Standards:

420J1 is equivalent to

• ASTM: 420J1
• AISI: 420J1
• JIS: SUS420J1
• EN: 1.4028
• DIN: X20Cr13
• UNS: S42010

420J2 is equivalent to

• ASTM: 420J2
• AISI: 420J2
• JIS: SUS420J2
• EN: 1.4031
• DIN: X46Cr13
• UNS: S42020

Chemical Composition

• 420J1: Contains 0.16-0.25% carbon, 12-14% chromium, and small amounts of manganese, phosphorus, sulfur, and silicon.
• 420J2: Contains 0.26-0.40% carbon, 12-14% chromium, and similar amounts of manganese, phosphorus, sulfur, and silicon.

The higher carbon content in 420J2 contributes to its greater hardness and wear resistance than 420J1​​.

Corrosion Resistance

Both grades offer good corrosion resistance in mild environments, but 420J1 typically has slightly better resistance due to its lower carbon content, which makes it less prone to corrosion in humid or saltwater conditions​.

Mechanical Properties

• Tensile Strength:420J2 generally has higher tensile strength due to its higher carbon content.
• Hardness: After heat treatment, 420J2 achieves higher hardness levels than 420J1.
• Yield Strength:420J2 also has a higher yield strength, which benefits applications requiring more robust mechanical performance.
  
  

Applications

• 420J1:Used in food preparation equipment, kitchen knives, industrial blades, mechanical parts, and surgical instruments.
• 420J2:Preferred for making diving knives, common kitchen knives, surgical instruments, springs, and mechanical parts that require higher hardness and wear resistance ​.

Processing and Machinability

Both grades can be machined and processed using standard techniques for stainless steels, but 420J2 may be more challenging to machine due to its higher hardness after heat treatment. Both can be welded, though care must be taken to avoid brittleness and cold cracking.

Summary

• 420J1:Lower carbon content, better corrosion resistance, easier to machine.
• 420J2:Higher carbon content, greater hardness, and tensile strength, better for applications requiring higher mechanical performance.

Corrosion Resistance:

420J1 stainless steel offers moderate resistance to corrosion, particularly in mild environments. With at least 12% chromium, it provides good corrosion resistance, which can be maximized after quenching and surface grinding or polishing. In the hardened state, 420J1 has good corrosion resistance to atmospheres, foods, fresh water, weak alkalis and acids, steam, sterilizing solutions, crude oil, and gasoline.

Heat Resistance:

420J1 stainless steel has good resistance to oxidation up to 650°C.

Machinability:

In the annealed state, 420J1 is relatively easy to machine. However, once hardened to above 30 HRC, machining becomes more challenging.

Welding:

While 420J1 is weldable due to its excellent hardenability, it is generally not preferred for welding applications.

Hot Working:

For hot working, heat the material to 1800°F – 1950°F (982°C – 1066°C). Do not work below 1500°F.

Cold Working:

Cold working is possible but requires more force compared to 304 stainless steel.

Annealing:

Anneal at 735°C – 785°C followed by air cooling. In the annealed state, 420J1 exhibits good ductility. It can be hardened to a maximum of about 50 HRC, which is the highest hardness among 12% chromium stainless steels.

Hardening:

Due to its high carbon content, 420J1 has higher strength and hardness compared to grades like 410 and 416 stainless steel. In the hardened state, it offers good corrosion resistance to atmospheres, foods, fresh water, weak alkalis and acids, steam, sterilizing solutions, crude oil, and gasoline. However, martensitic stainless steels, such as 420J1, are designed for high hardness, which may compromise other properties. Its corrosion resistance is lower than common austenitic stainless steels, and it has reduced ductility at low temperatures. Additionally, it can lose strength if over-tempered at high temperatures, making it unsuitable for use above the relevant tempering temperature.

Corrosion Resistance of 420 J2 Stainless Steel

Similar to 420J1.

Heat Resistance of 420 J2 Stainless Steel

420J2 stainless steel has good resistance to oxidation up to approximately 750°C (1382°F). However, prolonged exposure to high temperatures can reduce its hardness and strength.

Machinability of 420 J2 Stainless Steel

In the annealed condition, 420J2 stainless steel is relatively easy to machine. Machining becomes more difficult when the material is hardened above 30 HRC. The addition of sulfur in 420F variant improves machinability.

Welding of 420 J2 Stainless Steel

420J2 can be welded, but it requires preheating to 150-320°C (302-608°F) and post-weld tempering to restore the mechanical properties. Generally, welding is not recommended due to the risk of cracking and distortion.

Hot Working of 420 J2 Stainless Steel

For hot working, heat the material to 1100-1300°C (2012-2372°F). Do not work the material below 900°C (1652°F). After hot working, the material should be annealed to relieve stress.

Cold working of 420 J2 Stainless Steel

Cold working is possible but requires more effort compared to 304 stainless steel. 420J2 has lower ductility, making it more challenging to cold work.

Annealing of 420 J2 Stainless Steel

Anneal at 820-900°C (1508-1652°F) followed by slow furnace cooling or air cooling. Annealing ensures the best balance of ductility and toughness, making it suitable for further processing.

Hardening of 420 J2 Stainless Steel

420J2 stainless steel can be hardened through heat treatment. The material should be heated to 980-1035°C (1796-1895°F) and then quenched in oil or air. The hardness can reach up to 50 HRC. Tempering is performed at 150-370°C (302-698°F) to achieve the desired combination of hardness and toughness.

Application of 420 J2 Stainless Steel

420J2 is widely used in applications requiring high hardness and moderate corrosion resistance. Typical applications include:

• Cutlery and knife blades
• Surgical instruments
• Scissors
• Shear blades
• Needle valves
• Pump components
• Valve components and shafts
• Dental and surgical instruments
• Cutting tools