400 Series Stainless Steel: 410, 420 and 430 Compared

Written by: Emma, Technical Sales Engineer  |  Reviewed by: Ethan, Materials Engineer  |  Updated: July 2026

The 400 series is a family of stainless steel grades characterized by low or zero nickel content. Unlike the widely known 300 series (304/316), which rely on nickel to stabilize their austenitic structure, the 400 series achieves its properties through a combination of chromium content and controlled carbon levels. This family encompasses two fundamentally different metallurgical categories: martensitic grades (such as 410 and 420) and ferritic grades (such as 430). Understanding this distinction is essential for making informed procurement decisions.

The core differences between 400 series and 300 series stainless steels can be summarized in five dimensions:

• Nickel content: 400 series grades contain little to no nickel, making them significantly less sensitive to nickel price volatility — a key procurement advantage when nickel markets are unstable.
• Microstructure: 300 series grades are austenitic (FCC); 400 series grades are either martensitic (BCC/BCT, 410/420) or ferritic (BCC, 430).
• Magnetism: All 400 series grades are magnetic in all conditions. Annealed 300 series grades are non-magnetic.
• Heat treatment hardening: Martensitic 410 and 420 can be hardened by quench-and-temper heat treatment. Ferritic 430 and austenitic 300 series grades cannot.
• Cost structure: Because 400 series avoids nickel, the raw material cost is generally lower and more stable than 300 series equivalents — though this must be weighed against differences in corrosion resistance and formability.

1. What Is 400 Series Stainless Steel?

The 400 series is defined by its metallurgical structure rather than by a single set of properties. All grades within this series contain chromium as the primary alloying element — typically 11–18% depending on the grade — but contain little to no nickel. This nickel-free composition produces two distinct microstructural families:

• Martensitic stainless steels (410, 420): Body-centered cubic (BCC) at elevated temperature transforming to body-centered tetragonal (BCT) upon quenching. These grades can be hardened by heat treatment and offer a combination of moderate corrosion resistance with high strength and wear resistance.
• Ferritic stainless steels (430): Body-centered cubic (BCC) structure that remains stable at all temperatures. These grades cannot be hardened by heat treatment but offer good corrosion resistance, excellent formability, and immunity to chloride stress corrosion cracking.

All 400 series stainless steels are magnetic, which is a normal characteristic of their ferritic or martensitic structure and does not indicate poor quality or low corrosion resistance.

The following table summarizes the fundamental characteristics of the three most common 400 series grades:

2. Chemical Composition of 410, 420 and 430 Stainless Steel

The chemical composition of 400 series grades is defined by ASTM A240 for sheet and plate and ASTM A276 for bars and shapes. The following table presents the specified composition ranges (weight percent, maximum unless a range is given):

Key takeaway for procurement: The performance of 400 series stainless steel is primarily determined by three variables: carbon content (controls hardness and strength), chromium content (controls corrosion resistance), and microstructure (martensitic vs. ferritic, which determines heat treatability). When specifying any 400 series grade, the heat treatment condition must be clearly stated — the same chemistry in different heat treatment conditions can produce radically different properties.

3. Metallurgical Difference: Martensitic vs Ferritic Stainless Steel

The fundamental distinction within the 400 series is between martensitic and ferritic stainless steels. While both are chromium-based and nickel-free, their metallurgical behavior — and therefore their applications — are entirely different.

Martensitic Grades (410 / 420)

Martensitic stainless steels contain sufficient carbon to allow the formation of martensite upon rapid cooling (quenching) from the austenitizing temperature. This transformation produces a hard, strong, body-centered tetragonal structure. Key characteristics include:

• Heat treatable: Can be hardened by quenching and tempering to achieve a wide range of hardness levels — from approximately 20 HRC in the annealed condition to over 50 HRC after hardening (420).
• High strength: Yield and tensile strengths significantly exceed those of ferritic and austenitic grades in the hardened condition.
• Good wear resistance: The hard martensitic structure provides excellent resistance to abrasive and adhesive wear — making these grades suitable for valve seats, pump shafts, and cutting tools.
• Lower toughness than austenitic grades: Particularly at low temperatures and in the as-hardened condition. Tempering improves toughness at the expense of some hardness.
• Welding requires precautions: Preheating and post-weld heat treatment are often necessary to avoid cracking and to restore mechanical properties in the heat-affected zone.

