Cutting Tool Engineering
October 2012 / Volume 64 / Issue 10

Tempering heat-treatment costs

By CTE Staff

Outsourcing heat treatment of parts can be costly and require lengthy turnaround times—which are especially problematic in emergency and weekend situations. Therefore, LMC Industries Inc. recently added a dual-chamber furnace for heat treating tool steels to its cadre of equipment. LMC, Arnold, Mo., is a metal stamping and plastic injection-molding company that serves the automotive industry.

According to Toolroom Manager Max Vogl, LMC wanted a furnace for its tooling facility, which supports its stamping and molding operations, to reign in the cost of outsourcing heat treatment and improve heat-treatment turnaround time.

After searching the Web and talking to various furnace manufacturers, LMC determined the Model HL82-H24 from Lucifer Furnaces Inc., Warrington, Pa., was the best fit as far as versatility and price. In addition, both a tool shop and steel supplier highly recommended the furnace.

Courtesy of LMC Industries

LMC’s dual-chamber heat-treatment furnace from Lucifer Furnaces has a high-temperature upper chamber and a lower tempering chamber.

“We needed a furnace that heats up high enough to handle all our tool steels, including powder metals such as CPM (Crucible Particle Metal),” Vogl said. “Regular tool steel requires a temperature around 1,800° F whereas CPM requires temperatures in the 2,150° F to 2,200° F range.”

The furnace has 5 " of multilayered firebrick and mineral wool block insulation for energy efficiency and to maintain a low outer shell temperature. The upper chamber measures 9 "×12 "×24 " and heats to 2,300° F. The lower tempering chamber has the same dimensions, is built with 4.5 " of insulating firebrick and mineral wool block and heats to 1,200° F. Both chambers are controlled by Honeywell UDC 2500 microprocessor-based, proportioning temperature controllers, with a separate high-limit controller on the upper chamber.

The dual-chamber design saves time. “With one chamber, there is a lot of waiting,” Vogl said. “You have to heat treat the part, wait until the chamber cools down, and then put the same part in the chamber but at a lower temperature. With two chambers, you can go right from one chamber to the other. While the tempering chamber is being used, you can put more pieces in the first one.”

Vogl also appreciates that the Model HL82-H24 is compact and easy to operate. “It took us only about 3 or 4 days of heat treating various parts to figure out how to make them come out right,” he said.

LMC plans to use the furnace to remove the 0.003 "- to 0.005 "-deep, white cast layer wire EDMing creates by tempering its punches and die sections. “We are still working out how to use the furnace to remove the white layer,” he said.

Tempering also removes the stresses and relieves high hardness on the surface edge, Vogl noted, adding that punches can break if stresses aren’t relieved. “When stamping, you are punching steel against steel, which starts to put stresses in the punches and die sections,” he continued. “So after every one, two or three cycles—we haven’t decided yet what that number needs to be—before we sharpen our punches and die sections, we want to put them in the lower chamber just below the tempering stage. That should relieve the stresses.”

Otherwise, Vogl noted, LMC experiences premature chipping on those punches and die sections. Those sections either have to be sharpened more frequently or scrapped.

Overall, LMC is satisfied with the Lucifer furnace and would recommend it to any company in the same type of business.

Vogl also noted that “since we bought the furnace, we haven’t sent one piece out to be heat treated. One furnace takes care of all our needs. In the future, I’m sure there will be times the pieces are bigger than our furnace can handle, but, for now, it services our needs.”

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