420 Stainless Steel vs. 316 Stainless Steel: What’s the Difference?

 

Choosing the right stainless steel is challenging. Many engineers and buyers struggle to decide between 420 stainless steel and 316 stainless steel. The wrong choice can lead to unexpected corrosion, higher costs, or machining difficulties. Fortunately, by understanding their differences in composition, properties, and performance, you can make the right choice for your CNC machining project.

• Tip: Always consider your application’s environment (corrosive, high-wear, or high-temperature) before selecting a stainless steel grade to avoid costly reworks.

 

420 stainless steel is a hardenable martensitic steel known for high wear resistance, while 316 stainless steel is an austenitic grade with excellent corrosion resistance. Choose 420 for cutting tools and wear parts; select 316 for marine, chemical, or medical applications.

 

Now that you know the core difference, let’s dive deeper into the composition, properties, and machining performance of 420 stainless steel vs. 316 stainless steel to help you choose wisely.

 

 

 

What is 420 Stainless Steel?

 

420 stainless steel (SS420) is a martensitic stainless steel with high carbon content. It can be heat-treated to achieve good hardness (up to 50 HRC), making it ideal for cutting tools, surgical instruments, and wear-resistant parts. However, compared with austenitic grades, its corrosion resistance is lower, especially in harsh or marine environments.

 

For CNC machining, 420 stainless steel CNC machined parts are preferred when hardness, wear resistance, and polishability are more important than corrosion resistance. Common applications include knives, molds, pump shafts, and certain aerospace components.

 

• Tip: Because 420 stainless steel is prone to rust in humid or salty conditions, always consider surface treatments or coatings if your project requires corrosion resistance.

 

 

 

What is 316 Stainless Steel?

 

316 stainless steel (SS316) is an austenitic stainless steel containing molybdenum (2–3%), which gives it excellent corrosion resistance, especially against chlorides and chemicals. It is widely used in marine, chemical, food processing, and medical industries where resistance to rust, pitting, and high temperatures is critical.

 

For CNC machining, 316 stainless steel CNC machined parts are popular due to their strength, durability, and resistance to harsh environments. While softer than martensitic grades like 420, it is easier to weld and maintain stability under extreme conditions.

 

• Tip: Although 316 stainless steel has higher initial costs than 420, it often reduces long-term maintenance and replacement expenses in corrosive environments.

 

 

 

 

 

 

420 Stainless Steel vs. 316 Stainless Steel: Key Differences

 

 

When comparing 420 stainless steel and 316 stainless steel, it’s essential to understand their differences in composition, properties, and performance. These factors determine their suitability for various industries, from cutting tools and molds to marine equipment and medical implants. Below, we’ll look at each property to help you choose the right material.

• Tip: Always evaluate your project’s priority — is it hardness, corrosion resistance, or cost? This will guide whether 420 or 316 stainless steel is the better option.

 

 

 

Composition

• 420 stainless steel: Higher carbon (0.15–0.4%) content, which improves hardness but lowers corrosion resistance.
• 316 stainless steel: Contains molybdenum (2–3%) and higher nickel, offering excellent resistance to chlorides and acidic environments.

Note: For CNC machining factories, composition directly impacts machinability and performance — selecting the wrong steel grade may increase tool wear and project costs.

 

 

Hardness

• 420 stainless steel: Can reach up to 50 HRC after heat treatment, making it one of the hardest stainless steels available.
• 316 stainless steel: Generally softer (around 15–20 HRC), but maintains good strength and toughness.

Tip: Choose 420 if you need sharp edges or high wear parts. For structural durability and weldability, 316 is superior.

 

 

Corrosion Resistance

• 420 stainless steel: Moderate resistance, but vulnerable to rust in humid, salty, or chemical environments.
• 316 stainless steel: Excellent resistance to seawater, chemicals, and acidic conditions.

Tip: For marine and medical CNC machined parts, 316 stainless steel is the safe choice. Avoid 420 unless corrosion is not a critical factor.

 

 

Wear Resistance

• 420 stainless steel: Outstanding wear resistance due to high hardness, suitable for knives, molds, and bearings.
• 316 stainless steel: Lower wear resistance, not ideal for heavy friction applications.

