Abstract
A significant amount of scale is produced during casting of ingots and processing of hot-rolled products. In manufacturing steel, during the various rolling operations, the amount of scale produced is approximately 0.1% of the annual production of the rolling mills. The quality of the thin sheet during rolling is affected by the behavior of the iron oxide layers formed on their surfaces. For this reason, acids and oils are used for the descaling of slabs and billets by means of pressurized water. The calamine, contaminated by these various acids and used oils, is rejected and stored involuntarily on important areas and pollutes soil and groundwater. Micrographic observations as well as X-ray diffraction analysis have shown that calamine consists mainly of iron oxides. Hematite and magnetite become the main components for oxidation times greater than 1 hour. Characterization tests have shown that calamine is dense (ρ = 4.8 g/cm3), its particle size is variable depending on the degree of oxidation (from 0.5 to 10 mm). Simultaneous thermal analysis showed that an increase in mass of the calamine sample with a release of heat. Studies are underway for the physico-chemical characterization of the soils of the storage areas.
Highlights
1 Introduction Until the last decade, the scale, slag, dust and sludge generated by integrated steel plants wascalled waste, but this term has been replaced with by-product and sometimes product due to intensive re-utilization of these materials
Mill scale is one of these materials produced in the processing of steel during continuous casting, reheating and hot rolling operations
Water sprays remove the scale formed during these operations and mill scale is accumulated as a by-product in all iron and steel companies, either integrated iron and steel companies or mini steel mills and small mill shops
Summary
The scale, slag, dust and sludge generated by integrated steel plants wascalled waste, but this term has been replaced with by-product and sometimes product due to intensive re-utilization of these materials. The quality of the thin sheet steel during the process of rolling is allocated by the formation of the layers of scale on the surface of the sheet steel to the cost all the operation of deformation along the hot rolling mill process. To minimize his growth inside the furnace, we have to respect certain necessary conditions among which the content in smokes which has to be between 1.5 - 2.5 %. The steel where our scrap is collected is an extra-soft hot rolled low-carbon steel according to the international standard ISO 11949 for packaging called black iron, tinplate
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