When heavy plates 60–100 mm in thickness are produced by means of the TMCP+ACC technology at NLMK DanSteel, it uses the Mill Quarto 4200 , which among other includes the following basic equipment: a continuous multizone reheating furnace (Figure 2a), a four-high reversible stand (Figure 2b), an accelerated cooling unit (Figure 2c) and a hot plate leveler (Figure 2d).
The continuous walking beam reheating furnace has 6 zones and a capacity of up to 120 t/h. It runs on natural gas with a heating value of up to 40 MJ, the maximum specific consumption of heat for slab heating being 38 m3/t. Slabs are moved in the furnace in three independent rows. The first and the third row are used to reheat slabs 200–250 mm in thickness, the middle row is used to reheat the slabs 310-400 mm in thickness (Figure 2a), which makes it possible to control the heating time depending on the thickness and slab chemistry. The target slab discharging temperature and the required heating time are ensured by means of an automated control system and a mathematical metal heating model.
The four-high stand with a 4.550 mm long working roll body makes it possible to implement intensive TMCP modes to obtain heavy plates with a given set of mechanical properties and high precision geometry to meet the requirements of EN 10029 and similar tolerance standards. The stand is equipped with a roll shifting system (CVC plus), a roll bending control system (WRB), and a hydraulic roll gap control plant (HGC). These systems in combination with the self-adapting mathematical modeling of heating and rolling processes ensures a stable flow of metal in the deformation zone when slabs up to 400 mm in thickness are rolled in the first passes in intensive deformation modes.
The 24 m long accelerated cooling unit (AC) makes it possible to implement intensive water/air cooling modes for heavy plate processing, including multistage processing. The AC is equipped with 18,240 nozzles, 45 independent control and adjustment sections, endand sideedge masking systems, an oscillation option, and operates in 5 different modes: 1) Interstage cooling; 2) Accelerated cooling; 3) Direct quenching; 4) Soft cooling; 5) Multistage final cooling.
The design of the 9-roller hot plate leveler enables the automated levelling of the TMCP heavy plates up to 120 mm in thickness in the temperature range of 350-850 °C. The maximum levelling speed is 2.5 m/s. The HPL is equipped with tilted crossbars with independent adjusting screws. The maximum levelling force is 29 MN.
Due to the fact that the TMCP+ACC process has a large number of adjustable and controllable technological parameters, the main line of the NLMK DanSteel Mill Quarto 4200 operates in the automatic mode and is equipped with 16 pyrometers, 3 thermal scanners and more than 50 sensors that track metal position and movement in the flow of the main line of the rolling mill. The data received from these devices are combined into manufacturing database packages at the L2 automation level and are used to self-adapt the control models of the continuous furnace, the rolling stand and the accelerated cooling unit.