Hardness 14 HRC with SA516GR70 2

[jbesson]

Hello Everybody,

The NACE require 22HRC maxi to prevent HIC effects on C.S. and the use is to select "soft" material like SA516GR65 to reach this value.

Is it realistic to select SA516GR70 if target for welding hardness is 14HRC after PWHT ?

 

[gr2vessels]

It depends.
You can purchase grade 70 with limited carbon content down to 0.23% and equivalent carbon of 0.43%;- the hardness will not be 14 HRC, but will be less than 22 HRC. Any higher carbon, the hardness after PWHT is likely to exceed 22 HRC. That's the reason perhaps to select lower grade, say grade 60, which has a bit less strength, thus the minimum thickness will increase, but you can rest assured that all the other NACE requirements will be met easily. This is a very simplistic way to describe the "NACE" material selection process, but is easy to remember and easy to understand. More carbon, higher hardness.
cheers,
gr2vessels

 

[stanweld]

14 HRC is not considered a valid test with the diamond indentor (Rockwell B scale should be used). Hardness is is somewhat equivalent to 94 HRB. You should have no problem meeting that value with PWHT provided the material is not very thick and the carbon equivalent is increased by the steel manufacturer to meet the minimum tensile requirements. You can always compensate for increased C.E. with moderate increases in PWHT hold temperature and time.

Be sure to specify that the steel be made to fine grain practice with aluminum additions and that niobium or vanadium additions are not permitted for this purpose.