September_AMP_Digital

FEATURE A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 2 0 4 3 T he adoption of laser heat treatment (LHT) in Europe has been universally successful, and LHT has become essentially mainstreamed there. Yet LHT is barely practiced in the U.S. for several reasons. For example, LHT as a process is still not well understood in the U.S. and there is a scarcity of reliable LHT job shops in the country. Also, data on LHT’s cost, quality, and schedule improvements has not yet influenced U.S. decisionmakers. The authors of this article believe LHT is poised for rapid adoption in the U.S. OEM community. This article presents a basic technical introduction to LHT and the results of a case study of LHT cost savings in automotive trimming/form dies. DESCRIPTION OF LASER HEAT TREATING Laser heat treating, also referred to as laser harden- ing, is a process in which a laser beam (with a typical spot size between 0.5 x 0.5-in. and 2 x 2-in.) illuminates the sur- face of ametal part for the purpose of heating it to a desired temperature, typically above the metallurgical transition temperature, for both the metal’s surface and its heat af- fected zone (HAZ). When the laser heat source is removed, the thermal mass of themetal rapidly quenches the heated area by conduction, with the result that the treated part of the metal has the desired hardness. The details of the laser beam’s operation can be fine- tuned to exercise precise control over all aspects of the LASER HEAT TREATING CUTS COSTS AND SHORTENS SCHEDULES IN THE MANUFACTURE OF AUTOMOTIVE DIES Automotive die OEMs throughout Europe are using laser heat treatment to deliver parts fast, with superior quality, at lower cost. Aravind Jonnalagadda* Synergy Additive Manufacturing, Clinton Township, Michigan 6 *Member of ASM International hardening process, delivering energy with great precision, and allowing for rapid quenching. Importantly, depending on geometry, LHT also allows treatment via line-of-sight for areas that are difficult to reach by other means. BENEFITS OF LASER HEAT TREATING Compared to conventional heat treatment tech- niques, such as induction, furnace, and flame heat treat- ment, LHT’s benefits include: • Consistent hardness depth. By allowing precise, millisecond-level feedback control of the delivery of energy to the metal itself, LHT can produce a HAZ with exacting specifications, including consistent hardness depth. • Minimal to zero distortion. Laser heat treatment automatically delivers the smallest possible total energy to the die under treatment for any size HAZ. This intrinsic feature of LHT automatically results in minimal to zero distortion in most large sizes of automotive dies. • Precise application of beam energy to work spot. Flames or coils need not be in close proximity to the work area, resulting in the heat being applied only to the intended area, with minimal to zero heating of adjoining areas. • No hard milling is required on large automotive dies. Because of LHT’s low-to-zero dimensional distortion, post treatment material removal is limited to tiny amounts, which can be removed by polishing and abrasion, with no hard milling required on most automotive stamping dies. Laser heat treating in the fabrication and mainte- nance of automotive dies usually results in cost savings, primarily from the complete elimination of the post hard- ening dimensional restoration processes. LASER HEAT TREATABLE MATERIALS Any steel with greater than 0.2% carbon content is treatable by LHT. The LHT treated dies are generally as hard, or harder than, conventionally treated dies. Fig. 1 — Laser heat treatment of a stamping die. 5