Improvement of the quality indicators of cast iron rolling rolls

Statement of the problem. Regarding the implementation of the stage aimed at determining the field of trade-off of the properties of the mechanical properties for the material of the studied rolls, it should be noted that most of the criteria characterizing the workability and efficiency of the technology are set by the State Technical Service of Ukraine, state technology and other regulatory documents within permissible limits. These regulatory documents are intended to support the technological process in the optimal working zone of parameters, which allows to achieve the maximum possible productivity and product quality. Purpose and problem statement . The goal is to develop a method for evaluating and controlling the mechanical properties of cast iron rolls depending on the influence of their chemical composition and structure. To achieve the set goal, it is necessary to develop and test a method of determining the area of compromise of the mechanical properties of cast iron rolls; implement the possibility of predicting the mechanical properties of the rolls by adjusting their chemical composition within the limits of standard technology; to achieve an optimal combination of mechanical properties σв, σзгин, KC and НСD, based on the defined limits of the content of the components of the chemical composition. Research material and methods. As a material for this study, cast rolled iron rolls of the SSHKHN design (a sample of 283 smelters with a total weight of 800 tons) were accepted. Modifiers (Foundrisil, Elmag-600, Elmag-900, Vl 57 (M), Barinoc, Elgraf) were used in the manufacture of rolls. Mechanical properties (σb, σbeяnding, KC and НSD) were determined for the working area of the barrels of cast iron rolls of the СШХН execution (up to 50 mm deep) with a smooth barrel on standardized equipment. Experimental results and their discussion. Based on the analysis of the results of active and passive experiments, using the grapho-analytical method, the areas with the most effective combination of mechanical properties for graded rolls (areas of compromise of quality criteria) were determined depending on their chemical composition and structure parameters. For rolls made of SSHKN, the area of compromise combines the areas of permissible values of each of the mechanical properties: σВ=240…460 МPа, σЗГИН=330…940 МPа, КС=9…33 кJ/m2, HSD=40…60, taking into account the entire range of applied cooling conditions in the metal form. Scientific novelty. The method of determining the area of compromise of the mechanical properties of cast iron rolls has been developed and tested. For the first time, a compromise zone was established, which provides the most effective combination of mechanical properties (strength limit σB, bending strength σbend, impact toughness CS and hardness HSD) for the working surface area of grade-rolled rolling rolls with spherical graphite alloyed with chromium and nickel (СШХН-41, СШХН-45, СШХН-47, СШН-50). This area is determined by the specific limits of the content of components, chemical composition and parameters of the structure, which includes the percentage of spheroidal graphite, lamellar pearlite and carbides Conclusions. The method of determining the area of compromise of the mechanical properties of cast iron rolls has been developed and tested. It is possible to predict the mechanical properties by adjusting the chemical composition of the rolls within the limits of the state-of-the-art technology. An optimal combination of mechanical properties σв, σzhyn, KC and НSD, based on the defined limits of the content of the components of the chemical composition, has been achieved.