SUS420j1 vs. SUS420j2: What’s the difference?

SUS420J1 and SUS420J2 are two common grades of martensitic stainless steel defined under the Japanese JIS G4303 standard. Both are known for their good hardness, moderate corrosion resistance, and widespread use in cutlery, medical instruments, and tools. However, they differ mainly in carbon content, which significantly affects their mechanical properties.

In this article, we'll compare SUS420J1 vs. SUS420J2 in terms of chemical composition, mechanical properties, hardness, corrosion resistance, and applications - and answer some frequently searched questions.

 

SUS420j1 vs. SUS420j2 stainless steel.pdf

 

What material is SUS420J1?

Standard: JIS G4303

Equivalent to: AISI 420A / 1.4021

Carbon Content: Approximately 0.15%

Chromium Content: 12–14%

Typical applications: Surgical instruments, scissors, pump shafts, valves, household knives

 

What material is SUS420J2?

Standard: JIS G4303

Equivalent to: AISI 420C / 1.4028

Carbon Content: Approximately 0.30%

Chromium Content: 12–14%

Typical applications: High-end knives, razor blades, molds, mechanical parts requiring wear resistance

 

SUS420J1 vs. SUS420J2 – Key Differences

Property	SUS420J1	SUS420J2
Carbon Content	~0.15%	~0.30%
Hardness (HRC)	Up to ~48	Up to ~52
Toughness	Higher	Lower
Wear Resistance	Moderate	High
Corrosion Resistance	Good (mild environments)	Slightly lower
Weldability	Better	Moderate to poor
Machinability	Good	Fair

SUS420j1 vs. SUS420j2:  Chemical Composition Comparison

Element	SUS420J1 (%)	SUS420J2 (%)
Carbon (C)	0.15 max	0.26–0.35
Chromium (Cr)	12.0–14.0	12.0–14.0
Manganese (Mn)	≤1.00	≤1.00
Silicon (Si)	≤1.00	≤1.00
Phosphorus (P)	≤0.04	≤0.04
Sulfur (S)	≤0.03	≤0.03

🔹 What is the difference between SUS420J1 and SUS420J2?

The primary difference is carbon content: SUS420J2 contains more carbon, resulting in higher hardness and wear resistance but slightly lower corrosion resistance and toughness.

🔹 Is SUS420J2 better than SUS420J1?

For applications that demand edge retention and high wear resistance (e.g., blades or molds), SUS420J2 is better. For general use with more toughness and easier processing, SUS420J1 is preferred.

🔹 Are SUS420J1 and SUS420J2 magnetic?

Yes, both grades are martensitic stainless steels and are magnetic in all conditions.

🔹 Can SUS420J1 and SUS420J2 be heat treated?

Yes. Both can be hardened by heat treatment. SUS420J2 achieves higher hardness levels due to its higher carbon content.

🔹 Are SUS420J1 and SUS420J2 rust-proof?

They offer moderate corrosion resistance, suitable for mildly corrosive environments. They are not as corrosion resistant as austenitic grades like 304 or 316.