Brinell hardness

Brinell hardness (HB) is generally used when materials are softer, such as steel before heat treatment or after annealing. Rockwell hardness (HRC) is generally used for materials with higher hardness, such as hardness after heat treatment, and so on.
Q355D hot-rolled steel plate hardness 140-190HB
Hardness of 45 steel after quenching and tempering: 210-250 HB
42CrMo quenched and tempered with a hardness of 250-350HB or 28-35HRC; Hardness after surface induction hardening 55-60HRC
40Cr quenched and tempered with a hardness of 250-350HB; Hardness before tempering is less than 240HB
The hardness before 20MnV tempering is less than 187HB; Hardness 58-62HRC after surface carburization treatment
The hardness before 20Cr heat treatment is less than 179HB; Hardness after quenching and tempering 20-28HRC; Hardness 58-62HRC after surface carburization treatment
NM400, Hardox 400, Hardness HB400
NM500, Hardox 500, Hardness HB500