DP600 steels are characterized by a dual phase ferritic-martensitic microstructure, to which they owe their exceptionally favourable combination of high strength and good ductility. One of the production methods for this grade of steel is the hot rolling process. Despite the fact that these steels have been produced on an industrial scale for almost 40 years, they are still being studied intensively, with new research on the formation of their microstructure and properties published every year. This article focuses on the characteristics of DP600 steel produced on a hot rolling mill for applications in automotive industry. The article presents the results of mechanical properties tests and microstructure analysis of DP600 steel obtained in an industrial hot rolling process. The general characteristic of DP600 steel presented in this article, is supplemented with statistical analysis of correlations between chemical composition, selected process parameters and mechanical properties of hot rolled DP600 steel.

The force required for plastic deformation of steel in the hot rolling process is an important parameter which impacts roll wear, strip steering in finishing stands, shape and profile of the rolled strip and energy consumption. Theoretically, the roll force could be effectively decreased by rolling strips with higher temperatures and a lower speed or by reducing the strips input thickness. Due to the required mechanical properties of hot rolled strips as well as the continuous drive toward increased rolling line productivity and cost optimisation, in most cases, it is impossible to lower roll force by changing these two parameters. Roll gap lubrication effectively decreases the roll force, and lowering the friction between the work roll's surface and rolled material reduces roll force by 5% to 20%. Lower roll force brings obvious results in lower energy consumption, but even more important are benefits coming from lower work roll wear and improved strip shape and profile. These issues are particularly important during the hot rolling of dual-phase steel, which due to relatively low final rolling temperature (FRT), requires a higher roll force resulting from increased steel yield stress at lower temperatures.

In this article, the entire energy embodied in a sewage system has been estimated. The concepts of LCC, LCA and EE have been taken into consideration. The estimation of this energy is calculated from the moment of extracting the raw materials, through its transportation, to the making of a final product. The choice of materials and production technology is an important aspect here. This article considers the construction procedure of a gravity and gravity-pump sewage system, including estimating the amount of energy. In order to calculate the energy embodied in a sewage system, not only the cost of materials and transportation need to be taken into account but also the energy needed for laying a pipeline in the ground, system operation and the lifetime of the system’s components. The article aims to estimate the entire energy embodied in both aforementioned sewage system type. The most rational solution has been chosen.

DP600 steel is widely used in the automotive industry due to its exceptionally favourable combination of high tensile strength and good ductility. In the hot-rolling process, DP600 steel is produced by use of controlled cooling of the rolled strip from temperature above Ar3 to temperature below Ms. In this process, it is quite difficult to control key process parameters such as the time or temperature, and the final microstructure of the material is also affected by the degree of deformation of the material at various stages of the process. This paper presents a statistical analysis of the effect of chemical composition and selected hot rolling process parameters on the microstructure of DP600 sheet with respect to its mechanical properties. Based on industrial data from hot rolling mill combined with extended microstructure analysis, it was possible to find correlations between some of the analysed parameters and material properties. Among many correlations discussed in this work, most notable are those between martensite morphology and mechanical properties, between Mn and Si concentration and martensite morphology and between rolling speed, strain, cooling rate and mechanical properties.