Blank Heating Research Articles

Multi-criteria optimization of technological parameters of microwave baking of whipped yeast-free bread without crust

In order to reduce energy consumption and baking time of churned yeast-free bakery products, to improve their quality, it is relevant to use effective sources of energy supply to test blanks. For uniform heating of test blanks throughout the entire volume, their ultra-high-frequency heating during baking is of the greatest interest, which makes it possible to increase the efficiency of production. One of the well-known methods of studying the baking process of whipped, yeast-free, unskilled bread was the method of mathematical modeling based on the formalization of a mathematical model. Experiment planning is the most effective in obtaining maximum information about the modeling object with a minimum amount of experimental research. In this paper, the modeling and optimization of the technological parameters of microwave baking of whipped yeast-free bread with the use of experimental statistical methods is considered. The mass of the dough piece and the power of microwave baking were chosen as the main factors. The output parameters were the duration of baking until ready, the package and the height of the bread. Based on the results of the central compositional rotatable planning of the experiment, mathematical models in the form of regression equations are constructed that adequately describe the processes under study. Statistical processing of experimental data was performed according to the criteria of Student, Kohren and Fisher (with a confidence probability of 0.95). The mathematical interpretation of regression equations is given. Optimization of the parameters of microwave baking of churned yeast-free bakery products was carried out by the method of indeterminate Lagrange multipliers. The optimal values of the main factors of the experiment were determined: the mass of the test piece – 465 g; the power of microwave baking - 865 W, which ensures the smallest bread roll – 1.2% and the maximum bread height - 78.5 mm with a minimum duration of baking bread – 3.4 min.

STAMPING BY ROLLING BLANKS USING ADVANCED ENERGY-EFFICIENT INDUCTION HEATING

The article presents the results of development and research of technological schemes of cold forming by rolling (CFR) of blanks. Expansion of the technological capabilities of the processes of COP and improving the quality of products is based on the control of active friction forces and deformability of the processed metals. The main limiting factors in the application of SHO processes are insufficient ductility of metals, which causes the risk of destruction of workpieces, as well as relatively large deformation forces that cause unfavorable operating conditions of the rolling bearing unit. The solution of these problems is facilitated by the transition to hot SHO. However, the problems of manufacturing by the hot SHO method of products from tubular and solid cylindrical billets have been little studied to date. An effective process of billets heating is induction heating, but its application is characterized by relatively low efficiency. In this work, it is recommended to use new materials and technology for the manufacture of induction heaters for the implementation of hot SHO, which open up opportunities for improving induction heating equipment for industrial applications. The use of new generation induction heaters to replace other heating methods in metalworking has significant advantages: higher efficiency; less scattered magnetic fields; less complexity of the coil design; increased geometric freedom; no water cooling is required. In order to study the hot SHO, devices for rolling billets with conical and cylindrical rolls were designed and manufactured. Physical modeling of hot SHO by using solid cylindrical lead billets was carried out. It is experimentally proved that the process of hot SHO allows to achieve significant degrees of deformation even at unfavorable stress-strain state and insignificant power of the equipment. Thus, the process of induction heating of blanks can be quite effective when processing them by hot SHO.

Reduction of deformation forces and loads on tool during cold forming of complex parts by using of preliminary low-temperature heating of blanks

The computer simulation results of cold forming of complex parts made of 20G2R and 32CrB4 steels and by using of preliminary low-temperature heating of blanks up to 250 °С are presented. Decreasing of deformation forces up to 1.5 times and of the loads on the working tool from 1.2 to 1.5 times is established.

Application and schemes of induction preliminary heating in magnetic-pulse treatment of metals

The features of the processes of magnetic-pulse processing of metals in traditional schemes of technological processes of modern industrial production are highlighted. The work is a brief description of the state, application, and also proposed induction pre-heating schemes in industrial magnetic-pulse processing of metals. A method for increasing the efficiency of performing specified production operations is considered. The use of preheating leads to a significant improvement in the quality of production operations while reducing energy consumption. New directions of magnetic-pulse processing of metals are noted, implying the transformation of the natural repulsive forces of the metal of the processed object into the forces of magnetic-pulse attraction with a decrease in the operating frequencies of the acting fields. A significant decrease in operating frequencies makes it possible not only to go from repulsion to attraction, but also to go from working with ferromagnetic metals to non-ferromagnetic ones. For example, it becomes possible to attract aluminum blanks. Examples of the use of induction heating of metal blanks in modern industry are given. Various devices used for these operations, offered on the modern market, by both domestic and foreign manufacturers, are considered. The physics of Lenz-Joule heat release is described, the result of which is the induction heating of conductors by Foucault currents in the external electromagnetic field of the instrument. Schemes are proposed for the practical implementation of preliminary induction heating during magnetic-pulse processing of metal blanks, allowing the use of both autonomous devices for exciting eddy currents and a stationary connection, for the same purpose, of an additional source of electricity. As a result of the work, the possibility of increasing the efficiency by increasing the plasticity of the metal when heating the workpiece, as well as possible limitations of the described technology associated with an increase in the active resistance of metals with an increase in the Lenz-Joule heat release is noted.