Ferritic Grade (430)

Ferritic stainless steels maintain a body-centered cubic structure at all temperatures. Without a phase transformation, they cannot be hardened by heat treatment. Key characteristics include:

• Not hardenable by heat treatment: Strength can only be increased through cold working.
• Good corrosion resistance: At 16–18% chromium, 430 provides better general corrosion resistance than 410 or 420, though it lacks molybdenum for chloride pitting resistance.
• Excellent resistance to chloride stress corrosion cracking (SCC): This is a significant advantage over austenitic 304/316 in environments where SCC is a concern.
• Low thermal expansion and good thermal conductivity: Useful in applications involving temperature cycling, such as automotive exhaust components and heat exchangers.
• Good formability: 430 can be deep drawn, bent, and formed more readily than martensitic grades.

4. 410 Stainless Steel Properties

UNS S41000 is the most widely used martensitic stainless steel grade in the 400 series. It contains approximately 11.5–13.5% chromium with a maximum carbon content of 0.15%, placing it in the low-carbon martensitic category.

Mechanical Properties

The mechanical properties of 410 are highly dependent on heat treatment condition (reference: ASTM A240 / ASTM A276, typical values):

Key Characteristics

• Corrosion resistance: Provides good resistance to atmospheric corrosion, fresh water, steam, and mild chemical environments. Not recommended for chloride-rich or marine environments.
• Wear resistance: Good in the hardened condition; moderate in the annealed condition.
• Weldability: Weldable with appropriate preheat (200–300°C) and post-weld heat treatment. Filler metal should match or exceed the base metal chromium content.
• Machinability: Good in the annealed condition; more difficult after hardening.

Typical Applications

Valves and valve components, pump shafts, fasteners and bolts, turbine blades, steam turbine parts, cutlery, and general mechanical parts requiring moderate corrosion resistance combined with strength.

410 is not a high-corrosion-resistance grade. Its value proposition is specifically: moderate corrosion resistance + high strength + heat treatability + lower cost than austenitic grades. Buyers should not specify 410 expecting it to perform like 304 in corrosive environments.

5. 420 Stainless Steel Properties

UNS S42000 is a higher-carbon variant of the 410 martensitic composition. The minimum carbon content of 0.15% (and typically higher in practice) enables 420 to achieve significantly higher hardness levels than 410 after heat treatment — making it the grade of choice when hardness and wear resistance are the primary requirements.

How 420 Differs from 410

• Higher carbon: Carbon ≥ 0.15% vs. ≤ 0.15% for 410. This enables a harder martensite after quenching.
• Higher achievable hardness: 420 can reach approximately 48–55 HRC in the hardened condition, compared with 25–40 HRC for 410 (typical values).
• Better edge retention: The higher hardness directly translates to better cutting edge retention — a critical property for blades and cutting instruments.
• Lower corrosion resistance after hardening: As hardness increases, corrosion resistance decreases. This trade-off is inherent to martensitic stainless steels and must be carefully evaluated.

Mechanical Properties (Typical, After Heat Treatment)

Typical Applications

Surgical and dental instruments, professional knives and blades, shear blades, molds and dies, cutting tools, valve seats, and bearing components. The common thread across all applications: 420 is selected when cutting performance, edge retention, and wear resistance are more important than maximum corrosion resistance.

6. 430 Stainless Steel Properties

UNS S43000 is the most common ferritic stainless steel grade, with a chromium content of 16–18%. Unlike 410 and 420, 430 cannot be hardened by heat treatment — its strength comes from its chromium content and cold working. Among the three grades discussed in this article, 430 offers the best general corrosion resistance.

