David Symington is an innovator, though you won’t get him to admit it. Truth is, the amateur flute player has become a bit of a musical metallurgist. These days, the ex trader likes to experiment with titanium, zirconium, and other materials for stoppers and other flute components, eliciting new sounds out of an ages-old instrument.

In fact, the flute is the oldest known wind instrument, dating back to the 900 B.C (an early Chinese version called a ch’ie). The instrument has come a long way since its first note.

According to Symington, “The modern concert flute is basically a tube made out of wood or one of a variety of metals and about 67 cm long. It is commonly divided into three parts: the head, the body, and the foot and is kept in its case, split down into these three components, which are re-assembled when it is used.” The instrument has a little sister, the piccolo, which plays an octave above the flute.

Inside the head of most flutes, there is a cylindrical cork faced with a metal disc, which provides an airtight seal. It’s jammed precisely in place between the hole in the head (across which the player blows) and the open end of the head. Without the cork or a cork substitute, the instrument will not sound. The open end of the head is stopped with the crown.

The substitution of the cork by a cylindrical metal stopper held in position by a rubber O-ring was first proposed and implemented by Ernest J. Eggs and his son Leslie in the 1960s, according to Symington. “They claimed that the cork dampened the sound, and its substitution by a metal stopper would improve matters,” he says, “and they were, in my opinion, right.”

Symington knows his subject well. “I started playing the recorder when I was about 12 and turned to the transverse flute when about 14,” he points out. “I do not remember what attracted me to the instrument in the first place.” Whatever it was, he hasn’t lost interest.

The flute maker Robert Bigio makes a stopper similar in principle to that of the Eggs’, but made of a plastic. Symington gave it a try. “I was using a Bigio Delrin (a type of plastic) stopper and found it improved the tone of the instrument as compared with the result using the cork supplied by the maker of my instrument,” he says. “My flute is an open-hole type, that is the perforated key plates are stopped by the fingers. This can be awkward, so I stopped two of the perforations with plugs. This improved the tone. On the underside of the plugs facing inside the tube there were metal studs to which I attributed this improvement. I then conjectured that substituting the plastic stopper in the head with a metal one might have a good effect.”

His perceptivity led to a series of experiments with different metals. Since 2002, Symington has tested a symphony’s-worth of stopper materials, including aluminum (“light airy tone”), tin (“uninteresting”), brass (“unremarkable”), copper (“bright and resonant”), lead (“unusual”), gold (“expensive”), and tungsten (“powerful and responsive, but with an arid, empty tone”) among many others. The oddest material the innovator has used is Indium, which he says provides a “very good sound”, but is so soft that “even putting the rubber O-ring on damaged it.”

Among the long list of metals with which Symington has experimented, a few stand out musically speaking. These include sister metals titanium, zirconium and hafnium. He compares their sounds with cork as “markedly more direct, louder and more interesting — like a wine with fruity flavours — and more flexible.” Symington says that “there is a family resemblance” between hafnium, zirconium, and titanium, but that “titanium gives a light sound” while “zirconium is fuller and hafnium fuller still. They all are bright and bell-like.”

To-date, the only zirconium stopper maker Symington knows of is Bigio. “He has made some few commercial sales of zirconium stoppers for flutes to professional players, and the feedback from the purchasers has been enthusiastic,” he says. “A couple of sales of zirconium stoppers to piccolo players have been made, and these have been well received by their owners.” There may also be other applications for these metals in other components and even different instruments. “We are investigating the possibility of making a ‘head’ out of zirconium, but do not yet know how practical the idea is,” says the inventive musician. “One zirconium crown has been made, and the result is good.” He mentions saxophone mouthpieces as another candidate for metals “and perhaps the mouthpieces of brass instruments might be a fruitful field for experiment.”

Not one to miss a note, Symington insists on making it clear that his remarks regarding the quality of sound apply to his experience as a player rather than as a listener. “Other experienced players find marked differences between different types of stoppers,” he says. “To listeners, the effects are more subtle and difficult to discern. This emphasis on the judgment of the players rather than the auditors may sound odd to the non-musician, but is of great importance to the player.”

To that end, Symington will continue experimenting with metals because his music is most important to him. Restless in his pursuit of new sounds, he is currently considering *niobium, another metal produced by Wah Chang.

For the moment though, he’s found a metal that really resonates with him. “I have played in one operatic concert using a zirconium stopper,” he pipes up. “I use one habitually for private chamber music and duet sessions.” Sounds like zirconium is music to this innovator’s ears.
David Symington can be reached on the telephone in the U.K. at 011 44 20 8788 1331. Robert Bigio’s products can be found at www.bigio.com. For more information on Allegheny Technologies’ “Metals that Make our World,” visit www.alleghenytechnologies.com.


* Niobium is next to zirconium in Period 5 of the Periodic Table and has the atomic number 41 (zirconium 40). Symington conjectures that niobium, being close in atomic structure to zirconium, may share its musical qualities or be even better. “There is only one way to find out and that is to make a niobium stopper and try it,” he writes.

Holtzman and his colleagues never lost sight of commercializing explosive welding. “At the outset, we decided to pursue the process so as to desensitize the variables such that operations could be conducted routinely under non-research conditions by manufacturing units,” he says. “This work was extraordinarily successful and by adjusting the speed of the explosive and the spatial conditions, we were able to work out proper parameters for a wide variety of metal combinations.”

