Steel suitable for heat/cool cycling

[Mowest3]

We have an application that requires the building of a mock-up for training firefighters. The mock-up will be steel (plate/sections and approximately 30 feet long and 10 foot high) and will be exposed to a fuel-rich propane fire (probably in the 600ºC or higher range). The duration of the fire will be sufficiently long to ensure the mock-up has achieved near maximum temperature and since it is a firefighter trainer it will be hit with multiple streams of cold water.

Therefore, the structure will experience repeated heating and quenching cycles and, with a planned life of 15 years, the number of cycles will be in the 25000 range.

ASTM A387 chrome-molybdenum alloy steel seems to be suitable for the temperature but what effect would the quenching have on performance (mainly buckling)?

Any guidance on what steel alloy(s) would suit so that a performance and cost comparison could be carried out?

 

[unclesyd]

We have a pretty comprehensive fire training ground where we have actual equipment, tank car, tank truck and totes. All the piping setups are normal use piping such as SA 106 Gr B. I don' think any of the steel structures are anything other than A 36 Steel. The present training ground was put in service in 1980 and is used on the average of 2 times a month by both our people and the surrounding community departments. During the summer there is one period where it is used nearly everyday for a periodof two weeks.

 

[Mowest3]

At our facility we are using some A36 and some Corten steels. The mock-ups have been in use for about eight years and have suffered from buckling, sagging and cracking. The maintainers are having difficulty welding the cracks or adding localised reinforcement.
I was hoping for that magic material (boiler plate or something like that)but it may be more realistic to replace a welded skin with a bolted plate skin over a stronger armature.
Do frequent heat/cool cycles affect the weldability of steel?

 

[unclesyd]

You are not going get much help from the rusting of the steel sheets by using any other CS material. You will get the distortion no matter what the sheet material. Some help can be accomplished by design and fabrication technique. The key point is remove all the constraint on the metal components as possible.
We don't attempt much repair beyond the support frame. Welding can be a problem due to the severs oxidation and corrosion around the crack, along with the possibility that there maybe some burnt metal. To do a weld repair you essentially have to get to clean metal.
This area is a high maintenance area of the finest kind.

 

[Mowest3]

Thanks unclesyd,
You have confirmed my thoughts.
I agree about removing the restraints, I was planning to use oversized holes to allow for panel expansion.
Using the A36 will help keep the costs down as well.

 

[Compositepro]

Curvature and joints can due a lot to relieve stress due to temperature cycling. A large flat sheet can be the worst for warping. This is because the restraint is in the sheet itself and at a maximum when flat.