Cross groove large flat head self tapping screw (cross tip)

　　Strength: surface hardening 400HV Material: carbon steel, alloy steel

　　Material: 1022

　　Material description: C 0.18-0.23 Mn 0.70-1.00 S ≤ 0.050 P ≤ 0.040 Si is selected from the following range: maximum 0.10, 0.10-0.20, 0.15 0.35, 0.20 0.40, 0.30 0.60

　　Surface treatment: Blackening (quenching)

　　Surface treatment content: Blackening is a common method of metal heat treatment, which is to create a layer of oxide film on the metal surface to isolate air and achieve the purpose of rust prevention. When the appearance requirements are not high, blackening treatment can be used, and the surface of steel parts can be blackened, also known as bluing.

　　Risk reminder: The hardness value of hardened steel on the surface of fasteners is ≥ 320HV, and there is a risk of hydrogen embrittlement during electroplating