BASF has signed an exclusive cooperation agreement with the British-Canadian company Intelligent Engineering Ltd. (IE) for further development of the innovative Sandwich Plate System™ (SPS). The SPS technology, jointly developed by BASF Group company Elastogran and IE, is rapidly becoming established in the shipbuilding industry for the repair and construction of ship segments. New SPS applications for the civil engineering market are now being developed and a SPS licensee has already completed an initial reference project with the construction of a road bridge in Canada.

“We responded to the needs of our customers in the construction industry,” said Dr. John Feldmann, member of the Board of Executive Directors of BASF Aktiengesellschaft, when asked to explain the background to the new application for the high-tech material. “Our intention was to develop a genuine alternative to conventional steel bridge construction that would be more cost-effective and of the highest quality. We achieved precisely that with SPS.”

Because of their sandwich structure – steel-polyurethane-steel – SPS components are much less susceptible to corrosion than conventional constructions. SPS structures are also lighter and faster to build and also offer built-in protection against fire and vibration. In the case of the road bridge, built by SPS licensee Canam Manac Group Inc., in Saint Martin de Beauce, Quebec, Canada, SPS reduced the weight of the 22 meter bridge deck by 60 percent compared with concrete. And there are no negative effects on the stability of the bridge construction – on the contrary. “Our SPS polyurethane is extremely stable and does not become brittle with age. This makes SPS structures more durable than conventional solutions,” said Georg Knoblauch, who is in charge of SPS technology development at Elastogran.

This reference project in Canada opens up a second high-growth SPS market for BASF and IE. A number of bridge projects are currently under development around the world. For example, ThyssenKrupp Technologies, a SPS licensee, is currently evaluating the feasibility of the system for the construction of mobile bridge elements suitable for use at roadwork sites. SPS elements for this application are currently being subjected to repetitive stress testing at BASF’s laboratories in Ludwigshafen. The Steel Construction Department of the Aachen University of Technology (RWTH) is monitoring the test process as an independent scientific institution.

Elastogran and Intelligent Engineering are also collaborating on other applications where the outstanding material properties of the patented technology can be utilized. For instance, SPS offers many potential benefits for the construction of sports stadiums and arenas. “SPS bleachers or stands are 70 percent lighter than conventional concrete structures and are very effective at absorbing the vibrations induced when thousands of fans jump to their feet to celebrate a goal,” explained Knoblauch. This weight saving may also help in the design of earthquake-resistant buildings.

BASF is a world leader in technology for polyurethane specialties. The Elastogran Group is responsible for BASF’s polyurethanes business in Europe. BASF and Elastogran expect increasing SPS applications to result in substantial growth in the global market for polyurethane specialties. Polyurethanes are versatile plastics with a huge range of applications and their properties can be customized to suit individual uses. Polyurethane products are used in the automotive industry, for thermal insulation in construction and refrigeration technology, in the electronics industry, in the manufacture of shoes and furniture as well as in sports and leisure articles.

Background

Quench tempered steel linings in six cyclones at a Canadian cement plant required patching at an annual cost of $60,000 to $80,000, nearly half of which was allocated to material costs.

According to maintenance supervisor Joe Sato of Canada Cement Lafarge’s Exshaw, Alberta, facility, abrasive limestone and shale clinker up to ½-in. diam were wearing holes through the pre-cleaning cyclone’s surface, and were causing leaks.

Because of disappointing results with quench tempered steel as the patching material, Canada Cement Lafarge ordered a lining material made of fused cast basalt, which is resistant to the abrasive effects of clinker and can withstand the cyclone’s 250°C (480°F) environment. The material has a Mohs rating of 8-8.5 (a diamond is 10).
Fused Cast Basalt Custom Shapes

Custom-shaped tiles of the fused cast basalt were set in a mastic mortar inside the six cyclones, each over 36 ft tall and 10 ft diam.
Installation And Attachment

Installation of the ceiling tiles by a seven-man construction crew involved fusing a metal bar into the back of each tile and then welding the bar to the cyclone’s inner surface. This attachment method was used to completely isolate the support system from abrasion.

The method also was used because of weight and gravity considerations to produce a more secure hold on the ceiling’s surface as opposed to using adhesives only.
Downtime and Cost Recovery

“Since the installation in early 1986,” said Sato, “there has been no downtime at any of the six cyclones, and company officials are considering lining eight other cyclones in the same way this year.” Estimated life for the basalt linings is 20 years, with a manufacturer claimed cost recovery period of about four years.

During installation of the basalt linings, workers discovered that the lowest section of the cone bottom had been lined with the same cast basalt material by the original cyclone supplier before being put into service around 1980.

Typically, abrasive effects are the worst here, but there had been no downtime with that portion of the system, so that company officials were assured of the new lining’s future performance.

American Utility Metals are the premier distributor of Cromgard, the Utility grade Stainless Steel in the Americas. Providing our customers with the product they need, at the lowest possible cost to the satisfaction of our customers.

American Utility Metals is built upon a solid foundation of its people. The management of company is dedicated, knowledgeable and enthusiastic towards providing our customers with a high quality product that improves efficiencies and lowering costs.

The company is certified to ISO 9001:2000 standards, an international quality certification. With this certification in 2004, American Utility Metals is among 1% of metal centers in the United States that is ISO 9001:2000 certified.

Our headquarters are located next to the Mississippi River in Baton Rouge, Louisiana. Also with a sales office in Colorado Springs, and stock locations and facilities in Akron, Baltimore, Atlanta, Miami, and the San Francisco Bay Area, we can respond to our customer's demands with speed and efficiency.

Technical and multilingual commercial support is available to customers and potential users of Utility Stainless Steel across the continent.

At American Utility Metals we are focused on a single product - Utility Stainless Steel - offering many advantages to a wide range of industries. Our application expertise is extensive and we can provide technical assistance to help you make the most of Utility Stainless Steel's benefits whether this means design, welding and fabrication, materials handling, training or post production support.

Utility Stainless Steel is a 12% Chromium ferritic stainless steel. It is a low cost utility stainless steel, which meets ASTM A240-UNS-S41003. It also conforms to the European grade 1.4003, included in European specification EN 10088.

Scientists at the University of Virginia have announced the discovery of a non-magnetic amorphous material that is three times stronger than conventional steel and has superior anti-corrosion properties. A future variation of the new material, called DARVA-Glass 101, could be used for making ship hulls, lighter automobiles, tall buildings, corrosion-resistant coatings, surgical instruments and recreational equipment. The scientists say commercial use of the material could be available within three to five years.