Note: Using 316 in high-wear conditions may increase part replacement costs over time.

 

 

Oxidation Resistance

• 420 stainless steel: Good oxidation resistance up to 650 °C, but not suitable for long-term high-temperature exposure.
• 316 stainless steel: Withstands oxidation up to 870 °C, making it more suitable for high-temperature environments.

 

Welding

• 420 stainless steel: Difficult to weld; preheating and post-weld heat treatment are required to avoid cracking.
• 316 stainless steel: Excellent weldability, making it widely used in fabricated structures.

Tip: If your CNC project requires welded assemblies, 316 stainless steel is the better option.

 

 

Heat Resistance

• 420 stainless steel: Performs well under moderate heat but loses corrosion resistance above 400 °C.
• 316 stainless steel: Retains corrosion and oxidation resistance at higher temperatures, up to 870 °C.

 

Machinability

• 420 stainless steel: Better machinability in the annealed condition, though hardness increases tool wear after heat treatment.
• 316 stainless steel: More challenging to machine due to toughness and work hardening, requiring specialized cutting tools.

Tip: To reduce machining costs, consider annealed 420 stainless steel for high-hardness projects, but prepare for higher tool wear when machining hardened material.

 

 

Cost

• 420 stainless steel: Lower initial material cost, but higher maintenance if corrosion resistance is required.
• 316 stainless steel: Higher upfront cost, but reduced long-term expenses in corrosive environments.

 

Applications

• 420 stainless steel CNC machined parts: Knives, surgical tools, molds, pump shafts, bearings.
• 316 stainless steel CNC machined parts: Marine equipment, chemical tanks, food processing machines, medical implants.

Tip: When outsourcing CNC machining services, clearly define the working environment of your part to avoid material mismatches that increase overall costs.

 

 

420 Stainless Steel vs. 316 Stainless Steel: Key Differences

 

 

 

• Tip: Use this table as a quick reference when discussing material selection with CNC machining factories — it helps avoid confusion and costly mistakes.

 

 

 

420 and 316 Stainless Steel: Advantages and Disadvantages

 

 

 

420 Stainless Steel (SS420)

 

Advantages:

• High hardness after heat treatment (up to 50 HRC).
• Excellent wear resistance, ideal for cutting edges and molds.
• Lower material cost compared to 316.
• Good polishability for mirror finishes.

Disadvantages:

• Lower corrosion resistance, especially in salty or humid environments.
• Difficult to weld and requires pre/post-heat treatment.
• Limited performance at high temperatures.
• Higher maintenance costs in corrosive applications.

Tip: Use 420 stainless steel for applications where hardness and wear resistance are more important than corrosion resistance, such as knives, molds, and pump shafts.

 

 

316 Stainless Steel (SS316)

 

Advantages:

• Outstanding corrosion resistance, even in marine and chemical environments.
• Excellent weldability and formability.
• Maintains oxidation resistance at high temperatures (up to 870 °C).
• Longer service life in harsh conditions.

Disadvantages:

• Higher material cost than 420.
• Lower hardness, making it unsuitable for heavy-wear parts.
• More difficult to machine due to toughness and work hardening.

Tip: Choose 316 stainless steel for CNC machined parts used in marine, food, chemical, or medical industries — it offsets higher upfront costs with long-term savings.

 

 

 

 

420 Stainless Steel vs. 316 Stainless Steel: Property Comparison

 

 

The performance of 420 stainless steel (SS420) and 316 stainless steel (SS316) comes down to their chemical composition. Elements like carbon, chromium, nickel, and molybdenum define hardness, corrosion resistance, weldability, and machinability. Understanding these differences helps engineers and CNC machining factories select the best material for specific applications.

• Tip: Always check material certifications when sourcing stainless steel — small variations in composition can significantly affect machining performance and final part quality.

 

420 Stainless Steel vs. 316 Stainless Steel: Chemical Composition

 

 

 

• Tip: Notice that 316’s added nickel and molybdenum dramatically improve its corrosion resistance, while 420’s higher carbon content allows it to be hardened for cutting and wear applications.

