Experimental Study And Numerical Simulation Of Hot Steel Plate Laminar Cooling On The Runout Table

Approximately 30% of steel are hot-rolled to flat products annually in the world. The properties of hot-rolled flat steel is decided by the subsequent cooling process, these are the cooling rate and the uniformity of the temperature. Therefore, controlled cooling on the runout table is one of the most important processes in the steel industry. The controlled cooling after hot-roll which is began to be used in the last 80s, especially widely used laminar flow cooling technology in recent decade, have greatly improved the efficiency of production and reduced consumption of energy resource, but the adjustability of the cooling capability, the uniformity of the temperature distribution in the plate and the veracity coiling temperature are far from the expectation. Plate warp and poor stress uniformity are often encountered in actual production, and even worse for middle and heavy steel plate. The key to improve controlled cooling technique understands the affection that process factor to cooling, according to the material of steel plate and the properties desired, control the process factors veraciously.However, the instantaneous impingement boiling heat transfer in laminar cooling is rather complicated, the temperature rate at the plate surface reaches as high as 2100°C/s, and it is influenced by many factors, it is difficult to develop a deep and systemic research. In this article, a universal experiment table is designed and built to study the laminar cooling process. In order to obtain accurate temperature data of high temperature and high cooling rate, it is the first step to choose thermocouple and fix the thermocouples. In this article, K type thermocouple was selected and they are fixed by a through aperture-groove-cover method. A set of NI high speed data system and Labview are employed to obtain the temperature 0.8mm under surface. Detailed experiments are carried out to study some key factors such as water rate, nozzle diameter, number of nozzles and the distance from the nozzle to plate. An inverse heat conduction model and a 3-d unsteady heat conduction model with inner heat source were developed, and corresponding code was programmed by FORTRAN. The results of computing program are checked. Surface temperature of test points and heat transfer coefficient(HTC) as well as heat flux at surface are worked out by inverse heat transfer program align with experiment data, which provides integrated information for the study of the affection of factors to the cooling process. Further, at the base of 3-d unsteady heat conduction program and heat transfer coefficient, it is easy to get the temperature field of the whole plate. The result shows that the temperature change is quite different in different location. The temperature drop in the plate rises with the increase of impingement velocity and size. But the HTC in the cross zone of several jets and impingement zone hardly changes. The computing route and research result provide reference to the control of laminar cooling in actual production.