• INNOVATION:
  ATI Wah Chang Introduces OmegaBond™ Advanced Tubing Technology
  
  
• CORROSION LAB CHRONICLES:
  Pickled Zirconium Autoclave Proves an Ideal Solution for Tests
  
  
• ZIRCONIUM:
  The Switch Is On™
  
  
• TITANIUM:
  ATI 425™ Titanium Alloy Adopted by ASTM (Grade 38)
  
  
• SPOTLIGHT:
  — Tosdale Selected by ASTM Board for 2006 Award of Merit
  — Sutherlin Receives TPA Publication Award for Best Technical Article
  
  
• CASE IN POINT:
  AL 2003™: A Lean Duplex Stainless Alloy for PRessure Vessel Applications — ASME Code Case 2503
  
  
• PEOPLE:
  On the Move at Wah Chang
  
  
• EVENTS:
  Reactive Metals Welding Seminar
  
  
• INFORMATION

In 2004, ATI Wah Chang and Snamprogetti, S.p.A began working together to jointly bring to market a new series of advanced tubing solutions for urea plants using Snamprogetti's process technology. Snamprogetti, S.p.A. is a leading engineering firm engaged in the design and licensing of urea manufacturing technology. The result of this collaboration was OmegaBond™ advanced tubing technology which could enable urea and other chemical processing manufacturers to realize numerous benefits. Recognized benefits include: a reduction in corrosion-related down time, reduced maintenance related costs, potential energy savings, and finally the technology should allow for more aggressive operating conditions with higher process yields.

The urea process is an ideal environment for OmegaBond™ tubing and provides several good examples of corrosion problems commonly found in the chemical processing industry. By providing background on the urea process, an overview of materials historically used in the process, a summary of challenges associated with existing materials technologies and designs used in the process, the need for a new solution is easily justified.




HISTORY OF THE UREA PROCESS

The urea production process involves chemicals and conditions that corrode and/or erode most ordinary materials of construction. Plant designers and operators have been working for years to minimize unplanned downtime and maintenance. Such optimization has occurred by varying operating parameters and construction materials. While significant progress has been made, some urea plants continue to experience unplanned maintenance and downtime due to materials-related equipment malfunctions or failures.

Selection criteria for materials of construction in urea plants are dictated by localized process operating parameters. Materials of construction have changed as the urea manufacturing process has evolved and materials technology has improved. Stainless steel has historically been regarded as the baseline material of construction for corrosion resistance in many different applications, including urea plants. Conditions in portions of urea strippers have proven problematic for stainless steel. Even with tight temperature and chemistry controls, it is always necessary to add some level of passivation air to protect stainless steels used in urea strippers to prevent premature failure by corrosion.

Reactive metals (titanium and in particular zirconium) have proven themselves to be very corrosion resistant to the chemical environment encountered in a urea plant. These materials, when properly designed and fabricated, withstand the most severe conditions. Titanium has been used extensively in the urea process and was one of the original materials of construction in urea strippers. While titanium is successfully used in the urea process, materials limitations and related cost have driven engineers to look at other material options. Much current interest focuses on zirconium due to the metal’s unsurpassed performance in severe chemical processes. Zirconium components have not been retrofitted widely into existing urea process equipment because of the cost and technology associated with physically connecting new zirconium parts with the existing non-zirconium parts. Zirconium’s properties make joining it to other metals difficult, and standard joining methods typically will not produce a joint with properties adequate for service in severe environments. The perceived difficulty fabricating zirconium has been a contributing factor for limited adoption, causing designers to specify other metals to avoid the difficulty of the joint.

This new innovative technology for joining corrosion resistant metals has distinct, advantageous applications in urea production and could have the same advantages in other chemical processing applications. Zirconium can now be used in the most aggressive parts of a urea plant without replacing an entire process component, thus avoiding some difficulties that are currently encountered with some methodologies.





COMMON UREA PROCESSING CONDITIONS

Industrial urea production is accomplished at very high pressures and temperatures. In a typical urea process, carbon dioxide (CO₂) and ammonia (NH₃) are reacted under the conditions of 180ºC and 150 bar to produce ammonium carbamate (H₂NCOONH₄) as an intermediate product.

