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What is SS304 Stainless Steel?
The overview of the standard SS304 grade
Stainless Steel 304 (SS304) stands as one of the most versatile and widely used grades of stainless steel in the global machinery industry. First developed in the early 20th century, this austenitic chromium-nickel alloy has become the benchmark for corrosion-resistant materials in various industrial applications.
SS 304 is an austenitic stainless steel that belongs to the 300-series family. It is primarily composed of iron, chromium, and nickel, with typical concentrations of 18–20% chromium and 8–10.5% nickel and this is why the term “18/8 stainless steel” is often used synonymously with SS 304.
SS304, SS304L and SS304H
Stainless Steel 304 and its variants, SS304L and SS304H, represent cornerstone materials in the austenitic stainless steel family, widely recognized for their exceptional corrosion resistance and mechanical properties.
Compared with the standard SS304 grade, SS304L, with its lower carbon content (maximum 0.03%), offers superior welding characteristics and enhanced resistance to intergranular corrosion.
Conversely, SS304H features a higher carbon content (0.04-0.10%) and is specifically engineered for high-temperature applications.
| Property | SS304 | SS304L | SS304H |
| Chemical Composition (%) | |||
| Carbon (C) | 0.08 max | 0.03 max | 0.04-0.10 |
| Chromium (Cr) | 18-20 | 18-20 | 18-20 |
| Nickel (Ni) | 8-10.5 | 8-12 | 8-11 |
| Manganese (Mn) | 2.0 max | 2.0 max | 2.0 max |
| Silicon (Si) | 0.75 max | 0.75 max | 0.75 max |
| Phosphorus (P) | 0.045 max | 0.045 max | 0.045 max |
| Sulfur (S) | 0.030 max | 0.030 max | 0.030 max |
These variants have been developed to address specific industrial needs while maintaining the fundamental benefits of the SS304 family. SS304L has become the preferred choice in industries requiring extensive welding operations, such as chemical processing and nuclear applications, where maintaining structural integrity under corrosive conditions is paramount.
SS304H, with its enhanced creep resistance and higher strength at elevated temperatures, finds its niche in high-temperature operations, particularly in power generation facilities and heat exchanger applications where temperatures can exceed 500°C (932°F).
Key Properties of SS304
Mechanical Properties
Whether in construction, manufacturing, or marine applications, SS304 continues to prove its reliability and versatility, which is prized for its impressive mechanical properties, and below is a summary of the key mechanical properties of SS304:
| Property | Value |
| Tensile Strength | 505 MPa (73,000 psi) |
| Yield Strength | 215 MPa (31,200 psi) |
| Elongation | 40% (minimum) |
| Hardness | 70 HRB |
| Modulus of Elasticity | 200 GPa (29,000 ksi) |
Chemical Composition
As an austenitic stainless steel, SS304 is primarily composed of iron, chromium, and nickel, along with other elements that enhance its characteristics.
The following table summarizes the typical chemical composition of SS304 stainless steel:
| Element | Typical Composition (%) | Role in the Alloy |
| Iron (Fe) | Balance | Base metal |
| Chromium (Cr) | 18.0 – 20.0 | Enhances corrosion resistance |
| Nickel (Ni) | 8.0 – 11.0 | Improves ductility and toughness |
| Carbon (C) | ≤ 0.08 | Reduces risk of intergranular corrosion |
| Manganese (Mn) | ≤ 2.0 | Aids in hardness and toughness |
| Silicon (Si) | ≤ 1.0 | Enhances oxidation resistance |
| Phosphorus (P) | ≤ 0.045 | Maintains ductility |
| Sulfur (S) | ≤ 0.03 | Improves machinability |
Physical Properties
The material exhibits remarkable physical characteristics that make it ideal for diverse applications:
- Density: 8.0 g/cm³
- Melting Point: 1450-1500°C (2642-2732°F)
- Thermal Conductivity: 16.2 W/m·K at 100°C
- Specific Heat Capacity: 500 J/kg·K
- Electrical Resistivity: 72 µΩ·cm at 20°C
Corrosion Resistance
One of the most celebrated characteristics of SS 304 is its corrosion resistance. It is highly resistant to oxidation, rusting, and pitting, particularly in environments with exposure to water or mild chemicals.
However, it may not perform as well as SS 316 in chloride-rich conditions, where the latter’s higher molybdenum content offers enhanced resistance.
