Hot - dip galvanizing. Part 1: Non stationary model of temperature profile

Abstract

The hot-dip galvanizing is an effective method for protecting ferrous materials against the corrosion. This technique consists of applying a deposit by immersing the parts in a molten zinc bath, at temperatures between 440ºC and 460ºC for a certain amount of time and their subsequent cooling. This work had the purpose of modeling the heating profile of a galvanizing cell at a non-stationary regime using the node method and considering heat transfer by radiation, free convection and conduction. The cell has the dimensions: 7100 x 1600 x 1350 mm (length x width x depth) and the heat generation takes place by electric resistances. Through an iterative process, assuming Δx=Δy=0,178m and a time interval Δt=0,011h, the temperature gradient at 420 points of the cell (x; y) was estimated as a function of time and the heat transfer coefficients, satisfying the expected technical requirements. The results allowed increasing the knowledge about the cell heating for the subsequent process automation, the correspondence between the established operating time and that predicted by the model was satisfactory. The temperature range between 526°C to 538°C at the heat source was estimated to be probably the most convenient to end the heating operation.