Mechanical Properties (Annealed, per ASTM A240)

Key Characteristics

• Corrosion resistance: At 16–18% chromium, 430 provides the best general corrosion resistance among common 400 series grades. It resists atmospheric corrosion, fresh water, many food acids, and mild chemical environments. However, it lacks molybdenum and nickel, so it does not match 304 in aggressive chloride service.
• Magnetic: Always magnetic due to its ferritic structure.
• Formability: Good cold formability; can be deep drawn and bent. Better formability than martensitic 410 and 420.
• Polishing ability: Excellent — can achieve a bright, high-quality surface finish, making it popular for decorative and architectural applications.
• Thermal properties: Low thermal expansion coefficient (similar to carbon steel) and good thermal conductivity — advantageous in applications involving temperature cycling.
• Not hardenable by heat treatment: Strength and hardness can only be increased by cold working.

Typical Applications

Kitchen appliances (sinks, dishwasher interiors, oven liners), automotive trim and exhaust components, decorative panels and architectural cladding, household equipment, indoor elevator interiors, and food processing equipment (non-corrosive environments). 430 is the most widely used ferritic grade and accounts for a significant share of 400 series production globally.

7. Understanding the Difference Between 410, 420 and 430 Stainless Steel

Grade selection within the 400 series is not about which grade is "better" — it is about which grade matches the specific performance requirements of the application. The following table provides a selection framework based on common procurement scenarios:

8. Corrosion Resistance of 400 Series Stainless Steel

The 400 series does not represent a uniform level of corrosion resistance. Each grade must be evaluated individually against the specific service environment. The general hierarchy of corrosion resistance within the three common grades is: 430 > 410 > 420 (hardened condition).

410 Corrosion Resistance

410 provides good resistance to atmospheric corrosion, fresh water, steam, and many mild chemical environments. It resists oxidation up to approximately 650°C in intermittent service. It is not suitable for chloride-containing environments, seawater, or reducing acids. The corrosion resistance is best in the hardened-and-tempered condition rather than annealed.

420 Corrosion Resistance

420 in the hardened condition has the lowest corrosion resistance of the three grades discussed here. The higher carbon content, while essential for achieving high hardness, reduces the chromium available in solid solution to form the passive film. Buyers should expect that hardened 420 will show corrosion before 410 or 430 in the same environment — this is an inherent trade-off for hardness.

430 Corrosion Resistance

With 16–18% chromium, 430 provides the best general corrosion resistance among the three grades. It resists atmospheric corrosion, fresh water, many food acids, and oxidizing environments effectively. It is resistant to chloride stress corrosion cracking — a critical advantage over 304 in certain applications. However, it is susceptible to pitting in chloride-containing environments and is not a substitute for 316L or duplex grades in marine service.

9. Welding and Fabrication Considerations

The welding and fabrication behavior of 400 series grades varies significantly between martensitic and ferritic types. Procurement specifications should include welding and forming requirements to ensure the correct grade and condition are supplied.

410 Welding

• Weldable with appropriate precautions
• Preheat to 200–300°C is recommended to reduce the risk of hydrogen-induced cracking
• Post-weld heat treatment (PWHT) at 650–750°C is typically required to restore toughness and reduce residual stress
• Matching or slightly over-alloyed filler metal (e.g., ER410) should be used

420 Welding

• More difficult to weld than 410 due to higher carbon content, which increases hardenability and cracking risk
• Preheat and PWHT are mandatory for most applications
• Not recommended for critical welded structures; consider 410 or a PH grade if welding is essential

430 Welding

• Weldable but with limitations due to ferritic grain growth in the heat-affected zone, which can reduce toughness
• Low heat input and controlled interpass temperature are essential
• Stabilized variants (e.g., 439, 441) are preferred when extensive welding is required
• 430 has better formability than 410 and 420 for non-welded fabrication

Procurement recommendation: When ordering 400 series material for welded fabrication, communicate the following to your supplier: (1) intended welding process, (2) whether PWHT will be performed, (3) required mechanical properties in the as-welded or post-weld condition, and (4) any corrosion testing requirements after welding.

10. Applications of 410, 420 and 430 Stainless Steel

11. Limitations and Common Selection Mistakes

Mistake 1 — Assuming 400 Series Is a Cheaper Version of 304: 400 series grades lack nickel and molybdenum, which fundamentally limits their corrosion resistance compared with 304. While 430 may appear similar to 304 in indoor environments, it will perform differently in chloride-containing or aggressive service. Treating 400 series as a direct cost-saving substitute for 304 without verifying the corrosion environment is a common and costly error.

