Study On Heat Insulation Effect And Thermal Shock Failure Mechanism Of Cr₂O₃ Coating On The Straightening Roller Of Continuous Casting Machine

Slab continuous casting technology occupies an important position in the iron and steel industry.Compared with the traditional ingot casting technology,this technology has a variety of significant advantages,mainly in the following aspects:high yield of metal,simple production process,less energy consumption,good quality of casting billet,etc.As an important part of continuous casting machine,the straightening roller of caster has a very bad working environment.Under the combined action of high temperature slab heat transfer and internal cooling water cooling,the surface of the roller is prone to thermal fatigue damage,such as surface cracks and surface shedding.The surface quality of the tension straightening roller largely affects the surface quality of the billet,so it is very important to reduce the surface temperature of the straightening roller and improve the working environment of the roller.In this paper,a layer of Cr₂O₃ coating is prepared by plasma spraying on the surface of the tension straightening roller to achieve the above purpose.The simulation of the conventional straightening roller and the roller with Cr₂O₃ coatings are carried out by the finite element simulation software ABAQUS.The differences of the surface temperature and equivalent stress of two kinds of tension straightening rolls are compared.The thermal insulation effect of the coating is preliminarily considered by means of simulation technology.Secondly,the surface temperature test of the tension roller is designed.Cr₂O₃coatings were prepared on the experimental roll surface by using high level equipment and better technological parameters.According to the actual conditions,a suitable temperature test point was selected to observe the roll surface temperature under different roller positions and different rotating speeds.The actual effect of the coating is considered by the experimental method,and the results are verified with the finite element simulation results.Subsequently,specimens with Cr₂O₃ coatings were prepared.The thermal shock test was carried out to analyze the failure modes of the coating after several cycles of thermal cycling.The surface and cross sections of samples were observed before and after thermal shock by SEM.From the microscopic point of view,the effect of thermal shock on the internal structure of coating is explored.Finally,the appropriate coating life prediction model is selected.The coating life was preliminarily estimated.The thermal barrier coating on the surface of the tension straightening roller can significantly reduce the maximum temperature and the fluctuation amplitude,the actual heat insulation effect is obvious.It effectively improves the working environment of the roller body,and has a good application prospect in prolonging the service life of the pull straightening roller.