The past two years have seen some frenetic activity in all commodities with speculation, supply interruptions, surges in demand, currency fluctuations and ballooning stocks having all contributed to an unpredictable market and often inexplicable price movements, says Durban-based manufacturer and distributor of stainless steel products Euro Steel, which is also a member of the Southern Africa Stainless Steel Development Association.
The pricing of austenitic stainless steel closely follows the cost of nickel owing to, in part, that, while nickel may make up a small percentage of stainless steel in mass (8% in grade 304), it contributes to 60% of the cost, reports the company, adding that, over the past two years to three years, the nickel price has increased to over $50 000/t and retreated to below $10 000/t.
The surging price of nickel impacted on the price of nickel-containing grades of stainless steel and this trend motivated end-users to explore other options, Euro Steel reports. This, in turn, gave rise to renewed interest in non-nickel-containing grades of stainless steel.
“There are options, and stainless steel is not as complicated as many people think. In layman’s terms, chrome is what makes steel ‘stainless’ (all stainless steels have a minimum of 11% chrome), nickel is added to help with the workability and to extend the ductility, and molybdenum can be added to improve the corrosion resistance. By adding nickel to ferritic stainless steel, it causes its structure to become austenitic and it loses its magnetism. This may not immediately appear significant, but one needs to consider that the majority of promotion, marketing and development of stainless steel, as a whole, has been funded and guided by the Nickel Development Institute (NDI),” Euro Steel states.
The NDI aims to promote the nickel-containing grades. “While there are occasional, almost reluctant, fleeting references to superior ferritic corrosion-resistance performances in a number of their publications, clearly the preference is given to the nickel- containing grades (those that are nonmagnetic). “For years, the market has been indoctrinated into believing that magnetic is bad and nonmagnetic is good, which resulted in the majority of the market perceiving magnetic stainless to be less corrosion resistant, which it is not.”
Euro Steel CEO Colin Wilson says: “We are building up a substantial library of successful
applications of these ferritic and duplex stainless applications in the fishing, catering, wine, petrochemicals, architectural and pulp and paper industries, and we are only too happy to research and advise on any enquiry.”
The company says that grade 444 stainless steel is an example of a chrome and molybdenum-containing ferritic (magnetic) stainless steel, which has superior pitting resistance compared with grade 316. There are a number of applications where the 316 stainless steel grade is specified, and, in such instances, for example, applications are susceptible to stress corrosion cracking and are inappropriate.
Another family of stainless steel is called the duplex class, a mixture of austenitic (chromium-nickel stainless steel) and ferritic structures (plain chro- mium stainless category). This combination, reports Euro Steel, offers more strength than either of the stainless steels mentioned, and provides high resistance to stress corrosion cracking (formation of cracks caused by a combination of corrosion and stress) and is suitable for heat exchangers, desalination plants and marine applications.
Although there has been an increased interest in low-nickel or non-nickel grades of stainless steel, one area of particular concern is the family of stainless steel known as the 200 series, a low nickel and reduced chrome-containing stainless steel, reports the company.
“Because the 200 series grades are austenitic, they are not magnetic and are, therefore, difficult to distinguish from the widely used 300 series grades, such as the 304 or the 316, which are also nonmagnetic. “This has led to cases of 201 stainless steel being sold as 304, resulting in confusion and corrosion failures in the marketplace, not to mention the adverse effects of scrap contamination and dilution,” says the company.
These issues can be catastrophic for the overall reputation of the industry, says Wilson.