Nov_Dec_AMP_Digital

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 6 12 13 FEATURE T o accomplish lean manufacturing of steel parts, companies should consider potential cost savings throughout the entire manufacturing chain—includ- ing steelmaking, forging and casting, machining, and heat treatment. As one approach, the intensive-quenching (IQ) process [1] is an effective cost-saving step in the lean manu- facturing of steel products. IQ offers an alternative way to quench steel parts. It is an interrupted quench method conducted in highly agitat- ed water, which eliminates the random film-boiling process in quenching and enables the quench process to be consis- tent at the part surface for every part, every time. Very high “current” surface compressive stresses developed in the part’s shell from the beginning of the IQ process hold the part during quenching, preventing cracking and reducing distortion. Beneficial compressive stresses remain in the part surface layer after the quench. The IQ process known as direct-from-forge IQ (DFIQ), is implemented immediately after forging, while the IQ process known as IntensiQuench is used as a final heat treatment after machining is complete. Because the quench is consistent, all part properties—in- cluding distortion—are the same for each part at each part location. This consistency is what permits the part manufac- turer to achieve lean manufacturing. This article describes how using DFIQ and Intensi- Quench can significantly reduce the cost of manufacturing steel products when engineered into the lean part-making value stream. DFIQ REDUCES MANUFACTURING COSTS The effect of quenching immediately after plastic de- formation of steel parts (hot forging) was first studied in the former Soviet Union in the 1960s and later in Japan in the 1980s [2-4] . It was demonstrated that rapid cooling immedi- ately after hot forging improves mechanical properties (ten- sile and yield strength, elongation, and reduction in area) by more than 20% compared with those obtained using conventional post-forging heat treatment where parts are cooled to room temperature, then reheated and normalized INTENSIVE QUENCHING FOR LEAN MANUFACTURING OF STEEL PARTS Intensive quenching enables manufacturers to improve part performance at a lower cost than other available methods. Michael Aronov,* Nikolai Kobasko, FASM,* Joseph Powell,* and William Andreski, IQ Technologies Inc., Akron, Ohio Jon Tirpak, FASM,* Advanced Technology International, Summerville, S.C. prior to further quench and temper heat treating. Mechan- ical properties improve due to both the “freezing” of dislo- cations in steel grains created during plastic deformation of the part, and formation of finer grains (finer martensitic mi- crostructure) in the material. By comparison, in convention- al plastic deformation processes, parts are air cooled after forging, allowing dislocations to relax. Two reasons that quenching immediately after forging was not commercialized were that conventional quenching in oil is not suitable in forging operations due to potential fire hazard, and conventional water quenching is applicable only to forgings made of water-quench steel grades and sim- ple shapes due to the high probability of cracking. Because IQ can use water as a quenchant, it overcomes these two hurdles. In an ongoing project funded by the U.S. Department of Defense, IQ Technologies Inc. (IQT) designed and built a portable 600-gallonDFIQ system(patent pending) to quench forgings immediately after plastic deformation (Fig. 1). The main DFIQ system components include a steel tank; pump; special quenchant-agitation system to provide the hot forg- ing with a suitably intensive, uniform heat extraction rate *Member of ASM International Fig. 1 — Portable 600-gallon DFIQ system (patent pending) for quenching forgings.