I have toi wonder about a few things though.
What type of steel do they use. I mean masts tend to flex and work a fair bit. If you use low carbon (mild) steel, then you are going to be putting a lot of weight aloft in sidewall thickness and in the end the masts will develop wrinkles.
If you use hi carbon or spring steel then you will work harden it and eventually develop brittle faults at the exact "working" points.
And it will not take long either.
The only solution I could come up with to these issues is to go with a hybrid steel manufacturing process so that you either have a spiral welded tube structure that tends to equalize stresses and reduce work hardening, or you can go with a pattern welded structure like old gun barrels used to be (A folded/layered combination of high and mild carbon steel) The cost of producing a mast length tube of pattern welded steel makes my brain cringe.
And I could put that steel to much better uses!
So what sort of steel is used for the masts? (the light pole notwithstanding, though it is a scary/cute concept).
If it is just a surface plated mild steel such as used for lightpoles, do they need to run about a gazillion shrouds and stays to try and keep the mast extra rigid so that the surface hardening doesn''t just crack off and fall to the deck?
I love steel. I work in steel everyday and have bought my house and boat on the proceeds of what I can make it do....But I think steel masts are one fo the dumbest ideas since concrete boats (or maybe they belong together).
More answers please....