Snamprogetti utilizes the ammonia stripping process, depicted above. In the Snamprogetti process, excess NH₃ is used to strip NH₃ and CO₂ from the decomposition of unconverted ammonium carbamate. This process usually occurs in a “stripper”, a vertical falling film heat exchanger, at a temperature of approximately 205ºC and pressure of about 150 bar. The insides of the tubes in the stripper are generally considered to have the worst corrosion issues.

Ammonium carbamate is the primary corrosive species in this environment. Very few materials can withstand ammonium carbamate in these conditions.


REACTIVE METALS IN UREA PRODUCTION

Titanium and zirconium are both used extensively in the chemical process industry and have similar properties in many corrosive environments. They both tend to form adherent passive oxide layers that protect the bulk metal from further corrosion. This layer renders them highly corrosion resistant in most chemical media.

Another characteristic they share is that both are non-toxic and biocompatible. Their corrosion products are generally simple non-toxic oxides. This attribute is a distinct advantage when the product is sold to the agriculture industry. In a typical 2500 TPD urea plant, the total stripper surface area of the stainless steel tubes is approximately 870 m2. According to Dr. T.L. Yau, a corrosion rate of 50µm/y (2mpy) corresponds to over 0.87 kg (almost 2 lbs) of metal dissolving from stainless tubes each day.[2] This fact deserves serious consideration since many other common materials of construction contain metals, such as chromium and nickel, which would be undesirable contaminants in the urea process because the end product is used in fertilizer. It can be expected that maximum limits on metallic impurities contained in urea-based fertilizer products will continue to be lowered by both customer and legislative mandate.


Titanium

Titanium has been used extensively in the urea industry and has many attributes that allow it to provide good service life. Although titanium does resist direct corrosion by ammonium carbamate, its oxide layer is prone to erosion. This leads to localized erosion where high fluid velocities abrade the protective layer. This phenomenon causes the tubes to wear at predictable rates. While titanium is not very sensitive to the urea chemical environment, the erosion leads to a limited lifetime in service. Some plant operators have extended titanium stripper life by tearing down and rebuilding the stripper after several years of service.

In order to utilize titanium in a urea stripper, the titanium tubes must be welded to a suitable substrate. Titanium cannot be successfully welded directly to ferrous alloys; specifically, a weldment made by joining two dissimilar metals results in a joint that can be expected to exhibit poor mechanical and corrosion performance. To avoid a dissimilar metal weldment, the interior surfaces of the stripper’s upper and lower chambers and tubesheets are explosively clad with titanium. Cladding provides a titanium surface onto which the titanium tubes can be welded. A limitation in this configuration is that stainless steel cannot be used as the tubing material due to the incompatibility of the two metals during fusion welding. Previously, when re-tubing a titanium stripper, the choice of material has been limited to titanium, which historically has been subject to large swings in price and availability.


Zirconium

It is generally recognized that zirconium is an ideal candidate for urea service. It had been successfully implemented in acetic acid production and other extreme corrosive organic processes, showing virtually no corrosion. In non-urea applications, heat exchangers constructed of solid zirconium have exhibited virtually no corrosion, even after 25 years of chemical processing service.

In urea service, metal’s limited initial application was largely due to the perceived exotic nature of the metal by plant designers, end users, and fabricators; however, what these few applications proved was that zirconium could work effectively in urea service and should be considered as a potential material option for appropriate severe service equipment.

Zirconium has an added advantage in that its thermal conductivity is approximately twice that of titanium. This attribute allows equipment designed to the same specifications as titanium to operate at a higher efficiency.

One of the primary factors limiting the use of zirconium is the fact that it cannot be welded to other metals using standard techniques. The similarities in physical properties between zirconium and titanium might lead one to believe that they could be successfully fusion welded. The metals are completely miscible in each other and form a complete solid solution alloy series with no inter-metallic compounds or discrete phases. Indeed, a serviceable (although hard and brittle) weld can be made between zirconium and titanium.

Due primarily to the difference in lattice size of the respective oxides, the resultant alloys in the welded section suffer the somewhat non-intuitive consequence of being less corrosion resistant than either of the parent metals. This fact, coupled with the lower-ductility weld zone prevents fusion welding from being a commonly used method of joining the two reactive metals, especially in a highly corrosive environment.