The material, made up of steel alloys that possess a randomised arrangement of atoms -- thus “amorphous steel” -- was discovered by modifying an earlier version of amorphous steel known as DARVA-Glass 1 reported by the U.Va. researchers at the Fall 2002 meeting of the Materials Research Society. In May of this year they reported on DARVA-Glass 101 in the Journal of Materials Research.

“Amorphous steels can potentially revolutionise the steel industry,” said Joseph Poon, professor of physics at U.Va. and principal investigator for the team that has discovered the material and is now making alterations of it for possible future use in mass production.

Poon’s U.Va. co-investigators are Gary Shiflet, professor of materials science and engineering, and Vijayabarathi Ponnambalam, materials physicist. Their amorphous steel project at U.Va is sponsored by the Defense Advanced Research Projects Agency’s Structural Amorphous Metals Program.

According to Poon, researchers have been trying for years to make amorphous steel in sizes large enough to have practical use. The U.Va researchers have succeeded in producing large-size amorphous steel samples that can be further scaled up. They achieve this by adding a small dose of a rare earth element or yttrium to DARVA-Glass 1. The researchers believe that the large size rare earth or yttrium atom causes destabilisation of the competing crystal structure wherein the significant atomic level stress can lead to the formation of the amorphous structure. These discoveries make the U.Va. researchers optimistic that the material will be economically available within the decade.

In a separate work, a group led by C.T. Liu, a materials scientist at the Oak Ridge National Laboratory in Tennessee, has also reported on large size amorphous steel similar to DARVA-Glass 101 in the June issue of Physical Review Letters, also by modifying the DARVA-Glass 1 discovered by the U.Va scientists.

Poon said the amorphous steel is extremely strong, but brittle in its current state. “We need to toughen the material more,” he said. “We can always make it better.”

According to the U.Va. researchers, amorphous steel can be machined as well as manipulated like a plastic. “It can be squeezed, compressed, flattened and shaped.” Poon said.

The material is of particular interest to the Navy for making non-magnetic ship hulls, particularly for submarines, which are detectable by the magnetic field of their hulls. The amorphous steel that the U.Va. team is refining is non-magnetic, potentially making a ship invisible to magnetism detectors and mines that are detonated by magnetic fields. The new material also may be useful for producing lighter but harder armour-piercing projectiles. The publicly traded company Liquidmetal Technologies owns an exclusive license to the amorphous steel invented by the U.Va. scientists.

Other possible uses include recreational equipment such as tennis racquets, golf clubs and bicycles as well as electronic devices.

Background

Tampa Electric Company (TEC), Tampa, Florida, is no stranger to ash line maintenance. Its Big Bend Station, located 15 miles south of Tampa in Apollo Beach and its Gannon Station, located just 10 miles north of Big Bend on Tampa Bay, are both coal-fired power plants. Thousands of feet of pipe snake through the plants, conveying the abrasive bottom and fly ash created by the burning of the coal. Big Bend Station with a 1755 MW capacity is TEC's newest and largest power plant. It provides more than half of the company's total generating capability. The Station burns approximately 14,000 tons of bituminous Kentucky coal every day.

Big Bend Units One, Two and Three with a combined capacity of 1285 MW, burn low sulfur coal. Big Bend Four with a 470 MW capacity burns standard sulfur coal and is equipped with a flue gas desulfurization system (FGD) or "scrubber" to remove the sulfur, one of the first to be designed and installed in the United States to produce commercial grade gypsum as a by-product.
Transporting Abrasive Materials

Built between 1957 and 1967, Gannon Station has six service units and a capacity of 1230 MW. It burns low sulfur coal. At both plants, the company had experienced problems with hardened steel and cast iron slag sluice lines. The hardened steel lines lasted an average of eight to 18 months; the cast iron sections often had to be changed or rotated every four to six months.

Mike Zsuffa, a technician at TEC, said, "We tried a little bit of everything. Mild steel and fiberglass. Slag is just very, very abrasive."
Pipe Abrasion Testing

In the late 1970s, plans to build Big Bend Four and conversion plans at Gannon Station provided TEC with an opportunity to solve its persistent pipeline abrasion problems. TEC engineering set up an on-site test to determine what type of pipe could withstand the abrasive ash. Several pipe manufacturers were invited to submit samples for testing.

Eight manufacturers of PVC pipe, unlined fiberglass pipe, fiberglass pipe lined with ceramic tile, carbon steel, cast iron, basalt lined pipe and ceramic component pipe submitted samples. To ensure fairness, the test pipe was installed in similar locations and in areas where wear was usually most severe.
ABRESIST Basalt Lined Pipe

Some of the test pipe failed in minutes, some in hours. Others lasted months and longer. A basalt-lined pipe manufactured by Abresist Corporation, Urbana, Indiana, was among the pipes that lasted the longest and was still in service where it was tested until it was replaced in 1990. Commenting on the results, Rex Morgado, Tampa Electric Engineering Technician, said, "The amount of wear was significant in all the others, but not ABRESIST®."
Cost Evaluations

TEC officials reviewed the results and talked with another utility that used the basalt lined pipe. After factoring in cost evaluations and a ten-year warranty from Abresist, they chose to install the basalt lined pipe.

The ten-year warranty was twice the normal usually given. Abresist asked only that they be allowed to inspect the pipe at five and ten year intervals.
Installation

Two, mile long, ten-inch basalt pipelines were installed at Big Bend. One pipeline conveys bottom ash; the other line conveys fly ash. Jetpulsion™ power drives the ash and water through the pipe at a velocity of eight to 12' per second. Big Bend is a closed loop system so the water from the slurry is run through weirs to retention ponds for reuse.
Pipeline Conversion

At the same time TEC was building Big Bend Four, they were converting some of the units at Gannon Station to coal-fired units. Initially, all six units burned coal. During the 1970s, four of the units had been converted to oil-fired to meet environmental requirements. The other two units had continued to burn low-sulfur coal.

In the early 1980s as oil prices began to rise, TEC reconverted the oil burning units to coal burning units that used low-sulfur coal.

