Avaliação das causas de rupturas de arames no processo de trefilação do aço equivalente ao ABNT1005 na unidade industrial da Arcelormittal em Juiz de Fora MG

Abstract

Competitiveness in the market forces companies to become increasingly effective in their production processes. Therefore, it is essential to reduce interruptions in your processes. The main reason of production downtime of thin gauge drawn wire (1.24mm to 1.65mm), equivalent to ABNT 1005 steel, from ArcelorMittal in Juiz de Fora is the wire breakage. The possible causes of this anomaly are: residual scale, mechanical damage to the wire rod, poor wire lubrication, excessive reduction, non-standard die geometry and low boron-to-nitrogen ratio. This work aimed to study the main causes of wire breakage in the production process of thin gauge drawn wire, equivalent to ABNT 1005 steel, in the industrial unit of Juiz de Fora in Minas Gerais State, in addition to implementing actions that aim to eliminate or at least minimize the causes, thus increasing the efficiency and productivity of the process. It was identified that the main causes were: residual scale in the wire, low boron-to-nitrogen ratio and failure in lubrication due to the high temperature of the wire during the process. A design of experiments (DOE) was performed in the Stelmor (rolling) in order to establish the optimal process parameters to obtain better oxide composition, which should have at least 80% of FeO (wustite). Regarding the boron-to-nitrogen ratio, it was evident that the lower the ratio between boron and nitrogen, the greater the number of ruptures. The strain-hardnening coefficient was also calculated in different runs with different boron-to-nitrogen ratios. It was found that the high temperature of the wire impairs lubrication. Through the implementation of the actions, there was a reduction in downtimes due to wire breakage and, consequently, an increase in production. The increase was 3,300t from 2016 (start of work) to 2019, representing a growth of 21.70%