Courtesy of Outokumpu
A series of grades which compete with 304/304L in corrosion resistance. The absence of nickel produces a lower cost alternative. The ferritic structure gives excellent deep drawability and stress corrosion cracking resistance but disadvantages in welding of thick sections and stretch forming.
Equivalent EN and UNS grade designations: 1.4510 1.4509 1.4621 1.4622 1.4611 S43035 S43940 S44500
Approximate Composition – 17-21% Cr plus combinations of stabilising elements like Ti and Nb (Exact composition ranges vary between EN and ASTM standards).
These grades combine the following characteristics:
- Good pitting corrosion resistance similar to 304
- Excellent resistance to stress corrosion cracking, better than standard austenitic grades 304 and 316
- Excellent deep drawing properties, slightly better than austenitic grades
- Reduction in ridging and roping during forming compared to unstabilised ferritic grades like 430
- Lower thermal expansion and higher thermal conductivity than austenitic grades
- Limited stretch formability compared to austenitic grades due to lower ductility
- Limit on welding to about 5 mm due to poor weld toughness from rapid grain growth
- Loss of toughness at sub-zero temperatures
This series of grades has been used extensively over the years for a number of familiar applications such as exhaust systems and washing machine tubs. They are being targeted at competing with 304 in applications where the limitations on weld thickness and stretch forming are not an issue. The stainless steel mills are frequently introducing new grades of this type so it is worth checking for an up to date list of available grades.
Applications which illustrate these features include:
Exhaust systems, washing machine tubs, cladding, wall panels, roofing, handrails, catering equipment, water tubing, sugar processing, fuel cells, portable pizza ovens, lifts.