304 Stainless Steel Pipes and Tubes

In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5%[1] to 11% chromium content by mass.

SS Grade 304L, the low carbon version of 304, does not require post-weld annealing and so is extensively used in heavy gauge components (over about 6mm). Grade 304H with its higher carbon content finds application at elevated temperatures. The austenitic structure also gives these grades better toughness, even down to cryogenic temperatures. Essentially, Grade 304 is an austenitic chromium alloy which is also known as an "18/8" stainless as the make-up of the steel is 18% chromium and 8% nickel. 

Type 304 stainless steel is a T 300 Series Stainless Steel austenitic. It has a minimum of 18% chromium and 8% nickel, combined with a maximum of 0.08% carbon. It is defined as a Chromium-Nickel austenitic alloy. SS Grade 304 is the standard "18/8" stainless that you will probably see in your pans and cookery tools.

Chemical Formula
Fe, <0.08% C, 17.5-20% Cr, 8-11% Ni, <2% Mn, <1% Si, <0.045% P, <0.03% S

Product Specification:

304 Stainless Steel Pipes and Tubes Product Range
304 Stainless Steel Pipes and Tubes Specifications: ASTM A/ASME SA213/A249/A269/A312/A358 CL. I to V ASTM A789/A790
304 Stainless Steel Pipes and Tubes Sizes (Seamless): 1/2" NB - 16" NB
304 Stainless Steel Pipes and Tubes Sizes (ERW): 1/2" NB - 24" NB
304 Stainless Steel Pipes and Tubes Sizes (EFW): 6" NB - 100" NB

304 Stainless Steel Pipes and Tubes Wall Thickness available:
Schedule 5S - Schedule XXS (heavier on request)

Type 304 Stainless Steel has excellent welding and deep drawing characteristics - it is easy to fabricate, easy to clean and aesthetically pleasing to the eye. 

Applications of Grade 304 Stainless Steel

• Typical applications include:
• Food processing equipment, particularly in beer brewing, milk processing & wine making.
• Kitchen benches, sinks, troughs, equipment and appliances
• Architectural panelling, railings & trim
• Chemical containers, including for transport
• Heat Exchangers
• Woven or welded screens for mining, quarrying & water filtration
• Threaded fasteners
• Springs

304 & 304L plate and pipes have same properties and in many cases are stocked with Dual Certification, where it is concluded that each item has properties and a composition which comply with both steel types. Grade 304H cannot be included in this equation due to the steel's higher carbon content which is intended for use in elevated temperature applications.

304 Stainless Steel Pipes and Tubes Composition
Typical compositional ranges for grade 304 stainless steels are given in table 1.

Table 1. Composition ranges for 304 grade stainless steel

304 Stainless Steel Pipes and Tubes Mechanical Properties
Typical mechanical properties for grade 304 stainless steels are given in table 2.

304 Stainless Steel Pipes and Tubes Physical Properties
Typical physical properties for annealed grade 304 stainless steels are given in table 3.

Table 3. Physical properties of 304 grade stainless steel in the annealed condition

304 Stainless Steel Pipes and Tubes Grade Specification Comparison
Approximate grade comparisons for 304 stainless steels are given in table 4.

Table 4. Grade specifications for 304 grade stainless steel

304 Stainless Steel Pipes and Tubes Corrosion Resistance

Excellent in a wide range of atmospheric environments and many corrosive media. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures, reducing to about 150mg/L at 60°C.

304 Stainless Steel Pipes and Tubes Heat Resistance

Good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of 304 in the 425-860°C range is not recommended if subsequent aqueous corrosion resistance is important. Grade 304L is more resistant to carbide precipitation and can be heated into the above temperature range.

Grade 304H has higher strength at elevated temperatures so is often used for structural and pressure-containing applications at temperatures above about 500°C and up to about 800°C. 304H will become sensitised in the temperature range of 425-860°C; this is not a problem for high temperature applications, but will result in reduced aqueous corrosion resistance.

304 Stainless Steel Pipes and Tubes Heat Treatment

Solution Treatment (Annealing) - Heat to 1010-1120°C and cool rapidly. These grades cannot be hardened by thermal treatment.

304 Stainless Steel Pipes and Tubes Welding

Excellent weldability by all standard fusion methods, both with and without filler metals. AS 1554.6 pre-qualifies welding of 304 with Grade 308 and 304L with 308L rods or electrodes (and with their high silicon equivalents). Heavy welded sections in Grade 304 may require post-weld annealing for maximum corrosion resistance. This is not required for Grade 304L. Grade 321 may also be used as an alternative to 304 if heavy section welding is required and post-weld heat treatment is not possible.