Zirconium and ferrous alloys cannot be welded successfully by standard techniques because the physical and chemical properties are too different. The result of such a weld would be a conglomeration of brittle inter-metallic compounds and discrete phases of the two metals with no mechanical integrity.

As with titanium-to-titanium fusion welds, fusion welds of zirconium-to-zirconium make high quality joints when proper welding techniques are used.


STAINLESS STEEL: THE ORIGINAL WORKHORSE OF THE INDUSTRY

Stainless steels have a long history in urea service. Due to their relative affordability and widespread use throughout multiple industries, there are a large number of specialized alloys for specific applications and much work has been done on improving the performance of stainless steel for use in urea strippers. Most of this work focuses on two strategies: tightening the compositional limits on the stainless alloys used in the most aggressive parts of the plant and the introduction of passivation air into the process stream.

The performance of stainless steels in urea service has been found to be very sensitive to the chemical composition of the stainless steel being used. For this reason, Type 316L Urea Grade stainless steel was developed with extra-low carbon content and with the other elements very tightly controlled. Other alloys have also been developed with some success, including 25Cr-22Ni-2Mo and other proprietary materials. The tight chemical specifications in these steels reduce much of the performance variability by altering the concentration of elements that do not perform well in urea service.

The addition of passivation air to the process stream is necessary to protect stainless steel from rapid failure. For stainless steel in urea service, the chromium component forms an adherent oxide layer that protects the base metal from excessive corrosion. For this reason, it is necessary to ensure that the surface of the steel is continuously wetted by oxygenated process solution. If the conditions become reducing, the chromium oxide layer loses its effectiveness and corrosion may occur at a more accelerated rate.

Another related problem occurs when the oxygenated process solution leaks into a crevice. In this situation, the crevice sets up an environment that is no longer oxidizing enough to maintain the protective layer. Additionally, the use and application of passivation air is problematic. Compressors, pumps, and distribution systems must be installed to supply a steady stream of air at the correct rate. If any component should fail and interrupt the air supply, the plant equipment can experience severe and rapid corrosion.

Adding air to the process stream may also reduce the efficiency of the overall process by introducing an inert substance that must then be removed downstream. Any passivation air added to the urea process must be removed after stripping. This removal adds both process costs and hazards.
Even with these control measures in place, stainless steel still exhibits corrosion. Furthermore, using stainless steel puts an upper temperature constraint on plant operators of about 205ºC, reducing reaction rates, yields, and capacity.


Steel and Zirconium Bi-metallic Tubes

Bi-metallic tubing is a large-scale adoption of zirconium that uses stainless steel as the material of construction for the structural component of the tubes with a mechanically fitted interior liner of zirconium. This design is intended to put the most corrosion-resistant material on the inside of the tubes where the greatest potential for corrosion exists. It allows the stainless steel jacket to bear the structural load and gives fabricators a stainless steel outer layer of tube to weld into a stainless steel tubesheet. Bi-metallic strippers have been successfully employed at many urea plants and can be successfully utilized, given careful adherence to known operating conditions and limitations. However, even with close adherence to proper operating conditions, the tubes at the bottom of the stripper will continue to suffer corrosion related issues due to the high temperature associated with the process.

A more robust solution over the current bi-metallic design is desired to ensure a higher factor of safety with respect to materials design and performance. For example, because the upper and lower stripper chambers and the tubesheets, in a typical bi-metallic unit, are manufactured from solid un-clad stainless steel, passivation air is still needed to prevent rapid corrosion. Furthermore, the lack of a true bond between the zirconium and stainless steel may allow carbamate solution to penetrate between the zirconium liner and the stainless steel outer tube. As this penetration is localized and occurs outside the bulk fluid flow, a crevice environment is created in which the media is not thoroughly oxygenated. In such cases, the isolated fluid becomes very corrosive to the stainless steel and is often times in a location where detection is difficult.


THE CURRENT SITUATION

Currently, two of the dominant materials of construction in service in urea strippers are bi-metallic and titanium and, as we’ve discovered, both configurations have their respective advantages and disadvantages.

