Pengendalian Proses Baja Karbon Tinggi di Pabrik Billet Baja PT Krakatau Steel (Persero) Tbk, Cilegon

Abstract

Process control is used to guarantee a product/service that was produced to meet certain specification and has high uniformity over time. Process control generally uses quality control charts that is used to detect the causes of high variability a product. Quality control charts that was used in this study was Generalized Variance control chart and Individual Hotelling T2 control chart. The Individual Hotelling T2 control chart was done after the Generalized Variance control chart was under control. Based on the results of the Generalized Variance (GV) control chart and the Hotelling T2 control chart using a confidence level of 99.73%, the process of high carbon steel was under control after observations that were outside the control limits were removed, which means variance and average of the process was under control. However, the identification of the previously uncontrolled observations was done first. One way to determine the variables (elements) that affected the out of control observation was to calculate the decomposition value of out of control observations. Based on these values, it indicated that the variables mainly causes out of control observation were Cu, Ni, S, and P.