ABSTRACT The consistency of cooling greatly influences the quality of L‐beams. In this paper, the process of cooling high‐temperature L ‐beams by multi‐jet impingement is numerically simulated. The VOF model and Realizable k–ε turbulence model were used, and the reliability of the Realizable k–ε turbulence model was verified using experiments. The jet flow rate is mainly 3–11 L/min. Numerical simulation calculations were used to obtain the distribution law of pressure, streamline, and wall shear of the flow field of the multi‐nozzle jet impinging on the surface of the L‐beam, as well as the distribution of Nusselt number of the L‐beam and the temperature distribution at 1/2 thickness. The results suggest that the cooling uniformity of the L‐beam can be enhanced by extending the cooling duration of the short edge or by concurrently increasing the water flow and time of the short edge. Based on the above strategy, a relevant industrial test program was developed. After the jet impingement cooling experiment, the L‐beam's surface temperature differential decreased by 43.9°C, and the bending of the L‐beam was decreased by 10.4 cm. The maximum value of the magnetic field gradient associated with the stress in the L ‐ beams was reduced by up to 80.2%.

Microstructural transformation has an important effect on residual stress. In this study, the experimental steel specimens were subjected to jet impact cooling. The residual stresses in the surface layers of the specimens at the end of cooling were determined using X-ray diffraction. A two-dimensional thermal-metallurgical-mechanical coupling model was established, using which the microstructure distribution and stress distribution of the specimen as well as the distribution of the associated strain can be calculated. The simulation calculation results were compared with experimental test results, and relevant analyses were carried out. The results show that the difference in the final shrinkage of different parts of the specimen leads to the difference in the tensile and compressive states of the residual stress. The larger the difference in shrinkage at different locations of the specimen, the higher the residual stress. The maximum difference in the sum of transformation strain and cooling shrinkage strain increased from 9 x 10-5 to 0.00614, and the maximum value of residual stress increased by 263.25 MPa. The microstructural transformation during the cooling process mainly affects the residual stress by generating transformation strains and causing changes in the coefficient of thermal expansion.

Flotation pulp phase bubble images are captured from the pulp solution within the flotation cell and exhibit characteristics such as quantity and size that are closely related to flotation operating conditions. In this study, two specialized devices were employed to obtain bubble images from the flotation pulp solution: an underwater camera (UC) for in-situ collection of pulp phase bubbles and a bubble diameter analyzer (BDA) for ex-situ collection. The advantages and disadvantages of traditional thresholding segmentation and various deep learning models for segmenting pulp phase bubbles were compared. A segmentation model specifically designed for segmenting flotation pulp phase bubbles, named KSMPB-Net, was proposed based on the Kolmogorov-Arnold Networks (KAN) structure. The training results of the model demonstrated that, compared to the U-Net model, the KSMPB model achieved a 10.7% improvement in segmentation accuracy (MIoU), reaching an MIoU of 0.9985, while reducing the training loss by 65% to a value of 0.011. Feature analysis results further revealed that the quantity and size of flotation pulp phase bubbles were closely associated with air flow rate, impeller speed, and pulp concentration. Moreover, under laboratory experimental conditions, the in-situ image collection method outperformed the ex-situ image collection method. Applying deep learning-based methods to flotation bubble analysis facilitates the optimization of flotation conditions based on bubble characteristics, thereby advancing the integration of pulp phase bubble analysis into the intelligent control processes of industrial flotation operations.