During the conversion, TEC installed approximately 1200' of 8" ABRESIST basalt lined pipe to convey bottom ash slurry from Gannon One, Two, Three and Four to dewatering bins. Over ten million gallons of saltwater and bottom ash slurry are moved through the pipe at 110 psi by high pressure saltwater pumps.
Long Term Results

Over the long haul, how did the basalt lined pipe withstand the abrasion?
5 Year Results

In 1989, at the five-year warranty inspection at Big Bend and Gannon, the straight pipe showed little to no wear. At elbows and turns, where the flow direction changes and wear is usually most severe, there was only an 3.18mm (1/8") of wear or less. ABRESIST elbow lining is 30mm (1.18") thick while standard straight pipe is 22.3mm (7/8"). In some places, the swirl pattern from the original manufacturing process was still evident.
10 Year Results

At the ten-year inspection in July 1994 at Big Bend Four, the basalt pipe once again showed little wear, even in the elbows. Some of the original glazing was even still visible.

During the ten-year inspection at Gannon Units One, Two and Four showed some wear, about 4mm (.158") was observed near the pipe ends. The rest of the pipe showed little wear.

At Gannon Unit Three, one 90 degree elbow exhibited more wear, about 8-10mm (.316" to .394"). This same elbow was inspected at the five-year mark.

Morgado was on hand at both the five- and ten-year warranty inspection. He said, "Even though the wear was atypical, there was not much difference between the five- and ten-year inspections with this elbow."
Maintenance Cost Savings

Commenting on the warranty inspections, Morgado said, "The pipe didn't need to be turned at the five-year inspection and this time (at the ten-year inspection) it didn't need to be turned either. The basalt lined pipe has saved ten years of yearly maintenance and related costs."

Due to the excellent performance of the basalt lined pipe, TEC subsequently installed ABRESIST pipe in Gannon Five and Six and Big Bend One, Two and Three. Morgado said, "Based on previous experience with the basalt pipe, we installed ABRESIST to convey all of the bottom ash at Gannon."

Background

ABRESIST® basalt lined steel pipe used to convey abrasive bottom ash at American Electric Power's Gavin Plant consists of 12 lines of 10" and 12" ID ABRESIST pipe. Older ABRESIST pipe, still serviceable after almost 20 years of use, was interspersed with the new ABRESIST pipe.
Coal Fired Electricity Generating Plant

American Electric Power's (AEP) Gavin Power Plant located on the Ohio River in Cheshire, OH is the largest electricity generating station in Ohio.

Built in 1973 with operation beginning in 1974, the plant has a generating capacity of 2.6 million kilowatts and consists of two-1.3 million kilowatt units. Energy created by the power plant is pumped into a grid which supplies power to a seven state area.

The coal fired plant burns about 20,000 tons of coal daily or 6 million tons of coal annually when both units are functioning. The bituminous coal burned by the plant has an ash content of 19%. With a consistency of coarse sand, the bottom ash is extremely abrasive.
Abrasion Resistant Basalt Lined Pipe

In 1973, ABRESIST basalt lined pipe and elbows were installed during initial construction. The straight sections of pipe had a 7/8" thick basalt lining. The elbows had an 11/8" wall.
Low Levels Of Pipe Wear

When AEP installed scrubbers at the plant recently, the bottom ash pipe had to be moved to make room for the new equipment. As workers removed the original basalt pipe they discovered that much of it had withstood 19 years of erosion associated with bottom ash and was reusable.

The straight sections placed in 1973 showed only 20% wear. The original elbows received more abrasion from the change in flow direction and showed more wear. The basalt lined pipe has handled all of the plant's bottom ash since its construction and is still use.
Durability and Pricing

According to AEP officials, the durability of the basalt lined pipe coupled with Abresist's competitive pricing were deciding factors in deciding to go with Abresist again. For the new construction, workers laid 4000' of 10" pipe and 2500' of 12" basalt lined steel pipe. The original basalt lined pipe was interspersed with the new pipe. Any pipe not reused was stockpiled for future use.

The new 10" and 12" pipe came in 18' sections and was epoxy coated. Like the original pipe, the straight sections had 7/8" basalt lining; the elbows had 1-1/8" lining.

Background

Blue Circle’s Sparrows Point, MD. plant has been using a basalt-lined pipe for handling abrasive blast furnace slag for 17 years without needing to replace it.
Basalt Lined Pipe Key to Problem Solving

Granulated blast furnace slag is extremely abrasive. Moving the granulated slag slurry wears pipes and elbows, resulting in downtime and higher maintenance costs. Blue Circle Cement’s Sparrows Point, MD. facility is well aware of the problems that moving this abrasive material can cause. The company produces about 850,000 tons of slag cement annually.

A water granulating/grinding operation that turns slag left over from the production of iron into slag cement, the Blue Circle plant is the first and oldest of its kind to be built in the United States. It is the largest producer of the granulated blast furnace slag in one location in the country, producing 2,850 tpd of slag cement.
NewCem Slag Cement

The slag cement produced by Blue Circle is called NewCem. Used as a Portland Cement additive, NewCem can replace as much as 70% of Portland cement in concrete mixes. The proportion is based on the specific job requirement, and the conditions and desired characteristics of the concrete. NewCem provides specific concrete properties such as improved workability; permeability; resistance to sulfates and chlorides; and resistance to alkali-silica reaction.

It has a greater strength potential and produces a lighter color product, say its makers. Used in numerous general construction applications, NewCem is preferred by many engineers and concrete suppliers who produce high-performance concrete. The product meets ASTM 0-989, Grade 120, and AASHTO M-302 standard specifications of ground granulated blast-furnace slag for use in concrete and mortars. In the last decade, NewCem has been used in an estimated 40 million cu yd of concrete.

The slag cement production plant at Sparrows Point was designed specifically to handle slag produced by Bethlehem Steel’s huge “L” blast furnace and went online in March 1981. One of the largest producing blast furnaces in the western hemisphere, the “L” furnace produces about 8,000 tpd of iron. The furnace runs continuously 365 days a year. To keep pace with the furnace. Blue Circle also runs 24 hours a day, three shifts a day. The Blue Circle plant and the steel mill plant are located near each other on the Chesapeake Bay.

Prior to the construction of the Sparrows Point plant, some of the slag produced by the steel mill was used as a fill material, but the majority of the slag was considered unusable waste material. Today, using the water granulation system Blue Circle consistently converts all of the “L” furnace slag into the high quality slag that is used to make cement.
Blown Pipe, Worn Elbows and Other Problems

Engineers who designed the Blue Circle slag cement plant wanted to avoid blown pipe, worn elbows, and other problems that might result in downtime and high maintenance costs. They were well aware of the problems associated with moving the high volume of slag produced by the blast furnace.

The slag, composed of a chemical combination of lime, silica, alumina, and magnesia, is extremely abrasive. It would take a special type of product to handle the high volume and the harsh nature of the slag.

