What Is The Difference Between S31803 (F51) And S32205 (F60)?

If you have not heard of F51 and F60 before, they are essentially duplex and super duplex stainless steel grades taken from one of the most widely referenced standards for the supply of stainless steels, ASTM A182. This standard applies to forged or rolled alloy and stainless-steel pipe flanges, forged fittings and valves and parts for high-temperature service. According to ASTM A182, the ‘F’ in F51 stands for forged. 

How To Differentiate Between F51 and F60

Following the development of duplex stainless steels, their initial specification was captured as UNS S31803 (F51). However, a number of the leading manufacturers were consistently producing this grade to the upper end of the allowable specification. This reflected their desire to maximise the corrosion performance of the alloy, aided by the development of the AOD steelmaking process that allowed tighter control of composition. In addition, it also allowed the level of nitrogen additions to be influenced, rather than just present as a background element. Therefore, the highest performing duplex grade sought to maximise the levels of chromium (Cr), molybdenum (Mo) and nitrogen (N). The difference between a duplex alloy whose composition meets the bottom of the specification, versus one that hits the top of the specification can be several points based upon the formula PREN = %Cr + 3.3 %Mo + 16 % N.

In order to differentiate the duplex stainless steel produced at the top end of the composition range, a further specification was introduced, namely UNS S32205. Duplex stainless steel made to the S32205 (F60) caption will fully meet the S31803 (F51) caption, whereas the reverse is not true. Therefore S32205 (F60) can be dual-certified as S31803 (F51).

Contact Langley Alloys

Langley Alloys is a leading steel distributor for worldwide applications. We operate primarily from our facilities in the USA and UK. As part of our duplex stainless steel range, our Sanmac 2205 alloys have ASTM A182 F51/F60 specifications. If you’re looking for more information on Sanmac 2205 for your application, please contact our expert team and we will be happy to assist you.