Ultra Fast Cooling of a Hot Steel Plate by Using High Mass Flux Air Atomized Spray

Abstract

In the current research, the ultra fast cooling (UFC) of a hot stationary AISI‐304 steel plate has been investigated by using air atomized spray at different air and water flow rates. The initial temperature of the plate, before the cooling starts, is kept at 900°C or above. The spray was produced from a full cone internal mixing air atomized spray nozzle at a fixed nozzle to plate distance; and the average spray mass flux was varied from 130 to 370 kg m−2 s by selecting different combinations of air and water flow rates. The surface heat flux and surface temperature calculations have been performed by using INTEMP software and the calculated results have been validated by comparing with the measured thermocouple data. The heat transfer analysis indicates that the cooling occurs in the transition boiling regime up to surface temperature of 500°C and thereafter it changes to nucleate boiling regime. The superposed flow of air on the hot plate enhances the cooling in the temperature range of 900–500°C by sweeping the partially evaporated droplets from the hot surface. However, due to the high percentage of fine water droplets in the resultant spray produced at higher air flow rates, the maximum cooling rate is achieved at the medium air flow rate of 30 N m3 h−1. The cooling rate (182°C s−1) produced by an air atomized spray is found to be in the UFC regime of a 6 mm thick steel plate. The findings of this research can be considered as the basis for the fabrication of cooling system in the run‐out table of a hot strip mill.

Surfactant-Based Cu–Water Nanofluid Spray for Heat Transfer Enhancement of High Temperature Steel Surface

“…The set-up mainly consists of a cooling section with nozzle arrangement, a data acquisition system, an air loop and water coolant circuits which supply the air and coolants to the nozzle and a recycling coolant circuit to the liquid reservoir. The flow rates of air and water are 30 m 3 /hr and 10 l/min respectively maintained throughout all the experiments, which have been optimized earlier for the current experimental set-up [14]. The test plate used is AISI 304 designated stainless steel of dimensions 100 mm × 100 mm × 6 mm, and is arranged 60 mm below the nozzle orifice for cooling.…”

“…However, the method of achieving UFC is hardly disclosed and large amount of liquid coolant used is another drawback for the environmental and economic constraints of industries [10]. Mohapatra et al [14] found the easier way to get the ultrafast cooling on a 6 mm thick plate using high mass flux air-atomized water spray system and it was further enhanced by using inclined spray impingement by Ravikumar et al [15]. During the process of spray cooling of high temperature surfaces, the droplets cannot completely evaporate.…”

Industrial Furnaces for Steel Processing – 90 Years of Continuous Improvement

“…Ultra‐fast cooling is realized with water jets and/or water/air jets in metal processing. This phenomenon is important for the controlled cooling of plates, 6xxx grade aluminum and ultra‐high strength steel strips.…”

Comparison of the Microstructure of M2 Steel Fabricated by Continuous Casting and with a Sand Mould

“…The dendrite size and center shrinkage cavity are developed as a result of the slow cooling conditions. The cooling rate is key to the quality of M2 steel [19] and an appropriate cooling rate has a positive effect on relieving internal defects in the billet such as cracks and center shrinkage cavities [20,21].…”