Adequação do limite de escoamento de um aço de alta resistência micro ligado ao titânio, utilizando ferramentas da qualidade através da metodologia seis sigma

Abstract

The present project, has the objective to demonstrate adjustting the production parameters of a newly modified steel, using quality tools to adapt the product features according to costumer requeriments. The analyzes were made from a continuous annealing line and laboratory scale with annealing heat treatments, to try to find the main influences of the processo on the yield strength and morphological microstructure of the steel studied. The material studied was a HSS (High Strength Steel) titanium microalloyed, type 340MPa, with ferrite-pearlite microstructure and has application in the automotive industry. The modification mentioned occurred in the steel chemical composition due to productivity problems in cold rolling, caused by excessive workloads of the old material and the growing market demand for this type of steel. Therefore, this change has the purpose to produce smaller workloads and consequently an increase in productivity in the cold rolling, this process is prior to continuous annealing. The six sigma methodology was applied in the steel production process on na industrial plant. For results obtained in the laboratory, the DOE (Design Of Experiments). The main parameters found were the soak temperature, strip speed or time of material in the soak temperature, material thickness and steel grade. In conclusion, the temperature was the most important variable found. An ideal temperature range is presented, in which this steel has the yield strength, according to costumer specifications.