Your Heat Treatment Cycle Times


Lower


Non-contact load temperature sensing allows the operator to more accurately judge when a load is at temperature.


Thomas Karnezos and Robert Voigt, Pennsylvania State Univ., University Park, Pennsylvania


rule to determine when a load has reached its desired temperature (or is “on-heat”), often resulting in an overly conservative determination of load temperatures and longer than necessary cycle times. With more quantita- tive control of heat treatment cycles, the point at which the load uniformly reaches its target temperature could be determined with increased


M


any heat treat operators to- day use visual cues and the hour-per-inch


precision. This could facilitate shorter heat treatment cycles with process time reductions and energy savings. Recently, a technique origi-


Fig. 1. Shown is the typical temperature profi le for an annealing cycle.


nally developed for wrought steel producers, direct load sensing, has been shown to be effective in more ac- curately determining load temperature without using furnace load instrumentation (thermocouples). By analyz- ing the rate of change of the surface temperature of a load using a non-contact infrared sensor to infer when the cen- ter of the load has reached


The three loads tested with on-heat prediction through aggressive infrared detection were a rectangle (Fig. 2, left), a cylinder (Fig. 3, center) and a rod bundle (Fig. 4, right). The results showed the method is independent of load characteristics and is applicable to most furnace types.


MODERN CASTING / March 2010 47


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