Study On Dust Removal Mechanism And Control System Of Iron Oxide Scale Ash Of Hot Rolled Strip

The national 14 th five year plan and the long-term goal outline for 2035 clearly put forward to promote the high-end and green manufacturing of raw materials such as steel.In the field of hot rolling,comprehensively and deeply purifying the hot rolling production environment and restraining the negative impact of dust and oxide particles on the surface quality of strip are common problems in the industry to improve the quality of hot rolling products.However,the hot-rolled strip is affected by high load,high speed,strong vibration and other factors in the high-temperature rolling process.The dust formed by high-temperature oxidation particles is not only easy to float in the rolling mill,but also easy to be pressed into the strip surface by the roll to form surface quality defects,which seriously affects the hot-rolled production environment and strip surface quality.According to statistics,the average occurrence rate of hot-rolled sheet iron ash defects in the national iron and steel industry is1.05～2.4%.The total amount of re judgment and waste products caused by sheet iron ash is up to 3.4 million tons every year,which seriously restricts the quality improvement of high-end hot-rolled products such as high-strength steel and automobile panels.At present,70% of domestic hot rolling units use water spray to reduce dust.When rolling silicon steel and stainless steel products,the dust reduction efficiency is only 20～30%,resulting in the loss of surface temperature of rolled products and affecting the thermal system.Therefore,the removal of scale ash from hot rolled strip has always been an important scientific and technical problem to be solved in the production process of hot rolled strip.In this paper,the formation mechanism and distribution characteristics of strip scale dust,dust removal mechanism and theory,strip surface dust defect detection and dust removal control technology and methods are studied to realize the effective removal of strip scale dust,so as to further improve the production environment and strip surface quality.The main research contents are as follows:1)Based on the analysis of the formation mechanism and diffusion process of iron oxide scale ash,the particle size,composition and wetting characteristics of iron oxide scale ash of hot rolled strip are analyzed,and the distribution characteristics of iron oxide scale ash near roughing and finishing mills during hot rolling are studied.On this basis,the theory and efficiency of atomization dust removal in high temperature environment are studied theoretically,thus,it lays a theoretical foundation for the dust removal of iron oxide scale ash in hot strip rolling.2)The relationship between temperature,pressure and atomization dust removal efficiency in rough and finish rolling of hot rolled strip was studied.The formation process and influencing factors of atomized droplets were analyzed by using fluid mechanics theory.The relationship between droplet size and spray pressure,nozzle diameter and spray angle at normal temperature was obtained.Based on the particle aggregation mechanism,the atomization dust removal efficiency model of the combination of dust particles and atomized particles in the real state is established;a multiphase flow model is used to simulate the movement of droplets inside and outside the nozzle at normal temperature.The relationship between droplet size and nozzle diameter and spray pressure is explored,and the relationship between droplet velocity and particle size distribution and nozzle diameter,spray pressure and spray angle is explored.The temperature distribution and droplet evaporation around the rolling mill are simulated and analyzed by using the temperature field and component model,and the relationship between droplet evaporation rate and droplet particle size and temperature is established.Based on this,the dust removal efficiency of roughing and finishing rolling of hot strip is obtained.3)The identification and segmentation method of iron sheet ash defects on the surface of strip steel based on Mask-RCNN is proposed,and the iron sheet ash defect pictures are generated through WGAN,which effectively solves the problem of low identification and segmentation accuracy caused by few iron sheet ash defect pictures on the surface of strip steel.On this basis,the minimum circumscribed rectangle of iron dust defects on the surface of strip steel,i.e.pitting and foreign matter pressing,is obtained by MER method.Based on this,the size and distribution law of iron dust defects on the surface of strip steel are analyzed,which provides an effective detection means for strip steel dust removal control method.4)An accurate control method of water spray pressure based on Fuzzy Adaptive PID for atomization dust removal is proposed,and an atomization dust removal control system for roughing and finishing rolling is developed to realize the efficient dust removal of iron oxide scale ash in roughing and finishing mills in the process of strip hot rolling.The atomization dust removal effect of the dust removal control system is verified by experiments.Based on the theoretical analysis of atomization dust removal mechanism and dust removal efficiency of hot-rolled strip,this paper puts forward the detection method of dust defects on the surface of strip steel,develops the accurate control system and equipment of atomization dust removal,and has been successfully applied to the hot-rolled strip production line,so as to effectively reduce the environmental pollution of hot-rolled strip mill and improve the surface quality of strip steel.