TWI Industrial Member Report Summary 528/1995
B J Ginn
Low cost stainless steels, such as UNS S32304, can offer advantages over both carbon and austenitic steels for certain applications. Such materials have enhanced corrosion resistance compared to carbon steel, and superior strength and hardness compared to austenitic grades.
Stainless steel type UNS S32304 has a typical chemical composition of 23%Cr 4%Ni and 0.030%C, giving a duplex ferrite/austenite structure. Cost savings of around 20% can arise with this alloy, by comparison, on a weight basis, to a 316L austenitic stainless steels, because of its reduced alloy content, in particular the molybdenum level. Further savings arise because the alloys higher strength enables thinner sections to be employed.
There are many potential engineering applications for type UNS S32304 steel e.g. heat exchangers, condensers, reinforcement bars, hand railing and culverts. A substantial proportion of total tonnage manufactured is in the form of 1-3mm thick sheet, and this project examined the properties of joints produced in sheet material. The laser and resistance welding processes were evaluated and compared with TIG (with filler) and MIG weldments made in the same material. Microstructural examination was undertaken with tensile and hardness testing, and corrosion tests both in ferric chloride and in warm, dilute chloride solutions to simulate domestic hot water applications.