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Powdered metals on the march.

Powdered metals on the march Powdered-metal (P/M) technology is a cost-effective way to make complicated shapes in large quantities. The process involves compacting a metal powder inside a shaped cavity at high pressure, then heating the compact in a furnace. About 70 percent of all P/M parts serve the US auto industry, and there about 150 companies in the US competing in the market. Most are located in Ohio, Indiana, Illinois, and Pennsylvania. But one is in the South!

As P/M manufactures go, Martin Technologies Inc, Huntsville, AL, is a company that marches to a different drummer, both in location and performance. While others mass produce inexpensive P/M parts from low-alloy steels and bronze, Martin specializes in precision high-alloy parts and high-strength components produced in limited quantities that often number in the hundreds rather than the hundreds of thousands. And they offer solutions, not just products.

For example, they used their problem-solving capability to help develop a safer practice round for US Navy aircraft. After a strike, the so-called frangible projectile had been ricocheting off the ground and hitting low-flying aircraft, cracking canopies and causing other damage.

For 10 years, many companies had attempted to develop a projectile that could be fired into armor plate, wet sand, or water and disintegrate on impact. No one succeeded, however, until Martin created a blend of powdered metal sintered in a special atmosphere. The new material maintains its toughness during firing, yet has a high degree of frangibility on impact.

At a recent shoot-off, the firm's target projectile was the only one to meet all the Navy's testing requirements, according to Tony Martin, chairman of the firm. As an added benefit, his engineers developed a technique to form the rotating band integrally with the main projectile body, eliminating a manufacturing step.

Consistent shaped charges

Shaped-charge penetrators that shoot through walls and armors present a different kind of challenge. The critical component in the penetrator is a copper cone. Normally made from deep-drawn bar stock, these cones sometimes have surface irregularities that result in inconsistent firing. And, new variable-shape penetrators can't be produced by deep drawing.

To solve these problems, Martin developed a proprietary P/M technique for making the copper cones. The company has been producing the cones on a limited bases for several years, improving consistency of firing and accuracy of penetration. Furthermore, the firm's engineers project that they can produce the cones for less than one-third the current cost.

The cost of hard work

"Manufacturing high-strength precision parts is a whole new ball game in P/M technology," says Tony Martin. "Conventional P/M parts are made by subjecting the powdered metal to pressures of about 30 tons/sq in. But we apply much higher pressures, up to 50 tons/sq in. To do this, we must specify expensive tungsten carbide and CPM-10V steel for punches and dies.

"These materials are difficult to work, and the pressures employed are at the outer limits of the metals' yield strengths. Thus our tools and dies must be made to very exacting dimensions. For example, we hold die-set components to 0.0004" tolerances."

High-precision capability enables the firm to take on difficult engineering problems such as a recent job for a defense-electronics firm. The company needed a receptacle for a cable assembly used in military aircraft. The part's walls were so thin (0.035" to 0.020") that it could not be cast, and machining it would cost too much.

Martin thus designed high-precision tooling to make a high-density P/M component, which was sintered and restruck to ensure that it met specifications.

PHOTO : Chairman Tony Martin notes his firm was founded in England in 1954, carrying European

PHOTO : expertise to the US when it moved to Alabama in 1976. He's flanked by P/M copper cone at

PHOTO : left, frangible projectile at right.
COPYRIGHT 1989 Nelson Publishing
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Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Publication:Tooling & Production
Date:Aug 1, 1989
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