heating 1080 steel

[alexphillips]

We are arc welding the entire inside of a 1080 steel cyclinder, 9 1/2" ID 3/4" wall thickness by about 9". We are worried about deforming the outside of this wall as this will be used as a mold and don't want failure at high pressures. Hooking a thermocouple to the outside of this mold, what temperature should I be worried about the 1080 steel's physical properties?

 

[MiketheEngineer]

I can't imagine that you will not distort the cylinder as you locally apply the weld.

To what degree - I don't know or whether that will affect your final mold.

You might have to re-machine the OD to get the accuracy you want or need.

Try one.

 

[alexphillips]

The idea is to weld the entire ID to then machine it back to its high tolerance (there is a deep scratch running along the ID). That much welding would cause the mold to reach very high temperatures, but are these temperatures going to effect any properties of the steel? I know that we want to stay under about 720C or else the metal will start to go through a transformation and change its properties (ttt/ct diagrams). Will it do the same at a lower temperature, heated for probably an hour?

 

[MintJulep]

With a high carbon steel like 1080 not only the temperature, but also the rate of heating and cooling matter.

Since you haven't mentioned how the part was previously heat treated it seems likely that you don't know.

But after you weld the entire ID, certainly it will have very different properties than it did before you started welding.

 

[Cockroach]

Your talking weld repair.

It is highly unlikely that you will get any membrane distortion, we're talking about a 3/4 inch wall! What is highly important is to have the proper pre-heat, in order to get the proper weld penetration into the alloy sub matrix, followed by a controlled post heat back to ambient. So you slow down the cooling rate in order to mitigate thermal residual stressing.

Note that by the code, 3/4 inch wall and greater need to be HTSR. I believe this also applies to weld repair. Memory is foggy, but I'm pretty sure that applies.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[saplanti]

I agree with MintJulep on the issue. Even if you have a good procedure you may still experience cracks during/after welding.

If you are trying to put a thin deposit layer, sometimes metal spraying under controlled atmosphere is cheaper and better.

Sometimes, it is better to make a new one instead of repairing for certain type materials, or replace the welding with a liner suitable for the operation.

These may not be the answers what you are looking for, but it is better to mention.

 

[metengr]

Weldability of this material is difficult because of the high carbon content. Preheat on the roder of 500 deg F will be required and even possible PWHT may be required to assure no locally hardened material near or under the weld deposit.