Stainless Steel Grade 304

 Product Data Sheet – Stainless Steel

Grades 304, 304L, 304H  UNS-S30400, S30403, S30409

Grade 304 is the most commonly used stainless steel. It is an austenitic, corrosion resistant steel with excellent strength, toughness, fabrication characteristics and weldability. The low carbon version, 304L, may be required for full corrosion resistance when thicker sections are welded. The 304H version has a guaranteed minimum carbon content, which ensures good strength at high temperatures.

Typical Applications

Brewing and dairy equipment, evaporators, drums, barrels, heat exchangers, hospital equipment, refrigeration parts, chemical and food processing, shop fittings, bench tops, kitchens, kitchen utensils, sinks, wash troughs, urinals, hand rails, dishwashers, clothes dryers, ovens, heating trays, air conditioning equipment, guttering and rain water goods, counters and display cabinets, hot and cold food bars, commercial oven hoods, beer barrels.

Chemical Composition

(AS1449 / ASTM A240 – Flat Products)

Carbon Silicon Manganese Phosphorus Sulphur Nickel Chromium Nitrogen
304
Specification (max)
0.08 0.75 2.00 0.045 0.030 8.00 – 10.50 18.00 – 20.00 0.10
(typical)
0.045 0.49 1.22 0.028 0.005 8.3 18.2 0.045
304L
Specification (max)
0.03 0.75 2.00 0.045 0.030 8.00 – 12.00 18.00 – 20.00 0.10
(typical)
0.020 0.42 1.46 0.028 0.005 9.1 18.3 0.048
304H
Specification (max)
0.04 – 0.10 0.75 2.00 0.045 0.030 8.00 – 10.50 18.00 – 20.00
(typical)
0.049 0.49 1.25 0.028 0.005 8.3 18.3 0.043

Mechanical Properties

(AS1449 / ASTM A240 – Flat Products)

Thickness 0.2% Proof Stress Tensile Strength Elongation Hardness
Unit MPa MPa % HB (max)
304
Specification (min)
205 520 40 202
typical values
0.3 – 3.5mm 260 660 55 160
3.6 – 6mm 250 600 55 160
> 6mm 240 580 55 155
304L
Specification (min)
170 485 40 183
304H
Specification (min)
205 520 40 202

Description

Grade 304 contains 18% chromium, which makes it resistant to many corrosive environments. It is austenitic in structure because of the 8% nickel it contains. The very tough and ductile austenitic structure gives grade 304 excellent formability and fabrication characteristics.

In most applications the steel is used where its corrosion resistance gives long lasting appearance and service life. The ease of cleaning and of maintaining a hygienic surface on the steel make it excellent for many purposes.

The low carbon version, 304L, may be required for full corrosion resistance when sections thicker than about 6mm are welded. The version with guaranteed high carbon, 304H, may be required for elevated temperature service, such as pressure vessels.

Availability

Austral Wright Metals can supply this grade as plate, coil, sheet, strip, round, hexagon, flat bar, angles, tube, pipe and welding consumables.

Finishes

No1 (hot rolled, annealed and pickled), 2D (cold rolled), 2B (cold rolled, skin passed), N4 (polished), BA (bright annealed).

Flat products are available surface protected with white polyethylene (PE) film. Protection with blue poly vinyl chloride (PVC) for deep drawing or black PVC (for heavy forming) is also available.

Corrosion Resistance

Grade 304 has excellent corrosion resistance in many environments. Austral Wright Metals will be pleased to provide advice for specific applications.

Grade 304 gives good service in atmospheric conditions, resisting most environments except for marine conditions, or where industrial pollution is heavy. Best appearance is maintained where the design allows even rain washing of the surface, or where dirt deposits are occasionally washed off the steel.

Grade 304 has given excellent service in some situations in potable water. Pitting and crevice corrosion may occur at higher chloride content, and 200 ppm is accepted as the upper limit.

Grade 304 is not generally used in seawater, due to the probability of crevice corrosion developing under sediments, precipitation and biofouling.

Stainless Steel Grade 304 crevice

Grade 304 may suffer stress corrosion cracking in solutions containing chloride ions at temperatures over about 60°C. Stress corrosion cracking should be considered for all corrosion services where the corrosive liquid may contain chloride.

Physical Properties

(Typical, annealed)

Property
At
Value
unit
Density
7,900
kg/m³
Melting Range
1400 – 1450
°C
Modulus of Elasticity
20°C
193
GPa
Shear Modulus
20°C
77
GPa
Poisson’s Ratio
20°C
0.30
Thermal Conductivity
100°C
16.2
W / m. °C
Electrical Resistivity
25°C
0.72
micro-ohm . m
Electrical Conductivity
25°C
1.25
% IACS
Specific Heat
500 J/kg. °C
Relative Magnetic Permeability
1.02
Coefficient of Expansion
0 – 100°C 17.2 /°C
0 – 315°C 17.8 /°C
0 – 540°C 18.4 /°C

Toughness

Austenitic stainless steels are inherently tough, maintaining the ductile fracture mode and high absorbed energy in impact tests to cryogenic temperatures (-200°C).

Pressure Vessels

AS1210, Pressure Vessels, allows the use of grade 304 up to a temperature of 800°C. The standard allows the use of higher design stresses at all temperatures for 304H.

High Temperature Corrosion

The generally accepted maximum service temperatures for grade 304 in air are 870°C for intermittent service and 925°C for continuous service.

Cleanability

Grade 304 is often used for food equipment, where cleaning for the removal of bacteria is vital. The cleanability of 304 stainless steel is superior to many other materials.

Cold Fabrication

Grade 304 is readily workable, by the standard methods of sheet metal working, with the exception that it cannot be oxygen cut. Plasma cutting is normal. The deep drawing capability of grade 304 is outstanding.

Forging

304 is one of the easier austenitic stainless steels to forge, at temperatures above 925°C.

Machinability

Grade 304 is relatively easy to machine, although more difficult than carbon steel. More power is required to machine grade 304. Cutting speed should be lower, the feed higher, tooling and equipment heavier. The machinability of 304 is about 60% that of AISI B1112 resulphurised free cutting carbon steel. A free machining version of 304 is available as bar.

Heat Treatment

Solution annealing is performed at 1065 – 1120°C, followed by rapid cooling to prevent the precipitation of the chromium carbides. 304 cannot be hardened by heat treatment. Stress relieving is rarely required due to the high ductility of 304.

Weldability

Grade 304 is readily weldable by most fusion techniques (GTAW / TIG, GMAW / MIG / MAG, MMAW / stick, SAW), with no preheat, postheat or control of interpass temperature needed. Welding with the common austenitic filler metals, such as grades 308, 308L, 309, 309L, 316 or 316L (or the silicon containing versions) will retain corrosion resistance and strength. Grades 308 and 308Si are prequalified weld metals to AS1554.6:1994 for welding grade 304 to itself, or to most other austenitic grades.

The technical advice and recommendations made in this Product Data Sheet should not be relied or acted upon without conducting your own further investigations, including corrosion exposure tests where needed. Please consult current editions of standards for design properties. Austral Wright Metals assumes no liability in connection with the information in this Product Data Sheet. Austral Wright Metals supplies a comprehensive range of stainless steels, copper alloys, nickel alloys and other high performance metals for challenging service conditions. Our engineers and metallurgists will be pleased to provide further data and applications advice.
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