Abstract:
Arcelor Mittal Brasil, through its commitment of improving the performance of the enterprise more and more, of sharing with the society its vision of being the most admired steel producer of the world and also of continuing to assure progress in every aspect of sustainability, has returned, since 2017, with its investments in the technical capacitation field, aiming to achieve continuous improvement of the company (6sigma).
The market of steel is even more selective and strict nowadays, requiring a very meticulous analysis of each step in the production processes with the main goal of reaching high levels of accomplishment and quality. Since 2009, the Hot Strip Mill is upon a production increase procedure, with the startup of the second reheating furnace and overall improvement of the production process, going from 2,5 Mtons/year of production to the actual 4,1 Mtons/year, with an expected production of 4,5 Mtons/year in 2022.
In the hot coils production process, the process rolls represent one of the main items regarding the cost of operation due to its high price, apart from being a factor of great importance in the quality, since the rolls are the tools in direct contact with the laminate. Therefore, the rolls manufacturers are in constant development, aiming to increase these tools wear resistance and dimensional metallurgical stability, factors combined with adequate mechanical resistance and fracture tenacity.
In this scenario of increased production and because of the fact that the wear of the rolls affect directly the coils production cost, some statistical analysis were conducted with the 6sigma methodology, pursuing to verify and evaluate the working conditions of the rollers in the mill of Arcelor Mittal Tubarão. In 2018 it was initiated an work in the Rolls factory via blackbelt 6sigma, to study the tribology applied to the rolls wear, the operation conditions, the campaign and fatigue during its lifetime. This research has shown a great reduction in the rolls consumption (Work rolls, backup or vertical edge), increase in the mill production, reduction into the CAPEX of the rolls as well as in costs measured indirectly (energy, FTE, lubricants).
Another important factor was the financial feedback (ebitda) to the company. About R$ 16 million less in CAPEX of the rolls, 32 hours of increased production in function of the rolls campaign improvement, as well as a dispended cost of R$ 18 million that would be required in order to afford a new grinding machine, wich would be necessary to attend the conditions of the annual production.
