Study on exit temperature evolution during extrusion for large-scale thick-walled Inconel 625 pipe by FE simulation

Abstract

The extruded large-scale thick-walled pipes made from Inconel 625 alloy are widely used in many fields such as in the oil and chemical industry, thermal power generation, nuclear power plant, aerospace, and defense industry. However, the nonuniform distribution of grain size along the thickness and length directions of the extruded pipe always appears, which has a great influence on the mechanical property and uniformity of the pipe. The inhomogeneous distribution of the exit temperature in the entire extrusion process is the decisive factor leading to the grain nonuniformity of the extruded pipe. Therefore, it is necessary but difficult to reveal the evolution of the exit temperature under some key extrusion parameters in order to effectively control the exit temperature uniformity. In this paper, a thermomechanical coupled finite element (TMC-FE) model, which can precisely predict the hot deformation behavior of the extrusion process for large-scale thick-walled Inconel 625 pipe, has been firstly developed based on the DEFORM-2D platform. And then, the influence of key extrusion parameters, namely extrusion speed (V), initial billet temperature (T b), extrusion ratio (λ), and friction (μ), on the exit temperature was revealed by comprehensive simulations. In addition, using the standard deviation of exit temperature (SDexit) as the measure indicator of the exit temperature uniformity, we also disclosed the influence of the key process parameters on the exit temperature uniformity in detail. The results show that with the increase of V, T b, and μ, the uniformity of exit temperature in the entire process firstly becomes better and then gets worse. The larger λ can result in a more uniform exit temperature. In consideration of the obtained results, within the feasible window of the key extrusion parameters defined in this paper, the conditions of T b = 1,100–1,150 °C, V = 125–150 mm/s, μ = 0.015–0.02, and a larger extrusion ratio (λ) are suggested for the extrusion of large-scale thick-walled Inconel 625 pipe in order to get more uniform exit temperature.