Improvement of thermal conductivity of diamond/Al composites by optimization of liquid-solid separation process

Diamond/Al composites have been considered as the new generation of thermal management material. The critical challenge is that Al4C3 with deteriorating properties is easily generated at the interface of composites by conventional powder metallurgy and infiltration processes. This paper presents an independently developed liquid-solid separation (LSS) technology for fabricating diamond/Al composites with Cr-coated diamond particles. The key parameters of the LSS process such as the blank heating rate and its heating mode, the squeeze casting temperature and pressure, and pressurization time were optimized. Cr coating of the diamond particles led to improved interface characteristics. The higher thermal conductivity of diamond/Al composite with Cr-coated diamond particles is attributed to the favorable interfacial products of Al13Cr2 and AlCr2. Thermal conductivity of 40 vol.% Cr-coated diamond particles reinforced diamond /Al composites prepared by LSS with the optimal process was 309.20 W m−1 K−1, 108.06 % higher than that of the composite without the Cr coating. The results showed that relative density is a critical factor in optimizing of the bending strength, compressive strength, and thermal conductivity of the composites. No harmful intermetallic Al4C3 is generated at the interface of the composite. LSS technology is the new low-cost and compact method for the fabrication of diamond/Al composites with high thermal conductivity, which has the prospect of industrial application.

MODELING OF A SYSTEM FOR AUTOMATIC REGULATION OF THE TENSION MODE IN THE ROUGHING GROUP OF STANDS OF A CONTINUOUS SECTION MIL

The subject of the research is automatic control system modeling features for tensioning of stands roughing group, which takes into account changes in the rolling speed at exit of the previous stand and entrance to the next stand. Control systems for high-speed rolling on section mills are the most critical systems, since the trouble-free operation of rolling mill largely depends on their work. Rolling speed control is understood to mean tension regulation in the roughing group of stands and stabilization of the rolling loop in the finishing groups. The influence of such technological factors as uneven heating of blanks, change in the crimping mode in stands, etc. leads to the appearance of tension or back-up forces, deviation of rolled loop from the specified values. Tension rolling, in contrast to loop rolling, is a stable rolling mode. However, (at significant values of tension in the rolled products) such a rolling mode leads to different thicknesses of the finished product. The loop rolling mode is an unstable mode and is impossible without automatic control systems. Both in the tension rolling mode and in the free rolling mode with a loop, it is necessary to study automatic control systems in order to determine the possibilities of compensating for disturbing influences and obtaining rolled products of the given accuracy. Therefore, the main task of the automatic control system is to maintain the rolling mode with the lowest possible tension. To achieve this goal, direct control of the tension of the rolled strip with modern technical means is rather difficult, and the operation of tension control systems is based on indirect methods of measuring it, and the study of the system efficiency is reduced to modeling the process itself. The developed model consists of three stands and two inter-stand spaces, since it takes into account changes in rolling speed at the exit of previous stand and the entrance to the next stand. It is due to this that adequate simulation results are obtained that are close to the real rolling process.
 Keywords: automation, rolls, stand, inter-stand spacing, modeling, loop tension, rolling mill, roughing group.

A Comparison of the Performance of Constant and Dual Height Pin Fins in Phase Change Material Cooling Technique

Abstract This experimental study explores the passive cooling of electronic devices using phase change materials (PCM). Pin fin configurations made of aluminum are considered as thermal conductive enhancers and eicosane as the PCM for the study. The experiment considers four different heat sinks, with 40 and 56 numbers of pin fins. For the same number of pin fin, dual and constant height fin arrangements are study. The volume fractions of TCEs are 9%, 11%, 13%, and 16%. Apart from these heat sinks, a heat sink with no fin (blank heat sink) is considered for baseline comparison. Five different heat fluxes are considered (ranging from 1.17 kW/m2 to 2.35 kW/m2). The effect of number of fins, type of fins, and volumes of PCM has been reviewed. It has been observed that the introduction of fins enhances the heat transfer. An elongation in operational time is achieved in the case of dual height heat sinks compared to constant height heat sink filled with PCM. All the experiments are performed in a temperature-controlled room to avoid environment fluctuation.

