heat treating brazed part

[TRX]

I have a fairly complex workpiece that needs to be made of 4140 steel. Looking at it, I realized a great amount of time, stock, and hassle could be saved if it could be welded or brazed together from separate pieces before heat treat.

Heat treat temperature for 4140 runs around 850C, just above the melting point for common brazes. But there are high temperature bronze brazes that melt at 900 to 1100C depending on formulation.

The general idea is: machine the bits, braze at 900C, finish machine assembly, heat treat at 850C.

Before I go off in this direction, does anyone see a problem? "We do what all the time" or "yeah, that's what the data sheets say, but it'll still fall apart in the oven"?

[Russ Hanscom]

Not my area of expertese, but could you add a few screws to assure it does not fall apart at temp?

[TRX]

Unfortunately, no. Though it wouldn't be a problem to make a fixture to hold it together through the head treat process.

[Harold_V]

Something about the idea troubles me, but I can't put a finger on just what it might be.

Some coppper alloys are hot short. Could that be an issue?

Harold

[TRX]

That's a valid question. I can call the vendor and ask them about it. Which might not be a bad idea anyway...

[steamin10]

If you can fit it up for a soaking furnace, then why not just furnace braze the thing. It could come out much neater than hand brazing, and eliminate hot spot distortion.

[Harold_V]

Ya' know----I was just thinking about this project. Seems to me that if it requires heat treated 4140, soldering, or otherwise connecting pieces instead of making it from a solid piece may be counter productive. Of course, there may be something I don't understand, but I expect fabricating, unless it's done by welding, won't come anywhere near the strength of a solid piece.

Welding 4140 is possible, but it requires immediate furnace work.

Hogging the item out of solid stock is looking real good to me right now.

Harold