metal strength loss & heat treatment.

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I know when you weld something, the area where you weld, and the area around it lose some of it's strength due to the heat. I know this is extremely true with aluminium. I can understand how this idea would be difficult with big things, but with smaller things is it possible to heat treat at home? If so what are the formulas? Ie. how long should you put it in the oven and at what temp? And at what increment should you bring it down? From what I understand, steel is generally kept in an oven of something in the 600s Fahrenheit for so many hours then brought out to cool.What are you opinions on this idea? I know generally one goes with a a piece of metal shaped and sized(metal diameter) to provide adequate strength for the application, so it already has suffecient strength and heat treatment could be looked at as a waste of time since essentially you're giving the metal extra strength it wont need. But is what I'm saying possible?
Reply:http://weldingweb.com/vbb/showthread.php...highlight=kilnDownload the pdf on the link in post 4.  There is a ton to know about heat treatment and the old "get it to cherry red then dump it in oil" wont get you very far...But it is a fascinating science and you should enjoy reading about itMechanical Engineer
Reply:Let me Google that for you.
Reply:Welds on aluminum may only be 64% the strength of the parent material.Steel is much better. and as high as 85% or more.Some aluminum like 5052 if you pass a rich oxy flame over it it will get much softer.If you put water on hot 6061 it will get soft as butter. That is called annealing.Many times steel is annealed to make a metal stampings and then re hardened.IT is a complex process. IT has to be done in a very particular sequence of heating for each type of metal.With steel there is water hardened, oil hardened and air hardened steels.You have to know what you have.It is a very in depth study and very specific.AWS certified welding inspectorAWS certified welder
Reply:Originally Posted by Donald BranscomWelds on aluminum may only be 64% the strength of the parent material.Steel is much better. and as high as 85% or more.
Reply:Thanks blue and donald, very helpful replies. I will read more about it to learn more. This is pretty interesting to me.
Reply:Originally Posted by KelvinIs that all? Are you sure?I'm just a hobbyist but I would have thought that it would depend on the parent metal, the filler metal and any post-weld heat treatment. I would have thought that in some cases (for example using 70ksi filler on 34ksi steel) the weldment would be STRONGER than the parent.Must the weldment necessarily always be weaker than the parent metal? Sumpin don't sound right here!If so, next time, I'll use Gorilla glue!
Reply:Originally Posted by Donald BranscomThere is much more. You would need a very specific question to get the right information.There are different areas too as mentioned.Hardening, annealing(softening), pre heat before welding, stess relief, reduction from heating and cooling cycles, and each metal and type has its own parameters for all of these processes.HAZ (heat affected zone) studies of different types of welding on different metals andmuch more. It gets deep and wide.
Reply:Let me simplify the question: Originally Posted by KelvinMust the weldment necessarily always be weaker than the parent metal?
Reply:Specifics count. Aluminum is a different animal than steel, than copper, than titanium, etc., etc. Everything gets rearranged at an atomic level after welding. It all has to do with the amount of heat applied, and with the speed of the application of that heat, and with the cooling rate as well. The transition zone between weld metal and parent metal is the area of greatest disruption, in my own words.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Kelvin, there was a discussion here about overmatching the weldment by using 4130 filler on a 4130 weldment.  The Miller experts recomended that ER70-2 or ER80 be used to dilute the puddle and prevent the overmatch unless there was a plan for post weld heat treatment.  If you will search this site it will give you a good bit to read and I think it will help to answer your question.  All of that is way beyond me, but I did read it and got a lot from what I read.  Hope this helps.BobI'm spending my Kids inheritance, I dont like him that much anyway!!!!!!Enuff tools to do the job, enough sense to use em.Anybody got a spare set of kidneys?  Trade?