Research Of Cold-rolled SUS301and SUS304Stainless Steel Strip Flatness And Mechanical Properties

Cold rolled technology is the main measure to produce the stainless steel stripwhich is a kind of high value-added product. Good strip shape and mechanicalproperty of cold rolled stainless steel are required for attaining well useableperformance, but it is difficult to control precisely them in practical production. Theproblem of the strip shape and mechanical property of SUS301, SUS304stainlesssteel strip with285mm~380mm width and below0.5mm thickness which is producedby650twelve high rolling mill in certain enterprise is studied by considering rollshifting process optimization, low temperature stress relieving annealing processoptimization and BP neural network for predicting the surface hardness of stainlesssteel stirp. In addition, test equipment, such as universal tensile test machine, stressmeasuring instrument, SEM, XRD and scientific analysis method includingmathematical statistics, numerical simulating and neural network are also adopted toanalyze the change rules of strip shape and mechanical properties for stainless steelstirp.Four aspects are studied in this paper. Firstly, the regular of proper roll shiftingset value play a key role on strip shape control of cold rolled stainless steel is obtainedthrough the actual data of twelve high rolling mill. Reasonable roll shifting set valueshould be made basing on width changes in real production process. Secondly,considering the aspect that tension set of continuous annealing furnace can be appliedto optimize the steel shape and mechanical property. The study focuses on theSUS301stainless steel with0.5mm in thickness and conducts the stress reliefannealing experiment on cold rolled steel at the condition of same temperature butdifferent tension, measuring its mechanical properties and inner residual stressdistribution after annealing as well as getting the laws of tension effect on mechanicalproperties and inner residual stress distribution of the strip at different annealingcondition. Thirdly, taking measures to optimize the annealing temperature andholding time of the continuous furnace. The study assesses SUS301with0.25mm inthickness and compares mechanical properties, tensile fracture surface, microstruct-ures of the alloy on different heat treatment systems, obtaining the optimal annealing process to keep mechanical properties of stainless steel stable through a series ofexperiments. In the end, a nonlinear reflection model is built for predicting the surfacehardness of the stainless steel by using BP neural network. It is based on the model topredict the surface hardness of the stainless steel, the relative error between predictedand tested results of the surface hardness is between-2.63%and2.76%, and thesimulation results show that the predicting result has a high accuracy. Besides, thecollection of illustrative plates of predicting data were achieved by this model, at thesame time, the conclusion that the variation of reduction rate affects surface hardnesssignificantly is also obtained.According to this study, a new idea and solution is provided to improve stripshape and mechanical properties in actual production. Besides, correlation theory andproduction data are also applied to support the actual production on the rolling processand low temperature annealing process.