Research On Microstructure And Properties Of Hot Rolled Double-Sides Enamel Steel

Enamel products have strong acid and alkali resistance,durability,wear resistance,easy forming and other advantages.It is popular with the vast number of consumers.This paper's purpose is to develop a method which is for hot rolled double-sides enamel steel.It requires that the yield strength after firing is more than 340 MPa,and its resistance to fish-scaling sensitivity(TH value)reached more than 10min/mm2.The objective of this research is to provide a guidance for production of the factory.In this paper,the properties of hot rolled double-sides enamel steel were studied:first,the chemical composition of experimental steel was designed and smelted,then calculated the precipitation temperature of each phase in experimental steel by Thermo-calc software.At last,we studied the effects of heating temperature,finishing temperature and coiling temperature on the precipitation behavior of titanium precipitates and resistance to fish-scaling properties.In addition,we studied the effect of after firing on microstructure and properties.We obtained the following conclusions:(1)Heating temperature can affect the dissolution of titanium precipitates.The higher of the heating temperature,the more of titanium precipitates to be dissolved.It will help get less than 10nm dispersion of Ti precipitation under the subsequent rolling process.The finishing rolling temperature mainly affect the distribution of titanium precipitates.The high finishing rolling temperature conducive to the inter-phase precipitates;the low finishing rolling temperature is forming the random of precipitates.The size of inter-phase precipitates is smaller than the random precipitates.The coiling temperature mainly affects the precipitation of TiC,while higher coiling temperature is benefit to small TiC precipitates.When coiling temperature is 600?,there is little TiC in ferrite.(2)Results of hydrogen permeation show that:there is a close correlation between TH value and the size and volume fraction of titanium precipitates.The smaller size of precipitates and larger the volume fraction is,the larger value TH is.The high heating temperature conducive to the re-precipitation of titanium precipitates,and the finer precipitates can be obtained and TH value will be lager.The high finishing rolling temperature is favorable to forming the small TiC,so we can get greater value of TH.the high coiling temperature is and the more TiC precipitation in ferrite get,the resistance to fish-scaling sensitivity of TH is higher.(3)The microstructure of hot rolled double-sides enamel steel is mainly polygonal ferrite and some of carbides,the heating temperature can affect the uniformity of ferrite,and the grain uniformity of the high heating temperature is poor.The effect of finishing rolling temperature on the grain size is small.The tissue retain the rolling states with lower coiling temperature.When coiling temperature is 700?,the grain re-crystallization occurred and the rolling state has obvious improved.(4)Hot rolled double-sides enamel steel after firing twice 850? with 10min,the microstructure was changed into equiaxed ferrite,obvious carbide precipitated at grain boundaries.The precipitation of titanium in enamel steel has decreased significantly after firing,the value of TH is down to 4min/mm2.The mechanical properties of yield strength has greatly reduced after firing.The yield strength of experimental steel in different process reached more than 560 MPa before firing,and it reduced to about 400MPa after firing,and the elongation increased from 24%to 30%.After firing the impact power can reach more than 100J.Therefore,the mechanical properties and resistance to fish-scaling properties of hot rolled double-sides enamel steel can meet the requirements of products.