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[martin]

Hey dave you ve got my concerns now.. I need to double check the oven temp... If have brought the 6061 to zero temper that might be a problem. What if i brought temp back up to 350-400 and let cool on its own.. Or can i bring thetemper back.. I am seeing the temper cut in half if brought to 775 degrees.. Do you anyone i can discuss this further in detail...

[Blue_Heron]

Originally Posted by martin

Do you anyone i can discuss this further in detail...

Unfortunately, my knowledge of metallurgy is only enough to get me in trouble. I had metal shop in High School (Stranahan class of '78) and the shop teacher showed us how to spin an ash tray out of aluminum sheet. It became work hardened and he used an oxy-acetylene torch to soften (anneal) it so he could work it some more.

In college, I took scuba to get my PE credits and they told a horror story about someone who had done a fancy baked enamel finish on their scuba tanks and the next time they were filled they exploded because the baking process had annealed the aluminum.

More recently, I read where a manufacturer of aluminum wheels (949 Racing) told a customer that he had voided his warranty by having his wheels powder coated.

So I don't know what temperature it takes to anneal 6061. It probably depends on whether the material was tempered or not. I'd start by asking the manufacturer of the bracket.
Dave

[martin]

After some reasearch,, the oven was set at the low end of the annealing .680 degrees The bracket was on top so maybe it did not get so hot cause the water spray to adjust temp and ash is at the top.. My guess... I did speak to a shop in jacksonville they do tempering.. He was very helpful on at what temp to bring the metal.. He said 960 once at 960 then quench in boing water. The bring back up to 360 for ten hours.. That should bring back to t6... If you skip the las t part of reheating.. Then it will be t4 .. If i brought bracket to anneall.. Or 0 then the strength is 18000 psi verse 47000 psi.tensile.... And shear is at no greater then8000psi verses25000
Elongation to failure at 15 percent... So i basiclly cut the strength to 1/3... The guy said he could try to temper it at a cost of 600... But cant gurantee that it will look like a bracket when done...
I am goin to go with the later and see what happends..

dave do you know what kind of forces are put on theses brackets?

[martin]

Originally Posted by Blue_Heron

Unfortunately, my knowledge of metallurgy is only enough to get me in trouble. I had metal shop in High School (Stranahan class of '78) and the shop teacher showed us how to spin an ash tray out of aluminum sheet. It became work hardened and he used an oxy-acetylene torch to soften (anneal) it so he could work it some more.

In college, I took scuba to get my PE credits and they told a horror story about someone who had done a fancy baked enamel finish on their scuba tanks and the next time they were filled they exploded because the baking process had annealed the aluminum.

More recently, I read where a manufacturer of aluminum wheels (949 Racing) told a customer that he had voided his warranty by having his wheels powder coated.

So I don't know what temperature it takes to anneal 6061. It probably depends on whether the material was tempered or not. I'd start by asking the manufacturer of the bracket.
Dave

Sounds like your metallurgy is enough to keep you out of trouble lol...yes it was tempured.. I saw on the angle that it was 6061t

[FishStretcher]

Because I do things like this sort of analysis at work and if I were to say something else I shoulder some liability, I would have to say you need to either scrap it or find someone who can confidently identify the material and process it correctly.

But I would still say that, even if I didn't have to. What you did was sort of anneal the aluminum, assuming it is 6061. Which greatly weakens it, and it isn't clear what the path back to the original strength is. Not to mention the welds are pretty discolored, so that is suspect or at least worth investigating.
Solution heat treatment and artificial aging is different from annealing, and you are likely to wind up with a pretzel. That process involves a specific high temperature for a short time and a water quench, possibly a straightening, and then an artificial age at a raised temperature.

If you can be confident that there is adequate strength margin built into the bracket as originally built because it was welded and then never post weld heat treated, then that is up to you, but that argument doesn't seem sound unless you can get agreement from the manufacturer.

If you are really hanging 2 outboards off it, then to me the cost of a bracket versus two outboards makes for an easy decision from a financial risk perspective, let alone a personal safety perspective- it should be replaced with a known good bracket.

Sorry for the bad news.

You asked about this in my old aluminum bracket analysis thread. Which was made of a specific alloy made for welding and no post weld heat treat and no annealing, so it is pretty different.

[martin]

Originally Posted by FishStretcher

Because I do things like this sort of analysis at work and if I were to say something else I shoulder some liability, I would have to say you need to either scrap it or find someone who can confidently identify the material and process it correctly.

But I would still say that, even if I didn't have to. What you did was sort of anneal the aluminum, assuming it is 6061. Which greatly weakens it, and it isn't clear what the path back to the original strength is. Not to mention the welds are pretty discolored, so that is suspect or at least worth investigating.
Solution heat treatment and artificial aging is different from annealing, and you are likely to wind up with a pretzel. That process involves a specific high temperature for a short time and a water quench, possibly a straightening, and then an artificial age at a raised temperature.

If you can be confident that there is adequate strength margin built into the bracket as originally built because it was welded and then never post weld heat treated, then that is up to you, but that argument doesn't seem sound unless you can get agreement from the manufacturer.

If you are really hanging 2 outboards off it, then to me the cost of a bracket versus two outboards makes for an easy decision from a financial risk perspective, let alone a personal safety perspective- it should be replaced with a known good bracket.

Sorry for the bad news.

You asked about this in my old aluminum bracket analysis thread. Which was made of a specific alloy made for welding and no post weld heat treat and no annealing, so it is pretty different.

Hey i appreciate the reply..i would never hold anybody liable for my mistake... Just needed some insight thats all. I will check with manufacturer. And hear what they have say...unfortunately for me as of right now it doesn't sound good..

[martin]

Well looking for a bracket... But still not giving up yet on the other one... Checking oven range.. Going to try to temper tjis bracket... If it still looks like. Bracket when the quench is done then i will use it.. Stay tuned for an exciting event...
Anything has got to be more exciting then fairing the stern... That is where i am at now... Almost done.... Then off to primer545 and then a high build allthe way around....
Then545 and color.. Sanded hull and filled pin holes and scratches with lw fair.. By awl grip noticed a couple dry spot and delamination.. Of gel coat and mat.. Ground and filled with epoxy....
For the record.?" I WILL Never cut off another transom skin again.... not in this life time

[Entourage]

I WILL Never cut off another transom skin again.... not in this life time


Lol. I hear ya there.

[martin]

You know it is sad when you and your straight line sander are on first name terms.. I am finally putting up my sander and laying some primer on her. Sat if weather permits... Need to hurry up Code Enforcement sent me another notice. Need to repeat I will not cut another transom skin off again.. All in all I got her pretty fair. I have decided to bottom paint cause of the tanins in my canal.. There always seems to be a scum line that I cannot clean off.

[martin]

Ready for paint