Metalurgy lesson ?

[mhorowit]

Assume we are heating a strip of metal with the intention of forming it around a tube. We heat it to the high end of the red scale (not into white) and then form the strap. I assume we then play the torch over the metal to cool it slowly. At what point are we in danger of causing a change in the metal so as to make it brittle or otherwise harm it? - Mike

[Hank Jarrett]

Re: Metalurgy lesson ?

Depends on the metal and the actual temperature you get to. The alloy agents and cooling rates have a strong effect depending on LOTS of factors. To give you the answer you ASKED for, you would need a graduate class in metallurgy.
Don't sweat it. To give you the answer you NEED, you don't want an answer from a desk jockey rocket scientist. Get a GOOD welder or blacksmith to SHOW you. You need to actually SEE the color change and how the metal behaves as it is heated and cooled (do you know what color "straw" is?).
I have had the "book smart" part, and worked with a really GOOD welder. When it's time to cut, bend, weld and form the metal, go WORK WITH the guy who actually handles the metal. Us desk jockeys are pretty useless.
Hank

[Pearson]

Re: Metalurgy lesson ?

Mike,

The metal doesn't need to be at the high end of the red scale. But if you just get it to a nice glowing red hot, you should be able to do as Mark Julicher said and tap it into shape with a small ballpeen hammer. Once it starts to heat up, keep the flame away from the edges and pull it farther away to control the amount of heat. Keep the flame moving at all times and allow the metal time to heat up. A lot of people try to heat up metal too quickly. If you start seeing tiny little sparks jumping out of the metal, that is TOO hot. I suggest you practice on a scrap piece of the same type of metal before you work on the actual piece.

[jCandlish]

Re: Metalurgy lesson ?

Use a (very) lightly carborizing flame. Remember, the flame goes into the matrix. Don't burn the carbon out of the steel with too much oxygen.

[VictorBravo]

Re: Metalurgy lesson ?

Us desk jockeys are pretty useless.

That's the first time I've ever been able to legitimately say Hank is full of s**t in all the time I've been here.

[Ragwing nut]

Re: Metalurgy lesson ?

just need to bring it up enough to move the metal. assuming this is with 4130 you do not need to post heat, just let it air cool and it will return to annealed condition as before you heated it. What you do not want to do is dip it in water to quench it. That will temper the steel

[mhorowit]

Re: Metalurgy lesson ?

just need to bring it up enough to move the metal. assuming this is with 4130 you do not need to post heat, just let it air cool and it will return to annealed condition as before you heated it. What you do not want to do is dip it in water to quench it. That will temper the steel

That's great, -Mike

[mhorowit]

Re: Metalurgy lesson ?

just need to bring it up enough to move the metal. assuming this is with 4130 you do not need to post heat, just let it air cool and it will return to annealed condition as before you heated it. What you do not want to do is dip it in water to quench it. That will temper the steel

Under what circumstances can I form 4130 without applying heat? - Mike

[Ragwing nut]

Re: Metalurgy lesson ?

Depends on the bend you need to make. If you can cold form it, go for it. I cold form 95% of the time

[mhorowit]

Re: Metalurgy lesson ?

Depends on the bend you need to make. If you can cold form it, go for it. I cold form 95% of the time

This would be the bushing end of the streamline tube on the landing gear; it gets squashed at the end - MIke

PS - When you replaced that tube, did you notice a piece of metal inside the tube; some kind of stub?

[Ragwing nut]

Re: Metalurgy lesson ?

Are you talking about bending the strap? Is the stub at the top of the gear?

[mhorowit]

Re: Metalurgy lesson ?

Are you talking about bending the strap? Is the stub at the top of the gear?

The stub is at the top of the gear; the stub seems to fit into the streamlined tube. I'll know more as my deconstruction continues.

UPDATE: it is now an hour later and I have managed to remove enough of the weld to see that it's not a stub just internal to the streamline tube, but a piece that's welded to the larger part of the gear, fits into a slot in the streamline tube!

I tried bending the strap using heat and it worked fine. My question regarding working metal cold referred to the end of the streamlined tube the strap attaches to. The end is smashed a bit so to intersect smoothly with the small piece of tube that holds the bushing - Mike

[Ragwing nut]

Re: Metalurgy lesson ?

The stub is at the top of the gear; the stub seems to fit into the streamlined tube. I'll know more as my deconstruction continues.

UPDATE: it is now an hour later and I have managed to remove enough of the weld to see that it's not a stub just internal to the streamline tube, but a piece that's welded to the larger part of the gear, fits into a slot in the streamline tube!

I tried bending the strap using heat and it worked fine. My question regarding working metal cold referred to the end of the streamlined tube the strap attaches to. The end is smashed a bit so to intersect smoothly with the small piece of tube that holds the bushing - Mike

Easier to heat and roll the end of the streamline tube than force it cold.

The stub is a tie brace to reinforce the welded area to further prevent failure. Same method also applied in the struts

[jCandlish]

Re: Metalurgy lesson ?

Attached please find "Fig 23. Streamline tube splicing using round tube (applicible to landing gears)." Reference CAM18.6141

The complete CAM18 is available from: http://www.candlish.net/taylorcraft/caa-18.pdf

The first few (extra) pages are black. Don't let them fake you out.

[mhorowit]

Re: Metalurgy lesson ?

Easier to heat and roll the end of the streamline tube than force it cold.

Yep; just trying to understand when to work something cold and when to use heat.

The stub is a tie brace to reinforce the welded area to further prevent failure. Same method also applied in the struts

That's what I was thinking; that significantly complicates what I thought was going to be difficult only because of the heat required. I've been using my die grinder to deconstruct that cluster (slow and tedious); is there a smarter way and do you have a drawing for the tie brace? - Mike