JIS G4304 / G4312 SUS 420J1 Stainless Steel Composition & Medium‑Hardness Martensitic Properties

SUS 420J1 is a medium‑hardness martensitic stainless steel defined in JIS G4304 / G4312. With 12–14% chromium and about 0.15% carbon, it can be hardened through quenching to achieve moderate hardness and wear resistance.

It is widely used for knives, scissors, appliance components, mechanical parts, automotive trim, and general wear‑resistant structures. Compared with 420J2, it offers better formability and is suitable for applications requiring both hardness and workability. SUS 420J1 is supplied as sheets, strips, bars, and wires. It is a cost‑efficient stainless steel for household hardware, appliances, and light mechanical applications.