Papers by Keyword: Quenching

Abstract: The paper compares the technical characteristics of two thermochemical treatment (TCT) lines for self-tapping screws at OJSC MMK-Metiz. Quenching on TCT line 1 is carried out in the furnace by AUTOMATION SERVICE, while quenching on TCT line 2 is carried out in the furnace by KOHNLE. The authors described quenching and tempering schedules in these two furnaces, studied the microstructure of screws at all process stages, determined technical parameters and properties of finished products after thermochemical treatment. The research showed that the best performance had TCT 2 by KOHNLE. The metallographic analysis indicated more stable parameters of the layer thickness after nitrocarburizing, core and surface hardness, which was in full compliance with regulatory documents. By introducing a better structure of a new TCT line by KOHNLE, a TCT process period became shorter, and a range of self-tapping screws might be extended entailing a higher output of finished products.

Abstract: This research was conducted to examine the comparison of tensile strength and microstructure between two different aluminum heat treatments. This study aims to compare the microstructure and tensile strength of aluminum 7075 specimens after undergoing solution heat treatment at a temperature of 495°C with soaking time for 30 minutes and experiencing quenching cooling and those without solution heat treatment. The data collection process was carried out by conducting tensile testing and microstructural testing with two specimens each. The test results will be analyzed using tensile strength data and visual microstructure analysis. From the results of the analysis of tensile and microstructural test data, it can be concluded that only the 7075 aluminum specimen with a thickness of 1.4 mm shows the greatest decrease in tensile strength and spread of Mg-Zn and Fe-Al particles, when compared to specimen 7075 with a thickness of 0.6 mm which on the other hand, undergo the separation of Mg-Zn and Fe-Al particles. Meanwhile, the Al 7075 specimen with a thickness of 2.5 mm, the changes that occur only in the diffusion of Mg-Zn particles, which have a slight spread, appear a little faint.

Abstract: The cigarette industry produces wastes from tobacco leaves and clove flowers which is called Jengkok. The wastes contain metal Arsenic (As), a toxic metalloid chemical element that is dangerous for the environment. The organic compounds in the wastes can be decomposed using pyrolysis, a chemical process at elevated temperatures in the absence of oxygen. The purpose of this study is to examine the chemical compositions and characteristics of biochar produced from quenching technology treatment in the pyrolysis process using a Rotary Kiln machine. The variables used were the temperatures ranging from 400, 450, 500, 550, 600°C, the duration from 30, 35, to 40 minutes, and water quenched temperature at 25°C. The Biochar water content and temperature produced were then observed. The results analysis included properties test, ultimate analysis, namely elemental testing using the SEM-EDX method and proximate analysis. This research found that water quenched treatment produces Biochar of Jengkok from tobacco is bases (pH. 9-10), and low bulk density. The specific characteristic is C-organic, N, and O has a large enough value, while the optimal processing time is 40 minutes at a temperature of 550 °C, a time of. Therefore, biochar from jengkok is very good for farming with acid soil conditions.

Abstract: The quenching is one of the most used mechanisms for increase the strength of aluminium alloys sheets. The purpose of quenching is to keep the super-saturated solid solution formed during the solution heat treatment as intact by rapid cooling. In order to establish the influence of the addition of polymer in the quenching water on the distortion and residual stresses of the aluminium alloy sheets, several tests were performed with different concentrations of the polymer in demineralized water. The experiments were performed on 6082 aluminium alloy sheets with a thickness of 5 mm. The quenching of the samples was done by immersion in a stainless steel vessel with a capacity of 10 liters. The obtained results show that the addition of polymer in demineralized water positively influences the deformation of aluminium alloy sheets. In this way, a correlation between the polymer concentration and the deformation of the plates was established. Regarding the internal stresses, no correlation was identified with the level of polymer used in demineralized water.

Abstract: The formation energy of martensite nuclei in the austenite matrix is calculated. Nanoclusters with ferromagnetic order, which exist in austenite above the Curie temperature, reduce the formation energy of a critical martensite nucleation center when exposed to an external magnetic field. The data obtained are explained by the magnetic separation of the initial phase under the action of a magnetic field. A fluctuation increase in nanovolumes with a ferromagnetic order in austenite increases the energy in a atoms group of the matrix phase with a parallel spins arrangement. As a result, the nucleation rate of the martensite phase increases and the martensitic transformation proceeds more completely.