Engineers found the answer in a basalt lined pipe manufactured by Abresist Corp., Urbana, Ind. They specified 19-in.-diam Abresist pipe for the new plant and eliminated many of the problems caused by the harsh slag.

Approximately 2,000 ft of the basalt lined pipe is used to move the slag through the processing system. For nearly two decades, the basalt-lined pipe withstood the abrasion from the slag and still does not need to be replaced. In addition to the pipe.

Blue Circle also lined its agitation tanks with the basalt. It was installed in the tanks in 1989 and did not need to be reworked for a decade.
Converting Iron/Slag To NewCem

The production of slag cement at Blue Circle begins after the blast furnace finishes producing iron. During iron production the iron/slag mixture is drawn from the blast furnace at four tap holes - two located on the east side of the furnace, two on the west. Only one hole per side may be opened at any one time, and they are alternated every 28 days. The molten iron has a greater density than that of the slag and is drawn off using a dam structure as it flows from the tap hole down a runner in the cast house floor.

The molten iron is collected for further processing while the molten slag flows over the dam, down the hot runner, and out of the furnace building.
Molten Slag Conversion

At this point. Blue Circle takes over and the conversion of molten slag into cement begins. The granulating system was constructed as close to the blast furnace as possible to ensure a good flowing product. As molten slag cools, its viscosity increases, making it more difficult to granulate. All pipe used to convey the abrasive slag is lined with Abresist basalt wear-resistant linings.

Blue Circle maintains four hot runners and four blow boxes. The molten slag flows from the furnace at 3 to io tons per minute to the blow boxes. Based on the condition of the molten slag, it is diverted to a pit for air-cooling or is granulated.

The hot runner channels the molten slag into the blow box. Here the molten slag is quenched under high-volume water sprays. A water/slag ratio of 10 to 1 is maintained to assure rapid quenching. The shock cooling instantly vitrifies the molten slag into a glassy sand-like material that has a glass content of 95% to 98%. The slag is monitored to ensure that no iron carryover enters the blow box.

If molten iron is detected, it is diverted to the pit before quenching to prevent explosions.
Refractory Lined Steel Runners

From here, the granulated slag and water slurry flows from the blow box to agitation tanks in steel, refractory-lined channels called the cold runners. Blue Circle has two cold runners and two agitation tanks on each side of the furnace. Each agitation tank is serviced by two 15,000-gpm slurry pumps.

The slurry enters the agitation tank tangentially, inducing a swirling action while more slurry is added. The agitation keeps the slag suspended in the slurry so it can be easily pumped from the furnace area via 1,000-hp hydraulic variable-speed pumps to one of five filter beds on site. The system is designed to ensure that a constant level of slurry is maintained in the agitation tank.

From the agitation tank, the slurry line, which is lined with Abresist basalt lining, empties into the distribution box. The distribution box constructed with a ceramic tiled lining and a series of gates allows the operator to select which filterbed receives the slurry. Blue Circle has five 2,58o-cu-ft capacity filter beds. In the filterbeds, a gravel filter is used to separate the slag from the water.
Grinding Plant Processing

A series of drainage pipes collects the process water and channels it from the filterbed leaving the slag granules behind. The process water returns through three collector pipes to the main collection pipe. The granulated slag from the filterbeds is removed by a bridge crane and transported via conveyor to the storage silos. From there, the raw slag goes to the grinding plant for processing.

During the grinding operation, fineness is closely controlled on an hourly basis to ensure that the hydraulic activity of the slag is uniform and exceeds the stringent strength requirements of ASTM-C-989 specifications.

After grinding, NewCem is stored in two 20,000-ton-capacity silos. From there, the product is distributed along the eastern seaboard to construction industry customers. It is shipped via truck, rail and class A ocean barges to markets as far north as Boston, Mass., and as far south as Jacksonville, Fla.
17 Years And Still Going

In 1999, Bethlehem Steel shut the Sparrows Point steel mill plant down to reline its “L” blast furnace and relocate the slag runners.

Because of the changes at the steel mill pipe almost two decade sold was replaced. The rest was still in good condition.

Bill Sanders, Blue Circle’s operational maintenance coordinator, said, “Much of the pipe was good. But we replaced it anyway. Especially in the areas that might cause us problems in the future if they would blow during operation. We replaced the pipe in the critical areas that are hard to get to and that take the most pounding. The pipe was not in bad condition, we just took the opportunity to replace it.”

The company also examined the straight pipe on the bridge to the filters. Sanders said, “The pipe bridge piping is not a critical area like elbows and bends, but it needed to be looked at. We pulled the bridge pipe out, checked it, and decided it showed little to no wear. It could last another five to seven years, if not longer, based on the blast furnace output. We didn’t need to replace any of the Abresist basalt-lined pipe on the bridge.”

The company did not consider using another brand of pipe. Erin Altemos, plant process engineer, remarking on the longevity of the pipes, said, “We specified the best in 1981. The reliability we need is there. It lasts. Why change? You can’t get much better customer service when you have a problem and the president of the company comes in and directs the repairs.”
Agitation Tanks

Like the pipes that crisscross the compound, the sides of the agitating tanks at Sparrows Point were basalt lined as well. In 1999' the company decided to address the few issues they were having with the lining in the tanks.

Once again, the company went to Abresist for the solution.
Basalt Linings

The basalt lining on the tanks had been installed in 1989 and was not originally specified when the plant was built. The corrosive nature of the atmosphere at the plant eroded the tanks from the outside. “The basalt lining did not completely withstand the impact, but it had a longer life than anything else,” Sanders said.

“The Abresist panels were not worn out. Some of the tiles were being knocked off of the panel due to impact.”

Altemos added, “Impact is a big problem with the tanks. We had to replace sections of the tank lining that were damaged. We had experience with Abresist. Joe [Accetta, president of Abresist] and Ray [Albertson, Abresist sales representative], helped us get around the problem and solve it.”

The Abresist team advised the company to use Alresist high-density alumina ceramic tiles that were manufactured into curved panels. Rated 9 on the Mohs scale of hardness, they provided the level of abrasion and impact resistance needed to withstand the impact of the slag. The Alresist plates were installed in the tanks in 1999 with the help of Jeff Howard, Abresist technician.

Summing up Blue Circle’s longtime relationship with Abresist, Sanders said, “The reason we keep coming back to Abresist is the product performance and their customer service.”