A flow condensation experiment was performed in a 300 mm long mini channel with a diamond pin fin array. The working fluid is R134a and four pin fin arrays were tested, including different channel widths of 1.0, 1.2, and 1.4 mm, as well as fin angles of 60 degrees and 90 degrees. The experimental system used in previous studies was adopted to obtain the local heat transfer coefficient. The measurements were done within the saturation pressure range of 600-1500 kPa with mass flux ranging from 160 to 450 kg/m(2)s. The experimental results indicated that the local heat transfer coefficient increases with an increase in vapor quality, mass flux, and heat flux whereas it decreases with an increase in saturation pressure. The influence of heat flux and pin fin array structure on heat transfer coefficient was more significant in the high vapor quality region relative to that of the low vapor quality region. Higher fin density and larger fin angles contribute to improved condensation. With a diamond fin angle of 60 degrees, the heat transfer coefficient of the pin fin array with a fin density of 0.22 is 24 %similar to 56 % higher than that of the pin fin array with a fin density of 0.16. For the pin fin array with the same fin density, the heat transfer coefficient at fin angle 90 degrees is 1.1-1.4 times that at fin angle 60 degrees.Additionally, the performance evaluation criteria named Penalty Factor was applied to evaluate the performance of the pin fin array, and SG60_3 outperforms the other channel, corresponding to a fin angle of 60 degrees and channel widths of 1.4 mm. The Penalty Factor value of SG60_3 is 70 %similar to 80 % of that of the other three pin fin array. The existing correlations fail to give a reasonable prediction for the heat transfer coefficient of the present experimental data. Therefore, a new correlation accounting for the effects of geometric sizes of pin fin array and heat flux was developed with the maximum mean absolute deviation of 7.48 % on four test channels. The present study can provide valuable knowledge on the design optimization of mini channel condensers with pin fin array.

The bending deformation problem and internal residual stress of hot-rolled L-beams affect the quality and subsequent use performance of L-beams. In this paper, the computational model of the L-beam air-cooling process is established by using ABAQUS finite element software, which reveals the reasons for three times deformation of the L-beam from the perspectives of phase change expansion and metal cooling contraction. In order to control the deformation and residual stress of the L-beam, four experimental schemes were determined with the cooling method, water pressure, and the opening and closing state of the cooling unit of the cooler as variables. The temperature distribution, deformation before straightening, warping deformation after cutting, and magnetic field distribution curves of L-beams before and after rapid cooling under different experimental schemes were examined, and the microstructure and properties of L-beams were examined and the results were analyzed. The results show that the cooling uniformity of the L-beam can be improved by rapid cooling, which can effectively reduce the amount of bending per meter of the L-beam before straightening, the amount of warping deformation after cutting, and reduce the level of residual stress inside the L-beam, and at the same time can refine the microstructure and improve the properties. In this study, the amount of bending per meter and warpage deformation after cutting of L-beams were reduced by up to 67.3% and 85.7%, respectively, and the maximum value of the magnetic field gradient associated with the stresses in the L-beams was reduced by up to 80.2%.

The state of austenite grains has an essential role in the microstructure transformation and mechanical properties of alloy steel during heat treatment or subsequent hot working. The initial microstructure of alloy steel is inseparable from the nucleation and growth of austenite grains. Hence, in this work, high carbon low alloy steel with the initial microstructure of lamellar pearlite and grain boundary cementite was selected, and the effect of cementite dissolution on austenite grain growth was analyzed from the perspective of the phase transition dilatometer curve. Three nucleation sites in high carbon low alloy steel were found by multi-perspective characterization, forming two types of austenite grains: pearlite-austenite grain and cementite-austenite grain. Under cementite pinning and solute drag effect, the growth of the prior austenite grains was retarded during the isothermal temperatures process. The average size of prior austenite grains increased only from 65.1 μm (1050 °C) to 69.8 μm (1150 °C). This work provides a foundation for optimizing the prior austenite grains state by utilizing grain boundary cementite dissolution.

