Investigation of Electromagnetic Properties of Tool Hard Alloys under the Influence of High Temperatures

The article shows the developed installation for determination of temperature of maximum operability of replaceable cutting hard-alloy plates on the basis of study of change of electromagnetic properties. The method of research is given. Tests of images were carried out to time of heating of the replaceable cutting plates from solid B35 alloy. The heating temperature interval was selected according to the temperature mode of the process of cutting difficult materials. Heating was carried out to 1000˚ C. The results of the study were obtained to determine the temperature of maximum operability of replaceable cutting hard alloy plates based on the study of the change in electromagnetic properties for alloy В35 amounted to 460-730 ° С.

Semiconductor metal oxide sensor for hydrogen sulphide operating under non-stationary temperature conditions

The aim of the work was to create a selective gas sensor for hydrogen sulphide. As a result of adding ammonia to the zinc acetate solution, centrifuging the obtained zinc hydroxide and subsequent calcination, a polydisperse zinc oxide powder with a grain size of 5–50 nm was obtained. The material was characterized using X-ray phase analysis and transmission electron microscopy. Subsequently, silver nitrate and terpeniol were added to the zinc oxide nanopowder to form a paste. The gas-sensitive material was obtained by applying the resulting paste on a special dielectric substrate and subsequent calcination, as a result of which the terpeniol burned out, and the silver nitrate turned into an oxide (the mass fraction of the silver was 3%). A non-stationary temperature mode for the operation of the sensor was selected, in which, after rapidheating of the sensor to 450 °C (2 seconds), slow (13 seconds) cooling to 100 °C occurred. Each subsequent heating-cooling cycle with a total period of 15 seconds began immediately after the end of the previous cycle. The use of an unsteady temperature mode in combination with the selection of the composition of the gas-sensitive layer made it possible to obtain a response of 200 for a hydrogen sulphide concentration of 1 ppm. Along with an increase in sensitivity, a significant increase in selectivity was also observed. The cross-sensitivity for the determination of hydrogen sulphide and other reducing gases (CO, NH3, H2) was more than three orders of magnitude. Thus, this sensor can be used to detect hydrogen sulphide even in the presence of interfering components. The use of highly selective sensors in the tasks of qualitative andquantitative analysis can significantly simplify the calibration in comparison with “electronic nose” devices. Devices based on highly selective sensors do not require the use of mathematical methods for processing multidimensional data arrays.

Development of a model of the optimal temperature mode of the main gas pipeline operation

The influence of the ambient air temperature on changes in the parameters and thermophysical characteristics of the gas pumped through the underground pipeline was investigated. This was done because there are no scientifically sound recommendations for the optimal gas temperature after coolers at the compressor station. The presence of the site of inversion of heat exchange between gas and soil – a change in the direction of heat exchange along the length of the gas pipeline was revealed. It was proved that the air temperature above the soil surface should be substituted into the formula for calculating the change in gas temperature along the length of the pipeline between compressor stations. This made it possible to determine quantitative changes in the thermophysical and hydraulic characteristics of the gas along the pipe length, in particular, the change in density, viscosity, heat capacity, flow regime. It is shown that the change in air temperature during the year leads to a change in the gas pressure at the end of the gas pipeline section up to 0.15 MPa. A change in air temperature by 10 °С leads to a change in gas temperature by approximately 5 °С. Analytical studies made it possible to develop practical recommendations for the power-saving operation of air coolers at compressor stations. It was determined that the optimum gas temperature at the cooler outlet will be the temperature at which the heat exchange inversion point along the length of the gas pipeline coincides with the location of the subsequent station. It is shown how to control gas cooling in air coolers. In particular, by shutting down one of several operating devices and changing the speed of the fan drive. The developed recommendations will make it possible to quickly regulate the temperature mode of the underground gas pipeline operation at optimal power consumption for the operation of the gas cooling system after gas compression

