№ 12 (150) (2023)

In oxidizing environments, nickel and its alloys are prone to immunization and therefore the corrosion rate of equipment made of these materials is significantly reduced. Nickel and its alloys are widely used for the manufacture of equipment in contact with alkaline solutions. However, at high temperatures and high alkali flow rates, there is a possibility of contact wear of the metal surface of sodium hydroxide crystals due to the low hardness of nickel. Replacing nickel pipes with ones made of cheaper corrosion-resistant steels would solve the problem of rational design of equipment and pipelines of enterprises associated with the production of sodium hydroxide. The paper presents the results of comparative tests of corrosion resistance of 10X23H18 steel and Nickel 201 alloy in aqueous alkali caustic soda solutions of various concentrations. On a study basis, it can be concluded that the dissolution rate of 10X23H18 steel is significantly less than the dissolution rate of Nickel 201 alloy. It should be noted that with an increase in the concentration of solutions, the corrosion rate of steel gradually decreases, which is not the case for nickel-based alloy. Besides, judging from the results of hardness measurement, 10X23H18 steel can be distinguished due to its high resistance to abrasive wear. According to the scale of corrosion resistance, both materials are absolutely resistant. Since 10X23H18 steel has a lower cost compared to Nickel 201 alloy, it can be recommended substitutionally for the manufacture of the equipment operating in sodium hydroxide solutions at ambient conditions.

The issues of high-temperature forming for the production of elliptical steel beaded bottoms, used in vessels and apparatuses with an internal diameter from 300 to 1800 mm, made of carbon, alloy and ply steels, are viewed. There is information that the authors have been studying this forming process of a workblank with no temperature pattern change. There is also data on examples of tests that allow reducing the thickness difference in the bottom plate from the standard 15 % of relative deformations to 12%. It is shown that the use of a variable temperature pattern will make it possible to increase the extraction coefficient by several times and obtain vessels consisting of two body parts. It is noted that the issue of the influence of changes in the hardening curve when heated on the stability of hot-temperature forming has not been viewed in technical publications yet. The possibility of using the QForm program for the analysis of the stress-strain state for high-temperature forming has been studied. The simulation of the heating of the billet in a gas furnace is carried out. As a result of the calculation, a temperature pattern and a distortion of the shape of the workblank were obtained. Comparison with the experiment revealed good convergence of the results in terms of temperatures and qualitative coincidence of the workblank shape. It is noted that QForm simulates the locations of the places of maximum relative deformations quite well, that is coincident with the results of experimental die forming and theoretical solutions for draw-forming of parts with a spherical bottom. Based on the results of the work, recommendations are given for obtaining bottom plates according to the first class of accuracy, when the maximum relative deformations in thickness should not exceed 4,0 %.

Despite huge prospects for the layer-by-layer synthesis of products, which makes it possible to produce parts of a unique shape, the widespread use of the method face the problems of making a proper microgeometry of the product surface, which due to the peculiarities of layer-by-layer production is rather rough, and mechanical methods of machine working often do not admit the possibility of figure-shaped parts post processing. The article studies the problem of ensuring the quality of the plastic parts surface layer obtained by additive technologies. For this purpose, it is proposed to use ultrasonic processing technologies. The existing methods of using ultrasonic vibrations in the production of plastic parts are analyzed: the manufacture of wire for 3D printing with additives, which results in an increase in the mechanical properties of the product. Besides, liquid treatment of a solvent-loaded product in order to remove supporting elements. Studies have been carried out on the finishing of parts in a solvent aerosol obtained by ultrasonic spraying. This method has a number of advantages in comparison with the treatment in solvent vapors obtained during its heating, which include the possibility of regulating the size of droplets, their moving speed, aerosol concentration, caused by changing the modes of ultrasonic treatment. As a result of experimental studies, it is found that the use of this treatment method eventuates an increase in the quality of the sample surfaces to be worked, and besides, it reduces the height parameters of roughness in the direction perpendicular to the layered growth of the product by more than a factor of ten. The mechanism of changing the microgeometry of the surface is as follows: when aerosol droplets contact the surface, part of the material forming the protrusions dissolves and fills valleys, while in the liquid state; after finishing the work, the material polymerizes, generating a surface with improved features.

A technique for correcting a machining mode with time-varying parameters has been developed. The technique allows minimizing the impact of the uncertainty of technological information caused by the incorrectness of mathematical dependencies and models used for calculating the parameters of the process or due to the lack of initial data for the selection of parameters of mathematical models. It provides for the corrective dependencies and models according to the current information with respect to the output parameters. The correction of the mode elements is performed according to the results of comparing the calculated and actual values of the output and current process parameters. The calculated functions of changing the output parameters over time are determined. The routine for determining the interrelated current and output parameters of the processing process allows calculating their values depending on the operating time of the tool. According to the results of comparing the calculated values of the process parameters with the values that should be obtained at a time equal to the efficient tool life, the correction of the mode elements is performed. If the calculated values of the output parameters do not exceed their limit values, then the operation mode should be intensified for the sake of increasing productivity. The intervals of variation by controlled factors are determined, which allow changing the output parameters at a time equal to the efficient tool life by the desired value. When calculating the intervals of variation by controlled factors at the first stages of mode adjustment, they are guided by the initial models and dependencies describing the process. The necessary result may not be achieved due to the uncertainty of the information, including the incorrectness of the models. Therefore, if necessary, the subsequent stages of mode adjustment are put into operation. Based on the actual values of the output parameters, the process models are adjusted, and the variation intervals by controlled parameters are calculated using adjusted models. The application of the developed method of mode correction makes it possible to increase the turning performance by 30…35 % while ensuring the required quality of the machined parts within a given period of tool durability.

A methodological approach to the formation and description of data on the design and technological features of parts under technological preparation of machining industries is presented, the difference, if compared to other well-known approaches, lies in recording of additional data that is not explicitly reflected in the reference design. As an additional information component, it is proposed to use: information on the mutual influence of one elementary surface on another or others, i.e. dimensioning specifications of other surfaces; data on the dimensional features of each elementary surface, which is not shown in the drawings; extreme geometric shape deviations for elementary surfaces and also mutual arrangement between elementary surfaces; data on the design bases of the part in question. The formation of a database of machined parts is given graphically, which makes it possible to use a wide range of mathematical tools technique in the creation of formalized models, providing their uncomplicated adaptation for using in existing computer-aided design systems. The analysis of additional design and technological parameters allows assessing the interdependence of the dimensions and characteristics of each of the part surfaces and the parameters of other surfaces, ensuring the quality of decision-making at the stages of technological preparation based on increasing the degree of reliability of information flows. The obtained results expand the possibilities of conducting dimensional analysis of the basic, operational and interoperation connections of the developed technical processes, increasing the level of automation in design procedures. Produced graphical models, aimed at reducing the complexity of design actions outline, are able to expand, due to the approximation to the traditional data specification of technological equipment, the possibility of taking into account the state of production capacities in machining production on a real time scale. They also contribute to the deciding modern issues on effective engineering complexes formation.