The Scenario

When stainless steel pipework is used in plumbing systems, joining can be expensive, time consuming and difficult. There is an incentive to use simple joining methods which will increase the popularity of stainless steel installations for industrial and domestic use. This opportunity was pursued by Lancashire Fittings in association with British Steel.
Options

· mechanical fastening (fittings are expensive);

· soldering (time consuming, careful cleaning needed, uses corrosive chemicals);

· adhesive bonding.
What Was Done

A study by Lancashire Fittings in association with British Steel identified the possibility of using an anaerobic adhesive. Short term tests were favourable and an initial evaluation resulted in the selection of Loctite 638.

Pre-treatment of the pipework involves roughening the surface of the fitting and pipe with emery cloth, after which a ring of retaining adhesive is applied to the fitting and tubing. Once the tube is inserted into the fitting, the joint sets within two minutes, and develops full strength in two to four hours.

In terms of cost, the adhesive retails at US$25 per 5 ml, which corresponds to US$1 per joint. This is considerably cheaper than the cost of alternative assembly approaches.
Benefits

Lancashire Fittings now recommend adhesives as the first choice for joining stainless steel fittings, as the method is simple and cheap. The company is happy to give a 40 year guarantee for cold water systems, and does not anticipate problems with hot water up to 90°C or cleaning fluids.

The introduction of adhesive bonding has been found to increase the popularity of the fittings, and this has led to higher sales.

Bonded pipework sections are being evaluated as part of a 20 year experiment to prove joint durability. Sections of cold and hot water system within the test installation in a Lancashire Fittings Building are removed at regular intervals for mechanical testing and examination at Leeds University. Currently, performance has been successful for eight years. To assist tradesmen, Lancashire Fittings have produced a pamphlet describing the procedures used for joining their fittings to thin wall tubing.
Implications

The excellent integrity of cylindrical joints made using anaerobic retaining adhesives has been illustrated. Other applications for this class of adhesive include bearing retention, automotive transmission components and refrigeration heat exchangers.

The Scenario

As a result of in-service external corrosion, a steel water pipeline was suffering from loss of wall thickness, with leaks in some areas. A cost effective repair method was required, as the water company did not wish to replace the pipeline.
Available Options

· cut out grossly corroded sections, replace with patches or new pipe lengths, and repair by welding on site (expensive, long installation downtime);

· use adhesive bonding to repair cavities and holes in the pipeline.
What Was Done

Two types of adhesive bonding approach were considered:

· to fill up the cavities and restore the external surface;

· to repair holes of up to 5 mm in diameter.
Cavities

The procedure adopted was to degrease the damaged surfaces using a trichloroethene product, abrade, and then fill with a mastic compound such as Araldite 64257, hardener HY 850 and silica filler. A similar approach was used to rebuild the external coating, except that the epoxy was reinforced with layers of glass fibre chopped strand mat.
Holes

Both the corroded area and a steel patch (200 x 200 x 2 mm) were cleaned and degreased. Priming and anticorrosion treatment was applied and a patch bonded in place using epoxy adhesive. The patches were held in position by a series of metal straps until the cure was complete.
Benefits

Satisfactory pipeline performance was obtained by use of the above adhesive repair method. Complete replacement of the pipeline was avoided.
Implications

Provided resistance to humidity is achieved, the use of adhesive repairs is attractive for this type of application.

Background

Developments in advanced materials, more than anything else, have contributed to the spectacular progress in thrust-to-weight ratio of the aero gas turbine. This has been achieved in the main through the substitution of titanium and nickel alloys for steel, fig 1. Aluminium has virtually disappeared from the aero engine, and the future projection illustrates the potential for composites of various types. The aero engine designer requires a much wider range of materials than the airframe designer because the temperature range is large, whereas a civil airframe, even that of Concorde, lies entirely within the capability of aluminium. Materials also supply the enabling technology for equally significant improvements in performance and reliability.

The RB211 and Trent families of engines provide good illustrations of the link between material capabilities and engine performance. Civil engine programmes are becoming the drivers for materials development, replacing the military programmes that were the leaders at the beginning of the gas turbine era. The earlier approach of technology transfer from military to civil is tending to switch direction.

The turbine entry temperatures of modern civil engines are now approaching those of the latest military combat engines, and the longer operational lives expected by airlines place greater demands on materials technology.
Design Parameters

The key design parameters are fan airflow, which is related directly to thrust, particularly at take-off, and the pressure ratio and flow size of the core, which determine the fuel consumption and climb thrust for a given engine size. Take-off thrust is determined by the airflow, with a direct relationship to fan diameter. Increasing physical size places considerable importance on design, not only for low weight but also for structural stiffness.

Core engine size is equally important The power output to drive the fan is determined by core mass flow and combustor temperature rise. Component development provides increased temperature capability, but the physical size of the compressor is not easily changed and mass flow through the core can only be increased by supercharging to higher overall pressure ratios.

Three examples of aerospace components - the fan blade, the rear of the high-pressure compressor and the high-pressure turbine illustrate how materials are responding to the required performance and design parameters. They also highlight the potential of advanced materials such as titanium and nickel alloys, plus the possibilities for composite materials. In the production of larger diameter, low weight fan blades, the contribution of advanced materials is vital, not only in terms of density but also through advanced methods of fabrication. New materials must also be able to withstand the demands for increasing compressor delivery temperature and turbine entry temperature. Specific fuel consumption depends on thermal as well as propulsive efficiency. Thermal efficiency depends in turn on the maximum temperature of the cycle, as with any heat engine. Maximising efficiency within the design compromise on each component is clearly important for fuel consumption.
Summary

• Civil aero-engine performance development has depended heavily on advances in materials, not only by virtue of their properties but also in their manufacturing and processing.

• In all phases of activity, simultaneous consideration of service duty and manufacturing process is vital. This demands the closest co-operation between the engine manufacturer and suppliers.

• Composite materials - each appropriate to its operating temperature environment will become increasingly important, but the pace of their introduction will depend on success in achieving low cost manufacture and cost effective exploitation.

• The world's aero-engine industry is grateful for the contributions that new materials have made, and looks eagerly for more to provide better products at lower cost.