Nonparametric control algorithm for metal temperature mode on site BOF – CCM

A two-level control system for the temperature mode of smelting, out-of-furnace processing and preparation for casting of low-carbon steel G/ET is proposed in the conditions of BOF shop-2 of JSC “United West Siberian Metallurgical Combine”. Depending on the technological scheme, it is possible to design various control systems for the steelmaking complex with sequential, parallel and combined inclusion of individual operations and processes. The control system of a sequential group of objects is considered on the example of steel G/ET. The control system includes an external control loop that allows coordinated control of the shop departments by optimizing the mode of technological process conducting at the facility, taking into account the actual operation performed at the previous facility. The implemented nonparametric algorithm of dual control allows the decision-maker to perform joint operational adjustment of control actions for local control loops. The temperature mode of the melts of low-carbon steel G/ET is analyzed and it is revealed that the processing time of the steel ladle at each stage of the BOF – CCM technological route has a significant impact on the steel temperature mode. In accordance with this, the criteria for temperature control quality are formed. The results of computational experiment showed that the introduction of a control unit with a decision-maker contributes to the rational control of metal temperature mode in the BOF – CCM site, and as a result, obtaining a given chemical composition and temperature of steel within narrower limits. It allows one to eliminate deviations from the contact schedule of the main units, and to increase the number of melts in the series and the rate of continuous casting.

Modeling of Non-Stationary Heating of Steel Plates with Fire-Protective Coatings in Ansys under the Conditions of Hydrocarbon Fire Temperature Mode

The results of the experimental determination of temperature from a non-heating surface of steel plates with a fire-protective coating under conditions of fire exposure under the hydrocarbon fire temperature regime are presented. A calculated finite element model of the system “steel plate-flame retardant” was constructed to simulate the non-stationary heating of such a system in the ANSYS R17.1 software complex. The reliability of the numerical simulation results is estimated by real test, the adequacy of the developed model to the real processes occurring when heating the steel plates with fire-protective coating under the conditions of hydrocarbon fire temperature mode is made.

The structure, phase composition, and residual stresses of diffusion boride layers formed by thermal-chemical treatment on the die steel surface

Introduction. Control and management of technological residual stresses (TRS) are among the most critical mechanical engineering technology tasks. Boriding can provide high physical and mechanical properties of machine parts and tools with minimal impact on the stress state in the surface layers. The purpose of this work is to determine the temperature modes of diffusion boriding, contributing to a favorable distribution of TRS in the surface layer of die steel 3Kh2V8F. The paper considers the results of studies on the TRS determination by the experimental method on the UDION-2 installation in diffusion layers on the studied steel surface. Boriding was carried out in containers with a powder mixture of boron carbide and sodium fluoride as an activator at a temperature of 950 °C and 1050 °C for 2 hours. The obtained samples of steels with a diffusion layer were examined using an optical microscope and a scanning electron microscope (SEM); determined the layers' microhardness, elemental, and phase composition. The experiments resulted in the following findings: as the boriding temperature rose from 950 °C to 1050 °C, the diffusion layer's thickness increased from 20 to 105 μm. The low-temperature mode of thermal-chemical treatment (TCT) led to the formation of iron boride Fe2B with a maximum boron content of 6 % and a microhardness up to 1250 HV. A high-temperature mode resulted in FeB formation with a top boron content of 11 % and a microhardness up to 1880 HV. Results and Discussions. It is found that boriding at 950 °C led to a more favorable distribution of compression TRS in the diffusion layer. However, significant TRS fluctuations in the diffusion layer and the adjacent (transitional) zone could affect the operational properties after TCT at a given temperature. An increase in the TCT temperature led to tensile TRS's appearance in the layer's upper zone at a depth of up to 50 μm from the surface. Despite tensile stresses on the diffusion layer surface after high-temperature TCT, the distribution of TCT is smoother than low-temperature boriding.

