To the forecast of martensitic transformation development during sink drawing of austenitic steel pipes

Abstract

The work aim is the mathematical modeling of the austenitic steel pipes sink drawing process to establish the effect of the pipe wall thickness on the material stress-strain state and to predict the martensitic transformation development. The drawing process was simulated for thin-walled and thick-walled pipes by the finite element method using the DEFORM-2D software package. There are determined the shape change and deformations distribution, the deformations intensity and the average normal stress for seven variants of pipes with different wall thickness ratios and diameter are determined. Distribution patterns for two extreme variants are shown. The difference is shown in the stress state at the drawing process of thin-walled and thick-walled pipes. The change in the average normal stress in time t of a particle passage through the deformation zone for the outer and the inner surfaces for a thin-walled and extra thick-walled pipe is given. In either case, the compression stresses up to –400 MPa for the inner surface and tensile stresses for the outer surface up to +200 MPa are prevail at the entrance to the deformation zone. Inside the deformation zone, a thin-walled pipe is characterized by the presence of approximately equal compressive stresses both on the outer surface and on the inner one. However, the stresses are close to zero outside and reach –600 MPa inside for a thick-walled pipe. The deformation zone numerical simulation in the sink drawing made of austenitic steel showed that there are differences in the stress-strain state in the case of processing thin-walled and thick-walled pipes. The performed calculations and comparison with the literature data on the stress state influence on the cold martensitic transformation process made it possible to predict the development of this transformation in the drawing process. It was revealed that during thin-walled pipes drawing process are created more favorable conditions for the phase transition development.This work was performed with partial financial support of Resolution No. 211 of the Government of the Russian Federation, contract No. 02.A03.21.