Simulation of the Distortion of Long Steel Profiles During Cooling

Abstract

A complex thermomechanical model for simulating the transient fields of the temperature, microstructure, stress, strain, and displacement during quenching of steel profiles is introduced. The thermoplastic material model is formulated on the basis of J2-plasticity theory with a temperature- and phase fraction-dependent yield limit. Coupling effects such as dissipation, phase transformation enthalpy, and transformation-induced plasticity are considered. The validity of the model is verified by comparing the simulation results with available experimental measurements. The introduced model serves as a basis for optimizing the cooling conditions for reducing residual stresses and distortions. The simulation results for T and L profiles of two different types of steel are described.

Numerical Simulation with Thorough Experimental Validation to Predict the Build-up of Residual Stresses during Quenching of Carbon and Low-Alloy Steels

“…Thermal conductivity and specific heat of austenite, martensite, bainite, and pearlite as a function of temperature (°C). [28][29][30] Constituent Thermal conductivity (W/m °C) Heat capacity (J/kg °C) (Table 1) of microconstituent i (pearlite, bainite, or martensite), and is the change in volume fraction of this microconstituent per unit temperature variation, obtained from the microstructure evolution model. To define the boundary condition for the strain-stress simulations, the whole quenched bar surface was assumed free from forces or stresses.…”

Sensitivity of material properties on distortion and residual stresses during metal quenching processes

“…Our previous works (Pietzsch et al, 2005(Pietzsch et al, , 2007Brzoza et al, 2006;Kaymak and Specht, 2007;Kaymak, 2007;Nallathambi et al, 2008) are focused to the optimum cooling strategies through a modified HTC profile which reduces the distortion and residual stresses simultaneously. Apart from the external parameters which control the quenching process, the internal parameters which significantly dominate in the quenching process are the material properties.…”

Distortion and Residual Stresses during Metal Quenching Process

“…During an equal cooling, the temperature gradient is not uniform due to the mass distribution with respect to the locations of the boundaries. The distortion can be eliminated by increasing the local cooling at mass lumped regions [6]. This fact is verified in this section with the first cooling strategy as shown in Fig.…”

“…The temperaturedependent material properties of the individual phases can be found in reference [6]. The distortion of the long profiles is represented by their curvature.…”

“…The total deformation observed in the quenching process is less than 4%. Therefore, using the advantage of small deformation theory, the total strain E can be additively decomposed into four components as in [6] …”