SUS420J2 Stainless Steel: High-Carbon Martensitic Grade for Enhanced Wear Resistance

SUS420J2 is a high-carbon variant of the 420 series martensitic stainless steel (C=0.26%-0.35%, Cr=12.0%-14.0%). Compared with SUS420J1, its higher carbon content improves hardenability and wear resistance. After quenching and tempering, the hardness can reach 52-57HRC, which is suitable for components requiring higher wear resistance and edge retention.

Core Parameters

Chemical Composition (wt%): C=0.26-0.35, Si≤1.00, Mn≤1.00, P≤0.040, S≤0.030, Cr=12.00-14.00, Fe=Balance

Mechanical Properties (Quenched & Tempered): Tensile Strength ≥820MPa, Yield Strength ≥620MPa, Elongation ≥12%, Hardness 52-57HRC

Service Temperature: -20℃ to 300℃ (continuous service)

Equivalent Grades: EN 1.4028, UNS S42020, GB/T 30Cr13

Performance Advantages: Higher hardness and excellent wear resistance than SUS420J1; good grindability, can be polished to a semi-mirror finish; strong edge retention, suitable for cutting tools; good dimensional stability after heat treatment; cost-effective compared with high-carbon martensitic grades such as 440 series.

Typical Applications: High-hardness kitchen knives, hunting knives, utility knives, bearing balls and raceways, valve seats for medium-pressure systems, mold cores for wear-resistant plastic molding, measuring tools (such as gauges), textile machine needles, marine hardware.

Practical Q&A

Q1: What heat treatment process should be adopted for SUS420J2 to achieve high hardness? A1: Quench at 1000-1070℃, oil cool + temper at 150-200℃, air cool. This process can ensure hardness of 52-57HRC. It should be noted that tempering at 300-450℃ should be avoided, as this temperature range will cause temper brittleness and significantly reduce impact toughness.

Q2: How does the wear resistance of SUS420J2 compare with SUS420J1? A2: In the standard abrasive wear test, the wear loss of SUS420J2 after 1000 cycles is only 0.02g, while that of SUS420J1 is 0.035g. The wear resistance of SUS420J2 is 1.5-2 times that of SUS420J1, which is more suitable for high-wear scenarios.

Q3: Can SUS420J2 be cold worked? A3: Cold working is difficult in the hardened state due to high hardness. It should be cold worked in the annealed state (hardness ≤229HB), and the single deformation should not exceed 20% to avoid cracking. Intermediate annealing (780-830℃, air cool) is required after multiple cold working processes.

Q4: What measures can be taken to improve the corrosion resistance of SUS420J2? A4: After heat treatment, perform passivation treatment with 20% nitric acid solution (room temperature, 30 minutes) to form a dense chromium oxide film; apply anti-rust oil or paint on the surface for protection in humid or corrosive environments; avoid long-term contact with acidic media and chloride ions.

Q5: Is SUS420J2 suitable for making bearing components? A5: Yes. It is suitable for low-speed and medium-load bearing balls and raceways. Its high hardness (52-57HRC) and good wear resistance can ensure the service life of bearings. For high-speed and high-load bearings, it is recommended to use SUS440C with higher hardness and wear resistance.