Study On The Defects And Their Mechanism In The Deep-drawing Process For The Polymer Laminated Steel Can Forming

With the improvement of food packaging requirements,laminated steel which laminates of electrolytic chromium coated steel(ECCS)sheets coated with a polymer layer have become increasingly popular for packaging of food and beverages.Since the advent in 1990 s in Japan,polymer laminated steel has been popular throughout the world for its superior performance,environmental protection of product and process,competitive advantage in the price.It`s technology development and product application dynamics has been the focus of attention of the industry.As a kind of food packaging material,the main problem encountered in the application of the laminated steel products is the delamination on the interface and film breakage during the drawing process which lost the barrier effect between the metal substrate and the canned content.This paper focuses on the defects and their mechanism in the process of deep drawing of laminated steel.The main contents of this paper are as follows:(1)Analysis on defect types and forming causes of deep drawing process of coated iron.Mainly through the analysis of laminated steel cans deep drawing process,forming equipment and die structure,drawing process and deep drawing process of the laminated steel,and the resulting defects and their causes.The typical defects in the process of the laminated steel cans forming are surface scratches,deep drawing mark and interfacial corrosion.The characteristics,causes,hazards and evolution mechanism of th e defects are further studied.(2)Morphological characteristics of different strain zones during plastic deformation process of the laminated steel.According to the uniaxial strain specimen obtained under the uniaxial tension of the testing machine and the three-way strain specimen obtained by the drawing die,coated iron can.Through surface roughness measurement,surface topography observation,cross-sectional morphology and cross-section microstructure observation,Based on the deep drawing process and principle of the laminated steel cans,study the characteristics of the morphological changes and the evolution of the profile of the laminated steel substrate and the laminated steel cans film;Based on interface defect type,evolution law and distribution characteristics,study the relationship between the features and evolution of the morphological in different deformation zones and the generation and expansion of the defects.(3)Analysis on the change of interfacial adhesion in different strain zones during the plastic deformation process.According to the uniaxial strain specimen obtained under the uniaxial tension of the testing machine and the three-way strain specimen obtained by the drawing die,based on the comprehensive evaluation principle of interface adhesion by scratch method and the description method of the interface binding energy by stripping area,study the effects of plastic deformation on the interfacial bonding strength by a macro scratch test.