The paper presents the study of internal defects resulting from the continuous casting of steels. The 50 samples were taken from a total of 20 continuously cast bits of different steel grades. The investigation of the causes of internal defects, shown on the analyzed samples, started from the assumption that the secondary metallurgy was performed correctly. The following internal defects have been evident: internal cracks (axial cracks, section cracks), central porosity and marginal punctuation impurities.

In this presentation are evidenced instrumental characterization by Electronic Scanning Microscopy (SEM) equipped with EDS / WDS of aluminum alloys such 2024 alloy with multiple synergistic purposes as: acquisition of new knowledge, increase the amount of information obtainable about the material, increasing the efficiency and the quality of the tests, characterization of special destination alloys and assessing their conformity with the specified requirements. In this direction, it requires both the knowledge the test methods (theoretical basis, test method, procedure relating to the method, quality assurance testing) as well material characteristics investigated. These aspects are necessary for test system design, and preliminary interpretation of experimental results.

Aim of the study is to present the technological process of obtaining cast iron with lamellar graphite for use in the manufacture of cylinder liners, and to identify the main alloying elements and track their influence on the mechanical properties of cast iron with lamellar graphite. Also paper presents analysis of 20 batches of cast iron with lamellar graphite, which are made of cylinder liners, in terms of chemical composition and the mechanical properties. After the analysis of the 20 castings of cast iron Fc 250 it is observed that: the increase in the carbon content shows a decrease of the tensile strength and hardness of the gray cast iron; the increase in silicon content shows a decrease in hardness and tensile strength. Decreasing the amount of graphite and especially the alloy of silicon iron lead to hardness increase 1% Si increases hardness by 50 HB). A statistical analysis has been performed on the data obtained that accounts for changes in alloying additions. A modeling and optimization of mechanical properties (tensile strength and hardness) was performed according to the percentages of carbon, silicon and manganese. Mathematical modeling found that the hardness and traction resistance of the cast iron decreased with the increase in carbon, silicon and manganese content.