A direct resistance heating method for shaped blank

Direct electric resistance heating allows fast and uniform heating of rectangular blanks in hot forming process. To adapt this technology for any blank shape, a solution is proposed by splitting the part in several rectangular strips heated by electric generators. By optimizing the number, the orientation and the dimensions of rectangular strips to reduce added material and energy costs, this method is applied in the case of a windscreen upright blank. From a 3D thermoelectric model taking into account the imperfection of contact between the blank and the electrodes, integrating a PID-controller and the electrical power limitations, a heating demonstrator of this part is developed. This heating method has proved to be effective in heating shaped blanks quickly and uniformly during the hot stamping process.

Evaluation of 22MnB5 Steel Austenitization Sub-Models for Simulating the Heating Phase of Hot Stamping

The heating phase of hot stamping is the most time-and energy-intensive part of the process, and therefore offers significant potential to improve process efficiency. This requires a robust thermometallurgical model that predicts the blank heating profile and the austenitization progress inside a roller hearth furnace. In this paper, an IM austenitization model for 22MnB5 steel is derived using dilatometry data and evaluated against a JMAK type model using temperature profiles of coupons heated within a laboratory-scale muffle furnace and blanks heated within a roller hearth furnace. The austenitization rates predicted by the two models are then compared to the inferred austenitization processes from those temperature profiles. The result shows that the IM model has potential to capture the trend of austenitization process, especially the rapid pearlite dissolution at the beginning of the transformation, whereas the JMAK type model is too restrictive and fails in this regard.

Analysis on three typical abnormal microstructures of overhead power line suspension clamps

This article lists three typical abnormal microstructures of overhead power line suspension clamps, including inclusion, flake graphite and cementite network. A series of tests including macro check, hardness measurement, composition tests, Energy-dispersive x-ray analysis and metallographic observation have been carried out. The experimental results showed that the causes of abnormal microstructures mainly include: high content of impurities, flake graphite blank and unfulfilled annealing heat treatment. It is suggested to strengthen the supervision on suspension clamps before using, and focus on the quality inspection of metallographic structure and composition.

Investigation of material properties of tailored press hardening parts using numerical and physical simulation

In order to assure good resistance performances, automobile manufacturers are looking for high strength steel, especially for structural parts of body in white, which are formed by hot stamping process. With the aim of guaranteeing specific crash behavior, various technologies have been developed to provide tailored properties.Typical tailored component is the B-pillar, which is studied in this work. In general, the pillar must be with greater resistance in some areas, while in others it must have greater toughness to absorb the energy of a possible impact. The tailored technology investigated in this work is the tailored tempering, in which different areas of the component experience different cooling histories leading to requested final mechanical properties.The methodology used to investigate custom properties involves a first designing phase implemented with Finite Element (FE) commercial programs; FE simulations were performed to investigate the Press Hardening process of a 22MnB5 boron steel blank and in particular the thermo-mechanical cycles related with both the high-resistance and high-toughness regions of the pillar.In the second phase of the proposed approach, the obtained thermo-mechanical cycles have been physically simulated, by using Gleeble 3185 system. The following consecutive steps was reproduced on home-designed specimens: (i) Blank heating for the complete austenitization (at a temperature of 930° C for 4 min). (ii) The heat loss due to the transport phase of the blank from the oven to the press. iii) The mechanical deformation of the blank due to the stamping phase. iv) The quenching phase of the part. (v) The cooling on air of the B-Pillar.Finally, micro-hardness tests have been performed on the specimens subjected to physical simulation. FE model predictions and micro-hardness tests are in good agreement, showing that tailored tempering effectively leads to differentiation of the mechanical properties.

The Effect of Elevated Temperature on the Drawability of a Circular Deep Drawn Metal Cup

Product quality is one of the important aspects in deep drawing practice and the variation in process temperature was claimed to improve the quality. Therefore, in this research, the effect of the heating temperature on the drawability of a circular metal cup has been investigated. Firstly, circular metal cups of aluminium, mild steel and stainless steel were drawn from the blank diameters of 60 mm, 65 mm, and 70 mm. The experiment was conducted at room temperature followed by at 100 °C, 150 °C and 200 °C. The Taguchi method was selected as the design of experiment approach, and L9 (34) array design methodology was adopted in this experimental research. The drawability was measured based on the punching force needed to deform the sheet metal blanks. The deep drawing process was conducted at room, and elevated temperature conditions and the response factor was analysed and compared through the analysis of variance (ANOVA) statistical approach. The results obtained from ANOVA indicate that the blank material has a significant influence on the deep drawing process followed by the blank size, heating temperature and heating technique. The optimal parameter combinations are blank diameter of 60 mm, heating temperature of 200 °C and the die and punch heating technique. Out of the three materials investigated, aluminium has a better drawability compared to mild steel and stainless steel.