Titanium has a generally predictable life expectancy in urea service. Unit life is dictated by erosion generally observed inside the top part of the stripper tubes. To extend the life of titanium strippers, operators have rebuilt the unit half way through the unit’s service life, or physically turned the unit 180 degrees. Some operators have experienced operational issues with corrosion products, principally titanium oxide, being released into the urea plant downstream of the stripping process. Due to the current cost and availability of titanium, costs of major maintenance associated with re-building a stripper at mid-life, and other operational issues, other materials options are being evaluated.

Due to the limitations with bi-metallic and/or titanium, new tubing solutions are being evaluated to service numerous existing and planned urea plants.


OMEGABOND™ TUBING SOLUTIONS

ATI Wah Chang has been working on a new set of material solutions to address the problems previously enumerated. The result is a robust, novel approach that serves as a platform to put the optimal corrosion resistant material locations in the process where it is needed. At their core, these solutions provide high-integrity, repeatable metallurgical bonds between two different materials while avoiding the limitations of fusion welding. The metallurgical bond provides the necessary integrity and prevents the corrosive process solution from attacking vulnerable material. For example, this enables zirconium to be used as the tubing material in a titanium stripper without using problematic dissimilar-metal fusion welds. This new technology has the capability to greatly simplify stripper tubing retrofits while at the same time upgrading the metallurgy used in the stripper.

These new tubing solutions utilize solid-state joining technology where the interface between the two metals never reaches a molten state. By not allowing them to melt together, an alloy of the two does not form. Instead, the metals are plastically “forged” together at a temperature less than 50% of their melting points. The resultant joint has virtually no diffusion zone, no inter-metallic compounds, and no alloying. Likewise, the heat affected zone is negligible, if present at all.

The two primary solid-state joining technologies in use in this development are extrusion bonding and inertia welding. Due to the lack of a significant transition zone or diffusion layer in either, both create high integrity, repeatable bonds that are strong and ductile. Likewise, the corrosion resistance should be the same as the parent metal.


Extrusion Bonded Tube

The process of extrusion bonding entails several metallurgical process steps. The outer titanium billet is prepared with a large axial hole. The inner zirconium liner is prepared and fitted inside the titanium billet. The two are then assembled in a proprietary process that includes machining, cleaning, and assembly.

The billet is then extruded and a metallurgical bond is formed between the inner zirconium and the outer titanium. The extruded tube is then cold reduced in multiple steps and finished to the appropriate final size. The resultant extrusion-bonded tubing exhibits a seamless protective barrier on the titanium, and with a metallurgical bond, there is no opportunity for corrosive solution to leak between the joined metals.

Inertia Welded Tube

Inertia welding is a process also commonly known as friction welding. It consists of spinning one of the two pieces to be joined at a pre-determined speed. The other piece is held in a fixed mandrel. Just prior to pressing the parts together, the drive is disconnected from the flywheel of the rotating part. As the parts are pressed together, the rotational inertia is converted to heat. The interface of the two parts is locally heated to about 80 percent of the melting point and the axial force applied forges the parts together. In the immediate joint, the two metals plastically deform, swirling and mixing. As this happens, the soft metal at the interface is forged out of the joint, forming a flash of material that must be removed. Since this joining occurs below the melting point and for a very short period of time, there is no alloying of the metals.

The frictional heating that occurs is highly localized and dissipates quickly. The adjacent metal has no heat affected zone, and thus the corrosion properties of the metal adjacent to the joint are virtually the same as the parent metal. One notable characteristic of this type of weld is that it is highly repeatable. Once the parameters of surface condition, rotational speed, and axial force are determined, there is very little variability in the quality of weld between individual specimens.

OmegaBond™ Advanced Tubing Solutions Urea Applications

Using these two primary enabling technologies, ATI Wah Chang and Snamprogetti envision two potential configurations for retrofitting existing titanium strippers or constructing new titanium units.

The first configuration consists of using a solid zirconium tube with extrusion bonded tubes that are inertia welded onto either end (see Figure 7). This configuration provides a sound titanium outer surface for direct fusion welding onto the titanium clad tubesheet, together with the protection of solid zirconium for the length of the tube.

