Study On Strengthening Mechanism Of Plasma Spraying Composite Coating On Tension Straightening Roller Of Continuous Caster

Continuous casting machine is the basic equipment for achieving continuous slab cast-ing technology.However,as a key component of continuous casting machine,the tension leveling roller is prone to peeling,cracking,and even bending of the roller surface under harsh production environment,which reduces the service life of the tension leveling roller.Therefore,improving the strength of the tension leveling roller in continuous casting machine has important research significance.In this paper,the composite coating prepared by plasma spraying technology was applied to the surface of the tension straightening roll.Through experimental analysis,finite element simulation and actual production test,the performance of composite coating pull rollers is evaluated,and the strengthening mechanism of composite coatings is studied,aiming to improve the working life of continuous casting machine pull rollers.The experiment used H13 steel material as substrate.Three kinds of composite coating samples including WC-20Cr₃C₂-7Ni,WC-20Cr₃C₂-7Ni containing 30wt.%8YSZ and WC-20Cr₃C₂-7Ni containing 50wt.%8YSZ were prepared.Scanning electron microscope was used to observe the cross section of each sample.The results showed that the coating compactness of WC-20Cr₃C₂-7Ni sample was poor.With the addition of 30wt.%8YAZ and 50wt.%8YSZ,the grain was refined,and the compactness of the composite coating was also improved.In order to further observe the microstructure of the composite coating,the elements and phases of the composite coating were detected by energy spectrometer and X-ray diffractometry.The results showed that there was metallurgical bonding between the two materials,and the WC phase decarburized during high temperature spraying,resulting in WC1-x and W phases.Hardness,scratch and friction wear tests were carried out on each sample coating.The results showed that the hardness of each sample coating was much greater than that of the matrix material,and with the addition of 30wt.%8YAZ and 50wt.%8YSZ,the average hardness of the composite coating first became larger and then smaller.Three sample coatings had good scratch resistance,and the adhesion between the tissues of the composite coating became more stable with the addition of 8YSZ.The composite coating doped with30wt.%8YSZ has the best wear resistance,and the wear forms are mainly abrasive wear and fatigue wear.The finite element simulation software was used to model the tension roller tension slab and calculate the temperature field and stress field distribution of conventional pull roller and each sample coating pull roller under the same production conditions.The results showed that the three sample coatings had thermal insulation effect,and with the addition of WC-20Cr₃C₂-7Ni material to 8YSZ,the better the thermal insulation effect of the composite coating.At the same time,with the enhancement of the thermal insulation effect of the coating,the equivalent force of the tension roller is also greatly reduced.Three kinds of the composite coating tensioning rollers were applied to the slab production in a steel enterprise.The actual production data show that the working life of the tensioning roller is greatly improved compared with the conventional tensioning roller.The fatigue life of the tensioning roller doped with 30wt.%8YAZ composite coating is the longest,which is about 1.3 times higher than that of the conventional tensioning roller.According to the improved Manson-Coffin life prediction model and life accumulation theory,the failure life of WC-20Cr3C2-7Ni and doped 30wt.%8YAZ and 50wt.%8YSZ composite coatings were 17 days,25.6 days and 18.4 days,respectively.It indicates that the fatigue failure life of the composite coating doped with 30wt.%8YAZ is the longest.