Comparing SS 304 to ferritic grades like SS 430, it consistently outperforms in both corrosion resistance and mechanical flexibility, further highlighting its versatility.
Industrial Applications of SS304
SS 304’s adaptability allows it to be employed across diverse industries. In industrial applications, it is a popular choice for chemical processing equipment, storage tanks, and heat exchangers due to its ability to resist corrosion from various chemicals and its structural integrity under high pressures and temperatures.
Food Processing Equipment
SS304’s non-reactive nature and excellent cleanability make it the preferred choice for food processing equipment. Its ability to maintain product purity while resisting sanitizing agents has established it as the industry standard for:
- Storage tanks and vessels
- Processing equipment
- Conveyor systems
- Commercial kitchen equipment
- Brewing and distillation systems
Chemical Processing
In chemical processing, SS304 excels due to its resistance to various chemical compounds:
- Reaction vessels
- Storage tanks
- Pipeline systems
- Heat exchangers
- Pressure vessels
Medical and Pharmaceutical Applications
The material’s high corrosion resistance and ease of sterilization make it essential in:
- Surgical instruments
- Laboratory equipment
- Pharmaceutical processing equipment
- Medical storage solutions
- Clean room components
Marine Industry Applications
Stainless Steel 304 plays a crucial role in marine applications, where its exceptional corrosion resistance against saltwater environments makes it indispensable for both vessel construction and port infrastructure.
While not as resistant to chlorides as higher-grade alloys like SS316, SS304 remains a cost-effective choice for above-waterline applications and interior marine components.
Key marine applications include:
- Deck fittings and hardware
- Interior cabin components and furnishings
- Ventilation systems and ducting
- Non-structural railings and handrails
- Storage tanks for non-critical fluids
- Galley equipment and food preparation areas
- Interior piping systems
- Decorative trim and architectural elements
Automotive Industry Applications
In the automotive sector, SS304 has established itself as a premier material for exhaust system components and decorative trim elements, offering an optimal combination of heat resistance, durability, and aesthetic appeal.
Its ability to withstand high temperatures while maintaining structural integrity makes it particularly valuable in exhaust manifolds and catalytic converter housings. The material’s excellent formability and weldability enable automotive manufacturers to create complex shapes and designs while maintaining strict quality standards.
Principal automotive applications include:
- Exhaust system components and manifolds
- Catalytic converter housings
- Heat shields and thermal barriers
- Decorative trim and moldings
- Fuel system components
- Structural reinforcements
- Interior support brackets
- Engine compartment hardware and fittings
The comparison of SS304 with other stainless steel
Comparison with Common Austenitic Grades
SS304 vs. SS316
When compared to SS316/316L, SS304 offers comparable corrosion resistance in most environments but shows reduced resistance to chlorides and certain aggressive chemicals.
While SS316 contains 2-3% molybdenum for enhanced pitting resistance, SS304’s absence of this element results in a more economical option for less demanding environments. This cost advantage has made SS304 the preferred choice in many general-purpose applications where extreme chemical resistance isn’t required.
Key differences between SS304 and SS316:
- The presence of Molybdenum (Mo) in SS316 is the main distinguishing factor
- SS316 has better corrosion resistance, especially in chloride environments
- SS316 is preferred for more aggressive environments
- SS304 is more cost-effective for general applications
| Characteristics | SS304 | SS316 |
| Chemical Composition | 18-20% Cr, 8-10.5% Ni, 0.08% C max, 2% Mn max, 1% Si max, No Mo | 16-18% Cr, 10-14% Ni, 0.08% C max, 2% Mn max, 1% Si max, 2-3% Mo |
| Tensile Strength (MPa) | 515-720 | 515-690 |
| Yield Strength (MPa) | 205 min | 205 min |
| Chloride Resistance | Moderate | Excellent |
| Pitting Resistance | Good | Superior |
| Maximum Service Temperature | 870°C | 870°C |
| Relative Cost | Lower | 15-20% higher |
| Typical Applications | Food processing, Kitchen equipment, General purpose, Indoor applications, Architectural | Marine environments, Chemical processing, Pharmaceutical, Offshore equipment, High chloride environments |
| Weldability | Excellent | Excellent |
SS304 vs. SS301
The comparison with SS301 reveals another dimension of austenitic stainless steel capabilities. SS301, with its lower nickel content, exhibits higher strength after cold working but slightly reduced corrosion resistance compared to SS304.
