The hardness of S32750 varies from one product form to another, and from batch to batch, but the common specifications cap it. Solid bar supplied to ASTM A182, ASTM A276 and ASTM A479 is limited to a maximum of 310 HB (Brinell), while NACE MR0103-2015 limits wrought and cast super duplex to a maximum of 32 HRC (Rockwell C).
Why hardness is controlled
NACE MR0103-2015 is widely referenced for metals used across the oil and gas industry. Its full title is "Petroleum, petrochemical and natural gas industries - Metallic materials resistant to sulphide stress cracking in corrosive petroleum refining environments".
The standard targets metals used in the presence of H2S, where hydrogen charging and sulphide stress cracking (SSC) can occur. High strength can reduce susceptibility to cracking, but high hardness is known to greatly increase the likelihood of failure, so controlling hardness is an important measure.
Hardness testing is non-destructive and needs less sample preparation than many other measurements, so it is easy to carry out both during production as a quality-control check and by the user during field inspection.
What we stock
We stock S32750 solid bar in sizes from 5/8" to 20" (15.87-508mm) diameter, plate up to 3" (76.2mm) thick, plus pipes in scheduled sizes, fittings and flanges.