Manganese in A36

The manganese in A36 (basically a carbon steel) is very low (only 0.75%)

This level of Mn is usually for refining purpose - remove harmful S (by MnS) etc. And hence this percentage of S is not important whether the plate is 1/4" or 4"

Check this site

http://www.matweb.com/search/datasheet.aspx?matguid=d1844977c5c8440cb9a3a967f8909c3a

and

http://www.roymech.co.uk/Useful_Tables/Matter/Alloy_Steels.html

Both the above sites are extremely informative, and not only for this case (Roymech and keytometals)

Hence don't bother if the Mn is less tha some 1.5% or so.

However check the carbon Equivalent that is affected due to the presense of Mn. (Mn/6) which may affect weldability and other HT properties.

http://en.wikipedia.org/wiki/Equivalent_carbon_content

In ASME code Section II, Part A, in Table 2 for Chemical Requirements of material A 36, where there no indication to Mn %, this means that no requirements for that percent up to 3/4" thickness is required, where for higher thicknesses, the requirements are essential. This is clear from the note shown under the table, Note 1 - Where ". . ." appears in this table, there is no requirement. The heat analysis for manganese shall be determined and reported as described in the heat analysis section of Specification A 6lA 6M.

Thanx pal