In this paper, numerical simulations of single-jet impingement cooling and double-jet impingement cooling processes of heated L-shaped steel are carried out using the VOF model. The SIMPLEC pressure–velocity coupling algorithm and realizable k-ε model are used for the solution. The effects of jet position, water flow, and jet distance in the single-jet condition are analyzed in the simulations. The distributions of impact pressure, turbulence kinetic energy, and Nusselt number were obtained, as well as the variation of the peak values of these three factors with the jet position, water flow, and jet distance. The water flow rate is 3–11 L/min, and the jet distance is 5–25 cm. The effect of the distance between the two nozzles on the jet cooling uniformity under the dual jet condition was also analyzed. The distance between the two nozzles was 15–45 mm. The results showed that the variation of water flow rate had a greater effect on the ability of jet cooling compared with the jet position and jet distance, and the heat transfer efficiency also increased gradually with the increase of water flow, but the increased rate of heat transfer efficiency decreased gradually. When the flow rate increased from 3 to 11 L/min, the maximum instantaneous cooling rates at 1/4 of the thickness of the short side upper side, long side upper side, short side lower side, and long side lower side positions increased by 38.9%, 48.5%, 48.2%, and 32.9%, respectively. To ensure that the jet does not shift, the jet distance should be less than or equal to 10 cm. In the case of the double jet, the nozzle distance is 1.5 cm, and the cooling uniformity of the cooling area between the two nozzles is better. The peak Nusselt number in the cooling area of each part under the double jet cooling condition increased by 5%, 9.4%, 10.2%, and 13.3%, respectively, compared with the single jet.

The uniformity of cooling affects the organizational properties and product quality of the L-beam. Problems such as bending deformation of the L-beam and excessive residual stresses inside the finished product are mainly caused by uneven cooling. The jet angle is an important cooling parameter in the cooling process of L-beam. In this study, the flow field and cooling law during jet cooling of hot-rolled L-beams were investigated by means of numerical simulation using the jet angle as a variable. The jet angle is -45 degrees similar to 30 degrees on the lower surface of the short edge of the L-beam due to space limitation, and the jet angle is -45 degrees similar to 45 degrees on the rest of the parts, and the other process parameters are kept unchanged. The velocity distribution, pressure, water flow, and temperature distribution on the cooling surface and the average heat transfer coefficient were analyzed. The results show that the jet angle has a significant effect on the cooling of each part of the L-beam. With the increase of the jet angle, the asymmetry of water velocity, pressure distribution, water flow distribution, and temperature distribution on the surface of the cooling surface increased significantly. The distribution of heat flux corresponds well to the distribution of temperature. As the jet angle increases the surface average heat transfer coefficient gradually decreases, and the maximum average heat transfer coefficient appears in the vertical jet. Gravity will also have a certain effect on the cooling of the L-beam.

In recent decades, research on 60Si2Mn spring steel has focused on decarburization and ignored its oxidation behavior. However, Si affects the oxide layer structure of 60Si2Mn spring steel, so it significantly impacts the decarburization behavior. Because the effect of the oxide layer structure on its decarburization behavior has not been systematically clarified, this paper examines it for 60Si2Mn spring steel in dry air using a combination of experiments and first-principles calculations. It was found that at 1000 degrees C and 1100 degrees C, the oxide layer was mainly composed of the Fe2O3 + Fe3O4 + FeO/Fe2SiO4 layers. Decarburization was significantly hindered by Fe2SiO4. Fe2SiO4 has a much higher crack formation energy (3.14 J/m2) than FeO (0.51 J/m2), which indicates that it is more difficult to form cracks in the Fe2SiO4 layer. It is difficult for the gas produced by the reaction between FeO and C to diffuse out through a crack in the inner FeO/Fe2SiO4 oxide layer, which hinders decar-burization. The presence of a Fe2SiO4layer is effective in providing decarburized protection.

Gas leakage source localization is a matter of utmost security concern. However, the conventional mechanism model fails to accurately depict the actual diffusion environment during a leak, leading to diminished accuracy and substantial deviations in source estimation. To overcome this limitation and bolster the precision and reliability of gas leakage source localization, we introduce an improved adaptive PSO-LSTM algorithm. By leveraging field detection data obtained from ABB's Ability™ high-precision gas leakage detection system, we enhance the conventional particle swarm optimization algorithm (PSO) by fine-tuning learning factors and other critical parameters. Moreover, to harness the profound interpretability of the mechanism model and the potent learning capabilities of the LSTM neural network (data model), we substitute the fitness function of the traditional Gaussian plume diffusion model with training outcomes from the LSTM neural network, employing a sizable dataset. Empirical findings underscore that our refined algorithm attains superior accuracy and robustness in estimating source locations.

