Development of a carburizing and quenching simulation tool: Determination of heat transfer boundary conditions in salt

Authors:
Publisher website
Google Scholar
Abstract
In the numerical simulation of the quenching of steel parts, it is desirable to limit the thermal problem to one of conduction in the solid part, with Newtonian cooling on the surface. This avoids the solution of highly transient, non-Boussinesq conjugate heat transfer problems which often involve mixed convection. Of course, the heat transfer coefficient h{sub 1} is in general a function of local surface temperature, and may depend strongly on the part geometry and other parameters. In order to obtain appropriate heat transfer coefficients for quenching thick rings in salt, we solve the conjugate heat transfer problem for representative geometries and determine the heat transfer coefficient from the calculated heat flux at the solid-fluid interface. This is done in a two-stage approach. First, we examine fully coupled solutions obtained from first principles without adjustable empirical parameters using an adaptive finite difference code applicable to simple shapes. The purpose of this part of the procedure is to gain insight into the physics of immersion, free convection and forced convection and to determine the most appropriate forms of the physical properties in the salt. Validation for simple shapes is accomplished by comparison with experimental data reported in the literature. Second, empiricalmore » modifications to physical properties and simplified governing equations are used to account for conduction-dominated heat transfer on initial contact and subsequent forced convection during immersion, based on results of the first calculations, so that a commercial finite-volume CFD code can be used to model complex shapes and flow in a quench tank. These results are compared with experimental data for thick rings quenched in salt, and used to calculate surface heat transfer coefficients as functions of temperature and location from the resulting heat flux at the part surface. « less
Funding Information
  • USDOE, Washington, DC (United States)
  • Department of the Air Force, Washington, DC (United States)
  • DOE (AC05-96OR22464)