The object of research is hypoeutectic cast iron intended for cast parts operating under abrasive friction conditions. Such parts are mixer blades, the operational properties of which include durability, assessed by abrasion resistance and strength. To give the blades such properties, cast irons, which are materials of the blades, are alloyed with elements that contribute to the formation of carbides of various compositions. The main problem that impedes the targeted selection of materials for mixer blades or finished blades from different materials or different chemical composition is the lack of substantiated selection criteria. If the shipment is carried out only with the provision of data on the chemical composition of the alloy, it is necessary to be able to evaluate the expected mechanical properties, in particular abrasion resistance and strength. Using the methods of regression analysis, a mathematical model has been obtained that includes two regression equations, which allows for a targeted selection of the chemical composition that provides the maximum possible value of mechanical properties – ultimate strength and coefficient of wear resistance. Optimization of the chemical composition, carried out according to this model, made it possible to determine the following chemical composition: C=2.94 %, Ceq=3.3 %, Ti=1.56 %, providing the maximum ultimate strength σb=391 MPa; C=2.78 %, Ceq=3.14 %, Ti=1.61 %, providing a maximum wear resistance coefficient Kwr=12 %. In the case of priority of the strength criterion, the calculated optimal chemical composition makes it possible to reduce the mass-dimensional characteristics of the mixing units of the mixers. A procedure is proposed for using this model to select a batch of blades with the expected best performance properties
The object of study in this work is cast iron with lamellar graphite, modified with two types of modifiers – FeSi75 and FeSi40V7. In this work, the influence of vanadium on the mechanical properties of cast iron used for castings for engineering purposes was determined. The existing problem lies in the fact that ignorance of the influence of the alloying element on the mechanical properties of the alloy does not allow determining its consumption rates during the melting process. This can lead to unnecessary costs for materials for melting and casting, and not be justified in terms of the expected improvement in properties. To determine the effect of vanadium on properties, three indicators of the quality of cast iron are considered: tensile strength, stiffness, and a generalized quality index for mechanical properties. A decision is proposed on the procedure for checking the significance of the influence of vanadium within the considered range of variation V=0.04–0.078 % on these indicators. It has been established that the introduction of vanadium into cast iron as part of the FeSi40V7 modifier leads to a decrease in the tensile strength by 4 %, but to an increase in rigidity by 2 %. A significant influence of vanadium with a probability of 95 % was also established with respect to the generalized quality indicator for mechanical properties – the introduction of vanadium contributes to a drop in this indicator by about 5 %. As a result, it was concluded that the use of vanadium in the composition of FeSi40V7 within the final content in cast iron at the level of 0.04–0.078 % can be expedient only if it is necessary to increase the hardness of cast iron due to the promotion of carbide formation during alloy crystallization. The presented study will be useful for machine-building enterprises that have foundries in their structure, where cast iron is smelted for the manufacture of castings.
The mechanism of discontinuous chip formation has been studied less than the mechanism of continuous chip formation. However, when most modern materials having specific physical and mechanical properties are subject to machining, such processes are featured by discontinuous chip formation. The paper describes the basic dependencies of discontinuous chip parameters on machining modes. This is a trial undertaken to introduce an explanation of how the basic factors of the cutting process influence over parameters of chip formation.
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