Deciding between SS 410 and SS 420? Here is the short answer for immediate clarity: The primary difference will be in carbon content and hardness. SS 410 is a general-purpose martensitic stainless steel known for high strength and moderate corrosion resistance, making it ideal for stressed parts like pump shafts and fasteners. SS 420 contains higher carbon, allowing it to achieve significantly higher hardness (up to 50-55 HRC) after heat treatment, which makes it the superior choice for cutlery, surgical instruments, and wear-resistant molds.
If you are sourcing materials for heavy engineering, automotive components, or industrial machinery, understanding these subtle chemical shifts is most important to avoiding failure in the field.
At Vishwa Stainless Pvt. Ltd., we manufacture premium SS Bright Bars, Hex Bars, and Precision Wires in both grades, ensuring you get the exact machining properties your project demands.
Quick Comparison: SS 410 vs. SS 420
For procurement managers and engineers on the go, here is the technical breakdown:
|
Feature |
SS 410 (UNS S41000) |
SS 420 (UNS S42000) |
|
Primary Characteristic |
General Purpose Martensitic |
High-Hardness “Cutlery Grade” |
|
Carbon Content |
Low (0.08% – 0.15%) |
High (> 0.15%) |
|
Typical Hardness |
~35–45 HRC (Hardened) |
~50–55 HRC (Hardened) |
|
Wear Resistance |
Good |
Excellent |
|
Corrosion Resistance |
Moderate (Water, Steam, Air) |
Moderate (Requires polished surface) |
|
Best For |
Pump shafts, valves, fasteners |
Knives, surgical tools, molds |
|
Cost |
Generally Lower |
Slightly Higher |
Need material that balances cost with durability?
Explore our SS Bright Round Bars available in both 410 and 420 grades.
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What is SS 410 Stainless Steel?
SS 410 is the basic martensitic stainless-steel grade. It contains 11.5% to 13.5% chromium and a small amount of carbon. It is designed for highly stressed parts that need a combination of strength and corrosion resistance.
Because it can be heat-treated to a wide range of mechanical properties, it is often the “go-to” grade for engineers to design parts that will face steam, hot gases, or mild acids.
Applications of SS 410:
- Industrial: Pump shafts, valve stems, and turbine blades.
- Fasteners: Bolts, screws, and nuts (See our SS Bright Hex Bars).
- Automotive: Exhaust components and manifolds.
What is SS 420 Stainless Steel?
SS 420 is essentially a high-carbon version of SS 410. With a minimum of 12% chromium and higher carbon content (sometimes up to 0.40% or more in modified versions), it is capable of being hardened to a much higher degree.
It is often referred to as “cutlery grade” steel because it can hold a sharp point and withstand significant wear and tear. However, this hardness comes at the expense of ductility; SS 420 is less flexible than SS 410.
Applications of SS 420:
- Precision Tools: Surgical instruments, shear blades, and needle valves.
- Cutlery: Professional knives and cutting tools.
- Manufacturing: Plastic molds and hand tools.
- Components: Precision SS Bright Bars for wear-prone machinery parts.
The Core Differences: A Detailed Technical Breakdown
When selecting between these two grades for SS Cold Drawn Bars or Piston Rod Quality Bars, you need to look deeper than just the price tag.
1. Chemical Composition (Carbon is King)
The defining difference is the Carbon (C) percentage.
- SS 410: Contains 0.08 – 0.15% Carbon. This lower carbon level maintains some ductility and makes the steel easier to weld and machine compared to 420.
- SS 420: Contains > 0.15% Carbon (and can go higher). This extra carbon forms chromium carbides during heat treatment, which provides the material with its exceptional hardness and wear resistance.
2. Hardness and Mechanical Properties
If your application involves grinding, cutting, or abrasive wear, SS 420 wins.
- SS 410 typically reaches a hardness of 35–45 HRC after quenching and tempering. It is strong, but not “brittle hard.”
