Research On Forging Process For Ultra-high-strength Steel Aircraft Landing Gear

The landing gear is one of the key components of aircraft, which could support the aircraft weight and absorb impact energy. The landing gear has great performance of strength, toughness, corrosion resistance, as well as fatigue resistance. At present, the landing gear has many problems, such as laggard production mode, large forming load, not up to standard grain size and so on. The landing gear forging process was investigated on the eighty thousand tons hydraulic press by integral die forging process in this paper. The main research contents include:(l)The deformation parameters on flow stress and dynamic recrystallization behavior were studied, to establish the high temperature plastic deformation flow stress model of23Co13Ni11Cr3Mo ultra-high-strength steel by isothermal compression experiment of Gleeble-1500. The results show that the flow stress decreases with the increase of temperature, and increases with increasing strain rate. Dynamic recrystallization behavior is more obvious at high temperature and low deformation rate.(2)The micro structure of the ultra-high-strength steel were analyzed by Leica-DMI5000M metallographic microscope, to study the deformation parameters on dynamic recrystallization, and established23Co13Ni11Cr3Mo ultra-high-strength dynamic recrystallization model basing on the theoretical and experiment. The results show that dynamic recrystallization grain size is smaller, fully and good process stability at deformation temperature of1000-1100℃.When deformation rate is low, grain size is larger, but the distribution is uniform. When deformation rate is high, the grain size is small, but the distribution is not uniform.(3) The forging process model for the ultra-high-strength steel landing gear were established, By the DEFORM finite element simulation platform to formulate the forging process for landing gear on the eighty thousand tons hydraulic press. Different process parameters were studied on the forming regularity of the influence of landing gear. The results show that the Pre-Final forging process greatly reduces the forming load, and we can manufacture the landing gear on the eighty thousand tons hydraulic press. Increasing deformation temperature could decrease the forming load, and improve the metal fluidity, to fill easily. Reducing the forming speed could improve the deformation uniformity of the landing gear, and avoid local defects. Under the deformation temperature of1050-1100℃and the forming speed of1-5mm/s condition, the landing gear forging forming load is under eighty thousand tons, and the landing gear forging forming effect is good and the deformation is uniform.(4)The landing gear forging microstructure evolution model was established basing on the23Co13Ni11Cr3Mo ultra-high-strength steel landing gear forging process model. We have studied the different process parameters on dynamic recrystallization of the landing gear forging. The results show that with increase of the deformation, the grain size is smaller. Under the deformation temperature of1050℃and the forming speed of5mm/s condition, the landing gear forging microstructure is most ideal, the average dynamic recrystallization fraction reaches to79.8%, the average grain size is20.4μm, which reaches to level8～8.5.