The second configuration consists of a solid zirconium tube with solid titanium tube inertia welded onto the ends (see Figure 8). This also gives a solid titanium substrate that can be welded directly into the titanium clad tubesheet. In practice, the inertia weld could be located inside the tubesheet, outside of the hottest part of the stripper. The ferrule that fits into the top of the tube could be modified to protect the titanium end and the inertia weld from erosion resulting from the high velocity fluid in that region of the tube.

In addition to these configurations, ATI Wah Chang is also capable of manufacturing long lengths of extrusion bonded zirconium and titanium products with or with out the inertia welded solutions.






MECHANICAL AND CORROSION PROPERTIES OF NEW TUBE SOLUTIONS

Testing and evaluation of the mechanical and corrosion properties of these new tubes is ongoing. There are currently samples being evaluated through field trials in operating strippers. Currently, all materials in urea service appear to perform as expected.

Extensive testing and prototype manufacturing is underway. Preliminary test results are summarized in Figures 10-12.

These graphs indicate that the strength of the inertia weld bond is very comparable to fusion welds. All mechanical test specimens ruptured in the base metal NOT in the weldment.

ADVANTAGES AND APPLICATIONS OF OMEGABOND™ TECHNOLOGY

As detailed in the graphs, the new tubing solutions offer direct and indirect benefits to urea producers. The direct benefits involve the enhanced performance of the urea stripper due to improvements in materials technology and unit design. The indirect benefits include expected improvement in urea plant operating maintenance, operating cost reduction, and improved return on capital investment.

The new products will effectively facilitate the use of a reactive metals solution that is expected to resist corrosion and erosion in the most severe urea service by incorporating metallurgical bonding technologies that eliminate the potential of process fluid penetrating and damaging process tubing. The new solutions can be retrofitted or fabricated by conventional methods into existing titanium-clad or newly-constructed urea strippers.

These new products will also enable urea plants to run at higher efficiency with less downtime. Due to the design of these advanced solutions and the elimination of stainless steel, the use of additional passivation air in the stripper can also be eliminated. The cost of maintaining associated compressor systems and air removal after stripping will result in energy, labor, and other unit cost savings. The improvements in stripper technology will likely allow units to be operated at a higher temperature, which may enhance the stripping reaction. Most importantly, the new materials technology will address maintenance events witnessed by some urea producers. The cost of unit downtime can be significant; for example a 2,000 ton per day plant supplying urea at $250 USD per ton incurs an opportunity cost in excess of $500,000 USD for each day of unscheduled downtime.


REFERENCES

Why are more and more process industries specifying fewer commonly known alloys? Traditionally alloys like 316 stainless steel, C-2000, C276, B-3 nickel alloys and titanium alloys have been used in the process industry applications. What are they specifying in place of these materials?

Many are choosing zirconium alloys instead of nickel and titanium alloys because of the relative cost, performance and availability for certain end use applications.

Over the past few years, the cost of energy, labor and raw materials (i.e. nickel, chromium and molybdenum) has risen significantly. The rising cost of the raw materials can also be directly related to greater demand in the market place. The expansion of the Chinese and Indian economies is also cited as a primary driver behind the global supplies of raw material and energy being lower.

When considering the supply of titanium, it is prudent to note that aerospace and military applications are leading the demand, which consequently depletes the supply, leaving less titanium for use in other applications and increasing the deliverability times.

Zirconium is currently being used more and more due to its lower price, improved performance and faster deliverability. In many cases, zirconium may cost less, be more readily available than alternative alloys, and have superior performance in many corrosive process environments.

How have zirconium prices been so stable over the years, when other corrosion resistant alloys costs have skyrocketed? One reason can be attributed to the fact that zircon sand, the raw material zirconium is made from, is not in short supply. Another factor is that zirconium is not traded on any metal exchange and is therefore not subject to speculation. Because the amount of zirconium produced is small relative to the nickel and titanium based alloys it manages to avoid the metal exchanges.

The confluence of these factors: global economic growth, increased raw material costs, increased energy costs and the method in which the raw materials are bought and sold, has come together to produce an environment where zirconium alloy applications may cost less than nickel and titanium based corrosion resistant alloys.

For more detailed information about corrosion resistant zirconium products, contact Wah Chang at 541-967-6977.

The switch is on!