- SS 420 can reach 50–55 HRC (Rockwell C). This makes it one of the hardest standard stainless-steel grades available.
3. Corrosion Resistance
Both grades are martensitic, meaning they are not as corrosion-resistant as the 300-series (like SS 304 or SS 316).
- SS 410: Resists corrosion well in dry atmospheres, fresh water, and steam. It is often used in petrochemical applications where mild acids are present.
- SS 420: Has similar corrosion resistance to 410 in the hardened condition. However, because of its higher carbon content, it is slightly more susceptible to pitting if the surface is not polished.
- For maximum corrosion resistance, both grades should be hardened and polished.
4. Machinability and Weldability
- Machining: SS 410 is generally easier to machine than SS 420 due to its lower hardness. If you run a CNC workshop, SS 410 will cause less tool wear.
- Welding: Both grades are difficult to weld because they air-harden. However, SS 410 is easier to weld than SS 420. SS 420 usually requires pre-heating and post-weld heat treatment to prevent cracking.
Selection Guide: When to Choose Which Stainless Steel?
Are you a Purchase Head or Design Engineer trying to finalize your BOM (Bill of Materials)? Use this simple checklist:
Choose SS 410 if:
- You need high strength but also need some toughness/ductility.
- The part will be subjected to high stress or vibration (e.g., bolts, pump shafts).
- Cost is a significant factor (410 is usually more economical).
- You require SS Class-2 Bars for general engineering.
Choose SS 420 if:
- Hardness and wear resistance are your top priorities.
- The part is a cutting tool, blade, or mold.
- The component will not face high-impact shock (which could snap brittle materials).
- You need a polished, mirror-like finish for aesthetic or hygiene reasons (e.g., medical tools).
Final Thoughts: Quality Matters
Whether you choose SS 410 for its toughness or SS 420 for its hardness, the quality of the raw material defines the success of your final product. Poor heat treatment or inconsistent chemical composition can lead to cracks, premature wear, and costly recalls.
At Vishwa Stainless Pvt. Ltd., we ensure every Bright Bar, Square Bar, and Wire leaving our facility meets strict international standards.
Need help selecting the right grade?
- [Get a Quick Quote] for SS 410/420 Bright Bars.
- [Check Our Product Range] to see our full range of sizes and finishes.
- [Contact Our Experts] for technical advice on your next project.
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Frequently Asked Questions (FAQs)
1. Does SS 420 rust faster than SS 410?
Both grades have similar corrosion resistance, but SS 420 can be slightly more prone to rust if left in the annealed (soft) condition or if the surface is rough. In the hardened and polished condition, SS 420 resists rust well in mild environments.
2. Is SS 410 magnetic?
Yes, both SS 410 and SS 420 are magnetic in all conditions (annealed and hardened). This distinguishes them from austenitic grades like SS 304, which are non-magnetic.
3. Can you heat treat SS 410 to get the same hardness as SS 420?
Generally, no. The carbon content in SS 410 limits its maximum hardness to around 45 HRC. To get the >50 HRC required for knife edges or high-wear molds, you must switch to the higher-carbon SS 420.
4. Which grade is better for machining?
SS 410 is better for machining than SS 420. However, if machinability is your only concern, you might consider SS 416, which is a free-machining version of SS 410. (Ask us about our SS Peeled Bars for machining efficiency).
5. Are SS 410 and SS 420 food safe?
It depends on the application. They are excellent for cutlery (knives) but are not suitable for food storage containers or processing tanks (like milk tankers), where the steel has prolonged contact with acidic food. For storage, use SS 304 or SS 316.
6. What is the difference between SS 410/420 and SS 304?
SS 410/420 are Martensitic: they are magnetic, heat-treatable, and extremely hard (best for tools/wear). SS 304 is Austenitic: it is non-magnetic, cannot be hardened by heat, but has superior corrosion resistance (best for pipes/tanks).