 

 

 

420 Stainless Steel vs. 316 Stainless Steel: Physical Properties

 

 

Physical properties such as density, melting point, conductivity, corrosion resistance, and machinability directly affect how stainless steel performs in real-world applications. Comparing 420 stainless steel (SS420) and 316 stainless steel (SS316) helps engineers and CNC machining factories match the right material to the working environment and processing requirements.

• Tip: Physical property differences often decide whether a part is more suitable for high-temperature, high-wear, or corrosive conditions — consider these before material selection.

 

Property Comparison Table

 

 

 

• Tip: If your CNC machined part requires high thermal conductivity (like molds), 420 stainless steel is a better choice. For projects exposed to seawater or chemicals, 316 stainless steel is essential.

 

 

 

420 Stainless Steel and 316 Stainless Steel: Mechanical Properties

 

 

The mechanical properties of stainless steels define their performance under stress, wear, and fatigue. 420 stainless steel (SS420) stands out for hardness and wear resistance, while 316 stainless steel (SS316) is valued for toughness, ductility, and corrosion resistance. Comparing these properties helps determine which grade fits best for CNC machined parts in demanding industries.

• Tip: Always match mechanical properties to your part’s function — high wear tools need hardness (420), while structural or marine parts benefit from toughness and corrosion resistance (316).

 

Mechanical Property Comparison

 

 

 

 

• Tip: For cutting tools, knives, and molds, 420 stainless steel is the right choice due to hardness and wear resistance. For marine, food, and medical parts, 316 stainless steel performs better thanks to ductility and corrosion resistance.

 

 

 

420 Stainless Steel vs. 316 Stainless Steel: Heat Treatment

 

 

 

 

420 Stainless Steel (SS420)

 

420 stainless steel is heat-treatable, which is one of its key advantages. The process typically involves:

• Annealing: Heated to 840–900 °C, followed by slow furnace cooling to improve machinability.
• Hardening: Heated to 980–1,040 °C, then quenched in oil or air to achieve high hardness (up to 50 HRC).
• Tempering: Reheated at 150–370 °C to balance hardness and toughness depending on application.

This flexibility makes 420 ideal for cutting tools, knives, and wear-resistant CNC machined parts.

• Tip: Improper tempering can make 420 brittle — always consult experienced CNC machining factories to optimize heat treatment for your part’s function.

 

316 Stainless Steel (SS316)

 

Unlike 420, 316 stainless steel is not hardenable by heat treatment. Its strength and toughness come from its austenitic structure. Instead, it can be strengthened by:

• Cold working: Rolling or forging increases hardness and tensile strength.
• Annealing: Heated to 1,040–1,120 °C, followed by rapid cooling (water quench) to restore corrosion resistance and ductility.

This makes 316 best suited for corrosive and high-temperature environments rather than cutting or wear applications.

• Tip: If you need corrosion resistance with higher strength, consider cold-worked 316 stainless steel — it offers better performance without sacrificing durability.

 

 

420 Stainless Steel vs. 316 Stainless Steel: Heat Treatment

 

 

 

• In short: 420 stainless steel benefits from heat treatment to increase hardness, while 316 stainless steel relies on cold working and annealing to maintain toughness and corrosion resistance.

 

 

 

 

420 Stainless Steel vs. 316 Stainless Steel: Applications and Uses

 

 

 

 

 

        

Key Insight:

• 420 stainless steel is chosen when hardness, edge retention, and wear resistance are priorities.
• 316 stainless steel is chosen when corrosion resistance, toughness, and biocompatibility are critical.

 

 

 

 

420 Stainless Steel vs. 316 Stainless Steel: Cost and Price

 

 

Cost is a critical factor when selecting stainless steel for CNC machined parts. While 420 stainless steel (SS420) typically has a lower upfront price, 316 stainless steel (SS316) can reduce long-term maintenance costs due to its superior corrosion resistance. Understanding both initial and ongoing costs helps optimize project budgets.

• Tip: Always consider the total cost of ownership, including replacement, maintenance, and machining difficulties, rather than just material price.

