Study of Skid Mark during Reheating and Rough Rolling
|Course||Thermal Power Engineering|
|Keywords||skid mark skid walking beam reheating furnace mathematical model delay for rolling rough rolling|
The main problem of reheating slab is nonuniform temperature and skid mark is an important influence factor. In order to reduce skid mark, the direct method is installing thermoduric skid on cooling pipe. Generation and hazard of skid mark, application and development of different structural skid are introduced in this paper. Slab temperature and temperature difference of skid mark in reheating furnace and rough rolling are simulated.Based on a walking beam furnace, a two dimensional mathematical model of slab and one dimensional mathematical model of skid are built. This model amends the neglected third dimension. The third dimension has no grid, and two cross-sections are calculated. Skid mark is the lightest when skid contacts with two cross-sections alternately, which called the most advantage condition; skid mark is the heaviest when skid contacts with one cross-section all the time, which called the most disadvantage condition. Therefore, this model has less calculation quantity than three-dimension model and more correct than two-dimension model. Applying total heat absorption factor method, heat flux to slab surface is calculated. Considering shelter of skid and pipe package to slab bottom surface, heat flux to slab bottom surface has been corrected.Two conditions called the most advantage condition and the most disadvantage condition are simulated. Slab temperature and temperature difference of skid mark under two conditions are calculated. Isotherm of slab when it discharges is plotted and difference of the result under two conditions is compared.The reheating process is also simulated when slab charges hotly. Temperature of skid mark with reheating time and isotherm of slab are obtained. Compared cold charging with hot charging, we know that temperature difference of skid mark, temperature difference of cross-section and average temperature of slab are almost the same.Delay for rolling is a typical dynamic process in reheating furnace. Changes of skid mark when slab delays or steps are simulated. Two representative locations in each zone are chosen to calculate temperature difference of skid mark whose change with time at different furnace temperatures are also analyzed.In the rolling production line, there is on-line detective device for surface temperature of slab behind rough rolling. So the process of rough rolling and descaling is simulated in this paper.