Abstract: Currently, hard alloys are common tool materials; they are widely used in the tool manufacturing industry. Due to the presence of refractory carbides in its structure, hard-alloy tools feature a high hardness of 80 to 92 HRA (73 to 76 HRC); a high heat resistance (from 800 °С to 1,000 °С); therefore, they can be used at speeds that are several times higher than cutting speeds of high-speed steel grades. Hard alloys are used in the form of plates that are either mechanically fixed on or soldered to tool holders. The main operational parameters, that determine the hard-alloy tool operation mode, are hardness, wear resistance, and bending strength. The operational parameters of alloy are highly dependent on its structure, phase composition, lattice block sizes, and micro-stress values [1-20]. The main methods to enhance physical and mechanical properties of hard-alloy plates are improvement of manufacturing technology, including production of fine-grained alloys and microalloying, as well as applying composite coating by vacuum deposition, which allows to increase the tool resistance 1.5 to 2 times.

Abstract: The quantitative microstructure - impact toughness relationships in two batches of the same steel grade subjected to quenching and tempering (Q&T) have been established via characterization using EBSD technique and FIB visualization. The EBSD-based criterion for separation of structural constituents in microstructure of Q&T low carbon low alloy steels is proposed. Impact toughness differences between two steel batches subjected to nominally identical Q&T are caused by the changes in the volume fraction of structural constituents caused by various cooling conditions at quenching stage. High volume fraction of bainite containing more distorted bainitic ferrite and the highest amount of brittle cementite precipitates leads to the increase in strength and to the decrease in impact toughness.

Abstract: The spectroscopic performance of Er³⁺ doped glass at 0.55 mm emission contain different nanoparticles NPs have been comparatively evaluated. Glass containing 1.0 mol % of Er³⁺ doped with different NPs (Ag, Co and Fe ) have been prepared using melt quenching technique. X-ray diffraction analysis reveals the all the prepared samples are amorphous. The UV-Vis absorption spectra of all glasses show several prominent peaks at 525 nm, 660 nm, 801nm, 982 nm and 959 nm due to transition from ground state ⁴I_15/2 to different excited of ²H_11/2, ⁴F_9/2, ⁴I_9/2, ⁴I_11/2, and ⁴I1_3/2. The emission of Er³⁺ at 0.55 mm for glass contain Ag NP shows significant enhancement about 3 folds up to 0.6 mol%. On the other hand, the emission of Er³⁺ at 0.55 mm for glass containing Fe NPs and Co NPs intensely quench probably due to the energy-transfer from Er³⁺ ion to NPs and magnetic contributions.

Abstract: During heat treatment of machine parts and tools, besides the usual task of ensuring a high complex of mechanical and operational properties, there is a problem of distortion of products in the process of heat treatment and the need for editing operations (which are carried out manually and require significant labor costs). The known methods do not solve the problem of removing distortion for thin-walled parts of the ring shape completely. This paper shows the technical possibility of using the energy of a constant magnetic field for the "internal" straightening of products during heat treatment in the temperature range of super-plasticity of transformation. The use of special equipment makes it possible to eliminate virtually the distortion of thin-walled parts of the ring shape and to improve their mechanical properties.

Abstract: The article established a modelling that predicted and measured the quenching and pre-stretching stress in 7050 aluminum alloy thick plate in order to make the alloy suitable enough for manufacturing in the aerospace industries. The results show that both the rolling direction component stress and the transverse direction component stress have a “M” distribution along the plate thickness of 7050 aluminum alloy thick plate, but the level is slightly different, but the level is slightly different. The maximum value of quenching residual stress is about 187MPa in the 80mm thick of 7050 plate. Pre-stretching of the heat treated and quenched alloy to 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0% and 3.5% to reduce the residual stresses. It has been recorded that more than 90% reduction of residual stresses were observed in a pre-stretching rage of 2-3%. Measuring the surface residual stresses of the alloy by ultrasonic methods and measuring the internal residual stresses of the alloy by crack compliance methods. The two methods are used to verify the model. The difference between the measurement and the simulation is within 40MPa. The experimental data of the ultrasonic and the crack compliance methods were found to correspond well with the simulated models. This shows that the simulation model can effectively predict the evolution of residual stress in 7050 aluminum alloy thick plate, and the simulation model can also be reconstructed and inspected through the experimentally measurement.