Microstructural Evolution in Multiway Loading-Forming Process of AISI 5140 Steel Triple Valve Body
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INTRODUCTION
MULTIWAY loading technology, in which the billet is loaded in the horizontal and vertical directions at the same time or in sequence, provides an efficient approach to form integral triple valves with high strength.[1–3] However, multiway loading-forming of triple valve body is a complex plastic forming process under coupled effects of multifactors. The metal undergoes complicated unequal deformation, especially microstructural evolution, such as dynamic recrystallization (DRX). For a certain material of the triple valve, the microstructural evolution during the forming process is mainly affected by forming parameters (i.e., loading speed of the punch, initial temperature of the billet, and friction factor). The microstructural evolution especially the final microstructure and its distribution directly determines the quality, mechanical property, and usage life-span of the formed valve. Hence, it is important in terms of optimal design and precise control of performance to study the microstructural evolution and the effects of forming parameters in the multiway loading-forming process of triple valve body. Xu[4] and Hu et al.[2] investigated the multi-ram forging of tee joint by means of 2D finite element (FE) modeling, and found that horizontal rams were under partial load. Gontarz[3] executed physical experiment and numerical simulation of forming of valve drop forging with three cavities, and found that the
ZHICHAO SUN and HE YANG, Professors, are with the State Key Lab of Solidification Processing, Department of Materials Science and Engineering, Northwestern Polytechnical University, P.O. Box 542, Xi’an, Shaanxi 710072, P.R. China. Contact e-mail: zcsun@nwpu. edu.cn Manuscript submitted January 10, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
magnitude of the strain had a significant influence on the forming quality and work done. Zhang et al.[5] simulated the multiway loading process of multiported valves based on coupled thermal–mechanical FE method, and compared the forming processes of the tee valve and cross valve and effects of two billet placement ways. Sun et al.[6] analyzed the deformation and temperature nonuniformity in forming of AISI-5140 triple valve by multiway loading. The multiway loading-forming process has been studied by experiment, theory, and FE methods.[3,5,6] Meanwhile, hot deformation and microstructural evolution behaviors of AISI 5140 were studied by experiment and the DRX volume fraction and grain size models were regressed, which have been applied in cross wedge rolling and validated.[7–10] However, by now, relatively little work related to microstructural evolution in multiway loading-forming of triple valves has been presented. For modeling and simulation of microstructure in hot plastic forming, there are three kinds of methods, including direct simulation method (i.e., stochastic method), phase-field method, and FE numerical method. The stochastic methods (e.g., the Monte Carlo approach and the Cellular Automata method) are suitable for complex dynamic system simulatio
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