SS 304

SS 304 is the abbreviation of Stainless Steel 304, which is the most widely used austenitic chromium-nickel stainless steel. Its nominal composition is 18% chromium and 8% nickel, so it is also called 18/8 stainless steel. SS304 stainless steel has lower corrosion resistance than SS316 and is slightly higher than SS302. SS304 density is 7,930 kg/m3 (0.286 lb/in3), melting point is 1400-1450 °C (2550-2650 °F), thermal conductivity is 16.2 W/m·K at 100 °C (9.4 Btu/ft·h·°F at 212 °F), tensile strength is 515 MPa (75 ksi), yield strength is 205 MPa (30 ksi).

Stainless steel types 1.4301 and 1.4307 are also known as grades 304 and 304L respectively. Type 304 is the most versatile and widely used stainless steel. It is still sometimes referred to by its old name 18/8 which is derived from the nominal composition of type 304 being 18% chromium and 8% nickel.  Stainless steel 304 is an austenitic grade that can be severely deep-drawn. This property has resulted in 304 being the dominant grade used in applications like sinks and saucepans.

Difference between SS304L and SS304H

• 304L Stainless Steel:  Type 304L is the low-carbon version of Stainless steel 304. It is used in heavy gauge components for improved weldability. Some products such as plate and pipe may be available as “dual certified” material that meets the criteria for both 304 and 304L.
• 304H Stainless Steel: 304H, a high carbon content variant, is also available for use at high temperatures.

Property data given in this document is typical for bar products covered by EN 10269:2013. ASTM, EN or other standards may cover products sold. It is reasonable to expect specifications in these standards to be similar but not necessarily identical to those given in this datasheet.

Specification

maximum of 0.08% carbon. It is defined as a Chromium-Nickel austenitic alloy. Grade 304 is the standard "18/8" stainless that you will probably see in your pans and cookery tools. Grade 304L is the low-carbon version of 304.

• ASTM: A167, A240, A276, A313, A314, A368, A473, A478, A479, A492, A493, A511, A554, A580, A666
• UNS: S30200
• AMS: 5515, 5516, 5788

Chemical Composition, %

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Applications of Stainless Steel 304

Stainless steel 304 is typically used in:

• Sinks and splashbacks
• Saucepans
• Cutlery and flatware
• Architectural panelling
• Sanitaryware and troughs
• Tubing
• Brewery, dairy, food and pharmaceutical production equipment
• Springs, nuts, bolts and screws

Physical Properties 

• Density: 8.00 g/cm³
• Melting Point: 1450 °C
• Modulus of Elasticity: 193 GPa
• Electrical Resistivity: 0.72 x 10⁶ Ω.m
• Thermal Conductivity: 16.2 W/m.K
• Thermal Expansion: 17.2 x 10⁶/K

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Linear Coefficient of Thermal Expansion

Thermal Conductivity 212°F (100°C)

• 9.4 BTU/hr/ft2/ft/°F
• 16.3 W/m-°K

Electrical Resistivity (Annealed Condition)

• 29.1 Microhm-in at 68°F
• 74 Microhm-cm at 20°C

Specific Heat

• 0.12 BTU/lb-°F (32 – 212°F)
• 500 J/kg-°K (0 –100°C)

Heat Resistance of Stainless Steel 304

Stainless steel 304 has good resistance to oxidation in intermittent service up to 870°C and in continuous service to 925°C. However, continuous use at 425-860°C is not recommended if corrosion resistance in water is required. In this instance, 304L is recommended due to its resistance to carbide precipitation.

Where high strength is required at temperatures above 500°C and up to 800°C, grade 304H is recommended. This material will retain aqueous corrosion resistance.

Hot Working of Stainless Steel 304

Fabrication methods, like forging, that involve hot working should occur after uniform heating to 1149-1260°C. The fabricated components should then be rapidly cooled to ensure maximum corrosion resistance.

Heat Treatment of Stainless Steel 304

Stainless steel 304 cannot be hardened by heat treatment. Solution treatment or annealing can be done by rapid cooling after heating to 1010-1120°C.

Fabrication of Stainless Steel 304

Fabrication of all stainless steels should be done only with tools dedicated to stainless steel materials. Tooling and work surfaces must be thoroughly cleaned before use. These precautions are necessary to avoid cross-contamination of stainless steel by easily corroded metals that may discolour the surface of the fabricated product.

Mechanical Properties of Stainless Steel 304

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Corrosion Resistance of Stainless Steel 304

Stainless steel 304 has excellent corrosion resistance in a wide variety of environments and when in contact with different corrosive media. Pitting and crevice corrosion can occur in environments containing chlorides. Stress corrosion cracking can occur at temperatures over 60°C.

Machinability

Stainless steel 304 has good machinability. Machining can be enhanced by using the following rules:

• Cutting edges must be kept sharp. Dull edges cause excess work hardening.
• Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material.
• Chip breakers should be employed to assist in ensuring the swarf remains clear of the work
• The low thermal conductivity of austenitic alloys results in heat concentrating at the cutting edges. This means coolants and lubricants are necessary and must be used in large quantities.

Welding of Stainless Steel 304

Fusion welding performance for Stainless steel 304 is excellent both with and without fillers. Recommended filler rods and electrodes for stainless steel 304 is grade 308 stainless steel. For 304L the recommended filler is 308L. Heavy welded sections may require post-weld annealing. This step is not required for 304L. Grade 321 may be used if post-weld heat treatment is not possible.

The Austenitic stainless steels are considered to be the most weldable of the high-alloy steels and can be welded by all fusion and resistance welding processes. Types 302, 304, 304L and 305 alloys are typical of the austenitic stainless steels.

Two important considerations in producing weld joints in the austenitic stainless steels are: (1) preservation of corrosion resistance, and (2) avoidance of cracking.

A temperature gradient is produced in the material being welded which ranges from above the melting temperature in the molten pool to ambient temperature at some distance from the weld. The higher the carbon level of the material being welded, the greater the likelihood that the welding thermal cycle will result in chromium carbide precipitation which is detrimental to corrosion resistance. To provide material at the best level of corrosion resistance, low carbon material (Type 304L) should be used for material put in service in the welded condition. Alternately, full annealing dissolves the chromium carbide and restores a high level of corrosion resistance to the standard carbon content materials.

Weld metal with a fully austenitic structure is more susceptible to cracking during the welding operation. For this reason, Types 302, 304, and 304L alloys are designed to resolidify with a small amount of ferrite to minimize cracking susceptibility. Type 305, however, contains virtually no ferrite on solidification and is more sensitive to hot cracking upon welding than the other alloys.