However, I did stay at a holiday inn once... :twisted:

These are just facts. :eek:

Al, Larry, 1/8" is the starting dimension for me to consider a member to be "thin."

I knew I would be opening up a can of worms here... Then again, that's usually the case when most of us are either really bored or just feel like having some fun with the topic because once again - they're (including myself after the Steelers got trounced last week! :cry:

) bored and cannot wait for FOOTBALL!!! :yell:

Respectfully,
Henry

By 803056

Date 09-18-2011 19:12

Hello Henry;

I stand by my position that pulse GMAW is difficult to replicate if the fabricator is using several different power supplies from several different manufacturers.

If the manufacturer uses one model, from the same manufacturer, he might find a place for pulse mode transfer. However, I challenge them to set two different machines from two different manufacturers to run the same without using an oscilloscope.

I currently have a problem with one of my clients. Several years ago they had a few older power supplies that had pulsing capability. When they tried to purchase new ones, the same model was no longer produced. They purchased two new machines figuring they could set them to run the same as the old machines. It never happened. They could not get the new machines to run properly using the setting from the old machines. They got rid of the old machines and went with the newer models and requalified their WPSs. Now they are ready to expand again and they are concerned they will encounter the same problems they did the last time.

Here's my question to you:

A) Do they buy new machines and hope the new programs produce acceptable results?

B) Do they buy new machines with new programs and requalify their WPSs using the new machines? That will require separate WPSs for each of the different models.

C) Do they try buying a couple of new machines that are the same old model with the same old programs so they can use the same WPSs and supporting PQRs?

Keep a couple of things in mind;

1) The controls on the new power supplies don't use the same terminology as the older models.
2) The meters on the power supplies show average voltage and current, not instantaneous parameters.
3) the frequency of the output of the power supplies is unknown as is the slope of the pulses, the duration of the pulses, or whether the output of the machines are constant current or constant voltage.

Don't misunderstand my position, as I said, a manufacturer that only has to contend with machines from one manufacturer and all are of the same model can produce consistent weld quality. The problem is when trying to mix and match machines from different manufacturers and different model types. Few companies have the in-house talent to program the machines to run the same, hence the problems I see every day.

Lincoln used to have a program that would allow you to connect a laptop to the power supply and see what was going on. The laptop became an oscilloscope, but it was usable with only one model power supply produced by Lincoln. I would have no objection if that approach was made available by all the manufacturers for each model they sold. Then it would be relatively easy to set all the machines to run the same. Then a WPS qualified by testing could be used on nearly any power supply. However, we haven't gotten to that point, hence the problems.

Most manufacturers assume they are getting good weld quality because the welds "look good". It isn't until the mechanical properties of the welds are tested that they discover there are problems. There nothing like a PQR to demonstrate the system is running properly. You cannot believe how many times I've been told, "We never had a problems with our welds before you came in." What they fail to mention is that they never tested their welders or their WPSs before I got involve and it is amazing how everything goes to the devil with the first test weld. One can only imagine what their weld quality was really like before they qualified their procedures and welders.

Best regards - Al

By ssbn727 (*****)

Date 09-18-2011 21:00 Edited 09-18-2011 21:28

Al remember who you are responding to... I know welding equipment inside out and have repaired many, many pieces of equipment as well as many, many systems when I was a factory authorized welding equipment repairman for Lincoln, Miller, Thermal Dynamics and Back then ESAB was known as "L-Tec"... :yell:

With that being said, It's pretty obvious that if one has more than one name brand of power source that produces a pulse spray type output, the parameters will indeed be different. :eek:

However, my point was the fact that both of these companies use the same power sources and other necessary equipment to produce repeatability throughout their respective shops. That is a fact as I mentioned in my previous post. :lol:

Anyone in their right mind would not populate their welding power sources with a red one here and a blue on there with a yellow one added in the mix so that one could say that they have the primary colors with the exception of black and white because of the fact that unlike the primary colors when mixed, these various power sources would not be able to produce the same results when used with the same parameters on each power source if they are applied to every very different brand power source.

It is an expensive proposition to change over completely to one type of power source from the same manufacturer but, when the situation justifies it, the results are very good both for the customer and the fabricator. Just like a fabricator doesn't always have to purchase a Welding Robot if their current or future needs do not justify the large investment.

With respect to pre-qualified WPS's are concerned, I agree that an SWPS is really not a good place to use as a pre-qualified Aluminum WPS however, nobody said that it couldn't be used... The ANSI/NAMM standard does have some WPS's that are pre-qualified according to sections 1 thru 4 as long as they're not structural joints which would then fall under AWS D1.2, and all one has to do is to review section 5 in the standard... Still Larry, you didn't mention previously that the WPS had to be structural so there are some exceptions out there regarding pre-qualified WPS's for Aluminum... :roll:

Al, you know what you can do with your so called "philosophy..."
The same that I can do with mine! :twisted:

