Sponsored By

November 24, 1999

3 Min Read
A big breakthrough in small MIM powders

Though the manufacturing technology to make larger MIM parts has existed for some time, the economic incentive to produce these parts has been nonexistent, largely because of the high price of MIM powders. Powder pricing is only a fraction of part cost when the parts are 1g or less. However, in larger parts, powder pricing can account for up to 50 percent of part cost.

The limited yields of MIM powders, usually 10 µm in size, also are raising the specter of powder shortages for small parts, even those produced in standard alloys. Most powders are sold to the press and sintering business. It typically consumes powders sized at 60 µm. The smaller 10-µm-sized MIM powders, often considered waste, account for less than 10 percent of yield. They are expensive to collect and process. Sifting costs are often equal to atomizing costs. Press and sintering reportedly is growing at only 3 to 5 percent/year. But MIM is growing 20 to 30 percent/year, or more.

Gunther Schulz, managing director of a year-old company called Wideflow, has developed a new gas atomization technology engineered to manufacture MIM powders faster, better, and cheaper. It produces powders on demand in all the most commonly used ferrous and nonferrous metals and alloys, exotic alloys, and precious metals.

His process could ensure an ample supply of powders to meet the rapidly growing market for small MIM parts. And it could make the dream of molding large MIM parts a practical reality by reducing powder costs from 30 to 50 percent.

Melt Film Atomization
Schulz’s solution rests in his patented nozzle system design. Conventional radial diameter melt nozzles used in gas atomization produce a stream of coarse, 50- to 80-µm powders. Another special gas atomizing process supplies 10-µm powers, but only with a typical throughput of a few kg/hr. If the throughput is increased, the powders get coarser. With other special powder-making processes, only low melting alloys can be used, and raw materials must be supplied in special shapes.

Wideflow’s system has a slit, linear orifice melt delivery design. It produces a stabilized flow of a thin film of melt with consistent physical properties. Productivity is not limited by melt throughput.

Throughput can be adjusted simply by increasing or decreasing the orifice slit length. Powder properties and characteristics remain the same. An armada of round orifice nozzles would be required to match the throughput of Wideflow’s melt film nozzle system. While passing the converging part of a deLaval gas nozzle in parallel with the melt film, gas molecules, which are capable of operating at constant velocities in a self-laminarizing flow, press onto the melt film, stabilizing it on all sides. The shear stress and acceleration also speed up the melt film and reduce film thickness.

Lead-time Reductions
Schulz estimates a production-scale Wideflow system could produce 10-µm spherical powder particles at a 600 kg/hr throughput. A typical run could be done in 30 minutes, and the atomizer could be quickly and easily cleaned out for another run.

Powder orders could conceivably be turned around in one day, instead of the fortnight it typically takes to sift 10-µm powders. And shifting from inert gases like argon and nitrogen to helium could reduce powder particle sizes even further for micro-MIM applications.

Wideflow’s first pilot plant in Ohrdruf, Germany should be up and running Q1 2000. It is being constructed to atomize more than 300 kg/hr of stainless steel per nominal batch capacity of 60 liters. Other metals and alloys also can be produced, depending on customer preference.

Schulz says he would like to concentrate his pilot plant production on newer types of specialty alloys that are difficult to produce by any other means. Expansions to two or three Wideflow production atomizers are scheduled for within three to five years. He intends to sell powders directly to MIM houses that prepare their own feedstocks, and to cooperate with all of the major suppliers of precompounded feedstocks.

Contact information
Wideflow Metal Powder Production & Engineering
Ohrdruf, Germany
Gunther Schulz
Phone: +49 (3624) 3317-11
Fax: +49 (3624) 3317-29
E-mail: [email protected]

Sign up for the PlasticsToday NewsFeed newsletter.

You May Also Like