Short Track

CAN FREEZING PARTS MAKE THEM STRONGER? Pete Paulin president of 300 Below Inc. in Decatur, Illinois, uses deep cryogenics to make racing-engine parts more durable. In some instances, processing the arts cryogenically has doubled and even tripled their productive life, which is good news for racers. The company has processed crankshafts, camshafts, cylinder heads, connecting rods and blocks. Can Freezing Parts Make Them Stronger The word "cryogenics" is derived from two Greek words "kryos," which means cold or freezing, and "genes," meaning born or produced. "Deep" cryogenics (below 300 degrees Fahrenheit has created many new applications in ultra-cold temperature physics. Some recently developed fields are superconductors, cryo-biology, the superconducting super-collider and maritime magneto-hydrodynamic drives. Cryogenic processing is also a space-age process which significantly extends the productive life of metal tools, machine parts and engine components. Pete Paulin has developed a new highly efficient cryogenic process called "electric dry." He refined the process developed by Ed Busch, a longtime heat treater in Michigan who originally developed the cryogenic process. Paulin's company, 300 Below Inc., was founded in 1991 in Decatur, lL, where they cryogenically process tooling dies, cutters, drills, etc. They have also processed such diverse items as musical instruments, razor blades, golf balls, guitar strings, camera mounts for outer space and knife blades. In 1994, 300 Below also cryogenically treated components of the world's fastest Harley-Davidson. One automotive racer who had torn down his engine after every seven races found that Paulin's cryo-processing allowed him to run an amazing 32 races without a rebuild. Another motorcycle racer who usually rebuilt his motor after almost every meet (at a cost of $250 to $400 each time) now uses the one-time treatment to make the engine perform for the whole season. Even national champion Go Kart racers are claiming a 1/4-second-per-lap increase due to 300 Below's cryogenic treatments. Automotively, 300 Below has processed crankshafts, camshafts, cylinder heads, connecting rods and blocks. Cylinder heads and blocks have been processed for shops after they have been welded. Welding creates stresses within the metal. Cryogenic processing returns the metal to its original state by stress relieving and stabilizing the metal, making it more durable and less susceptible to micro-cracking after welding. Racers and manufacturers have experimented with applying dry ice to heat-treated metals (approximately -110°F) to change the molecular structure of the part. But studies have found that the effect of the shallow (-110 degrees) cold treatments is minimal unless performed as part of the initial heat-treatment cycle. Heat treating is what gives steel its hardness, toughness, wear resistance and ductility. Even performed properly, heat treatment cannot remove all the retained austenite (large, unstable partides of carbon carbide) from a piece of steel. It is at cryogenic temperatures (-300°F) that the molecules change, making all the retained austenite turn to martensite, a more dense, refined mix that is smaller and more uniform than austenite. Dry cryogenic processing physically transforms the micro-structure into a new, more refined, uniform substructure, which is stronger. The dry cryogenic process doesn't expose the material to liquids, thus eliminating the risk of thermal shock. The material is computer cooled very slowly, held at a temperature for a determined period of time, then slowly allowed to return to room temperature. The entire process is electronically controlled to perform to a precise time table (20 to 60 hours), allowing the material to adjust to the progressively cooler environment, then return to ambient temperature. "This process will improve the life of any metal component that is treated," said Paulin, president of 300 Below. The process will also thermally stress relieve a part. Stress is the enemy of steel if it is not imparted in a uniform manner. Stress boundary areas are susceptible to micro cracking, which leads to fatigue and eventual failure. A study performed at The Polytechnic Institute of Jassy, Romania, used a scanning electron microscope with a microscopic counting device to evaluate additional changes to the structure of steel. The Jassy study found the number of countable small carbides increased on the surface of a heat treatable steel from 33,000 per square millimeter to over 80,000 per square millimeter, as a result of cryogenic processing. This increase in carbides adds greatly to the wear resistance of a part. The carbides make a refined flat "super-hard" surface on the metal (like two pieces of smooth glass rubbed together have much lower friction than two pieces of sandpaper rubbed together). A refined surface structure is not only more wear resistant, but also reduces friction and heat, allowing more rapid movement and greater horsepower. An additional study by the Department of Mechanical Engineering at Louisiana Tech University supports the increased life claim. Their scientists found that for various metal samples soaked at -320°F, the wear resistance was approximately 2.6 times greater than that for samples soaked at -120°F. The drag racing applications for processed steel products are numerous and can be of great benefit to racers who are on a tight budget. Even the aluminum aftermarket engine blocks used by professional racers can be treated cryogenically. Think of an ice cube dropped into a cup of coffee. Differential cooling or heating of a mass creates stress because it is expanding or contracting at a different rate on the outside surface than at the core. The ice cube cracks. Aluminum castings have built-in stress due to the shrinkage of the molten metal as it cools in the molds. Moving the entire mass at the same temperature through the temperature cycle will stress relieve it homogeneously. Among the properties which define the qualities for racing engines, durability is one of the most important. The exciting proven results of 300 Below's testing are decisive in establishing the benefits of cryogenic treatment. Paulin points out that one treatment will last the life of the part. The inexpensive cost for processing parts cryogenically is based on the size, weight and type of part. Some of 300 Below’s case histories have shown a doubling or even tripling of productive life.

 

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