Background

The sport of fencing is one of only four to have featured at every modern Olympic games. Until recently much of the equipment used had changed relatively little since its inception, but lately technological advances, and challenges to its Olympic status, have led to the adoption of several innovative materials, with varying degrees of success. Swords, masks and clothing have all seen changes, the most recent development being the transparent mask, intended both to improve visibility for the competitor, and make the sport more enjoyable for the spectator.
The Blade

There are three disciplines in modern fencing foil, epee and sabre, each involving a different target area, employing a different weapon, and demanding a different technique. A feature common to all three disciplines is that the blades regularly break, turning a safe piece of sports equipment into a potentially lethal weapon. Analysis of the fracture surfaces reveals the characteristic features of fatigue crack growth, which is understandable given that a successful attacking lunge can cause a blade to bend with a radius of curvature in the region of 200mm. Repeated bending during a blade's lifetime, coupled with surface damage from impacts with the opponent's blade, result in the accumulation of damage in the form of microcracks, which initiate fatigue failure. This is a particular problem with cheaper blades made from medium carbon steel.
Blade Materials and Manufacture

These blades are manufactured by quenching and tempering at 300 to 500°C, resulting in a tempered martensitic structure with a yield stress of between 1500 and 1700MNm-2. A more expensive foil material is maraging steel, which has a yield stress in the region of 2000MNm-2 and an increased lifetime. The critical defect size for fast fracture of the maraging steel blades is over four times larger than in standard carbon steel types, which explains the extended lifetime. However, although the lifetime of the maraging blades is longer, they still fail by brittle fracture, resulting in a sharp edge that can penetrate the opponents clothing and cause serious injury.

A variety of other materials have been investigated for the foil, from glass and carbon fibre composites, to dual phase steels that contain fibres of martensite with an interpenetrating austenite phase. This dual phase steel material has demonstrated high strength and exceptional toughness, with Charpy impact tests showing that blade samples are able to absorb 360J impact energy without breaking into two pieces, compared to 10J for conventional medium carbon steel blades. The toughness originates from the inclusion of the austenite phase, which is ductile under the impact conditions and deflects the crack along the length of the blade, requiring re-initiation in an adjacent fibre of martensite if the growth is to continue.

Surprisingly this grade of steel has never become a standard production grade for fencing blades. Two reasons have been cited, one of which is the higher cost, the other the different feel of the blade, which makes it unpopular with fencers. The same explanations apply to glass and carbon fibre composite blades and, despite these investigations into new materials for blades, conventional materials have not yet been replaced.
Face Masks

This is not the case for the protective face masks used in the sport. There has long been a desire within fencing to enable clear vision of the opponent, something that is compromised by the current designs based on a close metal mesh. Although numerous attempts have been made to replace the metal designs over the years, no solution has offered any degree of consistent safety or clarity of vision. The pace of development has quickened in recent years due to threats from the International Olympic Committee to exclude fencing from the games unless it modernised itself. A key point in this demand was the need to make competitors' faces visible to spectators and television audiences during competition. The IOC’s demand catalysed a development drive that had until that point been very gradual.
Masks for the Future

Many fencing equipment manufacturers have responded to the challenge to produce a clear mask, and one company that has been successful is the UK-based manufacturer Leon Paul. The company has developed a clear mask made from the Lexan grade of polycarbonate (figure 1), a polymer chosen for its combination of excellent optical clarity and high impact resistance. The material is incorporated in two forms, a single 3mm section covered with another layer 0.5mm thick. The thinner, disposable outer layer protects the base layer from environmental stress cracking that could occur on exposure to organic solvent. It also protects the base layer from the effects of stress concentration due to blade damage on the surface of the mask.

Tests at the Italian Fencing Federation laboratory comparing metal and polymer masks have shown that the polymer sections outperformed the conventional metal mesh sections. In drop tests from heights of 55cm with a mass of 2.4kg fastened to a steel spike (section 3 x 3mm square, with a pyramidal point angle of 60°) the metal mesh was penetrated, whereas the Lexan visor was only marked with an impression of the pyramidal point. Tests on complete masks also showed that the Lexan based masks did not deform, while the metal mesh versions did and to an extent deemed sufficient to injure the fencer. Although the Olympic future of fencing is still uncertain the new mask technology will certainly play a major role in preserving the current status of the sport.
Protective Clothing

A third area of fencing to evolve in recent years is the protective clothing. Traditionally made from heavy gauge cotton fabric, the advent of Kevlar led to protective panels being woven into the garments to afford a high degree of localised protection. However, Kevlar suffers from a major disadvantage. It degrades when washed in biological washing powder or exposed to UV light. With due care and attention there is no degradation in protection, but the legal implications of selling such a garment encouraged manufacturers to look for alternatives. Today fencing clothing is made from a blend of cotton and high strength polymer fibres such as ballistic nylon, a combination that affords resistance to penetration of over 800N, and protection that is not localised.

Background

Alloy steels differ from carbon steels in that they have compositions that extend beyond the limits set for carbon steels. Usually this refers to constituents such as boron, carbon, chromium, manganese, molybdenum, silicon and vanadium. They also have chromium contents less than 4%. Steels with chromium contents of greater than 4% become classified as stainless or tool steels. As a general guide, an alloy steel will have:

· Manganese content >1.65%

· Silicon content >0.5%

· Copper content >0.6%

The American Iron and Steel Institute (AISI) naming system is one of the most widely accepted systems.

Designations usually consist of a four digit number, but sometimes this extends to five. The first two digits indicate what the major alloying element is, while the last 2 or three indicate the carbon content in hundredths of a percent.

Example: AISI 1340 is a manganese containing alloy steel with a 0.40% average carbon content.

Table 1. Summarises AISI designations for alloy steels.

		Main Alloying Elements
13	xx: 1.75Mn	Manganese
23	xx: 3.50Ni	Nickel
31	xx: 1.25Ni, 0.65-0.80Cr	Nickel-Chromium
40	xx: 0.20-0.25Mo	Molybdenum
41	xx: 0.50-0.95Cr, 0.12-0.30Mo	Chromium-Molybdenum
43	xx: 1.82Ni, 0.50-0.80Cr, 0.25Mo	Nickel-Chromium-Molybdenum
44	xx: 0.40-0.52Mo	Molybdenum
46	xx: 0.85-1.82Ni, 0.20-0.25Mo	Nickel-Molybdenum
47	xx: 1.05Ni, 0.45Cr, 0.20-0.35Mo	Nickel-Chromium-Molybdenum
48	xx: 3.5Ni, 0.25Mo	Nickel-Molybdenum
50	xx: 0.27-0.65Cr	Chromium
50	xx: 0.50Cr, 1.00C	Chromium
51	xx: 0.80-1.05Cr	Chromium
51	xx: 1.02Cr, 1.00C	Chromium
52	xx: 1.45Cr, 1.00C	Chromium
61	xx: 0.60-0.95Cr, 0.10-0.15V	Chromium-Vanadium
81	xx: 0.30Ni, 0.40Cr, 0.12Mo	Nickel-Chromium-Molybdenum
86	xx: 0.55Ni, 0.50Cr, 0.25Mo	Nickel-Chromium-Molybdenum
87	xx: 0.55Ni, 0.50Cr, 0.25Mo	Nickel-Chromium-Molybdenum
88	xx: 0.55Ni, 0.50Cr, 0.20-0.35Mo	Nickel-Chromium-Molybdenum
92	xx: 1.45-2.0Si, 0.65-0.85Mn,<0.65cr	Silicon-Manganese
93	xx: 3.25Ni, 1.20Cr, 0.12Mo	Nickel-Chromium-Molybdenum
94	xx: 0.45Ni, 0.40Cr, 0.12Mo	Nickel-Chromium-Molybdenum

