Cooling Temperature and Heat Transfer Coefficients in Cylindrical Heat Exchangers

The parameters behavior that characterize the process was carried out through an experimental investigation to obtain the cooling temperature, heat transfer coefficients and the heat flow in mineral coolers. The values of water temperature, water flow and mineral temperature were recorded at the inlet and outlet of the cylindrical cooler. Experiments were carried out with five values of the mass flow, keeping the cylinder revolutions constant. The calculation procedure for the system was obtained, in the mineral coolers the heat transfer by conduction, convection and evaporation predominates as a function of the cooling zone. A reduction in temperature is shown with increasing length, the lowest temperature values were obtained for a mass flow of 8 kg/s. The mineral outlet temperature should not exceed 200 oC, therefore it is recommended to work with the mass flow less than 10 kg/s that guarantees the cooling process.

Height of Water Pool in the Roll Nip of Secondary Cooling Zone in Continuous Slab Caster: Application of Open Channel Hydraulics

In continuous casting of steel, the strand is cooled in the upper part of the secondary cooling zone with water sprayed by nozzles towards the strand surface. The water accumulates in the nip of the lower roll of a roll pair, forming a water pool which then drains off towards the ends of the roll. In the present work, open channel hydraulics was applied for computation of the water pool height in the nip between roll and strand in continuous slab casting. The differential equation describing the change of pool height for the spatially varied flow with increasing discharge was solved with the Runge–Kutta technique using as boundary condition the pool height at the end of the nip. The effects of the Manning friction factor n and the energy coefficient α were determined in sets of computation. It was shown that the hydraulic theory could predict water profiles in the nip of continuous casting rolls to a good approximation.

Analisis Pengendalian Kualitas Produk Menggunakan Pendekatan Statistical Quality Control (SQC) di PT. Samcon

PT. Samcon merupakan perusahaan yang memproduksi kapasitor yang kegiatan produksinya terbagi menjadi beberapa proses, dimana masing-masing proses dikerjakan oleh departemen yang berbeda.Tujuan dari penelitian ini adalah untuk mengetahui tingkat kerusakan, mengidentifikasi faktor-faktor penyebab kerusakan serta merekomendasikan tindakan perbaikan. Metode yang digunakan yaitu metode Statistical Quality Control (SQC) yang dilakukan dengan alat bantu statistik diantaranya: checksheet, histogram, diagram pareto, peta kendali dan fishbone diagram. Hasil penelitian menunjukkan bahwa kerusakan produk terbanyak terjadi di departemen coating dan didominasi oleh tiga jenis kerusakan yaitu coating NG (59,71%), popo (11,71%) dan doriogiri (10,43%), hasil analisis peta kendali untuk jumlah total keluar sebesar 46,7%. Tindakan yang dilakukan untuk meminimalkan kerusakan yaitu dengan mengadakan training and education untuk operator, membuat cooling zone, memeriksa penyangga deji sebelum digunakan, membersihkan heater dan pully secara berkala, melakukan perawatan dan pemeriksaan bearing, menambah fasilitas pendingin ruangan, mengganti wheel, memeriksa powder sebelum digunakan, dan mengganti sensor pengisian powder dengan sistem timer.

Improvement the Round Bloom Continuous Casting Technology at JSC “Ural Steel”

The results of assessment of macrostructure and surface quality of round blooms 455 mm in diameter, cast on 4-strand continuous casting machine (CCM) at JSC “Ural Steel” are presented. The analysis of technological casting parameters of round blooms 455 mm in diameter (from steel grade “2”) at bloom caster of JSC “Ural Steel” are completed. Violations in casting temperature and rate parameters, which deteriorate thermal conditions of solidification and quality of continuous casting blooms, have been revealed. The main causes of unsatisfactory bloom quality have been determined, which are the increased overheating of cast metal and irrational secondary cooling mode. The results of the experiment to evaluate the surface temperature dynamics of a round bloom in the secondary cooling zone are presented, which confirmed the inefficiency of the secondary cooling mode for the defect-free bloom formation. As a result of thermal calculations of round blooms solidification of 455 mm in diameter, rational coolant flow rates by secondary cooling sections for bloom caster of JSC “Ural Steel” have been proposed. Optimized secondary cooling parameters provide a softer secondary cooling of the round bloom, which reduces the probability of the surface and internal defects development.

