420J2

Soft and very rust-resistant. Used almost exclusively for replaceable blades, where it is thrown away rather than sharpened.

Typical hardness

54-56 HRC

Edge retention

1/5

Toughness

3/5

Corrosion resistance

4/5

Ease of sharpening

5/5

1-5 is a relative ranking drawn from published composition and hardness, not a lab measurement. Higher is better on every axis, and no steel is a 5 across the board — edge retention and toughness pull against each other.