Stainless Steel 420

General Characteristics

Stainless Steel 420 (W-Nr. 1.4034; UNS S42000) is a martensitic stainless steel known for its enhanced hardness and mechanical strength, compared to Type 410. It is magnetic both in the annealed and hardened states, but reaches its maximum performance only after full heat treatment (hardening and tempering).
Therefore, this alloy is ideal for applications where hardness and wear resistance are priorities, without completely sacrificing corrosion protection.

Corrosion resistance:

It is important to note that 420 stainless steel offers effective corrosion resistance only in the hardened or hardened and tempered condition. In this form, its corrosion behavior is comparable to that of Type 410.
For applications exposed to moist or mildly corrosive environments, heat treatment becomes mandatory to ensure optimal protection of the material.

Physical Properties:

• Melting temperature: 1450 – 1510 °C
• Density: 7.75 g/cm³
• Specific gravity: 7.7
• Elastic modulus: 200 GPa

Mechanical Properties:

Note: values are indicative for the annealed state, which is not recommended for final use.

Welding

Welding of stainless steel 420 is generally not recommended, as the alloy tends to harden upon air exposure. However, if welding is required:

• Preheating at 149–204°C (300–400°F) is recommended
• Post-weld tempering for 2 hours is necessary
• Recommended filler metal: AWS E/ER420

Heat Treatment

Two main heat treatment procedures apply:

• Annealing: Heat to 840–900°C, followed by slow cooling in furnace to 600°C, then air cooling
• Soft annealing: Heat to 735–785°C, followed by air cooling

Therefore, heat treatment is essential for achieving the maximum performance of this alloy, especially in demanding industrial applications.