From the literature, We got the following information.

       Technically, both of these materials have almost identical physical properties and chemical composition. Only difference is that carbon content is (0.04%) higher in SA-515 (C=0.31%) as compared to SA-516 (C=0.27%). Moreover, A515 and A516 is that A515 is produce to coarse grain practices and for use in high temperature applications such steam piping or pressure vessels, since coarse grains good resistant for creep deformation and helps to minimize the graphitization. A516 is produced to fine grain practices in order to maximum the fracture toughness. For vessels or components that operate above ambient temperature service, SA 515 is acceptable plate material because you would be above the ductile to brittle transition temperature in service. For vessels that operate at or below ambient temperature service, the SA 516 plate material would be specified because of improved impact properties or notch toughness per ASME Section VIII Div. 1 or Div. 2 minimum design metal temperature requirements.

·       

ASTM A-515 Standard Specification for Pressure Vessel Plates, Carbon Steel, for Intermediate and Higher Temperature Services

·        ASTM A-516 Standard Specification for Pressure Vessel Plates, Carbon Steel, for Moderate and Lower Temperature Service

·        As per ASME Sec. II Part D for Sec. VIII Div. 1, both the materials have the same high temperature limit that is 538 deg C and working temperature is 427 deg C.

We would like to know, for boiler applications at a particular temperature, which material (B/N SA515Gr70 and SA516Gr70) will work better ?