Armour-plate production depends on retained industrial skill

Would modern casting and metallurgy reduce the time needed to make naval armour plate?

Only with an active industrial base; retained practice and current process knowledge matter as much as newer metallurgy.

Repeated production reduces waste and improves speed because workers and facilities retain current process knowledge. Recreating thick naval armour after a long break would therefore remain difficult, whereas an uninterrupted industrial base could apply newer techniques to produce a better version more efficiently.