ADJUSTMENT OF RESONANCE FREQUENCY IN H-STRUCTURES ACCELERATING

It is necessary to adjust the resonant frequency of the accelerating structures during operation of high-frequency linear accelerators on the H-wave. The deviation of the resonant frequency of the resonator from the calculated value is due to the connection of input devices and control of RF power when changing the level of matching of the resonator with the feeder line that transports the RF power to the resonator, as well as when changing the temperature mode of the resonator. The problem is especially urgent when the accelerator structure consists of several resonators. The paper presents the designs of several resonant frequency tuners and the results of their research. The influence of the change of the frequency of oscillations excited in the accelerating structure on the parameters of the accelerated beam is considered.

Energy analysis of the production line for canned carrot production

An energy-saving scheme for the production of candied carrots has been developed. The developed scheme includes: washing of raw materials with 1 % NaHCO3 solution, reduction of water consumption for blanching, reduction of syrup consumption for saturation of raw materials with sugar. A new drying technology is introduced: candied fruits are dried in a variable temperature mode, namely: in the initial stages with a heat agent at a temperature of 70 °C, at the final stage – with a heat agent at a temperature of 20 °C. The process of modeling the traditional and energy-saving scheme of candied carrot production in the universal simulation software ChemCad is carried out. The simulation results are analyzed. It is proved that the total energy efficiency of the implemented technology is 340.4 MJ / h or 354.6 kJ / kg of finished product.

INFLUENCE OF HEAT TREATMENT ON DIE STEEL 4Kh4N5М4F2 AND ESTABLISHMENT OF ITS PHYSICAL AND MECHANICAL PROPERTIES

The results of researches after heat treatment (hardening and tempering) of alloyed structural steel of grade 4Kh4N5М4F2 in cast and forged state are given. It is recommended to carry out partial recrystallization (incomplete annealing) of the experimental steel (4Kh4N5М4F2) at a temperature of 750±20 °С. It is recommended to carry out thermo-deformation treatment (forging at a temperature of 1170±20 °C), which doubled the grain yield of hardened steel and increased the toughness five times after tempering. The optimal temperature mode of hardening (1095±5 °С) of cast and forged steel, the hardness of which coincides at the level of 56 HRC, is established. The grain score in cast and forged state (№ 3–№ 6 and № 6–№ 8, respectively) of the investigated steel depending on the quenching temperature (1050–1110 °С) is shown. The dependence between hardness and specific electrical conductivity of steel after hardening in comparison with cast and forged state is established. It is established that at optimized modes of heat treatment of the investigated steel it was determined by the minimum value of the parameter – specific electrical conductivity. Thus, for the optimal value of the tempering temperature of steel (1095 ºC), the specific electrical conductivity was 0,075 Ohm•mm2/ m, and at tempering (595 ºC) – 0,0415 Ohm•mm2/m. The methodical approach after hardening of steel is offered that allows carrying out control of a temperature mode at heating of the stamp tool. It is established that after hardening of steel, forged has the highest conductivity than cast. Physico-mechanical properties (strength threshold, impact strength, hardness, microhardness in the metal structure and specific electrical conductivity) of the investigated hardened steel (cast and forged) after tempering are presented. An increase in the hardness and strength of cast steel during tempering at temperatures from 450 to 500 °C, which is provided by the release of the carbide component, where there is an intensive increase in microhardness. It was found that the tempering brittleness of the investigated steel at a temperature of 475±15 °C. An anomalous decrease in impact strength (up to 15 J/cm2) and an intensive increase in the specific electrical conductivity of cast and forged steel at tempering brittleness are shown. The increase of microhardness of the investigated steel is established, which promotes increase of wear resistance and increase of service life of the stamping tool. It is established that during reheating (tempering), the conductivity in steel increases, and the structurally sensitive mechanical characteristic (impact strength) changes intensively, which increases twice in the range of tempering brittleness temperatures of 475±15 ºС. This makes it possible to increase the service life of the press tool (die) made of steel 4Kh4N5M4F2 for hot deformation of aluminum alloy in the temperature range 450-500 °C.