ATI Wah Chang is pleased to announce that Mr. Jack Tosdale was recently selected by the ASTM as a recipient of the 2006 Award of Merit. Established in 1949 by the ASTM Board of Directors, the Award of Merit is the highest society award granted to an individual member for distinguished service and outstanding participation in ASTM committee activities. Mr. Tosdale was recognized for his dedicated service to the ASTM B10 Committee on Reactive and Refractory Metals and Alloys and for his service to the F04 Committee on Medical and Surgical Materials and Devices. Over the last 16 years, he has also contributed to numerous other ASTM committees, subcommittees and task groups relating to metallurgical materials and issues.

Mr. Tosdale has been with Wah Chang for over 25 years and has leveraged his extensive background in Metallurgical Engineering to make numerous contributions in the areas of metallurgy, material failure analysis, corrosion engineering, process analysis and manufacturing statistics, and process development. Mr. Tosdale’s dedication and commitment to Wah Chang and organizations like ASTM make him a valuable resource for the betterment of our customers and the metallurgical community.

Mr. Tosdale can be reached at 541-926-4211 x6777 or jack.tosdale@wahchang.com.

Rick Sutherlin, Manager of Technical Services for Wah Chang, was recently recognized by the Fabricator’s & Manufacturers Association (FMA) and the Tube & Pipe Association (TPA) at the FMA & TPA 35th Annual Banquet. Mr. Sutherlin received the TPA Publication Award for Best Technical Article, “Welding Zirconium and Zirconium Alloys”, a three part series that was published in the Tube & Pipe Journal in 2005. The article addresses various issues related to welding zirconium including: metallurgy, weld preparation, shielding techniques, welding techniques and additional methods of joining refractory metals.

Mr. Sutherlin’s knowledge and expertise with corrosion resistant metals spans over 30 years starting with a degree in Metallurgical Engineering. Since 1977, Mr. Sutherlin has made countless contributions to Wah Chang in the areas of applications engineering, failure analysis, corrosion testing and research, fabrication and welding. More notably, his experience has brought educational credibility to Wah Chang in the form of an International Corrosion Conference where industry professionals from around the world gather to share ideas and gain knowledge on corrosion-related issues.

To receive a copy of “Welding Zirconium and Zirconium Alloys”, please contact Rick Sutherlin at rick.sutherlin@wahchang.com or by phone at 541-967-6942.

ASME Code Case 2503 allows use of an economical, high strength, lean duplex stainless steel alloy, AL 2003™ alloy (United States Patent Number 6,623,569, granted September 23, 2003) in ASME pressure vessel construction. High strength, good weldability, formability, and ductility make this alloy a desirable choice for pressure vessel construction.


BACKGROUND

The lower alloy content of AL 2003 alloy (20% Cr, 3.5% Ni, 1.7% Mo, 0.17% N, balance Fe) makes it a lower cost alternative to austenitic Type 316L and duplex 2205 alloys. When heat-treated properly, the balanced composition of AL 2003 alloy produces a microstructure that consists of nearly equal proportions of the austenite and ferrite phases. The microstructure and composition of the AL 2003 alloy provide stress-corrosion cracking resistance that is superior to that of Types 316 or 317, and a yield strength that is more than double that of conventional austenitic stainless steels.

With reduced levels of Cr and Mo, the AL 2003 alloy is more resistant than AL 2205™ material to detrimental phases such as sigma. The AL 2003 alloy was created for use in environments where resistance to general corrosion and chloride stress corrosion cracking is important.


ASME CODE CASE 2503 (UNS S32003)

ASME Code Case 2503 was approved by the Board on Pressure Technology Codes and Standards on January 19, 2006. The Section VIII Division 1 Code Case has the potential to reduce the cost of equipment fabricated from AL 2003 alloy, compared to 316L or 317L austenitic stainless steel and S31803 austenitic-ferritic stainless steel.

The composition and mechanical properties of AL 2003 alloy are shown in Tables 1 and 2. The Code Case includes allowable stresses for plate, sheet, strip, tube and pipe. The maximum allowable stress values allowed in the case are shown in Table 4a and 4b and plotted graphically along with corresponding values for S31803 duplex and S31603 austenitic stainless steels in Figure 1. Design Allowable Stresses for AL 2003 alloy per Code Case 2503 are more than 50% higher than for S31603 at most temperatures.







