420 Stainless Steel: High-Hardness for Industrial Use

Stainless Steel 420: The "Practical Choice" Among Martensitic Stainless Steels

Stainless Steel 420 is a typical martensitic stainless steel, commonly specified in American standards such as ASTM A276/A480. It is widely used in structural components and tools for medium to low corrosion environments due to its combination of moderate corrosion resistance and heat-treatable strengthening properties.

Its chemical composition has clear specifications: carbon content ≥0.15%, which is the core basis for its ability to increase hardness through quenching and tempering; manganese content ≤1.00% and silicon content ≤1.00%, these two elements mainly play a role in deoxidation and improving processing performance, and their low content control can reduce negative impacts on corrosion resistance; chromium content 12.00%-14.00%, chromium forms a passive film on the steel surface, which is the key to its corrosion resistance. Although lower than austenitic stainless steels (such as 304 with 18%-20% chromium), it can already handle common scenarios such as fresh water and weak acids and alkalis.

In terms of performance, 420 steel has a martensitic structure at room temperature, with a hardness of approximately HB220 in the annealed state. After quenching (heated to 980-1050°C followed by oil cooling) and low-temperature tempering (150-300°C), its hardness can be increased to HRC50-55 while retaining certain toughness, making it suitable for scenarios requiring wear resistance and a certain degree of strength. However, its corrosion resistance depends on the integrity of the surface passive film. Long-term exposure to high salt spray and strong corrosive environments can easily cause rust, requiring surface polishing or coating protection.

Application scenarios are concentrated in: cutting tools (such as kitchen scissors, fruit knives), medical devices (such as surgical forceps, tweezers), valve components, bearing rings, and mechanical parts requiring moderate corrosion resistance and high hardness. It is a classic martensitic stainless steel model that balances "practical corrosion resistance" and "cost control".