 

Cost Comparison Table

 

 

 

• Tip: For high-wear parts that don’t face corrosion, 420 is cost-effective. For marine, chemical, or food applications, 316 may cost more upfront but saves money over time due to durability and lower replacement needs.

 

 

 

420 Stainless Steel vs. 316 Stainless Steel: National Standards and Equivalent Grades

 

 

Stainless steel grades are standardized internationally to ensure consistent performance in CNC machining and manufacturing. Knowing the national standards and equivalent grades of 420 and 316 stainless steel helps engineers source the correct material for specific applications and verify compatibility across suppliers.

• Tip: Always check the standard and certification of your stainless steel material to avoid mismatches that can affect machining quality and part longevity.

 

420 Stainless Steel Standards and Equivalents

 

 

 

 

316 Stainless Steel Standards and Equivalents

 

 

• Tip: When ordering CNC machined parts, referencing international equivalents ensures you get consistent mechanical properties and corrosion resistance regardless of the supplier’s country.

 

 

 

 

How to Choose Between 420 and 316 Stainless Steel?

 

 

Selecting between 420 stainless steel (SS420) and 316 stainless steel (SS316) depends on the application environment, mechanical demands, and cost considerations. Understanding their strengths and weaknesses ensures you pick the right material for your CNC machined parts, reducing failures, maintenance, and overall project costs.

• Tip: Focus on your part’s priority — hardness/wear resistance vs corrosion resistance — before making a final decision.

 

When Should You Use 420 Stainless Steel?

• High Hardness and Wear: Ideal for knives, cutting tools, molds, bearings, and other parts that require edge retention or wear resistance.
• Dry or Low-Corrosion Environments: Suitable when corrosion resistance is not critical.
• Cost-Sensitive Projects: Lower initial material cost compared to 316 stainless steel.
• CNC Machining Considerations: Easier to machine in annealed condition; hardness increases after heat treatment.

Tip: Avoid using 420 stainless steel in marine, chemical, or highly humid environments — it will corrode faster without protective coatings.

 

 

When Should You Use 316 Stainless Steel?

• Corrosive or Marine Environments: Excellent resistance to seawater, chemicals, and acidic conditions.
• Medical, Food, or Chemical Equipment: Safe for implants, food processing machinery, and chemical tanks.
• Welded or Complex Parts: Excellent weldability and formability for fabricated components.
• Long-Term Durability: Reduces maintenance and replacement costs in harsh conditions.

Tip: While 316 stainless steel has a higher upfront cost, it often lowers long-term expenses due to superior corrosion resistance and extended service life.

 

 

How to Choose Between 420 and 316 Stainless Steel

 

 

        

• Tip: Use this table as a quick guide — pick 420 when hardness and wear matter most, and choose 316 when corrosion resistance and durability are critical.

 

 

 

 

 

Are 420 Stainless Steel or 316 Stainless Steel Right for Your Project?

 

Choosing between 420 stainless steel (SS420) and 316 stainless steel (SS316) depends on your project’s functional requirements and environmental conditions. Both grades have distinct advantages that make them suitable for different CNC machined parts.

 

 

Choose 420 Stainless Steel if:

• Your parts require high hardness and wear resistance.
• The environment is dry or low-corrosive.
• You are focused on cost efficiency for cutting tools, molds, or wear-prone components.

 

Choose 316 Stainless Steel if:

• Your parts will be exposed to corrosive or marine environments.
• Toughness and long-term durability are critical.
• You need weldability and formability for complex or fabricated parts.
• You require biocompatibility for medical or food-grade applications.

Tip: Before final selection, consult your CNC machining factory about part size, machining complexity, and environmental exposure to avoid costly material mistakes.

 

 

 

 

 

VMT: Providing Stainless Steel CNC Machining Parts Services Factory

 

At VMT CNC Machining, we specialize in delivering high-precision stainless steel CNC machined parts, including both 420 stainless steel (SS420) and 316 stainless steel (SS316). Our expertise ensures that each part meets your mechanical, corrosion resistance, and dimensional requirements, whether for industrial, medical, marine, or consumer applications.