Code Case 2503 material was assigned to External Pressure Chart HA-5 of Section II, Part D, the same as is used for most other austenitic-ferritic stainless steels. All other rules for Section VIII, Division 1 applicable to austenitic-ferritic stainless steels must be met.

To use the case, Code Case 2503 must be referenced in the documentation and marking of the material and must be shown on the Manufacturer’s Data Report. Thus, AL 2003 material for pressure vessel applications should be ordered to the requirements of Code Case 2503.


HIGHER ALLOWABLE DESIGN TEMPERATURE

The 650ºF (343ºC) limit on the maximum design temperature is as high as or higher than other duplex stainless steels. This is based on improved resistance of AL 2003 alloy to embrittlement at elevated temperatures, compared to S31803 and other higher-alloy duplex materials. Allowable stresses for the material were based on new elevated temperature tests conducted to 1000ºF (538ºC) by ATI Allegheny Ludlum.


WELDING FILLER METAL

Code Case 2503 requires separate welding qualifications. It is expected that AL 2003 alloy will eventually be assigned to the P-10H group along with S31803 and other widely-used austenitic-ferritic stainless steels. AWS E2209 (Shielded Electrodes), and ER2209 (Bare Electrodes) over-matching filler metal, developed for use with S31803, provide readily available filler metals for welding AL 2003 alloy. These are listed in AWS A5.5-96 and A5.9-93 (ASME SFA-5.5 and SFA-5.9), respectively. These fillers provide matching strength and over-matching corrosion resistance.


UNS NUMBERS AND ASTM SPECIFICATIONS

AL 2003 alloy has been assigned. UNS Number S32003. UNS S32003 is covered by ASTM specifications for several wrought products, as listed in Table 3.








CORROSION PERFORMANCE

AL 2003 alloy exhibits corrosion performance superior to Type 317L stainless steel in many environments. The critical pitting temperature (CPT) of AL 2003 alloy is 20ºC higher than that of type 316L stainless steel and a few degrees above type 317L as measured in the ASTM G 150 test. The high resistance of AL 2003 alloy to chloride stress-corrosion cracking (SCC) is shown in Table 5.




OTHER APPLICATIONS FOR AL 2003 ALLOY

S32003 alloy has been certified as an acceptable material for use in drinking water treatment and distribution systems by NSF International in Appendix C of NSF/ANSI Standard 61:2005.


PRE-PUBLICATION COPY OF CODE CASE 2503 AVAILABLE FROM ATI ALLEGHENY LUDLUM

Code Case 2503 will be published by American Society for Mechanical Engineers, Boiler and Pressure Vessel Code, Three Park Avenue, New York, New York 10016-5990 in Supplement 9 to the 2004 Code Cases. In the interim, a copy of the Code Case and an authorizing letter from ASME are available from ATI Allegheny Ludlum.

For more information about AL 2003 alloy for pressure vessel applications, contact Dr. Dave Bergstrom at dbergstrom@alleghenyludlum.com or reach him by phone at 724-226-6417.

NANCY BEAUDRY

Nancy Beaudry recently accepted a Project Coordinator position with the Business Development Department at Wah Chang. After receiving her B.S. in Chemical Engineering from Iowa State University, Nancy went to work for both Monsanto Enviro-Chem, Inc. and Monsanto Corporate, as a technical service representative. During her time at Monsanto Nancy also took on various plant engineering positions. Since that time, Nancy has also gained a wealth of experience in the areas of sales, marketing and project management.

As a Project Coordinator, Nancy will primarily be focusing her efforts in projects that involve chemical processes and medical applications. She will also be heavily involved in the management and evaluation of new business development initiatives at Wah Chang.

“Nancy’s background in chemical engineering and experience with Monsanto make her an ideal candidate for working on projects involving chemical processes”, says Andy Nichols, Director of Marketing. “We are pleased that Nancy elected to join Wah Chang, and we look forward to having her as a part of our team.”

Ms. Beaudry can be reached by phone at 541-926-4211 x6711 or by e-mail at nancy.beaudry@wahchang.com.