Investigation of the influence of forming parameters on the springback of hot-stamped hat-shaped parts

The application of hot stamping parts has become a dominant approach to achieve lightweight design and increase crashworthiness performance in the automotive industry. Compared to the cold stamping parts, the main feature of the hot stamped component is its high strength and good size stability. However, recent studies have shown that the springback or size deviation of hot stamped parts caused some assembly problems. This paper aims to investigate the influence of forming parameters on the part’s springback via a hot stamping hat-shaped die. Three different forming parameters with the same blank heating temperature (930°C) were conducted in the study: (1) transfer time 8 sec/die quenching 15 sec (2) transfer time 8 sec/die quenching 8 sec and (3) transfer time 18 sec/die quenching 15 sec. The selected forming parameters are used to evaluate the effect of the before-forming blank temperature and die-opening blank temperature on the springback of the hot stamping parts. The results show that the case 3 with a prolonged transfer time causes a small portion of ferrite phase formation in the hot-stamped part, resulting in the decrease of the tensile strength and a more significant springback is observed.

Study on Forming Technology of TBM Disc Cutter Ring

The tunnels and underground projects bring an unprecedented development of hard rock tunneling technology. The forming process and material properties of the 20 inch disc cutter ring has been studied by the finite element simulation and test methods. The effects of blank size, blank heating temperature, mold preheating temperature and friction coefficient on the forming load, minimum surface temperature and blank deformation uniformity of 20 inch cutter ring were analyzed. The results show the optimum combination of the forming process of the 20 inch disc cutter ring is when the blank height is 90 mm, the blank heating temperature is 1200 °C, the preheating temperature is 280 °C, and the friction coefficient is 0.2. Compression test and hardness test were carried out on the edge material of the cutter ring. The test results show that when the temperature exceeds 600 °C, the hardness and compressive strength of the cutter ring material will drop sharply. Therefore, the TBM should be properly cooled during construction. The research results in this paper can provide a basis for the optimization of TBM disc cutter ring processing technology and engineering applications.

Improving the Performance of the Annular Furnace at PAO ChTPZ

Abstract—The productivity of rolling and pipe-rolling mills and the product quality may be improved by heating the metal billet in furnaces with minimum oxidation and decarburization. That is possible in annular furnaces, which are widely used in the rolling of pipe and railroad wheels. High-quality heating permits the creation of metal structure with specified thermophysical and operational properties, as well as the plasticity required for subsequent machining. In the present work, the operation of an annular furnace used to heat pipe blanks before rolling at PAO Chelyabinskii Trubokatnyi Zavod (ChTPZ) is analyzed. Thermal problems are considered: in particular, the high fuel consumption in heating blanks and high external temperatures of the walls and roof; the low rate of blank heating; and the serious leakage of air into the furnace’s working space. In addition, a defect of the gas-burner design is that the gas supply cannot be regulated, despite the wide load range (including periodic shutdown). Finally, practically no use is made of the thermal energy in the exhaust gases. In the analysis of these problems, the heating of the metal is calculated, and the thermal balance of the annular furnace is formulated. The analysis reveals factors that decrease the energy efficiency of the existing furnace design. Measures are proposed for furnace modernization so as to decrease the fuel productivity and increase the productivity: for example, the use of fiber refractories; regenerator burners; and barriers that are not water-cooled. To assess the effectiveness of these measures, we formulate the thermal balance of the redesigned annular furnace and analyze its thermal operation. The proposed measures are expected to provide significant economic benefit and to improve the heating of the metal, with decrease in fuel consumption and increase in productivity. In particular, after reconstruction, increase in the furnace’s total efficiency (by 18.1%) and thermal efficiency (by 31.0%) is expected, as well as decrease in fuel consumption by 48.3 kg CF/t.