In the post-Moore era, System-on-Wafer (SoW) has been proposed to overcome the intractable advanced process nodes issues faced by Systems-on-Chip (SoC). SoW primarily relies on advanced packaging technologies such as 2.5D, 3D, and fan-out packagings that must be cost-effective and reliable. Consequently, the cooling or thermal management issues are especially challenging since SoW concentrates the thermal power onto the wafer scale. Here, this paper proposes a high-efficient and flexible embedded liquid cooling solution for the thermal management of a 4-inch SoW. The following structures by directly etching micrometer-sized channels in the backside of a wafer were considered: serpentine, parallel, spiral, and six-quadrant microchannel networks with straight-line shapes at a depth of 100 mu m. The thermal resistance, pumping power, average heat transfer coefficient, and cooling coefficient of performance of different microchannel heat sinks (MCHS) were evaluated with a constant volumetric flow rate of cooling water. The simulation results revealed that for a 4-inch SoW with a heat flux of 13 W/cm(2) and a water flow rate of 0.12 L/min, the serpentine microchannel enabled the smallest temperature rise due to the highest effective heat transfer coefficient. However, the sixquadrant microchannel facilitated the energy efficiency of the heat sink, which can be attributed to the lowest pumping power. The liquid cooling experiments were then performed to verify that the maximum temperature of a SoW embedded with a parallel structure was decreased by more than 39% compared to that of the SoW with natural cooling. The embedded waferlevel microchannel architectures could afford feasible approaches for the thermal management of the upcoming SoW integration.

残余应力是异形断面型钢热轧生产中普遍存在的问题.应力引发型钢变形,是影响相关产品成材率的重要因素之一.针对异形断面型钢的残余应力问题,本文主要从残余应力的测试与研究方法、应力产生原因和应力控制几个方面对国内外研究现状进行阐述.最后做出总结,以期为异形断面型钢残余应力的研究以及应力的控制提供借鉴.

During the hot‐rolling process, the 60Si2Mn spring steel is exposed to both dry air and water vapor at high temperatures. However, no precise mechanism or theory is developed to explain the effect of water vapor on the oxide layer from a microscopic atomic perspective. The high‐temperature oxidation of 60Si2Mn spring steel with dry and wet air is investigated herein using a combination of experiments and first‐principles calculations. After high‐temperature oxidation in both dry and wet air, the 60Si2Mn spring steel generates a typical three‐layer structure consisting of Fe2O3, Fe3O4, and FeO + SiO2/Fe2SiO4; however, the oxide layer produced in wet air is significantly thicker. Furthermore, the phase transformation from Fe3O4 to Fe2O3 occurs in the middle Fe3O4 layer, which is associated with H protons derived from H2O molecules penetrating into oxide layers and promoting the development of Fe vacancies in the center of the tetrahedral interstices. The high porosity of the Fe3O4 layer essentially encourages Fe and O diffusion, hence enhancing the growth of the oxide layer and facilitating the transformation from Fe3O4 to Fe2O3. These findings provide a more detailed mechanistic explanation of how water vapor affects the high‐temperature oxidation of 60Si2Mn spring steel at the atomic level.

With the development of electronic products towards high-density integration and high power, the system-on-wafer (SoW) packaging is a promising technology. In this paper, heat dissipation capability of a wafer-level cooling system was researched based on the finite element modelling (FEM). We built a 3D integration model to research heat dissipation capabilities with different flow rates and fluidic channel depths. The results showed that there was a positive correlation between flow rate and heat dissipation capacity of the fluidic channel. With the same water flow rate, the heat dissipation capacity gradually increased as the channel depth decreased. This paper also presents a cooling system based on a wafer-level fluidic channel for the SoW packaging application. A 4-inch silicon wafer with a thickness of 500 mu m was used as a substrate of the SoW. Nine dummy heating chips were attached on the wafer to mimic the heat situation when the SoW was working. Compared with an average temperature of 120 degrees C of dummy heating chips with natural air cooling, an average temperature of 55 degrees C was measured using the wafer- level fluidic channels. When the flow rate inside the channel was 1.5 L/min, the heat dissipation capacity of the fluidic channel cooling system was 0.14 W/ mm(2), and the thermal resistance was 0.141 degrees C/W. This is a significant improvement in wafer-level cooling performance, indicating that the microfluidic channel cooling system is highly effective in dissipating heat.

