Nov_Dec_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 1 7 5 8 15 14 required by the IQ process; convey- or to transport parts through the quenchant; loading/unloading ta- ble; sludge buster to clean forging scale from the quenchant; chiller to maintain quenchant tempera- ture within an allowable range; and system controls. Environmentally friendly Daphne Genuine Intensi- Quench quenchant, a low concen- tration solution of organic salt in plain tap water jointly developed by IQT and Idemitsu Kosan Co., Ja- pan, is used for the DFIQ system. The combination of the uniform, in- tensive delivery of the quenchant to the hot part surface with the unique cooling properties of the quenchant minimizes the duration of the initial film-boiling stage of cooling. This in turn results in more uniform cooling of the forging, drastically reducing the probability of part cracking. DFIQ trials with actual forgings in production condi- tions were conducted at Bula Forge and Machine (Cleve- land), Welland Forge (Canada), and Clifford Jacobs Forge (Champaign, Ill.). Figure 2 shows some processed forgings in- cluding keys, pindle adapters, tines, and lugs. Forgings were made of AISI 1045, 4140, 4340, and 8640 steels for materials characterization studies. One set of keys was processed us- ing DFIQ followed by a self-tempering process only, i.e., the part surface layer was tempered by residual heat from the hot core. Another set of keys was heat treated using tradi- tional methods: air cooled after forging, reheated, quenched in oil, and tempered for two hours at 700 ° F. Keys from both sets had the same hardness of 50-51 HRC [5] . The studies illustrated that DFIQ significantly improves material mechanical properties compared with those ob- tained using conventional heat treatment. For example, the tensile strength of 4140 alloy steel after conventional heat treatment was 222,000 psi, and increased to 287,000 psi after DFIQ, while impact strength improved from5 to 14 ft-lb. Tensile and impact strength for 4140 after DFIQ are even higher than those for conventionally heat treated higher alloy 4340 steel (i.e., 262,000 psi and 8 ft-lb). This illustrates the possibility of substituting a less expensive, lower alloy steel for a higher alloy steel using DFIQ, and still obtaining the same or better mechanical properties—achieving both easier machinability and lower material cost. DFIQ can also eliminate the need for normalizing, or both normalizing and annealing processes after forging, resulting in a significant reduction of production lead times, energy consumption, and overall cost of the heat treatment process. Additional savings from DFIQ come from eliminating shipping costs and lead time between forging and heat treat- ing shops. For example, the DFIQ-processed pintle adapters followed by furnace tempering met customer specifications without being normalized, annealed, reaustenitized, and oil quenched and tempered. Production flow diagrams com- paring pintle adapters made using conventional manufac- turing and DFIQ are shown in Fig. 3. In addition, DFIQ forgings have very little surface scale, because the parts are not reheated two times after the initial Fig. 2 — Examples of forgings processed using DFIQ. Fig. 3 — Production flow diagrams for conventionally and DFIQ processed pintle adapter forgings.