Mistake 2 — Selecting 420 Based Solely on Hardness Without Considering Corrosion: 420 achieves its high hardness through carbon content, which reduces available chromium for passivation. Specifying hardened 420 for an application that also requires meaningful corrosion resistance will result in premature failure. Always evaluate both hardness and corrosion requirements together.

Mistake 3 — Using 430 for High-Strength Mechanical Parts: 430 is a ferritic stainless steel that cannot be hardened by heat treatment. It has yield strength comparable to annealed 410 (~205 MPa minimum per ASTM A240) but cannot achieve the elevated strength levels that hardened 410 or 420 can deliver. For load-bearing mechanical components, martensitic grades are the appropriate choice within the 400 series.

Mistake 4 — Ignoring Magnetic Requirements: All 400 series grades are magnetic. If the application requires non-magnetic material — for example, certain medical imaging equipment or electronic enclosures — the 400 series is unsuitable regardless of other properties. Verify magnetic requirements before specifying the grade family.

Mistake 5 — Ignoring Heat Treatment Condition in the Purchase Order: The same 410 chemistry can be supplied annealed (~90 HRB) or hardened-and-tempered (~30 HRC). Without specifying the heat treatment condition, the supplier cannot guarantee that the delivered material will meet the intended mechanical requirements. Always state the required condition (annealed, hardened, tempered) on the PO.

12. How to Select the Right 400 Series Stainless Steel Grade

Use the following decision framework to narrow your grade selection within the 400 series:

Question 1: Do you need high hardness (>45 HRC)?
→ Select 420. It is the only grade among the three that reliably achieves hardness above 45 HRC after heat treatment.

Question 2: Do you need mechanical strength, wear resistance, and moderate corrosion resistance?
→ Select 410. It offers the best balance of strength and corrosion resistance among the martensitic 400 series grades.

Question 3: Do you need general corrosion resistance and a decorative finish at lower cost?
→ Select 430. With 16–18% chromium and excellent polishability, it is the go-to grade for appearance-driven applications.

Question 4: Will the component be welded?
→ Among the three, 410 is the most weldable martensitic grade (with preheat and PWHT). 420 presents more welding challenges due to its carbon content. For ferritic applications requiring welding, consider stabilized variants (439, 441) instead of standard 430.

Question 5: Do you need chloride resistance?
→ None of the three 400 series grades discussed here offer reliable chloride pitting resistance. If the service environment contains chlorides, evaluate 316L, duplex 2205, or super duplex 2507 instead.

13. Procurement Guidance for 400 Series Stainless Steel

A complete purchase specification eliminates ambiguity and reduces the risk of receiving material that does not meet requirements. The following elements should be included in any 400 series procurement:

Example Purchase Specification:

Avoid generic specifications such as "400 series stainless steel sheet." A complete specification enables the supplier to provide the correct material and documentation — without it, the supplier must make assumptions about grade, standard, and condition that may not align with your requirements.

14. How Shangyou Supports 400 Series Stainless Steel Supply

Shaanxi Shangyou Stainless Steel Co., Ltd. supplies 410, 420, and 430 stainless steel in plate, sheet, coil, bar, and strip forms, supported by the following quality assurance measures:

• ASTM compliance verification — material verified against ASTM A240, ASTM A276, and applicable standards
• Chemical composition review — Cr, C, Mn, Si, P, S confirmed against specification requirements
• Heat number traceability — full traceability from mill heat to delivered product
• MTC 3.1 documentation — mill-certified test certificates provided as standard
• PMI testing coordination — positive material identification available upon request
• Surface inspection — finish verification (2B, BA, No.4, etc.) per order requirements
• Dimensional inspection — thickness, width, length, flatness verified before dispatch

15. Frequently Asked Questions

Q1: What is 400 series stainless steel?
The 400 series is a family of chromium-based stainless steels containing little to no nickel. It includes both martensitic grades (such as 410 and 420), which can be hardened by heat treatment, and ferritic grades (such as 430), which cannot. All 400 series grades are magnetic and generally offer lower cost and more stable pricing than nickel-containing 300 series grades.

