Improvement of the Thermocouple Method for Testing Energy-Intensive Emulsions for Compatibility with the Sulfide Ores

The results are presented concerning improving the thermostatic method for studying the chemical compatibility of modern industrial emulsion explosives based on the ammonium nitrate with surrounding materials, the increased reactivity of which can lead to spontaneous ignition and even explosion. An assessment of the compatibility of emulsion explosives with sulphide ores was conducted using an original thermocouple methodology developed at the D. Mendeleyev University of Chemical Technology of Russia, fixation of the thermal effects of the interaction of shell-free explosives based on the ammonium nitrate with sulfide minerals. Improved thermocouple method allows to determine chemical compatibility of the industrial explosives with the reactive rocks. It is distinguished by the possibility of continuous recording of the thermocouple measurements during tests using an oscilloscope and combines the reliability of the results with small laboratory weights of the test samples (no more than 20 g, which ensures safety testing). Temperature measurement accuracy is ± 2 °С. It is concluded that the method used is able to identify the cases of the most dangerous interaction from the practice point of view using the emulsion explosives when the pyrite content in the ore exceeds 85 %. The results of experiments on the applicability of thermocouple measurements to testing low-activity rocks, highly reactive pyrite ores, mixed sulfide ores of medium activity, as well as on the identification of the main regularities of heat release during the interaction of emulsion explosives with the sulfide ores are considered.

Investigation of Thermal Fields at Phase Boundaries in Powder Mixtures that are Subject to Melting and Chemical Transformation

An important part of the process of parts hardening by the induction surfacing method is the heating of hard alloy particles and flux in charge mixture. The article describes comprehensive studies on measurement and simulation of temperatures at phase boundaries in complex melting and heat-sensitive powder mixtures. To record the temperature in the induction surfacing process, it is proposed to apply CA micro-thermocouple method and the thermal indication method using SHS compositions. The developed methods for complex temperature recording in the process of induction surfacing allow to determine the melting temperature of the charge mixture and its single components.

Measurements of Temperature and Emissivity Distributions on a High-Temperature Surface Using an Auxiliary Light Source Method

A method to simultaneously measure two-dimensional temperature and emissivity distributions on high-temperature diffuse surfaces is developed using an auxiliary light source. The high-temperature diffuse surface is irradiated from the hemispherical space with the auxiliary light source switched “on” or “off.” Two images of the effective radiation intensity are obtained in quick succession for the two states to determine the temperature and emissivity distributions. The measurement method and uncertainty models show that the effect of the unknown emissivity on the accuracy of the temperature field measurement can be eliminated. The optical pyrometer is a color charge coupled device (CCD) sensor with a quartz lamp array used as the auxiliary light source to illustrate the measurement method. An oxidized W–Ni–Fe alloy sample is heated at high temperatures of 600–1000 °C by a 700 W induction-heating device. The distributions of the effective radiation intensities from the sample surface during the “on” and “off” states of the lamp array are measured in the three color channels (R, G, and B channels) to calculate the temperature and emissivity distributions. The temperature measurement uncertainties are less than 4 °C for a temperature range of 600–900 °C. The temperature measurements are experimentally validated by the thermocouple method only with a small temperature difference. The emissivities calculated from the three color channels are very close with a range of 0.855–0.957. The relative uncertainties in the emissivities for channels R and G are less than 2.0%, while the relative uncertainty for channel B data was higher at 2.8% and 7.5% due to lower measurement signals in channel B. This analysis may provide a useful method for measuring the temperatures of high-temperature diffuse surfaces by successfully compensating for the effects of unknown or changing emissivities.

The Temperature in the Cutting Zone when Applying Deformational Cutting to Form a Hardened Layer

Deformational cutting is a promising method of increasing wear resistance of friction surfaces by creating a strain hardened surface layer on them. An important factor influencing the deformational cutting process is the temperature in the cutting zone, therefore, it is necessary to obtain calculation formulas for predicting it. In this paper, the temperature change during deformational cutting of non-hardened austenitic steel in order to form a hardened layer was studied in relation to the cutting parameters: cutting depth, feed and cutting speed. Austenitic steel was selected as a promising material for strain hardening by the deformational cutting method. Temperature measurements were carried out using the natural thermocouple method. An empirical formula for calculating the temperature in the cutting zone depending on the cutting parameters was obtained.