Btw, to answer your questions regarding the customer you referred to... I would hunt around for the same power source as the one they currently have since there are always some "floaters" around to be found to add to their inventory... What do I mean by "floaters" Al? They are power sources that are available for purchase from many different welding equipment suppliers who buy these power sources from fabricators, companies or even welding supply stores that want to lighten up their inventory and sell these either at a loss or for profit depending on who they are. Somebody who knows how equipment moves around from place to place would know where to look. :eek:

Lincoln does still produce the "Power Wave" series of power sources that do what you mentioned... The point is that even if the power sources were exactly the same model and make, and produced during the same time frame... The two would still not produce exactly the same output parameters as the other one would, and this is why their respective outputs are listed in the specs of the power source with tolerances - even if the differences between the two are in such a small category of measurement when compared to the differences between name brand power sources or even different model #'s of the same brand. :lol:

In other words, I do not disagree with you Al, or Larry... You guys just misunderstood what I was saying... You know - semantics. :eek:

Respectfully,
Henry

By ssbn727 (*****)

Date 09-18-2011 05:06 Edited 09-18-2011 06:48

Hmmm, is this one an SWPS for Aluminum?

B2.1-22-015: 2011 (SWPS) FOR; GAS TUNGSTEN ARC WELDING OF ALUMINUM (M/P/S-22 TO M/P/S-22), 18 THROUGH 10 GAUGE, IN THE AS-WELDED CONDITION, WITH OR WITHOUT BACKING; SITE LICENSE (2011)

http://pubs.aws.org/product_info.php?products_id=941&osCsid=a904ea27175be64130e120fa3abc5116

Well, it's not GMAW Aluminum Larry... :eek:

Here's what NASA has to say about prequalified or Standard WPS's:

"“Prequalified” or “Standard Welding Procedure Specifications” shall not be permitted for production use on Class A or B welds made on flight hardware."

However, class C, D &E welds are mute with regards to that statement and here's the .pdf to read and ponder on:

"Process Specification for the Manual Arc Welding of Aluminum Alloy Hardware"

8.2 WELDING PROCEDURE SPECIFICATION

"A Welding Procedure Specification (WPS) is a qualified written working procedure that must be developed before beginning production for each unique weld type to be produced. Qualification support documentation in the form of a Procedure Qualification Record (PQR) shall be maintained on file to show proof of process/procedure capability using the WPS.

The WPS shall be traceable by means of serialized nomenclature and shall show traceability to the applicable PQR(s). The WPS used for production welding shall meet the requirements of AWS B2.1 and shall be certified by the responsible M&P organization at the operating facility, prior to use in production.

If a qualified WPS does not exist prior to welding of production parts, one shall be qualified according to AWS B2.1 “Standard Test Weldments” at a minimum. “Prequalified” or “Standard Welding Procedure Specifications” shall not be permitted for production use on Class A or B welds made on flight hardware."

This, and other references can be found on pages 15 & 16 of 19 in the .pdf, and the class c,d & e welds are in the beginning of the .pdf on page 5 of 19. Here's the link:

http://mmptdpublic.jsc.nasa.gov/prc/7180g.pdf

Respectfully,
Henry

By ssbn727 (*****)

Date 09-18-2011 07:30 Edited 09-18-2011 07:32

Here's another on Larry...

http://www.naamm.org/landing_pages/MBG_533-09.pdf

Look on page 8 (Page 12 of 19 of the .pdf) for "Section 5 Qualification"... However, this is after all a "Standard." :eek:

Respectfully,
Henry

By Lawrence (*****)

Date 09-18-2011 13:09

I'll stick with the notion that there are no prequalified WPS's for Aluinum.

An SWPS (Standard Welding Procedure Specification) is backed by as many as 10 PQR's. They all will be listed on the doccument.

Prequalified WPS for aluminum simply don't exist, because there are no codes that have such a provision.

By 803056

Date 09-18-2011 19:21 Edited 09-18-2011 19:56

I've had too many instances where I've qualified welders that attempted to follow SWPS only to fail miserably. I usually end up having to write new WPSs that can actually be used to deposit a good weld. Actually, I can say that I've never had a welder pass a performance test using only a SWPS as their guide.

Back to my philosophy that the WPS should list ranges for the parameters that give the welder a reasonable chance of success. The SWPSs fail the smell test miserably.

Best regards - Al

By ssbn727 (*****)

Date 09-18-2011 21:36

Not even the NASA code I previously listed Larry?

Respectfully,
Henry

By Lawrence (*****)

Date 09-19-2011 02:32

The NASA docccument you mentioned earlier is not a code :)

It refers to several codes... None of them contain prequalified WPS for aluminum.

By ssbn727 (*****)

Date 09-19-2011 05:14 Edited 09-19-2011 05:19

You are correct Larry... It is a process specification...

Now could you explain to us the difference between a "standard" and a "code?"

Also, is an SWPS prequalified if it has up to 10 PQR's to refer to?

Respectfully,
Henry

By Lawrence (*****)

Date 09-19-2011 11:22

Henry...

I really like the NASA doccument. But if you sit the thing side by side to AWS B2.1 or AWS D1.2 it's pretty easy to see they are not the same thing. I'll let you come up with the definitions.

Next... No, an SWPS is not prequalified if it has up to 10 PQR's to refer to... It's "qualified"