Effects Of Cold Rolling And Heat Treatment Process On Microstructures And Properties Of Food-grade Tinplate

Tinplate is widely used in the food packaging industry due to its good matching of strength and deep-drawing properties,and is often used as a raw material for packaging containers such as cans and lids.The production of two-piece food packaging cans has a high requirement on the thickness reduction ability and deep drawing performance of tinplate.At present in China,high-quality tinplate substrates still heavily rely on imports.In recent years,domestic demand for tinplate has been increasing,and the price of imported tinplate substrates has increased annually.Therefore,it is of practical significance and application value to conduct the research on the process-microstructure-performance relationship of tinplate,and to develop high-quality tinplate strips for cans that meet the performance requirements.In this thesis,a series of cold rolling and heat treatment experiments are designed using tinplate substrates provided by a domestic steel company as the research object and IF steel as the auxiliary contrast material.Based on the microstructure characterization,mechanical properties and forming performance testing,the influence of cold rolling reduction and annealing temperature on the properties of tinplate structure is explored,and the differences in the structure and properties of tinplate and IF steel are compared and analysed.And this can provide experimental support for alloy design and process optimization of high-performance tinplate.As the cold rolling reduction increases,the ferrite grains in the annealed structure gradually refine.When the cold rolling reduction ratio is 80%or less,as the reduction increases,the strength of the annealed tinplate increases,but the elongation does not change significantly,and the r value increases.When the cold rolling reduction exceeds 80%,the elongation,n value and r value of the annealed tinplate significantly decrease,and its deep-drawing performance is less likely to meet the performance indicators of two-piece cans.As the cold rolling reduction increases,the temperature at which recrystallization of the experimental steel finishes gradually decreases.When the cold rolling reduction rate is 84%or less,and the annealing temperature is in the range of 680?710?,the microstructure,strength and elongation of the experimental steel do not change significantly.When the cold rolling reduction ratio is 90%,as the annealing temperature increases,the ferrite grain size in the structure gradually increases,the strength decreases,and the r value increases.The results of EBSD reveal that increasing the cold rolling reduction or increasing the annealing temperature promotes the formation of {111}<hkl>texture,which is beneficial to the increase of the r value of the material,and thus can improve the deep drawing performance of the material.The evolution of microstructure and properties of tinplate and IF steel during annealing under the same cold-rolling reduction is compared-The results indicate that the strength of annealed tinplate is significantly higher than that of IF steel,but its elongation and formability are lower.And the {111}<hkl>texture of IF steel is remarkably stronger than that of tinplate.The research results of this thesis can provide numerical support for the optimization of process parameters in the actual production of the steel company.The comparison for the microstructure and properties of tinplate and IF steel can underlie the alloy composition design of the further development of the high-quality tinplate for two-piece cans.