L-beam is a widely used structural steel. The study of the three-stage bending deformation mechanism of L-beam under non-uniform cooling conditions is of great significance to ensure the quality, improve the yield of steel, and reduce the stress level in the finished L-beam. However, it is difficult to investigate experimentally due to the high temperature and simultaneous changes of various influencing factors during the air-cooling process of the L-beam. Numerical simulation provides a convenient and feasible method to study the bending deformation mechanism of the L-beam. To investigate the effects of phase transformation and cooling shrinkage on the bending deformation of AH36 L-beam, a three-dimensional thermal-metallurgical-mechanical coupling model was established in this study; the microstructure distribution, hardness, strain, deformation status, and stress during the air cooling of L-beam were calculated. The results show that the microstructure distribution and deformation condition calculated by the model considering the phase transformation effect better agree with the actual situation. Considering the phase change effect is the key to improving the accuracy of the model calculation. The change of heat transfer coefficient caused by phase transformation affects the deformation tendency of the L-beam, while the transformation strain affects the amount of deformation of the L-beam. The alternating changes in the sum of the transformation strain and the cooling shrinkage strain result in a change of stress state which ultimately also results in a three-stage bending deformation of the L-beam.

L型钢在轧后空冷过程中会产生复杂的3次弯曲变形,严重影响了其成材率,冷却过程中3次变形产生的机制尚不明确.为了研究相变对L型钢冷却弯曲变形的影响,基于ABAQUS二次开发环境,编写了USD-FLD、UEXPAN和HETVAL子程序,对L型钢轧后冷却过程中的组织转变、相变潜热、相变应变和变形量进行了计算.研究了5组不同的模拟状态,从相变应变和冷却收缩应变的角度分析了L型钢轧后冷却过程中弯曲变形的原因.研究结果表明:L型钢的3次弯曲变形是相变应变和冷却收缩应变交互作用的结果,相变引起的应变和冷却收缩应变影响着L型钢的弯曲变形趋势,而相变潜热和相变应变则影响着型钢的弯曲变形量.

Aiming at the demand for performance control in the production process of hot-rolled ribbed bar, the finite difference method was used to establish a temperature prediction model during the cooling process. The calculation accuracy of the temperature model depends to a large extent on the selection of heat transfer coefficient. In this study, the industrial production data was cleaned and screened by the clustering algorithm to obtain training sample data, and based on BP neural networks, the mapping relationship between different influencing factors and heat transfer coefficient was established. According to the change of production conditions, the heat transfer coefficient is learned adaptively, which improves the prediction accuracy of the model. By comparing the predicted and actual temperature values over a period of time, the deviation between most predicted and actual values is less than 20 degrees C, and the deviation is reduced by about 30 degrees C compared with that before the BP network was used to study the heat transfer coefficient. Under the constraints of the target temperature and the temperature difference between the inside and outside of the section, the precise control of the cooling temperature of the hot-rolled ribbed bar is realized by the calculation of the temperature prediction model.

根据分子离子共存理论,建立了CaO-SiO2-MgO-A12O3-TiO2含钛高炉渣活度模型,模型计算结果与实验测定结果吻合较好.利用该模型并结合相图计算分析了碱度和w(TiO2)对含钛高炉渣主要组元活度的影响.结果表明,含钛高炉渣中钛的主要赋存相是CaO· TiO2,l 500℃时典型含钛高炉渣中CaO· TiO2的活度为0.18.随着碱度和w(TiO2)增加,CaO·TiO2活度先增后减.当碱度区间在1.08 ～ 3.08,w(TiO2)在26％ ～ 43％的条件下,有利于CaO· TiO2活度的增加,促进钛组分在钙钛矿中富集.CaO· TiO2活度最大值所需碱度随TiO2含量的增加而增加,当含钛高炉渣中w(TiO2)为20％～28％时碱度为1.34～1.63,对促进钛在钙钛矿中的富集是有利的.