If there is any mechanical connection (including stove cement) between the cast iron and steel, the differing rates of expansion and contraction will quickly become a problem. Gaps will open up and I would think that the steel would also be much more prone to warping. I would contact the Morso company or a reliable dealer/repairer for advice.

The part I need to replace is a smoke shelf inside the combustion chamber that is not cemented to the sides of the stoves but only rests on small lugs inside the stove.

...that the steel would also be much more prone to warping...

I think there lies the problem as I don't know how much more the steel is going to warp compared to the cast iron as it is directly exposed to the flames.

This was my actual question to the members of this list. I am hoping to get away with 3/8" steel instead of the original 1/4" cast iron but I don't know.

If somebody knows the answer please tell me.

Thanks again

Thierry

Were you able to solve this problem? How? We have the same one/
Thanks