If I were you, I wouldn't carry a big steel wallet during my trips. Since you put your seed phrases on a steel wallet, I assume you intended to create a cold wallet, so a cold wallet should be kept in a safe place, not in your pocket during the trip. If you still want to keep some metals, then just create a metal keychain and imprint your wallet's seed phrases. I think no one in the airport can have an issue with that because that's a keychain and it doesn't contain anything illegal, just a few non-offensive words.
New fear unlocked! I never assumed that a seed phrase would be possibly read under an airport x machine!
So, OP the previous message is totally a sensible suggestion: seed phrases are nice to be held in a secure place, those are no need to ever be taken out of of that secure place.