Background

Materials selections must be given detailed attention at every stage of the design, construction and operation of systems and equipment for application in offshore oil and gas production. Full attention must be given to general corrosion resistance, selective corrosion resistance (by pitting and crevice attack) and stress corrosion cracking susceptibility in sour hydrogen sulphide environments if failures, loss of production and costly maintenance are to be avoided. Even more important than these considerations is the need to maintain offshore safety. Thus the specification and use of materials which combine corrosion resistance with high mechanical strength is a fundamental requirement.

A greater understanding of the offshore environment and more detailed knowledge of the conditions under which offshore structures and systems have to operate will obviously contribute to the selection of the correct materials.

Corrosion in Sea Water and Offshore Environments

Sea water is highly corrosive and offshore installations are often exposed to temperature extremes. The corrosion resistance of a material is therefore equally as important as mechanical strength. The introduction of chlorine by adding hypochlorite solution to sea water to give biofouling resistance can reduce the corrosion resistance of certain stainless steels, particularly under crevice conditions. Hydrocarbon process systems often have to withstand the potentially corrosive effects of hydrogen sulphide and acid conditions associated with the dissolved carbon dioxide which is often present. Corrosion can weaken elements of an otherwise well designed ,structure or affect individual equipment components to such an extent that they cease to be serviceable. Unfortunately, the fight against corrosion itself can lead to equally damaging side effects such as the release of nascent hydrogen. This can be generated as a result of cathodic protection measures adopted to protect a structure or by dissimilar metal coupling. The presence of such hydrogen can given rise to hydrogen-induced cracking of steels and nickel base alloys.

Alloys for Offshore Applications

Metals manufacturers have spent much time and effort in developing alloys specifically to meet offshore needs. The alloys developed have had to be suitable for shafts and bolting as wellas many other applications. These have included sea water and process pipework, water injection and booster pumps, line shaft pumps, emergency shutdown valves, anchorages and tensioners for riser protection systems, multiphase pumps and remotely operated vehicle components.

The Development of Marinel

One particularly significant corrosion-resistant alloy (CRA) development led to the introduction of an ultra high strength cupronickel alloy (Marinel), approximately five years ago. This alloy was added to the range of alloys available for selection with reference to particular equipment where corrosion and hydrogen embrittlement could occur offshore. Most high strength iron and nickel based alloys and titanium alloys are prone to hydrogen embrittlement, the effect usually becoming more severe as the strength increases. Thus these alloys when operating in a high-stress condition will be more susceptible to hydrogen embrittlement than the same alloys operating under lower stress. Hydrogen embrittlement is of particular concern where high strength (usually B7 carbon steel, 720 N.mm^-2 yield point) bolting is used on subsea structures. The operating stress level usually taken to represent a critical situation with respect to hydrogen embrittlement is that given by the yield stress of B7 carbon steel which has the value of 720 N.mm^-2.

Use of Cathodic Protection

Cathodic protection by sacrificial anodes or impressed current is extensively used to protect subsea structures from corrosion. This technique can generate hydrogen which, if absorbed, may lead to embrittlement of metallic components with the resultant danger of premature failure. The time-dependent nature of the ingress of hydrogen may mean that an apparently unaffected subsea critical component, for example a bolt, fails in an instant after it has performed satisfactorily for several years in service. Failure occurs when the residual ductile core is reduced in area by an encroaching hydrogen embrittlement front to a cross-section which cannot carry the load placed upon it. As an example, the failure of alloy K-500 riser clamp bolts has been reported in the April 1985 issue of Materials Performance (p37). Charging of UNS N 05500 (high strength 70Ni-3OCu alloy) with hydrogen has been shown to result in the hydrogen embrittlement of nonmagnetic drill collars. This has been thought to be due to galvanic coupling of the collars with carbon steel (see the October 1986 issue of Materials Performance, p28). It has also been suggested that a documented example of cracking in high strength steel legs of jack-up rigs was associated with hydrogen-induced stress corrosion cracking, the hydrogen being generated by the cathodic protection system operating in hydrogen sulphide contaminated seawater (February 1989 issue of Veritec Offshore Technology Journal).

Transport of Hydrogen into a Metal

The entry of hydrogen into a metal can be purely diffusion-controlled, or can be assisted by dislocation transport and the latter effect has been experimentally demonstrated by the measurement of hydrogen permeation rates through nickel whilst it is undergoing plastic deformation (see volume 13, 1979 of Scripta Metallurgica, pp 927-932). Dislocation sweep-in of hydrogen from the surface in the case of several different metals has been found to be consistent with the calculated energy of activation of hydrogen-induced cracking (see pp 233-239 of the proceedings of the 1976 TMSAIME international conference on the effects of hydrogen on the behaviour of metals). During hydrogen transport, the hydrogen can be deposited at various ‘trap-sites’ or internal discontinuities such as grain boundaries or precipitates.

Susceptibility to Hydrogen Embrittlement

These can take the form of ‘reversible’ traps which the hydrogen can subsequently leave, or ‘irreversible’ traps, which the hydrogen cannot leave and which tend to encourage local fracture through a lowering of the surface energy of the material. The effectiveness of the traps in promoting hydrogen embrittlement is related to the degree of strengthening present in the material matrix, as it is well established that materials in a higher strength state (i.e. cold worked or age hardened) are more susceptible to hydrogen embrittlement than the same materials in a lower strength condition. Thus, measurement of both the hydrogen entry kinetics of a metal (or alloy) and the ability of the metal to trap hydrogen would give an indication of its hydrogen embrittlement susceptibility. Overall solubility of hydrogen does have an influence on hydrogen embrittlement characteristics, as iron, nickel and titanium have relatively high hydrogen solubilities (>1cc/cc) and these materials are more susceptible to hydrogen embrittlement than aluminium and copper alloys, whose solubilities are generally less than 0.1 cc/cc. The hydrogen diffusion coefficients of steel and titanium are greater than 10^-6 cm².s^-1, whereas the hydrogen diffusion coefficients of nickel, aluminium and copper alloys are approximately 10^-10 cm².s^-1, although this does not take into account dislocation transport or grain boundary diffusion.