The effort proved well worthwhile. Commercial operations began in 1963, then in 1965, DuPont used the explosion welding process to produce the clad metals needed by the US Mint for new coinage. During the next three years, the team made over 70 million pounds of dime, quarter, and half dollar blanks. John Banker, a former DuPont employee and currently Vice President at DMC Clad Metal, jokes, “DuPont made lots of money making money.”

Holtzman recalls that it wasn’t all easy-going. “The US Government made the change from silver to clad coins in 1965,” he says. “We at DuPont produced 30,000 tons of Cu-Ni/Cu/Cu-Ni clad metal strip for the Philadelphia and Denver Mints in the first three years (1965-1967). Our billets were 6 inches thick and were rolled, starting hot, to the required gage.

The first two small runs led to low yield due to a billet temperature a bit too high for the clad even though it would have been fine for the outer layer. Had we made coins from these, George Washington would have appeared to have a case of measles. We reduced the temperature and the process went smoothly thereafter.”

Eventually, DuPont dropped out of the coin business and concentrated on developing other markets for the technology. “In time, the copper companies from whom we bought the metals and who rolled our billets learned to make the clads (by roll-bonding of strip) and made it impossible for us to compete further in the Government procurement,” Holtzman says. “We took great pride in the fact we never supplied the mints with anything other than high quality product.”

Coinage was one of a number of early applications for explosion welding. According to Banker, DuPont had invested “significantly” in explosion welding research and development during the 1960s, and the investment paid off. “When I joined the (DuPont) Detaclad team in 1969, there were over 20 metallurgists and technicians developing everything from shipbuilding products to multi-layer razor blades,” he says.

Early clad products included stainless steel to steel for large tube sheets and pressure vessels for chemical processing plants. “These were followed quickly by titanium to steel and other metal/steel combinations that would normally form intermetallic compounds and prevent bonding by standard methods,” according to Holtzman. “These combinations included vanadium, tantalum, zirconium, Hastelloy®*[1] alloys and aluminum.” He also points out that aluminum/steel “clads” were used importantly as transition joints by the Electrical and Marine Industries as the metallurgical bonds proved advantageous over mechanical bonding processes.

“An especially rewarding moment came for me when I gave a presentation to a conference in Norway in 1964 in which I showed slides of huge explosively welded stainless steel/ steel clads being used for commercial tube sheets,” Holtzman recalls. “This came at a time when other research organizations in the field were showing pictures of pieces explosively welded that were only several inches in size. The lead we had over others was a source of great satisfaction to all of us at the Eastern Laboratory of DuPont who had participated in our state-of-the-art effort.”

Zirconium is well known for its corrosion resistance in pure hydrochloric acid, as shown in Figure 1. The data clearly demonstrates the wide range of zirconium’s corrosion resistance in HCl solutions; for example, at 10% acid concentration, the temperature limit for zirconium is above 250°C, and at 37%, the limit is about 130°C. Figure 1 also shows that, with the exception of tantalum, the temperature limits for the other metals and alloys in hydrochloric acid are much lower.





However, zirconium is also known for its vulnerability to localized corrosion in oxidizing chloride solutions because of its low breakdown potential. Breakdown potential refers to the electrochemical potential at which pitting is initiated due to breakdown of the passive oxide film.
Oxidizing species, especially ferric ion, often exist in acidic solutions. This localized corrosion has been observed in chloride solutions with varying amounts of ferric ions at the Wah Chang Corrosion Laboratory, as shown in Table 1.





Corrosion is mostly a surface phenomenon, and surface condition often plays an important role in the initiation and propagation of localized corrosion. Zirconium is a soft metal, so it can be easily embedded with foreign particles. These particles may be embedded during fabrication due to the use of unclean steel tooling, such as is used for roll or press brake forming and roller expansion, as well as from material handling equipment. In most applications, embedded iron particles will not present a problem; however, in hydrochloric acid and other acidic chloride applications, these particles may produce harmful effects. For example:

Test results (as given in Table 2) demonstrate that there is an enormous difference between the mill finish and the HF-HNO3 etched zirconium samples in boiling 10% ferric chloride solution. Properly cleaned zirconium performs well in oxidizing chloride solutions, environments which have been regarded as incompatible for zirconium.





The primary goals in surface cleaning are to remove surface contaminants and to smooth out surface features. Listed below are some suggestions that will help improve the surface cleanliness of zirconium vessels:

.

LYNN DAVIS
President

PARRY WALBORN
Vice President — Commercial

ANDY NICHOLS
Director of Marketing

GARY KNEISEL
Director of Sales

KIRK RICHARDSON
Editor

Copyright ©2004 Wah Chang. All rights reserved. Reproduction of this newsletter by any means, in whole or in part, without written permission is prohibited by law. Outlook is published quarterly by Wah Chang. The newsletter contains information on reactive and refractory metals, including hafnium, niobium, titanium, vanadium and zirconium, as well as chemicals. The properties listed herein are average values based on laboratory and field test data from a number of sources. They are indicative only of the results obtained in such tests and should not be considered as guaranteed maximums or minimums. The starburst logo and Wah Chang are registered trademarks of ATI Properties, Inc.