Numerical Calculation About Influence of Crystallizer Structure on the Stress Evolution Process of Horizontal Continuous Casting of Copper Tubes

The horizontal continuous casting plays a key role in the production of inner grooved copper tubes. In order to improve the accuracy of the temperature field model of the copper tubes horizontal continuous casting process, the model heat transfer coefficient was validated through temperature measurement experiment of graphite crystallizer. The finite element model of stress field evolution was established, based on considering the temperature and microstructure changes. It was found that tensile stress was generated in the outer layer of the casting billet and compressive stress was generated in the inner layer, when the casting billet entered the primary cooling zone. The paper investigated the mechanism of the liquid inlet number and shape on the microstructure and stress distribution after the casting billet was solidified. When the number of liquid inlets was 6, the ratio of the semimajor axis of ellipsoid to the short semi-axis was 3:2 and the backward tilt angle was 10°, the equivalent stress value of the casting billet was smaller and the grains were dense and uniform. This paper promotes the research of horizontal continuous casting process and provides measurable reference for improving the quality of casting billet in the further.

Calculation and modeling of surface high-frequency pipe heat treatment parameters

This article describes a device developed and manufactured on the basis of the Physical-Technical Institute of the National Academy of Sciences of Belarus, an induction hardening complex, and a range of parts suitable for processing. In addition, the article provides an example of the development of a technology for hardening parts from the moment a drawing of a part is obtained, indicating the required parameters of the hardened layer, until the determination of the technology of hardening, determining the type of inductor used and determining the necessary parameters of hardening, such as: size of the heating zone, size of the cooling zone, speed of mutual movement of the part and inductor, as well as the type and pressure of the quenching fluid. The article also presents examples of simulation results, various processes of heating and cooling parts using the UNIVERSAL 2D program, and offers an example of analysis of the data and possible ways to adjust the heating parameters in order to obtain the desired result, which allows to obtaining hardened layers of parts of the desired size and hardness. The importance of the stage of modeling of heating modes, especially in the case of large workpieces, is noted. Thus, the insufficient cooling rate of such parts can lead to warping, especially at a too high quenching temperature and heating depth. Self-tempering significantly affects the hardness values of the deep layers. Various combinations of heating modes for one type of parts are selected individually, according to the requirement of a customer and the type of generator used. The higher the depth of the heating zone, the higher the effect of self-tempering on the deeper layers is.

Comparison of Optimization-Regulation Algorithms for Secondary Cooling in Continuous Steel Casting

The paper presents the comparison of optimization-regulation algorithms applied to the secondary cooling zone in continuous steel casting where the semi-product withdraws most of its thermal energy. In steel production, requirements towards obtaining defect-free semi-products are increasing day-by-day and the products, which would satisfy requirements of the consumers a few decades ago, are now far below the minimum required quality. To fulfill the quality demands towards minimum occurrence of defects in secondary cooling as possible, some regulation in the casting process is needed. The main concept of this paper is to analyze and compare the most known metaheuristic optimization approaches applied to the continuous steel casting process. Heat transfer and solidification phenomena are solved by using a fast 2.5D slice numerical model. The objective function is set to minimize the surface temperature differences in secondary cooling zones between calculated and targeted surface temperatures by suitable water flow rates through cooling nozzles. Obtained optimization results are discussed and the most suitable algorithm for this type of optimization problem is identified. Temperature deviations and cooling water flow rates in the secondary cooling zone, together with convergence rate and operation times needed to reach the stop criterium for each optimization approach, are analyzed and compared to target casting conditions based on a required temperature distribution of the strand. The paper also contains a brief description of applied heuristic algorithms. Some of the algorithms exhibited faster convergence rate than others, but the optimal solution was reached in every optimization run by only one algorithm.