Q2: Is 400 series stainless steel magnetic?
Yes, all 400 series stainless steels are magnetic. This is a result of their ferritic or martensitic crystal structure and is completely normal. Magnetism in stainless steel is not an indicator of quality — it simply reflects the metallurgical structure. Austenitic grades like 304 and 316 are non-magnetic in the annealed condition due to their different crystal structure.

Q3: What is the difference between 410 and 420 stainless steel?
The primary difference is carbon content: 410 has a maximum of 0.15% carbon, while 420 has a minimum of 0.15% carbon (and typically higher). This higher carbon content allows 420 to achieve significantly greater hardness after heat treatment (up to ~55 HRC vs. ~40 HRC for 410, typical values). The trade-off is that hardened 420 has lower corrosion resistance than 410. Choose 410 for balanced strength and corrosion resistance; choose 420 when hardness and wear resistance are the priorities.

Q4: Is 430 stainless steel corrosion resistant?
Yes, 430 provides the best general corrosion resistance among common 400 series grades, with 16–18% chromium. It resists atmospheric corrosion, fresh water, many food acids, and mild chemical environments. It is resistant to chloride stress corrosion cracking. However, it does not match 304 in aggressive environments and is not suitable for seawater or chloride-rich service where pitting resistance is required.

Q5: Can 410 stainless steel be hardened?
Yes. 410 is a martensitic stainless steel that can be hardened by heating to approximately 950–1050°C (austenitizing), followed by oil or air quenching, and then tempering at 200–700°C to achieve the desired balance of hardness and toughness. Typical hardness after hardening ranges from 25 to 40 HRC depending on tempering temperature.

Q6: Is 420 stainless steel good for knives?
Yes, 420 is widely used for knives, blades, and cutting instruments. Its higher carbon content enables hardness levels of 48–55 HRC after heat treatment, providing excellent edge retention. For premium knives, higher-carbon variants (420HC) or other grades (440C) may be used, but standard 420 offers a good balance of hardness, corrosion resistance, and cost for general-purpose cutlery and tooling applications.

Q7: Is 430 stainless steel better than 304?
"Better" depends on the application. 430 is more cost-effective, has more stable pricing (no nickel), and is resistant to chloride stress corrosion cracking. However, 304 offers superior general corrosion resistance, better toughness, excellent weldability, and is non-magnetic. 430 is not a direct replacement for 304 — it is a different material for different applications. Evaluate the specific service conditions before substituting.

Q8: Can 400 series stainless steel be welded?
It depends on the grade. 410 is weldable with appropriate preheat (200–300°C) and post-weld heat treatment. 420 is more difficult to weld due to its higher carbon content and requires strict procedure control. 430 can be welded but is susceptible to grain growth in the heat-affected zone, which reduces toughness; stabilized ferritic variants (e.g., 439, 441) are preferred for welded fabrication. Always specify welding requirements when ordering material for fabrication.

Q9: What is the difference between ferritic and martensitic stainless steel?
Ferritic stainless steels (e.g., 430) have a body-centered cubic structure that is stable at all temperatures; they cannot be hardened by heat treatment and offer good formability and corrosion resistance. Martensitic stainless steels (e.g., 410, 420) can be hardened by quenching from elevated temperature, which transforms the structure to hard martensite. This fundamental difference determines how each type is used: ferritic for corrosion resistance and appearance, martensitic for strength and wear resistance.

Q10: How do I choose between 410, 420 and 430 stainless steel?
Start with the primary performance requirement. If you need high hardness (>45 HRC), select 420. If you need mechanical strength plus moderate corrosion resistance, select 410. If you need general corrosion resistance and a decorative finish at lower cost, select 430. Then verify: welding requirements, magnetic requirements, heat treatment condition, and whether the corrosion environment is within the selected grade's capability. If chloride resistance is needed, consider moving outside the 400 series entirely.

Technical References

• ASTM A240 — Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip
• ASTM A276 — Standard Specification for Stainless Steel Bars and Shapes
• ASTM A479 — Standard Specification for Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels
• ASM Handbook Volume 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys
• Outokumpu Stainless Steel Handbook
• British Stainless Steel Association — Technical Datasheets for 410, 420, and 430