 

Why Choose VMT:

• Precision Machining: Advanced CNC equipment for tight tolerances and complex geometries.
• Material Expertise: Skilled in handling martensitic 420 and austenitic 316 stainless steel to optimize hardness, corrosion resistance, and machinability.
• Customized Solutions: We provide tailored CNC machining services for prototypes, small batches, or mass production.
• Quality Assurance: Rigorous inspection ensures that all stainless steel CNC machined parts meet international standards.
• Cost-Effective Production: Efficient processes minimize material waste and reduce production costs.

Tip: Clearly communicate your project’s requirements (hardness, corrosion resistance, machining complexity) to VMT to achieve optimal part performance and cost efficiency.

 

 

 

 

 

Conclusion

 

Choosing between 420 stainless steel (SS420) and 316 stainless steel (SS316) depends on your project’s mechanical demands, environmental conditions, and cost considerations.

420 Stainless Steel is ideal for parts requiring high hardness, wear resistance, and edge retention, such as knives, molds, and industrial tools. Its lower cost and heat-treatable properties make it suitable for dry or low-corrosion environments.

 

316 Stainless Steel excels in corrosion resistance, toughness, and long-term durability, making it perfect for marine, chemical, food, and medical applications. Although it has a higher upfront cost and is more difficult to machine, it reduces maintenance and replacement expenses over time.

 

By understanding the composition, physical properties, mechanical performance, heat treatment, applications, and cost differences, engineers and designers can make informed decisions for their CNC machined parts. Partnering with a reliable CNC machining factory like VMT ensures that both SS420 and SS316 parts meet precision, quality, and performance standards, maximizing the success of your project.

 

• Tip: Evaluate both the short-term cost and long-term durability before selecting the stainless steel grade to ensure optimal performance and value.

 

 

 

 

 

FAQs

 

 

1. Which is Better, SS316 or SS410?

• SS316 is better for corrosion resistance, toughness, and long-term durability, making it ideal for marine, chemical, and medical applications.
• SS410 (similar to 420) is better for hardness and wear resistance, suitable for knives, cutting tools, and molds.

 

2. Does 420 Stainless Steel Rust?

 

Yes, 420 stainless steel can rust if exposed to moisture, salt, or acidic environments, especially if not properly coated or maintained.

 

 

3. Which is Better, 304 or 420 Stainless Steel?

• 304 stainless steel is better for corrosion resistance and forming, commonly used in food, chemical, and kitchen applications.
• 420 stainless steel is superior for hardness and wear resistance, ideal for knives, molds, and tools.

 

4. Which is Cheaper, 304 Stainless Steel or 316 Stainless Steel?

 

304 stainless steel is generally cheaper than 316 due to lower nickel and molybdenum content.

 

 

5. What is the Cheapest Grade of Stainless Steel?

 

430 stainless steel and 304 stainless steel are among the most affordable grades, depending on market conditions.

 

 

6. Which Stainless Steel is Best for Cooking?

 

304 stainless steel is widely preferred for cookware and kitchen equipment due to excellent corrosion resistance, durability, and food safety.

 

 

7. Does 420 Stainless Steel Rust?

 

Yes, repeated: 420 stainless steel is prone to rust if exposed to water, salt, or acidic conditions, especially without proper maintenance.

 

 

8. Which is Cheaper, 316 or 316L?

 

316 stainless steel is slightly cheaper than 316L, which has lower carbon content for better weldability and reduced risk of corrosion.

 

 

9. Is 430 Stainless Steel Cheaper than 304?

 

Yes, 430 stainless steel is generally cheaper than 304, but it has lower corrosion resistance and is magnetic.

 

 

10. What Grade of Stainless Steel is Best?

 

The “best” grade depends on application:

• SS420/SS410 for hardness and wear.
• SS304 for general corrosion resistance and food applications.
• SS316 for harsh environments requiring corrosion resistance and toughness.

Tip: Choose stainless steel based on your environment, mechanical needs, and cost, not just popularity — this ensures your CNC machined parts perform reliably.