JIANGSU HAOHUA INDUSTRY GROUP

Title

Super-ferritic Stainless Steels - The Cost Effective Answer for Heat Transfer Tubing

Source

CORROSION 2008, March 16 - 20, 2008 , New Orleans LA

Copyright

2008. NACE International

Keywords

High performance stainless steels, super-ferritic stainless steels, super-austenitic stainless steels, super-duplex stainless steels, heat exchanger tubing, stainless steel corrosion resistance, vibration, erosion,

thermal conductivity

Preview

ABSTRACT

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.

INTRODUCTION

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.

Chemical Composition:

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:

OD: 12.7-38.1mm

WTH: 0.4-2.5mm

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

2.BOP Exchangers

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