Control is Key to Low-Temperature Process
Now in his 80s, Ed Busch of Berkeley, Michigan is considered the father of the commercial deep cryogenic processing industry. Busch got into freezing in the late 1960s after spending more than 20 years in the heat-treating business. Around that time, his customers began to inquire about liquid nitrogen immersion, a process thought to increase the life of tool steels, post heat-treating.
Busch's compliance with these requests yielded disappointing results. Instead of becoming stronger, the tools emerged from their liquid nitrogen baths cracked, warped, and brittle. Intrigued by the promise of cryogenics nevertheless, Busch decided to research the subject in depth. His initial efforts would prove almost as frustrating as his early experiments with liquid nitrogen. With surprisingly little written information on cryogenics available, the process was more or less a mystery.
"The lack of information was kind of odd considering the long history of cryogenics," Busch comments. "The process is as old as the watch. Ages ago, Swiss watchmakers stabilized the delicate components of their timepieces by storing them in mountain caves.
"They left them there for three years or more, but wound up with superior parts. Cryogenic treatment is one of the trade secrets of Swiss watch-making, and one of the primary reasons that timepieces produced in that country have enjoyed a reputation for excellence that continues to this day."
By accident or design, cryogenics remained a well-kept secret for centuries. The technology did not become widespread until the era of the Second World War, when Allied manufacturers treated weapons, chains, gears, and tools with dry ice and liquid nitrogen to increase strength and durability, and extend wear life. The manufacturers were confident that the process worked, but didn't quite know how to best achieve the desired results. They experimented with liquid nitrogen immersion, which didn't work any better then that it does today: The outside of the part cooled instantly while the inside hurried to catch up, resulting more often than not in cracking.
More experimentation followed. The parts were sprayed with liquid nitrogen, were partially immersed in it, or were slow-cooled by being suspended over steaming vats of it. When none of the tests rendered a flawless cryogenic tempering process, the researchers returned to the drawing board. Then the war ended, and the technology went into retirement once again. In 1966, Busch sold his heat-treating business to launch Materials Improvement, Inc., the world's first deep cryogenic processing company. He salvaged a cryogenerator from a retired naval aircraft carrier, and used it to develop the prototype of the dry cryogenic processors in use today. This new technology was a vast improvement over earlier attempts at cryogenic processing because it allowed for temperature control while "ramping down," maintaining frigid temperatures for an extended period of time. As a result of this procedure, the problems that had laid cryogenics low for so many years were finally overcome. Thermal shock, bowing, and cracking were avoided by bringing the climate inside the processor back to room temperature very, very slowly. Deep cryogenic processing had finally arrived.
"Once we perfected the process we had to sell it," Busch remembers. "But that would prove almost as tough as coming up with the process in the first place. Cryogenics was still mostly unknown back then, and many people dismissed it as voodoo. Skeptics labeled me a con man but that didn't stop Materials Improvement from attracting business. One of our first clients was a manufacturer of guitar strings. Country star, Roy Clark was their customer, and when he was touring a lot, he would bust several strings a day. That ended once the company brought their strings to us for freezing. After that, Roy was able to play his guitar without interruption, and we wound up processing six thousand pounds of product for the string manufacturer every month."
Job Shop Technology Magazine, March 2002; by D. Douglas Graham