This makes SS301 more suitable for structural applications where strength is paramount, while SS304 maintains superiority in applications requiring optimal corrosion resistance and formability.
Key differences to note:
- SS301 has lower nickel content but higher carbon content, accordingly, it has superior strength after cold working
- SS301 is primarily used in applications requiring high strength, where it exhibits stronger work-hardening characteristics
- SS304 offers better corrosion resistance
| Characteristics | SS304 | SS301 |
| Chemical Composition | 18-20% Cr, 8-10.5% Ni, 0.08% C max, 2% Mn max, 1% Si max | 16-18% Cr, 6-8% Ni, 0.15% C max, 2% Mn max, 1% Si max |
| Tensile Strength (MPa) | 515-720 | 758-955 (after cold working) |
| Yield Strength (MPa) | 205 min | 275 min (can reach 700+ after cold working) |
| Corrosion Resistance | Excellent | Good |
| Work Hardening Rate | Moderate | High |
| Maximum Service Temperature | 870°C | 850°C |
| Relative Cost | Standard | Slightly lower (due to less nickel) |
| Typical Applications | Food processing, Chemical equipment, Kitchen equipment, General purpose, Architectural applications | Aircraft components, Railway cars, Structural applications, Spring applications, High-strength requirements |
| Formability | Excellent | Good (but hardens quickly during forming) |
| Magnetic Properties | Non-magnetic (annealed) | Becomes magnetic when cold worked |
SS304 vs. SS310
SS310, with its higher chromium and nickel content, outperforms SS304 in high-temperature applications but comes at a significantly higher cost. This comparison exemplifies the important balance between performance requirements and economic considerations that engineers must evaluate.
The differences between SS304 and SS310:
- SS310 has significantly higher chromium and nickel content, so it excels in high-temperature applications (up to 1150°C)
- SS310 offers superior oxidation and corrosion resistance
- SS304 is cost-effective, while SS310 is considerably more expensive due to higher alloy content
| Characteristics | SS304 | SS310 |
| Chemical Composition | 18-20% Cr, 8-10.5% Ni, 0.08% C max, 2% Mn max, 1% Si max | 24-26% Cr, 19-22% Ni, 0.25% C max, 2% Mn max, 1.5% Si max |
| Tensile Strength (MPa) | 515-720 | 515-690 |
| Yield Strength (MPa) | 205 min | 205 min |
| Maximum Service Temperature | 870°C | 1150°C |
| Oxidation Resistance | Good | Excellent |
| High Temperature Strength | Moderate | Excellent |
| Relative Cost | Standard | 50-60% higher |
| Typical Applications | Food processing, Chemical equipment, General purpose, Architectural, Kitchen equipment | Heat treatment equipment, Furnace parts, Kiln liners, High-temp chemical processing, Jet engine components |
| Weldability | Excellent | Good |
| Corrosion Resistance | Good | Excellent |
Comparison with Other Stainless Steel Families
SS304 vs. SS430
The relationship between SS304 and ferritic stainless steels (400 series) highlights distinct performance characteristics. Ferritic grades like SS430 offer good corrosion resistance at a lower cost due to their minimal nickel content, but they lack the formability and weldability of SS304. This fundamental difference influences their respective applications, with SS304 dominating in scenarios requiring complex fabrication or welded constructions.
Key differences between SS304 and SS430:
- SS430 is a ferritic grade with minimal nickel content, so it is more economical
- SS430 is magnetic while SS304 is non-magnetic
- SS430 has better thermal conductivity but limited weldability
- SS430 has a lower thermal expansion, making it more stable in temperature changes
- SS304 offers better corrosion resistance and formability and a higher work hardening capability.
| Characteristics | SS304 | SS430 |
| Type | Austenitic | Ferritic |
| Chemical Composition | 18-20% Cr, 8-10.5% Ni, 0.08% C max, 2% Mn max, 1% Si max | 16-18% Cr, 0.75% Ni max, 0.12% C max, 1% Mn max, 1% Si max |
| Tensile Strength (MPa) | 515-720 | 450-600 |
| Yield Strength (MPa) | 205 min | 205 min |
| Magnetic Properties | Non-magnetic | Magnetic |
| Maximum Service Temperature | 870°C | 816°C |
| Corrosion Resistance | Excellent | Good |
| Formability | Excellent | Moderate |
| Weldability | Excellent | Limited (prone to grain growth) |
| Relative Cost | Higher | 30-40% lower |
| Typical Applications | Food processing, Chemical equipment, Kitchen equipment, General purpose, Architectural | Automotive trim, Appliance parts, Decorative applications, Interior components, Low-stress structural |
| Work Hardening | Significant | Minimal |
| Thermal Expansion | Higher (17.3 × 10⁻⁶/°C) | Lower (10.4 × 10⁻⁶/°C) |
| Heat Conductivity | 16.2 W/m·K | 23.9 W/m·K |
SS304 vs. SS420/SS440
Martensitic stainless steels, such as SS420 and SS440, provide superior hardness and wear resistance compared to SS304 but sacrifice corrosion resistance and ductility.
