To give you the correct answer,there are 2 types of steel rods as there is 2 types of steel cranks
you have "cast "steel which is fitted in stock Cosworth engines,this is stronger than normal "cast" iron like in pinto and RS Turbos ect
Then you have the proper stuff "Billet" steel,which is a billet of graded steel which is then machined to make a crank or a con rod,this process is time consuming so you pay more money,but its the ultimate in strength
hope this answers your question