Stainless Steel 420 forHardened & Wear-Resistant Components

Key manufacturing characteristics of SS 420

• Extreme Hardenability: Capable of reaching high Rockwell C hardness (up to 50-52 HRC) through quenching and tempering.
• Superior Edge Retention: The high carbon content allows for the creation of razor-sharp edges that remain durable under repeated use.
• Magnetic Properties: Like all martensitic steels, it is strongly magnetic, which is useful for specialized electronic or automated sorting applications.
• Moderate Corrosion Resistance: Provides good resistance to the atmosphere, fresh water, and mild acids when fully hardened and surface-polished.
• High Tensile Strength: Once heat-treated, it offers exceptional load-bearing capacity and resistance to mechanical fatigue.
• Excellent Polishing Response: Can be ground and polished to a mirror finish, which simultaneously improves its corrosive defense.

Mechanical and physical properties of Stainless 420

SS 420 is defined by its ability to be transformed via heat. In its annealed state, it is relatively easy to machine, but its true value is realized after hardening. It is generally selected over Stainless Steel 304 when surface hardness and wear life are more critical than maximum chemical resistance.

Strengths and advantages of SS 420

1. Exceptional Wear Resistance: Outperforms 304 and 316 in sliding contact and abrasive environments.
2. Tunable Ductility: Tempering allows engineers to balance hardness against the risk of brittleness.
3. Excellent Machine-to-Hardness Ratio: Machines well in the annealed state before becoming extremely tough post-heat treat.
4. Mirror Finishing: Responds better to high-luster polishing than almost any other stainless grade.
5. Cost-Effective High Strength: Provides tool-steel performance with the added benefit of being stainless.
6. Atmospheric Resilience: Resists rust in domestic and industrial environments effectively.

Trade-offs and limitations of Stainless 420

1. Lowest Corrosion Resistance in Family: Corrosion resistance is lower than 410 and significantly lower than Stainless Steel 316.
2. Condition-Dependent Protection: Maximum corrosion resistance is only achieved when the material is fully hardened and polished.
3. Poor Weldability: High carbon content makes it prone to cracking; requires extensive pre-heating and post-weld annealing.
4. Brittleness: If not tempered correctly, high hardness can lead to sudden fracture under impact loading.
5. Not for Marine Use: Should not be used in chloride-rich or saltwater environments.

Fabrication and machining considerations for SS 420

Common applications for Stainless Steel 420

SS 420 is a staple for high-wear CNC machined components across the medical and industrial sectors.

• Surgical and dental instruments (scalpels, forceps, probes)
• Needle valves and high-pressure pump components
• Plastic injection molds and die inserts
• Shear blades, industrial knives, and cutters
• Hardened fasteners and high-torque screws
• Ball bearings and valve seats
• Hand tools and high-end cutlery
• Gauges and precision measurement hardware

When Stainless Steel 420 is the right material choice

Select 420 when your project requires a metal that can be 'as hard as a tool' while remaining stainless.

• When the part requires a razor-sharp cutting edge or high surface hardness
• When wear resistance is more important than extreme chemical corrosion defense
• When the component must be magnetic for sensing or latching
• When parts will be polished to a mirror finish for medical or aesthetic use
• When a cost-effective alternative to expensive tool steels is required for mild environments