Factors Affecting the Life of Steel Grating Bars in Roasting Cars

Abstract

To understand the factors affecting the working life of 40Kh24N12SL steel grating bars in roasting cars, we compare data regarding the grating bars after operation with the results of simulating their operating conditions. The results obtained by finite-element modeling are highly reliable. In modeling, the maximum possible number of boundary conditions is specified on the basis of the data regarding the grating bars already obtained and literature data. Modeling shows that a considerable temperature is formed over the part’s cross section, with local heating zones. The heating is predictable and is associated with the supply of coolant to the working zone in the course of operation. Over time, zones with large internal stress and strain are formed locally in the part. The appearance of these zones depends strongly on the presence of structural inhomogenities of the part and is thought to be associated with the geometric complexity of the casting. In the presence of shrinkage cavities, all of the stress and strain values increase sharply, especially at local maxima. The distribution of the local zones with high stress and strain remains practically unchanged in the presence of shrinkage cavities. Analysis of the position of the zones with high stress and strain sheds light on the grating bar failure by cracking in the course of operation. The presence of shrinkage cavities in the metal is found to be a major cause of the buckling, cracking, and fracture of 40Kh24N12SL steel grating bars in roasting cars. Simulation of the operating conditions permits explanation of the defect formation in the grating bars in accordance with observational data.