How exactly does A193 Grade B7M differ from A193 Grade B7
Q: How exactly does A193 Grade B7M differ from A193 Grade B7 ?
A: There are some significant differences in both the mechanical properties and the testing requirements of
A193B7M and A193B7. For instance, A193B7M has a minimum tensile strength of 100 ksi for diameters under
4”. The minimum tensile strength for A193B7 is 125 ksi for diameters under 2-1/2”, and 115 ksi for 2-1/2” – 4”
diameter. Hardness is probably the most significant difference between A193B7M & A193B7. The maximum
hardness of ASTM A193B7M is 235 HB or 99 HRB, while the maximum hardness of A193B7 is 321 HB or
35 HRC. The most notable difference from a manufacturing perspective is that when providing A193B7M bolts,
every individual bolt or stud in the lot must be hardness tested. A193B7M fasteners will also require a different
grade of heavy hex nut than A193B7, which would be ASTM A194 Grade 2HM.
While A193B7 is specified relatively often in the construction industry, A193B7M is a specification that is not
seen as regularly. This makes it important to understand the differences between the two specifications so that
the correct material is ultimately provided.