The Effort Of Cold Rolling And Tensile Test On The Corrosion Of Nickel Electrodeposited Steel

Surface modification by electrodeposited nickel coating is an important technology which has been widely used in practical applications due to their good appearance and corrosion resistance. The nickel coating is often electrodeposited on the steel substrate and its thickness is 1-20μm. The grain size is micrometer or nanometer. With the development of this material, the process technique that the nickel is firstly electrodeposited on the steel substrate and the coating and substrate are wholly formed has been partially instead of the process technique that the steel is firstly formed and then the production surface is electrodeposited nickel coating. Lots of processing techniques following plating have been employed to improve its mechanical, physic-chemical properties of nickel coating. Deeply-draw nickel steel strip produced by Leed material company is a kind of newly high property battery cover materials. Processes including heat treatment and cold rolling have been contributed to its improved adhesion between coating and substrate, good welding-ability deeply-draw property and enhanced corrosion resistance. In this case, as a newly high property battery cover material, nickel coating electrodeposited on low carbon steel strip has been welcomed and demanded with rapid development of battery industry.While the electroplated nickel coating was used as shell material of good quality battery, the coating /substrate composite must be deeply drawn twelve times separately and sequentially. In order to produce a useful battery cover, the initially simple geometry of sheet metals has to be transformed into a more complicated geometry without material failure or deterioration in material properties. So it is necessary to study the coating's performance on deformation conditions under which the residual stress may be severely acted. The efforts of processing technique on corrosion behavior of nickel coating, otherwise, need to be systematically studied.The investigations of this master thesis are divided into two parts. In the first part, the effect of cold rolled deformation on corrosion property of nickel electrodeposited steel was been studied. In the second part, the corrosion behaviors and microstructure of nickel electrodeposited steel after tensile tests have been studied.In the first chapter, related research background and research status were introduced at first. Then the background of this master thesis was interpreted. In the second chapter, the theory of electrochemical measurements and X-ray diffraction method to measure the residual stress were introduced. In the third chapter, the effect of rolling reduction on the microstructure of nickel electrodeposited steel and the relationships between the microstructure and the corrosion resistance were investigated. In the forth chapter, the fracture and corrosion behavior of nickel electrodeposited steel under tensile test condition were studied.