Difference between A193 grades B7 / B7M and B8 / B8M

[jbesson]

Hy everybody,

I found on the threads that grade B7M was to be used in place of grade B7 in case of sour service, they have same chemistery and allowable stress.

For grades B8 and B8M chemistery is different but allowable stress are same, what about the use in sour service ?

Thanks in advance.

 

[TVP]

B8 or B8M can be used, as long as they are ASTM A 193 Class 1 (carbide solution treated, maximum hardness 223 HB/96 HRB). The requirements are listed in NACE MR0175/ISO 15156 Part 2. This specification only describes the requirements for sour service, and does not cover the requirements for other corrosion mechanisms (general, pitting, crevice, etc.).

 

[stanweld]

Hardness is further limited (lower limits) for B7M vs B7.