Tenova LOI-Italimpianti tracking simulator for high flexibility roller hearth furnaces

摘要

ROLLER hearth furnaces (RHF) connect the casting section of thin slab casters such as the CSP (Compact Strip Production - an SMS technology) plant to the rolling mill. Although the thin slabs enter the RHF at an elevated temperature from the continuous caster they need to be further heated to the rolling temperature (typically 1050-1200 deg C depending on steel grade). For completing such a task a relatively short time is required - compared to the reheating time of a walking beam furnace which is normally charged with cold stock. The total length of a RHF needs to be longer than the minimum length necessary just for heating the slab as additional length is necessary corresponding to the length of the slab so it can be held in a soaking zone after the heating zone should a delay on the mill occur. In this way, while the continuous casting machines are feeding the RHF with thin slabs, it is possible to perform on-line maintenance at the finishing mill (such as roll changes). This otherwise empty space inside the RHF available for holding slabs during the mill stop (or the corresponding time available for filling up the furnace) is normally called the 'buffer' or 'buffer-time'. The buffer length required depends on the casting speed (which can be adjusted only within small limits) and the rolling speed. The target is to keep the length of the buffer as short as possible while being able to accommodate all the possible slabs in terms of their length, charging temperature, casting speed and rolling speed. This condition corresponds to the minimum RHF length for the required production mix while avoiding slowing down the continuous caster or even being forced to scrap slabs if the furnace becomes full.