Nickel-Copper Alloys and Hydrogen Embrittlement

Two alloys which are interesting to compare are the age hardening nickel-copper alloy K-500 and age hardening cupronickel Marinel, which have similar mechanical properties and hydrogen diffusion characteristics. In comparing the chemical composition of these two alloys, see Table 1, it is apparent that they contain almost the same basic elements, the major difference between them being the Cu:Ni ratio. In the case of Marinel the high Cu:Ni ratio renders the alloy immune to hydrogen embrittlement and this has been found to be largely due to the reduced ability of this alloy to trap the hydrogen irreversibly.

Table 1. Typical composition of bolting.

Material	Ti	Cr	Mn	Nb	Cu	Ni	Fe	Al
K-500	0.6	-	1.0	-	30	Bal.	1.0	2.8
Marinel	-	0.4	5.0	0.7	Bal.	18	1.0	1.8

Marinel in Offshore Applications

In offshore situations many developments have widely employed Marinel bolting for splash zone and subsea. Bolting subsea has been used with 13Cr steel, 22Cr duplex and 25Cr duplex steel manifold, valve and choke flanges. Subsea developments using the alloy include Lyell, Strathspey, Nelson, Heidrun, Johnston and Nelson.

Good galling resistance obviates the need for a lubricant during assembly and nuts can be readily removed after a period of service if required.

For the Conoco Lyell subsea manifold Marinel bolting was chosen for its greater mechanical strength and corrosion resistance compared with grade 660 steel. The bolts were bolt tensioned and assembled without lubricant. Stud bolts have been subjected to a laboratory examination after 18 months service (nearly 12 months with the manifold in operation) and apart from the expected calcareous deposit, appeared completely unaffected by service.

Duplex Stainless Steels in Offshore Applications

A most significant contribution to the fight against corrosion offshore has been made by duplex stainless steels. These have often been adopted on offshore structures in preference to carbon steel or other stainless steels. The value of the duplex stainless steel is that it combines the basic toughness of the more common austenitic stainless steels with the higher strength and improved corrosion resistance of ferritic steels. The optimum chemical composition of these steels provides a high level of corrosion resistance in chloride media together with high mechanical strength and ductility. Other benefits include the ability of some duplex stainless steels to be used at quite low sub-zero temperatures and be able to resist stress corrosion cracking.

A significant feature of duplex stainless steel is that its pitting and crevice corrosion resistance is greatly superior to that of standard austenitic alloys. Pitting resistance equivalent numbers (PREN), a standard industry measure, are often in the high 30s while the latest duplex alloys exceed a PREN of 40. This is an increasingly common specification for certain offshore duties. However, PREN numbers only provide an approximate grading of alloys and do not account for the microstructure of the material. An acceptance corrosion test on material in the supply condition is so much more meaningful.

The Evolution of Duplex Stainless Steels

Ferralium alloy 255 was the world’s first commercial 25% chromium duplex stainless steel when it was introduced over 20 years ago. It pioneered the use of a deliberate nitrogen addition in order to improve ductility and corrosion resistance. Further research has demonstrated the importance of using duplex stainless steels containing both nitrogen and copper.

Super Duplex Stainless Steels for Offshore Applications

For offshore and indeed, onshore applications, the availability of a super duplex (25% chromium) stainless steel alloy in a variety of forms is important. For example, bar, forgings, castings, sheet, plate, pipe/tube, welding consumables, flanges, fittings, dished ends and fasteners are available. In terms of other benefits, the high allowable design stress of this alloy type in comparison with other duplex stainless steels and austenitic stainless steels, including 6% Mo type, is significant. It also offers excellent castability, weldability and machinability. These features are complemented by excellent fatigue resistance and galvanic compatibility with other high alloy stainless steels.

Twenty-two percent chromium stainless steels provide better pitting resistance and resistance to crevice corrosion than type 316 stainless steel by virtue of a more stable passive film and also have greater mechanical strength. However, for optimum corrosion resistance, a 25% chromium high alloy duplex stainless steel is required and these alloys are often referred to as super duplex stainless. Even within this category, it is important to select the correct grade of material to get versatility in handling a wide range of corrosive media and for confidence that the alloy will cope with any excursions or transient operating conditions which make the environment more aggressive.

Materials Selection for Offshore Applications

Offshore structures themselves present different requirements of materials depending upon whether their application is topside, splash zone or subsea. Topside, duplex materials are suitable for a wide range of bolting applications and material such as Ferralium alloy 255 provide up to B7 steel strength, excellent corrosion resistance and a service life equal to the life of the system, thereby contributing to reduced maintenance costs. In the splash zone, the alloy has already demonstrated its suitability for sea water resistance with over 15 years service on North Sea installations and has been widely employed for riser bolting and components on riser protection system on TLPs.

Emergence of New Super Duplex Stainless Steels

Improved materials in the super duplex stainless steel category continue to be developed by manufacturers offering better or differently combined characteristics, features and benefits. These alloys, generally with a PREN > 40, are produced to conform to a number of UNS designations which appear in ASTM product form specifications. Castings and wrought forms are available. Typical of recent developments is Ferralium alloy SD40 (conforming to UNS S 32550) with a PREN > 40.0 and providing a minimum 0.2% proof stress of 550N.mm^-2 and a UTS of 760 N.mm^-2. This 25% chromium super duplex material results from a carefully controlled composition and balanced austenitic/ferritic structure with a substantial content of molybdenum and nitrogen.

Applications for Super Duplex Stainless Steels

Applications which can benefit from the use of these high alloy super duplex steels involve piping systems, pumps (where the good erosion and abrasion resistance is employed), valves, heat exchangers and diverse other equipment.

Recently, the excellent corrosion resistance of the new super duplex Ferralium alloy SD40 has been exploited for subsea electrical connectors on the Saga Snorre and Total South Ellon developments. In one case the super duplex material was chosen to replace standard austenitic stainless steel which had suffered from corrosion attack.

Figure 1. Super duplex stainless steel alloy is available in a variety of forms for both on and offshore applications.

Conclusions

Several types of alloys have been developed in recent years to combat the degradation of existing alloys by corrosion attack and in some cases hydrogen embrittlement in the harsh offshore environment. Super (25 Cr) duplex stainless steels and an ultra high strength cupronickel have provided the solution to many material selection dilemmas.