Finite Element Simulation And Experimental Study On Multi-Directional Extrusion Process Of Deep-Hole Three-Way Valve Body

The development of nuclear power industry has put forward higher requirements for the quality of valves.However,the traditional casting and tailor-welded valves cannot meet the requirements of nuclear grade in terms of strength and corrosion resistance.The subsequent processing of valves produced by ordinary forging process is large,resulting in material waste and performance damage.Multi-directional extrusion can realize the one-time forming of three-way valve body,which is the preferred process for manufacturing high-performance valve body parts.However,at present,the research on multi-directional extrusion related processes of deep-hole three-way nuclear valve body forgings has not yet achieved a breakthrough.In this paper,the multi-directional extrusion process is used to form the nuclear grade 42 Cr Mo steel deep hole three-way valve body parts,and the vertical main hole depth is more than 250 mm.The finite element simulation technology is used to simulate and analyze the multi-directional extrusion forming process of the three-way valve body,determine the process parameters,and finally verify the rationality of the process through the forming test.By analyzing the structure of the deep hole three-way valve body parts,the forgings and inspection requirements were designed.The volume of cylindrical 42 Cr Mo alloy steel billet was calculated.A horizontal parting multi-directional extrusion die was designed.The forming process was developed : the die was preheated to 400°C,the billet was heated to 1200°C,the upper die core and the upper die sleeve were closed downward,the vertical hole of the forging was formed by vertical punch,the horizontal hole was formed by horizontal punch,and the die was opened after forming.The multi-directional extrusion clamping and forming process of three-way valve body were simulated by Deform finite element software,and the microstructure evolution of forgings was simulated based on Deform secondary development.The maximum equivalent strain is 5.540,the minimum equivalent strain is 0.007,and the average equivalent strain is 1.410.The maximum equivalent stress is 77.1MPa,the minimum equivalent stress is 2.0 MPa,and the average equivalent stress is 22.8MPa.The peak extrusion force of vertical punch is 313.2k N,and the peak extrusion force of horizontal punch is 486.0k N.The forgings achieve complete dynamic recrystallization,and the maximum dynamic recrystallization grain size is 103μm,which is 97μm smaller than the original size,and the refinement is obvious.The influence law of different height-diameter ratio of blank is obtained: the average value of equivalent strain and the extrusion force of vertical punch decrease with the decrease of height-diameter ratio,and the recrystallized grain size increases.The reasonable billet diameter is Ф180mm.Based on the simulation results,the multi-directional extrusion forming test of deep hole tee forgings was carried out.The forgings were well filled,and the forming force was consistent with the simulation results.The results of appearance inspection,magnetic particle inspection,ultrasonic inspection and size inspection all met the requirements,indicating that the process was reasonable and feasible.