Finite Element Modeling of Thermo-mechanical and Metallurgical Behavior of Type 304 Stainless Steel in Cold Strip Rolling

Abstract

A finite element-based, integrated process model is presented for the coupled analysis of the thermo-mechanical and metallurgical behavior of type 304 stainless steel occurring in the entire tandem mill during cold strip rolling. The validity of the proposed model is examined through comparison with measurements. The model's capability of revealing the effect of diverse process parameters is demonstrated through a series of process simulation.KEY WORDS: Type 304 stainless steel; finite element method; thermo-mechanical behavior; metallurgical behavior; cold strip rolling. model 5) was adopted for the prediction of the evolution of the martensite during cold rolling.Under constant temperature, strain rate and stress state, volume fraction of martensite may be described as: Where the kinetic parameter a 0 and b, strong function of temperatures, were determined from the experimental observation, which were shown in Figs. 1(a) and 1(b), respectively. n, ė y , and M, taken from the references, 4,5) are described in Table 1. The predicted fraction of martensite evolution was in good agreement with the measurements, as shown in Fig. 2..Considering that the aforementioned martensite is mainly generated under the condition of the deformation in the rolling process, the fraction of martensite evolution can be determined based on the strain and temperature fields, as follows:........... (3) Where, d f m /de may be determined from Eq. (1). FE Model for Analysis of Rigid-viscoplastic DeformationA steady-state, rigid-viscoplastic deformation behavior of the strip was adopted in the present investigation. The detailed finite element formulation may be seen in the references. 9,10) The flow stress s of the strip within two phases of austenite and martensite may be represented by the mixed rule 4,5) : Where C g1 -C g5 , and C aЈ1 -C aЈ5 , taken from the references, 4,5) were described in Table 2.Assume that the strain rate may be decomposed into the Vol. 43 (2003) .(9)Parameters R and Dh, taken from the references, 4,5) may be found in Table 1. With respect to the high process speed in the tandem cold rolling process, ė trans and ė v may be neglected when comparing to ė p , which was verified from the comparison of mean values among these three components by FEM analysis. We found that plastic strain rate ė p (ϭ32.8 (1/s)) was extremely much larger than the summation of the other two components ė trans and ė v (ϭ1.04 (1/s)). FE Model for Analysis of Heat Transfer in the Strip and in the RollThe governing equation for steady state heat transfer in the strip as well as that in the roll is given by (10) where r is the density; u i represent the components of the velocity vector and Q represents the heat dissipated by plastic deformation. Note that Qϭse¯in the strip and Qϭ0 in the roll, when the roll deformation is purely elastic. Q l represents the latent heat discharged during phase transformation according to the references, 4 Where, f˙m, the rate of the fraction of martesite, was determined by finite difference method.In t...

Thermomechanical behaviours of strip and work-rolls in cold rolling process

“…Prakash et al [8] and Chandra and Dixit [9] have modelled the process using a rigid-plastic mechanical behaviour for the strip and in this way they studied the deformation pattern of the metal in the deformation zone. Sun et al [10] have investigated mechanical as well as metallurgical behaviours of austenitic stainless steels during cold rolling. Rao and Lee [11] have utilized a two-dimensional elastic-plastic finite element solution to predict deformation behaviour during cold strip rolling processes.…”