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Thread: Normalize welded clusters and temperature crayon

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    Registered User proppastie's Avatar
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    Normalize welded clusters and temperature crayon

    I read conflicting statements....the heat after welding a cluster is "just stress relief" ....heat it to "blood Red" to re-normalize the cluster....There are temperature crayons that should melt at the proper temperature for a proper normalization, however the thought occurs to me that the torch might melt the mark before the metal is soaked to the proper temperature. ...


    Has anyone used these crayons on welded clusters, any tricks... does it work? is the cluster normalized or just stress relieved (annealed)

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    Re: Normalize welded clusters and temperature crayon

    Unless you heat the whole structure, you cant normalize. Term can be slang for the stress relieving local joints. Crayons are nice to make sure you hit the temp marks. Just depends on how precise the engineering needs to be.

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    Re: Normalize welded clusters and temperature crayon


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    Registered User proppastie's Avatar
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    Re: Normalize welded clusters and temperature crayon

    Quote Originally Posted by TFF View Post
    Unless you heat the whole structure, you cant normalize. Term can be slang for the stress relieving local joints. Crayons are nice to make sure you hit the temp marks. Just depends on how precise the engineering needs to be.
    Well we start out with normalized tube.... not sure what you are saying here. can/cannot re-normalize weld clusters after welding normalized 4130 steel tube fuselage using temperature crayons? Can/cannot re-normalize weld clusters under any circumstances?

    Anyone use them on aircraft fuselages?

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    Re: Normalize welded clusters and temperature crayon

    To normalize 4130 you have to stick the whole thing in an oven at 500F for like a half an hour. No one I know has a 20 ft oven. 4130 was designed so it is still strong enough as welded , depending on the quality of the welding job. If your joint is normal airplane clusters that is how they are designed. The plus side of the joints stressed relieved is that they are less brittle. If you need a bracket or fitting that needs the extra strength, that is more doable. The tubes have to be vented if normalizing. I know of a helicopter company who experimented with one of their producion 4130 tube structures that was not vented and it came back with tubes sucked in where they were not vented.

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    Re: Normalize welded clusters and temperature crayon

    Quote Originally Posted by TFF View Post
    To normalize 4130 you have to stick the whole thing in an oven at 500F for like a half an hour.
    500F is way low, but it might stress relieve the area.

    Normalization of steels require on the order of 1300-1400F. Yep, red hot throughout. Then it has to be cooled in still air.

    We do not need it in 4130 airplane parts. Lots of airplanes out there with weld clusters just warmed up with a torch and allowed to cool, and we do not hear about them falling out of the sky because of failed welds.

    Billski

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    Re: Normalize welded clusters and temperature crayon

    Lots, also, with TIG welded clusters that had no post-weld treatment and have been flying trouble-free for years.


    BJC

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    Re: Normalize welded clusters and temperature crayon

    Quote Originally Posted by wsimpso1 View Post
    500F is way low, but it might stress relieve the area.

    Normalization of steels require on the order of 1300-1400F. Yep, red hot throughout. Then it has to be cooled in still air.

    We do not need it in 4130 airplane parts. Lots of airplanes out there with weld clusters just warmed up with a torch and allowed to cool, and we do not hear about them falling out of the sky because of failed welds.

    Billski
    To go further, in Tony Bingelis "The Sport Plane Builder" Page 58 talks about normalizing/stress relieving, with tempering to 1050 (Blood Red Color) 125,000 PSI RC25, vs 1650 (Salmon Color) 95,000 PSI Normalized... 1/3 more than annealed (62,000 psi ?).

    For fittings designed in shear/tension (not a good practice I know) this is perhaps significant. (Although doubling the size of tubing at one or two joints may not be that much weight.)

    Anyway the the thought was to use temperature crayons and I wondered if anyone here has. The amount of experience and expertise here is pretty amazing.

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    Re: Normalize welded clusters and temperature crayon

    Quote Originally Posted by proppastie View Post

    Anyway the the thought was to use temperature crayons and I wondered if anyone here has. The amount of experience and expertise here is pretty amazing.
    You really don't need the crayons if you just learn to read the color of the hot metal. The metal's black body color is directly tied to it's temperature.

    Click image for larger version. 

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    Conventional wisdom and practices yield conventional results. If that is good enough for you:
    Problem solved.

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    Re: Normalize welded clusters and temperature crayon

    I've had some of my gas welded clusters and joints analyzed by a lab many, many years ago. They cut them, looked at them with microscopes, x-rayed them, tensile tested them, bent them back and forth, hammered them and generally abused the hell out of them. The minimum strength they found in theses pieces was 87% of the original normalized 4130 tubing. I was happy with that and used a very conservative figure based on that number for design purposes.

    These joints were not stress relieved or post-weld heated; I just played the torch over them and let them cool somewhat gradually once the weld was completed and made sure they didn't get draughts on them. That is all there is too it, no need to overthink it.
    "Aeronautical engineering is highly educated guessing, worked out to five decimal places. Fred Lindsley, Airspeed."

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