Fe 52 and Fe 42B material of construction for an Aboveground Staorage Tank 1

[nuk4]

A 9 course EFRT with diameter as 76.2m, Height as 21.9m, built in 1971 and still in-service states that course 1 - 7 was constructed with Fe52 material while the 8th/9th course was built with Fe42B material.
Am unable to find the material equivalent for material of construction and require help. Please kindly help.

 

[bimr]

These are cross referenced in the following charts:

http://www2.coromant.sandvik.com/coromant/pdf/smallparts/catalogue/P144-148.pdf

http://www.ruukki.com/~/media/Files...-grades-comparison-designation-and-codes1.pdf