18-8 Stainless Steel: A Comprehensive Guide to Properties and Uses

by AMC

Posted on November 15, 2023 at 12:57 PM

18-8 Stainless Steel: A Comprehensive Guide to Properties and Uses

What is 18-8 stainless steel?

18-8 stainless steel, also known as 304-grade stainless steel, earns its name from its composition—containing approximately 18% chromium and 8% nickel. The remainder consists of iron and a mix of several other elements. Noteworthy designations for this type of stainless steel include 301, 302, and 304.

Key Characteristics:

  • Chemical Composition: Belonging to the 300 series, 18.8 stainless steel boasts a composition of approximately 18% chromium and 8% nickel, contributing to its superior properties.
  • Tensile Strength: With a tensile strength range of 80-200,000 psi, 18.8 stainless steel exhibits robust mechanical properties, ensuring reliability in various applications.
  • Corrosion Resistance: A notable feature is its commendable resistance to corrosion, surpassing that of the 400 series. This attribute enhances its suitability for environments demanding longevity and durability.

18-8 Stainless Steel Chemical Compositions

Chemical Composition, %
ASTM AISI (UNS) C, ≤ Si, ≤ Mn, ≤ P, ≤ S, ≤ Cr Ni N, ≤ Product
ASTM A240/A240M 304 (UNS S30400) 0.07 0.75 2.00 0.045 0.030 17.5-19.5 8.0-10.5 0.10 Plate, Sheet, and Strip
ASTM A276A/276M 0.08 1.00 2.00 0.045 0.030 18.0-20.0 8.0-11.0 Bars and Shapes

Properties of 18.8 Stainless Steel

  • Corrosion Resistance: Within the 18-8 types, minimal distinctions in corrosion resistance exist. However, subtle variations in chemical composition can render certain grades more resistant to specific chemicals or atmospheric conditions. Notably, 18.8 stainless steel exhibits superior corrosion resistance, outperforming counterparts in the 400 series stainless steel.
  • Magnetic Characteristics: A distinctive feature is its non-magnetic nature, setting it apart from materials in the 400 series. This property expands its utility, particularly in applications where magnetic interference is undesirable.
  • Hardenability: 18.8 stainless steel demonstrates hardenability solely through the cold working process. This characteristic contributes to its versatility, allowing for customized applications in various industries.

18-8 Stainless Steel Mechanical Properties

Mechanical Properties
ASTM Type AISI (UNS) Tensile Strength, (MPa), ≥ Yield Strength, ≥ (MPa) at 0.2% Offset Elongation in 50 mm (%, ≥) Reduction of Area, %, ≥ Brinell Hardness, (HBW) ≤ Rockwell Hardness, (HRBW) ≤ Product Condition
ASTM A240/A240M 304 (UNS S30400) 515 205 40 201 92 Plate, Sheet, and Strip
ASTM A276A/276M 515 205 40 50 Bars and Shapes Hot finished
620 310 30 40 Cold finished, Dia ≤ 12.7mm
515 205 30 40 Cold finished, Dia. > 12.7mm

18-8 Stainless Steel Material Properties or Physical Properties

  1. Density: 7.9 g/cm³ (Equivalent to 7900 kg/m³ or 7.9 x 10³ kg/dm³)
  2. Melting Point: Approximately 1400-1450°C (2552-2642°F)
  3. Magnetic Properties: Generally non-magnetic, distinguishing it from the magnetic 400 series stainless steels.
  4. Specific Heat Capacity: 500 J/(kg·K) or 0.12 BTU/(lb·°F)
  5. Electrical Resistivity: 720 Ω·mm²/m (Equivalent to 720 μΩ·m)
  6. Modulus of Elasticity (Elastic Modulus): Around 193 GPa (Equivalent to 193 kN/mm² or 193 × 10³ MPa)
  7. Thermal Diffusivity: Approximately 3.8 x 10⁻⁶ m²/s
  8. Thermal Conductivity: Typically 16-24 W/(m·K)
  9. Coefficient of Thermal Expansion: 16-17 x 10⁻⁶/K or 16-17 μm/(m·K)

Type 304 Physical Properties
Density, g/cm3 (lb/in3) 7.93 (0.286)
Melting point, °C (°F) 1400-1450 (2550-2650)
Specific heat capacity, J/kg·K (Btu/lb ·°F) 500 (0.12) at 20 °C (68 °F)
Electrical resistivity, μΩ·m 0.72 at 20 °C (68 °F)
Conductivity, %, IACS 2.5
Magnetic permeability 1.02 (Approximate)
Elastic modulus (Modulus of Elasticity), GPa (106 psi) 193 (28)
Thermal diffusivity, mm2/s (in2/s) 3.84 (0.006)
Thermal conductivity, W/m·K (Btu/ft·h·°F) 16.2 (9.4) at 100 °C (212 °F)
21.5 (12.4) at 500 °C (932 °F)
Coefficient of thermal expansion (CTE), 10-6/K (μin./in·°F) 17.2 (9.6) at 0-100 °C (32-212 °F)
17.8 (9.9) at 0-315 °C (32-600 °F)
18.4 (10.2) at 0-538 °C (32-1000 °F)

Applications of 18/8 Stainless Steel:

Widely utilized across industries, 18/8 stainless steel is a versatile material with applications in the petroleum and chemical industry, metallurgical machinery, aerospace industry, food processing equipment, instruments, household appliances, and hardware manufacturing. It serves as the foundation for intermediate products, including steel sheets, plates, tubes, pipes, bars, flats, rods, and wires. In its final form, 18/8 stainless steel is transformed into a myriad of products such as kitchenware, tableware, medical devices, machinery parts, wire mesh, filters, and architectural and decorative metal products. The material's unique combination of strength, corrosion resistance, and aesthetic appeal makes it indispensable in various manufacturing processes.

18-8 stainless steel equivalent grade
US European Union ISO Japan China
Standard Type Standard Grade (Steel Number) Standard Grade (ISO Number) Standard Grade Standard Grade
ASTM A276/A276M;
ASTM A240/A240M;
(UNS S30400)
EN 10088-1; EN 10088-2; EN 10088-3 X5CrNi18-10 (1.4301) ISO 15510 X5CrNi18-10 JIS G4303; JIS G4304; JIS G4305; SUS304 GB/T 20878;
GB/T 1220;
GB/T 3280
06Cr19Ni10 (New designation)
(UNS S30403)
X2CrNi18-9 (1.4307);
X2CrNi19-11 (1.4306)
X2CrNi19-11 (4306-304-03-I) SUS304L 00Cr19Ni10;
022Cr19Ni10 (New name)

In summary, 18/8 stainless steel plays a vital role across a multitude of industries, serving as a foundational material for various intermediate and final products. Its combination of strength, corrosion resistance, and aesthetic appeal makes it a preferred choice in diverse applications.

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