Papers by Keyword: Bar Rolling

Abstract: A new groove design method of uniform strong strain of bar rolling was proposed based on the principle of strong plastic deformation to manufacture ultra-fine grain(UFG), and flat-oval groove type with the characteristics of big crushed and multidirectional deformation was set up. The numerical analysis model of hot continuous bar rolling process was created using nonlinear finite element method. The study of the law of plastic strain distribution after each rolling pass of the caliber series indicated that the caliber can satisfy with the precise size and shape, and can also better introduce the plastic strain to the center of cross section and get uniform strong strain. The largest strain was more than 5.0 in the center of cross section, in which condition ultra-fine grain can be fabricated. Therefore, this study provides important theoretical basis for the ultra-fine grain of bar rolling development.

Abstract: In order to predict the forward slip value correctly, this article established regression model of forward slip in oval-round and round-oval pass rolling, predicted the forward slip values in ach pass in Ф12 and Ф16 round bar rolling for a factory, measured forward slip of lead rods in experimental mill using geometrical modeling method. The results showed that the model of forward slip has great practical value for proper design rolling speed, rolling schedule, thereby ensuring the continuous rolling process carried out smoothly

Abstract: This study investigates the shape evolution of the pinholes on the bloom surfaces, which are originated from the continuous casting process, during multi-pass hot bar rolling. It is important to track the shape evolution of the pinholes since they can be formed as the sharp surface cracks after hot bar rolling and can initiate the surface bursts in the cold forging process. It is very hard to track the deformation behavior of the pinholes with detection tools during hot rolling, so the numerical simulations can be properly utilized. In general, the size of the pinholes in the bloom surface is order of micrometer although the bloom size is order of millimeter. This size discrepancy between them makes it difficult to discretize the domain including the pinholes for the finite element (FE) simulations. To overcome this limitation of the conventional FE simulation, multi-scale technique coupling the macro and micro models was developed in current study. This technique was implemented into the commercial simulation code, DEFORM-3D. The developed multi-scale simulation technique was capable of simulating the shape evolution of the pinholes through multi-pass hot bar rolling successfully. It is concluded that aspect ratio of the initial pinhole should be larger than 2.0 approximately to prevent it folded.

Abstract: Main works on microstructure prediction on superalloys during hot forming processes deal with close die forging of 718 alloy. In this paper, we focused our interest towards incremental hot forming process. In that case, matters become more complex, due to the partially recrystallized microstructure we have to take into account at the beginning of each pass. An original method is presented in this paper, still using a phenomenological approach, according to Avrami formulation, with two main additional assumptions, in order to carry out computation on microstructure evolution during the process. Examples with comparisons between real and computed microstructure (recristallyzed fraction, different populations of grain size) enable us to valid our model for bar forging.