Grade Specification Comparison
Approximate grade comparisons for 304 stainless steels are given in table 4.
These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted.
Possible alternative grades to 304 grade stainless steel
Why it might be chosen instead of 304
A higher work hardening rate grade is required for certain roll formed or stretch formed components.
Lower work hardening rate is needed for cold forging of screws, bolts and rivets.
Higher machinability needed, and the lower corrosion resistance, formability and weldability are acceptable.
Higher resistance to pitting and crevice corrosion is required, in chloride environments
Better resistance to temperatures of around 600-900 °C is needed…321 has higher hot strength.
A lower cost is required, and the reduced corrosion resistance and resulting discolouration are acceptable.
A lower cost is required, and the reduced corrosion resistance and fabrication characteristics are acceptable.
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 200 mg/L chlorides at ambient temperatures, reducing to about 150 mg/L at 60 °C.
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.
Solution Treatment (Annealing) - Heat to 1010-1120 °C and cool rapidly. These grades cannot be hardened by thermal treatment.
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.
It is common for 304 and 304L to be stocked in "Dual Certified" form, particularly in plate and pipe. These items have chemical and mechanical properties complying with both 304 and 304L specifications. Such dual certified product does not meet 304H specifications and may be unacceptable for high temperature applications.
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
Woven or welded screens for mining, quarrying & water filtration