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New Preco Thermal Feedback Sensor Improves the Accuracy of Laser Heat Treating and Reduces Scrap

Laser Balling of Medical Tubes

10 Minute Beam Dump into Block of Steel - The Process Control Chart plots a 10 minute beam dump into a steel block. The chart depicts the amount of power required to bring the spot to 1200C at the onset of the test followed by the lower required power to maintain the spot at 1200C for the 10 minute cycle. The block did not overheat nor did the laser spot melt the steel during the 10 minute cycle.

Customers who need to heat treat (harden) selected areas in transformation hardenable metal components (such as large machined parts, gears, spindles and certain small parts) can dramatically improve the repeatability of the process with Preco’s new process control package now being offered to our heat treating customers.

“Better laser hardening process control can prevent damage to parts and reduce waste of valuable material,” says Dave Krattley, Vice President Sales, Metals Market. “A lot of parts that are good candidates for laser hardening have high dollar value by the time they are ready for laser heat treating, which is usually one of the last steps. Improper laser hardening could result in scrapped parts and be very costly.”

The key to the system’s accuracy is its thermal feedback sensor. “We use a 2-color pyrometer to measure the surface temperature of the part we are processing,” Steve Nelson (the Preco Process Engineer who helped develop the product) explains. “This unit is connected to our laser control card which adjusts laser power real time to maintain the desired surface temperature of the part being processed. We are able to hold the temperature to within +/- 1 percent of the target.”

The real time thermal feedback also is important to accommodate variations in material from lot to lot.

Preco was interested in adding this technology to its portfolio of options because of the need for a more robust laser heat treating process. The tolerance range for achieving customer specifications can be very tight according to Nelson. “If too little energy is used, proper hardness and case depth won’t be achieved,” he says. “On the other hand, too much energy can melt the surface.”

The new Preco technology will be especially useful in the automotive, heavy equipment, aerospace and manufacturing industries where transformation hardenable steel components need to be hardened in select areas (wear surfaces) while maintaining the necessary ductility of the base metal in the rest of the work piece.

Laser hardenability of some common alloys
Medium-Carbon Steels
Low-Carbon Steels
Spheroidized Steels
High-Carbon Steels
Pearlitic Cast Iron
Ferritic Cast Irons
Low-Alloy Steels
Cast Steels

Some laser hardening advantages are:

  • Precise control of heat input of localized areas
  • Refined microstructure in case with unchanged adjacent substrate
  • Minimal or no distortion
  • No quenchants required
  • Uniform hardness values in case
  • Time efficient process

Preco has a variety of system solutions for this technology based on the size of parts and desired throughput. Preco can retrofit some of our legacy equipment already in the field as well. Preco also has this technology available for contract manufacturing customers at its Contract Manufacturing Services operation in Somerset, Wisconsin. If you would like to see a demonstration, visit Preco’s Somerset facility or see it at the IMTS Show at Chicago’s McCormick Place, September 10-15. For more information, contact Dave Krattley at 715-247-3285, extension 1162.

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