4043 vs 4643 on T6-6061 base

By Lawrence (*****)

Date 03-07-2007 13:50

Here is what Alcotec says about 4643
"Filler alloy 4643 was developed for welding the 6xxx series base alloys and developing high mechanical properties in the post weld heat-treated condition. This filler alloy was developed by taking the well-known alloy 4043 and reducing the silicon and adding .10 to .30 % magnesium. This chemistry introduces Mg2Si into the weld metal and provides a weld that will respond to heat treatment."

If you are not going to post weld heat treat I see no advantage to 4643

By SWP

Date 03-07-2007 14:25

If this will not be post weld heat treated, 5356 is another choice and it will provide higher weld strength.
Also, just thinking that 1/2" may be a bit thick for AC with Argon and no preheat. Other options are a Helium/argon mix with AC, or DCEN with Helium.

By Kix

Date 03-07-2007 14:45

OK so witch is cheaper 4043-4643 or5356? They are not preheating nor are they post weld heat treating. i will hopefully be able to get them to at least start preheating here in the near future. I am also suggesting argon helium mix, but what would be a good mix? 75/25 OR 50/50 or something else? They were using 5356 and went to 4643 for a reason i have yet to find out.

By aevald

Date 03-07-2007 15:41

Hello Kix, I don't know that you will find an appreciable difference in the cost for any of these alloys, but I haven't bought any of this rod for quite some time either. As far as why your people switched to the 4000 series rod, that might have to do with cracking issues. Sometimes the 5000 series fillers will be more crack suseptable than the 4000's, especially if they aren't using any sort of preheat. Just a few thoughts, regards, aevald

By franciscocl7 (*)

Date 03-08-2007 23:39

Actualy we still welding a 1/2" 6061-T6 plate with a novel joint, IEA (Indirect Electric Arc) only by a pass of weldin but in flat position, it has been demostrate that IEA increase the mechanical properties 35% in as weld condition. We use GMAW in spray transfer.

By Lawrence (*****)

Date 03-07-2007 16:36

Here is another interesting little tidbit.

Not exactly on topic, but there have been some similar aluminum threads lately and this a a good thing to take note of.

Precipitaiton hardenable aluminum alloys will regain significant tensile strength (from about 24 ksi as welded back up to nearly 40 ksi) by naturally aging.

So with the selection of a heat treatable alloy, over time, even the weld zone will gain significantly in mechanicals over just a few weeks.

The graph I'm trying to attach is by the ASM Mommittee on Heat Treating of Aluminum Alloys.

By Kix

Date 03-07-2007 16:50

So in laymans terms your trying to say you benefit significantly in the weld strength area with post weld heat treat or by ageing? The load testing on the part is meeting well over the rating they were given with the current procedure they're using so i think they are trying to make this procedure as simple as they can to save a buck. They are also haveing tremendous distortion issues witch i have to come up with a solution for.

By Lawrence (*****)

Date 03-07-2007 17:19

I think the data says strength can be gained with both methods, <still, more with treatment than with aging>.

The reason I posted is that there might be some folks who would think that the enormous loss in tensile strength from welding will in no way be recovered without post weld heat treatment. I think this data says there is some pretty significant recovery naturally over time.

This may have some influence on engineering decisions when choosing a non heat treatable filler like 4043 which will not strengthen with post treatment or time.

I knew welded Precipitation hardenable aluminum would age strenghten over time... I had not previously paid much attention to the surprisingly short cycles necessary to see gains.

By Kix

Date 03-07-2007 17:38

So if we're not going to use post weld heat treat do you recomend the 4043 filler because over time it will grow stronger?

By Lawrence (*****)

Date 03-07-2007 17:42

I'm not making any recommendations :)

No engineer here.

4043 is non heat treatable... no strength gain over time

4643 is designed especially for heat treatable alum and will gain via time or treatments.

Just injecting some good data into the conversation :)

By GRoberts (***)

Date 03-08-2007 01:43

Lawrence,
I definately agee with you on the weld metal. My question is about the HAZ. I believe that one of the weak regions in the HAZ is from over-ageing on the heat treatable alloys. Time won't help this area recover will it? I'm thinking it won't, but I could be wrong.

By Lawrence (*****)

Date 03-08-2007 03:20

G

I'm going to have to ask an egg head friend about the HAZ... Good quesiton!

By DaveBoyer (*****)

Date 03-08-2007 04:14

Lawrence: I am interested to hear what Your "egg head" friend has to say about the HAZ. I have read that some the strength will recover with the passage of time, but I had no information about how much or how long. I mentioned this on the thread where the guy's test coupons were failing in the HAZ at about 20KSI. I asked how soon after welding they were testing, but got no reply. From Your chart it looks like most of what recovery can be had comes in about 4 days.

By franciscocl7 (*)

Date 03-08-2007 19:51

I guess there is a confution, Heat Tretable Alloys can't recover strenth with passage of time.

Theres is an Research: Malin, V., Study of metallurgical phenomena in the HAZ of 6061-T6 aluminum welded joints. Welding Journal, 1995: p. 305s-317s.

There is the solution

By franciscocl7 (*)

Date 03-08-2007 20:09

Another researcher: R.Y. Hwang, C.P.C., The study on microstructural and mechanical properties of weld heat affected zone of 7075-T651 aluminum alloy. Scripta Materialia, 1997. 38(2): p. 215-221.

He welds with GTAW 7075 T651 aluminun alloys. I hope it helps you.

By Lawrence (*****)

Date 03-08-2007 20:33 Edited 03-08-2007 20:37

Francisco is right!

I was totally off base with the notion that the chart applied... The chart does not speak to "as welded" conditions.

Tony Anderson CEng from Alcoa/Esab set me straight, in part this is how he explained it:
"Most 6061 is welded in the -T6 condition, however, regardless of the temper, when we weld on the 6061 material we change the temper. If we weld on -T4 or -T6 we will typically partially anneal the HAZ from the heat input during the welding operation.
Because the HAZ is no longer in the solution heat treated condition (but partially or fully annealed) after welding it will not naturally age.

If you take a 6061-T4 (solution heat treated) material and allow it to stand at room temperature after heat treatment, it will naturally age in accordance with the charts that you have.
However, if you weld on a 6061-T4 or a 6061-T6 you will change the heat treated condition of the HAZ (from solution heat treated and naturally aged -T4, or solution heat treated and artificially aged -T6, to over aged and or partially annealed) and lower the strength of the HAZ. The HAZ will not regain its strength through natural aging.

As for the use of a heat treatable filler alloy (4643), this will not change anything in the HAZ, unless post weld heat treatment is performed."

By franciscocl7 (*)

Date 03-08-2007 22:43 Edited 03-09-2007 01:05

Lawrence

I´m totally agree with you.
Then the porpouse of filler alloy 4643 is to give strenth of metal weld owing the formation and dispersion of Mg2Si precipitates during PWHT.

That´s right?

By DaveBoyer (*****)

Date 03-09-2007 04:49

Francisco - Is there a way to acess the Welding Journal article You mentioned here on this website?

By franciscocl7 (*)

Date 03-09-2007 15:17

No. The article is to old, 1995, you must to access to welding journal magazine: Malin, V., Study of metallurgical phenomena in the HAZ of 6061-T6 aluminum welded joints. Welding Journal, 1995: p. 305s-317s.

Theres is another research Grong, he has been study about welding aluminum.

I have only the article in pdf. of Hwang.