304/304L Stainless Steel

304 Stainless is a low carbon (0.08% max) version of basic 18-8 also known as 302. Type 302 has 18% chromium and 8% nickel.

Type 304 has slightly lower strength than 302 due to its lower carbon content. Type 304 finds extensive use in welding applications because the low carbon permits some exposure in the carbide precipitation range of 800°F - 1500°F without the need for post-annealing operations.

However, the severity of corrosive environments may necessitate annealing after welding or the use of 304L.

Type 304L has a carbon content of 0.03% or less. This alloy can be used in the as-welded condition without becoming susceptible to intergranular corrosion.

Specifications - Stainless Steel 304/304L

  • ASTM:A312, A376,A358, A269,A249, A403, A182, A351
  • ASME: SA312, SA376
  • Pressure SA358,SA269, SA249,SA403, SA182, SA351
TP304/ 304L Welded Stainless Steel Pipe

TP304/ 304L Welded Stainless Steel Pipe

Chemical Composition - Stainless Steel 304/304L

Element Percentage by Weight Maximum Unless Range is Specified
304 304L 304H
Carbon 0.08 0.030 0.04-0.10
Manganese 2.00 2.00 2.00
Phosphorus 0.045 0.045 0.045
Sulfur 0.030 0.030 0.030
Silicon 0.75 0.75 0.75
Chromium 18.00
20.00
18.00
20.00
18.00
20.00
Nickel 8.0
10.50
8.0
12.00
8.0
10.5
Nitrogen 0.10 0.10 0.10

The main constituents of 304 stainless steel - other than iron - are Chromium and Nickel.

304 contains 18 - 20% Chromium (Cr). Chromium is the essential chemical in all stainless steel and it is that which forms the thin passive layer that makes the metal "stainless"

304 also contains 8-10.5% Nickel (Ni). This is added to make the Austenitic structure more stable at normal temperatures. 

The nickel also improves high-temperature oxidation resistance makes the steel resistant to stress corrosion cracking.

Where the steel is to be stretched formed a lower percentage (8%) of nickel should be selected. If the steel is to be deep drawn a higher percentage is better (9% or more).

In addition a number of other chemicals may be present but these are expressed as maximum permited levels with the exception of the increased quantity of carbon required in 304H - i.e. a minimum of .04% and a maximum of 0.10%

*Maximum carbon content of 0.04% acceptable for drawn tubes

Typical Mechanical Properties-Stainless Steel 304/304L

Grade Tensile Strength Rm N/mm²
Yield Strength Rp 0.2, N/mm² Elongation (%)
304 Annealed 500-700 195 40
304L Annealed 460-680 180 40

Physical Properties

Data  Metric English
Density 8 g/cc 0.289 lb/in³

 Mechanical Properties

Hardness, Brinell 123 123 Converted from Rockwell B hardness.
Hardness, Knoop 138 138 Converted from Rockwell B hardness.
Hardness, Rockwell B 70 70  
Hardness, Vickers 129 129 Converted from Rockwell B hardness.
Tensile Strength, Ultimate 505 MPa 73200 psi  
Tensile Strength, Yield 215 MPa 31200 psi at 0.2% offset
Elongation at Break 70 % 70 % in 50 mm
Modulus of Elasticity 193 - 200 GPa 28000 - 29000 ksi  
Poisson's Ratio 0.29 0.29  
Charpy Impact 325 J 240 ft-lb  
Shear Modulus 86 GPa 12500 ksi  

Electrical Properties

Electrical Resistivity 7.2e-005 ohm-cm 7.2e-005 ohm-cm at 20°C (68°F); 1.16E-04 at 650°C (1200°F)
Magnetic Permeability 1.008 1.008 at RT

Thermal Properties

Design Features - Stainless Steel 304/304L

  • Oxidation resistance up to 1650°F for continuous service and up to 1500°F where cyclic heating is involved.
  • General purpose corrosion resistance.
  • Non-hardenable except by cold working.
  • Non-magnetic except when cold worked.
  • May be susceptible to chloride stress corrosion cracking.
  • Used where field working is employed.

Typical Applications - Stainless Steel 304/304L

  • Sanitary
  • Dairy and food processing
  • Heat exchangers, evaporators
  • Feedwater heaters

Tensile Requirements - Stainless Steel 304/304L

  • Tensile Strength (KSI): 70
  • Yield Strength (KSI): 25

Each alloy represents an excellent combination of corrosion resistance and fabricability. This combination of properties is the reason for the extensive use of these alloys which represent nearly one half of the total U.S. stainless steel production. The 18-8 stainless steels, principally Alloys 304, 304L, and 304H, are available in a wide range of product forms including sheet, strip, and plate. The alloys are covered by a variety of specifications and codes relating to, or regulating, construction or use of equipment manufactured from these alloys for specific conditions. Food and beverage, sanitary, cryogenic, and pressure-containing applications are examples.

