Cryogenic processing, the deep chilling of tool steel so that the molecular makeup of the metal is brought to cryogenic stillness in order to improve wear characteristics, is not a new technology. In the past, tool makers would bury components in snow banks for weeks or even months to improve their wear resistance. Castings were always left outside in the cold for months or years to age and stabilize.
Today's dry process is computer controlled, using a prescribed schedule and maintained at -300 °F for a particular time before slowly returning the parts to room temperature. Prior to the deep cryogenic step, many tool steels require a preconditioning step consisting of a short temper. After being subjected to the deep freeze, the materials must be tempered to about +300 °F. This temperature varies for different materials, and the processing time varies for different material cross sections.
Cryo processing improves performance and increases the life of metalcutting tools, blades, punches, dies, slitters, shears and knives, and increases abrasive wear resistance, raises the tensile strength and decreases brittleness with only one permanent treatment. It creates a denser molecular structure and closes the grains structure, resulting in a larger contact surface area that reduces friction, heat and wear. Cryogenic treatment changes the entire structure, not just the surface. Subsequent refinishing or regrinding operations do not affect the permanent improvements of the processing.
CryoPlus Inc. reported that it has been cryogenically treating broaches and drills for Lincoln Electric Motors with exceptional results. Glenn Pisching, Manufacturing Engineer, stated that his two broaches have broached over 500 rotors and are still cutting clean. "Untreated broaches needed to be re-sharpened at a cost of $234 after 200 rotors," he said. "The broaches cost between $3,000 and $14,000, so doubling the life between sharpenings is quite a savings. Lincoln operators were plunge drilling with Cleveland Twist TiN coated 12 inch and 18 inch long drills and continually breaking them. After the cryogenic treatment they can go right on through and keep on drilling between 12 inches to 18 inches all the way through. The drills have better than doubled the life." The drills cost between $20 and $30 and they were going through about five to seven per day.
Pisching was particularly impressed with what cryogenic processing has done for his premium quality H13 molds. Molten aluminum is poured into the molds to cast rotors. Exposed to very high temperatures, molds are usually susceptible to heat checks, the aluminum starts sticking and it is harder to release the casting from the mold. "But right now, the mold that I have in this process has not even shown that type of wear and it should have," he said. "It has not shown any type of heat checking yet."
"Today's limited acceptance and use of cryogenic treatment is basically attributed to a lack of understanding the technology," said the spokesperson. "Changes to the material micro structure are not visible with a standard laboratory metallograph or any other standard mechanical testing. Material hardness remains about the same. When the cryo treated tool does wear, the degree of wear reportedly is less severe, slower and more uniform. Therefore, less material must be removed to resharpen it. Customers have reported a material removal rate of less than half the normal material removed in resharpening. Cryo treating reduces the cost of the product by having longer tool life, less scrap, fewer rejections and above all, less costly downtime."
For more information contact:
CryoPlus, Inc
Kathi Bond-President
2429 N. Millborne Rd
Wooster, OH 44691
330-683-3375
kathicryo@aol.com
www.cryoplus.com