Vol 49, No 4 (2019)

Abstract—Analysis of the smelting and casting of cylindrical ingots of Inconel 718 alloy produced in a vacuum induction furnace at PAO Ruspolimet shows that existing technology does not ensure the production of a dense ingot of the required quality on account of porosity in the axial zone and segregation of elements such as chromium, nickel, and niobium. The results show that the casting and solidification of the Inconel 718 ingots must be corrected so as to obtain high-quality dense ingots, without changing the basic features of the production process: a 3-t vacuum induction furnace, a ceramic lining based on aluminum oxide (Al₂O₃), a cylindrical mold for ingots of diameter 410 mm, and a mold of diameter 450 mm for vacuum-arc remelting. By means of Thermo-Calc software (2017a version), the solidus temperature for equilibrium solidification (1211°C) and nonequilibrium solidification (1091°C) are refined. On the basis of the results, by computer simulation of the casting processes, the casting rate is corrected by decreasing the diameter of the casting nozzle from 32 to 28 mm and the casting temperature from 1470 to 1460°C. A batch of ingots is produced by the corrected technology. Transverse templates are taken from such a sample to determine the chemical composition, and longitudinal sections are taken for metallographic analysis. Metallographic data indicate decrease in porosity of the ingot’s axial zone and decrease in the segregation. On the basis of the results, the introduction of appropriate changes in the casting technology is proposed. Computer simulation of the casting and solidification processes permits the development of a technology in which high-quality ingots are produced in the first step. All of the products meet the customer requirements.

Abstract—In the operation of cutters with parallel blades, three periods may be identified: pressing of blades into the metal; cutting; and cleavage (separation). The greatest force is required around the onset of cutting. Since one of the blades is immobile, the other must pass through the whole thickness of the metal in the course of cutting. For example, if the metal thickness is 20 mm, the upper blade must travel a distance of 20 mm to complete the cutting process. In the case of two mobile blades moving in opposite directions, the cutting forces will be less. If the metal thickness is 20 mm, each blade must travel a distance of 10 mm in the complete cutting process. To simplify the design in the case of two mobile blades, they must both be powered by a single drive. The question that arises here is whether opposing motion of the blades is possible with guaranteed strength of the components transmitting the force to the blades. A kinematic cutter design with blades that move in parallel within the vertical plane is proposed. A benefit of this design is that, in opposing cutter motion, less cutting force is required. In addition, the force from each blade is distributed to two rods, with decrease in the load on each one. Since the blades move in opposite directions, the main cutting force is distributed over the components of the mechanism and transmitted to the motor. That decreases the load on the frame and the foundation in cutting. In opposing motion of the blades, cleavage of the metal occurs more rapidly. That permits concentration of the maximum force at the cut, with minimum load on the motor. The section removed from the metal does not travel under the roller at the end of cutting, and therefore no lower mobile table is required. The degree of mobility of the proposed mechanism is determined from the Chebyshev formula; its value is one. A special method is used for kinematic analysis of the blades; this method is based on the point of intersection of the connecting rods.

Abstract—Industrial continuous casting machines in Russia mainly employ imported electromagnetic-stirring systems located outside the mold. In case of breakage, the stators of such stirreres must be sent back to the manufacturer for repair. To decrease import dependence, an electromagnetic-stirring system that may be completely dismantled has been developed at the Russian Research Institute of Metallurgical Machinery. This design permits preventive maintenance and repairs in the plant’s electrical shop, without the need for expensive materials or equipment.

Abstract—On the basis of laboratory experiments on an ITs Termodeform-MGTU test system, the production of rolled plates with large thickness from pipe steel of improved strength (R_t 0.5 = 505–610 MPa, R_m = 570–680 MPa) and cold resistance (KV^–48 ≥ 170 J, DWTT^–55 ≥ 90%) is introduced in the 5000 rolling mill at PJSC MMK. To ensure high cold resistance, the formation of predominantly quasi-polygonal and polygonal (polyhedral) ferrite is optimal. It is found that, if the steel microstructure includes a considerable quantity of bainite, the performance of the steel in drop tests is impaired. By means of the Gleeble 3500 test system, the thermokinetic diagram of supercooled-austenite decomposition is plotted for the new low-carbon pipe steel, with up to 1% Ni.

Abstract—The influence of vanadium on the microstructure, carbide deposition, and hardness of the chromonickel indefinite iron alloyed with ferrovanadium in the working layer of rollers is investigated. The microstructure of iron alloyed with nonnitrided ferrovanadium consists of primary dendrites; ledeburite; a small quantity of graphite; complex carbides MeC and carboborides Me(C, B) containing niobium, titanium, vanadium and chromium; and also chromium carbides of plate or needle morphology. In samples alloyed with nitrided ferrovanadium, the complex carbonitrides Me(C, N) are also seen. With increase in vanadium content, the proportion of these particles increases from 0.17 to 0.9% for samples alloyed with nonnitrided ferrovanadium and from 0.45 to 0.9% for samples alloyed with nitrided ferrovanadium. Their mean area varies from 1.5 to 2 μm² and from 1.4 to 1.8 μm², respectively. In iron alloyed with nitrided ferrovanadium, the maximum hardness (770 HV at a vanadium concentration of 0.4%) is greater than in samples alloyed with nonnitrided ferrovanadium (710 HV at a vanadium concentration of 0.3%).