Alloy 304 is the standard alloy since AOD technology has made lower carbon levels more easily attainable and economical. Alloy 304L is used for welded products which might be exposed to conditions which could cause intergranular corrosion in service.

Alloy 304H is a modification of Alloy 304 in which the carbon content is controlled to a range of 0.04-0.10 to provide improved high temperature strength to parts exposed to temperatures above 800°F.

304 Stainless steel FAQs

Grade 304 is an austenitic steel with excellent welding and forming characteristics.

What is Stainless Steel 304, 304L, 304H?

These stainless steels are widely used in the petrochemical and food industries due to their corrosion resistance, tensile strength and ability to accommodate higher temperatures. There is a trade-off between corrosion resistance and temperature characteristics according to the specific grade.

Properties

The key elements in 304 are Chromium and Nickel which give it excellent resistance to corrosion.

It has good resistance to corrosion, it is malleable and ductile and has good weldability. The austenitic structure allows it to be deep drawn without intermediate annealing.

It is also unnecessary to anneal it following welding thin sections. It is widely used in the food industry, water, architectural, cryogenic and high-temperature applications.

Widely used for good quality cutlery where it is described as 18/8 referring to the percentages of Chromium and Nickel.

What are the main uses of stainless 304?

The range of properties of 304 mean that it is used in many industries.

Its resistance to corrosion makes it suitable for use in the food industry, particularly dairy, wine and beer production or processing.

Its malleability makes it easily formed into sinks, troughs and other kitchen appliances and it can be spun easily making it suitable for the production of pots and pans.

A good choice for architectural applications being less expensive than 316. Its corrosion resistance makes it an excellent choice for internal panelling or other fittings and it is also suitable for use externally when away from the marine environment. It is however not as resistant to chloride corrosion as 316 and if there is salt spray in the atmosphere it is generally best to use 316.

The combination of corrosion resistance and formability make it a good choice for chemical containers - including those used for transportation.

It has good heat resistance and is therefore widely used in heat-exchangers. Where particularly high temperatures 304H should be considered

What are its main benefits of 304?

Corrosion Resistance

304 has good corrosion resistance in a wide range of atmospheric conditions and to many corrosive media. It is however subject to pitting corrosion in chloride environments particularly in warm conditions.

It is also subject to stress corrosion cracking above 60o.

It is generally resistant to concentrations of about 200mg/litre of chlorides at 20o but this drops to about 150mg/litre at 60o.

Heat Resistance

304 is not generally regarded as a grade to be selected when very high temperatures are expected but it may have certain benefits. It resists oxidisation in continuous use up to 925o and in intermittent use to 870o. However, using it in a temperature range between 425o and 860o can result in carbide precipitation and subsequently intergranular corrosion.

304L, with its lower carbon content, is less prone to carbide precipitation and can be used at these temperatures.

304H has greater strength at high temperatures and may be the steel of choice where both high-temperature resistance and corrosion resistance are required. Thes requirements are often found in flue gas chimneys where gasses may condense forming aggressive often acidic liquids.

What are the limitations 304?

In common with other austenitic stainless steels, 304 grade has strong work hardening characteristics. Clearly, in some cases, this can be an advantage, but generally, it is an issue to be considered carefully.

If it is likely to be an issue, discussion with the producer can be valuable as minor variations to the precise composition and process can have benefits.

Where heavy sections have to we welded, post-weld annealing may be necessary to restore corrosion resistance.

Variants - 304L & 304H

The two main variants of grade 304 are the low carbon form 304L and the high carbon form 304H

304L has a maximum of 0.30% carbon. This reduces the tendency for carbide precipitation when welding. Carbide precipitation can result in intergranular corrosion.

304H has between 0.04 and 0.1% carbon. This gives it greater strength at high temperature but does make it more vulnerable to carbide precipitation when welding.

Since 304 has as having a maximum of 0.08% carbon, there are potential overlaps in the specifications which means that it is not uncommon to find dual specification.

304L clearly has less than 0.08% carbon and can, therefore, be described as 304/304L.

304 may have up to 0.08% carbon so if its carbon content is between 0.04 a

Forms available

Stainless 304, 304H, 304L Forms Available

  • Tube
  • Pipe
  • Fittings
  • Flanges
  • Special Sections
  • Sheet
  • Plate
  • Flat Bar
  • Round Bar
  • Hollow Bar
  • Angles
  • i Beam
  • U Channel


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