November_December_2021_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 | N O V E M B E R / D E C E M B E R 2 0 2 1 4 1 follow time-temperature recipes by mixing gases from the hot and cold chambers. Figure 1 shows the front of the quenching chamber, where the parts are loaded. Figure 2 shows the back of the unit. The electrical panel, with the HMI unit, is in the fore- ground of Fig. 2, with the cold chamber directly behind it, and the hot chamber to its right. Figure 3 shows the HMI. The HMI allows access to, and manipulation of, the system logic and parameters, as well as being where recipes are entered, and processes monitored. Shown in Fig. 3 is the process monitoring function, which allows the user to view the recipe setpoint and the actual temperature of the gas entering the quench chamber, while also monitoring the position of all the various valves required to operate the equipment. The tables on the right of the screen show the temperature values of several thermal couples locat- ed within the chamber or thermocouples attached to a quench probe or part. EQUIPMENT OPERATION The unit was constructed at Atmosphere Engineering and shipped to Akron Steel Treating in Ohio, where it was installed and tested. This first prototype unit requires heat- ing to be performed in a separate furnace, with the part transferred by rail cart to the DCGQ unit after austenization is complete; future production equipment should inte- grate controlled heating, as well as cooling. The DCGQ unit is preheated to a predefined temperature during the aus- tenitization process in preparation for quench; the preheat temperature is alloy and part geometry dependent. The DCGQ recipe programmed into the HMI begins once the front-loading door is closed. Figure 4 shows a comparison of the temperature of the quench gas entering the cham- ber (“Chamber Inlet PV”) and the recipe setpoint tempera- ture (“Chamber Inlet SP”) with no hot part in the chamber. The recipe consists of 50°C temperature reductions over two minutes, starting at 425°C, with 20-min holds at each temperature step. Figure 4 shows that the unit logic works well, and the system has no issues following the time-temperature rec- ipe. The system did struggle a bit at lower temperatures, but still maintained the process temperature within 5°C of the recipe setpoint temperature, which was the tolerance programmed into the unit. The time-temperature recipe shown in Fig. 4 rep- resents schedules required for various geometries. For geometries with a thin, uniform cross-sectional thickness, such as rings, the designed temperature reductions can be relatively large, and the ramp and hold times can be short, 6 Fig. 1 — Front of the DCGQ prototype unit. Fig. 2 — Back of the DCGQ unit. Fig. 3 — Human machine interface on DCGQ prototype unit showing process monitoring functionality. 7