Marking of performance grades of set screws

① The performance grade of set screw is indicated by number and letter "H". The number represents 1 / 10 of the minimum Vickers hardness value, and H represents hardness. There is no grade 14H, 22H and 33H for the hexagon socket set screw.

② 14H grade, The maximum contents of P, s and Pb in free cutting steel are 0.11%, 0.34% and 0.35% respectively.

③ Surface hardening is allowed for 14H grade square head screw.

④ 22H ~ 45H grade, steel with maximum lead content of 0.35% can be used.

⑤ 45H grade alloy steel shall contain one or more alloying elements of chromium, nickel, vanadium or boron.

⑥ 22H grade, If the demander adopts Rockwell hardness test, the minimum value of HRB and the maximum value of HRC shall be adopted.