Originally developed back in the late 1970's, the current generation of super-ferritic stainless steels have become a cost-effective choice for heat exchanger tubing. When they were first developed, the goal was to have an alternative
to titanium grade 2 in applications such as seawater and other high chloride applications. At that time, titanium
was in was high priced and had a long lead time, not unlike today. over the last 10 years, the majority of the
seawater capable high- performance stainless steel literature and usage has been focused on super-austenitic (6% and 7% Mo alloys) and super duplex alloys. While the performance of these alloys is very good,
today's nickel and molybdenum material prices have driven the price of these alloys skyward.
The power industry has recognized the effectiveness super-ferritics and over 78,000,000 feet are in usage since
beginning in early 1980. The low nickel and moderate molybdenum content for excellent chloride resistance,
has driven a substantially increased use of the super-ferritic alloys. This paper traces usage in power plant heat exchanger applications and compares properties
such as corrosion resistance, mechanical and physical properties and compares them to the other seawater
and MIC resistant grades.
Recent worldwide demand has driven nickel and molybdenum prices to record high values. Alloys containing
significant amounts of nickel and molybdenum, such as the austenitic and duplex grades, have experienced
significant price increases and some spot shortages have resulted in some regions. Today's super-austenitic
prices are about three times the value of late 2003. With low nickel content and reasonable molybdenum content,
super-ferritic stainless steels are now proving to be the most cost effective.
Typical Chemical Composition of Super-Ferritic Alloys(available in full paper)
UNS44660 Super Ferritic Alloyed SS Condenser Tubing
In Power Station Equipments, The choice ofcondenser tubes is vital to the investment and maintenance costs
of the whole equipments.LSI are going to forecast the direction of the market of application of superferritic
stainless steel tubes in condensers and analysis the advantages ofsuper ferritic stainless steel tubes
compared with normal austenitic stainlesssteel tubes and titanium tubes from the aspects of
chemicalcompositions,anti-corrosion capabilities, physical properties and mechanicalproperties
of super ferritic stainless steel tubes.
S44660 super ferritic stainless steel tube istheir high contents of Chromium and Molybdenum, and it has
Titanium and niobiumas stabilizing elements. The organization of material makes them with highstrength
properties, good elongation and low rate of work hardening.
Characteristics of material:
Super ferritic stainless steel is a kind ofalloy be used for anti-pitting corrosion,crevise corrosion and stress corrosionunder the environment of chloride.
It has good heat conductivities,highanti-chloridion corrosion and marine life corrosion, extremely high modulus ofelasticity,high fatigue strength and
hardness impact attack resistance,coefficient of linear expansion will be the same as carbon steel and unit
pricewill be equal or economic than titanium tubes.
Weldability to other stainless steels
Compared with Titanium, No easier to havehydrogen brittleness phenomenon.
Dimension LSI provide:
Max. Length: 20 Meters
Standards: ASME SA268,ASME SA688,ASMESA803,ASTM A268.
This alloy is specifically designed forapplications where chloride induced pitting, crevice and stress corrosion
cracking may be encountered and is used in:
1.Electric Power Plant Condensers and FeedwaterHeaters
3.Various Heat Exchangers in Chemical,Petrochemical and Refining Applications
4.Desalination Heat Exchangers
5.Flue Gas Handling Systems
One industry that has adopted high performance stainless steels is power production. Kovach6 has summarized
the history and performance of high performance stainless steel use in power plant condensers through the late
1990's. The meters of condenser tubing shipped in each year is documented separated by stainless group
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