Short austenitization treatment with subsequent press hardening: Correlation between process parameters, microstructure and mechanical properties

This study discusses contact heating of blanks as a time- and cost-saving alternative to conventional heating in radiation furnaces for press hardening of high-strength car body elements. Different from radiation furnaces, where the process takes up to 10 min, contact heating allows to austenitize the material within seconds. Various experimental series were carried out to investigate the influence of short austenitization on the microstructure and resulting mechanical properties after subsequent press hardening. Attention was given to the individual effects on the relevant processing parameters of the production chain “contact heating – press hardening”. Those include thickness and initial state of the material, cooling rate as well as the presence of post-treatment (cathodic dip coating). The obtained results were compared both to the conventionally austenitized and press-hardened material as well as to the requirements of the industrial standard. Finally, the feasibility of the process was proven by considering the example of press hardening of a door impact beam.

Heating schemes and process parameters of induction heating of aluminium sheets for hot stamping

Induction heating is one of the most popular metal heating technologies due to its high heating rate and high energy efficiency. This method is suitable for heating workpieces/blanks in different shapes, sizes and materials. Although induction heating of metal sheets has already been investigated by various research organizations and industrial companies, information concerning the induction heating of aluminium blanks is limited. Considering that hot stamping of aluminium sheets for automotive and aerospace applications is currently attracting a lot of attentions, it is timely important to gain more understanding on this technology by conducting in-depth investigations. Especially, investigations are required to address issues relating to the uneven temperature distributions developed in the metal sheets when they are heated, so that optimum designs could be obtained to improve the technology and its applications. This paper presents an in-depth analysis conducted recently for the investigation into heating schemes and process parameters in induction heating of aluminium sheets, mainly using 3D FE simulations, based on a general experimental validation. Different material, coil geometric and power-setting factors were considered during the modelling and analysis to examine their effects on the heating efficiency and developed temperature profiles. It was revealed from the simulations that design features of the induction coils affect the uniformity of the developed temperatures in the metal sheets. It is shown that an optimised combination of the coil design and the power setting could help to achieve higher heating rates, at the same time, also to achieve higher temperature-distribution uniformity. At the end of this paper, a discussion of practical factors that affect applications of induction heating of aluminium sheets for hot stamping applications is presented.

Hardness Prediction in Hot Stamping Process by Local Blank Heating Based on Quench Factor Analysis

Recently, the hot stamping process using local blank heating has been widely used to manufacture lightweight and crashworthy automotive parts. However, the hardness prediction of hot stamped parts produced using local blank heating is difficult because it involves many process variables, such as the heating temperature, heating time, and cooling rate. The purpose of this study was to predict the hardness of hot stamped parts fabricated using local blank heating based on quench factor analysis (QFA). The volume fraction of austenite was measured to consider the phase transformation in the heating stage, and it was expressed by the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation. Additionally, a dilatometry test was performed to measure the hardness according to the cooling rates, which was used to determine the material constants for QFA. Finite-element simulation was performed to predict the temperature histories during the hot stamping process and the results were used to predict the hardness according to QFA with the JMAK equation. A hot stamping experiment with local blank heating equipment was performed, and the predicted and experimental results were compared for verification of the proposed hardness prediction method.

Advanced induction heating system for hot stamping

The development of a rapid uniform heating process for blanks is needed to perform hot stamping processes. To solve the problem of inhomogeneous temperature distribution in conventional induction heating systems, a heating block has been added to an induction system and investigated to determine if it can achieve rapid and uniform blank heating. To characterize the effects of incorporating the heating block, the temperature distributions of various coil geometry have been experimentally analyzed. The results show that the proposed induction heating system makes it possible to achieve rapid and uniform blank heating, which is used to conduct stable hot stamping. The mechanical properties of a hot stamped part confirm that the proposed heating method is a feasible alternative method for hot stamping products, and that it yields excellent results. This system for the reduction of heating time requires less installation space compared to a conventional electric furnace and achieves uniform heating, which results in improved product quality and reduced manufacturing costs.

Deconsolidation of C/PEEK blanks: on the role of prepreg, blank manufacturing method and conditioning

The combination of rapid automated lay-up and stamp forming has great potential for rapid manufacturing of lightweight load carrying components of thermoplastic composites. However, deconsolidation during blank heating is currently limiting the applicability of rapid lay-up blanks. This experimental work investigates the origin of deconsolidation in blanks produced by advanced fiber placement (AFP) versus traditional press consolidation. The influence of moisture on deconsolidation is investigated through deconsolidation experiments in a convection oven, as well as thermo-mechanical and residual gas analyses. The experiments revealed that thermal expansion of dissolved moisture is the main deconsolidation mechanism for press-consolidated blanks, but not for AFP blanks, which are suggested to deconsolidate mainly due to the release of frozen-in fiber stresses present in the used prepreg.