Desenvolvimento do fio-máquina com o aço 1010 para produção de vergalhão CA60 em laminadores a frio

Abstract

Today's steel market is increasingly competitive, where every extra minute of production is a huge gain in financial results. In 2022, a steel mill in Ceará used 5.5mm 1008 steel wire rod to produce 3.40mm CA60 rebars and 5.5mm 1012 steel wire rod to produce 4.20mm CA60 rebars, two different raw materials for two different products, However, these materials presented opportunities, such as difficulties in meeting the property requirements of the Brazilian standard ABNT NBR 7480, which sets out the minimum requirements for rebar, so there was a need to develop a new technology for producing this material. The aim of this work is to develop a wire rod in 1010 steel so that it is suitable for the hot rolling process and then the cold rolling process, so that during the hardening process it achieves the desired properties, significantly reducing the generation of non-conforming products, as well as having a single steel that would produce both 3.40mm and 4.20mm CA60 rebar. This development was carried out by producing a pilot batch of 30 tonnes of SAE 1010 steel, where three temperature values were tested during hot rolling and then subjected to the hardening process (cold rolling), reducing its section to 4.20mm and 3.40mm. This material was validated by means of tensile tests carried out on a calibrated machine using an extensometer, as well as characterising the material for each temperature parameter by measuring its grain size, which is a determining factor for characteristics such as the yield strength. The results showed that the higher the hot rolling temperature, the larger the grain size, which consequently improves the values of the material's elastic ratio, which is the breaking limit divided by the yield limit, a parameter that is normative and which is very difficult to achieve using different steels, especially 1012, thus showing that the hot rolling temperature is a determining factor for the cold rolling process, favouring the achievement of the appropriate elastic ratio for the product