This trade-off makes them ideal for cutting tools and surgical instruments, while SS304 remains preferred for general corrosion-resistant applications.
SS304 vs. DSS
Duplex stainless steels(DSS) represent a more recent development, combining characteristics of both austenitic and ferritic grades. These grades often outperform SS304 in strength and pitting resistance but come with higher initial costs and more complex fabrication requirements.
The common duplex stainless steels typically include the following grades:
- 2205 (UNS S31803/S32205)
- 2507 (UNS S32750)
- 2304 (UNS S32304)
- 329 (UNS S32900)
- 2101 (UNS S32101)
2507 (UNS S32750) is also considered a super duplex stainless steel. This type of stainless steel has a higher content of chromium, molybdenum, and nitrogen, which provides excellent corrosion resistance and mechanical properties.
Frequently Asked Questions About SS304 Stainless Steel
What are the best fabrication methods for SS304?
SS304 can be fabricated using various methods:
- Welding (TIG, MIG, and resistance welding)
- Machining (requires appropriate cutting speeds and tools)
- Forming (excellent for deep drawing and spinning)
- Cold working (can increase strength but may induce some magnetism)
The material should be properly cleaned and passivated after fabrication to maintain corrosion resistance.
How should SS304 be maintained?
To maintain SS304’s appearance and performance:
- Clean regularly with mild detergents
- Avoid chloride-containing cleaners
- Remove surface contamination promptly
- Polish if necessary to restore appearance
- Periodically inspect for signs of corrosion or damage
- Maintain proper passivation layer
What are the material grades similar to SS304?
Related grades include:
- 304L (lower carbon content for better welding)
- 321 (titanium stabilized for high-temperature use)
- 347 (niobium stabilized for high-temperature use)
- 302 (slightly lower alloy content)
These grades offer specific advantages for particular applications while maintaining similar basic properties to SS304.
Is SS304 food-safe?
Yes, SS304 is completely food-safe and complies with FDA requirements for food contact materials.
It is non-toxic, non-reactive with food products, and resistant to corrosion from food acids. This makes it ideal for food processing equipment, commercial kitchens, and food storage applications.
What are the limitations of SS304?
Important limitations to consider:
• Susceptible to chloride stress corrosion cracking
• Not recommended for marine environments
• Can become slightly magnetic when cold worked
• May not be suitable for high-stress applications at elevated temperatures
• More expensive than carbon steel alternatives
Can SS304 be used in marine environments?
SS304 can handle mild marine environments but is not the best choice for prolonged exposure to saltwater or heavily chlorinated conditions. Salt can cause pitting and stress corrosion over time.
For applications directly in or near seawater, SS316 is a better option due to its higher molybdenum content, which enhances resistance to chloride-induced corrosion.
Can SS 304 be recycled?
Yes, SS 304 is 100% recyclable and retains its properties even after multiple recycling cycles. This makes it an environmentally friendly material choice for applications where sustainability is a concern.
Does SS 304 need a protective coating?
In most cases, SS 304 does not require a protective coating due to its natural chromium oxide layer, which protects it from corrosion. However, in environments with extreme exposure, protective coatings or periodic passivation treatments may be used to enhance its resistance and lifespan.
Additional coatings are only necessary in three specific cases:
When exposed to highly aggressive chemicals like concentrated chlorides or strong acids,
When specific colors are needed for aesthetic purposes,
When special surface properties such as non-stick characteristics are required.
For standard industrial and commercial applications, maintaining a clean surface is sufficient to preserve SS 304’s inherent protective properties.
Can SS 304 withstand freezing temperatures?
SS 304 performs well in low-temperature environments and retains its toughness and ductility even at cryogenic temperatures.
This makes it suitable for applications such as liquid gas storage and transportation.
